Published today in the journal Nature Communications, the paper “Trivalent Titanium in High-Titanium Lunar Ilmenite” confirms titanium in a reduced, trivalent state in a black, metal-rich lunar mineral called ilmenite. It’s a state only possible in low-oxygen environments, conditions researchers refer to as “reducing.”
“Models have suggested that these reducing conditions may have varied at different locations and times across the surface of the Moon,” says lead author Advik Vira, a graduate student in the School of Physics who recently earned his doctoral degree. “We hope our microscopy technique can be a valuable step in mapping and understanding the Moon’s 4.5-billion-year history.”
The team anticipates that their technique could be used on many of the lunar samples collected more than 50 years ago by the Apollo missions in addition to the Apollo Next Generation Samples — a group of lunar samples that have been stored under pristine conditions — and new samples from the planned Artemis missions, with Artemis II slated for launch this spring. The technique might also be applicable to samples collected from the far side of the Moon and returned in 2024 by the Chang’e-6 mission.
“The Moon holds clues not only to its own past, but also to the earliest eras of Earth’s evolution — history that has long since been erased from our planet,” Vira says. “This study is a step toward understanding the history of both and a reminder that there is still so much left to learn from the lunar rocks we’ve brought back to Earth.”
The School of Physics research team included corresponding authors Vira and Professor Phillip First; in addition to graduate student Roshan Trivedi; undergraduate students Gabriella Dotson, Keyes Eames, Dean Kim, and Emma Livernois; and Professor Zhigang Jiang, along with Institute for Matter and Systems Materials Characterization Facility Senior Research Scientist Mengkun Tian; School of Chemistry and Biochemistry Senior Research Scientist Brant Jones and Thom Orlando, Regents' Professor in the School of Chemistry and Biochemistry with a joint appointment in the School of Physics.
The Georgia Tech team was joined by Addis Energy Senior Geochemist Katherine Burgess; Macalester College Assistant Professor of Geology Emily First; along with Lawrence Berkeley National Laboratory Research Scientist Harrison Lisabeth, Senior Scientist Nobumichi Tamura, and Postdoctoral Fellow Tyler Farr, who recently earned a Ph.D. from Georgia Tech’s George W. Woodruff School of Mechanical Engineering.
The investigation began with a dark gray rock called a lunar basalt. Formed when ancient magma erupted on the Moon’s surface, minerals crystallized as it cooled — preserving key information in their structures. Billions of years later, the rock was brought to Earth by the 1972 Apollo 17 mission, where a small piece is now stored at Georgia Tech’s Center for Lunar Environment and Volatile Exploration Research (CLEVER), a NASA Solar System Exploration Research Virtual Institute (SSERVI) center led by Orlando.
As a NASA virtual institute, CLEVER supports researchers exploring lunar conditions and developing tools for the upcoming crewed Artemis missions, and provided the lunar samples for this research. The SSERVI also plays a critical role in training the next generation of planetary researchers: both Vira and Farr earned their Ph.D.s while on the CLEVER team.
“At CLEVER, we are very interested in understanding the impacts of space weathering,” Vira says. “We implemented modern sample preparation and advanced microscopy techniques to image samples at the atomic level, and were curious to apply it more broadly to the collection of Apollo rocks in the Orlando Lab. This sample caught our attention.”
“When we imaged an ilmenite crystal from the lunar basalt, what struck us first was how uniform and perfect the crystal structure was,” he recalls. “We found no defects from space weathering and instead saw an undamaged, pristine crystal — undisturbed for 3.8 billion years.”
To investigate further, the team analyzed small chips of the rock with Burgess, a member of the RISE2 SSERVI team and then a geologist at the U.S. Naval Research Laboratory. Using state-of-the-art electron microscopy and spectroscopy techniques, Vira determined the oxidation state of the elements in the ilmenite present.
In spectroscopy measurements, each element leaves a distinct ‘signature,’ Vira explains. “When we brought our results back to Georgia Tech’s Materials Characterization Facility, Mengkun (Tian) noticed something unusual: the signature showed titanium might be present in the trivalent state.”
The presence of trivalent titanium had long been suspected in this lunar mineral. The team was intrigued.
With funding from Georgia Tech’s Center for Space Technology and Research (CSTAR), Vira returned to the U.S. Naval Research Laboratory to analyze additional samples. The results confirmed that more titanium was present than the mineral’s formula (FeTiO₃) predicts — indicating a portion of the titanium present was trivalent.
“That led me to place our measurements in terms of the broader geological context,” Vira shares. Working with First, Vira explored how ilmenite with trivalent titanium could help reconstruct the nature of ancient magmas from the Moon, especially the chemical availability of oxygen.
“Because its location on the Moon was noted during the Apollo mission, we know exactly where this rock is from, and we can determine how old the rock is,” he explains. “When coupled with our trivalent titanium measurements, we can use that information to estimate the reducing conditions for this specific region at the specific time our rock formed.”
If the upcoming Artemis missions return samples suitable for the team’s technique, these rocks could provide a new window into ancient lunar geology. The research also highlights that many lunar samples already on Earth could be reexamined to look for trivalent titanium.
“There is still so much to learn from the lunar samples we have already brought to Earth,” Vira says. “It’s a testament to the long-term value of each sample return mission. As technology continues to advance, this type of work will continue to give us critical insights into our planet and our place in the universe for years to come.”
DOI: 10.1038/s41467-026-69770-w
Funding: This work was directly supported by the NASA SSERVI under CLEVER. Researchers were also supported by the NASA RISE2 SSERVI and the Heising-Simons Foundation. Funding for collaborations between the U.S. Naval Research Laboratory and Georgia Tech for the investigation of lunar minerals was provided by the Georgia Tech Center for Space Technology and Research. Sample preparation was performed at the Georgia Tech Institute for Matter and Systems, which is supported by the National Science Foundation. This work utilized the resources of the Advanced Light Source, a user facility supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, and was supported in part by previous breakthroughs obtained through the Laboratory Direct.
]]>Selena Langner
College of Sciences
Georgia Institute of Technology
Amino acids also play a critical role commercially where they are manufactured and added to pharmaceuticals, dietary supplements, cosmetics, animal feeds, and industrial chemicals — an energy-intensive process leading to greenhouse gas emissions, resource consumption, and pollution.
A landmark new system developed at Georgia Tech could lead to an alternative: a commercially scalable, environmentally sustainable method for amino acid production that is carbon negative, using more carbon than it emits.
The breakthrough builds on a method that the team pioneered in 2024 and solves a key issue – increasing efficiency to an unprecedented 97% and reducing the bioprocess cost by over 40%. It’s the highest reported conversion of CO2 equivalents into amino acids using any synthetic biology system to date.
Published in the journal ACS Synthetic Biology, the study, “Cell-Free-Based Thermophilic Biocatalyst for the Synthesis of Amino Acids From One-Carbon Feedstocks,” was led by Bioengineering Ph.D. student Ray Westenberg and Professor Pamela Peralta-Yahya, who holds joint appointments in the School of Chemistry and Biochemistry and School of Chemical and Biomolecular Engineering. The team also included Shaafique Chowdhury (Ph.D. ChBE 25) and Kimberly Wennerholm (ChBE 23); alongside University of Washington collaborators Ryan Cardiff, then a Ph.D. student and now a Chain Reaction Innovations Fellow at Argonne National Laboratory, and Charles W. H. Matthaei Endowed Professor in Chemical Engineering James M. Carothers; in addition to Pacific Northwest National Laboratory Synthetic Biology Team Leader Alexander S. Beliaev.
"This work shifts the narrative from simply reducing carbon emissions to actually consuming them to create value,” says Peralta-Yahya. “We are taking low-cost carbon sources and building essential ingredients in a truly carbon-negative process that is efficient, effective, and scalable.”
The work builds on the cell-free technology the team used in their earlier study. “Previously, we discovered that a system that uses the machinery of cells, without using actual living cells, could be used to create amino acids from carbon dioxide,” Peralta-Yahya explains. “But to create a commercially viable system, we needed to increase the system’s efficiency and reduce the cost.”
The team discovered that bits of leftover cells were consuming starting materials, and — like a machine with unnecessary gears or parts — this limited the system’s efficiency. To optimize their “machine,” the team would need to remove the extra background machinery.
"Leftover cell parts were using key resources without helping produce the amino acids we were looking for,” says Peralta-Yahya. “We knew that heating the system could be one way to purify it because heat can denature these components.”
The challenge was in how to protect the essential system components from the high temperatures, she adds. “We wondered if introducing enzymes produced by a heat-loving bacterium, Moorella thermoacetica, might protect our system, while still allowing us to denature and remove that inefficient background machinery.”
The results were astounding: after introducing the enzymes, heating and “cleaning” the system, and letting it cool to room temperature, synthesis of the amino acids serine and glycine leaped to 97% yield — nearly three times that of the team’s previous system.
To make the system viable for large-scale use, the team also needed to reduce costs. “One of the most costly components in this system is the cofactor tetrahydrofolate (THF),” Peralta-Yahya shares. “Reducing the amount of THF needed to start the process was one way to make the system more inexpensive and ultimately more commercially viable.”
By linking reaction steps so waste from one step fueled the next, the team devised a method to recycle THF within the system that reduces the amount of THF needed by five-fold — lowering bioprocessing costs by 42%.
“This decrease in cost and increase in yield is a critical step forward in creating a method with real potential for use in industry and manufacturing,” Peralta-Yahya says. “This system could pave the way for moving this carbon-negative technology out of the lab and onto the continuous, industrial scale."
Funding: The Advanced Research Project Agency-Energy (ARPA-E); U.S. Department of Energy; and the U.S. Department of Energy, Office of Science, Biological and Environmental Research Program.
DOI: https://doi.org/10.1021/acssynbio.5c00352
]]>Selena Langner
College of Sciences
Georgia Institute of Technology
The project, inspired by an Atlanta Science Festival event hosted by School of Chemistry and Biochemistry Assistant Professor Andrew McShan, develops an innovative outreach and teaching module around nuclear magnetic resonance (NMR) techniques, and is designed for easy adoption in introductory chemistry and biochemistry courses.
Published earlier this year in the Journal of Chemical Education, the study, “Automated Chemical Profiling of Wine by Solution NMR Spectroscopy: A Demonstration for Outreach and Education” was led by a team from the School of Chemistry and Biochemistry including lead author McShan, Ph.D. students Lily Capeci, Elizabeth A. Corbin, Ruoqing Jia, Miriam K. Simma, and F. N. U. Vidya, Academic Professional Mary E. Peek, and Georgia Tech NMR Center Co-Directors Johannes E. Leisen and Hongwei Wu.
“NMR is one of the most widely used analytical tools in chemistry and the life sciences, and Georgia Tech hosts one of the most cutting-edge NMR centers in the world,” McShan says. “Our study shows that you don’t need advanced training to appreciate how powerful tools like NMR work and how those tools are used in research.”
All materials, tutorials, and data are freely available via online tutorials and a YouTube video, enabling educators to replicate or adapt the activity even in settings with limited access to NMR facilities.
From families with K-12 students to undergraduates to adults with no prior chemistry experience, nearly 130 visitors explored wine chemistry at the Georgia Tech NMR Center during the Atlanta Science Festival event. With McShan’s guidance, they identified and quantified more than 70 chemical components that influence wine taste, aroma, and quality by analyzing the chemical composition, structure, and dynamics of molecules.
Taking on the role of wine investigators (a real-world application of NMR), the group investigated examples of wine fraud, learning to identify harmful additives like methanol, antifreeze, and lead acetate – additives that played roles in both historical and modern wine scandals.
“By connecting the science to something familiar like wine, we were able to spark curiosity and excitement across age groups,” says McShan. “This a framework for how complex analytical techniques can be made inclusive, interactive, and inspiring whether in the classroom or at a science festival.”
The study underscores the potential of NMR and other powerful technologies as outreach opportunities – from engaging the public to better teaching undergraduate students.
“After the event, adults said they learned how chemical composition affects wine characteristics and how NMR is used in research and industry,” McShan says. “Younger participants learned key concepts about wine composition and found benefits from the sensory elements, like watching the spectrometer in action.”
They aim to use these takeaways to continue developing outreach tools. “My end goal is to develop NMR into a practical teaching tool by grounding the technique in real-world examples,” adds McShan. “Using this approach is a clear avenue to introducing the general public to the world-class instruments used by researchers at Georgia Tech and exposing undergraduate students to the powerful analytical techniques they are likely to encounter throughout their careers.”
Funding: National Science Foundation
]]>When centimeter-long aquatic worms, such as T. tubifex or Lumbriculus variegatus, are placed in a Petri dish filled with sub-millimeter sized sand particles, something surprising happens. Over time, the worms begin to spontaneously clean up their surroundings. They sweep particles into compact clusters, gradually reshaping and organizing their environment.
In a study recently published in Physical Review X, a team of researchers show that this remarkable sweeping behavior does not require a brain, or any kind of complex interaction between the worms and the particles. Instead, it emerges from the natural undulating motion and flexibility that the worms possess.
The study was co-led by Saad Bhamla, associate professor in Georgia Tech’s School of Chemical and Biomolecular Engineering, and Antoine Deblais of the University of Amsterdam.
Deblais said: “It is fascinating to see how living worms can organize their surroundings just by moving.” Bhamla added: “Their activity and flexibility alone are enough to collect particles and reshape their environment.”
By building simple robotic and computer models that mimic the living worms, the researchers discovered that only these two ingredients – activity and flexibility – are sufficient to reproduce the sweeping and collecting effects. The result is a self-organized, dynamic form of environmental restructuring driven purely by motion and shape.
Order emerges
The results do not just teach us a surprising lesson about worms. Understanding how these organisms spontaneously collect particles has much broader implications. On the technological side, what the researchers have learned could inspire the design of soft robots that clean or sort materials without needing sensors or pre-programmed intelligence.
Such robots, like the worms, would simply move and let order emerge from motion. “Brainless” machines of this sort could perhaps one day help remove microplastics or sediments from aquatic environments, or perform complex tasks in unpredictable terrains.
From a biological perspective, the results also offer insights into how elongated living organisms – not just worms, but also filamentous bacteria, or cytoskeletal filaments – can structure and modify their own habitats through simple physical interactions. Understanding this structuring and modifying behaviour has been a central question for, e.g., earthworms in their role in soil aeration.
From a biological perspective, the results also offer insights into how elongated living organisms – not just worms, but also filamentous bacteria, or cytoskeletal filaments – can structure and modify their own habitats through simple physical interactions. Understanding this structuring and modifying behaviour has been a central question for, e.g., earthworms in their role in soil aeration.
Team effort
This project grew out of curiosity about how living systems shape their environment without centralized control. Initial experiments with worms, conducted by Harry Tuazon (Bioengineering PhD 2024) at Georgia Tech, showed the unexpected particle collection patterns. This led the team to attempt to reproduce the behavior using robotic and simulated counterparts – something that worked surprisingly well. In the project, experimentalists and theorists worked side by side, allowing the team to uncover the physical principles behind this seemingly purposeful behavior.
Co-first author Rosa Sinaasappel conducted the robot experiments at the University of Amsterdam. “By mimicking the worms’ motion with simple brainless robots connected by flexible rubber links, we could pinpoint the two ingredients that are essential for the sweeping mechanism,” she said.
Co-first author Prathyusha Kokkoorakunnel Ramankutty, a research scientist in the Bhamla Lab at Georgia Tech, performed the computer simulations of the behavior. “Our computational model, built on simple ingredients like propulsion and flexibility, shows that this principle works across different scales and can be adapted for new designs, as demonstrated by a soft robotic sweeper that autonomously ‘cleans’ and reorganizes particles without programmed intelligence,” she explained.
The researchers will continue to investigate this type of behaviour in the future. While a mathematical model of active sweeping is now presented in a simple form, many challenging questions raised by this complex system remain open for theoreticians.
Multiple groups of students helped greatly with the robot experiments, doing projects in the lab. Their efforts ranged from performing the experiments to replacing the in total about 200 batteries, after perhaps one of the most difficult tasks: wrestling them free from the child-proof packaging.
CITATION:
Particle Sweeping and Collection by Active and Living Filaments, Sinaasappel, R., Prathyusha, K. R., Tuazon, Harry, Mirzahossein, E., Illien, P., Bhamla, Saad, and A. Deblais. Physical Review X (2026)
Students and faculty from the School of Computational Science and Engineering (CSE) are leading the Georgia Tech contingent at the SIAM Conference on Computational Science and Engineering (CSE25). The Society of Industrial and Applied Mathematics (SIAM) organizes CSE25, occurring March 3-7 in Fort Worth, Texas.
At CSE25, the School of CSE researchers are presenting papers that apply computing approaches to varying fields, including:
[Related: GT CSE at SIAM CSE25 Interactive Graphic]
“In CSE, researchers from different disciplines work together to develop new computational methods that we could not have developed alone,” said School of CSE Professor Edmond Chow.
“These methods enable new science and engineering to be performed using computation.”
CSE is a discipline dedicated to advancing computational techniques to study and analyze scientific and engineering systems. CSE complements theory and experimentation as modes of scientific discovery.
Held every other year, CSE25 is the primary conference for the SIAM Activity Group on Computational Science and Engineering (SIAG CSE). School of CSE faculty serve in key roles in leading the group and preparing for the conference.
In December, SIAG CSE members elected Chow to a two-year term as the group’s vice chair. This election comes after Chow completed a term as the SIAG CSE program director.
School of CSE Associate Professor Elizabeth Cherry has co-chaired the CSE25 organizing committee since the last conference in 2023. Later that year, SIAM members reelected Cherry to a second, three-year term as a council member at large.
At Georgia Tech, Chow serves as the associate chair of the School of CSE. Cherry, who recently became the associate dean for graduate education of the College of Computing, continues as the director of CSE programs.
“With our strong emphasis on developing and applying computational tools and techniques to solve real-world problems, researchers in the School of CSE are well positioned to serve as leaders in computational science and engineering both within Georgia Tech and in the broader professional community,” Cherry said.
Georgia Tech’s School of CSE was first organized as a division in 2005, becoming one of the world’s first academic departments devoted to the discipline. The division reorganized as a school in 2010 after establishing the flagship CSE Ph.D. and M.S. programs, hiring nine faculty members, and attaining substantial research funding.
Ten School of CSE faculty members are presenting research at CSE25, representing one-third of the School’s faculty body. Of the 23 accepted papers written by Georgia Tech researchers, 15 originate from School of CSE authors.
The list of School of CSE researchers, paper titles, and abstracts includes:
Bayesian Optimal Design Accelerates Discovery of Material Properties from Bubble Dynamics
Postdoctoral Fellow Tianyi Chu, Joseph Beckett, Bachir Abeid, and Jonathan Estrada (University of Michigan), Assistant Professor Spencer Bryngelson
[Abstract]
Latent-EnSF: A Latent Ensemble Score Filter for High-Dimensional Data Assimilation with Sparse Observation Data
Ph.D. student Phillip Si, Assistant Professor Peng Chen
[Abstract]
A Goal-Oriented Quadratic Latent Dynamic Network Surrogate Model for Parameterized Systems
Yuhang Li, Stefan Henneking, Omar Ghattas (University of Texas at Austin), Assistant Professor Peng Chen
[Abstract]
Posterior Covariance Structures in Gaussian Processes
Yuanzhe Xi (Emory University), Difeng Cai (Southern Methodist University), Professor Edmond Chow
[Abstract]
Robust Digital Twin for Geological Carbon Storage
Professor Felix Herrmann, Ph.D. student Abhinav Gahlot, alumnus Rafael Orozco (Ph.D. CSE-CSE 2024), alumnus Ziyi (Francis) Yin (Ph.D. CSE-CSE 2024), and Ph.D. candidate Grant Bruer
[Abstract]
Industry-Scale Uncertainty-Aware Full Waveform Inference with Generative Models
Rafael Orozco, Ph.D. student Tuna Erdinc, alumnus Mathias Louboutin (Ph.D. CS-CSE 2020), and Professor Felix Herrmann
[Abstract]
Optimizing Coupled Systems: Insights from Co-Design Imaging and Optical Chemistry
Assistant Professor Raphaël Pestourie, Wenchao Ma and Steven Johnson (MIT), Lu Lu (Yale University), Zin Lin (Virginia Tech)
[Abstract]
Multifidelity Linear Regression for Scientific Machine Learning from Scarce Data
Assistant Professor Elizabeth Qian, Ph.D. student Dayoung Kang, Vignesh Sella, Anirban Chaudhuri and Anirban Chaudhuri (University of Texas at Austin)
[Abstract]
LyapInf: Data-Driven Estimation of Stability Guarantees for Nonlinear Dynamical Systems
Ph.D. candidate Tomoki Koike and Assistant Professor Elizabeth Qian
[Abstract]
The Information Geometric Regularization of the Euler Equation
Alumnus Ruijia Cao (B.S. CS 2024), Assistant Professor Florian Schäfer
[Abstract]
Maximum Likelihood Discretization of the Transport Equation
Ph.D. student Brook Eyob, Assistant Professor Florian Schäfer
[Abstract]
Intelligent Attractors for Singularly Perturbed Dynamical Systems
Daniel A. Serino (Los Alamos National Laboratory), Allen Alvarez Loya (University of Colorado Boulder), Joshua W. Burby, Ioannis G. Kevrekidis (Johns Hopkins University), Assistant Professor Qi Tang (Session Co-Organizer)
[Abstract]
Accurate Discretizations and Efficient AMG Solvers for Extremely Anisotropic Diffusion Via Hyperbolic Operators
Golo Wimmer, Ben Southworth, Xianzhu Tang (LANL), Assistant Professor Qi Tang
[Abstract]
Randomized Linear Algebra for Problems in Graph Analytics
Professor Rich Vuduc
[Abstract]
Improving Spgemm Performance Through Reordering and Cluster-Wise Computation
Assistant Professor Helen Xu
[Abstract]
Students and faculty from the School of Computational Science and Engineering (CSE) are leading the Georgia Tech contingent at the SIAM Conference on Computational Science and Engineering (CSE25). The Society of Industrial and Applied Mathematics (SIAM) organizes CSE25, occurring March 3-7 in Fort Worth, Texas.
]]>“Research in lanthanides has already yielded significant dividends for society in terms of technological development,” La Pierre added.
The researchers hope to discover new tools for mining critical REEs, including improving lanthanide separation and recycling processes. When mining these elements, lanthanide elements are frequently mixed together. The separation process is painstaking and inefficient, generating a significant amount of waste. But with increasing global demand for REEs, the U.S. faces a supply issue. Figuring out how to improve lanthanides separation, potentially through oxidation chemistry, will ultimately enhance the supply of these critical elements.
— Anne Wainscott-Sargent
Funding: This research was supported by grants from the National Science Foundation and the U.S. Department of Energy.
The Blavatnik Awards are presented by the Blavatnik Family Foundation and are administered by the New York Academy of Sciences. They honor the most promising early-career researchers in the U.S., across life sciences, chemistry, and physical sciences, and engineering. The awards are among the most prestigious and competitive in science.
This dual recognition underscores Georgia Tech’s growing national leadership in high-impact, interdisciplinary research.
Ryan Lively, Thomas C. DeLoach Jr. Endowed Professor in the School of Chemical and Biomolecular Engineering, is recognized in the Chemical Sciences category for pioneering scalable technologies that will reduce industrial carbon emissions and energy use. He develops new materials that can capture carbon and separate chemicals, using much less energy than conventional methods. His innovations could make industry cleaner and play a key role in addressing climate change.
Matthew McDowell, Carter N. Paden Jr. Distinguished Chair in the George W. Woodruff School of Mechanical Engineering holds a joint appointment in the School of Materials Science and Engineering. Recognized in the Physical Sciences and Engineering category for groundbreaking battery research, he and his team develop new materials to make batteries last longer and store more energy. He has discovered ways to visualize how battery materials change during use — insights that help improve the performance and safety of future energy technologies.
This year’s 18 finalists were selected from 310 nominees. On Oct. 7, 2025, three laureates will be announced at a gala at New York City’s American Museum of Natural History. Each laureate will receive $250,000, the largest unrestricted scientific prize for early-career researchers in the U.S.
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Two Georgia Tech researchers, Ryan Lively and Matthew McDowell, have been named finalists for the 2025 Blavatnik National Awards for Young Scientists, one of the nation’s most prestigious honors for early career researchers. Lively is recognized for developing scalable chemical engineering technologies that reduce carbon emissions and energy use, while McDowell is honored for pioneering advanced battery materials that improve safety, lifespan, and energy storage. Their dual recognition highlights Georgia Tech’s growing national leadership in high-impact, interdisciplinary research with broad implications for climate and energy.
To ease this environmental burden, industry has worked to adopt renewable biopolymers in place of traditional plastics. However, developers of sustainable packaging have faced hurdles in blocking out moisture and oxygen, a barrier critical for protecting food, pharmaceuticals, and sensitive electronics.
Now, researchers at the Georgia Institute of Technology have developed a biologically based film made from natural ingredients found in plants, mushrooms, and food waste that can block moisture and oxygen as effectively as conventional plastics. Their findings were recently published in ACS Applied Polymer Materials.
“We’re using materials that are already abundant in and degrade in nature to produce packaging that won’t pollute the environment for hundreds or even thousands of years,” said Carson Meredith, a professor in Georgia Tech’s School of Chemical and Biomolecular Engineering (ChBE@GT) and executive director of the Renewable Bioproducts Institute. “Our films, composed of biodegradable components, rival or exceed the performance of conventional plastics in keeping food fresh and safe.”
Meredith’s research team has worked for more than a decade to develop environmentally friendly oxygen and water barriers for packaging. While earlier research using biopolymers showed promise, high humidity continued to weaken the barrier properties.
However, Meredith and his collaborators found a fix using a blend of these natural ingredients: cellulose (which gives plants their structure), chitosan (derived from crustacean-based food waste or mushrooms), and citric acid (from citrus fruits).
“By crosslinking these materials and adding a heat treatment, we created a thin film that reduced both moisture and oxygen transmission, even in hot, humid conditions simulating the tropics,” said lead author Yang Lu, a former postdoctoral researcher in ChBE@GT.
The barrier technology developed by the researchers consists of three primary components: a carbohydrate polymer for structure, a plasticizer to maintain flexibility, and a water-repelling additive to resist moisture. When cast into thin films, these ingredients self-organize at the molecular level to form a dense, ordered structure that resists swelling or softening under high humidity.
Even at 80 percent relative humidity, the films showed extremely low oxygen permeability and water vapor transmission, matching or outperforming common plastics such as poly(ethylene terephthalate) (PET) and poly(ethylene vinyl alcohol) (EVOH).
“Our approach creates barriers that are not only renewable, but also mechanically robust, offering a promising alternative to conventional plastics in packaging applications,” said Natalie Stingelin, professor and chair of Georgia Tech’s School of Materials Science and Engineering (MSE) and a professor in ChBE@GT.
The research team has filed for patent protection for the technology (patent pending). The research was supported by Mars Inc., Georgia Tech’s Renewable Bioproducts Institute, and the U.S. Department of Defense through the National Defense Science and Engineering Graduate Fellowship Program. Eric Klingenberg, a co-author of the study, is an employee of Mars, a manufacturer of packaged foods.
Citation: Yang Lu, Javaz T. Rolle, Tanner Hickman, Yue Ji, Eric Klingenberg, Natalie Stingelin, and Carson Meredith, “Transforming renewable carbohydrate-based polymers into oxygen and moisture-barriers at elevated humidity,” ACS Applied Polymer Materials, 2025.
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As Schmidt Polymaths, the researchers pursue new approaches compared to previous work. The new cohort of polymaths will answer questions like how to expand access to healthcare with low-cost technologies, what happens to our chromosomes when we age and how to create more accurate computer simulations of climate.
Bhamla, associate professor in ChBE@GT, is the first Schmidt Polymath from Georgia Tech. He will develop low-cost technologies to tackle planetary-scale challenges, including AI-enabled point-of-care diagnostics in low-resource environments, and he will also engineer autonomous morphing machines that adapt, evolve and learn like living systems.
The eight selected scientists represent the fifth cohort of the highly selective Schmidt Polymaths program. Awardees must have been tenured—or achieved similar status—within the previous three years. Previous cohorts have used the award to design new sensor devices, perform experiments at atomic resolutions, analyze trees of life with faster and more efficient algorithms, discover new mathematical formulas assisted by AI, and more.
Drawn from universities worldwide and selected through a competitive application process, Schmidt Polymaths are required to demonstrate past ability and future potential to pursue early-stage, novel research that would otherwise be challenging to fund—even without the current dramatic declines in U.S. funding for science.
“Our world is one deeply interconnected system---but to study it more deeply, we’ve divided it into increasingly narrow categories,” said Wendy Schmidt, who co-founded Schmidt Sciences with her husband Eric. “Schmidt Polymaths see the bigger picture, pursue answers beyond boundaries and expand the edges of what’s possible. Their work can help steer us all toward a healthier future, for people and the planet.”
About Schmidt Sciences
Schmidt Sciences is a nonprofit organization founded in 2024 by Eric and Wendy Schmidt that works to accelerate scientific knowledge and breakthroughs with the most promising, advanced tools to support a thriving planet. The organization prioritizes research in areas poised for impact including AI and advanced computing, astrophysics, biosciences, climate, and space—as well as supporting researchers in a variety of disciplines through its science systems program.
RELATED: Forbes featured Bhamla in the article: Saad Bhamla Is A Polymath
]]>Imagine if building new medicines or sustainable materials were as straightforward as snapping together LEGO® bricks. That’s the goal of a new project led by the Georgia Institute of Technology that could help transform the future of biomanufacturing.
The project, headed by Professor Mark Styczynski in Georgia Tech’s School of Chemical and Biomolecular Engineering (ChBE@GT), recently received a $9.2 million grant from the National Science Foundation Directorate for Technology, Innovation and Partnerships (NSF TIP) to accelerate the adoption of cell-free systems in biomanufacturing.
Promising Technology
Biotechnology has largely relied on living cells for production of products such as medicines, fragrances, or renewable fuels. But working with living cells can be complex and expensive.
Cell-free systems, by contrast, strip biology down to its essential parts, the enzymes and molecules that carry out life’s chemical reactions. This can simplify and speed up biomanufacturing, making it easier to scale.
The challenge, Styczynski explained, is that most cell-free projects still require custom-built setups. “Right now, engineering biology is like reinventing the wheel for every application,” he said. “You have to figure out how all the parts fit together each time. We want to change that by making ready-to-use modules that work right out of the box.”
Styczynski’s project, called Meta-PURE (PUrified Recombinant Elements), will create eight standardized modules, each designed for a key function in cell-free systems, such as generating energy, producing proteins, or assembling complex molecules.
“Like interchangeable puzzle pieces, these modules can be mixed and matched to support different applications,” Styczynski said.
Demonstrating Uses
His team will demonstrate the system’s versatility by producing santalene (a plant-derived fragrance used widely in consumer products), GamS protein (a tool that can improve cell-free processes), and a bacteriophage (a virus that can be safely used in research and the development of new therapeutic treatments).
These examples highlight the technology’s potential across industries ranging from pharmaceuticals and agriculture to chemicals and sustainable materials.
“We want to make these tools so that someone in industry can create their molecule or product more quickly and efficiently, and get it out the door,” Styczynski said.
“Right now, cell-free systems are mostly limited to high-value products because the cost is too high. The goal is to drive costs down and productivity up, so we can move closer to commodity chemicals like biofuels or monomers for polymers, not just niche applications. One of our partners recently developed a butanol process that shows where this can go,” he said.
NSF Initiative
Styczynski’s team is one of four recently awarded an inaugural investment of $32.4 million to help grow the U.S. bioeconomy. The initiative is called the NSF Advancing Cell-Free Systems Toward Increased Range of Use-Inspired Applications (NSF CFIRE).
“NSF is resolute in our commitment to advancing breakthroughs in biotechnology, advanced manufacturing, and other key technologies of significance to the U.S. economy,” said Erwin Gianchandani, assistant director for NSF TIP. “The novel approaches from these four CFIRE teams will speed up and expand the adoption of cell-free systems across a variety of industries and ensure America’s competitive position in the global bioeconomy.”
Collaborative Effort
While ChBE@GT is the lead, Meta-PURE is a broad collaboration with partners across academia, industry, and government. Co-principal investigators include Paul Opgenorth, co-founder and vice president of development at the biotech firm eXoZymes; Nicholas R. Sandoval, associate professor of Tulane University’s Department of Chemical and Biomolecular Engineering; and Anton Jackson-Smith, founder of the biotech startup b.next.
Meta-PURE will also train graduate students and postdocs in partnership with industry, government, and other universities, helping prepare trainees to be the future of a highly interdisciplinary U.S. bioeconomy. The team will also engage the scientific community on the implementation of metrics and standards in cell-free biotechnology to better facilitate broad adoption and interoperability of not just the results of the Meta-PURE project, but of cell-free efforts more broadly.
Nanoparticles – the tiniest building blocks of our world – are constantly in motion, bouncing, shifting, and drifting in unpredictable paths shaped by invisible forces and random environmental fluctuations.
Better understanding their movements is key to developing better medicines, materials, and sensors. But observing and interpreting their motion at the atomic scale has presented scientists with major challenges.
However, researchers in Georgia Tech’s School of Chemical and Biomolecular Engineering (ChBE) have developed an artificial intelligence (AI) model that learns the underlying physics governing those movements.
The team’s research, published in Nature Communications, enables scientists to not only analyze, but also generate realistic nanoparticle motion trajectories that are indistinguishable from real experiments, based on thousands of experimental recordings.
A Clearer Window into the Nanoworld
Conventional microscopes, even extremely powerful ones, struggle to observe moving nanoparticles in fluids. And traditional physics-based models, such as Brownian motion, often fail to fully capture the complexity of unpredictable nanoparticle movements, which can be influenced by factors such as viscoelastic fluids, energy barriers, or surface interactions.
To overcome these obstacles, the researchers developed a deep generative model (called LEONARDO) that can analyze and simulate the motion of nanoparticles captured by liquid-phase transmission electron microscopy (LPTEM), allowing scientists to better understand nanoscale interactions invisible to the naked eye. Unlike traditional imaging, LPTEM can observe particles as they move naturally within a microfluidic chamber, capturing motion down to the nanometer and millisecond.
“LEONARDO allows us to move beyond observation to simulation,” said Vida Jamali, assistant professor and Daniel B. Mowrey Faculty Fellow in ChBE@GT. “We can now generate high-fidelity models of nanoscale motion that reflect the actual physical forces at play. LEONARDO helps us not only see what is happening at the nanoscale but also understand why.”
To train and test LEONARDO, the researchers used a model system of gold nanorods diffusing in water. They collected more than 38,000 short trajectories under various experimental conditions, including different particle sizes, frame rates, and electron beam settings. This diversity allowed the model to generalize across a broad range of behaviors and conditions.
The Power of LEONARDO’s Generative AI
What distinguishes LEONARDO is its ability to learn from experimental data while being guided by physical principles, said study lead author Zain Shabeeb, a PhD student in ChBE@GT. LEONARDO uses a specialized “loss function” based on known laws of physics to ensure that its predictions remain grounded in reality, even when the observed behavior is highly complex or random.
“Many machine learning models are like black boxes in that they make predictions, but we don’t always know why,” Shabeeb said. “With LEONARDO, we integrated physical laws directly into the learning process so that the model’s outputs remain interpretable and physically meaningful.”
LEONARDO uses a transformer-based architecture, which is the same kind of model behind many modern language AI applications. Like how a language model learns grammar and syntax, LEONARDO learns the "grammar" of nanoparticle movement, identifying hidden reasons for the ways nanoparticles interact with their environment.
Future Impact
By simulating vast libraries of possible nanoparticle motions, LEONARDO could help train AI systems that automatically control and adjust electron microscopes for optimal imaging, paving the way for “smart” microscopes that adapt in real time, the researchers said.
“Understanding nanoscale motion is of growing importance to many fields, including drug delivery, nanomedicine, polymer science, and quantum technologies,” Jamali said. “By making it easier to interpret particle behavior, LEONARDO could help scientists design better materials, improve targeted therapies, and uncover new fundamental insights into how matter behaves at small scales."
CITATION: Zain Shabeeb , Naisargi Goyal, Pagnaa Attah Nantogmah, and Vida Jamali, “Learning the diffusion of nanoparticles in liquid phase TEM via physics-informed generative AI,” Nature Communications, 2025.
Researchers at Georgia Tech’s School of Chemical and Biomolecular Engineering (ChBE) have developed a promising approach for removing carbon dioxide (CO₂) from the atmosphere to help mitigate global warming.
While promising technologies for direct air capture (DAC) have emerged over the past decade, high capital and energy costs have hindered DAC implementation.
However, in a new study published in Energy & Environmental Science, the research team demonstrated techniques for capturing CO₂ more efficiently and affordably using extremely cold air and widely available porous sorbent materials, expanding future deployment opportunities for DAC.
Harnessing Already Available Energy
The research team – including members from Oak Ridge National Laboratory in Tennessee and Jeonbuk National University and Chonnam National University in South Korea – employed a method combining DAC with the regasification of liquefied natural gas (LNG), a common industrial process that produces extremely cold temperatures.
LNG, which is a natural gas cooled into a liquid for shipping, must be warmed back into a gas before use. That warming process often uses seawater as the source of the heat and essentially wastes the low temperature energy embodied in the liquified natural gas.
Instead, by using the cold energy from LNG to chill the air, Georgia Tech researchers created a superior environment for capturing CO₂ using materials known as “physisorbents,” which are porous solids that soak up gases.
Most DAC systems in use today employ amine-based materials that chemically bind CO2 from the air, but they offer relatively limited pore space for capture, degrade over time, and require substantial energy to operate effectively. Physisorbents, however, offer longer lifespans and faster CO₂ uptake but often struggle in warm, humid conditions.
The research study showed that when air is cooled to near-cryogenic temperatures for DAC, almost all of the water vapor condenses out of the air. This enables physisorbents to achieve higher CO₂ capture performance without the need for expensive water-removal steps.
“This is an exciting step forward,” said Professor Ryan Lively of ChBE@GT. “We’re showing that you can capture carbon at low costs using existing infrastructure and safe, low-cost materials.”
Cost and Energy Savings
The economic modeling conducted by Lively’s team suggests that integrating this LNG-based approach into DAC could reduce the cost of capturing one metric ton of CO₂ to as low as $70, approximately a threefold decrease from current DAC methods, which often exceed $200 per ton.
Through simulations and experiments, the team identified Zeolite 13X and CALF-20 as leading physisorbents for this DAC process. Zeolite 13X is an inexpensive and durable desiccant material used in water treatment, while CALF-20 is a metal-organic framework (MOF) known for its stability and CO2 capture performance from flue gas, but not from air.
These materials showed strong CO₂ adsorption at -78°C (a representative temperature for the LNG-DAC system) with capacities approximately three times higher than those found in amine materials that operate at ambient conditions. They also released the captured and purified CO₂ with low energy input, making them attractive for practical use.
“Beyond their high CO2 capacities, both physisorbents exhibit critical characteristics such as low desorption enthalpy, cost efficiency, scalability, and long-term stability, all of which are essential for real-world applications,” said lead author Seo-Yul Kim, a postdoctoral researcher in the Lively Lab.
Leveraging Existing Infrastructure
The study also addresses a key concern for DAC: location. Traditional systems are often best suited for dry, cool environments. But by leveraging existing LNG infrastructure, near-cryogenic DAC could be deployed in temperate and even humid coastal regions, greatly expanding the geographic scope of carbon removal.
“LNG regasification systems are currently an untapped source of cold energy, with terminals operating at a large scale in coastal areas around the world,” Lively said. “By harnessing even just a portion of their cold energy, we could potentially capture over 100 million metric tons of CO₂ per year by 2050.”
As governments and industries face increasing pressure to meet net-zero emissions goals, solutions like LNG-coupled near-cryogenic DAC offer a promising path forward. The next steps for the team include continued refinement of materials and system designs to ensure performance and durability at larger scales.
“This is an exciting example of how rethinking energy flows in our existing infrastructure can lead to low-cost reductions in carbon footprint,” Lively said.
The study also demonstrated that an expanded range of materials could be employed for DAC. While only a small subset of materials can be used at ambient temperatures, the number that are viable grows substantially at near-cryogenic temperatures.
“Many physisorbents that were previously dismissed for DAC suddenly become viable when you drop the temperature,” said Professor Matthew Realff, co-author of the study and professor at ChBE@GT. “This unlocks a whole new design space for carbon capture materials.”
Citation: Seo-Yul Kim, Akriti Sarswat, Sunghyun Cho, MinGyu Song, Jinsu Kim, Matthew J. Realff, David S. Sholl, and Ryan P. Lively, “Near-Cryogenic Direct Air Capture using Adsorbents,” Energy & Environmental Science, 2025.
Along with insulin, it also could be used for semaglutide — the popular GLP-1 medication sold as Ozempic and Wegovy — and a host of other top-selling protein-based medications like antibodies and growth hormone that are part of a $400 billion market.
These drugs usually have to be injected because they can’t overcome the protective barriers of the gastrointestinal tract. Georgia Tech’s new capsule uses a small pressurized “explosion” to shoot medicine past those barriers in the small intestine and into the bloodstream. Unlike other designs, it has no complicated moving parts and requires no battery or stored energy.
“This study introduces a new way of drug delivery that is as easy as swallowing a pill and replaces the need for painful injections,” said Mark Prausnitz, who created the pill in his lab with former Ph.D. student Joshua Palacios and other student researchers.
In animal lab tests, they showed their capsule lowered blood sugar levels just like traditional insulin injections. The researchers reported their pill design and study results DATE in the Journal of Controlled Release.
Read about the technology on the College of Engineering website.
]]>“Malaria kills over 500,000 annually with the mortality rate substantially higher in Africa,” says Frooman. “Our research explores how specific peptides bind to proteins that trigger immune responses.”
Frooman originally hoped the research would help her learn how to think like a scientist and gain basic lab knowledge.
She gained those skills and more, quickly becoming recognized as an exceptional researcher.
“Marielle is one of the most passionate and talented undergraduate researchers I have ever worked with,” says Andrew McShan, McShan Lab principal investigator and associate professor in the School of Chemistry and Biochemistry. “She is also a caring mentor and motivated future leader who wants to change the world. Her malaria research has the potential to provide real therapeutic outcomes, including better designs for vaccines and immunotherapy.”
Frooman’s journey into undergraduate research began with persistence. After a year and a half of searching for lab opportunities, she attended a School of Chemistry and Biochemistry research showcase. She approached several graduate students and professors with no success, until she met McShan.
“Our first meeting was so relaxed and friendly that I didn’t even realize Professor McShan was the principal investigator,” admits Frooman. “That’s how it all started.”
Once she officially joined the lab, Frooman contributed to every stage of the research, including designing experiments, performing computational and wet lab work, analyzing data, and writing and presenting the paper.
The team faced several challenges.
“The research was delayed by failure after failure,” says Frooman. “But each setback taught us something valuable.”
The team’s biggest challenge involved trying to grow crystals of the peptide/HLA (protein) complexes to determine how they fit together. They spent two years attempting various methods, but nothing worked.
Guided by McShan, Frooman and the team then came up with the idea of using computational modeling to enable a deeper understanding of how the peptides and proteins interact at both biophysical and structural levels.
“Utilizing the computational modeling enabled us to see the best bindings and turned into a game-changing insight for our research, potentially leading to the design of more effective malaria treatments and vaccines,” explains Frooman.
She is quick to credit Georgia Tech and McShan for providing her with such a valuable learning experience.
“At many universities, undergraduates rarely do meaningful research, but at Tech, it’s a priority,” explains Frooman. “I’m extremely grateful for the opportunity to grow in such a supportive environment, and to learn from mentors like Professor McShan who lead by example and make time for every student.”
Her advice to other undergraduates entering research?
“Embrace your failures. They make the successes even more rewarding,” shares Frooman.
On campus, Frooman is president of the Student Affiliates of the American Chemical Society and Cleanup Crew at GT, a member of Alpha Phi International Fraternity, and a campus tour guide who serves on their executive board.
She especially loves being a tour guide as it allows her to share her love of Georgia Tech and its people:
“Everyone is unapologetically themselves and fully invested in their major or interests. As someone who loves chemistry, I enjoy being surrounded by people who are just as dedicated to their passions.”
Frooman is a recipient of the Chance Family Scholarship, presented to two School of Chemistry and Biochemistry upperclassmen, recognizing their academic excellence, research contributions, and potential for career success in the field.
Recently, she shifted her research focus to organic synthetic chemistry and now works in the Gutekunst Lab. Her career goals include earning a Ph.D. in Chemistry with an emphasis on natural product synthesis, the lab-based creation of complex chemical compounds found in nature.
“I’ve seen what university labs can do,” says Frooman. “I hope to one day lead my own lab, advancing impactful research and mentoring the next generation of scientists.”
]]>Students and faculty from the School of Computational Science and Engineering (CSE) are leading the Georgia Tech contingent at the SIAM Conference on Computational Science and Engineering (CSE25). The Society of Industrial and Applied Mathematics (SIAM) organizes CSE25, occurring March 3-7 in Fort Worth, Texas.
At CSE25, the School of CSE researchers are presenting papers that apply computing approaches to varying fields, including:
[Related: GT CSE at SIAM CSE25 Interactive Graphic]
“In CSE, researchers from different disciplines work together to develop new computational methods that we could not have developed alone,” said School of CSE Professor Edmond Chow.
“These methods enable new science and engineering to be performed using computation.”
CSE is a discipline dedicated to advancing computational techniques to study and analyze scientific and engineering systems. CSE complements theory and experimentation as modes of scientific discovery.
Held every other year, CSE25 is the primary conference for the SIAM Activity Group on Computational Science and Engineering (SIAG CSE). School of CSE faculty serve in key roles in leading the group and preparing for the conference.
In December, SIAG CSE members elected Chow to a two-year term as the group’s vice chair. This election comes after Chow completed a term as the SIAG CSE program director.
School of CSE Associate Professor Elizabeth Cherry has co-chaired the CSE25 organizing committee since the last conference in 2023. Later that year, SIAM members reelected Cherry to a second, three-year term as a council member at large.
At Georgia Tech, Chow serves as the associate chair of the School of CSE. Cherry, who recently became the associate dean for graduate education of the College of Computing, continues as the director of CSE programs.
“With our strong emphasis on developing and applying computational tools and techniques to solve real-world problems, researchers in the School of CSE are well positioned to serve as leaders in computational science and engineering both within Georgia Tech and in the broader professional community,” Cherry said.
Georgia Tech’s School of CSE was first organized as a division in 2005, becoming one of the world’s first academic departments devoted to the discipline. The division reorganized as a school in 2010 after establishing the flagship CSE Ph.D. and M.S. programs, hiring nine faculty members, and attaining substantial research funding.
Ten School of CSE faculty members are presenting research at CSE25, representing one-third of the School’s faculty body. Of the 23 accepted papers written by Georgia Tech researchers, 15 originate from School of CSE authors.
The list of School of CSE researchers, paper titles, and abstracts includes:
Bayesian Optimal Design Accelerates Discovery of Material Properties from Bubble Dynamics
Postdoctoral Fellow Tianyi Chu, Joseph Beckett, Bachir Abeid, and Jonathan Estrada (University of Michigan), Assistant Professor Spencer Bryngelson
[Abstract]
Latent-EnSF: A Latent Ensemble Score Filter for High-Dimensional Data Assimilation with Sparse Observation Data
Ph.D. student Phillip Si, Assistant Professor Peng Chen
[Abstract]
A Goal-Oriented Quadratic Latent Dynamic Network Surrogate Model for Parameterized Systems
Yuhang Li, Stefan Henneking, Omar Ghattas (University of Texas at Austin), Assistant Professor Peng Chen
[Abstract]
Posterior Covariance Structures in Gaussian Processes
Yuanzhe Xi (Emory University), Difeng Cai (Southern Methodist University), Professor Edmond Chow
[Abstract]
Robust Digital Twin for Geological Carbon Storage
Professor Felix Herrmann, Ph.D. student Abhinav Gahlot, alumnus Rafael Orozco (Ph.D. CSE-CSE 2024), alumnus Ziyi (Francis) Yin (Ph.D. CSE-CSE 2024), and Ph.D. candidate Grant Bruer
[Abstract]
Industry-Scale Uncertainty-Aware Full Waveform Inference with Generative Models
Rafael Orozco, Ph.D. student Tuna Erdinc, alumnus Mathias Louboutin (Ph.D. CS-CSE 2020), and Professor Felix Herrmann
[Abstract]
Optimizing Coupled Systems: Insights from Co-Design Imaging and Optical Chemistry
Assistant Professor Raphaël Pestourie, Wenchao Ma and Steven Johnson (MIT), Lu Lu (Yale University), Zin Lin (Virginia Tech)
[Abstract]
Multifidelity Linear Regression for Scientific Machine Learning from Scarce Data
Assistant Professor Elizabeth Qian, Ph.D. student Dayoung Kang, Vignesh Sella, Anirban Chaudhuri and Anirban Chaudhuri (University of Texas at Austin)
[Abstract]
LyapInf: Data-Driven Estimation of Stability Guarantees for Nonlinear Dynamical Systems
Ph.D. candidate Tomoki Koike and Assistant Professor Elizabeth Qian
[Abstract]
The Information Geometric Regularization of the Euler Equation
Alumnus Ruijia Cao (B.S. CS 2024), Assistant Professor Florian Schäfer
[Abstract]
Maximum Likelihood Discretization of the Transport Equation
Ph.D. student Brook Eyob, Assistant Professor Florian Schäfer
[Abstract]
Intelligent Attractors for Singularly Perturbed Dynamical Systems
Daniel A. Serino (Los Alamos National Laboratory), Allen Alvarez Loya (University of Colorado Boulder), Joshua W. Burby, Ioannis G. Kevrekidis (Johns Hopkins University), Assistant Professor Qi Tang (Session Co-Organizer)
[Abstract]
Accurate Discretizations and Efficient AMG Solvers for Extremely Anisotropic Diffusion Via Hyperbolic Operators
Golo Wimmer, Ben Southworth, Xianzhu Tang (LANL), Assistant Professor Qi Tang
[Abstract]
Randomized Linear Algebra for Problems in Graph Analytics
Professor Rich Vuduc
[Abstract]
Improving Spgemm Performance Through Reordering and Cluster-Wise Computation
Assistant Professor Helen Xu
[Abstract]
Students and faculty from the School of Computational Science and Engineering (CSE) are leading the Georgia Tech contingent at the SIAM Conference on Computational Science and Engineering (CSE25). The Society of Industrial and Applied Mathematics (SIAM) organizes CSE25, occurring March 3-7 in Fort Worth, Texas.
]]>Led by Loren Williams (Georgia Institute of Technology) and Moran Frenkel-Pinter (The Hebrew University of Jerusalem) and published in Nature Chemistry, the team’s paper investigates how chemical mixtures evolve over time, offering new insights into the origins of biological complexity.
“Our research applies concepts from evolutionary biology to chemistry,” explains Williams, a professor in the School of Chemistry and Biochemistry. “We know that everything in biology can be reduced to chemistry, but the idea of this paper is that in the right conditions, chemistry can evolve, too. We call this chemical evolution.”
While much research has focused on individual chemical reactions that could lead to biological molecules, this study establishes an experimental model to explore how entire chemical systems evolve when exposed to environmental changes.
“Chemical evolution is chemistry that keeps changing and doing new things,” Williams explains. “It’s unending chemical change, but with exploration of new chemical spaces. We wondered if we could set up a system that does that without introducing new molecules ourselves — instead we had the system oscillate between wet and dry conditions.”
In nature, these systems might look like a landscape where water condenses, and then dries out, over and over again — conditions that arise naturally from the day-night cycles of our planet.
The study identified three key findings — chemical systems can continuously evolve without reaching equilibrium, avoid uncontrolled complexity through selective chemical pathways, and exhibit synchronized population dynamics among different molecular species. This suggests that environmental factors played a key role in shaping the molecular complexity needed for life to emerge.
“This research offers a new perspective on how molecular evolution might have unfolded on early Earth,” says Frenkel-Pinter, assistant professor in the Institute of Chemistry at The Hebrew University of Jerusalem. “By demonstrating that chemical systems can self-organize and evolve in structured ways, we provide experimental evidence that may help bridge the gap between prebiotic chemistry and the emergence of biological molecules.”
Beyond its relevance to origins-of-life research, the study’s findings may have broader applications in synthetic biology and nanotechnology. Controlled chemical evolution could be harnessed to design new molecular systems with specific properties, potentially leading to innovations in materials science, drug development, and biotechnology.
This research is shared jointly with The Hebrew University of Jerusalem newsroom.
]]>As the Los Angeles fires quickly spread starting Jan. 7, with wind gusts approaching 100 mph, scientists observed a 110-fold rise in airborne lead levels. This spike had receded by Jan. 11.
The fires enabled the first real-time data on airborne lead, thanks to a pioneering air quality measurement network known as Atmospheric Science and Chemistry (ASCENT), a nationwide initiative funded by the National Science Foundation, operating in 12 sites across the U.S.
ASCENT measured tiny particles smaller than 2.5 micrometers in diameter (PM2.5) — small enough to enter the lungs and bloodstream. Unlike typical wildfires that burn natural materials such as grass and trees, the Eaton Canyon and Palisades fires burned through infrastructures like homes, including painted surfaces, pipes, vehicles, plastics, and electronic equipment. This raised concerns about the toxicity of these particles in the air, especially since many of the buildings were constructed before 1978, when lead paint was still commonly used.
Lead is a toxic air contaminant that poses significant health risks, particularly for children, who are more vulnerable to its neurodevelopmental effects. While chronic lead exposure is well-documented, the effects of short-term spikes, like those recorded during these fires, are less understood.
“Our work through ASCENT,” said Sally Ng, Georgia Tech’s Love Family Professor of Chemical and Biomolecular Engineering and Earth and Atmospheric Sciences and the network’s principal investigator, “has provided us with new insights into the air we breathe, with unprecedented levels of detail and time resolution. Beyond the mass concentration of PM2.5 that is typically measured, we are now able to detect a wide range of chemical components in the aerosols in real time, to better understand and evaluate to what extent one is exposed to harmful pollutants.”
Investigators used several instruments to obtain hourly measurements at the ASCENT monitoring site in Pico Rivera, approximately 14 miles south of the Eaton Canyon fire, to assess atmospheric lead during the wildfires.
“Our findings showcased the importance of having real-time measurements of the chemical species that comprise particulate matter,” said California Institute of Technology Ph.D. candidate in atmospheric chemistry and ASPIRE researcher Haroula Baliaka. “During the LA fires, we provided the public with timely information about what they were breathing and how air quality evolved in the days that followed.”
This research has been published in the CDC’s Morbidity and Mortality Weekly Report.
"David Sherrill's leadership role in IDEaS as associate director, together with his interdisciplinary background in chemistry and computer science, makes him the right person to support this transition as interim executive director," said Julia Kubanek, professor and vice president for interdisciplinary research at Georgia Tech.
Sherrill succeeds Srinivas Aluru who will be taking a new position as Senior Associate Dean in the College of Computing. Aluru, a Regents' Professor in the School of Computational Science and Engineering, co-founded IDEaS and served as its co-executive director (2016-2019) and then as executive director (2019-date), spanning eight and a half years. Under his leadership IDEaS grew to more than 200 affiliate faculty spanning all colleges, encompassing multiple state, federal, and industry funded centers. Notable among these is the South Big Data Hub, catalyzing the Southern data science community to collectively accelerate scientific discovery and innovation, spur economic development in the region, broaden participation and diversity in data science, and the CloudHub, a Microsoft funded center that provides research funding and cloud resources for innovative applications in Generative Artificial Intelligence. More recently, Aluru established the Center for Artificial Intelligence in Science and Engineering (ARTISAN), and expanded the Institute’s research staff to provide needed cyberinfrastructure, software resources, and expertise to support faculty projects with large data sets and AI-driven discovery. "I've had the pleasure of serving as Associate Director of IDEaS since it was founded by Srinivas Aluru and Dana Randall, and I'm excited to step into this interim role.” said Sherrill. “IDEaS has an important mission to serve the many faculty doing interdisciplinary research involving data science and high performance computing."
Sherrill’s research group focuses on the development of ab initio electronic structure theory and its application to problems of broad chemical interest, including the influence of non-covalent interactions in drug binding, biomolecular structure, organic crystals, and organocatalytic transition states. The group seeks to apply the most accurate quantum models possible for a given problem and specializes in generating high-quality datasets for testing new methods or machine-learning purposes.
Sherrill earned a B.S. in chemistry from MIT in 1992 and a Ph.D. in chemistry from the University of Georgia in 1996. From 1996-1999 Sherril was an NSF Postdoctoral Fellow, working under M. Head-Gordon, at the University of California, Berkeley.
Sherrill is a Fellow of the American Association for the Advancement of Science (AAAS), the American Chemical Society, and the American Physical Society, and he has been Associate Editor of the Journal of Chemical Physics since 2009. Sherrill has received a Camille and Henry Dreyfus New Faculty Award, the International Journal of Quantum Chemistry Young Investigator Award, an NSF CAREER Award, and Georgia Tech's W. Howard Ector Outstanding Teacher Award. In 2023, he received the Herty Medal from the Georgia Section of the American Chemical Society, and in 2024, he was elected to the International Academy of Quantum Molecular Science.
--Christa M. Ernst
]]>
Research Communications Program Manager,
Topic Expertise: Robotics | Data Sciences| Semiconductor Design & Fab
A study led by Georgia Tech is showcasing a new resource to help researchers understand the structure and function of these interactions — called assemblies — at both molecular and functional levels. The work is published in the Nature-family journal Communications Chemistry.
Called BioDolphin — short for Biological Database of Lipid-Protein Highly Inclusive Interactions — the resource is the first comprehensive, annotated database of protein-lipid interactions. Integrated into a user-friendly web server, BioDolphin is freely accessible to all. Users can easily view and download interaction data and systematically analyze lipid-protein assemblies.
“Understanding lipid-protein interactions is crucial in advancing our understanding of human health and disease treatment,” says the study’s corresponding author, Andrew McShan. “BioDolphin is the first resource to collect this type of information for all kinds of proteins, not just those found in membranes. And because it is publicly available, this information is now at the tips of researchers’ fingertips.”
“BioDolphin as a comprehensive database of lipid–protein binding interactions” is led by McShan, an assistant professor in the School of Chemistry and Biochemistry at Georgia Tech, alongside first author Li-Yen (Zoey) Yang, Bioinformatics Ph.D. student; School of Computational Science and Engineering Assistant Professor Yunan Luo; and Kaike Ping, a Ph.D. student at Virginia Tech.
A curated database with richly annotated information, BioDolphin contains over 127,000 lipid-protein binding interactions. And while most databases of lipid-protein assemblies have focused solely on a specific type of protein — membrane proteins — BioDolphin expands beyond that.
“BioDolphin enables us to globally define the structural features of lipid-protein assemblies across the eight different classes of lipid compounds to understand their cellular function and roles in disease,” says McShan, adding that the database also provides information on paired lipid-protein annotation, experimental binding affinities, intermolecular interactions, and atomic structures across a wide range of lipid-protein interactions — all available to anyone with an internet connection.
“In the past, this research has been limited because lipids are notoriously difficult to study in the lab,” McShan says. "BioDolphin changes the paradigm. It is the first time that anyone has collected, annotated, and analyzed the known structural universe of lipid-protein interactions across all organisms.”
It’s a rapidly developing field. McShan was recently awarded a prestigious Curci grant for cutting-edge cancer research into lipid-based universal immunotherapies and vaccines.
Beyond research applications, the team hopes that BioDolphin will be a resource for biochemistry students.
“The database can serve as a tool for teachers and students studying these protein-lipid interactions, which is often an underdeveloped topic in biology and biochemistry courses,” McShan says. “I hope that BioDolphin is a valuable resource for the researchers of today — and that it can also be a building block for the researchers of tomorrow.”
Funding: Shurl and Kay Curci Foundation, NSF Advanced Cyberinfrastructure Coordination Ecosystem: Services & Support (ACCESS) program, NIH National Institute of General Medical Sciences (NIGMS), Partnership for an Advanced Computing Environment (PACE) at the Georgia Institute of Technology, and Taiwan Ministry of Education Government Scholarship to Study Abroad program.
DOI: https://doi.org/10.1038/s42004-024-01384-z
]]>Contact: Jess Hunt-Ralston
]]>And while our bodies naturally make amino acids, manufacturing them for commercial use can be costly — and that process often emits greenhouse gasses like carbon dioxide (CO2).
In a landmark study, a team of researchers has created a first-of-its kind methodology for synthesizing amino acids that uses more carbon than it emits. The research also makes strides toward making the system cost-effective and scalable for commercial use.
“To our knowledge, it’s the first time anyone has synthesized amino acids in a carbon-negative way using this type of biocatalyst,” says lead corresponding author Pamela Peralta-Yahya, who emphasizes that the system provides a win-win for industry and environment. “Carbon dioxide is readily available, so it is a low-cost feedstock — and the system has the added bonus of removing a powerful greenhouse gas from the atmosphere, making the synthesis of amino acids environmentally friendly, too.”
The study, “Carbon Negative Synthesis of Amino Acids Using a Cell-Free-Based Biocatalyst,” published today in ACS Synthetic Biology, is publicly available. The research was led by Georgia Tech in collaboration with the University of Washington, Pacific Northwest National Laboratory, and the University of Minnesota.
The Georgia Tech research contingent includes Peralta-Yahya, a professor with joint appointments in the School of Chemistry and Biochemistry and School of Chemical and Biomolecular Engineering (ChBE); first author Shaafique Chowdhury, a Ph.D. student in ChBE; Ray Westenberg, a Ph.D student in Bioengineering; and Georgia Tech alum Kimberly Wennerholm (B.S. ChBE ’23).
There are two key challenges to synthesizing amino acids on a large scale: the cost of materials, and the speed at which the system can generate amino acids.
While many living systems like cyanobacteria can synthesize amino acids from CO2, the rate at which they do it is too slow to be harnessed for industrial applications, and these systems can only synthesize a limited number of chemicals.
Currently, most commercial amino acids are made using bioengineered microbes. “These specially designed organisms convert sugar or plant biomass into fuel and chemicals,” explains first author Chowdhury, “but valuable food resources are consumed if sugar is used as the feedstock — and pre-processing plant biomass is costly.” These processes also release CO2 as a byproduct.
Chowdhury says the team was curious “if we could develop a commercially viable system that could use carbon dioxide as a feedstock. We wanted to build a system that could quickly and efficiently convert CO2 into critical amino acids, like glycine and serine.”
The team was particularly interested in what could be accomplished by a ‘cell-free’ system that leveraged some process of a cellular system — but didn’t actually involve living cells, Peralta-Yahya says, adding that systems using living cells need to use part of their CO2 to fuel their own metabolic processes, including cell growth, and have not yet produced sufficient quantities of amino acids.
“Part of what makes a cell-free system so efficient,” Westenberg explains, “is that it can use cellular enzymes without needing the cells themselves. By generating the enzymes and combining them in the lab, the system can directly convert carbon dioxide into the desired chemicals. Because there are no cells involved, it doesn’t need to use the carbon to support cell growth — which vastly increases the amount of amino acids the system can produce.”
While scientists have used cell-free systems before, one of the necessary chemicals, the cell lysate biocatalyst, is extremely costly. For a cell-free system to be economically viable at scale, the team needed to limit the amount of cell lysate the system needed.
After creating the ten enzymes necessary for the reaction, the team attempted to dilute the biocatalyst using a technique called ‘volumetric expansion.’ “We found that the biocatalyst we used was active even after being diluted 200-fold,” Peralta-Yahya explains. “This allows us to use significantly less of this high-cost material — while simultaneously increasing feedstock loading and amino acid output.”
It’s a novel application of a cell-free system, and one with the potential to transform both how amino acids are produced, and the industry’s impact on our changing climate.
“This research provides a pathway for making this method cost-effective and scalable,” Peralta-Yahya says. “This system might one day be used to make chemicals ranging from aromatics and terpenes, to alcohols and polymers, and all in a way that not only reduces our carbon footprint, but improves it.”
Funding: Advanced Research Project Agency-Energy (ARPA-E), U.S. Department of Energy and the U.S. Department of Energy, Office of Science, Biological and Environmental Research Program.
DOI: 10.1021/acssynbio.4c00359
]]>The new algorithm is faster than existing methods while remaining highly accurate. The solver surpasses the limits of current models by demonstrating scalability across chemical system sizes ranging from large to small.
Computer scientists and engineers benefit from the algorithm’s ability to balance processor loads. This work allows researchers to tackle larger, more complex problems without the prohibitive costs associated with previous methods.
Its ability to solve block linear systems drives the algorithm’s ingenuity. According to the researchers, their approach is the first known use of a block linear system solver to calculate electronic correlation energy.
The Georgia Tech team won’t need to travel far to share their findings with the broader high-performance computing community. They will present their work in Atlanta at the 2024 International Conference for High Performance Computing, Networking, Storage and Analysis (SC24).
[MICROSITE: Georgia Tech at SC24]
“The combination of solving large problems with high accuracy can enable density functional theory simulation to tackle new problems in science and engineering,” said Edmond Chow, professor and associate chair of Georgia Tech’s School of Computational Science and Engineering (CSE).
Density functional theory (DFT) is a modeling method for studying electronic structure in many-body systems, such as atoms and molecules.
An important concept DFT models is electronic correlation, the interaction between electrons in a quantum system. Electron correlation energy is the measure of how much the movement of one electron is influenced by presence of all other electrons.
Random phase approximation (RPA) is used to calculate electron correlation energy. While RPA is very accurate, it becomes computationally more expensive as the size of the system being calculated increases.
Georgia Tech’s algorithm enhances electronic correlation energy computations within the RPA framework. The approach circumvents inefficiencies and achieves faster solution times, even for small-scale chemical systems.
The group integrated the algorithm into existing work on SPARC, a real-space electronic structure software package for accurate, efficient, and scalable solutions of DFT equations. School of Civil and Environmental Engineering Professor Phanish Suryanarayana is SPARC’s lead researcher.
The group tested the algorithm on small chemical systems of silicon crystals numbering as few as eight atoms. The method achieved faster calculation times and scaled to larger system sizes than direct approaches.
“This algorithm will enable SPARC to perform electronic structure calculations for realistic systems with a level of accuracy that is the gold standard in chemical and materials science research,” said Suryanarayana.
RPA is expensive because it relies on quartic scaling. When the size of a chemical system is doubled, the computational cost increases by a factor of 16.
Instead, Georgia Tech’s algorithm scales cubically by solving block linear systems. This capability makes it feasible to solve larger problems at less expense.
Solving block linear systems presents a challenging trade-off in solving different block sizes. While larger blocks help reduce the number of steps of the solver, using them demands higher computational cost per step on computer processors.
Tech’s solution is a dynamic block size selection solver. The solver allows each processor to independently select block sizes to calculate. This solution further assists in scaling, and improves processor load balancing and parallel efficiency.
“The new algorithm has many forms of parallelism, making it suitable for immense numbers of processors,” Chow said. “The algorithm works in a real-space, finite-difference DFT code. Such a code can scale efficiently on the largest supercomputers.”
Georgia Tech alumni Shikhar Shah (Ph.D. CSE 2024), Hua Huang (Ph.D. CSE 2024), and Ph.D. student Boqin Zhang led the algorithm’s development. The project was the culmination of work for Shah and Huang, who completed their degrees this summer. John E. Pask, a physicist at Lawrence Livermore National Laboratory, joined the Tech researchers on the work.
Shah, Huang, Zhang, Suryanarayana, and Chow are among more than 50 students, faculty, research scientists, and alumni affiliated with Georgia Tech who are scheduled to give more than 30 presentations at SC24. The experts will present their research through papers, posters, panels, and workshops.
SC24 takes place Nov. 17-22 at the Georgia World Congress Center in Atlanta.
“The project’s success came from combining expertise from people with diverse backgrounds ranging from numerical methods to chemistry and materials science to high-performance computing,” Chow said.
“We could not have achieved this as individual teams working alone.”
]]>The new algorithm is faster than existing methods while remaining highly accurate. The solver surpasses the limits of current models by demonstrating scalability across chemical system sizes ranging from large to small.
Computer scientists and engineers benefit from the algorithm’s ability to balance processor loads. This work allows researchers to tackle larger, more complex problems without the prohibitive costs associated with previous methods.
Its ability to solve block linear systems drives the algorithm’s ingenuity. According to the researchers, their approach is the first known use of a block linear system solver to calculate electronic correlation energy.
The Georgia Tech team won’t need to travel far to share their findings with the broader high-performance computing community. They will present their work in Atlanta at the 2024 International Conference for High Performance Computing, Networking, Storage and Analysis (SC24).
]]>Compartmentalization is how all living systems are organized today — from proteins and small molecules sharing space in separate phases to dividing labor and specialized functions within and among cells.
Now, with $6 million in support from NASA, a team of researchers led by Georgia Tech’s Frank Rosenzweig will study the organizing principles of compartmentalization in a five-year project called Engine of Innovation: How Compartmentalization Drives Evolution of Novelty and Efficiency Across Scales.
It's one of seven new projects selected recently by NASA as part of its Interdisciplinary Consortia for Astrobiology Research (ICAR) program. ICAR is embedded among NASA’s five Astrobiology Research Coordination Networks (RCNs). Rosenzweig is co-lead for the RCN launched in 2022, LIFE: Early Cells to Multicellularity.
“We’re excited by the prospect of exploring this fundamental question through the interplay of theory and experiment,” said Rosenzweig, professor in the School of Biological Sciences, whose team of co-Investigators includes biochemists, geologists, cell biologists, and theoreticians from leading NASA research centers: Jeff Cameron, Shelley Copley, Alexis Templeton, and Boswell Wing from the University of Colorado Boulder; Josh Goldford and Victoria Orphan from California Institute of Technology; and John McCutcheon from Arizona State University. Collaborating with them is Chris Kempes, professor at the Santa Fe Institute.
Rosenzweig is also eager to eventually collaborate with existing ICAR teams, such as MUSE, led by the University of Wisconsin’s Betül Kaçar, a former Georgia Tech postdoctoral researcher, and newly selected teams, such as Retention of Habitable Atmospheres in Planetary Systems, led by Dave Brain at University of Colorado Boulder.
Meanwhile, he plans to build upon Georgia Tech’s outstanding reputation in astrobiology, where a cluster of researchers, such as Jen Glass, Nick Hud, Thom Orlando, Amanda Stockton, and Loren Williams, among others, is engaged in a diverse range of work supported by NASA.
“This is just the latest chapter in a long history of excellence in NASA research at Georgia Tech, one written by my colleagues across the Institute,” Rosenzweig said.
]]>CLEVER is the successor to Orlando’s pioneering REVEALS (Radiation Effects on Volatiles and Exploration of Asteroids and Lunar Surfaces) center, and both are part of NASA’s Solar System Exploration Research Virtual Institute (SSERVI) program.
REVEALS and CLEVER look ahead to the return of humans to the moon for sustained periods — a key part of NASA’s plan for space exploration in the coming decade. Volatiles such as water, molecular oxygen, methane, and hydrogen are crucial to supporting human activity on the moon. Dust is also important since the space-weathered particles can pose health effects to astronauts and hazards to the technology and hardware.
The interdisciplinary group of researchers supported by CLEVER will study how the solar wind and micrometeorites produce volatiles, research how ice and dust behave in the lunar environment, develop new materials to deal with potential dust buildup, and invent new analysis tools to support the upcoming crewed missions of the Artemis program.
“The resources and knowledge that CLEVER will produce will be useful for the sustainable presence of humans on the moon,” Orlando says. “We have the correct mix of fundamental science and exploration — real, fundamental, ground-truth measurements; very good theory/modeling; and engineering — an easy mix with Georgia Tech and outside partners.”
Orlando adds that CLEVER adopts a unique perspective on the challenges of understanding how to operate on Earth’s moon. “The atomic and molecular view of processes with angstrom distances and femtosecond time scales can help unravel what is happening on planetary spatial scales and geological time frames,” he says. “We can also translate our knowledge into materials, devices, and technology pretty quickly, and this is necessary if we want to help the Artemis astronauts.”
CLEVER includes investigators from Georgia Tech, University of Georgia, the Florida Space Institute, University of Hawaii, Auburn University, Space Sciences Institute, the Johns Hopkins University Applied Physics Laboratory, Lawrence Berkeley National Laboratory, NASA Ames, NASA Kennedy Space Center, and partners in Italy and Germany. In addition to pursuing a blend of fundamental science and mission support, CLEVER will also emphasize the research and career development of students and young investigators, another important goal of the SSERVI system.
Writer: M.G. Finn
Art: Brice Zimmerman
]]>Lignin is one of the most plentiful organic polymers on Earth, making up about 20 to 30 percent of the dry mass of wood and other plants.
Despite this abundance, lignin’s complex structure has challenged researchers in breaking it down into useful components that can be used in the sustainable production of chemicals, plastics, and fuels. Therefore, lignin is often discarded as waste during the production of paper and other plant-based products.
However, researchers at the Georgia Institute of Technology have developed an approach that could transform lignin into valuable chemicals more efficiently than ever before.
The researchers published their findings in the journal ACS Sustainable Chemistry & Engineering on using a method known as mechanocatalysis, which uses physical forces, such as vibration or rotation, in a ball mill to drive chemical reactions without the need for solvents, heat, or high pressure.
Carsten Sievers, a professor in Georgia Tech’s School of Chemical and Biomolecular Engineering (ChBE), explained that the first step in a lignin biorefinery is depolymerization, which breaks lignin down into small molecules.
Led by a team of University of Alaska Fairbanks and Georgia Tech researchers that includes School of Earth and Atmospheric Sciences Professor Rodney Weber, the researchers' latest findings are published in Science Advances.
In the study, the team leveraged state-of-the-art thermodynamic tools used in global air quality models, with an aim to better understand how reducing the amount of primary sulfate in the atmosphere might affect sub-zero air quality conditions.
The project stems from the 2022 Alaskan Layered Pollution and Chemical Analysis project, or ALPACA, an international project funded by the National Science Foundation, the National Oceanic and Atmospheric Administration and European sources. It is part of an international air quality effort called Pollution in the Arctic: Climate Environment and Societies.
Read the full story in the University of Alaska Fairbanks newsroom.
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Rod Boyce
University of Alaska Fairbanks
The Tech group dubbed its method PRODIGY (PROjected DIffusion for controlled Graph Generation). PRODIGY enables diffusion models to generate 3D images of complex structures, such as molecules from chemical formulas.
Scientists in pharmacology, materials science, social network analysis, and other fields can use PRODIGY to simulate large-scale networks. By generating 3D molecules from multiple graph datasets, the group proved that PRODIGY could handle complex structures.
In keeping with its name, PRODIGY is the first plug-and-play machine learning (ML) approach to controllable graph generation in diffusion models. This method overcomes a known limitation inhibiting diffusion models from broad use in science and engineering.
“We hope PRODIGY enables drug designers and scientists to generate structures that meet their precise needs,” said Kartik Sharma, lead researcher on the project. “It should also inspire future innovations to precisely control modern generative models across domains.”
PRODIGY works on diffusion models, a generative AI model for computer vision tasks. While suitable for image creation and denoising, diffusion methods are limited because they cannot accurately generate graph representations of custom parameters a user provides.
PRODIGY empowers any pre-trained diffusion model for graph generation to produce graphs that meet specific, user-given constraints. This capability means, as an example, that a drug designer could use any diffusion model to design a molecule with a specific number of atoms and bonds.
The group tested PRODIGY on two molecular and five generic datasets to generate custom 2D and 3D structures. This approach ensured the method could create such complex structures, accounting for the atoms, bonds, structures, and other properties at play in molecules.
Molecular generation experiments with PRODIGY directly impact chemistry, biology, pharmacology, materials science, and other fields. The researchers say PRODIGY has potential in other fields using large networks and datasets, such as social sciences and telecommunications.
These features led to PRODIGY’s acceptance for presentation at the upcoming International Conference on Machine Learning (ICML 2024). ICML 2024 is the leading international academic conference on ML. The conference is taking place July 21-27 in Vienna.
Assistant Professor Srijan Kumar is Sharma’s advisor and paper co-author. They worked with Tech alumnus Rakshit Trivedi (Ph.D. CS 2020), a Massachusetts Institute of Technology postdoctoral associate.
Twenty-four Georgia Tech faculty from the Colleges of Computing and Engineering will present 40 papers at ICML 2024. Kumar is one of six faculty representing the School of Computational Science and Engineering (CSE) at the conference.
Sharma is a fourth-year Ph.D. student studying computer science. He researches ML models for structured data that are reliable and easily controlled by users. While preparing for ICML, Sharma has been interning this summer at Microsoft Research in the Research for Industry lab.
“ICML is the pioneering conference for machine learning,” said Kumar. “A strong presence at ICML from Georgia Tech illustrates the ground-breaking research conducted by our students and faculty, including those in my research group.”
Visit https://sites.gatech.edu/research/icml-2024 for news and coverage of Georgia Tech research presented at ICML 2024.
]]>The Tech group dubbed its method PRODIGY (PROjected DIffusion for controlled Graph Generation). PRODIGY enables diffusion models to generate 3D images of complex structures, such as molecules from chemical formulas.
Scientists in pharmacology, materials science, social network analysis, and other fields can use PRODIGY to simulate large-scale networks. By generating 3D molecules from multiple graph datasets, the group proved that PRODIGY could handle complex structures.
In keeping with its name, PRODIGY is the first plug-and-play machine learning (ML) approach to controllable graph generation in diffusion models. This method overcomes a known limitation inhibiting diffusion models from broad use in science and engineering.
]]>The findings are the latest product of the Molecular Transducers of Physical Activity Consortium (MoTrPAC), a ten-year effort launched in 2016 by the National Institutes of Health (NIH) to uncover how exercise improves and maintains our health at the molecular level.
Georgia Institute of Technology bioanalytical chemist Facundo Fernández and Emory University biochemist Eric Ortlund lead one of the Consortium’s Chemical Analysis Sites, joining researchers across the country to collect and translate data from animals and more than 2,000 volunteers into comprehensive maps of the cellular changes throughout the body in response to exercise.
The $226 million MoTrPAC NIH Common Fund investment also hopes to help people with chronic illnesses identify specific physical activities to improve individual health, and to potentially unearth therapeutic targets — medicines that might mimic the positive effects of exercise.
MoTrPAC’s latest group of papers details data from studies in rats, uncovering how endurance exercise affects biological molecules and “all tissues of the body,” as well as tissues and gene expression, along with striking tissue differences between male and female organisms.
Read more:
Facundo M. Fernandez, is Regents’ Professor and Vasser Woolley Foundation Chair in Bioanalytical Chemistry at Georgia Tech. He also serves as associate editor of the Journal of the American Society for Mass Spectrometry (JASMS).
Eric Ortlund is a professor in the Department of Biochemistry at Emory University and a member of the Discovery and Developmental Therapeutics Research Program at Winship Cancer Institute.
Study co-authors from Georgia Tech also include David A. Gaul (School of Chemistry and Biochemistry, along with Samuel G. Moore (Petit Institute of Bioengineering and Biosciences). Emory University co-authors also include Tiantian Zhang and Zhenxin Hou (Department of Biochemistry).
Funding: The MoTrPAC Study is supported by multiple NIH grants and institutes, as well as the National Science Foundation (NSF), the Knut and Alice Wallenberg Foundation, and NORC at the University of Chicago.
NIH grants include: U24OD026629 (Bioinformatics Center), U24DK112349, U24DK112342, U24DK112340, U24DK112341, U24DK112326, U24DK112331, U24DK112348 (Chemical Analysis Sites), U01AR071133, U01AR071130, U01AR071124, U01AR071128, U01AR071150, U01AR071160, U01AR071158 (Clinical Centers), U24AR071113 (Consortium Coordinating Center), U01AG055133, U01AG055137 and U01AG055135 (PASS/Animal Sites); as well as NHGRI Institutional Training Grant in Genome Science 5T32HG000044; National Heart, Lung, and Blood Institute of the National Institute of Health F32 postdoctoral fellowship award F32HL154711; National Institute on Aging P30AG044271 and P30AG003319.
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Jess Hunt-Ralston
Director of Communications
College of Sciences
Georgia Tech
Anthony (Tony) Van Witsen
Health Sciences Writer
Woodruff Health Sciences Center
Emory University
Andréa Harris, Ph.D., M.S.P.H., S.C.P.M.
Health Science Policy Analyst
Office of Strategic Coordination – The Common Fund
Division of Program Coordination, Planning, and Strategic Initiatives
Office of the Director, NIH
Introduced in 1953, Marshall Scholars include Supreme Court justices, Pulitzer and Nobel Prize winners, members of Congress, MacArthur “genius grant” winners, and Olympic gold medalists and serve as a “living embodiment of the enduring special relationship between the U.K. and America.”
Though they conduct research in different areas, Janecka and Haaris share the goal of using this opportunity to assist others.
When Maeve Janecka was diagnosed with endometriosis at the age of 16, she was confused — not by her condition, but rather by the lack of treatment and diagnostic options for a disease that affects one in 10 women worldwide.
While she endured symptoms for three years, Janecka explains that the average case of endometriosis can go undiagnosed for 10 years, causing debilitating pain, organ damage, and infertility. Following the completion of her bachelor's degree in chemical engineering, Janecka will use the Marshall Scholarship to pursue a doctor of philosophy in women’s and reproductive health at Oxford's Endometriosis Care Center, where she plans to conduct research into emerging treatment options and diagnostic improvements.
"Women suffer in silence for a really long time," she said, also noting that diagnosing the condition typically requires invasive surgery. "I am passionate about making sure that more women know what endometriosis is and that we have more options available for diagnosis and treatment, because your quality of life can be so much better with the right medical attention."
Living with this disease has motivated Janecka to help others, and her time at Georgia Tech has allowed her to pursue her dream of identifying solutions.
"Being a Georgia Tech student, you get used to seeing a problem, thinking of ways to solve it, and wanting to be the one to bring about change. Tech has empowered me to enter a field that needs innovation and investment, as women's health is one of the least funded areas in the medical field," she said.
Janecka, who is also a Stamps President's Scholar and was among the Institute's five 2023 Barry M. Goldwater Scholarship recipients, has always felt like her time at Georgia Tech was a gift she intended to make the most of. She advises other students to maximize their time on campus by taking full advantage of the resources available to them, including PURA travel awards and the Institute's Fellowships Office.
Haaris Jilani will graduate from Georgia Tech with a bachelor's degree in biomedical engineering, but as he prepares to continue his academic career at the Imperial College of London, he carries the Institute's mission with him.
"I'm really passionate about doing work that advances scientific knowledge and translates into innovations that can improve the lives of patients," he said.
As Jilani began to develop his career path, the potential and the unknowns of stem cell research sparked his interest. He sought out labs on campus at the intersection of stem cell research and biomaterial science.
"Stem cells can do so many interesting things, but we don't really know a lot about how they work. So, we're not only learning about how the cells work, but it’s about trying to manipulate them to do things that you want them to do," he said.
Through Johnna Temenoff's lab, Jilani's research has focused on applying stem cell treatments in regenerative medicine therapies for musculoskeletal injuries, and he hopes to create noninvasive treatments for injuries that currently need surgery or are deemed untreatable.
When he arrives in the U.K., he intends to broaden his understanding of stem cell treatments for different aspects of care, examining its potential in skin regeneration.
"It's not a part of the body that I have necessarily focused on before, but a lot of the scientific principles are the same with stem cells and how they evolve into different types of cells needed for skin healing," he said.
While he'll spend at least a year abroad, Jilani, who is also a Stamps President's Scholar, feels like his time at Georgia Tech has not come to an end. He hopes to return to pursue a Ph.D. in biomedical engineering and eventually become a professor with a research lab of his own.
Fellowships often enable students to craft a more tailored experience than a traditional graduate school experience, and Georgia Tech's Fellowships Office aids students in the process of applying for prestigious awards such as the Marshall Scholarship. Staff members work with students each step of the way with their applications, reading drafts of essays, and arranging mock interviews.
Karen Mura, prestigious fellowships advisor, worked closely with both of this year's Marshall Scholars as they applied for this and other awards.
"Maeve and Haaris are both extraordinary students with immense potential to make a difference in the world," Mura said. "They have persevered through challenges and setbacks. Both have worked tirelessly on their applications, improving them with each revision. It has been a pleasure to assist them on their academic path and to observe their personal growth. I am eager to hear about their future accomplishments."
]]>Institute Communications
For additional information about fellowships, contact karen.mura@gatech.edu.
]]>For example, even an everyday chemical reaction, like toasting bread, can substantially change in speed and outcome — by increasing the heat, the speed of the reaction increases, toasting the bread faster. Adding another chemical ingredient — like buttering the bread before frying it — also changes the outcome of the reaction: the bread might brown and crisp rather than toast. The lesson? Certain chemical reactions can be accelerated or changed by adding or altering key variables, and understanding those factors is crucial when trying to create the desired reaction (like avoiding burnt toast!).
Chemists currently use quantum chemistry techniques to predict the rates and energies of chemical reactions, but the method is limited: predictions can usually only be made for up to a few hundred atoms. In order to scale the predictions to larger systems, and predict the environmental effects of reactions, a new framework needs to be developed.
Jesse McDaniel (School of Chemistry and Biochemistry) is creating that framework by leveraging computer modeling techniques. Now, a new NSF CAREER grant will help him do so. The National Science Foundation Faculty Early Career Development Award is a five-year grant designed to help promising researchers establish a foundation for a lifetime of leadership in their field. Known as CAREER awards, the grants are NSF’s most prestigious funding for untenured assistant professors.
“I am excited about the CAREER research because we are really focusing on fundamental questions that are central to all of chemistry,” McDaniel says about the project.
“Chemical reactions are inherently quantum mechanical in nature,” McDaniel explains. “Electrons rearrange as chemical bonds are broken and formed.” While this type of quantum chemistry can allow scientists to predict the rates and energies of different reactions, these predictions are limited to only tens or hundreds of atoms. That’s where McDaniel’s team comes in. They’re developing modeling techniques based on quantum chemistry that could function over multiple scales, using computer models to scale the predictions. They hope this will help predict environmental effects on chemical reaction rates.
By developing modeling techniques that can be applied to reactions at multiple scales, McDaniel aims to expand scientist’s ability to predict and model chemical reactions, and how they interact with their environments. “Our goal is to understand the microscopic mechanisms and intermolecular interactions through which chemical reactions are accelerated within unique solvation environments such as microdroplets, thin films, and heterogenous interfaces,” McDaniel says. He hopes that it will allow for computational modeling of chemical reactions in much larger systems.
As a theoretical and computational chemist, McDaniel’s chemistry experiments don’t take place in a typical chemistry lab — rather, they take place in a computer lab, where Georgia Tech’s robust computer science and software development community functions as a key resource.
“We run computer simulations on high performance computing clusters,” McDaniel explains. “In this regard, we benefit from the HPC infrastructure at Georgia Tech, including the Partnership for an Advanced Computing Environment (PACE) team, as well as the computational resources provided in the new CODA building.”
“Software is also a critical part of our research,” he continues. “My colleague Professor David Sherrill and his group are lead developers of the Psi4 quantum chemistry software, and this software comprises a core component of our multi-scale modeling efforts.”
In this respect, McDaniel is eager to to involve the next generation of chemists and computer scientists, showcasing the connection between these different fields. McDaniel’s team will partner with regional high school teachers, collaborating to integrate software and data science tools within the high school educational curriculum.
“One thing I like about this project,” McDaniel says, “is that all types of chemists — organic, inorganic, analytical, bio, physical, etc. — care about how chemical reactions happen, and how reactions are influenced by their surroundings.”
]]>It’s the kind of massive undertaking that would result in vastly improved precision therapies for patients. And it’s the kind of journey that starts with a single cell. Coskun and team are off to a fast start with the introduction of a new integrative technique for profiling human tissue that enables researchers to capture the geography, structure, movement, and function of molecules in a 3D picture.
The researchers described their new approach, the Single Cell Spatially resolved Metabolic (scSpaMet) framework, in the journal Nature Communications on Dec. 13. The study builds on a technique Coskun’s team developed and described in a 2021 article, “3D Spatially resolved Metabolomic profiling Framework,” published in Science Advances. In that work, the team introduced a technique that measures the activity of metabolites and proteins as part of a comprehensive profile of human tissue samples.
“Earlier we couldn’t achieve single-cell resolution, but with this new approach, we can,” said Coskun, Bernie Marcus Early Career Professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University. “With this new approach, we can get spatial details of proteins and metabolites in single cells– no one else has yet reached this level of high subcellular resolution.”
He added, “We’re pioneering a new field of research with this work, single cell spatial metabolomics.”
Human tissue is spatially crowded with all kinds of stuff, so investigators need tools that can see clearly into, through, and around that multilayered biological traffic – everything, all at once, in high-definition 3D. With scSpaMet, Coskun’s team can capture single cell details such as the naturally occurring lipids, proteins, as well as metabolites (with their multiple functions, including energy conversion and cell signaling). And other details, like those provided by researchers: Intracellular and surface markers are used to label and track cell activity and behavior.
The team broadened the scope of this study, extending its investigation beyond human tonsil tissue.
“We showed the crucial role of immune cells in lung cancer for the study of lung cancer for the study of immunometabolism of T cells and macrophages as they interact with tumors,” Coskun said. “Then we created dynamic immune metabolic changes in tonsils as they go through germinal center reactions to give rise to the antibody-producing cells. Finally, we demonstrated the role of immune cells in the endometrium, a membrane in the uterus that might lead to conditions impacting a woman’s health.”
The wide-angled study required plenty of cross-country collaboration with other institutions, although Coskun’s lab guided the wide-angled study, integrating its expertise in bioimaging, chemistry, tissue biology, and artificial intelligence.
Cold Spring Harbor Laboratory (New York) provided access to its endometrium tissue bank. Oak Ridge National Laboratory (Tennessee) provided data from its complex metabolic imaging instrumentation, to further demonstrate how single cell spatial metabolomics imaging can generate rich data.
The University of California-Davis provided kidney biospecimens as both fixed tissue and frozen embedded tissue, in two halves of the same sample, “so we could demonstrate the effect of tissue preparation on the sensitivity of our single cell spatial metabolomics pipeline,” Coskun said.
The team also included Thomas Hu and Mayar Allam, graduate researchers in Coskun’s lab, who guided the research as lead authors, and Walter Henderson, a research scientist who manages the IEN/IMat Materials Characterization Facility at Georgia Tech.
The ability to generate single cell spatial metabolic profiling of individual patients can reveal a world of possibility and potential for clinicians who need to fully understand a patient’s biophysical makeup to contrive the best treatment options.
“For example, it can provide mechanisms of how immune responses can be boosted by adding dietary molecules along with immunotherapies,” Coskun said. “It can also help adjust the dose of cell-based treatments, based on the body mass index of individual patients, whether they are obese or not.”
Coskun believes this new arena of single cell metabolomics research his lab is developing will complement the field of single cell genomics, which has led to genomic medicine. His team’s comprehensive exploration and imaging of the geography of normal and unhealthy human tissues – of every single cell – can further explain cellular regulation in ways that were previously overlooked, due to the lack of technology.
He envisions a future in which a patient’s BMI, dietary habits, and exercise commitments, along with their single cell spatial metabolomic atlas of disease progression, will be analyzed all together to find optimum therapies that can work with biologics and metabolic boosting regimens, potentially increasing the survival of cancers, women’s diseases, and metabolic disorders.
“We will have opportunities to talk about spatial single cell metabolomic medicine, to stratify patients and design next-generation combination therapies with an integrated view of genes and chemical activity roadmaps, for more efficient management of cancer and other diseases,” Coskun said.
In creating their scSpaMet framework, the researchers must integrate expensive machines that live in the worlds of nanotechnology and chemistry right now. The system will require clinical-friendly optimizations to be able to run single cell metabolic imaging measurements in healthcare settings. Coskun expects the cost and user-friendliness will be improved in the near future to reach the bedside.
“When researchers achieved single cell sequencing, it was a revolutionary moment in medicine,” Coskun said. “Now, we believe single cell spatial metabolic profiling will push the medical practice into new heights.”
This research was supported by the Burroughs Wellcome Fund, and the Bernie Marcus Early Career Professorship, as well as the National Science Foundation (Grant ECCS-1542174), (Grant ECCS-2-25462), American Cancer Society, and National Institutes of Health grants (R21AG081715, R21AI173900, and R35GM151028)
Citation: Thomas Hu, Mayar Allam, Shuangyi Cai, Walter Henderson, Brian Yueh, Aybuke Garipcan, Anton V. Ievlev, Maryam Afkarian, Semir Beyaz, and Ahmet F. Coskun. “Single-cell spatial metabolomics with cell-type specific protein profiling for tissue systems biology,” Nature Communications (Dec. 13, 2023)
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For example, CLDDs can be used to manage chronic medical conditions, such as diabetes, where maintaining precise control over mediation dosage is critical.
While they hold immense promise for improving patient outcomes and treatment adherence, CLDDs have only recently entered clinical use due to the difficulty in integrating the sensing and actuating components of human-machine Interfaces (HMIs).
Researchers at Georgia Tech’s School of Chemical and Biomolecular Engineering have published an article in Device that provides a comprehensive overview of advancements, strengths, and challenges associated with various CLDD approaches.
Examples of devices already in use include insulin pumps, implantable pain pumps, and epilepsy neurostimulators.
In the paper, titled “Communication Protocols Integrating Wearables, Ingestibles, and Implantables for Closed-Loop Therapies,” the researchers explore both passive and active CLDDs.
Passive devices (typically implantable or ingestible) can release drugs over extended periods without active, real-time monitoring, while active CLDDs incorporate real-time monitoring and feedback mechanisms to adjust drug delivery in response to changing circumstances.
“Active closed-loop, drug-delivery systems are poised to usher in a new generation of remote, personalized healthcare driven by human-machine interfaces,” said study co-author Alex Abramson, an assistant professor in Georgia Tech’s School of Chemical and Biomolecular Engineering.
“But to accentuate the shift from passive to active CLDDs, the integration of advanced sensors and actuators is crucial,” added Ramy Ghanim, a PhD student in Abramson’s lab and co-author of the paper.
Sensors in CLDDs continuously monitor specific health parameters in the body (e.g., blood glucose levels for diabetics), and that data is fed to actuators that determine if a specific treatment is needed (such as releasing insulin).
Communication Systems
In the article, the researchers explore various methods for communication transmission in CLDDs, including hardwiring, radio frequency (RF) wireless communication such as Bluetooth, ultrasound, and in-body communication (harnessing the body itself for data transfer through methods like ionic, biochemical, and optical communication). Each method comes with unique advantages and challenges, according to the researchers.
Challenges in developing advanced HMIs include battery size constraints, powering requirements, data transmission rates, and locational dependance.
One big challenge is making sure these devices work no matter where they are inside a patient. Like a cellphone working best near a Wi-Fi router, these devices need to be in the right place to communicate effectively. Sometimes, they move around inside the body, which can be a problem.
The paper explores potential solutions to various challenges, including energy harvesting techniques, wireless powering, and location tracking systems. Ensuring secure data transmission and protection against hacking is also crucial, the researchers noted.
Benefits to Patients
Benefits of CLDDs include simplicity by automating treatment, reducing side effects by delivering medication precisely in a timely manner, and cost-effectiveness by reducing hospitalizations and complications associated with patient non-compliance.
Up to half of all patients requiring frequent and redundant dosages are noncompliant, sometimes missing doses due to complex treatment regimens, according to the researchers. Consequences include decreased quality of life, preventable disease progression, and an estimated annual cost of $528.4 billion in U.S. healthcare expenditure solely due to suboptimal medication therapy.
“Closed-loop drug delivery systems are poised to transform the landscape of chronic illness treatment by enhancing therapeutic release profiles and easing drug administration, thereby improving patients’ quality of life, decreasing medical expenditures, and improving compliance,” Abramson said.
CITATION: Ramy Ghanim, Anika Kaushik, Jihoon Park, and Alex Abramson, “Communication Protocols Integrating Wearables, Ingestibles, and Implantables for Closed-Loop Therapies,” Device, https://www.cell.com/device/fulltext/S2666-9986(23)00144-8, 2023
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In those cases, a delivery system must bind with the drug and then release it precisely where and when it will be most effective. However, the same system doesn’t work for every drug — for example, the methods used for capturing and releasing a small-molecule medication won’t work if you want to deliver a biologic drug.
That’s where OZ-Link hopes to make a significant impact.
“What’s unique about our technology is that, whether the carrier system is an antibody, nanoparticle, polymer, or hydrogel, it connects to whatever the drug is,” said Kasie Collins, CEO and co-founder of OZ-Link, a startup company growing in the lab of Georgia Tech researcher M.G. Finn, professor, chair, and James A. Carlos Family Chair for Pediatric Technology in the School of Chemistry and Biochemistry. “Our technology is designed to be compatible with both small molecules and biologics.”
The early-stage company is working to demonstrate that its system can provide sustained, extended release in ways that can be varied from days to weeks. Small-molecule drugs (the most common drugs on the market) and biologics (the fastest emerging class of drugs) can both benefit from this type of delivery, but in different ways and over different time frames, depending on the target.
Currently, there is nothing on the market capable of doing that effectively, and drug manufacturers large and small are intrigued by the notion of such precise biocompatible delivery. Based on the feedback that OZ-Link has received from its potential client base, the company is at work now on its next phase of research and development.
“We’re in the process of developing our first preclinical prototype, featuring our programmable drug delivery system for the extended release of protein therapeutics,” said Collins, whose team has entered a new partnership that will help the fledgling company focus on developing its technology.
OZ-Link was notified recently that it had been selected for commercialization support and funding through the Biolocity Fund for 2023-24. Biolocity, based in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University, is a philanthropic program that supports early-stage medical technologies from both campuses.
In addition to CEO Collins, OZ-Link’s founding leadership team includes Steve Seo, chief operating officer; Jasmine Hwang, chief scientific officer; and Wenting Shi, a Ph.D. candidate whose dissertation research plays a critical role in the further development of the Oz-Link technology. All are members or affiliates of the Finn lab.
They recently participated in Biolocity U, a program that provides business and legal counseling, lectures, internship opportunities, and other tools for startups. After making a final pitch, they were selected for funding.
“We had just finished doing customer discovery at a local conference when we got the news about Biolocity, which was so important. It allows us to do critical feasibility studies, which are necessary for follow-on funding efforts,” Collins said. “Additionally, it allows the team to work on OZ-Link research and development full time.”
The company also was part of the inaugural cohort that completed the Nucleate Activator program in Atlanta last semester. This program supports next generation bioentrepreneurs with mentorship, workshops, networking, and a pitch competition. OZ-Link won the Regional High Impact Culture Award, which recognizes cutting-edge scientific ideas with the greatest positive impact on society.
The foundation of the company is right there in its name, which comes from the chemical structures in OZ-Link’s technology: ozanorbornadiene (also called OND) and azanorbornadiene (ZND) molecules. “We use this small-molecule technology as a means of linking the therapeutic cargo to a drug delivery system,” Collins said.
The company is in the process of developing its first viable product, which would deliver injectable protein drugs. But that’s just the beginning.
“The technology is at a nascent stage now, but our feasibility data will help us secure co-development partnerships down the road,” Collins said. “Such partnerships would give us an opportunity to broaden our scope and demonstrate that we can deliver different types of drugs in an efficient, programmable manner.”
]]>In the race to develop new pharmaceuticals, an increasing number of biochemists are looking to discover new natural products – and uncover the mechanisms that produce and influence them. And Georgia Tech School of Chemistry and Biochemistry Assistant Professor Vinayak Agarwal is helping lead that charge. “I’m interested in how and why natural products are created in nature, what we can learn from their processes, and how we can harness nature's capabilities for interesting applications,” Agarwal says.
Now a $700,000 NSF CAREER grant will help him do so. The National Science Foundation Faculty Early Career Development Award is a five-year funding mechanism designed to help promising researchers establish a personal foundation for a lifetime of leadership in their field. Known as CAREER awards, the grants are NSF’s most prestigious funding for untenured assistant professors.
Agarwal’s award specifically focuses on his research into peptides, short strings of amino acids that make up proteins. “We’re making new types of peptides and modified peptides,” Agarwal explains. “Modifications in a lot of antibiotics that we use are actually peptides.” Over 100 peptide-based drugs are currently available in the US, where they’re used to treat conditions ranging from type-2 diabetes to MS.
While peptides are naturally made in the body, they can also be synthesized in the lab, where they’re modified using different enzymes. By harnessing these enzymes, peptides can be better tailored to suit needs – they can be changed to interact with biologies in different ways, an essential aspect of creating new medicines.
Discovering and studying the enzymes that modify peptides is a key part of Agarwal’s research, as is understanding the mechanisms that these enzymes use to recognize and bind to the peptides. This is called “enzymatic modification,” and it’s a lush playing field for discovering new chemical reactions. “We want to solve the need of the chemistry community when it comes to peptide modifications, providing new reactions to the community regarding peptide development and peptide modification,” Agarwal says.
While gene mining has revealed some enzymes that might be useful in modifying peptides, the reactions caused by these enzymes and the resulting structure of the peptide are not fully understood: in-situ research is needed. Agarwal’s first goal is to discover new chemical reactions between peptides and enzymes by leveraging in vivo synthetic biology (inside living organisms) and in vitro biochemistry experiments (outside of living organisms).
Agarwal also hopes to better understand how peptides and proteins interact, and why so many chemical reactions depend on them. “Peptide-protein interactions and modification of peptides is a central tenet of all biological processes,” Agarwal explains. “We want to know how and why peptides are chosen by nature as scaffolding for chemical reactions.”
Leveraging in vivo synthetic biology and in vitro biochemistry experiments means a lot of hands-on research. “The team is making peptides in the lab using an E. coli bacteria,” Agarwal explains. “We provide genes to an E. coli bacteria, and it modifies the chemistries using specific enzymes.”
What does this research look like? Petri dishes. A lot of petri dishes. And a lot of opportunities for students. “One of our key goals is to use our interdisciplinary training to engage underserved students in research and lab experience. We want to educate, train, and diversify the next generation of scientists,” Agarwal says. “We are designing new courses in the laboratory which introduces undergraduates to new coursework and experiments in peptide science.”
Some of these opportunities are already bearing fruit: Agarwal recently collaborated with a team of undergraduates over a semester-long lab course, which included conducting laboratory research and publishing their findings.
Now, Agarwal plans to use this new CAREER grant to further expand opportunities for undergraduates, and will develop original curriculum starting with peptide-based lab research together with scientific communication and writing.
“The training that students are going to get provides a broad experience in biological and chemical science,” Agarwal says. “We want our students to learn mechanisms for peptide modifications, but the training is broadly applicable. It will prepare them to move forward in STEM – and especially graduate studies – but will also prepare them for industry careers, government and regulatory science, graduate studies, and more. This kind of background is applicable in all fields.”
All in all, Agarwal expects the research to span across this decade and into the next. There’s excitement in that timeline, too – ten-plus years of teaching, discovery, and opportunities for students, at Georgia Tech and beyond.
“For me, the biggest thing is student progress, as well as curriculum development and training,” Agarwal says. “That’s my driving force.”
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Nga Lee “Sally” Ng, Love Family Professor in Georgia Tech’s School of Chemical and Biomolecular Engineering, School of Earth and Atmospheric Sciences, and School of Civil and Environmental Engineering, led a study to investigate the formation and properties of SOA from the nitrate radical oxidation of two common monoterpenes, compounds found in many plants. Monoterpenes represent an important class of biogenic volatile organic compounds (VOCs) and their oxidation by nitrate radicals is a substantial source of SOA globally. Specifically, her research team examined the monoterpenes α-pinene and limonene, which are both emitted in large quantities from trees.
In findings published in the journal Nature Communications in the paper, “Non-linear effects of secondary organic aerosol formation and properties in multi-precursor systems,” Ng’s team found that oxidizing mixtures of monoterpenes simultaneously produced different results than observed through oxidizing them separately in laboratory chamber experiments. Given the chemical complexity of VOC reactions and SOA formation, previous experiments have mostly only studied one VOC compound at a time. In this study, Ng’s team used advanced mass spectrometry techniques to probe chemistry of multi-VOC reactions from the bulk to molecular level.
“Our results highlight that unlike what is currently assumed in atmospheric models, the interaction of products formed from individual VOCs should be accounted for accurately to describe SOA formation and its climate and health impacts," Ng said.
Ng explained that one might have expected α-pinene and limonene to have the same potential to form SOA when they are oxidized as mixtures simultaneously compared to when they are oxidized separately. But what the researchers found was approximately a 50% percent enhancement in the formation of SOA from α-pinene and about a 20% reduction in limonene SOA formation.
“In this case, one plus one does not equal two,” Ng said. “We do not get a linear reaction in the simultaneous oxidation experiment like we do in the sequential experiment. New products are being made by the interaction of the two monoterpenes.”
Ng’s study examined α-pinene and limonene in a nighttime setting when nitrate radical chemistry prominently happens. Nitrate radicals are produced by traffic emissions and ozone.
“Aerosol chemistry does not stop at night,” Ng said. After sunset, the nitrogen oxide compounds and ozone can react with the emissions from trees to produce organic aerosols. “At night, oxidation still takes place, but nighttime interactions have not been well studied.”
Ng said she hopes this research will lead to further studies to examine VOCs in the atmosphere and how they interact together. “Studying the interaction of two VOCs is really just the beginning,” Ng said. “It’s a big step froward, but there’s still a long way to go to understand the complexity of the atmosphere, where hundreds of VOCs are emitted and reacting at the same time.”
This work was supported by the National Science Foundation (NSF) CAREER AGS-1555034 (N.L.N), the National Oceanic and Atmospheric Administration (NOAA) NA18OAR4310112 (N.L.N), and the Eckert Postdoctoral Fellowship from the School of Chemical and Biomolecular Engineering at Georgia Institute of Technology (T.B.). The FIGAERO-HR-ToF- CIMS has been purchased through the NSF Major Research Instrumentation (MRI) Grant 1428738 (N.L.N).
CITATION: Masayuki Takeuchi, Thomas Berkemeier, Gamze Eris, Nga Lee Ng, "Non-linear effects of secondary organic aerosol formation and properties in multi-precursor systems," Nature Communications, December 2022. https://doi.org/10.1038/s41467-022-35546-1
]]>As the Covid-19 pandemic has increased the importance of assessing indoor air quality and ventilation in public spaces such as universities, Georgia Tech researchers have identified that in-situ measurements of either carbon dioxide (CO2) or particulate matter (PM) by low-cost sensors can be used to perform such calculations in classrooms – an insight that could be useful for schools with limited resources or access to only one type of air quality monitor.
Measuring indoor pollutant levels provides initial insight into indoor air quality, but a more comprehensive metric to understand indoor air quality and pollutant exposure is the air change rate, or air changes per hour (ACH) – the number of times that the total air volume in a room or space is removed and replaced in an hour, explained Nga Lee “Sally” Ng, Love Family Professor in Georgia Tech’s School of Chemical and Biomolecular Engineering and School of Earth and Atmospheric Sciences.
Her research team monitored a large lecture hall at Georgia Tech over extended periods of time in Spring and Fall 2021, measuring the levels of CO2 and aerosols, also known as PM, using low-cost sensors. Exposure to PM with a diameter smaller than 2.5 mm (PM2.5) has been associated with cardiopulmonary diseases and millions of deaths per year. Over the course of the pandemic, it is also becoming clear that aerosols can spread the Covid-19 virus through the air.
CO2 and PM levels can vary substantially in the classroom depending on the time of day. Student breathing during class times increases CO2, while their movements can resuspend PM that had deposited to surfaces into the air. Periodic cleaning (fogging) of the classroom during 2021 also generated aerosols.
In a paper published in the journal Building and Environment, the researchers reported that measuring CO2 levels alone over extended time periods should be sufficient to predict the decay rate of aerosols in a room. Both CO2 and PM provide comparable estimates of air change rates.
CO2 monitors are low cost and more accessible to institutions with limited resources than advanced techniques involving the release of chemicals into the air to measure air change rates, Ng said. PM monitors are also relatively inexpensive and could provide an even better picture of aerosol dynamics, she added.
“In reality, there are many situations in which someone wishing to use a PM or CO2 sensor to evaluate the risk of a virus transmission will only have access to a single sensor and limited other resources,” said PhD student Sabrina Westgate, the lead author of the paper. “The analysis provided in this work presents a case for the feasibility of using either a low-cost CO2 or PM sensor to do just this.”
But the key is continuous measurement over a long period of time to characterize the air change rates, Westgate said. If the calculated air change rate of a room regularly falls below recommended values, it indicates that room ventilation or particle removal methods (such as installing portable air cleaners) should be improved, or that breaks between classroom use should be increased.
Professor Ng said, “To our knowledge, this is the first study that comprehensively evaluates and compares the decay rates of occupant-emitted CO2 and particles of different sizes (PM1, PM2.5, and PM10) in a mechanically ventilated, university classroom using in-situ measurements. Our results provide new, data-driven insights into the practicality of using in-situ air quality monitoring to evaluate ventilation.”
The team employed a technique commonly used to quantity ventilation – analyzing the decay rate of tracer gases – to determine and compare occupancy-based CO2 and PM decay rates.
This specific study focused on a single classroom, but it is part of a larger project by Ng’s team to continuously monitor air quality in more than 30 classrooms across the Georgia Tech campus since 2020. The team has worked with the company QuantAQ to install sensors in these classrooms. The sensors are providing real-time air quality data that will help guide future measures to improve air quality.
Ng credits Georgia Tech’s Departments of Environmental Health and Safety and Facilities Management for their efforts to improve air quality on campus, including installing air purifiers, during the pandemic.
“Indoor air quality is an important topic, and a pandemic makes it even more so,” says Ng, whose research focuses on aerosol chemistry, air quality, and health effects.
CITATION: Westgate, S., and Ng, N. L.: Using in-situ CO2, PM1, PM2.5, and PM10 measurements to assess air change rates and indoor aerosol dynamics, Building and Environment, 109559, https://doi.org/10.1016/j.buildenv.2022.109559, 2022.
FUNDING: This work is supported by the GT Covid-19 Rapid Response fund and the NSF Graduate Research Fellowship under Grant No. DGE-2039655.
Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the view of the sponsoring agency.
This multi-institution EFRC, known as the Center for Understanding & Controlling Accelerated and Gradual Evolution of Materials for Energy (UNCAGE-ME), has advanced understanding of how acid gases interact with energy-related materials since its inception in 2014. The Center, with Georgia Tech as the lead participating institution, was first renewed for four years of funding in 2018.
“The selection for a third phase of funding is unusual, and speaks to the impact of the research already reported by the center in its first two phases,” said Christopher Jones, the John F. Brock III School Chair in Chemical & Biomolecular Engineering. “I believe this is attributable to the strong leadership provided by our current and former directors, Ryan Lively and Krista Walton. An additional constant throughout all three phases of the center has been strong collaboration between Georgia Tech, Oak Ridge National Laboratory, Lehigh University, and the University of Alabama.”
In the next four-year phase, UNCAGE-ME will leverage capabilities developed over the last eight years to address basic science questions associated with the evolution of materials to be used in clean energy technologies, including systems designed to capture and convert CO2 from the air into useful chemicals.
“Two of the most basic commodity chemicals in the clean energy economy will be H2 and CO2. A special emphasis has been given to these two molecules with DOE’s Energy Earthshots that were announced in November 2021 – the Hydrogen Shot and the Carbon Negative Shot” said Ryan Lively, a professor in Georgia Tech’s School of Chemical and Biomolecular Engineering and the director of UNCAGE-ME.
“These are all-hands-on-deck calls for innovations in technologies and approaches that will reduce the cost of clean hydrogen by 80% to $1 per 1 kg in one decade and remove CO2 from the atmosphere and durably store it at meaningful scales for less than $100/net metric ton of CO2-equivalent,” said Krista Walton, professor in ChBE as well as the inaugural director of UNCAGE-ME.
To help reach these goals, UNCAGE-ME will employ an interdisciplinary, matrixed research structure that combines novel materials synthesis, in situ characterization techniques, molecular modeling, and data science approaches to achieve an unprecedented level of design, prediction, and control over (electro)catalysts, sorbents, and membranes.
From 2014 to 2022, the UNCAGE-ME’s research accomplishments (appearing in more than 200 publications) provided detailed descriptions of the impact of acid gas exposure on metal-oxides, metal-organic frameworks, carbons, supported amines, porous organic cages, and other materials. This fundamental knowledge base directly supports the mission of the DOE’s Basic Energy Sciences program to provide the foundational science to guide the development of new energy technologies under realistic process environments.
“The College of Engineering is proud to continue leading this important initiative for an additional four years,” said Raheem Beyah, dean of the College of Engineering and Southern Company Chair. “This second renewal from DOE is a testament to Krista and Ryan’s leadership, as well as the vision and innovation of a science team comprised of Georgia Tech researchers and our collaborators around the nation.”
In addition to Georgia Tech, the partner institutions for UNCAGE-ME include Oak Ridge National Laboratory, the University of Alabama, University of Florida, University of California Riverside, Lehigh University, Sandia National Laboratory, and the University of Michigan.
Julia Kubanek, professor and vice president for interdisciplinary research at Georgia tech, said it takes partnership across the Institute to support faculty in developing complex centers such as UNCAGE-ME.
“Research centers like this one benefit from collaborations among faculty experts and grants administrator staff in our schools and colleges, contracting officials in Research Administration, plus two other sets of critical partners: the Office of Research Development, which supports complex proposal preparation, and the interdisciplinary research institutes IRIs,” Kubanek said.
“The IRIs gather information from our Office of Federal Relations and host workshops to help faculty prepare and form teams. In this case, the Strategic Energy Institute, Institute for Materials, and Renewable Bioproducts Institute were all involved in ensuring that faculty had advance notice of this competition and could make the most of expert advice,” she said.
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A team of Georgia Tech researchers brings us one step closer to understanding those properties. Their new study, published in Science Advances, for the first time brings tracking and measurement to organic semiconductor photoexcitations: particles put into “excited” or energized quantum states by light.
The semiconductors’ primary photoexcitations, called Frenkel excitons, dictate the optical qualities in those semiconductors. They can, in principle, form bonded pairs called biexcitons, but these have never been identified unambiguously. Quantifying those reactions will help researchers learn more about their properties to unlock future uses, such as more efficient and sustainable batteries and solar cells, biosensors, and new types of lasers.
“It’s a window into the basic electronic structure and properties of these materials,” says study co-author Carlos Silva Acuña, a professor with joint appointments in the School of Chemistry and Biochemistry and School of Physics, “but also into these tech applications we care about. How do we convert electrical energy to light? Or in photovoltaic applications, how do we convert solar light into electrical power? It’s more about understanding and discovering the very basic fundamental properties of materials that will allow the design of tailored materials that optimize a particular function.”
Silva Acuña and Natalie Stingelin, a professor with joint appointments in the School of Materials Science and Engineering and the School of Chemical and Biomolecular Engineering, led a team of researchers that tweaked traditional spectroscopy — how light or any other form of radiation is emitted and absorbed by materials — to track and measure the energy coming from Frenkel biexcitons. The researchers wanted to know how those photoexcitations form “bonds” between each other, how excitons find the right partners to form biexcitons, and how stable those exciton partners are.
The scientists used different spectroscopy techniques such as non-linear and coherent versions, which give researchers more flexibility in determining the energies flying back and forth between pairs of excitons. “The idea is an advanced spectroscopy that allows us to dissect interactions between excitations,” Silva Acuña says. “It’s designed to measure or resolve the interaction energy between different photoexcitations,” adding that the researchers can dissect with more detail where light from the biexcitons falls on the spectrum.
Those interactions are the foundation for any future quantum (atomic and subatomic) science applications for organic semiconductors, “because all the quantum phases we might want to induce are all governed by their interactions, and the interactions between photoexcitations are key.”
The global organic semiconductor market is expected to grow by $90.8 billion between 2020 and 2024, according to Berkshire Hathaway company Business Wire. Yet while composite semiconductors have well-studied and defined optical signatures, that’s not quite the case for organic semiconductors. “We could not find a clear optical signature of biexcitons,” Silva Acuña says. “That’s what has made them more challenging. There is a lot of theoretical prediction and calculation, but not really any experimental measurement” preceding the new Georgia Tech research, he explains.
“We can for the first time unambiguously identify bound excitons and characterize their nature. They’re attracted to what energy, repulsed by what energy, and why? How do those details relate to molecular structure?” he says. “What would we need to change to change those properties? How do we discover new materials with tailored properties?”
Silva Acuña also notes an unexpected finding in the research: Excitons that interact with each other in different polymer chains attract each other to form biexcitons — while excitons in the same polymer chain repel each other. “It’s a little bit counterintuitive that you can have two excitons repel each other, and yet they bind,” he says.
If the interaction energy between excitons is strong, a lot of excitons will end up as bound biexcitons, Silva Acuña adds. If science decides that can help add more functions to those materials, “Maybe we can design them to be even more strongly bound.” Or if it’s decided that those bonds need to be weaker for certain functions, “How can we turn them off? It’s all about material discovery.”
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DOI: science.org/doi/10.1126/sciadv.abi5197
Authors: Along with Silva-Acuña (C.S.-A.) and Stingelin (N.S.), co-authors of the study include: Elizabeth Gutiérrez-Meza, Ravyn Malatesta, and David A. Valverde-Chávez (all of the School of Chemistry and Biochemistry at Georgia Tech), Hongmo Li and Seong-Min Kim (both of the School of Materials Science and Engineering at Georgia Tech), Ilaria Bargigia and Ajay Ram Srimath Kandada (Department of Physics and Center for Functional Materials at Wake Forest University), Eric R. Bittner and Hao Li (Department of Chemistry at University of Houston), and Sergei Tretiak (Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory). C.S.-A. acknowledges support from the School of Chemistry and Biochemistry and the College of Sciences at Georgia Tech.
Funding: The work at Georgia Tech was funded by the National Science Foundation [DMR-1904293 (to C.S.-A.) and DMREF-1729737 (to N.S. and C.S.-A.)]. C.S.-A. acknowledges support from the School of Chemistry and Biochemistry and the College of Sciences at Georgia Tech. The work at the University of Houston was funded in part by the National Science Foundation (CHE-1664971 and DMR-1903785) and the Robert A. Welch Foundation (E-1337). This work was also conducted in part at the Center for Integrated Nanotechnologies, a U.S. Department of Energy and Office of Basic Energy Science user facility.
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The Georgia Institute of Technology, or Georgia Tech, is a top 10 public research university developing leaders who advance technology and improve the human condition. The Institute offers business, computing, design, engineering, liberal arts, and sciences degrees. Its nearly 44,000 students representing 50 states and 149 countries, study at the main campus in Atlanta, at campuses in France and China, and through distance and online learning. As a leading technological university, Georgia Tech is an engine of economic development for Georgia, the Southeast, and the nation, conducting more than $1 billion in research annually for government, industry, and society.
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]]>Hannah Choi of the School of Mathematics and Henry S. “Pete” La Pierre of the School of Chemistry and Biochemistry are among 118 early career researchers across the United States and Canada named as 2022 Sloan Fellows.
"Today's Sloan Research Fellows represent the scientific leaders of tomorrow," says Adam F. Falk, president of the Alfred P. Sloan Foundation. "As formidable young scholars, they are already shaping the research agenda within their respective fields — and their trailblazing won't end here."
Sloan Research Fellowships are some of the most competitive and prestigious awards available to early career researchers. They are also often seen as a marker of the quality of an institution’s science faculty — and proof of an institution’s success in attracting the most promising junior researchers to its ranks. Since the first Fellowships were awarded in 1955, nearly 50 faculty from Georgia Institute of Technology have received the honor.
“I am extremely excited and honored to be named a Sloan Fellow,” Choi says. “I am deeply grateful to my research group members, mentors, colleagues and collaborators who made this possible, and I appreciate support from the School of Mathematics and the College of Sciences very much.”
Choi plans to use the grant to expand on current research projects on biological neural networks. “Specifically, with this grant, I hope to investigate computational roles of network complexities manifested by diverse neural dynamics and intricate connectivity among different types of neurons, in data-driven, functional neural networks across multiple scales, modalities, and systems. This study, therefore, will help us better understand how robust and efficient computation emerges from the unique complexity of biological neural networks, which then can be applied to innovate neuromorphic computing.”
The Choi Research Group in Mathematical Neuroscience’s primary goal “is to understand how efficient and adaptable neural coding emerges from complex connectivity structure and rich neural dynamics in both biological and artificial neural networks at multiple scales.”
La Pierre leads the La Pierre Research Group, with an aim to “disentangle the complex electronic structure of f-block materials,” according to the group’s website. F-block elements, also known as lanthanides and actinides, are heavy metals found at the bottom two rows of the Periodic Table.
La Pierre will use the award funds to support postdoctoral fellows and graduate students to take on several new lines of inquiry in lanthanide and actinide magnetism.
“I am quite excited to be included among this year’s Sloan Research Fellows,” La Pierre says. “It’s (a group of) extremely talented colleagues. I am also particularly humbled by my colleagues’ support for this award.”
Several current and former College of Sciences researchers — along with a number of College of Engineering faculty — are also recent recipients of Sloan Fellowships:
Four College of Sciences early career researchers were also named 2020 Scialog Fellows for a new research initiative, Signatures of Life in the Universe. Scialog Fellows are jointly sponsored by the Research Corporation for Science Advancement and Alfred P. Sloan Foundation:
Beyond Sloan Research Fellowships, the Sloan Foundation awards approximately 200 grants per year, totaling roughly $80 million dollars in annual commitments in support of research and education in science, technology, engineering, mathematics, and economics.
That list includes a number of Georgia Tech recipients, most recently 2021 recipient Nicholas (Nick) Hud, professor, School of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Biosciences; 2020 recipient Matthew McDowell, associate professor, George W. Woodruff School of Mechanical Engineering in the College of Engineering; and 2019 recipients Kaye Husbands Fealing, dean and Ivan Allen Jr. Chair, Ivan Allen College of Liberal Arts and Julia Melkers, professor, School of Public Policy, Ivan Allen College of Liberal Arts.
]]>Editor: Jess Hunt-Ralston
Director of Communiations
College of Sciences
Fortunately, our bodies evolved to produce antioxidant enzymes such as Cu/Zn (copper/zinc) superoxide dismutase, or SOD1, which detoxifies certain harmful oxidants. In a weird twist, SOD1 is the only antioxidant enzyme that can take on one specific oxidant, superoxide, only to produce another ROS: hydrogen peroxide.
A team of Georgia Tech researchers have published a study that found an even stranger twist to this oxidant-antioxidant tale: SOD1 (good for cells) produces hydrogen peroxide (bad for cells) which stimulates the production of another important cellular antioxidant known as NADPH (also good for cells; more on this in a moment.)
“Yes, you heard that right,” says Amit Reddi, associate professor in the School of Chemistry and Biochemistry. “SOD1, an antioxidant enzyme, produces an oxidant, hydrogen peroxide, which in turn stimulates the production of another (good) antioxidant.”
Reddi is a co-author of this research along with Matthew Torres, associate professor in the School of Biological Sciences; Claudia Montllor-Albalate, former Reddi Lab member who received her Ph.D. in 2020 from the School of Chemistry and Biochemistry; Hyojung Kim, School of Chemistry and Biochemistry Ph.D. candidate; Annalise Thompson, a third-year graduate student in Reddi’s lab; and Alex Jonke, research scientist with the School of Biological Sciences.
Their study, “SOD1 Integrates Oxygen Availability to Redox Regulate NADPH Production and the Thiol Redoxome” is published in the Proceedings of the Natural Academy of Sciences (PNAS).
The NADPH/GAPDH connection
NADPH (nicotinamide adenine dinucleotide phosphate) is an important metabolite that is produced in cells. It provides a source of electrons that can act as an antioxidant and for the biosynthesis of numerous biomolecules, including fatty acids, amino acids, nucleotides, and cholesterol.
“NADPH is not only used as an antioxidant, but also to build new biomolecules to sustain cell proliferation,” Reddi says. “How do cells know to make enough NADPH to support aerobic life? We discovered that SOD1 senses oxygen availability via superoxide, and then converts this to hydrogen peroxide, which in turn inactivates an enzyme responsible for the breakdown of glucose, glyceraldehyde phosphate dehydrogenase (GAPDH).” That inactivation causes the build-up of metabolites that are re-routed to a pathway that synthesizes NADPH.
The story behind the SOD1 revelation
The PNAS research study began with a casual conversation in 2014 between Reddi and Torres at the former café in the Parker H. Petit Institute for Bioengineering and Biosciences (IBB).
“Given the very collaborative and collegial nature of faculty across the College of Sciences, and the Institute as a whole, it was easy to grab a coffee and discuss these ideas,” Reddi says. Work in the Reddi lab includes potential signaling roles for SOD1 and the hydrogen peroxide it produces; but understanding the extent to which these factors regulate signaling required a systems-level understanding of how widespread targets of SOD1 are in a cell.
Torres focuses on mass spectrometry-based proteomics (the study of all proteins produced and modified by an organism or system) to probe cell-wide signaling networks, so it seemed to Reddi like a perfect fit.
Then, Reddi says, Montllor-Albalate made the discovery that SOD1-derived hydrogen peroxide can regulate NADPH production and adaptation to aerobic life. Meanwhile, Kim, a joint student of the Reddi and Torres labs, drove the work to identify proteome-wide targets of SOD1-derived hydrogen peroxide.
The conversation in IBB led to a 2016 grant from the National Institutes of Health to study the topic further. The resulting paper “we feel will make a strong impact in the field of redox biology and signaling,” Reddi adds.
SOD1’s potential in future cancer therapy
SOD1 is often thought of as an appealing anti-cancer therapeutic because of its ability to scavenge superoxides. The theory is that if SOD1 is inactivated, cancer cells will be at a disadvantage.
Reddi says his team’s results “suggest this very simple approach may need to be reconsidered, because the hydrogen peroxide that is produced by SOD1 plays broader roles in metabolism — and regulates many other enzymes and pathways. For instance, many cancer cells are addicted to glucose (sugars) and have an increased reliance on it for energy and metabolism, with GAPDH being a key enzyme in the process. Our findings that SOD1-derived hydrogen peroxide inactivates GAPDH would suggest that inhibiting SOD1 in certain cancers could actually result in elevated GAPDH activity, and increased metabolism of glucose, which may be detrimental in fighting cancer.”
Torres and Reddi are continuing their collaboration to investigate other aspects of SOD1 and hydrogen peroxide signaling in cancer metabolism and its implications for disease progression.
doi.org/10.1073/pnas.2023328119
This work was supported by GM118744 to Reddi and Torres, and Blanchard Fellowship to Reddi.
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Most engineers and scientists agree that this an extremely exciting and busy time to be working in the space industry. Several new things are happening above the Earth’s atmosphere. Tourists can now pay private companies for a short trip to space, private industry is developing spacecraft for NASA missions, and a robotic helicopter is currently exploring Mars.
NASA and private companies also have their sights set on the moon. NASA’s Artemis program has a goal of landing humans on the moon in 2025 to begin building a base camp. This long-term human presence on the lunar surface will help NASA prepare for human space exploration missions of greater distance and duration, including an eventual crewed flight to Mars.
Academic research institutions are also playing a role in lunar exploration. Georgia Tech students and faculty are building Lunar Flashlight, a small satellite that will orbit the moon and search for lunar ice. The joint effort in the Daniel Guggenheim School of Aerospace Engineering (AE School) and the Georgia Tech Research Institute is expected to launch in 2022.
AE School assistant professor Koki Ho works on the development of mathematical theories and their application to space mission analysis, design, and optimization.
“One of the big questions currently being investigated is how humans may be able to use resources from the moon in future missions,” said Ho. “For instance, can lunar ice be converted to drinking water or to make rocket fuel? If so, new processes such as these will play a role in the design of future space missions and spacecraft. They would allow humans to pick up resources from the moon on the way to Mars.”
In addition to utilizing lunar resources, there are other challenges to overcome if people will someday have extended stays on the moon. For more than 20 years, NASA has had a safe, continuous human presence 240 miles above Earth on the International Space Station. The moon, however, is 244,000 miles away from the planet. If an emergency occurred on the moon and astronauts needed to abort a mission, it would take them at least 3 days to return home, as compared to the few hours it currently takes to travel between the ISS and Earth.
“The role of autonomy is going to be really important, and the spacecraft and life support systems will have to manage themselves at a greater level than what we have now,” said former NASA astronaut Sandy Magnus, a professor of the practice at Georgia Tech. “Currently an army of folks in mission control on Earth track a host of system functions. But if you can build good autonomous systems, they will track themselves.”
Magnus explains that these challenges and new technologies facing NASA will require multidisciplinary expertise.
“It’s not just you have an avionics problem, or a thermal problem, or a materials problem,” said Magnus, who received her Ph.D. from Georgia Tech’s School of Materials Science and Engineering in 1996. “It’s normally much more complex than that. Therefore, I think one of the strengths that Georgia Tech brings to the whole enterprise is the fact that its campus has a lot of cross-disciplinary and multidisciplinary research.”
Ho agrees, noting that the collaborative nature on campus that brings together a multitude of expertise areas creates expanded opportunities for faculty and student collaboration.
“This is what makes Georgia Tech unique,” said Ho. “This is the most collaborative environment that I’ve been a part of in my research career. And with this collaboration, a team of research labs can develop something more ambitious than what one professor can achieve.”
Once they graduate, many aerospace students find their first jobs at NASA, SpaceX, or companies contracted to build spacecraft, such as Lockheed Martin and Northrop Grumman.
Professor Stephen Ruffin, associate chair for undergraduate programs in the AE School, says the School’s academic program prepares students well. Another key part of their success is what the students do outside of the traditional classroom in Georgia Tech’s makerspaces.
“Many of our students are involved in design-build-fly activities such as design competitions where they analyze and build various aerospace systems, then compete against teams at other universities,” said Ruffin. “Our students are graduating with an understanding of the science associated with these technologies, while also getting a real hands-on understanding of how you actually manufacture these systems and how you ensure robustness in these systems.”
As engineers develop and test new strategies that could bring Americans back to the moon and beyond, researchers in Georgia Tech’s College of Sciences are wondering about potential life elsewhere in the solar system.
“Discovering life beyond Earth would fundamentally change humanity’s perspective on our place in the universe,” said School of Earth and Atmospheric Sciences associate professor Jennifer Glass. “Integrating astrobiology – the search of life in the universe – into space missions in order to know if and when we detect life on other planetary bodies, including exoplanets, is an exciting challenge currently underway.”
Ruffin adds that continuing to push the boundaries beyond Earth will spur new technologies and industries that will benefit society, while helping the U.S. maintain its lead in the space arena.
“Going to the moon and Mars will allow for amazing science to be conducted,” said Ruffin. “We’ll be able to learn more about the history of our solar system, understand what’s happening to our planets, and create a better world for us here on Earth.”
“I am very honored to have been named the Sepcic Pfeil endowed chair,” Lieberman says. “Pfeil is one of our most successful Ph.D. graduates. She attended graduate school at a time when there were far fewer female students, and no tenured female faculty members. Her decision to endow this position is terrific, and it expands upon involvement to tangibly improve the camaraderie and peer mentorship of female graduate students in our department.”
Kelly Sepcic Pfeil, a member of the College of Sciences Advisory Board, received her M.S. in Chemistry in 1992 and her Ph.D. in the same discipline in 2003. She and her husband David established the fund in 2020 to counter statistics showing less than 20% of STEM faculty positions nationwide are held by women, with most of those assistant professor positions, considered a launch point for academic careers. And many of those women choose to eventually leave academia and enter the private sector.
“Students need more role models,” Pfeil says. “If young women and minority students don’t see more women in faculty positions, they may be discouraged from obtaining STEM degrees. That could lead to even fewer women in these disciplines. We are building a pipeline for women in STEM, and that pipeline starts in academia,” she explained in the Georgia Tech spring 2020 issue of Philanthropic Quarterly.
About Raquel Lieberman
Lieberman researches protein folding and misfolding, particularly when it comes to proteins that are linked to early-onset, inherited forms of glaucoma. A second major project involves the study of membrane-spanning proteolytic enzymes that are related to those involved in producing amyloid-beta associated with Alzheimer's disease.
“With this new role, I hope to grow my research program dealing with the molecular aspects of protein misfolding in human diseases and continue to mentor a diverse group of trainees,” Lieberman says. “I share Pfeil’s commitment and passion for doing what I can to ensure the future generation of scientists will better reflect the makeup of the general population. All of society will benefit.”
Lieberman is also the College's recent recipient of the Gretzinger Moving Forward Award, which is named for Ralph Gretzinger (’70 Math) and his late wife Jewel. That award recognizes the leadership of a school chair or senior faculty member who has played a pivotal role in diversifying the composition of tenure-track faculty, creating a family-friendly work environment, and providing a supportive environment for early career faculty.
About Kelly Sepcic Pfeil
Sepcic Pfeil spent 14 years at Coca-Cola, where she was responsible for flavor development and ingredient quality for the company’s global product and flavor lines. She left in 2007 to become vice president for Frito-Lay North America’s new product innovation, and later vice president of PepsiCo’s global strategy and portfolio management teams for snacks. In 2015, she formed her own firm, ArrowInno, which provides product design and innovation consulting to food and beverage companies.
Sepcic Pfeil has also served as an instructor for the Georgia Tech School of Chemistry and Biochemistry summer program, "Concept to Market" innovation course, for three years. She leads an annual offsite event for Tech's Women in Chemistry program on career and professional development, and also serves on Georgia Tech’s President’s Board and the School of Chemistry and Biochemistry Advisory Board.
]]>Saad Bhamla, a professor in the School of Chemical and Biomolecular Engineering at Georgia Tech, recently received an Outstanding Investigator Award from the National Institute of General Medical Sciences, part of the National Institutes of Health, to continue studying Spirostomum and attempt to build machines based on similar principles. The grant will provide his research group with $1.98 million in funding over five years.
For Bhamla, the comparison between the organism and the engine is more than just an analogy. He is now working to build something directly akin to a micro-engine, with pistons and cylinders made out of synthetic cells similar to Spirostomum.
“That's basically the stuff of my dreams,” Bhamla said.
Once built, he believes that these molecular engines might prove far more efficient than other miniaturized power sources. The chief difficulty will be making a synthetic cell that functions like Spirostomum, Bhamla said. Today, most synthetic cells do very different things, like producing lab-grown meat.
“We still think of them as basically bags of fluid,” said Bhamla. “They don't move, they just hang around in test tubes.”
Over the last few years, Bhamla and colleagues have learned more about how Spirostomum works. Its capabilities come from its use of an unconventional fuel, calcium, rather than adenosine triphosphate (ATP), the molecule that powers most human cells.
In a preprint from 2019, Bhamla and Xinjing Xu, then an undergraduate student at Georgia Tech, figured out exactly what makes the organism contract. They found that when calcium binds to Spirostomum’s skeletal mesh, it forces each cell of the skeleton to coil tight.
One of Bhamla’s current doctoral students, Xiangting Lei, is already examining how to replicate this mechanism in a synthetic cell. She is investigating how to give the cell external triggers so that engineers can make it contract whenever they want. Bhamla plans to use the funds from the grant to hire several more graduate students to study these systems.
The goal is to create modern versions of what were historically known as mechanochemical machines. A rich literature on these chemically-powered machines had been created in the sixties, only to be forgotten, Bhamla said. It seemed to be a classic case of science getting ahead of itself.
“They didn't have the right optical tools and soft materials to do this,” said Bhamla. “This is a great time to revisit [the research] because I think this time, we might be able to have much more success.”
About Georgia Tech
The Georgia Institute of Technology, or Georgia Tech, is a top 10 public research university developing leaders who advance technology and improve the human condition. The Institute offers business, computing, design, engineering, liberal arts, and sciences degrees. Its nearly 40,000 students representing 50 states and 149 countries, study at the main campus in Atlanta, at campuses in France and China, and through distance and online learning. As a leading technological university, Georgia Tech is an engine of economic development for Georgia, the Southeast, and the nation, conducting more than $1 billion in research annually for government, industry, and society.
]]>The award will establish a network of 12 sites around the United States, including locations in national parks and some of the country’s largest cities. Each will be outfitted with state-of-the-art instruments for characterizing the properties of aerosols. These sites will form what is officially called the Atmospheric Science and mEasurement NeTwork (ASCENT).
Data from ASCENT will allow researchers to address a variety of questions about how the composition and abundance of aerosols are changing, such as how the modernization of electrical production (coal to natural gas to renewable) and transportation (gasoline to electric vehicles) affect air pollution and climate-relevant variables.
“This is an incredibly exciting opportunity,” said Ng, a professor in Georgia Tech’s School of Chemical and Biomolecular Engineering and School of Earth and Atmospheric Sciences. “ASCENT represents a key advancement in atmospheric measurement infrastructure in the U.S. For the first time, we will be able to acquire comprehensive, high time-resolution, long-term characterization of aerosols over a wide range of geographical regions. ASCENT will provide the critical, fundamental knowledge for informing science-based decisions on climate change, air quality, and minimizing inequalities in air pollution exposure.”
ASCENT will also advance understanding of the adverse health impacts of PM2.5 (particulate matter with a diameter smaller than 2.5 micrometers). Exposure to PM2.5 has been associated with cardiopulmonary diseases and millions of deaths per year.
“ASCENT's long-term, advanced chemical composition and particle size measurements will facilitate transformative studies to unravel specific aerosol types and properties responsible for their adverse health effects,” Ng said. “This will contribute to building a foundation to define future regulations in the U.S. for protecting public health, as aerosol sources and properties continue to evolve in a changing world.”
Aerosols impact climate by changing the Earth’s energy balance via direct absorption or scattering of solar radiation and altering the albedo (surface reflection), formation of clouds, and precipitation. The Intergovernmental Panel on Climate Change assessment established that the aerosol effects represent the single largest source of uncertainty in understanding climate change.
According to NSF, ASCENT will also allow U.S. researchers to remain competitive in a global research environment. The 2016 National Academies report on The Future of Atmospheric Chemistry Research emphasized the critical need for long-term atmospheric chemistry measurements, recommending that the NSF take the lead to establish synergies with existing sites.
Currently, several aerosol monitoring networks exist in the United States, but none have the capability of measuring aerosol chemical and physical properties at high time-resolution (highly regular intervals of measurement, in the order of minutes).
The ASCENT network’s 12 sites across the United States are strategically located in rural, urban, and remote sites that have pre-existing infrastructure for atmospheric monitoring. Five ASCENT sites are in the National Core Network (NCore), which is a subset of the Chemical Speciation Network (CSN). Four rural sites are in the Interagency Monitoring of PROtected Visual Environment (IMPROVE) network. Other ASCENT sites are located in NSF’s National Ecological Observatory Network (NEON), the South Coast Air Quality Management District (AQMD) in California, and the Houston Network of Environmental Towers (HNET) in Texas.
Each site will be equipped with four advanced instruments: an Aerosol Chemical Speciation Monitor (ACSM, non-refractory aerosols), Xact (trace metals), Aethalometer (black/brown carbon), and Scanning Mobility Particle Sizer (SMPS, aerosol number size distribution and concentration).
The sites include: Delta Junction, Alaska; Cheeka Peak/Makah, Washington; Los Angeles/Pico Rivera, California; Rubidoux, California; Joshua Tree National Park, California; Yellowstone National Park, Wyoming; Denver, Colorado; Houston, Texas; Pittsburgh, Pennsylvania; New York City; Atlanta, Georgia; and Great Smoky Mountain National Park, Tennessee.
On the education and outreach side of the project, ASCENT has specific recruitment, mentoring, training, and career development plans for graduate and undergraduate students, with an emphasis on underrepresented groups. One of the ASCENT locations is on tribal land and the project will train tribal air quality staff and perform outreach to interested tribal members. ASCENT will also provide training and educational opportunities for the state agency and National Park Service site operators.
In collaboration with the National Center for Atmospheric Research, a comprehensive database and web interface will be developed to provide research communities, educators, policy makers, the public, etc. with free and open access to all ASCENT data.
In addition to lead principal investigator (PI) Ng, co-PIs on the ASCENT project include Professor Armistead Russell of Georgia Tech’s School of Civil and Environmental Engineering, Professor Roya Bahreini of the University of California-Riverside, and Professor Ann Dillner of the University of California-Davis, with Senior Research Scientist Christina Higgins of the Georgia Tech Research Institute serving as project manager.
Other ASCENT partner institutions and academics include the University of Alaska Fairbanks (Professor Jingqiu Mao), University of Washington (Professor Joel Thornton), California Institute of Technology (Professor John Seinfeld), Harvey Mudd College (Professor Lelia Hawkins), University of Wyoming (Professor Shane Murphy), University of Colorado Boulder (Professor Jose Jimenez), Roger Williams University (Professor Robert Griffin), University of Houston (Professor James Flynn), Carnegie Mellon University (Professors Allen Robinson and Albert Presto), Yale University (Professor Drew Gentner), University of North Carolina at Chapel Hill (Professor Jason Surratt), and the National Center for Atmospheric Research (Jeff de La Beaujardiere and Eric Nienhouse).
Ng said: “I look forward to working with the team and the greater atmospheric community to build this amazing network and all the new and exciting research opportunities that ASCENT will enable for the many years to come.”
]]>The challenge is that xylenes travel in threes and are virtually identical, making it extremely difficult to efficiently separate and purify para-xylene from its less used siblings such as ortho-xylene. These molecules’ size differs by one-tenth of a nanometer. However, membranes with tiny pores engineered to differentiate these molecules can potentially enable this important separation.
Building on long-term research with ExxonMobil, researchers at the Georgia Institute of Technology have uncovered new insights into the fabrication of carbon membranes that have the potential to drive significant cost savings once the solution for xylene isolation separation is scaled for industrial use.
The findings were reported in the September 6, 2021 issue of the Proceedings of the National Academy of Sciences.
The work focuses on “carbon-based molecular sieves,” made by heating thin layers of materials in such a way as to drive off all the atoms other than carbon, resulting in a charcoal-like substance that has molecule-sized holes. In 2016 researchers at Georgia Tech and Exxon Mobil first demonstrated that a new carbon-based molecular sieve membrane could successfully separate xylene molecules and extract the super-useful para-xylene from the pack.
Now, Georgia Tech has advanced this work, devising improved carbon barriers that allows the skinnier p-xylene to slip through more rapidly, while rejecting the wider molecules. Importantly, the team discovered a powerful relationship between the bonding chemistry of the carbons and the mobility of xylenes through the carbon membranes.
The performance of the carbon membranes — if realized at industrial scales — could significantly lower energy costs compared with refining processes such as the standard crystallization method or adsorption-based method. The former approach involves freezing the xylene molecules in which only the para-xylene forms crystals, making it easy to isolate, but requiring substantial energy investment. The latter approach reduces energy consumption compared to crystallization but requires expensive and complex equipment to operate. The issue with membranes, according to Georgia Tech researchers, is the approach has only worked well in the lab environment, not in an industrial setting.
“We have made more stable materials by changing the polymer precursor we use. Then by changing how we transform the polymer into the carbon, we’ve made the membranes more productive,” said Ryan Lively, an associate professor in Georgia Tech’s School of Chemical & Biomolecular Engineering and the paper’s corresponding author.
Just how much more productive? The team has shown the new materials can lead to purification systems that are estimated to be “three to six times lower cost than other state-of-the-art methods,” Lively said.
Lively estimates that separation and purification account for around half the energy consumed in producing commodity chemicals and fuels. Globally, the amount of energy used in conventional separation processes for aromatics, for example, benzene toluene, is equal to that produced by about 20 average-sized power plants.
This advancement could have a big impact on petrol chemical energy consumption. The research was funded by ExxonMobil and builds on more than 15 years of collaborative research effort between Georgia Tech and the global oil and gas leader.
“Through collaboration with strong academic institutions like Georgia Tech, we are constantly exploring new, more efficient ways to produce the energy, chemicals, and other products consumers around the world rely on every day," said Vijay Swarup, vice president of research and development at ExxonMobil Research and Engineering Company.
The Georgia Tech researchers also uncovered new insights regarding the carbon structure itself. The team observed that subtle changes in the ratio of three dimensional to two-dimensional carbon centers in the membrane led to impressively large changes in the mobility of xylene isotherms within that material. They observed that a change in this ratio (the sp3/sp2 carbon ratio) from 0.2 to 0.7 led to a factor of 1000 increase in the productivity of the membrane. Surprisingly, the membrane largely maintained its selectivity, or its ability to do the xylene isomer separation, despite these changes in carbon structure.
“The more three-dimensional carbons are in there, the higher the productivity,” said M.G. Finn, professor and chair of Georgia Tech’s School of Chemistry and Biochemistry and co-corresponding author on the article. “The more you crank up productivity, while maintaining the same selectivity, the less membrane you need to handle the same amount of xylene feed. From a design perspective, it shows that you have this enormous control over how the membrane works by making very small changes in the carbon chemistry,” Finn concluded.
ExxonMobil Research & Engineering funded this research.
Citation: Yao Ma, Nicholas C. Bruno, Fengyi Zhang, M. G. Finn, and Ryan P. Lively. “Zeolite-like performance for xylene isomer purification using polymer-derived carbon membranes.” PNAS (Proceedings of the National Academy of Sciences of the United States of America). https://doi.org/10.1073/pnas.2022202118
]]>Led by Associate Professor Nga Lee “Sally” Ng in Georgia Tech’s School of Chemical and Biomolecular Engineering and the School of Earth and Atmospheric Sciences, the team evaluated the effect of a hydroxyl radical generator in an office setting. Hydroxyl radicals react with odors and pollutants, decomposing them, and hydroxyl radical generators have been marketed to inactivate pathogens such as coronaviruses.
However, Ng’s study found that in the process of cleaning the air, the hydroxyl radicals generated by the device reacted with volatile organic compounds present in the indoor space. This led to chemical reactions that quickly formed organic acids and secondary organic aerosols that can cause health problems. Secondary organic aerosols is a major component of PM2.5 (particulate matter with a diameter smaller than 2.5 mm), and exposure to PM2.5 has been associated with cardiopulmonary diseases and millions of deaths per year.
The paper, “Formation of oxidized gases and secondary organic aerosol from a commercial oxidant-generating electronic air cleaner,” is published in the journal Environmental Science and Technology Letters.
While the pandemic has made various types of electronic cleaners increasingly popular, Ng explained that consumers are probably not aware of the secondary chemistry taking place in the air, with the pollutants generated not being directly emitted by the cleaning device itself.
“There are increasing concerns regarding the use of electronic air cleaners as these devices can potentially generate unintended byproducts via oxidation chemistry similar to that in the atmosphere,” Ng said.
Two types of air cleaning technologies are commonly used to remove indoor pollutants such as particles or volatile organic compounds and to inactivate pathogens: mechanical filtration and electronic air cleaners that generate ions, reactive species, or other chemical products such as photocatalytic oxidation, plasma, and oxidant-generating equipment (e.g., ozone, hydroxyl radical), among others.
Ng’s team selected a hydroxyl generator for the study to measure the oxygenated volatile organic compounds and the chemical composition of particles generated by the device in an office on the Georgia Tech campus.
While previous research reported pollutant formation from various electronic air cleaners (ionizers, plasma systems, photocatalytic systems with ultraviolet lamps, etc.), Ng believes that her team’s study is the first to monitor the chemical composition of secondary pollutants in both gas and particle phases during the operation of an electronic device that dissipates oxidants in a real-world setting.
Advanced instrumentation made Ng’s study possible. Gas-phase organic compounds were measured using a high-resolution time-of-flight chemical ionization mass spectrometer, purchased through a National Science Foundation major instrumentation grant. The study received support from Georgia Tech’s Covid-19 Rapid Response fund.
Ng noted that future studies on air cleaning technology should not be limited to inactivation of viruses or reduction of volatile organic compounds, but should also evaluate potential oxidation chemistry and the formation of unintended harmful gaseous and particulate chemicals.
“More studies need to be conducted on the effects of these devices in a variety of environments,” Ng said. “Electronic air cleaners greatly rose in prominence because of the pandemic, and now there are a lot of these devices out there. Millions of dollars are being spent on these devices by businesses and schools. The market is huge.
“Our results show that care must be taken when choosing an adequate and appropriate air cleaning technology for a particular environment and task,” she said.
Ng stressed the importance of future studies concerning the unintended effects of electronic purifiers, as these devices are not currently well regulated and do not have testing standards.
“There needs to be more peer-reviewed scientific data on electronic air cleaners,” Ng said. “We hope that additional studies will lead to more government guidelines and regulation.”
CITATION: Joo et al., “Formation of oxidized gases and secondary organic aerosol from a commercial oxidant-generating electronic air cleaner.” (Environmental Science & Technology Letters) https://pubs.acs.org/doi/10.1021/acs.estlett.1c00416
About the Georgia Institute of Technology
The Georgia Institute of Technology, or Georgia Tech, is a top 10 public research university developing leaders who advance technology and improve the human condition.
The Institute offers business, computing, design, engineering, liberal arts, and sciences degrees. Its nearly 40,000 students representing 50 states and 149 countries, study at the main campus in Atlanta, at campuses in France and China, and through distance and online learning.
As a leading technological university, Georgia Tech is an engine of economic development for Georgia, the Southeast, and the nation, conducting more than $1 billion in research annually for government, industry, and society.
Media Relations Contacts: Jason Maderer (jmaderer3@gatech.edu) or Brad Dixon (braddixon@gatech.edu).
Writer: Brad Dixon
]]>The study measured the filtration efficiency of submicron particles passing through a variety of different materials. For comparison, a human hair is about 50 microns in diameter while 1 millimeter is 1,000 microns in size.
“A submicron particle can stay in the air for hours and days, depending on the ventilation, so if you have a room that is not ventilated or poorly ventilated then these small particles can stay there for a very long period of time,” said Nga Lee (Sally) Ng, associate professor and Tanner Faculty Fellow in the School of Chemical and Biomolecular Engineering and the School of Earth and Atmospheric Sciences.
The study was conducted during spring 2020, when the pandemic triggered a global shutdown of most institutions. Communities faced massive shortages of personal protective equipment, prompting many people to make their own homemade masks. Georgia Tech quickly set up the study since it already had “a great system for testing filtration efficiency using existing instruments in the lab,” Ng recalled.
The study’s findings were used to shape homemade face mask recommendations here last April, with the comprehensive study findings published on March 22 in the journal Aerosol Science and Technology.
In all, the researchers tested 33 different commercially accessible materials not limited to cloth fabrics, including single-layer woven fabrics such as cotton and woven polyester, blended fabrics, nonwoven materials, cellulose-based materials, materials commonly found and used in hospitals, and various filter materials.
“We learned there was a lot of variability in filtration performance even in the same type of material,” Ng said.
"We found commercially available materials that provide acceptable levels of submicron particle rejection while still maintaining air flow resistance similar to a surgical mask,” said Ryan Lively, an associate professor and John H. Woody Faculty Fellow in the School of Chemical and Biomolecular Engineering. “These materials combine fabric fiber density, a maze-like structure, and fiber surface chemistry to effectively reject submicron particles.”
The best-performing materials for homemade masks were blackout drapery and sterilization wrap widely used for packing surgical instruments. Both materials are commercially available.
The researchers said people should avoid using filters such as a HEPA/MERV or vacuum bags unless they are certified to be fiberglass-free since often such filters on their own may release glass fibers that can be inhaled. Other materials to avoid for masks include loose-knitted material, batting fabric, felt, fleece, or shiny, reusable shopping bags.
Multilayered samples performed much better than single-layer samples, but people should pay attention to breathability. The two-layered and three-layered samples tested show an overall filtration efficiency of about 50% for submicron particles. Mask fit is also important since particles can easily escape through gaps at the nose or through the sides of the mask.
The analysis showed that properly fitted and multilayer masks reject 84% of particles expelled by a person when one person wears it. Two people donning these types of masks reduces particle transmission by 96%.
A final takeaway of the research was the importance of universal mask wearing.
“The best way to protect ourselves and others is to reduce exhaled particles at the source, and the source is our face,” Ng said, adding, “That really gets amplified when everyone starts wearing masks.”
She expressed optimism that the findings will motivate people to more widely embrace mask wearing if they are sick and need to be in public.
“Not everyone understands the importance of airborne virus transmission, and the importance of wearing a mask,” she said. “I hope that the practice will continue to help reduce the release of these viral particles into the environment and help protect others.”
In addition to Ng and Lively, the researchers included Taekyu Joo, Masayuki Takeuchi, Fobang Liu, Matthew P. Rivera, and Bahnisikha Dutta from Georgia Tech; Joy Barr and Eric Parker from theClubhou.se; Emily S. Blum and John H. Tipton from the Global Center for Medical Innovation; and Julia Varnedoef from Cobb County (Georgia) Schools.
The work was supported by the Center for the Science and Technology of Advanced Material and Interfaces (STAMI) at Georgia Tech.
CITATION: Joo, Taekyu, et al, “Evaluation of Particle Filtration Efficiency of Commercially Available Materials for Homemade Face Mask Usage.” (Aerosol Science and Technology, 2021) https://doi.org/10.1080/02786826.2021.1905149.
***
The Georgia Institute of Technology, or Georgia Tech, is a top 10 public research university developing leaders who advance technology and improve the human condition.
The Institute offers business, computing, design, engineering, liberal arts, and sciences degrees. Its nearly 40,000 students, representing 50 states and 149 countries, study at the main campus in Atlanta, at campuses in France and China, and through distance and online learning.
As a leading technological university, Georgia Tech is an engine of economic development for Georgia, the Southeast, and the nation, conducting more than $1 billion in research annually for government, industry, and society.
Research News
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]]>The melt-infiltration technology developed by materials science researchers at the Georgia Institute of Technology uses electrolyte materials that can be infiltrated into porous yet densely packed, thermally stable electrodes. The one-step process produces high-density composites based on pressure-less, capillary-driven infiltration of a molten solid electrolyte into porous bodies, including multilayered electrode-separator stacks.
“While the melting point of traditional solid state electrolytes can range from 700 degrees Celsius to over 1,000 degrees Celsius, we operate at a much lower temperature range, depending on the electrolyte composition, roughly from 200 to 300 degrees Celsius,” explained Gleb Yushin, a professor in the School of Materials Science and Engineering at Georgia Tech. “At these lower temperatures, fabrication is much faster and easier. Materials at low temperatures don’t react. The standard electrode assemblies, including the polymer binder or glue, can be stable in these conditions.”
The new technique, to be reported March 8 in the journal Nature Materials, could allow large automotive Li-ion batteries to be made safer with 100% solid-state nonflammable ceramic rather than liquid electrolytes using the same manufacturing processes of conventional liquid electrolyte battery production. The patent-pending manufacturing technology mimics low-cost fabrication of commercial Li-ion cells with liquid electrolytes, but instead uses solid state electrolytes with low melting points that are melted and infiltrated into dense electrodes. As a result, high-quality multi-layered cells of any size or shape could be rapidly manufactured at scale using proven tools and processes developed and optimized over the last 30 years for Li-ion.
“Melt-infiltration technology is the key advance. The cycle life and stability of Li-ion batteries depend strongly on the operating conditions, particularly temperature,” Georgia Tech graduate student Yiran Xiao explained. “If batteries are overheated for a prolonged period, they commonly begin to degrade prematurely, and overheated batteries may catch on fire. That has prompted nearly all electric vehicles (EV) to include sophisticated and rather expensive cooling systems.” In contrast, solid-state batteries may only require heaters, which are significantly less expensive than cooling systems.
Yushin and Xiao are encouraged by the potential of this manufacturing process to enable battery makers to produce lighter, safer, and more energy-dense batteries.
“The developed melt-infiltration technology is compatible with a broad range of material chemistries, including so-called conversion-type electrodes. Such materials have been demonstrated to increase automotive cell energy density by over 20% now and by more than 100% in the future,” said co-author and Georgia Tech research scientist Kostiantyn Turcheniuk, noting that higher density cells support longer driving ranges. The cells need high-capacity electrodes for that performance leap.
Georgia Tech’s technique is not yet commercially ready, but Yushin predicts that if a significant portion of the future EV market embraces solid-state batteries, “This would probably be the only way to go,” since it will allow manufacturers to use their existing production facilities and infrastructure.
“That’s why we focused on this project – it was one of the most commercially viable areas of innovation for our lab to pursue,” he said.
Battery cell prices hit $100 per kilowatt hour for the first time in 2020. According to Yushin, they will need to drop below $70 per kilowatt hour before the consumer EV market can fully open. Battery innovation is critical to that occurring.
The Materials Science lab team currently is focused on developing other electrolytes that will have lower melting points and higher conductivities using the same technique proven in the lab.
Yushin envisions this research team’s manufacturing advance opening the floodgates to more innovation in this area.
“So many incredibly smart scientists are focused on solving very challenging scientific problems, while completely ignoring economic and technical practicality. They are studying and optimizing very high-temperature electrolytes that are not only dramatically more expensive to use in cells but are also up to five times heavier compared with liquid electrolytes,” he explained. “My goal is to push the research community to look outside that chemical box.”
In addition to Yushin, Xiao and Turcheniuk, co-authors included Aashray Narla, Ah-Young Song, Alexandre Magasinski, Ayush Jain, Sheirley Huang, and Haewon Lee from Georgia Tech, and Xiaolei Re from both Georgia Tech and Chongqing Technology and Business University in China.
This work was mostly supported by Sila Nanotechnologies Inc., a Georgia Tech startup, with characterization performed at the Materials Characterization Center at Georgia Tech. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsoring organization.
Gleb Yushin is co-founder, CTO, and a stockholder of Sila. Yushin is entitled to royalties derived from Sila’s sale of products related to the research described in this paper. This study could affect his personal financial status. The terms of this arrangement have been reviewed and approved by Georgia Tech in accordance with its conflict of interest policies.
CITATION: Y. Xiao, et al., “Electrolyte Melt-Infiltration for Scalable Manufacturing of Inorganic All-Solid-State Lithium-Ion Batteries.” (Nature Materials, 2021) https://dx.doi.org/10.1038/s41563-021-00943-2.
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]]>Conducted in July 2020, the study included monitoring both the number of particles and their total mass across a broad range of indoor locations, including 19 commercial flights in which measurements took place throughout departure and arrival terminals, the boarding process, taxiing, climbing, cruising, descent, and deplaning. The monitoring could not identify the types of the particles and therefore does not provide a direct measure of coronavirus exposure risk.
“We wanted to highlight how important it is to have a high ventilation rate and clean air supply to lower the concentration of particles in indoor spaces,” said Nga Lee (Sally) Ng, associate professor and Tanner Faculty Fellow in the School of Chemical and Biomolecular Engineering and the School of Earth and Atmospheric Sciences at the Georgia Institute of Technology. “The in-flight cabin had the lowest particle mass and particle number concentration.”
The study, believed to be the first to measure both size-resolved particle mass and number in commercial flights from terminal to terminal and a broad range of indoor spaces, has been accepted for publication in the journal Indoor Air and posted online at the journal’s website. Supported by Delta Air Lines, the research may be the first to comprehensively measure particle concentrations likely to be encountered by passengers from terminal to terminal.
As scientists learn more about transmission of the coronavirus, the focus has turned to aerosol particles as an important source of viral spread indoors. Infected people can spread the virus as they breathe, talk, or cough, creating particles ranging in size from less than a micron — one millionth of a meter — to 1,000 microns. The larger particles quickly fall out of the air, but the smaller ones remain suspended.
“Especially in poorly ventilated spaces, these particles can be suspended in the air for a long period of time, and can travel to every corner of a room,” Ng said. “If they are viral particles, they can infect people who may be at a considerable distance from a person emitting the particles.”
To better understand the circulation of airborne particles, Delta approached Ng to conduct a study of multiple indoor environments, with a strong focus on air travel conditions. Using handheld instruments able to measure the total number of particles and their mass, Georgia Tech researchers examined air quality in a series of Atlanta area restaurants, stores, offices, homes, and vehicles — including buses, trains, and private automobiles.
They trained Delta staff to conduct the same type of measurements in terminals, boarding areas, and a variety of aircraft through all phases of flight. The Delta staff recorded their locations as they moved through the terminals, and the instruments produced measurements consistent with the restaurants and stores they passed on their way to and from boarding and departure gates.
“The measurements started as soon as they stepped into the departure terminal,” Ng said. “We were thinking about the whole trip, what a person would encounter from terminal to terminal.”
In flight, aircraft air is exchanged between 10 and 30 times per hour. Some aircraft bring in exclusively outside air, which at cruising altitude is largely free of pollutant particles found in air near the ground. Other aircraft mix outdoor air with recirculated air that goes through HEPA filters, which remove more than 99% of particles.
In all, the researchers evaluated measurements from 19 commercial flights with passenger loads of approximately 50%. The flights included a mix of short- and medium-length flights, and aircraft ranging from the CRJ-200 and A220 to the 757, A321, and 737.
Among all the spaces measured, restaurants had the highest particle levels because of cooking being done there. Stores were next, followed by vehicles, homes, and offices. The average sub-micron particle number concentration measured in restaurants, for instance, was 29,400 particles per cubic centimeter, and in offices it was 2,473 per cubic centimeter.
“We have quite a comprehensive data set to look at the size distribution of particles across these different spaces,” Ng said. “We can now compare indoor air quality in a variety of different spaces.”
Because of the portable instruments used, the researchers were unable to determine the source of the particles, which could have included both biological and non-biological sources. “Further studies can include direct measurements of viral loads and tracing particle movements in indoor spaces,” she added.
Jonathan Litzenberger, Delta’s managing director of Global Cleanliness Strategy, said the research helps advance the company’s goals of protecting its customers and employees.
“Keeping the air clean and safe during flight is one of the most foundational layers of protection Delta aims to provide to our customers and employees,” he said. “We are always working to better understand the travel environment and confirm that the measures we are implementing are working.”
Overall, the study highlights the importance of improving indoor air quality as a means of reducing coronavirus transmission.
“Regardless of whether you are in an office or an aircraft, having a higher ventilation rate and good particle filtration are the keys to reducing the total particle concentration,” said Ng. “That should also reduce the concentration of any viral particles that may be present.”
In addition to Ng, the researchers included Jean C. Rivera-Rios, Taekyu Joo, Masayuki Takeuchi, and Thomas M. Orlando from Georgia Tech; and Tracy Bevington, John W. Mathis, Clifton D. Pert, Brandon A. Tyson, Tyler M. Anderson-Lennert, and Joshua A. Smith from Delta Air Lines.
CITATION: Jean C. Rivera-Rios, et al, “In-flight particulate matter concentrations in commercial flights are likely lower than other indoor environments.” (Indoor Air, 2021) https://doi.org/10.1111/ina.12812
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]]>Water separation by evaporators is effective but uses large amounts of energy. That’s significant given that the United States currently is the world’s second-largest producer of paper and paperboard. The country’s approximately 100 paper mills are estimated to use about 0.2 quads (a quad is a quadrillion BTUs) of energy per year for water recycling, making it one of the most energy-intensive chemical processes. All industrial energy consumption in the United States in 2019 totaled 26.4 quads, according to Lawrence Livermore National Laboratory.
An alternative is to deploy energy-efficient filtration membranes to recycle pulping wastewater. But conventional polymer membranes — commercially available for the past several decades — cannot withstand operation in the harsh conditions and high chemical concentrations found in pulping wastewater and many other industrial applications.
Georgia Institute of Technology researchers have found a method to engineer membranes made from graphene oxide (GO), a chemically resistant material based on carbon, so they can work effectively in industrial applications.
“GO has remarkable characteristics that allow water to get through it much faster than through conventional membranes,” said Sankar Nair, professor, Simmons Faculty Fellow, and associate chair for Industry Outreach in the Georgia Tech School of Chemical and Biomolecular Engineering. “But a longstanding question has been how to make GO membranes work in realistic conditions with high chemical concentrations so that they could become industrially relevant.”
Using new fabrication techniques, the researchers can control the microstructure of GO membranes in a way that allows them to continue filtering out water effectively even at higher chemical concentrations.
The research, supported by the U.S. Department of Energy-RAPID Institute, an industrial consortium of forest product companies, and Georgia Tech’s Renewable Bioproducts Institute, was reported recently in the journal Nature Sustainability. Many industries that use large amounts of water in their production processes may stand to benefit from using these GO nanofiltration membranes.
Nair, his colleagues Meisha Shofner and Scott Sinquefield, and their research team began this work five years ago. They knew that GO membranes had long been recognized for their great potential in desalination, but only in a lab setting. “No one had credibly demonstrated that these membranes can perform in realistic industrial water streams and operating conditions,” Nair said. “New types of GO structures were needed that displayed high filtration performance and mechanical stability while retaining the excellent chemical stability associated with GO materials.”
To create such new structures, the team conceived the idea of sandwiching large aromatic dye molecules in between GO sheets. Researchers Zhongzhen Wang, Chen Ma, and Chunyan Xu found that these molecules strongly bound themselves to the GO sheets in multiple ways, including stacking one molecule on another. The result was the creation of “gallery” spaces between the GO sheets, with the dye molecules acting as “pillars.” Water molecules easily filter through the narrow spaces between the pillars, while chemicals present in the water are selectively blocked based on their size and shape. The researchers could tune the membrane microstructure vertically and laterally, allowing them to control both the height of the gallery and the amount of space between the pillars.
The team then tested the GO nanofiltration membranes with multiple water streams containing dissolved chemicals and showed the capability of the membranes to reject chemicals by size and shape, even at high concentrations. Ultimately, they scaled up their new GO membranes to sheets that are up to 4 feet in length and demonstrated their operation for more than 750 hours in a real feed stream derived from a paper mill.
Nair expressed excitement for the potential of GO membrane nanofiltration to generate cost savings in paper mill energy usage, which could improve the industry’s sustainability. “These membranes can save the paper industry more than 30% in energy costs of water separation,” he said.
Georgia Tech continues to work with its industrial partners to apply the GO membrane technology for pulp and paper applications.
This work is supported by the U.S. Department of Energy (DOE) Rapid Advancement in Process Intensification Deployment (RAPID) Institute (#DE-EE007888-5-5), an industrial consortium comprising Georgia-Pacific, International Paper, SAPPI, and WestRock, and the Georgia Tech Renewable Bioproducts Institute. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsoring organizations.
CITATION: Zhongzhen Wang, et al., “Graphene Oxide Nanofiltration Membranes for Desalination under Realistic Conditions.” (Nature Sustainability, 2021) https://doi.org/10.1038/s41893-020-00674-3.
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The technology being developed, termed Beam Enabled Accurate Mapping & Molecular Analyte Profiling (BeamMap), combines data from scanning electron microscopy and a new mode of desorption electrospray ionization mass spectrometry (DESI-MS) to simultaneously determine surface topology and chemical makeup. BeamMap uses an electron beam and a focused nanospray of electrified liquid to gather the two types of information, which is correlated with help of image processing software. The research is funded by the National Institute of Health’s National Institute of General Medical Sciences (NIGMS).
“To make this breakthrough tool, we need to be able to provide both topological and chemical information at resolutions on the scale of micrometers and sub-micrometers to be able to discover molecular makeup and biological function at a sub-cellular level,” said Andrei Fedorov, Professor and Rae S. and Frank H. Neely Chair in the George W. Woodruff School of Mechanical Engineering at the Georgia Institute of Technology. “This will require simultaneous advances, and we will be pushing the limits of both imaging tools and what mass spectrometers can do.”
Because of the use of mass spectrometry for molecular sensing, BeamMap will be able to characterize proteins, metabolites, and lipid chemistry without requiring an a priori knowledge of what chemical species are present. With its ability to correlate chemical information with topological information acquired with focused electron and ion-spray beams in vacuum, the new instrument is expected to provide an order of magnitude improvement in the resolution of electrospray-based techniques, with chemical imaging resolution of approximately 250 nanometers and electron microscopy topological resolution of about 50 nanometers. BeamMap should be useful in fundamental and clinical biology, medicine, analytical chemistry, and bioengineering.
“Processes that are currently invisible to us could actually be seen using BeamMap, so we will have evidence for things we can only speculate about now,” Fedorov said. “Being able to see what is happening at the subcellular level will allow us to get a better understanding of how biological systems behave. That will allow us to create hypotheses for how cells and tissues interact with the environment, potentially leading to a whole host of new therapeutic applications.”
Among the major challenges that require an innovative research approach are the creation of soft ionization and highly local sample extraction necessary for keeping the biomolecules intact and the ability to effectively deliver the charged molecules to the vacuum environment of the mass spectrometer, he said.
“We will need to fine-tune the energy of the beam that sprays on the substrate to provide the resolution we need,” Fedorov said. “We need to extract live biomolecules and ionize them without disrupting their structure. To do this, we will have to use the softest possible ionization.”
The instrument will use the electrospray technique to create charged molecules of solvent focused in a beam about 100 nanometers in diameter. As the beam of charged solvent molecules hits the surface of the biological sample, it will ablate molecules from sample’s surface and move them into the surrounding vacuum environment of the SEM imaging chamber. The molecules will be charged and volatilized by the impinging nano-electrospray at a precisely tuned energy input, and then be extracted for immediate analysis in the mass spectrometer.
In parallel, an electron beam that can be focused down to 10 nanometers will be scanning and profiling the structures and features of the surfaces from which the molecules are being extracted by the electrospray. Correlating data from the two beams will provide information about the chemical makeup of the cell surface, the organelles and intracellular structures being imaged topologically.
Using multiple passes of the two beams will allow removal of layers from the samples, allowing internal structures to be mapped. Fedorov said producing each image will require several minutes, the timing limited by the speed at which the samples can be moved into the mass spectrometer and analyzed.
The characterization will be done in an electron microscope vacuum chamber, with the samples on a stage that can be moved in three dimensions. The stage will also provide cooling and hydration for the living samples during the imaging process.
The idea for the instrument came from a discussion with Andrés García, Regents' Professor in the George Woodruff School of Mechanical Engineering and executive director of Georgia Tech’s Institute for Bioengineering and Bioscience. García studies pancreatic cells as part of research into diabetes, and plans to use information from the new technique to develop a better understanding of the disease.
“BeamMap is an exciting technological advance that will provide unparalleled biological and chemical information with high spatial resolution to analyze complex biological processes,” García said. “We are very much looking forward to applying it to understand diabetes disease progression.”
This research was supported by Award 1R01GM138802-01 from the National Institute of General Medical Sciences (NIGMS) of the National Institutes of Health. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the NIH.
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]]>The possible treatment, which could become the first non-drug, non-surgical, long-acting therapy for glaucoma, uses the injection of a natural and biodegradable material to create a viscous hydrogel — a water-absorbing crosslinked polymer structure — that opens an alternate pathway for excess fluid to leave the eye.
“The holy grail for glaucoma is an efficient way to lower the pressure that doesn’t rely on the patient putting drops in their eyes every day, doesn’t require a complicated surgery, has minimal side effects, and has a good safety profile,” said Ross Ethier, professor and Georgia Research Alliance Lawrence L. Gellerstedt Jr. Eminent Scholar in Bioengineering in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University. “I am excited about this technique, which could be a game-changer for the treatment of glaucoma.”
The research, which was supported by the National Eye Institute and the Georgia Research Alliance, was published Dec. 7 in the journal Advanced Science. The research was conducted in animals, and shows that the approach significantly lowered the intraocular pressure.
As many as 75 million people worldwide have glaucoma, which is the leading cause of irreversible blindness. Glaucoma damage is caused by excess pressure in the eye that injures the optic nerve. Current treatments attempt to reduce this intraocular pressure through the daily application of eyedrops, or through surgery or implantation of medical devices, but these treatments are often unsuccessful.
To provide an alternative, Ethier teamed up with Mark Prausnitz, professor and J. Erskine Love Jr. Chair in the School of Chemical and Biomolecular Engineering at Georgia Tech, to use a tiny hollow needle to inject a polymer preparation into a structure just below the surface of the eye called the suprachoroidal space (SCS). Inside the eye, the material chemically crosslinks to form the hydrogel, which holds open a channel in the SCS that allows aqueous humor from within the eye to drain out of the eye through the alternative pathway.
There are normally two pathways for the aqueous humor fluid to leave the eye. The dominant path is through a structure known as the trabecular meshwork, which is located at the front of the eye. The lesser pathway is through the SCS, which normally has only a very small gap. In glaucoma, the dominant pathway is blocked, so to lessen pressure, treatments are created to open the lesser pathway enough to let the aqueous humor flow out.
In this research, the hydrogel props open the SCS path. A hollow microneedle less than a millimeter long is used to inject a droplet (about 50 microliters) of the hydrogel-precursor material. That gel structure can keep the SCS pathway open for a period of months.
“We inject a viscous material and keep it at the site of the injection at the interface between the back of the eye and the front of the eye where the suprachoroidal space begins,” Prausnitz said. “By opening up that space, we tap a pathway that would not otherwise be utilized efficiently to remove liquid from the eye.”
The injection would take just a few minutes, and would involve a doctor making a small injection just below the surface of the eye in combination with numbing and cleaning the injection site. In the study, the researchers, including veterinary ophthalmologist and first author J. Jeremy Chae, did not observe significant inflammation resulting from the procedure.
The pressure reduction was sustained for four months. The researchers are now working to extend that time by modifying the polymer material — hyaluronic acid — with a goal of providing treatment benefits for at least six months. That would coincide with the office visit schedule of many patients.
“If we can get to a twice-a-year treatment, we would not disrupt the current clinical process,” Prausnitz said. “We believe the injection could be done as an office procedure during routine exams that the patients are already getting. Patients may not need to do anything to treat their glaucoma until their next office visit.”
Beyond extending the time between treatments, the researchers will need to demonstrate that the injection can be repeated without harming the eye. The procedure will also have to be tested in other animals before moving into human trials.
“The idea of having a ‘one-and-done’ treatment that lasts for six months would be particularly helpful for those whose access to healthcare is non-optimal,” Ethier said. “Having a long-acting therapy would have an additional advantage during times of pandemic or other disruption when access to healthcare is more difficult.”
This research was supported by a grant from the National Eye Institute (R01 EY025286) and by the Georgia Research Alliance. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the funding agencies.
Mark Prausnitz serves as a consultant to companies, is a founding shareholder of companies, and is an inventor on patents licensed to companies developing microneedle-based products (Clearside Biomedical). These potential conflicts of interest have been disclosed and are being managed by Georgia Tech. J. Jeremy Chae, Jae Hwan Jung, Ethier, and Prausnitz are listed as co-inventors on an IP filing related to this study.
CITATION: J. Jeremy Chae, et al., “Drug-free, Non-surgical Reduction of Intraocular Pressure for Four Months After Suprachoroidal Injection of Hyaluronic Acid Hydrogel.” (Advanced Science, 2020) https://doi.org/10.1002/advs.202001908
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]]>Biochemical information about the body most commonly comes from analysis of blood — which represents only 6% of bodily fluids — but valuable information may also be found in other bodily fluids that are traditionally hard to get. Researchers have now developed a way to extract dermal interstitial fluid (ISF), which circulates between cells in bodily tissues, using a simple through-the-skin technique that could provide a new approach for studying the metabolic products of cells, obtaining diagnostic biomarkers, and identifying potential toxins absorbed through the skin. Because the dermal interstitial fluid doesn’t clot like blood, the microneedle-based extraction could offer a new approach for continuous monitoring of glucose and other key health indicators.
Results of a human trial on the microneedle-based ISF sampling is reported Nov. 25 in the journal Science Translational Medicine. The study, conducted by researchers from the Georgia Institute of Technology and Emory University, was supported in part by the National Institutes of Health and Children’s Healthcare of Atlanta.
“Interstitial fluid originates in the blood and then leaks out of capillaries to bring nutrients to cells in the body’s tissues. Because interstitial fluid is in direct communication with the cells, it should have information about the tissues themselves beyond what can be measured from testing the blood,” said Mark Prausnitz, Regents Professor and J. Erskine Love Jr. Chair in Georgia Tech’s School of Chemical and Biomolecular Engineering. “This microneedle-based technique could provide a minimally invasive and simple way to access this interstitial fluid to make it available for medical diagnostic and research applications.”
ISF has been difficult to sample. Indwelling instruments for monitoring glucose in ISF already exist, and other researchers have used surgically implanted tubing and vacuum-created blisters to extract ISF through the skin, but these techniques are not suitable for routine clinical diagnostic use.
The researchers, led by first author Pradnya Samant, used a patch containing five solid stainless steel microneedles that were a hundredth of an inch in length. By pressing the patch at an angle into the skin of 50 human subjects, they created shallow micropores that reached only into the outer layer of skin containing ISF. The researchers then applied a suction to the area of skin containing the pores and obtained enough ISF to do three types of analysis. For comparison, they also took blood samples and obtained ISF using the older blister technique.
To accurately determine the biomarkers available in the ISF, the researchers needed to avoid getting blood mixed with the ISF. Though major blood vessels don’t exist in the outer layers of skin, capillaries there can be damaged by the insertion of the microneedles. In their studies, the researchers found that if they slowly ramped up the suction after inserting the microneedles, they could obtain fluid clear of blood.
The overall extraction procedure took about 20 minutes for each test subject. The procedure was well tolerated by the volunteers, and the microscopic pores healed quickly within a day, with minimal irritation.
The extracted fluid was analyzed at Emory University using liquid chromatography-mass spectrometry techniques to identify the chemical species it contained. Overall, there were about 10,000 unique compounds, most of which were also found in the blood samples. However, about 12% of the chemical species were not found in the blood, and others were found in the ISF at higher levels than in the blood.
“The skin is metabolically active, and it is full of cells that are changing the fluid,” Prausnitz said. “We found that some of the compounds were unique to the ISF, or enriched there, and that is what we were hoping to find.”
While not all the compounds unique to the ISF could be analyzed, the research team identified components of products that are applied to the skin — such as hand lotions — and pesticides that may enter the body through the skin. This discovery could set the stage for use of the microneedle technique for dermatological and toxicology studies.
“If you want to look at what accumulates in the skin over time, this may provide a way to obtain information about those kinds of exposures,” Prausnitz said. “These are materials that may accumulate in the tissues of our body, but are not found in the bloodstream.”
The researchers also determined the pharmacokinetics of caffeine and the pharmacodynamics of glucose — both small molecules — from the ISF, indicating that that dynamic biomarker information could be obtained from the technique. Those measurements suggested that ISF could provide a means for continuously monitoring such compounds, taking advantage of the fact that the fluid does not clot.
“We were encouraged that we found a good correlation between the blood and interstitial fluid glucose, which suggests we might be able to have a continuous glucose monitoring system based on this technology,” Prausnitz said. A microneedle-based system could provide a less invasive alternative to existing implantable glucose sensors by allowing the sensing components to remain on the surface of the skin.
In future research, Prausnitz would like to reduce the time required to extract the ISF and simplify the process by eliminating the vacuum pump. Additional study of the compounds found in the fluid could also show whether they have medical diagnostic value.
“We’d like to make this microneedle-based technique available to the research community to make ISF routinely available for study,” he said. “Tissue interstitial fluid could be a novel source of biomarkers that complements conventional sources. This research provides a means to study this further.”
The research team also included Nicholas Raviele and Juan Mena-Lapaix from Georgia Tech; and Megan M. Niedzwiecki, Douglas I. Walker, Gary W. Miller, Vilinh Tran, Eric I. Felner, and Dean P. Jones from Emory University.
CITATION: Pradnya P. Samant, "Sampling interstitial fluid for human skin using a microneedle patch." (Science Translational Medicine, 25 November 2020) https://stm.sciencemag.org/content/12/571/eaaw0285
This work was supported in part by the U.S. National Institutes of Health (U2CES026560, P30ES020953, R01ES023485, P30ES019776, S10OD018006) and by Children’s Healthcare of Atlanta. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the funding agencies.
Mark Prausnitz is an inventor of patents licensed to companies developing microneedle-based products, is a paid advisor to companies developing microneedle-based products, and is a founder/shareholder of companies developing microneedle-based products (Micron Biomedical). This potential conflict of interest has been disclosed and is managed by Georgia Tech. Pradnya P. Samant and Prausnitz are inventors on a patent application (WO2019126735A1) submitted by Georgia Tech Research Corporation that covers ISF collection methods presented in this study.
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]]>Utilizing data about the properties of more than 200 existing MOFs, the machine learning platform was trained to help guide the development of new materials by predicting an often-essential property: water stability. Using guidance from the model, researchers can avoid the time-consuming task of synthesizing and then experimentally testing new candidate MOFs for their aqueous stability. Already, researchers are expanding the model to predict other important MOF properties.
Supported by the Office of Science’s Basic Energy Sciences program within the U.S. Department of Energy (DOE), the research was reported Nov. 9 in the journal Nature Machine Intelligence. The research was conducted in the Center for Understanding and Control of Acid Gas-Induced Evolution of Materials for Energy (UNCAGE-ME), a DOE Energy Frontier Research Center located at the Georgia Institute of Technology.
“The issue of water stability with MOFs has existed in this field for a long time, with no easy way to predict it,” said Krista Walton, professor and Robert "Bud" Moeller faculty fellow in Georgia Tech’s School of Chemical and Biomolecular Engineering. “Rather than having to do the synthesis and experimentation to figure this out for each candidate MOF, this machine learning model now provides a way to predict water stability given a set of desired features. This will really speed up the process of identifying new materials for specific applications.”
MOFs are a class of porous and crystalline materials that are synthesized from inorganic metal ions or clusters connected to organic ligands. They are known for their easily tunable components that can be customized for specific applications, but the large number of potential combinations makes it difficult to choose MOFs with the desired properties. That’s where artificial intelligence can help.
Machine learning is playing an increasingly important role in materials science, said Rampi Ramprasad, professor and Michael E. Tennenbaum Family Chair in the Georgia Tech School of Materials Science and Engineering and Georgia Research Alliance Eminent Scholar in Energy Sustainability.
“When materials scientists plan the next set of experiments, we use the intuition and insights that we have accumulated from the past,” Ramprasad said. “Machine learning allows us to fully tap into this past knowledge in the most efficient and effective manner. If 200 experiments have already been done, machine learning allows us to exploit all that has been learned from them as we plan the 201st experiment.”
Beyond experimental data, machine learning can also use the results of physics-based simulations. And unlike simulations, the results from machine learning models can be instantaneous. The machine learning algorithm improves as it receives more information, he noted, and both negative and positive results are useful.
“Great discoveries are as important as not-so-exciting discoveries — failed experiments — because machine learning uses both ends of the spectrum to get better at what it does,” Ramprasad said.
The machine learning model used information Walton and her research team had gathered on hundreds of existing MOF materials, both from compounds developed in her own lab and those reported by other researchers. To prepare the information for the model to learn from, she categorized each MOF according to four measures of water stability.
“The couple hundred data points used to build the model represented years of experiments,” Walton said. “I spent basically the first half of my career working to understand this water stability problem with MOFs, so it’s something we have studied extensively.”
Using the model, researchers who are developing new adsorbents and other porous materials for specific applications can now check their proposed formulas to determine the likelihood that a new MOF would be stable in the presence of water. That could be particularly helpful for researchers who don’t have this particular expertise or who don’t have easy access to experimental methods for examining stability.
“The MOF community is diverse, with a variety of subfields. Not everyone has the chemical intuition about which materials’ features lead to good framework stability, and experimental evaluation often requires specialty equipment that many labs may not have or wouldn’t otherwise need for their specific subfield. However, with good predictive models, they wouldn’t necessarily need to develop it to choose a material for a specific application,” Walton said. “This capability potentially opens up this field to a broader group of researchers that could accelerate application development.”
While screening for water stability is important, Ramprasad says it’s just the beginning of the potential benefits from the project. The machine learning model can be trained to predict other properties as long as a sufficient amount of data exists. For instance, the team is already teaching their model about factors affecting methane absorption under varying levels of pressure. In that case, simulations will provide much of the data from which the model will learn.
“We will have a very strong predictor that will tell us if a new MOF would be stable under aqueous conditions and a good candidate for methane uptake,” he said. “What we are doing is creating a universal and scalable machine learning platform that can be trained on new properties. As long as the data is available, the model can learn from it, and make predictions for new cases.”
In addition to those already mentioned, recent Georgia Tech postdoctoral fellow Rohit Batra and Georgia Tech graduate students Carmen Chen and Tania G. Evans were also coauthors on the Nature Machine Intelligence paper.
Ramprasad has experience with machine learning techniques applied to other materials and application spaces, and recently coauthored a review article, “Emerging materials intelligence ecosystems propelled by machine learning,” about a range of artificial intelligence applications in materials science and engineering. Intended to demystify machine learning and to review success stories in the materials development space, it was published, also on Nov. 9, 2020, in the journal Nature Reviews Materials.
In addition to Ramprasad, coauthors on the Nature Review Materials paper included Batra and Le Song, associate professor in the Georgia Tech College of Computing.
This work was supported as part of the Center for Understanding and Control of Acid Gas-Induced Evolution of Materials for Energy (UNCAGE-ME), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under award no. DE-SC0012577.
CITATION: Rohit Batra, Carmen Chen, Tania G. Evans, Krista S. Walton, and Rampi Ramprasad, “Prediction of water stability in metal–organic frameworks using machine learning.” (Nature Machine Intelligence, 2020) https://doi.org/10.1038/s42256-020-00249-z
CITATION: Rohit Batra, Le Song, and Rampi Ramprasad, “Emerging materials intelligence ecosystems propelled by machine learning.” (Nature Reviews Materials, 2020) https://www.nature.com/articles/s41578-020-00255-y.
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]]>The low-noise, solution-processed, flexible organic devices offer the ability to use arbitrarily shaped, large-area photodiodes to replace complex arrays that would be required with conventional silicon photodiodes, which can be expensive to scale up for large-area applications. The organic devices provide performance comparable to that of rigid silicon photodiodes in the visible light spectrum — except in response time.
“What we have achieved is the first demonstration that these devices, produced from solution at low temperatures, can detect as little as a few hundred thousand photons of visible light every second, similar to the magnitude of light reaching our eye from a single star in a dark sky,” said Canek Fuentes-Hernandez, principal research scientist in the School of Electrical and Computer Engineering at the Georgia Institute of Technology. “The ability to coat these materials onto large-area substrates with arbitrary shapes means that flexible organic photodiodes now offer some clear advantages over state-of-the-art silicon photodiodes in applications requiring response times in the range of tens of microseconds.”
The development and performance of large-area, low-noise organic photodiodes are described in the Nov. 6 issue of the journal Science. The research was supported by multiple organizations, including the Office of Naval Research, the Air Force Office of Scientific Research, and the U.S. Department of Energy’s National Nuclear Security Administration.
Organic electronic devices are based on materials fabricated from carbon-based molecules or polymers instead of conventional inorganic semiconductors such as silicon. The devices can be made using simple solution and inkjet printing techniques instead of the expensive and complex processes involved in the manufacturing of conventional electronics. The technology is now widely used in displays, solar cells, and other devices.
The organic photodiodes use polyethylenimine, an amine-containing polymer surface modifier found to produce air-stable, low work-function electrodes in photovoltaic devices developed in the laboratory of Bernard Kippelen, Joseph M. Pettit Professor at Georgia Tech. The use of polyethylenimine was also shown to produce photovoltaic devices with low levels of dark current — the electrical current that flows through a device even in the dark. This meant the materials could be useful in photodetectors for capturing faint signals of visible light.
“Over the years, the dark current levels were reduced so much that measurement equipment had to be redesigned to detect an electronic noise corresponding to a fluctuation of one electron in one millionth of a second,” Fuentes-Hernandez, the paper’s first author, said. “This work reflects sustained team efforts made in the Kippelen group over more than six years and encompasses part of the Ph.D. work of recent graduates Talha Kahn and Wen-Fang Chou. These collective efforts produced the scientific insights needed to demonstrate organic photodiodes with this level of performance.”
One application for the new devices is in pulse oximeters now placed on fingers to measure heart rate and blood oxygen levels. Organic photodiodes may allow multiple devices to be placed on the body and operate with 10 times less light than conventional devices. This could enable wearable health monitors to produce improved physiological information and continuous monitoring without frequent battery changes. Other potential applications include human-computer interfaces such as touchless gesture recognition and controls.
A future application is detection of ionizing radiation by scintillation — a flash of light emitted by a phosphor when struck by a high energy particle. Lowering the level of light that can be detected would improve the sensitivity of the device, allowing it to detect lower levels of radiation. Detecting radiation emitted from vehicles or cargo containers requires a large detector area, which would be easier to make from organic photodiodes than from arrays of silicon photodiodes.
Organic photodiodes could have similar advantages in X-ray equipment, where doctors want to use the smallest level of radiation possible to minimize the dose delivered to the patient. Here again, sensitivity, large area, and flexible form factor should give organic photodiodes an advantage over silicon-based arrays.
“We are working on improving the response time of the photodetector because producing fast photodetectors would enable many additional important applications,” Fuentes-Hernandez said. “There’s a real need to develop photodetector technologies that are more scalable, and one of the motivations of this work is to advance organic technology that we know is cost effective for scaling.”
The organic photodiodes can show electronic noise current values in the tens of femtoampere range and noise equivalent power values of a couple of hundreds of femtowatt. Key performance factors of the organic photodiodes compare well with silicon except in the area of response time, where researchers are working on a hundred-fold improvement to enable future applications.
“Because we use materials that are processed from inks using printing techniques, they are not as ordered as crystalline materials,” Kippelen said. “As a result, the carrier mobility and the velocity of the carriers that can move through these materials are lower, so you can’t get the same fast signals you get with silicon. But for many applications you don’t need picosecond or nanosecond response time.”
For Kippelen, the photodiode work shows the results of a 25-year effort to improve the performance of organic electronic materials. That work, part of Georgia Tech’s Center for Organic Photonics and Electronics, has involved extensive device modeling to understand the basic science, and research to continuously boost performance of the materials.
“Organic thin films absorb light more efficiently than silicon, so the overall thickness you need to absorb that light is very small,” Kippelen said. “Even if you scale their area up, the overall volume of your detector remains small with organics. If you increase the area of a silicon detector, you have a larger volume of materials that at room temperature will generate a lot of electronic noise.”
The photodiodes made in Kippelen’s lab use an active layer just 500 nanometers thick. A gram of the material, roughly the size of a fingertip, could coat the surface of an office desk.
Kippelen hopes the Science paper will help open new doors for organic semiconductors.
“Advances like this will allow us to change the conventional wisdom that switching to organic materials that can lead to scalable devices would mean giving up performance,” he said. “We can’t anticipate all the new applications that could be enabled by this advance.”
In addition to those already mentioned, the research team included Larissa Diniz, Julia Lukens, Felipe A. Larrain, and Victor A. Rodriguez-Toro, all associated with Kippelen’s lab.
This research was supported by the Department of the Navy, Office of Naval Research Awards N00014-15 14-1-0580 and N00014-16-1-2520; through the MURI Center for Advanced Organic Photovoltaics (CAOP); by the Air Force Office of Scientific Research through Award No. FA9550-16-1-0168, the Department of Energy / National Nuclear Security Administration (NNSA) awards DE-NA0002576 through the Consortium for Nonproliferation Enabling Capabilities (CNEC), and award DE-NA0003921 through the Consortium for Enabling Technologies and Innovation. Support also came from the Chilean National Commission for Scientific and Technological Research through the Doctoral Fellowship program ‘‘Becas Chile,’’ Grant 72150387; from the Colombian Administrative Department of Science, Technology, and Innovation through the program Fulbright-Colciencias; from the National Science Foundation through the Research Experiences for Undergraduates program; and from the Brazil Scientific Mobility Program through an Academic Training Opportunities grant.
CITATION: Canek Fuentes-Hernandez, et al., “Large-area low-noise flexible organic photodiodes for detecting faint visible light.” (Science 2020).
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]]>Looking like any other small vial of clear liquid, these programmable drugs would communicate directly with our biological systems, dynamically responding to the information flowing through our bodies to automatically deliver proper doses where and when they are needed. These future medicines might even live inside us throughout our lives, fighting infection, detecting cancer and other diseases, essentially becoming a therapeutic biological extension of ourselves.
We are years away from that, but the insights gained from research in Gabe Kwong’s lab are moving us closer with the development of ‘enzyme computers’ — engineered bio-circuits designed with biological components, with the capacity to expand and augment living functions.
“The long-term vision is this concept of programmable immunity,” said Kwong, associate professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University, who partnered with fellow researcher Brandon Holt on the paper, “Protease circuits for processing biological information,” published Oct. 6 in the journal Nature Communications. The research was sponsored by the National Institutes of Health.
The story of this paper begins two years ago when, Holt said, “our lab has a rich history of developing enzyme-based diagnostics; eventually we started thinking about these systems as computers, which led us to design simple logic gates, such as AND gates and OR gates. This project grew organically and we realized that there were other devices we can build, like comparators and analog-digital convertors. Eventually this led to the idea of taking an analog-to-digital converter and using that to digitize bacterial activity.”
Ultimately, they assembled cell-free bio-circuits that can combine with bacteria-infected blood, “with the basic idea that it would quantify the bacterial infection — the number of bacteria — then calculate and release a selective drug dose, essentially in real time,” said Holt, a Ph.D. student in Kwong’s Laboratory for Synthetic Immunity and lead author of the paper.
The researchers sought to construct bio-circuits that use protease activity to process biological information under a digital or analog framework (proteases are enzymes that break down proteins into smaller polypeptides and amino acids). The team built its analog-to-digital converter with a tiny device, made only of biological materials, that changed signals from bacteria into ones and zeroes. Then, the circuit used these numbers to choose the proper dosage of drugs needed to kill the bacteria without overdosing.
That’s the traditional approach — bio-circuits digitizing molecular signals, allowing operations to be carried out by Boolean logic. The second part of the team’s new paper takes a more nuanced approach, with a focus on analog circuits as opposed to digital. “We treat protease activity as multi-valued, signals between one and zero,” Holt said.
That multi-valued approach led to yet another idea, and ultimately to the bigger picture of analog bio-circuits.
“We got tempted by this idea of fuzzy logic, where you can think about what happens if there’s a signal between zero and one,” he added. “That’s more like an analog circuit. We were really inspired by this concept, so we decided to build analog bio-circuits with the same basic materials as before — proteases and peptides. And we were able to solve a mathematical oracle problem, Learning Parity with Noise.”
The ability to process information from the biomolecular environment with an analog framework is critical, according to Kwong.
“Fuzzy logic is interesting because biology doesn’t think in zeroes and ones,” he said. “Biology operates as a spectrum. So if you think about enzymatic activity, it’s never just on and off. It’s on, and the activity can be anywhere between zero and one. So the long term goal is to recognize that biology is not as simple as a digital electronic circuit. You actually need some capacity to work with analog signals.”
This work was funded by an NIH Director’s New Innovator Award (Award No. DP2HD091793) as well as an R01 from the NCI (GR10003709). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the NIH.
Competing interests: Gabe Kwong is co-founder of and consultant to Glympse Bio, which is developing products related to the research described in this paper. This study could affect his personal financial status. The terms of this arrangement have been reviewed and approved by Georgia Tech in accordance with its conflict of interest policies. Holt and Kwong are listed as inventors on a patent application pertaining to the results of the paper. The patent applicant is the Georgia Tech Research Corporation. The application 24 number is PCT/US19/051833. The patent is currently pending/published (publication no. WO 25 2020/061257). The biological analog-to-digital converter and the analog protease circuits are covered in the patent.
CITATION: Brandon Holt, Gabe Kwong. “Protease circuits for processing biological information.” (Nature Communications, 2020) (https://www.nature.com/articles/s41467-020-18840-8)
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]]>Conducted by researchers at the Georgia Institute of Technology using two pathogens similar to the novel coronavirus, the study found that ozone can inactivate viruses on items such as Tyvek gowns, polycarbonate face shields, goggles, and respirator masks without damaging them — as long as they don’t include stapled-on elastic straps. The study found that the consistency and effectiveness of the ozone treatment depended on maintaining relative humidity of at least 50% in chambers used for disinfection.
“Ozone is one of the friendliest and cleanest ways of deactivating viruses and killing most any pathogen,” said M.G. Finn, chair of Georgia Tech’s School of Chemistry and Biochemistry, who led the study. “It does not leave a residue; it’s easy to generate from atmospheric air, and it’s easy to use from an equipment perspective.”
Findings of the research are described in a paper posted to the medRxiv preprint server and will be submitted to a journal for peer review and publication. Ozone can be produced with inexpensive equipment by exposing oxygen in the atmosphere to ultraviolet light, or through an electrical discharge such as a spark.
During local and regional peaks in coronavirus infection, shortages of personal protective equipment (PPE) can force hospitals and other healthcare facilities to reuse PPE that was intended for a single use. Facilities have used ultraviolet light, vaporized hydrogen peroxide, heat, alcohol and other techniques to disinfect these items, but until recently, there had not been much interest in ozone disinfection, Finn said.
Ozone is widely used for disinfecting wastewater, purifying drinking water, sanitizing food items, and disinfecting certain types of equipment — even clothing. Ozone disinfection cabinets are commercially available, taking advantage of the oxidizing effects of the gas to kill bacteria and inactivate viruses.
“There was no reason to think it wouldn’t work, but we could find no examples of testing done on a variety of personal protective equipment,” Finn said. “We wanted to contribute to meeting the needs of hospitals and other healthcare organizations to show that this technique could work against pathogens similar to the coronavirus.”
Phil Santangelo, a virologist in the Wallace H. Coulter Department of Biomedical Engineering, recommended two respiratory viruses — influenza A and respiratory syncytial virus (RSV) – as surrogates for coronavirus. The two are known as “enveloped” viruses because, like coronavirus, they are surrounded by a lipid outer membrane. Influenza and RSV are less dangerous than the SARS-CoV-2 coronavirus, allowing the Georgia Tech researchers to study them without high-containment laboratory facilities.
Santangelo, Finn, and their team devised a test procedure in which solutions containing the two viruses were placed onto samples of the PPE materials under study. The solutions were allowed to dry before the samples were placed in a chamber into which ozone was introduced at varying concentrations as low as 20 parts per million. After treatment for different lengths of time, the researchers tested the PPE samples to determine whether or not any of the viruses on the treated surfaces could infect cells grown in the laboratory. The entire test procedure required about a day and a half.
“The protocol we set up reports very sensitively on whether or not the virus could reproduce, and we found that the ozone was very successful in rendering them harmless,” Finn said. “Oxidizing biological samples to a significant extent is enough to inactivate a virus. Either the genetic material or the outer shell of the virus would be damaged enough that it could no longer infect a host cell.”
Loren Williams, a professor in School of Chemistry and Biochemistry, introduced the research team to a manufacturer of ozone disinfection chambers, which allowed evaluation of the equipment using the test protocol. During the test, the researchers learned that having sufficient relative humidity in the chamber — at least 50% — was essential for rapidly inactivating the viruses in a consistent manner.
After subjecting face masks and respirators to ozone disinfection, the team worked with Associate Professor Nga Lee (Sally) Ng from the School of Chemical and Biomolecular Engineering and the School of Earth and Atmospheric Sciences to evaluate the filtration capabilities of the items. The ozone treatment didn’t appear to negatively affect the N-95 filtration material.
But it did damage the elastic materials used to hold the masks in place. While the elastic headbands could be removed from the masks during ozone disinfection, removing and replacing them on a large scale may make the treatment technique impractical. Otherwise, however, ozone may offer an alternative technique for disinfecting other types of PPE.
“Ozone would be a viable method for hospitals and other organizations to disinfect garments, goggles, and gloves,” Finn added. “It is inexpensive to produce, and we hope that by sharing information about what we’ve found, healthcare facilities will be able to consider it as an option, particularly in low-resource areas of the world.”
Beyond those already mentioned, the research involved Emmeline Blanchard from the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University; Justin Lawrence, Taekyu Joo, and Britney Schmidt from the Georgia Tech School of Earth and Atmospheric Sciences; Minghao Xu from the Georgia Tech School of Chemistry and Biochemistry; and Jeffrey Noble from the Parker Petit Institute for Bioengineering and Bioscience.
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]]>Fractionation of crude oil mixtures using heat-based distillation is a large-scale, energy-intensive process that accounts for nearly 1% of the world’s energy use: 1,100 terawatt-hours per year (TWh/yr), which is equivalent to the total energy consumed by the state of New York in a year. By substituting the low-energy membranes for certain steps in the distillation process, the new technology might one day allow implementation of a hybrid refining system that could help reduce carbon emissions and energy consumption significantly compared to traditional refining processes.
“Much in our modern lives comes from oil, so the separation of these molecules makes our modern civilization possible,” said M.G. Finn, professor and chair of Georgia Tech’s School of Chemistry and Biochemistry. Finn also holds the James A. Carlos Family Chair for Pediatric Technology. “The scale of the separation required to provide the products we use is incredibly large. This membrane technology could make a significant impact on global energy consumption and the resulting emissions of petroleum processing.”
Reported in the July 17 issue of the journal Science, the paper is believed to be the first report of a synthetic membrane specifically designed for the separation of crude oil and crude-oil fractions. Additional research and development will be needed to advance this technology to industrial scale.
Membrane technology is already widely used in such applications as seawater desalination, but the complexity of petroleum refining has until now limited the use of membranes. To overcome that challenge, the research team developed a novel spirocyclic polymer that was applied to a robust substrate to create membranes able to separate complex hydrocarbon mixtures through the application of pressure rather than heat.
Membranes separate molecules from mixtures according to differences such as size and shape. When molecules are very close in size, that separation becomes more challenging. Using a well-known process for making bonds between nitrogen and carbon atoms, the polymers were constructed by connecting building blocks having a kinked structure to create disordered materials with built-in void spaces.
The team was able to balance a variety of factors to create the right combination of solubility – to enable membranes to be formed by simple and scalable processing – and structural rigidity – to allow some small molecules to pass through more easily than others. Unexpectedly, the researchers found that the materials needed a small amount of structural flexibility to improve size discrimination, as well as the ability to be slightly “sticky” toward certain types of molecules that are found abundantly in crude oil.
After designing the novel polymers and achieving some success with a synthetic gasoline, jet fuel, and diesel fuel mixture, the team decided to try to separate a crude oil sample and discovered that the new membrane was quite effective at recovering gasoline and jet fuel from the complex mixture.
“We were initially trying to fractionate a mixture of molecules that were too similar,” said Ben McCool, a senior research associate at ExxonMobil and one of the paper’s coauthors. “When we took on a more complex feed, crude oil, we got fractionalization that looked like it could have come from a distillation column, indicating the concept’s great potential.”
The researchers worked collaboratively, with polymers designed and tested at Georgia Tech, then converted to 200-nanometer-thick films, and incorporated into membrane modules at Imperial using a roll-to-roll process. Samples were then tested at all three organizations, providing multi-lab confirmation of the membrane capabilities.
“We have the foundational experience of bringing organic solvent nanofiltration, a membrane technology becoming widely used in pharmaceuticals and chemicals industries, to market,” said Andrew Livingston, professor of chemical engineering at Imperial. “We worked extensively with ExxonMobil and Georgia Tech to demonstrate the scalability potential of this technology to the levels required by the petroleum industry.”
The research team created an innovation pipeline that extends from basic research all the way to technology that can be tested in real-world conditions.
“We brought together basic science and chemistry, applied membrane fabrication fundamentals, and engineering analysis of how membranes work,” said Ryan Lively, associate professor and John H. Woody faculty fellow in Georgia Tech’s School of Chemical and Biomolecular Engineering. “We were able to go from milligram-scale powders all the way to prototype membrane modules in commercial form factors that were challenged with real crude oil – it was fantastic to see this innovation pipeline in action.”
ExxonMobil’s relationship with Georgia Tech goes back nearly 15 years and has produced innovations in other separation technologies, including a new carbon-based molecular sieve membrane that could dramatically reduce the energy required to separate a class of hydrocarbon molecules known as alkyl aromatics.
“Through collaboration with strong academic institutions like Georgia Tech and Imperial, we are constantly working to develop the lower-emissions energy solutions of the future," said Vijay Swarup, vice president of research and development at ExxonMobil Research and Engineering Company.
In addition to Finn, Livingston, Lively, and McCool, the paper’s authors include Kirstie Thompson and Ronita Mathias, Georgia Tech graduate students who are co-first authors; Daeok Kim, Jihoon Kim, Irene Bechis, Andrew Tarzia, and Kim Jelfs of Imperial; and Neel Rangnekar, J.R. Johnson, and Scott Hoy of ExxonMobil.
CITATION: Kirstie Thompson, et al., “N-Aryl Linked Spirocyclic Polymers for Membrane Separations of Complex Hydrocarbon Mixtures” (Science 2020). https://science.sciencemag.org/content/369/6501/310
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]]>The professor at the Georgia Institute of Technology rallied colleagues and partners around the cause in March, and by early June, they had replaced a key component of hand sanitizer, created a new supply chain, and initiated their own donation of 7,000 gallons of a newly designed sanitizer to medical facilities.
Its name: Han-I-Size White & Gold, named for the colors of Georgia Tech. The new supply chain also may ensure that hand sanitizer producers across the country do not run out of the main active ingredient, alcohol, but the team’s path to success was a stony labyrinth.
“This project was on life support so many times because people did not understand how severe this shortage was going to be,” said Marder, a Regents Professor in Georgia Tech’s School of Chemistry and Biochemistry. “I called hospitals and institutions to assess the need and heard the same thing over and over: ‘No, we just got a delivery. We have no need. You’re wasting your time.’”
Marder was not. Contacts at major chemical suppliers of hand sanitizer ingredients said that a critical shortage of alcohol, particularly the one usually in hand sanitizer, isopropanol, was coming.
“Isopropanol plants in the U.S. were running at full capacity and still didn’t have enough. People were using pharmaceutical-grade ethanol now, too, but it was also in short supply. We weren’t going to have enough of either; I mean the whole United States was running low,” Marder said.
Marder hastily drafted Chris Luettgen, a professor of practice in Georgia Tech’s School of Chemical and Biomolecular Engineering, George White, interim vice president of Georgia Tech’s Office of Industry Collaboration, and Atif Dabdoub, a Georgia Tech alumnus and owner of a local chemical company, Unichem Technologies, Inc.
To the three chemists and the business professional, it seemed simple: Mix alcohol with water, peroxide, and the moisturizer glycerin then bottle and ship it. That bubble burst quickly.
Luettgen, who had worked in the consumer products industry for 25 years at Kimberly-Clark Corporation and knew how to take products to market, had to plow through constant unexpected supply chain barriers and bureaucracy while White forged connections between companies. Neither the supply chain nor the business relationships had existed before, and the teams’ phones stayed glued to their ears night and day as they created them from scratch.
“When I worked for Kimberly-Clark, getting a new product out would take the company nine to 18 months, and the three of us had to get this done in weeks. The demand was there, and people were getting sick in some cases from lack of sanitizing. We felt speed was necessary to meet the growing demand. Seth told me to push this across the goal line, and I put everything into it,” Luettgen said.
“Georgia Tech is about the power to convene. Companies and stakeholders are eager to come to the table here to make things happen,” White said about forging new business ties. “Not everyone has that incredible recognition as a problem solver with the brainpower amassed here.”
Purchasing truckloads of alcohol was priority one.
Boutique liquor distilleries in Georgia were already converting to sanitizer ethyl alcohol production, but output was nowhere near enough to meet demand. ExxonMobil connected the team with Eco-Energy, a company that handles fuel-grade ethanol as a gasoline additive.
“The amount of ethanol that’s made for fuel in the U.S. is 1,500 times the amount of the isopropanol made. They could drain off about 1 percent of what is used for fuel and double or triple the amount of alcohol available for hand sanitizer in this country. And the fuel companies wouldn’t even notice it was gone, especially since hardly anyone was driving anymore,” Marder said.
But then prospective hand sanitizer distributors crimped their noses at that ethanol, saying it smelled odd.
“I thought, ‘This has the makings of a screenplay.’ I asked the distributor if we could come over to smell a sample for ourselves,” White said. “It needed a little love.”
Eco-Fuels produced the highly refined ethanol and then processed it through carbon filtration to increase purity and reduce odor. Atlanta-based chemical manufacturer, Momar, Inc., oversaw production, packaging, and distribution of Han-I-Size White & Gold.
The Georgia Tech team garnered funding through a donation from insurer Aflac Incorporated allocated through the Global Center for Medical Innovation (GCMI), a Georgia Tech affiliated non-profit organization that guides new experimental medical solutions to market. Aflac’s gift of $2 million through GCMI has also expedited the development, production, and purchase of other PPE to donate to health care workers.
In addition, GCMI helped guide the hand sanitizer through regulatory processes and to market. In a another development, the U.S. Food and Drug Administration was also aware of the dire shortage of alcohol for sanitizer and issued waivers for the pandemic to allow for use of ethanol in sanitizers without having to meet usual specifications.
Arkema, Inc. donated hydrogen peroxide, which was delivered to PSG Functional Materials, which mixed and packaged the product then shipped with no delivery fee to Atlanta. Though water is ubiquitous, hand sanitizer requires purified water, and the Coca-Cola Company donated a tanker truck of it just when White was pondering desperate measures.
“If I have to get a truck to go pick up water and drive it, I’ll do it myself,” he said.
Finally, the first few hundred gallons of donated Han-I-Size White & Gold rolled into Piedmont Healthcare in Atlanta and Brightmoor Nursing Center in Griffin, Georgia, in the second week of June 2020.
GCMI is facilitating donations of the 7,000 gallons nationwide. Separate from the Aflac-financed donations, Momar will continue to manufacture the new hand sanitizing formula commercially to include in its regular product lineup, and Georgia Tech will be able to purchase it at a reduced rate to help protect researchers now returning to their labs.
The new supply chain, the first of its kind, of “waiver-grade” ethanol has given hand sanitizer producers across the country a new opportunity to re-supply America.
“Hopefully, we helped solved a national need,” Luettgen said.
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]]>Flow of lithium ions into and out of alloy battery anodes has long been a limiting factor in how much energy batteries could hold using conventional materials. Too much ion flow causes anode materials to swell and then shrink during charge-discharge cycles, causing mechanical degradation that shortens battery life. To address that issue, researchers have previously developed hollow “yolk-shell” nanoparticles that accommodate the volume change caused by ion flow, but fabricating them has been complex and costly.
Now, a research team has discovered that particles a thousand times smaller than the width of a human hair spontaneously form hollow structures during the charge-discharge cycle without changing size, allowing more ion flow without damaging the anodes. The research was reported June 1 in the journal Nature Nanotechnology.
“Intentionally engineering hollow nanomaterials has been done for a while now, and it is a promising approach for improving the lifetime and stability of batteries with high energy density,” said Matthew McDowell, assistant professor in the George W. Woodruff School of Mechanical Engineering and the School of Materials Science and Engineering at the Georgia Institute of Technology. “The problem has been that directly synthesizing these hollow nanostructures at the large scales needed for commercial applications is challenging and expensive. Our discovery could offer an easier, streamlined process that could lead to improved performance in a way that is similar to the intentionally engineered hollow structures.”
The researchers made their discovery using a high-resolution electron microscope that allowed them to directly visualize battery reactions as they occur at the nanoscale. “This is a tricky type of experiment, but if you are patient and do the experiments right, you can learn really important things about how the materials behave in batteries,” McDowell said.
The team, which included researchers from ETH Zürich and Oak Ridge National Laboratory, also used modeling to create a theoretical framework for understanding why the nanoparticles spontaneously hollow — instead of shrinking — during removal of lithium from the battery.
The ability to form and reversibly fill hollow particles during battery cycling occurs only in oxide-coated antimony nanocrystals that are less than approximately 30 nanometers in diameter. The research team found that the behavior arises from a resilient native oxide layer that allows for initial expansion during lithiation — flow of ions into the anode — but mechanically prevents shrinkage as antimony forms voids during the removal of ions, a process known as delithiation.
The finding was a bit of a surprise because earlier work on related materials had been performed on larger particles, which expand and shrink instead of forming hollow structures. “When we first observed the distinctive hollowing behavior, it was very exciting and we immediately knew this could have important implications for battery performance,” McDowell said.
Antimony is relatively expensive and not currently used in commercial battery electrodes. But McDowell believes the spontaneous hollowing may also occur in less costly related materials such as tin. Next steps would include testing other materials and mapping a pathway to commercial scale-up.
“It would be interesting to test other materials to see if they transform according to a similar hollowing mechanism,” he said. “This could expand the range of materials available for use in batteries. The small test batteries we fabricated showed promising charge-discharge performance, so we would like to evaluate the materials in larger batteries.”
Though they may be costly, the self-hollowing antimony nanocrystals have another interesting property: they could also be used in sodium-ion and potassium-ion batteries, emerging systems for which much more research must be done.
“This work advances our understanding of how this type of material evolves inside batteries,” McDowell said. “This information will be critical for implementing the material or related materials in the next generation of lithium-ion batteries, which will be able to store more energy and be just as durable as the batteries we have today.”
In addition to McDowell, the paper’s authors include Matthew Boebinger from Georgia Tech; Olesya Yarema, Maksym Yarema, and Vanessa Wood from the Department of Information Technology and Electrical Engineering at ETH Zürich , and Kinga Unocic and Raymond Unocic from the Center for Nanophase Materials Science at Oak Ridge National Laboratory.
This work was performed at the Georgia Tech Materials Characterization Facility and the Institute for Electronics and Nanotechnology, a member of the National Nanotechnology Coordinated Infrastructure, which is supported by the National Science Foundation (Grant ECCS-1542174). Support also came from the Department of Energy Office of Science Graduate Student Research Program for research performed at Oak Ridge National Laboratory. A portion of this research was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. Support was also provided by a Sloan Research Fellowship in Chemistry from the Alfred P. Sloan Foundation and by the Swiss National Science foundation via an Ambizione Fellowship (no. 161249). The content is solely the responsibility of the authors and does not necessarily represent the official views of the sponsoring organizations.
CITATION: Matthew G. Boebinger, et al., “Spontaneous and reversible hollowing of alloy anode nanocrystals for stable battery cycling” (Nature Nanotechnology, 2020). https://doi.org/10.1038/s41565-020-0690-9
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]]>The goal is to supply a broad initiative by the governor’s office involving multiple universities and partners to rapidly produce and administer more tests. At least 35 volunteers at Georgia Tech, while adhering to social distancing, are reorienting labs normally used for scientific discovery to do larger-scale production of biochemical components.
“We are inventing new ways of doing things like an electronic buddy system so people can be alone – but not alone – while they work in the lab. The technical part is actually the easiest. The logistics of testing, data security, and regulatory considerations – those things are more challenging,” said Loren Williams, a professor in Georgia Tech’s School of Chemistry and Biochemistry.
Williams and the researchers are supporting Georgia Governor Brian Kemp’s COVID-19 State Lab Surge Capacity Task Force, which is a project managed through the Georgia Tech Research Institute (GTRI). GTRI is also leading the coordination and integration of data management across the lab surge effort.
“We are providing technical and project management of the effort which is focused on increasing the state’s ability to expand testing beyond current limitations,” said Mike Shannon, GTRI’s lead in the project and a principal research engineer at GTRI.
The science behind coronavirus testing is complementary to the researchers’ usual work. That includes understanding proteins associated with glaucoma, figuring out how RNA and DNA evolved in the first place, or whether ribosomes – lumps of RNA and protein key to translating genetic code into life – may exist on exoplanets.
Williams’ research team studies the last topic, and some of their work is related to the core of coronavirus testing, a chemical reaction that amplifies the virus’ genetic fingerprint. It is called a reverse transcription polymerase chain reaction (RT-PCR), and it transcribes trace amounts of coronavirus’ RNA code into ample amounts of corresponding DNA in the lab for easy analysis.
“His lab members are very familiar with RT-PCR, and when the lack of tests became apparent, they swung into action. The group grew from there, based on the technical needs for the project,” said Raquel Lieberman, another leading scientist in the effort and also a professor in Georgia Tech’s School of Chemistry and Biochemistry.
“Every day, very talented, hardworking people with perfect skill sets come out of the woodwork and ask to help,” Williams said.
The group has teams that engineer the production of enzymes or other chemicals needed for RT-PCR to work: Two central enzymes are reverse transcriptase, which converts RNA to DNA and Taq polymerase, which rapidly replicates DNA. Another important component is ribonuclease inhibitor, which slows coronavirus RNA decay.
Other researchers develop processes for mass production or implementation of COVID-19 safety procedures; the list goes on. Some colleagues telework; others work in labs but spaced far from each other while they wear masks.
“The group is planning to produce enough enzyme components for hundreds of tests per day,” said Vinayah Agarwal, an assistant professor in Georgia Tech’s School of Chemistry and Biochemistry and School of Biological Sciences. “Using these components, we will also build cheaper and more robust testing kits going forward.”
Instructions already exist for some of the ingredients for the test, but they are not readily available because the rights to them are exclusive.
“Intellectual property and other proprietary issues hinder our effort,” Lieberman said. “But we have received help from scientists all over the world to piece together protocols on how to make what we need.”
The state wants to increase current testing capacities by 3,000 more tests per day. The task force also includes teams from Augusta University Health System, Georgia State University, Emory University, University of Georgia, and the Georgia Public Health Laboratory. The task force lead is Captain Kevin Caspary who is with the Georgia National Guard.
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]]>“Our expectation is that frontline healthcare workers interacting with COVID-19 patients will use certified PPE,” said Ryan Lively, an associate professor in Georgia Tech’s School of Chemical and Biomolecular Engineering. “But for situations that don’t involve intimate and prolonged interactions with COVID-19 infected individuals, we believe that DIY cloth face masks combined with proper social distancing etiquette will help slow the spread of this virus.”
While the underlying physics of filtration are complicated, Lively and colleagues believe that two or more layers of a tightly woven, knitted, or nonwoven fabric can provide at least a partial barrier to virus-containing droplets, which combined with social distancing, can reduce the likelihood of virus transmission.
“Equally, important though, is the way that users fit, wear, handle, and remove the face mask,” said Mark Losego, an assistant professor in Georgia Tech’s School of Materials Science and Engineering. “Because the mask will be touching your face, it and your hands should be clean before putting it on. The mask should be snug but not uncomfortable.”
Gaps around the nose and chin should be minimized. Once wearing the mask, you should avoid touching or moving the mask; don’t pull the mask down to cough or sneeze! The mask is expected to capture germs, so it should be removed by touching only the straps; otherwise, you will contaminate your hands.
Equally important to blocking virus-containing droplets is that the mask materials be breathable and non-hazardous for inhalation. “For example, there is some danger of glass fibers within HEPA or MERV filters being inhaled if appropriate blocking layers are not included,” said Lively. “Most apparel or home goods textiles are safe. However, if you smell a chemical odor from the material, you should probably avoid using it for a mask.”
Upon returning home from an errand, the mask should be discarded or thrown in the clothes washer and cleaned before being used again. If the fabric mask does get wet from another individual’s cough or sneeze, the mask should be removed quickly at a safe distance. The team recommends reviewing both the World Health Organization (WHO) link and Centers for Disease Control and Prevention (CDC) guidelines for mask wearing.
A new website (www.research.gatech.edu/rapid-response) has been created to bring together recommendations and templates for making face masks. The website provides guidance for making unsewn, sewn, glued, or 3D-printed face masks.
The recommendations resulted from consulting with a team of experts in materials, chemical and mechanical engineering, filtration processes, and production design. “We have also interacted with relevant stakeholders, including hospitals and manufacturers, and studied the peer-reviewed literature to make recommendations based on scientific evidence,” said Lively.
On the website, the researchers suggest alternatives for materials that are in short supply. For instance, high-performance HEPA furnace filters can be used with 3D printed masks to create a respirator, provided the HEPA filters are installed in between two blocking layers of nonwoven fabric. Reusable polypropylene grocery bags without a shiny film can be used as the droplet-repelling outer shell of the masks.
The new website includes directions, recommendations, files for 3D printers and more. The team is actively testing fabric materials to provide more specific recommendations for which fabrics to use and which to avoid. A rudimentary DIY test using a water spray bottle is described to make an initial assessment of how suitable a fabric is for a mask.
Masks produced or tested with directions from the site do not meet the standards of federal agencies such as NIOSH, OSHA or the FDA.
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]]>Now researchers at the Georgia Institute of Technology have developed a new method that could one day replace conventional pressure treating as a way to make lumber not only fungal-resistant but also nearly impervious to water – and more thermally insulating.
The new method, which was reported February 13 in the journal Langmuir and jointly sponsored by the Department of Defense, the Gulf Research Program, and the Westendorf Undergraduate Research Fund, involves applying a protective coating of metal oxide that is only a few atoms thick throughout the entire cellular structure of the wood.
This process, known as atomic layer deposition, is already frequently used in manufacturing microelectronics for computers and cell phones but now is being explored for new applications in commodity products such as wood. Like pressure treatments, the process is performed in an airtight chamber, but in this case the chamber is at low pressures to help the gas molecules permeate the entire wood structure.
“It was really important that this coating be applied throughout the interior of the wood and not just on the surface,” said Mark Losego, an assistant professor in the School of Materials Science and Engineering. “Wood has pores that are about the width of a human hair or a little smaller, and we used these holes as our pathways for the gases to travel throughout the wood’s structure.”
As the gas molecules travel down those pathways, they react with the pore’s surfaces to deposit a conformal, atomic-scale coating of metal oxide throughout the interior of the wood. The result is wood that sheds water off its surface and resists absorbing water even when submerged.
In their experiments, the researchers took finished pine 2x4s and cut them into one-inch pieces. They then tested infusing the lumber with three different kinds of metal oxides: titanium oxide, aluminum oxide and zinc oxide. With each, they compared the water absorption after holding the lumber under water for a period of time. Of the three, titanium oxide performed the best by helping the wood absorb the least amount of water. By comparison, untreated lumber absorbed three times as much water.
“Of the three chemistries that we tried, titanium oxide proved the most effective at creating the hydrophobic barrier,” said Shawn Gregory, a graduate student at Georgia Tech and lead author on the paper. “We hypothesize that this is likely because of how the precursor chemicals for titanium dioxide react less readily with the pore surfaces and therefore have an easier time penetrating deep within the pores of the wood.”
Losego said that the same phenomena exist in atomic layer deposition processes used for microelectronic devices.
“These same titanium oxide precursor chemistries are known to better penetrate and conformally coat complex nanostructures in microelectronics just like we see in the wood,” Losego said. “These commonalities in understanding fundamental physical phenomena – even in what appear to be very different systems – is what makes science so elegant and powerful.”
In addition to being hydrophobic, lumber treated with the new vapor process also resists the mold that eventually leads to rot.
“Interestingly, when we left these blocks sit in a humid environment for several months, we noticed that the titanium oxide treated blocks were much more resistant to mold growth than the untreated lumber,” Gregory added. “We suspect that this has something to do with its hydrophobic nature, although there could be other chemical effects associated with the new treatment process that could also be responsible. That’s something we would want to investigate in future research.”
Yet another benefit of the new process: vapor-treated wood was far less thermally conductive compared to untreated wood.
“A lot of attention is paid in home building to insulating the cavities between the structural components of a home, but a massive amount of the thermal losses are caused by the wood studs themselves,” said Shannon Yee, an associate professor in the George W. Woodruff School of Mechanical Engineering and a co-author on the paper with expertise in thermal systems. “Lumber treated with this new process can be up to 30 percent less conductive, which could translate to a savings of as much as 2 million BTUs of energy per dwelling per year."
This material is based upon work supported by the Office of Naval Research through grant No. N00014-19-1-2162, the Department of Defense through the National Defense Science & Engineering Graduate Fellowship Program, the Gulf Research Program managed by the National Academies, and a donation from Roxanne Westendorf. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsoring agencies.
CITATION: Shawn A. Gregory, Connor P. McGettigan, Emily K. McGuinness, David Misha Rodin, Shannon K. Yee, and Mark D. Losego, “Single-Cycle Atomic Layer Deposition (1cy-ALD) on Bulk Wood Lumber for Managing Moisture Content, Mold Growth, and Thermal Conductivity,” (Langmuir, February 2020). http://dx.doi.org/10.1021/acs.langmuir.9b03273
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]]>Meredith, who earned his undergraduate degree at Georgia Tech (B.S., chemical engineering), has been on the ChBE faculty since 2000. He also served as the school’s associate chair for graduate studies between 2012-2019.
“Carson and his research team have pioneered the use of sustainable technologies for a variety of important applications,” said Raheem Beyah, Georgia Tech’s Vice President for Interdisciplinary Research. “We are pleased that he will be leading our Renewable Bioproducts Institute as it develops new products, processes and technologies for industries that include paper and packaging, biochemicals and fuels, and bio-composites and nanocellulose.”
Meredith’s lab researches the surfaces and interfaces of advanced materials, emphasizing renewable components, sustainable processing, and bioinspired designs in adhesives, composites, foams, and coatings, among other things. Borrowing their ideas from nature, Meredith and his team are addressing the needs of human societies through food security, renewables, and energy efficiency, utilizing natural materials.
“We’ve focused on using cellulose nanomaterials to make alternatives to conventional plastic for all kinds of things, including high performance food packaging that prevents spoilage, and we’re looking at ways in which we can replace some plastics used in paints and coatings,” said Meredith, who has been an RBI investigator for 10 years.
“Society is demanding alternatives to plastics that accumulate in the environment, and I’m excited that RBI is positioned to offer solutions,” he added. “There’s a tremendous amount of energy coming from industry to develop new bioproducts.”
After earning his undergraduate degree from Georgia Tech, Meredith earned a Ph.D. in chemical engineering from the University of Texas at Austin and served as a postdoctoral researcher at the National Institutes of Standards and Technology (NIST) before returning to Georgia Tech as a faculty member.
RBI, comprised of 50 faculty researchers from six colleges and research centers across Georgia Tech, began as the Institute of Paper Chemistry in 1929 in Wisconsin. Moving to Georgia Tech 60 years later as the Institute for Paper Science and Technology, it was renamed the Renewable Bioproducts Institute in 2014, buoyed by a $43.6 million gift from the Institute of Paper Chemistry Foundation (IPCF), which supports the institute’s expanded aim of research to unlock the potential of biomass material for a wide range of products.
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]]>Plans for the device, known as the ElectroPen, are being made available, along with the files necessary for creating a 3D-printed casing.
“Our goal with the ElectroPen was to make it possible for high schools, budget-conscious laboratories, and even those working in remote locations without access to electricity to perform experiments or processes involving electroporation,” said M. Saad Bhamla, an assistant professor in Georgia Tech’s School of Chemical and Biomolecular Engineering. “This is another example of looking for ways to bypass economic limitations to advance scientific research by putting this capability into the hands of many more scientists and aspiring scientists.”
In a study reported January 10 in the journal PLOS Biology and sponsored by the National Science Foundation and the National Institutes of Health, the researchers detail the method for constructing the ElectroPen, which is capable of generating short bursts of more than 2,000 volts needed for a wide range of laboratory tasks.
One of the primary jobs of a cell membrane is to serve as a protective border, sheltering the inner workings of a living cell from the outside environment.
But all it takes is a brief jolt of electricity for that membrane to temporarily open and allow foreign molecules to flow in — a process called electroporation, which has been used for decades in molecular biology labs for tasks ranging from bacterial detection to genetic engineering.
Despite how commonplace the practice has become, the high cost of electroporators and their reliance on a source of electricity have kept the technique mostly within the confines of academic or professional labs. Bhamla and undergraduate student Gaurav Byagathvalli set out to change that, with help from collaborators Soham Sinha, Yan Zhang, Assistant Professor Mark Styczynski, and Lambert High School teacher Janet Standeven.
"Once we decided to tackle this issue, we began to explore the inner workings of electroporators to understand why they are so bulky and expensive,” said Byagathvalli. “Since their conception in the early 1980s, electroporators have not had significant changes in design, sparking the question of whether we could achieve the same output at a fraction of the cost. When we identified a lighter that could produce these high voltages through piezoelectricity, we were excited to uncover new mysteries behind this common tool."
In addition to the piezoelectric lighter crystal – which generates current when pressure is applied to it – the other parts in the device include copper-plated wire, heat-shrinking wire insulator, and aluminum tape. To hold it all together, the researchers designed a 3D-printed casing that also serves as its activator. With all the parts on hand, the device can be assembled in 15 minutes, the researchers reported.
While the ElectroPen is not designed to replace a lab-grade electroporator, which costs thousands of dollars and is capable of processing a broad range of cell mixtures, the device is still highly capable of performing tasks when high volumes are not required.
The researchers tested several different lighter crystals to find ones that produced a consistent voltage using a spring-based mechanism. To understand more about how the lighters function, the team used a high-speed camera at 1,057 frames per second to view device mechanics in slow motion.
“One of the fundamental reasons this device works is that the piezoelectric crystal produces a consistently high voltage, independent of the amount of force applied by the user,” Bhamla said. “Our experiments showed that the hammer in these lighters is able to achieve acceleration of 3,000 G’s, which explains why it is capable of generating such a high burst of voltage.”
To test its capabilities, the researchers used the device on samples of E. coli to add a chemical that makes the bacterial cells fluorescent under special lights, illuminating the cell parts and making them easier to identify. Similar techniques could be used in a lab or in remote field operations to detect the presence of bacteria or other cells.
The team also evaluated whether the device was easy to use, shipping the assembled ElectroPens to students at other universities and high schools.
“The research teams were able to successfully obtain the same fluorescence expression, which I think validates how easily these devices can be disseminated and adopted by students across the globe,” Bhamla said.
To that end, the researchers have made available the plans for how to build the device, along with digital files to be used by a 3D printer to fabricate the casing and actuator. Next steps of the research include testing a broader range of lighters looking for consistent voltages across a wider range, with the goal of creating ElectroPens of varying voltages.
This research was supported by the National Science Foundation (NSF) under grant No. 1817334, the Mindlin Foundation under grant No. MF19-1T1P03, and the National Institutes of Health (NIH) under grant No. R01-EB022592. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsoring organizations.
CITATION: Gaurav Byagathvalli, Soham Sinha, Yan Zhang, Mark P. Styczynski, Janet Standeven, and M. Saad Bhamla, “ElectroPen: An ultralow-cost electricity-free, portable electroporator.” (PLOS Biology, January 2020) https://doi.org/10.1371/journal.pbio.3000589
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]]>Polymer brushes are surfaces normally covered with nanoscale bristles made of polymers, spaghetti-like molecular chains that are synthesized chemically. But in a new study, a team led by researchers at the Georgia Institute of Technology stumbled onto a biological technique to improve on the brushes by growing the bristles into giants 100 times the usual length.
“We were putting the enzyme onto a surface to observe it for a totally different experiment, but we put too much on the surface too densely, and – boom – we ended up with the thickest, longest polymer brush we’d ever seen or heard of,” said Jennifer Curtis, who led the study and is an associate professor in Georgia Tech’s School of Physics. “They were so big you could actually see them under an optical microscope instead of having to feel them with an atomic force microscope or use other methods needed for more customary polymer brushes.”
The researchers diverted attention from the original study to pursue the freakishly large new brush.
To bacteria encroaching on them, the brush’s bristles are a virtually impenetrable, squishy thicket that keeps microbes out in lab observations. It hinders the spread of biofilms, bacterial colonies that join together to form a tough material that makes killing the bacteria difficult.
“The human immune system has a hard time with biofilms. Antibiotics don’t work very well on them either. In water filtration, biofilms can stick tenaciously, too. If you have a hyaluronan brush on a surface, a biofilm can’t stick to it,” Curtis said.
Hyaluronan, the compound in the bristles, is a polysaccharide, a chain of sugar molecules, and is naturally widespread in and around our cells. It is also known to many from its use in cosmetic moisturizers.
The enzyme that makes the hyaluronan bristles on the brush is hyaluronan synthase, and it circumvents more tedious chemical synthesis by effortlessly extruding extremely long bristles. The enzymes also can replace bristles when they break off, something chemically synthesized brushes cannot do, which limits those brushes’ durability. Still, use of the synthase is unorthodox.
“Brush people say, ‘What are these enzymes doing here?’ because they’re looking for chemistry, and biologists wonder what the brush has to do with biology,” Curtis said.
The team published the new study, Self-regenerating giant hyaluronan polymer brushes, in the journal Nature Communications in December 2019. The research was funded by the National Science Foundation.
The researchers engineered bacteria to overabundantly produce the enzyme by inserting hyaluronan synthase genes from the bacteria Streptococcus equisimilis into E. coli then they harvested the enzyme.
“We shattered the bacteria into a bunch of non-living gooey fragments then adhered their membrane to surfaces, and the synthase extruded the brushes,” Curtis said.
The enzymes can be switched on and off, and adjusting salt concentration or pH in the solution around the brushes makes the bristles extend to a straight form or curl up into a retracted form. Functional additives like antibacterials could be embedded in brushes.
Something like a catheter could conceivably one day be coated with brushes to remain bacteria-free, and the thickness of the wiggly brushes would also act as a lubricant by preventing frictive contact with the surface beneath them. Some human cells key to the healing process are actually able to sink through the bristles, which could have potential for medicine.
“For a chronic wound that won’t heal, you may be able to design a bandage that encourages new cell growth but keeps bacteria out,” Curtis said.
The researchers’ fortuitous detour into the giant brush has expanded possibilities for their original intent of studying enzymatic hyaluronan in isolation.
“We constantly deal with the coupling of biochemistry, chemical signaling, and mechanics, so having something that isolates the mechanics from the signaling so we can focus on just the mechanics is really useful,” Curtis said.
Wenbin Wei and Jessica Faubel of Georgia Tech were the study’s first authors. These researchers co-authored the study: Hemaa Selvakumar, Daniel T. Kovari, Joanna Tsao, Amar T. Mohabir, Michelle Krecker, and Michael A. Filler from Georgia Tech; Felipe Rivas, Elaheh Rahbar, and Adam Hall from the Virginia Tech-Wake Forest University School of Biomedical Engineering and Sciences; and Jennifer Washburn and Paul Weigel from the University of Oklahoma. The research was funded by the National Science Foundation (grants #0955811, 1709897 and 1205878). Any findings, conclusions, and recommendations are those of the authors and not necessarily of the National Science Foundation.
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The new partnership aims to advance techniques to process, measure and analyze cell, gene, tissue-engineered, and regenerative medicine products, as well as cell-based drug discovery products.
“We are poised to make a significant impact in how cells and regenerative medicine products are manufactured across the world through this new strategic partnership,” said Krishnendu Roy, Robert A. Milton Chair and professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University.
Roy will serve as one of the Charter Board Members for the new International Standards Coordinating Body (SCB), which was recently established in coordination with National Institute of Standards and Technology (NIST) and Alliance for Regenerative Medicine (ARM).
“Georgia Tech has already taken a leadership role in development of best practices and analytical standards that will impact biomanufacturing and innovation through the national roadmap on cell manufacturing developed by the National Cell Manufacturing Consortium (NCMC) and the newly established Marcus Center for Therapeutic Cell Characterization and Manufacturing (MC3M),” Roy said.
Compared to traditional pharmaceuticals, which are made primarily through chemical processes, biological medicines, also known as biopharmaceuticals, are much more challenging to produce. With medicines like cell-therapies, gene therapies and engineered tissues, finding ways to produce larger quantities at a time while ensuring high-quality and safety is a key challenge.
“The SCB’s long-term mission is to efficiently and effectively support sector standards development to accelerate product development and scalability, and streamline regulatory submission review and approval,” said Robert A. Preti, chairman of ARM and president of cell manufacturing industry partner PCT, a Caladrius Company.
The new standards initiative comes on the heels of the establishment of two National Manufacturing Innovation Institutes announced last December. One, the Institutes for Innovation in Manufacturing Biopharmaceuticals (NIIMBL), which the U.S. Department of Commerce is supporting with a five-year, $70 million grant is a consortium of more than 150 companies, academic institutions and other organizations focused towards working on improving the way biopharmaceuticals are produced, with a goal of bringing down costs and finding ways to get the drugs into the hands of clinicians and patients faster. The second, Advanced Regenerative Manufacturing Institute (ARMI) is funded by the Department of Defense and focuses on biofabrication of engineered tissues as replacement of damaged and diseases organs as well as for therapeutics development. Georgia Tech is poised to play key roles in these initiatives as well.
These synergistic national and international activities further establish Georgia Tech as a leading academic institution in the biopharmaceutical area, Roy said. In January 2016, Georgia Tech announced the Marcus Center as a research center devoted to developing processes and techniques to manufacture living cells. The center was made possible by a $15.7 million grant from the Atlanta-based Marcus Foundation. This center intends to work closely with NIIMBL and ARMI to further leverage these unique private-public partnerships and develop transformative technologies to bring cell-based therapies and regenerative medicines to clinic faster and at a lower cost.
]]>Research News
]]>Metals from brakes and other automotive systems are emitted into the air as fine particles, lingering over busy roadways. Now, researchers at Georgia Institute of Technology have shown how that cloud of tiny metal particles could wreak havoc on respiratory health.
In a study published January 31 in the journal Environmental Science & Technology, the researchers described how vehicle-emitted metals such as copper, iron and manganese interact with acidic sulfate-rich particles already in the air to produce a toxic aerosol.
“There’s a chain reaction happening in the air above busy highways,” said Rodney Weber, a professor in Georgia Tech’s School of Earth & Atmospheric Sciences. “Acidic sulfate in the atmosphere comes into contact with those metals emitted from traffic and changes their solubility, making them more likely to cause oxidative stress when inhaled.”
The study, which was sponsored by the National Science Foundation and the U.S. Environmental Protection Agency, showed how the metals are emitted mainly in an insoluble form but slowly become soluble after mixing with sulfate.
“Sulfate has long been associated with adverse health impacts,” said Athanasios Nenes, a professor and Georgia Power Scholar in the School of Earth & Atmospheric Sciences and the School of Chemical & Biomolecular Engineering. “The old hypothesis was that the acidic sulfate burns your lung lining, which in turn leads the bad health effects. But there is not enough acid in the air alone to really have that impact.”
But sulfate plays a key role in making metals soluble before they are inhaled, which could explain the association of sulfate with adverse health impacts, the researchers said.
The researchers collected samples of ambient particulate matter in two locations in Atlanta – one near a major interstate highway and another urban site 420 meters away from the roadway. They analyzed the chemical content, size distribution and acidity of the samples.
A significant amount of the ambient sulfate found was similar in size to the metal particles, suggesting that the ambient sulfate and metals were mixed within individual particles, which over hours or days would allow the acidic sulfate to convert the metal into a soluble form.
To quantify just how dangerous the aerosol could be, the researchers developed a high throughput analytical system for a chemical assay – called oxidative potential – that simulates the toxic response that such a mix would have on cellular organisms. This instrument was used to generate large data sets on ambient aerosol oxidative potential, which when utilized in an earlier epidemiological study, researchers at Georgia Tech and Emory University found that the chemical assay was statistically associated with hospital admissions in Atlanta for asthma and wheezing.
In the new study, the researchers observed that the peak toxicity indicated by the assay was closely correlated to those particles that contained the largest amount of soluble metals, which occurred only when metallic particles mixed with highly acidic sulfate.
“That’s the smoking gun,” Nenes said. “The sulfate essentially dissolves those metals; when you breathe in those particles, the metals could be absorbed directly into the blood stream and cause problems throughout the body. For the first time, a mechanism emerges to explain why small amounts of acidic sulfate can adversely affect health.”
While the sample taken from the testing site located farther away from the highway had less particulate metal, there was still enough to cause an increase in the oxidative potential, showing that roadway pollution could travel through the air and potentially cause problems in surrounding areas as well.
Dust from brakes and tires isn’t the only source of metals in the air. Incinerators and other forms of combustion also produce mineral dust and metallic particles, which could mix with sulfate to trigger a similar reaction.
The researchers noted that while the amount of particulate sulfate in the southeastern United States has decreased during the past 15 years as sulfur dioxide emissions from power plants have fallen, there’s still enough acidic sulfate in the air to keep the pH of particles very low, in the range of 0 to 2, transforming insoluble ambient metals to a soluble form.
“Vehicle tailpipe emissions are going down, but these kinds of emissions from braking will remain to some extent, even if you drive an electric car,” Weber said. “Therefore, this kind of process will continue to play out in the future and will be an important consideration when we look at the health effects of particulate matter.”
This material is based upon work supported by the National Science Foundation under Grant No. 1360730 and the U.S. Environmental Protection Agency under Grant No. RD834799. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation or the U.S. Environmental Protection Agency.
CITATION: Ting Fang, Hongyu Guo, Linghan Zeng, Vishal Verma, Athanasios Nenes and Rodney J. Weber, “Highly acidic ambient particles, soluble metals and oxidative potential: A link between sulfate and aerosol toxicity,” (Environmental Science & Technology, 2017). http://dx.doi.org/10.1021/acs.est.6b06151.
]]>Research News
]]>The $2 million award from the U.S. Food and Drug Administration (FDA) focuses on finding ways to apply continuous manufacturing methods to beta-lactam antibiotics, a class of drugs that includes widely-used antibiotics such as amoxicillin.
“These infection-fighting antibiotics are critically important for the healthcare system, and our goal is to make these medications easier and more cost-effective to produce,” said Andreas Bommarius, a professor in the School of Chemical and Biomolecular Engineering, one of the researchers leading the project.
Georgia Tech was one of three research institutions chosen by the FDA to explore how to translate manufacturing techniques already in use in food and chemical production to making certain antibiotics that now are often imported into the United States.
The Georgia Tech team will focus on the early stages of drug synthesis, while Massachusetts Institute of Technology and Rutgers University will address later stages of the manufacturing process.
“Continuous manufacturing utilizes technologies that offer clear benefits for both patients and industry,” FDA Commissioner Scott Gottlieb said when announcing the awards.
“The approach has the potential to shorten production times and improve the efficiency of manufacturing processes. These benefits translate to lower cost of production and thus the cost of medicine.”
Traditionally, the pharmaceutical industry has relied on batch manufacturing for medicine production. With continuous manufacturing, costs associated with starting up and shutting down production are reduced due to the continuous nature of the manufacturing approach. Other potential advantages includes faster ramp-up production during times of shortages and more consistent product quality.
During the project, researchers at Georgia Tech will develop a process to continuously synthesize, crystalize and isolate both cephalexin and amoxicillin, which are examples of two major types of beta-lactam antibiotics.
“Our design is intended to enable beta-lactam active pharmaceutical ingredient production in dedicated, compact, less capital-intensive plants, which in turn is envisioned to lead to better access to medicines for patients and ultimately to less expensive drugs,” Bommarius said.
The new FDA-backed project is among several initiatives at Georgia Tech involving research into ways of bringing down the cost of producing medications. Other projects included a federally-backed initiative to advance medications made from cells, such as vaccines and autoimmune drugs, as well as therapies using living cells to treat a range of conditions.
A separate initiative is aimed at advancing technologies for manufacturing therapeutic cells. Researchers at Georgia Tech were also recently awarded a three-year, $1.8 million grant from the U.S. Food and Drug Administration to develop a scalable manufacturing system for cord-tissue derived cells.
]]>Read More: Want to Beat Antibiotic-Resistant Superbugs? Rethink Strep Throat Remedies
Research News
]]>In a bid to reduce the amount of energy used in chemical separations, researchers at the Georgia Institute of Technology are working on membranes that could separate chemicals without using energy-intensive distillation processes.
“The vast majority of separations out in the field in a variety of industries are thermally-driven systems such as distillation, and because of that we spend an inordinate amount of energy on these separation processes – something like 10 to 15 percent of the global energy budget is spent on chemical separations,” said Ryan Lively, an associate professor in Georgia Tech’s School of Chemical & Biomolecular Engineering. “Separations that avoid the use of heat and a chemical phase-change are much less energy intense. In practice, using them could produce a 90 percent reduction in energy cost.”
Plastic membranes are already able to separate certain molecules based on size and other differences, such as in seawater desalination. But until now, most membranes have been unable to withstand harsh solvent-rich chemical streams while also performing challenging separation tasks.
In a study published July 18 in Chemistry of Materials and sponsored by the Department of Defense and the National Science Foundation, the researchers outline a process for taking a polymer-based membrane and infusing it with a metal oxide network. The resulting membrane is far more effective at standing up to harsh chemicals without degrading.
“After placing the pre-fabricated membrane inside of our reactor, we simply expose it to metal-containing vapors that infuse themselves inside the membrane material,” said Mark Losego, an assistant professor in the School of Materials Science and Engineering. “This process is called vapor phase infiltration, and it creates a uniform network of metal oxide throughout the polymer membrane. We call it a ‘hybrid’ membrane.”
Not only was the hybrid membrane better able to withstand solvents, its chemical separation capabilities also improved.
“Some chemicals that need to be separated are very similar in terms of their size, shape and other properties, which makes them even harder to process using membranes,” Lively said. “These new hybrid membrane are much more selective. They can separate chemicals that are more similar to each other.”
The research team, which included graduate students Fengyi Zhang, Emily McGuinness and Yao Ma, tested the new hybrid membranes in harsh chemicals such as tetrahydrofuran, dichloromethane and chloroform, organic solvents that dissolve the pure polymer membrane in minutes. The hybrid membranes remained stable for several months during testing.
The researchers also tested separating two chemicals very close in size. The hybrid membranes were able to differentiate aromatic molecules that differed in size by as little as 0.2 nanometers.
“One of the most exciting things about this work was how straightforward this process is from a manufacturing perspective,” Losego said. “We’re essentially taking pre-made membranes and applying a treatment to them. That’s something that would be very simple to translate to an industrial scale.”
Future research on the membranes will involve looking at how to fine tune the oxide infusions and make new types of hybrid membranes capable of separating a variety of other chemicals.
This material is based upon work supported by the Department of Defense through the National Defense Science & Engineering Graduate Fellowship Program and the National Science Foundation under grant Nos. CBET 1653153 and ECCS-1542174. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsoring agencies.
CITATION: Emily K. McGuinness, Fengyi Zhang, Yao Ma, Ryan P. Lively and Mark D. Losego, “Vapor Phase Infiltration of Metal Oxides into Nanoporous Polymers for Organic Solvent Separation Membranes,” (Chemistry of Materials, July 2019). http://dx.doi.org/10.1021/acs.chemmater.9b01141
]]>Research News
]]>The research team devised a way to create silica-based hollow spheres around 200 nanometers in size, each with one small hole in the surface that could enable the spheres to encapsulate a wide range of payloads to be released later at certain temperatures only.
In the study, which was published on June 4 in the journal Angewandte Chemie International Edition, the researchers describe packing the spheres with a mixture of fatty acids, a near-infrared dye, and an anticancer drug. The fatty acids remain solid at human body temperature but melt a few degrees above. When an infrared laser is absorbed by the dye, the fatty acids will be quickly melted to release the therapeutic drug.
“This new method could allow infusion therapies to target specific parts of the body and potentially negating certain side effects because the medicine is released only where there’s an elevated temperature,” said Younan Xia, professor and Brock Family Chair in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University. “The rest of the drug remains encapsulated by the solid fatty acids inside the bottles, which are biocompatible and biodegradable.”
The researchers also showed that the size of the hole could be changed, enabling nanocapsules that release their payloads at different rates.
“This approach holds great promise for medical applications that require drugs to be released in a controlled fashion and has advantages over other methods of controlled drug release,” Xia said.
An earlier method for achieving controlled drug release involves loading the temperature-sensitive material into low-density lipoproteins, which is often referred to as “bad cholesterol.” Another method involves loading the mixture into gold nanocages. Both have disadvantages in how the material used to encapsulate the drugs interact with the body, according to the study.
To make the silica-based bottles, the research team started by fabricating spheres out of polystyrene with a small gold nanoparticle embedded in its surface. The spheres are then coated with a silica-based material everywhere except where the gold nanoparticle is embedded. Once the gold and polystyrene are removed, only a hollow silica sphere with a small opening remains. To adjust the size of the opening, the researchers simply changed the size of the gold nanoparticle.
The process to load the bottles with their payload involves soaking the spheres in a solution containing the mixture, removing the trapped air, then washing away the excess material and payload with water. The resulting nanocapsules contain an even mixture of the temperature-sensitive material, the therapeutic drug, and the dye.
To test the release mechanism, the researchers then put the nanocapsules in water and used a near-infrared laser to heat the dye while tracking the concentration of the released therapeutic. The test confirmed that without the use of the laser, the medicine remains encapsulated. After several minutes of heating, concentrations of the therapeutic rose in the water.
“This controlled release system enables us to deal with the adverse impacts associated with most chemotherapeutics by only releasing the drug at a dosage above the toxic level inside the diseased site,” said Jichuan Qiu, a postdoctoral fellow in the Xia group.
This research was supported by the National Science Foundation under grant No. ECCS-1542174 through the National Nanotechnology Coordinated Infrastructure. The work was also supported by the China Scholarship Council through a graduate student fellowship. The content is the responsibility of the authors and does not necessarily represent the official views of the sponsoring agencies.
CITATION: Jichuan Qiu, Da Huo, Jiajia Xue, Guanghui Zhu, Hong Lui, and Younan Xia, “Encapsulation of a Phase-Change Material in Nanocapsules with a Well-Defined Hole in the Wall for the Controlled Release of Drugs,” (Angewandte Chemie International Edition, July 2019). http://dx.doi.org/10.1002/anie.201904549
]]>Research News
]]>A $1.7 million award from the National Science Foundation (NSF) will help a team at the Georgia Institute of Technology develop much cheaper ways to separate chemicals using membranes that could potentially replace energy-intensive distillation processes.
“Membranes have the potential to reduce energy consumption in chemical separation processes by as much as 90%,” said Mark Losego, an assistant professor in the School of Materials Science and Engineering, and the principal investigator for the project. “But most of today’s mass-manufactured membrane materials degrade under the chemical conditions required for many important chemical separations.”
Recently, Losego’s research team in collaboration with Ryan Lively, an associate professor in Georgia Tech’s School of Chemical and Biomolecular Engineering and co-PI on the project, described a new process for taking a polymer-based membrane and infusing it with a metal oxide network. The resulting membrane is far more effective at standing up to harsh chemicals without degrading.
“Plastic membranes are easy to mass manufacture, but they tend to dissolve when used with harsh chemicals, while inorganic membranes are more stable but are difficult to produce in large quantities,” Losego said. “This new process creates a membrane with the best characteristics of both types of materials, one that we call a hybrid membrane.”
The new process involves placing a prefabricated plastic membrane inside a reactor, which exposes the membrane to metal-containing vapors that infuse inside the material. This process is called vapor phase infiltration, and it creates a uniform network of metal oxide throughout the polymer membrane.
The new grant will enable researchers to use computer simulations and data analytics to speed up the process of finding new ways to infuse inorganic materials into polymer-based membranes, with the goal of developing a range of new membranes that could be used for a variety of separation tasks.
“Atomic simulations and data-driven methods such as machine learning can significantly accelerate the design and discovery of new application-specific materials,” said Rampi Ramprasad, a professor in the School of Materials Science and Engineering and another co-PI on the project.
The machine learning process involves taking materials data that is already available and using powerful computers to automatically and progressively learn their strengths and weaknesses and how those materials might combine to form materials with new properties.
“These methods allow us to virtually screen thousands of new materials before they are made to provide guidance for the specific types of materials that should be made and tested,” Ramprasad said.
This new NSF program will combine data collected from experiments with computational simulations to accelerate the development of these hybrid membrane materials, enabling new separation processes that lower production costs and are more environmentally friendly.
This new project will be funded through the National Science Foundation’s Designing Materials to Revolutionize and Engineer our Future, Award 1921873. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.
]]>Research News
]]>Architected materials are comprised of micron and nanoscale structures like crossbeams, arches, domes, and spirals, much like the elements of a building’s architecture. Researchers from the California Institute of Technology, the Georgia Institute of Technology, and ETH Zurich have made an architected material that shifts the shapes of these structures.
When a slight current is applied, nanoscale beams thicken and bend into arches that increasingly bow as the current is boosted. The material maintains the new shape even when the current is off, and the shape can be changed back by reversing the current. Both are novel characteristics.
Most materials that are designed to change their internal structure require a persistent external stimulus to remain in the new form. The new nanomaterial deforms through an electrochemical silicon-lithium alloy reaction that holds its form without applied current.
The study’s authors describe the material and its variable properties in detail in a study published in the journal Nature on Sept. 12, 2019. The research was funded by the Office of Naval Research and the National Science Foundation.
“At the core of this accomplishment, you’re changing the geometry not by a little, which would be easy to do, but by a lot and variably, which is hard. And you’re doing it by electrochemistry that works the way a battery does,” said Claudio Di Leo, an assistant professor in the Daniel Guggenheim School of Aerospace Engineering at Georgia Tech.
Di Leo’s team modeled the architectures’ nanoscale mechanics, which are driven by lithium ions and silicon, for the research, which was led by Caltech materials science professor Julia Greer. Her lab then created the material using an innovative ultra-high-resolution 3D printing process called two-photon lithography and tested it.
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Architectures of this class of materials can be periodic – uniformly tiled or stitched like a lattice – or non-periodic, that is, a tailored knit that molds physical properties. They can also be applied creatively, as the study’s first author, Caltech graduate research assistant Xiaoxing Xia, demonstrated by working structural “defects” into the material. The defects formed Caltech’s logo when current was applied.
“The most intriguing part of this work to me is the critical role of defects in such dynamically responsive architected materials,” Xia said.
“I have always had a particular liking for defects, and this time Xiaoxing managed to first uncover the effect of different types of defects on these metamaterials and then used them to program a particular pattern that would emerge in response to electrochemical stimulus,” Greer said.
In the future, materials like this could make batteries and other energy storage devices lighter, safer, and more durable. Also, waves of phonons – special excitations in certain materials that help determine their conductivity – propagate through one architecture in the material, but then the shift in architecture blocks the waves. This was not the study’s main achievement, but still a promising feature and possible opportunity for expanded research.
Also READ: Nanohydrogel Delivers Healing Stem Cells to Injured Elderly Muscles
Coauthors include Caltech postdoctoral researcher Carlos Portela, as well as Arman Afshar of Georgia Tech, and Dennis M. Kochmann of ETH Zurich in Switzerland. The research was funded by the Vannevar-Bush Faculty Fellowship, the Office of Naval Research, and the National Science Foundation (grant CMMI-1825132). Any findings, conclusions or recommendations are those of the authors and not necessarily of the funding agencies.
CalTech media relations contact: Robert Perkins, rperkins@caltech.edu
Georgia Tech media relations contact: Ben Brumfield, ben.brumfield@comm.gatech.edu
]]>The protected Pacific reefs were populated by diverse corals and shimmered with colorful fish, said researchers who snorkeled off of Fiji to collect samples for the study. Oceanic ecologists from the Georgia Institute of Technology compared coral potions from these reefs, where fishing was prohibited, with those from heavily fished reefs, where seaweed inundated corals because few fish were left to eat it.
The medicated solutions, or potions, may contain a multitude of chemicals, and the researchers did not analyze their makeup. This is a possible next step, but here the researchers simply wanted to establish if the potions offered any real defense against pathogens and how warming and overfishing might weaken it.
“I thought I probably wouldn’t see antibiotic effects from these washes. I was surprised to see such strong effects, and I was surprised to see that reef protections made a difference,” said the study’s first author, Deanna Beatty.
“There is a lot of argument now about whether local management can help in the face of global stresses – whether what a Fijian village does matters when people in London and Los Angeles burn fossil fuels to drive to work,” said Mark Hay, the study’s principal investigator, Regents Professor and Harry and Linda Teasley Chair in Georgia Tech’s School of Biological Sciences.
“Our work indicates that local management provides a degree of insurance against global stresses, but there are likely higher temperatures that render the insurance ineffective.”
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The researchers collected three coral species along with seawater surrounding each species at protected reefs and at overfished reefs. In their Georgia Tech lab, they tested their solutions against the pathogen Vibrio coralliilyticus at 24 degrees Celsius (75.2 Fahrenheit), an everyday Fijian water temperature, and at 28 degrees (82.4 F), common during ocean heating events.
“We chose Vibrio because it commonly infects corals, and it’s associated with coral bleaching in these warming events. It’s related to other bleaching pathogens and could serve as a model for them as well,” Hay said.
“We chose 24 C and 28 C because they’re representative of the variations you see on Fijian reefs these days. Those are temperatures where the bacteria are more benign or more virulent,” Beatty said.
The data showed that warming disadvantaged all potions against Vibrio and conservation aided a potion from a key coral species. The team, which included coauthor Kim Ritchie from the University of South Carolina Beaufort, published its study in the journal Science Advances on Oct. 2. The research was funded by the National Institutes of Health’s Fogarty International Center, the National Science Foundation, and the Simons Foundation.
The unprotected reefs’ shabby appearance portended their effects on the one potion associated with a key coral species.
“When you swim out of the no-fishing area and into the overfished area, you hit a hedge of seaweed. You have about 4 to 16% corals and 50 to 90% seaweed there. On the protected reef, you have less than 3% seaweed and about 60% corals,” Hay said.
Hay has researched marine ecology for over four decades and has seen this before, when coral reefs died off closer to home.
“Thirty years ago, when Caribbean reefs were vanishing, I saw overfishing as a big deal there, when seaweed took over,” he said, adding that global warming has become an overriding factor. “In the Pacific, many reefs that were not overfished have been wiped out in warming events. It just got too hot for too long.”
The potions are products of the corals and associated microbes, which comprise a biological team called a holobiont.
To arrive at potions focused on chemical effects, the researchers agitated the coral holobionts and ocean water then freeze-dried and irradiated the resulting liquid to destroy remnants of life that could have augmented chemical action. Some viruses may have withstood sterilization, but it would have weakened any effect they may have had, if there were any.
Then the researchers tested the potions on Vibrio.
“All of the solutions’ defenses were compromised to varying extents at elevated temperatures where we see corals getting sick in the ocean,” Hay said.
But reef protection benefited the potion taken from the species Acropora millepora.
“The beneficial effect in the solution tested in the lab was better when Acropora came from protected areas, and this difference became more pronounced at 28 degrees Celsius,” said Beatty, who finished her Ph.D. with Hay and is now a postdoctoral researcher at the University of California, Davis.
Of the three species with potions that were tested, Acropora millepora may be a special one.
It is part of a genus – larger taxonomic category – containing about 150 of the roughly 600 species in Pacific reefs, and Acropora are core builders of reef structures. They grow higher as sea level rises, helping maintain healthy positions for whole reefs.
“Acropora are big and branching and make lots of crevices where fish live. The evolution of lots of reef fish parallels the evolution of Acropora in particular,” Hay said.
If fish can hang on, they may buy Acropora more time, and coral reefs perhaps, too.
Also READ: When Coral Species Vanish, Their Absence Can Imperil Surviving Corals
These researchers coauthored the study: Deanna Beatty, Jinu Valayil, Cody Clements, and Frank Stewart of Georgia Tech. The research was funded by the National Institutes of Health (grant 2 U19 TW007401-10), the National Science Foundation (grant OCE 717 0929119), the Simons Foundation (grant 346253), and the Teasley Endowment. Any findings, conclusions, or recommendations are those of the authors and not necessarily of the sponsors. DOI: https://doi.org/10.1126/sciadv.aay1048
Writer & Media Representative: Ben Brumfield (404-272-2780), email: ben.brumfield@comm.gatech.edu
Georgia Institute of Technology
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Atlanta, Georgia 30332-0181 USA
These innards include plasmids, which are loops of DNA. They are not the same DNA strands behind reproduction and cell construction, but function instead like nano-organs with genetic programs that normally guide bacterial cell processes. In a study led by the Georgia Institute of Technology, researchers engineered their own plasmids to direct other parts extracted from bacteria to make the blood test work.
The new technology showed high potential as a basis for an inexpensive, easy malnutrition test that could be expanded to include many vital nutrients and other health indicators.
The new, experimental test is freeze-dried to a powder that is kept at everyday temperatures, could be read in the field, and may be suitable for precise analysis with an applicable smartphone app. It could overcome the clinical and logistical travails of other tests, including refrigerated transport to the field or back to a lab, as well as lost time.
The test not only detects zinc but also quantifies its clinically relevant levels, which is necessary to detect malnourishment and is one of the new test’s main innovations. Aid agencies could use a field version of the test to get immediate information to quickly influence policy decisions on nutritional interventions.
Two billion people worldwide suffer from micronutrient deficiencies, which claim millions of lives each year, according to the Centers for Disease Control and Prevention. Zinc deficiency alone was blamed for more than 450,000 deaths in 2009, according to a study in the European Journal of Clinical Nutrition.
But spotting malnutrition is tricky.
“In the developing world today, many people may get enough calories but miss out on a lot of nutrients. You can look at someone and tell if they're getting enough calories but not if they're getting sufficient amounts of developmentally important nutrients,” said Mark Styczynski, who led the study and is an associate professor in Georgia Tech’s School of Chemical and Biomolecular Engineering.
“The impact is greatest on pregnant mothers and children under the age of 5, which is when they have the highest mortality,” he said.
The research team, which included collaborators from Northwestern University, published their study in the journal Science Advances on September 25, 2019. The research was funded by the National Institutes of Health, the National Science Foundation, the Air Force Research Laboratory, the Defense Advanced Research Projects Agency, the David and Lucille Packard Foundation, and the Camille Dreyfus Teacher-Scholar Program.
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Engineering with bacterial innards is at least 25 years old, with research accelerating in the past decade. But this new test flags small molecules, like zinc or iodine, another big innovation.
The quantification of zinc ions in this particular study was the proof of concept for plans to measure many small molecules relevant to in-field tests. The researchers could quickly expand the test to assess levels of the six vital small-molecule nutrients, micronutrients, that are highly relevant to nutritional fieldwork.
“We may be able to reasonably quickly make new tests for iron, B12, folate, iodine, and vitamin A,” Styczynski said. “We could also quantify bigger molecules like DNA and proteins to help figure out how bad a viral outbreak is.”
“Detecting the presence or absence of something like Ebola or pregnancy is important. But being able to say how much of something you have, like a nutrient or a virus, without having to haul equipment through the field to do it has been lacking. The ability to do it could open a lot of doors in diagnostics and treatment,” Styczynski said.
The ease of use of the experimental zinc test stands in stark contrast to the labors required to engineer it. The researchers started off using live bacteria that changed colors in reaction to zinc, but that approach hit snags.
“The test took too long, and the volume of blood and bacteria we would need was not clear,” Styczynski said. “So, we went cell-free. You take the bacteria and remove the outside and the genome –– the main DNA –– and you’re left with this rich mixture of heavily reactive parts, to which you can add your own genetic program on the plasmids.”
Cell-free approaches allow bacterial innards to be dosed like compounds in a chemical reaction, making the test predictable, reliable, and suitable for standardization. The researchers built two plasmids to drive the test's processes.
“One has the genes taken from E. coli for an enzyme that breaks down a big sugar into smaller sugars. The other one controls how much of a regulator gene is being turned on in response to levels of zinc,” Styczynski said.
The test uses a signal molecule that is partly a big sugar and starts out yellow, but once the plasmid makes an enzyme that cleaves the sugar, the molecule turns purple. Zinc levels regulate how much enzyme is made –– more zinc means more enzyme and more purple. If the test remains yellow, zinc is perilously low.
When tested in serum, i.e. blood, its rich biology clutters the reaction, and in the real world, that clutter differs from person to person and would skew color schemes from patient to patient.
The researchers solved this with a chemical trick to make a calibration system that flows with that skew. For the actual test, the zinc regulated how the plasmids alter the color, but the study’s first author, Monica McNerney, flipped things for the calibrator.
To make its reference points, she maxed out zinc levels and varied the levels of plasmids point by point, resulting in a scale of colors.
The test and the plasmid-varied calibration points both received the serum to be tested, and the clutter shifted the test and the calibration points in an identical manner. The changed color of the test could be accurately compared to the colors of the calibration points to ascertain zinc levels.
The colors are in the visible range, not fluorescent, so they require no device to read. The speed of color change could reveal more detail about nutrient levels, perhaps via an analysis of smartphone video taken of the test.
Also READ: Long-held view is wrong about microbiomes' exclusive, generous bacterial collaborations
These researchers coauthored the study: Yan Zhang and Paige Steppe from Georgia Tech, and Adam Silverman and Michael Jewett from Northwestern University. The research was funded by the National Institutes of Health’s National Institute of Biomedical Imaging and Bioengineering (grants R01-EB022592 and R35-GM119701), the National Science Foundation (grants MCB-1254382 and DGE-1650044), the Air Force Research Laboratory Center for Excellence for Advanced Bioprogrammable Nanomaterials (grant FA8650-15-2-5518), the Defense Advanced Research Projects Agency’s Living Foundries (award HR0011-15-C-0084) the David and Lucille Packard Foundation, and the Camille Dreyfus Teacher-Scholar Program. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the funders.
Writer & Media Representative: Ben Brumfield (404-272-2780), email: ben.brumfield@comm.gatech.edu
Georgia Institute of Technology
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Atlanta, Georgia 30332-0181 USA
From dawn to dusk, peanut plants emit volatile organic compounds (VOCs) that vary in types and patterns depending on how they respond to various stresses. Growers typically rely on indirect monitoring methods such as soil moisture testing to assess the health of plants in their fields. But directly testing stress response could be faster more accurate and offer a wider range of diagnoses. Now scientists are working on gas-collection devices that growers could deploy in fields or on plants.
“We want to learn the best ways to detect and measure gases that could correlate to various plant conditions such as drought,” said Wayne Daley, associate division chief and principal research engineer with the Agricultural Technology Research Program at the Georgia Tech Research Institute (GTRI).
About 1.67 million acres of peanuts were harvested in the U.S. in 2017, according to the U.S. Department of Agriculture — 160,000 in Florida and 850,000 in Georgia. Peanuts are a $2.2 billion crop in Georgia, accounting for 23 percent of the state’s row and forage crop income, according to the Georgia Peanut Commission.
Daley and his co-investigators are collaborating with Diane Rowland, Barry Tillman and Alina Zare, all affiliated faculty of the University of Florida’s Center for Stress Resilient Agriculture, to identify and design collection methods for VOCs in an outdoor field site, an environmental chamber and a greenhouse in Florida. The GTRI team includes chemists Judy Song and Dan Sabo and data scientists Olga Kemenova and Milad Navaei.
“This type of advanced technology is what is critically needed for our growers to remain economically viable,” said Rowland, professor of physiology at the University of Florida. “Resource use efficiency in farming, including rapidly responding to counteract stress events such as drought, is the key not only to environmental stewardship, but also for remaining profitable under rising input costs.”
Still, detecting relevant gases in the field remains a giant challenge.
“Peanut plants release VOCs at very low concentrations that are difficult to measure,” said Daley. “We want to learn which VOCs are significant and tell us about stresses that are of interest to growers.” In a previous study, Daley and other GTRI scientists learned that VOC signatures are different among peanut plants at various degrees of drought intensity.
During the 2017 growing season, GTRI researchers placed glass rods coated with gas-absorbent material near peanut plants. The rods were taken to the lab and excited to release the absorbed gases, which were identified and measured. But a field site is a complex environment with many confounding factors.
Now the researchers are evaluating this gas-measurement technique to study peanut plants grown in controlled lab conditions.
During the 2017 growing season, researchers from University of Florida collected the field data from peanut plants using polydimethylsiloxane-coated stir bars (Twisters). The collected gases were sent to GTRI for identification and analysis using a thermal desorption unit.
Now the researchers are evaluating this gas-measurement technique to study peanut plants grown in controlled lab conditions.
A peanut plant’s seasonal growth stages affect the amounts and types of VOCs it releases. Even the time of day affects these emissions.
“We are building an environmental chamber in which we can mimic the humidity, lighting, and nutrients of a natural field on a Florida day from the morning to evening with appropriate humidity,” said Daley. “This is the first step to test and evaluate the gas measurement technique in controlled conditions. Once we know more about its performance and how to apply it, then we’ll take it to the University of Florida to be studied with plants in a greenhouse.”
The team is developing a baseline of peanut VOC “families” that could be identified in the environmental chamber. Each peanut stressor also could be associated with a distinct family of VOCs. For instance, researchers could simulate a drought in the chamber to study the associated VOCs. But there may be background families of VOCs that compete with or confuse a drought gas test.
“We need to understand how the peanut plant responds to both health and stress conditions to be able to fully utilize VOCs for drought detection” said Sabo, a GTRI research scientist.
“We are investigating how interference gases compete for space on the absorbent material,” said Song, a GTRI senior research engineer. “The experiment in the environmental chamber will be able to help us gain an understanding of how these interference gases and stressed-based VOCs interact and interfere with one another. With this knowledge we will be able to make accurate and meaningful measurements.”
Once researchers understand the ambient complexity of an outdoor peanut field, they could develop and refine a specialized gas test for peanut drought stress indicators, which could help farmers improve irrigation scheduling or prevent aflatoxins, which are potential carcinogens.
“You could probably develop and instrument the field with reliable compact sensors that allow for quick and convenient VOC collection and assessment,” said Daley. “Or we could envision robots manually taking samples.”
This project is funded by Southern Peanut Research Initiative Project (#D7984.2.0.0.0) and USDA-National Institute of Food and Agriculture Grant (#D8585.0.0.0.0)
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]]>Neuristors already exist today in labs, in small quantities, and to fuel the quest to boost neuristors’ power and numbers for practical use in brain-like computing, the U.S. Department of Defense has awarded a $7.1 million grant to a research team led by the Georgia Institute of Technology. The researchers will mainly expand work on new metal oxide materials that buzz electronically at the nanoscale to emulate the way human neural networks buzz with electric potential on a cellular level.
But to walk expectations back from the distant sci-fi future into the scientific present: The research team has developed neuristor materials to build, for now, an intelligent light sensor, and not some artificial version of the human brain, which would require hundreds of trillions of circuits.
“We’re not going to reach circuit complexities of that magnitude, not even a tenth,” said Alan Doolittle, a professor at Georgia Tech’s School of Electrical and Computer Engineering. “Also, currently science doesn’t really know yet very well how the human brain works, so we can’t duplicate it.”
But an artificial retina that can learn autonomously appears well within reach of the research team from Georgia Tech and Binghamton University. Despite the term “retina,” the development is not a medical implant, but it could be used in advanced image recognition cameras for national defense and police work.
At the same time, it significantly advances brain-mimicking, or neuromorphic, computing. The research field that takes its cues from what science already does know about how the brain computes to develop exponentially more powerful computing.
The retina is comprised of an array of neuristors, which combines the words “neuron” and “transistor” to refer to ultracompact circuits. The neuristors sense light, compute an image out of it and store the image. All three of the functions would occur simultaneously and nearly instantaneously.
“The same device senses, computes and stores the image,” Doolittle said. “The device is the sensor, and it’s the processor, and it’s the memory all at the same time.” A neuristor itself is comprised in part of devices called memristors inspired by the way human neurons work.
[Also READ: The Brain, Cosmos in the Cranium -- brain research in a nutshell]
That cuts out loads of processing and memory lag time that are inherent in traditional computing.
Take the device you’re reading this article on: Its microprocessor has to tap a separate memory component to get data, then do some processing, tap memory again for more data, process some more, etc. “That back-and-forth from memory to microprocessor has created a bottleneck,” Doolittle said.
A neuristor array breaks the bottleneck by emulating the extreme flexibility of biological nervous systems: When a brain computes, it uses a broad set of neural pathways that flash with enormous data. Then, later, to compute the same thing again, it will use quite different neural paths.
Traditional computer pathways, by contrast, are hardwired. For example, look at a present-day processor and you’ll see lines etched into it. Those are pathways that computational signals are limited to.
The new memristor materials at the heart of the neuristor are not etched, and signals flow through the surface very freely, more like they do through the brain, exponentially increasing the number of possible pathways computation can take. That helps the new intelligent retina compute powerfully and swiftly.
The retina’s memory could also store thousands of photos, allowing it to immediately match up what it sees with the saved images. The retina could pinpoint known terror suspects in a crowd, find missing children, or identify enemy aircraft virtually instantaneously, without having to trawl databases to correctly identify what is in the images.
It could even autonomously learn to extrapolate further information, like calculating the third dimension of a face out of data from a two-dimensional image. Even if you take away the optics, the new neuristor arrays still advance artificial intelligence. Instead of light, a surface of neuristors could absorb massive data streams at once, compute them, store them, and compare them to patterns of other data, immediately.
“It will work with anything that has a repetitive pattern like radar signatures, for example,” Doolittle said. “Right now, that’s too challenging to compute, because radar information is flying out at such a high data rate that no computer can even think about keeping up.”
The research project’s title acronym CEREBRAL may hint at distant dreams of an artificial brain, but what it stands for spells out the present goal in neuromorphic computing: Cross-disciplinary Electronic-ionic Research Enabling Biologically Realistic Autonomous Learning.
The intelligent retina’s neuristors are based on novel metal oxide nanotechnology materials unique to Georgia Tech. They allow computing signals to flow flexibly across pathways that are electronic, which is customary in computing, and at the same time make use of ion motion, which is more commonly known from the way batteries and biological systems work.
The new materials have already been created, and they work, but the researchers don’t yet fully understand why.
Much of the project is dedicated to examining quantum states in the materials and how those states help create useful electronic-ionic properties. Researchers will view them by bombarding the metal oxides with extremely bright x-ray photons at the recently constructed National Synchrotron Light Source II.
Grant sub-awardee Binghamton University is located close by, and Binghamton physicists will run experiments and hone them via theoretical modeling.
The neuristors are created mainly by the way the metal oxide materials are grown in the lab, which has some advantages over building neuristors in a more wired way.
This materials-growing approach to creating part of the computational structure is conducive to mass production. Also, though neuristors in general free signals to take multiple pathways, Georgia Tech’s neuristors do it much more flexibly thanks to chemical properties.
“We also have a sea of lithium, and it’s like an infinite reservoir of computational ionic fluid,” Doolittle said. The lithium niobite imitates the way ionic fluid bathes biological neurons and allows them to flash with electric potential while signaling. In a neuristor array, the lithium niobite helps computational signaling move in myriad directions.
“It’s not like the typical semiconductor material, where you etch a line, and only that line has the computational material,” Doolittle said.
“Unlike any other previous neuristors, our neuristors will adapt themselves in their computational-electronic pulsing on the fly, which makes them more like a neurological system,” Doolittle said. “They mimic biology in that we have ion drift across the material to create the memristors (the memory part of neuristors).”
Brains are far superior to computers at most things, but not all. Brains recognize objects and do motor tasks much better. But computers are much better at arithmetic and data processing.
Neuristor arrays can meld both types of computing, making them biological and algorithmic at once, a bit like Commander Data’s brain.
LISTEN: How neurons make the brain compute -- audio report
LISTEN: Wondrous facts about the brain -- audio report
The research is being funded through the U.S. Department of Defense’s Multidisciplinary University Research Initiatives (MURI) Program under grant number FOA: N00014-16-R-FO05. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of those agencies.
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]]>The device, a portable centrifuge for preparing scientific samples including DNA, is reported May 21 in the journal PLOS Biology. The co-first author of the paper is Gaurav Byagathvalli, a senior at Lambert High School in Georgia. His colleagues are M. Saad Bhamla, an assistant professor at the Georgia Institute of Technology; Soham Sinha, a Georgia Tech undergraduate; Janet Standeven, Byagathvalli’s biology teacher at Lambert; and Aaron F. Pomerantz, a graduate student at the University of California, Berkeley.
“I am exceptionally proud of this paper and will remember it 10, 20, 30 years from now because of the uniquely diverse team we put together,” said Bhamla, who is an assistant professor in Georgia Tech’s School of Chemical and Biomolecular Engineering.
From a Rainforest to a High School
Together the team demonstrated the device, dubbed the 3D-Fuge because it is created through 3D printing, in two separate applications. In a rainforest in Peru the 3D-Fuge was an integral part of a “lab in a backpack” used to identify four previously-unknown plants and insects by sequencing their DNA. Back in the United States, a slightly different design enabled a new approach to creating living bacterial sensors for the potential detection of disease. That work was conducted at Lambert High School for a synthetic biology competition.
Thanks to social media and a preprint of the PLOS Biology paper on BioRxiv, the 3D-Fuge has already generated interest from around the world, including emails from high-school teachers in Zambia and Kenya. “It’s awesome to see research not just remain isolated to one location but see it spread,” said Byagathvalli. “Through this, we’ve realized how much of an impact simple yet effective tools can have, and hope this technology motivates others to continue along the same path and innovate new solutions to global issues.”
To better share the work, the team has posted the 3D-Fuge designs, videos, and photos online available to anyone.
Frugal Science
One focus of Bhamla’s lab at Georgia Tech is the development of tools for frugal science, or real research that just about anyone can afford. The tools behind state-of-the-art science often cost thousands of dollars that make them inaccessible to those without serious resources.
Centrifuges are a good example. A small benchtop unit costs between $3,000 and $5,000; larger units cost many times that. Yet the devices are necessary to produce concentrated amounts of, say, genomic materials like DNA. By rapidly spinning samples, they separate materials of interest from biological debris.
The Bhamla team found that the 3D-Fuge works as well as its more expensive cousins, but costs less than $1.
An Ancient Toy
The 3D-Fuge is based on earlier work by Bhamla and colleagues at Stanford University on a simple centrifuge made of paper. The “paperfuge,” in turn, was inspired by a toy composed of string and a button that Bhamla played with as a child. He later discovered that these toys, known as whirligigs, have existed for some 5,000 years.
They consist of a disk – like a button – with two holes, through which is threaded a length of flexible cord whose ends are knotted to create a single loop with the disk in the middle. That simple contraption is then swung with two hands until the button is spinning and whirring at very fast speeds.
The earlier paperfuge uses a disk of paper. To that disk Bhamla glued small plastic tubes filled with a sample. He and colleagues reported that the device did indeed create high-quality samples.
In late 2017 Bhamla was separately approached by the Lambert High team and Pomerantz to see if the paperfuge could be adapted for the larger samples they needed (the paperfuge is limited to small samples of ~1 microliter—or one drop of blood).
Together they came up with the 3D-Fuge, which includes cavities for tubes that can hold some 100 times more of a sample than the paperfuge. The team developed two equally effective designs: one for field biology (led by Pomerantz) and the other for the high-school’s synthetic biology project (led by Byagathvalli).
Bhamla notes that the 3D-Fuge has some limitations. For example, it can only process a few samples at a time (some applications require thousands of samples). Further, because it’s 10 times heavier than the paperfuge, it can’t reach the same speeds or produce the same forces of that device. That said, it still weighs only 20 grams, slightly less than a AA battery.
“But it works,” said Bhamla. “All you need is an [appropriate] application and some creativity.”
This work was funded by the National Science Foundation (award no.181733), the Mindlin Foundation, and the Jacobs Institute Innovation Catalyst Award.
CITATION: Gaurav Byagathvalli, Aaron F. Pomerantz, Soham Sinha, Janet Standeven, and M. Saad Bhamla, “A 3D-printed hand-powered centrifuge for molecular biology,” (PLOS Biology, 2019) https://doi.org/10.1371/journal.pbio.3000251
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]]>A paper on the research was published in a recent issue of the Journal of the American Chemical Society (JACS).
Electrochromic materials change color upon the application of a small electrical potential or voltage. For the last 20 years John R. Reynolds, a professor at the Georgia Institute of Technology, has been studying and developing electrochromic materials that can switch from a wide range of vibrant colors to clear.
But these materials, known as cathodically coloring polymers, have a drawback. Their transmissive, or clear, state is not completely clear. Rather, in this state the material has a light blue tint. “That’s fine for many applications — including rear-view mirrors that cut the glare from oncoming cars by turning dark — but not for all potential uses,” said Reynolds, who has joint appointments in the School of Chemistry and Biochemistry and the School of Materials Science and Engineering at Georgia Tech.
For example, the Air Force is working toward visors for its pilots that would automatically switch from dark to clear when a plane flies from bright sunlight into clouds. “And when they say clear, they want it crystal clear, not a light blue,” Reynolds said. “We’d like to get rid of that tint.”
Toward a Solution
There is another family of electrochromic materials that can change color when exposed to an oxidizing voltage. These materials, known as anodically coloring electrochromes (ACEs), are colorless materials that turn colored upon oxidation. But there has been a knowledge gap in the science behind the colored oxidized states, known as radical cations. Researchers have not understood the absorption mechanism of these cations, and so the colors could not be controllably tuned.
Introducing Dylan T. Christiansen, a graduate student in the Reynolds group. While tinkering with some ACE molecules, he experimented with a new approach to controlling color in radical cations. Specifically, he created four different ACE molecules by making tiny changes to the ACEs’ molecular structures that have little effect on the neutral, clear state, but significantly change the absorption of the colored or radical cation state.
The results were spectacular. “I expected some color differences between the four molecules, but thought they’d be very minor,” Christiansen said. Instead, upon the application of an oxidizing voltage, the four molecules produced four very different colors: two vibrant greens, a yellow, and a red. And unlike their cathodic counterparts, they are crystal clear in the neutral state, with no tint. Finally, just like mixing inks, the researchers found that a blend of the molecules that switch to green and red made a mixture that is clear and switches to an opaque black. Suddenly those Air Force visors that switch from crystal clear to black looked more attainable.
“The beauty of this is it’s so simple. These minor chemical changes — literally the difference of a few atoms — have such a huge impact on color,” said Aimée L. Tomlinson, a professor in the Department of Chemistry and Biochemistry at the University of North Georgia and the third author of the paper with Reynolds and Christiansen.
What’s Going On?
How could such tiny changes have such an effect? That’s where Tomlinson, a computational chemist, comes in.
For the last five years she has been analyzing Reynolds’ electrochromic materials with computational models that provide insights into what’s happening at the sub-molecular level. Using those models, coupled with Christiansen’s data for the new ACE molecules, she was able to show how the small chemical changes that were made can drastically alter the electronic structure of the molecules’ radical cation states, and ultimately control the color.
The work continues to generate insights into new ACE molecules thanks to continuous feedback between Tomlinson’s models and the experimental data. The models help guide efforts in the lab to create new ACE molecules, while the experimental data from those molecules makes the models ever stronger.
Tomlinson notes that because the work is also helping to illuminate how radical cations work — they are still not well understood — it could help others manipulate them for future use in fields beyond electrochromism.
Reynolds commented on the serendipitous nature of the initial discovery. “I think what makes science really interesting is that [sometimes] you see something you really did not expect, you pursue it, and you end up with something that is better than you expected when you started.”
This work was funded by the Air Force Office of Scientific Research. Tomlinson also acknowledges the support of her university, while Reynolds acknowledges support for his electrochromic polymer research program from NXN Licensing. Any opinions or conclusions are those of the authors and do not necessarily represent the views of the sponsoring organizations.
CITATION: Dylan T. Christiansen, Aimée L. Tomlinson, and John R. Reynolds, “New Design Paradigm for Color Control in Anodically Coloring Electrochromic Molecules”(Journal of the American Chemical Society, February 22, 2019). https://pubsdc3.acs.org/doi/10.1021/jacs.9b01507
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]]>A report published recently in the Journal of Controlled Release describes a technique for administering contraceptive hormones through special backings on jewelry such as earrings, wristwatches, rings or necklaces. The contraceptive hormones are contained in patches applied to portions of the jewelry in contact with the skin, allowing the drugs to be absorbed into the body.
Initial testing suggests the contraceptive jewelry may deliver sufficient amounts of hormone to provide contraception, though no human testing has been done yet. A goal for the new technique is to improve user compliance with drug regimens that require regular dosages. Beyond contraceptives, the jewelry-based technique might also be used for delivering other drugs through the skin.
“The more contraceptive options that are available, the more likely it is that the needs of individual women can be met,” said Mark Prausnitz, a Regents Professor and the J. Erskine Love Jr. chair in the School of Chemical and Biomolecular Engineering at the Georgia Institute of Technology. “Because putting on jewelry may already be part of a woman’s daily routine, this technique may facilitate compliance with the drug regimen. This technique could more effectively empower some women to prevent unintended pregnancies.”
This proof-of-concept research was supported by the U.S. Agency for International Development (USAID) under a subcontract funded by FHI 360.
Contraceptive jewelry adapts transdermal patch technology that is already used to administer drugs that prevent motion sickness, support smoking cessation, and control the symptoms of menopause, but have never been incorporated into jewelry before. Contraceptive patches are also already available, but Prausnitz believes pairing them with jewelry may prove attractive to some women – and allow more discreet use of the drug delivery technology.
“There is a lot of experience with making and using conventional transdermal patches,” he said. “We are taking this established technology, making the patch smaller and using jewelry to help apply it. We think that earring patches can expand the scope of transdermal patches to provide additional impact.”
Postdoctoral Fellow Mohammad Mofidfar, Senior Research Scientist Laura O’Farrell and Prausnitz tested the concept on animal models, first on ears from pigs. Test patches mounted on earring backs and containing the hormone levonorgestrel were also applied to the skin of hairless rats. To simulate removal of the earrings during sleep, the researchers applied the patches for 16 hours, then removed them for eight hours. Testing suggested that even though levels dropped while the earrings were removed, the patch could produce necessary amounts of the hormone in the bloodstream.
The earring patch tested by the researchers consisted of three layers. One layer is impermeable and includes an adhesive to hold it onto an earring back, the underside of a wristwatch or the inside surface of a necklace or ring. A middle layer of the patch contains the contraceptive drug in solid form. The outer layer is a skin adhesive to help stick to skin so the hormone can be transferred. Once in the skin, the drug can move into the bloodstream and circulate through the body.
If the technique ultimately is used for contraception in humans, the earring back would need to be changed periodically, likely on a weekly basis.
The contraceptive jewelry was originally designed for use in developing countries where access to health care services may limit access to long-acting contraceptives such as injectables, implants and IUDs. However, Prausnitz says the technology may be attractive beyond that initial audience. “We think contraceptive jewelry could be appealing and helpful to women all around the world,” said Prausnitz.
The researchers tested patches adhered to earring backs, about one square centimeter in area, and placed them tightly on the skin of the test animals. Earring backs and watches may be most useful for administering drugs because they remain in close contact with the skin to allow drug transfer. The dose delivered by a patch is generally proportional to the area of skin contact.
“The advantage of incorporating contraceptive hormone into a universal earring back is that it can be paired with many different earrings,” Prausnitz noted. “A woman could acquire these drug-loaded earring backs and then use them with various earrings she might want to wear.”
Though transdermal drug-delivery patches have been available since 1979, testing would be required to determine whether the earring patch is safe and effective. In addition, research would be required to determine whether the concept would be attractive to women in different cultures.
“We need to understand not only the effectiveness and economics of contraceptive jewelry, but also the social and personal factors that come into play for women all around the world,” Prausnitz said. “We would have to make sure that this contraceptive jewelry concept is something that women would actually want and use.”
The technique could potentially be used to deliver other pharmaceuticals, though it would only be suitable for skin-permeable drugs that require administration of quantities small enough to fit into the patches.
“We think there are uses beyond contraceptive hormones, but there will always be a limitation that the drug has to be effective with a low enough dose to fit into the limited space in the patch,” Prausnitz said. “It also should be a drug that would benefit from continuous delivery from a patch and that is administered to a patient population interested in using pharmaceutical jewelry.”
The earring patch is designed to add another contraceptive option for women. “Pharmaceutical jewelry introduces a novel delivery method that may make taking contraceptives more appealing,” he added. “Making it more appealing should make it easier to remember to use it.”
This work was made possible by the generous support of the American people through the U.S. Agency for International Development (USAID). The contents are the responsibility of the authors and do not necessarily reflect the views of FHI 360, USAID or the United States Government. This research was supported by USAID cooperative agreement AID-OAA-15-00045 under a subcontract funded by FHI 360 as a proof-of-concept study (https://www.fhi360.org/projects/envision-fp).
CITATION: Mohammad Mofidfar, Laura O’Farrell and Mark R. Prausnitz, “Pharmaceutical jewelry: Earring patch for transdermal delivery of contraceptive hormone,” (Journal of Controlled Release, 2019) https://doi.org/10.1016/j.jconrel.2019.03.011
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]]>When the body’s immune system has just begun attacking cells of a transplanted organ, the new method’s particles send a fluorescent signal into the urine. In a new study, researchers at the Georgia Institute of Technology and Emory University validated the method in a mouse model, and they have engineered the sensor with highly biocompatible components, which could make the path to potential future trials easier.
A patient may feel fine, and a biopsy may look deceptively clean when T cells have already begun attacking a transplanted organ. The sensor particle, a nanoparticle, detects a T cell weapon, an enzyme called granzyme B, that pushes a transplanted organ’s cells into the self-destruction process called apoptosis.
“Before any organ damage can happen, T cells have to produce granzyme B, which is why this is an early detection method,” said Gabe Kwong, a co-principal investigator in the study and an assistant professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University.
“This is sensitive enough to possibly detect budding rejection before you see significant injury to the transplanted organ and that could help clinicians treat early to prevent damage,” said Dr. Andrew Adams, co-principal investigator and an associate professor of surgery at Emory University School of Medicine. “Right now, most tests are aimed at organ dysfunction, and sometimes they don’t signal there is a problem until organ function is below 50 percent.”
Kwong and Adams published the study’s results in the journal Nature Biomedical Engineering on February 18, 2019. The research was funded by the National Institutes of Health, the National Science Foundation and the Burroughs Wellcome Fund.
The nanoparticles are put together with iron oxide in the middle like a ball. It is double-coated with dextran, a sugar, and polyethylene glycol, a common ingredient in laxatives, to keep the body from disposing of it too quickly.
Bristles made of amino acids stick out from the iron ball with fluorescent “reporter” molecules attached to their tips.
The particles are injected intravenously. They are too big to accumulate in native tissue or to pass through the kidneys and out of the body but small enough to accumulate in the tissue of struggling transplanted organs, where they keep a lookout for rejection.
Once T cells start secreting granzyme B, it severs amino acid strands in the transplanted organ’s cells, triggering the cells to unravel and die.
“The nanoparticles’ bristles mimic granzyme’s amino acid targets in the cells, so the enzyme cuts the bristles on the nanoparticle at the same time,” said Kwong who directs the Laboratory for Synthetic Immunity in the Coulter Department. “That releases the reporter molecules, which are so small that they easily make it through the kidney’s filtration and go into the urine.”
In the experiment, the animals’ urine glowed and could be seen in their bladders in near-infrared images.
[Ready for graduate school? Here's how to apply to Georgia Tech.]
The researchers plan to augment their new sensor to detect the other major cause of transplant rejection, attacks by antibodies, which are not living cells but proteins the body creates to neutralize foreign entities.
“Antibodies kill their target cells through similar types of enzymes. In the future, we envision a single sensor to detect both types of rejection,” Kwong said. But there is even more potential.
“This method could be adapted to tease out multiple problems like rejection, infection or injury to the transplanted organ,” Adams said. “The treatments for all of those are different, so we could select the proper treatment or combination of treatments and also use the test to measure how effective treatment is.”
Biopsies are currently the gold standard in detection but they can go wrong, and the wide, long needle can damage tissue.
“The biggest risk of a biopsy is bleeding and injury to the transplanted organ,” Adams said. “Then there’s the possibility of infection. You’re also just taking a tiny fraction of the transplanted organ to determine what’s going on with the whole organ, and you may miss rejection or misdiagnose it because the needle didn’t hit the right spot.”
The urine test gets a more global reading on the whole organ, and it has other advantages over biopsies.
“The biopsy is not predictive. It’s a static snapshot. It’s like looking at a photo of people in mid-jump. You don’t know if they’re on their way up or on their way down. With a biopsy, you don’t know whether rejection is progressing or regressing,” Kwong said.
“Our method measures biological activity rates, and that tells us where things are going.”
That could also allow clinicians to carefully dose powerful immunosuppressant medications that the vast majority of transplant patients receive.
“Adjusting the dose is very difficult but very important because heavy immunosuppression increases occurrence of infections and patients who receive it also get cancer more often,” Kwong said.
For this experiment, the researchers used small skin grafts on mice and got a very clear, timely signal from the nanoparticle sensor. Since organ transplants represent a lot more tissue, the researchers believe that any occurrence of organ rejection would trigger a much larger signal from the sensor.
[Also read: 'Demolition Handshakes' Kill Precursor T Cells That Pose an Autoimmune Threat]
These authors contributed to this research: Co-first authors Quoc Mac of the Coulter Department and Dave Mathews of the Emory Transplant Center; Justin Kahla, Claire Stoffers, Olivia Delmas, and Brandon Alexander Holt of the Coulter Department. The research was funded by the Burroughs Wellcome Fund, the National Institutes of Health (awards DP2HD091793, 5T32EB006343, and DK109665) and its National Institute of Allergy and Infectious Diseases (grant U01AI132904); the National Science Foundation (grant DGE-1650044). Any findings, conclusions or recommendations are those of the authors and do not necessarily reflect those of the funding agencies.
Writer & Media Representative: Ben Brumfield (404-660-1408), email: ben.brumfield@comm.gatech.edu
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How white blood cells called neutrophils work has not been understood well on a micron level, but researchers have gotten a closer look by chemically modeling one of their combat weapons, a kind of web, and trying it out on bacteria. The researchers then successfully double-teamed the bacteria with an antibiotic and their synthetic version of the white blood cell's web.
“One of their (the cells') weapons are neutrophil extracellular traps, also called NETs,” said J. Scott VanEpps, assistant professor of emergency medicine at the University of Michigan. VanEpps co-led the study with Shuichi Takayama from the Georgia Institute of Technology.
NETs are microscopic networks of fibers made primarily of DNA that neutrophils produce to capture bacteria.
“It’s amazing to think that molecular DNA tape, on which our genetic code is recorded, can also be used as a bacteria-lassoing web. White blood cells can act like cellular Spidermen that net bacterial micro-villains to protect our body,” said Takayama, who is a professor in Georgia Tech’s Petit Institute for Bioengineering and Biosciences and in the Wallace H Coulter Department of Biomedical Engineering at Georgia Tech and Emory University.
Takayama and VanEpps synthesized a rough chemical imitation of the NETs to study how they work by snaring bacteria in the lab in vitro. They also found antibiotics killed bacteria more effectively when combined with the synthetic web than when applied alone. The researchers published their results in the journal Advanced Materials on January 20, 2018.
“Although there are literally hundreds of different ingredients in natural NETs, we were able to recreate a lot of their structure and function with just two ingredients,” VanEpp said. “They look and function very similar to NETs produced by those neutrophil white blood cells and the synthesis method is much simpler than isolating them from neutrophils.”
The researchers first used their microwebs to snare and kill bacteria in order to better understand how white blood NETs work. Then they combined their microwebs with antibiotics in vitro to test for increased drug effectiveness.
Their results imply that the presence of white blood cell NETs in the body may increase the effectiveness of antibiotics. Also, the synthetic microwebs may have medical potential on their own.
“As bacteria develop resistance even to last-resort antibiotics, there is worry of untreatable infections. We found that microwebs can help antibiotics break through such resistance,” said Takayama, who is also Price Gilbert, Jr. Chair in Regenerative Engineering and Medicine at Georgia Tech.
“The knowledge gained in this study could be helpful in the future in designing new and better antibiotics that mimic the body’s natural defense mechanisms, as well as potentially change how we dose antibiotics given the potential synergy between the immune system and certain antibiotics,” VanEpps said.
The new microwebs also serve as a foundation for future research on even more functions of DNA ejected outside of cells.
“The ability to readily customize the microweb composition opens many opportunities to engineer new DNA materials that mimic biology and increase our understanding of the role of NETs and other types of extracellular DNA in the body,” Takayama said.
These authors contributed to this study: Yang Song from Georgia Tech; Usha Kadiyala, Priyan Weerappuli, Srilakshmi Yalavarthi, Cameron Louttit, Jason S. Knight, and James J. Moon from the Unversity of Michigan; Jordan J. Valdez and David S. Weiss from Emory University School of Medicine. The research was funded by the National Institutes of Health: the National Institute of Allergy and Infectious Diseases, the National Institute of General Medical Sciences; and the National Heart, Lung, and Blood Institute, (grants: NIH NIAID U19 AI116482, R01 AI141883, and K08 AI128006; NIGMS R01 GM123517; NHLBI R01 HL134846 and U01 CA210152), the Veterans Administration (merit award BX‐002788), and a Burroughs Wellcome Fund Investigator in the Pathogenesis of Infectious Disease award.
Writers / media contacts:
Kylie Urban, University of Michigan, kylieo@med.umich.edu
Ben Brumfield, Georgia Institute of Technology, ben.brumfield@comm.gatech.edu, 404-660-1408
]]>In the lab, researchers at the Georgia Institute of Technology were surprised to see them do it under conditions thought to be common on Earth just before first life evolved: in plain water, with no catalysts, and at room temperature.
The neat spiraling also elegantly integrated another compound which today forms the backbone of RNA and DNA. The resulting structure had features that strongly resembled RNA.
The study has come a step closer to answering a chicken-egg question about the evolutionary path that led to RNA (from which DNA later evolved): Did the spiral come first, and did this structure influence which molecular components made it later into RNA because they fit well into the spiral?
“The spiraling could have had a reinforcing effect. It could have facilitated the molecules getting connected together that have the same chirality (curve) to connect into a common backbone that is compatible with the helical twist,” said the study’s principal investigator Nicholas Hud, a Regents Professor in Georgia Tech’s School of Chemistry and Biochemistry.
The researchers published the new study in the journal Angewandte Chemie in December 2018. The research was funded by the National Science Foundation and the NASA Astrobiology Program under the Center for Chemical Evolution. The center is headquartered at Georgia Tech, and Hud is its principal investigator.
The study’s resulting polymers were not RNA but could be have been an important intermediate step in the early evolution of RNA. For building blocks, the researchers used base molecules referred to as “proto-nucleobases,” highly suspected to be precursors of nucleobases, main components that transport genetic code in today’s RNA.
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The study had to work around a paradox in chemical evolution:
Making RNA or DNA using their actual nucleobases in the lab without the aid of the enzymes of living cells that usually do this job is more than a herculean task. Thus, although RNA and DNA are ubiquitous on Earth now, their evolution on pre-life Earth would appear to have been an anomaly requiring erratic convergences of extreme conditions.
By contrast, the Georgia Tech researchers’ model of chemical evolution holds that precursor nucleobases self-assembled easily to into ancestral prototypes -- that were polymer-like and referred to as assemblies -- which later evolved into RNA.
“We would call these ‘proto-nucleobases’ or ‘ancestral nucleobases,’” Hud said. “For our overall model of chemical evolution, we’re saying that these proto-nucleobases, which self-assemble into these long strands, could have been part of a very early stage before modern nucleobases were incorporated.”
One main suspected proto-nucleobase in this experiment -- and in previous experiments on the possible the evolution of RNA -- was triaminopyrimidine (TAP). Cyanuric acid (CA) was another. The researchers highly suspect TAP and CA were parts of a proto-RNA.
The chemical bonds that hold together assemblies of the two suspected proto-nucleobases were surprisingly strong but non-covalent, which is akin to connecting two magnets. In RNA the main bonds holding together modern nucleobases are covalent bonds, akin to welding, and enzymes make those bonds in cells today.
A helix can spiral two ways, left-handed or right-handed. In chemistry, a molecule can also be handed, or chiral, making for “L” or “D” forms of the molecule.
Incidentally, the building blocks of today’s RNA and DNA are all the D form, which make a right-handed helix. Why they evolved like this is still a mystery.
Batches of TAP and CA the researchers started out with produced roughly equal amounts of right and left-handed helices, but something stood out: Whole regions of a batch were biased in one direction and were separate from other regions that spiraled mostly the other way.
“The propensity for the molecules to choose one helical direction was so strong that large regions of the batches were made up predominantly of assemblies that were unidirectionally twisted,” Hud said.
This was surprising because the individual molecules of TAP and CA had no chirality of their own, neither L nor D. Still, the twists had a preferred direction.
The researchers added two more experiments to test how strongly their RNA-like assemblies preferred making one-handed helices.
First, they introduced a smidgeon of compounds similar to TAP and CA, but which had L or D chirality, to nudge the spiraling direction. The whole batch conformed to the chirality of the respective additive, resulting in assemblies twisting in a unified direction as helices do in RNA and DNA today.
“It was the new world record for the smallest amount of a chiral dopant (additive) that would flip a whole solution,” said Suneesh Karunakaran, the study’s first author and a graduate researcher in Hud’s lab. “This demonstrated how easy it would be in nature to get abundant amounts of unified helices.”
Second, they put the sugar compound ribose-5-phosphate together with TAP to more closely emulate the current building blocks of RNA. The ribose fell into place, and the resulting assembly spiraled in a direction dictated by the ribose chirality.
“This molecule easily formed an RNA-like assembly that was surprisingly stable, even though the pieces were only held together by non-covalent bonds,” Karunakaran said.
The study’s results under such simple conditions represent a leap forward in experimental evidence for how the helical twist of biomolecules could have already been in place long before life emerged.
The research also expands a growing body of evidence supporting an unconventional hypothesis by the Center for Chemical Evolution, which dispenses with the need for a narrative that rare cataclysms and unlikely ingredients were necessary to produce life’s early building blocks.
Instead, most biomolecules likely arose in several gradual steps, on quiet, rain-swept dirt flats or lakeshore rocks lapped by waves. Precursor molecules with the right reactivity enabled those steps readily and produced abundant materials for further evolutionary steps.
In the lab, helix self-assemblage was so productive that it outstripped a detection device’s capacity to examine the output. Regions a square millimeter or more in size were packed with unidirectionally spiraled polymer-like assemblies.
“To look at them I had to make adjustments to the equipment,” said Karunakaran. “I punched holes in a foil and put it in front of the beam of our spectropolarimeter.”
That worked but needed improvement, so Hud took to his basement at home to build an automated scanner that could handle the experiment’s bountiful results. It revealed large regions of helices with the same handedness.
Also READ: This actually happened: Strip all the lynchpins from the ribosome and it still works
Brian J. Cafferty, Angela Weigert-Muñoz and Gary B. Schuster of Georgia Tech co-authored the research. It was funded by the National Science Foundation and the NASA Astrobiology Program under the NSF Center for Chemical Evolution (grant CHE-1504217). Nicholas Hud is also Associate Director of the Parker H. Petit Institute for Bioengineering and Bioscience. Any findings, recommendations or conclusions are those of the authors and not necessarily of the funding agencies.
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]]>Comparing the quantum properties of these emerging so-called hybrid semiconductors with those of their established predecessors is about like comparing the Bolshoi Ballet to jumping jacks. Twirling troupes of quantum particles undulate through the emerging materials, creating, with ease, highly desirable optoelectronic (light-electronic) properties, according to a team of physical chemists led by researchers at the Georgia Institute of Technology.
These same properties are impractical to achieve in established semiconductors.
The particles moving through these new materials also engage the material itself in the quantum action, akin to dancers enticing the floor to dance with them. The researchers were able to measure patterns in the material caused by the dancing and relate them to the emerging material’s quantum properties and to energy introduced into the material.
These insights could help engineers work productively with the new class of semiconductors.
The emerging material’s ability to house diverse, eccentric quantum particle movements, analogous to the dancers, is directly related to its unusual flexibility on a molecular level, analogous to the dancefloor that joins in the dances. By contrast, established semiconductors have rigid, straight-laced molecular structures that leave the dancing to quantum particles.
The class of hybrid semiconductors the researchers examined is called halide organic-inorganic perovskite (HOIP), which will be explained in more detail at bottom along with the “hybrid” semiconductor designation, which combines a crystal lattice -- common in semiconductors -- with a layer of innovatively flexing material.
Beyond their promise of unique radiance and energy-efficiency, HOIPs are easy to produce and apply.
“One compelling advantage is that HOIPs are made using low temperatures and processed in solution,” said Carlos Silva, a professor in Georgia Tech’s School of Chemistry and Biochemistry. “It takes much less energy to make them, and you can make big batches.” Silva co-led the study alongside Ajay Ram Srimath Kandada from Georgia Tech and the Istituto Italiano di Tecnologia.
It takes high temperatures to make most semiconductors in small quantities, and they are rigid to apply to surfaces, but HOIPs could be painted on to make LEDs, lasers or even window glass that could glow in any color from aquamarine to fuchsia. Lighting with HOIPs may require very little energy, and solar panel makers could boost photovoltaics’ efficiency and slash production costs.
The team led by Georgia Tech included researchers from the Université de Mons in Belgium and the Istituto Italiano di Tecnologia. The results were published on January 14, 2019, in the journal Nature Materials. The work was funded by the U.S. National Science Foundation, EU Horizon 2020, the Natural Sciences and Engineering Research Council of Canada, the Fond Québécois pour la Recherche, and the Belgian Federal Science Policy Office.
Semiconductors in optoelectronic devices can either convert light into electricity or electricity into light. The researchers concentrated on processes connected to the latter: light emission.
The trick to getting a material to emit light is, broadly speaking, to apply energy to electrons in the material, so that they take a quantum leap up from their orbits around atoms then emit that energy as light when they hop back down to the orbits they had vacated. Established semiconductors can trap electrons in areas of the material that strictly limit the electrons’ range of motion then apply energy to those areas to make electrons do quantum leaps in unison to emit useful light when they hop back down in unison.
“These are quantum wells, two-dimensional parts of the material that confine these quantum properties to create these particular light emission properties,” Silva said.
There is a potentially more attractive way to produce the light, and it is a core strength of the new hybrid semiconductors.
An electron has a negative charge, and an orbit it vacates after having been excited by energy is a positive charge called an electron hole. The electron and the hole can gyrate around each other forming a kind of imaginary particle, or quasiparticle, called an exciton.
“The positive-negative attraction in an exciton is called binding energy, and it’s a very high-energy phenomenon, which makes it great for light emitting,” Silva said.
When the electron and the hole reunite, that releases the binding energy to make light. But usually, excitons are very hard to maintain in a semiconductor.
“The excitonic properties in conventional semiconductors are only stable at extremely cold temperatures,” Silva said. “But in HOIPs the excitonic properties are very stable at room temperature.”
Excitons get freed up from their atoms and move around the material. In addition, excitons in an HOIP can whirl around other excitons, forming quasiparticles called biexcitons. And there’s more.
Excitons also spin around atoms in the material lattice. Much the way an electron and an electron hole create an exciton, this twirl of the exciton around an atomic nucleus gives rise to yet another quasiparticle called a polaron. All that action can result in excitons transitioning to polarons back. One can even speak of some excitons taking on a “polaronic” nuance.
Compounding all those dynamics is the fact that HOIPs are full of positively and negatively charged ions. The ornateness of these quantum dances has an overarching effect on the material itself.
The uncommon participation of atoms of the material in these dances with electrons, excitons, biexcitons and polarons creates repetitive nanoscale indentations in the material that are observable as wave patterns and that shift and flux with the amount of energy added to the material.
“In a ground state, these wave patterns would look a certain way, but with added energy, the excitons do things differently. That changes the wave patterns, and that’s what we measure,” Silva said. “The key observation in the study is that the wave pattern varies with different types of excitons (exciton, biexciton, polaronic/less polaronic).”
The indentations also grip the excitons, slowing their mobility through the material, and all these ornate dynamics may affect the quality of light emission.
The material, a halide organic-inorganic perovskite, is a sandwich of two inorganic crystal lattice layers with some organic material in between them – making HOIPs an organic-inorganic hybrid material. The quantum action happens in the crystal lattices.
The organic layer in between is like a sheet of rubber bands that makes the crystal lattices into a wobbly but stable dancefloor. Also, HOIPs are put together with many non-covalent bonds, making the material soft.
Individual units of the crystal take a form called perovskite, which is a very even diamond shape, with a metal in the center and halogens such as chlorine or iodine at the points, thus “halide.” For this study, the researchers used a 2D prototype with the formula (PEA)2PbI4.
Also READ: Perking up and Crimping the 'Bristles' of Polyelectrolyte Brushes
The study was co-authored by Félix Thouin (co-first author), David A. Valverde-Chávez (co-first author), and Ilaria Bargigia, all of Georgia Tech; Claudio Quarti and David Beljonne of the Université de Mons in Belgium; Daniele Cortecchia and Annamaria Petrozza of the Istituto Italiano di Tecnologia. The research was funded by EU Horizon 2020 (project 705874); the Natural Sciences and Engineering Research Council of Canada; Fond Québécois pour la Recherche: Nature et Technologies; the National Science Foundation (grant 1838276); Interuniversity Attraction Pole program of the Belgian Federal Science Policy Office (PAI 6/27) and the Fonds de la Recherche Scientifique de Belgique (FNRS-F.R.S.). Beljonne is an F.R.S. director. Any findings, opinions, and conclusions are those of the authors and not necessarily of the funding agencies.
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]]>But now a new study reveals, in fine detail, things that make these special bristles collapse -- and also recover. The research increases understanding of these chemical brushes that have many potential uses.
Polyelectrolyte brushes look a bit like soft bushes, such as shoeshine brushes, but they are on the scale of large molecules and the “bristles” are made of polymer chains. Polyelectrolyte brushes have a backing, or substrate, and the polymer chains tethered to the backing like soft bristles have chemical properties that make the brush potentially interesting for many practical uses.
But polymers are stringy and tend to get tangled or clumped, and keeping them straightened out, like soft bristles, is vital to the function of these micron brushes. Researchers at the Georgia Institute of Technology, the University of Chicago, and the Argonne National Laboratory devised experiments that caused polyelectrolyte brush bristles to collapse and then recover from the collapse.
They imaged the processes in detail with highly sensitive atomic force microscopy, and they constructed simulations that closely matched their observations. Principal investigator Blair Brettmann from Georgia Tech and the study’s first authors Jing Yu and Nicholas Jackson from the University of Chicago published their results on December 8, 2017, in the journal Science Advances.
Their research was supported by the U.S. Department of Energy, the National Science Foundation, and the Argonne National Laboratory.
The potential future payoff for the researchers’ work spans industrial materials to medicine.
For example, polyelectrolyte brushes make for surfaces that have their own built-in lubrication. “If you attach the brushes to opposing surfaces, and the bristles rub against each other, then they have really low friction and excellent lubrication properties,” said Blair Brettmann, who led the study and recently joined Georgia Tech from the University of Chicago.
Polyelectrolyte brushes could also one day find medical applications. Their bristles have been shown to simulate DNA and encode simple proteins. Other brushes could be engineered to repel bacteria from surfaces. Some polyelectrolyte brushes already exist in the body on the surface of some cells.
Polyelectrolyte brushes can do so many different things because they can be engineered in so many variations.
“When you build the brushes, you have a lot of control,” said Brettmann, who is an assistant professor in Georgia Tech’s School of Materials Science and Engineering. “You can control on the nanoscale how far apart the polymer chains (the bristles) are spaced on the substrate and how long they are.”
For all their great potential, polyelectrolyte brushes are also complex and sensitive, and a lot of research is needed to understand how to optimize them.
The polymer chains have positive and negative ionic, or electrolytic, charges alternating along their lengths, thus the name “polyelectrolyte.” Chemists can string the polymers together using various chemical building blocks, or monomers, and design nuanced charge patterns up and down the chain.
There’s more complexity: Backing and bristles are not all that make up polyelectrolyte brushes. They’re bathed in solutions containing gentle electrolytes, which create a balanced ionic pull from all sides that props the bristles up instead of letting them collapse or entangle.
“Often these mixtures have a bunch of other stuff in them, so the complexity of this makes it really hard to understand fundamentally,” Brettmann said, “and thus hard to be able to predict behavior in real applications.”
When other chemicals enter into these well-balanced systems that make up polyelectrolyte brushes, they can make the bristles collapse. For example, the addition of very powerful electrolytes can act like a flock of wrecking balls.
In their experiment, Brettmann and her colleagues used a powerful ionic compound built around yttrium, a rare earth metal with a strong charge. (The ion was trivalent, or had a valence of 3.) The ionic forces from just a low dose of the yttrium electrolyte made the polymer bristles curl up like clumps of sticky spaghetti.
Then the researchers increased the concentration of the gentler ions, which restored support, propping the bristles back up. Atomic force microscope imaging revealed highly regular patterns of collapse and re-extension.
These patterns were reflected well in the simulations; the reliability of the effects of the ions on collapse and recovery even more so. The ability to build such an accurate simulation reflects the strong consistency of the chemistry, which is good news for potential future research and practical applications.
For all the dysfunction that bristle collapses can cause, the ability to collapse them on purpose can be useful. “If you could collapse and reactivate the bristles systematically, you could adjust the degree of lubrication, for example, or turn lubrication on and off,” Brettmann said.
The brushes also could regulate chemical reactions involving micro- and nanoparticles by extending and collapsing the bristles.
“Coatings and films are often made by carefully combining engineered particles, and you can use these brushes to keep these particles suspended and separate until you’re ready to let them meet, bond, and form the product,” Brettmann said.
When the polyelectrolyte brush’s bristles are extended, they act as a barrier to hold the particles apart. Collapse the bristles out of the way on purpose, and the particles can come together.
The experiments were performed with very clean, robust, and uniform compounds unlike the jumble of chemicals that can exist in natural or even industrial systems.
“The bristles we used were polystyrene sulfonate, which is a very strong polyelectrolyte, not sensitive to pH or much else,” Brettmann said. “Biopolymers like polysaccharides, for example, are a lot more sensitive.”
Like many experiments, this one was a departure from real-world conditions. But by creating a foundation for understanding how these systems work, Brettmann wants eventually to be able to move on to sensitive scenarios to realize more of polyelectrolyte brushes’ practical potential.
Also READ: Paper-based supercapacitor
The study was co-authored by Xin Xu, Marina Ruths, Juan de Pablo and Matthew Tirrell. The research was funded by the U.S. Department of Energy Office of Science, Program in Basic Energy Sciences, Materials Sciences and Engineering Division, the National Science Foundation’s Division of Civil, Mechanical, and Manufacturing Innovation (grants 1562876 and 1161475), the Argonne National Laboratory Maria Goeppert Mayer Named AQ41Fellowship. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of those sponsors.
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The research provides the proof-of-principle for a new technique to study crystal formation in real-time, with potential applications for other materials, including alloys and oxides. Data from the study produced “nanometric phase diagrams” showing the conditions that control the structure of cobalt nanocrystals as they form.
The research, reported November 13 in the Journal of the American Chemical Society, was sponsored by the National Science Foundation, and used U.S. Department of Energy-supported synchrotron X-ray beam lines at Brookhaven National Laboratory and Argonne National Laboratory.
“We found that we could indeed control formation of the two different crystalline structures, and that the tuning factor was the pH of the solution,” said Hailong Chen, an assistant professor in the George W. Woodruff School of Mechanical Engineering at the Georgia Institute of Technology. “Tuning the crystalline structure allowed us to control the functionality and properties of these materials. We believe this methodology could also be applied to alloys and oxides.”
In bulk cobalt, crystal formation favors the hexagonal close-pack (HCP) structure because it minimizes energy to create a stable structure. At the nanoscale, however, cobalt also forms the face-centered cubic (FCC) phase, which has a higher energy. That can be stable because the high surface energy of small nanoclusters affects the total crystalline energy, Chen said.
“When the clusters are small, we have more tuning effects, which is controlled by the surface energy of the OH minus group or other ligands,” he added. “We can tune the concentration of the OH minus group in the solution so we can tune the surface energy and therefore the overall energy of the cluster.”
Working with researchers from the two national laboratories and the Department of Materials Science at the University of Maryland, Chen and graduate research assistant Xuetian Ma examined the polymorphic structures using theoretical, experimental and computational modeling techniques.
Experimentally, the researchers reduced cobalt hydroxide in a solution of ethylene glycol, using potassium hydroxide to vary the pH of the solution. The reaction takes place under high pressure – about 1,800 pounds per square inch – and at more than 200 degrees Celsius.
In the laboratory, the researchers use a heavy steel containment vessel that allowed them to analyze only the reaction results. To follow how the reaction took place, they needed to observe it in real time, which required development of a containment vessel small enough to allow for X-ray transmission while handling the high pressure and high temperature at the same time.
The result was a reaction vessel made of a high-strength quartz tube about a millimeter in diameter and about two inches long. After the cobalt hydroxide solution was added, the tube was spun to both facilitate the chemical reaction and average the X-ray signal. A small heater applied the necessary thermal energy and a thermocouple measured the temperature.
Ma and Chen used the setup during four separate trips to beam lines at the National Synchrotron Light Source II at Brookhaven, and the Advanced Photon Source at Argonne National Laboratory. X-rays passing through the reaction chamber to a two-dimensional detector provided continuous monitoring of the chemical reaction, which took about two hours to complete.
“When they started forming a detectable spectrum we captured the X-ray diffraction spectrum and continued to observe it until the crystal cobalt formed,” Ma explained. “We were able to observe step-by-step what was happening from initial nucleation to the end of the reaction.”
Data obtained by varying the pH of the reaction produced a nanometric phase diagram showing where different combinations produced the two structures.
The X-ray diffraction results confirmed the theoretical predictions and computational modeling done by Yifei Mo, an assistant professor in the A. James Clark School of Engineering at the University of Maryland. Mo and colleagues Adelaide Nolan and Shuo Zhang used density functional theory to describe how the crystal would nucleate under differing conditions.
The success with cobalt suggests the methodology could be used to produce nanometric phase diagrams for other materials, including more complex alloys and oxides, Chen said.
“Our goal was to build a model and a systematic understanding about the formation of crystalline materials at the nanoscale,” he said. “Until now, researchers had been relying on empirical design to control growth of the materials. Now we can offer a theoretical model that would allow systematic prediction of what kinds of properties are possible under different conditions.”
As a next step, the Georgia Tech researchers plan to study alloys, to further improve the theoretical model and experimental approach.
In addition to those already mentioned, the research also included Jianming Bai and Lijun Wu from Brookhaven National Laboratory and Wenqian Xu from Argonne National Laboratory.
CITATION: Xuetian Ma, et al., “Guiding Synthesis of Polymorphs of Materials Using Nanometric Phase Diagrams,” (Journal of the American Chemical Society, 2018) https://pubs.acs.org/doi/pdf/10.1021/jacs.8b11029
Support was provided by the National Science Foundation under grant number 1605692 and 1739884. Support was also received from the National Science Foundation under award 1550423 and from the computational facilities from the University of Maryland supercomputing resources, the Maryland Advanced Research Computing Center (MARCC), and the Extreme Science and Engineering Discovery Environment (XSEDE) supported by National Science Foundation award DMR150038. This research used resources of the beamline X14A of the National Synchrotron Light Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under contract no. DE-AC02-98CH10886, and Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by National Laboratory under contract no. DE-AC02-06CH11357. TEM work was supported by the U.S. Department of Energy, Office of Basic Energy Science, Division of Materials Science and Engineering, under contract DE-SC0012704. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsor organizations.
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]]>Election to NAI Fellow status recognizes academic inventors who have demonstrated a prolific spirit of innovation in creating or facilitating outstanding inventions that have made a tangible impact on quality of life, economic development and the welfare of society.
Separation processes, such as those used in the chemical processing industry, consume almost 15 percent of world energy, making them a focus for research efforts aimed at reducing energy consumption. Koros’ research has applications across many areas of industry.
“Dr. Koros has shown the way to expand energy-efficient separations across the large-scale separation process spectrum, with the potential to achieve a full order-of-magnitude reduction in energy intensity compared to conventional processes,” the NAI nomination said. “High-efficiency hollow-fiber membrane and sorbent modules, suitable for feeds of a billion standard cubic feet per day, are enabling aspects of his work. Defect-free hollow fibers with ultrathin skins and hybrid membranes and sorbents combining metal organic frameworks enable new opportunities that were only dreams four decades before his leadership showed the way.”
Beyond his own research, Koros has helped educate 89 Ph.D., 26 M.S. and 32 post-doctoral researchers, many of whom are now working in positions where they can bring about adoption of the new separations technologies.
“His discoveries on scalable manufacturing of asymmetric carbon molecular sieve hollow fibers open the door to a whole new generation of large scale energy-efficient separation processes,” the nomination added. “With more than 400 refereed publications and more than 34 issued U.S. patents, Dr. Koros has introduced energy-efficient gas-separation technology to the chemical processing industries, with a focus on fundamental scientific principles enabled by practical technology.”
With the election of the 2018 class, there are now over 1,000 NAI Fellows, representing more than 250 research universities and government and non-profit research institutes. The 2018 Fellows are named inventors on nearly 4,000 issued U.S. patents, bringing the collective number of patents held by all NAI Fellows to more than 35,000 issued U.S. patents.
“I am very proud to welcome another class of outstanding NAI Fellows, whose collective achievements have helped shape the future and who each day work to improve our world,” said Paul R. Sanberg, President of the NAI. “Each of these new NAI Fellows embodies the Academy’s mission through their dedication, creativity and inventive spirit. I look forward to working collaboratively with the new NAI Fellows in growing a global culture of innovation.”
About the National Academy of Inventors
The NAI is a member organization comprising U.S. and international universities, governmental and non-profit research institutes. The NAI recognizes inventors with patents issued from the U.S. Patent and Trademark Office to enhance the visibility of academic technology and innovation and to translate the inventions of its members to benefit society. The NAI publishes the multidisciplinary journal, Technology & Innovation. www.academyofinventors.org
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]]>Although the mechanisms are intertwined with biochemical processes, they also work mechanically, grasping, tugging and clamping, say researchers at the Georgia Institute of Technology, who, for a new study in the journal Nature Immunology, measured responses to physical force acting upon these elimination mechanisms.
The mechanisms’ purpose is to make dangerously aggressive developing immune cells called thymocytes destroy themselves to keep them from attacking the body, while sparing healthy thymocytes as they mature into T cells. Understanding these selection mechanisms, which ensure T cells aggressively pursue hordes of infectors and cancers but not damage healthy human tissue, could someday lead to new immune-regulating therapies.
Usually, researchers pursue such mechanisms using chemistry experiments, but Georgia Tech’s Cheng Zhu, who led the study, makes atypical discoveries via physical experiments to observe effects of forces between key proteins in living cells.
“Experiments where the proteins are isolated and used in chemical reactions in vitro miss this force dynamic,” said Zhu, a Regents Professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University. “Before our work, force was not considered as a factor in thymocyte selection and now it is.”
In this study, they discovered a loop of physical signals resembling a double-handed handshake that encourages cell apoptosis. It is described in more detail below.
The medical significance of this field of research was highlighted by the 2018 Nobel Prize in medicine, which was awarded to other researchers at other institutions, James Allison of MD Anderson Cancer Center and Tasuku Honjo of Kyoto University. Allison and Honjo received the prize for their cancer therapies exploiting T cell regulating mechanisms intertwined with those that the Georgia Tech researchers study.
Georgia Tech's Zhu and first authors Jinsung Hong and Chenghao Ge published their new research paper on November 12, 2018. The research was funded by the National Cancer Institute, the National Institute of Allergy and Infectious Diseases, and the National Institute of Neurological Disorders and Stroke. The agencies are part of the National Institutes of Health.
Like blood cells, human thymocytes are born in bone marrow, but they travel to the thymus, a small organ just below the neck, where they run a gauntlet of selection tests. Failing any one selection means cell self-destruction; passing all selections promotes thymocytes to T cells that depart the thymus to battle our bodies’ foes.
One selection checks T cell receptors (TCR), which are on the thymocyte’s membrane, to ensure they are properly formed then to see if they recognize self-antigens, i.e. molecules that identify the body’s own cells. Then another selection, called negative selection, tests TCRs to make sure they don’t react too aggressively to self-antigens.
Cells that pass these checks then have TCRs that tolerate self- yet react to enemy antigens.
“You don’t want the cells with strongly grabbing receptor sites to turn against the body itself,” said Zhu, whose study focused on negative selection.
In negative selection, other cells extend self-antigens on their membrane to interact with the thymocytes’ T cell receptors. Those interactions seal the thymocytes’ fate: advance or die.
Studying forces in those interactions revealed a new signaling loop with mechanical properties analogous to a two-handed grip and tug by the thymocyte.
The first hand would be the T cell receptor itself, and the other cell presenting the self-antigen would be like someone else’s hand holding a special ball out to the T cell’s first hand. The handshake begins as the self-antigen gives a signal to the T cell receptor.
If the TCR reacts too strongly to the self-antigen, the thymocyte adds the second, assisting hand, which comes in from the side to make a two-handed handshake. The additional hand is a lever called CD8 (cluster of differentiation 8), which connects to key mechanisms inside the thymocyte and is considered part of the TCR site.
For about two weeks in the thymus, multiple T cell receptor sites engage in one- or two-handed handshakes, which send signals into the thymocyte that make it either mature into a T cell or begin the process of programmed cell death.
The researchers found that the two-handedness markedly resisted the force applied to break the grip between the T cell receptor and the self-antigen, thus prolonging the duration of the handshake. A long grip sent signals for the thymocyte to die.
“That’s the study’s elegant finding,” Zhu said. “That the force is significant for the selection to work.”
The researchers also made the novel discovery that CD8’s handshake participation constitutes a signal coming from inside the thymocyte back out to the self-antigen in answer to its initial signal.
“The inside-out return signal had not yet been reported for this T cell receptor,” Zhu said.
Together, the outside-in and inside-out signals create a feedback loop that perpetuates the handshake:
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Coauthors on the study were: Prithiviraj Jothikumar, Zhou Yuan, Baoyu Liu, Ke Bai, Kaitao Li, William Rittase, all of Georgia Tech at the time of the research; Miho Shinzawa and Alfred Singer of the National Cancer Institute at the National Institutes of Health; Brian Evavold, Khalid Salaita and Yun Zhang of Emory University; Amy Palin and Paul Love of the NIH Eunice Kennedy Shriver National Institute of Child Health and Development; and Xinhua Yu of University of Memphis. The research was funded by the National Cancer Institute (NCI) (grant CA214354), the National Institute of Allergy and Infectious Diseases (NIAID) (grants AI124680, AI096879), the National Institute of Neurological Disorders and Stroke (NINDS) (grant NS071518). The funders belong to the National Institutes of Health. Hong and Bai now research at NIAID; Liu and Evavold now research at the University of Utah. Zhu is also in Georgia Tech’s George W. Woodruff School of Mechanical Engineering and in Georgia Tech’s Petit Institute for Bioengineering and Bioscience. Any findings, opinions or recommendations are those of the authors and not necessarily of the funding agencies
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]]>Thanks to a specialized X-ray source at Lawrence Berkeley National Laboratory, researchers at the Georgia Institute of Technology have confirmed the existence of a long-hypothesized interaction between nitrogen and titanium dioxide (TiO2) – a common photoactive material also known as titania – in the presence of light. The catalytic reaction is believed to use carbon atoms found as contaminants on the titania.
If the nitrogen-fixing reaction can be scaled up, it might one day help power clean farm-scale fertilizer production that could reduce dependence on capital-intensive centralized production facilities and costly distribution systems that drive up costs for farmers in isolated areas of the world. Most of the world’s fertilizer is now made using ammonia produced by the Haber-Bosch process, which requires large amounts of natural gas.
“In the United States, we have an excellent production and distribution system for fertilizer. However, many countries are not able to afford to build Haber-Bosch plants, and may not even have adequate transportation infrastructure to import fertilizers. For these regions, photocatalytic nitrogen fixation might be useful for on-demand fertilizer production,” said Marta Hatzell, an assistant professor in Georgia Tech’s Woodruff School of Mechanical Engineering. “Ultimately, this might be a low-cost process that could make fertilizer-based nutrients available to a broader array of farmers.”
Hatzell and collaborator Andrew Medford, an assistant professor in Georgia Tech’s School of Chemical and Biomolecular Engineering, are working with scientists at the International Fertilizer Development Center (IFDC) to study the potential impacts of the reaction process. The research was reported October 29 in the Journal of the American Chemical Society.
The research began more than two years ago when Hatzell and Medford began collaborating on a materials mystery that originated with a 1941 paper published by Seshacharyulu Dhar, an Indian soil scientist who reported observing an increase in ammonia emitted from compost subjected to light. Dhar suggested that a photocatalytic reaction with minerals in the compost could be responsible for the ammonia.
Since that paper, other researchers have reported nitrogen fixation on titania and ammonia production, but the results have not been consistently confirmed experimentally.
Medford, a theoretician, worked with graduate research assistant Benjamin Comer to model the chemical pathways that would be needed to fix nitrogen on titania to potentially create ammonia using additional reactions. The calculations suggested the proposed process was highly unlikely on pure titania, and the researchers failed to win a grant they had proposed to use to study the mysterious process. However, they were awarded experimental time on the Advanced Light Source at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory, which allowed them to finally test a key component of the hypothesis.
Specialized equipment at the lab allowed Hatzell and graduate student Yu-Hsuan Liu to use X-ray photoelectron spectroscopy (XPS) to examine the surface of titania as nitrogen, water and oxygen interacted with the surfaces under near-ambient pressure in the dark and in the light. At first, the researchers saw no photochemical nitrogen fixation, but as the experiments continued, they observed a unique interaction between nitrogen and titania when light was directed at the minerals surface.
What accounted for the initial lack of results? Hatzell and Medford believe that surface contamination with carbon – likely from a hydrocarbon – is a necessary part of the catalytic process for nitrogen reduction on the titania. “Prior to testing, the samples are cleaned to remove nearly all the trace carbon from the surface, however during experiments carbon from various sources (gases and the vacuum chamber) can introduce trace amount of carbon back onto the sample,” Hatzell explained. “What we observed was that reduced nitrogen species only were detected if there was a degree of carbon on the sample.”
The hydrocarbon contamination hypothesis would explain why earlier research had provided inconsistent results. Carbon is always present at trace levels on titania, but getting the right amount and type may be key to making the hypothesized reaction work.
“We think this explains the puzzling results that had been reported in the literature, and we hope it gives insights into how to engineer new catalysts using this 75-year-old mystery,” Medford said. “Often the best catalysts are materials that are very pristine and made in a clean room. Here you have just the opposite – this reaction actually needs the impurities, which could be beneficial for sustainable applications in farming.”
The researchers hope to experimentally confirm the role of carbon with upcoming tests at Pacific Northwest National Laboratory (PNNL), which will allow them to directly probe the carbon during the photocatalytic nitrogen fixation process. They also hope to learn more about the catalytic mechanism so that they can better control the reaction to improve efficiency, which is currently less than one percent.
The research reported in the journal did not measure ammonia, but Hatzell and her students have since detected it in lab scale tests. Because the ammonia is currently produced at such low levels, the researchers had to take precautions to avoid ammonia-based contamination. “Even tape used on equipment can create small quantities of ammonia that can affect the measurements,” Medford added.
Though the amounts of ammonia produced by the reaction are currently low, Hatzell and Medford believe that with process improvements, the advantages of on-site fertilizer production under benign conditions could overcome that limitation.
“While this may sound ridiculous from a practical perspective at first, if you actually look at the needs of the problem and the fact that sunlight and nitrogen from the air are free, on a cost basis it starts to look more interesting,” Medford said. “If you could operate a small-scale ammonia production facility with enough capacity for one farm, you have immediately made a difference.”
Hatzell credits cutting-edge surface science with finally providing an explanation to the mystery.
“Since earlier investigators looked at this, there have been significant advances made in the area of measurement and surface science,” she said. “Most surface science measurements require the use of ultra-high vacuum conditions which do not mimic the catalytic environment you aim to investigate. The near ambient pressure XPS at Lawrence Berkeley National lab, allowed us to take a step closer to observing this reaction in its native environment.”
The research was supported by startup funds from Georgia Tech to Hatzell and Medford, and by Georgia Tech’s Serve-Learn-Sustain initiative. The effort also received a boost from Georgia Tech’s Technological Innovation: Generating Economic Results (TI:GER®) program, which supported research into potential stakeholders for scale-up of the process.
In addition to those already mentioned, the research included Marm B. Dixit and Kelsey B. Hatzell from Vanderbilt University and Yifan Ye and Ethan J. Crumlin from Lawrence Berkeley Laboratory.
This research used resources of the Advanced Light Source, which is a DOE Office of Science User Facility under contract number DE-AC02-05CH11231.
CITATION: Benjamin M. Comer, et al., “The Role of Adventitious Carbon in Photo-catalytic Nitrogen Fixation by Titania,” (Journal of American Chemical Society, 2018). http://dx.doi.org/10.1021/jacs.8b08464
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]]>Though the cell is in the lab, it has high potential to someday electrically power homes and perhaps cars, say the researchers at the Georgia Institute of Technology who led its development. In a new study in the journal Nature Energy the researchers detailed how they reimagined the entire fuel cell with the help of a newly invented fuel catalyst.
The catalyst has dispensed with high-priced hydrogen fuel by making its own out of cheap, readily available methane. And improvements throughout the cell cooled the seething operating temperatures that are customary in methane fuel cells dramatically, a striking engineering accomplishment.
Methane fuel cells usually require temperatures of 750 to 1,000 degrees Celsius to run. This new one needs only about 500, which is even a notch cooler than automobile combustion engines, which run at around 600 degrees Celsius.
That lower temperature could trigger cascading cost savings in the ancillary technology needed to operate a fuel cell, potentially pushing the new cell to commercial viability. The researchers feel confident that engineers can design electric power units around this fuel cell with reasonable effort, something that has eluded previous methane fuel cells.
“Our cell could make for a straightforward, robust overall system that uses cheap stainless steel to make interconnectors,” said Meilin Liu, who led the study and is a Regents Professor in Georgia Tech’s School of Materials Science and Engineering. Interconnectors are parts that help bring together many fuel cells into a stack, or functional unit.
“Above 750 degrees Celsius, no metal would withstand the temperature without oxidation, so you’d have a lot of trouble getting materials, and they would be extremely expensive and fragile, and contaminate the cell,” Liu said.
“Lowering the temperature to 500 degrees Celsius is a sensation in our world. Very few people have even tried it,” said Ben deGlee, a graduate research assistant in Liu’s lab and one of the first authors of the study. “When you get that low, it makes the job of the engineer designing the stack and connected technologies much easier.”
The new cell also eliminates the need for a major ancillary device called a steam reformer, which is normally required to convert methane and water into hydrogen fuel.
Liu, deGlee, co-first author Yu Chen, who is a postdoctoral researcher in Liu’s lab, and co-first author Yu Tang of the University of Kansas, published the results of their research on October 29, 2018. Their work was funded by the Office of Basic Energy Sciences and the Advanced Research Projects Agency-Energy (ARPA-E), both in the U.S. Department of Energy. It was also funded by the National Science Foundation’s Division of Chemistry.
The research was based on a type of fuel cell with high potential for commercial viability, the solid oxide fuel cell (SOFC). SOFCs are known for their versatility in fuels they can use.
If it goes to market, though the new cell might not power automobiles for a while, it could land sooner in basements as part of a more decentralized, cleaner, cheaper electrical power grid. The fuel cell stack itself would be about the size of a shoebox, plus ancillary technology to make it run.
“The hope is you could install this device like a tankless water heater. It would run off of natural gas to power your house,” Liu said. “That would save society and industry the enormous cost of new power plants and large electrical grid expansions.”
“It would make homes and businesses more power independent,” Liu said. “That kind of system would be called distributed generation, and our sponsors want to develop that.”
Hydrogen is the best fuel for powering fuel cells, but its cost is exorbitant. The researchers figured out how to convert methane to hydrogen in the fuel cell itself via the new catalyst, which is made with cerium, nickel and ruthenium and has the chemical formula Ce0.9Ni0.05Ru0.05O2, abbreviated CNR.
When methane and water molecules come into contact with the catalyst and heat, nickel chemically cleaves the methane molecule. Ruthenium does the same with water. The resulting parts come back together as that very desirable hydrogen (H2) and carbon monoxide (CO), which the researchers surprisingly put to good use.
“CO causes performance problems in most fuel cells, but here, we’re using it as a fuel,” Chen said.
H2 and CO continue on to further catalyst layers that make up the anode, the part of the fuel cell that yanks off electrons, making the carbon monoxide and hydrogen positively charged ions. The electrons travel via a wire - creating the electricity flow - toward the cathode.
There, oxygen, which is very electron-hungry, sucks up the electrons, closing the electrical circuit and becoming O2- ions. Ionized hydrogen and oxygen meet and exit the system as water condensation; the carbon monoxide and oxygen ions meet to become pure carbon dioxide, which could be captured.
For the energy produced, fuel cell technology creates far, far less carbon dioxide than combustion engines.
In some fuel cells, the water in the initial reactions must be introduced from the outside. In this new fuel cell, it’s replenished in the last reaction phase, which forms water that cycles back to react with the methane.
The new catalyst, CNR, manufactured by research collaborators at the University of Kansas, is the outer layer of the anode side of the cell and doubles as a protectant against decay, extending the life of the cell. CNR has strong cohort catalysts in inner layers and on the other side of the cell, the cathode.
On the cathode end, oxygen’s reaction and movement through the system are usually notoriously slow, but Liu’s lab has recently sped it up to raise the electricity output by using what’s called nanofiber cathodes, which Liu’s lab developed in a prior study. (A tailored double perovskite nanofiber catalyst enables ultrafast oxygen evolution.)
“The structures of these various catalysts, as well as the nanofiber cathodes, all together allowed us to drop the operating temperature,” Chen said.
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The following people coauthored the research: Bote Zhao, Lei Zhang, Seonyoung Yoo, Kai Pei, Jun Hyuk Kim and Yong Ding of Georgia Tech; Yuechang Wei and Franklin Feng Tao of the University of Kansas, and Ziyun Wang and P. Hu of The Queen’s University of Belfast. The research was funded by the U.S. Department of Energy under the following agencies and programs: Advanced Research Projects Agency-Energy (ARPA-E) REBELS program (award DE-AR0000502), and SECA Core Technology Program (award DE-FE0031201), the Catalysis program of the Office of Basic Energy Sciences (grant DE- SC0014561). It was also funded by the Division of Chemistry of the National Science Foundation (award 1462121). Any results, conclusions, and opinions are those of the authors and not necessarily of the funding agencies.
DOI: 10.1038/s41560-018-0262-5
Writer & Media Representative: Ben Brumfield (404-660-1408), ben.brumfield@comm.gatech.edu
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NASA has navigated our solar system with spacecraft and landers, but still, our celestial neighbors remain vast frontiers, particularly in the search for life. Now, an alliance of researchers will accelerate the quest to find it.
The NASA Astrobiology Program has announced the establishment of the Network for Life Detection, NFoLD, which connects researchers to pursue the detection of life and clues thereof on our neighboring planets and their moons. NFoLD includes an oceanic research alliance led by the Georgia Institute of Technology.
It is called Oceans Across Space and Time, OAST, and has received a $7 million NASA Astrobiology grant with the long-range goal of extracting secrets from present and past oceans on Mars, Jupiter’s icy moon Europa, and Saturn’s moon Enceladus. But OAST will also ramp up the study of the conditions that spawned first life in Earth’s oceans.
“With OAST, we finally hit the perfect mix of people, science questions, and supporting activities to really go after some of the most important unknowns in astrobiology,” said Britney Schmidt, OAST’s principal investigator and an assistant professor in Georgia Tech’s School of Earth and Atmospheric Sciences.
NFoLD is one of five new Research Coordination Networks that the NASA Astrobiology Program has announced. The other RCNs pull together research communities that include the study of early Earth and its chemistry, evolution, distant habitable worlds, and exoplanet systems.
Oceans Across Space and Time could one day help NASA put a submarine on a rocket to Europa to look for life in the ocean beneath its ice crust. Or OAST could join NFoLD colleagues to help NASA explore parched Martian landscapes that once were oceans.
But the path to our space neighbors leads through studying Earth. Field and lab experiments on our planet will divulge more knowledge about chemical and biological evolutionary strategies so that researchers can develop instruments and methodology that reliably detect signs of life on other planets and moons.
"We don't yet have a slam-dunk measurement that we could make on another planet to definitively say ‘this is life,’” said Schmidt, who coordinates OAST and led the application efforts to establish it. “OAST’s main goal is to take a suite of technologies into the field on Earth to make measurements side-by-side while returning samples to the lab to understand.”
Then, when that is very finely honed, send it aloft.
One of NFoLD’s goals is to participate in future astrobiology space missions from the start so that they can successfully identify target spots on other planets or moons where signs of life could actually be detected if present.
"A major challenge for life detection is where on a given planet or moon to look for life,” said Jeff Bowman, deputy principal investigator of OAST and an assistant professor at Scripps Institution of Oceanography at UC San Diego. “The density of life on our own planet extends across several orders of magnitude. Look for life in the wrong place and Earth could appear lifeless.”
OAST’s team has the expertise to bridge earthly data and celestial goals.
Many of its 18 co-investigators and their teams have already explored biogeochemistry in our own planet’s eons-old rock record, in the atmosphere, the oceans, and the icecaps with an eye to extrapolating the data to other worlds. Other OAST researchers have helped design Mars probes or build robotic submarines intended to one day dive into Europa’s subsurface ocean to detect life or at least a hint of it.
“OAST researchers have expertise in detecting and characterizing life in a variety of harsh environments like the Antarctic, the deepest ocean trenches, and lakes with extreme chemistry and salinity,” Bowman said. “We will leverage this expertise to understand how life may be distributed in different ocean environmental extremes around the solar system.”
OAST includes investigators from Scripps Institution of Oceanography at the University of California San Diego; the University of Kansas; Louisiana State University; the Massachusetts Institute of Technology; Stanford University; the Blue Marble Space Institute of Science; the University of Texas; Colgate University; the University of California, the University of Central Florida; the University of Auckland; York University; the University of Otago, and the New Zealand National Institute of Water and Atmospheric Research.
“I'm particularly proud of the high number of women and pre-tenure scientists we've engaged through our project,” said Schmidt. Five leaders in OAST are women, and 12 researchers are early career or pre-tenure. The project will also support graduate and undergraduate students as well as postdoctoral researchers through the NASA Postdoctoral Program.
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]]>In the system inside cells that translates genetic code into life, he replaced about 1,000 essential linchpins with primitive substitutes to see if the translational system would survive and function. It seemed impossible, yet it went swimmingly, and Bray had compelling evidence that the system would have worked as it is today in extremely harsh conditions 4 billion years ago when it evolved.
The experiment’s success reaffirmed the translational system’s place at the earliest foundations of life on Earth and its robustness through the eons.
Every living thing exists because the translational system receives messages from DNA delivered to it by RNA and translates the messages into proteins. The system centers on a cellular machine called the ribosome, which is made of multiple large molecules of RNA and protein and is ubiquitous in life as we know it.
“There’s nothing alive without ribosomes,” said Loren Williams, a professor at the Georgia Institute of Technology’s School of Chemistry and Biochemistry. “The ribosome is about the oldest and most universal part of biology, and its origins go very far back to a time not too long after Earth had formed and cooled.”
Those linchpins that hold it all together and that Bray yanked out and replaced were metal ions (atoms with charges, in this case positive).
In today’s ribosome, and in the whole translational system, the linchpins are magnesium ions, and Bray’s experiment replaced them all with iron ions and manganese ions, which were overabundant on primordial Earth. Williams and Jennifer Glass, the principal investigators in the new study, also had their doubts the system would hold up without the magnesium.
“I thought, ‘It’s not going to work, but we might as well try the moonshot’,” said Williams who has led similar work before but on simpler molecules. “The fact that swapping out all the magnesium in the translational system actually worked was mind-boggling.”
That’s because in living systems today, magnesium helps shape ribosomes and help them work. It is needed in addition to the ribosome for some 20 enzymes of the translational system. It’s one reason why dietary magnesium (Mg) is so important.
“The number of different things magnesium does in the ribosome and in the translational system is just enormous,” said Williams. “There are so many types of catalytic activities in translation, and magnesium is involved in almost all of them.”
When first life evolved, fissures in Earth’s crust still belched lava and meteor impacts were still common. There was no breathable oxygen and the planet was brimming with iron and manganese.
This may have made them attractive for the translational system to use as the dominant ions. Magnesium was likely involved, too, though it was probably less available than today.
The researchers wanted to know if the translational system first evolved to function with those other metals as their linchpins. So, Bray, a graduate research assistant in Williams’s and in Glass’s lab, swapped out the magnesium ions for them, tabula rasa.
“We didn’t have any substantial reason to believe it would work, and it was a huge surprise to all of us when it did,” Bray said. And it strongly corroborated that the translational system would have thrived under early Earth conditions.
Bray, co-first author Timothy Lenz and co-principal investigators Glass and Williams published their results in the journal Proceedings of the National Academy of Sciences on November 9, 2018. The research was funded by the NASA Exobiology program. Glass is an assistant professor in Georgia Tech’s School of Earth and Atmospheric Sciences.
Amazingly, the atomic swaps barely changed the shape of the ribosome.
“It’s totally unbelievable this would work because biology makes very specific use of things. Change one atom and it can wreck a whole protein,” Williams said. “When we probed the structure, we saw that all three metals do essentially the same thing to the structure.”
When they tested the performance of the translational system with iron replacing magnesium, it was 50 to 80 percent as efficient as normal (with magnesium). “Manganese worked even better than iron,” Bray said.
“I think these may be textbook-rewriting results since the whole field of ribosome research involves magnesium,” Bray said. “Now, with what we’ve done, it’s no longer the case that only magnesium works.”
Bray incubated ribosomes in the presence of magnesium, iron, or manganese inside a special chamber with an artificial atmosphere devoid of oxygen, like the Earth four billion years ago.
He found that the magnesium replacement went far beyond atoms in the ribosome.
“Surrounding the ribosome is also a huge cloud of magnesium atoms. It’s called an atmosphere, or shell, and engulfs it completely. I replaced everything, including that, and the whole system still worked.”
Eons down the road, the evolution of the translational system in the presence of magnesium may have given it an adaptive advantage. As oxygen levels on Earth rose, binding up free manganese and iron, and making them less available to biology, magnesium probably comfortably assumed the thousands of roles it occupies in the translational system today.
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These researchers coauthored the study: Jay Haynes, Jessica Bowman, Anton Petrov, Amit Reddi, and Nicholas Hud, all of Georgia Tech. The research was funded by the NASA Exobiology program (grants NNX14AJ87G, NNX16AJ28G, and NNX16AJ29G). Findings, conclusions, opinions, and recommendations in the material are those of the authors and not necessarily of NASA.
Study in PNAS: http://www.pnas.org/content/early/2018/10/30/1810140115
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]]>“What we have here is the proof of concept of an integrated system for manufacturing complex origami. It has tremendous potential applications,” said Glaucio H. Paulino, the Raymond Allen Jones Chair and professor at the School of Civil and Environmental Engineering at the Georgia Institute of Technology and a leader in the growing field of origami engineering, or using the principles of origami, mathematics and geometry to make useful things. Last fall Georgia Tech became the first university in the country to offer a course on origami engineering, which Paulino taught.
The researchers used a relatively new kind of 3D printing called Digital Light Processing (DLP) to create groundbreaking origami structures that are not only capable of holding significant weight but can also be folded and refolded repeatedly in an action similar to the slow push and pull of an accordion. When Paulino first reported these structures, or “zippered tubes,” in 2015, they were made of paper and required gluing. In the current work, the zippered tubes – and complex structures made out of them – are composed of one plastic (a polymer) and do not require assembly.
The work was reported in a recent issue of Soft Matter, a journal published by the Royal Society of Chemistry. The primary authors are Paulino; H. Jerry Qi, The Woodruff Faculty Fellow in Georgia Tech’s George W. Woodruff School of Mechanical Engineering; and Daining Fang of Peking University and the Beijing Institute of Technology. Other authors are Zeang Zhao, a visiting student at Georgia Tech now at Peking University; Qiang Zhang of Peking University; and Xiao Kuang and Jiangtao Wu of Georgia Tech.
An Emerging Technology
There are many different types of 3D printing technologies. The most familiar, inkjet, has been around for some 20 years. But until now, it has been difficult to create 3D-printed structures with the intricate hollow features associated with complex origami because removing the supporting materials necessary to print these structures is challenging. Further, unlike paper, the 3D-printed materials could not be folded numerous times without breaking.
Enter DLP and some creative engineering. According to Qi, a leader in the emerging field collaborating with Fang’s group at Peking University, DLP has been in the lab for a while, but commercialization only began about five years ago. Unlike other 3D printing techniques, it creates structures by printing successive layers of a liquid resin that is then cured, or hardened, by ultraviolet light.
For the current work, the researchers first developed a new resin that, when cured, is very strong. “We wanted a material that is not only soft, but can also be folded hundreds of times without breaking,” said Qi. The resin, in turn, is key to an equally important element of the work: tiny hinges. These hinges, which occur along the creases where the origami structure folds, allow folding because they are made of a thinner layer of resin than the larger panels of which they are part. (The panels make up the bulk of the structure.)
Together the new resin and hinges worked. The team used DLP to create several origami structures ranging from the individual origami cells that the zippered tubes are composed of to a complex bridge composed of many zippered tubes. All were subjected to tests that showed they were not only capable of carrying about 100 times the weight of the origami structure, but also could be repeatedly folded and unfolded without breaking. “I have a piece that I printed about six months ago that I demonstrate for people all the time, and it’s still fine,” said Qi.
What’s Next?
What’s next? Among other things, Qi is working to make the printing even easier while also exploring ways to print materials with different properties. Meanwhile, Paulino’s team recently created a new origami pattern on the computer that he is excited about but that he has been unable to physically make because it is so complex. “I think the new system could bring it to life,” he said.
The principal funders of the work were the Air Force Office of Scientific Research (FA9550-16-1-0169), the National Science Foundation (CMMI-1462894, CMMI-1462895, and CMMI-1538830), the Raymond Allen Jones Chair at Georgia Tech, the National Natural Science Foundation of China, and the National Materials Genome Project of China.
CITATION: Zeang Zhao, et al., “3D printing of complex origami assemblages for reconfigurable structures,” (Soft Matter 39, 2018) http://dx.doi.org/10.1039/c8sm01341a
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]]>Using microfluidic technology to advance the preparation of samples from the chemically complex bioreactor environment, the researchers have harnessed electrospray ionization mass spectrometry (ESI-MS) to provide online monitoring that they believe will provide for therapeutic cell production the kind of precision quality control that has revolutionized other manufacturing processes.
“The way that the production of cell therapeutics is done today is very much an art,” said Andrei Fedorov, Woodruff Professor in the George W. Woodruff School of Mechanical Engineering at the Georgia Institute of Technology. “Process control must evolve very quickly to support the therapeutic applications that are emerging from bench science today. We think this technology will help us reach the goal of making these exciting cell-based therapies widely available.”
By measuring very low concentrations of specific compounds secreted or excreted by cells, the technique could also help identify which biomolecules – of widely varying sizes – should be monitored to guide the control of cell health. Ultimately, the researchers hope to integrate their label-free monitoring directly into high-volume bioreactors that will produce cells in quantities large enough to make the new therapies available at a reasonable cost and consistent quality.
Development of the Dynamic Mass Spectrometry Probe (DMSP) was supported by the National Science Foundation (NSF) Engineering Research Center for Cell Manufacturing Technologies (CMaT), which is headquartered at Georgia Tech. The work was reported September 10 in the journal Biotechnology and Bioengineering.
Traditional ESI-MS techniques have revolutionized analytical chemistry by allowing precise identification of complex biological compounds. Because of complex sample preparation requirements, existing approaches to ESI-MS require too much time to be useful for continuous monitoring of cell growth in bioreactors, where maintaining narrow parameters for specific indicators of cellular health is critical. Biological samples also contain salts, which must be removed before introduction into the ESI-MS system.
To accelerate the analytical process, Fedorov and a team that included graduate research assistant Mason Chilmonczyk and research engineer Peter Kottke used microfluidic technology to help separate compounds of interest from the salts. Salt removal uses a monolithic device in which a size-selective membrane with nanoscale pores is placed between two fluid flows, one the chemically complex sample drawn from the bioreactors and the other salt-free water with conditioning compounds.
The smaller salt molecules readily diffuse out of the sampled bioreactor flow through the nanopores, while the larger biomolecules mostly remain for the subsequent ESI-MS analysis. Meanwhile, chemical additives are at the same time introduced into the sample mixture through the same membrane nanopores to enhance ionization of the target biomolecules in the sampled mixture for improved ESI-MS analysis.
“We have used advanced microfabrication techniques to create a microfluidic device that will be able to treat samples in less than a minute,” said Chilmonczyk. “Traditional sample preparation can require hours to days.”
The process can currently remove as much as 99 percent of the salt, while retaining 80 percent of the biomolecules. Introduction of the conditioning chemicals allows the molecules to accept a greater charge, improving the capability of the mass spectrometer to detect low concentration biomolecules, and to measure large molecules.
“We can detect really high molecular weight molecules that the mass spectrometer normally wouldn’t be able to detect,” Fedorov said. “The size difference in the molecules of interest can be dramatic, so the improvement in the limit of detection across a broad range of analyte molecular weights will allow this technique to be more useful in cell manufacturing.”
Because they use state of the art microfabrication techniques, the DMSP devices can be mass produced, allowing sampling to be scaled up to include multiple bioreactors at low cost. The small size of the device channels – which are just five microns tall – allows the system to produce results with samples as small as 20 nanoliters – with the potential for reducing that to as little as a single nanoliter.
“We need to monitor small concentrations of large biomolecules in this messy environment in a production line in such a way that we can check at any point how the cells are doing,” Fedorov said. “This system could continuously monitor whether certain molecules are excreted or secreted at a reduced or increased rate. By correlating these measurements with cell health and potency, we could improve the manufacturing process.”
Before the analytical techniques can be applied to quality control, the researchers must first identify biomolecules that indicate health of the growing cells. By sampling the bioreactor content locally in the immediate vicinity of cells and allowing identification of very small quantities of biochemicals, the DMSP technology can help researchers identify changes in molecular concentrations – which range from pico-molar to micro-molar – that may indicate the state of cells in the bioreactors. This would prompt adjustment of conditions in a bioreactor just in time to return to the state of healthy cell growth.
“In this situation, we often can’t see the trees for the forest,” said Fedorov. “There is a lot of material available, but we are looking for just a handful of individual trees that indicate the health of the cells. Because the forest is overgrown, the few selected trees we need to examine are hard to find. This is a grand challenge technologically.”
The research team also included Research Scientist Hazel Stevens and Professor Robert Guldberg, who is now at the University of Oregon.
CITATION: Mason A. Chilmonczyk, Peter A. Kottke, Hazel Y. Stevens, Robert E. Guldberg and Andrei G. Fedorov, “Dynamic Mass Spectrometry Probe (DMSP) for ESI?MS Monitoring of Bioreactors for Therapeutic Cell Manufacturing,” (Biotechnology and Bioengineering, 2018). https://dx.doi.org/10.1002/bit.26832
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]]>The researchers at the Georgia Institute of Technology made the chemical medley in the lab to closely mimic membraneless organelles, mini-organs in cells that are not contained in a membrane but exist as pools of watery solutions, or puddles. And their model demonstrated how, with just a few ingredients, the organelles could carry out fine-tuned biological processes.
The researchers published the results of their study in the journal ACS Applied Materials & Interfaces for the September 26, 2018 issue. The research was funded by the National Institutes of Health’s National Institute of General Medical Science and by the National Science Foundation.
A quick look at membraneless organelles should aid in understanding the research’s significance.
Organelles that are pools of watery solutions and not objects with membranes are a fairly recent discovery. A prime example is the nucleolus. It resides inside of the cell’s nucleus, which is an organelle that does have a membrane.
In the past, researchers thought the nucleolus disappeared during cell division and reappeared later. In the meantime, researchers have realized that the nucleolus has no membrane and that during cell division it gets diffused the way water bubbles do in vinaigrette dressing that has been shaken up.
“After cell division, the nucleolus comes back together as a single compartment of fluid,” said Shuichi Takayama, the study’s principal investigator and a professor in the Wallace E. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University.
Membraneless organelles can be made up of a few different aqueous solutions, each with different solutes like proteins or sugar or RNA or salt. Differences in the thermodynamics of the solutions, that is, how their molecules bounce around, keep them from merging into a single solution.
Instead, they phase separate the way oil and water do, even after intermingling. But there’s no oil in this case.
“They’re all waters,” Takayama said. “They just don’t mix with each other because they have different solutes.”
During intermingling, important things happen. The nucleolus, for example, is vital to DNA transcription. But the synthetic set-up, a collection of watery solutions made by the study’s first author, Taisuke Kojima, carried out a simpler series of reactions that demonstrated how membraneless organelles could process sugar.
“We had three phases of solutions that each held different reactants,” Kojima said. “It was like a ball with three layers: an outer solution, an intermediate solution, and a core solution. Glucose was in the outer layer; an enzyme, glucose oxidase, was in the second layer, and horseradish peroxidase was in the core along with a colorimetric substrate that gave us a visible signal when the last reaction we were looking for occurred.”
The glucose in the outer layer interfaced with the glucose oxidase in the second layer, which catalyzed the glucose to hydrogen peroxide. It landed in the second layer and interfaced with the horseradish peroxidase in the core layer, which catalyzed the hydrogen peroxide along with the compound that turns colors, which changed the color of the core layer.
“This type of cascading reaction is what one would expect to see membraneless organelles perform,” Takayama said.
The cascade even transported each reaction product from one compartment to the next, something very typical in biological processes, like organs digesting food or an organelle processing molecules.
Part of the reaction took the researchers by surprise, and it resulted in a novel discovery.
“When researchers think about membraneless organelles, we often think that the reactions inside them are more efficient when their enzymes and substrates are in the same compartment,” Takayama said. “But in our experiments, that actually slowed the reaction down. We said, ‘Whoa, what’s going on here?’”
“When the substrate is in the same place where the product of the reaction also builds up, the enzyme sometimes gets confused, and that can impede the reaction,” said Kojima, who is a postdoctoral researcher in Takayama’s lab. “I was pretty surprised to see it.”
Kojima put the enzymes and substrate into separate solutions, which interfaced but did not merge to a single solution, and the reaction in his synthetic organelle worked efficiently. This showed how unexpected subtleties may be fine-tuning organelle chemistry.
“It was a Goldilocks regime, not too much contact between substrate and enzyme, not too little, just right,” Takayama said.
“Sometimes, in a cell, a substrate is not abundant and may need to be concentrated in its own little compartment and then brought into contact with the enzyme,” Takayama said. “By contrast, some substrates can be very abundant in the nucleus, and it might be important to partition them off from enzymes to get just enough contact for the right kind of reaction.”
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Also read: Buzzing Cancer Drugs into Malignancies in the Brain
The research was funded by the National Institutes of Health’s National Institute of General Medical Science (grant R01 GM12351) and by the National Science Foundation (grant CBET 0939511). Findings, opinions, and conclusions are those of the authors and not necessarily of the NIH.
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Three Atlanta area universities jointly launched a nuclear magnetic resonance collaboration called the Atlanta NMR Consortium to optimize the use of this technology that provides insights into relevant chemical samples containing so many compounds that they can otherwise easily elude adequate characterization. The consortium has been operating since July 2018.
Take, for example, crab urine. It’s packed with hundreds to thousands of varying metabolites, and researchers at the Georgia Institute of Technology wanted to nail down one or two of them that triggered a widespread crab behavior. Without access to NMR they may not have found them at all even after an extensive search.
The spectrometer pulled the right two needles out of the haystack, so the researchers could test them on the crabs and confirm that they were initiating the behavior.
Emory University, Georgia State University and Georgia Tech already have NMR technology, but the Atlanta NMR Consortium will enable them to fully exploit it while cost-effectively staying on top of upgrades.
“NMR continues to grow and develop because of technological advances,” said David Lynn, a chemistry professor at Emory University.
That means buying new machines every so often, and one new NMR spectrometer can run into the millions; annual maintenance for one machine can cost tens of thousands of dollars. Thus, reducing costs and maximizing usage makes good sense.
The human body, sea-side estuaries, and rock strata present huge collections of compounds. NMR takes inventory of complex samples from such sources via the nuclei of atoms in the molecules.
A nucleus has a spin, which makes it magnetic, and NMR spectrometry’s own powerful magnetism detects spins and pinpoints nuclei to feel out whole molecules. These can be large or small, from mineral compounds with three or four component atoms to protein polymers with tens of thousands of parts.
Researchers in medicine, biochemistry, ecology, geology, food science – the possible list is exhaustive -- turn to NMR to untangle their particular molecular jungles. The consortium wants to leverage that diversity.
“As we go in different directions, we will benefit from a cohesive community of people who know how to use NMR for a wide range of problems,” said Anant Paravastu, an associate professor in Georgia Tech’s School of Chemical and Biomolecular Engineering.
“The most important goal for us is the sharing of our expertise,” said Markus Germann, a professor of chemistry at Georgia State.
Consortium members will benefit the most from the pooled NMR resources, but non-partners can also book access. Read more about the Atlanta NMR Consortium here on Georgia Tech’s College of Sciences website
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]]>Facilities such as electric power networks, manufacturing operations and water purification plants are among the potential targets for malicious actors because they use programmable logic controllers (PLCs) to open and close valves, redirect electricity flows and manage large pieces of machinery. Efforts are underway to secure these facilities, and helping operators become more skilled at detecting potential attacks is a key part of improving security.
“The goal is to give operators, researchers and students experience with attacking systems, detecting attacks and also seeing the consequences of manipulating the physical processes in these systems,” said Raheem Beyah, the Motorola Foundation Professor in the School of Electrical and Computer Engineering at the Georgia Institute of Technology. “This system allows operators to learn what kinds of things will happen. Our goal is to make sure the good guys get this experience so they can respond appropriately.”
Details of the simulator were presented August 8 at Black Hat USA 2018, and August 13 at the 2018 USENIX Workshop on Advances in Security Education. The simulator was developed in part by Atlanta security startup company Fortiphyd Logic, and supported by the Georgia Research Alliance.
The simulated chemical processing plant, known as the Graphical Realism Framework for Industrial Control Simulations (GRFICS), allows users to play the roles of both attackers and defenders – with separate views provided. The attackers might take control of valves in the plant to build up pressure in a reaction vessel to cause an explosion. The defenders have to watch for signs of attack and make sure security systems remain operational.
Of great concern is the “man-in-the-middle” attack in which a bad actor breaks into the facility’s control system – and also takes control of the sensors and instruments that provide feedback to the operators. By gaining control of sensors and valve position indicators, the attacker could send false readings that would reassure the operators – while the damage proceeded.
“The pressure and reactant levels could be made to seem normal to the operators, while the pressure is building toward a dangerous point,” Beyah said. Though the readings may appear normal, however, a knowledgeable operator might still detect clues that the system has been attacked. “The more the operators know the process, the harder it will be to fool them,” he said.
The GRFICS system was built using an existing chemical processing plant simulator, as well as a 3D video gaming engine running on Linux virtual machines. At its heart is the software that runs PLCs, which can be changed out to represent different types of controllers appropriate to a range of facilities. The human-machine interface can also be altered as needed to show a realistic operator control panel monitoring reaction parameters and valve controller positions.
“This is a complete virtual network, so you can set up your own entry detection rules and play on the defensive side to see whether or not your defenses are detecting the attacks,” said David Formby, a Georgia Tech postdoctoral researcher who has launched Fortiphyd Logic with Beyah to develop industrial control security products. “We provide access to simulated physical systems that allow students and operators to repeatedly study different parameters and scenarios.”
GRFICS is currently available as an open source, free download for use by classes or individuals. It runs on a laptop, but because of heavy use of graphics, requires considerable processing power and memory. An online version is planned, and future versions will simulate the electric power grid, water and wastewater treatment facilities, manufacturing facilities and other users of PLCs.
Formby hopes GRFICS will expand the number of people who have experience with the security of industrial control systems.
“We want to open this space up to more people,” he said. “It’s very difficult now to find people who have the right experience. We haven’t seen many attacks on these systems yet, but that’s not because they are secure. The barrier for people who want to work in the cyber-physical security space is high right now, and we want to lower that.”
Beyah and Formby have been working for several years to increase awareness of the vulnerabilities inherent in industrial control systems. While the community still has more to do, Beyah is encouraged.
“Several years ago, we talked to a lot of process control engineers as part of the NSF’s I-Corps program,” he said. “It was clear that for many of these folks then, security was not a major concern. But we’ve seen changes, and lots of people are now taking system security seriously.”
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]]>A new study led by the Georgia Institute of Technology suggests that nitrous oxide, known for its use as the dental sedative laughing gas, may have played a significant role.
The research team carried out experiments and atmospheric computer modeling that in detail substantiated an existing hypothesis about the presence of nitrous oxide (N2O), a powerful greenhouse gas, in the ancient atmosphere. Established research has already pointed to high levels of carbon dioxide and methane, but they may not have been plentiful enough to sufficiently keep the globe warm without the help of N2O.
Jennifer Glass, an assistant professor at Georgia Tech, and Chloe Stanton, formerly an undergraduate research assistant in the Glass lab at Georgia Tech, published the study in the journal Geobiology on Wednesday, August 22, 2018. Their work was funded by the NASA Astrobiology Institute. Stanton is now a graduate research assistant at the Pennsylvania State University.
The study focused on the middle of the Proterozoic Eon, over a billion years ago. The proliferation of complex life was still a few hundred million years out, and the pace of our planet’s evolution probably appeared deceptively slow.
“People in our field often refer to this middle chapter in Earth’s history roughly 1.8 to 0.8 billion years ago as the ‘boring billion’ because we classically think of it as a very stable period,” said Stanton, the study’s first author. “But there were many important processes affecting ocean and atmospheric chemistry during this time.”
Chemistry in mid-Proterozoic ocean was heavily influenced by abundant soluble ferrous iron (Fe2+) in oxygen-free deep waters.
“The ocean chemistry was completely different back then,” said Glass, the study’s principal investigator. “Today’s oceans are well-oxygenated, so iron rapidly rusts and drops out of solution. Oxygen was low in Proterozoic oceans, so they were filled with ferrous iron, which is highly reactive.”
In lab experiments, Stanton found that Fe2+ in seawater reacts rapidly with nitrogen molecules, especially nitric oxide, to yield nitrous oxide in a process called chemodenitrification. This nitrous oxide (N2O) can then bubble up into the atmosphere.
When Stanton plugged the higher fluxes of nitrous oxide into the atmospheric model, the results showed that nitrous oxide could have reached ten times today’s levels if mid-Proterozoic oxygen concentrations were 10 percent of those today. This higher nitrous oxide would have provided an extra boost of global warming under the Faint Young Sun.
Nitrous oxide could have also been what some ancient life breathed.
Even today, some microbes can breathe nitrous oxide when oxygen is low. There are many similarities between the enzymes that microbes use to breathe nitric and nitrous oxides and enzymes used to breathe oxygen. Previous studies have suggested that the latter evolved from the former two.
The Georgia Tech model provides a plentiful source of nitrous oxide in ancient iron-rich seas for this evolutionary scenario. And prior to the Proterozoic, when oxygen was extremely low, early aquatic microbes could have already been breathing nitrous oxide.
“It’s quite possible that life was breathing laughing gas long before it began breathing oxygen,” Glass said. “Chemodenitrification might have supplied microbes with a steady source of it.”
Also READ: Cold Suns, Warm Exoplanets, and Methane Blankets
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The paper was co-authored by Chris Reinhard of Georgia Tech, James Kasting of the Pennsylvania State University, Nathaniel Ostrom and Joshua Haslun of Michigan State University, and Timothy Lyons of the University of California Riverside. The research was funded by grant NNA15BB03A from the NASA Astrobiology Institute. Findings, opinions, and conclusions are those of the authors and not necessarily of the NASA Astrobiology Program.
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]]>Researchers at the Georgia Institute of Technology engineered a molecular matrix, a hydrogel, to deliver muscle stem cells called muscle satellite cells (MuSCs) directly to injured muscle tissue in patients whose muscles don’t regenerate well. In lab experiments on mice, the hydrogel successfully delivered MuSCs to injured, aged muscle tissue to boost the healing process while protecting the stem cells from harsh immune reactions.
The method was also successful in mice with a muscle tissue deficiency that emulated Duchene muscular dystrophy, and if research progresses, the new hydrogel therapy could one day save the lives of people suffering from the disease.
Simply injecting additional muscle satellite cells into damaged, inflamed tissue has proven inefficient, in part because the stem cells encounter an immune system on the warpath.
“Any muscle injury is going to attract immune cells. Typically, this would help muscle stem cells repair damage. But in aged or dystrophic muscles, immune cells lead to the release a lot of toxic chemicals like cytokines and free radicals that kill the new stem cells,” said Young Jang, an assistant professor in Georgia Tech’s School of Biological Sciences and one of the study’s principal investigators.
Only between 1 and 20 percent of injected MuSCs make it to damaged tissue, and those that do, arrive there weakened. Also, some tissue damage makes any injection unfeasible, thus the need for new delivery strategies.
“Our new hydrogel protects the stem cells, which multiply and thrive inside the matrix. The gel is applied to injured muscle, and the cells engraft onto the tissues and help them heal,” said Woojin Han, a postdoctoral researcher in Georgia Tech’s School of Mechanical Engineering and the paper’s first author.
Han, Jang and Andres Garcia, the study’s other principal investigator, published their results on August 15, 2018, in the journal Science Advances. The National Institute of Arthritis and Musculoskeletal and Skin Diseases of the National Institutes of Health funded the research.
Hydrogels often start out as water-based solutions of molecular components that resemble crosses, and other components that make the ends of the crosses attach to each other. When the components come together, they fuse into molecular nets suspended in water, resulting in a material with the consistency of a gel.
If stem cells or a drug are mixed into the solution, when the net, or matrix, forms, it ensnares the treatment for delivery and protects the payload from death or dissipation in the body. Researchers can easily and reliably synthesize hydrogels and also custom-engineer them by tweaking their components, as the Georgia Tech researchers did in this hydrogel.
“It physically traps the muscle satellite cells in a net, but the cells also grab onto chemical latches we engineered into the net,” Han said.
This hydrogel’s added latches, which bond with proteins protruding from stem cells’ membranes, not only increase the cells’ adhesion to the net but also hinder them from committing suicide. Stem cells tend to kill themselves when they’re detached and free-floating.
The chemical components and the cells are mixed in solution then applied to the injured muscle, where the mixture sets to a matrix-gel patch that glues the stem cells in place. The gel is biocompatible and biodegradable.
“The stem cells keep multiplying and thriving in the gel after it is applied,” Jang said. “Then the hydrogel degrades and leaves behind the cells engrafted onto muscle tissue the way natural stem cells usually would be.”
In younger, healthier patients, muscle satellite cells are part of the natural healing mechanism.
“Muscle satellite cells are resident stem cells in your skeletal muscles. They live on muscle strands like specks, and they’re key players in making new muscle tissue,” Han said.
“As we age, we lose muscle mass, and the number of satellite cells also decreases. The ones that are left get weaker. It’s a double whammy,” Jang said. “At a very advanced age, a patient stops regenerating muscle altogether.”
“With this system we engineered, we think we can introduce donor cells to enhance the repair mechanism in injured older patients,” Han said. “We also want to get this to work in patients with Duchene muscular dystrophy.”
“Duchene muscular dystrophy is surprisingly frequent,” Jang said. “About 1 in 3,500 boys get it. They eventually get respiratory defects that lead to death, so we hope to be able to use this to rebuild their diaphragm muscles.”
If the method goes to clinical trials, researchers will likely have to work around the potential for donor cell rejection in human patients.
Also READ: Punching Cancer with RNA Knuckles Wrapped in Hydrogel
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The following researchers coauthored the paper: Shannon Anderson, Mahir Mohiuddin, Shadi Nakhai, and Eunjung Shin from Georgia Tech; Isabel Freitas Amaral, and Ana Paula Pêgo from the University of Porto in Portugal, and Daniela Barros from Georgia Tech and the University of Porto. The research was funded by the National Institute of Arthritis and Musculoskeletal and Skin Diseases of the National Institutes of Health (awards # R21AR072287 and R01AR062368). Any opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect views of the National Institutes of Health.
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]]>The iconic research magazine applauded Dahlman because, as it stated in its headline, “His method makes it possible to test 300 drugs at once.” The “35” roster is noted for having anticipated the successes of Zuckerberg and Page, as well as that of Helen Greiner, co-founder of iRobot, Jonathan Ive, chief designer at Apple, and other consummate go-getters in industry, technology, and research.
Dahlman felt honored to join the list, which was published on June 27, but also humbled.
“I wouldn’t put myself in the same category as those people, but research colleagues who have made this list have gone on to make very significant contributions to science,” said Dahlman, an assistant professor at the Georgia Institute of Technology.
“It’s hard to get on that list, so I was thrilled, and a little surprised,” he said. “It also comes with certain expectations to live up to.”
What Dahlman scrutinizes with his methods are, more precisely, nanoparticles designed to deliver a drug or gene therapy.
He calls his invention “DNA-barcoding," because it tracks hundreds of different nanoparticles at once to see how well they hit targeted tumor cells by loading up each one of the particles with its own custom-coded piece of DNA. Researchers can inject the particles all at once into a live mouse then later excise the tumor and sequence the DNA strands to see which nanoparticles best delivered their payloads to tumor cells.
The top nanoparticles could be loaded up with an effective therapy for targeted delivery.
“DNA makes for a fantastic tracker,” Dahlman said. “There are thousands to millions to billions of code combinations. It’s nature’s way of storing information, so we can exploit that.”
DNA barcoding has upended other methods of tracking nanoparticles. It has flatly nullified the results of tracking via lab samples, in vitro. And barcoding has left traditional tracking in vivo, in live mice, which can only follow one or a few particles at a time, in the dust.
The Review cited specifically DNA barcoding’s potential for honing nanoparticles’ aim at cancer cells, but there are many possible uses.
“It can be for any cell type. We’re also using it for heart disease and for Parkinson’s,” Dahlman said.
Dahlman gives the real credit for the “35” kudos to the graduate students and postdoctoral researchers in his Lab for Precision Therapies in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University.
“They have done a lot of the actual work,” Dahlman said. “If you don’t get good students, you won’t be able to do anything, and the school here should get a lot of credit for recruiting them.”
The graduate students were jazzed to see their principal investigator on a pedestal.
“We were all super excited and all huddled around the computer looking at James’s profile and at the other people on that list to see what they accomplished to get on that list,” said Ph.D. student Cory Sago, who chose Georgia Tech largely because of Dahlman.
Past Georgia Tech researchers named in the “35” list include microneedle patch co-inventor Mark Prausnitz, and microfluidics engineer and genotype-phenotype researcher Hang Lu. More Georgia Tech graduates, mainly from master’s programs, have appeared on the MIT Technology Review roster for making notable entrepreneurial waves.
Dahlman’s inclusion in the 2018 edition of “35 Innovators Under 35” follows a string of prior acknowledgments and fellowships awarded Dahlman by the National Science Foundation, the Defense Advanced Research Projects Agency, the National Institutes of Health and private foundations.
The MIT Technology Review was founded at the Massachusetts Institute of Technology in 1899, and later became independent but maintains its affiliation with MIT. Dahlman received his Ph.D. jointly from MIT and Harvard Medical School in 2014 and was a postdoctoral researcher at their shared Broad Institute, which is dedicated to improving human health through genomics.
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]]>Some questions and answers below will help elucidate the researchers’ findings about O2 production inside PSII.
“Photosynthesis in plants and algae can be compared to an artificial solar cell,” said principal investigator Bridgette Barry, who is a professor in Georgia Tech’s School of Chemistry and Biochemistry. “But, in photosynthesis, light energy fuels the production of food (carbohydrates) instead of charging a battery. O2 is released from water as a byproduct.”
Barry, first author Zhanjun Guo, and researcher Jiayuan He published their research on May 11, 2018, in the journal Proceedings of the National Academy of Sciences. Their work was funded by the National Science Foundation.
Many details are still unknown, but here are some basic workings that were already well-established going into this new study.
PS II is a biochemical complex made mostly of large amino acid corkscrew cylinders and some smaller such cylinders strung together with amino acid strands. The reaction cycle that extracts the O2 from H2O occurs at a tiny spot, which the study focused on.
For scale, if PSII were a fairly tall, very wide building, the spot might be the size of a large door in about the lower center of the building, and the metal cluster would be located there. Intertwined in the proteins would be sprawling molecules that include beta-carotene and chlorophyll, a great natural photoelectric semiconductor.
“Photons from sunlight bombard photosystem II and displace electrons in the chlorophyll,” Barry said. “That creates moving negative charges.”
The metal catalyst acts like a capacitor, building up charge that it uses to expedite four chemical reactions that release the O2 by removing four electrons, one-by-one, from two water molecules. In the process, water also spins off four H+ ions, i.e. protons, from two H2O molecules.
An additional highly reactive compound near the metal cluster acts as a "switch" to drive the electron movement in each step of the reaction cycle. It's a common amino acid called tyrosine, a little building block on that mammoth protein building.
This is where the new study’s insights come in to describe details of what's going on between the tyrosine and the cluster.
The light reactions remove one electron from tyrosine, making it what’s called an unstable radical, and the radical version of tyrosine strongly attracts a new electron.
It very quickly gets that new electron from the metal cluster. As PSII absorbs photons, the taking of an electron from tyrosine and its radical’s grabbing of a new one from the cluster repeats rapidly, making the tyrosine a kind of flickering switch.
“The tyrosine radical drives the cycle around, and what they (Guo and He) did in the lab was to develop a way of seeing the radical reaction in the presence of the metal cluster,” Barry said.
Guo and He also found that the calcium atom in the cluster has key interactions with tyrosine.
Figuring out how to make the reactions observable was painstaking. The researchers isolated some PSII from spinach, and they slowed it way down by cooling it in the dark.
Then they gave it a burst of red light to prepare one step in the reaction cycle, then a green flash to take the electron from tyrosine. Then the electrons slowly returned to the tyrosine.
The researchers observed the processes via vibrational spectroscopy, which revealed qualities of tyrosine’s chemical bonds. The researchers also examined the calcium and discovered a special interaction between it and tyrosine.
“A new thing we saw was that the calcium ion made the tyrosine twist a certain way,” Barry said. “It turns out that the tyrosine may be a very flexible switch.”
The researchers also swapped out calcium for other metals and found that the calcium fulfills this role quite optimally.
“Oxygen photosynthesis really is the great fueler life on our planet,” Barry said.
About two billion years ago, the photosynthesis that generates O2 exploded, and as breathable oxygen filled Earth’s oceans and atmosphere, life began evolving into the complex variety we have today. There are also pragmatic reasons for studying photosynthesis.
“You could work with it to make crops more productive,” Barry said. “We may have to repair and adapt the photosynthesis process someday, too.”
Environmental stresses could possibly weaken photosynthesis in the future, calling for biochemical tweaks. Also, natural photosynthesis is an exceptionally good model for photoelectric semiconductors like those used in emerging energy systems.
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The research was funded by the National Science Foundation (grant MCB-14-11734). Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect views of the National Science Foundation.
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]]>Researchers at the Georgia Institute of Technology have engineered a chemical trap that exhaustively catches what are called glycoproteins, including minuscule traces that have previously escaped detection.
Glycoproteins are protein molecules bonded with sugar molecules, and they’re very common in all living things. Glycoproteins come in myriad varieties and sizes and make up important cell structures like cell receptors. They also wander around our bodies in secretions like mucus or hormones.
But some glycoproteins are very, very rare and can serve as an early signal, or biomarker, indicating there’s something wrong in the body – like cancer. Existing methods to reel in glycoproteins for laboratory examination are relatively new and have had big holes in their nets, so many of these molecules, especially those very rare ones produced by cancer, have tended to slip by.
“These tiny traces are critically important for early disease detection,” said principal investigator Ronghu Wu, a professor in Georgia Tech’s School of Chemistry and Biochemistry. “When cancer is just getting started, aberrant glycoproteins are produced and secreted into body fluids such as blood and urine. Often their abundances are extremely low, but catching them is urgent.”
This new chemical trap, which took Georgia Tech chemists several years to develop and is based on a boronic acid, has proven extremely effective in lab tests including on cultured human cells and mouse tissue samples.
“This method is very universal,” said first author Haopeng Xiao, a graduate research assistant. “We get over 1,000 glycoproteins in a really small lab sample.”
In comparison tests with existing methods, the chemical trap, a complex molecular construction reminiscent of an octopus, captured exponentially more glycoproteins, especially more of those trace glycoproteins.
Wu, Xiao and Weixuan Chen, a former Georgia Tech postdoctoral researcher, who was also first author of the study alongside Xiao, published their results in the journal Nature Communications. The research was funded by the National Science Foundation and the National Institutes of Health.
For chemistry whizzes, here’s a short summary of how the researchers made the octopus. They took a good thing and doubled then tripled down on it.
Those who recall high school chemistry class may still know what boric acid is, as do people who use it to kill roaches. Its chemical structure is an atom of boron bonded with three hydroxyl groups (H3BO3).
Boronic acids are a family of organic compounds that build on boric acid. There are many members of the boronic acid family, and they tend to bond well with glycoproteins, but their bonds can be less reliable than needed.
“Most boronic acids let too many low-abundance glycoproteins get away,” Wu said. “They can catch glycoproteins that are in high abundance but not those in low abundance, the ones that tell us more valuable things about cell development or about human disease.”
But the Georgia Tech chemists were able to leverage the strengths of boronic acids to develop a glycoprotein capturing method that works exceptionally well.
First, they tested several boronic acid derivatives and found that one called benzoboroxole strongly bound with each sugar component on the glycopeptide. (“Peptide” refers to the basic chemical composition of a protein.)
Then they stitched many benzoboroxole molecules together with other components to form a "dendrimer," which refers to the resulting branch- or tentacle-like structure. The finished large molecule resembled an octopus ready to go after those sugar components.
In its middle, similarly positioned to an octopus's head, was a magnetic bead, which acted as a kind of handle. Once the dendrimer caught a glycoprotein, the researchers used a magnet to grab the bead and pull out their chemical octopus along with its ensnared glycopeptides (e.g. glycoproteins).
“Then we washed the dendrimer off with a low pH solution, and we had the glycoproteins analyzed with things like mass spectrometry,” Wu said.
The researchers have some ideas about how medical laboratory researchers could make practical use of the new Georgia Tech method to detect odd biomolecules emitted by cancer, such as antigens. For example, the chemical octopus could improve detection of prostate-specific antigens (PSA) in prostate cancer screenings.
“PSA is a glycoprotein. Right now, if the level is very high, we know that the patient may have cancer, and if it’s very low, we know cancer is not likely,” Wu said. “But there is a gray area in between, and this method could lead to much more detailed information in that gray area.”
The researchers also believe that developers could leverage the chemical invention to produce targeted cancer treatments. Immune cells could be trained to recognize the aberrant glycoproteins, track down their source cancer cells in the body and kill them.
The research’s potential for science goes far beyond its possible future medical applications.
The fields of genomics and proteomics have made great strides. Following in their footsteps, this new molecular trap could advance the study of the rising field of glycoscience.
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Georgia Tech’s Johanna Smeekens coauthored the research paper. The research was funded by the National Science Foundation (CAREER award CHE-1454501), and the National Institutes of Health (R01GM118803). Findings and any opinions are those of the authors’ and not necessarily of the funding agencies.
]]>Georgia Institute of Technology
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Atlanta, Georgia 30332-0181 USA
Some novel materials that sound too good to be true turn out to be true and good. An emergent class of semiconductors, which could affordably light up our future with nuanced colors emanating from lasers, lamps, and even window glass, could be the latest example.
These materials are very radiant, easy to process from solution, and energy-efficient. The nagging question of whether hybrid organic-inorganic perovskites (HOIPs) could really work just received a very affirmative answer in a new international study led by physical chemists at the Georgia Institute of Technology.
With significant effort, researchers succeeded in testing an existing HOIP and observed a “richness” of semiconducting physics created by what could be described as electrons dancing on chemical underpinnings that wobble like a funhouse floor in an earthquake. That bucks conventional wisdom because established semiconductors rely upon rigidly stable chemical foundations, that is to say, quieter molecular frameworks, to produce the desired quantum properties.
“We don’t know yet how it works to have these stable quantum properties in this intense molecular motion,” said first author Felix Thouin, a graduate research assistant at Georgia Tech. “It defies physics models we have to try to explain it. It’s like we need some new physics.”
Their gyrating jumbles have made HOIPs challenging to examine, but the team of researchers from a total of five research institutes in four countries succeeded in measuring a prototypical HOIP and found its quantum properties on par with those of established, molecularly rigid semiconductors, many of which are graphene-based.
“The properties were at least as good as in those materials and may be even better,” said Carlos Silva, a professor in Georgia Tech’s School of Chemistry and Biochemistry. Not all semiconductors also absorb and emit light well, but HOIPs do, making them optoelectronic and thus potentially useful in lasers, LEDs, other lighting applications, and also in photovoltaics.
The lack of molecular-level rigidity in HOIPs also plays into them being more flexibly produced and applied.
Silva co-led the study with physicist Ajay Ram Srimath Kandada. Their team published the results of their study on two-dimensional HOIPs on March 8, 2018, in the journal Physical Review Materials. Their research was funded by EU Horizon 2020, the Natural Sciences and Engineering Research Council of Canada, the Fond Québécois pour la Recherche, the Research Council of Canada, and the National Research Foundation of Singapore.
Commonly, semiconducting properties arise from static crystalline lattices of neatly interconnected atoms. In silicon, for example, which is used in most commercial solar cells, they are interconnected silicon atoms. The same principle applies to graphene-like semiconductors.
“These lattices are structurally not very complex,” Silva said. “They’re only one atom thin, and they have strict two-dimensional properties, so they’re much more rigid.”
“You forcefully limit these systems to two dimensions,” said Srimath Kandada, who is a Marie Curie International Fellow at Georgia Tech and the Italian Institute of Technology. “The atoms are arranged in infinitely expansive, flat sheets, and then these very interesting and desirable optoelectronic properties emerge.”
These proven materials impress. So, why pursue HOIPs, except to explore their baffling physics? Because they may be more practical in important ways.
“One of the compelling advantages is that they’re all made using low-temperature processing from solutions,” Silva said. “It takes much less energy to make them.”
By contrast, graphene-based materials are produced at high temperatures in small amounts that can be tedious to work with. “With this stuff (HOIPs), you can make big batches in solution and coat a whole window with it if you want to,” Silva said.
For all an HOIP’s wobbling, it’s also a very ordered lattice with its own kind of rigidity, though less limiting than in the customary two-dimensional materials.
“It’s not just a single layer,” Srimath Kandada said. “There is a very specific perovskite-like geometry.” Perovskite refers to the shape of an HOIPs crystal lattice, which is a layered scaffolding.
“The lattice self-assembles,” Srimath Kandada said, “and it does so in a three-dimensional stack made of layers of two-dimensional sheets. But HOIPs still preserve those desirable 2D quantum properties.”
Those sheets are held together by interspersed layers of another molecular structure that is a bit like a sheet of rubber bands. That makes the scaffolding wiggle like a funhouse floor.
“At room temperature, the molecules wiggle all over the place. That disrupts the lattice, which is where the electrons live. It’s really intense,” Silva said. “But surprisingly, the quantum properties are still really stable.”
Having quantum properties work at room temperature without requiring ultra-cooling is important for practical use as a semiconductor.
Going back to what HOIP stands for -- hybrid organic-inorganic perovskites – this is how the experimental material fit into the HOIP chemical class: It was a hybrid of inorganic layers of a lead iodide (the rigid part) separated by organic layers (the rubber band-like parts) of phenylethylammonium (chemical formula (PEA)2PbI4).
The lead in this prototypical material could be swapped out for a metal safer for humans to handle before the development of an applicable material.
HOIPs are great semiconductors because their electrons do an acrobatic square dance.
Usually, electrons live in an orbit around the nucleus of an atom or are shared by atoms in a chemical bond. But HOIP chemical lattices, like all semiconductors, are configured to share electrons more broadly.
Energy levels in a system can free the electrons to run around and participate in things like the flow of electricity and heat. The orbits, which are then empty, are called electron holes, and they want the electrons back.
“The hole is thought of as a positive charge, and of course, the electron has a negative charge,” Silva said. “So, hole and electron attract each other.”
The electrons and holes race around each other like dance partners pairing up to what physicists call an “exciton.” Excitons act and look a lot like particles themselves, though they’re not really particles.
In semiconductors, millions of excitons are correlated, or choreographed, with each other, which makes for desirable properties, when an energy source like electricity or laser light is applied. Additionally, excitons can pair up to form biexcitons, boosting the semiconductor’s energetic properties.
“In this material, we found that the biexciton binding energies were high,” Silva said. “That’s why we want to put this into lasers because the energy you input ends up to 80 or 90 percent as biexcitons.”
Biexcitons bump up energetically to absorb input energy. Then they contract energetically and pump out light. That would work not only in lasers but also in LEDs or other surfaces using the optoelectronic material.
“You can adjust the chemistry (of HOIPs) to control the width between biexciton states, and that controls the wavelength of the light given off,” Silva said. “And the adjustment can be very fine to give you any wavelength of light.”
That translates into any color of light the heart desires.
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ALSO read this materials article: Turbocharging Fuel Cells with a Multifunctional NanoCatalyst
Coauthors of this paper were Stefanie Neutzner and Annamaria Petrozza from the Italian Institute of Technology (IIT); Daniele Cortecchia from IIT and Nanyang Technological University (NTU), Singapore; Cesare Soci from the Centre for Disruptive Photonic Technologies, Singapore; Teddy Salim and Yeng Ming Lam from NTU; and Vlad Dragomir and Richard Leonelli from the University of Montreal. The research was funded by: The EU Horizon 2020’s Curie Fellowship (project 705874); the EU 2020 Research and Innovation Program (Grant #643238 SYNCHRONICS); the Natural Sciences and Engineering Research Council of Canada and Fond Québécois pour la Recherche: Nature et Technologies; the Canadian Foundation for Innovation, the Natural Science and Engineering Research Council of Canada; and the National Research Foundation of Singapore (NRF-CRP14-2014-03). Any findings and opinions are those of the authors and not necessarily of the funding agencies.
]]>Georgia Institute of Technology
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Atlanta, Georgia 30332-0181 USA
The sluggishness comes from a chemical bottleneck, the rate of processing oxygen, a key ingredient that helps fuel cells, which are related to batteries, produce electricity. The new catalyst, a nanotechnology material developed by engineers at the Georgia Institute of Technology, markedly speeds up oxygen processing and is the subject of a new study.
Partly to accommodate oxygen’s limitations, fuel cells usually require pure hydrogen fuel, which reacts with the oxygen taken in from the air, but the costs of producing the hydrogen have been prohibitive. The new catalyst is a potential game-changer.
“It can easily convert chemical fuel into electricity with high efficiency,” said Meilin Liu, who led the study and is a Regents’ Professor in Georgia Tech’s School of Material Science and Engineering. “It can let you use readily available fuels like methane or natural gas or just use hydrogen fuel much more efficiently,” Liu said.
The catalyst achieves the efficiency by rushing oxygen through a fuel cell’s system. “It’s more than eight times as fast as state-of-the-art materials doing the same thing now,” said Yu Chen, a postdoctoral research associate in Liu’s lab and the study’s first author.
There are a few types of fuel cells, but the researchers worked to improve solid oxide fuel cells, which are found in some prototypical fuel cell cars. The research insights could also aid in honing supercapacitors and technology paired with solar panels, thus advancing sustainable energy beyond the new catalyst’s immediate potential to improve upon fuel cells.
Liu and Chen published their study in the March issue of the journal Joule. Their research was funded by the U.S. Department of Energy and by the Guangdong Innovative and Entrepreneurial Research Program. The fuel cell work from Liu’s lab has already attracted significant energy industry and automotive industry interest.
Though they work differently from fuel cells and are much less efficient and clean, combustion engines make a useful metaphor to aid in understanding how fuel cells and the new catalyst work.
In a combustion engine, fuel from a tank and oxygen from the air come together to react in an explosion, producing energy that turns a crankshaft. Adding a turbocharger speeds the process up by mixing fuel and oxygen together more quickly and rushing them to combustion.
Currently, in fuel cells, hydrogen fuel from a tank and oxygen from the air also drive a process that produces energy, in this case, electricity. The two ingredients do come together in a reaction, but one very different from combustion, and much cleaner.
One end of the fuel cell, the anode, removes electrons from the hydrogen atoms in what’s called oxidation and sends the electrons through an external circuit as electric current to the cathode on the other side. There, oxygen, which is notoriously electron hungry, sucks the electrons up in what’s called reduction, and that keeps the electricity flowing.
The hydrogen, now positively charged, and the oxygen, now negatively charged, meet up to form water, which is the fuel cell’s exhaust.
In that reaction chain, oxygen is the slow link in two ways: Oxygen’s reduction takes longer than hydrogen’s oxidation, and the reduced oxygen moves more slowly through the system to meet with hydrogen. Analogous to the turbocharger, the new catalyst pushes the oxygen forward.
The catalyst is applied as a sheer coating only about two dozen nanometers thick and is comprised of two connected nanotechnology solutions that break both oxygen bottlenecks.
First, nanoparticles highly attractive to oxygen grab the O2 molecule and let inflowing electrons quickly jump onto it, easily reducing it and tearing it into two separate oxygen ions (each one an O2-). Then a series of chemical gaps called oxygen vacancies that are built into the nanoparticles’ structures suck up the oxygen ions like chains of vacuum cleaners passing the ions hand to hand to the second phase of the catalyst.
The second phase is a coating that is full of oxygen vacancies that can pass the O2- even more rapidly toward its final destination.
“The oxygen goes down quickly through the channels and enters the fuel cell, where it meets with the ionized hydrogen or another electron donor like methane or natural gas.”
The ions meet to make water, which exits the fuel cell. In the case of methane fuel, pure CO2 is also emitted, which can be captured and recycled back into fuel.
In the first stage, there are two different flavors of nanoparticle at work. Both have cobalt, but one contains barium and the other praseodymium, a rare-earth metal that can be pricey in high quantities.
“Praseodymium is in such very small amounts that it doesn’t impact costs,” Liu said. “And the catalyst saves lots of money on fuel and on other things.”
High operating temperatures in existing fuel cells require expensive protective casings and cooling materials. The researchers believe the catalyst could help lower the temperatures by reducing electrical resistance inherent in current fuel cell chemistry. That could, in turn, reduce overall material costs.
The second stage of the catalyst is a lattice that contains praseodymium and barium, as well as calcium and cobalt (PBCC). In addition to its catalytic function, the PBCC coating protects the cathode from degradation that can limit the lifetime of fuel cells and similar devices.
The underlying original cathode material, which contains the metals lanthanum, strontium, cobalt, and iron (LSCF), has become an industry standard but comes with a caveat.
“It’s very conductive, very good, but the problem is that strontium undergoes a diminishment called segregation in the material,” Liu said. “One component of our catalyst, PBCC, acts as a coating and keeps the LSCF a lot more stable.”
LSCF manufacturing is already well-established, and adding the catalyst coating to production could be likely reasonably achieved. Liu also is considering replacing the LSCF cathode completely with the new catalyst material, and his lab is developing a yet another catalyst to boost fuel oxidation reactions at the fuel cell’s anode.
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Coauthors of the study were: Seonyoung Yoo, Yong Ding, Ruiqiang Yan, Kai Pei, Chong Qu, Lei Zhang, Ikwhang Cha, Bote Zhao, Ben deGlee, and Ryan Murphy of Georgia Tech; YongMan Choi from the SABIC Technology Center in Saudi Arabia; Yanxiang Zhang from the Harbin Institute of Technology in China; Huijun Chen, Yan Chen, Chenghao Yang and Jiang Liu from the South China University of Technology. The research was funded by the U.S. Department of Energy SECA Core Technology Program (grants FC FE0026106 and DE-FE0031201) and the Guangdong Innovative and Entrepreneurial Research Team Program (grant 2014ZT05N200). Any opinions or findings are those of the authors and not necessarily of the funding agencies.
]]>Georgia Institute of Technology
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Atlanta, Georgia 30332-0181 USA
But for researcher Nicholas Hud, asteroids play an entirely different role: that of time capsules showing what molecules originally existed in our solar system. Having that information gives scientists the starting point they need to reconstruct the complex pathway that got life started on Earth.
Director of the NSF-NASA Center for Chemical Evolution at the Georgia Institute of Technology, Hud says finding molecules in asteroids provides the strongest evidence that such compounds were present on the Earth before life formed. Knowing what molecules were present helps establish the initial conditions that led to the formation of amino acids and related compounds that, in turn, came together to form peptides, small protein-like molecules that may have kicked off life on this planet.
“We can look to the asteroids to help us understand what chemistry is possible in the universe,” said Hud. “It’s important for us to study materials from asteroids and meteorites, the smaller versions of asteroids that fall to Earth, to test the validity of our models for how molecules in them could have helped give rise to life. We also need to catalog the molecules from asteroids and meteorites because there might be compounds there that we had not even considered important for starting life.”
Hud was a panelist at a press briefing “Asteroids for Research, Discovery, and Commerce” February 17 at the 2018 annual meeting of the American Association for the Advancement of Science (AAAS) in Austin, Texas.
NASA scientists have been analyzing compounds found in asteroids and meteorites for decades, and their work provides a solid understanding for what might have been present when the Earth itself was formed, Hud says.
“If you model a prebiotic chemical reaction in the laboratory, scientists can argue about whether or not you had the right starting materials,” said Hud. “Detection of a molecule in an asteroid or meteorite is about the only evidence everyone will accept for that molecule being prebiotic. It’s something we can really lean on.”
The Miller-Urey experiment, conducted in 1952 to simulate conditions believed to have existed on the early Earth, produced more than 20 different amino acids, organic compounds that are the building blocks for peptides. The experiment was kicked off by sparks inside a flask containing water, methane, ammonia and hydrogen, all materials believed to have existed in the atmosphere when the Earth was very young.
Since the Miller-Urey experiment, scientists have demonstrated the feasibility of other chemical pathways to amino acids and compounds necessary for life. In Hud’s laboratory, for instance, researchers used cycles of alternating wet and dry conditions to create complex organic molecules over time. Under such conditions, amino acids and hydroxy acids, compounds that differ chemically by just a single atom, could have formed short peptides that led to the formation of larger and more complex molecules – ultimately exhibiting properties that we now associate with biological molecules.
“We now have a really good way to synthesize peptides with amino acids and hydroxy acids working together that could have been common on the early Earth,” he said. “Even today, hydroxy acids are found with amino acids in living organisms – and in some meteorite samples that have been examined.”
Hud believes there are many possible ways that the molecules of life could have formed. Life could have gotten started with molecules that are less sophisticated and less efficient than what we see today. Like life itself, these molecules could have evolved over time.
“What we find is that these compounds can form molecules that look a lot like modern peptides, except in the backbone that is holding the units together,” said Hud. “The overall structure can be very similar and would be easier to make, though it doesn’t have the ability to fold into as complex structures as modern proteins. There is a tradeoff between the simplicity of forming these molecules and how close these molecules are to those found in contemporary life.”
Geologists believe the Earth was very different billions of years ago. Instead of continents, there were islands protruding from the oceans. Even the sun was different, producing less light but more cosmic rays – which could have helped power the protein-forming chemical reactions.
“The islands could have been potential incubators for life, with molecules raining down from the atmosphere,” Hud said. “We think the key process that would have allowed these molecules to go to the next stage is a wet-dry cycling like what we are doing in the lab. That would have been perfect for an island out in the ocean.”
Rather than a single spark of life, the molecules could have evolved slowly over time in gradual progression that may have taken place at different rates in different locations, perhaps simultaneously. Different components of cells, for example, may have developed separately where conditions favored them before they ultimately came together.
“There is something very special about peptides, nucleic acids, polysaccharides and lipids and their ability to work together to do something they couldn’t have done separately,” he said. “And there could have been any number of chemical processes on the early Earth that never led to life.”
Knowing what conditions were like on the early Earth therefore gives scientists a stronger foundation for hypothesizing what could have taken place, and could offer hints to other pathways that may not have been considered yet.
“There are probably a lot more clues in the asteroids about what molecules were really there,” said Hud. “We may not even know what we should be looking for in these asteroids, but by looking at what molecules we find, we can ask different and more questions about how they could have helped get life started.”
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Media Relations Contact: John Toon (404-894-6986) (jtoon@gatech.edu).
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]]>The butcher is a common enzyme called presenilin, which chops lengthy protein building blocks down to useable shorter lengths. It resides in membrane spaces that evade ready experimental detection, but in a new study, researchers at the Georgia Institute of Technology and Oak Ridge National Laboratory (ORNL) have illuminated presenilin using a neutron beam produced by the world's most powerful research nuclear reactor.
Presenilin is one of many mysterious protein structures residing in our cell membranes, where they are essential to life.
“One-third of our genome goes to work to encode intramembrane proteins,” said Raquel Lieberman, an associate professor in Georgia Tech’s School of Chemistry and Biochemistry. “Some of them are huge and do super complex biochemistry.”
Presenilin is an enzyme, more particularly an intramembrane protease. There are four classes of these, and they are needed, among other things, for: Alerting to and defending against infectors, and cell differentiation and development.
If the latter two go wrong, that can lead to cancer.
Now, the researchers have gotten their first figurative mugshot of an intramembrane protein, the presenilin. Technically speaking, the researchers worked with a presenilin cousin found in microbes -- M. marisnigri intramembrane aspartyl protease or MmIAP -- but here we will use presenilin and MmIAP interchangeably for simplicity’s sake.
The measurement was low-resolution but revealed enough to establish that the protein structure is more simply put together than previously believed, and that surprised the scientists.
“Our sample shows that this is a monomer all by itself,” Lieberman said. “We were expecting a dimer or a trimer.” That means it was made up of one long strand, mostly coiled up like a spring, instead of doubled-up or tripled-up curly strands.
Presenilin (MmIAP) is armed with two chemical knives, aspartates, that reliably make cuts on peptides, subunits that make up proteins. And a second new study by the same researchers illuminated how the cleaving works.
Presenilin can trim peptides into building blocks helpful to its own cells, or whittle bad peptide chunks that end up in amyloid-beta plaque, a suspect in Alzheimer’s disease. Or presenilin can aid and abate hepatitis C viruses by carving components it needs to reproduce.
Understanding how presenilin works could one day prove useful to medical research. “If you could find a way to interfere with it selectively, you could stop the spread of hepatitis C in the body,” Lieberman said.
The researchers, led by Lieberman and neutron scattering scientist Volker Urban from ORNL, published the revelations of the neutron scattering on February 6, 2018, in Biophysical Journal. The new insights into presenilin functioning are to officially publish in March in the Journal of Biological Chemistry but the study is currently available online without embargo. First authors were Swe-Htet Naing of Georgia Tech and Ryan Oliver of Oak Ridge.
Research was funded by the National Science Foundation, the National Institutes of Health, and the U.S. Department of Energy.
By going to the High Flux Isotope Reactor (HFIR), the scientists were reaching for the big gun to make presenilin (MmIAP) come out of hiding.
HFIR’s neutron beams were cooled to minus 253 degrees Celsius (minus 424 degrees Fahrenheit) to slow the neutrons down, so they could probe molecular features of the biological samples.
Presenilin and other intramembrane proteins warrant such proverbial desperate measures. They live in a lipid environment and hate water about the way cats do, and that’s a problem for researchers studying them.
“When you have proteins that are not soluble in water, you’re in trouble,” Lieberman said. “The usual techniques to analyze them become very, very difficult, if not impossible. And when you chemically bootstrap these proteins to be able use these water-soluble methods, you have really poor chances of seeing the protein’s actual structure that performs its function.”
Images derived from water-based analytical methods in Lieberman’s lab have not completely jibed with presenilin’s function. For one, the enzyme’s cutting surfaces have been too far apart. The neutron beam’s revelations indicated a form that seemed more logical.
“Our shape was tighter, and made more sense with presenilin’s function in its natural setting in the membrane,” Lieberman said.
The presenilin (MmIAP) samples examined at the HFIR were suspended in a solution friendly to the hydrophobic protein. Ironically, presenilin and other intramembrane proteases often hydrolyze peptides, in other words, they add water to them.
“These proteases are confined to the lipid cell membrane where there is no water. Since water is required for hydrolysis, it has to come from outside the membrane,” Lieberman said. “How that happens is yet another mystery that needs uncovering.”
The precision and consistency, with which the presenilin homologue MmIAP cleaved peptides, impressed the researchers.
“When we used a model synthetic peptide, it cleaved only at very specific positions on the peptide,” Lieberman said. “When we switched to a real biological peptide, it also cleaved very exactly.”
The researchers put the presenilin through various mutations, which had little to no effect on its cleaving abilities. That could mean that its baseline functioning is nearly immune to genetic interference.
On a chilling note, when the researchers observed the microbial presenilin cousin, MmIAP, cutting amyloid-beta precursor peptides, it always made the chop in a way notorious for amyloid’s association with Alzheimer’s disease.
“We never saw the cut that made what is typically viewed as the ‘good’ amyloid, A-beta-40,” Lieberman said. “We only saw cuts that led to the ‘bad’ amyloid, A-beta-42.”
More research would be needed to explain why that happened; if the same is true for presenilin in human cell membranes, and also if some regulator prevents the creation or accumulation of so much bad amyloid in healthy cells.
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Kevin Weiss from Oak Ridge National Laboratory coauthored the study in Biophysical Journal. Sibel Kalyoncu, David Smalley, Hyojung Kim, Xingjian Tao, Josh George, Alex Jonke, Ryan Oliver, and Matthew Torres coauthored the study in the Journal of Biological Chemistry. Research was funded by the National Science Foundation’s Division of Molecular and Cellular Biosciences (grant 0845445), and the National Institutes of Health (grant R01GM112662 and R01GM118744). Neutron scattering research conducted at the Bio-SANS instrument, a DOE Office of Science, Office of Biological and Environmental Research resource, used resources at the High Flux Isotope Reactor, a DOE Office of Science, Scientific User Facility operated by the Oak Ridge National Laboratory. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsors.
]]>Georgia Institute of Technology
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Atlanta, Georgia 30332-0181 USA
Light of specific wavelengths causes the nanoparticles to assemble and disassemble on demand, allowing the dynamic organization of the nanoparticles for smart in vitro drug release. By including chemotherapy molecules in the nanoparticle structures when they are assembled, the molecules could be drawn into tumors – and then released with the application of a light at a shorter wavelength that triggers disassembly through photo-cleavage.
In addition to such a dynamic self-assembly and disassembly, the encapsulation and release of chemotherapy molecules could also be achieved by reversible covalent bonding of anticancer drugs to the polymeric “hairs” situated on the surface of nanoparticles. And by absorbing the same light that triggers the drug release, the gold nanoparticles could also heat the cancer cells, providing a double punch.
In a broad range of other applications, the nanoparticle self-assembly process could also be triggered by environmental factors including temperature, pH or solvent polarity by rationally designing the polymeric hairs. In this study, gold nanoparticles were used, but the process could also make self-assembled nanoparticles from a variety of metals and metal oxides. By tailoring the surface of nanoparticles with water-absorbing polymers containing near-infrared responsive components, the drug release could be performed in vivo.
The spherical gold nanoparticles can be replaced with more complex shaped nanomaterials – such as hollow nanoparticles, nanorods, or nanotubes – to render a better absorption of near-infrared light to penetrate biological tissues. No testing of these nanoparticles has been done so far in living cells or organisms.
The research was supported by the Air Force Office of Scientific Research and the National Science Foundation, and was reported January 31 in the early edition of the journal Proceedings of the National Academy of Sciences. Materials scientists from the Georgia Institute of Technology and South China University of Technology co-authored the paper.
“We envision that these photo-responsive polymer-capped gold nanoparticles could one day serve as nano-carriers for drug delivery into the body using our robust and reversible process for assembly and disassembly,” said Zhiqun Lin, a professor in the Georgia Tech School of Materials Science and Engineering. “Used in cancer therapy, this process could increase the impact of a treatment by heating the cancer cells while introducing the drug compound into the tumor.”
Under light, the assemblies of photo-sensitive nanoparticles separate over a period of hours at a rate that can be controlled by the intensity and wavelength of the light. “Because the disassembly can be turned on and off at will, we could provide a timed release of the drug by controlling the short-wavelength light exposure,” Lin added.
The hairy nanoparticles are fabricated around a tiny core of beta-cyclodextrin from which polymer chains of poly(acrylicacid)-block-poly(7-methylacryloyloxy-4-methylcoumarin) (PAA-b-PMAMC) are grown. That material attracts water-soluble metal precursors, which use the space within the polymer hairs as nano-reactors to form gold nanoparticles.
To these inner structures – which are hydrophilic PAA polymers – the researchers add hairs made from the hydrophobic monomer MAMC. These materials are sensitive to light, and cause the nanoparticles to self-assemble through a photo-dimerization process – crosslinking – when subjected to light at a wavelength of 365 nanometers.
The assembly process can be reliably reversed on demand using a shorter wavelength at 254 nanometers.
“Once the polymer chains from adjacent gold nanoparticles begin to photo-crosslink, they bring nanoparticles together via a self-assembly process to generate large assemblies of nanoparticles,” said Lin. “This process is completely reversible and can be repeated in many cycles.”
The research team incorporated dye molecules into the self-assembled nanoparticles to simulate what might be done to incorporate and then release chemotherapy agents. A magnetic oxide material incorporated into the nanoparticles could allow the assemblies to be directed to a tumor site by an external magnet, and could also support diagnostic imaging.
Beyond the activity of the drugs, the plasmonic effects of the gold nanoparticles could heat the nanoparticles when they are subjected to light, attacking the cancer cells through a second route.
In addition to the potential medical uses, the self-assembly technique could have applications in optics, optoelectronics, magnetic technologies, sensing materials and devices, catalysis and nanotechnology. The technique could also lead to new basic research in crystallization kinetics, using the self-assembly process to create “artificial crystals” held together by polymer chains.
Lin’s lab has worked on the amphiphilic star-shaped block polymers for several years, adding new features and exploring new capabilities for the nanoparticle systems.
“Our work provides a design strategy that allows the manipulation of both the outer block and the inner block of a star-shaped block co-polymer,” he said. “Our fundamental contribution in this work is to judiciously prepare a star-shaped block co-polymer in which the inner block has the capability to coordinate with metal precursors while the outer block allows photo-responsive materials to interact, which in turn renders the crafting of photo-responsive gold nanoparticles for light-enabled reversible and reliable self-assembly.”
The research team included Yihuang Chen, associated with both Georgia Tech and the South China University of Technology; Zewei Wang, Yanjie He, Young Jun Yoon, and Jaehan Jung, associated with Georgia Tech, and Guangzhao Zhang from South China University of Technology.
This work is supported by the Air Force Office of Scientific Research (Grant FA9550-16-1-0187) and the National Science Foundation (Civil, Mechanical, and Manufacturing Innovation Grants 1562075 and 1727313; Division of Materials Research Grant 1709420). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the sponsors.
CITATION: Yihuang Chen, et al., “Light-enabled reversible self-assembly and tunable optical properties of stable hairy nanoparticles,” (Proceedings of the National Academy of Sciences, 2018). http://www.pnas.org/content/early/2018/01/30/1714748115.
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]]>Beyond decoding crab-eat-crab alarm triggers, pinpointing these compounds for the first time opens new doors to understanding how chemicals invisibly regulate marine wildlife. Insights from the study by researchers at the Georgia Institute of Technology could someday contribute to better management of crab and oyster fisheries, and help specify which pollutants upset them.
In coastal marshes, these urinary alarm chemicals, trigonelline and homarine, help to regulate the ecological balance of who eats how many of whom -- and not just crabs.
Blue crabs, which are about hand-sized and are tough and strong, eat mud crabs, which are about the size of a silver dollar and thin-shelled. Mud crabs, on the other hand, eat a lot of oysters, but when blue crabs are going after mud crabs, the mud crabs hide and freeze, so far fewer oysters get eaten than usual.
Humans are part of the food chain, too, eating oysters as well as blue crabs that boil up a bright orange. The blue refers to the color of markings on their appendages before they’re cooked. Thus, the blue crab urinary chemicals influence seafood availability for people, as well.
The fact that blue crab urine scares mud crabs was already known. Mud crabs duck and cover when exposed to samples taken in the field and in the lab, even if the mud crabs can’t see the blue crabs yet. Digestive products, or metabolites, in blue crab urine trigger the mud crabs’ reaction, which also makes them stop foraging for food themselves.
“Mud crabs react most strongly when blue crabs have already eaten other mud crabs,” said Julia Kubanek, who co-led the study with fellow Georgia Tech professor Marc Weissburg. “A change in the chemical balance in blue crab urine tells mud crabs that blue crabs just ate their cousins,” Kubanek said.
Figuring out the two specific chemicals, trigonelline and homarine, that set off the alarm system, out of myriad candidate molecules, is new and has been a challenging research achievement.
“My guess is that there are many hundreds of chemicals in the animal’s urine,” said Kubanek, who is a professor in Georgia Tech’s School of Biological Sciences, in its School of Chemistry and Biochemistry, and who is also Associate Dean for Research in Georgia Tech’s College of Sciences.
The researchers applied technology and methodology from metabolomics, a relatively new field used principally in medical research to identify small biomolecules produced in metabolism that might serve as early warning signs of disease. Kubanek, Weissburg, and first author Remington Poulin published their results the week of January 8, 2017, in the journal Proceedings of the National Academies of Science.
The research was funded by the National Science Foundation.
Trigonelline has been studied, albeit loosely, in some diseases, and is known as one of the ingredients in coffee beans that, upon roasting, breaks down into other compounds that give coffee its aroma. Homarine is very similar to trigonelline, and, though apparently less studied, it’s also common.
“These chemicals are found in many places,” Kubanek said. But picking them out of all those chemicals in blue crab urine for the first time was like finding two needles in a haystack.
Often, in the past, researchers trying to narrow down such chemicals have started out by separating them out in arduous laboratory procedures then testing them one at a time to see if any of them worked. There was a good chance of turning up nothing.
The Georgia Tech researchers went after all the chemicals at one time, the whole haystack, using mass spectrometry and nuclear magnetic resonance spectroscopy.
“We screened the entire chemical composition of each sample at once,” Kubanek said. “We analyzed lots and lots of samples to fish out chemical candidates.”
The researchers discovered spikes in about a dozen metabolites after blue crabs ate mud crabs. They tested out those pee chemicals that spiked on the mud crabs, and trigonelline and homarine distinctly made them crouch.
“Trigonelline scares the mud crabs a little bit more,” Kubanek said.
More specifically, high concentrations of either of the two did the trick. “It’s clear that there was a dose-dependent response,” said Weissburg, who is a professor in Georgia Tech’s School of Biological Sciences. “Mud crabs have evolved to hone in on that elevated dose.”
“Most crustaceans are walking noses,” Weissburg said. “They detect chemicals with sensors on their claws, antennae and even the walking legs. The compounds we isolated are pretty simple, which suggests they might be easily detectable in a variety of places on a crab. This redundancy is good because it increases the likelihood that the mud crabs get the message and not get eaten.”
Evolution preserved the mud crabs with the duck-and-cover reaction to the two chemicals, which also influenced the ecological balance, in part by pushing blue crabs to look for more of their food elsewhere. But it influenced other animal populations as well.
“These chemicals are staggeringly important,” Weissburg said. “The scent from a blue crab potentially affects a large number of mud crabs, all of which stop eating oysters, and that helps preserve the oyster populations.”
All of that also impacts food sources for marine birds and mammals: Just by the effects of two chemicals, and there are so many more chemical signals around. “It’s hard for us to appreciate the richness of this chemical landscape,” Weissburg said.
As scientists learn more, influencing these systems could become useful to ecologists and the fishing industry.
“We might even be able to use these chemicals to control oyster consumption by predators to help preserve these habitats, which are critical, or to help oyster farmers. That’s becoming important in Georgia fisheries,” Weissburg said.
Pollutants in pesticides and herbicides are known to interfere with estuaries’ ecologies. “It will be a lot easier to test how strong this is by knowing specific ecological chemicals,” Weissburg said.
By the way, trigonelline and homarine are not pheromones.
“Pheromones are signaling molecules that have a function within the same species, like to attract mates,” Kubanek said. “And blue crabs and mud crabs are not the same species.”
“In this case, the mud crabs have evolved to chemically eavesdrop on the blue crabs’ pee. You might call trigonelline and homarine fear-inducing cues.”
Identifying such metabolites, also called small molecules, and their effects is the latest chapter in constructing the catalog of life molecules. “Everyone knows about the human genome project, identifying genomes; then came transcriptomes (molecules that transcribe genes),” Kubanek said. “Now we’re pretty far along with proteomics (identifying proteins), but we’re just now figuring out metabolomes.”
The paper was co-authored by Serge Lavoie, Katherine Siegel, and David Gaul. The research was funded by the National Science Foundation Division of Ocean Sciences (grant OCE-1234449). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsor.
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The new structure gives thin-film transistors stability comparable to those made with inorganic materials, allowing them to operate in ambient conditions – even underwater. Organic thin-film transistors can be made inexpensively at low temperature on a variety of flexible substrates using techniques such as inkjet printing, potentially opening new applications that take advantage of simple, additive fabrication processes.
“We have now proven a geometry that yields lifetime performance that for the first time establish that organic circuits can be as stable as devices produced with conventional inorganic technologies,” said Bernard Kippelen, the Joseph M. Pettit professor in Georgia Tech’s School of Electrical and Computer Engineering (ECE) and director of Georgia Tech’s Center for Organic Photonics and Electronics (COPE). “This could be the tipping point for organic thin-film transistors, addressing long-standing concerns about the stability of organic-based printable devices.”
The research was reported January 12 in the journal Science Advances. The research is the culmination of 15 years of development within COPE and was supported by sponsors including the Office of Naval Research, the Air Force Office of Scientific Research, and the National Nuclear Security Administration.
Transistors comprise three electrodes. The source and drain electrodes pass current to create the “on” state, but only when a voltage is applied to the gate electrode, which is separated from the organic semiconductor material by a thin dielectric layer. A unique aspect of the architecture developed at Georgia Tech is that this dielectric layer uses two components, a fluoropolymer and a metal-oxide layer.
“When we first developed this architecture, this metal oxide layer was aluminum oxide, which is susceptible to damage from humidity,” said Canek Fuentes-Hernandez, a senior research scientist and coauthor of the paper. “Working in collaboration with Georgia Tech Professor Samuel Graham, we developed complex nanolaminate barriers which could be produced at temperatures below 110 degrees Celsius and that when used as gate dielectric, enabled transistors to sustain being immersed in water near its boiling point.”
The new Georgia Tech architecture uses alternating layers of aluminum oxide and hafnium oxide – five layers of one, then five layers of the other, repeated 30 times atop the fluoropolymer – to make the dielectric. The oxide layers are produced with atomic layer deposition (ALD). The nanolaminate, which ends up being about 50 nanometers thick, is virtually immune to the effects of humidity.
“While we knew this architecture yielded good barrier properties, we were blown away by how stably transistors operated with the new architecture,” said Fuentes-Hernandez. “The performance of these transistors remained virtually unchanged even when we operated them for hundreds of hours and at elevated temperatures of 75 degrees Celsius. This was by far the most stable organic-based transistor we had ever fabricated.”
For the laboratory demonstration, the researchers used a glass substrate, but many other flexible materials – including polymers and even paper – could also be used.
In the lab, the researchers used standard ALD growth techniques to produce the nanolaminate. But newer processes referred to as spatial ALD – utilizing multiple heads with nozzles delivering the precursors – could accelerate production and allow the devices to be scaled up in size. “ALD has now reached a level of maturity at which it has become a scalable industrial process, and we think this will allow a new phase in the development of organic thin-film transistors,” Kippelen said.
An obvious application is for the transistors that control pixels in organic light-emitting displays (OLEDs) used in such devices as the iPhone X and Samsung phones. These pixels are now controlled by transistors fabricated with conventional inorganic semiconductors, but with the additional stability provided by the new nanolaminate, they could perhaps be made with printable organic thin-film transistors instead.
Internet of things (IoT) devices could also benefit from fabrication enabled by the new technology, allowing production with inkjet printers and other low-cost printing and coating processes. The nanolaminate technique could also allow development of inexpensive paper-based devices, such as smart tickets, that would use antennas, displays and memory fabricated on paper through low-cost processes.
But the most dramatic applications could be in very large flexible displays that could be rolled up when not in use.
“We will get better image quality, larger size and better resolution,” Kippelen said. “As these screens become larger, the rigid form factor of conventional displays will be a limitation. Low processing temperature carbon-based technology will allow the screen to be rolled up, making it easy to carry around and less susceptible to damage.
For their demonstration, Kippelen’s team – which also includes Xiaojia Jia, Cheng-Yin Wang and Youngrak Park – used a model organic semiconductor. The material has well-known properties, but with carrier mobility values of 1.6 cm2/Vs isn’t the fastest available. As a next step, they researchers would like to test their process on newer organic semiconductors that provide higher charge mobility. They also plan to continue testing the nanolaminate under different bending conditions, across longer time periods, and in other device platforms such as photodetectors.
Though the carbon-based electronics are expanding their device capabilities, traditional materials like silicon have nothing to fear.
“When it comes to high speeds, crystalline materials like silicon or gallium nitride will certainly have a bright and very long future,” said Kippelen. “But for many future printed applications, a combination of the latest organic semiconductor with higher charge mobility and the nanostructured gate dielectric will provide a very powerful device technology.”
This research was supported in part by the Center for Organic Photonics and Electronics at Georgia Tech, by the Department of the Navy, Office of Naval Research Awards N00014-14-1-0580 and N00014-16-1-2520, through the MURI Center for Advanced Photovoltaics (CAOP), by the Air Force Office of Scientific Research through Award No. FA9550-16-1-0168, by the National Nuclear Security Administration Award DE-NA0002576 through the Consortium for Nonproliferation Enabling Technologies (CNEC). Seminal work on the concept of using a bilayer gate dielectric in OFETs was funded in part by Solvay S.A. and described in part in issued patent No. US 9,368,737 B2.
CITATION: Xiaojia Jia, Canek Fuentes-Hernandez, Cheng-Yin Wang, Youngrak Park, Bernard Kippelen, “Stable organic thin-film transistors,” (Science Advances, 2018).
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]]>In the solution-based process, precursor chemicals adsorb to nanocrystal seeds before being reduced to atoms that fuel growth of the nanocrystals. The kinetics data is based on painstaking systematic studies done to determine growth rates on different nanocrystal facets — surface structures that control how the crystals grow by attracting individual atoms.
In an article published December 11 in the journal Proceedings of the National Academy of Sciences, a research team from the Georgia Institute of Technology provided a quantitative picture of how surface conditions controlled the growth of palladium nanocrystals. The work, which will later include information on nanocrystals made from other noble metals, is supported by the National Science Foundation.
“This is a fundamental study of how catalytic nanocrystals grow from tiny seeds, and a lot of people working in this field could benefit from the systematic, quantitative information we have developed,” said Younan Xia, professor and Brock Family Chair in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University. “We expect that this work will help researchers control the morphology of nanocrystals that are needed for many different applications.”
A critical factor controlling how nanocrystals grow from tiny seeds is the surface energy of the crystalline facets on the seeds. Researchers have known that energy barriers dictate the surface attraction for precursors in solution, but specific information on the energy barrier for each type of facet had not been readily available.
“Typically, the surface of the seeds that are used to grow these nanocrystals has not been homogenous,” explained Xia, who is also the Georgia Research Alliance Eminent Scholar in Nanomedicine and holds joint appointments in School of Chemistry & Biochemistry and School of Chemical & Biomolecular Engineering. “You may have different facets on the crystals, which depend on the arrangement of the atoms below them. From the standpoint of precursors in the solution around the seeds, these surfaces have different activation energies which determine how difficult it will be for the precursors or atoms to land on each surface.”
Xia’s research team designed experiments to assess the energy barriers on various facets, using seeds in a variety of sizes and surface configurations chosen to have only one type of facet. The researchers measured both the growth of the nanocrystals in solution and the change in concentration of palladium tetrabromide (PdBr4 2-) precursor salt.
“By choosing the right precursor, we can ensure that all the reduction we measure is on the surface and not in the solution,” he explained. “That allowed us to make meaningful measurements about the growth, which is controlled by the type of facet, as well as presence of a twin boundary, corresponding to distinctive growth patterns and end results.”
Over the course of nearly a year, visiting graduate research assistant Tung-Han Yang studied the nanocrystal growth using different types of seeds. Rather than allowing nanocrystal growth from self-nucleation, Xia’s team chose to study growth from seeds so they could control the initial conditions.
Controlling the shape of the nanocrystals is critical to applications in catalysis, photonics, electronics and medicine. Because these noble metals are expensive, minimizing the amount of material needed for catalytic applications helps control costs.
“When you do catalysis with these materials, you want to make sure the nanocrystals are as small as possible and that all of the atoms are exposed to the surface,” said Xia. “If they are not on the surface, they won’t contribute to the activity and therefore will be wasted.”
The ultimate goal of the research is a database that scientists can use to guide the growth of nanocrystals with specific sizes, shapes and catalytic activity. Beyond palladium, the researchers plan to publish the results of kinetic studies for gold, silver, platinum, rhodium and other nanocrystals. While the pattern of energy barriers will likely be different for each, there will be similarities in how the energy barriers control growth, Xia said.
“It’s really how the atoms are arranged on the surface that determines the surface energy,” he explained. “Depending on the metals involved, the exact numbers will be different, but the ratios between the facet types should be more or less the same.”
Xia hopes that the work of his research team will lead to a better understanding of how the autocatalytic process works in the synthesis of these nanomaterials, and ultimately to broader applications.
“If you want to control the morphology and properties, you need this information so you can choose the right precursor and reducing agent,” said Xia. “This systematic study will lead to a database on these materials. This is just the beginning of what we plan to do.”
In addition to the researchers already mentioned, the study also included Shan Zhou, Kyle Gilroy, Legna Figueroa-Cosme, Yi-Hsien Lee and Jenn-Ming Wu.
This work was supported in part by a research grant from the NSF (CHE 1505441) and startup funds from the Georgia Institute of Technology. The electron microscopy studies were performed at Georgia Tech’s Institute for Electronics and Nanotechnology, a member of the National Nanotechnology Coordinated Infrastructure supported by the NSF (ECCS-1542174).
CITATION: Tung-Han Yang, et al., “Autocatalytic surface reduction and its role in controlling seed-mediated growth of colloidal metal nanocrystals,” (Proceedings of the National Academy of Sciences, 2017). http://dx.doi.org/10.1073/pnas.1713907114
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]]>The replicability of results from scientific studies has become a major source of concern in the research community, particularly in the social sciences and biomedical sciences. But many researchers in the fields of engineering and the hard sciences haven’t felt the same level of concern for independent validation of their results.
A new study that compared the results reported in thousands of papers published about the properties of metal organic framework (MOF) materials – which are prominent candidates for carbon dioxide adsorption and other separations – suggests the replicability problem should be a concern for materials researchers, too.
One in five studies of MOF materials examined by researchers at the Georgia Institute of Technology were judged to be “outliers,” with results far beyond the error bars normally used to evaluate study results. The thousands of research papers yielded just nine MOF compounds for which four or more independent studies allowed appropriate comparison of results.
“At a fundamental level, I think people in materials chemistry feel that things are reproducible and that they can count on the results of a single study,” said David Sholl, a professor and John F. Brock III School Chair in the Georgia Tech School of Chemical and Biomolecular Engineering. “But what we found is that if you pull out any experiment at random, there’s a one in five chance that the results are completely wrong – not just slightly off, but not even close.”
Whether the results can be more broadly applied to other areas of materials science awaits additional studies, Sholl said. The results of the study, which was supported by the U.S. Department of Energy, were published November 28 in the ACS journal Chemistry of Materials.
Sholl chose MOFs because they’re an area of interest to his lab – he develops models for the materials – and because the National Institute of Standards and Technology (NIST) and the Advanced Research Projects Agency-Energy (ARPA-E) had already assembled a database summarizing the properties of MOFs. Co-authors Jongwoo Park and Joshua Howe used meta-analysis techniques to compare the results of single-component adsorption isotherm testing – how much CO2 can be removed at room temperature.
That measurement is straightforward and there are commercial instruments available for doing the tests. “People in the community would consider this to be an almost foolproof experiment,” said Sholl, who is also a Georgia Research Alliance Eminent Scholar in Energy Sustainability.
The researchers considered the results definitive when they had four or more studies of a given MOF at comparable conditions.
The implications for errors in materials science may be less than in other research fields. But companies could use the results of a just one or two studies to choose a material that appear to be more efficient, and in other cases, researchers unable to replicate an experiment may simply move on to another material.
“The net result is non-optimal use of resources at the very least,” Sholl said. “And any report using one experiment to conclude a material is 15 or 20 percent better than another material should be viewed with great skepticism, as we cannot be very precise on these measurements in most cases.”
Why the variability in results? Some MOFs can be finicky, quickly absorbing moisture that affect adsorption, for instance. The one-in-five “outliers” may be a result of materials contamination.
“One of the materials we studied is relatively simple to make, but it’s unstable in an ambient atmosphere,” Sholl explained. “Exactly what you do between making it in the lab and testing it will affect the properties you measure. That could account for some of what we saw, and if a material is that sensitive, we know it’s going to be a problem in practical use.”
Other factors that may prevent replication include details that were inadvertently left out of a methods description – or that the original scientists didn’t realize were relevant. That could be as simple as the precise atmosphere in which the material is maintained, or the materials used in the apparatus producing the MOFs.
Sholl hopes the paper will lead to more replication of experiments so scientists and engineers can know if their results really are significant.
“As a result of this, I think my group will look at all reported data in a more nuanced way, not necessarily suspecting it is wrong, but thinking about how reliable that data might be,” he said. “Instead of thinking about data as a number, we need to always think about it as a number plus a range.”
Sholl suggests that more reporting of second, third or fourth efforts to replicate an experiment would help raise the confidence of data on MOF materials properties. The scientific publishing system doesn’t currently provide much incentive for reporting validation, though Sholl hopes that will change.
He also feels the issue needs to be discussed within all parts of the scientific community, though he admits that can lead to “uncomfortable” conversations.
“We have presented this study a few times at conferences, and people can get pretty defensive about it,” Sholl said. “Everybody in the field knows everybody else, so it’s always easier to just not bring up this issue.”
And, of course, Sholl would like to see others replicate the work he and his research team did. “It will be interesting to see if this one-in-five number holds up for other types of experiments and materials,” he added. “There are other certainly other areas of materials chemistry where this kind of comparison could be done.”
This research was supported by the U.S. Department of Energy through grant DE-FE0026433 and by the Center for Understanding and Control of Acid Gas-Induced Evolution of Materials for Energy (UNCAGE-ME), an Energy Frontier Research Center funded by U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award #DE-SC0012577. Any opinions, findings, conclusions or recommendations expressed herein are those of the author(s) and do not necessarily reflect the views of sponsors.
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CITATION: Jongwoo Park, Joshua D. Howe, and David S. Sholl, “How Reproducible Are Isotherm Measurements in Metal-Organic Frameworks?,” (Chemistry of Materials, 2017). http://pubs.acs.org/doi/10.1021/acs.chemmater.7b04287
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]]>While the specific mechanism by which the nanotextured material kills bacteria requires further study, the researchers believe tiny spikes and other nano-protrusions created on the surface puncture bacterial membranes to kill the bugs. The surface structures don’t appear to have a similar effect on mammalian cells, which are an order of magnitude larger than the bacteria.
Beyond the anti-bacterial effects, the nano-texturing also appears to improve corrosion resistance. The research was reported December 12 in the journal ACS Biomaterials Science & Engineering by researchers at the Georgia Institute of Technology.
“This surface treatment has potentially broad-ranging implications because stainless steel is so widely used and so many of the applications could benefit,” said Julie Champion, an associate professor in Georgia Tech’s School of Chemical and Biomolecular Engineering. “A lot of the antimicrobial approaches currently being used add some sort of surface film, which can wear off. Because we are actually modifying the steel itself, that should be a permanent change to the material.”
Champion and her Georgia Tech collaborators found that the surface modification killed both Gram negative and Gram positive bacteria, testing it on Escherichia coli and Staphylococcus aureus. But the modification did not appear to be toxic to mouse cells – an important issue because cells must adhere to medical implants as part of their incorporation into the body.
The research began with a goal of creating a super-hydrophobic surface on the stainless steel in an effort to repel liquids – and with them, bacteria. But it soon became clear that creating such a surface would require the use of a chemical coating, which the researchers didn’t want to do. Postdoctoral Fellows Yeongseon Jang and Won Tae Choi then proposed an alternative idea of using a nanotextured surface on stainless steel to control bacterial adhesion, and they initiated a collaboration to demonstrate this effect.
The research team experimented with varying levels of voltage and current flow in a standard electrochemical process. Typically, electrochemical processes are used to polish stainless steel, but Champion and collaborator Dennis Hess – a professor and Thomas C. DeLoach, Jr. Chair in the School of Chemical and Biomolecular Engineering – used the technique to roughen the surface at the nanometer scale.
“Under the right conditions, you can create a nanotexture on the grain surface structure,” Hess explained. “This texturing process increases the surface segregation of chromium and molybdenum and thus enhances corrosion resistance, which is what differentiates stainless steel from conventional steel.”
Microscopic examination showed protrusions 20 to 25 nanometers above the surface. “It’s like a mountain range with both sharp peaks and valleys,” said Champion. “We think the bacteria-killing effect is related to the size scale of these features, allowing them to interact with the membranes of the bacterial cells.”
The researchers were surprised that the treated surface killed bacteria. And because the process appears to rely on a biophysical rather than chemical process, the bugs shouldn’t be able to develop resistance to it, she added.
A second major potential application for the surface modification technique is food processing equipment. There, the surface treatment should prevent bacteria from adhering, enhancing existing sterilization techniques.
The researchers used samples of a common stainless alloy known as 316L, treating the surface with an electrochemical process in which current was applied to the metal surfaces while they were submerged in a nitric acid etching solution.
Application of the current moves electrons from the metal surface into the electrolyte, altering the surface texture and concentrating the chromium and molybdenum content. The specific voltages and current densities control the type of surface features produced and their size scale, said Hess, who worked with Choi – then a Ph.D. student – and Associate Professor Victor Breedveld in the School of Chemical and Biomolecular Engineering, and Professor Preet Singh in the School of Materials Science and Engineering, to design the nanotexturing process.
To more fully assess the antibacterial effects, Jang engaged the expertise of Andrés García, a Regents’ Professor in Georgia Tech’s Woodruff School of Mechanical Engineering, and Graduate Student Christopher Johnson. In their experiments, they allowed bacterial samples to grow on treated and untreated stainless steel samples for periods of up to 48 hours.
At the end of that time, the treated metal had significantly fewer bacteria on it. That observation was confirmed by removing the bacteria into a solution, then placing the solution onto agar plates. The plates receiving solution from the untreated stainless steel showed much larger bacterial growth. Additional testing confirmed that many of the bacteria on the treated surfaces were dead.
Mouse fibroblast cells, however, did not seem to be bothered by the surface. “The mammalian cells seemed to be quite healthy,” said Champion. “Their ability to proliferate and cover the entire surface of the sample suggested they were fine with the surface modification.”
For the future, the researchers plan to conduct long-term studies to make sure the mammalian cells remain healthy. The researchers also want to determine how well their nanotexturing holds up when subjected to wear.
“In principle, this is very scalable,” said Hess. “Electrochemistry is routinely applied commercially to process materials at a large scale.”
CITATION: Yeongseon Jang, et al., “Inhibition of Bacterial Adhesion on Nano-Textured Stainless Steel 316L by Electrochemical Etching,” (ACS Biomaterials Science & Engineering, 2017). http://pubs.acs.org/doi/abs/10.1021/acsbiomaterials.7b00544
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]]>NASA astrobiologists from the Georgia Institute of Technology have developed a comprehensive new model that shows how planetary chemistry could make that happen. The model, published in a new study in the journal Nature Geoscience, was based on a likely scenario on Earth three billion years ago and was actually built around its possible geological and biological chemistry.
The sun produced a quarter less light and heat then, but Earth remained temperate, and methane may have saved our planet from an eon-long deep-freeze, scientists hypothesize. Had it not, we and most other complex life probably wouldn’t be here today.
The new model combined multiple microbial metabolic processes with volcanic, oceanic and atmospheric activities, which may make it the most comprehensive of its kind to date. But while studying Earth’s distant past, the Georgia Tech researchers aimed their model light-years away, wanting it to someday help interpret conditions on recently discovered exoplanets.
The researchers set the model’s parameters broadly so that they could apply not only to our own planet but potentially also to its siblings with their varying sizes, geologies, and lifeforms.
“We really had an eye to future use with exoplanets for a reason,” said Chris Reinhard, the study’s principal investigator and an assistant professor in Georgia Tech’s School of Earth and Atmospheric Sciences. “It’s possible that the atmospheric methane models that we are exploring for the early Earth represent conditions common to biospheres throughout our galaxy because they don’t require such an advanced stage of evolution like we have here on Earth now.”
Reinhard and first author Kazumi Ozaki published their Nature Geoscience paper on December 11, 2017. The research was supported by the NASA Postdoctoral Program, the Japan Society for the Promotion of Science, the NASA Astrobiology Institute and the Alfred P. Sloan Foundation.
Previous models have examined the mix of atmospheric gases needed to keep Earth warm in spite of the sun’s former faintness, or studied isolated microbial metabolisms that could have made the needed methane. “In isolation, each metabolism hasn’t made for productive models that accounted well for that much methane,” Reinhard said.
The Georgia Tech researchers synergized those isolated microbial metabolisms, including ancient photosynthesis, with geological chemistry to create a model reflective of the complexity of an entire living planet. And the model’s methane production ballooned.
“It’s important to think about the mechanisms controlling the atmospheric levels of greenhouse gases in the framework of all biogeochemical cycles in the ocean and atmosphere,” said first author Ozaki, a postdoctoral assistant.
Also READ: The Earth is not a lab beaker; it’s a shifty, humongous lab
The Georgia Tech model strengthens a leading hypothesis that attempts to explain a mystery called the “faint young Sun paradox” pointed out by iconic late astronomer Carl Sagan and his Cornell University colleague George Mullen in 1972.
Astronomers noticed long ago that stars burned brighter as they matured and weaker in their youths. They calculated that about two billion years ago, our sun must have shone about 25 percent fainter than it does today.
That would have been too cold for any liquid water to exist on Earth, but paradoxically, strong evidence says that liquid water did exist. “Based on the observation of the geological record, we know that there must have been liquid water,” Reinhard said, “and in some cases, we know that temperatures were similar to how they are today, if not a little warmer.”
Sagan and Mullen postulated that Earth’s atmosphere must have created a greenhouse effect that saved it. Back then, they suspected ammonia was at work, but chemically, that idea proved less feasible.
“Methane has taken a lead role in this hypothesis,” Reinhard said. “When oxygen and methane enter the atmosphere, they chemically cancel each other out over time in a complex chain of chemical reactions. Because there was extremely little oxygen in the air back then, it would have allowed for methane to build up much higher levels than today.”
At the core of the model are two different types of photosynthesis. But three billion years ago, the dominant type of photosynthesis we know today that pumps out oxygen may not have even existed yet.
Instead, two other very primitive bacterial photosynthetic processes likely were essential to Earth’s ancient biosphere. One transformed iron in the ocean into rust, and the other photosynthesized hydrogen into formaldehyde.
“The model relied on lots of volcanic activity spewing out hydrogen,” Ozaki said. Other bacteria fermented the formaldehyde, and other bacteria, still, turned the fermented product into methane.
The two photosynthetic processes served as the watch spring of the model’s clockwork, which pulled in 359 previously established biogeochemical reactions spanning land, sea and air.
The model was not the type of simulation that produces a video animation of Earth’s ancient biogeochemistry. Instead, the model mathematically analyzed the processes, and the output was numbers and graphs.
Ozaki ran the model more than 3 million times, varying parameters, and found that if the model contained both forms of photosynthesis operating in tandem, that 24 percent of the runs produced enough methane to create the balance needed in the atmosphere to maintain the greenhouse effect and keep ancient Earth, or possibly an exoplanet, temperate.
“That translates into about a 24 percent probability that this model would produce a stable, warm climate on the ancient Earth with a faint sun or on an Earth-like exoplanet around a dimmer star,” Reinhard said. “Other models that looked at these photosynthetic metabolisms in isolation have much lower probabilities of producing enough methane to keep the climate warm.”
“We’re confident that this rather unique statistical approach means that you can take the basic insights of this new model to the bank,” he said.
Other explanations for the “faint young Sun paradox” have been more cataclysmic and perhaps less regular in their dynamics. They include ideas about routine asteroid strikes stirring up seismic activity thus resulting in more methane production, or about the sun consistently firing coronal mass ejections at Earth, heating it up.
Also READ: Some good news on climate change and methane
The research was co-authored by Eiichi Tajika, Peng K. Hong and Yusuke Nakagawa of the University of Tokyo. The research was supported by the NASA Postdoctoral Program, the Japan Society for the Promotion of Science (grant 25120006), the NASA Astrobiology Institute (grant NNA 15BB03A) and the Alfred P. Sloan Foundation (grant FR-2015-65744). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of those sponsors
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The research, published November 13, 2017, in the journal Nature Materials, focused on organic semiconductors, a class of materials prized for their applications in emerging technologies such as flexible electronics, solar energy conversion, and high-quality color displays for smartphones and televisions. In the short term, the advancement could particularly help with organic light-emitting diodes that operate at high energy to emit colors such as green and blue.
“Organic semiconductors are ideal materials for the fabrication of mechanically flexible devices with energy-saving, low-temperature processes,” said Xin Lin, a doctoral student and a member of the Princeton research team. “One of their major disadvantages has been their relatively poor electrical conductivity. In some applications, this can lead to difficulties and inefficient devices. We are working to improve the electrical properties of organic semiconductors.”
Semiconductors, typically made of silicon, are the foundation of modern electronics because engineers can take advantage of their unique properties to control electrical currents. Among many applications, semiconductor devices are used for computing, signal amplification, and switching. They are used in energy-saving devices such as light-emitting diodes and devices that convert energy such as solar cells.
Essential to these functionalities is a process called doping, in which the semiconductor’s chemical makeup is modified by adding a small amount of chemicals or impurities. By carefully choosing the type and amount of dopant, researchers can alter semiconductors’ electronic structure and electrical behavior in a variety of ways.
In their Nature Materials paper, the researchers have described a new approach for greatly increasing the conductivity of organic semiconductors, formed of carbon-based molecules rather than silicon atoms. The dopant, a ruthenium-containing compound, was a reducing agent, which means it added electrons to the organic semiconductor as part of the doping process. The addition of the electrons was the key to increasing the semiconductor’s conductivity. The compound belongs to a newly-introduced class of dopants called dimeric organometallic dopants. Unlike many other powerful reducing agents, these dopants are stable when exposed to air but still work as strong electron donors both in solution and solid state.
Georgia Tech’s Seth Marder, a Regents Professor in the School of Chemistry and Biochemistry, and Stephen Barlow, a research scientist in the school, led the development of the new dopant. They called the ruthenium compound a “hyper-reducing dopant.”
They said it was unusual, not only in its combination of electron donation strength and air stability but also in its ability to work with a class of organic semiconductors that have previously been very difficult to dope. In studies conducted at Princeton, the researchers found that the new dopant increased the conductivity of these semiconductors by about a million times.
The ruthenium compound was a dimer, meaning it consisted of two identical molecules, or monomers, connected by a chemical bond. As is, the compound proved relatively stable and, when added to these difficult-to-dope semiconductors, it did not react and remained in its equilibrium state. That posed a problem because to increase the conductivity of the organic semiconductor, the ruthenium dimer needed to split and release its two identical monomers.
Princeton’s Lin, the study’s lead author, said the researchers looked for different ways to break up the ruthenium dimer and activate the doping. Eventually, he and Berthold Wegner, a visiting graduate student from the group of Norbert Koch at Humboldt University, took a hint from how photosynthetic systems work. They irradiated the system with ultraviolet light, which excited molecules in the semiconductor and initiated the reaction. Under exposure to the light, the dimers were able to dope the semiconductor, leading to a roughly 100,000 times increase in the conductivity.
After that, the researchers made an interesting observation.
“Once the light was turned off, one might naively expect the reverse reaction to occur and the increased conductivity to disappear,” said Georgia Tech’s Marder, who is also associate director of the Center for Organic Photonics and Electronics (COPE) at Georgia Tech. “However, this was not the case.”
The researchers found that the ruthenium monomers remained isolated in the semiconductor, increasing conductivity, even though thermodynamics should have returned the molecules to their original configuration as dimers. Antoine Kahn, a Princeton professor who led the research team, said the physical layout of the molecules inside the doped semiconductor provides a likely answer to this puzzle. The hypothesis is that the monomers are scattered in the semiconductor in such a way that it was very difficult for them to return to their original configuration and re-form the ruthenium dimer. To recombine, he said, the monomers would have to have faced in the correct orientation, but in the mixture, they remained askew. So, even though thermodynamics showed that dimers should reform, most never snapped back together.
“The question is why aren’t these things moving back together into equilibrium,” said Kahn, who is Stephen C. Macaleer '63 Professor in Engineering and Applied Science. “The answer is they are kinetically trapped.”
In fact, the researchers observed the doped semiconductor for over a year and found very little decrease in the electrical conductivity. Also, by observing the material in light-emitting diodes fabricated by the group of Barry Rand, an assistant professor of electrical engineering at Princeton and the Andlinger Center for Energy and the Environment, the researchers discovered that doping was continuously re-activated by the light produced by the device.
“The light activates the system more, which leads to more light production and more activation until the system is fully activated, said Marder, who is Georgia Power Chair in Energy Efficiency. “This alone is a novel and surprising observation.”
The paper was co-authored by Kyung Min Lee, Michael A. Fusella, and Fengyu Zhang, of Princeton, and Karttikay Moudgil of Georgia Tech. Research was funded by the National Science Foundation (grants DMR-1506097, DMR-1305247), the Department of Energy’s Energy Efficiency & Renewable Energy Solid-State Lighting program (award DE-EE0006672) and the DoE’s Office of Basic Energy Sciences, Division of Materials Sciences and Engineering (award DE-SC0012458), the Deutsche Forschungsgemeinschaft (project SFB 951) and the Helmholtz Energy-Alliance Hybrid Photovoltaics project.
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]]>Transferring the gallium nitride sensors to metallic foils and flexible polymers doubles their sensitivity to nitrogen dioxide gas, and boosts response time by a factor of six. The simple production steps, based on metal organic vapor phase epitaxy (MOVPE), could also lower the cost of producing the sensors and other optoelectronic devices.
Sensors produced with the new process can detect ammonia at parts-per-billion levels and differentiate between nitrogen-containing gases. The gas sensor fabrication technique was reported November 9 in the journal Scientific Reports.
“Mechanically, we just peel the devices off the substrate, like peeling the layers of an onion,” explained Abdallah Ougazzaden, director of Georgia Tech Lorraine in Metz, France and a professor in Georgia Tech’s School of Electrical and Computer Engineering (ECE). “We can put the layer on another support that could be flexible, metallic or plastic. This technique really opens up a lot of opportunity for new functionality, new devices – and commercializing them.”
The researchers begin the process by growing monolayers of boron nitride on two-inch sapphire wafers using an MOVPE process at approximately 1,300 degrees Celsius. The boron nitride surface coating is only a few nanometers thick, and produces crystalline structures that have strong planar surface connections, but weak vertical connections.
Aluminum gallium nitride (AlGaN/GaN) devices are then grown atop the monolayers at a temperature of about 1,100 degrees Celsius, also using an MOVPE process. Because of the boron nitride crystalline properties, the devices are attached to the substrate only by weak Van der Waals forces, which can be overcome mechanically. The devices can be transferred to other substrates without inducing cracks or other defects. The sapphire wafers can be reused for additional device growth.
“This approach for engineering GaN-based sensors is a key step in the pathway towards economically viable, flexible sensors with improved performances that could be integrated into wearable applications,” the authors wrote in their paper.
So far, the researchers have transferred the sensors to copper foil, aluminum foil and polymeric materials. In operation, the devices can differentiate between nitrogen oxide, nitrogen dioxide, and ammonia. Because the devices are approximately 100 by 100 microns, sensors for multiple gases can be produced on a single integrated device.
“Not only can we differentiate between these gases, but because the sensor is very small, we can detect them all at the same time with an array of sensors,” said Ougazzaden, who expects that the devices could be modified to also detect ozone, carbon dioxide and other gases.
The gallium nitride sensors could have a wide range of applications from industry to vehicle engines – and for wearable sensing devices. The devices are attractive because of their advantageous materials properties, which include high thermal and chemical stability.
“The devices are small and flexible, which will allow us to put them onto many different types of support,” said Ougazzaden, who also directs the International Joint Research Lab at Georgia Tech CNRS.
To assess the effects of transferring the devices to a different substrate, the researchers measured device performance on the original sapphire wafer and compared that to performance on the new metallic and polymer substrates. They were surprised to see a doubling of the sensor sensitivity and a six-fold increase in response time, changes beyond what could be expected by a simple thermal change in the devices.
“Not only can we have flexibility in the substrate, but we can also improve the performance of the devices just by moving them to a different support with appropriate properties,” he said. “Properties of the substrate alone makes the different in the performance.”
In future work, the researchers hope to boost the quality of the devices and demonstrate other sensing applications. “One of the challenges ahead is to improve the quality of the materials so we can extend this to other applications that are very sensitive to the substrates, such as high-performance electronics.”
The Georgia Tech researchers have previously used a similar technique to produce light-emitting diodes and ultraviolet detectors that were transferred to different substrates, and they believe the process could also be used to produce high-power electronics. For those applications, transferring the devices from sapphire to substrates with better thermal conductivity could provide a significant advantage in device operation.
Ougazzaden and his research team have been working on boron-based semiconductors since 2005. Their work has attracted visits from several industrial companies interested in exploring the technology, he said.
“I am very excited and lucky to work on such hot topic and top-notch technology at GT-Lorraine,” said Taha Ayari, a Ph.D. student in the Georgia Tech School of ECE and the paper’s first author.
In addition to Ougazzaden, the research team includes Georgia Tech Ph.D. students Taha Ayari, Matthew Jordan, Xin Li and Saiful Alam; Chris Bishop and Youssef ElGmili, researchers at Institut Lafayette; Suresh Sundaram, a researcher at Georgia Tech Lorraine; Gilles Patriarche, a researcher at the Centre de Nanosciences et de Nanotechnologies (C2N) at CNRS; Paul Voss, an associate professor in the Georgia Tech School of ECE; and Jean Paul Salvestrini, a professor at Georgia Tech Lorraine and adjunct professor in the Georgia Tech School of ECE.
The research was supported by ANR (Agence Nationale de Recherche), the National Agency of Research in France through the “GANEX” Project.
CITATION: Taha Ayari, et al., “Gas sensors boosted by two-dimensional h-BN enabled transfer on thin substrate foils: towards wearable and portable applications,” (Scientific Reports, 2017). http://dx.doi.org/10.1038/s41598-017-15065-6
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]]>It was a Y-shape. That made it an extreme oddity significant to science, and possibly someday to medicine, too, particularly in the treatment of certain types of blindness.
“A protein like this one has never been reported before. There are extremely few Y-shapes in proteins at all,” said Raquel Lieberman, who led the study. Lieberman is a structural biologist at the Georgia Institute of Technology, and an expert on myocilin, a protein sometimes implicated in a form of hereditary glaucoma.
Glaucoma is the second most common cause of blindness globally, and hereditary glaucoma is just one category of the disease. Genetic mutations in myocilin are a major cause of hereditary glaucoma, which can strike at a particularly young age, including in childhood.
There are other shapes in proteins that look similar to the Y, but there are key differences.
“Antibodies look a little like this, but in antibodies, separate proteins that are the products different genes fit together to make a kind of Y-shape,” Lieberman said. “This Y is encoded by one single gene sequence. That makes this absolutely unique.”
In addition to being the ostensible unicorn of protein structures, it turned out to be the central binding element of myocilin. The Y ties together major components to nail down myocilin’s overall form, overturning previous conceptions about the protein's appearance.
Although the Y hasn’t been particularly implicated in glaucoma, its existence could meaningfully alter the way researchers understand myocilin and how it works in the eye. When myocilin goes wrong, or “misfolds,” it makes fibrils that damage tissue called the trabecular meshwork that normally allows the fluid inside the eye to drain and relieve interior pressure.
“If you kill the cells that make this drainage work, it’s going to clog, and pressure inside the eye will increase,” said Lieberman, who is an associate professor in Georgia Tech’s School of Chemistry and Biochemistry. That pressure can kill parts of the retina or optic nerve, leading to irreversible partial or total blindness.
But though myocilin is common in many parts of our bodies, its normal, healthy role in the eye and, for that matter, what functions the protein has in the body at all are still a mystery.
“I think if we knew what this protein was doing in the trabecular meshwork, we would understand much more about glaucoma in general,” Lieberman said. “This research lets us know more about what myocilin is.”
Lieberman published her results on October 19, 2017, in the journal Structure. The research was funded by the National Eye Institute and the National Institute of General Medical Sciences, both at the National Institutes of Health, by the National Science Foundation, and by the U.S. Department of Energy Office of Science.
The focus of studies so far has been on a part of myocilin that is the main culprit in a form of hereditary glaucoma, a protein structure called the olfactomedin domain, which Lieberman has also studied extensively. It looks like a protein propeller with five blades that surround a hole in the center.
“When a myocilin propellor misfolds, it unravels and forms amyloid fibrils (stringy abnormal proteins) that kill cells that maintain the trabecular network,” Lieberman said. "Until now, our work led us to believe that the propellers floated around individually as independent units, and not bound together in groups."
“All we knew before was that, in solution, those olfactomedins were just monomers. They didn’t seem to make up anything of a higher order, except when they unraveled into amyloid fibers, stuck together and blocked fluid flow,” Lieberman said.
Also READ: A fake virus unleashes immune system on an ugly tropical disease
The Y alters the picture.
It anchors the propellers in groups of four. Two propellers (olfactomedin domains) each appear to be connected to either tip of the Y’s branches probably by amino acid strings. With the Y, the overall myocilin looks like four pinwheels on strings tied to a slingshot.
Adding to the new discoveries: The Y itself is sticky, like glue. It’s even annoying to handle in the lab.
“It was sticking to the plastic, sticking to the glass, sticking to the membrane, to beads,” Lieberman said. “It’s super sticky. That may serve a biological function.”
Perhaps the Y fastens the propellers to surfaces. It’s not yet known. “But we think the main function is to pair and separate out these olfactomedin domains,” Lieberman said.
Mutations in the Y aren’t significantly associated with glaucoma. “When it mutates, it misfolds, but not in a way that causes all that cell death,” Lieberman said.
But in its normal role, the Y just might promote the speed of misfolding of the propeller protein (olfactomedin domain) that’s implicated in hereditary glaucoma. When misfolded proteins come into contact with good proteins, the misfolded ones tend to make the good ones misfold, too.
“If these propeller proteins are clustered together because of the Y, and one of them misfolds, it’s going to recruit the others,” Lieberman said. “Having them tied together in groups will only magnify the contagion.”
The Y-shape, also termed tripartite, is made up of what are called “coiled coils.” They’re pairs of short protein coils, a bit like two pieces of Slinky or coiled telephone cords, and they can be stretched similarly to a Slinky and then contract back in a similar way.
Coiled coils are very common in our bodies.
“Coiled coils represent three to five percent of our genome,” Lieberman said. “They’re found in muscle contraction, in molecule transport up and down neurons. Lots of extracellular proteins (proteins that function outside of cells) also have them.”
The Y’s branches are each a pair of coiled coils, each called a dimer, and in the trunk, they come together to form a group of four coiled coils called a tetramer.
Also READ: New nano-fight against #1 killer clogged arteries
Coauthors of this study were Shannon Hill, Elaine Nguyen, Rebecca Donegan, Athéna Patterson-Orazem, Anthony Hazel, and James Gumbart. The research was funded by the National Institutes of Health’s National Eye Institute (grant R01EY021205) and National Institute of General Medical Sciences (grants 9P41 GM103622 and 1S10OD018090-01); by the National Science Foundation (grant MCB-1452464); by the U.S. Department of Energy Office of Basic Energy Sciences (contract W-31-109-Eng-38). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the sponsors.
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]]>Because of their symmetrical fractal wiring patterns, the devices can be cut to the size needed to provide the voltage and power requirements for specific applications. The modular generators could be inkjet printed on flexible substrates, including fabric, and manufactured using inexpensive roll-to-roll techniques.
“The attraction of thermoelectric generators is that there is heat all around us,” said Akanksha Menon, a Ph.D. student in the Woodruff School of Mechanical Engineering at the Georgia Institute of Technology. “If we can harness a little bit of that heat and turn it into electricity inexpensively, there is great value. We are working on how to produce electricity with heat from the body.”
The research, supported by PepsiCo, Inc. and the Air Force Office of Scientific Research, was reported online in the Journal of Applied Physics on September 28th.
Thermoelectric generators, which convert thermal energy directly into electricity, have been available for decades, but standard designs use inflexible inorganic materials that are too toxic for use in wearable devices. Power output depends on the temperature differential that can be created between two sides of the generators, which makes depending on body heat challenging. Getting enough thermal energy from a small contact area on the skin increases the challenge, and internal resistance in the device ultimately limits the power output.
To overcome that, Menon and collaborators in the laboratory of Assistant Professor Shannon Yee designed a device with thousands of dots composed of alternating p-type and n-type polymers in a closely-packed layout. Their pattern converts more heat per unit area due to large packing densities enabled by inkjet printers. By placing the polymer dots closer together, the interconnect length decreases, which in turn lowers the total resistance and results in a higher power output from the device.
“Instead of connecting the polymer dots with a traditional serpentine wiring pattern, we are using wiring patterns based on space filling curves, such as the Hilbert pattern – a continuous space-filling curve,” said Kiarash Gordiz, a co-author who worked on the project while he was a Ph.D. student at Georgia Tech. “The advantage here is that Hilbert patterns allow for surface conformation and self-localization, which provides a more uniform temperature across the device.”
The new circuit design also has another benefit: its fractally symmetric design allows the modules to be cut along boundaries between symmetric areas to provide exactly the voltage and power needed for a specific application. That eliminates the need for power converters that add complexity and take power away from the system.
“This is valuable in the context of wearables, where you want as few components as possible,” said Menon. “We think this could be a really interesting way to expand the use of thermoelectrics for wearable devices.”
So far, the devices have been printed on ordinary paper, but the researchers have begun exploring the use of fabrics. Both paper and fabric are flexible, but the fabric could be easily integrated into clothing.
“We want to integrate our device into the commercial textiles that people wear every day,” said Menon. “People would feel comfortable wearing these fabrics, but they would be able to power something with just the heat from their bodies.”
With the novel design, the researchers expect to get enough electricity to power small sensors, in the range of microwatts to milliwatts. That would be enough for simple heart rate sensors, but not more complex devices like fitness trackers or smartphones. The generators might also be useful to supplement batteries, allowing devices to operate for longer periods of time.
Among the challenges ahead are protecting the generators from moisture and determining just how close they should be to the skin to transfer thermal energy – while remaining comfortable for wearers.
The researchers use commercially-available p-type materials, and are working with chemists at Georgia Tech to develop better n-type polymers for future generations of devices that can operate with small temperature differentials at room temperatures. Body heat produces differentials as small as five degrees, compared to a hundred degrees for generators used as part of piping and steam lines.
“One future benefit of this class of polymer material is the potential for a low-cost and abundant thermoelectric material that would have an inherently low thermal conductivity,” said Yee, who directs the lab as part of the Woodruff School of Mechanical Engineering. “The organic electronics community has made tremendous advances in understanding electronic and optical properties of polymer-based materials. We are building upon that knowledge to understand thermal and thermoelectric transport in these polymers to enable new device functionality.”
Among the other prospects for the materials being developed are localized cooling devices that reverse the process, using electricity to move thermal energy from one side of a device to another. Cooling just parts of the body could provide the perception of comfort without the cost of large-space air conditioning, Yee said.
This research was supported by the Air Force Office of Scientific Research (AFOSR) under Award No. FA9550-15-1-0145 and by PepsiCo, Inc. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsors.
CITATION: Kiarash Gordiz, Akanksha K. Menon, Shannon K. Yee, “Interconnect Patterns for Printed Organic Thermoelectric Devices with Large Fill Factors, (Journal of Applied Physics, 2017). http://dx.doi.org/10.1063/1.4989589
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]]>Ancestors of the first protein molecules, which are key components of all cells, could have been bountiful on pre-life Earth, according to a new study led by researchers at the Georgia Institute of Technology, who formed hundreds of possible precursor molecules in the lab. Then they meticulously analyzed the molecules with latest technology and new algorithms.
They found that the molecules, called depsipeptides, formed quickly and abundantly under conditions that would have been common on prebiotic Earth, and with ingredients that would have likely been plentiful.
And some of the depsipeptides evolved into new varieties in just a few days, an ability that, eons ago, could have accelerated the birth of long molecules, called peptides, that make up proteins.
The new NASA-affiliated research adds to a growing body of evidence suggesting that the first polymers of life may have arisen in variations of daily processes still observed on Earth today, such as the repeated drying and refilling of pond water. They may not have all zapped into existence as a result of blazing cataclysms, an image often associated with the creation of the first chemicals of life.
“We want to stay away from scenarios that are not readily possible,” said Facundo Fernández, a professor in Georgia Tech’s School of Chemistry and Biochemistry, and one of the study’s principal investigators. “Don’t deviate from conditions that would have been realistic and reasonably common on prebiotic Earth. Don’t invoke any unreasonable chemistry.”
Scientists have long puzzled over how the very first proteins formed. Their long-chain molecules, polypeptides, can be tough to make in the lab under abiotic conditions.
Some researchers have toiled to build tiny chains, or peptides, sometimes under more extreme scenarios that probably occurred less often on early Earth. The yields have been modest, and the resulting peptides have had only a couple of component parts, whereas natural proteins have a large variety of them.
But complex molecules of life likely did not arise in one dramatic step that produced final products. That’s the hypothesis that drives the research of Fernández and his colleagues at the NSF/NASA Center for Chemical Evolution, headquartered at Georgia Tech and based on close collaboration with the Scripps Research Institute.
Instead, multiple easier chemical steps produced plentiful in-between products that were useful in subsequent reactions that eventually led to the first biopolymers. The depsipeptides produced in this latest study could have served as such a chemical stepping stone.
They look a lot like regular peptides and can be found today in biological systems. “Many antibiotics, for example, are depsipeptides,” Fernández said.
Fernández, his Georgia Tech colleagues Martha Grover and Nicholas Hud, and Ram Krishnamurthy from Scripps published their study on August 28, 2017, in the journal Proceedings of the National Academy of Sciences. First author Jay Forsythe, formerly a postdoctoral researcher at Georgia Tech, is now an assistant professor at the College of Charleston. Research was funded by the National Science Foundation and the NASA Astrobiology Program.
The new study joins similar work about the formation of RNA precursors on prebiotic Earth, and about possible scenarios for the formation of the first genes. The collective insights may someday help explain how first life arose on Earth and also aid astrobiologists in determining the probability of life existing on other planets.
To understand depsipeptides and the significance of the researchers’ results, it’s helpful to start by looking at peptides, which are chains of amino acids. When the chains get really long they are called polypeptides, and then proteins.
Living cells have machinery that reads instructions in DNA on how to link up amino acids in a specific order to build very specific peptides and proteins that have functions in a living cell. For a protein to have function in a cell, its polypeptide chains have to clump up like sticky yarn to form useful shapes.
Before cells and DNA existed on an Earth devoid of life, for polypeptides to form, amino acids had to somehow jostle together in puddles or on the banks of rivers or lakes to form chains. But peptide bonds can be tough to form, especially long chains of them.
Other bonds, called ester bonds, form more easily, and they can link up amino acids with very similar molecules called hydroxy acids. Hydroxy acids are so much like amino acids that they can, in some cases, function as their stand-in doubles.
The researchers mixed three amino acids with three hydroxy acids in a water solution and they formed depsipeptides, chains of amino acids and hydroxy acids held together by intermittent ester and peptide bonds. The hydroxy acids acted as an enabler to put the chains together that would have otherwise been difficult to form.
The primordial soup may have lapped its depsipeptides onto rocks, where they dried out in the sun, then rain or dew dissolved them back into the soup, and that happened over and over. The researchers mimicked this cycle in the lab and watched as the depsipeptide chains further developed.
“We call it an environmental cycling approach to making these early peptides,” said Fernández, who is Vasser Woolley Foundation Chair in Bioanalytical Chemistry. Like nature: Make the soup, dry it out, repeat.
In the lab, the drying temperature was 85 degrees Celsius (185 degrees Fahrenheit), although the reaction has been shown to work at temperatures of 55 and 65 degrees Celsius (131 to 149 degrees Fahrenheit). “If you think about early Earth having a lot of volcanic activity and an atmospheric mix that promoted warming, those temperatures are realistic on many parts of an early Earth,” Fernández said.
Early Earth took hundreds of millions of years to cool, and temperatures in the hundreds of degrees are hypothesized to have been commonplace for a long time. Even today, the hottest deserts can reach over 55 degrees Celsius.
Since ester bonds break more easily, in the experiment, the chains tended to come apart more at the hydroxy acids and hold together between the amino acids, which were connected by the stronger peptide bonds. As a result, chains could re-form and link up more and more amino acids with each other into sturdier peptides.
In a kind of square-dance, the stand-in hydroxy acids often left their amino acid partners in the chain, and new amino acids latched onto the chain in their place, where they held on tight. In fact, a number of the depsipeptides ended up being composed almost completely of amino acids and had only remnants of hydroxy acids.
“Now we know how peptides can form easily,” Fernández said. “Next, we want to find out what’s needed to get to the level of a functional protein.”
READ: Possible precursor of RNA forms spontaneously in water
To identify the more than 650 depsipeptides that formed, the researchers used mass spectrometry combined with ion mobility, which could be described as a wind tunnel for molecules. Along with mass, the additional mobility measurement gave the researchers data on the shape of the depsipeptides.
Algorithms created by Georgia Tech researcher Anton Petrov processed the data to finally identify the molecules.
To illustrate how potentially bountiful depsipeptides could have been on prebiotic Earth: The researchers had to limit the number of amino acids and hydroxy acids to three each. Had they taken 10 each instead, the number of theoretical depsipeptides could have climbed over 10,000,000,000,000.
“Ease and bounty are key,” Fernández said. “Chemical evolution is more likely to progress when components it needs are plentiful and can join together under more ordinary conditions.”
Also READ: Was the Secret Spice in Primal Gene Soup a Thickener?
Also READ: The work of the NSF/NASA Center for Chemical Evolution
Georgia Tech’s Calvin Millar and Sheng-Sheng Yu also coauthored this study. The research was funded by the National Science Foundation and the NASA Astrobiology Program, under the NSF/NASA Center for Chemical Evolution (CHE-1504217). Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the sponsoring agencies.
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]]>No vaccine is available against Leishmania yet, but researchers have now come closer to changing that. A new experimental vaccine, made with a proprietary biological particle developed at the Georgia Institute of Technology, has immunized laboratory mice that were genetically altered to mimic the human immune system.
The vaccine exploits a weakness in Leishmania’s tricky chemical camouflage, which normally hides it from the victim’s disease-fighting cells, to trigger a forceful immune response against the parasite, according to a new study.
Leishmania are the second-deadliest parasites in the world, topped only by malaria, according to the World Health Organization. There are some 30 strains of Leishmania.
They are transmitted mainly through the bite of a phlebotomine sand fly, which feeds on blood, and global warming is expanding the insect’s potential habitat northward from Latin America. The outbreak regions closest to the United States of leishmaniasis, the disease caused by the parasite, have come within roughly 300 miles of the border.
As with many diseases, many people who contract Leishmania, the parasite, may develop leishmaniasis, the disease, with varying symptoms, or perhaps even show no outward signs of the disease. But when it breaks out, it can cause large skin boils, and some forms severely eat away at the nose and lips, even removing parts of them.
If another form of the parasite gets into the bloodstream, it can damage the liver and spleen in a deadly form of the disease called visceral leishmaniasis, also known as black fever.
“If you don’t treat it, within 20 to 40 days visceral leishmaniasis very often kills the victim,” said Alexandre Marques, a professor in the parasitology department of the Universidade Federal de Minas Gerais in Brazil, and one of the lead researchers on the new experimental vaccine. Conventional treatment, though mostly effective, can leave behind small numbers of the parasite, which can lead the patient to relapse or act as a carrier, in a similar manner as malaria.
A vaccine could be better at halting or averting outbreaks.
Leishmania, which are single-cell organisms about the size of large bacteria, have been a scourge in about 90 countries in South America, Africa, the Middle East, Asia and southern Europe. For decades, researchers have worked to find a vaccine against them and similar parasites without success.
“In comparison to viruses and bacteria, these are much more complex organisms and more difficult to crack,” said M. G. Finn, who also led work on the new vaccine. Finn is a professor in Georgia Tech’s School of Biological Sciences and in the School of Chemistry and Biochemistry, which he also chairs.
The new vaccine leverages intimate knowledge that Marques’s team has gained living and working on the edge of leishmaniasis outbreak regions. “Alex’s (Marques’s) students collect the sand flies, then they extract the parasites in the lab and do complex mass spectrometry and other tests to study their molecular makeup in impressive detail,” Finn said.
The team has uncovered minute details on the outer surface of Leishmania that make it vulnerable to a human immune reaction. The potential new vaccine, invented at Georgia Tech, employs a fake virus as bait to attract major immune system forces to these weaknesses to attack them.
The fake virus, or virus-like particle, is not infectious, and the body destroys it after use. Finn’s lab has developed many variations of such particles in recent years, and other products containing it have already been through phase II human clinical trials.
Marques and Finn published the results of their vaccination development and testing on September 13, 2017, in the journal ACS Central Science. The research was funded by the National Institutes of Health, Children’s Healthcare of Atlanta, and Brazil’s National Council for Scientific and Technological Development.
Here are some questions and answers to help readers better understand how the vaccine would leverage Leishmania’s chemical camouflage.
What’s so tricky about Leishmania’s chemical camouflage?
The parasites cover themselves in carbohydrates, which look like food and also cover all other cells in the body. So, to the body, the Leishmania cells look inoffensive, and the immune system mostly leaves them alone.
What’s the chink in the camouflage?
Some of those carbohydrates do actually trigger a mild human immune response. It’s not strong enough to really battle leishmaniasis, but it gives Marques and Finn’s vaccine a foot in the door.
It’s lucky that humans, and some other primates, have this particular immune reaction, because other mammals don’t, so this vaccine wouldn’t work on them. Incidentally, that’s why, to test the new vaccine, the laboratory mice have to be genetically altered to make their immune systems react to the carbohydrates the way ours does.
How does the fake virus work?
“We use the virus-like particle to highlight a key carbohydrate on the surface of Leishmania clearly to the body. This coaxes its immune system into reacting strongly against it as a foreign structure,” Finn said.
The immune system goes after the fake virus like guard dogs after an invader. The researchers attach the odd carbohydrate to the fake virus, and that makes the immune system recognize that carbohydrate as a serious threat. Immune cells then hunt it down, and, in the process, destroy the parasite that produces it.
When could a vaccine be on the market?
It’s too early to stoke hopes because a lot has to happen before any drug or vaccine can hit the market. But the researchers have some interesting arguments for moving on to human testing.
“Normally, in medical testing, you would test next in rabbits or infected cats or dogs,” Finn said. “But they don’t have the right immune system. The only other possibilities are genetically altered pigs, or certain primates, or humans.”
As mentioned, the fake virus is a biological nanoparticle that has been tested in humans before without showing toxicity. Also, the researchers want to add some more kinds of Leishmania camouflage carbohydrates to the fake virus to give the vaccine even more punch.
Isn’t leishmaniasis limited to poverty regions with poor hygiene?
Absolutely not.
It can take hold anywhere people and animals live in high density and certain species of sand flies, and some other insects, can thrive. The insects like warmer weather, which is why climate change is causing the sand fly’s habitat to spread north.
“People in developed countries in climates that were cooler will have to start caring about this, as global warming encourages this to spread to them,” Marques said.
Another potentially deadly insect-borne tropical disease called Chagas disease has already made it to three southern U.S. states, and the same researchers are working on a vaccine against it, too.
M. G. Finn is a highly cited award-winning chemist. The Thompson Reuters news agency included Finn in its 2013 predictions of possible winners of that year’s Nobel Prize in Chemistry. (That year’s prize went to different well-deserving researchers and their achievements.)
Finn is most widely known for his research on click chemistry. A famous study in partnership with Nobel Prize winning chemist Karl Barry Sharpless, and Harmuth Kolb, "Click Chemistry: Diverse Chemical Function from a Few Good Reactions," has been cited more than 10,000 times, according to Google Scholar.
Finn also holds the James A. Carlos Family Chair for Pediatric Technology at Georgia Tech.
Co-authors of this study were Ana P. Venuto, Luiza C. B. Santos, Carlos Ramon Nascimento Brito, Edward Valencia, Caroline Junqueira, Adalberto A. P. Filho, Mauricio R. V. Sant'Anna, Nelder F. Gontijo, Daniella C. Bartholomeu, Ricardo T. Fujiwara, Ricardo T. Gazzinelli from the Universidade Federal de Minas Gerais, and Craig S. McKay and Carlos A. Sanhueza from Georgia Tech. Funders of the research were: The Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPQ) Brazil, the National Institute of General Medical Sciences at the National Institutes of Health (grant number R01 GM101421), and Children’s Healthcare of Atlanta. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of those sponsors.
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]]>Now, chemists at the Georgia Institute of Technology have developed a new method to more safely and, by extension, easily produce these shear films, which change their color with the help of a tiny electric current. This could make them available to many industries that have not been able to feasibly use them before.
In manufacturing, electrochromic films are often coated onto other materials, such as the surface of a mirror, as inks. They are usually based in solvents that are flammable and have toxic fumes, making them unsuitable for many work settings that rely on printing and spraying machinery to apply colors.
Georgia Tech researchers have developed electrochromic film inks that are water-based, making them safer for diffuse application in settings where the kinds of safety precautions and protective equipment that are standard in handling volatile organic chemicals would be impractical.
“Where people print is not always in chemically safe environments,” said John Reynolds, a professor in Georgia Tech’s Schools of Chemistry and Biochemistry and Material Science and Engineering. So Reynolds and the study’s first author Brian Schmatz, who came up with the water-based method, set out to make electrochromic film inks safer for everyday environments.
There were some hurdles to pulling it off. The finished product had to electrically operate comparable to films that are applied in an organic solvent, and also be water-resistant in spite of the water-based production. Schmatz’s method also needed to be logistically and financially realistic for producers to implement.
The researchers published details on their solution and how it has met the criteria in the journal ACS Central Science on August 16, 2017. Should the chemical process progress to production, the future may see more windows, prescription glasses, or even textiles that switch between colors and shades of darkness with the click of a button or with the help of a light-detecting switch.
That’s how many self-dimming rear-view mirrors work: The high-beams of the motorist behind you hit a light sensor that applies a mild electric field to the mirror, and that activates the color-changing, or electrochromic, film, which switches to a darker tint.
The Reynolds lab’s electrochromic films are made with conjugated polymers, colorful and electroactive organic molecules. They easily let go of a few of their more loosely attached electrons, and when they do, their colors shift.
If the colored films are on a clear surface, when the color vanishes, the surface becomes clear. The surface has to be conductive so that a small voltage (about 1 volt) can be applied to bump the electrons off the conjugated polymer or help them jump back on.
The tints don’t have to be gray, blue, brown, or otherwise straight-laced. “We can make any color,” Reynolds said.
Because of previous inks’ organic solvents, applying electrochromic films in the past has come with significant safety requirements. Their costs could become prohibitive if the job is big, say, if a company wanted to cover the windows of an office building with an electrochromic film.
“Most research labs use chlorobenzene as a solvent. It’s pretty toxic. It’s carcinogenic, slightly volatile as well,” Schmatz said. “So, it’s not something people want to work with at scale.”
Also, people may simply find the smell of an organic chemical in their workplace unpleasant. Examples of organic solvent smells most everyone has experienced are kerosene, gasoline, or rubbing alcohol.
Water as a solvent is much safer, but it can present other challenges. Conjugated polymers are produced in organic solvents and do not inherently dissolve in water. Also, films printed from water-based inks might wash out in the rain or smudge in high humidity.
Schmatz’s invention combines the best of both worlds by using an organic solvent and an aqueous solvent in phases.
First, the conjugated polymer is produced in an organic solvent to assure quality material is made. That’s also aligned with chemical industry practices.
“Chemical companies really do a lot of this kind of processing, and it’s advantageous to keep this as it is, so the companies can keep doing what they’re doing and add this product more easily,” Schmatz said.
But then Schmatz alters the conjugated polymer – the ink’s active ingredient, so to speak -- which is usually not water soluble, so that it will indeed dissolve in water.
“We embed a chemical trigger within the polymer. It’s activated through a high pH water wash, and that transforms the organic soluble polymer into a water soluble polyelectrolyte,” he said. “The reason we want to do all of this is so we can produce the polymer in an organic solvent, but then print the polymer from a water-based ink.”
To make sure that the film doesn’t smear or run after printing and that it functions well when it’s completed, Schmatz cleaves off that added chemical trigger from the conjugated polymer by shining ultraviolet light on the electrochromic film.
The water-soluble chemical chain then becomes a simple residue that can be wiped or rinsed off. What’s left is a robust, pure conjugated polymer film, which can no longer dissolve in water or organic solvents.
Reynolds envisions electrochromic films on various materials, including some other than glass or plastic. “You could apply this to camouflage, for example, with the right textiles, and have a sensor connected to a battery, and have it switch the colors to match the changing lightness or darkness of a soldier’s surroundings.”
Aside from electrochromics, these conjugated polymers are also being explored for printed transistors, solar cells, chemical and bio-sensors, light emitting displays and bioelectronics. Reynold’s group has access to a number of delivery methods to test application of conjugated polymers.
“Georgia Tech is a focused engineering university and has application capabilities you can find right here,” Reynolds said. “The various methods of printing or spraying are here – airbrush, blade coater, ink jet. And if we don’t have something, we can build it here.”
Also READ: Rainbow of possibilities with electrochromic polymers
Georgia Tech’s Zhibo Yuan, Augustus Lang, Jeff Hernandez and Elsa Reichmanis co-authored the study. Research was funded by the Office of Naval Research of the U.S. Department of Defense (grant N00014-16-1-2165), the National Science Foundation (grant DMR-1507205.) Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of those agencies.
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]]>Cancer cells kill most often by crawling away from their original tumors to later re-root in vital parts of the body in a process called metastasis. Now, a research team led by the Georgia Institute of Technology has developed a new treatment to thwart cancer's spread through the body by, in a sense, breaking cancer cells’ legs.
Cancer cells often cover themselves with bristly leg-like protrusions that enable them to creep. The researchers have used minuscule gold rods heated gently by a laser to mangle the protrusions, according to a new study. The treatment prevented cell migration, a key mechanism in metastasis, in experiments on common laboratory cultures (in vitro) of cancerous human cells.
The method could potentially, in the future, offer clinicians going after individual tumors a weapon to combat cancer’s deadly spread at the same time. The medical field is currently less than well-equipped to stop metastasis.
“If cancer stays in a tumor in one place, you can get to it, and it’s not so likely to kill the patient, but when it spreads around the body, that’s what really makes it deadly,” said lead researcher Mostafa El-Sayed, Julius Brown Chair and Regents Professor at Georgia Tech’s School of Chemistry and Biochemistry.
The treatment can also easily kill cancer cells, but in this experiment, it was vital to specifically show that it greatly slowed cell migration. The method is not scheduled for human testing.
The experimental treatment also spared healthy cells, in these and in prior experiments, making the method potentially much less taxing on patients than commonly used chemotherapy. In past tests in animal models, the researchers have uncovered no toxic side effects from the gold used in the treatment, and have found no observable damage to healthy tissue from the low-energy laser.
And they did not see recurrence of the treated cancer.
“The method appears to be very effective as a locally administered treatment that also protects the body from cancer’s spread away from the treated tumors, and it is also very mild, so it can be applied many times over if needed,” El-Sayed said.
El-Sayed, co-lead author Ronghu Wu, and first authors Yue Wu and Moustafa Ali published the results of their current in vitro experiments, a new development in photothermal gold nanorod therapy, on June 26, 2017, in the Proceedings of the National Academy of Sciences. The research was funded by the National Science Foundation and the National Institutes of Health.
To understand how the treatment works, let’s take a close-up look at a cell and some things that happen to it in malignant cancer.
Many people think of cells as watery balloons -- fluid encased in a membrane sheath with organelles floating around inside. But that picture is incomplete. Cells have support grids called cytoskeletons that give them form and that have functions.
The cytoskeletons also form bristly protrusions called filopodia, which extend out from a weave of fibers called lamellipodia that are on the cell’s fringes. The protrusions normally help healthy cells shift their location in the tissue that they are part of.
But in malignant cancer, normally healthy cell functions often lunge into destructive overdrive. Lamellipodia and filopodia are wildly overproduced.
“All these lamellipodia and filopodia give the cancer cells legs,” said Yue Wu, a graduate student in bioanalytical chemistry. “The metastasis requires those protrusions, so the cells can travel.”
The gold nanorods thwart the protrusions in two ways. The rods are comprised of a small collection of gold atoms – nano refers to something being just billionths of meters (or feet) in size.
First, El-Sayed’s nanorods are introduced locally, where they encumber the leggy protrusions on cancerous cells. The rods are coated with molecules (RGD-peptides) that make them stick specifically to a type of cell protein called integrin.
“The targeted nanorods tied up the integrin and blocked its functions, so it could not keep guiding the cytoskeleton to overproduce lamellipodia and filopodia,” said Yan Tang, a postdoctoral assistant in computational biology who worked on the study. The binding of the integrin alone slowed down the migration of malignant cells.
But healthy cells were not targeted. “There are certain, specific integrins that are overproduced in cancerous cells,” said Moustafa Ali, one of the study’s first authors. “And you don’t find them so much in healthy cells.”
In the second phase, researchers hit the gold nanoparticles with a low-energy laser of near-infrared (NIR) light. It brought the migration of the cancer cells to an observable halt.
“The light was not absorbed by the cells, but the gold nanorods absorbed it, and as a result, they heated up and partially melted cancer cells they are connected with, mangling lamellipodia and filopodia,” Ali said. “It didn’t kill all the cells, not in this experiment. If we killed them, we would not have been able to observe whether we stopped them from migrating or not.”
If desired, the treatment can also be adjusted to kill the cells.
Early experiments in animal models in vivo with hotter lasers didn’t work as well. “That caused inflammation, which made it possible to heat one time only,” Ali said. “As a result, that high temperature would wipe out many cancer cells, but not all of them. Some hidden ones might have survived, and also still been able to migrate.”
“This gentle laser didn’t burn the skin or damage tissue, so it could be dosed multiple times and more thoroughly stop the cancer cells from being able to travel,” said researcher Ronghu Wu.
The researchers presently envision treating head, neck, breast, and skin cancers with direct, local nanorod injections combined with the low-power near-infrared laser, which can hit the gold nanorods 2-3 centimeters (a bit under or over an inch) deep inside tissue. “But it could go as deep as 4-5 centimeters,” Ali said.
Deeper tumors could conceivably be treated with deeper injections of nanorods. “Then you’d need to go in with a fiber optic or endoscopic laser,” El-Sayed said. Injecting the nanorods directly into the bloodstream as a broad treatment would not currently be a viable option.
El-Sayed’s group has previously published in vivo experiments in mice in the Proceedings of the National Academy of Sciences together with Emory University School of Medicine. That study showed no observable toxicity from the gold in mice 15 months after treatment.
“A lot of it ended up in the liver and spleen,” El-Sayed said. “But the functions of these organs appeared intact upon examination, and treated mice were alive and healthy over a year later.”
Mostafa El-Sayed is one of the world’s most highly decorated and cited living chemists, and a pioneer of nanoscience and technology. Among his many recognitions are the President’s National Medal of Science, awarded by President George W. Bush, and the Priestley Medal, the American Chemical Society’s highest honor. President Barack H. Obama appointed El-Sayed to the President’s National Medal of Science Committee. El-Sayed also participated in the nomination of chemistry Nobel Laureate Ahmed Zewail.
El-Sayed is known throughout physical chemistry for “El-Sayed’s Rule,” which handles complexities of electron spin orbits, and which has found a lasting place in photochemistry textbooks. After losing his wife to cancer in 2005, El-Sayed dedicated his knowledge and research to ending the scourge.
Also read: Cancer and Technology
Also read: Punching Cancer with RNA Knuckles
The following authors also contributed to this research: Haopeng Xiao and Tiegang Han from Georgia Tech, and Kuangcai Chen and Ning Fang from Georgia State University. This research was funded by the National Science Foundation Division of Chemistry (grants 1608801, CAREER Award CHE-1454501), and the National Institutes of Health Nanotechnology Study Section (grant 1R01GM115763). Any opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the funding agencies.
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]]>The process, which uses parallel plates to create a meniscus of ink containing the metal halide perovskite precursors, could be scaled up to rapidly generate large areas of dense crystalline film on a variety of substrates, including flexible polymers. Operating parameters for the fabrication process were chosen by using a detailed kinetics study of perovskite crystals observed throughout their formation and growth cycle.
“We used a meniscus-assisted solution printing technique at low temperature to craft high quality perovskite films with much improved optoelectronic performance,” said Zhiqun Lin, a professor in the School of Materials Science and Engineering at the Georgia Institute of Technology. “We began by developing a detailed understanding of crystal growth kinetics that allowed us to know how the preparative parameters should be tuned to optimize fabrication of the films.”
The new technique is reported July 7 in the journal Nature Communications. The research has been supported by the Air Force Office of Scientific Research (AFOSR) and the National Science Foundation (NSF).
Perovskites offer an attractive alternative to traditional materials for capturing electricity from light, but existing fabrication techniques typically produce small crystalline grains whose boundaries can trap the electrons produced when photons strike the materials. Existing production techniques for preparing large-grained perovskite films typically require higher temperatures, which is not favorable for polymer materials used as substrates – which could help lower the fabrication costs and enable flexible perovskite solar cells.
So Lin, Research Scientist Ming He and colleagues decided to try a new approach that relies on capillary action to draw perovskite ink into a meniscus formed between two nearly parallel plates approximately 300 microns apart. The bottom plate moves continuously, allowing solvent to evaporate at the meniscus edge to form crystalline perovskite. As the crystals form, fresh ink is drawn into the meniscus using the same physical process that forms a coffee ring on an absorbent surface such as paper.
“Because solvent evaporation triggers the transport of precursors from the inside to the outside, perovskite precursors accumulate at the edge of the meniscus and form a saturated phase,” Lin explained. “This saturated phase leads to the nucleation and growth of crystals. Over a large area, we see a flat and uniform film having high crystallinity and dense growth of large crystals.”
To establish the optimal rate for moving the plates, the distance between plates and the temperature applied to the lower plate, the researchers studied the growth of perovskite crystals during MASP. Using movies taken through an optical microscope to monitor the grains, they discovered that the crystals first grow at a quadratic rate, but slow to a linear rate when they began to impinge on their neighbors.
“When the crystals run into their neighbors, that affects their growth,” noted He. “We found that all of the grains we studied followed similar growth dynamics and grew into a continuous film on the substrate.”
The MASP process generates relatively large crystals – 20 to 80 microns in diameter – that cover the substrate surface. Having a dense structure with fewer crystals minimizes the gaps that can interrupt the current flow, and reduces the number of boundaries that can trap electrons and holes and allow them to recombine.
Using films produced with the MASP process, the researchers have built solar cells that have power conversion efficiencies averaging 18 percent – with some as high as 20 percent. The cells have been tested with more than 100 hours of operation without encapsulation. “The stability of our MASP film is improved because of the high quality of the crystals,” Lin said.
Doctor-blading is one of the conventional perovskite fabrication techniques in which higher temperatures are used to evaporate the solvent. Lin and his colleagues heated their substrate to only about 60 degrees Celsius, which would be potentially compatible with polymer substrate materials.
So far, the researchers have produced centimeter-scale samples, but they believe the process could be scaled up and applied to flexible substrates, potentially facilitating roll-to-roll continuous processing of the perovskite materials. That could help lower the cost of producing solar cells and other optoelectronic devices.
“The meniscus-assisted solution printing technique would have advantages for flexible solar cells and other applications requiring a low-temperature continuous fabrication process,” Lin added. “We expect the process could be scaled up to produce high throughput, large-scale perovskite films.”
Among the next steps are fabricating the films on polymer substrates, and evaluating other unique properties (e.g., thermal and piezotronic) of the material.
This research was supported by the Air Force Office of Scientific Research (MURI FA9550-14-1-0037; FA9550-16-1-0187) and National Science Foundation (CMMI-1562075). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsoring agencies.
CITATION: Ming He, Bo Li, Xun Cui, Beibei Jiang, Yanjie He, Yihuang Chen, Daniel O’Neil, Paul Szymanski, Mostafa A. EI-Sayed, Jinsong Huang and Zhiqun Lin, “Meniscus-assisted solution printing of large-grained perovskite films for high-efficiency solar cells,” (Nature Communications, 2017). http://dx.doi.org/10.1038/ncomms16045.
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]]>Known as Dry Ion Localization and Locomotion (DRILL), the new device creates a swirling flow that can separate electrospray droplets depending on their size. In this application, one of many potential uses for DRILL, the smaller droplets are directed to enter the mass spectrometer, while the larger ones – which still contain solvent – remain in the vortex flow until the solvent evaporates. Removing the solvent allows analysis of additional ions that may be lost in current techniques and reduces the chemical “noise” that inhibits selectivity of the mass spectrometer.
“A major challenge for detecting small quantities of biomolecules using mass spectrometry technology is that we can’t see everything that is actually in the sample,” said Matthew Torres, an assistant professor in Georgia Tech’s School of Biological Sciences. “The DRILL device provides a new way to solve that problem by increasing the number of ions we can get into the mass spec instrument so we can productively detect them. The ions are there now, but not necessarily in a form that the mass spec can handle.”
Developed by researchers at the Georgia Institute of Technology with support from North Carolina State University, DRILL can be added to existing electrospray ionization mass spectrometers without modifying them.
“The principle is to make the droplets rotate and use inertia to separate them out by size,” explained Andrei Fedorov, a professor in Georgia Tech’s Woodruff School of Mechanical Engineering. “We want the droplets to stay in the flow long enough to remove the solvent. In practice, smaller droplets remain in the center, where they are can be removed first for analysis, while the larger ones remain on the edge of the flow until they are dried.”
The key idea of DRILL is based on Fedorov’s 2007 invention “Confining/Focusing Vortex Flow Transmission Structure, Mass Spectrometry Systems, and Methods of Transmitting Particles, Droplets, and Ions." (US Patent No. 7,595,487). In the past three years, the DRILL device has been developed with support from the National Institute of General Medical Sciences of the National Institutes of Health, and its latest version was described June 14 in the American Chemical Society journal Analytical Chemistry.
In electrospray ionization (ESI), an electric potential is applied to a solution inside a capillary, producing a strong electric field at the spray capillary tip. That leads to the expulsion of an aerosol containing charged droplets that carry the molecules to be analyzed. The ejected droplets then break up into smaller droplets, creating a plume that expands spatially beyond the inlet intake capacity of the mass spectrometer, resulting in sample loss. The DRILL device provides an effective interface for collection and transmission of charged analytes from ionization sources, such as ESI, to detection devices, such as mass spectrometers, resulting in significantly improved detection capability.
As much as 80 to 90 percent of large biopolymers (proteins, peptides, and DNA) are currently lost to analysis using existing ESI-MS techniques, which have grown in importance to the life sciences community. Capturing all of the biopolymers could lead to new discoveries, said Torres, whose lab studies post-translational changes in proteins. By allowing analysis of large biomolecules, DRILL could facilitate top-down proteomics in which complete protein molecules could be studied without the need to enzymatically break them up into smaller pieces before MS analysis.
“This could allow us to see combinatorial modifications that exist on a single protein molecule,” said Torres. “It’s very important for us to understand how proteins communicate with one another, and DRILL may allow us to do that by more effectively removing the solvent from these types of samples.”
The Georgia Tech researchers are using DRILL in their lab to interface between liquid chromatography and the ESI-MS instrument. Multiple electrodes and inlet/outlet ports enable precise control over the flow generation and guiding electric field inside the DRILL, so the device can be configured for a variety of uses, Fedorov noted. In a general sense, DRILL adds a new approach for manipulating the trajectory of charged droplets, which, when combined with hydrodynamic drag forces and electric field forces, provides a rich range of possible operational modes.
DRILL can improve the signal-to-noise ratio by a factor of 10 in the detection of angiotensin I, a peptide hormone, and boost the sensitivity for angiotensin II ten-fold to picomole levels. DRILL demonstrated improved signal strength – up to 700-fold – for eight of nine peptides included in a test extract of biological tissue.
DRILL could potentially allow the study of entire cell contents, analyzing thousands of different molecule types simultaneously. That could allow researchers to see how these molecules change over time to detect problems in chemical pathways and to determine why drugs work in some people and not others.
“This could be a huge advance for biologists and others who are interested in protein biochemistry and cell biology because it enhances the sensitivity of the analytical technical and overcomes a major hurdle in studying large biological molecules,” Torres added. “We expect to be able to see things we haven’t been able to see before.”
The Georgia Tech researchers have been collaborating with David Muddiman, a professor in the Department of Chemistry at North Carolina State University, on developing DRILL and its analytical characterization using state-of-the-art mass spectrometry experiments. A unique contribution of the North Carolina State University researchers is in using a powerful statistical method called “design of experiments” to guide the multi-parameter optimization of the DRILL device, resulting in identification of a sweet spot for optimal operation.
Fedorov and Torres hope to expand use of the DRILL device beyond Georgia Tech laboratories and further enhance its design. Among the near-term improvements planned is the addition of internal heating to accelerate the removal of solvent. “We see many additional improvements that will allow DRILL to further enhance the ESI-MS process,” said Fedorov. “We plan to continue evolving it as more labs start to use the device.”
In addition to those already named, the paper’s co-authors include Peter A. Kottke, Jung Y. Lee and Alex P. Jonke from Georgia Tech and Chinthaka A. Seneviratne and Elizabeth S. Hecht from North Carolina State University.
Research reported in this publication was supported by the National Institute of General Medical Sciences of the National Institutes of Health under Award Number R01GM112662. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
CITATION: Peter A. Kottke, et al., “DRILL: An ESI-MS interface for improved sensitivity via inertial droplet sorting and electrohydrodynamic focusing in a swirling flow,” (Analytical Chemistry, 2017). http://dx.doi.org/10.1021/acs.analchem.7b01555.
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]]>A phase I clinical trial conducted by Emory University in collaboration with researchers from the Georgia Institute of Technology has found that influenza vaccination using Band-Aid-like patches with dissolvable microneedles was safe and well-tolerated by study participants, was just as effective in generating immunity against influenza, and was strongly preferred by study participants over vaccination with a hypodermic needle and syringe. The microneedle patch vaccine could also save money because it is easily self-administered, could be transported and stored without refrigeration, and is easily disposed of after use without sharps waste.
Results of the study are published June 27, 2017 in the medical journal The Lancet. The research was supported by the National Institute of Biomedical Imaging and Bioengineering of the National Institutes of Health.
“Despite the recommendation of universal flu vaccination, influenza continues to be a major cause of illness leading to significant morbidity and mortality,” said first author Nadine Rouphael, M.D., associate professor of medicine (infectious diseases) at Emory University School of Medicine and principal investigator of the clinical trial. “Having the option of a flu vaccine that can be easily and painlessly self-administered could increase coverage and protection by this important vaccine.”
The first-in-human clinical trial of the flu vaccine patches began in June 2015 with 100 participants aged 18-49 who were healthy and who had not received the influenza vaccine during the 2014-15 flu season. The study was conducted at the Hope Clinic of the Emory Vaccine Center in Atlanta. The study was carried out under an Investigational New Drug Application authorized by the FDA.
Participants were randomized into four groups: (1) vaccination with microneedle patch given by a health care provider; (2) vaccination with microneedle patch self-administered by study participants; (3) vaccination with intramuscular injection given by a health care provider; and (4) placebo microneedle patch given by a health care provider.
“People have a lot of reasons for not getting flu vaccinations,” said senior co-author Mark Prausnitz, Ph.D., Georgia Tech Regents professor of chemical and biomolecular engineering. “One of the main goals of developing the microneedle patch technology was to make vaccines accessible to more people. Traditionally, if you get an influenza vaccine you need to visit a health care professional who will administer the vaccine using a hypodermic needle. The vaccine is stored in the refrigerator, and the used needle must be disposed of in a safe manner. With the microneedle patch, you could pick it up at the store and take it home, put it on your skin for a few minutes, peel it off and dispose of it safely, because the microneedles have dissolved away. The patches can also be stored outside the refrigerator, so you could even mail them to people.”
Study results showed that vaccination with the microneedle patches was safe, with no adverse events reported. Local skin reactions to the patches were mostly faint redness and mild itching that lasted two to three days. No new chronic medical illnesses or influenza-like illnesses were reported with either the patch or the injection groups. Antibody responses generated by the vaccine, as measured through analysis of blood samples, were similar in the groups vaccinated using patches and those receiving intramuscular injection, and these immune responses were still present after six months. More than 70 percent of patch recipients reported they would prefer patch vaccination over injection or intranasal vaccination for future vaccinations.
No significant difference was seen between the doses of vaccine delivered by the health care workers and the volunteers who self-administered the patches, showing that participants were able to correctly self-administer the patch. After vaccination, imaging of the used patches found that the microneedles had dissolved in the skin, suggesting that the used patches could be safely discarded as non-sharps waste. The vaccines remained potent in the patches without refrigeration for at least one year.
The microneedle patches used in the study were designed at Georgia Tech and manufactured by the Global Center for Medical Innovation in Atlanta.
Prausnitz has been working for many years to develop the microneedle patch technology. “It’s very gratifying and exciting to have these patches tested in a clinical trial, and with a result that turned out so well. We now need to follow this study with a phase II clinical trial involving more people, and we hope that will happen soon.”
The researchers also are working to develop microneedle patches for use with other vaccines, including measles, rubella and polio.
“From the very start of this project,” said Prausnitz, “our team at Georgia Tech has been working with the Emory team to develop the microneedle patches, and the success of the project has been due to the strong collaboration between Georgia Tech engineers and the bioscience and medical experts at Emory.” Prausnitz holds the J. Erskine Love Jr. Chair in the School of Chemical and Biomolecular Engineering.
The authors summarized: “Influenza vaccination using microneedle patches is well-tolerated, well-accepted, and results in robust immunologic responses, whether administered by health care workers or by the participants themselves. These results provide evidence that microneedle patch vaccination is an innovative new approach with the potential to improve current vacination coverage and reduce immunization costs.”
In addition to Rouphael and Prausnitz, other study authors include co-senior author Mark J. Mulligan, M.D., executive director of the Hope Clinic of the Emory Vaccine Center; Emory researchers Michele Paine, Regina Mosley, Paula M. Frew, Tianwei Yu, Natalie J. Thornburg, Sarah Kabbani, Lilin Lai, Elena V. Vassilieva, Ioanna Skountzou, and Richard W. Compans; and Georgia Tech researchers Sebastien Henry, Devin V. McAllister, Haripriya Kalluri, and Winston Pewin.
This study was funded by a grant from the National Institute of Biomedical Imaging and Bioengineering of the National Institutes of Health (U01 EB012495). One of the researchers received support through a training grant from the National Institute of Allergy and Infectious Diseases (T32 AI074492). The Georgia Research Alliance provided instrumentation support. The content is solely the responsibility of the authors and does not necessarily represent the official views of the sponsoring agencies.
Prausnitz has co-founded a company called Micron Biomedical that is licensing patents related to this study. Micron Biomedical is poised to move the microneedle patch technology forward, bring it further into clinical trials, commercialize it and ultimately make it available to patients.
Prausnitz and several other Georgia Tech researchers are inventors of the microneedle patch technology used in this study and have ownership interest in Micron Biomedical. They are entitled to royalties derived from Micron Biomedical’s future sales of products related to the research. These potential conflicts of interest have been disclosed and are overseen by Georgia Institute of Technology and Emory University.
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]]>By heating the ethene in stages to a temperature of slightly more than 700 degrees Celsius -- hotter than had been attempted before – the researchers produced pure layers of graphene on a rhodium catalyst substrate. The stepwise heating and higher temperature overcame challenges seen in earlier efforts to produce graphene directly from hydrocarbon precursors.
Because of its lower cost and simplicity, the technique could open new potential applications for graphene, which has attractive physical and electronic properties. The work also provides a novel mechanism for the self-evolution of carbon cluster precursors whose diffusional coalescence results in the formation of the graphene layers.
The research, reported as the cover article in the May 4 issue of the Journal of Physical Chemistry C, was conducted by scientists at the Georgia Institute of Technology, Technische Universität München in Germany, and the University of St. Andrews in Scotland. In the United States, the research was supported by the U.S. Air Force Office of Scientific Research and the U.S. Department of Energy’s Office of Basic Energy Sciences.
“Since graphene is made from carbon, we decided to start with the simplest type of carbon molecules and see if we could assemble them into graphene,” explained Uzi Landman, a Regents’ Professor and F.E. Callaway endowed chair in the Georgia Tech School of Physics who headed the theoretical component of the research. “From small molecules containing carbon, you end up with macroscopic pieces of graphene.”
Graphene is now produced using a variety of methods including chemical vapor deposition, evaporation of silicon from silicon carbide – and simple exfoliation of graphene sheets from graphite. A number of earlier efforts to produce graphene from simple hydrocarbon precursors had proven largely unsuccessful, creating disordered soot rather than structured graphene.
Guided by a theoretical approach, the researchers reasoned that the path from ethene to graphene would involve formation of a series of structures as hydrogen atoms leave the ethene molecules and carbon atoms self-assemble into the honeycomb pattern that characterizes graphene. To explore the nature of the thermally-induced rhodium surface-catalyzed transformations from ethene to graphene, experimental groups in Germany and Scotland raised the temperature of the material in steps under ultra-high vacuum. They used scanning-tunneling microscopy (STM), thermal programed desorption (TPD) and high-resolution electron energy loss (vibrational) spectroscopy (HREELS) to observe and characterize the structures that form at each step of the process.
Upon heating, ethene adsorbed onto the rhodium catalyst evolves via coupling reactions to form segmented one-dimensional polyaromatic hydrocarbons (1D-PAH). Further heating leads to dimensionality crossover – one dimensional to two dimensional structures – and dynamical restructuring processes at the PAH chain ends with a subsequent activated detachment of size-selective carbon clusters, following a mechanism revealed through first-principles quantum mechanical simulations. Finally, rate-limiting diffusional coalescence of these dynamically self-evolved cluster-precursors leads to condensation into graphene with high purity.
At the final stage before the formation of graphene, the researchers observed nearly round disk-like clusters containing 24 carbon atoms, which spread out to form the graphene lattice. “The temperature must be raised within windows of temperature ranges to allow the requisite structures to form before the next stage of heating,” Landman explained. “If you stop at certain temperatures, you are likely to end up with coking.”
An important component is the dehydrogenation process which frees the carbon atoms to form intermediate shapes, but some of the hydrogen resides temporarily on, or near, the metal catalyst surface and it assists in subsequent bond-breaking process that lead to detachment of the 24-carbon cluster-precursors. “All along the way, there is a loss of hydrogen from the clusters,” said Landman. “Bringing up the temperature essentially ‘boils’ the hydrogen out of the evolving metal-supported carbon structure, culminating in graphene.”
The resulting graphene structure is adsorbed onto the catalyst. It may be useful attached to the metal, but for other applications, a way to remove it will have to be developed. Added Landman: “This is a new route to graphene, and the possible technological application is yet to be explored.”
Beyond the theoretical research, carried out by Bokwon Yoon and Landman at the Georgia Tech Center for Computational Materials Science, the experimental work was done in the laboratory of Professor Renald Schaub at the University of St. Andrews and in the laboratory of Professor Ueli Heiz and Friedrich Esch at the Technische Universität München. Other co-authors included Bo Wang, Michael König, Catherine J. Bromley, Michael-John Treanor, José A. Garrido Torres, Marco Caffio, Federico Grillo, Herbert Frücht, and Neville V. Richardson.
The work at the Georgia Institute of Technology was supported by the Air Force Office of Scientific Research through Grant FA9550-14-1-0005 and by the Office of Basic Energy Sciences of the U.S. Department of Energy through Grant FG05-86ER45234. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the sponsoring organizations.
CITATION: Bo Wang, et al., “Ethene to Graphene: Surface Catalyzed Chemical Pathways, Intermediates, and Assembly,” (Journal of Physical Chemistry C). http://dx.doi.org/10.1021/acs.jpcc.7b01999
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]]>The technique involves projecting a grayscale pattern of light and dark shapes onto a thin layer of liquid acrylate polymer placed in a plate or between two glass slides. A photoinitiator material mixed into the polymer initiates a crosslinking reaction when struck by light from an ordinary LED projector, causing a solid film to form. A light-absorbing dye in the polymer serves as a regulator for the light. Due to the complicated interaction between the evolution of the polymer network and volume shrinkage during photo curing, areas of the polymer that receive less light exhibit more apparent bending behavior.
When the newly-created polymer film is removed from the liquid polymer, the stress created in the film by the differential shrinkage causes the folding to begin. To make the most complex origami structures, the researchers shine light onto both sides of the structures.
Origami structures produced so far include tiny tables, capsules, flowers, birds and the traditional miura-ori fold – all about a half-inch in size. The origami structures could have applications in soft robots, microelectronics, soft actuators, mechanical metamaterials and biomedical devices.
“The basic idea of our method is to utilize the volume shrinkage phenomenon during photo-polymerization,” said Jerry Qi, a professor in the Woodruff School of Mechanical Engineering at Georgia Tech. “During a specific type of photopolymerization, frontal photopolymerization, the liquid resin is cured continuously from the side under light irradiation toward the inner side. This creates a non-uniform stress field that drives the film to bend along the direction of light path.”
Details of the work were published April 28 in the journal Science Advances. The research was supported by the National Science Foundation, the Air Force Office of Scientific Research and the Chinese Scholarship Council. It is believed to be the first application to create self-folding origami structures through the control of volume shrinkage during patterned photopolymerization.
The process that creates the shrinkage phenomenon is considered harmful in other uses of the polymer.
“Volume shrinkage of polymer was always assumed to be detrimental in the fabrication of composites and in the conventional 3-D printing technology,” said Daining Fang, a co-author of the paper and a professor at Peking University when the research was done. “Our work shows that with a change of perspective, this phenomenon can become quite useful.” Fang is now at Beijing Institute of Technology.
To make the most complex shapes with bending in both directions, the researchers can flip the patterned film over to create crosslinking on the other side.
“We have developed two types of fabrication processes,” said Zeang Zhao, a Ph.D. student at Georgia Tech and Peking University. “In the first one, you can just shine the light pattern towards a layer of liquid resin, and then you will get the origami structure. In the second one, you may need to flip the layer and shine a second pattern. This second process gives you much wider design freedom.”
Light is shined onto the film for five to ten seconds, which produces a film about 200 microns thick. “The areas that receive light become solid; the other parts of the pattern remain liquid, and the structure can then be removed from the liquid polymer,” said Qi. “The technique is very simple.”
Frontal photopolymerization is a process in which a polymer film is continuously cured from one side in a thick layer of liquid resin. In the presence of strong light attenuation, the solidification front initiates at the surface upon illumination and propagates toward the liquid side as the irradiation time increases. The process can be delicately tuned by controlling the illumination time and the light intensity, and the method has been used to fabricate microfluidic devices and synthesize microparticles.
The researchers used poly(ethylene glycol) diacrylate in this demonstration, but the technique should work with a broad range of photocurable polymers. An orange dye was used in the demonstration, but other dyes could produce structures in a range of different colors.
For the proof-of-principle, Zhao created a PowerPoint pattern by hand. To scale the process up, the system could be connected to a computer-aided design (CAD) tool for generating more precise grayscale patterns.
Qi believes the technique could be used to produce structures as much as an inch in size. “The self-folding requires relatively thin films which might not be possible in larger structures,” he said.
Added Qi, “We have developed a simple approach to fold a thin sheet of polymer into complicated three-dimensional origami structures. Our approach is not limited by specific materials, and the patterning is so simple that anybody with PowerPoint and a projector could do it.”
This research was supported by NSF awards CMMI-1462894, CMMI-1462895, and EFRI-1435452; and the Air Force Office of Scientific Research grant 15RT0885. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the sponsoring organizations.
CITATION: Zeang Zhao, Jiangtao Wu, Xiaoming Mu, Haosen Chen, H. Jerry Qi, and Daining Fang, “Origami by frontal photopolymerization,” (Science Advances, 2017).
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]]>Each week in April, we will publish more stories about our autism-related work.
Researchers at Emory University and Georgia Tech demonstrated this connection in two new papers published by Nature Chemistry: “Design of multi-phase dynamic chemical networks” and “Catalytic diversity in self-propagating peptide assemblies.”
“In the first paper we showed that you can create tension between a chemical and physical system to give rise to more complex systems. And in the second paper, we showed that these complex systems can have remarkable and unexpected functions,” said David Lynn, a systems chemist at Emory who led the research. “The work was inspired by our current understanding of Darwinian selection of protein misfolding in neurodegenerative diseases.”
The Lynn lab is exploring ways to potentially control and direct the processes of these proteins – known as prions – adding to knowledge that might one day help to prevent disease, as well as open new realms of synthetic biology. For the current papers, Emory collaborated with the research group of Martha Grover, a professor in the Georgia Tech School of Chemical & Biomolecular Engineering, to develop molecular models for the processes.
Darwin’s theory of evolution by natural selection is well-established – organisms adapt over time in response to environmental changes. But theories about how life emerges – the movement through a pre-Darwinian world to the Darwinian threshold – remain murkier.
The researchers started with single peptides and engineered in the capacity to spontaneously form small proteins, or short polymers. “These protein polymers can fold into a seemingly endless array of forms, and sometimes behave like origami,” Lynn explained. “They can stack into assemblies that carry new functions, like prions that move from cell-to-cell, causing disease.”
This protein misfolding provided the model for how physical changes could carry information with function, a critical component for evolution. To try to kickstart that evolution, the researchers engineered a chemical system of peptides and coupled it to the physical system of protein misfolding. The combination results in a system that generates step-by-step, progressive changes, through self-driven environmental changes.
“The folding events, or phase changes, drive the chemistry and the chemistry drives the replication of the protein molecules,” Lynn said. “The simple system we designed requires only the initial intervention from us to achieve progressive growth in molecular order. The challenge now becomes the discovery of positive feedback mechanisms that allow the system to continue to grow.”
The researchers used mathematical modeling to help guide the experimental work.
“Modeling requires us to formulate our hypotheses in the language of mathematics, and then we use the models to design further experiments to test the hypotheses,” said Grover. “In this project, the hypotheses were sometimes invalidated by these further experiments, but ultimately this led us to a better understanding of the underlying chemical and physical events and their interactions."
The research was funded by the McDonnell Foundation, the National Science Foundation’s Materials Science Directorate, Emory University’s Alzheimer’s Disease Research Center, the National Science Foundation’s Center for Chemical Evolution and the Office of Basic Energy Sciences of the U.S. Department of Energy.
Additional co-authors of the papers include: Toluople Omosun, Seth Childers, Dibyendu Das and Anil Mehta (Emory Departments of Chemistry and Biology); Ming-Chien Hsieh (Georgia Tech School of Chemical & Biomolecular Engineering); and Neil Anthony and Keith Berland (Emory Department of Physics).
- Written by Carol Clark, Emory University
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]]>Researchers at the Georgia Institute of Technology have shown that replacing conventional power supplies with TENG devices for charging the molecules being analyzed can boost the sensitivity of mass spectrometers to unprecedented levels. The improvement also allows identification to be done with smaller sample volumes, potentially conserving precious biomolecules or chemical mixtures that may be available only in minute quantities.
Though the mechanism by which the enhancement takes place requires more study, the researchers believe the unique aspects of the TENG output – oscillating high voltage and controlled current – allow improvements in the ionization process, increasing the voltage applied without damaging samples or the instrument. The research, which was supported by the National Science Foundation, NASA Astrobiology Program and the Department of Energy, is reported February 27 in the journal Nature Nanotechnology.
“Our discovery is basically a new and very controlled way of putting charge onto molecules,” said Facundo Fernández, a professor in Georgia Tech’s School of Chemistry and Biochemistry who uses mass spectrometry to study everything from small drug molecules to large proteins. "We know exactly how much charge we produce using these nanogenerators, allowing us to reach sensitivity levels that are unheard-of – at the zeptomole scale. We can measure down to literally hundreds of molecules without tagging.”
Fernández and his research team worked with Zhong Lin Wang, a pioneer in developing the TENG technology. Wang, a Regents professor in Georgia Tech’s School of Materials Science and Engineering, said the TENGs provide consistent charging levels that produce quantized ion pulses of adjustable duration, polarity and frequency.
“The key here is that the total charge delivered in each cycle is entirely controlled and constant regardless of the speed at which the TENG is triggered,” said Wang, who holds the Hightower Chair in the School of Materials Science and Engineering. “This is a new direction for the triboelectric nanogenerators and opens a door for using the technology in the design of future instrumentation and equipment. This research demonstrates another practical impact of TENG technology.”
Mass spectrometry measures the mass-to-charge ratio of ions to identify and quantify molecules in both simple and complex mixtures. The technology is used across a broad range of scientific fields and applications, with molecules ranging from small drug compounds on up to large biomolecules. Mass spectrometry is used in biomedicine, food science, homeland security, systems biology, drug discovery and other areas.
But in conventional electrospray mass spec techniques, as much as 99 percent of the sample can be wasted during ionization, said Fernández, who holds the Vasser Woolley Foundation Chair in Bioanalytical Chemistry. That’s largely because in conventional systems, the mass analysis process is pulsed or scanned, while the ionization of samples is continuous. The new TENG pulsed power source allows scientists to time the ionization to match what’s happening inside the mass spectrometer, specifically within a component known as the mass analyzer.
Beyond improved sensitivity and the ability to analyze very small sample quantities, the new technique also allows ion deposition on surfaces, even non-conducting ones. That’s because the oscillating ionization produces a sequence of alternating positive and negative charges, producing a net neutral surface, Fernández said.
Mass spectrometers require large amounts of power for creating the vacuum essential to measuring the mass-to-charge ratio of each molecule. While it’s possible that future TENG devices could power an entire miniature mass spectrometer, the TENG devices are now used just to ionize samples.
“The nanogenerators could eliminate a big chunk of the mass spectrometer system because they wouldn’t need a more powerful device for making the ions,” Fernández said. “This could be particularly applicable to conditions that are extreme and harsh, such as on a battlefield or in space, where you would need a very robust and self-contained unit.”
Triboelectric nanogenerators, developed by Wang in 2012, use a combination of the triboelectric effect and electrostatic induction to generate small amounts of electrical power from mechanical motion such as rotation, sliding or vibration. The triboelectric effect takes advantage of the fact that certain materials become electrically charged after they come into moving contact with a surface made from a different material. Wang and his research team have developed TENGs with four different working modes, including a rotating disc that may be ideal for high throughput mass spectrometry experiments. This paper is the first publication about an application of TENG to an advanced instrument.
Wang’s team has measured voltage levels at the mass spec ionizer of between 6,000 and 8,000 volts. Standard ionizers normally operate at less than 1,500 volts. The technology has been used with both electrospray ionization and plasma discharge ionization, with the flexibility of generating single polarity or alternating polarity ion pulses.
“Because the voltage from these nanogenerators is high, we believe that the size of the sample droplets can be much smaller than with the conventional way of making ions,” Fernández said. “That increases the ion generation efficiency. We are operating in a completely different electrospray regime, and it could completely change the way this technology is used.”
The TENG technology could be retrofitted to existing mass spectrometers, as Fernández has already done in his lab. With publication of the journal article, he hopes other labs will start exploring use of the TENG devices in mass spectrometry and other areas. “I see potential not only in analytical chemistry, but also in synthesis, electrochemistry and other areas that require a controlled way of producing electrical charges,” Fernández said.
The research was initiated by postdoctoral fellows in the two laboratory groups, Anyin Li and Yunlong Zi. “This project really shows how innovation can happen at the boundaries between different disciplines when scientists are free to pursue new ideas,” Fernández added.
This work was jointly supported by NSF and the NASA Astrobiology Program, under the NSF Center for Chemical Evolution, CHE-1504217. Research was also supported by the U.S. Department of Energy, Office of Energy Sciences (Award DE-FG02-07ER46394), and the National Science Foundation (DMR-1505319). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsors.
CITATION: Anyin Li, Yunlong Zi, Hengyu Guo, Zhong Lin Wang, Facundo M. Fernández, “Triboelectric Nanogenerators for Sensitive Nano-Coulomb Molecular Mass Spectrometry,” (Nature Nanotechnology, 2016). http://dx.doi.org/10.1038/nnano.2017.17
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]]>Genetic therapies, such as those made from DNA or RNA, are hard to deliver into the right cells in the body. For the past 20 years, scientists have been developing nanoparticles made from a broad range of materials and adding compounds such as cholesterol to help carry these therapeutic agents into cells. But the rapid development of nanoparticle carriers has run into a major bottleneck: the nanoparticles have to be tested, first in cell culture, before a very small number of nanoparticles is tested in animals. With millions of possible combinations, identifying the optimal nanoparticle to target each organ was highly inefficient.
Using DNA strands just 58 nucleotides long, researchers from the University of Florida, Georgia Institute of Technology and Massachusetts Institute of Technology have developed a new testing technique that skips the cell culture testing altogether – and could allow hundreds of different types of nanoparticles to be tested simultaneously in just a handful of animals.
The original research was done in the laboratories of Robert Langer, the David H. Koch Institute Professor, and Daniel Anderson, the Samuel A. Goldsmith Professor of Applied Biology, at MIT. Supported by the National Institutes of Health, the research was reported February 6 in the journal Proceedings of the National Academy of Sciences.
“We want to understand at a very high level what factors affecting nanoparticle delivery are important,” said James Dahlman, an assistant professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University, one of Langer’s former graduate students, lead author on the study, and one of the paper’s corresponding authors. “This new technique not only allows us to understand what factors are important, but also how disease factors affect the process.”
To prepare nanoparticles for testing, the researchers insert a snippet of DNA that is assigned to each type of nanoparticle. The nanoparticles are then injected into mice, whose organs are then examined for presence of the barcodes. By using the same technologies scientists use to sequence the genome, many nanoparticles can be tested simultaneously, each identified by its unique DNA barcode.
Researchers are interested not only in which nanoparticles deliver the therapeutics most effectively, but also which can deliver them selectively to specific organs. Therapeutics targeted to tumors, for example, should be delivered only to the tumor and not to surrounding tissues. Therapeutics for heart disease likewise should selectively accumulate in the heart.
While much of the study was devoted to demonstrating control strategies, the researchers did test how 30 different particles were distributed in eight different tissues of an animal model. This nanoparticle targeting ‘heat map’ showed that some particles were not taken up at all, while others entered multiple organs. The testing included nanoparticles previously shown to selectivity enter the lungs and liver, and the results of the new technique were consistent with what was already known about those nanoparticles.
The single-strand DNA barcode sequences are about the same size as antisense oligonucleotides, microRNA and siRNA being developed for possible therapeutic uses. Other gene-based therapeutics are larger, and additional research would be needed to determine if the technique could be used with them. In the research reported this week, the nanoparticles were not used to deliver active therapeutics, though that would be a near-term next step.
“In future work, we are hoping to make a thousand particles and instead of evaluating them three at a time, we would hope to test a few hundred simultaneously,” Dahlman said. “Nanoparticles can be very complicated because for every biomaterial available, you could make several hundred nanoparticles of different sizes and with different components added.”
Once promising nanoparticles are identified with the screening, they would be subjected to additional testing to verify their ability to deliver therapeutics. In addition to accelerating the screening, the new technique may require fewer animals – perhaps no more than three for each set of nanoparticles tested.
There are a few caveats with the technique. To avoid the possibility of nanoparticles merging, only structures that are stable in aqueous environments can be tested. Only nontoxic nanoparticles can be screened, and researchers must control for potential inflammation generated by the inserted DNA.
In Langer and Anderson’s laboratory, Dahlman worked with Kevin Kauffman, who remains at MIT, and Eric Wang, now an assistant professor the University of Florida. Other co-authors of the paper included Yiping Xing, Taylor Shaw, Faryal Mir and Chloe Dlott, all of whom are at MIT.
“Nucleic acid therapies hold considerable promise for treating a range of serious diseases,” said Dahlman. “We hope this technique will be used widely in the field, and that it will ultimately bring more clarity to how these drugs affect cells – and how we can get them to the right locations in the body.”
CITATION: James E. Dahlman, et al., “Barcoded nanoparticles for high throughput in vivo discovery of targeted therapeutics.” (Proceedings of the National Academy of Sciences, 2017). http://www.pnas.org/content/early/2017/02/01/1620874114
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]]>Developed by researchers at the Georgia Institute of Technology and colleagues from three other institutions, the technique provides a new way of inducing p-type electrical doping in organic semiconductor films. The process involves briefly immersing the films in a solution at room temperature, and would replace a more complex technique that requires vacuum processing.
“Our hope is that this will be a game-changer for organic photovoltaics by further simplifying the process for fabricating polymer-based solar cells,” said Bernard Kippelen, director of Georgia Tech’s Center for Organic Photonics and Electronics and a professor in the School of Electrical and Computer Engineering. “We believe this technique is likely to impact many other device platforms in areas such as organic printed electronics, sensors, photodetectors and light-emitting diodes.”
Sponsored by the Office of Naval Research, the work was reported December 5 in the journal Nature Materials. The research also involved scientists from the University of California at Santa Barbara, Kyushu University in Japan, and the Eindhoven University of Technology in The Netherlands.
The technique consists of immersing thin films of organic semiconductors and their blends in polyoxometalate (PMA and PTA) solutions in nitromethane for a brief time – on the order of minutes. The diffusion of the dopant molecules into the films during immersion leads to efficient p-type electrical doping over a limited depth of 10 to 20 nanometers from the surface of the film. The p-doped regions show increased electrical conductivity and high work function, reduced solubility in the processing solvent, and improved photo-oxidation stability in air.
This new method provides a simpler alternative to air-sensitive molybdenum oxide layers used in the most efficient polymer solar cells that are generally processed using expensive vacuum equipment. When applied to polymer solar cells, the new doping method provided efficient hole collection. For the first time, single-layer polymer solar cells were demonstrated by combining this new method with spontaneous vertical phase separation of amine-containing polymers that leads to efficient electron collection at the opposing electrode. The geometry of these new devices is unique as the functions of hole and electron collection are built into the light-absorbing active layer, resulting in the simplest single-layer geometry with few interfaces.
“The realization of single-layer photovoltaics with our approach enables both electrodes in the device to be made out of low-cost conductive materials,” said Canek Fuentes-Hernandez, a senior research scientist in Kippelen’s research group. “This offers a dramatic simplification of a device geometry, and it improves the photo-oxidation stability of the donor polymer. Although lifetime and cost analysis studies are needed to assess the full impact of these innovations, they are certainly very exciting developments on the road to transform organic photovoltaics into a commercial technology.”
By simplifying the production of organic solar cells, the new processing technique could allow fabrication of solar cells in areas of Africa and Latin America that lack capital-intensive manufacturing capabilities, said Felipe Larrain, a Ph.D. student in Kippelen’s lab.
“Our goal is to further simplify the fabrication of organic solar cells to the point at which every material required to fabricate them may be included in a single kit that is offered to the public,” Larrain said. “The solar cell product may be different if you are able to provide people with a solution that would allow them to make their own solar cells. It could one day enable people to power themselves and be independent of the grid.”
Organic solar cells have been studied in many academic and industrial laboratories for several decades, and have experienced a continuous and steady improvement in their power conversion efficiency with laboratory values reaching 13 percent – compared to around 20 percent for commercial silicon-based cells. Though polymer-based cells are currently less efficient, they require less energy to produce than silicon cells and can be more easily recycled at the end of their lifetime.
“Being able to process solar cells entirely at room temperature using this simple solution-based technique could pave the way for a scalable and vacuum-free method of device fabrication, while significantly reducing the time and cost associated with it,” said Vladimir Kolesov, a Ph.D. researcher and the paper’s lead author.
Beyond solar cells, the doping technique could be more broadly used in other areas of organic electronics, noted Ph.D. researcher Wen-Fang Chou. “With its simplicity, this is truly a promising technology offering adjustable conductivity of semiconductors that could be applied to various organic electronics, and could have huge impact on the industry for mass production.”
Also at Georgia Tech, the research involved professors Samuel Graham and Seth Marder, both from the Center for Organic Photonics and Electronics. Beyond Georgia Tech, the project also involved Naoya Aizawa from Kyushu University; Ming Wang, Guillermo Bazan and Thuc-Quyen Nguyen from the University of California Santa Barbara, and Alberto Perrotta from Eindhoven University of Technology,
This work was funded in part by the Department of the Navy, Office of Naval Research Award No. N00014-14-1-0580 and N00014-16-1-2520, through the MURI Center CAOP, Office of Naval Research Award N00014-04-1-0313 and by the Department of Energy through the Bay Area Photovoltaic Consortium under Award Number DE-EE0004946. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsors.
CITATION: Vladimir A. Kolesov, et al., “Solution-based electrical doping of semiconducting polymer films over a limited depth,” (Nature Materials, 2016). http://dx.doi.org/10.1038/nmat4818
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]]>In a paper published this week in the journal Nature Materials, researchers from the Georgia Institute of Technology identified the opportunities they see ahead for scalable membrane materials based on rigid, engineered pore structures. They say the most promising materials are scalable for use in compact modules and take advantage of entropy at the molecular level to moderate the separation selectivity of membranes.
“It’s all about energy and carbon dioxide,” said William Koros, professor and Roberto C. Goizueta Chair in Georgia Tech’s School of Chemical and Biomolecular Engineering. “Chemical separations now consume half as much energy as the entire transportation sector – land, sea and air. Our goal is to assist industry to cut that by a factor of ten, which also means cutting the CO2 emissions. That’s not going to happen right away, but we have shown that the fundamentals of this technology work.”
A membrane is an engineered barrier that controls the sorting of components by selectively allowing molecules of a certain size to pass between the incoming feed stream and an outgoing permeate stream. Because they don’t require large inputs of energy – which usually would come from combustion of fuels – use of these membranes can dramatically reduce both energy consumed and carbon dioxide produced. The membranes are made from advanced polymers, hybrid materials and molecular sieves, with pore sizes tailored for the intended use.
The success of aqueous membranes used to produce purified water demonstrates the potential for lowering energy consumption. Spiral-wound module membranes dramatically reduced the cost of producing clean water, though large size differences between water molecules and contaminants made those processes technically easier than gas and liquid organics separations.
Koros’ lab focuses on gas separations, but the article also addresses liquid separation processes. For both applications, he and co-author Chen Zhang point out that to be practical, new materials must be scalable – able to be packed tightly to provide large amounts of surface area inside small modules. That is best done using hollow-fiber membranes produced using advanced versions of processes that were originally developed to make ordinary textile fibers.
“You’ve got to have something that is both high performance and able to be processed on the scale of acres per day,” said Koros, who is also a Georgia Research Alliance eminent scholar in membrane technology. “Scalability is every bit as important as the capability to do the separation. Exciting materials that are the size of a postage stamp won’t make a contribution.”
The two authors also argue for entropic separation techniques that are enabled by limiting the ability of molecules to diffuse through pores, depending on their molecular geometry. A molecule whose geometry makes it difficult to diffuse through a narrow opening may be excluded, while a molecule of approximately the same size but different geometry may diffuse through.
“You may ultimately be able to get the first molecule to go through, but it pays a price in entropy,” said Koros. “If a molecule has many options for passing through the membrane, it is actually in a lower energy state. When you reduce the number of options, you are raising the free energy.”
Research in the Koros lab has been supported for more than 20 years by the U.S. Department of Energy’s Office of Energy Science. Koros also has research projects with major energy producers and chemical companies, as well as the Georgia Research Alliance.
In their paper, Koros and Zhang, a research engineer in the School of Chemical and Biomolecular Engineering, identified five materials technologies with potential for improving gas separation processes. These include:
Liquid separation processes also have significant opportunities for improvement based on new materials being developed. These processes include:
The Nature Materials article focused on progress that had been made in the technology and future potential, with highlights on recent advances in Koros lab at Georgia Tech. The goal was to encourage development of new materials and make membrane scientists aware of the most promising paths.
“We want everybody to see this next-generation of materials and understand the processes that help attain the goals of reducing energy consumption and carbon dioxide production,” Koros added.
This research was supported by the Office of Energy Science of the U.S. Department of Energy (grant DE-FG02-04ER15510). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the Department of Energy.
CITATION: William J. Koros and Chen Zhang, “Materials for next-generation molecularly selective synthetic membranes,” (Nature Materials, 2017). http://dx.doi.org/10.1038/nmat4805.
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]]>The technique uses a solvent reaction with a bimetallic alloy – in which one of the metals is reactive – to form bundles of nanowires (nanofibers) upon reactive metal dissolution. The process is conducted at ambient temperature and pressure without the use of catalysts, toxic chemicals or costly processes such as chemical vapor deposition. The produced nanowires can be used to improve the electrical, thermal and mechanical properties of functional materials and composites.
The research, which was reported this week in the journal Science, was supported by the National Science Foundation and California-based Sila Nanotechnologies. The process is believed to be the first to convert bulk powders to nanowires at ambient conditions.
“This technique could open the door for a range of synthesis opportunities to produce low-cost 1D nanomaterials in large quantities,” said Gleb Yushin, a professor in the School of Materials Science and Engineering at the Georgia Institute of Technology. “You can essentially put the bulk materials into a bucket, fill it with a suitable solvent and collect nanowires after a few hours, which is way simpler than how many of these structures are produced today.”
Yushin’s research team, which included former graduate students Danni Lei and James Benson, has produced oxide nanowires from lithium-magnesium and lithium-aluminum alloys using a variety of solvents, including simple alcohols. Production of nanowires from other materials is part of ongoing research that was not reported in the paper.
The dimensions of the nanowire structures can be controlled by varying the solvent and the processing conditions. The structures can be produced in diameters ranging from tens of nanometers up to microns.
“Minimization of the interfacial energy at the boundary of the chemical reaction front allows us to form small nuclei and then retain their diameter as the reaction proceeds, thus forming nanowires,” Yushin explained. “By controlling the volume changes, surface energy, reactivity and solubility of the reaction products, along with the temperature and pressure, we can tune conditions to produce nanowires of the dimensions we want.”
One of the attractive applications may be separator membranes for lithium-ion batteries, whose high power density has made them attractive for powering everything from consumer electronics to aircraft and motor vehicles. However, the polymer separation membranes used in these batteries cannot withstand the high temperatures generated by certain failure scenarios. As result, commercial batteries may induce fires and explosions, if not designed very carefully and it’s extremely hard to avoid defects and errors consistently in tens of millions of devices.
Using low-cost paper-like membranes made of ceramic nanowires could help address those concerns because the structures are strong and thermally stable, while also being flexible – unlike many bulk ceramics. The material is also polar, meaning it would more thoroughly wetted by various battery electrolyte solutions.
“Overall, this is a better technology for batteries, but until now, ceramic nanowires have been too expensive to consider seriously,” Yushin said. “In the future, we can improve mechanical properties further and scale up synthesis, making the low-cost ceramic separator technology very attractive to battery designers.”
Fabrication of the nanowires begins with formation of alloys composed of one reactive and one non-reactive metal, such as lithium and aluminum (or magnesium and lithium). The alloy is then placed in a suitable solvent, which could include a range of alcohols, such as ethanol. The reactive metal (lithium) dissolves from the surface into the solvent, initially producing nuclei (nanoparticles) comprising aluminum.
Though bulk aluminum is not reactive with alcohol due to the formation of the passivation layer, the continuous dissolution of lithium prevents the passivation and allows gradual formation of aluminum alkoxide nanowires, which grow perpendicular to the surface of the particles starting from the nuclei until the particles are completely converted. The alkoxide nanowires can then be heated in open air to form aluminum oxide nanowires and may be formed into paper-like sheets.
The dissolved lithium can be recovered and reused. The dissolution process generates hydrogen gas, which could be captured and used to help fuel the heating step.
Though the process was studied first to make magnesium and aluminum oxide nanowires, Yushin believes it has a broad potential for making other materials. Future work will explore synthesis of new materials and their applications, and develop improved fundamental understanding of the process and predictive models to streamline experimental work.
The researchers have so far produced laboratory amounts of the nanowires, but Yushin believes that the process could be scaled up to produce industrial quantities. Though the ultimate cost will depend on many variables, he expects to see fabrication costs cut by several orders of magnitude over existing techniques.
“With this technique, you could potentially produce nanowires for a cost not much more than that of the raw materials,” he said. Beyond battery membranes, the nanowires could be useful in energy harvesting, catalyst supports, sensors, flexible electronic devices, lightweight structural composites, building materials, electrical and thermal insulation and cutting tools.
The new technique was discovered accidentally while Yushin’s students were attempting to create a new porous membrane material. Instead of the membrane they had hoped to fabricate, the process generated powders composed of elongated particles.
“Though the experiment didn’t produce what we were looking for, I wanted to see if we could learn something from it anyway,” said Yushin. Efforts to understand what had happened ultimately led to the new synthesis technique.
In addition to those already named, the research included Alexandre Magaskinski of Georgia Tech and Gene Berdichevsky of Sila Nanotechnologies.
Different aspects of this work were supported by National Science Foundation (grant 0954925) and Sila Nanotechnologies, Inc. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. Gleb Yushin and Gene Berdichevsky are shareholders of Sila Nanotechnologies.
CITATION: Danni Lei, Jim Benson, Alexandre Magasinski, Gene Berdichevsky, Gleb Yushin, “Transformation of bulk alloys to oxide nanowires,” (Science, 2017).
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]]>Researchers at the Georgia Institute of Technology are exposing these secrets -- micron-sized bumps and grooves -- and the intricate web of gene mutations possibly behind them in high detail. Their computational genetics work using digital optics could prove useful to understanding debilitating disorders.
“When these faint mutations come together, it gives you a ginormous boost in disease risk,” said Hang Lu, a professor who applies engineering and data science to the study of neurology.
“If you look at psychiatric diseases, anything that is relevant to humans, what you see is not that dramatic,” Lu said. “Brains of people who had schizophrenia, bipolar disorder, or autism don’t look physically very different from healthy brains. It’s not like they’re missing a chunk.”
Researchers led by Lu at Georgia Tech’s School of Chemical and Biomolecular Engineering have developed algorithms and special microscope slide to expose previously unseen neurological nuances and intricate mutations that may be behind them. But their findings could apply as well to computational genetics research pursuing other diseases such as autoimmune disorders.
Lu and former Georgia Tech researcher Adrianna San-Miguel published their latest results on Wednesday, November 23, 2016, in the journal Nature Communications. Their research was funded by the National Institute of General Medicine, and the National Institute on Aging, both agencies of the National Institutes of Health.
Lu has replaced the fallible human eye with a proficient computer to pin down faintest phenotypes, the geneticist’s term for physical traits based on genes. In the latest experiment, nerve proteins were marked to appear as dots on roundworms' undersides for the computer to scan.
When mutations occur, the dots can change ever so slightly. “To the naked eye, they’re just dots on a dark background,” Lu said. But the computer sees in them phenotypical shifts.
Roundworm Caenorbabditis elegans, used in the experiment, helps scientists understand what may be going on in humans, because its nerves share strong similarities with ours. Ultimately, Lu wants the insights gained in studying them to lead to localizing genetic biomarkers for diseases in humans.
The Georgia Tech scientists narrowed their focus to synapses on a single neuron where it connects to muscles. These “synaptic puncta” were tagged with a glowing green protein to form the dots.
Some mutations did cause big shifts in dot position and size that the naked eye could actually pick up. And traditionally, forward geneticists -- geneticists who follow changes in phenotypes to see if they can find genes that cause them -- have used their eyes and microscopes to pick out such really obvious changes.
But natural limitations on human perception have introduced a bias, Lu said. Her research aims to reduce it to boost the amount of data scientists can gather.
Here’s how the bias roughly works. Sorting mutants from non-mutants in the lab is usually tedious with the tiny worms, and that has consequences for science.
“The normal way of doing it would be to take a little platinum wire and literally go under the microscope, pick up a worm, drug it, mount it on a slide, and then you have to recover it alive, if you think it's interesting,” Lu said.
The tedium plus the limited abilities of the human eye lead researchers looking for mutations to single out worms that are markedly odd. Eye-popping phenotypes are namely likely to be caused by genotypic changes, i.e. mutations, so finding a clear phenotype is likely to lead to a successful research outcome.
As a result, researchers might overlook subtle samples. In addition, amassing enough of them to determine important nuances may prove too difficult to do, and quirks can get in the way, too. For example, a single weird-looking worm might not be a mutant at all.
“You can always find a ‘wildtype’ (basically normal worm) that looks nothing at all like a wildtype,” Lu said. “It’s just a crazy wildtype. Genotypically, it looks like everybody else, but phenotypically it’s so different."
Why? Because nature can be stochastic – sort of random -- and mess up an individual worm, even when there’s no mutated gene.
Looks can deceive the eye, but they’re less likely to fool a high-resolution camera connected to a computer and an algorithm that statistically examines faint variations in order to sort mutants from non-mutants.
Lu’s technique works via a transparent slide with tiny tubes that suck in one worm at a time under the computer's microscope. “Then we freeze the worm for a moment, so we can take its picture,” Lu said. “Then it unfreezes, and it’s totally okay.”
There’s a fork in the tube holding the worm. If the algorithm detects a mutant based on its synaptic puncta pattern in the image – even if this is not visible to the eye – the worm gets sucked down the first path for further study. If it isn’t a mutant, it gets sucked down the second path.
In the latest experiment, the algorithm analyzed phenotypic variations in the synaptic puncta of large worm populations. Parallel to that, the worms' genomes were analyzed to determine which phenotypical differences may be connected to mutated genes.
Then the researchers mapped out genotypes in relation to the differences in phenotypes they underpinned. What was so nuanced before that it was virtually invisible, turned out to be a large, filigree web.
Then there was a particularly lucky find that made for a good metaphor for the study and its potential to advance research. The scientists stumbled upon a very subtle allele – a variation of a gene caused by mutation.
The worms that had the allele were real mutants, but no one would have guessed it, because to the eye, they were completely neat and normal. They even behaved normally at first glance, and the researchers thought the computer may have sorted them out as mutants by mistake -- until a hitch turned up.
“After they swam for about 40 minutes, they got really, really weak and couldn’t swim well anymore,” Lu said. The allele seemed to be associated with some kind of neurological disorder.
“Seen as a metaphor, this is an example of how you might identify something that is relevant to a disease but incredibly subtle,” she said, “and you would never have found it using eyes and a microscope.”
The research paper was coauthored by Matthew M. Crane, Yuehui Zhao, and Patrick McGrath of Georgia Tech, and Peri Kurshan and Kang Shen of Stanford University. The research was funded by grants from the National Institutes of Health (numbers R01GM088333 and K99AG046911) Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the sponsoring agency.
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]]>These institutes for manufacturing innovation bring industry, academia and government partners together to leverage existing resources, collaborate and co-invest to nurture manufacturing innovation and accelerate commercialization.
The U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy Acting Assistant Secretary David Friedman announced the new institute Dec. 9 at the U.S. Council on Competitiveness’ 2016 National Competitiveness Forum. This new institute will be officially called the Rapid Advancement in Process Intensification Deployment, or (RAPID), Institute.
“Georgia Tech is proud to play a leading role in RAPID and the continued transformation of the all-important manufacturing sector,” said Steve Cross, executive vice president for research at Georgia Tech. “Advanced manufacturing is critical to the economic competitiveness of our country, and Georgia Tech’s role in this important initiative will help strengthen our leadership in Georgia and the nation as a leader in chemical processing.
Georgia Tech is one of 34 universities included in the RAPID Institute.
Georgia Tech’s undergraduate chemical engineering program is ranked No. 4 in the country, according to U.S. News & World Report, and Georgia Tech is No. 4 in the U.S. in federal research and development spending in chemical engineering, according to the National Science Foundation. Georgia Tech participates in five of the 10 institutes created by the administration to address manufacturing innovation, including Digital Manufacturing, Flexible Hybrid Electronics, Integrated Photonics, Additive Manufacturing, and Process Intensification.
The RAPID Institute will have up to $70 million in federal funding, subject to appropriations, and an additional $70 million in cost-share commitments from more than 130 partners. It will focus on developing breakthrough technologies to boost domestic energy productivity and energy efficiency by 20 percent in five years through manufacturing processes in industries such as oil and gas, pulp and paper, and various domestic chemical manufacturers.
Traditional chemical manufacturing relies on large-scale, energy-intensive processing. The new institute will leverage approaches to modular chemical process intensification — like combining multiple, complex processes such as mixing, reaction and separation into single steps — with the goal of improving energy productivity and efficiency, cutting operating costs, and reducing waste. In the chemical industry alone, these technologies have the potential to save more than $9 billion in process costs annually.
“Our investment in this cross-cutting technology is an investment in the future of U.S. manufacturing,” said Acting Assistant Secretary Friedman. “As we continue to expand the Manufacturing USA network, we provide greater opportunities for businesses of all sizes to solve their toughest technology challenges and unleash major savings in energy-intensive sectors like oil and gas, pulp and paper-making, and other industries.”
The RAPID Institute will serve as an American manufacturing leader convening companies, universities, industrial research organizations and national laboratories to focus on new technologies that maximize processes at the molecular level to save energy with every chemical reaction — adding up to big savings on the manufacturing floor. It is the fourth Energy Department-led institute in the multiagency network known as Manufacturing USA, or the National Network for Manufacturing Innovation (NNMI).
"RAPID is a great opportunity for experts at Georgia Tech to work on near-term solutions that will make the chemical processes in manufacturing more efficient," said David Sholl, John F. Brock III Chair of the School of Chemical and Biomolecular Engineering, who will serve as the interim chief technology officer for RAPID.
Collectively, the federal government’s commitment of more than $700 million to the 10 awarded Manufacturing USA institutes has been matched by more than $1.4 billion in non-federal investment from across industry, academia and state governments. The institutes, each led by manufacturing experts renowned in their field, have attracted more than 1,300 companies, universities and non-profits as members of Manufacturing USA. For more information about the RAPID Institute and participating organizations, visit Energy.gov.
]]>lance.wallace@comm.gatech.edu
]]>That last ingredient may have helped gene-like strands to copy themselves in puddles for the first time ever, billions of years ago when Earth was devoid of life, researchers at the Georgia Institute of Technology have found. Their novel discoveries add to a growing body of evidence that suggests first life may have evolved with relative ease, here and possibly elsewhere in the universe.
And they offer a straightforward answer to a gnawing 50-year-old question: How did precursors to the present-day genetic code first duplicate themselves before the existence of enzymes that are indispensable to that process today?
For generations, scientists pursuing an answer performed experiments in water but hit a wall.
Georgia Tech researchers Christine He and Isaac Gállego overcame it by adding an off-the-shelf viscous solvent (the thickener). In separate experiments with DNA then RNA, the copying process proceeded.
“I think it’s very, very different from anything that’s been done before,” said researcher He. “We can change the physical environment in an easy way, and promote these processes that wouldn’t happen in conditions ordinarily being used.”
Easy is crucial, said Martha Grover, a professor who oversaw the research at Georgia Tech’s School of Chemical and Biomolecular Engineering. Easy reactions are likely to be more productive and more prevalent.
“A simple and robust process like this one could have operated in a variety of environments and concentrations making it more realistic in moving evolution forward,” she said.
Grover’s lab and that of Nick Hud at Georgia Tech’s School of Chemistry and Biochemistry published the results on Monday, October 10, 2016 in the journal Nature Chemistry. Their research has been funded by the National Science Foundation and the NASA Astrobiology Program under the NASA/NSF Center for Chemical Evolution.
Earliest life was based on RNA, or a similar polymer, according to a hypothesis called the RNA World. In that scenario, on the evolutionary timeline, the self-replication of RNA strands long enough to be potential genes would roughly mark the doorstep to life.
Those long nucleotide chains may have been mixed together in puddles with shorter nucleotide chains. Heat from the sun would have made long strands detach from their helix structures, giving short ones a chance to match up with them, and become their copies.
But there’s a problem.
In water alone, when cooling sets in, the long chains snap back into their helix structure so rapidly that there’s no time for the matching process with the shorter chains. That snapping shut, which happens in both RNA and DNA, is called “strand inhibition,” and in living cells, enzymes solve the problem of keeping the long chains apart while gene strands duplicate.
“The problem is a problem in water, which everybody sort of looks at in prebiotic (pre-life) chemistry,” said graduate research assistant He. She felt it was time to rethink that, and her expertise in chemical engineering helped.
High viscosity has been known to slow down the movement of long strands of DNA, RNA and other polymers.
“It’s a little like making them swim in honey,” Grover said. Applying that to origin-of-life chemistry seemed obvious, because in prebiotic times, there probably were quite a few sticky puddles.
“In that solution, it gives the short nucleotides, which move faster, time to jump onto the long strand and piece together a duplicate of the long strand,” researcher He said. In her experiments, it worked.
And it produced an encouraging surprise. The DNA and RNA strands folded onto themselves forming shapes called hairpins.
“In the beginning, we didn’t realize the importance of the internal structure,” Christine He said. Then they noticed that the shape was helping keep RNA and DNA available for the pairing process. “Hairpin formation is integral to keeping them open,” Grover said.
But it also could have accelerated chemical evolution in another way. “The solution is selecting here for sequences that fold, and that would have more potential for functional activity – like a ribozyme,” said researcher He.
Ribozymes are enzymes made of RNA, and enzymes catalyze biochemical processes. To have them evolve in the same solution that promotes genetic code replication could have shortened the path to first life.
“You really need to amplify functional sequences for evolution to move forward,” Grover said. The folds were an unexpected side-effect, and finding them paves the way for future research.
The Georgia Tech scientists used real gene strands in their experiments, which may sound mundane, but in the past, some researchers have specially engineered DNA and RNA sequences in attempts to arrive at similar results.
He and Gállego’s use of a naturally occurring gene, rather than a specifically engineered sequence, shows that viscosity could have been a very general solution to promote copying of nucleic acids with mixed length and sequences.
To facilitate quick, clear outcomes, the Georgia Tech researchers used purified short nucleotide chains and applied them in ratios that favored productive reactions. But they had started out with messier, less pure ingredients, and the experience was worthwhile.
“Considering a pre-biotic soup, it’s probably messy; it’s got a lot of impurities,” Christine He said. “When we first started out with more impure nucleotides, it still worked. Maybe the same reaction really could have happened in a messy puddle billions of years ago.”
The viscous solvent was glycholine, a mixture of glycerol and choline chloride. It was not likely present on pre-biotic Earth, but other viscous solvents likely were.
Also, after the short strands matched up to each long one, the researchers did apply an enzyme to join the aligned short pieces into a long chain, in a biochemical process called ligation.
The enzymes would not have been present on a prebiotic Earth, and although there are chemical procedure for ligating RNA, “no one has developed a chemistry so robust yet that it could replace the enzyme,” Grover said.
Finding one that could have worked on a prebiotic Earth would be a worthy aim for further research.
READ: More about chemical engineering, viscosity and DNA
READ: Possible precusor of RNA forms spontaneously in water
Brandon Laughlin from Georgia Tech coauthored the paper. The research was funded by the National Science Foundation and the NASA Astrobiology Program under the NASA/NSF Center for Chemical Evolution (grant number CHE-1504217) and by the NSF Graduate Research Fellowship (grant number DGE-1148903). Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the sponsoring agencies.
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]]>The new material is based on polymer hollow fibers treated to retain their structure – and pore sizes – as they are converted to carbon through pyrolysis. The carbon membranes are then used in a new “organic solvent reverse osmosis” (OSRO) process in which pressure is applied to effect the separation without requiring a phase change in the chemical mixture.
The hollow carbon fibers, bundled together into modules, can separate molecules whose sizes differ by a fraction of a nanometer while providing processing rates superior to those of existing molecular sieve zeolites. Because it uses a commercial polymer precursor, the researchers believe the new membrane has potential for commercialization and integration into industrial chemical separation processes. The research was reported in the August 19 issue of the journal Science.
Separation is currently achieved through refining processes such as crystallization and adsorption with distillation, which are energy-intensive. Globally, the amount of energy used in conventional separation processes for alkyl aromatics is equal to that produced by about 20 average-sized power plants.
“We see this as a potentially disruptive technology in the way we separate xylenes and similar organic compounds,” said Benjamin McCool, one of the paper’s co-authors and an advanced research associate at ExxonMobil Corporate Strategic Research in Annandale, N.J. “If we can make this work on an industrial scale, it could dramatically reduce the energy required by these separation processes.”
Fabrication of the new membrane material begins with hollow polymer fibers approximately 200 microns in diameter, slightly thicker than the average human hair. The fibers have pore sizes of less than one nanometer, and are treated via cross-linking before they are converted to carbon through a pyrolysis process. The pore sizes of the fibers can be adjusted during the fabrication process.
“We take a scalable platform based on polymeric membranes and then turn those materials into inorganic molecular sieves,” explained Ryan Lively, an assistant professor in Georgia Tech’s School of Chemical & Biomolecular Engineering and the paper’s corresponding author. “Our membranes are mechanically robust and they can withstand the process conditions required by OSRO. They maintain advantageous mechanical properties and membrane performance as they are converted to carbon fiber.”
Lively and postdoctoral fellow Dong-Yeun Koh used the OSRO process in the laboratory to separate mixtures of para-xylene and ortho-xylene, molecules whose sizes differ by one-tenth of a nanometer. By applying pressure at room temperature, the membrane can convert the 50-50 mixture to an 85-15 mixture at a high flux relative to zeolite membranes.
“These molecules have incredibly similar sizes and properties, but the membranes can tell them apart,” said Lively. “This bulk cut of the mixture greatly enhances the concentration with a very low energy input. This mixture could then be fed into a conventional thermal process for finishing, which would reduce the total energy input dramatically.”
In industrial use, the membranes would be bundled together in modules that would be used in chemical facilities. “In practice, you would get as many modules as you needed for a particular application, and if the need increased, you could simply add more modules,” Lively said. “It would be totally scalable.”
Reverse osmosis membranes are already widely used in desalination to produce drinking water from saltwater, consuming a fraction of the energy required by thermally-driven process. Carbon fiber membranes are being used for gas separations, but the new OSRO process is believed to be the first use of reverse osmosis with carbon membranes to separate liquid hydrocarbons.
Though the membrane has demonstrated promising results, it still faces a number of challenges. The membranes will have to be tested with more difficult separations before they can be considered for commercialization and scale-up. Industrial mixtures normally contain multiple different organic compounds, and they may include materials that can foul membrane systems. The researchers will also have to learn to make the material consistently and demonstrate that it can withstand long-term industrial use.
“Because we are starting with commercially-available polymers and we are using commercial-type equipment, we can see a clear line-of-sight to commercialization with this technology,” McCool said. “It’s a big advantage that the membranes are being spun on a hollow-fiber line similar to that currently used in the industry. The time horizon to make this happen and the cost of production could be highly advantaged over other inorganic systems or more exotic materials like graphene.”
Development of the OSRO process resulted from a collaborative process in which Georgia Tech researchers worked closely with ExxonMobil scientists – including McCool and scientist Harry Deckman – to identify and overcome the challenges of industrial processing.
“ExxonMobil is a leader in its commitment to fundamental science," said Mike Kerby, ExxonMobil Corporate Strategic Research manager. “As part of our commitment, we continue to widen our research aperture through collaborations with academic research institutions to better enable us to identify potential breakthrough technologies to reduce greenhouse gas emissions, increase energy supplies and realize other environmental benefits.”
CITATION: Dong-Yeun Koh, et al., "Reverse Osmosis Molecular Differentiation of Organic Liquids using Carbon Molecular Sieve Membranes," (Science, 2016).
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]]>In minuscule amounts, it works in cells as an essential catalyst called a cofactor and as a signaling molecule to trigger other processes. Now, for the first known time, researchers have tracked those activities inside of cells.
But too high of a concentration is toxic.
“Poor heme management can cause things like Alzheimer’s, heart disease, and some types of cancers, so cells have to do a good job of managing how much heme is available,” said Amit Reddi, a biochemist and assistant professor at the Georgia Institute of Technology. “By having biosensors that can monitor heme in cells, we have this new window into how cells make this essential toxin available in carefully sparse concentrations,” he said.
‘Heme’ as in ‘hemoglobin’
People may recognize heme from its role at the core of hemoglobin, the component of red blood cells responsible for transporting oxygen. The ionic iron in the heme molecule is what attracts the oxygen molecule.
In hemoglobin, the heme is embedded tightly in protein, rendering it non-toxic. Many scientists have long assumed that heme, even in other cells, is basically always static, held tight by the proteins it works with.
But the researchers’ results shatter that assumption.
They published their findings in the journal Proceedings of the National Academy of Sciences, on May, 30, 2016. Their research is funded by the National Science Foundation and the National Institutes of Health.
Misconception dispelled?
Working with baker’s yeast cells, which, like human cells, are eukaryotes, the researchers observed heme being freed up to float around and participate in life processes.
“I think that we have possibly put a misconception to rest,” said lead researcher David Hanna, a graduate student at at the School of Chemistry and Biochemistry and Parker Petit Institute for Bioengineering and Biosciences, where Reddi also researches.
He was expecting to observe a pool of free, or “labile,” heme in the cells, and he did. “A lot of scientists believe in these fixed bonds, that all heme is tied up and buried inside proteins, but there are processes going on that defy that notion that they haven’t been able to explain.”
Now the research team lead by Hanna and Reddi can explain some of them via the labile heme pool. “No one’s shown this before. We have demonstrated that there is a pool of heme that increases and decreases. We’ve shown that there is an exchangeable pool of heme.”
Potentially hazardous nutrient
The labile heme serves as a nutrient instead of a poison. But to make sure things stay that way, heme needs to be carefully trafficked through the cell, Reddi said.
The research team designed a fluorescent sensor molecule to keep tabs on that. With heme at very low baseline levels, the sensor lit up bright green, then as heme concentration increased, it caused the light to fade out.
Using the heme sensors, Georgia Tech graduate student Osiris Martinez-Guzman found an enzyme, GAPDH, known for its involvement in breaking down sugar, that the team observed helping buffer cellular labile heme (iron protoporphyrin IX), which got tied up in proteins, leaving only a limited amount free for biochemical reactions.
When more labile heme is needed, nitric oxide, a signaling molecule, rapidly released heme from entangling proteins, so it could do jobs such as regulating gene expression.
‘Green Lantern’ glow
“If you increase nitric oxide, you see the green glowing sensor dim as the heme becomes labile then the glow brightens back up over time as heme gets bound up again,” Reddi said.
Not having a sensor was one reason labile heme has not been previously observed, so the Georgia Tech researchers used a ratiometric fluorescence approach to design one that could be described a little like the comic book superhero “Green Lantern.”
As hemes are attracted to him like, say, fans, they become clutter, said Reddi, the paper’s principal investigator. “He holds them in front of his green light, and they block it, making it appear dimmer.”
“Ratiometric fluorescent techniques have been around for a while, but our technique is new, because it specifically senses heme,” Reddi said. “We took a heme binding protein from bacteria and clipped it onto to green fluorescent protein.”
The researchers used a blue laser to charge up the lamp part of the sensor protein pair like a glow-in-the-dark sticker, then it re-emitted the green light. “You see this green image disappearing and reappearing depending on how much heme is available,” Reddi said. “You can see what’s happening in real time.”
Raven M. Harvey, Osiris Martinez-Guzman, Bindu Chandrasekharan and Gheevarghese Raju from Georgia Tech; Xiaojing Yuan, Iqbal Hamza from the University of Maryland, and F. Wayne Outten from the University of South Carolina coauthored the paper. The National Science Foundation funded the research under CAREER Award MCB 1552791, and the National Institutes of Health’s National Institute of Environmental Health Sciences funded it under grant number ES025661.
Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
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]]>In 2009, Andrew Lyon, then a professor of chemistry at the Georgia Institute of Technology, observed this dynamic resizing in a microgel system he had created, but the mechanism behind the self-healing process remained uncertain. Now, researchers believe they've finally solved the mystery, and what they've learned could also have implications for biological systems made up of soft organic particles not unlike the polymer microgels.
Using small-angle X-ray and neutron scattering techniques, the researchers carefully studied the structures formed by dense concentrations of the microparticles. They also used tiny piezoelectric pressure transducers to measure osmotic pressure changes in the system. Their conclusion: In dense assemblies of microparticles, counter ions bound to the microgels by electrostatic attraction come to be shared by multiple particles, increasing the osmotic pressure which then works to shrink the oversized particle.
“When the particles are close enough together, there is a point at which the cloud of ions can no longer be associated with individual particles because they overlap other particles,” said Alberto Fernandez-Nieves, an associate professor in the School of Physics at the Georgia Institute of Technology. “The ions create an imbalance between osmotic pressure inside and outside the larger particles, pushing them to de-swell – expel solvent to change size – to match the pressure of the system given by these delocalized ions. This is only possible because the microgel particles are compressible.”
The research is reported April 25 in the early edition of the journal Proceedings of the National Academy of Sciences. The work was supported by the Swiss National Science Foundation, and the research partnership between Georgia Tech and Children’s Healthcare of Atlanta.
The presence of non-uniform particles normally creates point defects in the crystals or prevents the formation of crystalline structures altogether. That’s true for structures formed from atoms, but not those formed from the microgels, which are soft cross-linked polymer particles immersed in a solvent. The microgels, which range in size from about 100 nanometers up to several microns in diameter, can exist in either swollen or non-swollen states, depending on such external conditions as temperature.
Lyon and his research group reported the self-healing nature of the colloidal crystals in the journal Angewandte Chemie International in 2009. They initially believed that what they were seeing resulted from energetic issues associated with formation of the crystals.
“We interpreted the phenomenon in terms of the overall lattice energy – the propensity of the microgels to form an ordered array – perhaps being larger than the energy required to collapse the defect microgels,” he said. “In other words, we believed there was an energetic penalty associated with disruption of the crystalline lattice that was greater than the energetic penalty associated with individual microgel de-swelling.”
Fernandez-Nieves initially supported that hypothesis, but later came believe there was more at work. For instance, the shrunken microgels, which are identifiable because of their higher optical density, freely move about just like the smaller ones, suggesting that the shrinkage doesn’t result from being crowded by the smaller particles.
In a collaboration with Researcher Urs Gasser and Ph.D. student Andrea Scotti at the Laboratory for Neutron Scattering and Imaging at the Paul Scherrer Institut in Switzerland, the researchers used X-ray and neutron scattering techniques to study the structure of the suspended microgels and the degree of swelling in the large microparticles of the colloidal crystals. The work confirmed that these larger particles had indeed de-swollen, even at concentrations far larger than those initially used by Lyon’s research team.
“The system is able to make point defects disappear, and the mechanism we have proposed allows us to understand why this occurs,” said Fernandez-Nieves. “What we have proposed is a mechanism to explain what we see happening, and we think this is a general mechanism that could potentially apply to a wider range of soft particles.”
As a next step, the research group expects to determine the ionic structure to confirm what the existing research has suggested. Fernandez-Nieves believes the work will generate more research with soft particle suspensions, for both experimentalists and theoreticians.
“There is indeed much more theory and simulation work needed to confirm what we propose and to fully understand how this self-healing process occurs,” he said. “This principle could be at play in a large number of contexts, including biological systems, in which there is a subtle balance between rigidity, osmotic pressure and ionic balance. This is a mechanism that doesn’t really involve the other particles in the assembly. It involves the ions.”
Lyon, now dean of the Schmid College of Science and Technology at Chapman University, believes the findings might go beyond creating better colloidal systems to provide insights into how living cells operate.
“By obtaining a deeper insight into microgel assemblies, we may be able to take advantage of the subtle energetic balances that determine the overall structures to create more complex, defect-tolerant assemblies,” he said. “The physics we uncovered here could be relevant for other crowded, soft-materials systems, such as the interior of the eukaryotic cells. Perhaps an extension of this knowledge will provide a better understanding of how the interior of a cell is organized, and how material is transported through this complex and crowded environment.”
CITATION: A. Scotti, et al., “Self-healing colloidal crystals: Why soft particles feel the squeeze,” Proceedings of the National Academy of Sciences, 2016).
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]]>In a comment article published April 26 in the journal Nature, two researchers from the Georgia Institute of Technology suggest seven energy-intensive separation processes they believe should be the top targets for research into low-energy purification technologies. Beyond cutting energy use, improved techniques for separating chemicals from mixtures would also reduce pollution, cut carbon dioxide emissions – and open up new ways to obtain critical resources the world needs.
Technologies applicable to those separation processes are at varying stages of development, the authors note. These alternative processes are now under-developed or expensive to scale up, and making them feasible for large-scale use could require a significant investment in research and development.
“We wanted to highlight how much of the world’s energy is used for chemical separations and point to some areas where large advances could potentially be made by expanding research in these areas,” said David Sholl, one of the article’s authors, chair of Georgia Tech’s School of Chemical & Biomolecular Engineering and a Georgia Research Alliance Eminent Scholar. “These processes are largely invisible to most people, but there are large potential rewards – to both energy and the environment – for developing improved separation processes in these areas.”
In the United States, substituting non-thermal approaches for purifying chemicals could reduce energy costs by $4 billion per year in the petroleum, chemical and paper manufacturing sectors alone. There’s also a potential for reducing carbon dioxide emissions by 100 million tons per year.
“Chemical separations account for about half of all U.S. industrial energy use,” noted Ryan Lively, an assistant professor in Georgia Tech’s School of Chemical & Biomolecular Engineering and the article’s second author. “Developing alternatives that don’t use heat could dramatically improve the efficiency of 80 percent of the separation processes that we now use.”
Dubbed the “seven chemical separations to change the world,” the list is not intended to be exhaustive, but includes:
Sholl and Lively conclude the paper by suggesting four steps that could be taken by academic researchers and policymakers to help expand the use of non-thermal separation techniques:
CITATION: David S. Sholl and Ryan P. Lively, “Seven chemical separations to change the world,” (Nature, Vol. 532, 2016). http://www.nature.com/news/seven-chemical-separations-to-change-the-world-1.19799
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]]>Now, researchers working with that hypothesis have achieved a significant advancement toward unlocking a longstanding evolutionary mystery -- how components of RNA and DNA formed from chemicals present on early Earth before life existed. It could also have implications on how astrobiologists view the probability of life elsewhere in the universe.
In surprisingly simple laboratory reactions in water, under everyday conditions, they have produced what could be good candidates for missing links on the pathway to the code of life.
And when those components joined up, the result even looked like RNA.
As the researchers’ work progresses, it could reveal that much of the original chemistry that led to life arose not in fiery cataclysms and in scarce quantities, but abundantly and gradually on quiet, rain-swept dirt flats or lakeshore rocks lapped by waves.
The research from the NSF/NASA Center for Chemical Evolution, headquartered at the Georgia Institute of Technology, is generously funded through a grant from the National Science Foundation and NASA. The recent results were published on April 25, 2016 in Nature Communications.
Pursuing the origins specifically of RNA, the close chemical relative of DNA, a research team led by Nicholas Hud, a professor in the School of Chemistry and Biochemistry at the Georgia Institute of Technology and director of the CCE, worked with a pair of potential chemical ancestors of the nucleobases of RNA.
For roughly half a century, scientists have hypothesized that life, which uses DNA to store genetic information, was preceded by life forms that used RNA very broadly. And RNA may have had a precursor, proto-RNA, with different but similar nucleotides (the “N” in RNA).
“Early Earth was a messy laboratory where probably many molecules like those needed for life were produced. Some survived and prospered, while others eventually vanished,” Hud said. “That goes for the ancestors of RNA, too.”
Using two molecules known as barbituric acid and melamine, the researchers formed proto-nucleotides so strongly resembling two of RNA’s nucleotides that it is tempting to speculate that they are indeed their ancestors.
The two ingredients would have been readily abundant for reactions on a prebiotic Earth, Hud said. “And they would have been well suited for primitive information coding,” he added.
Because of the resemblances and properties, some scientists already have speculated on an ancestral role for melamine and barbituric acid.
But the CCE scientists are careful not to jump to that conclusion just yet.
“To claim ancestry, we would have to show a mechanism by which these nucleotides we made in the lab could turn into the existing nucleotides in RNA,” said Ram Krishnamurthy, Hud’s collaborator from the Scripps Research Institute in La Jolla, California. “It’s a complex path that we’d have to at least design on paper, and we’re not there.”
Nonetheless, he’s exited about the results. “There are umpteen possibilities of how that mechanism could have happened. Barbituric acid and melamine may have been place holders that dropped out and allowed adenine and uracil to come together with ribose.”
Figuring out how adenine and uracil (nucleobases found in RNA today) combined with the sugar ribose (corresponding to the “R” in RNA) could answer one of the great questions of chemical evolution.
The formation of nucleotides from possible proto-nucleobases and ribose marks a significant advancement in research on the origin of life.
Nucleobases have been combined with other sugars in past studies, but the efficiency of the reactions discovered in this study is much greater than those of that past.
“We’re getting close to molecules that look the way life may have looked in early stages,” Krishnamurthy said.
A series of surprises added to the reactions’ scientific significance.
First, they occurred quickly and the resulting nucleotides spontaneously paired with each other in water, forming hydrogen bonds like the Watson-Crick base pairs that create the “ladder-rung” pattern inside RNA and DNA helixes.
Then the monomers formed long, supramolecular assemblages that look like strands of RNA when viewed with a high resolution microscope.
There has been no reported chemical reaction so far that has produced existing components of RNA under commonplace circumstances that spontaneously form Crick-Watson pairs in water.
And up until now, there had also been no report of a similar pair of nucleotides, like those produced with barbituric acid and melamine, behaving in a like manner, making this another first.
“It works even better then we thought,” Hud said. “It’s almost too easy.”
There was one small caveat.
“The reaction does not work as well if barbituric acid and melamine are present in the same solution before reacting with ribose because their strong attraction for each other can cause them to precipitate,” Hud said. So, the scientists completed the reaction involving barbituric acid separately from the one involving melamine.
But that should not have proven prohibitive on prebiotic Earth. Barbituric acid and melamine nucleotides could have been formed in separate locations, even in the same pond. And they could have very well been plentiful.
“These reactions are exceptionally productive, especially if you compare them to analogous reactions with existing RNA components, which do not produce any nucleotides under the same conditions,” Hud said.
If melamine and barbituric acid formed their respective nucleotides (C-BMP for barbituric acid and MMP for melamine) in separate puddles on the early Earth, then rain could have easily washed the components together, where they would have rapidly assembled into what could have been a precursor to proto-RNA.
“The question is: Can these self-assemblies make the transition into what makes up life today,” Krishnamurthy said.
The researchers hope their work will help expand the scientific community’s approach to chemical evolution.
“If you want to look at what brought about these properties of life you have to go back and consider all the other molecules that would have been present and see how they would have facilitated the molecules that are present in life today,” Krishnamurthy said.
Their work also could serve as a basis for important practical applications, such as the creation of DNA or RNA-like polymers that could spawn production of advanced materials and therapeutic agents.
The chemical reactions that produce the barbituric acid and melamine nucleotides don’t require the use of enzymes and extreme parameters like high heat and pressure. Reminiscent of click chemistry, they could contribute to safe, cost-effective and abundant industrial production.
In addition to those already named, the paper’s authors include Brian J. Cafferty, David M. Fialho and Jaheda Khanam, all from Georgia Tech.
This research was supported by the NSF Centers for Chemical Innovation Program and the NASA Astrobiology Program under the NSF/NASA Center for Chemical Evolution under grant number CHE-1004570. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NSF or NASA.
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]]>Put more scientifically, a piece of DNA’s movements are often counterintuitive to those of objects in our everyday grasp. Take a rod of rubber, for example. Bend it until its ends meet, and you can count on the elastic tension to snap it back straight when you let go, said biological physicist Harold Kim.
“That doesn’t always work that way with a piece of DNA. When you bend it into a loop, the elastic energy more often than not wants to bend the chain further in instead of pushing it back out,” said Kim, an associate professor at the Georgia Institute of Technology.
At the School of Physics, Kim is fine-tuning the observation of how biopolymers behave, in particular DNA at short lengths. He published his latest results on “Force distribution in a semiflexible loop” in the journal Physical Review E on April 18, 2016. The research is funded by National Institutes of Health. Georgia Tech’s James T. Waters coauthored the research paper.
In complex simulations, Kim studied the motions of DNA chains at lengths where they still have springy qualities, in order to understand their mechanochemical properties, or how they work as microscopic objects. In particular, he has illuminated the forces acting upon DNA bound up in short loops.
That’s a common and important shape that keeps DNA from expressing when it shouldn’t and then possibly messing up cell functioning.
Kim’s most significant counterintuitive find could improve understanding of how DNA snaps free from the proteins that bind them into those loops. He has observed that looped DNA, though on average very gentle in its motions, is beset by moments of unusually high force.
“It would be a little like a chaotic spring drawn up to a loop making pretty even jumbly movements then suddenly whipping out violently,” Kim said.
The range of observed forces on DNA loops breaks the bounds of what thermodynamics predicts. Even though the mean of the force distribution does indeed equal the thermodynamic force, the distribution of forces pushes past the anticipated norm, falling broadly outside a Gaussian distribution on both ends.
That’s a key determination.
It could help scientists in various disciplines predict the lifespans of many DNA loops and understand the frequency and likelihood of their undoing.
The forces contributing to those momentary jerks and snaps work on the whole contrary to one another. While that elastic energy works on DNA pieces in its ways, the forces of entropy push hard in their own ways.
Reflective of the universe overall, in Kim’s observations of springy DNA loops, entropy, here too, wins. Entropic forces slightly outdo the elastic forces.
And they, too, defy intuition.
To understand how, let’s take a look back at that rubber bar. When a short DNA chain is not looped but only bent, it acts more like the rubber bar. The elastic force dominates and mostly wants to push it back straight, while entropy mostly wants to keep it curvy.
Then, as the DNA chain lengthens a bit and loops: That relation starkly turns on its head.
The elastic force then pulls inward with vehemence, and the entropic force then pushes the chain outward with even more vigor.
The length of a DNA loop appears to contribute strongly to how likely these intermittent extreme forces are to destabilize its bond with the protein holding it shut.
That, incidentally, plays right into many scientists’ current discussions on other biopolymers.
“There’s a lot of speculation right now that the kinds of force-peaks we observed actually regulate the length of some biopolymers, so, in an interesting way, our observations and methods may help colleagues explore this idea more closely,” Kim said.
Kim’s group augmented thermodynamic calculations with a novel simulation method, “phase-space sampling.” It not only establishes the positon of molecular components in space but also their momentum at a given time.
This took into account the constant bombardment by water molecules, i.e. the “heat bath.”
This way, Kim was better able to access the fluctuating forces on looped DNA chains – and see more closely how they really wriggle.
The work is funded by the National Institutes of Health, grant number R01GM112882. Any conclusions or opinions are those of the authors and do not necessarily represent the official views of the NIH.
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]]>Though the idea must still be proven experimentally, the researchers believe that manipulating mass transfer using metamaterials could help reduce the energy required for certain chemical and biomolecular processes. The proposed technique would use specially-patterned polymeric materials to direct the flow of atoms by taking advantage of their specific physical properties.
A detailed explanation for how the technique could be used to separate a mixture of nitrogen and oxygen – by cloaking the nitrogen and concentrating the oxygen – was reported February 25 in the journal Scientific Reports. The research was supported by a seed grant from the American Chemical Society.
“We will control how the atoms cross the metamaterial, in which direction they will go,” said Martin Maldovan, an assistant professor in Georgia Tech’s School of Chemical & Biomolecular Engineering and School of Physics. “By designing the diffusivity of the metamaterials, we can make the atoms of one compound go one way, and the atoms of another compound go a different way. We are manipulating the physical properties to control the direction the atoms take through the metamaterial shell.”
Maldovan and Graduate Research Assistant Juan Manuel Restrepo-Flórez have evaluated their metamaterial using computational techniques, and plan to build a prototype separation device this summer. The work could have applications in such areas as chemical manufacturing, crystal growth of semiconductors, waste recovery of biological solutes or chemicals, and production of artificial kidneys.
The metamaterial technique could supplement traditional membranes, which control the passage of chemicals by varying solubility and diffusivity. Similar in principle to other metamaterials, the mass transfer technique can either direct chemicals around the shell, or concentrate them within the shell.
“Inside the metamaterial shell, you can tell one atom to do one thing, and another atom to do something else,” Maldovan said. “Our metamaterials will control the flow because they are anisotropic – certain directions are favored by the structure. We are controlling where the atoms go.”
Maldovan’s plan for the mass transfer metamaterials uses four different types of polymers, two with high diffusivity and two with low diffusivity. The size and patterning of blocks made from each material is determined by mathematical algorithms.
“With this metamaterial, we can control the direction the atoms can go using the trick of anisotropy,” he explained. “This would be in addition to separation based on solubility and diffusivity. We have added an important parameter to the toolbox of chemical engineers: where to send the atoms.”
In addition to separating atoms, the ability of the metamaterials to concentrate atoms could allow sensors to detect more dilute quantities, essentially amplifying the available chemical signal.
In their paper, the researchers show how to separate a 50-50 mixture of nitrogen and oxygen using available polymers that have the necessary properties. Each type of separation will require polymers with different properties, not all of which are available in existing materials, meaning not all chemical or biomolecular mixtures will be amenable to separation with the new technique.
The new separation process won’t replace traditional distillation and membrane separation processes, but could supplement them, Maldovan said.
“Distillation and evaporation are very energy intensive, but they are the workhorses of the chemical industry,” he said. “Membrane processes have been developed to reduce energy use. Our goal is to provide a technique that uses even less energy. This could lead to better and more efficient membranes that would provide better separation.”
The metamaterials will ultimately have to be fabricated at the micron scale to be effective. But Maldovan says prototypes can be made using larger structures – at the centimeter scale – to demonstrate the process.
“We need first to fabricate them, then optimize the design,” he said. “We know what needs to be fabricated, so future efforts will combine design, fabrication, and optimization.”
CITATION: Restrepo-Flórez, J. M. and Maldovan, M., “Mass Separation by Metamaterials,” (Scientific Reports, 2016) http://dx.doi.org/10.1038/srep21971.
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]]>At the macro-scale, the conversion of ethylene has long been considered among the reactions insensitive to the structure of the catalyst used. However, by examining reactions catalyzed by platinum clusters containing between 9 and 15 atoms, researchers in Germany and the United States found that at the nanoscale, that’s no longer true. The shape of nanoscale clusters, they found, can dramatically affect reaction efficiency.
While the study investigated only platinum nanoclusters and the ethylene reaction, the fundamental principles may apply to other catalysts and reactions, demonstrating how materials at the very smallest size scales can provide different properties than the same material in bulk quantities. Supported by the Air Force Office of Scientific Research and the Department of Energy, the research was reported January 28 in the journal Nature Communications.
“We have re-examined the validity of a very fundamental concept on a very fundamental reaction,” said Uzi Landman, a Regents’ Professor and F.E. Callaway Chair in the School of Physics at the Georgia Institute of Technology. “We found that in the ultra-small catalyst range, on the order of a nanometer in size, old concepts don’t hold. New types of reactivity can occur because of changes in one or two atoms of a cluster at the nanoscale.”
The widely-used conversion process actually involves two separate reactions: (1) dissociation of H2 molecules into single hydrogen atoms, and (2) their addition to the ethylene, which involves conversion of a double bond into a single bond. In addition to producing ethane, the reaction can also take an alternative route that leads to the production of ethylidyne, which poisons the catalyst and prevents further reaction.
The project began with Professor Ueli Heiz and researchers in his group at the Technical University of Munich experimentally examining reaction rates for clusters containing 9, 10, 11, 12 or 13 platinum atoms that had been placed atop a magnesium oxide substrate. The 9-atom nanoclusters failed to produce a significant reaction, while larger clusters catalyzed the ethylene hydrogenation reaction with increasingly better efficiency. The best reaction occurred with 13-atom clusters.
Bokwon Yoon, a research scientist in Georgia Tech’s Center for Computational Materials Science, and Landman, the center’s director, then used large-scale first-principles quantum mechanical simulations to understand how the size of the clusters – and their shape – affected the reactivity. Using their simulations, they discovered that the 9-atom cluster resembled a symmetrical “hut,” while the larger clusters had bulges that served to concentrate electrical charges from the substrate.
“That one atom changes the whole activity of the catalyst,” Landman said. “We found that the extra atom operates like a lightning rod. The distribution of the excess charge from the substrate helps facilitate the reaction. Platinum 9 has a compact shape that doesn’t facilitate the reaction, but adding just one atom changes everything.”
Nanoclusters with 13 atoms provided the maximum reactivity because the additional atoms shift the structure in a phenomena Landman calls “fluxionality.” This structural adjustment has also been noted in earlier work of these two research groups, in studies of clusters of gold which are used in other catalytic reactions.
“Dynamic fluxionality is the ability of the cluster to distort its structure to accommodate the reactants to actually enhance reactivity,” he explained. “Only very small aggregates of metal can show such behavior, which mimics a biochemical enzyme.”
The simulations showed that catalyst poisoning also varies with cluster size – and temperature. The 10-atom clusters can be poisoned at room temperature, while the 13-atom clusters are poisoned only at higher temperatures, helping to account for their improved reactivity.
“Small really is different,” said Landman. “Once you get into this size regime, the old rules of structure sensitivity and structure insensitivity must be assessed for their continued validity. It’s not a question anymore of surface-to-volume ratio because everything is on the surface in these very small clusters.”
While the project examined only one reaction and one type of catalyst, the principles governing nanoscale catalysis – and the importance of re-examining traditional expectations – likely apply to a broad range of reactions catalyzed by nanoclusters at the smallest size scale. Such nanocatalysts are becoming more attractive as a means of conserving supplies of costly platinum.
“It’s a much richer world at the nanoscale than at the macroscopic scale,” added Landman. “These are very important messages for materials scientists and chemists who wish to design catalysts for new purposes, because the capabilities can be very different.”
Along with the experimental surface characterization and reactivity measurements, the first-principles theoretical simulations provide a unique practical means for examining these structural and electronic issues because the clusters are too small to be seen with sufficient resolution using most electron microscopy techniques or traditional crystallography.
“We have looked at how the number of atoms dictates the geometrical structure of the cluster catalysts on the surface and how this geometrical structure is associated with electronic properties that bring about chemical bonding characteristics that enhance the reactions,” Landman added.
In addition to those already named, the research team included first-author Andrew Crampton, Marian Rotzer, Claron Ridge and Florian Schweinberger from the Catalysis Research Center at the Technical University of Munich.
The experimental work has been supported by the European Research Council (ERC) through the advanced research grant (246645-ASC3), and by the DFG through project HE3454/23-1. Support was also provided by the Air Force Office of Scientific Research (AFOSR) and by grant FG05–86ER45234 from the Office of Basic Energy Sciences of the US Department of Energy (DOE). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the sponsors.
CITATION: Andrew S. Crampton, et al., “Structure sensitivity in the nonscalable regime explored via catalyzed ethylene hydrogenation on supported platinum nanoclusters,” (Nature Communications 2016). http://dx.doi.org/10.1038/ncomms10389.
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]]>The research uses DNA strand displacement, a technology that has been widely used outside of cells for the design of molecular circuits, motors and sensors. Researchers modified the process to provide both “AND” and “OR” logic gates able to operate inside the living cells and interact with native messenger RNA (mRNA).
The tools they developed could provide a foundation for bio-computers able to sense, analyze and modulate molecular information at the cellular level. Supported by the Defense Advanced Research Projects Agency (DARPA) and the National Science Foundation (NSF), the research was reported December 21 in the journal Nature Nanotechnology.
“The whole idea is to be able to take the logic that is used in computers and port that logic into cells themselves,” said Philip Santangelo, an associate professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University. “These devices could sense an aberrant RNA, for instance, and then shut down cellular translation or induce cell death.”
Strand displacement reactions are the biological equivalent of the switches or gates that form the foundation for silicon-based computing. They can be programmed to turn on or off in response to an external stimuli such as a molecule. An “AND” gate, for example, would switch when both conditions were met, while an “OR” gate would switch when either condition was met.
In the switches the researchers used, a fluorophore reporter molecule and its complementary quenching molecule were placed side-by-side to create an “off” mode. Binding of RNA in one of the strands then displaced a portion of nucleic acid, separating the molecules and allowing generation of a signal that created an “on” mode. Two “on” modes on adjacent nucleic acid strands created an “AND” gate.
“Demonstrating individual logic gates is only a first step,” said Georg Seelig, assistant professor of computer science and engineering and electrical engineering at the University of Washington. “In the longer term, we want to expand this technology to create circuits with many inputs, such as those we have constructed in cell-free settings.”
The researchers used ligands designed to bind to specific portions of the nucleic acid strands, which can be created as desired and produced by commercial suppliers.
“We sensed molecules and showed that we could respond to them,” said Santangelo. “We showed that we could utilize native molecules in the cell as part of the circuit, though we haven’t been able to control a cell yet.”
Getting basic computing operations to function inside cells was no easy task, and the research required a number of years to accomplish. Among the challenges were getting the devices into the cells without triggering the switches, providing operation rapid enough to be useful, and not killing the human cell lines that researchers used in the lab.
“We had to chemically change the probes to get them to work inside the cell and to make them stable enough inside the cells,” said Santangelo. “We found that these strand displacement reactions can be slow within the cytosol, so to get them to work faster, we built scaffolding onto the messenger RNA that allowed us to amplify the effects.”
The nucleic acid computers ultimately operated as desired, and the next step is to use their switching to trigger the production of signaling chemicals that would prompt the desired reaction from the cells. Cellular activity is normally controlled by the production of proteins, so the nucleic acid switches will have to be given the ability to produce enough signaling molecules to induce a change.
“We need to generate enough of whatever final signal is needed to get the cell to react,” Santangelo explained. “There are amplification methods used in strand displacement technology, but none of them have been used so far in living cells.”
Even without that final step, the researchers feel they’ve built a foundation that can be used to attain the goal.
“We were able to design some of the basic logical constructs that could be used as building blocks for future work,” Santangelo said. “We know the concentrations of chemicals and the design requirements for individual components, so we can now start putting together a more complicated set of circuits and components.”
Cells, of course, already know how to sense toxic molecules and the development malignant tendencies, and to then take action. But those safeguards can be turned off by viruses or cancer cells that know how to circumvent natural cellular processes.
“Our mechanism would just give cells a hand at doing this,” Santangelo said. “The idea is to add to the existing machinery to give the cells enhanced capabilities.”
Applying an engineering approach to the biological world sets this example apart from other efforts to control cellular machinery.
“What makes DNA strand displacement circuits unique is that all components are fully rationally designed at the level of the DNA sequence,” said Seelig. “This really makes this technology ideal for an engineering approach. In contrast, many other approaches to controlling the cellular machinery rely on components that are borrowed from biology and are not fully understood.”
Beyond those already mentioned, the research team included Benjamin Groves, Yuan-Jyue Chen and Sergii Pochekailov from the University of Washington and Chiara Zurla and Jonathan Kirschman from Georgia Tech and Emory University.
This material is based on work supported by the Defense Advanced Research Projects Agency (DARPA) under contract W911NF-11-2-0068 and by National Science Foundation CAREER award 1253691. The content is solely the responsibility of the authors and does not necessarily represent the official views of DARPA or the NSF.
CITATION: Benjamin Groves, et al., “Computing in mammalian cells with nucleic acid strand exchange,” (Nature Nanotechnology, 2015). http://dx.doi.org/10.1038/nnano.2015.278
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]]>The new process generates structures that would be impossible to make using gas-phase focused electron beam-induced deposition (FEBID) techniques, and allows fabrication at rates up to five orders of magnitude faster than the gas-phase technique. And because it uses standard liquid solvents, the new process could take advantage of a broad range of precursor materials. Multiple materials can also be deposited simultaneously.
“By allowing us to grow structures much faster with a broad range of precursors, this technique really opens up a whole new direction for making a hierarchy of complex three-dimensional structures with nanoscale resolution at the rate that is demanded for manufacturing scalability,” said Andrei Fedorov, a professor in the George Woodruff School of Mechanical Engineering at the Georgia Institute of Technology. “This could provide a fundamental shift in the way this field will go.”
The research was supported by the U.S. Department of Energy’s Office of Science and reported in the journal Nano Letters. Applications for the rapid electron beam writing of topologically complex 3D nanostructures could include new types of electrode topologies for batteries and fuel cells, vertically-stacked electronic memory, substrates for controlling cell differentiation and tiny electrochemical conversion devices.
In the established FEBID process, an electron beam is used to write structures from molecules adsorbed onto a solid surface that provides support and nucleation sites for deposit growth. The precursors are introduced into the high-vacuum electron microscope chamber in gas phase. High-energy electrons in the beam interact with the substrate to produce the low-energy secondary electrons, which dissociate the adsorbed precursor molecules, resulting in deposition of solid material onto the substrate surface.
Though it enables precise atom-by-atom fabrication of nanostructures, the process is very slow because the low density of adsorbed gas molecules in the vacuum environment limits the amount of material available for fabrication. And structures must be fabricated from the substrate surface up at continually decreasing growth rate and from a limited number of precursor gases available.
Fedorov and his collaborators have dramatically accelerated the process by introducing electrically-charged liquid-phase precursors directly into high vacuum of the electron microscope chamber. Liquid-phase precursors had been demonstrated before, but the materials had to be enclosed in a tiny capsule where the reaction took place, limiting fabrication flexibility, capacity and utility of the approach for 3D nanofabrication.
The research team – including graduate student and first author Jeffrey Fisher, postdoctoral fellow Songkil Kim and senior research engineer Peter Kottke – used low volatility solvents such as ethylene glycol, dissolving a salt of silver in the liquid. In solution, the salt dissociates into silver cations, allowing production of silver metal deposits by electrochemical reduction reaction using solvated secondary electrons rather direct molecular decomposition.
The solvent containing the desired material ions is introduced into the chamber using a nanoelectrospray system composed of a tiny nozzle just a few microns in diameter. By applying the focused electric field to the nozzle, the fluid jet is drawn and delivers to the substrate forming a precisely controlled thin liquid film.
The electrospray produces nanometer-scale charged droplets from a Taylor cone jet just 100 nanometers in diameter, which coalesce upon impingement and form a thin film of the precursor on the solid substrate.
The research team used the electron beam itself to visualize the Taylor cone jet in the vacuum environment, the first time this has ever demonstrated, as well as to measure the thickness of the liquid film in situ by using a nanoscale “ruler” prefabricated on the deposition substrate. The electron beam then scans over the liquid film following a desired pattern, producing suitable energy electrons which solvate and reduce the cations, writing structures in precise formation from the precursor delivered by the electrified jet. Though evaporation of the solvent does occur, the nanoelectrospray can maintain a stable film long enough for the structures to form.
The combination of a denser precursor, reduction in material surface transfer problems and elimination of the need to break chemical bonds with the electron beam allows fabrication up to five orders of magnitude – a factor of 5,000 – faster than the earlier gas-phase technique.
“By changing the energy of the beam and current, we can preferentially grow nanostructures in 3D at much faster rate,” Fedorov said. “All of a sudden, there are a whole host of different applications that were not possible before.”
Varying the precursor type, film thickness, concentration of ions and the energy and current of the electron beam controls the kinds of structures that can be made, Fedorov said. Structures such as bridges connecting posts become possible because material can be written atop the thin films.
The researchers have fabricated carbon nanopillars five microns tall, wall-like nanostructures connecting two nanopillars, and suspended bridge-like arch nanostructures connecting nanopillars. The structures required growth times ranging from 2 to 40 seconds. Silver micropillars have also been fabricated.
The new process allows considerable flexibility in fabrication, opening the possibility of depositing more than one material simultaneously. That could allow production of alloys and composites, such as combinations of silver and gold. Or, one material could be used as a template to be coated by another material with the simple substitution of precursor materials.
So far, the Georgia Tech team has produced structures of silver and carbon, but the process could be used to fabricate a wide range of metallic and non-metallic nanomaterials. Metals produced using the technique can be highly pure because a carbon-producing precursor dissociation step can be mitigated.
The next step will be to understand the physics and chemistry governing the fabrication process to allow more precise control and to guide others who may wish to use it for their own specific applications.
“We expect that the role of the solvents is going to be very important in the kinds of kinetic pathways that we can control to produce many different kinds of structures with desired chemical make-up,” said Fedorov. “This gives us an opportunity to explore a regime of chemistry and physics that had previously been outside what we could study. We want to establish an understanding of the basic physics and chemistry of the process.”
Future work will include a study of how the interaction of beams with different energies, vacuum environments, solvents and concentrations of ionic species affect the outcome.
“We have demonstrated that we can electrospray liquid precursors inside a high vacuum environment of an electron microscope and then use electrons to facilitate useful chemical transformations,” said Fedorov. “We think this will enable scientists and engineers to make structures they had only been able to dream of before.”
This research was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under award number DE-SC0010729. The comments contained in this article are the responsibility of the authors and do not necessarily represent the official views of the Department of Energy.
CITATION: Jeffrey S. Fischer, Peter A. Kottke, Songkil Kim and Andrei G. Fedorov, “Rapid Electron Beam Writing of Topologically Complex 3D Nanostructures Using Liquid Phase Precursor,” (Nano Letters, 15 (12), 8385–8391, 2015). http://dx.doi.org/10.1021/acs.nanolett.5b04225
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]]>More than a billion people worldwide may be at risk for adequate zinc intake, but measuring zinc levels in blood samples currently requires sophisticated testing equipment not available in many affected areas. If field tests show the biosensor can successfully measure zinc levels, the researchers hope to extend the concept to other micronutrients, including vitamins.
“We think this is just enough technology to meet the needs,” said Mark Styczynski, an assistant professor in the School of Chemical & Biomolecular Engineering at the Georgia Institute of Technology. “The information we can provide could one day help nutritional epidemiologists and non-governmental organizations determine the populations of people that may need interventions to address nutritional deficiencies.”
The proof-of-concept work was reported in the September issue of the journal Metabolic Engineering. The research was supported by the Bill and Melinda Gates Foundation, the National Science Foundation and the National Institutes of Health.
The biosensor is based on modified Escherichia coli (E. coli), a bacterium that is frequently used in genetic engineering. E. coli has a transcriptional system that responds to the level of zinc in its environment, and the researchers have tuned it to trigger the production of purple, red and orange pigments. Genetic machinery for the production of those pigments was taken from other biological sources and introduced into the E. coli.
In practice, health professionals in the field would obtain blood samples from persons suspected of having a zinc deficiency. The blood samples would be spun on a simple mechanical device resembling an eggbeater to separate the plasma from the blood cells. The plasma would then be placed into a test tube or other container with a pellet containing the modified E. coli.
Once mixed with the plasma, the E. coli would multiply, producing the color corresponding to the level of zinc in the blood plasma. Purple would correspond to dangerously low levels, while red would indicate borderline levels, and orange normal levels. The color would be readily visible without any diagnostic or other electronic equipment.
“The process for the color change would take about 24 hours from when the plasma sample is added, though we are hoping to accelerate that,” said Styczynski.
The testing wouldn’t be done to identify individuals in need of treatment, but would be used to assess the nutritional needs of a larger population of people.
“Places where you are likely to encounter micronutrient deficiencies will typically be resource-poor countries, or perhaps locations suffering natural disasters,” Styczynski explained. “These deficiencies aren’t treated on an individual level, but are considered on a population level and used to treat a village or a region that may be affected. We could take samples from 50 or 100 people and be able to assess the nutritional status of an area.”
Because bacteria don’t have the same requirements for many vitamins relevant to human health, the researchers may have to change organisms when they develop tests for other micronutrients, like Vitamin A. Those tests will likely use a yeast organism which has also been extensively studied and into which sensing and pigment-producing genetic machinery can be introduced.
“Ultimately, we hope to be able to test for a whole suite of nutrients in a reasonably short period of time and at a relatively low cost because no equipment would be needed in the field,” Styczynski added.
As part of their research, Styczynski and graduate research assistants Daniel Watstein and Monica McNerney engineered pigment producing machinery into the E. coli. The red and orange colors, lycopene and beta-carotene, are produced by genes taken from Pantoea anantis, a plant pathogen. The purple color, violacein, came from a soil bacterium. Genes for producing the pigments were placed onto a plasmid and introduced into the bacterium.
The researchers used two zinc-sensing proteins within the E. coli and controlled the extent to which those proteins could turn the pigment producing genes on and off. This approach made the zinc-sensing proteins responsive to levels of zinc close to that expected to be found in blood plasma, and can be further used to allow them to turn on at arbitrary levels.
One of the challenges was to avoid producing amounts of pigment that might be toxic to the bacterium, while producing pigment quickly enough to be visible to the naked eye. And because the orange and red pigments are generated in the same metabolic pathway, the researchers needed to establish ways to produce only one or the other at a time – a challenge that their work shows can be feasibly addressed, though they are still working to fine-tune the implementation.
Styczynski believes this system is the first designed to measure blood micronutrients using bacteria without requiring diagnostic equipment. Other techniques have required specialized measurement equipment that is difficult to transport and maintain in the field.
“The general idea of bio-sensing is certainly out there, but we have taken the step of developing a system that doesn’t require equipment in the field,” he said. “We believe this will work well in low-resource areas.”
Among the next steps are development of techniques to freeze-dry the bacterium, and an assessment of the potential ecological impact of the modified bacterium. Styczynski hopes field trials can begin within the next two years.
“This is a convincing proof-of-principle, and we hope to begin the translational aspects of this system based on what we have already shown,” he added. “It’s a matter now of reducing this to practice for something that will ultimately be useful.”
This research was supported by the Bill & Melinda Gates Foundation under grant OPP1046289, the National Science Foundation under grant 1254382, and a National Institutes of Health training grant T32-EB006343. The content of this news release is the responsibility of the authors and does not necessarily represent the official views of the supporting agencies.
CITATION: Daniel M. Watstein, Monica P. McNerney and Mark P. Styczynski, “Precise metabolic engineering of carotenoid biosynthesis in Escherichia coli towards a low-cost biosensor.” (Metabolic Engineering, 2015). http://www.dx.doi.org/10.1016/j.ymben.2015.06.007
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]]>Take seaweed, for instance. Normally it's the enemy of coral, secreting toxic chemicals, blocking the sunlight, and damaging coral with its rough surfaces. But when hordes of hungry crown-of-thorns sea stars invade the reef, everything changes, reports a study published August 25 in the journal Proceedings of the Royal Society B.
Seaweeds appear to protect coral from the marauding sea stars, giving new meaning to the proverb: “The enemy of my enemy is my friend.” The findings demonstrate the complexity of interactions between species in ecosystems, and provide information that could be useful for managing endangered coral reefs.
“On the reefs that we study, seaweeds reduce coral growth by both chemical and mechanical means,” said Mark Hay, a professor in the School of Biology at the Georgia Institute of Technology and the paper’s senior author. “But we found that seaweeds can benefit corals by reducing predation by the crown-of-thorns sea stars. Corals surrounded by seaweeds were virtually immune to attack by the sea stars, essentially converting the seaweeds from enemies to friends.”
The research was supported by the National Science Foundation, the National Institutes of Health and the Teasley endowment at Georgia Tech.
Crown-of-thorns sea stars (Acanthaster planci) are a major problem in the Pacific, where populations of the organisms rise and fall in cycles. On the Great Barrier Reef, for example, coral cover has declined by more than 50 percent over 25 years, and the voracious spine-covered creatures – which can travel as much as 80 meters per day – get much of the blame.
“You don’t have to see the crown-of-thorns to know they have been on the reef,” said Cody Clements, a Georgia Tech graduate student in Hay’s lab and paper’s first author. “You can see where they have been because they leave trails of bleached white coral. All they leave behind are the coral skeletons.”
The sea stars climb onto favored corals, invert their stomachs out through their mouths, and digest away the corals’ living tissues – leaving white skeletons like a trail of bread crumbs that allowed Clements to not only see where the creatures had been, but also to track them to hiding places in the rocks.
During a two-year study in a marine protected area off the coast of the Fiji Islands, Clements used both observations and field experiments to examine the role of sea stars and seaweeds in the health of coral.
“Marine protected areas where we work are often surrounded by areas of coral reef that are degraded and have lots of seaweeds,” said Clements. “If seaweed is increasing in prevalence in these degraded areas, it’s likely that these predators will move into protected areas with more coral and less seaweed. That could compromise conservation efforts in these relatively small marine protected areas established to protect coral.”
Clements first assessed the impact of seaweeds by comparing the growth of corals surrounded by varying levels of seaweed cover. To accurately measure growth, he established test colonies of the coral Montipora hispida attached to the necks of plastic soft drink bottles. Matching bottle caps were nailed into seabed rock, allowing colonies to be unscrewed from their anchorages to be accurately weighed, then returned. He placed varying amounts of the seaweed Sargassum polycystum adjacent to each test colony.
“The seaweed had a negative effect on the growth of the coral, and the more seaweed that was present, the greater the impact I observed,” he said.
To study the relationship between sea star attacks and seaweed cover, Clements used photographs to assess the amount of sea star damage to different coral colonies outside the marine protected area, and related the damage to the amount of seaweed on corals in the attacked areas. Coral colonies that had been attacked had, on average, just eight percent seaweed coverage, while nearby colonies of the same species that had not been attacked averaged 55 percent coverage of seaweeds.
To more directly assess the protective role of the seaweed, Clements conducted an experiment. He fabricated ten cages in which he placed two Montipora coral colonies, one surrounded by varying levels of seaweed – between two and eight fronds – and the other lacking adjacent seaweeds. Into each cage he placed a sea star, then observed how much of each coral would be eaten.
“At the highest densities of seaweed, the sea stars were completely deterred,” Clements said. “They wouldn’t eat the coral surrounded by the seaweeds.” Coral surrounded by lower densities of seaweed were sometimes eaten, while the corals without seaweed protection were always consumed by the sea stars.
Researchers aren’t sure if the protective effects of the seaweed are mechanical or chemical – or perhaps both. But when Clements repeated the experiment with plastic aquarium seaweed instead of real seaweed, he found that it also had protective effects, suggesting the seaweed may be simply physical impediments making the coral difficult for the sea stars to find or consume.
Finally, Clements examined sea star feeding when the predator was given a choice between an unprotected coral it doesn’t normally consume (Porites cylindra) and Montipora – a favored prey – that had been surrounded by Sargussum. The sea stars didn’t eat the Montipora, and would wait as long as ten days before finally consuming the Porites.
“If you’ve got a choice between ice cream and broccoli, you’re going to choose ice cream – unless broccoli is the only thing you can get,” he said.
The varying relationship between coral and seaweed illustrates the kind of complexity scientists have to understand when studying species-diverse ecosystems such as coral reefs, Clements noted.
“In a scenario that didn’t involve the crown-of-thorns sea stars, interactions with the seaweed would have been negative for the coral,” he noted. “But when you add the crown-of-thorns into the equation, it can be beneficial for the coral to be associated with the seaweed. Even if it suffers reduced growth, that’s better than being eaten.”
Information from research like this can help scientists protect corals, which are essential to the survival of reef ecosystems.
“We are interested not only in how direct interactions between species play out, but also how these indirect interactions come into the picture and influence the wider community,” said Clements. “When it comes to coral reefs, that is very important because these interactions can affect the trajectory of an entire community of organisms.”
This research was supported by the National Science Foundation under grant OCE- 0929119, by the Fogarty International Center of the National Institutes of Health under grants U01-TW007401 and U19TW007401, and by the Teasley Endowment to Georgia Tech. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Science Foundation or the National Institutes of Health.
CITATION: Cody S. Clements and Mark E. Hay, “Competitors as accomplices: Seaweed competitors hide corals from predatory sea stars,” (Proceedings of the Royal Society B, 2015).
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]]>Nanotechnology involves the use of materials at the smallest scale, including the manipulation of individual atoms and molecules. Products that use nanoscale materials range from beer bottles and car wax to solar cells and electric and hybrid car batteries. If you read your books on a Kindle, quantum dots, a semiconducting material manufactured at the nanoscale, underpin the high-resolution screen.
And while there are already hundreds of products that use nanomaterials in various ways, there are still lots of unknowns about how these modern materials and the tiny particles they are composed of interact with the environment and living things.
“The purpose of the center is to explore how we can make sure these nanotechnologies come to fruition with little or no environmental impact,” explained Robert Hamers, director of the center and a professor of chemistry at the University of Wisconsin Madison. “We’re looking at nanoparticles in emerging technologies.”
In addition to UW-Madison, scientists from UW-Milwaukee, the University of Minnesota, the University of Illinois, Northwestern University and the Pacific Northwest National Laboratory have been involved in the center’s first phase of research. Joining the center for the next five-year phase are Tuskegee University, the University of Maryland-Baltimore County, Johns Hopkins University, the University of Iowa, Augsburg College, and the Georgia Institute of Technology.
Georgia Tech’s contributions will be in the areas of theoretical computational chemistry and assessment of the center’s overall impact. Rigoberto Hernandez, a professor in the Georgia Tech School of Chemistry and Biochemistry, will contribute expertise on how particles aggregate, assemble and interact with one another to create larger structures. Lizanne DeStefano, a professor in the Georgia Tech School of Psychology and director of the Center for Education Integrating Science, Mathematics and Computing (CEISMC) at Georgia Tech, will help assess the center’s impacts, both internally and externally, for students and other key stakeholders.
“One of our mandates is to develop a systematic approach for using theoretical and computational tools to select different nanomaterials or modifications of nanomaterials to meet desired properties,” said Hernandez. “We will help understand the multi-scale problem, which includes understanding the chemical properties at the size scale from a few Angstroms – where you can literally see atoms within molecules – all the way to the meter scale where you must address the behavior of an entire organism.”
One of three theoretical and computational chemists who will be part of the center’s second phase, Hernandez is looking toward development of a computational framework for modifying nanomaterials and predicting the extent to which they would provide a targeted function or behavior. An example of such a function might be energy conversion and related transformations necessary in future generations of fuel cells.
“While the research impact of the center is important, its most long term impact will involve training the next generation of scientists and researchers who will take leadership roles in industry and academe,” said DeStefano. “We want to create innovative educational programs at undergraduate and graduate levels that integrate theory and computation and produce students with broader technical skill sets and a deep understanding of nanoparticles. The goal is to impact education at Georgia Tech and all partner institutions.”
In addition to Hernandez and DeStefano, center efforts at Georgia Tech will also involve at least two graduate students and one postdoctoral fellow.
At UW-Madison, Hamers leads efforts in synthesis and molecular characterization of nanomaterials. Much remains to be learned about how nanoparticles affect the environment and the multitude of organisms – from bacteria to plants, animals and people – that may be exposed to them.
“Some of the big questions we’re asking,” said Hamers, “are how is this going to impact bacteria and other organisms in the environment? What do these particles do? How do they interact with organisms?”
For instance, bacteria, the vast majority of which are beneficial or benign, tend to be “sticky” and nanoparticles might cling to the microorganisms and have unintended biological effects.
“There are many different mechanisms by which these particles can do things,” Hamers added. “The challenge is we don’t know what these nanoparticles do if they're released into the environment.”
To get at the challenge, Hamers and his colleagues in the center are drilling down to investigate the molecular-level chemical and physical principles that dictate how nanoparticles interact with living things. Such studies, argues Hamers, promise a science-based understanding that can help ensure the technology leaves a minimal environmental footprint by identifying issues before they manifest themselves in the manufacturing, use or recycling of products that contain nanotechnology-inspired materials.
To help fulfill that part of the mission, the center has established working relationships with several companies to conduct research on materials in the very early stages of development.
“We’re taking a look-ahead view. We’re trying to get into the technological design cycle,” Hamers said. “The idea is to use scientific understanding to develop a predictive ability to guide technology and guide people who are designing and using these materials.”
Hernandez believes that the 21st century may be known as the “nanoparticle age” in the same way that last century was the “industrial age.” The challenge ahead, he says, is to avoid unexpected effects from these new materials and structures.
“In this century, there is little doubt that nanoparticles comprise a class of chemical compounds that are revolutionizing nearly everything that we touch, see or smell,” he said in a blog post at (EveryWhereChemistry.blogspot.com). “The challenge to chemists (and material scientists) is not just designing nanoparticles to solve particular problems, but to do so with materials that have no unintended consequences. Anticipating such unknown unknowns is a grand challenge, and the solution requires a team of scientists with expertise in making, measuring and modeling the nanoparticles in the upstream design side and in biology and ecology on the downstream side.”
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]]>If the material can be scaled up from laboratory samples, devices made from it could surpass traditional electrolytic capacitors for applications in electromagnetic propulsion, electric vehicles and defibrillators. Capacitors often complement batteries in these applications because they can provide large amounts of current quickly.
The new material is composed of a silica sol-gel thin film containing polar groups linked to the silicon atoms and a nanoscale self-assembled monolayer of an octylphosphonic acid, which provides insulating properties. The bilayer structure blocks the injection of electrons into the sol-gel material, providing low leakage current, high breakdown strength and high energy extraction efficiency.
“Sol-gels with organic groups are well known and fatty acids such as phosphonic acids are well known,” noted Joseph Perry, a professor in the School of Chemistry and Biochemistry at the Georgia Institute of Technology. “But to the best of our knowledge, this is the first time these two types of materials have been combined into high-density energy storage devices.”
The research, supported by the Office of Naval Research and the Air Force Office of Scientific Research, was reported July 14 in the journal Advanced Energy Materials.
The need for efficient, high-performance materials for electrical energy storage has been growing along with the ever-increasing demand for electrical energy in mobile applications. Dielectric materials can provide fast charge and discharge response, high energy storage, and power conditioning for defense, medical and commercial applications. But it has been challenging to find a single dielectric material able to maximize permittivity, breakdown strength, energy density and energy extraction efficiency.
Perry and colleagues in Georgia Tech’s Center for Organic Photonics and Electronics (COPE) had been working on other capacitor materials to meet these demands, but were not satisfied with the progress. The hybrid sol-gel materials had shown potential for efficient dielectric energy storage because of their high orientational polarization under an electric field, so the group decided to pursue these materials for the new capacitor applications.
Using an aluminized mylar film coated with the hybrid sol-gel capacitor material, they showed that the capacitor could be rolled and re-rolled several times while maintaining high energy density, demonstrating its flexibility. But they were still seeing high current leakage. To address that, they deposited a nanoscale self-assembled monolayer of n-octylphosphonic acid on top of the hybrid sol-gel. Less than a nanometer thick, the monolayer serves as an insulating layer.
“Our silica sol-gel is a hybrid material because it has polar organic groups attached to the silica framework that gives the sol-gel a high dielectric constant, and in our bilayer dielectric, the n-octylphosphonic acid groups are inserted between the sol-gel layer and the top aluminum layer to block charge injection into the sol-gel,” Perry explained. “It’s really a bilayer hybrid material that takes the best of both reorientation polarization and approaches for reducing injection and improving energy extraction.”
In their structures, the researchers demonstrated maximum extractable energy densities up to 40 joules per cubic centimeter, an energy extraction efficiency of 72 percent at a field strength of 830 volts per micron, and a power density of 520 watts per cubic centimeter. The performance exceeds that of conventional electrolytic capacitors and thin-film lithium ion batteries, though it doesn’t match the lithium ion battery formats commonly used in electronic devices and vehicles.
“This is the first time I’ve seen a capacitor beat a battery on energy density,” said Perry. “The combination of high energy density and high power density is uncommon in the capacitor world.”
Researchers in Perry’s lab have been making arrays of small sol-gel capacitors in the lab to gather information about the material’s performance. The devices are made on small substrates about an inch square.
“What we see when we apply an electric field is that the polarization response – which measures how much the polar groups line up in a stable way with the field – behaves in a linear way,” said Perry. “This is what you want to see in a capacitor dielectric material.”
The next step will be to scale up the materials to see if the attractive properties transfer to larger devices. If that is successful, Perry expects to commercialize the material through a startup company or SBIR project.
“The simplicity of fully solution-based processes for our dielectric material system provides potential for facile scale-up and fabrication on flexible platforms,” the authors wrote in their paper. “This work emphasizes the importance of controlling the electrode-dielectric interface to maximize the performance of dielectric materials for energy storage application.”
In addition to Perry, the research team included Yunsang Kim, Mohanalingam Kathaperumal and Vincent Chen from the Georgia Tech School of Chemistry and Biochemistry; Yohan Park from the Georgia Tech School of Materials Science and Engineering; Canek Fuentes-Hernandez and Bernard Kippelen from the Georgia Tech School of Electrical and Computer Engineering, and Ming-Hen Pan from the Naval Research Laboratory.
This research was supported by the Office of Naval Research Dielectric Films Program (Grant N000141110462) and U.S. Air Force Office of Scientific Research, BioPAINTS MURI Program (Grant FA9550-09-0669). The content of this article is solely the responsibility of the authors and does not necessarily represent the official views of the sponsoring agencies.
CITATION: Yunsang Kim, et al., “Bilayer Structure with Ultra-high Energy/Power Density Using Hybrid Sol-Gel Dielectric and Charge Blocking Monolayer, (Advanced Energy Materials, 2015). http://www.dx.doi.org/10.1002/aenm.201500767
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]]>The Georgia Institute of Technology and the National Academy of Engineers hosted a media roundtable Wednesday in Washington, D.C., on the topic: “10 Years after Katrina: Are American Cities Ready?”
While Katrina remains one of the deadliest and costliest hurricanes in U.S. history, in the immediate aftermath many people thought the problem was isolated to New Orleans because it was built below sea level, said Georgia Tech President Emeritus G. Wayne Clough.
Opinions have changed in recent years, said Clough, who led an independent panel investigation of the Department of Defense and response to the storm.
“Hurricane Sandy was a wake-up call that this could happen to anyone,” Clough said. “Sandy changed people’s minds and … in many ways had more of an impact than Katrina did.”
Panelists listed several cities at risk, including Miami, Tampa, Charleston and Norfolk.
Some cities are at risk because of geography, rising sea levels and climate change. However, too many cities fail to have the needed discussions and preparations because they have not recently felt the impact of a natural disaster, said Reggie DesRoches, the Karen and John Huff School Chair of Georgia Tech’s School of Civil and Environmental Engineering.
Increased emphasis on local communities is something government leaders, engineers and others should do to improve disaster resilience response, panelists said. While communities will receive help from their region, state and the federal government, there are many things local citizens must decide.
“Will they move off a barrier island or elevate their homes or invest in communications?” asked Lt. General Thomas Bostick, commanding general of the U.S. Army Corps of Engineers. “How do you adapt and come out stronger than you were?”
Since Katrina, the Corps is working more closely with stakeholders and is taking a more systematic approach that goes beyond infrastructure, Bostick said. This approach includes collaborating with local communities. During the recent flood season, the Tulsa district turned to social media and had more than 65 million hits, he said.
During the nearly 90-minute discussion, the six panelists answered questions posed by reporters from the Associated Press, Science News and U.S. News & World Report. Audience members, including guests of Georgia Tech and the National Academy of Engineering, also participated in the discussion.
While the panelists agreed much has been learned since Katrina and improvements have been made, they said deficiencies remain.
For example, there needs to be a deeper understanding of the social science and behavioral component surrounding natural disasters, said Lauren Sauer, associate director of the National Center for the Study of Preparedness and Catastrophic Event Response at Johns Hopkins University.
Alton Romig Jr., executive officer of the National Academy of Engineering, said there is a lack of clarity when it comes to communication and authority around natural disasters. A lot of tools fail to get “into the right hands at the right time,” he said.
Reporters asked about the logic in designing the New Orleans levees and floodwalls to withstand a 100-year storm – one with a 1 percent chance of occurring in any year. While that design allowed the city to withstand Hurricane Isaac, there are questions as to whether something stronger should have been built.
Greg Baecher, professor of civil engineering at the University of Maryland, explained the 100-year storm was based on protecting real estate. This country needs to come to an agreement as to what is an acceptable or tolerable risk for human life, said Baecher, who conducted inter-agency federal risk analysis after Hurricane Katrina.
“What is the right level of protecting people,” he asked. “It’s probably less frequent than a 1 percent storm.”
]]>Georgia Tech’s national media roundtable initiative brings together thought leaders from different organizations to discuss important issues.
This was Georgia Tech’s fourth roundtable. Others examined the future of online learning in higher education and how to attract more female engineers and African-American men into STEM.
This initiative is the result of a partnership between Georgia Tech’s Office of Development, Institute Communications, Office of Government and Community Relations and individual colleges.
]]>Capillary action draws water and other liquids into confined spaces such as tubes, straws, wicks and paper towels, and the flow rate can be predicted using a simple hydrodynamic analysis. But a chance observation by researchers at the Georgia Institute of Technology will cause a recalculation of those predictions for conditions in which hydrogel films line the tubes carrying water-based liquids.
“Rather than moving according to conventional expectations, water-based liquids slip to a new location in the tube, get stuck, then slip again – and the process repeats over and over again,” explained Andrei Fedorov, a professor in the George W. Woodruff School of Mechanical Engineering at Georgia Tech. “Instead of filling the tube with a rate of liquid penetration that slows with time, the water propagates at a nearly constant speed into the hydrogel-coated capillary. This was very different from what we had expected.”
The findings resulted from research sponsored by the Air Force Office of Scientific Research (AFOSR) through the BIONIC center at Georgia Tech, and were reported earlier this month in the journal Soft Matter.
When the opening of a thin glass tube is exposed to a droplet of water, the liquid begins to flow into the tube, pulled by a combination of surface tension in the liquid and adhesion between the liquid and the walls of the tube. Leading the way is a meniscus, a curved surface of the water at the leading edge of the water column. An ordinary borosilicate glass tube fills by capillary action at a gradually decreasing rate with the speed of meniscus propagation slowing as a square root of time.
But when the inside of a tube is coated with a very thin layer of poly(N-isopropylacrylamide), a so-called “smart” polymer (PNIPAM), everything changes. Water entering a tube coated on the inside with a dry hydrogel film must first wet the film and allow it to swell before it can proceed farther into the tube. The wetting and swelling take place not continuously, but with discrete steps in which the water meniscus first sticks and its motion remains arrested while the polymer layer locally deforms. The meniscus then rapidly slides for a short distance before the process repeats. This “stick-slip” process forces the water to move into the tube in a step-by-step motion.
The flow rate measured by the researchers in the coated tube is three orders of magnitude less than the flow rate in an uncoated tube. A linear equation describes the time dependence of the filling process instead of a classical quadratic equation which describes filling of an uncoated tube.
“Instead of filling the capillary in a hundredth of a second, it might take tens of seconds to fill the same capillary,” said Fedorov. “Though there is some swelling of the hydrogel upon contact with water, the change in the tube diameter is negligible due to the small thickness of the hydrogel layer. This is why we were so surprised when we first observed such a dramatic slow-down of the filing process in our experiments.”
The researchers – who included graduate students James Silva, Drew Loney and Ren Geryak and senior research engineer Peter Kottke – tried the experiment again using glycerol, a liquid that is not absorbed by the hydrogel. With glycerol, the capillary action proceeded through the hydrogel-coated microtube as with an uncoated tube in agreement with conventional theory. After using high-resolution optical visualization to study the meniscus propagation while the polymer swelled, the researchers realized they could put this previously-unknown behavior to good use.
Water absorption by the hydrogels occurs only when the materials remain below a specific transition temperature. When heated above that temperature, the materials no longer absorb water, eliminating the “stick-slip” phenomenon in the microtubes and allowing them to behave like ordinary tubes.
This ability to turn the stick-slip behavior on and off with temperature could provide a new way to control the flow of water-based liquid in microfluidic devices, including labs-on-a-chip. The transition temperature can be controlled by varying the chemical composition of the hydrogel.
“By locally heating or cooling the polymer inside a microfluidic chamber, you can either speed up the filling process or slow it down,” Fedorov said. “The time it takes for the liquid to travel the same distance can be varied up to three orders of magnitude. That would allow precise control of fluid flow on demand using external stimuli to change polymer film behavior.”
The heating or cooling could be done locally with lasers, tiny heaters, or thermoelectric devices placed at specific locations in the microfluidic devices.
That could allow precise timing of reactions in microfluidic devices by controlling the rate of reactant delivery and product removal, or allow a sequence of fast and slow reactions to occur. Another important application could be controlled drug release in which the desired rate of molecule delivery could be dynamically tuned over time to achieve the optimal therapeutic outcome.
In future work, Fedorov and his team hope to learn more about the physics of the hydrogel-modified capillaries and study capillary flow using partially-transparent microtubes. They also want to explore other “smart” polymers which change the flow rate in response to different stimuli, including the changing pH of the liquid, exposure to electromagnetic radiation, or the induction of mechanical stress – all of which can change the properties of a particular hydrogel designed to be responsive to those triggers.
“These experimental and theoretical results provide a new conceptual framework for liquid motion confined by soft, dynamically evolving polymer interfaces in which the system creates an energy barrier to further motion through elasto-capillary deformation, and then lowers the barrier through diffusive softening,” the paper’s authors wrote. “This insight has implications for optimal design of microfluidic and lab-on-a-chip devices based on stimuli-responsive smart polymers.”
In addition to those already mentioned, the research team included Professor Vladimir Tsukruk from the Georgia Tech School of Materials Science and Engineering and Rajesh Naik, Biotechnology Lead and Tech Advisor of the Nanostructured and Biological Materials Branch of the Air Force Research Laboratory (AFRL).
This research was supported by the Air Force Office of Scientific Research BIONIC Center through awards FA9550-09-1-0162 and FA9550-14-1-0269, AFOSR award FA-9550-14-1-0015, and by Georgia Tech’s Renewable Bioproducts Institute Fellowship. The content is solely the responsibility of the authors and does not necessarily represent the official views of the sponsors.
CITATION: J.E. Silva, et al., “Stick-Slip Water Penetration into Capillaries Coated with Swelling Hydrogel,” (Soft Matter, 11, pp. 5933-5939, 2015).
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]]>Research reported July 15 in the journal Angewandte Chemie International Edition demonstrates that important molecules of contemporary life, known as polypeptides, can be formed simply by mixing amino and hydroxy acids – which are believed to have existed together on the early Earth – then subjecting them to cycles of wet and dry conditions. This simple process, which could have taken place in a puddle drying out in the sun and then reforming with the next rain, works because chemical bonds formed by one compound make bonds easier to form with the other.
The research supports the theory that life could have begun on dry land, perhaps even in the desert, where cycles of nighttime cooling and dew formation are followed by daytime heating and evaporation. Just 20 of these day-night, wet-dry cycles were needed to form a complex mixture of polypeptides in the lab. The process also allowed the breakdown and reassembly of the organic materials to form random sequences that could have led to the formation of the polypeptide chains that were needed for life.
“The simplicity of using hydration-dehydration cycles to drive the kind of chemistry you need for life is really appealing,” said Nicholas Hud, a professor in the School of Chemistry and Biochemistry at the Georgia Institute of Technology, and director of the NSF/NASA Center for Chemical Evolution, which is supported by the NSF Centers for Chemical Innovation Program and the NASA Astrobiology Program. “It looks like dry land would have provided a very favorable environment for getting the chemistry necessary for life started.”
Origin-of-life scientists had previously made polypeptides from amino acids by heating them well past the boiling point of water, or by driving polymerization with activating chemicals. But the high temperatures are beyond the point at which most life could survive, and the robust availability of activating chemicals on the early Earth is questionable. The simplicity of the wet-dry cycle therefore makes it attractive to explain how peptides could have formed, Hud added.
The idea for combining chemically similar amino acids and hydroxyl acids was inspired by the demonstration that polyesters are easy to form by repetitive hydration-dehydration cycles and the fact that esters are activated to attack by the amino group of amino acids. The potential importance of this reaction in the earliest stages of life is supported by studies of meteorites, which revealed that both compounds would have been present on the prebiotic Earth.
Hydroxy acids combine to form polyester, better known as a synthetic textile fiber, and that reaction requires less energy than formation of the amide bonds needed to create peptides from amino acids. In the wet-dry cycles, formation of polyester comes first – which then facilitates the more difficult peptide formation, Hud said.
“The ester linkages that we are making in the polyester can serve as an activating agent formed within the solution,” he explained. “Over the course of a very simple chemical evolution, the polymers progress from having hydroxy acids with ester linkages to amino acids with peptide linkages. The hydroxy acids are gradually replaced through the wet and dry cycles because the ester bonds holding them together are not as stable as the peptide bonds.”
Experimentally, graduate student Sheng-Sheng Yu put the amino and hydroxy acid mixtures through 20 wet-dry cycles to produce molecules that are a mixture of polyesters and peptides, containing as many as 14 units. After just three cycles, and at temperatures as low as 65 degrees Celsius, peptides consisting of two and three units began to form. Postdoctoral fellow Jay Forsythe confirmed the chemical structures using NMR mass spectrometry.
“We allowed the peptide bonds to form because the ester bonds lowered the energy barrier that needed to be crossed,” Hud added.
On the early Earth, those cycles could have taken 20 days and nights – or perhaps much longer if the heating and drying cycles corresponded to seasons of the year.
Beyond easily forming the polypeptides, the wet-dry process has an additional advantage. It allows compounds like peptides to be regularly broken apart and reformed, creating new structures with randomly-ordered amino acids. This ability to recycle the amino acids not only conserves organic material that may have been in short supply on the early Earth, but also provides the potential for creating more useful combinations.
A combination of hydroxy and amino acids likely existed in the prebiotic soup of the early Earth, but analyzing such a “messy” reaction was challenging, Hud said. “We were led into this idea that a mixture might work better than separate components,” he explained. “It might have been messy at the start, but it’s easier to get going than a pristine chemical reaction.”
Beyond helping explain how life might have started, the wet-dry cycles could also provide a new way to synthesize polypeptides. Existing techniques produce the chemicals through genetic engineering of microorganisms, or through synthetic organic chemistry. The wet-dry cycling could provide a simpler and more sustainable water-based process for producing these chemicals.
The demonstration of peptide formation opens the door to asking other questions about how life may have gotten going in prebiotic times, said Ramanarayanan Krishnamurthy, a member of the research team and an associate professor of chemistry at the Scripps Research Institute. Future studies will include a look at the sequences formed, whether there are sequences favored by the process, and what sequences might result. The process could ultimately lead to reactions able to continue without the wet-dry cycles.
“If this process were repeated many times, you could grow up a peptide that could acquire a catalytic property because it had reached a certain size and could fold in a certain way,” Krishnamurthy said. “The system could begin to develop certain emergent characteristics and properties that might allow it to self-propagate.”
In addition to those already named, the paper’s authors include Irena Mamajanov, Martha A Grover, and Facundo M. Fernández, all from Georgia Tech.
This research was supported by the NSF Centers for Chemical Innovation Program and the NASA Astrobiology Program under the NSF/NASA Center for Chemical Evolution under grant number CHE-1004570. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NSF or NASA.
CITATION: Jay G. Forsythe, et al., “Ester-Mediated Amide Bond Formation Driven by Wet-Dry Cycles: A Possible Path to Polypeptides on the Prebiotic Earth,” (Angewandte Chemie International Edition, 2015).
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]]>Recent research has focused on the possibility of using interference effects in phonon waves to control heat transport in materials. Wave interference is already used to control electronic, photonic and acoustic devices. If a similar approach can be used in thermal transport, that could facilitate development of more efficient thermoelectric and nanoelectronic devices, improved thermal barrier coatings, and new materials with ultralow thermal conductivity.
A progress article published June 23 in the journal Nature Materials describes recent developments and predicts future advances in phonon wave interference and thermal bandgap materials.
“If you can make heat behave as a wave and have interference while controlling how far it moves, you could basically control all the properties behind heat transport,” said Martin Maldovan, an assistant professor in the School of Chemical and Biomolecular Engineering and School of Physics at the Georgia Institute of Technology, and the paper’s author. “This would be a completely new way to understand and manipulate heat.”
In the classic definition, heat consists of vibrations in the atomic lattices of materials. The more vibrations in a material’s structure, the hotter the material. And in the same way that white light is actually composed of many different colors of light, these thermal phonons are made up of many different frequencies – each carrying varying amounts of heat.
Recent developments have shown that thermal phonons can interfere with their own reflections. The observation suggests that thermal phonons must exist as waves similar to electronic, photonic or acoustic waves. This interference could potentially be used to modify the velocity of phonons and the density of states, creating energy bandgaps that are forbidden for phonon waves. Utilization of similar bandgaps in optical and electronic materials has been key to developing a wide range of useful devices.
Until now, heat transport in nanostructured materials has largely been controlled by introduction of atomic-scale impurities, interfaces, surfaces and nanoparticles that reduce heat flow by scattering the phonons diffusely. Controlling wave effects could facilitate new approaches involving the specular reflection and transmission of thermal vibrations at interfaces.
“Considering the remarkable success achieved when using electronic, photonic and phononic wave interference to manipulate electrons, light and sound waves, it is certainly valuable to extend these theories to thermal vibrations, thereby creating a fundamentally new approach for manipulating heat flow,” Maldovan wrote in the paper.
Thermoelectric materials capture waste heat from sources such as automobile exhausts or industrial processes to produce electricity. Improving these materials will require further reducing thermal conductivity to improve their efficiency.
On the other hand, microelectronics designers want to increase thermal conductivity to transfer heat away from powerful and tiny devices. Developers of fuel cells and other conversion devices also need to improve the control of heat.
Maldovan wrote the article to clarify issues involved in thermal transport, and to interest others into the field. Ultimately, researchers will use this new information about heat transport to design better materials.
“These new wave phenomena can be used to create materials with low thermal conductivity,” said Maldovan. “We are trying to create a thermal bandgap, but that is not so easy to do.”
The search for thermal phononic wave materials will focus on semiconductors much like those used in microelectronics, Maldovan said. But while the silicon used in microelectronics had a natural bandgap, scientists had to create a band gap in photonics and acoustic materials, and the same will be true for thermal materials. Likely materials include silicon-germanium, gallium and aluminum arsenide and certain oxide superlattices.
Researchers have for many years focused on how far heat may be transported in materials. For the future, research will address the velocity of that transport, and how much heat is moved in the process, Maldovan predicted. He compares heat transport to a more familiar issue – human transportation.
“If you want to move a lot of people, you need a bus that will carry a lot of people,” he said. “You also want a vehicle that can move quickly because if you move faster, you can carry more people farther in less time.”
The next few years should bring about significant clarification concerning the role of interference and bandgaps in thermal materials, Maldovan predicted. That will allow continued progress in the materials needed for thermal control.
“It’s now a very cool thing to understand heat,” he said.
CITATION: Martin Maldovan, “Phononic wave interference and thermal bandgap materials,” (Nature Materials, 2015). http://www.nature.com/nmat/journal/v14/n7/full/nmat4308.html
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]]>At its most basic level, foam is a bunch of bubbles squished together. Liquid foams, a state of matter that arises from tiny gas bubbles dispersed in a liquid, are familiar in everyday life, from beer to bathwater. They also are important in commercial products and processes, including pharmaceutical formulation, oil production, food processing, cleaning products, cosmetics, or hair and skin care products. Lightweight dry foams for the construction of buildings, automobiles and airplanes are key materials in the push for sustainability and energy efficiency. Making lightweight foam has one big challenge, however, keeping the foam stable.
A team of researchers from the Georgia Institute of Technology has developed a new type of foam – called capillary foam – that solves many of the problems faced by traditional foams. The new research shows for the first time that the combined presence of particles and a small amount of oil in water-based foams can lead to exceptional foam stability when neither the particles nor the oil can stabilize the foams alone.
“It’s very difficult to stabilize foams, and we want foams that are stable for months or years,” said Sven Behrens, study co-author and professor in the School of Chemical & Biomolecular Engineering at Georgia Tech. “We’ve developed a way to make foams that is much easier and more broadly applicable that what is traditionally used.”
The study was sponsored by the National Science Foundation (NSF). The research was published online October 3, 2014, in the journal Angewandte Chemie. The new capillary foams were developed by graduate student Yi Zhang, who is co-advised by Behrens and Carson Meredith, also a professor in the School of Chemical & Biomolecular Engineering.
The main ingredients for foam are air and water. Surfactants, which are similar to detergents, are then traditionally added to stabilize foams. Another traditional way to stabilize foam is to add microscopic particles, like talc powder. Both approaches require that the additive have a specific set of properties, which isn’t always possible with the materials available.
The new study demonstrates how the addition of a tiny amount of oil allows the use of particles with more general properties.
“It sounds like we’re making the system more complicated by adding oil to the mix, but it’s a small amount of oil that could be something as simple as vegetable oil,” Meredith said.
The new capillary foams expand the range of particles useful for stabilizing foams that are made of air and water. Air bubbles are stabilized by the combined action of the particles and the small amount of oil. This synergy of oil and particulate is counterintuitive because oils usually decrease foam stability and are commonly used as defoaming agents. But like the water-bridged grains of sand that hold a sand castle together, particles in the capillary foam form a stabilizing network connected by oil bridges.
“This is a novel phenomenon that people haven’t discussed before, so we need to know more about why this works,” Meredith said.
Lightweight dry foams made by this process could be used in many industries, from construction to automobile and airplane manufacturing.
“We’re looking at several different application areas where it could be used as a product,” Behrens said.
This research is supported by the Renewable Bioproducts Institute of Georgia Tech, by the National Science Foundation (awards CBET-1134398 and CBET-1160138), and by the Air Force Office of Scientific Research under award number FA9550-10-1-0555. Any conclusions or opinions are those of the authors and do not necessarily represent the official views of the sponsoring agencies.
CITATION: Yi Zhang, et. al., “A new class of liquid foams stabilized by synergistic action of particles and immiscible liquid.” (September 2014, Angewandte Chemie) http://dx.doi.org/10.1002/ange.201405816
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]]>Georgia Tech is the highest ranked Georgia university on the list. In addition, it is ranked 19th in the world for computer science and 23rd for chemistry. For overall science programs, Georgia Tech ranked 40th in the world according to the ARWU. Georgia Tech’s mathematics programs came in at number 41 in the world, and business programs ranked in the top 75.
Several indicators are used to differentiate the world’s institutions of higher education, including cited researchers, staff and faculty honors, and per capita performance. These rankings, which have been compiled since 2003 by Shanghai Jiao Tong University, are also broken down across disciplines and fields, including engineering, medicine, business, and science majors.
As an internationally recognized technological research university, Georgia Tech contributes vital research, ideas, and innovation to business, industry, government, and academia, regionally, nationally, and around the world.
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Damaged coral reefs emit chemical cues that repulse young coral and fish, discouraging them from settling in the degraded habitat, according to new research. The study shows for the first time that coral larvae can smell the difference between healthy and damaged reefs when they decide where to settle.
Coral reefs are declining around the world. Overfishing is one cause of coral collapse, depleting the herbivorous fish that remove the seaweed that sprouts in damaged reefs. Once seaweed takes hold of a reef, a tipping point can occur where coral growth is choked and new corals rarely settle.
The new study shows how chemical signals from seaweed repel young coral from settling in a seaweed-dominated area. Young fish were also not attracted to the smell of water from damaged reefs. The findings suggest that designating overfished coral reefs as marine protected areas may not be enough to help these reefs recover because chemical signals continue to drive away new fish and coral long after overfishing has stopped.
“If you’re setting up a marine protected area to seed recruitment into a degraded habitat, that recruitment may not happen if young fish and coral are not recognizing the degraded area as habitat,” said Danielle Dixson, an assistant professor in the School of Biology at the Georgia Institute of Technology in Atlanta, and the study's first author.
The study will be published August 22 in the journal Science. The research was sponsored by the National Science Foundation (NSF), the National Institutes of Health (NIH), and the Teasley Endowment to Georgia Tech.
The new study examined three marine areas in Fiji that had adjacent fished areas. The country has established no-fishing areas to protect its healthy habitats and also to allow damaged reefs to recover over time.
Juveniles of both corals and fishes were repelled by chemical cues from overfished, seaweed-dominated reefs but attracted to cues from coral-dominated areas where fishing is prohibited. Both coral and fish larvae preferred certain chemical cues from species of coral that are indicators of a healthy habitat, and they both avoided certain seaweeds that are indicators of a degraded habitat.
The study for the first time tested coral larvae in a method that has been used previously to test fish, and found that young coral have strong preferences for odors from healthy reefs.
"Not only are coral smelling good areas versus bad areas, but they’re nuanced about it," said Mark Hay, a professor in the School of Biology at Georgia Tech and the study's senior author. "They’re making careful decisions and can say, 'settle or don’t settle.'"
The study showed that young fish have an overwhelming preference for water from healthy reefs. The researchers put water from healthy and degraded habitats into a flume that allowed fish to choose to swim in one stream of water or the other. The researchers tested the preferences of 20 fish each from 15 different species and found that regardless of species, family or trophic group, each of the 15 species showed up to an eight times greater preference for water from healthy areas.
The researchers then tested coral larvae from three different species and found that they preferred water from the healthy habitat five-to-one over water from the degraded habitat.
Chemical cues from corals also swayed the fishes' preferences, the study found. The researchers soaked different corals in water and studied the behavior of fish in that water, which had picked up chemical cues from the corals. Cues of the common coral Acropora nasuta enhanced attraction to water from the degraded habitat by up to three times more for all 15 fishes tested. A similar preference was found among coral larvae.
Acropora corals easily bleach, are strongly affected by algal competition, and are prone to other stresses. The data demonstrate that chemical cues from these corals are attractive to fish and corals because they are found primarily in healthy habitats. Chemical cues from hardy corals, which can grow even in overfished habitats, were less attractive to juvenile fishes or corals.
The researchers also soaked seaweed in water and tested fish and coral preferences in that water. Cues from the common seaweed Sargassum polycystum, which can bloom and take over a coral reef, reduced the attractiveness of water to fish by up to 86 percent compared to water without the seaweed chemical cues. Chemical cues from the seaweed decreased coral larval attraction by 81 percent.
"Corals avoided that smell more than even algae that's chemically toxic to coral but doesn't bloom," Dixson said.
Future work will involve removing plots of seaweed from damaged reefs and studying how that impacts reef recovery.
A minimum amount of intervention at the right time and the right place could jump start the recovery of overfished reefs, Hay said. That could bring fish back to the area so they settle and eat the seaweed around the corals. The corals would then get bigger because the seaweed is not overgrown. Bigger corals would then be more attractive to more fish.
"What this means is we probably need to manage these reefs in ways that help remove the most negative seaweeds and then help promote the most positive corals," Hay said.
This research is supported by the National Science Foundation (NSF), under award number OCE-0929119, and the National Institutes of Health, under award number U01-TW007401. Any conclusions or opinions are those of the authors and do not necessarily represent the official views of the sponsoring agency.
CITATION: Dixson et al., "Chemically mediated behavior of recruiting corals and fishes: A tipping
point that may limit reef recovery." (August 2014, Science). http://www.sciencemag.org/content/345/6199/892
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]]>The study discovered a path from simple to complex compounds amid Earth’s prebiotic soup. More than 4 billion years ago, amino acids could have been attached together, forming peptides. These peptides ultimately may have led to the proteins and enzymes necessary for life’s biochemistry, as we know it.
In the new study, scientists analyzed samples from an experiment Miller performed in 1958. To the reaction flask, Miller added a chemical that at the time wasn’t widely thought to have been available on early Earth. The reaction had successfully formed peptides, the new study found. The new study also successfully replicated the experiment and explained why the reaction works.
“It was clear that the results from this old experiment weren’t some sort of artifact. They were real,” said Jeffrey Bada, distinguished professor of marine chemistry at the Scripps Institution of Oceanography at the UC San Diego. Bada was a former student and colleague of Miller’s.
The study was supported by the Center for Chemical Evolution at the Georgia Institute of Technology, which is jointly supported by the National Science Foundation and the NASA Astrobiology Program. The study was published online June 25 in the journal Angewandte Chemie International Edition.The work was primarily a collaboration between UC San Diego and the Georgia Institute of Technology in Atlanta. Eric Parker, the study’s lead author, was an undergraduate student in Bada’s laboratory and is now a graduate student at Georgia Tech.
Jeffrey Bada was Stanley Miller’s second graduate student. The two were close and collaborated throughout Miller’s career. After Miller suffered a severe stroke in 1999, Bada inherited boxes of experimental samples from Miller’s lab. While sorting through the boxes, Bada saw “electric discharge sample” in Miller’s handwriting on the outside of one box.
“I opened it up and inside were all these other little boxes,” Bada said. “I started looking at them, and realized they were from all his original experiments; the ones he did in 1953 that he wrote the famous paper in Science on, plus a whole assortment of others related to that. It’s something that should rightfully end up in the Smithsonian.”
The boxes of unanalyzed samples had been preserved and carefully marked, down to the page number where the experiment was described in Miller’s laboratory notebooks. The researchers verified that the contents of the box of samples were from an electric discharge experiment conducted with cyanamide in 1958 when Miller was at the Department of Biochemistry at the College of Physicians and Surgeons, Columbia University.
An electric discharge experiment simulates early Earth conditions using relatively simple starting materials. The reaction is ignited by a spark, simulating lightning, which was likely very common on the early Earth.
The 1958 reaction samples were analyzed by Parker and his current mentor, Facundo M. Fernández, a professor in the School of Chemistry and Biochemistry at Georgia Tech. They conducted liquid chromatography- and mass spectrometry-based analyses and found that the reaction samples from 1958 contained peptides. Scientists from NASA’s Johnson Space Center and Goddard Space Flight Center were also involved in the analysis.
The research team then set out to replicate the experiment. Parker designed a way to do the experiment using modern equipment and confirmed that the reaction created peptides.
“What we found were some of the same products of polymerization that we found in the original samples,” Parker said. “This corroborated the data that we collected from analyzing the original samples.”
In the experiment from 1958, Stanley Miller had the idea to use the organic compound cyanamide in the reaction. Scientists had previously thought that the reaction with cyanamide would work only in acidic conditions, which likely wasn’t widely available on early Earth. The new study showed that reactive intermediates produced during the synthesis of amino acids enhanced peptide formation under the basic conditions associated with the spark discharge experiment.
“What we’ve done is shown that you don’t need acid conditions; you just need to have the intermediates involved in amino acid synthesis there, which is very reasonable,” Bada said.
Why Miller added cyanamide to the reaction will probably never be known. Bada can only speculate. In 1958, Miller was at Columbia University in New York City. Researchers at both Columbia and the close-by Rockefeller Institute were at the center of studies on how to analyze and make peptides and proteins in the lab, which had been demonstrated for the first time in 1953 (the same year that Miller published his famous origin of life paper). Perhaps while having coffee with colleagues someone suggested that cyanamide – a chemical used in the production of pharmaceuticals – might have been available on the early Earth and might help make peptides if added to Miller’s reaction.
“Everybody who would have been there and could verify this is gone, so we’re just left to scratch our heads and say ‘how’d he get this idea before anyone else,’” Bada said.
The latest study is part of an ongoing analysis of Stanley Miller’s old experiments. In 2008, the research team found samples from 1953 that showed a much more efficient synthesis than Stanley published in Science in 1953. In 2011, the researchers analyzed a 1958 experiment that used hydrogen sulfide as a gas in the electric discharge experiment. The reactions produced a more diverse array of amino acids that had been synthesized in Miller’s famous 1953 study. Eric Parker was the lead author on the 2011 study.
“It’s been an amazing opportunity to work with a piece of scientific history,” Parker said.
This research is supported by the Center for Chemical Evolution at the Georgia Institute of Technology, which is jointly supported by the National Science Foundation and the NASA Astrobiology Program under award number NSF CHE-1004570. Any conclusions or opinions are those of the authors and do not necessarily represent the official views of the sponsoring agencies.
CITATION: Eric T. Parker, et al., “A Plausible Simultaneous Synthesis of Amino Acids and Simple Peptides on the Primordial Earth.” (Angewandte Chemie, June 2014). http://dx.doi.org/10.1002/anie.201403683
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]]>Around 4 billion years ago, the first molecules of life came together on the early Earth and formed precursors of modern proteins and RNA. Scientists studying the origin of life have been searching for clues about how these reactions happened. Some of those clues have been found in the ribosome.
The core of the ribosome is essentially the same in all living systems, while the outer regions expand and become complicated as species gain complexity. By digitally peeling back the layers of modern ribosomes in the new study, scientists were able to model the structures of primordial ribosomes.
“The history of the ribosome tells us about the origin of life,” said Loren Williams, a professor in the School of Chemistry and Biochemistry at the Georgia Institute of Technology. “We have worked out on a fine level of detail how the ribosome originated and evolved.”
The study was sponsored by the NASA Astrobiology Institute and the Center for Ribosomal Origins and Evolution at Georgia Tech. The results were published June 30 in the journal Proceedings of the National Academy of Sciences.
In biology, the genetic information stored in DNA is transcribed into mRNA, which is then shipped out of the cell nucleus. Ribosomes, in all species use mRNA as a blueprint for building all the proteins and enzymes essential to life. The ribosome’s job is called translation.
The common core of the ribosome is essentially the same in humans, yeast, bacteria and archaea – in all living systems. The Georgia Tech team has shown that as organisms evolve and become more complex, so do their ribosomes. Humans have the largest and most complex ribosomes. But the changes are on the surface – the heart of a human ribosome the same as in a bacterial ribosome.
“The translation system is the operating system of life,” Williams said. “At its core the ribosome is the same everywhere. The ribosome is universal biology.”
In the new study, Williams and Research Scientist Anton Petrov compared three-dimensional structures of ribosomes from a variety of species of varying biological complexity, including humans, yeast, bacteria and archaea. The researchers found distinct fingerprints in the ribosomes where new structures were added to the ribosomal surface without altering the pre-existing core.
Additions to the ribosome cause insertion fingerprints. Much like a botanist can carve back twigs and branches on a tree to learn about its growth and age, Petrov and Williams show how segments were continually added to the ribosome without changing the underlying structure. The research team extrapolated the process backwards in time to generate models of simple, primordial ribosomes.
“We learned some of the rules of the ribosome, that evolution can change the ribosome as long as it does not mess with its core,” Williams said. “Evolution can add things on, but it can’t change what was already there.”
For a video on the origins and evolution of the ribosome, visit: https://www.youtube.com/watch?v=ei6qGLBTsKM
This research is supported by the NASA Astrobiology Institute under award number NNA09DA78A. Any conclusions or opinions are those of the authors and do not necessarily represent the official views of the sponsoring agency.
CITATION: Anton S. Petrov, et al., “Evolution of the Ribosome at Atomic Resolution.” (June 2014, PNAS) http://www.pnas.org/cgi/doi/10.1073/pnas.1407205111
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]]>The researchers believe the process can be scaled up to inexpensively provide large membrane surface areas in compact modules. By replacing energy-intensive distillation or cryogenic techniques, these molecular sieving membranes could cut the cost of gaseous and liquid separations, reduce energy consumption – and lead to industrial processes that generate less carbon dioxide. The researchers have demonstrated that membranes produced with the new technique can separate hydrogen from hydrocarbon mixtures, and propylene from propane.
Development of the membrane fabrication methodology was described in the July 4, 2014, issue of the journal Science.
“This work opens up new ways of fabricating molecular sieving separation membranes using microscopic hollow fibers as a platform,” said Sankar Nair, a professor in the School of Chemical & Biomolecular Engineering at the Georgia Institute of Technology, and one of the paper’s co-authors. “Many of the separations that currently are done with energy-intensive techniques could one day be performed with membranes fabricated by a scaled-up version of our methodology.”
Energy-intensive separation processes are widely used in the industrial production of petro-based and bio-based fuels and chemicals, as well as a variety of other technological materials. The most common separation technique is distillation, which applies heat to chemical mixtures to drive off specific molecules according to their boiling points. Other techniques, such as crystallization, involve cooling to lower temperatures to separate the molecules from the mixtures.
In contrast, molecular sieving membranes use semipermeable materials to separate molecules from mixtures that are produced by chemical reactions or found in raw material feedstocks. The process may be driven by a pressure gradient, and relies on the membranes to preferentially pass certain molecules through their pore structures. Crystalline materials known as zeolites have been fabricated into membranes, but high membrane fabrication costs and a limited selection of materials have prevented their widespread use.
Metal-organic framework (MOF) materials offer an alternative with more benign fabrication methods and many thousands of material types available. But before MOF membranes could be used on a large scale, researchers had to find ways of producing them at low cost in large volumes.
The Georgia Tech technique for producing MOF membranes takes advantage of the large surface area that can be obtained by using large numbers of hollow fibers spun from inexpensive polymers. For instance, a one cubic meter hollow-fiber membrane module could contain as much as 10,000 square meters of membrane area.
The new fabrication process relies on a microfluidic technique for bringing the different reactants needed to form MOF membranes into contact inside the fibers. The inner diameter of the fibers may be 100 microns or less, limiting the amount of reactants present and changing the interplay of the physical and chemical forces that control membrane formation. By adjusting the flow and positioning of the reactants and their solvents, the researchers learned to control the location of the MOF membrane films, allowing their formation on the inside or outside of the fibers – and even within the structure of the fibers.
“We have combined a high-performance MOF material with a new fabrication technique to come up with a membrane that can be scaled up in an inexpensive way,” Nair explained. “A key realization behind this development is that if you want to scale up MOF membrane growth using hollow fiber modules, you have to first learn how to scale down their growth in the microscopic environments of individual hollow fibers.”
Once the researchers learned to fabricate a functional membrane using a single hollow fiber, they could simultaneously fabricate membranes in parallel on multiple hollow fibers that were pre-assembled into a module. The research reported in the journal produced membrane films made of the MOF ZIF-8 inside three fibers simultaneously. Ultimately, Nair believes large bundles of the polymer fibers could be pre-assembled into modules and then coated simultaneously with molecular sieving MOF membranes.
An important next step for the research is to develop a better microscopic understanding of the process.
“To optimize this technique and scale it up to thousands or even millions of fibers at a time, we need to dig deeper to understand how the chemical reactions and molecular transport processes leading to membrane formation can be controlled under the microscopic conditions that exist within the fibers,” Nair said.
Though the researchers have so far demonstrated the functionality of their membranes in gaseous separation processes of interest to the petrochemical industry, the membrane processing technique could have broader applications.
“The approach we have developed could open the door to a whole new class of molecular sieving, polycrystalline film membranes,” said Christopher Jones, a professor in the School of Chemical & Biomolecular Engineering and another of the paper’s co-authors. “Such membranes could revolutionize how oil and chemical companies carry out gas and liquid separations, for example, by replacing energy-intensive and expensive cryogenic distillation processes with more energy-friendly membrane separations.”
In addition to those already mentioned, the research team included first author Andrew J. Brown, a graduate student in the Georgia Tech School of Chemistry and Biochemistry. Other researchers included William J. Koros, a professor in the School of Chemical & Biomolecular Engineering; Nicholas A. Brunelli, now an assistant professor in the Department of Chemical and Biomolecular Engineering at The Ohio State University; Kiwon Eum, a graduate student in the Georgia Tech School of Chemical & Biomolecular Engineering; postdoctoral fellow Fereshteh Rashidi; and researcher J.R. Johnson, who is now at SABIC.
This work was supported by Phillips 66 Company.
CITATION: Andrew J. Brown, et al., “Interfacial Microfluidic Processing of Metal-Organic Framework Hollow Fiber Membranes, (Science 2014).
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]]>“We are extremely grateful to the Institute of Paper Chemistry Foundation for entrusting us with this generous gift,” said Georgia Tech President G.P. “Bud” Peterson. “Through the Renewable Bioproducts Institute, we will maximize Georgia Tech’s and the state of Georgia’s strengths in sustainability and innovation to develop real-world applications as well as educate the next generation of leadership in the forest and bioproducts industry.”
The Institute of Paper Chemistry Foundation represents the legacy of the Institute of Paper Chemistry (IPC), founded in Appleton, Wisconsin, in 1929 to provide scientific research and future leaders for the paper industry. IPC became the Institute of Paper Science and Technology (IPST) when it relocated to Atlanta in 1989. It subsequently merged with Georgia Tech in 2004.
Last week, Georgia Tech announced that the Institute would be renamed the Renewable Bioproducts Institute (RBI) to reflect its expanding engagement with a broader range of biomaterials processing industries. Like the university’s other nine interdisciplinary research institutes representing Georgia Tech’s core research areas, RBI brings together a multidisciplinary capability to identify opportunities and address the complex challenges of its industry and government research partners.
“We believe the relaunching of the Institute as the Renewable Bioproducts Institute is a natural development in its evolution and an important advance in its progress,” said IPCF board chair George Lanier. “Georgia Tech is demonstrating its commitment to this industry, which is so important to Georgia and the nation. The industry’s emerging opportunities can be effectively developed there.”
All interdisciplinary research institutes at Georgia Tech are designed to facilitate research collaborations with industries and other partners to develop opportunities in strategic market areas, emphasizing economic development and applied technology.
“We deeply appreciate the confidence IPCF has placed in us,” said RBI executive director Norman Marsolan, “and we will continue its legacy of growth in bioproducts research and industry leadership development. We are on the threshold of a new era of development of this renewable, sustainable natural resource, and we pledge our efforts to justify IPCF’s faith in us by contributing to the full realization of its potential.”
The Renewable Bioproducts Institute benefits from a significant endowment originating with the Institute of Paper Chemistry. That endowment has contributed to the support of more than 1,500 graduate alumni through the years and currently supports more than 50 paper science and engineering students who advance the research mission of IPST/RBI through their faculty-directed research. RBI will continue to build on that legacy by working closely with industrial partners to foster an innovative, competitive and profitable bioproducts industry, while the endowment will continue to support graduate studies in paper science and engineering.
For more information on RBI, please visit http://www.news.gatech.edu/features/renewable-bioproducts-institute.
]]>The current design integrates nanotechnology and radio-frequency identification (RFID) capabilities into a small working prototype. An array of sensors uses carbon nanotubes and other nanomaterials to detect specific chemicals, while an RFID integrated circuit informs users about the presence and concentrations of those vapors at a safe distance wirelessly.
Because it is based on programmable digital technology, the RFID component can provide greater security, reliability and range – and much smaller size – than earlier sensor designs based on non-programmable analog technology. The present GTRI prototype is 10 centimeters square, but further designs are expected to squeeze a multiple-sensor array and an RFID chip into a one-millimeter-square device printable on paper or on flexible, durable substrates such as liquid crystal polymer.
“Production of these devices promises to become so inexpensive that they could be used by the thousands in the field to look for telltale chemicals such as ammonia, which is associated with explosives," said Xiaojuan (Judy) Song, a GTRI senior research scientist who is principal investigator on the project. "This remote capability would inform soldiers or first responders about numerous hazards before they encountered them."
Wireless sensors could also be valuable for identifying and understanding air pollution, she said. Inexpensive sensors that detect ammonia and nitrogen oxides (NOx) could be fielded in large numbers, giving scientists increased knowledge of the location and intensity of pollutants.
The availability of such chips might also help companies detect food spoilage. And healthcare facilities could benefit, as the presence of telltale chemicals informed caregivers of patient conditions and needs.
The present prototype contains three sensors along with an RFID chip. Future devices for field use might contain a much larger number of sensors based on various nanomaterials – including carbon nanotubes, graphene and molybdenum disulfide – depending on the types of chemicals to be detected.
"In general, having an extensive sensing array is the best approach," Song said. "For real-world applications, a variety of sensors offers better functionality, because they can work together to produce a more detailed and reliable picture of the chemical environment."
The RFID component in the GTRI device makes use of the 5.8 gigahertz (GHz) radio frequency, one of several radio bands reserved for industrial, scientific and medical (ISM) purposes. The GTRI component is believed to be the first RFID system that exploits this frequency.
The advantage of 5.8 GHz technology is that it will let RFID tags be made extremely small – in the area of one centimeter square, said Christopher Valenta, a GTRI research engineer who is co-principal investigator on the project. He explained that the digital transmission of data from RFID-based sensors does a much better job than earlier analog techniques based on interpretation of radio-frequency waveforms.
Specifically, digital signaling with 5.8 GHz RFID offers:
The GTRI team is currently gearing up to design a very small, 5.8 GHz RFID component. After fabrication and testing, the chip could be manufactured in large numbers inexpensively.
"It might take $400,000 to design and fabricate that first RFID chip, but all the subsequent copies might cost only a few pennies," said Valenta, who is a Ph.D. candidate in the School of Electrical and Computer Engineering.
The GTRI team successfully tested its prototype sensing system in a demonstration designed to resemble an airport checkpoint. The sensor array detected the targeted chemical despite emersion in a complex chemical environment, and the RFID component was able to transmit the sensors' readings.
The present GTRI prototype is semi-passive, so it requires power from an incoming signal beam in order to send data back to a remote reading device. However, future sensing devices might exploit ambient energy from solar or vibrational sources that would let them work at longer ranges with greater sensitivity.
The team is continuing to work on the important task of developing pattern recognition software that will support effective functioning of the sensor array.
"The prototype 5.8 GHz wireless sensing system promises to be flexible and highly scalable," Valenta said. "An advanced design might include an array of 10 or more different sensors, with electronics that could utilize those sensors to perform 25 different jobs, and yet still be tiny, robust and inexpensive."
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]]>In a proof-of-concept study, scientists selected a region for analysis on round or irregularly-shaped objects using a 3-D camera on a robotic arm, which mapped the 3-dimentional coordinates of the sample’s surface. The scientists programmed the robotic arm to poke the sample with an acupuncture needle. The needle collected a small amount of material that the robot deposited in a nearby mass spectrometer, which is a powerful tool for determining a substance’s chemical composition.
“You see the object on a monitor and then you can point and click and take a sample from a particular spot and the robot will go there,” said Facundo Fernandez, a professor in the School of Chemistry and Biochemistry, whose lab led the study. “We’re using an acupuncture needle that will touch very carefully on the surface of the object and then the robot will turn around and put the material inside of a high resolution mass spectrometer.”
The research was published online February 28 in the journal Analyst, a publication of the Royal Society of Chemistry. The research will be featured on the cover of an upcoming print issue. The work was supported by a National Science Foundation (NSF) Major Research Instrumentation Program (MRI) grant and by the National Science Foundation (NSF) and NASA Astrobiology Program, under the NSF Center for Chemical Evolution.
Mass spectrometry is a powerful tool for analyzing surface chemistry or for identifying biological samples. It’s widely used in research labs across many disciplines, but samples for analysis typically have to be cleaned, carefully prepared, and in the case of rocks, cut into thin, flat samples. The new robotic system is the first report of a 3-D mass spectrometry native surface imaging experiment.
“Other people have used an acupuncture needle to poke a sample and then put that in mass spec, but nobody has tried to do a systematic, three-dimensional surface experiment,” Fernandez said. “We are trying to push the limits.”
To show that the system was capable of probing a three-dimensional object, the researchers imprinted ink patterns on the surfaces of polystyrene spheres. The team then used the robotic arm to model the surfaces, probe specific regions, and see if samples collected were sufficient for mass spectrometry analysis. The researchers were able to detect inks of different colors and create a 3-D image of the object with sufficient sensitivity for their proof-of-principle setup, Fernandez said.
The research was the result of collaboration between Fernandez’s group, which specializes in mass spectrometry, and Henrik Christensen’s robotics group in the College of Computing. Christensen is the KUKA Chair of Robotics and a Distinguished Professor of Computing. He is also the executive director of the Institute for Robotics and Intelligent Machines (IRIM) at Georgia Tech.
“The initial findings of this study mark a significant step toward using robots for three-dimensional surface experiments on geological material,” Christensen said. “We are using the repeatability and accuracy of robots to achieve new capabilities that have numerous applications in biomedical areas such as dermatology.”
“It doesn’t happen very often that a group in mass spectrometry will have a very talented robotics group next to them,” Fernandez said. “If we tried to learn the robotics on our own it could take us a decade, but for them it’s something that’s not that difficult.”
Christensen’s team loaned a Kuka KR5 sixx R650 robot to Fernandez’s lab for the study. Afterwards, Fernandez’s lab purchased their own robot from Universal Robots. They have also upgraded to a new mass spectrometer capable of resolution nearly eight times higher than the one used in the study. They will soon begin replicating early Earth chemistry on rocks and analyzing the reaction products with their robotic sampling system.
“We really want to look at rocks,” Fernandez said. “We want to do reactions on rocks and granites and meteorites and then see what can be produced on the surface.”
The technology could also be applied to other research fields, Fernandez said. For example, the robot-mass spec combo might be useful to dermatologists who often probe lesions on the skin, which have distinct molecular signatures depending on if the lesion is a tumor or normal skin tissue.
This research is supported by the American Recovery and Reinvestment Act (ARRA) under the National Science Foundation (NSF) Major Research Instrumentation Program (MRI) (Grant number 0923179), and by the NSF and NASA Astrobiology Program under the NSF Center for Chemical Evolution (CHE-1004579). Any conclusions or opinions are those of the authors and do not necessarily represent the official views of the sponsoring agencies.
CITATION: Rachel V. Bennett, et al., “Robotic Plasma Probe Ionization Mass Spectrometry (RoPPI-MS) of Non-Planar Surfaces.” (Analyst, February 2014) http://dx.doi.org/10.1039/c4an00277f
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]]>By inserting enzymes from trees into the bacterium, first author and Georgia Tech graduate student Stephen Sarria, working under the guidance of assistant professor Pamela Peralta-Yahya, boosted pinene production six-fold over earlier bioengineering efforts. Though a more dramatic improvement will be needed before pinene dimers can compete with petroleum-based JP-10, the scientists believe they have identified the major obstacles that must be overcome to reach that goal.
Funded by Georgia Tech startup funds awarded to Peralta-Yahya’s lab and by the U.S. Department of Energy’s Office of Science, the research was reported February 27, 2014, in the journal ACS Synthetic Biology.
“We have made a sustainable precursor to a tactical fuel with a high energy density,” said Peralta-Yahya, an assistant professor in the School of Chemistry and Biochemistry and the School of Chemical and Biomolecular Engineering at Georgia Tech. “We are concentrating on making a ‘drop-in’ fuel that looks just like what is being produced from petroleum and can fit into existing distribution systems.”
Fuels with high energy densities are important in applications where minimizing fuel weight is important. The gasoline used to power automobiles and the diesel used mainly in trucks both contain less energy per liter than the JP-10. The molecular arrangement of JP-10, which includes multiple strained rings of carbon atoms, accounts for its higher energy density.
The amount of JP-10 that can be extracted from each barrel of oil is limited, and sources of potentially comparable compounds such as trees can’t provide much help. The limited supply drives the price of JP-10 to around $25 per gallon. That price point gives researchers working on a biofuel alternative a real advantage over scientists working on replacing gasoline and diesel.
“If you are trying to make an alternative to gasoline, you are competing against $3 per gallon,” Peralta-Yahya noted. “That requires a long optimization process. Our process will be competitive with $25 per gallon in a much shorter time.”
While much research has gone into producing ethanol and bio-diesel fuels, comparatively little work has been done on replacements for the high-energy JP-10.
Peralta-Yahya and collaborators set out to improve on previous efforts by studying alternative enzymes that could be inserted into the E. coli bacterium. They settled on two classes of enzymes – three pinene synthases (PS) and three geranyl diphosphate synthases (GPPS) – and experimented to see which combinations produced the best results.
Their results were much better than earlier efforts, but the researchers were puzzled because for a different hydrocarbon, similar enzymes produced more fuel per liter. So they tried an additional step to improve their efficiency. They placed the two enzymes adjacent to one another in the E. coli cells, ensuring that molecules produced by one enzyme would immediately contact the other. That boosted their production to 32 milligrams per liter – much better than earlier efforts, but still not competitive with petroleum-based JP-10.
Peralta-Yahya believes the problem now lies with built-in process inhibitions that will be more challenging to address.
“We found that the enzyme was being inhibited by the substrate, and that the inhibition was concentration-dependent,” she said. “Now we need either an enzyme that is not inhibited at high substrate concentrations, or we need a pathway that is able to maintain low substrate concentrations throughout the run. Both of these are difficult, but not insurmountable, problems.”
To be competitive, the researchers will have to boost their production of pinene 26-fold. Peralta-Yahya says that’s within the range of possibilities for bioengineering the E. coli.
“Even though we are still in the milligrams per liter level, because the product we are trying to make is so much more expensive than diesel or gasoline means that we are relatively closer,” she said.
Theoretically, it may be possible to produce pinene at a cost lower than that of petroleum-based sources. If that can be done – and if the resulting bio-fuel operates well in these applications – that could open the door for lighter and more powerful engines fueled by increased supplies of high-energy fuels. Pinene dimers, which result from the dimerization of pinene, have already been shown to have an energy density similar to that of JP-10.
Co-authors from the Joint BioEnergy Institute included Betty Wong, Hector Garcia Martin and Professor Jay D. Keasling, co-corresponding author of the paper.
CITATION: Stephen Sarria, et al., “Microbial Synthesis of Pinene,” (ACS Synthetic Biology, 2014). (http://dx.doi.org/10.1021/sb4001382).
This work was started at the DOE Joint BioEnergy Institute (JBEI) and finished at the Georgia Institute of Technology. The work at JBEI was funded by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research through contract DE-AC02-05CH11231 between Lawrence Berkeley National Laboratory and the U.S. Department of Energy. The work at the Georgia Institute of Technology was funded by startup funds awarded to the Peralta-Yahya laboratory. Any opinions expressed are those of the authors and do not necessarily represent the official views of the DOE.
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]]>What’s more, the new version will enable Apple iOS and Google Android mobile devices to run the software. Previously, the software worked only on Windows-based desktop and laptop computers. The Chemical Companion Decision Support System can be downloaded at (www.chemicalcompanion.org).
Although Chemical Companion originally targeted first responders in fire and rescue departments, today forensic teams and bomb squads also use it. Funded by the U.S. federal government’s Technical Support Working Group, U.S. Marine Corps Systems Command and Australia’s Department of the Prime Minister and Cabinet (now managed by the country’s Defence Science and Technology Organisation), the software is free to the military, law enforcement and fire departments. More than 1,200 active accounts are registered at ChemicalCompanion.org, with users in the United States, Australia, Canada, the United Kingdom, the Netherlands and Israel.
Whether the hazmat scene is due to a gas explosion, chemical spill, terrorist incident or bomb threat, the Chemical Companion helps mitigate risk. For example, a bomb squad can use it to determine potential scene blast, fragmentation and personnel standoff distances. It helps first responders decide how to decontaminate the scene and provide medical aid to victims. It also helps them determine what kind of protective equipment they need to wear and how long they can stay in a hot zone.
From E-reader to Integrated Toolkit
“When we first introduced the Chemical Companion, it functioned as an information portal with basic e-reader functionality that enabled first responders to access information without lugging a dozen or more books around with them,” said Gisele Bennett, director of the Georgia Tech Research Institute’s (GTRI) Electro-Optical Systems Lab and Chemical Companion’s principal investigator.
By entering details about a substance’s physical appearance or victims’ medical symptoms, the software allowed users to identify unknown chemicals at a hazmat scene and obtain information about their effects. “Today, however, Chemical Companion is more than just an information resource,” she said. “It has become a sophisticated decision-support system.”
Indeed, in the last two years, GTRI researchers have been developing a series of unique tools to enhance the Chemical Companion’s capabilities. These include, for example:
The respiratory protection tool – Released in August 2012, the respiratory protection tool takes users through a series of questions about environmental conditions and hazardous materials that may be present at a hazmat scene. The final screen delivers a recommendation on what type of respiratory protection is required. Respiratory protection comes in many forms, ranging from a half-face mask to a self-contained breathing apparatus (SCBA).
“Selection of the right equipment for a given environment can be confusing, so most first responders default to an SCBA which is heavy and restrictive,” explained Heyward Adams, a GTRI research scientist who serves as technical lead on the project. “The Chemical Companion’s respiratory protection tool allows users to determine the appropriate equipment to wear – providing full protection from the airborne threats with the minimum amount of equipment.”
The detection tool – First responders carry a variety of detector devices to help determine what chemical, biological and radiological threats may be present at a hazmat scene. The Chemical Companion’s detection tool augments the performance of these detectors by:
Taking measurements at a hazmat scene is no easy task, Adams said, noting that different detectors deliver readouts in different formats, such as a series of bars, parts per million or a color. “Unless you’re an expert in chemistry, these readouts are not easy to decipher,” he observed. “The Chemical Companion’s detection tool helps you know how to interpret the results and what to do with that information.”
Currently the Chemical Companion has more than 19 tools that have either launched or are being tested. Many of these tools complement each other, prompting researchers to investigate their integration. “The output of one tool could be the input for another,” Adams said. “Yet users might not realize that, so we’re creating links to make overlaps more intuitive.”
Users Drive New Features
Working closely with users has been critical to the Chemical Companion’s success.
In addition to rigorous testing and user trials before any new release, GTRI researchers host an annual workshop for users. This week-long event is instrumental in collecting feedback about the software’s structure and usability – whether it’s for developing a brand new tool or improving an existing feature.
“The workshops allow us to go through calculations of situations with different user groups,” said Bennett. “A forensics officer will approach a scene very differently than a first-responder or a firefighter.”
With that in mind, GTRI researchers have developed user preferences for three different audiences, along with country preferences that automatically populate national standards and units of measurement for the United States and Australia.
Another recent development sparked by the annual workshops is a tool for generating reports. Introduced in 2012, Chemical Companion’s Report Builder exports a PDF file that includes situational information, calculations and outputs performed by the software – even custom notes. “In some cases, this file becomes the actual after-action report that users turn in to their departments,” said Adams.
Beyond the Hazmat Scene
Because the Chemical Companion’s tools comprise multiple screens posing various questions and considerations, it has become an important training tool, points out Michael Logan, chief superintendent and scientific branch director of the Queensland Fire and Rescue Service in Brisbane, Australia. “It assists exercise writers with both the construction and accuracy of training scenarios,” explained Logan, who provides GTRI with research data and serves as a subject matter expert.
The tool also helps with emergency pre-planning, Logan said, explaining that the Chemical Companion can help estimate resources required or the effects of actions on an incident. “It enables users to challenge assumptions about incidents and the approaches that might be adopted to manage the emergencies.”
“The Chemical Companion’s combination of information and tools in one easy-to-use package makes a huge difference to users,” he continued. “It provides confidence to first responders about their safety and the communities they serve – as well as their actions. The software delivers consistent results no matter what the experience or expertise of the user during a very stressful time.”
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]]>The research, which involved nearly 100 people recruited in the metropolitan Atlanta area, found that test subjects could successfully apply a prototype vaccine patch to themselves. That suggests the self-administration of vaccines with microneedle patches may one day be feasible, potentially reducing administration costs and relieving an annual burden on health care professionals.
The study also suggested that the use of vaccine patches might increase the rate at which the population is vaccinated against influenza. After comparing simulated vaccine administration using a patch and by conventional injection, the percentage of test subjects who said they’d be vaccinated grew from 46 percent to 65 percent.
“Our dream is that each year there would be flu vaccine patches available in stores or sent by mail for people to self-administer,” said Mark Prausnitz, a Regent’s professor in the School of Chemical and Biomolecular Engineering at the Georgia Institute of Technology. “People could take them home and apply them to the whole family. We want to get more people vaccinated, and we want to relieve health care professionals from the burden of giving these millions of vaccinations.”
The research on patient acceptance of vaccine patch immunization was published online February 11, 2014, by the journal Vaccine and will appear in a later edition of the print journal. In addition to Georgia Tech researchers, the project also included scientists from Emory University and the Centers for Disease Control and Prevention (CDC). Research into the use of microneedle patches for influenza vaccination has been supported by the National Institutes of Health (NIH).
The study is believed to be the first published report of a head-to-head comparison between microneedle patches and traditional intramuscular injection for the administration of vaccines in human subjects. The patches consisted of arrays of 50 microscopic needles about as tall as the thickness of a few hairs. When used for vaccination, the patches would be pressed painlessly onto a person’s forearm to carry vaccine into the outer layers of skin, where they would prompt an immune reaction from the body.
The 91 study subjects, who had no previous experience with microneedle patches, were given brief instructions on applying the patches to themselves. Each volunteer applied three patches, had a fourth patch applied by a member of the research team, and received an injection of saline with a conventional hypodermic needle. Neither the patches nor the hypodermic needle actually carried a vaccine, and the study did not assess the efficacy of using microneedle patches for vaccinations in humans.
The researchers evaluated how well the volunteers were able to self-administer the microneedle patches. After the subjects pressed the patches into their skin, the researchers applied a dye to highlight the tiny holes made by the microneedles. By photographing the administration sites and counting the number of holes, they were able to assess the accuracy of the application.
“We found that everyone was capable of administering a microneedle patch appropriately, though not everyone did on the first try,” Prausnitz said.
Some of the subjects used an applicator that made a clicking sound when sufficient force was applied to the patch. Use of that feedback device improved the ability of subjects to correctly apply patches and virtually eliminated administration mistakes.
During the study, the volunteers were asked if they planned to receive a flu vaccination in the next year and if their intent to be vaccinated would change if it could be done with the patch. The percentage saying they’d be vaccinated jumped from 46 to 65 percent when the patch was an option.
“If this holds for the population as a whole, that would have a tremendous impact on preventing disease and the cost associated with both influenza and the vaccination process,” said Paula Frew, an assistant professor in the Emory University School of Medicine and a co-author of the study.
Interviewing the test subjects found strong support for self-administration of the flu vaccine.
“In addition to the preference for the vaccine patch, we found that a large majority of the people willing to be vaccinated would choose to self-administer the vaccine,” said James Norman, the study’s first author, who was a Georgia Tech graduate student when the research was conducted.
Study participants were asked to assess the pain associated with administering the patch and receiving the intramuscular injection. On a scale of one to 100, they rated the patches 1.5 on average, while the injection was rated 15.
Less than half the U.S. population receives vaccination against influenza each year. Several thousand Americans die of complications from the flu each year, and as many as 200,000 are hospitalized. Increasing the immunization rate could cut the deaths, hospitalizations and costs associated with the disease, Prausnitz noted.
Use of a vaccine patch could potentially also reduce the cost of vaccination programs. For influenza, the cost of storing and administering the vaccine – along with patient time to visit a clinic – accounts for as much as three-quarters of the total cost. If microneedle vaccine patches could be produced for about the same cost as current flu vaccines, self-administration could provide significant cost savings to the nation’s health care system.
Animal studies have shown that microneedle patches are at least as good as conventional intramuscular injections at conferring immunity to influenza. Prausnitz and his research team plan to begin a Phase 1 clinical study of the vaccine patches in humans during the spring of 2015. If that study shows promise, it could lead to larger studies and development of commercial patch manufacture.
If all goes well, the vaccine patch could be available within five years. Prausnitz expects it to be administered first by health care professionals before being made available for self-administration.
In addition to those already named, the study also involved Martin I. Meltzer, senior health economist with the CDC, and two Georgia Tech researchers: Jaya M. Arya and Maxine A. McClain.
Mark Prausnitz is an inventor on patents that have been licensed to companies developing microneedle-based products, is a paid advisor to companies developing microneedle-based products, and is a founder/shareholder of companies developing microneedle-based products. This potential conflict of interest has been disclosed and is managed by Georgia Tech and Emory University.
Research on the use of microneedle patches for influenza vaccination has been supported by the National Institute of Biomedical Imaging and Bioengineering, part of the National Institutes of Health (NIH/NIBIB), under award R01EB006369. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.
CITATION: James J. Norman, et al., “Microneedle Patches: Usability and Acceptability for Self-Vaccination Against Influenza,” (Vaccine, 2014). (http://dx.doi.org/10.1016/j.vaccine.2014.01.076)
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]]>The Georgia ImmunoEngineering Consortium (GIEC) will bring together engineers, physicians, chemists, physicists, computational scientists, immunologists and clinical investigators to better understand how the immune system works and how to precisely modulate it to target challenging diseases.
The research teams will focus on cancer, infectious diseases, autoimmune and inflammatory disorders (diabetes, lupus, multiple sclerosis, arthritis, fibrosis, asthma, inflammatory bowel disease, etc.), and areas of regenerative medicine including transplantation, bone and cartilage repair, and treatments for spinal cord injuries.
“The immune system and its multi-faceted role in human health and disease form the cornerstone of medical research, says Ignacio Sanz, MD, co-chair of the consortium steering committee. Sanz is Mason I. Lowance Chair of Allergy and Immunology and director of the Lowance Center of Human Immunology at Emory, director of rheumatology in the Department of Medicine in Emory School of Medicine, and a Georgia Research Alliance Eminent Scholar.
“This consortium not only combines the expertise of researchers throughout a variety of disciplines focused on the human immune response, but also reflects an increasing focus on engineering technologies and informatics in improving the diagnosis and treatment of challenging diseases.”
“By joining our immense strengths in immunology and bioengineering, we aspire to become an international leader in immunoengineering science; develop new technologies for prevention, rapid diagnosis, and treatment of immune-related disorders and train the next generation of physicians and engineers in this cutting edge research,” says Krishnendu Roy, PhD, co-chair of the consortium steering committee, director of the Center for ImmunoEngineering in the Parker H. Petit Institute for Bioengineering and Bioscience at Georgia Tech and Carol Ann and David D. Flanagan professor of biomedical engineering in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University.
Immunoengineering is the application of engineering tools and principles to better understand and monitor our immune system in health and in diseases. This knowledge is then used to develop more effective vaccines and therapies against a wide range of diseases like cancer, HIV, diabetes, multiple sclerosis, arthritis etc. and also to improve tissue regeneration, wound healing and transplantation, explain Sanz and Roy.
“Game-changing innovation and world-class scholarship occur at the boundaries of fields of study where collaborators bring different perspectives to challenging problems,” says Stephen E. Cross, executive vice president for research at Georgia Tech. “This is the essence of the successful 17-year partnership between engineering and science at Georgia Tech, and medical science and clinical practice at Emory.”
Existing centers and departments that will collaborate within the new consortium include the Center for ImmunoEngineering at Georgia Tech as well as the Emory Vaccine Center, Lowance Center for Human Immunology, Departments of Medicine, Microbiology and Immunology, Hematology and Oncology, and Pathology and Laboratory Medicine in Emory School of Medicine, the Emory-Children’s Pediatric Research Center, and Winship Cancer Institute, among others.
The consortium has partnered with the Georgia Research Alliance (GRA), a nonprofit organization that expands research and commercialization capacity in Georgia’s universities to launch new companies, create high-value jobs and transform lives.
“The Georgia ImmunoEngineering Consortium is a unique academic collaboration that represents strong opportunities to align our state’s extensive university research base with targeted life sciences industry development in Georgia,” says C. Michael Cassidy, GRA president and CEO. “GRA looks forward to seeing the new discoveries and commercial opportunities that result from this partnership.”
The consortium will also collaborate with research partners at the Centers for Disease Control and Prevention (CDC) and partners at various colleges and universities around Georgia, the United States, and around the world.
“Using engineering approaches to help unlock the biology of the immune system opens the door for exciting new discoveries that can alter human disease,” says David S. Stephens MD, vice president for research in Emory’s Woodruff Health Sciences Center, chair of the Department of Medicine in Emory University School of Medicine, and a member of the consortium steering committee.
Additional members of the steering committee from Georgia Tech include M.G. Finn and Susan Thomas, and from Emory include Rafi Ahmed and Edmund K. (Ned) Waller.
A symposium will celebrate the consortium launch:
Georgia ImmunoEngineering Symposium:
Feb. 28, 2014, 7 a.m. – 5 p.m.
Emory Conference Center
For more information about the consortium, please view the website.
- Holly Korschun, Emory University
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]]>But after talking with more than a hundred potential users of the device, she learned the real need was for a generic interface system able to connect a wide range of input devices – big button switches, joysticks, sip-and-puff straws and others – to the tablet computers. And it turned out that the market was much larger than Howard imagined, extending to adults with disabilities and potentially even persons with Alzheimer’s.
A professor in the Georgia Tech School of Electrical and Computer Engineering, Howard has now launched a company, Zyrobotics, to commercialize the device, and a prototype has already been developed. The company, run by a former graduate student, won’t be the next IBM, but it will help disabled children do what all kids want to do: play video games and interact with computers.
Assistance with refining the device came through the Innovation Corps (I-Corps™), a National Science Foundation program that helps NSF-funded researchers learn about starting up a company – and by talking to potential customers, determine whether there’s really a market for what they’ve developed.
“Without I-Corps, I wouldn’t have thought to pursue this,” said Howard, who holds the title of Motorola Foundation Professor. “They showed us how to talk about the technology in terms that the general public could understand. And I-Corps made us take a step back and ask if what we had developed was really of value to potential customers.”
I-Corps Innovation
A dozen Georgia Tech teams – each composed of a faculty member, entrepreneurial lead and industry mentor – have now gone through the six-week I-Corps program. About a third of them have, like Howard, revised their plans and decided to move forward with forming a company and creating a product based on the results of NSF-supported research. The program is part of a national effort to turn research discoveries into new companies and new products, supporting economic development and building understanding of what it means to be an entrepreneur.
“Through the Innovation Corps, NSF seeks to accelerate the development of new technologies, products and processes that arise from fundamental research,” said Rathindra (Babu) DasGupta, the NSF’s program director for I-Corps. “The goals of I-Corps are to spur translation of fundamental research, to encourage collaboration between academia and industry, and to train students to understand innovation and entrepreneurship.”
The program provides mentoring and funding designed to move the results of NSF-supported research through the early stages of company formation. “NSF investments strategically strengthen the nation’s innovation ecosystem by addressing the challenges inherent in the early stages of the innovation process,” DasGupta added.
I-Corps at Georgia Tech
Because of its long experience with forming companies from university research, in July 2012 Georgia Tech was selected to be among the first institutions to become ”nodes” teaching the I-Corps curriculum. The program is basically a boot camp that shows what it’s like to form a startup company – and ensures that there’s a real market for a fledgling company’s proposed product. About 25 teams from universities around the country participate each time the program is taught at one of the I-Corps nodes, including Georgia Tech.
“The I-Corps process is very similar to the scientific method, which scientists and engineers are familiar with,” explained Keith McGreggor, who directs the I-Corps program at Georgia Tech. “We use this process to turn fiction – what you might think is true – into fact by doing experiments and testing hypotheses in the real world with customers instead of in the laboratory.”
I-Corps puts faculty members and graduate students through a pressure cooker environment that simulates a real startup. Not everyone is cut out for entrepreneurship, McGreggor noted. Faculty members often have a skill set – collaborating with other researchers, teaching students and publishing papers – that’s different from the skills needed to produce products and services that non-researchers are willing to buy.
The centerpiece of the program is “customer discovery” in which the teams must talk with at least 100 potential customers about their proposed product. This interaction with the real world almost inevitably leads to what I-Corps calls “the pivot,” which occurs when the teams, based on the customer feedback, realize they’ve been developing a product for which there isn’t a market. In many cases, that realization leads to new, and successful, directions for the technology.
“Everyone starts out with one idea about what they want to do, and they almost always change to something else that they are also capable of doing,” McGreggor said. “It can be difficult for people to switch gears, but what’s beautiful about this program is that they do switch.”
At the end of the six weeks, the teams decide whether or not to go forward with their idea. For Georgia Tech teams, fledgling companies that emerge from the process can join VentureLab, a program that helps researchers form companies, create prototypes, bring in experienced management and obtain early-stage funding. VentureLab companies can go on to be members of the Advanced Technology Development Center (ATDC), Georgia Tech’s accelerator program that helps entrepreneurs launch and build successful companies.
Marketing MOFs
Krista Walton and David Sholl used the I-Corps process to confirm the market need for metal-organic frameworks (MOFs), a new materials technology with a broad range of potential market applications. With NSF support, the researchers had developed a way to scale up the synthesis of MOFs, a class of nanomaterials, but weren’t sure what direction to take next – a classic problem for technologies that have many possible applications.
“By talking with more than 100 potential customers, we went through numerous refinements in our understanding of how we can create a sustainable business with our technology,” said Sholl, who is now chair of Georgia Tech’s School of Chemical and Biomolecular Engineering. “We saw over and over again that the issues that obsess researchers doing fundamental research and the issues that matter to customers are often not the same.”
Talking with the customers required a large investment of time, but Sholl – who is also a Georgia Research Alliance Eminent Scholar in Energy Sustainability – was pleased with the level of interest in the technology. The potential customers he and Walton interviewed also identified applications they had never considered.
As a result of the process, Sholl and Walton – an associate professor in the School of Chemical and Biomolecular Engineering – formed Inmondo Tech, and are working with several initial customers to develop a first product.
Smartphone Questions
For Gregory Abowd, the benefits of I-Corps were different. A serial entrepreneur with a record of launching successful companies, Abowd felt he knew how to commercialize technology he developed that helps connect young patients with their doctors through handheld devices. But he wanted to apply I-Corps’ systematic process to starting up a new company.
“I’ve had some successful and unsuccessful startup efforts, but I really didn’t understand what were the important elements of the successful ones,” said Abowd, who is a Regents’ and Distinguished Professor in Georgia Tech’s School of Interactive Computing. “I was intrigued with the idea of being a little more structured going into this one, because I had learned there are an infinite number of ways to make mistakes in the business world.”
The company, established as L.S.Q. LLC in Georgia, will provide a way to ask questions of smartphone users at times when they aren’t actively using their handheld devices. Building on the original purpose of the technology, which was to boost interaction with children who have chronic diseases, Abowd sees many possible applications, including surveys designed for the small screens of mobile devices.
“We’ll ask questions at a point when people are interacting with their phones, but at a point of pause,” he explained. Abowd has assembled a team and is talking with potential customers. He expects to form a joint venture with a market research firm in early 2014 and develop a product quickly.
Advice to Others
What advice do the teams give faculty members and graduate students thinking about the I-Corps opportunity?
“There is a growing network to help with commercialization, both at Georgia Tech and around the country,” noted Abowd. “A successful startup requires a lot of effort, and it’s more than a full-time job. I-Corps gives you a six-week exposure to help you determine whether this is right for you.”
I-Corps requires a large investment of time, something that can be difficult if faculty members aren’t prepared for it, Howard noted. To be successful, at least one member of the team has to be available nearly full-time during the six-week program.
“I would recommend this 100 percent, and have already talked with other faculty members about I-Corps,” she said. “This process is very different from what we normally do in research and teaching, and it has changed the way I think about what I do. It was a great experience for us.”
I-Corps teams follow a rigorous application process designed to determine whether team members are truly committed to launching and building a startup, McGreggor noted. That can be daunting.
“I-Corps simulates a startup, so it puts a lot of heat on the team to see if they are going to stay together when they get into a company,” he said. “We challenge the researchers in ways that they have probably not been challenged since they were graduate students. It is exquisitely uncomfortable for some people.”
Broader Impacts
I-Corps has also changed the way that Georgia Tech approaches startup companies. Customer discovery and early pivoting to serve the marketplace, for instance, are now at the core of Georgia Tech’s VentureLab and Flashpoint programs, which serve all researchers regardless of their funding sources, McGreggor said.
“Faculty members are forced to look into the face of a world that may not want what they have produced,” McGreggor said. “What we’ve learned is that when entrepreneurs get it wrong, it’s usually because they are building something that nobody really wants. This has really changed our approach to doing things in VentureLab.”
The I-Corps approach has also changed the role of graduate students in the startup process, and opened it more to junior faculty members. In the past, VentureLab had assumed that only tenured faculty would have the time and flexibility to commit to a startup. Now, he says, the program makes no distinction among researchers, and realizes that the graduate students involved in developing a technology may be the right team members to go forward as part of the new company. That makes creating a startup a real alternative to traditional post-graduation opportunities.
Beyond the new enterprises begun, the I-Corps program is having a larger impact on the universities whose faculty members have participated.
“Additional successes of the program have been far-reaching,” said the NSF’s DasGupta. “Faculty are taking what they learned in I-Corps about innovation and technology transfer back to their universities and training their students differently. The participation of students and post-docs in I-Corps has also had favorable impacts: they report that their employability is enhanced by their participating in I-Corps.”
The program was launched in 2011, and continues to evolve as NSF tracks the results. In addition to its teams of researchers, entrepreneurs and mentors, I-Corps is also focusing on nodes and sites to bring the concepts to a larger group of NSF researchers.
“We continue to explore ways to expand the program’s impact nationally, and at the state and local levels,” DasGupta added.
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]]>By taking advantage of the native pollen grain shape and a non-natural oxide chemistry, this work provides a unique demonstration of tunable, bio-enabled multimodal adhesion. The spikes inherited from the sunflower pollen provide short range adhesion – over nanoscale distances – while the oxide chemistry provides an adhesion mode that operates over much longer distances – up to one millimeter.
The work was supported by the Air Force Office of Scientific Research, and has been accepted for publication in the journal Chemistry of Materials. A “just-accepted” version of the manuscript has appeared online.
“Pollen grains are inexpensive and sustainable templates that are readily available in large quantities,” said Ken Sandhage, a professor in the School of Materials Science and Engineering at the Georgia Institute of Technology. “Because pollen grains are already designed by nature for adhesion, we thought that it would be interesting to try to augment such natural behavior with an additional, non-natural mode of adhesion.”
Sandhage and graduate student Brandon Goodwin began by examining the microscopic shapes of several types of pollen – including ragweed, pecan and dandelion – before choosing particles from the sunflower (Helianthus annuus). The sunflower pollen grains are nearly spherical, but covered with spikes that can entangle with the hairs on bees’ legs, or adhere to surfaces via van der Waals forces at nanometer-scale distances, Sandhage explained.
The researchers washed the burr-like pollen particles with chloroform, methanol, hydrochloric acid and water to clean the surfaces and expose hydroxyl groups for chemically attaching their coating. They then applied iron oxide using an automated, layer-by-layer surface sol-gel process they had developed earlier for coating diatom shells made of silica. Reaction of the iron oxide precursor with the hydroxyl groups on the surface of the pollen particles resulted in a highly-conformal coatings.
The sol-gel process used alternating cycles of exposure to an iron (III) isopropoxide precursor solution and water to apply 30 thin layers of hematite (Fe2O3) onto the pollen. Heating the particles to 600 degrees Celsius then burned out the organic material from the original pollen grains and crystallized the iron oxide, leaving hollow 3D particles. The shells were then heated again in a controlled oxygen atmosphere to convert the hematite into magnetite (Fe3O4), which is more strongly magnetic.
“We examined individual pollen grains before and after firing, and we could see that the shape and surface features were well preserved,” said Sandhage, who is the B. Mifflin Hood Professor in the School of Materials Science and Engineering. “The conformal nature of the coating process allowed us to generate ceramic replicas that retained even tiny surface features on the starting pollen grains.”
The adhesion properties of the magnetic pollen-shaped particles were then analyzed by graduate student Ismael Gomez and professor Carson Meredith, both from Georgia Tech’s School of Chemical and Biomolecular Engineering. Gomez and Meredith used an atomic force microscope (AFM) tip to press the replicas onto a variety of surfaces, then measured the force required to remove them from the surfaces. They studied replica pollen adhesion to polyvinyl alcohol, polyvinyl acetate, polystyrene, silicon, nickel and neodymium-iron-boron – and compared the adhesion properties to those of the original sunflower pollen grains.
“We found that we achieved multimodal adhesion by retaining short-range van der Waals attraction, as exhibited by the native pollen, and gaining magnetic adhesion,” Sandhage said.
The layer-by-layer nature of the coating process allowed for control of the amount of magnetic material, and the magnetic properties of the pollen replicas. The researchers chose to apply 30 layers to achieve sufficient long-range magnetic behavior while retaining high-aspect-ratio, sharp spikes that provide for short-range van der Waals forces.
“Reproducibly generating large quantities of such cheap microparticles possessing high-aspect surface features over their entire particle surfaces would be quite challenging using synthetic top-down methods,” Sandhage said.
The Air Force Multidisciplinary University Research Initiative (MURI) that funded the work is aimed at both understanding adhesion in natural systems and controllably tailoring such adhesion. In future research supported by the MURI, Sandhage and Meredith plan to study other oxide materials and explore the variety of shapes available in pollen particles.
“Now that we know how to generate such particle replicas, there is certainly more chemical tailoring that we can explore for adhesion,” said Sandhage, who also holds an adjunct position in Georgia Tech’s School of Chemistry and Biochemistry. “Through the proper combination of pollen shape, synthetic chemistry and thermal treatments, we can significantly expand the range of properties of these pollen replicas.”
This research was supported by the U.S. Air Force Office of Scientific Research through award number FA9550-10-1-0555. Any conclusions are those of the authors and do not necessarily represent the official views of the U.S. Air Force.
CITATION: William Brandon Goodwin, Ismael J. Gomez, Carson Meredith and Kenneth H. Sandhage, “Conversion of Pollen Particles into Three-Dimensional Ceramic Replicas Tailored for Multimodal Adhesion.” (Chemistry of Materials, 2013): http:// dx.doi.org/10.1021/cm402226w
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]]>Typical drug delivery systems act more like sponges than bottles. For example, drugs are absorbed into polymer particles and then allowed to diffuse out over time. The researchers hope that the new system may allow for greater control of drug delivery. Cargo would stay inside the hollow polymer particle when plugged with a solid cork. When the cork is melted by body heat, the drugs would quickly flow out of the particle bottle.
“It’s just like when you open wine, you remove the cork,” said Younan Xia, a professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University. Xia also holds joint appointments in School of Chemistry and Biochemistry and the School of Chemical and Biomolecular Engineering at Georgia Tech.
The melting corks are made of fatty acids, derived from natural oils and fats. The length of the hydrocarbon chains on these molecules can be made longer or shorter to increase or decrease, respectively, the temperature at which they melt. This way, the fragrances in deodorants, for example, would be released only when a person gets hot and sweaty.
The new system for temperature-regulated release was detailed in a recent online edition of the journal Angewandte Chemie International Edition. The research was sponsored by the National Cancer Institute, a National Institutes of Health Director’s Pioneer Award, and startup funds from Georgia Tech. Funds were also provided by the Korea Science and Engineering Foundation (KOSEF) and the Korean Ministry of Education and Science.
Drug delivery systems have also been designed to release their cargoes in response to pH change, ultrasound, mechanical signals and electric or magnetic fields. Xia’s system is the first bottle-and-cork design, but it isn’t the first to release drugs in response to temperature. His system, however, has several advantages over other temperature-regulated delivery systems, such as quick and efficient loading of small molecules, macromolecules and even nanoparticles up to 100 nanometers in size. Other temperature-based systems can release their cargoes early. In Xia’s system, the contents are bottled up until the body hits the desired temperature and then they are quickly released.
“It’s like bottled water,” Xia said. “When you are thirsty, you can just drink it.”
The melting corks are made from a group of phase-changing materials — fatty acids or fatty alcohols — that change from solid to liquid when heated to specific melting points. As a proof of principle for the temperature-sensitive delivery system works, in the new study Xia’s lab loaded fluorescent dye into the hollow polymer particles. The holes were then corked with solid 1-tetradecanol, a fatty alcohol. After washing away any dye that might be stuck to the outer surfaces of the bottles, a fluorescent micrograph showed that all of the dye was completely bottled up.
The bottles were then heated to 25 and 37 degrees Celsius — just below the corks’ melting point — but no dye escaped, even after 4 days and vigorous washing in a buffer solution. This performance is better than other delivery systems, Xia said, which typically release some of the drug prematurely.
When bottles were heated to 39 degrees Celsius, the melting point of 1-tetradecanol, the corks melted and the dye was instantly released.
“You can bottle everything and then you put a stopper on top. Whenever you need it, just unplug it and things will come out quickly,” said Xia, who is a Georgia Research Alliance Eminent Scholar in Nanomedicine.
The corks tested in the study are expected to pose no harm once inside or on the human body. 1-tetradecanol and lauric acid, a fatty acid that has also been test as a cork, have very low toxicity in small doses, Xia said, because they are derived from natural fats and oils. These same fats are often used as ingredients for food and pharmaceuticals.
Xia said that hydrophobic drugs, such as the majority of anticancer treatments, could be easily loaded into the hollow particles for delivery inside the body. Future studies will examine this possibility in more detail in animal models. Hydrophilic drugs could also be delivered with this system, but the surface of the bottle would need to be modified.
The hollow polymer particles in Xia’s study were made of polystyrene, which couldn’t be injected safely into the body to deliver drugs, but would work in a scented body cream for applying to the skin.
Xia’s lab is currently working on making these microscale particle bottles out of polymers that are approved by the U.S. Food and Drug Administration, such as polycarprolactone, so they can bring translational capability to this system.
“No companies are making anything like this yet,” Xia said.
Dong Choon Hyun, a post-doctoral fellow at Georgia Tech, was the lead author of the study. Unyong Jeong, a materials science & engineering professor at Yonsei University in Korea, was a collaborator on the project.
This research is supported by the National Cancer Institute under award R01CA138527, the National Institutes of Health Director’s Pioneer Award (DP1OD000798), and startup funds from Georgia Tech. The research was also sponsored by KOSEF (008-05103) and a World Class University grant from NRF of the Korean Ministry of Education and Science (R32-20031). Any conclusions or opinions are those of the authors and do not necessarily represent the official views of the sponsoring agencies.
CITATION: D.C. Hyun, et al., “Microscale Polymer Bottles Corked with a Phase-Change Material for Temperature-Controlled Release,” (Angewandte Chemie International Edition, 2013). dx.doi.org/10.1002/anie.201305006
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]]>But at nanometer-size scales for water and potentially other fluids, whether the container is made of glass or plastic does make a significant difference. A new study shows that in nanoscopic channels, the effective viscosity of water in channels made of glass can be twice as high as water in plastic channels. Nanoscopic glass channels can make water flow more like ketchup than ordinary H2O.
The effect of container properties on the fluids they hold offers yet another example of surprising phenomena at the nanoscale. And it also provides a new factor that the designers of tiny mechanical systems must take into account.
“At the nanoscale, viscosity is no longer constant, so these results help redefine our understanding of fluid flow at this scale,” said Elisa Riedo, an associate professor in the School of Physics at the Georgia Institute of Technology. “Anyone performing an experiment, developing a technology or attempting to understand a biological process that involves water or another liquid at this size scale will now have to take the properties of surfaces into account.”
Those effects could be important to designers of devices such as high resolution 3D printers that use nanoscale nozzles, nanofluidic systems and even certain biomedical devices.
Considering that nano-confined water is ubiquitous in animal bodies, in rocks, and in nanotechnology, this new understanding could have a broad impact.
Research into the properties of liquids confined by different materials was sponsored by the Department of Energy’s Office of Basic Sciences and the National Science Foundation. The results were reported September 19 in the journal Nature Communications.
The viscosity differences created by container materials are directly affected by the degree to which the materials are either hydrophilic – which means they attract water – or hydrophobic – which means they repel it. The researchers believe that in hydrophilic materials, the attraction for water – a property known as “wettability” – makes water molecules more difficult to move, contributing to an increase in the fluid’s effective viscosity. On the other hand, water isn’t as attracted to hydrophobic materials, making the molecules easier to move and producing lower viscosity.
In research reported in the journal, this water behavior appeared only when water was confined to spaces of a few nanometers or less – the equivalent of just a few layers of water molecules. The viscosity continued to increase as the surfaces were moved closer together.
The research team studied water confined by five different surfaces: mica, graphene oxide, silicon, diamond-like carbon, and graphite. Mica, used in the drilling industry, was the most hydrophilic of the materials, while graphite was the most hydrophobic.
“We saw a clear one-to-one relationship between the degree to which the confining material was hydrophilic and the viscosity that we measured,” Riedo said.
Experimentally, the researchers began by preparing atomically-smooth surfaces of the materials, then placing highly-purified water onto them. Next, an AFM tip made of silicon was moved across the surfaces at varying heights until it made contact. The tip – about 40 nanometers in diameter – was then lifted up and the measurements continued.
As the viscosity of the water increased, the force needed to move the AFM tip also increased, causing it to twist slightly on the cantilever beam used to raise and lower the tip. Changes in this torsion angle were measured by a laser bounced off the reflective cantilever, providing an indication of changes in the force exerted on the tip, the viscous resistance exerted – and therefore the water’s effective viscosity.
“When the AFM tip was about one nanometer away from the surface, we began to see an increase of the viscous force acting on the tip for the hydrophilic surfaces,” Riedo said. “We had to use larger forces to move the tip at this point, and the closer we got to the surface, the more dramatic this became.”
Those differences can be explained by understanding how water behaves differently on different surfaces.
“At the nanoscale, liquid-surface interaction forces become important, particularly when the liquid molecules are confined in tiny spaces,” Riedo explained. “When the surfaces are hydrophilic, the water sticks to the surface and does not want to move. On hydrophobic surfaces, the water is slipping on the surfaces. With this study, not only have we observed this nanoscale wetting-dependent viscosity, but we have also been able to explain quantitatively the origin of the observed changes and relate them to boundary slip. This new understanding was able to explain previous unclear results of energy dissipation during dynamic AFM studies in water.”
While the researchers have so far only studied the effect of the material properties in water channels, Riedo expects to perform similar experiments on other fluids, including oils. Beyond simple fluids, she hopes to study complex fluids composed of nanoparticles in suspension to determine how the phenomenon changes with particle size and chemistry.
“There is no reason why this should not be true for other liquids, which means that this could redefine the way that fluid dynamics is understood at the nanoscale,” she said. “Every technology and natural process that uses liquids confined at the nanoscale will be affected.”
In addition to Riedo, co-authors of the paper included Deborah Ortiz-Young, Hsiang-Chih Chiu and Suenne Kim, who were at Georgia Tech when the research was done, and Kislon Voitchovsky of the Ecole Polytechnique Federale de Lausanne in Switzerland.
CITATION: Deborah Ortiz-Young, Hsiang-Chih Chiu, Suenne Kim, Kislon Voitchovsky and Elisa Riedo, “The interplay between apparent viscosity and wettability in nanoconfined water," (Nature Communications, 2013). http://www.nature.com/ncomms/2013/130919/ncomms3482/full/ncomms3482.html
This research was supported by the Office of Basic Energy Sciences of the U.S. Department of Energy (DOE) under grant DE-FG02-06ER46293 and by the National Science Foundation (NSF) under grants DMR-0120967, DMR-0706031 and CMMI-1100290. Any opinions or conclusions are those of the authors and do not necessarily reflect the official views of the DOE or NSF.
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]]>The technique could facilitate the use of nanoparticles for optical, electrical, optoelectronic, magnetic, catalysis and other applications in which tight control over size and structure is essential to obtaining desirable properties. The technique produces plain, core-shell and hollow nanoparticles that can be made soluble either in water or in organic solvents.
“We have developed a general strategy for making a large variety of nanoparticles in different size ranges, compositions and architectures,” said Zhiqun Lin, an associate professor in the School of Materials Science and Engineering at the Georgia Institute of Technology. “This very robust technique allows us to craft a wide range of nanoparticles that cannot be easily produced with any other approaches.”
The technique was described in the June issue of the journal Nature Nanotechnology. The research was supported by the Air Force Office of Scientific Research.
The star-shaped block co-polymer structures consist of a central beta-cyclodextrin core to which multiple “arms” – as many as 21 linear block co-polymers – are covalently bonded. The star-shaped block co-polymers form the unimolecular micelles that serve as a reaction vessel and template for the formation of the nanocrystals.
The inner blocks of unimolecular micelles are poly(acrylic) acid (PAA), which is hydrophilic, which allows metal ions to enter them. Once inside the tiny reaction vessels made of PAA, the ions react with the PAA to form nanocrystals, which range in size from a few nanometers up to a few tens of nanometers. The size of the nanoparticles is determined by the length of the PAA chain.
The block co-polymer structures can be made with hydrophilic inner blocks and hydrophobic outer blocks – amphiphilic block co-polymers, with which the resulting nanoparticles can be dissolved in organic solvents. However, if both inner and outer blocks are hydrophilic – all hydrophilic block co-polymers – the resulting nanoparticles will be water-soluble, making them suitable for biomedical applications.
Lin and collaborators Xinchang Pang, Lei Zhao, Wei Han and Xukai Xin found that they could control the uniformity of the nanoparticles by varying the volume ratio of two solvents – dimethlformamide and benzyl alcohol – in which the nanoparticles are formed. For ferroelectric lead titanate (PbTiO3) nanoparticles, for instance, a 9-to-1 solvent ratio produces the most uniform nanoparticles.
The researchers have also made iron oxide, zinc oxide, titanium oxide, cuprous oxide, cadmium selenide, barium titanate, gold, platinum and silver nanocrystals. The technique could be applicable to nearly all transition or main-group metal ions and organometallic ions, Lin said.
“The crystallinity of the nanoparticles we are able to create is the key to a lot of applications,” he added. “We need to make them with good crystalline structures so they will exhibit good physical properties.”
Earlier techniques for producing polymeric micelles with linear block co-polymers have been limited by the stability of the structures and by the consistency of the nanocrystals they produce, Lin said. Current fabrication techniques include organic solution-phase synthesis, thermolysis of organometallic precursors, sol-gel processes, hydrothermal reactions and biomimetic or dendrimer templating. These existing techniques often require stringent conditions, are difficult to generalize, include a complex series of steps, and can’t withstand changes in the environment around them.
By contrast, nanoparticle production technique developed by the Georgia Tech researchers is general and robust. The nanoparticles remain stable and homogeneous for long periods of time – as much as two years so far – with no precipitation. Such flexibility and stability could allow a range of practical applications, Lin said.
“Our star-like block co-polymers can overcome the thermodynamic instabilities of conventional linear block co-polymers,” he said. “The chain length of the inner PAA blocks dictates the size of the nanoparticles, and the uniformity of the nanoparticles is influenced by the solvents used in the system.”
The researchers have used a variety of star-like di-block and tri-block co-polymers as nanoreactors. Among them are poly(acrylic acid)-block-polystyrene (PAA-b-PS) and poly(acrylic acid)-blockpoly(ethylene oxide) (PAA-b-PEO) diblock co-polymers, and poly(4-vinylpyridine)-block-poly(tert-butyl acrylate)-block-polystyrene (P4VP-b-PtBA-b-PS), poly(4-vinylpyridine)-block-poly (tert-butyl acrylate)-block-poly(ethylene oxide) (P4VP-b-PtBA-b-PEO), polystyrene-block-poly(acrylic acid)-block-polystyrene (PS-b-PAA-b-PS) and polystyrene-block-poly(acrylic acid)-block-poly(ethylene oxide) (PS-b-PAA-b-PEO) tri-block co-polymers.
For the future, Lin envisions more complex nanocrystals with multifunctional shells and additional shapes, including nanorods and so-called “Janus” nanoparticles that are composed of biphasic geometry of two dissimilar materials.
This research was supported by the Air Force Office of Scientific Research (AFOSR) under awards FA9550-09-1-0388 and FA9550-13-1-0101. The conclusions expressed in this news releases are those of the principal investigator and do not necessarily represent the official views of the AFOSR.
CITATION: Xinchang Pang, Lei Zhao, Wei Han, Xukai Xin and Zhiqun Lin, “A general and robust strategy for the synthesis of nearly monodisperse colloidal nanocrystals,” (Nature Nanotechnology, 8, 426, 2013). http://dx.doi.org/10.1038/nnano.2013.85.
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]]>The paper takes advantage of the so-called "lotus effect" – used by leaves of the lotus plant – to repel liquids through the creation of surface patterns at two different size scales and the application of a chemical coating. The material, developed at the Georgia Institute of Technology, uses nanometer- and micron-scale structures, plus a surface fluorocarbon, to turn old-fashioned paper into an advanced material.
The modified paper could be used as the foundation for a new generation of inexpensive biomedical diagnostics in which liquid samples would flow along patterns printed on the paper using special hydrophobic ink and an ordinary desktop printer. This paper could also provide an improved packaging material that would be less expensive than other oil- and water-repelling materials, while being both recyclable and sustainable.
“Paper is a very heterogeneous material composed of fibers with different sizes, different lengths and a non-circular cross-section,” said Dennis Hess, a professor in the Georgia Tech School of Chemical and Biomolecular Engineering. “We believe this is the first time that a superamphiphobic surface – one that repels all fluids – has been created on a flexible, traditional and heterogeneous material like paper.”
Research leading to development of the superamphiphobic paper has been supported by the Institute for Paper Science and Technology (IPST) at Georgia Tech. Details were published online May 24 in the journal ACS Applied Materials & Interfaces.
The new paper, which is both superhydrophobic (water-repelling) and super oleophobic (oil-repelling), can be made from standard softwood and hardwood fibers using a modified paper process. In addition to Hess, the research team included Lester Li, a graduate research assistant, and Victor Breedveld, an associate professor in the School of Chemical and Biomolecular Engineering
Producing the new paper begins with breaking up cellulose fibers into smaller structures using a mechanical grinding process. As in traditional paper processing, the fibers are then pressed in the presence of water – but then the water is removed and additional processing is done with the chemical butanol. Use of butanol inhibits the hydrogen bonding that normally takes place between cellulose fibers, allowing better control of their spacing.
“The desirable properties we are seeking are mainly controlled by the geometry of the fibers,” Hess explained.
The second step involves using an oxygen plasma etching process – a technique commonly used in the microelectronics industry – to remove the layer of amorphous “fluffy” cellulose surface material, exposing the crystalline cellulose nanofibrils. The process thereby uncovers smaller cellulose structures and provides a second level of “roughness” with the proper geometry needed to repel liquids.
Finally, a thin coating of a fluoropolymer is applied over the network of cellulose fibers. In testing, the paper was able to repel water, motor oil, ethylene glycol and n-hexadecane solvent.
The researchers have printed patterns onto their paper using a hydrophobic ink and a desktop printer. Droplets applied to the pattern remain on the ink pattern, repelled by the adjacent superamphiphobic surface.
That capability could facilitate development of inexpensive biomedical diagnostic tests in which a droplet containing antigens could be rolled along a printed surface where it would encounter diagnostic chemicals. If appropriate reagents are used, the specific color or color intensity of the patterns could indicate the presence of a disease. Because the droplets adhere tightly to the printed lines or dots, the samples can be sent to a laboratory for additional testing.
“We have shown that we can do the operations necessary for a microfluidic device,” Hess said. “We can move the droplet along a pattern, split the droplet and transfer the droplet from one piece of paper to another. We can do all of these operations on a two-dimensional surface.”
For Hess, Li and Breedveld, creating a superhydrophobic suface was relatively straightforward because water has a high surface tension. For oils, which have a low surface tension, the key to creating the repellent surface is to create re-entrant – or undercut – angles between the droplets and the surface.
Previous examples of superamphiphobic surfaces have been made on rigid surfaces through lithographic techniques. Such processes tend to produce fragile surfaces that are prone to damage, Hess said.
The principal challenge has been to create high-performance in a material that is anything but geometrically regular and consistent.
“Working with heterogeneous materials is fascinating, but it’s very difficult not just to control them, because there is no inherent consistent structure, but also to change the processing conditions so you can get something that, on average, is what you need,” he said. “It’s been a real learning experience for us.”
The new paper has so far been made in samples about four inches on a side, but Hess sees no reason why the process couldn’t be scaled up. Though long-term testing of the new paper hasn’t been done, Hess is encouraged by what he’s seen so far.
CITATION: Lester Li, Victor Breedveld and Dennis Hess, “Design and Fabrication of Superamphiphobic Paper Surfaces,” (ACS Applied Materials & Interfaces, 2013).
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]]>The study shows that RNA is capable of catalyzing electron transfer under conditions similar to those of the early Earth. Because electron transfer, the moving of an electron from one chemical species to another, is involved in many biological processes – including photosynthesis, respiration and the reduction of RNA to DNA – the study’s findings suggest that complex biochemical transformations may have been possible when life began.
There is considerable evidence that the evolution of life passed through an early stage when RNA played a more central role, before DNA and coded proteins appeared. During that time, more than 3 billion years ago, the environment lacked oxygen but had an abundance of soluble iron.
“Our study shows that when RNA teams up with iron in an oxygen-free environment, RNA displays the powerful ability to catalyze single electron transfer, a process involved in the most sophisticated biochemistry, yet previously uncharacterized for RNA,” said Loren Williams, a professor in the School of Chemistry and Biochemistry at the Georgia Institute of Technology.
The results of the study were published online on May 19, 2013, in the journal Nature Chemistry. The study was sponsored by the NASA Astrobiology Institute, which established the Center for Ribosomal Origins and Evolution (Ribo Evo) at Georgia Tech.
Free oxygen gas was almost nonexistent in the Earth’s atmosphere more than 3 billion years ago. When free oxygen began entering the environment as a product of photosynthesis, it turned the earth’s iron to rust, forming massive banded iron formations that are still mined today. The free oxygen produced by advanced organisms caused iron to be toxic, even though it was – and still is – a requirement for life. Williams believes the environmental transition caused a slow shift from the use of iron to magnesium for RNA binding, folding and catalysis.
Williams and Georgia Tech School of Chemistry and Biochemistry postdoctoral fellow Chiaolong Hsiao used a standard peroxidase assay to detect electron transfer in solutions of RNA and either the iron ion, Fe2+, or magnesium ion, Mg2+. For 10 different types of RNA, the researchers observed catalysis of single electron transfer in the presence of iron and absence of oxygen. They found that two of the most abundant and ancient types of RNA, the 23S ribosomal RNA and transfer RNA, catalyzed electron transfer more efficiently than other types of RNA. However, none of the RNA and magnesium solutions catalyzed single electron transfer in the oxygen-free environment.
“Our findings suggest that the catalytic competence of RNA may have been greater in early Earth conditions than in present conditions, and our experiments may have revived a latent function of RNA,” added Williams, who is also director of the Ribo Evo Center.
This new study expands on research published in May 2012 in the journal PLoS ONE. In the previous work, Williams led a team that used experiments and numerical calculations to show that iron, in the absence of oxygen, could substitute for magnesium in RNA binding, folding and catalysis. The researchers found that RNA’s shape and folding structure remained the same and its functional activity increased when magnesium was replaced by iron in an oxygen-free environment.
In future studies, the researchers plan to investigate whether other unique functions may have been conferred on RNA through interaction with a variety of metals available on the early Earth.
In addition to Williams and Hsiao, Georgia Tech School of Biology professors Roger Wartell and Stephen Harvey, and Georgia Tech School of Chemistry and Biochemistry professor Nicholas Hud, also contributed to this work as co-principal investigators in the Ribo Evo Center at Georgia Tech.
This work was supported by NASA (Award No. NNA09DA78A). The content is solely the responsibility of the principal investigators and does not necessarily represent the official views of NASA.
CITATION: Chiaolong Hsiao, et al., “RNA with iron(II) as a cofactor catalyses electron transfer,” (Nature Chemistry, 2013). http://dx.doi.org/10.1038/nchem.1649
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]]>Using systematic experiments, researchers have investigated how surface diffusion – a process in which atoms move from one site to another on nanoscale surfaces – affects the final shape of the particles. The issue is important for a wide range of applications that use specific shapes to optimize the activity and selectivity of nanoparticles, including catalytic converters, fuel cell technology, chemical catalysis and plasmonics.
Results of the research could lead to a better understanding of how to manage the diffusion process by controlling the reaction temperature and deposition rate, or by introducing structural barriers designed to hinder the surface movement of atoms.
“We want to be able to design the synthesis to produce nanoparticles with the exact shape we want for each specific application,” said Younan Xia, a professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University. “Fundamentally, it is important to understand how these shapes are formed, to visualize how this happens on structures over a length scale of about 100 atoms.”
The research was reported April 8 in the early online edition of the journal Proceedings of the National Academy of Sciences (PNAS). The research was sponsored by the National Science Foundation (NSF).
Controlling the shape of nanoparticles is important in catalysis and other applications that require the use of expensive noble metals such as platinum and palladium. For example, optimizing the shape of platinum nanoparticles can substantially enhance their catalytic activity, reducing demand for the precious material, noted Xia, who is a Georgia Research Alliance (GRA) eminent scholar in nanomedicine. Xia also holds joint appointments in the School of Chemistry and Biochemistry and the School of Chemical and Biomolecular Engineering at Georgia Tech.
“Controlling the shape is very important to tuning the activity of catalysts and in minimizing the loading of the catalysts,” he said. “Shape control is also very important in plasmonic applications, where the shape controls where optical absorption and scattering peaks are positioned. Shape is also important to determining where the electrical charges will be concentrated on nanoparticles.”
Though the importance of particle shape at the nanoscale has been well known, researchers hadn’t before understood the importance of surface diffusion in creating the final particle shape.
Adding atoms to the corners of platinum cubes, for instance, can create particles with protruding “arms” that increase the catalytic activity. Convex surfaces on cubic particles may also provide better performance. But those advantageous shapes must be created and maintained.
Natural energetic preferences related to the arrangement of atoms on the tiny structures favor a spherical shape that is not ideal for most catalysts, fuel cells and other applications.
In their research, Xia and his collaborators varied the temperature of the process used to deposit atoms onto metallic nanocrystals that acted as seeds for the nanoparticles. They also varied the rates at which atoms were deposited onto the surfaces, which were determined by the injection rate at which a chemical precursor material was introduced. The diffusion rate is determined by the temperature, with higher temperatures allowing the atoms to move around faster on the nanoparticle surfaces. In the research, bromide ions were used to limit the movement of the added atoms from one portion of the particle to another.
Using transmission electron microscopy, the researchers observed the structures that were formed under different conditions. Ultimately, they found that the ratio of the deposition rate to the diffusion rate determines the final shape. When the ratio is greater than one, the adsorbed atoms tend to stay where they are placed. If the ratio is less than one, they tend to move.
“Unless the atomic reaction is at absolute zero, you will always have some diffusion,” said Xia, who holds the Brock Family Chair in the Department of Biomedical Engineering. “But if you can add atoms to the surface in the places that you want them faster than they can diffuse, you can control the final destination for the atoms.”
Xia believes the research may also lead to improved techniques for preserving the unique shapes of nanoparticles even at high operating temperatures.
“Fundamentally, it is very useful for people to know how these shapes are formed,” he said. “Most of these structures had been observed before, but people did not understand why they formed under certain conditions. To do that, we need to be able to visualize what happens on these tiny structures.”
Xia’s research team also studied the impact of diffusion on bi-metallic particles composed of both palladium and platinum. The combination can enhance certain properties, and because palladium is currently less expensive than platinum, using a core of palladium covered by a thin layer of platinum provides the catalytic activity of platinum while reducing cost.
In that instance, surface diffusion can be helpful in covering the palladium surface with a single monolayer of the platinum. Only the surface platinum atoms will be able to provide the catalytic properties, while the palladium core only serves as a support.
The research is part of a long-term study of catalytic nanoparticles being conducted by Xia’s research group. Other aspects of the team’s work addresses biomedical uses of nanoparticles in such areas as cancer therapy.
“We are very excited by this result because it is generic and can apply to understand and control diffusion on the surfaces of many systems,” Xia added. “Ultimately we want to see how we can take advantage of this diffusion to improve the catalytic and optical properties of these nanoparticles.”
The research team also included Xiaohu Xia, Shuifen Xie, Maochang Liu and Hsin-Chieh Peng at Georgia Tech; and Ning Lu, Jinguo Wang and Professor Moon J. Kim at the University of Texas at Dallas.
This research was supported by the National Science Foundation (NSF) under grant DMR-1215034 and by startup funds from Georgia Tech. Any conclusions expressed are those of the principal investigator and may not necessarily represent the official views of the NSF.
CITATION: Xia, Xiaohu, et al., “On the role of surface diffusion in determining the shape or morphology of noble-metal nanocrystals,” (Proceedings of the National Academy of Science, 2013). http://www.pnas.org/content/early/2013/04/05/1222109110
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]]>A low temperature, controllable and stable method has been developed to dope graphene films using self-assembled monolayers (SAM) that modify the interface of graphene and its support substrate. Using this concept, a team of researchers at the Georgia Institute of Technology has created graphene p-n junctions – which are essential to fabricating devices – without damaging the material’s lattice structure or significantly reducing electron/hole mobility.
The graphene was grown on a copper film using chemical vapor deposition (CVD), a process that allows synthesis of large-scale films and their transfer to desired substrates for device applications. The graphene films were transferred to silicon dioxide substrates that were functionalized with the self-assembled monolayers.
Information about creating graphene p-n junctions using self-assembled monolayers was presented on November 28, 2012 at the Fall Meeting of the Materials Research Society. Papers describing aspects of the work were also published in September 2012 in the journals ACS Applied Materials & Interfaces and the Journal of Physical Chemistry C. Funding for the research came from the National Science Foundation, through the Georgia Tech Materials Research Science and Engineering Center (MRSEC) and through separate research grants.
“We have been successful at showing that you can make fairly well doped p-type and n-type graphene controllably by patterning the underlying monolayer instead of modifying the graphene directly,” said Clifford Henderson, a professor in the Georgia Tech School of Chemical & Biomolecular Engineering. “Putting graphene on top of self-assembled monolayers uses the effect of electron donation or electron withdrawal from underneath the graphene to modify the material’s electronic properties.”
The Georgia Tech research team working on the project includes faculty members, postdoctoral fellows and graduate students from three different schools. In addition to Henderson, professors who are part of the team include Laren Tolbert from the School of Chemistry and Biochemistry and Samuel Graham from the Woodruff School of Mechanical Engineering. The project team also includes Hossein Sojoudi, a postdoctoral fellow, and Jose Baltazar, a graduate research assistant.
Creating n-type and p-type doping in graphene – which has no natural bandgap – has led to development of several approaches. Scientists have substituted nitrogen atoms for some of the carbon atoms in the graphene lattice, compounds have been applied to the surface of the graphene, and the edges of graphene nanoribbons have been modified. However, most of these techniques have disadvantages, including disruption of the lattice – which reduces electron mobility – and long-term stability issues.
“Any time you put graphene into contact with a substrate of any kind, the material has an inherent tendency to change its electrical properties,” Henderson said. “We wondered if we could do that in a controlled way and use it to our advantage to make the material predominately n-type or p-type. This could create a doping effect without introducing defects that would disrupt the material’s attractive electron mobility.”
Using conventional lithography techniques, the researchers created patterns from different silane materials on a dielectric substrate, usually silicon oxide. The materials were chosen because they are either strong electron donors or electron acceptors. When a thin film of graphene is placed over the patterns, the underlying materials create charged sections in the graphene that correspond to the patterning.
“We were able to dope the graphene into both n-type and p-type materials through an electron donation or withdrawal effect from the monolayer,” Henderson explained. “That doesn’t lead to the substitutional defects that are seen with many of the other doping processes. The graphene structure itself is still pristine as it comes to us in the transfer process.”
The monolayers are bonded to the dielectric substrate and are thermally stable up to 200 degrees Celsius with the graphene film over them, Sojoudi noted. The Georgia Tech team has used 3-Aminopropyltriethoxysilane (APTES) and perfluorooctyltriethoxysilane (PFES) for patterning. In principle, however, there are many other commercially-available materials that could also create the patterns.
“You can build as many n-type and p-type regions as you want,” Sojoudi said. “You can even step the doping controllably up and down. This technique gives you control over the doping level and what the dominant carrier is in each region.”
The researchers used their technique to fabricate graphene p-n junctions, which was verified by the creation of field-effect transistors (FET). Characteristic I-V curves indicated the presence of two separate Dirac points, which indicated an energy separation of neutrality points between the p and n regions in the graphene, Sojoudi said.
The group uses chemical vapor deposition to create thin films of graphene on copper foil. A thick film of PMMA was spin-coated atop the graphene, and the underlying copper was then removed. The polymer serves as a carrier for the graphene until it can be placed onto the monolayer-coated substrate, after which it is removed.
Beyond developing the doping techniques, the team is also exploring new precursor materials that could allow CVD production of graphene at temperatures low enough to permit fabrication directly on other devices. That could eliminate the need for transferring the graphene from one substrate to another.
A low-cost, low-temperature means of producing graphene could also allow the films to find broader applications in displays, solar cells and organic light-emitting diodes, where large sheets of graphene would be needed.
“The real goal is to find ways to make graphene at lower temperatures and in ways that allow us to integrate it with other devices, either silicon CMOS or other materials that couldn’t tolerate the high temperatures required for the initial growth,” Henderson said. “We are looking at ways to make graphene into a useful electronic or opto-electronic material at low temperatures and in patterned forms.”
This material is based on work supported by the National Science Foundation (NSF) under Grants CHE-0822697, CHE-0848833 and CMMI-0927736 and the Georgia Tech Materials Research Science and Engineering Center (MRSEC). The content of this article is solely the responsibility of the authors and does not necessarily represent the official views of the NSF.
CITATIONS: Sojoudi, Hossein, Creating Graphene p-n Junctions Using Self-Assembled Monolayers, ACS Applied Materials & Interfaces, dx.doi.org/10.1021/am301138v and Baltazar, Jose, Facile Formation of Graphene P-N Junctions Using Self-Assembled Monolayers, The Journal of Physical Chemistry C, dx.doi.org/10.1021/jp3045737.
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]]>In the study, the researchers developed a technique to dry and stabilize the measles vaccine – which depends on a live attenuated virus – and showed that it remained effective for at least 30 days after being placed onto the microneedles. They also demonstrated that the dried vaccine was quickly released in the skin and able to prompt a potent immune response in an animal model.
The microneedle technique could provide a new tool for international immunization programs against measles, which killed nearly 140,000 children in 2010. The research was reported online October 5 in the journal Vaccine, and will appear in a special issue of the journal. The research was supported by the Georgia Research Alliance – and indirectly by the Division of Viral Diseases and Animal Resources Branch of the CDC, and by the National Institutes of Health through its support of efforts to develop a microneedle-based influenza vaccine.
“We showed in this study that measles vaccine delivered using a microneedle patch produced an immune response that is indistinguishable from the response produced when the vaccine is delivered subcutaneously,” said Chris Edens, the study’s first author and a graduate student in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University.
Measles immunization programs now use conventional hypodermic needles to deliver the vaccine. Large global immunization programs therefore require significant logistical support because the vaccine must be kept refrigerated, large numbers of needles and syringes must be shipped, and the ten-dose vaccine vials must be reconstituted with sterile water before use.
Because it requires a hypodermic needle injection, measles immunization programs must be carried out by trained medical personnel. Finally, used needles and syringes must be properly disposed of to prevent potential disease transmission or reuse.
Use of microneedle patches could eliminate the need to transport needles, syringes and sterile water, reducing logistical demands. Vaccination could be done by personnel with less medical training, who would simply apply the patches to the skin and remove them after several minutes, making possible door-to-door campaigns similar to those used in polio vaccination. Single-use patches could also reduce the waste of vaccine that occurs when all ten doses in a vial cannot be used.
“A major advantage would be the ease of delivery,” said Mark Prausnitz, a professor in the Georgia Tech School of Chemical and Biomolecular Engineering, and one of the inventors of the microneedle patch. “Microneedles would allow us to move away from central locations staffed by health care personnel to the use of minimally-trained personnel who would go out to homes to administer the vaccine.”
Many countries in the Western Hemisphere have eliminated endemic transmission of the disease, though travelers often serve as sources for imported cases. However, measles remains the leading cause of vaccine-preventable death among children elsewhere in the world, prompting interest in alternative vaccination techniques.
“Measles is extremely infectious, and we need an immunization coverage rate of around 95 percent to interrupt its transmission,” said Dr. Paul Rota, Measles Laboratory Team Lead of CDC’s Division of Viral Diseases and one of the study’s co-authors. “Microneedles represent a real potential game-changer in developing strategies to get high global coverage for a measles vaccine.”
In their study, the CDC-Georgia Tech team first faced the challenge of converting a liquid vaccine to a formulation that could be readily applied to stainless steel microneedles and dried for packaging. The work was made more difficult by the fact that the vaccine contains an attenuated live virus whose integrity had to be maintained.
The researchers began by studying materials that could be combined with the vaccine to improve its stability in dry form. Ultimately, they obtained the best results by adding a sugar known as trehalose to the liquid vaccine. That formulation was applied to the microneedles – which were about 750 microns long – by dipping them into the solution and allowing the liquid to dry. The vaccine dose on the microneedles was controlled by the number of times the microneedles were dipped into the solution.
Cotton rats (Sigmodon hispidus) used in the study were divided into seven groups of five animals each for the testing. The comparison showed that vaccination with the microneedle technique produced an immune response that was statistically indistinguishable from that produced by vaccination with the hypodermic needles.
“The two major accomplishments of this study are that the vaccine can be stabilized on microneedles, and that it could dissolve in the skin to provide a good immune response,” Rota said.
To advance the microneedle technique, the researchers are now working to improve the stability of the dry vaccine with the goal of eliminating the need for refrigeration. They are also studying the use of polymer-based microneedles that would fully dissolve in the skin, removing the need to dispose of potentially infectious waste.
Ultimately, a microneedle-based measles vaccine will need to be evaluated for safety and efficacy in a non-human primate model and in several clinical trials before it can be used routinely in humans.
Microneedles are also being studied for administration of vaccines against influenza, polio, rotavirus, tuberculosis, and hepatitis B. The microneedle measles vaccine would likely find its first use in the developing world as part of measles elimination campaigns, and would probably not replace the Measles-Mumps-Rubella (MMR) vaccine used in the United States.
“This represents a different direction for us, which is campaign-mode global health vaccination,” said Prausnitz. “I see the greatest impact of the measles patch being in developing-country vaccination programs where the logistical advantages of this simple-to-use technology will have the most public health benefit.”
In addition to those already mentioned, the research team included Marcus L. Collins and Jessica Ayers, both from the CDC.
This research is supported by the Georgia Research Alliance (GRA) with indirect support from the Division of Viral Diseases and Animal Resources Branch of the Centers for Disease Control and Prevention (CDC) and the National Institutes of Health (NIH). The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH, CDC or GRA.
Mark Prausnitz is an inventor on patents and has a significant financial interest in a company that is developing microneedle-based products. This potential conflict of interest has been disclosed and is being managed by Georgia Tech and Emory University.
CITATION: Edens C., et al. “Measles vaccination using a microneedle patch,” Vaccine (2012). http://dx.doi.org/10.1016/j.vaccine.2012.09.062
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]]>Now, scientists have demonstrated an automated system that uses artificial intelligence and cutting-edge image processing to rapidly examine large numbers of individual Caenorhabditis elegans, a species of nematode widely used in biological research. Beyond replacing existing manual examination steps using microfluidics and automated hardware, the system’s ability to detect subtle differences from worm-to-worm – without human intervention – can identify genetic mutations that might not have been detected otherwise.
By allowing thousands of worms to be examined autonomously in a fraction of the time required for conventional manual screening, the technique could change the way that high throughput genetic screening is carried out using C. elegans.
Details of the research were reported August 19th in the advance online publication of the journal Nature Methods. The research has been supported by the National Institutes of Health (NIH), the National Science Foundation (NSF) and the Alfred P. Sloan Foundation.
“While humans are very good at pattern recognition, computers are much better than humans at detecting subtle differences, such as small changes in the location of dots or slight variations in the brightness of an image,” said Hang Lu, the project’s lead researcher and an associate professor in the School of Chemical & Biomolecular Engineering at the Georgia Institute of Technology. “This technique found differences that would have been almost impossible to pick out by hand.”
Lu’s research team is studying genes that affect the formation and development of synapses in the worms, work that could have implications for understanding human brain development. The researchers use a model in which synapses of specific neurons are labeled by a fluorescent protein. Their research involves creating mutations in the genomes of thousands of worms and examining the resulting changes in the synapses. Mutant worms identified in this way are studied further to help understand what genes may have caused the changes in the synapses.
One aspect the researchers are studying is why synapses form in the wrong locations, or are of the wrong sizes or types. The differences between the mutants and the normal or “wild type” worms indicate inappropriate developmental patterns caused by the genetic mutations.
Because of the large number of possible genes involved in these developmental processes, the researchers must examine thousands of worms – perhaps as many as 100,000 – to exhaust the search. Lu and her research group had earlier developed a microfluidic “worm sorter” that speeds up the process of examining worms under a microscope, but until now, there were two options for detecting the mutants: a human had to look at each animal, or a simple heuristic algorithm was used to make the sorting decision. Neither option is objective or adaptable to new problems.
Lu’s system, an optimized version of earlier work by her group, uses a camera to record three-dimensional images of each worm as it passes through the sorter. The system compares each image set against what it has been taught the “wild type” worms should look like. Worms that are even subtly different from normal can be sorted out for further study.
“We feed the program wild-type images, and it teaches itself to recognize what differentiates the wild type. It uses this information to determine what a mutant type may look like – which is information we didn’t provide to the system – and sorts the worms based on that,” explained Matthew Crane, a graduate student who performed the work. “We don’t have to show the computer every possible mutant, and that is very powerful. And the computer never gets bored.”
While the system was designed to sort C. elegans for a specific research project, Lu believes the machine learning technology – which is borrowed from computer science – could be applied to other areas of biology that use model genetic organisms. The system’s hardware and software are currently being used in several other laboratories beyond Georgia Tech.
“Our automated technique can be generalized to anything that relies on detecting a morphometric – or shape, size or brightness difference,” Lu said. “We can apply this to anything that can be detected visually, and we think this could be expanded to studying many other problems related to learning, memory, neuro-degeneration and neural developmental diseases that this worm can be used to model.”
Individual C. elegans are less than a millimeter long and thinner than a strand of hair, but have 302 neurons with well-defined synapses. While research using single cells can be simpler to do, studies using the worms are good in vivo models for many important processes relevant to human health.
Other researchers who contributed to this paper include student Jeffrey Stirman from Georgia Tech’s interdisciplinary program in bioengineering, Professor James Rehg from Georgia Tech’s School of Interactive Computing, and three researchers from the Department of Biology at Stanford University’s Howard Hughes Medical Institute: Chan-Yen Ou, Peri Kurshan, and Professor Kang Shen.
The autonomous processing facilitated by the new system could allow researchers to examine more animals more rapidly, potentially opening up areas of study that are not feasible today.
“We are hoping that the technology will really change the approach people can take to this kind of research,” said Lu. “We expect that this approach will enable people to do much larger scale experiments that can push the science forward beyond looking what individual mutations are doing in a specific situation.”
The project described was supported by Award Numbers R01GM088333, R21EB012803 and R01AG035317 from the National Institutes of Health. This material is also based on work supported by the National Science Foundation under Grant No. CAREER CBET-0954578. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National lnstitutes of Health or the National Science Foundation.
Citation: Matthew Crane, Jeffrey Stirman, Chan-Yen Ou, Peri Kurshan, James Rehg, Kang Shen & Hang Lu, Autonomous screening of C. elegans identifies genes implicated in synaptogenesis, DOI: 10.1038/NMETH.2141
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]]>However, a new study by a team of researchers from the University of Groningen and the Georgia Institute of Technology reveals a common mechanism underlying these traps and provides a theoretical framework to design trap-free plastic electronics. The results are presented in an advance online publication of the journal Nature Materials.
Plastic semiconductors are made from organic, carbon-based polymers, comprising a tunable forbidden energy gap. In a plastic light-emitting diode (LED), an electron current is injected into a higher molecular orbital, situated just above the energy gap. After injection, the electrons move toward the middle of the LED and fall down in energy across the forbidden energy gap, converting the energy loss into photons. As a result, an electrical current is converted into visible light.
However, during their passage through the semiconductor, a lot of electrons get stuck in traps in the material and can no longer be converted into light. In addition, this trapping process greatly reduces the electron current and moves the location where electrons are converted into photons away from the center of the device.
“This reduces the amount of light the diode can produce,” explained Herman Nicolai, first author of the Nature Materials paper.
The traps are poorly understood, and it has been suggested that they are caused by kinks in the polymer chains or impurities in the material.
“We’ve set out to solve this puzzle by comparing the properties of these traps in nine different polymers,” Nicolai explained. “The comparison revealed that the traps in all materials had a very similar energy level.”
The Georgia Tech group, led by Professor Jean-Luc Bredas in the School of Chemistry & Biochemistry, investigated computationally the electronic structure of a wide range of possible traps. “What we found out from the calculations is that the energy level of the traps measured experimentally matches that produced by a water-oxygen complex,” said Bredas.
Nicolai explains that “such a complex could easily be introduced during the manufacturing of the semiconductor material, even if this is done under controlled conditions.” The devices Nicolai studied were fabricated in a nitrogen atmosphere, “but this cannot prevent contamination with minute quantities of oxygen and water,” he noted.
The fact that the traps have a similar energy level means that it is now possible to estimate the expected electron current in different plastic materials. And it also points the way to trap-free materials. “The trap energy lies in the forbidden energy gap,” Nicolai explained.
This energy gap represents the difference in energy of the outer shell in which the electrons circle in their ground state and the higher orbital to which they can be moved to become mobile charge carriers. When such a mobile electron runs into a trap that is within the energy gap it will fall in, because the trap has a lower energy level.
“But if chemists could design semiconducting polymers in which the trap energy is above that of the higher orbital in which the electrons move through the material, they couldn’t fall in,” he suggested. “In this case, the energy level of the trap would be higher than that of the electron.”
The results of this study are therefore important for both plastic LEDs and plastic solar cells. “In both cases, the electron current should not be hindered by charge trapping. With our results, more efficient designs can be made,” Nicolai concluded.
The experimental work for this study was done in the Zernike Institute of Advanced Materials (ZIAM) at the faculty of Mathematics and Natural Sciences, University of Groningen, the Netherlands. The theoretical work to identify the nature of the trap was carried out at the School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics at the Georgia Institute of Technology, Atlanta, USA.
The work at the University of Groningen was supported by the European Commission under contract FP7-13708 (AEVIOM). The work at Georgia Tech was supported by the MRSEC program of the National Science Foundation under award number DMR-0819885.
Citation: H. T. Nicolai1, M. Kuik1, G. A. H.Wetzelaer1, B. de Boer1, C. Campbell2, C. Risko2, J. L. Brédas2,4 and P.W. M. Blom1,3* Unification of trap-limited electron transport in semiconducting polymers. Nature Materials, published online: 29 July 2012 | DOI: 10.1038/NMAT3384
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]]>There is considerable evidence that the evolution of life passed through an early stage when RNA played a more central role before DNA and coded proteins appeared. During that time, more than 3 billion years ago, the environment lacked oxygen but had an abundance of soluble iron.
In a new study, researchers from the Georgia Institute of Technology used experiments and numerical calculations to show that iron, in the absence of oxygen, can substitute for magnesium in RNA binding, folding and catalysis. The researchers found that RNA’s shape and folding structure remained the same and its functional activity increased when magnesium was replaced by iron in an oxygen-free environment.
“The primary motivation of this work was to understand RNA in plausible early earth conditions and we found that iron could support an array of RNA structures and catalytic functions more diverse than RNA with magnesium,” said Loren Williams, a professor in the School of Chemistry and Biochemistry at Georgia Tech.
The results of the study were published online on May 31, 2012 in the journal PLoS ONE. The study was supported by the NASA Astrobiology Institute.
In addition to Williams, Georgia Tech School of Biology postdoctoral fellow Shreyas Athavale, research scientist Anton Petrov, and professors Roger Wartell and Stephen Harvey, and Georgia Tech School of Chemistry and Biochemistry postdoctoral fellow Chiaolong Hsiao and professor Nicholas Hud also contributed to this work.
Free oxygen gas was almost nonexistent more than 3 billion years ago in the early earth’s atmosphere. When oxygen began entering the environment as a product of photosynthesis, it turned the earth’s iron to rust, forming massive banded iron formations that are still mined today. The free oxygen produced by advanced organisms caused iron to be toxic, even though it was -- and still is -- a requirement for life.
This environmental transition triggered by the introduction of free oxygen into the atmosphere would have caused a slow, but dramatic, shift in biology that required transformations in biochemical mechanisms and metabolic pathways. The current study provides evidence that this transition may have caused a shift from iron to magnesium for RNA binding, folding and catalysis processes.
The researchers used quantum mechanical calculations, chemical footprinting and two ribozyme assays to determine that in an oxygen-free environment, iron, Fe2+, can be substituted for magnesium, Mg2+, in RNA folding and catalysis.
Quantum mechanical calculations showed that the structure of RNA was nearly identical when it included iron or magnesium. When large RNAs fold into native, stable structures, negatively charged phosphate groups are brought into close proximity. The researchers calculated one small difference between the activity of iron and magnesium structures: more charge was transferred from phosphate to iron than from phosphate to magnesium.
Chemical probing under anaerobic conditions showed that iron could replace magnesium in compacting and folding large RNA structures, thus providing evidence that iron and magnesium could be nearly interchangeable in their interactions with RNA.
Under identical anaerobic conditions, the activity of two enzymes was enhanced in the presence of iron, compared to their activity in the presence of magnesium. The initial activity of the L1 ribozyme ligase, an enzyme that glues together pieces of RNA, was 25 times higher in the presence of iron. Activity of the hammerhead ribozyme, an enzyme that cuts RNA, was three times higher in the presence of iron compared to magnesium.
“The results suggest that iron is a superior substitute for magnesium in these catalytic roles,” said Williams, who is also director of the Center for Ribosomal Origins and Evolution at Georgia Tech. “Our hypothesis is that RNA evolved in the presence of iron and is optimized to work with iron.”
In future studies, the researchers plan to investigate what unique functions RNA can possess with iron that are not possible with magnesium.
This work was supported by NASA (Award No. NNA09DA78A). The content is solely the responsibility of the principal investigators and does not necessarily represent the official views of NASA.
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]]>“The mission of the Integrated Cancer Research Center is to facilitate integration of the diversity of technological, computational, scientific and medical expertise at Georgia Tech and partner institutions in a coordinated effort to develop improved cancer diagnostics and therapeutics,” McDonald explained.
For years, the study of cancer has been concentrated at major medical research institutions and cancer research has been traditionally viewed as falling exclusively within the bailiwick of the biological sciences. This is now changing for the better, according to McDonald.
“We are at a truly exciting crossroads in the history of cancer research where molecular biology, the computational sciences, engineering and nanotechnology are joining together in a unified effort to develop more effective cancer diagnostics and therapeutics,” added McDonald.
New high-throughput methods to molecularly characterize cancer cells have, in recent years, lead to tremendous strides in the development of novel diagnostics and the identification of new molecular targets for therapeutic intervention.
On the computational side, recently developed algorithms customized for the analysis of genomic, proteomic and other high volume datasets are providing a level of insight into cellular complexities never before imagined. The number of new technologies and devices arising from the fields of biomedical engineering and nanotechnology that have potential application to the area of cancer biology has tremendous promise.
McDonald’s enthusiasm for the new cancer center is shared by Robert Guldberg, PhD, executive director of the Parker H. Petit Institute for Bioengineering and Bioscience.
“Georgia Tech, particularly researchers throughout the IBB community, have been leaders in the development of collaborative approaches to both cancer diagnostics and therapeutics,” Guldberg explained. “This new center will bring together researchers from a wide-variety of backgrounds to tackle complex research problems in new and exciting ways.”
Visit the new Integrated Cancer Research Center website.
]]>The study also found that after the material is produced, its structural and chemical properties continue to evolve for more than a month as a result of continuing chemical reactions with hydrogen.
Understanding the properties of graphene oxide – and how to control them – is important to realizing potential applications for the material. To make it useful for nano-electronics, for instance, researchers must induce both an electronic band gap and structural order in the material. Controlling the amount of hydrogen in graphene oxide may be the key to manipulating the material properties.
“Graphene oxide is a very interesting material because its mechanical, optical and electronic properties can be controlled using thermal or chemical treatments to alter its structure,” said Elisa Riedo, an associate professor in the School of Physics at the Georgia Institute of Technology. “But before we can get the properties we want, we need to understand the factors that control the material’s structure. This study provides information about the role of hydrogen in the reduction of graphene oxide at room temperature.”
The research, which studied graphene oxide produced from epitaxial graphene, was reported on May 6 in the journal Nature Materials. The research was sponsored by the National Science Foundation, the Materials Research Science and Engineering Center (MRSEC) at Georgia Tech, and by the U.S. Department of Energy.
Graphene oxide is formed through the use of chemical and thermal processes that mainly add two oxygen-containing functional groups to the lattice of carbon atoms that make up graphene: epoxide and hydroxyl species. The Georgia Tech researchers began their studies with multilayer expitaxial graphene grown atop a silicon carbide wafer, a technique pioneered by Walt de Heer and his research group at Georgia Tech. Their samples included an average of ten layers of graphene.
After oxidizing the thin films of graphene using the established Hummers method, the researchers examined their samples using X-ray photo-emission spectroscopy (XPS). Over about 35 days, they noticed the number of epoxide functional groups declining while the number of hydroxyl groups increased slightly. After about three months, the ratio of the two groups finally reached equilibrium.
“We found that the material changed by itself at room temperature without any external stimulation,” said Suenne Kim, a postdoctoral fellow in Riedo’s laboratory. “The degree to which it was unstable at room temperature was surprising.”
Curious about what might be causing the changes, Riedo and Kim took their measurements to Angelo Bongiorno, an assistant professor who studies computational materials chemistry in Georgia Tech’s School of Chemistry and Biochemistry. Bongiorno and graduate student Si Zhou studied the changes using density functional theory, which suggested that hydrogen could be combining with oxygen in the functional groups to form water. That would favor a reduction in the epoxide groups, which is what Riedo and Kim were seeing experimentally.
“Elisa’s group was doing experimental measurements, while we were doing theoretical calculations,” Bongiorno said. “We combined our information to come up with the idea that maybe there was hydrogen involved.”
The suspicions were confirmed experimentally, both by the Georgia Tech group and by a research team at the University of Texas at Dallas. This information about the role of hydrogen in determining the structure of graphene oxide suggests a new way to control its properties, Bongiorno noted.
“During synthesis of the material, we could potentially use this as a tool to change the structure,” he said. “By understanding how to use hydrogen, we could add it or take it out, allowing us to adjust the relative distribution and concentration of the epoxide and hydroxyl species which control the properties of the material.”
Riedo and Bongiorno acknowledge that their material – based on epitaxial graphene – may be different from the oxide produced from exfoliated graphene. Producing graphene oxide from flakes of the material involves additional processing, including dissolving in an aqueous solution and then filtering and depositing the material onto a substrate. But they believe hydrogen plays a similar role in determining the properties of exfoliated graphene oxide.
“We probably have a new new form of graphene oxide, one that may be more useful commercially, although the same processes should also be happening within the other form of graphene oxide,” said Bongiorno.
The next steps are to understand how to control the amount of hydrogen in epitaxial graphene oxide, and what conditions may be necessary to affect reactions with the two functional groups. Ultimately, that may provide a way to open an electronic band gap and simultaneously obtain a graphene-based material with electron transport characteristics comparable to those of pristine graphene.
“By controlling the properties of graphene oxide through this chemical and thermal reduction, we may arrive at a material that remains close enough to graphene in structure to maintain the order necessary for the excellent electronic properties, while having the band gap needed to create transistors,” Riedo said. “It could be that graphene oxide is the way to arrive at that type of material.”
Beyond those already mentioned, the paper’s authors included Yike Hu, Claire Berger and Walt de Heer from the School of Physics at Georgia Tech, and Muge Acik and Yves Chabal from the Department of Materials Science and Engineering at the University of Texas at Dallas.
This research was supported by the National Science Foundation under grants CMMI-1100290, DMR-0820382 and DMR-0706031, and by the U.S. Department of Energy’s Office of Basic Energy Sciences under grants DE-FG02-06ER46293 and DE-SC001951. The content is solely the responsibility of the principal investigators and does not necessarily represent the official views of the National Science Foundation or the Department of Energy.
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]]>If mimicked by artificial systems, this photocatalytic process could provide abundant new supplies of oxygen and, possibly hydrogen, as a by-product of producing electricity. However, despite its importance to the survival of the planet, scientists don’t fully understand the complex process plants use to harness the sun’s energy.
A paper published April 2 in the journal Proceedings of the National Academy of Sciences moves scientists closer to that understanding by showing the importance of a hydrogen bonding water network in that portion of the photosynthetic machinery known as photosystem II. Using Fourier transform infrared spectroscopy (FT-IR) on photosystem II extracted from ordinary spinach, researchers at the Georgia Institute of Technology tested the idea that a network of hydrogen-bonded water molecules plays a catalytic role in the process that produces oxygen.
“By substituting ammonia, an analog of the water molecule that has a similar structure, we were able to show that the network of hydrogen-bonded water molecules is important to the catalytic process,” said Bridgette Barry, a professor in Georgia Tech’s School of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Biosciences. “Substituting ammonia for water inhibited the activity of the photosystem and disrupted the network. The network could be reestablished by addition of a simple sugar, trehalose.”
The research was supported by the National Science Foundation (NSF) and published in the Early Edition of the journal.
In the chloroplasts of green plants, algae and cyanobacteria, oxygen is produced by the accumulation of photo-induced oxidizing equivalents in a structure known as the oxygen-evolving complex (OEC). The OEC contains manganese and calcium ions. Illumination causes oxidation of manganese ions in the OEC. Short laser flashes can be used to step through the reaction cycle, which involves four sequential light-induced oxidation reactions. Oxygen is produced on the fourth step, and then is released from the OEC.
This so-called S state cycle resets with the binding of the substrate, water. Scientists have proposed that a hydrogen bond network, which includes multiple water molecules bound to manganese ions, calcium ions, and protein amide carbonyl (C=O) groups, forms an electrostatic network surrounding the OEC. In this scenario, the extensive hydrogen-bond network would then serve as a component of the catalyst, which splits off oxygen.
To study the process, Barry and graduate student Brandon Polander used precision FT-IR spectroscopy to describe how the network reacts to a short laser flash. The second harmonic of a pulsed Nd-Yag laser was used as the light source. This illumination causes the OEC to undergo one step in its catalytic cycle, the so-called S1 to S2 transition. An infrared spectrum was recorded before and after a laser flash to the photosystem sample, which was isolated from supermarket spinach.
The exquisite sensitivity of FT-IR spectroscopy allowed them to measure changes in the bond strength of the protein C=O groups. The energies of these C=O groups were used as markers of hydrogen bond strength. The brief laser flash oxidized a manganese ion and caused a change in the strength of the C=O bond, which reported an increase in hydrogen bonding to water molecules. When ammonia was added as an inhibitor, a decrease in C=O hydrogen bonding was observed instead. Addition of trehalose, which is known to change the ordering of water molecules at the surface of proteins, blocked this effect of ammonia.
The study describes the coordinated changes that must occur in the protein to facilitate the reaction and shows that the strength of the hydrogen-bonded network is important.
“This research helps to clarify how ammonia inhibits the photosystem, which is something that researchers have been wondering about for many years,” Barry explained. “Our work suggests that ammonia can inhibit the reaction by disrupting this network of hydrogen bonds.”
The research also suggests that in design of artificial devices that carry out this reaction, sustaining a similar hydrogen-bonding network may be important. The stabilizing effect of trehalose discovered by Polander and Barry may also be important.
Beyond the importance of understanding the photosynthetic process, the work could lead to new techniques for producing hydrogen and oxygen using sunlight. One possibility would be to add a biomimetic photocatalytic process to a photovoltaic system producing electricity from the sun.
“In terms of providing new sources of energy, we still have lessons to learn from plants about how they carry out these critical processes,” Barry said. “It would be a great advance for the planet to have new, sustainable, and inexpensive processes to carry out this reaction.”
Ultimately, she hopes the full water oxidizing cycle can be explored and potentially harnessed or imitated for oxygen and energy production.
“We are only looking at a single part of the overall reaction now, but we would like to study the entire cycle, in which oxygen is produced, to see how the interactions in the water network change and how the interactions with the protein change,” Barry said. “The work is another step in understanding how plants carry out this amazing series of photosynthetic reactions.”
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]]>Quickly and accurately detecting infections caused by S. aureus is critical because the pathogenicbacterium causes a broad spectrum of infections, ranging from acute to chronicdisease, which need to be treated in a prompt manner with the correctantibiotic.
The test uses mass spectrometry to quantify the number of S. aureus organisms in a large number ofsamples in just a few hours, compared to a day or two for culturing techniquestypically used to detect this bacterium.
“Our method for detecting staph infections using massspectrometry will be valuable in a variety of situations, but will be crucial whena large number of people need to be tested very quickly, which will ultimatelyimprove treatment,” said Facundo Fernández, an associate professor in theGeorgia Tech School of Chemistry and Biochemistry.
Details of the new staph infection detection method werepublished in the January issue of the journal Molecular and Cellular Proteomics. Partial funding for thisresearch was provided by 3M and the CDC/Georgia Tech seed award program.
Fernández together with Carrie Pierce, Jon Rees and JohnBarr from the CDC’s Division of Laboratory Sciences created this test.
“The simplicity of samplepreparation, the low cost of required reagents and the increased availabilityof mass spectrometers in clinical laboratories make this new method a cost-effectiveway to rapidly and effectively detect staph infections, which must be treatedquickly to prevent spread of the disease,” explained Pierce, a researchchemist at the CDC who also worked on the project as a graduate student at GeorgiaTech.
To run their test, the researchers first inject a knownamount of bacteriophage labeled with nitrogen-15 into a sample. The phages --which are viruses that infect bacteria -- infect only live S. aureus cells, which then multiply and amplify the phage signal. Followinga two-hour incubation, the researchers break up proteins from the phage shellinto component peptides using a trypsin digest technique.
Then they analyze the sample using liquid chromatography withtandem mass spectrometric detection. By detecting peptides from the proteinshell of the phage, the researchers can measure the concentration of S. aureus in the sample.
“The strength of this technique is coupling awell-characterized method for identifying bacteria with a modern detectiondevice, such as a mass spectrometer,” said Barr, biological mass spectrometry leadin the CDC’s Division of Laboratory Sciences. “By labeling input phage withheavy nitrogen isotopes, we were able to use mass spectrometry to effectivelydistinguish between the parent and progeny phage, thus enhancing theselectivity of the method.”
This prototype mass spectrometry-based technique has beenoptimized to detect low concentrations of bacteria that should allow cliniciansto diagnose staph infections without the need for a significant culture period.Coupled with standard laboratory robotics, the test will reduce manual laborand subjective interpretation of results inherent in traditional techniques.
“An exciting aspect of this phage method is that with smallmodifications to the procedures, resistance and susceptibility to a number ofdifferent antibiotics can be determined in addition to bacterialidentification,” said Rees. “This additional piece of information may be thekey to wide acceptance of the method.”
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]]>Grand Challenges Explorations funds scientists and researchers worldwide to explore ideas that can break the mold in how we solve persistent global health and development challenges. The Georgia Tech/CDC project is one of 110 Grand Challenges Explorations grants announced November 7th.
"We believe in the power of innovation -- that a single bold idea can pioneer solutions to our greatest health and development challenges," said Chris Wilson, director of global health discovery for the Bill & Melinda Gates Foundation. "Grand Challenges Explorations seeks to identify and fund these new ideas wherever they come from, allowing scientists, innovators and entrepreneurs to pursue the kinds of creative ideas and novel approaches that could help to accelerate the end of polio, cure HIV infection or improve sanitation."
Projects that are receiving funding show promise in tackling priority global health issues where solutions do not yet exist. This includes finding effective methods to eliminate or control infectious diseases such as polio and HIV as well as discovering new sanitation technologies.
The goal of the Georgia Tech/CDC project is to demonstrate the scientific and economic feasibility for using microneedle patches in vaccination programs aimed at eradicating the polio virus. Current vaccination programs use an oral polio vaccine that contains a modified live virus. This vaccine is inexpensive and can be administered in door-to-door immunization campaigns, but in rare cases the vaccine can cause polio. There is an alternative injected vaccine that uses killed virus, which carries no risk of polio transmission, but is considerably more expensive than the oral vaccine, requires refrigeration for storage and must be administered by trained personnel. To eradicate polio from the world, health officials will have to discontinue use of the oral vaccine with its live virus, replacing it with the more expensive and logistically-complicated injected vaccine.
Prausnitz and his CDC collaborators believe the use of microneedle patches could reduce the cost and simplify administration of the injected vaccine. Use of the patches, which carry vaccine into the body by dissolving into the skin, could eliminate the need for administration by highly-trained personnel and the "sharps" disposal problems of traditional hypodermic needles. Because skin administration produces an immune response with smaller doses of vaccine than traditional deep intramuscular injection, the researchers expect to reduce the per-person cost of vaccine. And by incorporating dried vaccine into the microneedles, they hope to eliminate the need for vaccine refrigeration -- a challenge in remote areas of the world.
"We envision vaccination campaigns in which minimally-trained personnel go door-to-door administering microneedle patches rather than oral polio vaccine," Prausnitz explained. "Our goal for this study will be to provide the data to scientifically justify moving the microneedle patch for polio vaccination into a human trial."
In research that will complement the Grand Challenges Exploration grant, Prausnitz and his team have also received funding from the World Health Organization (WHO) to support development of the polio vaccine application for microneedle patches. And in a project sponsored by the U.S. National Institutes of Health (NIH), Prausnitz and other Georgia Tech researchers are collaborating with Emory University scientists on development of a microneedle patch for administering flu vaccine.
About Grand Challenges Explorations: Grand Challenges Explorations is a US $100 million initiative funded by the Bill & Melinda Gates Foundation. Launched in 2008, Grand Challenge Explorations grants have already been awarded to nearly 500 researchers from over 40 countries. The grant program is open to anyone from any discipline and from any organization. The initiative uses an agile, accelerated grant-making process with short, two-page online applications and no preliminary data required. Initial grants of $100,000 are awarded two times a year. Successful projects have an opportunity to receive a follow-on grant of up to US $1 million. To learn more about Grand Challenges Explorations, visit www.grandchallenges.org.
About The Georgia Institute of Technology: The Georgia Institute of Technology is one of the world's premier research universities, ranked second among all U.S. colleges and universities in the amount of engineering research conducted. Ranked seventh among U.S. News & World Report's top public universities, Georgia Tech's more than 20,000 students are enrolled in its Colleges of Architecture, Computing, Engineering, Liberal Arts, Management and Sciences. Georgia Tech is among the nation's top producers of women and minority engineers. The Institute offers research opportunities to both undergraduate and graduate students and is home to more than 100 interdisciplinary units plus the Georgia Tech Research Institute.
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]]>Similarly, when a newly created drug doesn’t bind well to itsintended target, the drug won’t work. Scientists are then forced to go back tothe lab, often with very little indication about why the binding was weak. Thenext step is to choose a different pharmaceutical “combination” and hope forbetter results. Georgia Tech researchers have now generated a computer modelthat could help change that blind process.
Symmetry-adapted perturbation theory (SAPT) allowsscientists to study interactions between molecules, such as those between adrug and its target. In the past, computer algorithms that study thesenoncovalent interactions have been very slow, limiting the types of moleculesthat can be studied using accurate quantum mechanical methods. A research teamheaded by Georgia Tech Professor of Chemistry David Sherrill has developed acomputer program that can study larger molecules (more than 200 atoms) fasterthan any other program in existence.
“Our fast energy component analysis program is designed toimprove our knowledge about why certain molecules are attracted to one another,“ explained Sherrill, who also has a joint
appointment in the School of Computational Science and Engineering. “It can also show us how interactions between moleculescan be tuned by chemical modifications, such as replacing a hydrogen atom witha fluorine atom. Such knowledge is keyto advancing rational drug design.”
The algorithms can also be used to improve the understandingof crystal structures and energetics, as well as the 3D arrangement of biologicalmacromolecules. Sherrill’s team used the software to study the interactions betweenDNA and proflavine; these interactions are typical of those found between DNAand several anti-cancer drugs. The findings are published this month in the Journal of Chemical Physics.
Rather than selling the software, the Georgia Techresearchers have decided to distribute their code free of charge as part of theopen-source computer program PSI4, developedjointly by researchers at Georgia Tech, Virginia Tech, the University ofGeorgia and Oak Ridge National Laboratory. It is expected to be available in early 2012.
“By giving away our source code, we hope it will be adoptedrapidly by researchers in pharmaceuticals, organic electronics and catalysis,giving them the tools they need to design better products,” said Sherrill.
Sherrill’s team next plans to use the software to study thenoncovalent interactions involving indinavir, which is used to treat HIVpatients.
This project is supportedby the National Science Foundation (NSF) (Award No. CHE-1011360).The content is solely the responsibility of the principal investigators anddoes not necessarily represent the official views of the NSF.
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"The EFRI research teams will probe some profound aspects of the interface of biology and engineering," said Sohi Rastegar, director of EFRI. "If they are successful, the principles and theories uncovered in their investigations could unlock many technological opportunities."
This year, 14 transformative, fundamental research projects were awarded EFRI grants in two emerging areas: technologies that build on understanding of biological signaling, and machines that can interact and cooperate with humans.
The three Georgia Tech projects include:
The therapeutic robot could enhance, assist and improve motor skills in humans with varying motor capabilities and deficits. The goal of the project is to program a humanoid rehabilitation robot to perform a "partnered box step," which is a defined pattern of weight shifts and directional changes, solely based on interpreting movement cues from subtle changes in forces between the hands and arms of the robot and the person.
To do this, researchers at Georgia Tech and Emory University will study how humans use their muscles to walk, balance and generate force signals with the hands for guidance when moving in cooperation with another person. They will also study "rehabilitative partnered dance," which has been specifically adapted to help improve gait and balance in individuals with motor impairments.
"Our vision is to develop robots that will interact with humans as both assistants and movement therapists," explained principal investigator Lena Ting, an associate professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University. "We expect our project to have a long-term impact on quality of life of individuals with movement difficulties, such as those caused by Parkinson's disease, stroke and injury by improving fitness, motor skills and social engagement."
Working with Ting on the project are Emory University School of Medicine (geriatrics) assistant professor Madeleine Hackney, Coulter Department of Biomedical Engineering assistant professor Charlie Kemp and Georgia Tech School of Interactive Computing assistant professor Karen Liu.
For the second project, researchers at Georgia Tech and The City College of New York will investigate devices for "alternative perception" and the principles underlying the human-machine interaction. Alternative perception combines electronics and the other senses to emulate vision. In addition to aiding the visually impaired, the findings are expected to have other applications, such as the development of intelligent robots.
The researchers plan to untangle how humans learn to coordinate input from their senses -- e.g. vision, touch -- with movements, like reaching for a glass or moving through a crowded room. They will then map out how machines, such as robots and computers, learn similar tasks, to model devices that can assist humans.
The team envisions a multifunctional array of sensors on the body and has already developed prototypes for some of the devices. The full complement of wearable sensors would help a sightless person navigate by conveying information about his or her surroundings.
The researchers hope their findings on perception, and the prototypes they develop, will spawn a raft of wearable electronic devices to help blind people "see" their environment at a distance through touch, hearing and other senses. The technology would also benefit sighted individuals who must navigate in poor visibility, such as firefighters and pilots.
Principal investigator Zhigang Zhu, professor of computer science and computer engineering in City College's Grove School of Engineering, will collaborate with City College professor of psychology and director of the Program in Cognitive Neuroscience Tony Ro, City College professor of electrical engineering Ying Li Tian, Georgia Tech Woodruff School of Mechanical Engineering professor Kok-Meng Lee, and Georgia Tech School of Applied Physiology associate professor Boris Prilutsky.
The third project will address a fundamental question of developmental biology: what controls the spatial and temporal patterns of cell differentiation? Answering this question will lead to a better understanding of the basic principles of embryogenesis, explain origins of developmental disorders, and provide guidelines for tissue engineering and regenerative medicine.
The research will be conducted by principal investigator and Princeton University Department of Chemical and Biological Engineering associate professor Stanislav Shvartsman, Georgia Tech School of Chemical and Biomolecular Engineering associate professor Hang Lu, New York University Department of Biology professor Christine Rushlow, and University of Illinois at Urbana Champaign Department of Computer Science associate professor Saurabh Sinha.
Scientists know that among an embryo's first major developments is the establishment of its dorsoventral axis, which runs from its back to its belly. The researchers plan to study how this axis development unfolds -- specifically the presence and location of proteins during the process, which give rise to muscle, nerve and skin tissues.
To enable large-scale quantitative analyses of protein positional information along the dorsoventral axis, Lu and Shvartsman will further develop a microfluidic device they previously designed to reliably and robustly orient several hundred embryos in just a few minutes.
"By understanding this system at a deeper, quantitative level, we will elucidate general principles underlying the operation of genetic and multicellular networks that drive development," said Lu.
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Led by Mark Hay, a Georgia Tech professor of biology, the 10-day mission includes two Ph.D. students and a postdoctoral researcher who are living 50 feet below the surface in the unique underwater lab. Aquarius, which is about the size of a school bus, includes scientific laboratories and living quarters for up to six scientists who can live and work underwater for the entire length of the mission.
Hay's research team has been studying how seaweed and fish affect the health of coral reefs in the Pacific Ocean and Caribbean Sea. They have shown that the natural defenses of seaweed can harm the coral, and that plant-eating fish can control the growth of the noxious seaweed. The new studies will build on that knowledge and provide new information on the complex factors affecting reef ecosystems.
"Consumption of seaweed plays a critical role in structuring coral reefs and in selecting for algal traits that deter herbivorous fish," explained Hay, who holds the Harry and Linda Teasely Chair in the Georgia Tech School of Biology. "Recent studies have noted dramatic variance among species in the susceptibility of herbivorous fish to seaweed chemical and structural defenses. These differences can translate into dramatic direct effects of herbivore diversity on seaweed."
Because certain fish species eat specific seaweed species, and certain seaweeds are more damaging to coral than others, differences in the diversity of seaweed-eating fish can have a dramatic indirect effect on corals -- as well as on changes in the structure and function of the endangered reefs.
"Our mission to Aquarius will allow us to study experimentally how herbivore diversity may be managed to conserve and even restore reefs," Hay added. "In previous studies, we have demonstrated that herbivore diversity affected the function and structure of the coral reefs. We plan to build on that research in this new study through Aquarius."
During the 10-day mission, the researchers will evaluate changes in reef communities near Aquarius, where they have built large cages and enclosed different species of fish for the past ten months. Within the enclosures, they included specific species of fish, or mixes of different species. They will be evaluating the effects of these different fish and mixes of fish on the health and growth of the coral to determine:
* The long-term effects of the fish on the community structure;
* Which seaweeds are most damaging to corals and which herbivores can best control these species;
* How small mobile species and recruiting juvenile fish that can pass through the cage mesh respond to community changes;
* How algal chemical and mineral defenses generate the mechanisms driving these changes.
Field studies by Hay's group have previously shown that several common species of seaweed in both the Pacific and Caribbean can kill corals upon contact using chemical means.
While competition between seaweed and coral is just one of many factors affecting the decline of coral reefs worldwide, this chemical threat may provide a serious setback to efforts aimed at repopulating damaged reefs. Seaweeds are normally kept in check by herbivorous fish, but in many areas overfishing has reduced the populations of these plant-consumers, allowing seaweed to overpopulate coral reefs.
Other studies done by the group using a similar type of reef enclosure found that mixing two specific species of herbivorous fishes decreased seaweed cover by as much as 76 percent, increased coralline crusts that stimulate coral settlement by as much as 117 percent, increased coral growth by 22 percent, and prevented additional coral loss.
The new study will assess the impact of different species of seaweed-eating fish and compare those to previous results evaluating different mixes of fish.
The goal will be to determine which specific mixes of fish can control the most damaging of seaweeds and to evaluate the importance of herbivore diversity in suppressing seaweed and protecting corals. This information could be used to help manage fishing practices to protect the reefs.
"The particular biodiversity of herbivores may be as important as the density, or mass, of herbivores in determining the structure, function, and health of reef communities," Hay said. "We know too little of the species-specific effects of reef herbivores, how effects of multiple species sum to produce an overall effect, or which particular mix of herbivores is critical for suppressing aggressive seaweed to maintain reef function."
Coral reefs are declining worldwide, and scientists studying the problem had suspected that proliferation of seaweed was part of the cause -- perhaps by crowding out the coral or by damaging it physically.
By allowing scientists to remain on the ocean floor for long periods of time -- a capability known as saturation diving -- Aquarius helps researchers get more work done by extending the dive time at depth and eliminating the decompression time that would be required for returning to the surface each day. Owned by the National Oceanic and Atmospheric Administration, Aquarius is managed by the University of North Carolina Wilmington and located in the Florida Keys National Marine Sanctuary.
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]]>The capsule's structure -- hollow except for polymer chains tethered to the interior of the shell -- provides spatially-segregated compartments that make it a good candidate for multi-drug encapsulation and release strategies. The microcapsule could be used to simultaneously deliver distinct drugs by filling the core of the capsule with hydrophilic drugs and trapping hydrophobic drugs within nanoparticles assembled from the polymer chains.
"We have demonstrated that we can make a fairly complex multi-component delivery vehicle using a relatively straightforward and scalable synthesis," said L. Andrew Lyon, a professor in the School of Chemistry and Biochemistry at Georgia Tech. "Additional research will need to be conducted to determine how they would best be loaded, delivered and triggered to release the drugs."
Details of the microcapsule synthesis procedure were published online on July 5, 2011 in the journal Macromolecular Rapid Communications.
Lyon and Xiaobo Hu, a former visiting scholar at Georgia Tech, created the microcapsules. As a graduate student at the Research Institute of Materials Science at the South China University of Technology, Hu is co-advised by Lyon and Zhen Tong of the South China University of Technology. Funding for this research was provided to Hu by the China Scholarship Council.
The researchers began the two-step, one-pot synthesis procedure by forming core particles from a temperature-sensitive polymer called poly(N-isopropylacrylamide). To create a dissolvable core, they formed polymer chains from the particles without a cross-linking agent. This resulted in an aggregated collection of polymer chains with temperature-dependent stability.
"The polymer comprising the core particles is known for undergoing chain transfer reactions that add cross-linking points without the presence of a cross-linking agent, so we initiated the polymerization using a redox method with ammonium persulfate and N,N,N’,N’-tetramethylethylenediamine. This ensured those side chain transfer reactions did not occur, which allowed us to create a truly dissolvable core," explained Lyon.
For the second step in the procedure, Lyon and Hu added a cross-linking agent to a polymer called poly(N-isopropylmethacrylamide) to create a shell around the aggregated polymer chains. The researchers conducted this step under conditions that would allow any core-associated polymer chains that interacted with the shell during synthesis to undergo chain transfer and become grafted to the interior of the shell.
Cooling the microcapsule exploited the temperature sensitivities of the polymers. The shell swelled with water and expanded to its stable size, while the free-floating polymer chains in the center of the capsule diffused out of the core, leaving behind an empty space. Any chains that stuck to the shell during its synthesis remained. Because the chains control the interaction between the particles they store and their surroundings, the tethered chains can act as hydrophobic drug carriers.
Compared to delivering a single drug, co-delivery of multiple drugs has several potential advantages, including synergistic effects, suppressed drug resistance and the ability to tune the relative dosage of various drugs. The future optimization of these microcapsules may allow simultaneous delivery of distinct classes of drugs for the treatment of diseases like cancer, which is often treated using combination chemotherapy.
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]]>"These contrast agents fill the need for probes that can accurately image small numbers of bacteria in vivo and distinguish infections from other pathologies like cancer," said Niren Murthy, an associate professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University. "These probes could ultimately improve the diagnosis and treatment of bacterial infections, which remains a major challenge in medicine."
The imaging probes were described in the July 17, 2011 advance online edition of the journal Nature Materials. The research was sponsored by the National Science Foundation and National Institutes of Health.
Coulter Department postdoctoral fellows Xinghai Ning and Seungjun Lee led the project. University of Georgia Complex Carbohydrate Research Center postdoctoral associate Zhirui Wang; and Georgia State University Department of Biology associate professor Eric Gilbert and student Bryan Subblefield also contributed to the work.
In the United States in 2010, bacterial infections caused 40,000 deaths from sepsis and were the leading cause of limb amputations. A major limitation preventing the effective treatment of bacterial infections is an inability to detect them inside the body with accuracy and sensitivity. To image bacterial infections, probes must first deliver a large quantity of the contrast agent into bacteria.
"Most existing imaging probes target the bacterial cell wall and cannot access the inside of the bacteria, but maltodextrin-based imaging probes target a bacterial ingestion pathway, which allows the contrast agent to reach a high concentration within bacteria," said Murthy.
Maltodextrin-based imaging probes consist of a fluorescent dye linked to maltohexaose, which is a major source of glucose for bacteria. The probes deliver the contrast agent into bacteria through the organism's maltodextrin transporter, which only exists in bacterial cells and not mammalian cells.
"To our knowledge, this represents the first demonstration of a targeting strategy that can deliver millimolar concentrations of an imaging probe within bacteria," noted Murthy.
In experiments using a rat model, the researchers found that the contrast agent accumulated in bacteria-infected tissues, but was efficiently cleared from uninfected tissues. They saw a 42-fold increase in fluorescence intensity between bacterial infected and uninfected tissues. However, the contrast agent did not accumulate in the healthy bacterial microflora located in the intestines. Because systemically administered glucose molecules cannot access the interior of the intestines, the bacteria located there never came into contact with the probe.
They also found that the probes could detect as few as one million viable bacteria cells. Current contrast agents for imaging bacteria require at least 100 million bacteria, according to the researchers.
In another experiment, the researchers found that the maltodextrin-based probes could distinguish between bacterial infections and inflammation with high specificity. Tissues infected with E. coli bacteria exhibited a 17-fold increase in fluorescence intensity when compared with inflamed tissues that were not infected.
Additional laboratory experiments showed that the probes could deliver large quantities of imaging probes to gram-positive and gram-negative bacteria for internalization. Both types of bacteria internalized the maltodextrin-based probes at a rate three orders of magnitude faster than mammalian cells.
"Maltodextrin-based probes show promise for imaging infections in a wide range of tissues, with an ability to detect bacteria in vivo with a sensitivity two orders of magnitude higher than previously reported," said Murthy.
This project is supported by the National Science Foundation (NSF) (NSF Career Award No. BES-0546962) and the National Institutes of Health (NIH) (Award Nos. RO1 HL096796-01 and HHSN268201000043C). The content is solely the responsibility of the principal investigator and does not necessarily represent the official views of the NSF or NIH.
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New research presented on June 16, 2011 at the annual meeting of the International Society for Stem Cell Research (ISSCR) shows that systematically controlling the local and global environments during stem cell development helps to effectively direct the process of differentiation. In the future, these findings could be used to develop manufacturing procedures for producing large quantities of stem cells for diagnostic and therapeutic applications. The research is sponsored by the National Science Foundation and the National Institutes of Health.
"Stem cells don't make any decisions in isolation; their decisions are spatially and temporally directed by biochemical and mechanical cues in their environment," said Todd McDevitt, director of the Stem Cell Engineering Center at Georgia Tech and an associate professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University. "We have designed systems that allow us to tightly control these properties during stem cell differentiation, but also give us the flexibility to introduce a new growth factor or shake the cells a little faster to see how changes like these affect the outcome."
These systems can also be used to compare the suitability of specific stem cell types for a particular use.
"We have developed several platforms that will allow us to conduct head-to-head studies with different kinds of stem cells to determine if one type of stem cell outperforms another type for a certain application," said McDevitt, who is also a Petit Faculty Fellow in the Institute for Bioengineering and Bioscience at Georgia Tech.
Many laboratory growth methods allow stem cells to aggregate in three-dimensional clumps called "embryoid bodies" during differentiation. McDevitt and biomedical engineering graduate student Andres Bratt-Leal incorporated biomaterial particles directly within these aggregates during their formation. They introduced microparticles made of gelatin, poly(lactic-co-glycolic acid) (PLGA) or agarose and tested their impact on the assembly, intercellular communication and morphogenesis of the stem cell aggregates under different conditions by varying the microsphere-to-cell ratio and the size of the microspheres.
The researchers found that the presence of the biomaterials alone modulated embryoid body differentiation, but did not adversely affect cell viability. Compared to typical delivery methods, providing differentiation factors -- retinoic acid, bone morphogenetic protein 4 (BMP4) and vascular endothelial growth factor (VEGF) -- via microparticles induced changes in the gene and protein expression patterns of the aggregates.
By including tiny magnetic particles into the embryoid bodies during formation, the researchers also found they could use a magnet to spatially control the location of an aggregate and its assembly with other aggregates. The magnetic particles remained entrapped within the aggregates for the duration of the experiments but did not adversely affect cell viability or differentiation.
"With biomaterial and magnetic microparticles, we are beginning to be able to recreate the types of complex geometric patterns seen during early development, which require multiple cues at the same time and the ability to spatially and temporally control their local presentation," noted McDevitt.
While microparticles can be used to control differentiation by regulating the local environment, other methods exist to control differentiation through the global environment. Experiments by McDevitt and biomedical engineering graduate student Melissa Kinney have demonstrated that modulating hydrodynamic conditions can dictate the morphology of cell aggregate formation and control the expression of differentiated phenotypic cell markers.
"Because bioreactors typically impose hydrodynamic forces on cells to cultivate large volumes of cells at high density, our use of hydrodynamics to control cell fate decisions represents a novel, yet simple, principle that could be used in the future for the scalable efficient production of stem cells," added McDevitt.
Technologies capable of being directly integrated into bioprocessing systems will be the best choice for manufacturing large batches of stem cells, he noted. In the future, the development of multi-scale techniques that combine different levels of control -- both local and global -- to regulate stem cell differentiation may help the translation of stem cells into viable clinical therapies.
This project is supported by the National Science Foundation (NSF) (Award No. CBET 0651739) and the National Institutes of Health (NIH) (R01GM088291). The content is solely the responsibility of the principal investigator and does not necessarily represent the official views of the NSF or NIH.
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]]>"We can now make very narrow, conductive nanoribbons that have quantum ballistic properties," said Walt de Heer, a professor in the School of Physics at the Georgia Institute of Technology. "These narrow ribbons become almost like a perfect metal. Electrons can move through them without scattering, just like they do in carbon nanotubes."
De Heer discussed recent results of this graphene growth process March 21st at the American Physical Society’s March 2011 Meeting in Dallas. The research was sponsored by the National Science Foundation-supported Materials Research Science and Engineering Center (MRSEC).
First reported Oct. 3 in the advance online edition of the journal Nature Nanotechnology, the new fabrication technique allows production of epitaxial graphene structures with smooth edges. Earlier fabrication techniques that used electron beams to cut graphene sheets produced nanoribbon structures with rough edges that scattered electrons, causing interference. The resulting nanoribbons had properties more like insulators than conductors.
"In our templated growth approach, we have essentially eliminated the edges that take away from the desirable properties of graphene," de Heer explained. "The edges of the epitaxial graphene merge into the silicon carbide, producing properties that are really quite interesting."
The templated growth technique begins with etching patterns into the silicon carbide surfaces on which epitaxial graphene is grown. The patterns serve as templates directing the growth of graphene structures, allowing the formation of nanoribbons and other structures of specific widths and shapes without the use of cutting techniques that produce the rough edges.
In creating these graphene nanostructures, de Heer and his research team first use conventional microelectronics techniques to etch tiny "steps" -- or contours -- into a silicon carbide wafer whose surface has been made extremely flat. They then heat the contoured wafer to approximately 1,500 degrees Celsius, which initiates melting that polishes any rough edges left by the etching process.
Established techniques are then used for growing graphene from silicon carbide by driving the silicon atoms from the surface. Instead of producing a consistent layer of graphene across the entire surface of the wafer, however, the researchers limit the heating time so that graphene grows only on portions of the contours.
The width of the resulting nanoribbons is proportional to the depth of the contours, providing a mechanism for precisely controlling the nanoribbon structures. To form complex structures, multiple etching steps can be carried out to create complex templates.
"This technique allows us to avoid the complicated e-beam lithography steps that people have been using to create structures in epitaxial graphene," de Heer noted. "We are seeing very good properties that show these structures can be used for real electronic applications."
Since publication of the Nature Nanotechnology paper, de Heer's team has been refining its technique. "We have taken this to an extreme -- the cleanest and narrowest ribbons we can make," he said. "We expect to be able to do everything we need with the size ribbons that we are able to make right now, though we probably could reduce the width to 10 nanometers or less."
While the Georgia Tech team is continuing to develop high-frequency transistors -- perhaps even at the terahertz range -- its primary effort now focuses on developing quantum devices, de Heer said. Such devices were envisioned in the patents Georgia Tech holds on various epitaxial graphene processes.
"This means that the way we will be doing graphene electronics will be different," he explained. "We will not be following the model of using standard field-effect transistors (FETs), but will pursue devices that use ballistic conductors and quantum interference. We are headed straight into using the electron wave effects in graphene."
Taking advantage of the wave properties will allow electrons to be manipulated with techniques similar to those used by optical engineers. For instance, switching may be carried out using interference effects -- separating beams of electrons and then recombining them in opposite phases to extinguish the signals.
Quantum devices would be smaller than conventional transistors and operate at lower power. Because of its ability to transport electrons with virtually no resistance, epitaxial graphene may be the ideal material for such devices, de Heer said.
"Using the quantum properties of electrons rather than the standard charged-particle properties means opening up new ways of looking at electronics," he predicted. "This is probably the way that electronics will evolve, and it appears that graphene is the ideal material for making this transition."
De Heer's research team hopes to demonstrate a rudimentary switch operating on the quantum interference principle within a year.
Epitaxial graphene may be the basis for a new generation of high-performance devices that will take advantage of the material's unique properties in applications where higher costs can be justified. Silicon, today's electronic material of choice, will continue to be used in applications where high-performance is not required, de Heer said.
"This is an important step in the process," he added. "There are going to be a lot of surprises as we move into these quantum devices and find out how they work. We have good reason to believe that this can be the basis for a new generation of transistors based on quantum interference."
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]]>The therapy, known as adoptive T cell transfer, has shown encouraging results in clinical trials. This treatment involves removing disease-fighting immune cells called T cells from a cancer patient, multiplying them in the laboratory and then infusing them back into the patient's body to attack the cancer. The effectiveness of this therapy, however, is limited by the finite lifespan of T cells -- after many divisions, these cells become unresponsive and inactive.
Researchers at Georgia Tech and Emory University have addressed this limitation by developing a microfluidic device for sample handling that allows a statistical model to be generated to evaluate cell responsiveness and accurately predict cell "age" and quality. Being able to assess the age and responsiveness of T cells -- and therefore transfer only young functional cells back into a cancer patient's body -- offers the potential to improve the therapeutic outcome of several cancers.
"The statistical model, enabled by the data generated with the microfluidic device, revealed an optimal combination of extracellular and intracellular proteins that accurately predict T cell age," said Melissa Kemp, an assistant professor in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University. "Knowing this information will help facilitate the clinical development of appropriate T cell expansion and selection protocols."
Details on the microfluidic device and statistical model were published in the March issue of the journal Molecular & Cellular Proteomics. This work was supported by the National Institutes of Health, Georgia Cancer Coalition, and Georgia Tech Integrative Biosystems Institute.
Currently, clinicians measure T cell age by using multiple assays that rely on measurements from large cell populations. The measurements determine if cells are exhibiting functions known to appear at different stages in the life cycle of a T cell.
"Since no one measurement is a perfect predictor, it is advantageous to concurrently sample multiple proteins at different time points, which we can do with our microfluidic device," explained Kemp, who is also a Georgia Cancer Coalition Distinguished Professor. "The wealth of information we get from our device for a small number of cells far exceeds a single measurement from a population the same size by another assay type."
For their study, Kemp, electrical engineering graduate student Catherine Rivet and biomedical engineering undergraduate student Abby Hill analyzed CD8+ T cells from healthy blood donors. They acquired information from 25 static biomarkers and 48 dynamic signaling measurements and found a combination of phenotypic markers and protein signaling dynamics -- including Lck, ERK, CD28 and CD27 -- to be the most useful in predicting cellular age.
To obtain biomarker and dynamic signaling event measurements, the researchers ran the donor T cells through a microfluidic device designed in collaboration with Hang Lu, an associate professor in the Georgia Tech School of Chemical & Biomolecular Engineering. After stimulating the cells, the device divided them into different channels corresponding to eight different time points, ranging from 30 seconds to seven minutes. Then they were divided again into populations that were chemically treated to halt the biochemical reactions at snapshots in time to build up a picture of the signaling events that occurred as the T cells responded to antigen.
"While donor-to-donor variability is a confounding factor in these types of experiments, the technological platform minimized the experimental data variance and allowed stimulation time to be precisely controlled," said Lu.
With the donor T cell data, the researchers developed a model to assess which biomarkers or dynamical signaling events best predicted the quality of T cell function. The model found the most informative data in predicting cellular age to be the initial changes in signaling dynamics.
"Although a combination of biomarker and dynamic signaling data provided the optimal model, our results suggest that signaling information alone can predict cellular age almost as well as the entire dataset," noted Kemp.
In the future, Kemp plans to use this approach of combining multiple cell-based experiments on a microfluidic chip to integrate single-cell information with population-averaged techniques, such as multiplexed immunoassays or mass spectrometry.
This project is supported in part by the National Institutes of Health (NIH)(Grant No. R21CA134299). The content is solely the responsibility of the principal investigator and does not necessarily represent the official views of the NIH.
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]]>Using a novel analytical process, researchers at the Georgia Institute of Technology found that the complex antifungal molecules are not distributed evenly across the seaweed surfaces, but instead appear to be concentrated at specific locations – possibly where an injury increases the risk of fungal infection.
A Georgia Tech scientist reported on the class of compounds, known as bromophycolides, at the annual meeting of the American Association for the Advancement of Science (AAAS) Feb. 21, 2011 in Washington, D.C. The research, supported by the National Institutes of Health, is part of a long-term study of chemical signaling among organisms that are part of coral reef communities.
"The language of chemistry in the natural world has been around for billions of years, and it is crucial for the survival of these species," said Julia Kubanek, an associate professor in Georgia Tech’s School of Biology and School of Chemistry and Biochemistry. "We can co-opt these chemical processes for human benefit in the form of new treatments for diseases that affect us."
More than a million people die each year from malaria, which is caused by the parasite Plasmodium falciparum. The parasite has developed resistance to many anti-malarial drugs and has begun to show resistance to artemisinin -- today's most important anti-malarial drug. The stakes are high because half the world's population is at risk for the disease.
"These molecules are promising leads for the treatment of malaria, and they operate through an interesting mechanism that we are studying," Kubanek explained. "There are only a couple of drugs left that are effective against malaria in all areas of the world, so we are hopeful that these molecules will continue to show promise as we develop them further as pharmaceutical leads."
In laboratory studies led by Georgia Tech student Paige Stout from Kubanek’s lab -- and in collaboration with California scientists -- the lead molecule has shown promising activity against malaria, and the next step will be to test it in a mouse model of the disease. As with other potential drug compounds, however, the likelihood that this molecule will have just the right chemistry to be useful in humans is relatively small.
Other Georgia Tech researchers have begun research on synthesizing the compound in the laboratory. Beyond producing quantities sufficient for testing, laboratory synthesis may be able to modify the compound to improve its activity -- or to lessen any side effects. Ultimately, yeast or another microorganism may be able to be modified genetically to grow large amounts of bromophycolide.
The researchers found the anti-fungal compounds associated with light-colored patches on the surface of the Callophycus serratus seaweed using a new analytical technique known as desorption electrospray ionization mass spectrometry (DESI-MS). The technique was developed in the laboratory of Facundo Fernandez, an associate professor in Georgia Tech's School of Chemistry and Biochemistry. DESI-MS allowed researchers for the first time to study the unique chemical activity taking place on the surfaces of the seaweeds.
As part of the project, Georgia Tech scientists have been cataloging and analyzing natural compounds from more than 800 species found in the waters surrounding the Fiji Islands. They were interested in Callophycus serratus because it seemed particularly adept at fighting off microbial infections.
Using the DESI-MS technique, researchers Leonard Nyadong and Asiri Galhena analyzed samples of the seaweed and found groups of potent anti-fungal compounds. In laboratory testing, graduate student Amy Lane found that these bromophycolide compounds effectively inhibited the growth of Lindra thalassiae, a common marine fungus.
"The alga is marshalling its defenses and displaying them in a way that blocks the entry points for microbes that might invade and cause disease," Kubanek said. "Seaweeds don't have immune responses like humans do. But instead, they have some chemical compounds in their tissues to protect them."
Though all the seaweed they studied was from a single species, the researchers were surprised to find two distinct groups of anti-fungal chemicals. From one seaweed sub-population, dubbed the "bushy" type for its appearance, 23 different anti-fungal compounds were identified. In a second group of seaweed, the researchers found 10 different anti-fungal compounds — all different from the ones seen in the first group.
In the DESI-MS technique, a charged stream of polar solvent is directed at the surface of a sample under study at ambient pressure and temperature. The spray desorbs molecules, which are then ionized and delivered to the mass spectrometer for analysis.
"Our collaborative team of researchers from the Department of Biomedical Engineering and the College of Sciences has worked within the newly-formed Bioimaging Mass Spectrometry Center at Georgia Tech to better understand the mechanisms of chemical defenses in marine organisms," said Fernandez. "This is an example of cross-cutting interdisciplinary research that characterizes our institute."
Kubanek is hopeful that other useful compounds will emerge from the study of signaling compounds in the coral reef community.
"In the natural world, we have seaweed that is making these molecules and we have fungi that are trying to colonize, infect and perhaps use the seaweed as a substrate for its own growth," Kubanek said. "The seaweed uses these molecules to try to prevent the fungus from doing this, so there is an interaction between the seaweed and the fungus. These molecules function like words in a language, communicating between the seaweed and the fungus."
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]]>Red, green and blue lights from a projector activate light-sensitive microbial proteins that are genetically engineered into the worms, allowing the researchers to switch neurons on and off like light bulbs and turn muscles on and off like engines.
Use of the LCD technology to control small animals advances the field of optogenetics -- a mix of optical and genetic techniques that has given researchers unparalleled control over brain circuits in laboratory animals. Until now, the technique could be used only with larger animals by placement of an optical fiber into an animal's brain, or required illumination of an animal's entire body.
A paper published Jan. 16 in the advance online edition of the journal Nature Methods describes how the inexpensive illumination technology allows researchers to stimulate and silence specific neurons and muscles of freely moving worms, while precisely controlling the location, duration, frequency and intensity of the light.
"This illumination instrument significantly enhances our ability to control, alter, observe and investigate how neurons, muscles and circuits ultimately produce behavior in animals," said Hang Lu, an associate professor in the School of Chemical & Biomolecular Engineering at the Georgia Institute of Technology.
Lu and graduate students Jeffrey Stirman and Matthew Crane developed the tool with support from the National Institutes of Health and the Alfred P. Sloan Foundation.
The illumination system includes a modified off-the-shelf LCD projector, which is used to cast a multi-color pattern of light onto an animal. The independent red, green and blue channels allow researchers to activate excitable cells sensitive to specific colors, while simultaneously silencing others.
"Because the central component of the illumination system is a commercially available projector, the system's cost and complexity are dramatically reduced, which we hope will enable wider adoption of this tool by the research community," explained Lu.
By connecting the illumination system to a microscope and combining it with video tracking, the researchers are able to track and record the behavior of freely moving animals, while maintaining the lighting in the intended anatomical position. When the animal moves, changes to the light's location, intensity and color can be updated in less than 40 milliseconds.
Once Lu and her team built the prototype system, they used it to explore the "touch" circuit of the worm Caenorhabditis elegans by exciting and inhibiting its mechano-sensory and locomotion neurons. Alexander Gottschalk, a professor in the Johann Wolfgang Goethe-University Frankfurt Institute of Biochemistry in Frankfurt, Germany, and his team provided the light-sensitive optogenetic reagents for the Georgia Tech experiments.
For their first experiment, the researchers illuminated the head of a worm at regular intervals while the animal moved forward. This produced a coiling effect in the head and caused the worm to crawl in a triangular pattern. In another experiment, the team scanned light along the bodies of worms from head to tail, which resulted in backward movement when neurons near the head were stimulated and forward movement when neurons near the tail were stimulated.
Watch a movie showing Georgia Tech researchers illuminating the head of a worm expressing light-sensitive optogenetic reagents. The light produces a coiling effect in the head and causes the worm to crawl in a triangular pattern.
Watch a movie showing how researchers at Georgia Tech use light from an LCD projector to directly control the muscles of an immobilized worm.
Additional experiments showed that the intensity of the light affected a worm's behavior and that several optogenetic reagents excited at different wavelengths could be combined in one experiment to understand circuit functions. The researchers were able to examine a large number of animals under a variety of conditions, demonstrating that the technique's results were both robust and repeatable.
"This instrument allowed us to control defined events in defined locations at defined times in an intact biological system, allowing us to dissect animal functional circuits with greater precision and nuance," added Lu.
While these proof-of-concept studies investigated the response of C. elegans to mechanical stimulation, the illumination system can also be used to evaluate responses to chemical, thermal and visual stimuli. Researchers can also use it to study a variety of neurons and muscles in other small animals, such as the zebrafish and fruit fly larvae.
"Experiments with this illumination system yield quantitative behavior data that cannot be obtained by manual touch assays, laser cell ablation, or genetic manipulation of neurotransmitters," said Lu.
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]]>Scientists know that among an embryo's first major developments is the establishment of its dorsoventral axis, which runs from its back to its belly. Determining how this axis development unfolds -- specifically the presence and location of proteins during the process -- requires the ability to simultaneously monitor large numbers of embryos with different genetic backgrounds at several time points.
"Collecting and analyzing the signaling and transcriptional patterns of the dorsoventral axis typically requires manual manipulation of individual embryos to stand them on their ends, making it difficult to conduct high-throughput experiments that can achieve statistically significant results," said Hang Lu, an associate professor in the Georgia Tech School of Chemical & Biomolecular Engineering.
To enable large-scale quantitative analyses of protein positional information along the dorsoventral axis, Lu designed a microfluidic device that reliably and robustly orients several hundred embryos in just a few minutes.
Details of the device design and results from proof-of-concept experiments with fruit fly embryos were published in the Dec. 26 advance online edition of the journal Nature Methods. This project was supported by the National Science Foundation, the National Institutes of Health, the Alfred P. Sloan Foundation and the DuPont Young Professor program.
Lu designed and fabricated the device with the help of Kwanghun Chung and Emily Gong, who worked on the project as Georgia Tech graduate and undergraduate students, respectively. Fabricated from polydimethylsiloxane (PDMS), the compact device is the size of a microscope slide and contains approximately 700 traps for embryos, which are shaped like grains of rice but smaller in size.
In operation, fluid flows through an "S"-shaped channel wide enough for embryos of any orientation to move easily through it. The fluid efficiently directs the embryos toward the traps, while sweeping out extra and improperly trapped embryos.
"The flow pattern significantly increased the frequency at which embryos contacted the traps and were loaded into them," explained Lu. "Experimentally, we found on average 90 percent of the embryos became trapped in the device, which will be valuable for studies that only have a small number of embryos available."
When an embryo approaches an empty trap, it experiences non-uniform pressure and shear from the surrounding fluid. The resulting force flips the embryo vertically and inserts it into the cylindrical trap in an upright position, with its dorsoventral axis parallel to the ground. The embryo is then secured inside the trap, without any need for user intervention or control. The lock-in feature allows the device to be disconnected from the rest of the hardware and transported for imaging or storage with the embryos enclosed.
"At one point, we mailed a microfluidic embryo trap array device full of trapped fruit fly embryos to our collaborators at Princeton University, and upon arrival, the embryos were still upright in their locked traps," said Lu.
To demonstrate the device's capabilities, Lu collaborated with Stanislav Shvartsman, an associate professor in the Department of Chemical and Biological Engineering at Princeton University, and his graduate student Yoosik Kim. The Princeton researchers used the device to quantify gradients of signaling molecules called morphogens in fixed embryos and also used it to monitor nuclear divisions in live embryos.
In one experiment, the Princeton researchers determined the spatial extent of the distribution of Dorsal, a transcription factor that initiates the dorsal-to-ventral patterning of the Drosophila embryo. They also demonstrated that this gradient could be quantitatively compared between wild-type and mutant embryos.
"The trap array device provided a significant increase in the number of fixed and live embryos we could image simultaneously and allowed us to accurately resolve issues of interest to developmental biologists today," explained Lu.
In the future, scientists should be able to adapt the microfluidic device for studies of pattern formation and morphogenesis in other model organisms, such as zebrafish or worm embryos. Results of those studies will be important to the scientific community because many genes controlling development are similar in worms, fruit flies and mammals.
This project was supported by the National Science Foundation (NSF) (Award No. DBI‐0649833) and the National Institutes of Health (NIH) (Award No. R21NS058465). The content is solely the responsibility of the principal investigator and does not necessarily represent the official views of the NSF or NIH.
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]]>Biological and chemical sensing are active research areas because of their applications in clinical screening, drug discovery, food safety, environmental monitoring and homeland security. Using integrated photonics, the new class of sensors will be capable of detecting chemical agents -- such as toxins, pollutants and trace gases -- and biological agents -- such as proteins, viruses and antibodies -- simultaneously on the same chip.
"The proposed sensors will detect multiple biological and chemical threats on a compact integrated platform faster, less expensively and more sensitively than the current state-of-the-art sensors," said the center's leader Ali Adibi, a professor in the School of Electrical and Computer Engineering at Georgia Tech.
The Defense Advanced Research Projects Agency (DARPA) is funding the two-year $4.3 million center as one of its Centers in Integrated Photonics Engineering Research (CIPhER), which investigate innovative approaches that enable revolutionary advances in science, devices or systems. For its center, Georgia Tech is working with researchers from Emory University; Massachusetts Institute of Technology; University of California, Santa Cruz; and Yale University. The team also includes industry collaborators Rockwell Collins, Kotura, Santur Corporation and NanoRods.
To create an integrated chip that will simultaneously detect multiple biological and chemical agents, the researchers need to achieve three major goals:
• Design and fabricate photonic and optomechanical structures to sense differences in a sample's refractive index, Raman emission, fluorescence, absorption and mass;
• Functionalize the sensor surface with coatings that chemical and biological agents will attach to and create differences that can be detected; and
• Develop the sample preparation method and microfluidic sample delivery device, and connect the device to the coated photonic structure.
Adibi is leading the first thrust, which is primarily focused on fabricating the millimeter-square sensing structures and on-chip spectrometers that will enable multiplexing -- the detection of multiple agents using the same sensing modules. The sensors will detect changes in the refractive index, Raman emission, fluorescence, absorption spectra and optomechanical properties when a sample that includes specific biological or chemical particles interacts with the sensor coatings. Combining information obtained from the five different sensing modalities will maximize the sensor specificity and minimize its false detection rate, the researchers say.
"The goal is to achieve very high sensitivity for each modality and investigate the advantages of each modality for different classes of biological and chemical agents in order to develop a clear set of guidelines for combining different modalities to achieve the desired performance for a specific set of agents," explained Adibi.
Massachusetts Institute of Technology chemistry professor Timothy Swager is leading the second part of this project, which aims to design surface coatings that will achieve maximum sensor specificity in detecting multiple biological and chemical agents.
"We plan to develop glycan-based surface coatings to sense biological agents and polymer-based surface coatings to sense chemical agents," noted Adibi.
For the third thrust, which is being led by Massachusetts Institute of Technology electrical engineering associate professor Jongyoon Han, the researchers will develop optimal sample preparation and delivery techniques. Their goal is to maximize the biological or chemical particle concentration in the sample and limit detection time to minutes.
"In two years, we hope to have a lab-on-a-chip system that includes all of the sensing modalities with appropriate coatings and microfluidic delivery," said Adibi. "To show the feasibility of the technology, we plan to demonstrate the high sensitivity and high selectivity of each sensor individually and be able to use at least two of the sensing modalities simultaneously to detect two or three different chemical or biological agents."
In addition to those already mentioned, this center also includes Georgia Tech chemistry and biochemistry professor Mostafa El-Sayed, Georgia Tech materials science and engineering professor Kenneth Sandhage, Georgia Tech Nanotechnology Research Center senior research scientist David Gottfried, Emory University biochemistry chair Richard Cummings, University of California Santa Cruz electrical engineering professor Holger Schmidt, and Yale University electrical engineering associate professor Hong Tang.
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The five-year grant will be used to address key technical issues and advance the microneedle patch through a Phase I clinical trial. The grant will also be used to compare the effectiveness of traditional intramuscular injection of flu vaccine against administration of vaccine into the skin using microneedle patches. In animals, vaccination with dissolving microneedles has been shown to provide immunization better than vaccination with hypodermic needles.
"We believe that this technology will increase the number of people being vaccinated, especially among the most susceptible populations of children and the elderly," said Mark Prausnitz, a professor in the Georgia Tech School of Chemical and Biomolecular Engineering, and the project's principal investigator. "If we can make it easier for people to be vaccinated and improve the effectiveness of the vaccine, we could significantly reduce the number of deaths caused every year by influenza."
Vaccine-delivery patches contain hundreds of micron-scale needles so small that they penetrate only the outer layers of skin. Their small size would allow vaccines to be administered without pain -- and could allow people to apply the patches themselves without visiting medical facilities.
While the ability to immunize large numbers of people without using trained medical personnel is a key advantage for the microneedle patch, the researchers have learned that administering the vaccine through the skin creates a different kind of immune response -- one that may protect vaccine recipients better.
"We have seen evidence that the vaccine works even better when administered to the skin because of the plethora of antigen presenting cells which reside there," said Ioanna Skountzou, co-principal investigator for the project and an assistant professor in Emory University's Department of Microbiology and Immunology. "This study will allow us to determine how we can optimize the vaccine to take advantage of those cells that are important in generating the body's immune response."
Among the issues to be addressed in the five-year study are:
• Developing an administration system that will be simple to use, intuitive and reliable. "Our goal is to make these patches suitable for self-administration, so that anybody could take a patch out of an envelope, put it on, and have it work with high reliability," Prausnitz said.
• Studying the long-term stability of vaccine used in the patches, and optimizing technology for incorporating it into the dissolving microneedles. "We need to put the vaccine into a dry form in this patch," said Prausnitz. "That will require different processing than is normally done with vaccines. We expect that this dry vaccine will provide enough stability that the patches can be stored without refrigeration."
• Evaluating the economic, regulatory, social and medical implications of a self-administered vaccine. PATH, an international nonprofit organization, will assist with this work, and will help strategically address any issues. "We will be assessing the barriers that may exist to introduction of a self-administered flu vaccine so we can anticipate those issues and develop possible solutions," said Darin Zehrung, leader of the vaccine delivery technologies group at PATH.
The funding will come from the Quantum program of the National Institute of Biomedical Imaging and Bioengineering (NBIB), which is part of the NIH. The initiative is designed to bring new medical technologies into clinical use.
While the funding focuses specifically on influenza vaccination, the lessons learned may advance other microneedle applications -- including vaccination efforts in developing countries where skilled medical personnel are limited and concerns about re-use of hypodermic needles are significant.
Additional design and development of the microneedle patch will largely be done at Georgia Tech, with vaccine development, immunological studies and the Phase I trial carried out at Emory University. The trial, to be conducted by the Hope Clinic of the Emory Vaccine Center, is expected to take place during the final year of the grant, setting the stage for Phase II and Phase III clinical trials that would be required to obtain FDA approval.
Ultimately, the goal will be to produce an influenza vaccine delivery patch that could be made widely available. Prausnitz expects that will be done by an established company with the ability to manufacture and market the devices.
Microneedle drug and vaccine delivery systems have been under development at Georgia Tech and elsewhere since the 1990s. The technology got a significant boost in July of 2010 with publication of a study in Nature Medicine that showed mice vaccinated with dissolving microneedles were protected against influenza at least as well as mice immunized through traditional hypodermic needle injections.
The patches used in that study contained needles just 650 microns long, assembled into arrays of 100 needles. Pressed into the skin, the needles quickly dissolved into bodily fluids thanks to their hydrophilic polymer material, carrying the vaccine with them and leaving only a water-soluble backing. In contrast, use of hypodermic needles leaves the problem of "sharps" disposal.
Prausnitz hopes that the $10 million in NIH funding will help accelerate development of the microneedle patches to make them available for general use within five to ten years.
"This research will focus on optimizing the microneedle-based delivery of vaccines into the skin and understanding how this method affects immune responses both at the mucosal surfaces of the body and through the systemic response inside the body," added Skountzou. "Combined with the convenience of self-administration, painless application and absence of sharps waste, this novel immunization route could make the microneedle patch a powerful new weapon against infectious diseases."
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Sickle cell disease is a genetic condition present at birth that affects more than 70,000 Americans. It involves a single altered gene that produces abnormal hemoglobin -- the protein that carries oxygen in the blood. In sickle cell disease, red blood cells become hard, sticky and "C" shaped. Sickle cells die early, which causes a constant shortage of red blood cells. The abnormal cells also clog the flow in small blood vessels, causing chronic pain and other serious problems such as infections and acute chest syndrome.
"Even though researchers know sickle cell disease is caused by a single A to T mutation in the beta-globin gene, there is no widely available cure," said center director Gang Bao, the Robert A. Milton Chair in Biomedical Engineering in the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech and Emory University. "By directly and precisely fixing the single mutation, we hope to reduce or eliminate the sickle cell population in an individual's blood stream and replace the sickle cells with healthy red blood cells."
The center is one of eight NIH Nanomedicine Development Centers established in 2005 and 2006, a key initiative of the NIH's long-term nanomedicine research goals. The centers have highly multidisciplinary scientific teams that include biologists, physicians, mathematicians, engineers and computer scientists. Through an intense competition, the NIH selected four centers for second phase funding, including the one led by Georgia Tech.
In addition to experts in the Coulter Department of Biomedical Engineering at Georgia Tech and Emory University and the Department of Chemical and Biomolecular Engineering at Georgia Tech, researchers from Medical College of Georgia, Cold Spring Harbor Laboratory, New York University Medical Center, Massachusetts Institute of Technology, Stanford University and Harvard University are also members of the center.
The gene correction approach proposed by the research team to treat sickle cell disease involves delivering engineered zinc finger nucleases (ZFNs) -- genetic scissors that cut DNA at a specific site -- and DNA correction templates into the nuclei of hematopoietic stem cells isolated from the bone marrow of individuals with sickle cell disease.
The researchers chose hematopoietic stem cells because they are the precursors of all blood cells, including the cells rendered dysfunctional in sickle cell patients. Hematopoietic stem cells possess such potent regenerative potential that transplantation of even a single hematopoietic stem cell is sufficient to rebuild the entire blood system of an organism.
The researchers plan to engineer and optimize the ZFN proteins so they will induce a double-strand break in the DNA near the sickle cell disease mutation, thereby activating the gene for correction. The broken DNA ends will enter the homologous recombination repair pathway, which will use the genetic information provided by the donor template -- rather than the original flawed information -- to correct the mutation. When the gene-corrected hematopoietic stem cells are injected back in the body, they will produce healthy red blood cells to replace the sickle cells.
"This approach represents a significant paradigm shift in current gene targeting and gene therapy technology in that no viral-based vector or foreign DNA is used," explained Bao, who is also a Georgia Tech College of Engineering Distinguished Professor. "We think it's a promising approach because we do not need to fix all of the mutations in all cells; we only need to greatly reduce the sickle cell population by replacing those cells with healthy red blood cells."
There are significant challenges in achieving the goals of the center, including the need to dramatically increase the rate of homologous recombination-mediated gene correction, improve the activity and specificity of ZFNs to maximize gene correction efficiency and minimize potentially harmful off-target effects, deliver the components necessary for gene correction to hematopoietic stem cells with high efficiency and throughput, avoid unwanted genomic rearrangements and optimize the engraftment of ZFN-modified hematopoietic stem cells.
To increase the efficiency of gene correction in the hematopoietic stem cells, the proposed gene correction approach will require a shift in repair pathway choice from non-homologous end joining toward homologous recombination. To accomplish this, the researchers plan to use methods they developed in the last four years to visualize the assembly of repair complexes at double-strand break sites and develop interventions to shift pathway choice toward homologous recombination.
To control ZFN activity so that unwanted off-target effects or gene rearrangements can be minimized or avoided, the researchers plan to refine and optimize the design and production of the proteins and develop photoactivatable proteins for better temporal control of ZFN activity. In addition, by investigating the fate and dynamics of the engineered proteins and donor template in living cells, and the incidence and biological effects of undesired mutations and gene rearrangements, the research team will further improve the process.
With novel imaging probes and methods already developed in the Nanomedicine Center for Nucleoprotein Machines, the researchers will be able to observe and systematically optimize each step in the gene correction process. Once that is accomplished, the research team will demonstrate the gene correction approach in a mouse model of sickle cell disease. Their goal is to demonstrate that gene-corrected cells can reconstitute the mouse hematopoietic system and reverse the sickle cell disease phenotype, according to Bao.
"We want to focus on sickle cell disease to demonstrate this approach, but if we are successful, the same approach can be adopted to treat some of the other 6,000 estimated single gene disorders in the world today, such as cystic fibrosis and Tay-Sachs," noted Bao.
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