Title: Engineering Platforms for Human-Microbe Interaction Studies in Intestinal Tract: Materials Approach

Advisor:

Dr. Shuichi Takayama (Department of Biomedical Engineering, Georgia Institute of Technology)

Committee:

Dr. Blair Brettmann (School of Materials Science and Engineering, Georgia Institute of Technology)

Dr. Sam Brown (School of Biological Sciences, Georgia Institute of Technology)

Dr. Andrew Gewirtz (Institute for Biomedical Sciences, Georgia State University)

Dr. Athanasios Mantalaris (Department of Biomedical Engineering, Georgia Institute of Technology)

Date and time: Friday, October 15, 2021, at 1:00 PM (ET)

BlueJeans link: https://bluejeans.com/925961979/5491

Abstract:

Microbes inhabiting the gastrointestinal (GI) tract are exposed to dynamic luminal microenvironment such as changes in nutrient availability for multiple times throughout the day, and continuous mechanical stress by peristaltic bowel movement. Healthy microbial communities are able to maintain the homeostasis and protect host against pathogens. Epithelial and intraluminal oxygenation is one of many key features to assess the status of intestinal health. Steep oxygen gradient across the epithelium and micro-to-anaerobic lumen is shaped by the cooperation of host and microbial metabolism. Spatial oxygen distribution in a GI tract with dysbiotic microbiome and tissue inflammation, drifts away from the homeostatic condition. Many models have been developed to understand healthy host-microbe interactions and pathogenesis. Animal models are great for studying systemic responses but not suitable when microbes of interest are human-specific. Moreover, it is not necessary to control for surrounding gas environment. In vitro models allow flexibility and control over independent variables. However, these models miss some key physiologic features, and creating the characteristic intestinal oxygen microenvironment is challenging. Choosing the right model depends on the goal and design of the study. Static 2D models are relatively easy to setup but immature cellular and tissue-level functions can lead to misrepresentation of human physiology. Three-dimensional models develop higher maturity but are often limited in throughput due to increased complexity of the system.

The goal of this dissertation is to bridge the gap between the in vitro GI-microbe models by reducing the complexity in experimental setup. First, we developed a host-free microscale bacterial culture method using aqueous two-phase system (ATPS) and characterized passive oxygen control using the materials properties of ATPS and polydimethyl siloxane. Next, we showed the ATPS microscale culture is capable of supporting a co-culture of facultative and obligate anaerobes without the use of anaerobic chambers. Escherichia coli O157:H7, a human enteric pathogen, co-cultured with Bacteroides thetaiotaomicron, a human commensal, in low glucose ATPS culture showed enhanced virulence, which was comparable to the co-culture in anaerobic chamber. Lastly, we explored various ways to interface ATPS culture with human intestinal organoids and maintain physiologic oxygen microenvironment. We believe this culture method will be particularly useful for researchers in gastroenterology with little engineering background and provide valuable insights. Moreover, the properties of microscale ATPS bacterial culture will be useful for developing high throughput assays.