In addition to its annual lectures, ChBE hosts a weekly seminar throughout the year with invited lecturers who are prominent in their fields. Unless otherwise noted, all seminars are held on Wednesdays in the Molecular Science and Engineering Building ("M" Building) in G011 (Cherry Logan Emerson Lecture Theater) at 4 p.m. Refreshments are served at 3:30 p.m. in the Emerson-Lewis Reception Salon.

_____________

"New Ways to Make Biomembranes With Designer Functionality and Responsiveness"

Dan Hammer, Professor, Department of Chemical and Biological Engineering, University of Pennsylvania

Abstract:
Biological cells are surrounded by a plasma membrane made primarily of phospholipids that form a bilayer. This membrane is permselective and compartmentalizes the cell. A simple form of artificial cells is the vesicle, in which a phospholipid bilayer membrane surrounds and aqueous solution. However, there is no a priori reason why a membrane needs to be made of phospholipids. It could be made of any surfactant that forms a bilayer. Over the past 15 years, we have explored how different synthetic surfactants can be used to make artificial membranes that mimic but extend the properties of the membrane and vesicles. First, with collaborators from Minnesota and Penn we developed polymersomes - vesicles made with bilayers of self-assembled block-co-polymers - which have superior mechanical properties and large hydrophobic storage capacities. We have developed polymersomes for optical imaging, light triggered release, and use as soft matter stress sensors. Most recently, we have assembled membranes from the recombinant plant protein oleosin. We find that while many variants of oleosin make membranes, others make different supramolecular assemblies including micelles and sheets. Including functional domains such as targeting motifs and protease cleavable domains into oleosin is trivial through molecular biology. We show examples where oleosin can be used to target imaging agents and micelles to cells using cell adhesion binding motifs, and stabilize air bubbles for ultrasonic imaging.