SCIENCE AT THE EDGE SEMINAR

Friday, October 20 at 11:30am
Room 1400 Biomedical and Physical Sciences Bldg.
Refreshments at 11:15

Speaker: Mark Worden
         Department of Chemical Engineering and Materials Science
         Michigan State University
        
Title:   Nanostructured Interfaces that Express Protein Activities

Abstract:

Biological membranes perform many molecular processes that sustain life,
including transport, catalysis, maintaining electrochemical gradients,
recognition, and signaling.  Many of these processes can be reproduced in
the laboratory by incorporating proteins into interfaces that facilitate
the proteins' activities.  This presentation will describe three examples
of nanostructured interfaces designed to mimic the structure and/or function
of cell membranes.  Such biomimetic interfaces have potential applications
in biosensor arrays, high-throughput drug screening systems, and research
tools to study protein function.    

In the first example, liposomes or lipid bilayers were deposited onto
polyelectrolyte multilayer (PEM) microarrays formed by microcontact printing.
The charge and chemical makeup of the PEMs strongly influenced the degree of
liposome adsorption and rupture to form a bilayer.  Fluidity of the bilayer
was confirmed using fluorescence recovery after photobleaching.  In the
second example, a gold film was electrolessly deposited on a glass or plastic
slide and used to fabricate a biosensor based on dehydrogenase enzymes.
Colloidal gold particles were first adsorbed onto PEMs.  Additional gold was
then deposited from solution, resulting in a continuous, conductive film.  An
electron mediator, cofactor, and dehydrogenase enzyme were attached to the
gold, resulting in efficient electron transfer between the electrode and
enzyme.  Properties of the interface as a biosensor were characterized using
cyclic voltammetry and chronoamperometry.   In the third example, a lipid
bilayer was fabricated on an electrolessly deposited gold electrode and used
to express membrane-protein activity.  A lower lipid leaflet was tethered to
the gold using a thiol linkage.  The upper leaflet was then deposited
by liposome adsorption and rupture.  To demonstrate functionality of the
synthetic lipid bilayers, ion channels have been incorporated, and
electrochemical impedance spectroscopy has been used to monitor ion
transport across the bilayer.