Biomolecular material systems with encapsulated interface bilayers
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Biomolecular material systems with encapsulated interface bilayers Stephen A. Sarles1 and Donald J. Leo1 1 Center for Intelligent Material Systems and Structures, 310 Durham Hall, Dept. of Mechanical Engineering, Virginia Tech, Blacksburg, VA 24061, U.S.A. ABSTRACT In this paper we present a novel approach for interface bilayer formation in which the uptake of an aqueous lipid vesicle solution by two polymeric hydrogels contained in a substrate causes the gels to swell so as to come into contact within an internal oil-filled region of the device. An interface bilayer, similar to those formed using the droplet interface bilayer (DIB) method, forms upon contact in oil between the lipid-encased ends of the two gels. Experimental measurements provide initial evidence that gel swelling enables automatic bilayer formation within a few minutes after the addition of lipid solution. The approach presented herein works toward the development of a new portable, easy-to-use screening platform that features tailored interface bilayers for a wide variety of screening applications. INTRODUCTION Many of the transduction mechanisms that exist in living cells occur at the boundary of the cell, whereby the selective blockage or passage of chemical species through the cell membrane is used to detect and transmit information and energy into and out of the cell. Since the structure and composition of the cell membrane is a crucial part of the sensing process, the ability to construct artificial cell membranes, known as lipid bilayers, and incorporate functional proteins into these structures enables a wide variety of in vitro studies of both membrane material properties and transmembrane protein transduction, respectively. As a result, devices that feature lipid bilayers are of interest in developing new material platforms for performing high throughput drug screening1, 2, DNA sequencing3, and analyte sensing related to personal health monitoring and environmental toxin detection4. Unfortunately, many of methods used to assemble lipid bilayers require a skilled scientist and produce fragile membranes with limited use in laboratory environments and short durations. The droplet interface bilayer (DIB) method that was recently developed demonstrated that durable networks of liquid-supported lipid bilayers can be formed at the liquid interfaces of lipid-encased water droplets contained in immiscible oil. This method provides increased bilayer lifetimes for long-term study, but also enables the fabrication of large biomolecular networks formed with many lipid-encased droplets2, 5-7. However, the need to dispense and position individual droplets limits the use of DIB in medical screening applications. Microfluidic approaches to form liquid-supported interface bilayers have also been investigated8, 9, though these methods, along with an intensive device fabrication procedure, require precise flow control to initiate bilayer formation. In this paper, we demonstrate a novel approach for bilayer formation for use in a variety of screening applicat
