Miniaturized Silicon Apertures for Lipid Bilayer Reconstitution Experiments
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1191-OO08-05
Miniaturized silicon apertures for lipid bilayer reconstitution experiments Michael Goryll1 and Nipun Chaplot1 1 Arizona State University, Department of Electrical Engineering, Tempe, AZ 85287-5706, U.S.A. ABSTRACT Ion channels reconstituted into lipid bilayer membranes can be used as a very sensitive and selective platform for high-throughput drug screening applications. In order to employ suspended lipid bilayer membranes for these experiments in form of a “lab-on-a-chip” configuration, a robust and affordable platform is required. In our study, we investigated the feasibility of hosting lipid bilayer membranes across micron-size apertures ranging from 5 µm – 50 µm in silicon. On these substrates, lipid bilayers were formed and characterized concerning their seal resistance, capacitance and breakdown voltage. Seal resistance values of up to 60 GΩ could be achieved repeatedly on these substrates. INTRODUCTION Suspended lipid bilayer membranes are an ideal platform to study ion channel behavior, since they closely resemble the natural environment of the ion channels. However, these membranes have to be suspended to allow access to both sides for ion current measurements. The key feature of the membrane support structure is the high seal resistance between the bilayer lipid membrane and the solid support, which has to be on the order of Gigaohms. The commonly used plastic substrates for lipid bilayer suspension are limited when it comes to the miniaturization of the apertures as well as the reproducibility of the apertures. Materials such as PDMS [1] or glass [2] have been investigated as solid supports. Here, silicon microfabrication shows a way toward manufacturing a high density of identical apertures that can easily be combined with microfluidics for a truly integrated microanalysis approach. The process steps needed for silicon microfabrication are well-established and thus readily available and cost effective. With silicon being an ideal material when it comes to the fabrication, there are several drawbacks which make it unsuitable for bilayer attachment. Silicon dioxide is hydrophilic, thus the attachment of the inner hydrophobic membrane layer to the substrate surface is energetically not favorable. In previous studies we could show that a plasma-polymerized layer of tetrafluoroethylene (C4F8) renders the silicon surface hydrophobic and allows for a repeatable formation of bilayer lipid membranes across apertures in silicon. In earlier work, we chose the aperture size to be 100-150 µm in diameter to be comparable with commercially available substrates [3]. This, however, limits the minimum distance in an array platform. Consequently, a reduction in pore diameter is desirable, in particular since studies on apertures in reflowable Teflon membranes have shown that membranes across apertures on the order of few tens of microns show improved noise characteristics [4].
EXPERIMENT For our experiments, we used double-sided polished Si (001) wafers with a thickness of 380-420 µm. To enable lipid bilay
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