Droplet-based lipid bilayer system integrated with microfluidic channels for solution exchange

Abstract

This paper proposes a solution exchange of a droplet-based lipid bilayer system, in which the inner solution of a droplet is replaced for the purpose of efficient ion channel analyses. In our previous report, we successfully recorded the channel conductance of alpha-hemolysin in a bilayer lipid membrane using a droplet contact method that can create a spontaneous lipid bilayer at the interface of contacting droplets; this method is widely used as highly efficient method for preparing planar lipid membranes. When only pipetting droplets of the solution, this method is highly efficient for preparing lipid membranes. However, the drawback of droplet-based systems is their inability to exchange the solution within the droplets. To study the effect of inhibitors and promoters of ion channels in drug discovery, it would be beneficial to conduct a solution exchange of droplets to introduce membrane proteins and to apply or wash-out the chemicals. In this study, we propose a droplet contact method that allows for the solution exchange of droplets via microfluidic channels. We experimentally and numerically investigated the bilayer stability with respect to exchanging flow rates, and then demonstrated a binding assay of an alpha-hemolysin using one of its blockers. The solution exchange in this system was conducted in less than 20 s without rupturing the membrane. We believe that the proposed system will enhance the efficiency of ion channel analyses.

Stable Free-Standing Lipid Bilayer Membranes in Norland Optical Adhesive 81 Microchannels

“…Alternatively, polymethilsiloxane (PDMS) is a transparent biocompatible material, which allows low-cost and simple fabrication, but its use for the formation of free-standing lipid bilayers is hindered by swelling and deformability issues in several organic solvents 13 , which are often required for artificial lipid bilayer formation 14,15 .…”

Screening ion-channel ligand interactions with passive pumping in a microfluidic bilayer lipid membrane chip

“…We believe that this method provides a simple and efficient way of delivering compounds to ion channels, transporters, or nanopores incorporated in phospholipid bilayers. In contrast to conventional bilayer technology, the method provides a novel means of drug screening against ion channels using very small volumes of compound solutions (10-15 ll) compared to the state of the art, [19][20][21][22][23] significantly reducing the cost per screen. The chips are easy to manufacture on a wafer and could be reused if necessary.…”

“…This issue has been addressed by making smaller systems, incorporating micro-channels for solution exchange. 8,17,[19][20][21][22] For example, Stimberg et al described a flow channel, where the microfluidic channel and bilayer aperture are made separately and glued together and fluid is flown across the bilayer using a syringe pump. 19 Shao et al demonstrated a bilayer microfluidic platform that enabled rapid perfusion of liquid (>2.5 ll/min), with 100 ll samples, 21 and Le Pioufle et al demonstrated an array of wells, each with multiple small bilayers with fluidic access to both sides, where electrical recordings were performed by moving an Ag/AgCl electrode from well to well.…”

“…23 Tsuji et al described a droplet-interface bilayer system made using two droplets with microchannel perfusion of one droplet. 20 However, all the platforms described above require a syringe pump and a relatively large volume of electrophysiology buffer, and hence a relatively large amount of the compounds that potentially modulate channel activity.…”

Analysis and Application of Ion Channel Functions on Artificial Cell Membrane Using the Droplet Contact Method

“…and (G). The figure was modified from the author's previous paper 19) . s7βCD was lodged at the β-barrel of the αHL pore.…”