Storable droplet interface lipid bilayers for cell-free ion channel studies

Abstract

An artificially created lipid bilayer is an important platform in studying ion channels and engineered biosensor applications. However, a lipid bilayer created using conventional techniques is fragile and short-lived, and the measurement of ion channels requires expertise and laborious procedures, precluding practical applications. Here, we demonstrate a storable droplet lipid bilayer precursor frozen with ion channels, resulting in a droplet interface bilayer upon thawing. A small vial with an aqueous droplet in organic solution was flash frozen in -80 °C methanol immediately after an aqueous droplet was introduced into the organic solution and gravity draws the droplet down to the interface upon thawing. A lipid bilayer created along the interface using this method had giga-ohm resistance and typical specific capacitance values. The noise level of this system is favorably comparable to the conventional system. The subsequent incorporation of ion channels, alpha-hemolysin and gramicidin A, showed typical conductance values consistent with those in previous literatures. This novel system to create a lipid bilayer as a whole can be automated from its manufacture to use and indefinitely stored when frozen. As a result, ion channel measurements can be carried out in any place, increasing the accessibility of ion channel studies as well as a number of applications, such as biosensors, ion channel drug screening, and biophysical studies.