Development of an analytical system for ion channel proteins based on artificial bilayer lipid membranes: Screening of drug components that haveing side effects on herg channels for personalized medicine

The human ether-a-go-go related gene (hERG) channel is a cardiac voltage-dependent potassium channel, which plays a key role in action potential generation in the heart. Since a diverse group of drugs can adversely block hERG channels, and can sometimes induce life-threatening arrhythmias, it is highly important to develop an efficient system for assessing the potential risks of such drug side effects on the hERG channel. An artificially formed bilayer lipid membrane (BLM) with the incorporated ion channels is a strong candidate for this assay platform. However, two major problems associated with BLM systems reduce their experimental efficiency, namely, the instability of BLMs and a low efficiency of ion channel incorporation into BLMs. In this paper, we will discuss our recent approaches to address these issues through the combination with silicon (Si) microfabrication techniques, and also discuss the application of the BLM systems to a hERG assay platform. Mechanically stable solvent-free BLMs were formed in microapertures fabricated in Si chips. The edge of the aperture was tapered in both nano-and micro-meter scales, leading to a smooth contact between the BLMs and the aperture wall. Another approach for improving the stability of BLMs is based on surface modification of the Si chips. It was found that highly stable BLMs were formed in amphiphobic Si chips that had been treated with long-chain perfluorocarbons. Owing to the mechanical stability of the BLMs, we also developed a centrifugal method for the efficient incorporation of human ion channels, including hERG channels, into solvent-free BLMs. The method improves the probability of vesicle fusion between the BLMs and channel-containing proteoliposomes. We also combined the BLM system with cell-free protein synthesis. Single-channel currents of a cell-free synthesized hERG channel were clearly recorded. The channel currents were blocked by the addition of an antihistamine astemizole, whose adverse effect on the hERG channel is well-established. When the present stable BLM system is combined with various hERG channel genotypes, it will provide a potential platform for assessing the risks of drug side effects acting on hERG channels of each patient.