Electrical impedance spectroscopy for drug screening on ligand-gated ion channels.

Abstract

Ligand-gated ion channels (LGICs) are involved in many pathophysiological processes and represent a relevant, although challenging, target for drug discovery. The gold standards for studying the ligand-induced ion channel currents and their modulations by drugs are manual patch clamp or two-electrode voltage clamp (TEVC) electrophysiology, but the throughput is low. Higher throughput has been achieved with automated patch clamp instruments, but these have immense acquisition and significant operating costs. In a proof-of-concept study, we developed a reliable, easy to use and multiplexable microfluidic setup to screen the action of drugs at LGICs heterologously expressed in X. laevis oocytes by measuring the electrical impedance changes across the plasma membrane induced by ligand pulses. We validated our setup by simultaneous TEVC electrophysiology and tested the effects of the reference drugs suramin, TNP-ATP, PPADS or diazepam on oocytes expressing P2X2 or GABAAreceptors, respectively. The drugs modulate ATP-induced and GABA-induced currents of P2X2 and GABAA receptors, respectively. The results obtained with TEVC are similar in terms of drug efficacy to those obtained with simultaneously recorded membrane impedances, which are determined by electrical impedance changes. Thus, the study shows the reliability of our setup as a faster (higher throughput) and more cost-effective method for drug screening compared to conventional electrophysiological techniques. After multiplexing of the system, the setup may facilitate commercial and academic drug screening of ligand gated ion channels that are receiving less attention due to limitations in current assays. [Funded under the Excellence Strategy of the Federal Government and the Länder - OPSF671]