Monitoring extracellular K+ flux with a valinomycin-coated silicon nanowire field-effect transistor

Abstract

A silicon nanowire field-effect transistor (SiNW-FET) coated with a polyvinyl chloride (PVC) membrane containing valinomycin (VAL) was employed as a biosensor (referred to as VAL-PVC/SiNW-FET) to detect the K+-efflux from live chromaffin cells. The detection sensitivity of K+ with the VAL-PVC/SiNW-FET covers a broad range of concentrations from 10−6 to 10−2M. The apparent association constants between VAL and Li+, Na+, K+, and Cs+ in Tris buffer solution were determined to be 67±42, 120±23, 5974±115, and 4121±140M−1, respectively. By culturing chromaffin cells on the VAL-PVC/SiNW-FET, the conductance was significantly increased by nicotine stimulation in a bath buffer without Na+. The K+ concentration at the cell surface was determined to be ∼20μM under the stimulation of 5mM nicotine. These results demonstrate that the VAL-PVC/SiNW-FET is sensitive and selective to detect the released K+ from cells and is suitable for applications in cellular recording investigations.