Fluorescence measurement of membrane potential using micro optical probe system

Abstract

One of the most popular optical mode for monitoring membrane potential is fluorescence. In linear spectroscopic approach the fluorescence intensity is monitored as function of membrane potential. The purpose of this research is to develop a micro optical probe system for measuring membrane potential, in which fluorescent dye is used. This system has high spatial resolution for monitoring interaction between cells and is available for the analysis of functions and structures of the ion-channel. We measured the beamwaist of incident laser light, spectral properties of voltage-sensitive dye: NK2612 and temporal change of fluorescence intensity from cardiac cells stained with NK2612. The beamwaist of incident laser light is 1.5μm, the absorption maximum is 767nm and the fluorescent maximum is 843nm. Furthermore, we optimized the concentration of the voltage-sensitive dye: NK2612, confirmed fluorescence intensity is maximum when the concentration of the dye is 12.5μg/ml. Therefore, in our measurement the cardiac cells are stained with NK2612 solution of 12.5μg/ml. We observed the dependence of fluorescence intensity on the membrane potential and showed micro optical probe system is available for measuring membrane potential by fluorescence.