Application of ion-senstitive field effect transistors for measuring glial cell K+ transport

We report the fabrication and utilization of graphene-based, ion-sensitive field effect transistors (ISFETs) for measuring K+ efflux from immortalized and primary brain glial cells. There is currently an urgent need for developing new technologies for measuring cell membrane ion transport from primary cell cultures. K⁺-sensitive ISFETs were fabricated by coating the graphene surface with a polymer membrane containing the K⁺ ionophore valinomycin. Drain current versus gate voltage measurements demonstrated that the ISFETs display sensitivity to K+, but not to Na+ and Ca²+. To determine the feasibility of using ISFETs for recording cell membrane ion transport, ISFET sensors were inserted into recording chambers containing either primary rat glial cells or human U251-MG glioma cells. Activation of K⁺ channels in the glial cells resulted in a strong, time-dependent increase in the extracellular K⁺ concentration as measured with the ISFETs. Due to the noninvasive properties of the probes, the ISFETs will be useful for future multi-array, cell-based screening and toxicological studies of primary cell cultures.