Application of a metal–insulator–semiconductor (MIS) sensor for extracellular redox potential detection

Extracellular redox potential is an important regulator of cell–microenvironmental interactions. It works in concert with intracellular redox state to control the electron transport in redox signaling. The redox regulation can influence cell surface proteins such as receptors, transport proteins, and enzymes that contain thiol moieties, and then cause significant impact on cell proliferation, differentiation and apoptosis. The present work employs an electrochemical potentiometric means to probe extracellular redox potential of living cells. A metal–insulator–semiconductor structured sensor is used based on an AC photovoltage technique. The sensor has a sensitivity of 53.2 mV/log([Fe(II)]/[Fe(III)]) for Fe(II)/Fe(III) redox couple and 25.4 mV/log([CySS]/[Cys]2) for Cys/CySS couple. Then kidney cells are incubated on the sensor surface for physiological redox potential study. The potential is found to be reduced at physiological activity and the reduction rate is related with cell density. The reduction rate decreases after the inhibition of mitochondrial complex I. Evidence is presented that the mitochondrial electron transport chain has significant influence on the extracellular reduction rate.