A photovoltage-based integrated sensor for extracellular redox potential measurement and acidification detection

In this study, photovoltage technique is applied in the development of a monolithically integrated sensor for redox (reduction–oxidation) potential and pH measurement. The sensor employs the electrolyte–insulator–semiconductor structure, with deposition of a layer of gold metal on partial surface of insulator silicon dioxide. Silicon dioxide and gold layer on a single chip form two distinct sensing sites, by sharing the same measuring system, the detection of redox potential and pH variation can be realized. In this work, the sensor characteristics is tested, and the sensitivity for redox potential and pH measurement is 53.8 mV/log([Fe(II)]/[Fe(III)]) and 44.3 mV/pH respectively. To demonstrate the validity of the sensor in extracellular detection, neonatal rat kidney cells are cultured on the sensor surface and then packaged in a flow chamber, thus the acidification rate of metabolites and the redox potential variation in extracellular microenvironment can be continuously monitored. Experimental results indicate increasing acidification and reducing potentials under physiological conditions. The synthesis parameters have potentials in detail revelation of cell metabolism.