Measuring Both pH and O2 with a Single On-Chip Sensor in Cultures of Human Pluripotent Stem Cell-Derived Cardiomyocytes to Track Induced Changes in Cellular Metabolism

In vitro studies which focus on cellular metabolism can benefit from time-resolved readouts from the living cells. pH and O 2 concentration are fundamental parameters upon which cellular metabolism is often inferred. This work demonstrates a novel use of a ruthenium oxide (RuO x ) electrode for in vitro studies. The RuO x electrode was characterized to measure both pH and O 2 using two different modes. When operated potentiometrically, continuous pH reading can be obtained, and O 2 concentration can be measured chronoamperometrically. In this work, we demonstrate the use of the RuO x electrodes in inferring two different types of metabolism of human pluripotent stem cell-derived cardiomyocytes. We also show and discuss the interpretation of the measurements into meaningful extracellular acidification rates and oxygen consumption rates of the cells. Overall, we present the RuO x electrode as a versatile and powerful tool in in vitro cell metabolism studies, especially in comparative settings.