Measurements of CO2, lactic acid and sodium bicarbonate secreted by cultured cells using a flow-through type pH/CO2 sensor system based on ISFET

Abstract We developed a pH/CO 2 sensor system using two ion-sensitive field effect transistors (ISFETs) to evaluate the metabolic activity of cultured cells. One ISFET measures total pH changes and the other ISFET, covered with a gas-permeable silicon tube, measures pH changes due to CO 2 . These ISFETs were placed in a flow-through chamber with a window to be attached to a glass plate on which cells were cultured. Measurements were performed with a baseline solution of low buffer capacity. In the quantitative estimation of cellular products, we assumed that cells secreted CO 2 , lactic acid and sodium bicarbonate ( NaHCO 3 ), and then lactic acid and NaHCO 3 proceeded to the neutralization reaction to form sodium lactate and additional CO 2 . We applied this system to evaluate the metabolic activity of bovine aortic endothelial cells (BAEC) and rabbit aortic smooth muscle cells (RASMC). The production of CO 2 by RASMC was significantly higher than that by BAEC (204 ± 16 and 4.1 ± 0.3 × 10 8 molecules/cell/s, respectively). More NaHCO 3 than lactic acid was produced in RASMC, whereas they were not significantly different in BAEC.