A microfabricated reservoir-type oxygen sensor for measuring the real-time cellular oxygen consumption rate at various conditions

This paper presents a microfabricated reservoir-type oxygen sensor, which can accurately measure the solubilized oxygen concentration in real time, in order to measure the cellular oxygen consumption rate (OCR) in a solution containing cells. The fabricated oxygen sensor is composed of three-parts: electrochemical sensing electrodes, an oxygen-permeable membrane, and a reservoir for storing the solution. The oxygen transport rate through the membrane and the oxygen reaction rate at the working electrode (WE) surface are the two dominant parameters in determining the sensitivity of the oxygen sensor. The fabricated sensor showed a sensitivity of 2.84 A/cm² M and a 90% response time of 4.9 s in an average of 5 sensors when a 25,000 μm² WE and a 20 μm polydimethylsiloxane membrane were used. This is the first report in which the fastest response time has been achieved for the oxygen sensor. The fabricated sensor showed the repeatability with 154.05 ± 1.87 nA at the full-oxygen state and 2.77 ± 1.0 nA at the zero-oxygen state. The fabricated sensor was used to measure the uncoupled OCR of the L6 cells, and its result of 3.69 ± 0.30 was almost identical to the result of 3.70 ± 0.26 obtained from a commercial system.