Microfluidic oxygen sensor system as a tool to monitor the metabolism of mammalian cells

We present a sensor system to monitor the uptake of oxygen by mammalian cells as a direct indicator for the metabolism under consideration of the requirements for the usage in biolabs. That includes reliable oxygen sensing as well as a small footprint of the setup without sophisticated external equipment, the usage of compatible materials and the suitability for a high degree of integration and automation. These requirements are fulfilled by a system that consists of a microfluidic chip with an integrated oxygen-sensitive phosphorescent film, heater and temperature sensor, external optical read-out and 3D-printed holders and housing. The chip with the closed microfluidic chamber is made by clean-room technologies out of silicon and glass. An excitation LED and a small and low-cost Raspberry Pi camera are used to measure the phosphorescent signal. With this system, the concentration of dissolved oxygen can be determined with an accuracy of +/- 0.8% (air) for oxygen concentrations between 0 and 26% (air) and at any temperature between 23 and 41 degrees C. To demonstrate the capabilities, the oxygen consumption rates of HaCaT-cells (human keratinocyte cell line) are determined at different temperatures.