Question

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Optical oxygen sensors are based on fluorescence quenching in an appropriate dye by molecular oxygen.31 Measurement principles include the evaluation of fluorescence amplitude, fluorescence lifetime or phase shift in the case of modulated excitation light. For all principles, the transfer function follows the non-linear Stern–Volmer relation. This relation states that the output of the sensors is inversely proportional to the concentration plus a constant. This means that there is no clear zero-point and therefore two-point calibration is needed. The fluorescent dye can be embedded in a polymer as a single sensor spot or spread in a membrane coating on the whole surface of the cell culture vessel in order to measure spatial changes in oxygen concentration.32,33 In both cases, fluorescence excitation and readout can be carried out directly using LEDs or coupled through an optical fiber outside transparent cell culture vessels. This is a big advantage with respect to easy handling and sterilization of the cell culture vessels and allows separation of the single-use sensor spot from the reusable optical setup. Similar sensor spots can be read out with an inverted microscope.34

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Answer 1

Optical oxygen sensors are based on fluorescence quenching in an appropriate dye by molecular oxygen. Measurement principle of these sensors include evolution of fluorescence amplitude,lifetime and phase shift in the case of modulated excitation light. The transfer function follows the non linear stern volmer relation means output of the sensor is inversely proportional to concentration. This means there is no zero point and hence two calibration is needed. Then the fluorescent dye can be embedded in a polymer as single sensor spot or spread in a membrane coating of the whole surface of cell culture vessel in order to measure spatial changes in oxygen concentration. By using LED or optical fibre the fluorescent excitation is read out. This is having big advantages with respect to easy handling and sterilization of cell culture vessel and allows separation of single sensor spot, that can by read out with an inverted microscope.