Fluorimetric Oxygen Sensor for in Vitro Cell Models

A phase fluorimetric sensor targeted for the monitoring of dissolved oxygen concentration in microfluidic in vitro cell models is presented. The sensing surface of the sensor consists of oxygen sensitive fluorescent dyes (PtOEPK) embedded in a thin polystyrene film. The simulated fluorescence emission characteristics show highly anisotropic distribution, and an efficient optical read-out based on a parabolic lens is presented. Experimental results show that the applied sensing scheme allows one to use thin films (<500 nm), dilute dye-polymer ratios (0.025%), low power LED excitation (<1 mW), a simple phase locked photodiode read-out and yet achieve over 40 dB signal-to-noise ratio at 10 Hz data rate at physiologically relevant oxygen concentrations. These features are important in in vitro cell studies, as the potential cytotoxicity of the dyes and the sensing method (i.e. production of singlet oxygen) are reduced with low dye content and excitation power. In addition, thin and dilute polystyrene films are highly transparent and facilitate optical microscopy.