An optical PMMA biochip based on fluorescence anisotropy: Application to C-reactive protein assay

An optical platform for point of care testing (POCT) application is developed. The core of the platform is a miniaturised polymethylmetacrylate (PMMA) chip, that consists of two pieces of PMMA that have been custom-machined to produce flow channels, 500 μm in width and 400 μm in height, through which the analysed sample flows. Thanks to the fluorescence anisotropy, a large fraction of the fluorescence emitted by the sensing layer immobilised on the bottom of the PMMA cover travels along the thickness of the PMMA cover itself up to its end-face and it is collected by a plastic optical fibre connected to a photodetector. The potential of the optical chip is investigated with a sandwich assay for the C-reactive protein, one of the markers for inflammatory diseases. The assay covers the working range from 0.1 to 50 mg L−1 with a limit of detection of 0.004 mg L−1. Different combinations of capture and target antibodies were carefully investigated in order to achieve the best performances in terms of sensitivity and unspecific adsorption.