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A new optical platform for the interrogation of a polymethylmethacrylate (PMMA) multichannel array for chemical and biochemical parameters is described. It consists of a plastic chip formed by two pieces of PMMA properly shaped in order to obtain different microchannels, 500 mum in width and 400 mum in height. A fluorescent sensing layer is immobilized on the internal wall of the microchannel. The emitted light travels along the thickness of the upper PMMA piece and it is detected with an optical fiber connected with a spectrum analyzer. The anisotropy of the fluorescence emitted by the fluorophore immobilized at the liquid/plastic interface gives rise to preferential directions of the emitted fluorescence. The collection of the fluorescence at an angle of 50deg implies an amplification of roughly one order of magnitude in the ratio between the fluorescence signal and the scattered light. The optical platform was further characterized as a pH sensor and as potential chip for immunoassay. In the first case, the fluorescein dye is directly immobilized onto the internal wall of the channel and the fluorescence changes are measured as a function of the pH of the flowing sample. In the second case, a direct antigen-antibody interaction is carried out. The mouse-IgG is covalently immobilized onto the internal wall of the channel and the Cy5-labeled anti-mouse IgG is used for the specific interaction.
Date of Publication: July 2008