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A multilayer capillary fiber was designed for optical sensor applications and its optical properties were evaluated by using a fluorescent layer immobilized on its inner surface. This fiber structure combines a large interaction surface (the inner wall of the capillary fiber) for binding of fluorescent indicators with evanescent wave fluorescence measurement, whichmay facilitate the design ofpseudohomogeneous assays without separation ofthe bound from nonbound fluorescent indicator. The inner surface of the capillary was derivatized by aminosilanization, followed by biotinylation and addition of streptavidin. This biotin-streptavidin coating facilitates subsequent immobilization of any biotinylated species (e.g. antibodies, antigens etc.) participating in specific molecular recognition. We have evaluated some properties of this capillary fiber design by using fluorescent proteins immobilized on the inner wall of capillary by biotin-avidin-interaction. Fluorescence was excited by a HeNe-laser (fluorescent indicator APC; Aem —660 fllfl) d by a Arlaser (fluorescent indicator RPE, 'em 578 fliT!),and measured with a spectrum analyzer.
Key words: capillaryfiber, capillaryfluorescence, opticalfiber sensor, fluorescence sensor, biotinavidin bridge, biotin-streptavidin coating, fluorescent indicator, fluorescent protein, APCfi uorescence, RPE-fluorescence
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