THE SINGLE-MODE TAPERED OPTICAL-FIBER LOOP IMMUNOSENSOR

A novel single mode tapered optical fibre loop biochemical sensor base d on fluorescence spectroscopy has been developed. The fundamental fib re mode propagates through the tapered portion of an optical fibre and generates an evanescent field which penetrates into the aqueous envir onment surrounding the fibre where the bio-recognition event occurs. A two-step assay was used, in which the analyte was labelled secondaril y with a fluorescent dye, fluorescein isothiocyanate or tetramethyl rh odamine. When excited by the input argon ion laser light from the near end of the taper, generated fluorescence is coupled into the guided m ode of the fibre and collected at the far end of the taper. Methods of making the sensor chemically reusable were investigated. The high sen sitivity (75 pg/ml) of the single mode tapered loop device, combined w ith a simple immobilization protocol, provides a powerful tool for per forming immunoassays.