Remote fiber-optic biosensors based on evanescent-excited fluoro-immunoassay: Concept and progress

A homogeneous silica optical fiber with its coating and cladding removed will interact with its surroundings via evanescent-wave modes at the interface. Antibody or antigen molecules can be covalently linked to the silica-fiber surface. The immobilized biomolecules will bind complementary antigen or antibody from a surrounding solution. If the bound antigen or antibody is fluorescent, a fluoro-immunoassay can be performed. The sensitivity of such a sensor is enhanced in a competitive immunoassay mode, where a fluorescently labeled antigen or antibody competes for the binding sites on the immobilized bio-molecules, thereby providing a competitive binding fluoro-immunoassay. Such sensors have the potential for remote unattended pseudocontinuous monitoring of biomolecules.