<title>Miniature fiber optic sensor based on fluorescence energy transfer</title>

Abstract

Optical fiber biosensors based on fluorescence assays have several distinct advantages when measuring biological analytes such as metabolites, cofactors, toxins, etc. Not only are optical signals immune to electronic interferences, but the polychromatic nature of most fluorochemical assays provides more potentially useful data about the system being studied. One of the most common difficulties normally encountered with optical biosensors is the inability to routinely recalibrate the optical and electronic components of the system throughout the life of the sensor. With this in mind, we present an optical fiber assay system for glucose based on a homogeneous singlet/singlet energy transfer assay along with the electronic instrumentation built to support the sensor system. In the sensor probe, glucose concentrations are indirectly measured from the level of fluorescence quenching caused by the homogeneous competition assay between TRITC labeled concanavalin A (receptor) and FITC labeled Dextran (ligand). The FITC signal is used to indicate glucose concentrations and the TRITC signal is used for internal calibration. Data is also presented on a protein derivatization procedure that was used to prevent aggregation of the receptor protein in solution. Also, a molecular model is described for the singlet/singlet energy transfer interactions that can occur in a model system composed of a monovalent ligand (FITC labeled papain) and a monovalent receptor (TRITC labeled concanavalin A).