Optical sensing of glucose using phase-modulation fluorimetry

Abstract We describe a fluorescence assay of glucose based on flurorescence resonance energy transfer and phase-modulation measurements of the donor decay times. The assay is based on the decreased decay time of a donor fluorophore linked to Concanavalin A (ConA) upon binding of acceptor-labeled sugar. Displacement of the labeled sugars by glucose results in a decrease in energy transfer and an increase in the donor decay time. The assay was demonstrated with several donor-acceptor pairs, demonstrating the robustness and generally of this this approach. A competitive glucose assay was demonstrated with both low-molecular-weight acceptors and with acceptor-labeled dextran. Use as a polymeric acceptor would allow the glucose sensor to be placed behind a glucose-permeable barrier, as may be needed in clinical applications. The use of energy transfer allows the selection of excitation and emission wavelengths compatible with the desired light sources and optical properties of the samples. The use of the fluorescence decay times rather than intensities, makes the measurements mostly independent of probe photobleaching, light losses in the optics, instrumental drifts, and mostly independent of scattering and/or adsoprtion of the sample.