Near-infrared fluorescence lifetime assay for serum glucose based on allophycocyanin-labeled concanavalin A

We describe an assay scheme for glucose based on fluorescence resonance ene rgy transfer (FRET) between concanavalin A (con A), labeled with the near-i nfrared fluorescent protein allophycocyanin (APC) as donor, and dextran lab eled with malachite green (MG) as acceptor. Glucose competitively displaces dextran-MG and leads to reduction in FRET, assessed by time-domain fluores cence lifetime measurements using time-correlated single-photon counting. T he assay is operative in the glucose concentration range 2.5-30 mM, and the refore suitable for use in monitoring diabetes control. Albumin and serum i nhibit FRET but the interference can be prevented by removal of high molecu lar weight substances by membrane filters. APC shows promise for incorporat ion in an implanted glucose sensor which can be interrogated from outside t he body. (C) 2001 Academic Press.