A fluorescent glucose assay using poly-L-lysine and calcium alginate microencapsulated TRITC-succinyl-concanavalin A and FITC-dextran

Abstract

Glucose assays based on fluorescent quenching of fluorophores due to Fluorescent Resonance Energy Transfer (FRET) has previously been successfully developed in an aqueous medium. TRITC-succinyl-Con A and FITC-Dextran have been used to determine physiological glucose concentrations, based upon competitive binding between Con A, dextran, and glucose. In the absence of glucose, TRITC-succinyl-Con A binds with FITC-Dextran, and the FITC fluorescence is quenched. As glucose binds to TRITC-succinyl-Con A, FITC-Dextran is liberated. The resulting increase in FITC fluorescence is proportional to the concentration of glucose. The authors report on attempts to develop a polymer-based fluorescent sensor using FITC-Dextran and TRITC-Succinyl-Con A encapsulated in calcium alginate gel spheres surface modified with a sodium alginate and poly-L-lysine coating to stabilize the gel. In vitro experiments of the polymer spheres in a solution of dH/sub 2/O and glucose were conducted. The fluorescence change with increasing glucose concentration, ranging from 0 to 800 mg/mL, was linear from 0 to 600 mg/mL, with a reduced response at 800 mg/mL. This reduced response is likely due to the majority of the initially bound FITC-Dextran having been released.