Abstract
| - A fluorescence biosensor is described that is based on aphotopolymerized poly(ethylene glycol) (PEG) hydrogelincorporating fluorescein isothiocyanate dextran (FITC-dextran) and tetramethylrhodamine isothiocyanate concanavalin A (TRITC-Con A) chemically conjugated into thehydrogel network using an α-acryloyl, ω-N-hydroxysuccinimidyl ester of PEG-propionic acid. In the absence ofglucose, TRITC-Con A binds with FITC-dextran, and theFITC fluorescence is quenched through fluorescenceresonance energy transfer. Competitive glucose bindingto TRITC-Con A liberates FITC-dextran, resulting inincreased FITC fluorescence proportional to the glucoseconcentration. In vitro experiments of hydrogel spheresin a solution of 0.1 M phosphate-buffered saline (pH 7.2)and glucose were conducted for multiple TRITC-ConA/FITC-dextran ratios. Hydrogels were characterized onthe basis of the percent change in fluorescence intensitywhen FITC-dextran was liberated by increasing glucoseconcentrations. The optimum fluorescent change between0 and 800 mg/dL was obtained with a TRITC-ConA/FITC-dextran mass ratio of 500:5 μg/mL PEG. Fluorescent response was linear up to 600 mg/dL. At higherconcentrations, the response saturated due to the displacement of the majority of the FITC-dextran and toconcentration quenching by free FITC-dextran. Dynamicfluorescent change upon glucose addition was ∼10 minfor a glucose concentration step change from 0 to 200mg/dL.
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