Glucose sensors based on a responsive gel incorporated as a Fabry-Perot cavity on a fiber-optic readout platform

An optical sensor for detection of glucose is implemented by incorporating a carbohydrate sensitive hydrogel as a Fabry-Perot cavity at the end of optical fiber for high sensitivity readout of the gel length. The glucose sensing functionality was achieved by incorporating boronic acid moieties into an acrylamide-based hydrogel. The interaction between glucose and boronic acid changes the driving forces for gel swelling thus inducing a glucose sensitive hydrogel swelling. The effects on the carbohydrate swelling response, with respect to sensitivity and selectivity, by incorporation of a cationic monomer, dimethyl-aminopropyl acrylamide, into the boronic acid functionalized responsive gels were determined. The linear gel swelling response in aqueous solutions at aqueous 2.5 mM carbohydrates were determined to −1760 nm/mM for glucose whereas mannose, sucrose, fructose and galactose displayed a response of about 10% of the glucose response for the hydrogels containing 10 mol% dimethylaminopropyl acrylamide. This gel composition with 10 mol% dimethylaminopropyl acrylamide is the most promising for detection of glucose at physiological pH and ionic strength. A mechanism where carbohydrate specific stabilisation of the boronic acid group and possible carbohydrate mediated additional crosslinking of the elastically active polymer chains is suggested.