Glucose sensors with increased sensitivity based on composite gels containing immobilized boronic acid

Copolymerization of N-acryloyl-m-aminophenylboronic acid (NAAPBA) with acrylamide (AAm) on the surface of glass plates resulted in the formation of a hydrogel film with porous structure and capable of optical response to the changes in concentration of glucose in the contacting solution. The boronate specific dye, Alizarin Red S (ARS) was incorporated into hydrogel film to increase the sensitivity towards glucose and poly(N-vinylpyrrolidone) (PVP) was incorporated to prevent the dye leakage. The obtained boronate-containing polymer film responded to submicromolar concentration of glucose with optical density changes being a linear function of glucose concentration in the range from 0.1 to 1 mM. The PVP-ARS-containing gel exhibited a 10-fold higher glucose sensitivity compared with the colorless NAAPBA-AAm gel. The equilibrium dissociation constants of soluble ARS-PVP and ARS-NAAPBA-containing copolymer complexes at pH 7.3 were found to be 1.4 and 0.44 μM, respectively. The low dissociation constants enabled the preparation of the sensor with increased operational stability of at least two months allowing more than 20 assays of with no loss in the sensitivity or dye leakage.