ENZYMATIC-ACTIVITY OF GLUCOSE-OXIDASE ENCAPSULATED IN TRANSPARENT GLASS BY THE SOL-GEL METHOD

The sol-gel process is a technique that can be used to prepare optically transparent oxide glasses by hydrolysis and polycondensation of alkoxides.2Little or no heating is required, and consequently gels may be doped with molecules whose poor thermal stability precludes their incorporation in traditional inorganic hosts.3, 4The sol-gel method also has the advantage that it may be used to prepare transparent monoliths with dimensions on the order of centimeters, as well as uniform films and fibers. Previous studies focused on the incorporation of organic molecules to probe spectroscopically the sol-gel process as well as to develop new optical properties. To extend our studies to include enzymes and other proteins as dopants in optically transparent sol-gel glasses, we modified the conventional procedures for preparation of sol-gel glasses, successfully applied our modified procedure to the encapsulation of several colored metalloproteins, and observed full retention of their absorption spectra.5We found that the large proteins were securely trapped but small substrates could diffuse readily into and out of the sol-gel matrix.5Prior to our studies, Avnir and co-workers reported that trapping of the enzyme alkaline phosphatase in sol-gel glass produced a bioactive opaque powder with improved thermal stability relative to the free enzyme.4In this communication, we report the synthesis of transparent silicate glass monoliths of the dimensions 10 mm X 5 mm X 2 mm containing the enzymes glucose oxidase and peroxidase. In addition to measuring the changes in the absorption spectra of the products of the enzymatic reaction in the glass, we follow the formation of the products in solution and demonstrate that these new enzyme-containing sol-gel glasses are enzymatically active and can be used as the active medium in optically based glucose sensors. © 1992, American Chemical Society. All rights reserved.