A SCANNING FORCE MICROSCOPY STUDY OF POLY(PHENOL) FILMS CONTAINING IMMOBILIZED GLUCOSE-OXIDASE

Scanning force microscopy has been used to characterize poly(phenol) f ilms containing immobilized glucose oxidase (GOx). The films were grow n by electrochemical polymerization of phenol from neutral aqueous sol ution at highly ordered pyrolytic graphite (HOPG) electrodes. Scanning force microscopy, in contact mode, shows the surface topography of th e enzyme/polymer composite films. Films containing immobilized enzyme were found to be significantly rougher than either the bare substrate or enzyme free poly(phenol) films grown under the same conditions. The thickness of the electropolymerized films was determined by using the 'nanodozing' technique in which the scanning tip is used to scrape aw ay an area of the polymer film to reveal the HOPG surface beneath. Usi ng this method we find that the enzyme-containing films are 7.4 +/- 0. 8 nm thick whereas the enzyme free poly(phenol) films are 3 +/- 1.2 nm thick. Amperometric measurements using the tetrathiafulvalene/tetrath iafulvalenium (TTF/TTF+) couple as a redox mediator for oxidation of t he immobilized GOx confirm that the immobilized enzyme is catalyticall y active. Analysis of the amperometric response of the electrodes at d ifferent glucose concentrations allows us to determine the kinetic par ameters for the immobilized enzyme. The amperometric responses are con sistent with the presence of a thin active layer of GOx one or two mol ecules thick immobilized at the electrode surface and agree with the c onclusions from the scanning force microscopy study. (C) 1998 Elsevier Science S.A. All rights reserved.