SCANNING TUNNELING MICROSCOPY STUDY OF POLYPYRROLE FILMS AND OF GLUCOSE-OXIDASE AS USED IN A 3RD-GENERATION BIOSENSOR

We have studied the surface morphology of different forms of the organic conductor polypyrrole, which serves as the environment for immobilization of the redox enzyme glucose oxidase. Scanning tunnelling microscopy (STM) images of polypyrrole films, obtained electrochemically on highly oriented pyrolytic graphite, STM images of polypyrrole microtubules and STM images of glucose oxidase molecules adsorbed on a gold facet are presented and discussed. The conclusions from this study are: (i) the polypyrrole filmS, Prepared chemically or electrochemically, exhibit disordered non-crystalline structure; (ii) the polypyrrole surface corrugations and the dimensions of the glucose oxidase molecule are of the same order of magnitude, allowing strong adsorption of the enzyme to the conducting polymer. On the basis of these data, a model for the direct interaction between glucose oxidase and polypyrrole in the biosensor is proposed.