It is reported for the first time that direct electron-transfer processes between a polypyrrole (PPY) entrapped quinohemoprotein alcohol dehydrogenase from Gluconobacter sp. 33 (QH-ADH) and a platinum electrode take place via the conducting-polymer network. The cooperative action of the enzyme-integrated prosthetic groups--pyrroloquinoline-quinone and hemes--is assumed to allow this electron-transfer pathway from the enzyme's active site to the conducting-polymer backbone. A hypothetical model of the electron transfer is proposed which is supported by the influence of various parameters, such as, e.g., ionic strength and nature of the buffer salts. This unusual electron-transfer pathway leads to an accentuated increase of the K M app value (102 mM) and hence to a significantly increased linear detection range of an ethanol sensor based on this enzyme.

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An optimized material for the development of reagentless oxygen‐independent biosensors based on conducting polymers is described. Considering the prerequisites for a fast electron transfer between a redox enzyme and the electrode surface via an electron‐hopping mechanism, an Os‐complex‐modified pyrrole derivative with a long, flexible spacer chain has been synthesized. Copolymerization of the new mediator‐modified pyrrole monomer with pyrrole was optimized aiming on a higher mediator loading in the film. The feasibility of this material for the development of reagentless oxygen‐independent biosensors is demonstrated by entrapment of a PQQ‐dependent glucose dehydrogenase isolated from Erwinia sp. 34‐1 within this electrochemically grown redox‐polymer network.

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