Hydrogen peroxide sensitive biosensor based on plant peroxidases entrappedin Os-modified polypyrrole films

An amperometric hydrogen peroxide biosensor was designed based on horseradi sh and tobacco peroxidase entrapped into a conducting redox-polymer immobil ised on either glassy-carbon or platinum electrodes. A versatile one-step i mmobilisation method was carried out based on the electrochemical polymeris ation of a pyrrole monomer functionalised with an Os-complex. Cyclic voltam metry and constant potential amperometry performed with the different perox idases in solution or entrapped within the conducting redox-polymer film su ggests that the redox centre within the active site of horseradish peroxida se exhibits a better accessibility for the either free-diffusing or polymer -bound Os-complexes than that of tobacco peroxidase. Therefore, the obtaine d sensitivities for the reduction of H2O2 are significantly higher for the HRP-based sensors as compared with the tobacco peroxidase-based ones. The d irect reduction of H2O2 on the polymer backbone was identified as a side re action even though the bioelectroreduction through horseradish peroxidase i s a much more efficient reaction pathway. (C) 2001 Elsevier Science B.V. Al l rights reserved.