Direct electrochemistry and electrocatalysis with horseradish peroxidase in Eastman AQ films

Stable films made from ionomer poly(ester sulfonic acid) or Eastman AQ29 on pyrolytic graphite (PG) electrodes gave direct electrochemistry for incorp orated enzyme horseradish peroxidase (HRP). Cyclic voltammetry of HRP-AQ fi lms showed a pair of well-defined, nearly reversible peaks at about -0.33 V vs. SCE at pH 7.0 in blank buffers, characteristic of HRP heme Fe(III)/Fe( II) redox couple. The electron transfer between HRP and PG electrode was gr eatly facilitated in AQ films. The electrochemical parameters such as appar ent heterogeneous electron transfer rate constant (k(s)) and formal potenti al (E-alpha) were estimated by fitting the data of square-wave voltammetry (SWV) with nonlinear regression analysis. Reflectance absorption infrared ( RAIR) and UV-Vis absorption spectra demonstrated that HRP retained a near n ative conformation in AQ films. The embedded HRP in AQ films retained the e lectrocatalytic activity for oxygen, nitrite and hydrogen peroxide. Possibl e mechanism of catalytic reduction of H2O2 with HRP-AQ films was proposed. (C) 2001 Elsevier Science B.V. All rights reserved.