Direct electron transfer of Horseradish peroxidase on porous structure of screen-printed electrode

Disposable hydrogen peroxide biosensor was developed based on the direct electron transfer of horseradish peroxidase (H RP) on porous screen-printed carbon electrodes. Conventional screen-printing process was manually performed to fabricate the planar carbon electrodes, which were endowed with porous surfaces especially after anodizing pretreatment. The cyclic voltammetry experiment indicated a pair of stable and well-defined redox peaks with a formal potential of -0.33 V. And the formal potential was pH-dependent, having a slope of -55.2 mV/pH which indicated one electron transfer. The heterogeneous electron transfer rate constant k(s) was estimated to be 13.28 +/- 4.80 s(-1). Additionally, the sensitivity was 143.3 mA M-1 cm(-2) and the linear range was from 5.98 to 35.36 mu M. In Conclusion, the present work achieved the direct electron transfer of HRP on screen-printed electrodes without any promoters. The porous structure of screen-printed carbon electrodes facilitated the direct electron transfer between the active sites of HRP and the electrodes due to large amounts of conductive sites available on the surface for contacting with enzyme molecules. Moreover, the proposed biosensor could be mass-produced at low price, promising for commercial application. (C) 2008 Elsevier B.V. All rights reserved.