Direct electrochemistry and biosensing of hydrogen peroxide of horseradish peroxidase immobilized at multiwalled carbon nanotube/alumina-coated silica nanocomposite modified glassy carbon electrode

Direct electrochemistry and bioelectrocatalytic ability toward the reduction of hydrogen peroxide of horseradish peroxidase (HRP) were found at the multiwalled carbon nanotube/alumina-coated silica (MWCNT/ACS) nanocomposite modified glassy carbon electrode. The surface morphology of the HRP/MWCNT/ACS nanobiocomposite modified glassy carbon electrode was characterized by scanning electron microscopy. In cyclic voltammetric response, the immobilized HRP at the MWCNT/ACS nanocomposite modified glassy carbon electrode displayed a pair of well-defined and quasi-reversible redox peaks with a formal potential of -0.328V versus Ag/AgCl at a scan rate of 200 mV s(-1). The formal potential of HRP varied linearly in the range of solution pH values from 6.0 to 8.0 with a slope of -56 mV pH(-1), which is close to the theoretical value of -59 mV pH(-1) fora reversible one-electron coupled with one-proton electrochemical reaction process. Several important experimental variables were optimized. The optimized hydrogen peroxide biosensor exhibited a sensitivity of 0.157 A M-1 cm(-2), a detection limit of 0.63 mu M, a linear range of 1-500 mu M, and an apparent Michaelis-Menten constant of 0.39 mM. The performance of the prepared biosensor was evaluated with respect to four possible interferences. (C) 2009 Elsevier B.V. All rights reserved.