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 −0.328 V 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 for a 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 μM, a linear range of 1–500 μM, and an apparent Michaelis–Menten constant of 0.39 mM. The performance of the prepared biosensor was evaluated with respect to four possible interferences.