Reagentless biosensor for hydrogen peroxide based on self-assembled films of horseradish peroxidase/laponite/chitosan and the primary investigation on the inhibitory effect by sulfide

Horseradish peroxidase (HRP) was successfully incorporated into the laponite/chitosan (Chit)-modified glassy carbon electrode (GCE) using step-by-step self-assembly. The self-assembly processes were monitored by X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectra (EIS). Direct electrochemistry and electrocatalysis of the self-assembled HRP were investigated. Cyclic voltammetry of HRP/laponite/Chit/GCE, in anaerobic phosphate buffer solution (0.025 M PBS, pH 7.0), displayed a pair of stable and quasi-reversible peaks at potentials E-pa = 0.024 V and E-pc = -0.132 V vs. SCE, attributed to the HRP-Fe(III)/HRP-Fe(II) redox couple. The electrochemical reaction of the HRP/laponite/Chit/GCE exhibited a surface-controlled electrode process. The electron transfer rate constant was estimated to be 1.82 s(-1). The self-assembled HRP maintained its biological activity and exhibited an excellent electrocatalytic performance for the reduction of H2O2 with fast amperometric response (10 s). broad linear range (2.9 x 10(-5) to 1.4 x 10(-3) M), good sensitivity (19.7 +/- 0.5 mA M-1 cm(-2)) and low detection limit (5 x 10(-6) M) at a signal-to-noise ratio of 3. Moreover, the inhibitory of sulfide to the self-assembled HRP was also investigated. (C) 2010 Elsevier B.V. All rights reserved.