Direct electrochemistry and electrocatalysis of horseradish peroxidase based on clay-chitosan-gold nanoparticle nanocomposite

Gold nanoparticles stabilized by chitosan (AuCS) were hybridized with exfoliated clay nanoplates through electrostatic interaction. The resulting clay-chitosan-gold nanoparticle nanocomposite (Clay/AuCS) was used to modify glassy carbon electrode (GCE). HRP, a model peroxidase, was entrapped between the Clay/AuCS film and another clay layer. UV-vis spectrum suggested HRP retained its native conformation in the modified film. Basal plane spacing of clay obtained by X-ray diffraction (XRD) indicated that there was an intercalation-exfoliation-restacking process among HRP, AuCS and clay during the modified film drying. The immobilized HRP showed a pair of quasi-reversible redox peaks at -0.195 V (vs. saturated Ag/AgCl electrode) in 0.1 M PBS (pH 7.0), and the biosensor displayed a fast amperometric response to H2O2 with a wide linear range of 39 mu M to 3.1 mM. The detection limit was 9.0 mu M based on the signal to noise ratio of 3. The kinetic parameters such as a (charge transfer coefficient), k(s) (electron transfer rate constant) and K-m (Michaelis-Menten constant) were evaluated to be 0.53, 2.95 +/- 0.20 s(-1) and 23.15 mM, respectively. (C) 2007 Elsevier B.V. All rights reserved.