Direct electrochemistry and electrocatalysis of horseradish peroxidase immobilized in graphene oxide-Nafion nanocomposite film

Direct electron transfer of horseradish peroxidase (HRP) immobilized in graphene oxide (GO)-Nafion nanocomposite film and its application as a new biosensor was investigated with electrochemical methods. Immobilized HRP shows a pair of well-defined redox waves and retains its bioelectrocatalytic activity for the reduction of H2O2 and O-2. As a new sensor with excellent electrocatalytic response to the reduction of H2O2 and O-2, calibrations with good linear relationships were obtained from 1.0 mu mol L-1 to 1.0 mmol L-1 for H2O2 and from 0.5 mu mol L-1 to 18.6 mu mol L-1 for O-2 with the detection limits of 4.0 x 10(-7) mol L-1 for H2O2 and 1.0 x 10(-7) mol L-1 for O-2 at a signal-to-noise ratio of 3. Additionally, the responses showed Michaelis-Menten behavior with K-m(app) values of 0.684 mmol L-1 for H2O2 and 0.0160 mmol L-1 for O-2. Moreover, the cathodic peak current of an HRP/GO/Nafion/GCE biosensor decreases by less than 5% after 4 weeks. These results reveal that GO can be conveniently incorporated into a polymer nanocomposite for fabrication of new GO-based biosensors. (C) 2012 Elsevier Ltd. All rights reserved.