Direct electron transfer of horseradish peroxidase and its biosensor based on gold nanoparticles/chitosan/ITO modified electrode

Gold nanoparticles/chitosan modified indium tin oxide (ITO) coated glass electrode was prepared by a simple layer-by-layer self-assembly technique. Horseradish peroxidase (HRP) was successfully immobilized on the modified electrode by electrostatic adsorption. Direct electrochemistry and electrocatalysis of HRP were investigated. The composite film showed an obvious promotion for the direct electron transfer between HRP and the underlying electrode. The immobilized HRP exhibited an excellent electrocatalytic activity toward the reduction of H2O2. The catalysis currents increased linearly to the H2O2 concentration in a wide range of 2.0 x 10(-5) to 6.5 x 10(-3) M with a low detection limit of 3.5 x 10(-6) M. The calculated apparent Michaelis-Menten constant (K-m(app)) was 4.43mM.