A carbon nanotube/silica sol–gel architecture for immobilization of horseradish peroxidase for electrochemical biosensor

A novel third-generation biosensor for hydrogen peroxide (H2O2) has been constructed based on horseradish peroxidase (HRP) immobilized by the sol–gel (SG) technology on carbon nanotube (CNT)-modified electrode. CNT has good promotion effects on the direct electron transfer between HRP and the electrode surface and the SG network provides a biocompatible microenvironment for enzyme. The immobilized HRP retained its bioelectrocatalytic activity for the reduction of hydrogen peroxide and can respond to the change of concentration of H2O2 rapidly. The heterogeneous electron transfer rate constant was evaluated to be 2.8 ± 0.4 s−1. The amperometric response to H2O2 shows a linear relation in the range from 0.5 to 300 μmol l−1 and a detection limit of 0.1 μmol l−1 (S/N = 3). The K M app value of HRP immobilized on the electrode surface was found to be 1.35 mmol l−1. The biosensor exhibited high sensitivity, rapid response and excellent long-term stability.