Hydrogen peroxide sensor based on horseradish peroxidase-labeled Au colloids immobilized on gold electrode surface by cysteamine monolayer Original Research Article

A novel strategy to construct a sensitive amperometric sensor of H2O2 was described. Horseradish peroxidase (HRP) was successfully immobilized on nanometer-sized Au colloids, which were supported by thiol-tailed groups of cysteamine monolayer. The thiol-tailed groups were formed through the covalent binding of glutaraldehyde on a cysteamine-modified gold electrode. With the aid of the catechol mediator in the solution, HRP-labeled Au colloids displayed excellent electrocatalytical response to the reduction of H2O2, which increased with decreasing size of Au colloids. The sensors responded to H2O2 in the concentration range of 0.39 μM–0.33 mM, and reached 95% of the steady-state current in less than 5 s with the detection limit of 0.15 μM. The response showed a Michaelis–Menten behavior at larger H2O2 concentrations. The KappM values for the sensors based on different sized HRP-labeled Au colloids (colloid A–D) were found to be 0.11, 0.094, 0.054 and 0.064 mM, respectively. The low KappM values demonstrated that HRP immobilized on Au colloids exhibited a high affinity to H2O2 with no loss of enzymatic activity.