Direct electrochemistry of horseradish peroxidase immobilized on gold colloid/cysteine/nafion-modified platinum disk electrode

Direct electron transfer process of immobilized horseradish peroxidase (HRP) on a gold colloid-cysteine-nafion membrane, and its application as a biosensor were investigated by using electrochemical methods. The electrochemical characteristics of the biosensor were studied by cyclic voltammetry, linear sweep voltammetry and chronoamperometry. The modified process was characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The sensor displayed an excellent electrocatalytic response to the reduction of H2O2 without the aid of an electron transfer mediator. Analytical parameters such as pH and temperature were also studied. Linear calibration for H2O2 was obtained in the range 3.50 × 10−7 to 5.87 × 10−3 M under the optimized conditions. The sensor was highly sensitive to H2O2 with a detection limit of 1.05 × 10−7 M (S/N = 3), and the sensor achieved 95% of the steady-state current within 10 s. The sensor exhibited high sensitivity, selectivity and stability.