Biosensing improvement of horseradish peroxidase towards hydrogen peroxide upon modifying the accessible lysines

A biosensor for detection of hydrogen peroxide was designed based on immobilization of anthraquinone 2-carboxylic acid modified horseradish peroxidase. Direct electrochemistry of the modified enzyme exhibited a quasi-reversible voltammogram with a formal potential of −459 mV. The surface charge transfer rate constant, ks, and the charge transfer coefficient, αc, for electron transfer between the glassy carbon electrode and the modified enzyme were estimated to be 3.165 s−1 and 0.455, respectively. The modified electrode exhibited a remarkable electrocatalytic activity towards hydrogen peroxide. Under the optimized experimental conditions, H2O2 could be detected in a linear concentration range from 2.65 × 10−9 to 1.08 × 10−7 M and a detection limit of 1.44 × 10−9 M at S/N = 3. The response time was 6 s and when the electrode was stored at 4 °C, the biosensor was used repeatedly for 17 days with 10% deterioration in response.