Biomimetic behavior and nanomolar detection of hydrogen peroxide on an electrochemically pre-treated hematin modified glassy carbon electrode

An electrochemical pre-treatment of a glassy carbon electrode in sodium bicarbonate solution was performed to adsorb hematin (aHtin-GCE), an iron (III) porphyrin present in heme-containing proteins, in order to prepare a new biomimetic sensor for peroxidases. The aHtin-GCe presented peroxidase catalytic activity and a biomimetic behavior related to enzymes responsible for the reduction of H2O2. The previous glassy carbon surface functionalization in bicarbonate solution also proved to be an essential parameter to be controlled as it provides carboxylic acids terminations, which stabilizes the hematin molecule on the electrode surface. The aHtin-GCE kinetics fitted with the Michaelis-Menten model assume the formation of an enzyme-substrate complex in which H2O2 bonds to the electrochemically reduced iron(II) center with further reduction of the peroxide to peroxyl radical. The observation that lithium ions act as competitive inhibitors toward H2O2 also provided the insight toward the application of the aHtin-GCE as a model dispositive to evaluate peroxidase inhibitors. The aHtin-GCE peak current presented a linear correlation with the concentration of H2O2 from the 400 nM to 800 nM range with an experimental LoD of 0.11 μM.