Monitoring of hydrogen peroxide using a glassy carbon electrode modified with hemoglobin and a polypyrrole-based nanocomposite

We reported on a highly sensitive electrochemical biosensor that was fabricated by immobilizing hemoglobin (Hb) onto the surface of a glassy carbon electrode (GCE) modified with a nanocomposite made from polypyrrole@poly (styrene-alt-maleic anhydride) grafted with 4-aminobenzenesulfonate. Cyclic voltammograms of the modified GCE at pH 7 exhibited a pair of well-defined redox peaks, thus attesting the direct electron transfer from Hb to the electrode. The biosensor can be used to determine H2O2 and, if operated at a working voltage of -0.4 V, displays a linear response to H2O2 in the 0.8 mu M to 460 mu M concentration range, and a lower detection limit of 0.32 mu M. The surface coverage of active Hb, heterogeneous electron transfer rate constant (ks) and Michaelis-Menten constant (Km) of immobilized Hb are, respectively, 1.52 x 10(-9) mol cm(-2), 1.3 s(-1), and 0.45 mM. Additional features of this biosensor include stability, simplicity, and fast preparation at low-costs. It was successfully applied to the determination of hydrogen peroxide in rainwater samples where it displayed good accuracy and precision.