Direct electrochemistry and electrocatalysis of hydrogen peroxide using hemoglobin immobilized in hollow zirconium dioxide spheres and sodium alginate films

A biocompatible composite made from hollow zirconium dioxide microspheres (HZMS) and sodium alginate (SA) is presented and used for the construction of a biosensor for hydrogen peroxide using a gold electrode. The composition, morphology and size were studied by transmission electron microscopy. FT-IR and UV-vis spectroscopy revealed that hemoglobin (Hb) entrapped in the ZHMS retains its native structure. A pair of stable and well-defined quasi-reversible redox peaks of Hb is obtained, with a formal potential of -0.15 V at pH 7.0. The apparent heterogeneous electron transfer rate constant is 1.15 s(-1), indicating facile electron transfer that may result from the unique nanostructures and larger surface area of the HZMS. The amperometric response of the sensor varied linearly with the concentration of hydrogen peroxide in the range from 1.75 mu M to 4.9 mM, with a detection limit of 0.6 mu M (at S/N = 3). The apparent Michaelis-Menten constant (K-M(app)) is 1.6 mM. The biosensor possesses high sensitivity, good reproducibility, and long-term stability.