Direct electrochemical behavior of hemoglobin at surface of Au@Fe3O4 magnetic nanoparticles

Nanoparticles (NPs) consisting of an Fe3O4 core and a thin gold shell (referred to as Au@Fe3O4 NPs) were self-assembled on the surface of a glassy carbon electrode modified with ethylenediamine. Following adsorption of hemoglobin, its interaction with the NPs was studied by UV-Vis spectroscopy, electrochemical impedance spectroscopy, and cyclic voltammetry. Stable and well-defined redox peaks were observed at about -350 mV and -130 mV in pH 6.0 buffer. The modified electrode was used as a mediator-free sensor for hydrogen peroxide (H2O2), with a linear range from 3.4 A mu M to 4.0 mM of H2O2, and with a 0.67 A mu M detection limit (at an S/N of 3). The apparent Michaelis-Menten constant is 2.3 mM.