LAUSR

Stable magnetic nanocomposite of gold nanoparticles (Au-NPs) decorating Fe3O4 core was successfully synthesized by the linker of Boc-L-cysteine. Transmission electron microscope (TEM), energy dispersive X-ray spectroscopy (EDX) and cyclic voltammograms (CV) were performed to characterize the as-prepared Fe3O4@Au-Nps. The results indicated that Au-Nps dispersed homogeneously around Fe3O4 with the ratio of Au to Fe3O4 nanoparticles as 5–10/1 and the apparent electrochemical area as 0.121 cm2. After self-assembly of hemoglobin (Hb) on Fe3O4@Au-Nps by electrostatic interaction, a hydrogen peroxide biosensor was developed. The Fe3O4@Au-Nps/Hb modified GCE exhibited fast direct electron transfer between heme center and electrode surface with the heterogeneous electron transfer rate constant (Ks) of 3.35 s−1. Importantly, it showed excellent electrocatalytic activity towards hydrogen peroxide reduction with low detection limit of 0.133 μM (S/D=3) and high sensitivity of 0.163 μA μM−1, respectively. At the concentration evaluated, the interfering species of glucose, dopamine, uric acid and ascorbic acid did not affect the determination of hydrogen peroxide. These results demonstrated that the introduction of Au-Nps on Fe3O4 not only stabilized the immobilized enzyme but also provided large surface area, fast electron transfer and excellent biocompatibility. This facile nanoassembly protocol can be extended to immobilize various enzymes, proteins and biomolecules to develop robust biosensors.