Facile synthesis of Fe3O4@Al2O3 core-shell nanoparticles and their application to the highly specific capture of heme proteins for direct electrochemistry

In this study, magnetic core-shell Fe3O4@Al2O3 nanoparticles (NPs) attached to the surface of a magnetic glassy carbon electrode (MGCE) were used as a functional interface to immobilize several heme proteins including hemoglobin (Hb), myoglobin (Mb) and horseradish peroxidase (HRP) for fabricating protein/Fe3O4@Al2O3 film. Transmission electron microscope, UV-vis spectroscopy, electrochemical impedance spectroscopy, and cyclic voltammetry were used to characterize the films. With the advantages of the magnetism and the excellent biocompatibility of the Fe3O4@Al2O3 NPs, the protein/Fe3O4@Al2O3 film could be easily fabricated in the present of external magnetic field, and well retained the bioactivity of the immobilized proteins, hence dramatically facilitated direct electron transfer of heme proteins and excellent electrocatalytic behaviors towards H2O2 were demonstrated. The presented system avoids the complex synthesis for protecting Fe3O4 NPs, supplies a facile, low cost and universal way to immobilize proteins, and is promising for construction of third-generation biosensors and other bio-magnetic induction devices.