To utilize synergetic effect of graphene's higher conductivity and magnetic nanoparticles biocompatibility, an electrochemical nanobiosensor is constructed based on magnetic nanoparticle decorated graphene (MRGO) using Horseradish peroxidase (HRP) for H2O2 sensing. Sensors based on magnetic nanoparticles (MNP) and reduced graphene oxide (RGO) are studied for comparison. MNP, RGO and MRGO were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). XRD studies have confirmed successful synthesis of Fe3O4 MNPs, RGO and MRGO. TEM micrographs revealed uniform decoration of MNPs on graphene. FTIR confirmed the immobilization of HRP on MNP, RGO and MRGO. The MRGO based sensor exhibited higher sensitivity (48.08 mu A mu M-1 cm(-2)) compared to MNP (39.08 mu A mu M-1 cm(-2)) and RGO (41.08 mu A mu M-1 cm(-2)) based biosensors. (C) 2018 Elsevier B.V. All rights reserved.