A simple hydrogen peroxide biosensor based on a novel electro-magnetic poly(p-phenylenediamine)@Fe3O4 nanocomposite

• A novel biocompatible PpPDA@Fe3O4 nanocomposite was synthesized and used for sensor fabrication.
• The nanocomposite exhibited an excellent ability towards the immobilization of Hb.
• The biosensor exhibits an excellent activity towards the reduction of H2O2.
• The proposed biosensor showed high sensitivity and sub-micro molar detection limits.

The novel biocompatible poly(p-phenylenediamine) (PpPDA)–Fe3O4 nanocomposite (PpPDA@Fe3O4) was synthesized via emulsion polymerization. The PpPDA@Fe3O4 nanocomposite was characterized by Fourier transform infrared spectra (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and vibrating sample magnetometer (VSM). The PpPDA@Fe3O4 nanocomposite was then used as substrate for the immobilization of hemoglobin (Hb) and their bioelectrochemical behaviors were studied. Electrochemical impedance spectroscopy was used to confirm the adsorption of Hb onto the surface of PpPDA@Fe3O4 nanocomposite. The Hb immobilized on PpPDA@Fe3O4 nanocomposite retained its near-native conformations as characterized by the FT-IR. A pair of well-defined redox peaks of Hb was obtained at the Hb–PpPDA@Fe3O4 modified glassy carbon electrode (Hb–PpPDA@Fe3O4/GCE) through direct electron transfer between the protein and the underlying electrode. The proposed biosensor showed good reproducibility and high sensitivity to H2O2 with the detection limit of 0.21 µM (S/N=3). In the range of 0.5–400.0 µM, the catalytic reduction current of H2O2 was proportional to its concentration. The apparent Michaelis–Menten constant of Hb on the PpPDA@Fe3O4 nanocomposite was estimated to be 0.088 mM, showing its high affinity.