Prussian blue modified iron oxide magnetic nanoparticles and their high peroxidase-like activity

Prussian blue (PB) modified gamma-Fe2O3 magnetic nanoparticles (MNPs) featuring varying PB proportions were synthesized and characterized by TEM, FTIR, UV-vis, EDS, XRD and XPS. The magnetic properties and peroxidase-like catalytic activity of the synthesized nanoparticles were investigated. With increasing PB content, the magnetism could still maintain a high level. Peroxidase-like activity was enhanced as the PB proportion increased. Catalysis was found to follow Michaelis-Menten kinetics. The calculated kinetic parameters exhibited strong affinity with substrates and high catalytic activity, which are three orders of magnitudes larger than that for magnetite nanoparticles of similar size. Based on the high activity, an enzyme immunoassay model was established: staphylococcal protein A (SPA) was conjugated onto the surface of the nanoparticles to construct a new nanoprobe which was employed to detect IgG immobilized to 96-well plates. The results presented a linear absorbance enhancement with concentration of IgG, suggesting that PBMNPs serve as an inexpensive horseradish peroxidase (HRP) mimic enzyme with potential applications in bio-detection.