Synthesis of Zn-doped manganese ferrite nanoparticles via coprecipitation method for magnetic resonance imaging contrast agent

Two different preparations of biocompatible magnetic nanoparticles (MNPs), both (MnFe₂O₄ and Mn0.91Zn0.09Fe₂O₄) coated with methoxy polyethylene glycol aldehyde (m-PEG-CHO) were prepared through coprecipitation method. The prepared powder was reanalyzed for material structure with an X-ray diffractometer (XRD) and for particle size using a transition electron microscope (TEM). Magnetic saturation (MS) and coercivity (HC) of the formed particles were examined by a vibrating sample magnetometer (VSM). Surface structure of the samples was characterized by Fourier transform infrared spectroscopy (FTIR). Biocompatible ferrofluids were intravenously injected into four rabbits. Then the magnetic resonance (MR) images of brain were obtained by magnetic resonance imaging (MRI) experiments before and after intravenous injection of ferrofluids. The MNPs demonstrate super paramagnetic behavior with a spinel structure measuring 30-40nm in size. Doping of these magnetite nanoparticles with zinc resulted in decreases in crystallite size from 24.23nm to 21.15nm, the lattice parameter from 8.45Å to 8.43Å and the coercivity from 41.20Oe to 13.07Oe. On the other hand, saturation magnetization increased from 50.12emu/g to 57.36emu/g following zinc doping. Image exposure analysis revealed that the reduction of MR signal intensity for zinc-doped magnetite nanoparticles was more than nondoped nanoparticles (shorter T₂ relaxation time) thereby making the images darker.