Chitosan-coated nickel-ferrite nanoparticles as contrast agents in magnetic resonance imaging

We report evidence for the possible application of chitosan-coated nickel-ferrite (NiFe₂O₄) nanoparticles as both T₁ and T₂ contrast agents in magnetic resonance imaging (MRI). The coating of nickel-ferrite nanoparticles with chitosan was performed simultaneously with the synthesis of the nickel-ferrite nanoparticles by a chemical co-precipitation method. The coated nanoparticles were cylindrical in shape with an average length of 17 nm and an average width of 4.4 nm. The bonding of chitosan onto the ferrite nanoparticles was confirmed by Fourier transform infrared spectroscopy. The T₁ and T₂ relaxivities were 0.858±0.04 and 1.71±0.03 mM^-1 s^-1, respectively. In animal experimentation, both a 25% signal enhancement in the T₁-weighted mage and a 71% signal loss in the T₂-weighted image were observed. This demonstrated that chitosan-coated nickel-ferrite nanoparticles are suitable as both T₁ and T₂ contrast agents in MRI. We note that the applicability of our nanoparticles as both T₁ and T₂ contrast agents is due to their cylindrical shape, which gives rise to both inner and outer sphere processes of nanoparticles.