Ni-Fe ₂O ₄ nanoparticles as contrast agents for magnetic resonance imaging

Reported herein is the synthesis of a dextran coating on nickel ferrite (Ni-Fe ₂O ₄) nanoparticles via chemical coprecipitation. The aqueous solution of the synthesized nanoparticles showed good colloidal stability, and no precipitate was observed 20 months after the synthesis. The coated nanoparticles were found to be cylindrical in shape in the TEM images, and showed a uniform size distribution with an average length and diameter of er 7 and4 nm, respectively. The coated particles were evaluated as potential T ₁ and T ₂ contrast agents 8 or MRI. The T ₁ and T ₂ relaxations of the hydrogen protons in the water molecules in an aqueous solution of dextran-coated Ni-Fe ₂O ₄ nanoparticles were studied. It was found that the T ₁ relaxivity for the aqueous solution of dextran-coated nanoparticles was slightly greater than that of a commercial Gd-DTPA-BMA contrast agent. The T ₂ relaxivity, however, was almost twice that of the commercial Gd-DTPA-BMA contrast agent. Animal experimentation also demonstrated that the dextran-coated Ni-Fe ₂O ₄ nanoparticles are suitable for use as either T ₁ or T ₂ contrast agents in MRI.