Magnetic resonance imaging contrast agents comprising zinc-containing magnetic metal oxide nanoparticles

An MRI contrast agent comprising zinc-containing metal oxide nanoparticles have a chemical formula of:

• (a) ZnxFe3-xO4, wherein x=0.1-0.4,
• wherein the dispersibility of the zinc-containing metal oxide nanoparticles to water is in the range of 1 μg/ml to 500 mg/ml, and the hydrodynamic diameter of the nanoparticles that are dispersed in water is in the range of 1 nm to 500 μm;
• wherein the zinc-containing metal oxide nanoparticle itself is dispersed in water, or the zinc-containing metal oxide nanoparticle is coated with water-soluble multi-functional group ligands to be dispersed in an aqueous solution;
• wherein the zinc-containing metal oxide nanoparticles have a saturation magnetization of 100 emu/g or more (magnetic atom), wherein the zinc-containing metal oxide nanoparticles are prepared by a method comprising synthesizing water-insoluble, zinc-containing nanoparticles in organic solvents, and wherein the zinc-containing metal oxide nanoparticles comprise zinc incorporated into a tetrahedron interstitial hole.