Solid-state synthesis of monocrystalline iron oxide nanoparticle based ferrofluid suitable for magnetic resonance imaging contrast application

A new γ-Fe2O3 MION ferrofluid has been developed with a salt-assisted solid-state reaction. Characterizations show that the ferrofluid is composed of maghemite nanoparticles with a mean diameter of 2.7 nm. Though the nanoparticles are ultrafine, they are well crystallized, with a saturation magnetization value of 34.7 emu g-1, making them suitable for MRI applications. In spite of the absence of any surfactant, the ferrofluid can be stable for more than 6 months. An in vitro cytotoxicity test revealed good biocompatibility of the maghemite nanoparticles, suggesting that they may be further explored for biomedical applications. NMR measurements revealed significantly reduced water proton relaxation times T1 and T2. The MR images of the nanoparticles in aqueous dispersion were investigated using a 3 T clinical MR imager. These preliminary experiments have demonstrated the potential of the as-synthesized ultrafine, cap-free maghemite MIONs in functional molecular imaging for biomedical research and clinical diagnosis