Facile and Green Synthesis of Biocompatible and Bioconjugatable Magnetite Nanofluids for High-Resolution T2 MRI Contrast Agents

By using water as an exclusive solvent, a facile one-pot strategy was developed for the preparation of hydrophilic magnetite nanofluids coated with oxidized dextran. These as-synthesized magnetic nanofluids are highly water-soluble, biocompatible, and bioconjugatible for targeted detection because of the enriched carboxylate groups in the oxidized dextran shell. These nanoparticles are less than 10 nm and demonstrate strong magnetization, low cytotoxicity, and high T-2-weighted MR image signal intensity (r(2) = 250.5 mM(-1) s(-1) 3.7 times larger than the commercial product). Also, these magnetic nanofluids are highly stable in many kinds of aqueous media; even though a strong magnet is adjoined to the nanofluids, the whole colloid solution rather than the solid particle only is drawn to the side wall of the vial. These novel properties render this magnetic nanofluid desirable for wide bioapplications including MRI, highly efficient magnetic bioseparation, targeted drug delivery, and magnetic hypertherrnia.