Preparation of amino-functionalized magnetite nanoclusters by ring-opening polymerization and application for targeted magnetic resonance imaging

Here we developed a ring-opening polymerization strategy for preparation of biocompatible and amino-functionalized superparamagnetic iron oxide nanoclusters (SPIONCs). The functionalized SPIONCs could be further applied for folate-receptor (FR)-targeted magnetic resonance imaging (MRI). The citrate-stabilized SPIONCs were synthesized by solvothermal reaction using biocompatible trisodium citrate (Na3Cit) as the coordinating and stabilizing ligand and then the amino groups were covalently bonded to them through a ring-opening polymerization of epichlorohydrin and further treatment with ammonium hydroxide. The products were confirmed by XPS, FTIR, Zeta potential, and amino quantitative analysis. The amino-functionalized SPIONCs have good stability in aqueous solution and low cytotoxicity to cell lines. By in vitro MRI and quantitative element analysis, we demonstrated the FR-mediated delivery of the folic acid-conjugated SPIONCs (Fe3O4–FA) targeting FR-positive cell line such as human ovarian carcinoma cell. In conclusion, high magnetization, good stability, and effective FR-mediated uptake of the functionalized SPIONCs made them promising candidates for use as MRI contrast agents.