Monodisperse water-soluble Fe–Ni nanoparticles for magnetic resonance imaging

Monodispersed Fe–Ni nanoparticles (NPs) with the diameter around 9 nm were synthesized by high temperature pyrolysis of iron(III) acetylacetonate and nickel(II) acetylacetonate. Ligand exchange method with a bifunctional bisphosphonate was adopted to improve the water solubility. To prevent their biofouling and aggregate in the biological system, the prepared NPs were further covalent conjugated with the PEG acid. Their morphology and structure were confirmed by TEM, XRD and FTIR. NPs showed good magnetic properties with the saturation magnetization (Ms) of about 40 emu/g and the transverse relaxivity (r2) of about 43.1 mM−1 s−1 in aqueous solutions. Furthermore, Fe–Ni NPs showed low cytotoxicity in living cells. They can be uptaken by HeLa cells effectively and result in the obvious effect of T2-weighted MRI of labeled cells after internalization, making them potential contrast agents for MRI study.

Research highlights▶ Monodispersed Fe–Ni nanoparticles were synthesized. ▶ Fe–Ni nanoparticles were further covalent conjugated with the PEG acid. ▶ Fe–Ni nanoparticles showed low cytotoxicity in living cells. ▶ Fe–Ni nanoparticles can be used as a new nanoparticulate MRI contrast agent.