In situ surface functionalization of magnetic nanoparticles with hydrophilic natural amino acids

The surface of magnetic iron oxide nanoparticles has been modified with hydrophilic natural amino acids via an in situ method. A rapid ligand exchange reaction was induced at elevated temperatures to replace the original labile solvent layer with amino acids. The functionalized nanoparticles were quasi-spherical and well separated with an average diameter around 7 nm. The resulted products were examined to be highly crystalline and phase-pure Fe3O4. The present of amino acids on the surface of the nanoparticles was verified by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, which indicated successful ligand exchange. Zeta potential and dynamic light scattering measurement suggested that functionalized magnetic nanoparticles were well dispersed in both basic and acidic aqueous solution with small polydispersity. The uncoordinated amine groups are highly reactive and available for either conjugation with biocompatible polymers or attachment of small gold nanocrystals, so as to prepare dual-functional nanocomposite.