Superparamagnetic iron oxide nanoparticles coated with a folate-conjugated polymer

Folate-functionalized magnetic fluids were prepared by direct chemisorption of a folate-tetra(ethylene glycol)-poly(glycerol monoacrylate) (FA-TEG-PGA) conjugate on Fe₃O₄ nanoparticles. In the magnetic fluids, the PGA block of FA-TEG-PGA was chemisorbed onto the Fe₃O₄ nanoparticle surface through its 1,2-diol groups, while the TEG chain conjugated with FA extended into the water matrix. Characterization by transmission electron microscopy, X-ray diffraction and a vibrating sample magnetometer indicated that the pure Fe₃O₄ superparamagnetic nanoparticles were formed and the coating process did not significantly affect the size and structure of Fe₃O₄ nanoparticles. Fourier transform infrared spectroscopy, UV-vis spectroscopy, thermogravimetric analysis and X-ray photoelectron spectroscopy confirmed the successful coating of FA-TEG-PGA on the Fe₃O₄ nanoparticles, suggested a coating mechanism for the FA-TEG-PGA, and revealed the maximum weight ratio of FA-TEG-PGA to Fe₃O₄. The dispersion of FA-TEG-PGA-coated Fe₃O₄ nanoparticles possessed excellent stability over a wide range of pH and salt concentrations. Such folate-functionalized magnetic fluids are expected to be targeting contrast agents for magnetic resonance imaging (MRI) applications. This approach represents a new strategy to synthesize functionalized magnetic nanoparticles that form stable dispersions in water and facilitates potential biomedical applications of these magnetic nanoparticles.