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.