Synthesis of monodisperse magnetite nanoparticles via chitosan-poly (acrylic acid) template and their application in MRI

Ultrasmall magnetite nanoparticles were prepared by using chitosan-polyacrylic acid (CS-PAA) nanospheres as template. The CS-PAA hollow nanospheres could be prepared by polymerization of acrylic acid monomers in the presence of chitosan. The Fe3O4 loading was done by dissolving FeCl3 center dot 6H(2)O and FeSO4 center dot 7H(2)O into CS-PAA nanospheres solution followed by adding NH4OH. In finally, CS-PAA template could be removed by adjusting with HCl to pH < 1. The obtained particles were characterized by dynamic light scattering (DLS) in aqueous solution and observed by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and X-ray. The results revealed that the Fe3O4 nanoparticles were 3-5 nm in size with excellent dispersibility. From the magnetometer measurements data, the particles exhibited superparamagnetic property with saturation magnetizations of 40.7 emu/g. The MRI experiment on living rabbit showed that nanoparticles prepared by the current synthetic approach had a significant magnetic resonance signal enhancement in T2-weighted image of lymph nodes. (C) 2008 Elsevier B.V. All rights reserved.