Chitosan-coated Ferrite (Fe_30_4) Nanoparticles as a T2 Contrast Agent forMagnetic Resonance Imaging

摘要

Iron oxide (Fe_3O_4) nanoparticles coated with biocompatible chitosan were synthesized for use as an MRI (magnetic resonance imaging) contrast agent. The coating was performed simultaneously with the synthesis of the ferrite nanoparticles. A dynamic light-scattering spectrometer (DLS) and a transmission electron microscope (TEM) were used to measure the average diameter of the coated nanoparticles, which was 67.0 nm. Fourier transform infrared (FT-IR) measurements showed strong bonding of the chitosan molecules to the surfaces of the ferrite nanoparticles. The spin-lattice (T_1) and the spin-spin (T_2) relaxation times of the nuclear spins (hydrogen protons) in aqueous solutions of various concentrations of coated ferrite nanoparticles were determined using a nuclear magnetic resonance (NMR) spectrometer. Using these data, we found that the T1 and the T_2 relaxivities of the nuclear spins in aqueous solutions of ferrite nanoparticles were 0.00291 and 0.0691 ppm~(-1)sec~(-1), respectively. In particular, the value of the T_2 relaxivity was much larger than that of the commercial contrast agent GD-DTPA (gadolinium diethylenetriamine penta-acetic acid). A 31.7% intensity loss in the T_2 image of a rabbit liver was observed after injecting the aqueous solution of coated nanoparticles into the rabbit, which shows that our coated ferrite nanoparticles can be used as a T_2 MRI contrast agent.