Facile synthesis of ultrasmall PEGylated iron oxide nanoparticles for dual-contrast T_1-and T_2-weighted magnetic resonance imaging

摘要

The development of new types of high-performance nanoparticulate MR contrast agents with either positive (T_1) or dual-contrast (both positive and negative, T_1 + T_2) ability is of great importance. Here we report a facile synthesis of ultrasmall PEGylated iron oxide nanoparticles for dual-contrast T_1-and T_2-weighted MRI. The produced superparamagnetic iron oxide nanoparticles (SPIONs) are of high crystallinity and size uniformity with an average diameter of 5.4nm, and can be individually dispersed in the physiological buffer with high stability. The SPIONs reveal an impressive saturation magnetization of 94 emug ~(-1)Fe_3O_4, the highest r_1 of 19.7 mM~(-1)s~(-1) and the owest r_2/r_1 ratio of 2.0 at 1.5T reported so far for PEGylated iron oxide nanoparticles. T _1-and T_2-weighted MR images showed that the SPIONs could not only improve surrounding water proton signals in the T_1-weighted image, but induce significant signal reduction in the T_2-weighted image. The good contrast effect of the SPIONs as T_1 + T_2 dual-contrast agents might be due to its high magnetization, optimal nanoparticle size for T_1 + T_2 dual-contrast agents, high size monodispersity and excellent colloidal stability. In vitro cell experiments showed that the SPIONs have little effect on HeLa cell viability.