Facile synthesis of ultrasmall PEGylated iron oxide nanoparticles for dual-contrastT1- andT2-weighted magnetic resonance imaging

Abstract

The development of new types of high-performance nanoparticulate MR contrast agents with eitherpositive (T1) or dual-contrast (both positive and negative,T1 + T2) ability is of great importance. Here we report a facile synthesisof ultrasmall PEGylated iron oxide nanoparticles for dual-contrastT1- andT2-weighted MRI. The produced superparamagnetic iron oxide nanoparticles(SPIONs) are of high crystallinity and size uniformity with an average diameter of5.4 nm, and can be individually dispersed in the physiological buffer with highstability. The SPIONs reveal an impressive saturation magnetization of 94 emu g − 1 Fe3O4, the highestr1 of 19.7 mM − 1 s − 1 and thelowest r2/r1 ratio of 2.0 at 1.5 T reported so far for PEGylated iron oxide nanoparticles.T1- andT2-weightedMR images showed that the SPIONs could not only improve surrounding water proton signals in theT1-weighted image, but induce significant signal reduction in theT2-weighted image. The good contrast effect of the SPIONs asT1 + T2 dual-contrast agents might be due to its high magnetization, optimal nanoparticle size forT1 + T2 dual-contrast agents, high size monodispersity and excellent colloidal stability. In vitro cellexperiments showed that the SPIONs have little effect on HeLa cell viability.