Water-soluble superparamagnetic dysprosium-doped iron oxide flowerlike nanoclusters for high-resolution MR imaging

Abstract

Magnetic nanomaterials have great application prospects in water treatment, disease diagnosis and therapy, surface adsorption and other fields. Herein, the water-soluble, biocompatible and superparamagnetic dysprosium-doped iron oxide flowerlike nanoclusters (DyIO NCs) were synthesized by thermal decomposition of iron oleate and dysprosium oleate in high-boiling solvent of phenyl ether with α,ω-dicarboxyl poly(ethylene glycol) as a capping agent. The size of the nanoclusters and the amount of Dy ions in the clusters can be controlled by simply adjusting the reaction parameters. The DyIO NCs exhibited excellent colloid stability under physiological conditions. The saturation magnetization and transverse relaxivity (r2) of DyIO NCs were significantly improved by the doping of Dy ions. The r2 value of 21 nm Dy0.209Fe2.791O4 NCs was 485.6 mM−1s−1, which is 9 times that of Dy-doped iron oxide nanoparticles (55.6 mM−1s−1), 4 times that of commercial Feridex (123.6 mM−1s−1) and 2 times that of iron oxide nanoclusters (253.9 mM−1s−1). In vivo imaging showed that DyIO NCs exhibited long blood circulation time and excellent enhancement for T2-weighted magnetic resonance imaging. In addition, the DyIO NCs can be functionalized with tumor targeting ligand cyclic Arg-Gly-Asp peptide and fluorescein isothiocyanate isomer I. This study provides an effective strategy for the development of new sensitive nanoprobes and drug delivery systems, and other applications requiring strong magnetic responses.