Size-tunable NaGdF4 nanoparticles as T2 contrast agents for high-field magnetic resonance imaging

Abstract

It is important to get high-quality magnetic resonance images at high magnetic field (>3 T) for medical diagnoses. However, the efficiency of the commonly used magnetic resonance imaging (MRI) contrast agents (CAs) always decrease with the increasing of magnetic field intensity. Thus, it is necessary to design MRI CAs with high relaxivity at high magnetic field. In this study, the hydrophilic and biocompatible NaGdF₄@SiO₂ nanoparticles (NPs) were feasibly synthesized and exhibited highly effective T₂ contrast imaging at 7 T magnetic field. Furthermore, the obtained NPs had a higher r₂/r₁ value than the other typical T₂ CAs (such as Dy-based NPs and Fe-based NPs) at high magnetic field. The observed large r₂ of the current NaGdF₄@SiO₂ was mainly ascribed to the increased particle sizes. For in vivo application, 250 nm NaGdF₄@SiO₂ (with the highest relaxivity) as T₂-weighted MRI CAs was further assessed. Toxicity studies demonstrated that NaGdF₄@SiO₂ NPs exhibited little toxicity both in vitro and in vivo. Therefore, NaGdF₄@SiO₂ NPs with appropriate size could be used as high-performance T₂ CAs in the high magnetic field.