Effect of surface functionalities on relaxometric properties of MR contrast agents based on NaGdF4nanoparticles

Abstract

The oleate-capped β-NaGdF₄ nanoparticles (NPs) with uniform size and high crystallinity synthesized by thermal decomposition were converted to water-dispersible Gd³⁺–NaGdF₄, LF-NaGdF₄, and TETT-NaGdF₄ NPs via different surface modifications with GdCl₃, HCl, and carboxylic silane, respectively. The effect of surface functionalities on relaxation properties and T₁-weighted MR images were investigated. In vitro relaxivity measurements revealed that the r₁ value of Gd³⁺–NaGdF₄ (4.64 mM⁻¹ s⁻¹) was higher than that of TETT-NaGdF₄ (1.81 mM⁻¹ s⁻¹) and LF-NaGdF₄ (0.85 mM⁻¹ s⁻¹). In vivo liver MRI consistently showed that the T₁-weighted signal obtained from Gd³⁺–NaGdF₄ was stronger than that from TETT-NaGdF₄ and LF-NaGdF₄ at an equivalent Gd³⁺ dosage. These findings suggest that different surface functionalities play an important role in manipulating the relaxometric properties of NaGdF₄ NPs. In addition, the excellent biocompatibility of the water-dispersible NPs was demonstrated by in vitro cytotoxicity assays (MTT) in C6 cells and in vivo histological analyses (H&E) of major organs.