Ligand-free gadolinium oxide for in vivo T1-weighted magnetic resonance imaging

Abstract

Gadolinium oxide (Gd₂O₃), which can be used as a T₁-weighted magnetic resonance imaging (MRI) contrast agent, has attracted intense attention in recent years. In this paper, ligand-free monoclinic Gd₂O₃ nanocrystals of 7.1 nm in diameter are synthesized by a simple and green approach, namely microsecond laser ablation of a gadolinium (Gd) target in deionized water. These nanocrystals obtain high r₁ relaxivity of 5.53 s⁻¹ mM⁻¹, and their low toxicity was demonstrated by the cell viability of S18 cells and apoptosis in RAW264.7 cells. In vitro and in vivo MR images show these particles to be good T₁-weighted MRI contrast agents. Base on the experimental results and theoretical analysis, we suggest that the purity of the Gd₂O₃ contributes to its high r₁ relaxivity value, while the low toxicity is due to its good crystallinity. These findings show that laser ablation in liquid (LAL) is a promising strategy to synthesize ligand-free monoclinic Gd₂O₃ nanocrystals for use as high efficient T₁-weighted MRI contrast agents.