Dual-mode T₁ and T₂ magnetic resonance imaging contrast agent based on ultrasmall mixed gadolinium-dysprosium oxide nanoparticles: Synthesis, characterization, and in vivo application

A new type of dual-mode T₁ and T₂ magnetic resonance imaging (MRI) contrast agent based on mixed lanthanide oxide nanoparticles was synthesized. Gd³⁺ (⁸S_7/2) plays an important role in T₁ MRI contrast agents because of its large electron spin magnetic moment resulting from its seven unpaired 4f-electrons, and Dy³⁺ (⁶H_15/2) has the potential to be used in T₂ MRI contrast agents because of its very large total electron magnetic moment: among lanthanide oxide nanoparticles, Dy₂O₃ nanoparticles have the largest magnetic moments at room temperature. Using these properties of Gd³⁺ and Dy³⁺ and their oxide nanoparticles, ultrasmall mixed gadolinium-dysprosium oxide (GDO) nanoparticles were synthesized and their potential to act as a dual-mode T₁ and T₂ MRI contrast agent was investigated in vitro and in vivo. The D-glucuronic acid coated GDO nanoparticles (d_avg = 1.0 nm) showed large r₁ and r₂ values (r₂/r₁ ≈ 6.6) and as a result clear dose-dependent contrast enhancements in R₁ and R₂ map images. Finally, the dual-mode imaging capability of the nanoparticles was confirmed by obtaining in vivo T₁ and T₂ MR images.