Synthesis, magnetic properties, map images, and water proton relaxivities of D-glucuronic acid coated Ln₂O₃ nanoparticles (Ln = Ho and Er)

T₂ MRI contrast agents cannot be synthesized by using molecules but nanoparticles because appreciable magnetic moments at room temperature are needed. Recently, some of lanthanide (Ln) oxide nanoparticles have shown decent magnetic moments at room temperature and even at ultrasmall particle diameters. In this study, we explored D-glucuronic acid coated Ln₂O₃ nanoparticles (Ln=Ho and Er) with ultrasmall particle diameters. They showed decent magnetic moments at room temperature and as a result, appreciable transverse water proton relaxivities (r2s) at 1.5 tesla MR field. Clear dose-dependent contrast enhancements in R2 map images were observed in both samples. These results showed that D-glucuronic acid coated Ln₂O₃ nanoparticles (Ln = Ho and Er) would be potential T₂ MRI contrast agents at high MR fields.