Synthesis, Characterizations, and 9.4 Tesla T MR Images of Polyacrylic Acid-Coated Terbium(III) and Holmium(III) Oxide Nanoparticles.

Polyacrylic acid (PAA)-coated lanthanide oxide (LnO) nanoparticles (NPs) (Ln = Tb and Ho) with high colloidal stability and good biocompatibility were synthesized, characterized, and investigated as a new class of negative (T) magnetic resonance imaging (MRI) contrast agents at high MR fields. Their r values were appreciable at a 3.0 T MR field and higher at a 9.4 T MR field, whereas their r values were negligible at all MR fields, indicating their exclusive induction of T relaxations with negligible induction of T relaxations. Their effectiveness as T MRI contrast agents at high MR fields was confirmed from strong negative contrast enhancements in in vivo T MR images at a 9.4 T MR field after intravenous administration into mice tails.