Synthesis, Characterizations, and 9.4 Tesla T(2) MR Images of Polyacrylic Acid-Coated Terbium(III) and Holmium(III) Oxide Nanoparticles

Polyacrylic acid (PAA)-coated lanthanide oxide (Ln(2)O(3)) 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(2)) magnetic resonance imaging (MRI) contrast agents at high MR fields. Their r(2) values were appreciable at a 3.0 T MR field and higher at a 9.4 T MR field, whereas their r(1) values were negligible at all MR fields, indicating their exclusive induction of T(2) relaxations with negligible induction of T(1) relaxations. Their effectiveness as T(2) MRI contrast agents at high MR fields was confirmed from strong negative contrast enhancements in in vivo T(2) MR images at a 9.4 T MR field after intravenous administration into mice tails.