Magnetic Resonance Imaging and X-Ray Imaging Properties of Ultrasmall Lanthanide Oxide (Ln = Eu, Gd, and Tb) Nanoparticles Synthesized via Thermal Decomposition

Owing to their 4f electrons and high atomic numbers, lanthanide (Ln) elements impart lanthanide oxide (Ln₂O₃) nanoparticles with excellent biomedical imaging properties. This study reports synthesis for three types of ultrasmall and monodisperse Ln₂O₃ nanoparticles (Ln = Eu, Gd, and Tb) via thermal decomposition in oleylamine at 280 °C, followed by ligand exchange with citric acid (CA) to produce water-dispersible, CA-grafted Ln₂O₃ nanoparticles with high colloidal stability. The resulting CA-grafted Ln₂O₃ nanoparticles had average diameters of approximately 2 nm. We characterized their physicochemical properties, including in vitro cytotoxicity, magnetic resonance imaging properties (i.e., water proton spin relaxivities), and X-ray imaging properties (i.e., X-ray attenuation).