Ultrasonic assisted preparation of lanthanide-oleate complexes for the synthesis of multifunctional monodisperse upconversion nanoparticles for multimodal imaging.

The synthesis of multifunctional monodisperse upconversion nanoparticles (UCNPs) of high quality is highly desired for bioimaging. Lanthanide-oleate complexes are excellent precursors for the synthesis of high quality UCNPs with controllable size and shape. In this work, lanthanide-oleate complexes were prepared by an ultrasonic assisted procedure, and used as precursors for further synthesis of multifunctional monodisperse NaYF4:59% Yb3+, 0.5% Tm3+@NaYF4:20% Gd3+ nanoparticles without the need for further purification. Heavy doping of Yb3+ in the core and incorporation of Gd3+ in the shell made the UCNPs promising for upconversion luminescence (UCL), magnetic resonance (MR) and computed tomography (CT) multimodal imaging. The nanoparticles were further functionalized with bombesin peptide for in vivo UCL/MR/CT imaging of prostate tumors.