Luminescent up-converting nano-crystals for in vivo imaging

摘要

Luminescent nanoparticles are increasingly used as emitting labels in the design of fluorescence imaging probes, because of their outstanding optical properties, such as in the case of quantum dots, or their role in nano-assembling different functionalities, such as imaging, drug delivery, and therapy. In this work, the potentiality of up-converting nano-crystals for non invasive fluorescence imaging of small animal is explored. These up-converting nano-crystals are lanthanide doped oxide matrices, such as Y_2O_3:Er,Yb compositions. They are produced by a bottom-up process and a thermal treatment. They are functionalized by the coating of a thin polysiloxane shell layer, which can be further derivatized in order to graft biomolecules such as antibodies, peptides, or DNA. Contrary to classical luminescent particles for which light emission occurs at a wavelength superior to that of excitation, these materials emit at 564 and 661 nm upon excitation at 980 or 815 nm. These unique emission properties, due to a multi-photonic process, can allow imaging without any auto-fluorescence from the tissues in the wavelength detection window. Experiments in phantoms mimicking the optical absorption and diffusion of tissues show that these crystals can be detected 4 mm deep at a 10 mg/mL concentration. Luminescence measurements in mouse and the potentiality of these nano-crystals for in vivo imaging are discussed.