Radioisotope post-labeling upconversion nanophosphors for in vivo quantitative tracking

Area of Science:

• Nanotechnology
• Radiochemistry
• Bioimaging

Background:

• Lanthanide-based upconversion nanophosphors (UCNPs) show promise for bioimaging.
• Understanding the in vivo behavior of UCNPs is crucial but limited by current imaging tools.

Purpose of the Study:

• To develop a facile method for labeling UCNPs with a radioactive isotope for in vivo tracking.
• To investigate the biodistribution and fate of UCNPs in vivo using dual-modality imaging.

Main Methods:

• A cation-exchange-based postlabeling technique was employed to introduce samarium-153 ((153)Sm) into UCNPs.
• The (153)Sm-labeled UCNPs were characterized for their radioactive and upconversion luminescence properties.
• In vivo biodistribution studies were conducted using single-photon emission computed tomography (SPECT) and gamma counting.

Main Results:

• The (153)Sm postlabeling method is rapid (<1 min), efficient (>99% yield), and solvent-free.
• UCNPs were primarily accumulated in the liver and spleen, part of the mononuclear phagocyte system.
• The liver showed higher UCNP accumulation than the spleen, with slow excretion via bile.

Conclusions:

• Postlabeling UCNPs with (153)Sm provides a versatile strategy for dual-modality imaging (upconversion luminescence and SPECT).
• This method enables effective quantification and tracking of UCNP in vivo behavior.
• The developed nanoprobes are suitable for studying the fate of rare-earth nanoparticles in biological systems.