Optical properties of upconverting nanoparticles (UCNPs) and their applications

Abstract

Upconverting nanoparticles (UCNPs) have unique optical properties suitable for biological imaging. Particularly, β-NaYF4: Yb3+, Er3+ 20%, 2% UCNPs absorb 980-nm photons and emit three major emission band in the range of visible light. These emission bands have own emission pathway but especially the red emission band (center: 655-nm) pathway is controversial. In this research, we have revealed the dominant red emission pathway of β-NaYF4: Yb3+, Er3+ 20%, 2% UCNPs by using the 488-nm and 1540-nm photons. Also based on the superb optical properties for bio-imaging, we have constructed two-color bio-imaging system for the observation of UCNPs transfer between cells by mediation of extracellular vesicles (EVs). Exosomes which are included in extracellular vesicles are formed by inward budding inside of multi-vesicular body (MVB) during the mutation of MVB. We have found the polyethyleneglycol (PEG) treated UCNPs are encapsulated by exosomes and also can be transferred to another cell by the exosomes. And β-NaYF4: Yb3+, Er3+ 20% and 2% and β-NaYF4: Yb3+, Tm3+ 20%, 0.5% UCNPs have been used for observation of intercellular transfer through dual-channel bio-imaging system. In this observation, the UCNPs have been transferred to recipient cell and have been controlled by the recipient cell. Through this observation, we have proved that the PEGylated UCNPs are the suitable cargoes for the real-time exosomes tracking.