In vivo high-contrast visualization of upconversion nanoparticle labeled virus using time-resolved approach

Virus labeling is an ideal strategy to explore the interaction between virus and host cells. However, existed probes are limited in in vivo studies due to the poor imaging effects caused by tissue-depth and autofluorescence. Lanthanide-doped upconversion nanoparticles (UCNP) can be effectively excited in deeper bio-tissues, and its long fluorescence life-time is suitable for in vivo imaging using time-resolved luminescence imaging technology. In this study, lanthanide-doped UCNP was used to label viral envelope and nucleic acid, which could be used for in vitro and in vivo virus tracking. The in vitro results demonstrated that the UCNP-labeled Influenza A virus (UCNP-IAV) could be used for the study of virus internalization kinetics, and proved that the movement of UCNP labeled IAV was lysosome- and microtube-dependent. For in vivo study, pre-labeling and in situ labeling strategies were implemented to monitor the IAV infection. The results showed that the UCNP probe could provide high-quality images using time-gated strategy to effectively monitor the viral infection in vivo. Further, simultaneous tracking of IAV and adenovirus type-5 (Ad5) labeled by UCNP with different life-time was realized using time-resolved luminescence imaging technology. Hence, this paper provided a novel labeling method for virus tracking using UCNP, which was optimal to study the mechanism of virus infection in vitro and in vivo.