Spatio-temporally deciphering peripheral nerve regeneration in vivo after extracellular vesicle therapy under NIR-II fluorescence imaging

Extracellular vesicles (EVs) show potential as a therapeutic tool for peripheral nerve injury (PNI), promoting neurological regeneration. However, there are limited data on the in vivo spatio-temporal trafficking and biodistribution of EVs. In this study, we introduce a new non-invasive near-infrared fluorescence imaging strategy based on glucose-conjugated quantum dot (QDs-Glu) labeling to target and track EVs in a sciatic nerve injury rat model in real-time. Our results demonstrate that the injected EVs migrated from the uninjured site to the injured site of the nerve, with an increase in fluorescence signals detected from 4 to 7 days post-injection, indicating the release of contents from the EVs with therapeutic effects. Immunofluorescence and behavioral tests revealed that the EV therapy promoted nerve regeneration and functional recovery at 28 days post-injection. We also found a relationship between functional recovery and the NIR-II fluorescence intensity change pattern, providing novel evidence for the therapeutic effects of EV therapy using real-time NIR-II imaging at the live animal level. This approach initiates a new path for monitoring EVs in treating PNI under in vivo NIR-II imaging, enhancing our understanding of the efficacy of EV therapy on peripheral nerve regeneration and its mechanisms.