Background
In vivo fluorescence imaging in the second near-infrared (NIR-II, 1000-1700 nm) window using organic fluorophores has great advantages, but generally suffers from a relatively low fluorescence quantum yield (mostly less than 2%). In this study, organic nanoparticles (L1013 NPs) with a high fluorescence quantum yield (9.9%) were systhesized for in vivo imaging.
Conclusion
L1013 NPs demonstrate the potential for a range of clinical applications, especially for tumor surgery.
Methods
A molecule (BTPPA) with donor-acceptor-donor structure and aggregation-induced emission enabling moieties was prepared. BTPPA molecules were then encapsulated into nanoparticles (L1013 NPs) using a nanoprecipitation method. The L1013 NPs were intravenously injected into the mice (including normal, stroke and tumor models) for vascular and tumor imaging.
Results
L1013 NPs excited at 808 nm exhibit NIR-II emission with a peak at 1013 nm and an emission tail extending to 1400 nm. They have a quantum yield of 9.9% and also show excellent photo/colloidal stabilities and negligible in vitro and in vivo toxicity. We use L1013 NPs for noninvasive real-time visualization of mouse hindlimb and cerebral vessels (including stroke pathology) under a very low power density (4.6-40 mW cm‒2) and short exposure time (40-100 ms). Moreover, L1013 NPs are able to localize tumor pathology, with a tumor-to-normal tissue ratio of 11.7±1.3, which is unusually high for NIR-II fluorescent imaging through passive targeting strategy.