Sensitizing the Luminescence of Lanthanide-Doped Nanoparticles over 1500 nm for High-Contrast and Deep Imaging of Brain Injury.

Real-time and in situ visualization of cerebrovascular dysfunction is significant for studying brain injury, which however, is restricted by the complex brain structure and limited imaging strategies. Luminescence imaging in NIR-IIb region (1500-1700 nm) is a promising tool owing to its merits including deep penetration, high resolution, and fast data acquisition. Unfortunately, a luminescent material in this region with sufficient brightness and biocompatibility is scarce. Herein, Ag2Se quantum dot-sensitized lanthanide-doped nanocrystals (QDs-LnNCs) with emission beyond 1500 nm were fabricated to image the cerebrovascular structure and hemodynamics in ischemic stroke and traumatic brain injury. The sensitization by QDs provided an over 100-fold enhanced brightness of LnNCs and a remarkable penetration depth of 11 mm. Dynamic information of blood perfusion and flow rates were acquired and the damage of the blood-brain barrier in the two injury models was investigated. Our results proved QDs-LnNCs as a kind of competent nanomaterial for noninvasive brain imaging.