Highly stable and bright AIE dots for NIR-II deciphering of living rats

The emerging second near-infrared (NIR-II) fluorescence imaging has shown great promise for in vivo imaging of small animals such as mice, yet the onward movement to large-size animals such as rats is still undeveloped. In this work, for the first time, we report comprehensive NIR-II deciphering of brain blood vasculature and main organs of living rats based on aggregation-induced emission (AIE) dots. The AIE dots possess simultaneously high brightness, excellent stability with various treatments, and good biocompatibility. Thanks to the long emission range and high brightness, in vivo NIR-II fluorescence microscopic imaging with the AIE dots beyond 1200 nm allows for visualizing rat brain vasculature with high spatial resolution (∼4 μm) and deep penetration (700 μm), representing the highest penetration depth and best resolution of rat brain imaging yet achieved in the field. The NIR-II AIE dots also enable the detection of tiny vascular blockage in real time at the early stage of cerebral thrombosis. Furthermore, in vivo non-invasive monitoring of rat’s gastrointestinal tract and bladder in a high-contrast manner helps to better understand the digestive system and excretory processes. This work will inspire new insights into the development of advanced NIR-II technique for large animal imaging, rendering great promise for real applications.