High Temporal‐Resolution Imaging Single Immune Cell Migration in Vivo by Ultrabright NIR‐II Organic Probes

Given the implications of immune cell migration and cellular interaction in immune-oncology, infectious and inflammatory diseases, there is a long-standing interest in understanding, predicting, and ultimately manipulating immune cell migration therapeutically. However, real-time non-invasive in vivo immune cell tracking is considerably more challenging than static imaging, particularly when imaging highly motile cells. Here we introduce high-brightness second near-infrared (NIR-II, 1000-1700 nm) window organic probes (DCPDs, brightness > 5000 M^-1 cm^-1 in aqueous solution), enabling non-invasive high-speed single immune cell imaging in the brain with a temporal resolution up to ∼50 fps. The neutrophil migration patterns in the stroke mouse brain and their interactions with infused therapeutic mesenchymal stem cells can be profiled with real temporal dynamics. This advancement facilitates fundamental studies on understanding complex cellular functions in vivo, paving the way for investigating the effect of single-cell temporal dynamics on immune responses or disease-related biological processes.