Novel near-infrared II aggregation-induced emission dots for <i>in vivo</i> bioimaging

Near-infrared II fluorescence imaging holds great promise for <i>in vivo</i> imaging and imaging-guided surgery with deep penetration and high spatiotemporal resolution. However, most NIR-II aromatic luminophores suffer from the notorious aggregation-caused quenching (ACQ) effect in the aqueous solution, which largely hinders their biomedical application <i>in vivo</i>. In this study, the first NIR-II organic aggregation-induced emission (AIE) fluorophore (<b>HLZ-BTED</b>), encapsulated as nanoparticles (<b>HLZ-BTED</b> dots) for <i>in vivo</i> biomedical imaging, was designed and synthesized. The NIR-II AIE <b>HLZ-BTED</b> dots showed high temporal resolution, high photostability, outstanding water-solubility and biocompatibility <i>in vitro</i> and <i>in vivo</i>. The <b>HLZ-BTED</b> dots were further used for long-term breast tumor imaging and visualizing tumor-feeding blood vessels, long-term hind limb vasculature and incomplete hind limb ischemia. More importantly, as a proof-of-concept, this is the first time that non-invasive and real-time NIR-II imaging of the gastrointestinal tract in health and disease has been performed, making the AIE dots a promising tool for gastrointestinal (GI) tract research, such as understanding the healthy status of GI peristalsis, diagnosing and evaluating intestinal motility dysfunction, and assessing drug effects on intestinal obstruction.