Quaternary Ammonium Salt Based NIR‐II Probes for In Vivo Imaging

Abstract

Traditional luminescent materials including fluorescent probes suffer from notorious aggregation-caused quenching (ACQ) in aqueous solutions. Although several approaches such as the aggregation-induced emission (AIE) effect have been developed, it remains a significant challenge to identify an effective and efficient strategy to resolve this issue. Herein, quaternary ammonium salts <b>Q8PBn</b> and <b>Q8PNap</b> as a novel class of bright near infrared window II (NIR-II, 1,000 - 1,700 nm) probes were designed and synthesized, and the twisted intramolecular charge transfer (TICT) formation at the excited state can be effectively suppressed for the newly designed probes. Furthermore, <b>Q8PNap</b> complexation with fetal bovine serum (<b>Q8PNap</b>/FBS) significantly increased the quantum yield by ~ 32-fold compared with PEGylated tertiary amine <b>Q8P</b>, and <b>Q8PNap</b>/FBS was successfully used to achieve high spatial and temporal resolution imaging of hind limb vasculature, lymphatic system, and small tumor metastasis, as well as precise NIR-II imaging-guided tumor and lymph node surgery in small animal models for the first time.