Unlocking the NIR‐II AIEgen for High Brightness through Intramolecular Electrostatic Locking

• Published in: Angewandte Chemie International Edition 2024-07, Vol.63 (29), p.e202404142-n/a
• Main Authors: Wang, Xinyuan, Yang, Xueqin, Jiang, Guanyu, Hu, Zhubin, Liao, Tao, Wang, Guoxin, Zhang, Xun, He, Xinyuan, Zhang, Jianyu, Zhang, Jianquan, Cao, Wuke, Zhang, Kaizhen, Lam, Jacky W. Y., Sun, Jianwei, Sun, Haitao, Liang, Yongye, Tang, Ben Zhong
• Format: Article
• Language: English
• Subjects: aggregation-induced emission; Antigens; Biomedical materials; Biosensors; Brightness; Chemical compounds; Diagnosis; Electrostatic properties; Emissions; Encapsulation; Fluorescence; Fluorophores; Fluoroscopic imaging; imaging guided surgery; intramolecular electrostatic locking; lateral flow assay; Locking; Medical research; Molecular motion; Nanoparticles; Nanospheres; Near infrared radiation; NIR-II fluorophores; Nitrogen atoms; Polystyrene; Polystyrene resins; Sulfur; Tumors
• ISSN: 1433-7851; 1521-3773; 1521-3773
• DOI: 10.1002/anie.202404142

Fluorescent imaging and biosensing in the near‐infrared‐II (NIR‐II) window holds great promise for non‐invasive, radiation‐free, and rapid‐response clinical diagnosis. However, it's still challenging to develop bright NIR‐II fluorophores. In this study, we report a new strategy to enhance the brightness of NIR‐II aggregation‐induced emission (AIE) fluorophores through intramolecular electrostatic locking. By introducing sulfur atoms into the side chains of the thiophene bridge in TSEH molecule, the molecular motion of the conjugated backbone can be locked through intramolecular interactions between the sulfur and nitrogen atoms. This leads to enhanced NIR‐II fluorescent emission of TSEH in both solution and aggregation states. Notably, the encapsulated nanoparticles (NPs) of TSEH show enhanced brightness, which is 2.6‐fold higher than TEH NPs with alkyl side chains. The in vivo experiments reveal the feasibility of TSEH NPs in vascular and tumor imaging with a high signal‐to‐background ratio and precise resection for tiny tumors. In addition, polystyrene nanospheres encapsulated with TSEH are utilized for antigen detection in lateral flow assays, showing a signal‐to‐noise ratio 1.9‐fold higher than the TEH counterpart in detecting low‐concentration antigens. This work highlights the potential for developing bright NIR‐II fluorophores through intramolecular electrostatic locking and their potential applications in clinical diagnosis and biomedical research. The alkylthio side chain on the thiophene bridge affords sulfur—nitrogen electrostatic lock, substantially improving the fluorescent brightness of the aggregation‐induced emission luminogen (AIEgen) in the second near‐infrared (NIR‐II) window. The obtained NIR‐II AIEgen shows high signal‐to‐noise ratio in NIR‐II fluorescent imaging and high sensitivity in detecting low‐concentration antigens.