Constitutional Isomerization Enables Bright NIR‐II AIEgen for Brain‐Inflammation Imaging

• Published in: Advanced functional materials 2020-02, Vol.30 (7), p.n/a
• Main Authors: Liu, Shunjie, Chen, Chao, Li, Yuanyuan, Zhang, Haoke, Liu, Junkai, Wang, Ran, Wong, Sherman T. H., Lam, Jacky W. Y., Ding, Dan, Tang, Ben Zhong
• Format: Article
• Language: English
• Subjects: aggregation‐induced emission; Backbone; Bioaccumulation; Brain; brain inflammation; Chemical compounds; Emission; Fluorescence; fluorescence imaging; Inflammation; Infrared windows; Isomerization; Materials science; Medical imaging; Nanoparticles; near‐infrared II emission; neutrophils; Rotors; Twisting
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201908125

The shortage of high quantum yield (QY) organic fluorophores in the second near‐infrared window (NIR‐II) has become a bottleneck in bioimaging field. Now, a simple strategy is proposed to address this: constitutional isomerization on the basis of the molecular design philosophy of aggregation‐induced emission. With the combination of backbone distortion and rotor twisting, the resultant NIR‐II fluorophore 2TT‐oC6B displays an emission peak at 1030 nm and a QY of 11% in nanoparticles, one of the highest reported so far. Control molecules confirm that the distorted backbone and twisted rotors play equally important roles in determining the fluorescence properties of the NIR‐II fluorophores. To allow for the targeting ability to reach deeply located diseases, neutrophils (NEs) are used to penetrate the brain tissues and accumulate in the inflammation site. Herein, it is shown that NEs carrying 2TT‐oC6B nanoparticles can penetrate the blood‐brain‐barrier and visualize the deeply located inflammation through an intact scalp and skull. Notably, the bright 2TT‐oC6B contributes to a significantly enhanced signal‐to‐background ratio of 30.6 in the brain inflammation site. On the basis of the molecular design philosophy for aggregation‐induced emission (AIE), here, a constitutional isomerization strategy involving the combination of backbone distortion and rotor twisting is demonstrated. The resultant AIEgen displays a high quantum yield of 11% with an emission peak of 1030 nm. Further, neutrophils are creatively used as carriers to detect brain inflammation with a high signal‐to‐background ratio of 30.6.