Department of Chemistry, Hong Kong Branch of Chinese National Engineering Research Center for Tissue Restoration and Reconstruction, Guangdong-Hong Kong-Macau Joint Laboratory of Optoelectronic and Magnetic Functional Materials, Division of Life Science, and State Key Laboratory of Molecular Neuroscience, The Hong Kong University of Science and Technology, Kowloon, Hong Kong 999077, China.
Department of Chemistry, State Key Laboratory of Molecular Engineering of Polymers, Shanghai Key Laboratory of Molecular Catalysis and IChEM, Fudan University, Shanghai 200433, China.
J Am Chem Soc. 2022 Aug 24;144(33):15391-15402. doi: 10.1021/jacs.2c07443. Epub 2022 Aug 10.
Fluorescence imaging in the second near-infrared window (NIR-II, 1000-1700 nm) using small-molecule dyes has high potential for clinical use. However, many NIR-II dyes suffer from the emission quenching effect and extremely low quantum yields (QYs) in the practical usage forms. The AIE strategy has been successfully utilized to develop NIR-II dyes with donor-acceptor (D-A) structures with acceptable QYs in the aggregate state, but there is still large room for QY improvement. Here, we rationally designed a NIR-II emissive dye named TPE-BBT and its derivative (TPEO-BBT) by changing the electron-donating triphenylamine unit to tetraphenylethylene (TPE). Their nanoparticles exhibited ultrahigh relative QYs of 31.5% and 23.9% in water, respectively. By using an integrating sphere, the absolute QY of TPE-BBT nanoparticles was measured to be 1.8% in water. Its crystals showed an absolute QY of 10.4%, which is the highest value among organic small molecules reported so far. The optimized D-A interaction and the higher rigidity of TPE-BBT in the aggregate state are believed to be the two key factors for its ultrahigh QY. Finally, we utilized TPE-BBT for NIR-II photoluminescence (PL) and chemiluminescence (CL) bioimaging through successive CL resonance energy transfer and Förster resonance energy transfer processes. The ultrahigh QY of TPE-BBT realized an excellent PL imaging quality in mouse blood vessels and an excellent CL imaging quality in the local arthrosis inflammation in mice with a high signal-to-background ratio of 130. Thus, the design strategy presented here brings new possibilities for the development of bright NIR-II dyes and NIR-II bioimaging technologies.
基于小分子染料的近红外二区（NIR-II，1000-1700nm）荧光成像是有很大的临床应用潜力的。然而，在实际应用中，许多 NIR-II 染料都存在发射淬灭效应和极低的量子产率（QYs）。聚集态下具有给体-受体（D-A）结构且 QYs 可接受的 NIR-II 染料已经成功地利用 AIE 策略开发出来，但其 QY 仍有很大的提升空间。在此，我们通过将供电子的三苯胺单元改为四苯乙烯（TPE），合理设计了一种近红外二区发射染料，命名为 TPE-BBT 及其衍生物（TPEO-BBT）。它们的纳米颗粒在水中分别表现出超高的相对量子产率，分别为 31.5%和 23.9%。通过使用积分球，测量得到 TPE-BBT 纳米颗粒在水中的绝对量子产率为 1.8%。其晶体的绝对量子产率为 10.4%，这是迄今为止报道的有机小分子中最高的值。优化的 D-A 相互作用和 TPE-BBT 在聚集态下的更高刚性被认为是其超高 QY 的两个关键因素。最后，我们通过连续的 CL 共振能量转移和Förster 共振能量转移过程，利用 TPE-BBT 进行了近红外二区光致发光（PL）和化学发光（CL）生物成像。TPE-BBT 的超高 QY 实现了在小鼠血管中优异的 PL 成像质量，以及在小鼠局部关节炎炎症中优异的 CL 成像质量，其信号与背景比高达 130。因此，这里提出的设计策略为开发明亮的近红外二区染料和近红外二区生物成像技术带来了新的可能性。
