水溶性延迟荧光分子的设计合成与时间分辨成像的应用

Time-resolved luminescence techniques can eliminate the background signal from scattering and autofluorescence and greatly increase the signal-to-noise ratio. The probes used in time-resolved detection always possess long emission lifetimes, and the typical representatives were phosphorescence transition-metal (e.g., Ru(II), Ir(III), Pt(II), and Ln(III)) complexes. However the stablity and the toxicity of these complexes need to be considered in practical application. Alternatively, developing nonmetallic organic probes with long-lived luminescence is in great demand. ..Recently, new fluorophores based on thermally activated delayed fluorescence (TADF) has been developed comprehensively. These materials exhibited fluorescence with lifetimes from several microseconds to a few milliseconds which can compare with that of many transition-metal complexes. This long-lived fluorescence was due to the RISC (Reversed intersystem crossing) from triplet excited state. So these materials were mainly used in OLED (Organic Light-Emitting Diode) to take advantage of the triplet excitons to improve the electroluminescent efficiency. However, to our knowledge, few of these fluorophores have been used in designing probes for biological detection. There is a great space for developing other TADF-based probes for biological detections...In this project, water-soluble TADF molecules will be designed and synthesized. By incorporating hydrophilic groups and targeted groups on the aromatic rings, the solubility of the molecules would be improved, and these molecules may be used in time-resolved detection and imaging to eliminate the background signal from scattering and autofluorescence.

时间分辨技术在生物检测和成像中有重要应用。相对于稳态测量，时间分辨的测量可以有效去除背景荧光以及各种散射光的干扰，显著提高检测的信噪比。然而大部分用于时间分辨的探针都是过渡金属配合物，它们或多或少存在的稳定性和毒性的问题。为此发展纯有机的时间分辨探针非常必要。近些年热致延迟荧光型分子被广泛应用于有机发光二极管（OLED）领域。由于这类分子的激发单重态和三重态能级差异较小，因而激发三重态通过反向系间窜越可以回到单重态，进而发出较长寿命的延迟荧光。然而这类材料还很少用在生物探针分子的设计中。..本研究项目将设计并合成一系列水溶性延迟荧光分子探针，应用于水溶液中的检测和生物成像。计划将水溶性基团和生物靶向性基团修饰到延迟荧光型分子上，以改善分子的水溶性并实现分子探针的功能。项目还将结合时间分辨技术，选择性收集延迟荧光的长寿命激发态，就可以去除背景荧光、散射光的干扰，以提高检测和成像的信噪比。

时间分辨技术在生物检测和成像中有重要应用。相对于稳态测量，时间分辨的测量可以有效去除背景荧光以及各种散射光的干扰，显著提高检测的信噪比。然而大部分用于时间分辨的探针都是过渡金属配合物，它们或多或少存在的稳定性和毒性的问题。为此发展纯有机的时间分辨探针非常必要。近些年热致延迟荧光型分子被广泛应用于有机发光二极管领域。由于这类分子的激发单重态和三重态能级差异较小，因而激发三重态通过反向系间窜越可以回到单重态，进而发出较长寿命的延迟荧光。.鉴于延迟荧光材料具有较长的荧光寿命，本项目基于常用的给体和受体单元设计并合成了一些水溶性延迟荧光分子，以实现分子探针的功能。在我们合成的水溶性延迟荧光分子中，大多数在溶液中发光较弱，很可能是溶液极性增强了分子的电荷转移而导致荧光猝灭。不过，通过结合聚集诱导发光的性质，我们将2个延迟荧光探针成功用于细胞成像和线粒体成像。并结合时间分辨技术，选择性收集延长寿命荧光，达到降低背景荧光、散射光的干扰的目的。此外，本项目还发展了一种延迟荧光纳米粒子的制备方法：采用两亲性细胞穿膜肽包裹疏水的延迟荧光纳米粒子可以有效增强细胞摄入量，实现了快速的细胞成像。相对于共价修饰穿膜肽的荧光探针，该工作仅用一条穿膜肽实现了三种非共价连接的分子进入细胞，其操作方法更简便，成本更低。..本项目探究了延迟荧光分子在生物探针中的设计与应用，累积了相关的研究经验，通过聚集诱导发光等策略降低了氧分子对三重态的猝灭，为发展其它用于生物检测的延迟荧光探针提供了思路。同时这些工作极大拓展了非金属有机材料在时间分辨成像领域中的应用，相关的研究思路可用于发展其它类型的非金属长寿命激发态探针。