Key Laboratory for Polymer Chemistry and Physics, College of Chemistry, Central China Normal University, Wuhan, Hubei430079, PR China.
Chemistry. 2013 Jan 21;19(4):1311-9. doi: 10.1002/chem.201203137. Epub 2012 Dec 19.
Biothiols, such as cysteine (Cys) and homocysteine (Hcy), play very crucial roles in biological systems. Abnormal levels of these biothiols are often associated with many types of diseases. Therefore, the detection of Cys (or Hcy) is of great importance. In this work, we have synthesized an excellent "OFF-ON" phosphorescent chemodosimeter 1 for sensing Cys and Hcy with high selectivity and naked-eye detection based on an Ir(III) complex containing a 2,4-dinitrobenzenesulfonyl (DNBS) group within its ligand. The "OFF-ON" phosphorescent response can be assigned to the electron-transfer process from Ir(III) center and C^N ligands to the DNBS group as the strong electron-acceptor, which can quench the phosphorescence of probe 1 completely. The DNBS group can be cleaved by thiols of Cys or Hcy, and both the (3)MLCT and (3)LC states are responsible for the excited-state properties of the reaction product of probe 1 and Cys (or Hcy). Thus, the phosphorescence is switched on. Based on these results, a general principle for designing "OFF-ON" phosphorescent chemodosimeters based on heavy-metal complexes has been provided. Importantly, utilizing the long emission-lifetime of phosphorescence signal, the time-resolved luminescent assay of 1 in sensing Cys was realized successfully, which can eliminate the interference from the short-lived background fluorescence and improve the signal-to-noise ratio. As far as we know, this is the first report about the time-resolved luminescent detection of biothiols. Finally, probe 1 has been used successfully for bioimaging the changes of Cys/Hcy concentration in living cells.
生物硫醇，如半胱氨酸（Cys）和同型半胱氨酸（Hcy），在生物体系中起着至关重要的作用。这些生物硫醇水平的异常通常与许多类型的疾病有关。因此，Cys（或 Hcy）的检测非常重要。在这项工作中，我们合成了一种出色的“关-开”磷光化学传感器 1，用于基于其配体中含有 2,4-二硝基苯磺酰基（DNBS）基团的 Ir（III）配合物，对 Cys 和 Hcy 进行高选择性和肉眼检测。“关-开”磷光响应可以归因于 Ir（III）中心和 C^N 配体向作为强电子受体的 DNBS 基团的电子转移过程，这可以完全猝灭探针 1 的磷光。DNBS 基团可被 Cys 或 Hcy 的巯基裂解，而（3）MLCT 和（3）LC 态都负责探针 1 与 Cys（或 Hcy）反应产物的激发态性质。因此，磷光被打开。基于这些结果，提供了一种基于重金属配合物设计“关-开”磷光化学传感器的一般原理。重要的是，利用磷光信号的长发射寿命，成功实现了 1 在检测 Cys 中的时间分辨发光分析，这可以消除短寿命背景荧光的干扰，提高信噪比。据我们所知，这是关于生物硫醇的时间分辨发光检测的第一个报道。最后，探针 1 已成功用于活细胞中 Cys/Hcy 浓度变化的生物成像。
