School of Chemistry and Chemical Engineering, Southeast University, Nanjing, Jiangsu 211189, PR China.
School of Biological Science & Medical Engineering, Southeast University, Nanjing, Jiangsu 210096, PR China.
Bioorg Chem. 2022 Sep;126:105902. doi: 10.1016/j.bioorg.2022.105902. Epub 2022 May 24.
Cysteine (Cys) and homocysteine (Hcy) are involved in maintaining homeostasis in the body and are relevant to various diseases. While the level of Cys and Hcy is much lower than GSH in the living system, which leads to a major challenge to selectively identify Cys/Hcy in the presence of large amounts of GSH. In this paper, an AIE fluorescent probe SQM-NBD was obtained by connecting NBD to the hydroxyl group of the fluorophore SQM-OH for selective detection of Cys/Hcy. Probe SQM-NBD had no fluorescence itself. But, under the disturbance of GSH, the fluorescence signal of probe SQM-NBD could be turned on by Cys/Hcy. The study of the response mechanism showed that probe SQM-NBD could release both SQM-OH and Cys/Hcy-NBD after reacting with Cys/Hcy. While Cys/Hcy continued to quench the fluorescence of SQM-OH through the combination of Michael addition and the ion rich environment, resulting in only the fluorescence signal of Cys/Hcy-NBD being observed. SQM-NBD appeared superior sensitivity to Cys/Hcy, with LOD of 54 nM and 72 nM, respectively. Significantly, probe SQM-NBD realized the application of fluorescence imaging of Cys/Hcy in HeLa cells, indicating that probe SQM-NBD has the potential for Cys/Hcy identification under physiological and pathological conditions.
半胱氨酸 (Cys) 和同型半胱氨酸 (Hcy) 参与维持体内的内稳态，与各种疾病相关。虽然在活体系中 Cys 和 Hcy 的水平远低于 GSH，但这导致了在大量 GSH 存在的情况下选择性识别 Cys/Hcy 的主要挑战。在本文中，通过将 NBD 连接到荧光团 SQM-OH 的羟基上，得到了一种 AIE 荧光探针 SQM-NBD，用于选择性检测 Cys/Hcy。探针 SQM-NBD 本身没有荧光。但是，在 GSH 的干扰下，探针 SQM-NBD 的荧光信号可以被 Cys/Hcy 打开。对响应机制的研究表明，探针 SQM-NBD 在与 Cys/Hcy 反应后可以同时释放 SQM-OH 和 Cys/Hcy-NBD。而 Cys/Hcy 通过迈克尔加成和离子丰富环境的结合继续猝灭 SQM-OH 的荧光，导致仅观察到 Cys/Hcy-NBD 的荧光信号。SQM-NBD 对 Cys/Hcy 表现出优异的灵敏度，LOD 分别为 54 nM 和 72 nM。重要的是，探针 SQM-NBD 实现了 Cys/Hcy 在 HeLa 细胞中的荧光成像应用，表明探针 SQM-NBD 具有在生理和病理条件下识别 Cys/Hcy 的潜力。
