A benzothiazole derivative-based turn-on fluorescent probe for specific detection of Cys.

Cysteine (Cys) is a core biological thiol that regulates cellular redox homeostasis. Abnormal concentrations of Cys are closely related to tumorigenesis, neurodegenerative diseases, and metabolic disorders, and are often used as biomarkers for cancer cells. Therefore, detecting and analyzing its levels in the microenvironment of cancer cells is important. This study designed and synthesized a novel fluorescent probe HBT-T, whose basic structure is derived from 2-(2-hydroxyphenyl) benzothiazole (HBT). This probe employs both excited-state intramolecular proton transfer (ESIPT) and intramolecular charge transfer (ICT) mechanisms to selectively detect Cys. Upon reaction with Cys, a noticeable color change in the probe can be detected with the naked eye. This probe has low cytotoxicity, high sensitivity (detection limit as low as 1.92 μM), high selectivity, good water solubility, and stability, and can efficiently detect Cys within 15 s. Experiments have demonstrated that this probe is not only capable of reliably tracking both endogenous and exogenous Cys levels within live cells, but can also effectively detect Cys in zebrafish, demonstrating enormous potential for biomedical applications.