A visible and near-infrared dual-fluorescent probe for discrimination between Cys/Hcy and GSH and its application in bioimaging

Biothiols such as cysteine (Cys), homocysteine (Hcy) and glutathione (GSH) play important roles in various physiological and pathological processes, and due to their similar structures and reaction activities, it is still challenging to simultaneously discriminate between GSH and Cys/Hcy in vivo. Hence, a novel fluorescent probe for simultaneously discriminating GSH and Cys/Hcy in biological samples is highly desirable. Herein, we presented two enhanced fluorescent probes (Cy1 and Cy2) with doubly-activated dual emission for sensitive and discriminative detection of Cys/Hcy and GSH. The probes were constructed with IR-780 and NBD linked via an ether bond, which responds to GSH with near infrared (NIR) emission at 810 nm (λ_ex = 720 nm) and Cys/Hcy with visible green emission at 550 nm (λ_ex = 470 nm). The probe Cy2 is operable in human serum samples, thus holding promise for its diagnosis-related application. Notably, the results of fluorescence microscopy imaging indicated that Cy2 is suitable for visualization of exogenous and endogenous biothiols in living cells. Furthermore, desirable results were obtained when the probe Cy2 was applied for bioimaging in tumor-bearing mice and acute liver injury (ALI) mice models, which revealed encouraging clinical values of this probe.