A lipid droplet-targeted fluorescent probe for selective imaging of cysteine fluctuations in drug-induced liver injury.

Cysteine (Cys), an essential endogenous biothiol, plays crucial roles in cellular redox homeostasis, metabolic regulation, and detoxification. Abnormal Cys fluctuations are closely associated with various pathological processes, including liver injury. Lipid droplets are dynamic organelles involved in lipid metabolism and stress responses and are highly relevant to hepatic injury progression. Thus, fluorescent probes capable of both lipid droplet localization and Cys-specific recognition are valuable tools for visualizing Cys fluctuations in drug-induced liver injury-related microenvironments. Herein, a diphenylamine-modified fluorescent probe, BDC, was designed and synthesized for selective Cys imaging. By tuning the electron-donating unit, the response pattern of BDC toward biothiols was regulated, enabling selective recognition of Cys. Spectroscopic investigations showed that BDC displayed a significant fluorescence enhancement toward Cys, together with good selectivity, anti-interference ability, sensitivity, photostability, and suitable pH adaptability. Bioimaging experiments demonstrated that BDC could effectively visualize endogenous and exogenous Cys in living cells and showed favorable lipid droplet localization. Moreover, BDC was successfully applied to monitor Cys fluctuations in zebrafish and an APAP-induced liver injury model. This work provides a practical molecular tool for visualizing Cys dynamics in drug-induced liver injury-related biological systems.