A near-infrared fluorescent probe for monitoring hepatic cysteine dynamics in drug-induced liver injury guided by cholic acid group.

In this work, a liver-targeted NIR fluorescent probe CA-Cys for Cys was developed by integrating benzothiazole hemicyanine, an acrylate moiety responsive to Cys, and a cholic acid (CA) ligand. The CA group of CA-Cys recognizes the sodium-taurocholate cotransporting polypeptide (NTCP) specifically expressed on hepatocytes, enabling specific liver targeting and excellent resistance to disease interference. CA-Cys exhibits an excellent linear response to Cys with a detection limit of 0.54 μM, rapid response within 30 s, and favorable selectivity, without interference by other reactive sulfur species such as homocysteine, glutathione, hydrogen sulfide, etc. CA-Cys exhibits liver-targeted ability both in vitro and in vivo. Moreover, CA-Cys distinguishes liver cancer cells from normal liver cells by sensing intracellular Cys levels. CA-Cys can track the Cys changes in drug-induced liver injury (DILI) cell models and evaluate the therapeutic effect of N-acetylcysteine (NAC). In vivo and ex vivo imaging of mice showed that Cys accumulation induced by acetaminophen (APAP) mainly occurred in the liver, and NAC treatment effectively restored hepatic Cys homeostasis. This liver-targeted CA-Cys enables non-invasive real-time visualization of hepatic Cys at both cellular and animal levels, offering a practical tool for pathological research, diagnosis, and therapeutic monitoring of DILI.