A glutathione-activatable near-infrared fluorescent probe with a large Stokes shift for imaging 4T1 tumor and its ferroptosis

Some tumor cells have higher concentrations of glutathione (GSH) compared to normal cells, and ferroptosis can result in a significant decrease of GSH level in tumor cells. Thus, GSH can be employed as the biomarker for imaging some tumors and their ferroptosis. In this article, a GSH-activatable near-infrared fluorescent probe (QL-NF) with a large Stokes shift (110 nm) was developed for imaging 4T1 tumor and its ferroptosis. QL-NF employs the quinolinium-xanthene dye as the fluorophore and the 2-fluoro-4-nitrobenzene-1-sulfonate group as the response unit for GSH. QL-NF has a high selectivity and an applicable linear response range (0.50 mM-10.00 mM) for physiological GSH. Moreover, QL-NF was successfully used for imaging GSH in cancer cells and monitoring the concentration fluctuations of GSH during ferroptosis of cancer cells. Finally, QL-NF was further successfully employed for imaging 4T1 tumor and its ferroptosis in mice. All these results demonstrate that QL-NF is a useful tool for detecting GSH in vivo and imaging tumor ferroptosis, which is helpful for understanding tumor ferroptosis and further promoting the treatment of tumor.