Dual-Site Chemosensor for Monitoring ·OH-Cysteine Redox in Cells and In Vivo

The reaction between hydroxyl radical (^·OH) and cysteine (Cys) plays an important role in the redox balance of living cells. A deeper insight into this intracellular reaction modulation and process is necessary and draws great interest. A highly effective technique consists of the real-time visualization of the two bioactive species and the perception of their respective changes by using a fluorescent probe. In this study, a dual-site chemosensor SPI based on phenothiazine-cyanine was developed, which realized quantitative detection and real-time imaging of ^·OH and Cys at their own fluorescence channels (^·OH: λ_ex = 485 nm, λ_em = 608 nm; Cys: λ_ex = 426 nm, λ_em = 538 nm) without spectral crosstalk. The fluorescent sensor showed excellent anti-interference and selectivity for common biological substances, apart from the successful imaging of exogenous and endogenous ^·OH and Cys. We further visualized the redox dynamic reaction and explored the correlation of ^·OH and Cys generated by different inhibitors (sulfasalazine and (1S, 3R)-RSL3). Notably, the chemosensor also possesses the capacity to clearly monitor ^·OH and Cys in living mice and zebrafish. This study reports on the first chemosensor to investigate the process of intracellular redox modulation and control between ^·OH and Cys, which show potential to further explore some metabolic and physiological mechanisms.