Quinolone-based fluorescent probes for distinguished detection of Cys and GSH through different fluorescence channels

Biothiols, such as cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), play different crucial roles in maintaining redox homeostasis in biological systems. Owing to their similar structures and reactivity, they present great challenges for their distinguished detection. In this work, we have constructed three different types of quinolone-based fluorescent probes (QB-1,QB-2andQB-3) for the detection of biothiols. Among themQB-3, a red fluorescent probe, displays the best sensing performance such as high selectivity and good sensitivity for Cys (LOD = 0.17 mu M) and GSH (LOD = 0.46 mu M), and it can distinguish between Cys, GSH and Hcy through two different fluorescence channels; specifically, a turn-on fluorescence centred at 420 nm for Cys, ratiometric fluorescence at 643 nm/537 nm for GSH and no response for Hcy. Furthermore,QB-3has been successfully applied for the simultaneous detection of endogenous Cys and GSH in living cells.