A Reversible Fluorescent Probe for Real-Time Quantitative Monitoring of Cellular Glutathione

The ability to monitor and quantify glutathione (GSH) in live cells is essential in order to gain a detailed understanding of GSH-related pathological events. However, owing to their irreversible response mechanisms, most existing fluorescent GSH probes are not suitable for this purpose. We have developed a ratiometric fluorescent probe (QG-1) for quantitatively monitoring cellular GSH. The probe responds specifically and reversibility to GSH with an ideal dissociation constant (K-d) of 2.59 mM and a fast response time (t(1/2) = 5.82 s). We also demonstrate that QG-1 detection of GSH is feasible in a model protein system. QG-1 was found to have extremely low cytotoxicity and was applied to determine the GSH concentration in live HeLa cells (5.40 +/- 0.87 mM).