A coumarin-based “off-on” sensor for fluorescence selectivily discriminating GSH from Cys/Hcy and its bioimaging in living cells

- A new “off-on” sensor which can fluorescence discriminate GSH from Cys/Hcy at intracellular concentrations.
- The significantly different mechanisms enable the discrimination of GSH over Cys/Hcy through fluorescence response.
- The probe has a good cell membrane permeability that can be applied in bioimaging in living cells.

Glutathione (GSH) is the most abundant intracellular thiol with the concentration in the millimolar range. It has also been reported that GSH plays a crucial role in human pathologies, so it is meaningful to develop an effective probe for GSH. In this work, we report a coumarin-chlorine malononitrile “off-on” sensor for highly selective fluorescence detection of GSH over Cys/Hcy. The chlorine of the probe can be rapidly replaced by thiolates of biothiols through thiol-halogen nucleophilic substitution. The amino groups of Cys/Hcy but not GSH further replace the thiolate to form amino-substituted compound. Subsequently, an intramolecular Michael addition between the α,β-unsaturated malonitrile and thiol group may occur. However, GSH only forms thiol-substituted compound. The significantly different mechanisms enable the discrimination of GSH over Cys/Hcy through fluorescence response. Finally, fluorescence imaging of A549 cells indicated that probe 1 could be used for monitoring GSH in living cells. It would be a useful tool to understand the mechanisms of many related diseases.

The statement: A coumarin-based “off-on” sensor was designed and synthesized, which was able to fluorescence selectivily discriminate GSH from Cys/Hcy. The significantly different mechanisms enable the discrimination of GSH over Cys/Hcy through fluorescence response. Finally, fluorescence imaging of A549 cells indicated that 1 could be used for monitoring GSH in living cells.85