New Rhodamine-based sensor for high-sensitivity fluorescence tracking of Cys and simultaneously colorimetric detection of H 2 S.

Sulfhydryl-containing compounds including cysteine (Cys), homocysteine (Hcy), glutathione (GSH) and hydrogen sulfide (H ₂ S) are involved in many physiological processes. The development of single-molecule optical sensor for the distinguish detection of these bio-thiols is a critical and challenging effort. In this work, we designed a one-step synthesis of the Rhodamine-based sensor FR for specific fluorescent response of Cys and simultaneously colorimetric detection of H ₂ S, in which the aldehyde and fluorine groups act as response sites. Sensor FR displays significant fluorescence enhancement at 565 nm toward Cys with high selectivity and low detection limits (49 nM) due to the low background fluorescent signal of the spirocyclic closed-state in Rhodamine structure. Meantime, after treatment of H ₂ S, the color of the sensor changes significantly from colorless to blue-purple, which can be used as a visual colorimetric method to detect H ₂ S. These response mechanisms were systematically characterized by ¹ H NMR and Mass spectrometry. Finally, sensor FR could be used to monitor exogenous and endogenous of intracellular Cys changes.
Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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