A dual-response NIR fluorescent probe for separately and continuously recognizing H₂S and Cys with different...

Given the significant interactions between hydrogen sulfide (H₂S) and cysteine (Cys) in organisms, a dual-site multi-purpose fluorescent probe (Cy-NP) for H₂S and Cys was synthesized. Cy-NP is composed of two fluorophores: naphthalimide that emits in the visible region of 500-600 nm, and cyanine dye that emits in the NIR region of 700-800 nm. Cy-NP showed admirable sensitivity and selectivity for identifying H₂S and Cys by fluorescent signals with limits of detection as low as 0.15 μM and 1.4 μM, respectively. Furthermore, other biological thiols (especially GSH and Hcy) showed no positive response to Cy-NP compared with H₂S and Cys. The chemical mechanism of Cy-NP with H₂S and Cys in DMF/PBS (1/1, v/v, pH = 7.4) solution was verified by HRMS and DFT calculations. Further, Cy-NP was successfully applied to monitor H₂S released in raw meat and adapted to detect H₂S and Cys in MCF-7 cells independently and continuously.