A novel coumarin-thiazole conjugated ICT fluorescent probe for cysteine specific detection in food samples, living cells and zebrafish

• A novel coumarin-thiazole conjugated fluorescent sensor ( PC ) towards cysteine (Cys) was designed and synthesized. • PC features excellent sensitively (LOD = 55.0 nM), large Stokes shift (133 nm), rapid response time (15 min), colorimetric detection and high biocompatibility. • PC was applied to qualitatively detect Cys in actual food samples. • Applications of PC in fluorescence imaging of Cys in vitro and in vivo are successfully demonstrated. Inspired by the advantageous properties of coumarin and thiazole fluorophores, we rationally designed and developed a novel coumarin-thiazole conjugated fluorescent probe (PC), featuring an acryloyl ester group as the triggering and responding entity for the specific identification of cysteine (Cys). Probe PC exhibited a distinct color change (colorless to bright green), a large Stokes shift, excellent sensitivity, high selectivity, and strong anti-interference capabilities. the density function theory (DFT), high-resolution mass spectrometry (HRMS), and proton nuclear magnetic resonance ( 1 H NMR) assays further affirmed that the response mechanism encompasses an addition-cyclization reaction between the acryloyl domain of probe PC and the sulfhydryl and amino entities of Cys, engendering the liberation of a lustrous green fluorescent chromophore (PC OH) that can be visually discerned. Compared with previous reports, this is a new scaffold based on coumarin that achieves the quantitative determination of Cys in different food matrices in real-time. Furthermore, probe PC is effectively employed for visual imaging of Cys in A549 cells and five-day-old zebrafish, exhibiting low cytotoxicity and favorable cellular permeability, which demonstrated its practical application.