A new simple ESIPT-based fluorescent probe for rapid detection of cysteine with high sensitivity and specificity and bioimaging in living cells

Abstract Based on Excited-State Intramolecular Proton Transfer (ESIPT) fluorophore and an acrylate moiety as Michael addition and leaving site, a simple but colorimetric turn-on fluorescent probe FVCA was designed and synthesized. Upon addition of Cys to the solution of FVCA, the absorption spectra changed from 375 nm to 460 nm (Δ85 nm) and afforded visible color change from colorless to yellow. Meanwhile, the fluorescence emission spectra emerged at 554 nm with remarkable changes, accompanying with an obvious fluorescence color change from colorless to bright green. In addition, FVCA exhibited rapid response (∼ 60 s), high sensitivity (detection limit: 8.37 nM), large strokes shift (∼ 94 nm) and excellent selectively to Cys over other biological mercaptans. Moreover, FVCA had strong anti-interference ability for Cys without any interference from other biologically-relevant thiols even Hcy and GSH, even obvious visible and fluorescence color changes. More, the sensing mechanism was proved to be the ESIPT-based addition-cyclization reaction process by 1H-NMR, HRMS and TD-DFT. Importantly, FVCA can be used to image exogenous and endogenous Cys in living A549 cells with low toxicity.