A colorimetric/fluorescence dual-channel probe for highly discriminating detection of cysteine.

In this work, a novel fluorescence (FL) probe for selective and sensitive detection of Cys with colorimetric and FL dual signal changes was reported. The probe was synthesized by two step of sulfonamide reaction coupling between a sulfonyl benzoxadiazole (SBD) dye and dansyl chloride linked with rigid piperazine group. The probe showed a specific off-on response to Cys in aqueous solution with nanomolar LOD, and without interference by a range of amino acids and several competing analytes. Upon addition of Cys, the probe will undergo sequential substitution and intramolecular rearrangement reactions, yielding a 4-amino SBD derivative, which results in generation of strong yellow fluorescence emission at 575 nm accompanied by a two-step red shift in the absorption spectral. Moreover, it can be used for imaging of endogenous Cys in living cells.