A colorimetric and fluorescent chemodosimeter for discriminative and simultaneous quantification of cysteine and homocysteine

A highly selective, visible-light-excited and OFF-ON fluorescent chemodosimeter 1 employed conjugate addition/cyclization sequence mechanism, was designed and synthesized to discriminatively detect cysteine (Cys) and homocysteine (Hcy). The addition of Cys and Hcy resulted in the color of the solution of 1 changing from colorless to green under the simulation of physiological condition, and 1 could serve as a "naked-eye" indicator. Our chemodosimeter can detect Cys and Hcy quantitatively by fluorescence spectrometry method with a detection limit of 0.5 μM (for Cys) and 0.8 μM (for Hcy). To the best of our knowledge, 1 is the first visual and visible-light-excited fluorescent indicator for discriminative and simultaneous detection of Cys and Hcy. Furthermore, the mechanism of the reaction between 1 and Cys was confirmed using ESI-MS and fluorescence spectra.