A chloroacetate based ratiometric fluorescent probe for cysteine detection in biosystems

Abstract The specific detection of cysteine (Cys) over homocysteine (Hcy), glutathione (GSH) and other amino acids is of great significance for studying its biological functions as well as for the diagnosis of related diseases. Chloracetyl group was often used as reaction site for cysteine fluorescent probes for its sensitivity and selectivity. However, high background fluorescence and low stability are common problems encountered by such probes. Here, four chloracetyl group based fluorescent probes (C1, C2, C3 and H4) was synthesized for a comparative study. We found that the inefficient quenching ability of chloracetyl group turned into an advantage when connected with ratiometric fluorophore. With the modification of chloracetyl group, probe H4 displayed great ratiometric property and great selectivity for Cys, the stability was also improved. Additionally, the probe was successfully applied for detecting and real time imaging of Cys in fatal bovine serum and living HeLa cells with low toxicity.