Fluorometric determination and intracellular imaging of cysteine by using glutathione capped gold nanoclusters and cerium(III) induced aggregation

A turn-on fluorometric method is described for selective and sensitive detection of cysteine (Cys). Gold nanoclusters (Au NCs) capped with glutathione (GSH) are used as afluorescent probe. If Ce3+ ion are present, they will bind to the carboxy groups of theGSH-capped Au NC. This results in aggregation-induced emission enhancement (AIEE), best measured at excitation/emission wavelengths of 360/575nm. On addition of Cys, which has less steric hindrance compared with GSHand higher affinity for Ce3+, it will bind toCe(3+) through the carboxyl group and link with Au NCs via Au-S bond. Hence, the AIEE is increased and Cys can be quantified via this effect with a linear response in the 0.4-120molL(-1) Cys concentration range and a detection limit of 0.15molL(-1).