Colorimetric determination of cysteine by exploiting its inhibitory action on the peroxidase-like activity of Au@Pt core-shell nanohybrids

The authors report that the peroxidase-like activity of Au@Pt core-shell nanohybrids (Au@PtNHs) is selectively inhibited by cysteine. This finding has led to  a highly sensitive colorimetric assay for cysteine that is based on the nanohybrid-catalyzed oxidation of TMB by H2O2 to form a blue product. The method has a detection limit of 5.0 nM and a linear range from 10 nM to 20 μM. The assay is highly selective over other amino acids. It was successfully applied to the determination of cysteine in an injection containing a mixture of amino acids.