Enzyme mimics of Os/Ag nanoparticles for colorimetric detection of biothiols by smartphone

In this study, Os/Ag nanoparticles (Os/Ag NPs) with smaller K m and almost five times V max compared to Os NPs were prepared. This not only reduced the cost of nanozyme, but also improved the catalytic ability. Addition of L-Cysteine or glutathione (GSH) resulted in inhibitory effect on the peroxidase-like activity of Os/Ag nanozyme. Therefore, the L-Cysteine and GSH could be detected by absorption spectra method with limit of detection (LOD) of 0.22 μM and 0.2 μM, respectively. Moreover, a colorimetric sensing system for L-Cysteine and GSH based on portable paper strip and smartphone was fabricated with LOD of 1.72 μM and 1.4 μM, respectively. Furthermore, this method can be used in fetal bovine serum with recovery rates ranging from 89.42% to 109.0%. The sensing system exhibited good selectivity. This proposed colorimetric sensing assay holds great potential application in the detection of biothiols when no sophisticated equipment are available. Graphical abstract Scheme illustration for the colorimetric detection of L-Cysteine and GSH by use of smartphone