Amphiphilic protein controlled synthesis of rice-shaped copper oxide and its substrate dependent enzyme-mimicking activity

Rice-shaped protein–copper oxide hybrid (RSPCO) was prepared by one-pot method in the presence of amphiphilic proteins. The enzyme-mimicking activity of RSPCO depends much on the substrate structure. RSPCO shows superior peroxidase-like activity with 3,3′,5,5′-tetramethylbenzidine (TMB) as a substrate. RSPCO exhibits both peroxidase- and oxidase-like activities with 1,2-diaminobenzene (OPD) as the substrate. RSPCO does not exhibit peroxidase-/oxidase-like activity when using 2,2′-azinobis(3-ethylbenzthiazoline-6-sulfonic acid)diammonium salt (ABTS) as the substrate. Furthermore, pyrogallol (PA)-induced activity switching effect is dependent on the type of enzyme-like activity of nanozyme and the substrate structure. The different effect of PA on the enzyme-like activity of RSPCO attributes mainly to the different affinity of substrates toward RSPCO. PA can significantly inhibit the peroxidase-like activity of RSPCO with TMB used as the substrate. Due to the efficient inhibiting effect, an excellent PA colorimetric sensor with low limit of detection being 15 nM (signal-to-noise ratio of 3) was developed based on RSPCO. With the features of simplification and low cost, protein–copper oxide hybrid nanozymes has the potential application in medial, environmental, and food areas. The present work provides new information about activity–structure relationship of copper oxide nanozyme, which is important for the applications of nanozymes in practice.