Regulating the pro- and anti-oxidant capabilities of bimetallic nanozymes for the detection of Fe2+ and protection of Monascus pigments.

The emerging properties of mimicking enzymes open up new horizons for nanomaterials. Regulating their enzyme-like activity and exploiting their applications are currently the hot topics for nanozymes. Among their activities, the pro-oxidant and antioxidant capabilities of nanozymes are important to determine their unique physiological functions. In this paper, we demonstrate that PtRu NPs exhibit multiple enzyme-like activities (e.g. peroxidase, oxidase, ferroxidase, catalase and SOD) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity. The PtRu bimetallic nanozymes therefore show pro-oxidant and anti-oxidant functions. It was found that the enzyme-like activities of PtRu NPs are highly dependent on the Pt/Ru molar ratio and show a similar trend in the order of activity: Pt90Ru10 > Pt75Ru25 > Pt > Pt40Ru60, indicating that proper alloying of Pt with Ru can enhance both pro- and anti-oxidant capabilities. By employing the ferroxidase-like activity and catalase-like activity, we verified the applications of PtRu nanozymes in the detection of Fe2+ ions, and tried for the first time to protect Monascus pigments (MPs) from hydrogen peroxide oxidation. These results not only provide an effective way to optimize the pro- and anti-oxidant capabilities of nanozymes, but also provide prospects for the applications of nanozymes in protecting biologically active natural products.