Abstract: Excessive accumulation of reactive oxygen species (ROS) can trigger oxidative stress in cells, ultimately leading to cell death. Nanozymes, a class of nanomaterials with enzyme-like catalytic activity, are capable of scavenging ROS and protecting cells from oxidative damage. Polyoxometalates (POMs), known for their favorable redox properties and biocompatibility, have been considered as potential nanozyme candidates. However, their relatively low catalytic activity has hindered their practical applications. In this study, an isomorphic doping strategy with manganese (Mn) was employed to effectively enhance the enzyme-like activity of Keggin-type POM ([PMo₁₂O₄₀]^3⁻). It was found that appropriate Mn doping significantly improved both the catalase-like and superoxide dismutase-like activities of the POM, thereby enhancing its ability to eliminate excessive ROS and protect cells from oxidative stress-induced damage. The relationship among Mn doping levels, POM structure, and catalytic activity was systematically investigated. The results suggest that the synergistic electronic interaction between Mn and the Mo-O framework plays a crucial role in enhancing the catalase-like activity of the material. This work provides a preliminary exploration of design strategies for POM-based nanozymes and offers scientific insights for the development of antioxidant nanozymes.

Key words: polyoxometalates, oxidative stress, nanozyme, catalytic medicine