Catalytic and biological properties of Ag–Pt bimetallic nanoparticles: composition-dependent activity and cytotoxicity†

Due to their unique elemental compositions and interface coupling effects, bimetallic nanoparticles (BNPs), a class of nanoalloys, have attracted significant attention for applications in biomedicine, environmental remediation, and catalysis. BNPs, formed via the combination of two metal ions under light or thermal conditions, exhibit enhanced catalytic properties due to synergistic interactions between constituent metals, which result in optimized electronic structures, increased active sites, and reduced activation energy for catalytic reactions. However, BNPs may pose potential toxicity risks to organisms through bioaccumulation and environmental exposure. In this study, Ag–Pt nanoparticles (AP NPs) with varying molar ratios were synthesized and characterized to elucidate the relationship between composition, catalytic activity, and cytotoxicity. Catalytic assays revealed that AP NPs exhibited remarkable oxidase-like activity. Cytotoxicity tests revealed dose- and composition-dependent effects, with the AP55 (Ag : Pt at 5 : 5 ratio) exhibiting the highest cytotoxicity compared to monometallic counterparts at equivalent concentrations. Notably, the proportion of Ag in the AP NPs was identified as the dominant factor influencing catalytic activity and cytotoxicity. Mechanistic investigations attributed this cytotoxicity to the interplay of peroxidase-like catalytic activity, oxidative stress, and lysosomal ion release, disrupting cellular redox homeostasis and triggering apoptosis. Enzymatic assays further confirmed reductions in antioxidant defenses, including superoxide dismutase (SOD) and catalase (CAT) activities, amplifying reactive oxygen species (ROS) generation and oxidative damage. These findings underscore the critical role of catalytic behavior in mediating biological interactions and cytotoxic effects of BNPs. We establish a relationship between composition, oxidase-like activity, and cytotoxicity, providing insights into their potential biomedical applications and paving the way for the rational design of multifunctional nanomaterials with tunable biological effects.