Antibacterial Performance of Defect-Enriched PtPdCuFe High-Entropy Alloy Nanozymes.

Antibiotic resistance limits infected-wound treatment and motivates the search for antibiotic-independent antibacterial materials. Here we report monodisperse PtPdCuFe high-entropy alloy (HEA) nanozymes with multi-enzyme activities, 2.14 ± 0.18 nm in diameter, prepared by oleylamine-assisted pyrolysis. We propose that synergistic metal interactions and abundant defects may endow the nanozymes with pH-gated peroxidase-like (POD-like), catalase-like (CAT-like), and superoxide dismutase-like (SOD-like) activities. At pH 5.5, the nanozymes exert POD-like activity to decompose H2O2 into hydroxyl radicals (•OH), triggering an ROS burst that destroys the bacterial wall, causes intracellular content leakage, and ultimately kills bacteria. At pH 7.4, they exert SOD- and CAT-like activities: ~84% of H2O2 was removed within 25 min and O2 rose to ~50% within 60 s, indicating potential to alleviate wound hypoxia, yet to be validated in future animal experiments. At the lowest effective concentration tested (16 µg·mL-1), bactericidal efficiencies against Escherichia coli and Staphylococcus aureus were ~56% and ~57%, respectively. At 64 µg·mL-1, killing reached ~90%, with >90% of bacteria showing severe membrane disruption and protein leakage. At this concentration, ~90% of mammalian cells remained viable and the hemolysis rate stayed below 5%.