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%.