Biosynthesis of CuS nanozymes for synergistic antibacterial applications: Biosynthetic parameters optimization and antimicrobial mechanisms elucidation.

The imperative to address antibiotic-resistant bacterial infections necessitates the development of novel antibacterial materials and methodologies, with nanozymes exhibiting peroxidase-like activity emerging as a highly promising option. Here, sulfate-reducing bacteria served  as bioreactors to biosynthesize copper sulfide nanoparticles (Bio-CuS NPs) via dissimilatory sulfate reduction pathways. By optimizing cultivation parameters such as pH, Cu concentration, and carbon source, we successfully produced Bio-CuS NPs with a reduced size, enhanced crystallinity, and superior peroxidase-like activity. Comparative studies with chemically synthesized copper sulfide (Abio-CuS NPs) revealed that Bio-CuS NPs were coated with biomolecules, possessed a greater specific surface area, exhibited abundant sulfur vacancies, and demonstrated higher peroxidase-like activity. Leveraging these properties, Bio-CuS NPs demonstrated a 99.99 % antibacterial efficacy against Escherichia coli and Staphylococcus aureus within 2 h at low HO concentrations (0.8 mM). The antibacterial mechanism was attributed to the synergistic generation of hydroxyl radicals (·OH) and the release of Cu, which sequentially disrupted bacterial cell structure and ultimately led to metabolic dysfunction. In addition, the antibacterial Bio-CuS NPs exhibited outstanding biocompatibility, rendering them highly suitable for environmental applications. This study established a green biosynthesis platform for the production of nanozymes, highlighting the potential of bio-nanoparticles as sustainable antimicrobial agents with dual advantages of eco-friendly production and catalytic bactericidal efficacy.