Nanocellulose-directed ultrasmall copper nanoparticles for durable antimicrobial interfaces

Copper nanoparticles (CuNPs) are potent antimicrobial agents; however, their practical application is often limited by uncontrolled aggregation, poor control over particle size and distribution, oxidation-driven instability, and excessive Cu ion release, which can compromise long-term antimicrobial performance and increase cytotoxicity risks. We established a synthesis strategy in which TEMPO-oxidised cellulose nanofibers (TCNF) direct the nucleation and growth of ultrasmall, uniformly dispersed CuNPs that are immobilised along individual nanofibers. The resulting CuNP/TCNF hybrid was applied as a coating onto commercial polypropylene (PP) nonwoven fabrics used in surgical face masks. The coatings exhibited rapid and broad-spectrum antimicrobial activity, achieving complete inactivation of Staphylococcus aureus, Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Streptococcus pneumoniae within 30 min. The material also demonstrated ∼99% reduction of A/H1N1 influenza virus after 15 min. Notably, the antimicrobial performance was retained under high-humidity conditions mimicking respiration, and the coatings showed no cytotoxicity toward L929 fibroblasts over 48 h. Mechanistic studies revealed that immobilised CuNPs induce controlled intracellular reactive oxygen species accumulation, enabling efficient pathogen inactivation while minimising copper release. This nanocellulose-templated CuNP platform provides a sustainable, durable, and safe approach for potential next-generation antimicrobial textiles and surface coatings in health and medical sectors.