Abstract:

Objective The threat posed by bacterial and drug-resistant infections necessitates advanced antibacterial materials. This study enhances the efficacy of aminated polyacrylonitrile fibers through loading copper oxide nanoparticles， aiming to achieve high performance against MRSA and to elucidate the associated antibacterial mechanisms.

Method Aminated polyacrylonitrile fibers were functionalized with copper ions and in-situ reduced using ascorbic acid to deposit copper oxide nanoparticles. The composites were characterized by SEM， FT-IR， XRD and XPS. Antibacterial activity against E. coli， S. aureus， K. pneumoniae， E. faecalis， C. albicans and MRSA was evaluated via shaking flask assays. Mechanism studies included copper release measurement， Zeta potential analysis， bacterial morphology observation （SEM/TEM） and extracellular K⁺ detection.

Results A series of Cu₂O-loaded aminated polyacrylonitrile fibers were successfully synthesized. SEM analysis revealed that the smooth surface of pristine APAN fibers became progressively rougher with the incorporation of irregular spherical nanostructures upon Cu₂O loading. The sample with the best antibacterial performance was labeled as APC-30， and it exhibited the most homogeneous distribution of Cu₂O nanoparticles， with sizes ranging between 50-100 nm. FT-IR and XRD confirmed the successful coordination of copper and the presence of crystalline Cu₂O， with XRD peaks corresponding to （110）， （111）， （200）， （220）， and （311） planes. XPS analysis indicated the co-existence of both Cu（I） and Cu（II） species on the fiber surface， with APC-30 showing an optimal balance. Antibacterial assessments demonstrated outstanding performance. Within 2 h， the APC-30 fiber achieved inhibition rates of 97.65% against E. coli， 95.75% against S. aureus， 99.46% against K. pneumoniae， 99.35% against E. faecalis， 95.20% against C. albicans， and 93.96% against MRSA. Notably， against the high-risk pathogen MRSA at a concentration of 7×10⁸ CFU/mL， a dose of only 2.5 g/L of APC-30 resulted in a 99.98% reduction. Durability tests affirmed excellent wash resistance； after 30 laundering cycles， APC-30 retained antibacterial rates above 91% for E. coli and 88% for S. aureus. Mechanistic studies revealed a multi-modal action. APC-30 demonstrated a controlled copper ion release （up to 4.385 mg/L in solution）， which directly compromised bacterial membrane integrity as visualized via SEM/TEM， showing cell shrinkage， rupture， and deformation. The fiber surface possessed a positive Zeta potential （+18.7 mV）， facilitating electrostatic attraction with negatively charged bacterial cells. Furthermore， a significant increase in extracellular K⁺ concentration was detected after contact with APC-30， confirming cytoplasmic leakage and loss of membrane integrity. The synergistic effect between released copper ions and surface electrostatic interaction is proposed as the core antibacterial mechanism.

Conclusion This study successfully developed a high-performance antibacterial fiber composite by grafting amination and in-situ loading of Cu₂O nanoparticles onto polyacrylonitrile fibers. The optimized APC-30 fiber exhibited exceptional， rapid， and broad-spectrum antibacterial activity， including potent efficacy against drug-resistant MRSA， while maintaining remarkable durability through repeated washing. The antibacterial function is attributed to a synergistic mechanism involving controlled release of bactericidal copper ions， direct physical damage to microbial membranes， and electrostatic adhesion between fiber and cells. These findings underscore the potential of Cu₂O/APAN c

Key words: functional fiber, cuprous oxide, polyacrylonitrile, antibacterial property, antibacterial mechanism, broad-spectrum antibacterial, modified fiber