Novel Core-Shell Nanostructure of ε-Poly-L-lysine and Polyamide-6 Polymers for Reusable and Durable Antimicrobial...

Antimicrobial function in protective and medical textiles is an essential safety feature since textiles can become breeding grounds for microorganisms. Ideally, the antimicrobial function in textiles should be non-toxic, stable, and durable. This study explores a core-shell nanofiber with a core of the cationic biopolymer ε-poly-L-lysine (PL) and shell of structurally similar and biocompatible polyamide-6 (PA). The core-shell structure is expected to have a more stable antimicrobial function than its monolithic counterpart. Further, thermal crosslinking is expected to prevent rapid diffusion of the water-soluble PL. Therefore, this study establishes a comparison between a monolithic (control), a core-shell (CS), and a thermally crosslinked core-shell (CL-CS) nanofiber of PL and PA. Morphological analysis confirmed the successful generation of the core-shell nanofibers. All the samples exhibited hydrophilic behavior and antimicrobial function. However, the control sample showcased significantly reduced zones of inhibition in antimicrobial testing with 21 days of bacterial exposure (1.027 ± 0.072 cm²), as compared to 24 h bacterial exposure (1.347 ± 0.151 cm²). On the other hand, the zones of inhibition for 24 h vs. 21 days for CS (1.265 ± 0.042 cm² vs. 1.052 ± 0.235 cm²) and CL-CS (1.128 ± 0.161 cm² vs. 1.106 ± 0.047 cm²) showed no significant differences. Therefore, the core-shell structure allowed for sustainable and durable antimicrobial action. Lastly, the CL-CS sample exhibited reusable antimicrobial function owing to the core-shell structure paired with thermal crosslinking. This study showcases a fiber system with non-toxic, durable, and reusable antimicrobial function. This study builds grounds for the development and multifaceted holistic characterization of safe, stable, and scalable antimicrobial textiles.