Enhancing optical properties and antimicrobial efficiency of polyamide-6 for medical applications

Abstract Polyamide-6 (PA-6) fibers are valued for their high mechanical strength and cost-effectiveness, but their inherent hydrophobicity restricts their applicability. To enhance functionality, a grafting process was applied at both low and high yields, enabling effective treatment of PA-6 fibers with silver nanoparticles (Ag NPs) to impart antimicrobial properties. An in situ approach was employed to embed Ag NPs within the PA-6 fibers. The antimicrobial efficacy of the modified fibers was assessed against multidrug-resistant (MDR) pathogens, including methicillin-resistant, extended-spectrum beta-lactamase-producing, and quinolone- and carbapenem-resistant strains, using the shake flask method with optical density measurements. Fourier-transform infrared spectroscopy (FTIR) characterized the chemical changes associated with grafting and Ag NP incorporation. Scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDX) provided insights into fiber morphology and elemental composition, verifying the successful surface loading of Ag NPs. The Multiple Beam Fizeau fringes technique was used to evaluate optical properties, such as refractive index and birefringence, as indicators of structural changes. Although grafting reduced the optical properties initially, subsequent Ag NP treatment restored them. The PA-6-g-PAA 7%-t-Ag NPs fibers exhibited superior optical properties relative to PA-6-g-PAA 20.7%-t-Ag NPs fibers, though with lower antimicrobial impact on sensitive organisms. Conversely, PA-6-g-PAA 20.7%-t-Ag NPs showed significant antimicrobial activity against MDR pathogens. As a result, PA-6-g-PAA 20.7% is identified as the optimal choice, balancing effective antimicrobial properties with enhanced optical performance, suggesting its potential in antimicrobial fiber applications for medical use.