Stabilization of Ag Nanoparticles and ZnO–Ag Nanocomposite onto L-Methionine-Modified Cotton Fabric for Antibacterial Durability

Antimicrobial properties of metal and metal oxide nanoparticles (NPs) and nanocomposites (NCPs) can be a promising solution to reducing microbe infections. The objective of the present work was to develop washable antibacterial cotton fabrics grafted with L-methionine (MetCot) and coordinately bind silver (Ag) NPs, particularly zinc oxide–silver (ZnO–Ag) NCPs, to exploit their potential synergistic antibacterial properties. MetCot + Ag and MetCot + ZnO–Ag fabrics were analyzed chemically and physically by different techniques. Functionalization of MetCot, in situ, by the NPs and NCPs did not change the cotton fiber structure. The synthesized Ag NPs and ZnO NPs of high purity with an average particle size of 30 and 10 nm, respectively, were uniformly distributed and bound to MetCot. However, functionalization changed MetCot's color to dark yellow–brown shades. Based on essential properties and comfort, the reduction of approximately 12% in vapor permeability and water absorbability, along with a slight decrease in tensile strength and elongation after functionalization of approximately 5–12% for MetCot + Ag and MetCot + ZnO–Ag, should be within the industry's acceptable criteria. MetCot + Ag and MetCot + ZnO–Ag showed excellent antibacterial activity against E. coli and S. aureus after 50 wash cycles. A synergistic effect was observed with MetCot + ZnO–Ag over MetCot + Ag by approximately 7–13%. The amount of Ag NPs and ZnO NPs retained after 50 wash cycles ranged between 80% and 86%. This indicated strong binding to the fabrics. MetCot + Ag and MetCot + ZnO–Ag are biocompatible, as demonstrated by the indirect cytotoxicity assay using 3T3 fibroblast cells with overall cell viability of 95% after 1 and 7 days of exposure.