DBD Plasma treatment and chitosan layers - A green method for stabilization of silver nanoparticles on polyamide 6,6

The addition of silver nanoparticles (AgNPs) to biomedical textiles can be of great interest to protect the materials against microorganisms, providing higher durability, and also to prevent the spread of microorganisms by contact or release of active antimicrobial silver ions. Textiles can act as a containing or drug release system to prevent healthcare-associated infections and facilitate the wound healing process. However, the human and environmental over-exposure to AgNPs during manufacturing, handling and disposal is leading to numerous concerns due to the AgNPs toxicity that may comprise DNA perturbation and metabolism damage in healthy cells. Thus, improve the AgNPs deposition onto textiles and control their release is crucial to minimize or prevent the AgNPs side effects. Atmospheric dielectric barrier discharge (DBD) plasma treatment is a dry environmental-friendly and cost-competitive method allowing continuous and uniform processing of fibres surfaces without the use of any chemicals or costly gases. In this work, AgNPs were stabilized onto polyamide 6,6 fabrics (PA66) through DBD plasma treatment and the use of chitosan (Ch) layers. The different formulations were obtained by spray where one first layer of Ch was applied, followed by a second layer of nanoparticles dispersed in ethanol (Ch+AgNPs). A final chitosan protective layer was also considered (Ch+AgNPs+Ch) and samples with just AgNPs were used as control. The combination of DBD plasma treatment and different layers of Ch makes it possible to control the amount and oxidation state of nanoparticles in the composites and consequently, manage the antimicrobial performance of the fabrics. DBD plasma treatment revealed a crucial role in AgNPs adhesion (4.8 and 6.3 At%) by the increase of the surface roughness and the introduction of new functional groups onto fabrics surface. The first layer of Ch decreased the AgNPs adhesion in both untreated and DBD plasma-treated samples but treated samples showed higher concentration (1.7 and 4.1 At%). The antibacterial activity was evaluated against Staphylococcus aureus and Escherichia coli after 2 and 24h, showing a superior action in all samples with DBD plasma-treated samples after 24h. The Ch in the first layers of the composite delayed the antimicrobial action of the samples. However, the use of Ch in some cases enhance the antimicrobial action of the composites. The obtained coatings will allow the development of novel and safe wound dressings able to control the antimicrobial action.