Size and Aging Effects on Antimicrobial Efficiency of Silver Nanoparticles Coated on Polyamide Fabrics Activated by Atmospheric DBD Plasma

Abstract

This work studies the surface characteristics, antimicrobial activity, and aging effect of plasma-pretreated polyamide 6,6 (PA66) fabrics coated with silver nanoparticles (AgNPs), aiming to identify the optimum size of nanosilver exhibiting antibacterial properties suitable for the manufacture of hospital textiles. The release of bactericidal Ag(+) ions from a 10, 20, 40, 60, and 100 nm AgNPs-coated PA66 surface was a function of the particles' size, number, and aging. Plasma pretreatment promoted both ionic and covalent interactions between AgNPs and the formed oxygen species on the fibers, favoring the deposition of smaller-diameter AgNPs that consequently showed better immediate and durable antimicrobial effects against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus bacteria. Surprisingly, after 30 days of aging, a comparable bacterial growth inhibition was achieved for all of the fibers treated with AgNPs <100 nm in size. The Ag(+) in the coatings also favored the electrostatic stabilization of the plasma-induced functional groups on the PA66 surface, thereby retarding the aging process. At the same time, the size-related ratio (Ag(+)/Ag(0)) of the AgNPs between 40 and 60 nm allowed for the controlled release of Ag(+) rather than bulk silver. Overall, the results suggest that instead of reducing the size of the AgNPs, which is associated with higher toxicity, similar long-term effects can be achieved with larger NPs (40-60 nm), even in lower concentrations. Because the antimicrobial efficiency of AgNPs larger than 30 nm is mainly ruled by the release of Ag(+) over time and not by the size and number of the AgNPs, this parameter is crucial for the development of efficient antimicrobial coatings on plasma-treated surfaces and contributes to the safety and durability of clothing used in clinical settings.

Tannic acid-modified silver nanoparticles for wound healing: the importance of size

“…29 These results are in accordance with other studies showing size-related antibacterial effects of AgNPs. 30,31 The small AgNPs show better inhibitory properties owing to the larger surface to volume ratio as compared to larger spherical AgNPs. The antimicrobial properties of AgNPs are attributed to direct interaction of nanoparticles with bacteria membrane and intracellular proteins as well as to the presence of biocidal ionic silver released from nanoparticle surfaces.…”

“…The antimicrobial properties of AgNPs are attributed to direct interaction of nanoparticles with bacteria membrane and intracellular proteins as well as to the presence of biocidal ionic silver released from nanoparticle surfaces. [30][31][32] Although TA does not inhibit bacterial growth, the presence of TA on the particles' surface helps to increase interaction with the bacteria, since unmodified nanoparticles showed much lower MIC values (Table 1).…”

Silver nanoparticles as an effective disinfectant: A review

“…The bacterial inhibition is observed after 30 days in the presence of Ag NPs with size < 100 nm. Furthermore, a longer period bacterial inhibition is observed at lower concentration with 40-60 nm size Ag NPs [62]. Plasma treated polyester fabric developed for increasing binding property of Ag NPs and pre-treatment initiated both ionic and covalent interactions to create oxygen species on the fibres, resulting deposition of smaller size Ag NPs which promote antimicrobial property [63].The functional clothing has good scope in the market because it has designed to get better performance to the user in the extreme conditions.…”

Study on Surface Properties of Polyamide 66 Using Atmospheric Glow-Like Discharge Plasma Treatment

“…However, after the processed samples are laid up under air condition, the impurities will adsorb on the sample once more to reduce the hydrophilicity. So that the aging effect, i.e., the timeliness, is a significant influence factor under industrial application of the surface modification [29]. Comparing the data in the Table 4, laying up the processed samples Table 4 is focused on the timeliness of this kind of glow-like plasma treatment.…”