Chemical and physical transformations of silver nanomaterial containing textiles after modeled human exposure

Abstract

The antimicrobial properties of silver nanomaterials (AgNM) have been exploited in various consumer applications, including in textiles for use as wound dressings. Understanding how these materials chemically transform throughout their use is necessary to predict their efficacy during use and their behavior after disposal. The aim of this work was to evaluate chemical and physical transformations occurring to a commercial AgNM-containing wound dressing during modeled human exposure in synthetic sweat (SW) or simulated wound fluid (WF), which model human exposure scenarios. Scanning electron microscopy with energy dispersive X-ray spectroscopy (EDS) revealed the formation of micrometer-sized structures on the wound dressing surface after SW exposure while WF resulted in a largely featureless surface. Measurements by X-ray photoelectron spectroscopy (XPS) revealed a AgCl surface (consistent with EDS) while X-ray diffraction (XRD) found a mixture of zero valent silver and AgCl, suggesting the AgNM wound dressings surface formed a passivating AgCl surface layer after SW and WF exposure. For WF exposed wound dressings, XPS based findings revealed protein adsorption based on the nitrogen marker which adsorbed released silver at prolonged exposures. Silver release was evaluated by inductively coupled - plasma mass spectrometry which revealed a factor of 36 times more released silver in WF than in SW. Analysis suggests that the protein in WF sequestered a fraction of the released silver in the solution suggesting additional processing at the wound dressing surface occurred after the initial transformation to AgCl. To evaluate the impact on antimicrobial efficacy, zone of inhibition (ZOI) testing was conducted which found no significant change after modeled human exposure compared to the pristine wound dressing. The results presented here suggest AgNM-containing wound dressings transform chemically in simulated human fluids resulting in a material with comparable antimicrobial properties to the pristine wound dressings. Ultimately, knowing the resulting chemical properties of the AgNM wound dressings will allow more predictive models for fate.