Review of the effects of silver nanoparticle exposure on gut bacteria

Abstract

Gut bacteria are involved in regulating several important physiological functions in the host, and intestinal dysbacteriosis plays an important role in several human diseases, including intestinal, metabolic and autoimmune disorders. Although silver nanoparticles (AgNPs) are increasingly being incorporated into medical and consumer products due to their unique physicochemical properties, studies have indicated their potential to affect adversely the gut bacteria. In this review, we focus on the biotoxicological effects of AgNPs entering the gastrointestinal tract and the relationship of these effects with important nanoscale properties. We discuss in detail the mechanisms underlying the bactericidal toxicity effects of AgNPs and explore the relationships between AgNPs, gut bacteria and disease. Finally, we highlight the need to focus on the negative effects of AgNPs usage to facilitate appropriate development of these particles.

Silver Nanoparticles against Foodborne Bacteria. Effects at Intestinal Level and Health Limitations

“…In the case of antimicrobial silver nanoparticles with application in food industry, the subject of this review, the main human exposure source is through the oral-gastrointestinal tract [68]. The mean dietary exposure level of Ag-NPs is estimated at 70-90 µg/day [69]. After ingestion, the Ag-NPs come in contact with lumen of the oral cavity and esophagus.…”

“…There is little published information on the absorption rate of particulates through the epithelium of these two compartments, probably due to both a low surface area and a short residence time for most food matrices [68]. After that, during the gastrointestinal digestion process in the stomach and small intestine, the interaction of Ag-NPs with biological fluids can lead to its agglomeration, aggregation, and dissolution [69][70][71][72][73]. In addition, silver nanoparticle absorption (transcellular and paracellular transport and vesicular phagocytosis) through the gastrointestinal tract epithelium could take place.…”

“…In addition, silver nanoparticle absorption (transcellular and paracellular transport and vesicular phagocytosis) through the gastrointestinal tract epithelium could take place. Finally, the nanoparticles that escape the absorption process reach the colon where they could modulate the composition and/or activity of gut microbiota, affecting the production and toxicity of bacterial metabolites [69]. Part of the initial intake of nanoparticles could be extracted in feces.…”

Genotoxicity of Silver Nanoparticles

“…When AgNPs are internalized, they are usually stored in vesicles in the cytoplasm. There is no evidence that they the nucleus but there is a theoretical possibility of direct DNA contact when the nuclear membrane breaks down during mitosis [29,31]. Moreover, it is worth noting that AgNPs interactions with the cell membrane can also produce toxic effects, mainly due to oxidative stress.…”

“…routes, including inhalation, dermal contact and oral ingestion, which is the most significant route. According to Boudreau et al [57], the human dietary intake of silver generally varies from 0.4 to 27 μg a day; however, Vila et al [53] and Wijnhoven et al [46] claim that the dietary intake of AgNPs is between 70 to 90 μg a day, and, Li Tang and Xue [29], agree that the daily intake of silver in humans may be as high as 90 μg.…”