Mucus and microbiota as emerging players in gut nanotoxicology: The example of dietary silver and titanium dioxide nanoparticles

Abstract

Given the growing use of nanotechnology in many common consumer products, including foods, evaluation of the consequences of chronic exposure to nanoparticles in humans has become a major public health issue. The oral route of exposure has been poorly explored, despite the presence of a fraction of nanosized particles in certain food additives/supplements and the incorporation of such particles into packaging in contact with foods. After their ingestion, these nanoparticles pass through the digestive tract, where they may undergo physicochemical transformations, with consequences for the luminal environment, before crossing the epithelial barrier to reach the systemic compartment. In this review, we consider two examples, nanosilver and nanotitanium dioxide. Despite the specific features of these particles and the differences between them, both display a close relationship between physicochemical reactivity and bioavailability/biopersistence in the gastrointestinal tract. Few studies have focused on the interactions of nanoparticles of silver or titanium dioxide with the microbiota and mucus. However, the microbiota and mucus play key roles in intestinal homeostasis and host health and are undoubtedly involved in controlling the distribution of nanoparticles in the systemic compartment.

Review of the effects of silver nanoparticle exposure on gut bacteria

“…Currently, citrate, d ‐glucose, sodium dodecyl sulfate, polyvinylpyrrolidone (PVP), polyethylene glycol, amines, polysaccharides (including chitosan) and leaf extracts have been used as stabilizers in the manufacture of AgNPs (Krishnaraj et al, ; Sharma, Yngard, & Lin, ). Stabilizers are used to control the process of AgNP generation and thereafter prevent their aggregation (Liu, Cao, Tang, Chen, & Wang, ; Mercier‐Bonin, Despax, Raynaud, Houdeau, & Thomas, ). Both aggregation and surface coatings can change AgNP toxicity (Lu et al, ) by not only slowing down biodegradation but also significantly increasing antibacterial activity (Wang, Zhao, Zhu, Fang, & Ren, ).…”

“…(Albanese et al, ; Lesniak et al, ; Treuel et al, ; Walkey, Olsen, Guo, Emili, & Chan, ). Additionally, mucus plays an essential role in the preservation of intestinal homeostasis (Mercier‐Bonin et al, ), and Georgantzopoulou et al () found that intestinal mucus affects the transmission rate of different AgNPs. AgNP exclusion due to mucus, which results in the immobilization of larger‐sized particles, decreases their interaction with the cell membrane and consequently reduces their toxicity.…”

“…Stabilizers are used to control the process of AgNP generation and thereafter prevent their aggregation (Liu, Cao, Tang, Chen, & Wang, 2010;Mercier-Bonin, Despax, Raynaud, Houdeau, & Thomas, 2016).…”

“…3 | MECHANISMS OF SILVER NANOPARTICLE ANTIBACTERIAL TOXICITY 3.1 | Release of Ag + Previous studies showed that AgNPs are generally <100 nm and capable of releasing Ag + when exposed to air, water or saline solutions (Chernousova & Epple, 2013;Hadrup & Lam, 2014;Mercier-Bonin et al, 2016;You et al, 2012). Several studies indicated that Ag + ions are potentially lethal to pathogens (Liu et al, 1998;Park et al, 2009) and that the mechanisms associated with AgNP toxicity are largely explained by the action of Ag + .…”

Zinc Oxide Nanoparticles Influence Microflora in Ileal Digesta and Correlate Well with Blood Metabolites

“…Ag NPs and Ti 2 O NPs caused changes in the microbiota and mucus in intestine (Mercier-Bonin et al, 2016). Taylor et al (2015) used an in vitro colon model found that ZnO NPs caused significant changes to the microbial community’s phenotype, which might be related to overall health effects.…”