Cytotoxicity of Nanoparticles Contained in Food on Intestinal Cells and the Gut Microbiota

Abstract

Toxicity of nanoparticles (NPs) upon oral exposure has been studied in animals using physiological changes, behavior, histology, and blood analysis for evaluation. The effects recorded include the combination of the action on cells of the exposed animal and the reaction of the microorganisms that populate the external and internal surfaces of the body. The importance of these microorganisms, collectively termed as microbiota, for the health of the host has been widely recognized. They may also influence toxicity of NPs but these effects are difficult to differentiate from toxicity on cells of the gastrointestinal tract. To estimate the likelihood of preferential damage of the microbiota by NPs the relative sensitivity of enterocytes and bacteria was compared. For this comparison NPs with antimicrobial action present in consumer products were chosen. The comparison of cytotoxicity with Escherichia coli as representative for intestinal bacteria and on gastrointestinal cells revealed that silver NPs damaged bacteria at lower concentrations than enterocytes, while the opposite was true for zinc oxide NPs. These results indicate that silver NPs may cause adverse effects by selectively affecting the gut microbiota. Fecal transplantation from NP-exposed animals to unexposed ones offers the possibility to verify this hypothesis.

Is nano safe in foods? Establishing the factors impacting the gastrointestinal fate and toxicity of organic and inorganic food-grade nanoparticles

“…20 It has been estimated that adults may consume between 20 and 80 μg/day of silver, with only a fraction of this being in the form of nanoparticles. 12 At present there is still limited information about the potential toxicity of silver nanoparticles ingested with foods, 15 with some studies reporting no toxicity and others reporting appreciable toxicity. The GIT may be particularly susceptible to silver nanoparticle-induced toxicity since it contains the first tissues exposed to dietary nanoparticles after ingestion.…”

“…33 The strong antimicrobial activity of silver nanoparticles may also alter the nature of the gut microbiota, especially if they reach the colon. 12,34 The effects of the food matrix on the behavior of silver nanoparticles are ignored in cell culture studies, but one recent study showed that certain food components did have an appreciable impact on the absorption and toxicity of silver nanoparticles in intestinal cells. 35 A common issue with cell culture studies is that the dose of nanoparticles used is much higher than would ever be found in practice, and is therefore not physiologically relevant.…”

“…[67][68][69][70][71] The ability of TiO 2 nanoparticles to exhibit these toxic effects has been attributed to numerous mechanisms, including generation of ROS species that damage key cellular constituents, interference with efflux pumps and nutrient transporters, induction of inflammation, and alteration of the gut microbiota. 12,72,73 Anatase TiO 2 nanoparticles were reported to be more toxic to cells than rutile nanoparticles due to their higher photo-catalytic activity. 74 A cell culture study showed that a mixture of anatase and rutile forms caused more severe cytotoxic and genotoxic damage than pure anatase or pure rutile titanium dioxide nanoparticles.…”

“…It has been estimated that the intake of SiO 2 is around 20-50 mg/ day per person. 12 Studies have reported that the individual nanoparticles in commercial SiO 2 ingredients typically have diameters from about 10 to 50 nm, but that these nanoparticles often exist in the form of larger clusters, usually in the range 100-1000 nm. 80 Cell culture and animal feeding studies suggest that high levels of SiO 2 nanoparticles may cause adverse effects, such as cytotoxicity and generation of ROS.…”

“…11 Moreover, nanoparticles may damage the microbial cells that normally populate the human GIT, which could indirectly alter human health. 12 …”