The effects of orally administered Ag, TiO 2 and SiO 2 nanoparticles on gut microbiota composition and colitis induction in mice

Nanotechnology offers significant potential benefits to many fields, including food and agricultural industries, which have opportunities to provide products to the general public that could result in ingested nanoparticles (NPs). Herein, we explored the possible impacts of orally administered TiO2NPs, SiO2NPs and AgNPs on gut microbiota composition and colitis induction in mice. We administered the NPs to mice at doses of 2.5 mg/kg bw/day for 7 days, which was a dose relevant to human dietary intake for TiO2NPs and SiO2NPs or the acute oral exposure following medical oral application of AgNPs. No overall toxicity was recorded in mice exposed to TiO2NPs and SiO2NPs except increased pro-inflammatory cytokine levels (IL-1β, IL-6 and TNF-α) in the colons of mice that ingested SiO2NPs. The colitis-like symptoms induced in the mice that ingested AgNPs included high disease activity index and histological scores, disruption of microvilli and tight junctions in the intestinal epithelium, and up-regulation of pro-inflammatory cytokines. Gene analysis by 16S rRNA sequencing showed that AgNP ingestion induced shifts in the intra- and inter-phyla abundance of Bacteroidetes and Firmicutes, reduced the Firmicutes/Bacteroidetes ratio, increased the lowly abundant families of bacteria, and decreased the probiotic bacteria genus Lactobacillus. These results are similar to those reported in studies of other intestinal inflammatory disorders. SiO2NP ingestion in mice increased microbial species richness and diversity within the intestinal tract, and in particular, an obvious increase of the genus Lactobacillus was recorded. No obvious disturbance of gut microbiota was found in mice that ingested TiO2NPs. The study suggests that alterations in microbiota composition are associated with oral responses to nanoparticle exposure.