Impact of Short-Term Exposure of AuNCs on the Gut Microbiota of BALB/c Mice

: The widespread application of nanoparticles causes extensive public concern on their biological safety. However, up to date, few reports have been associated with the impact of metal nanoparticles on gut microbiota in vivo. In this study, gold nanoclusters (AuNCs) were orally administered to BALB/c mice for 7 days, and the dynamic effects of AuNCs on gut microbiota were investigated at 0 h, 4 h, 8 h, 1 d, 3 d and 7 d, respectively. Using high-throughput sequencing of V4-V5 regions of the 16S rRNA gene on the Illumina MiSeq platform, we found that gavage of AuNCs did not significantly change the gut microbiota diversity and community at the initial 3 days. Bacteroidetes, Firmicutes, Proteobacteria, Deferribacteres, Tenericutes and Actinobacteria were the six most abundant phylum in the control and AuNCs groups. However, the phylum Proteobacteria was significantly increased by AuNCs at 7 d (P < 0.05). At the genus level, Roseburia were notably decreased while Staphylococcus, Ureaplasma and Methylobacterium were dramatically increased by AuNCs at 7 d (P < 0.05). Taken together, gavage of AuNCs shifted the bacterial composition at 7 d. This is the first research to investigate the toxicity of AuNCs from the perspective of gut microbiota and opens up a new avenue for the safety or toxicity evaluation of AuNCs.