Effects of Oral Exposure to Mn-Doped ZnS Quantum Dots on Intestinal Tract and Gut Microbiota in Mice.

Yanjie Yang,Shaoping Ji,Shuangyu Lv,Xiaomei Zhang,Xu Wang,Ruixue Xia,Honggang Wang,Yuchen Zhou,Yu Feng

doi:10.3389/fphys.2021.657266

Abstract

Mn-doped ZnS quantum dots (QDs) with excellent optical properties have been explored in a wide range of fields. Their potential adverse effects on biological systems and human health should be evaluated before biological application. In the present study, we investigated the effect of Mn-doped ZnS QDs on the intestinal tract and gut microbiota structures at 2 h and 14 days (d) after 14 d repeated oral exposure in mice. Flame atomic absorption spectrophotometry (FAAS), histopathological examination, and transmission electron microscopy (TEM) were used to assess the absorption and toxicity of Mn-doped ZnS QDs on the intestinal tract. The 16S rRNA gene sequencing was used to evaluate the gut microbial communities. Mn-doped ZnS QDs did not accumulate in the duodenum, jejunum, ileum, or colon. The Zn content of feces was not significantly higher than in the control group. No major histological changes were found in these tissues. The intestinal microvilli remained regular, but swelling of mitochondria and endoplasmic reticulum was detected by TEM at 14 d after the last gavage. A total of 2,712 operational taxonomic units (OTUs) were generated. Mn-doped ZnS QDs treatment did not significantly change the α-diversity of Richness, Chao1, Shannon, and Simpson indexes. According to principal component analysis (PCA), Mn-doped ZnS QDs had no effect on the overall structure of the gut microbiota. No significant change occurred at the phylum level, while three genera were downregulated at 2 h and seven changed at 14 d after the last gavage. Our findings revealed that Mn-doped ZnS QDs had a little stimulation of the intestinal tract and gut microbiota, and oral administration may be a safe route for biological application (such as bioimaging and drug delivery).

Highlights

Quantum dots (QDs) are semiconductor nanomaterials with unique optical properties, such as broad excitation and narrow emission spectra (Yaghini et al, 2018)
The Zn content of the intestinal tract and fecal samples from the control group and mice gavaged for 14 d with Mn-doped ZnS QDs gavaged for 14 d mice were measured using Flame atomic absorption spectrophotometry (FAAS) (Figure 1)
Mice were subjected to repeated oral exposure to Mn-doped ZnS QDs for 14 d, and the toxicity in the intestinal tract and gut microbiota was assessed at 2 h and 14 d after the last gavage

Summary

Introduction

Quantum dots (QDs) are semiconductor nanomaterials with unique optical properties, such as broad excitation and narrow emission spectra (Yaghini et al, 2018). The fluorescence selfquenching may limit QDs application, but doping could avoid this problem due to the substantial ensemble Stokes shift (Yang Y. et al, 2015). Mn-doped ZnS QDs with excellent optical properties have been explored in biosensing, detecting, imaging, and drug delivery (Bwatanglang et al, 2016; Yang et al, 2019). The widespread production and application inevitably cause the direct and indirect release of Mn-doped ZnS QDs and their byproducts into the environment, which may lead to unpredictable health effects (Heim et al, 2015; Zhao et al, 2016). It is necessary to evaluate the potential toxic effects of Mn-doped ZnS QDs to understand their potential adverse effects on biological systems and human health. The characterization of the permeability and uptake of Mn-doped ZnS QDs in intestinal cells is indispensable before biological application

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