Ultrastructure of the gut epithelium in Acheta domesticus after long-term exposure to nanodiamonds supplied with food

•The influence of nanodiamonds (ND) on the gut epithelium of Acheta domesticus was investigated.•Changes in the epithelial ultrastructure depended on the ND concentration in food.•The epithelia of midgut and hindgut were damaged by the ND, although the foregut was not.•The ND supplied with food caused the activation of autophagy (mitophagy and reticulophagy).•Caution should be maintained when using nanodiamonds on a large scale.

The biosafety of nanoparticles and the potential toxicity of nanopollutants and/or nanowastes are all currently burning issues. The increased use of nanoparticles, including nanodiamonds (ND), entails the real risk of their penetration into food chains, which may result in the contamination of animal and, as a result, human food. Knowledge about changes in the ultrastructure of tissues in organisms that have been exposed to ND is still very limited. The aim of the study was to describe the ultrastructure of the gut epithelium in Acheta domesticus after exposure to different concentrations of ND (0, 20 or 200 μg g−1 – control, ND20 and ND200 groups, respectively) administered with food over a five-week period. The ultrastructure of the foregut, midgut and hindgut was assessed using Transmission Electron Microscopy (TEM). A number of changes in the structure of the gut in crickets that had consumed nanodiamond-contaminated food were observed. The epithelium of the midgut and hindgut were clearly damaged by ND, although the foregut was not affected. A positive relationship between the ND concentration in food and the degree of damage to the structure of epithelial cells was observed. Autophagy, especially mitophagy and reticulophagy, was activated in relation to the appearance of ND particles. A putative ND toxicity mechanizm is proposed. Extreme caution should be maintained when using nanodiamonds on a large scale.