Industrial Multi-walled Carbon Nanotubes Undergo Biodegradation in the Mouse Gastrointestinal Tract

The growing production and use of multi-walled carbon nanotubes (MWCNTs) increases the risk of their entry into food chains; therefore, it is necessary to assess the possibility of MWCNT removal and destruction in the gastrointestinal tract (GIT) of animals. The purpose of this study is to identify variants of destruction of industrial MWCNTs after passing through the mouse gastrointestinal tract using Raman spectroscopy and standard and analytical electron microscopy. Changes in the density of defects, wall perforations, and disintegration into small fragments have been recorded in MWCNTs isolated from feces. These changes are more clearly defined than the degradation of MWCNTs under the influence of gastric juice or hydrochloric acid alone. The nanotube biodegradation products retain their crystalline structure, which makes it possible to identify them by electron diffraction. No nanomaterial was detected in the cells or in the intercellular space of the gastric and colon mucosa. Therefore, it is shown that the gastrointestinal epithelium is an effective barrier to MWCNTs and the biodegradation of MWCNTs begins in the stomach and continues in the intestines, leading to their destruction.