Metabolomics Analysis for Unveiling the Toxicological Mechanism of Silver Nanoparticles Using an In Vitro Gastrointestinal Digestion Model

The increasing use of silver nanoparticles (AgNPs) in consumer products has led to concerns about potential health risks after oral exposure as a result of the transformation and absorption in the gastrointestinal tract (GIT). However, the intricate condition of the GIT poses challenges in understanding the fate and toxicity of AgNPs as they traverse from the mouth to the rectum. For an in-depth understanding of the nanobio interactions, we employed a simulated digestion model to investigate alterations in the physicochemical properties of AgNPs in vitro. Meanwhile, we investigated the underlying toxicological mechanisms of digested AgNPs in enterocytes through metabolomics analysis. In contrast to route means that primarily apply salt solutions to mimic dietary digestion, this in vitro model is a semidynamic sequential digestion system that includes artificial oral, gastric, and intestinal fluids, which are similar to those under physiological conditions including electrolytes, enzymes, bile, pH, and time of digestion. Our results suggest that the formation of Ag–Cl and Ag–S species within the simulated digestion model can lead to an increase in the size of digested AgNPs and that the acidic condition promotes the release of Ag⁺ from particles. More critically, the presence of digestive enzymes and high concentrations of salt enhances the uptake of Ag by human colon enterocytes, ultimately promoting ROS generation and exacerbating cytotoxicity. Metabolomics analysis further reveals that the sequentially digested AgNPs may disorder lipid metabolism, including the biosynthesis of unsaturated fatty acids and arachidonic acid metabolism, thus increasing the possibility of ferroptosis activation in enterocytes. These findings offer significant insights into the fate and potential adverse effects of AgNPs in the GIT, providing important implications for assessing the health risks of AgNPs via oral exposure.