Impact of food components and digestive enzymes on silver nanoparticles cytotoxicity in a coculture model of the intestinal barrier

Known as “the material of the 21st century”, nanomaterials have revolutionized many industrial sectors during the last decades. Concerning the food industry, engineered nanomaterials (ENMs) have been added intentionally in commercial food products to enhance their quality, safety or shelf-life but also to provide specific flavors or colors. Silver nanoparticles (AgNPs) are currently the nanomaterial found in the highest number of consumer products thanks to their antibacterial properties: dietary supplements, plastic food containers, fridges, … The inevitable use of these products leads to the unintentional exposure of consumer’s digestive system to AgNPs. Indeed, the risk of AgNPs ingestion due to their migration from the products is recognized and reported in many studies, such as their deleterious effects in vitro and in vivo. Such considerations raise the need of toxicological studies about AgNPs, especially that account for the physico-chemical transformations of AgNPs occurring when they are incorporated into food and digested as they transit the gastro-intestinal tract (GIT). Although the GIT and food have been demonstrated to alter AgNPs cell’s interactions, only few studies take in account these effects. In this master thesis however, we investigated the impact of food components and digestion on the toxicity of AgNPs. Thanks to a modelized food matrix and an in vitro digestion process, these two effects could be reproduced and their impact on the cytotoxic effect of AgNPs assessed in a coculture model of the human intestinal epithelium consisting of Caco-2 and HT29-MTX cells. The food matrix seemed to reduce AgNPs inherent toxicity while digestive enzymes worsened it. Together, digestive enzymes and food component induced such changes that the toxicity of AgNPs was also increased. Further characterization and protein quantification experiments gave us lines of explanations. Indeed, the presence of a protein corona is strongly indicated and can explain the protective effect of food components. Digested enzymes were suggested to alter AgNPs characteristics or have a potential higher activity consequently to their interaction with AgNPs. Our results indicate that toxicity of AgNPs can be strongly influenced by the presence of food components and digestive enzymes and reproducing both parameters is important to draw realistic and truthful interpretations. Further experiments should focus on the characterization of the composition of the protein corona upon incubation of AgNPs with the food matrix but also throughout the whole digestion process to have an insight of the new biological identity acquired by AgNPs.