Investigation of Twenty Metal, Metal Oxide, and Metal Sulfide Nanoparticles' Impact on Differentiated Caco-2 Monolayer Integrity

The use of engineered nanomaterials (ENMs) in foods and consumer products is rising, increasing the potential for unintentional ingestion. While the cytotoxicity of many ENMs has been investigated, less attention has been given to adverse impact on the intestinal barrier integrity. Chronical disruption of gastrointestinal integrity can have far reaching health implications. Using fully differentiated Caco-2 cells, the perturbation of intestinal barrier function and cytotoxicity were investigated for 20 metal, metal oxide, and metal sulfide ENMs. Caco-2 cells were exposed to 50 μg/mL ENMs for 24 hours. ENM formulations were characterized at 0 and 24 hours, and Sedimentation, Diffusion and Dosimetry Modeling was applied to calculate the effective dose of exposure during 24 hours. The apparent permeability coefficient (P) was determined for fluorescent labeled dextran (3,000 Da) and tight junction integrity was evaluated by immunofluorescence microscopy. Cytotoxicity was investigated by determining lactate dehydrogenase release (LDH) and cell metabolic activity (tetrazolium based MTS) assays. Four ENMs led to significantly increased P, (15.8% w/w% Ag-SiO nanoparticle (NP), 60 nm CdS NP, 100 nm VO flakes, and 50 nm ZnO NP), while one ENM (20 nm MgO NP) decreased P. With the exception of CdS NP, significantly increased P was not connected with cell cytotoxicity. The calculated effective dose concentration was not correlated with increased P. Our results illustrate that while many metal, metal oxide, and metal sulfide ENMs do not adversely affect monolayer integrity or induce cytotoxicity in differentiated Caco-2 cells, a subset of ENMs may compromise the intestinal integrity. This study demonstrated the use of differentiated Caco-2 monolayer and P as an endpoint to identify and prioritize ENMs that should be investigated further. The interaction between ENMs and the intestinal epithelium needs to be evaluated to understand potential intestinal barrier dysfunction and resulting health implications.