Toxicity of polyethylene terephthalate and polylactic acid nanoplastics, pristine and weathered in environmentally-relevant conditions, to human intestinal cells representative of genetic susceptibility to Crohn's disease

Environmental pollution by micro- and nanoplastics (MNPs) raises concerns about their toxicity to humans, particularly through ingestion. While the impact of native MNPs is increasingly documented, environmentally degraded MNPs remain poorly studied. We assessed the intestinal impact of biodegradable and non-biodegradable nanoplastics (NPLs), polyethylene terephthalate (PET) and poly-lactic acid (PLA), both pristine and weathered in environmental conditions. The response of an in vitro intestinal model representative of healthy populations was compared with that of a model of genetic susceptibility to inflammatory bowel disease (IBD), using HT29-MTX cells cocultured with Caco-2 cells expressing either wild-type or mutated nucleotide-binding oligomerization domain 2 (NOD2). Non-differentiated and differentiated cells were exposed for 24 h to these NPLs. Cellular uptake, cytotoxicity, genotoxicity, oxidative stress, inflammation, and epithelial barrier integrity were evaluated. Although PET and PLA accumulated in cells, they showed no significant toxicity. Therefore, as demonstrated for polystyrene NPLs, PLA and PET particles do not cause major toxic impact to intestinal cells upon acute exposure in vitro and, in this exposure scenario, weathering in environmental conditions does not increase their toxicity.