Food allergen binding to pristine PET nanoplastic and their effect on allergic immune responses in vitro

Plastic pollution is steadily increasing and has been linked to several diseases. At the same time, there has been an increase in allergic diseases over the past decades, with evidence suggesting a connection to environmental pollution. Since human exposure to plastic pollution is inevitable, the effects of nanoplastics (NPs) on allergic responses need to be elucidated. Therefore, we investigated the binding of food allergens to various pristine polyethylene terephthalate (PET) NPs, and their effect on allergic responses in vitro. We found that nanosized PET (nPET) NPs did not induce acute or long-term cytotoxicity in peripheral blood mononuclear cells and Caco-2 cells, nor did they cause epithelial barrier disruption using 5 µg mL^-1. Furthermore, allergen transport over Caco-2 monolayers was not affected by long-term exposure to nPET. Importantly, food allergens (bovine β-lactoglobulin, shrimp tropomyosin and bovine lactoferrin) were bound with different affinity to PET NPs (Kd 4.6-107.1 nM). This was reflected in the ability of the allergens to influence aggregation behavior, as well as in the varying amounts of allergen bound in the hard corona. When presented to monocyte derived dendritic cells, allergens in the nPET corona were taken up to a higher extent than allergens alone. However, no changes in activation of co-stimulatory markers were found. Finally, the allergenic activity of allergens in the nPET corona was preserved compared to allergen alone, assessed by a mediator release assay and basophil activation test. In conclusion, we found that PET NPs can carry allergens that are internalized to a higher extent by monocyte-derived dendritic cells than non-bound allergens and can activate effector cells ex vivo, which may affect the immune response in allergic individuals.