Surface functionalized polystyrene nanoplastics impair nutrient assimilation from corn kernels (Zea mays L.) in a simulated human digestive tract

Nanoplastics can be co-ingested with other food constituents by humans via food chain transfer, posing a potential risk to human health. Here, the impact of concentrations and surface chemistry (-COOH and -NH) of polystyrene nanoplastics (PS NPs) on nutrient bioaccessibility of corn kernels and the digestibility of corn starch was examined using a simulated gastrointestinal (INFOGEST) model. All types of PS NPs significantly reduced the bioaccessibility of phytochemicals in the corn, e.g., phenolic acids and flavonoids by 7-35 % and glucosides by 2-16 %. Moreover, the extent of starch digestion as determined by the glucose release was significantly decreased from 95 % to 74 % after exposure to three types of PS NPs. Phytochemicals with aromatic rings or hydroxyl groups could adsorb onto the PS NPs surfaces, and therefore not be available for absorption. Additionally, individual or aggregated PS NPs could adsorb onto starch granule surfaces, thereby inhibiting the ability of the digestive enzymes to access the surface of macronutrients. PS NPs could interact with the digestive enzymes (e.g., amylases, pepsins, and pancreatins) and reduce their activity by inducing conformational changes that compromise function. These findings have important implications for assessing the potential impact of ingested PS NPs on human nutrition and health.