The role of human intestinal mucus in the prevention of microplastic uptake and cell damage

An increase in plastic waste and its release into the environment has led to health concerns over microplastics (MPs) in the environment. The intestinal mucosal layer is a key defense mechanism against ingested MPs, preventing the migration of particles to other parts of the body. MP migration through intestinal mucus is challenging to study due to difficulties in obtaining intact mucus layers for testing and numerous formulations, shapes, and sizes of microplastics. Previous studies have primarily used mucus from animals, hydrogel models, and mucus samples from other parts of the body as substitutes. This study examines how different MP compositions, sizes (40-500 nm), and surface functionalizations alter MP migration through human intestinal mucus; how the mucus layer protects cells from MP uptake, toxicity, and inflammation; and how the intestinal mucus prevents the migration of other environmental toxins via MP particles. The presence of a mucus layer also provides critical protection against cytotoxicity, reactive oxygen species production, and uptake for all particles tested, although certain functionalizations, such as streptavidin, are particularly harmful to cells with high toxicity and inflammation. Understanding the properties that assist of impede the diffusion of MPs through mucus is relevant to the overall bioaccumulation and health effects of MPs as well as drug delivery purposes.