Micro- and nanoplastics differ in particle-mucus interactions: the sight on rheological properties, barrier dysfunction and microbiota dysbiosis

Abstract

Micro- and nanoplastics (MNPs) in food can cross the intestinal barrier and accumulate in multiple organs. Mucus serves as a vital defense against such invaders, but the nature of its interaction with MNPs remains unclear. In this study, we investigated changes in the rheological properties of mucus and the physicochemical properties of MNPs in co-incubation. The effects of MNPs on the mucus layer and gut microbiota were also assessed in vivo at environmentally relevant doses. MNPs adsorbed proteins in mucus, increasing apparent particle size, and reducing the surface charges. They broke the selective permeability of barrier and destroyed the histomorphology and microenvironment of microbiota in mice. Notably, nanoplastics were wrapped in mucus. They induced mucus secretion, crosstalk of microbiota, and reactive oxygen species (ROS) burst. Microplastics reduced the composite viscosity of mucus and thinned the mucus layer, facilitating diversification of harmful bacteria. Size plays a crucial role in particle-mucus interactions: nanoplastics tend to penetrate the mucus layer and disrupt microbial colonization, while microplastics contribute to mucus depletion. The physicochemical properties of MNPs and mucus characteristics affect microbial community, modulating the MNPs biotoxicity. These findings provide insights into mucus barrier homeostasis in health risk of MNPs.