Stronger Cytotoxicity is Exerted by Nano-/Microplastics Fibers in Lung and Intestinal Cells When Compared with Beads

Abstract

Nano/micro-plastics (NMPs) have emerged as important environmental factors due to their shape-dependent toxicity and potential threat to the environment and human health. Fibers, one of the most predominant shapes in the environment, tend to induce stronger damage when compared with beads. However, a lack of nanoscale fibrous NMP standards has limited the full assessment of their health risks. Here, we prepared polystyrene (PS)-Fibers (diameter = 500 nm and lengths of 5, 10, and 20 μm). First, in respiratory and intestinal epithelial cells, PS-Fibers elicited greater cytotoxicity than PS-Beads, with 10 μm fibers having the most pronounced effects. Second, a pronounced reduction in cell viability and healing ability induced by PS-Fibers was possibly attributed, at least in part, to length-dependent frustrated-phagocytosis-like interactions. These cytotoxic effects were associated with reactive oxygen species (ROS), apoptosis, and mitochondrial damage. Furthermore, the effects were consistently more potent for fibers than beads, with 10 μm fibers exhibiting the greatest toxicity. Fiber length was another key factor in exerting different toxicity levels. Thus, fibrous NMPs enhanced greater cytotoxicity than spherical NMPs, with fiber length a key factor. Among fiber lengths (5/10/20 μm), 10 μm PS-fibers induced the strongest cytotoxicity. ROS generation was the primary cytotoxicity driver mediated by NMPs. Our fibrous NMP preparations may support the development of a standards databank, while our assays confirm that shape-dependent NMP toxicity could provide toxicological evidence for environmental contaminant control.