Environmental protein corona on nanoplastics altered the responses of skin keratinocytes and fibroblast cells to the particles.

The surface of nanoplastic particles (NPs) in the aquatic environment is always modified by organic matter in water, including protein components. The modifications are likely to affect interactions at the nano-bio interface, leading to an altered cellular response in humans. This study aimed to identify the changes in skin cell responses to the NPs conditioned by the proteins in natural seawater. The NPs were first conditioned by natural seawater, allowing an environmental corona to develop on the surface of the NPs. This was confirmed by electron microscopy. The cell internalization pathways of NPs with or without environmental corona were identified on skin keratinocytes and fibroblast cells by selective blockage of one of the four classic cell endocytic pathways. The intracellular locations of those NPs in keratinocytes and fibroblasts were demonstrated by co-localization of the particles and cell organelles. We also determined the genetic response of the keratinocytes to the environmentally conditioned NPs. The results showed that new internalization pathways by keratinocytes and fibroblast cells were activated by the environmental corona on NPs compared to the original NPs without surface corona. The surface corona of NPs also altered the NPs' intracellular locations in both keratinocytes and fibroblasts. The internalization of NPs with environmental corona induced the production of toll-like receptor 4, tumor necrosis factor alpha, cyclooxygenase-2, and interleukin 8 in keratinocytes. Since these factors are all involved in inflammatory responses and immune cell regulation, they can potentially trigger proinflammatory and chemotactic effects in human skin.