Combined toxicity evaluation of polystyrene nanoplastics and Nano-ZnO of distinctive morphology on human lung epithelial cells

Despite increasing concerns on the co-exposure of nanoplastics (NPs) and heavy metals including zinc oxide nanoparticles (Nano-ZnO) in the public health, the systematic studies as well as available methodology of combined toxicity evaluation of Nano-ZnO/NPs are lacking. In this study, the single and combined toxicity of Nano-ZnO and polystyrene nanoplastics (PS-NPs) on human lung epithelial cells were evaluated by a combination of in vitro approach including real-time cell analysis (RTCA), cell counting kit-8 (CCK-8), oxidative stress, cell membrane integrity and apoptosis assay. RTCA was employed to dynamically monitor the effect of combined exposure of Nano-ZnO and PS-NPs on cell growth, in comparison with end-point CCK-8 assay. It was found that the cytotoxicity of different Nano-ZnO involved disintegration of cell membrane and causing oxidative stress and apoptosis while PS-NPs mainly induced oxidative stress and apoptosis. The proposed study not only pinpointed the distinctive interaction mode between Nano-ZnO and nanoplastics, but provided integrated approaches to environment and health risk assessment of co-exposed Nano-ZnO and nanoplastics.