Realistic polyethylene terephthalate nanoplastics and the size- and surface coating-dependent toxicological impacts on zebrafish embryos

Nanoplastics (NPs) as pollutants in aquatic environments and as a public health issue due to their accumulation in food chains are of increasing concern. However, previous studies have employed mainly commercial, chemically synthesized polystyrene model particles. Commercial NPs made of polyethylene terephthalate (PET), which is widely used in drinking bottles and packaging, are rarely manufactured, and thus have not been frequently studied in the laboratory. This seriously limits our understanding of their real environmental and biological effects. Herein, we employ a simple method for producing PET NPs directly from plastic bottles, preserving the PET chemical properties, and mimicking the mechanical breakdown process of plastics in nature. Using developing zebrafish embryos as an animal model, we investigate the bioaccumulation andin vivotoxicity of the produced PET NPs, which have diameter sizes of 20, 60-80, and 800 nm and are capped by two dispersing agents,i.e., BSA and SDS. This study demonstrates the size-dependent distribution and the size- and concentration-dependent toxicity of PET NPs in terms of hatching rate, heart rate, and ROS generation. It also reveals that the PETBSANP treatment groups exhibited higher-level abnormalities in heart rate and more severe oxidative damage than the PETSDSNP treatment groups. Taken together, this work proposes a novel mechanical preparation protocol for PET NPs and provides evidence relating to the toxicity of environmentally relevant NPs towards aquatic organisms.