Double-Sided Nano-ZnO: Superior Antibacterial Properties and Induced Hepatotoxicity in Zebrafish Embryos

Zinc oxide nanoparticles (Nano-ZnO) have been widely used in the food, cosmetics, and biomedical fields due to their excellent antibacterial and antioxidant properties. However, with the widespread application of Nano-ZnO, Nano-ZnO inevitably enters the environment and living organisms, causing harm to human health and ecosystem safety. Therefore, the biosafety and toxicological issues of Nano-ZnO are gradually being emphasized. Our study found that Nano-ZnO has superior antibacterial properties compared to ofloxacin in the fight against Staphylococcus aureus (S. aureus). Given that ofloxacin can inhibit bacterial-induced inflammation, we constructed a model of bacterial inflammation using S. aureus in zebrafish. We found that Nano-ZnO inhibited the NF-κB-mediated inflammatory signaling pathway. However, in the process, we found that Nano-ZnO caused hepatic steatosis in zebrafish. This suggested that Nano-ZnO had a certain hepatotoxicity, but did not affect liver development. Subsequently, we investigated the mechanism of hepatotoxicity produced by Nano-ZnO. Nano-ZnO triggered oxidative stress in the liver by generating ROS, which then induced endoplasmic reticulum stress to occur. It further activated srebp and its downstream genes fasn and acc1, which promoted the accumulation of fatty acid synthesis and the development of steatosis, leading to the development of nonalcoholic fatty liver disease (NAFLD). To address the hepatotoxicity of Nano-ZnO, we added carbon dots for the treatment of NAFLD. The carbon dots were found to normalize the steatotic liver. This provided a new strategy to address the hepatotoxicity caused by Nano-ZnO. In this work, we systematically analyzed the antibacterial advantages of Nano-ZnO in vivo and in vitro, explored the mechanism of Nano-ZnO hepatotoxicity, and proposed a new method to treat Nano-ZnO hepatotoxicity.