An in vivo study on the photo-enhanced toxicities of S-doped TiO₂ nanoparticles to zebrafish embryos (Danio rerio) in terms of malformation, mortality, rheotaxis dysfunction, and DNA damage

Abstract

The role of light on the acute toxicities of S-doped and Sigma TiO₂ nanoparticles in zebrafish was studied. Metrics included mortality for both, and rheotaxis dysfunction and DNA damage for S-doped only. It was found that the acute toxicity of S-TiO₂ nanoparticles was enhanced by simulated sunlight (SSL) irradiation (96-h LC₅₀ of 116.56 ppm) and exceeded that of Sigma TiO₂, which was essentially non-toxic. Behavioral disorder, in terms of rheotaxis, was significantly increased by treatment with S-TiO₂ nanoparticles under SSL irradiation. In order to further understand its toxicity mechanism, we investigated hair cells in neuromasts of the posterior lateral line (PLL) using DASPEI staining. Significant hair cell damage was observed in the treated larvae. The Comet assay was employed to investigate the DNA damage, which might be responsible for the loss of hair cells. Production of the superoxide anion (), a major ROS generated by TiO₂ nanoparticles, was assayed and used to postulate causative factors to account for these damages. Oxidative effects were most severe in the liver, heart, intestine, pancreatic duct, and pancreatic islet – results consistent with our earlier findings in the investigation of embryonic malformation. TEM micrographs, used to further investigate the fate of S-TiO₂ nanoparticles at the cellular level, suggested receptor-mediated autophagy and vacuolization. Our findings validate the benefit of using the transparent zebrafish embryo as an in vivo model for evaluating photo-induced nanotoxicity. These results highlight the importance of conducting a systematic risk assessment in connection with the use of doped TiO₂ nanoparticles in aquatic ecosystems.

• DNA damage
• phototoxicity
• rheotaxis dysfunction
• ROS
• S-TiO₂ NPs
• zebrafish

Acknowledgements

We sincerely thank Dr. D. D. Dionysiou (University of Cincinnati) for providing S-TiO₂ NPs. We also acknowledge the kind help from the following people: Dr. D. Senapati and Dr. R. Zhang of Jackson State University (JSU) on TEM analysis; Dr. J. J. Stevens, Dr. A. Walker, Dr. C. G. Yedjou (JSU), Ms. X. Hou and Dr. J. Wang (University of Mississippi Medical Center) on fluorescence imaging analysis; and Dr. Z. Arslan (JSU) on ICP-MS assay.

Declaration of interest

This study was supported by NSF-CREST program (National Science Foundation-Centers of Research Excellence in Science and Technology) with grant #HRD-0833178. In this study we used the JSU Molecular and Cellular Biology Core Lab which is supported by NIH RCMI grant (#5G12RR013459-12). The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.