Mutagenicity of ZnO nanoparticles in mammalian cells: Role of physicochemical transformations under the aging process

Abstract

Zinc oxide nanoparticles (ZnO NPs) potentially undergo physicochemical transformation in the environment, which may lead to unexpected environmental and health risks. The “aging” process is essential for better understanding the toxicity and fate of NPs in the environment. However, the mutagenic effects of aged ZnO NPs are still unexplored. The present study focused on investigating the physicochemical transformation during aging process and clarifying the mutagenicity of naturally aged ZnO NPs in human–hamster hybrid (A_L) cells. It was found that ZnO NPs underwent sophisticated physicochemical transformations with aging regardless of original morphology or size, such as the microstructural changes, the formation of hydrozincite (Zn₅(CO₃)₂(OH)₆) and the release of free zinc ions. Interestingly, the aged ZnO NPs were investigated to be able to result in much lower cytotoxicity while relatively high degree mutation than fresh ZnO NPs. With characterization of the soluble and insoluble fractions of aged ZnO NPs suspension, together with the control measurements using metal chelator (TPEN) and endocytosis inhibitor (Nystatin), it was revealed that the release of zinc ions and nanoparticle uptake made significantly different contributions to the mutagenicity of fresh and aged ZnO NPs. This study clearly demonstrated that the physicochemical transformation of ZnO NPs with aging plays important and comprehensive roles in the ZnO NPs-induced mutagenicity in mammalian cells.

• Aging process
• human–hamster hybrid (A_L) cell
• mutagenicity
• physicochemical transformation
• ZnO nanoparticles

Acknowledgements

The authors acknowledge the suggestions from Prof. Si J. Liu and Prof. Zhao X. Deng.

Declaration of interest

The authors declare no competing financial interest. The authors alone are responsible for the content and writing of the paper.

This work was supported in part by grants from Major National Scientific Research Projects, 2014CB932002; Strategic Leading Science & Technology Program (B), XDB14030502; National Natural Science Foundation of China grants U1232144 and 30570422; The Major/Innovative Program of Development Foundation of Hefei Center for Physical Science and Technology, 2014FXCX010.

Supplementary material available online

Supplementary Figures S1-S3.