Cell apoptosis and necrosis,

oxidative Stem Cells inhibitor stress, and cell cycle arrest raise the concern about the applications of ZnO NPs. On the other hand, not all nanomaterials have a particle size effect. It is suggested that 26-nm ZnO NPs appeared to have the highest toxicity, while a certain concentration of nano-ZnO with the average sizes of 62 nm and 90 nm had the same influence on the membrane integrity and cell cycle of Caco-2. Conclusions The results revealed that cytotoxicity exhibited dose- and time-dependent effects for different kinds of ZnO NPs. ZnO induces oxidative stress, decreases viability, and increases cell death in Caco-2 cells. The 26-nm ZnO NPs appeared to have the highest toxicity. Different sizes of ZnO NPs could cause a significant reduction in GSH and with increase in ROS and LDH. ZnO could also cause reduction of the G1 phase and an increase in the S phase and

CX-5461 concentration the G2 phase cells to repair damaged genes, while no differences were obtained between 62-nm and 90-nm ZnO NPs. Finally, there is still little knowledge about the detail of ZnO toxicity related with the nanoparticle sizes, including how they are transported in cells and how nanoparticles interact with the cell membrane and organelles. Acknowledgements This work was supported by the Zhejiang Provincial Key Laboratory of Biometrology and Inspection and Quarantine. We gratefully acknowledged the financial support from the Zhejiang Provincial Natural Science Foundation of China (Y2110952), Zhejiang Provincial Public Technology Application Research Project (2012C22052) and Hangzhou Science and Technology Development Project (20130432B66), General Administration of Quality Supervision, Inspection and LGX818 Quarantine of the People’s Republic of China (201310120), and the General Administration of Quality Supervision, Inspection and Quarantine of the People’s Republic of China (201410072). cAMP References 1. Di Pasqua AJ, Sharma KK, Shi YL, Toms BB, Ouellette W, Dabrowiak

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