<p>Effects of Zinc Oxide Nanoparticles in HUVEC: Cyto- and Genotoxicity and Functional Impairment After Long-Term and Repetitive Exposure in vitro</p>

Abstract

Purpose: The present study focuses on threshold levels for cytotoxicity after long-term and repetitive exposure for HUVEC as a model for the specific microvascular endothelial system. Furthermore, possible genotoxic effects and functional impairment caused by ZnO NPs in HUVEC are elucidated. Methods: Thresholds for cytotoxic effects are determined by the 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide (MTT) and Annexin V assay. To demonstrate DNA damage, single-cell microgel electrophoresis (comet) assay is performed after exposure to sub-cytotoxic concentrations of ZnO NPs. The proliferation assay, dot blot assay and capillary tube formation assay are also carried out to analyze functional impairment. Results: NPs showed to be spherical in shape with an average size of 45-55 nm. Long-term exposure as well as repetitive exposure with ZnO NPs exceeding 25 µg/mL lead to decreased viability in HUVEC. In addition, DNA damage was indicated by the comet assay after longterm and repetitive exposure. Twenty-four hours after long-term exposure, the proliferation assay does not show any difference between negative control and exposed cells. Forty-eight hours after exposure, HUVEC show an inverse concentration-related ability to proliferate. The dot blot assay provides evidence that ZnO NPs lead to a decreased release of VEGF, while capillary tube formation assay shows restriction in the ability of HUVEC to build tubes and meshes as a first step in angiogenesis. Conclusion: Sub-cytotoxic concentrations of ZnO NPs lead to DNA damage and functional impairment in HUVEC. Based on these data, ZnO NPs may affect neo-angiogenesis. Further investigation based on tissue cultures is required to elucidate the impact of ZnO NPs on human cell systems.

Zinc Oxide Nanoparticles Exhibit Favorable Properties to Promote Tissue Integration of Biomaterials

“…Previous studies described pro-angiogenic [22,23,[44][45][46] as well as anti-angiogenic [47][48][49][50] properties for ZnO NPs, indicating that the corresponding characteristics are strongly dependent on the type of nanoparticles and the environmental conditions. The importance of mild reactive oxygen species generation for the formation of blood vessels is well known [51].…”

Transition metals in angiogenesis – A narrative review

“…However, there have also been experiments conducted exposing cells directly to ZnO NPs, which resulted in antiangiogenic effects. Researchers tested NP concentrations from 1 to 50 μg/ml where cytotoxic effects started at 35 μg/ml [ 183 ]. HUVECs exposed directly to ZnO NPs at sub-cytotoxic concentrations displayed lower VEGF secretion rates and impaired capillary tube formation [ 183 ].…”

“…Researchers tested NP concentrations from 1 to 50 μg/ml where cytotoxic effects started at 35 μg/ml [ 183 ]. HUVECs exposed directly to ZnO NPs at sub-cytotoxic concentrations displayed lower VEGF secretion rates and impaired capillary tube formation [ 183 ]. These differing results may have to do with the difference in application and concentrations.…”

Copper and Zinc Particles as Regulators of Cardiovascular System Function—A Review

“…Poier and Tada-Oikawa supported the aforementioned results in rats. They found that doses of ZnO-NPs above 20 µg/mL reduced cell viability, increased apoptosis [63], as well as contributed to the formation of new blood vessels [64]. Additionally, it has been demonstrated that the duration of exposure to ZnO-NPs is crucial [62,63].…”