| Summary: | 碩士 === 國立臺灣大學 === 毒理學研究所 === 101 === Zinc oxide (ZnO) is a white powder that is insoluble in water, which is widely used as an additive in numerous materials and products including plastics, paints, foods. For material science applications, zinc oxide has high refractive index, antibacterial and UV-protection properties. ZnO are used in various products, including cosmetics and sunscreens due to UV-filtering properties. The production of engineered nanoparticles is growing rapidly as the field of nanotechnology continues to expand. Modern sunscreen contain insoluble ZnO nanoparticle (ZnO NPs), which is reflect ultraviolet (UV) more efficiently than larger particles. However, cosmetic research suggest that vesicle materials may enter human cell, like human liver cells (HepG2). Sunscreen products is the first contact with the skin, and the underlying mechanisms of zinc oxide adverse effects have not been fully characterized. This study was designed to investigate the cytotoxicity, oxidative stress and apoptosis by ZnO nanoparticles in human keratinocyte cell (HaCaT cell). Cell viability assays indicated an IC50 approximately 50 μg/ml of ZnO nanoparticles after 24 h of exposure. ZnO nanoparticles were found to induce reactive oxygen species (ROS) generation in HaCaT cells by flowcytometry and fluoresce microscopy. ZnO nanoparticles were also investigated using Annexin V staining for apoptosis analysis and P2 staining for necrosis analysis. ZnO nanoparticles displaced apoptosis at 18 hr and then necrosis at 24 hr. Additional, Hoechst 33342 staining revealed apoptosis in HaCaT cells after 50 μg/ml ZnO nanoparticles 18hr treatment. Atomic force microscopy (AFM) is a very high resolution type of scanning probe microscopy. It has been shown to be a powerful tool for imaging materials at the nanometer level and for observing the ultrastructure of a cell. This method is appropriate for measuring the change in the biophysical properties of the cell. AFM offers an advantages over morphological characterization technique used to study apoptosis. After ZnO nanoparticles treatment the HaCaT cells, the surface roughness was increased, the stiffness was decreased and the adhesion was no significant changed. In conclusion, this study demonstrated that ZnO nanoparticles induced cell death of HaCaT cells was via induction of ROS and apoptosis by biochemical feature and AFM.
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