Comparative Study On DNA Damage And Sub-chronic Toxicity Caused By Two Kinds Nano- And Micro-scale Materials

When the material dimension achieves to nano-scale, the physicochemical and biological properties would be changed significantly. Therefore, how to accurately evaluate the safety or risk of nano-materials has become research hotpots in toxicology. In this paper, we compared the cell toxicity, DNA damage and sub-chronic toxicity caused by nano- and micro-materials (zincoxide, titanium dioxide), and further to reveal the toxic characteristics caused by nano- and micro-materials, that provide an scientific evidence for correctly determined nano- materials safety evaluation and risk assessment.1,Comparative study on cytotoxicity and DNA damage caused by nano- and micro-ZnO. Cultured the A549 human lung adenocarcinoma cells, used the methyl tetrazolium cytotoxicity (MTT) assay and the single cell gel electrophoresis(comet assay) to compare the cytotoxicity and DNA damage caused by nano-ZnO(30nm) and micro-ZnO(≤1μm) at 25, 50, 100μg/mL. It was found that nano-ZnO at 50μg/mL have inhibited A549 cells.A reduction in cell viability as a function of both nano-ZnO concentration as well as exposure time was observed. But the micro-ZnO only when the concentration up to 100μg/mL and after 24h, the cell viability decline significantly. In addition nano-ZnO demonstrated a DNA damaging potential as evident from an increased the tail DNA content, Olive tail moment and comet tail length compared to control in the Comet assay after an exposure of 6 h, and as the dose increased from 25μg/mL to 50μg/mL, the injury severity increased; micro-ZnO did not induce the tail DNA content, Olive tail moment, comet tail length changed. Our data demonstrates that the cytotoxicity caused by nano-ZnO is significantly higher than the micro-ZnO. Nano-ZnO can induce DNA damage, but the micro- one did not. So the nano- and micro-ZnO may be with different cytoxicity and cytotoxic characteristics.2,Comparative study on cytotoxicity and DNA damage caused by nano- and micro- TiO₂. Used the same cell and test methods to the third part. It was showed that the cytotoxicity caused by nano-TiO₂ and micro-TiO₂ were similar. But compared to the micro-TiO₂, nano-TiO₂ inhibited A549 cells at 200μg/mL(P<0.05). In addition, nano-TiO₂ demonstrated a DNA damaging potential as evident from an increased the tail DNA content, Olive tail moment and comet tail length compared to control in the Comet assay after an exposure of 6 h; micro-TiO₂ did not induce the tail DNA content, Olive tail moment, comet tail length changed. Our data demonstrates that nano-TiO₂ particles possess a toxic potential in A549 cells which may be significantly higher than micro- ones; the toxic effects occurred earlier for time and lower for dose compared with micro-TiO₂, and nano-TiO₂ particles can induce DNA damage, but micro- one did not. In conclution, the nano-and micro-TiO₂ may be with different toxicity and toxic properties.3,Comparative study on sub-chronic toxicity in rats caused by nano- and micro- ZnO. SPF SD rats were used as the tested animals, they were randomly divided into 5 groups, n=8. Once a day for 42 days by intraperitoneal injection of the same dose(10mg/mL) of different scale nano-ZnO(30nm,50nm,100nm)and micro-ZnO(≤1μm),compared sub-chronic .The results showed that 30nm ZnO can lead to liver, sleep, kidney, bone marrow and testicular function or organizational changed, and other nano-ZnO without changes in renal function; micro-ZnO can cause lung and kidney coefficient increased, but has not seen functional or organizational change. Nano- and micro-ZnO can cause bone marrow blood cells proliferative anemia active, leading to increase the number of neutrophisl, but the relative proportion of lymphocytes and basophilic cells was decreased, which 30nm and 50nm were the most obvious. Our data demonstrates that the sub-chronic toxicity of nano-ZnO was significantly higher than the micro-one; the sensitivity target organs of nano-ZnO are the testes, liver, bone marrow and kidney;and with the scale reduced, the number of affected organs and the level of damage increased. The target organ of micro-ZnO is the bone marrow, but liver, kidney, lung are possible.4,Comparative study on sub-chronic toxicity in rats caused by nano- and micro-TiO₂. Used the same animals and test methods to the first part. The results showed that nano-and micro-TiO₂ all can induce bone marrow blood cells proliferative anemia active,but the nano- TiO₂ group was also observed liver function changed. The smaller of the scale, the higher of the toxic effect. Our data demonstrates that the target organs of nano-TiO₂ may be the liver and bone marrow, and the target organs of micro-TiO₂ may be bone marrow. The sub-chronic toxicity and the affected organs of nano- and micro-TiO₂ may be different.