| Summary: | 碩士 === 國立中興大學 === 動物科學系所 === 104 === The development of nano-technology hsa made some nanomaterials being applied in agriculture. The nanomaterials used as fertilizers for farming may be accumulated in the crops or in animal feedstuff many thereby be taken up by human leading to accumulation in the body. Thus, toxicological evaluations of nanomaterials are necessary for the biosafety. Nano calcium carbonate can be applied in agriculture, such as fertilizers for farming, or calcium supplements in feedstuff. In the study, the toxicity of two kinds of nano calcium carbonate (NCC A and B) were elaluated in vivo and in vitro. In acute toxicity study, 8 week-old C57BL/6 mice were orally infused with NCCs 8 and 2 g/kg body weight for 2 weeks. Results showed that there was no difference in feed intake, body weight, behaviors, and hepatic and renal pathology among treatments. In the micronucleus assay for genotoxicity, peripheral-blood cells were collected and evaluated for micronucleated polychromatic erythrocytes (MNPCEs). Results also showed that there was no increase in the frequency of micronuclei by NCC A and B. Futhermore, cytotoxicity analysis of NIH-3T3 cells exposed to 10, 50 and 100 μg/ml NCC A and B for 24 hours showed a slightly increased of lactate dehydrogenase (LDH) release, Electromicroscopic imaging showed both NCC and B could aggregate to form larger particle complexes and adhere to cell surface. Exposure to NCCs aslo promoted ROS generation and decrease of cellular SOD activity and GSH level. In apoptosis assay by Annexin V staining, cells exposed to 10, 50 and 100 μg/ml of NCCs for 48 hours did not or cause change apoptosis. Since most of nanomaterials exert cytoxicity through ROS production, 2 different ROS scavengers (apocynin and diphenyleneiodoniuml; NADPH oxidase inhibitor) and endocytosis inhibitor (Cytochalasin D; cytoskeleton polymerization inihibitor) were added into the cultures of cells in the presence of NCCs. Results suggested that all of the 3 pharmacological inhibitors could decease ROS generation. Except for apocynin, however, both diphenyleneiodoniuml and cytochalasin D at higher dosages increased cell apoptosis, suggesting that over scavenging of ROS by the 2 inihibitors, may exert detrimental effects leading to healthy cell death. In conclusion, results in the study suggested that NCC A and B had no effct on acute toxicity and genotoxicity in mice and exert very minor effects on cytotoxicity. Overall, the study has demonstrated the safety of the nano calcium carbonate A and B for potential use in agriculture.
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