- 學位論文
可再生金奈米團簇捕捉自由基之研究
Investigation of Regenerable Gold Nanocluster as Free Radical Scavenger
摘要
自由基是生物體老化或產生疾病的因子，會對生物體造成嚴重的影響，而抗氧化物具有平衡之特性，可以抑制自由基。金奈米團簇又被稱為一種人工型抗氧化劑，不但有特殊光學效應，還可與多種自由基反應，常作為生物探針。 本研究運用一鍋合成法製備表面接枝硫辛酸的金奈米團簇，進一步測試表面結構、物化特性及清除自由基的能力。利用常見抗氧化劑維他命C相互比較清除自由基之趨勢，且運用1,1-diphenyl-2-picrylhydrazyl (DPPH) radical與雙氧水分別和金奈米團簇反應，再藉由體內常見的抗氧化劑還原金奈米團簇，使用XPS和Ellman’s Reagent測定氧化還原過程中金奈米團簇表面之改變。 研究得知此材料粒徑約2.32nm的金奈米團簇，具有極亮之紅色螢光，能長期且穩定的抑制DPPH，若將DPPH自由基和雙氧水交互比較，發現兩者都會使金奈米團簇氧化，即失去清除自由基的能力，稱之氧化態，但呈現截然不同之光譜效應，加入雙氧水會增強螢光特性，反之DPPH螢光粹滅，間接發現金奈米團簇擁有氧化還原的狀態，最後加入谷胱甘肽作為還原劑，將氧化態的金奈米團簇還原，並使其擁有再次清除自由基之性質，但螢光強度皆會下降，然而在氧化還原的過程中發現團簇表面價態的改變和螢光強度有密切相關，也由Ellman’s Reagent驗證GSH參與還原反應，在體外模擬體內的循環，並且金奈米團簇可以藉由體內的生物循環達到再生，賦予金奈米團簇更多的應用和價值。
並列摘要
Free radicals are the factors that induce the cell's aging and produce related diseases, which can have a serious impact on the organism. Antioxidants have the ability to prevent and inhibit the free radicals. Gold nanocluster is also known as an artificial antioxidant, not only does it have a unique optical property but it can also react with a variety of free radicals, as a biological probe. In this study we have reported a 'one-pot synthesis' procedure to prepare fluorescent gold nanoclusters conjugated by lipoic acid, and further determined the surface structure, physical and chemical properties and the ability to scavenge free radicals. The trend of inhibiting free radicals was compared with vitamin C and gold nanoclusters, using 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and hydrogen peroxide reacted with gold nanoclusters, respectively, then renewal of the gold nanoclusters by common antioxidants from the body. In addition, X-ray photoelectron spectroscopy and Ellman's Reagent were used to measure the change in the surface of the gold nanoclusters during the redox process. The study found that the size of gold nanoclusters is about 2.32nm, with ultrabright luminescence, long-term and stable inhibition of DPPH. Comparing DPPH radical with hydrogen peroxide, we have found that both of them can oxidize gold nanoclusters, that is, they lose their ability to scavenge free radicals. They showed different spectral effects, indirectly found that the gold nanoclusters have a redox state. Finally, addition of glutathione to reduce the oxidation state of the gold nanoclusters and have the property to scavenge free radical again, but the fluorescence intensity decreased. However, the change of valence state of gold is closely related to the fluorescence intensity during the redox process. Ellman's Reagent also confirmed that GSH is involved in the reduction reaction and the in vivo circulation is implemented in this material. Moreover, the gold nanocluster can be regenerated by the biological cycle, ensuring gold nanoclusters have more applications and value.