奈米銀顆粒於缺氧環境的氧化宿命:有機硫醇及無機含氮物種之作用;Probing oxidative dissolution of silver nanoparticles in the anoxic environment: Effects of thiols and inorganic nitrogen species

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题名:	奈米銀顆粒於缺氧環境的氧化宿命:有機硫醇及無機含氮物種之作用;Probing oxidative dissolution of silver nanoparticles in the anoxic environment: Effects of thiols and inorganic nitrogen species
作者:	楊懿勤;Yang, Yi-Cin
贡献者:	環境工程研究所
关键词:	奈米銀顆粒;硫醇;氧化還原;無機含氮物種;氯離子;silver nanoparticles;thiols;redox reactions;nitrogen species;chloride
日期:	2022-01-24
上传时间:	2022-07-14 01:25:52 (UTC+8)
出版者:	國立中央大學
摘要:	奈米銀顆粒(AgNPs)是消費產品中最常見的人造奈米材料之一，此類新興物質最終將不可避免地在生產、使用和棄置的過程中被釋放到環境。從環境的角度為出發點來看，AgNPs被釋放到環境後會受到像是氧分子、天然有機質、配位子等環境因子的影響，使其結構與表面特性發生變化，進而影響AgNPs的生物有效性。之前的研究已經證實AgNPs在有氧的狀態下才有顯著的微生物毒性作用，背後的原因主要是由於元素銀被分子氧氧化成銀離子，進入細胞的銀離子與帶有硫醇官能基的蛋白質/酵素結合、以及銀離子本身所引起的氧化壓力所致，但過去文獻對於其他環境因子在缺氧時是否也能造成奈米銀的氧化研究卻相對甚少探討。有鑒於AgNPs在厭氧環境中受無機氯離子與有機硫醇物質等配位基影響的轉化反應及生物可利用性等機制尚不清楚，本研究利用自行合成的檸檬酸所包覆的AgNPs，在缺氧環境下探討AgNPs與硫醇化合物的互動是否可產生Ag(I)外，也試著說明在脫硝程序中無機含氮物種是否同樣具有氧化AgNPs的能力，並藉由調整系統中氯離子濃度來說明AgNPs於淡水及海水環境下的穩定性。本實驗使用離心超濾以及0.02 μm膜過濾器將AgNPs分離後，以ICP-OES測量AgNPs所釋放溶解的Ag(I)。試驗的結果觀察到在黑暗缺氧環境中，有亞硝酸鹽存在的情況下，添加氯化物濃度越高AgNPs氧化所釋放的Ag(I)就越高，但硝酸鹽則不會顯著影響AgNPs的氧化行為。除此之外，有機硫醇配位基也會使AgNPs轉化成Ag(I)，在越高的Ag/配位基莫耳比情況下，AgNPs的氧化程度也就越高。本研究更進一步調查腐植物質對AgNPs的影響，結果發現腐植物質如腐植酸及AQDS可顯著降低AgNPs轉化生成Ag(I)的濃度，說明腐植物質可能有助於減輕AgNPs毒性。本研究所得的這些成果預期將有助於評估及掌握AgNPs在生態環境的相關風險管理。 ;The production, use and disposal of silver nanoparticles (AgNPs) 3⁄4 one of the most common man-made nanoparticles in consumer products 3⁄4 will inevitably result in the release of these novel materials into the environment. From an environmental point of view, the stability of AgNPs will subsequently be affected by certain environmental factors, such as molecular oxygen, natural organic matter (NOM), and complexing agents, thereby affecting the eventual bioavailability of AgNPs. Previous studies have demonstrated that AgNPs can exhibit significant bactericidal activity under aerobic conditions due to oxidative dissolution of AgNPs to Ag(I) by dissolved oxygen and then the uptake of Ag(I) by cells. The resulting intracellular Ag(I) will interfere with the functions of thiol-containing proteins, leading to the cells subject to oxidative stress. However, few studies have been conducted to investigate the conversion of AgNPs in the absence of dissolved oxygen, in particular the interactions between AgNPs and certain chemical species that are normally encountered in the anoxic environment. In this study, synthetic citrate-coated AgNPs were used to explore the effect of metabolic denitrifying species, chloride and NOM (using humic acid, HA, as the model species) on AgNP transformation under deoxygenated conditions. Ag(I) was separated from AgNPs by centrifugal ultrafiltration or 0.02 μm membrane filter and quantified by ICP- OES. Results show that increases in chloride alone was able to result in elevated Ag(I) production. Compared to nitrite that significantly oxidize AgNPs to Ag(I), nitrate had little effect on AgNP oxidation. Thiols could also convert AgNPs to Ag(I), and the higher the Ag/ligand molar ratio, the more Ag(I) formation. HA and AQDS (a quinone representative compound) were observed to reduce the extent of AgNPs transformed into Ag(I), implying that humic substances may help mitigate the toxicity of AgNPs to microbes. Results obtained in this study may help assess and manage the risk of AgNPs in the environment.
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