[论文解读] Remarkable antibacterial activity of reduced graphene oxide functionalized by copper ions

Yusong Tu, Pei Li+8 more|arXiv (Cornell University)|Sep 20, 2020

Graphene and Nanomaterials Applications被引用 6

一句话总结

本研究证明，通过阳离子-π相互作用功能化的氧化石墨烯（rGO）修饰铜离子，表现出卓越且选择性的抗菌活性——其活性比游离铜离子强逾100倍，且对哺乳动物细胞无毒性。rGO将Cu²⁺离子递送并富集于细菌表面，诱导其发生氧化还原循环生成Cu⁺，通过靶向性氧化损伤显著增强杀菌效果。

ABSTRACT

Despite long-term efforts for exploring antibacterial agents or drugs, it remains challenging how to potentiate antibacterial activity and meanwhile minimize toxicity hazards to the environment. Here, we experimentally show that the functionality of reduced graphene oxide (rGO) through copper ions displays selective antibacterial activity significantly stronger than that of rGO itself and no toxicity to mammalian cells. Remarkably, this antibacterial activity is two orders of magnitude greater than the activity of its surrounding copper ions. We demonstrate that the rGO is functionalized through the cation-$π$ interaction to massively adsorb copper ions to form a rGO-copper composite in solution and result in an extremely low concentration level of surrounding copper ions (less than ~0.5 $μM$). These copper ions on rGO are positively charged and strongly interact with negatively charged bacterial cells to selectively achieve antibacterial activity, while rGO exhibits the functionality to not only actuate rapid delivery of copper ions and massive assembly onto bacterial cells but also result in the valence shift in the copper ions from Cu$^{2+}$ into Cu$^{+}$ which greatly enhances the antibacterial activity. Notably, this functionality of rGO through cation-$π$ interaction with copper ions can similarly achieve algaecidal activity but does not exert cytotoxicity against neutrally charged mammalian cells. The remarkable selective antibacterial activity from the rGO functionality as well as the inherent broad-spectrum-antibacterial physical mechanism represents a significant step toward the development of a novel antibacterial material and reagent without environmental hazards for practical application.

研究动机与目标

• 开发一种高效、环境友好的抗菌剂，最大限度降低对人类细胞的毒性。
• 克服传统抗菌剂的局限性，包括效力不足和环境危害。
• 探讨rGO通过表面功能化增强并引导金属离子抗菌活性的作用机制。
• 研究rGO-铜复合材料选择性靶向细菌而避免损伤哺乳动物细胞的机制。
• 展示rGO-铜体系作为广谱抗菌材料在实际应用中的潜力。

提出的方法

• 在水溶液中通过阳离子-π相互作用将Cu²⁺离子功能化修饰于还原氧化石墨烯（rGO）上。
• 通过XPS和ζ电位测量对rGO-Cu复合材料进行可控铜离子负载量的合成与表征。
• 采用标准培养和活菌计数法评估其对革兰氏阴性菌（大肠杆菌）和革兰氏阳性菌（金黄色葡萄球菌）的抗菌活性。
• 通过评估对哺乳动物细胞（如HEK293）的细胞毒性以确定选择性。
• 利用ICP-MS定量测定溶液中游离Cu²⁺浓度，确认复合材料形成后其浓度极低（约<0.5 µM）。
• 通过X射线光电子能谱（XPS）研究rGO表面铜离子价态变化（Cu²⁺至Cu⁺）情况。

实验结果

研究问题

• RQ1 通过铜离子功能化的rGO是否能显著增强其抗菌活性，相较于游离铜离子？
• RQ2 rGO与Cu²⁺之间的阳离子-π相互作用如何促进对细菌细胞的选择性靶向，而非哺乳动物细胞？
• RQ3 rGO在促进Cu²⁺向Cu⁺发生氧化还原转化过程中发挥何种作用？该过程如何增强抗菌效果？
• RQ4 rGO-Cu复合材料在多大程度上降低了溶液中游离Cu²⁺的浓度，从而最小化环境毒性？
• RQ5 rGO-Cu体系是否能在不引起中性哺乳动物细胞毒性的情况下表现出杀藻活性？

主要发现

• rGO-Cu复合材料的抗菌活性比相同浓度下的游离铜离子高出两个数量级。
• rGO功能化后，溶液中游离Cu²⁺离子浓度降低至约0.5 µM以下，表明实现了高效的离子固定化。
• rGO表面的铜离子呈正电荷，强烈吸引带负电的细菌细胞膜，实现靶向递送。
• XPS分析证实，rGO表面铜的价态从Cu²⁺转变为Cu⁺，该过程增强了氧化应激并提升了抗菌效果。
• rGO-Cu复合材料对哺乳动物细胞（如HEK293）无细胞毒性，表现出高度选择性。
• 该体系展现出广谱抗菌活性，并表现出杀藻效果，证实其在环境与生物医学应用中的潜力。