Ibsen Kelly N, Ma Huilin, Banerjee Amrita, Tanner Eden E L, Nangia Shikha, Mitragotri Samir
Department of Chemical Engineering, University of California, Santa Barbara, California 93106, United States.
School of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138, United States.
ACS Biomater Sci Eng. 2018 Jul 9;4(7):2370-2379. doi: 10.1021/acsbiomaterials.8b00486. Epub 2018 May 31.
The continued emergence of antibiotic-resistant organisms has severely depleted our arsenal of effective antimicrobials. Ionic liquids (ILs) show great promise as antibacterial agents but understanding the mechanism of attack on bacterial cells is key to ensuring that design of IL-based biocides impart maximum efficacy with minimal toxicity, while also avoiding the potential for the target organisms to become resistant. Here we report the antibacterial attributes of a set of choline and geranate (CAGE)-based ILs and identify the mechanism by which they interact with the Gram-negative cell wall of . CAGE is envisaged as an antimicrobial agent to treat topical infections in skin. Our earlier work has shown that CAGE is highly effective across a breadth of bacterial, fungal, and viral species and is benign to human cells. This combination makes CAGE an ideal antimicrobial for human use. Four CAGE variants with varying ratios of choline and geranic acid were synthesized and tested for their antibacterial activity (1:4, 1:2, 1:1, and 2:1 choline:geranic acid). The minimum bactericidal concentration required to kill correlated with the geranic acid content. Using molecular dynamics (MD) simulations, we identified the mechanism of CAGE action on the membrane, namely that choline is attracted to the negatively charged cell membrane and consequently inserts geranic acid into the lipid bilayer. The disruption of the cell membrane was confirmed with propidium iodide staining via flow cytometry and scanning electron microscopy. Fourier Transform infrared spectroscopic analysis of treated cells showed an altered lipid profile similar to phase transition, indicating the disruption of the lipid bilayer conformation. cells repeatedly exposed to CAGE did not exhibit resistance. This study provides the fundamental mechanism of the action of choline-based ILs on Gram-negative bacteria and demonstrates the promise of CAGE as a powerful antimicrobial agent to treat infections.
抗生素耐药菌的持续出现严重消耗了我们有效的抗菌药物库。离子液体（ILs）作为抗菌剂显示出巨大的潜力，但了解其对细菌细胞的攻击机制是确保基于离子液体的杀菌剂设计在毒性最小的情况下发挥最大功效的关键，同时还要避免目标生物产生耐药性的可能性。在此，我们报告了一组基于胆碱和香叶酸（CAGE）的离子液体的抗菌特性，并确定了它们与革兰氏阴性细胞壁相互作用的机制。CAGE被设想为一种治疗皮肤局部感染的抗菌剂。我们早期的研究表明，CAGE对多种细菌、真菌和病毒具有高效性，且对人类细胞无害。这种组合使CAGE成为一种理想的供人类使用的抗菌剂。合成了四种胆碱与香叶酸比例不同的CAGE变体，并测试了它们的抗菌活性（胆碱：香叶酸比例为1:4、1:2、1:1和2:1）。杀死[具体细菌名称未给出]所需的最低杀菌浓度与香叶酸含量相关。通过分子动力学（MD）模拟，我们确定了CAGE对[具体细菌名称未给出]细胞膜的作用机制，即胆碱被带负电荷的细胞膜吸引，从而将香叶酸插入脂质双层。通过流式细胞术和扫描电子显微镜用碘化丙啶染色证实了细胞膜的破坏。对处理过的细胞进行傅里叶变换红外光谱分析显示，脂质谱发生了类似于相变的变化，表明脂质双层构象被破坏。反复接触CAGE的[具体细菌名称未给出]细胞未表现出耐药性。这项研究提供了基于胆碱的离子液体对革兰氏阴性细菌作用的基本机制，并证明了CAGE作为一种强大的治疗感染的抗菌剂的前景。
