Department of Chemical and Biomolecular Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588, United States.
Nebraska Center for Materials and Nanoscience, Voelte-Keegan Nanoscience Research Center, University of Nebraska-Lincoln, Lincoln, Nebraska 68588-0298, United States.
ACS Appl Mater Interfaces. 2020 Nov 4;12(44):49346-49361. doi: 10.1021/acsami.0c12038. Epub 2020 Oct 22.
Cationic, π-conjugated oligo-/polyelectrolytes (CCOEs/CCPEs) have shown great potential as antimicrobial materials to fight against antibiotic resistance. In this work, we treated wild-type and ampicillin-resistant (amp-resistant) () with a promising cationic, π-conjugated polyelectrolyte (P1) with a phenylene-based backbone and investigated the resulting morphological, mechanical, and compositional changes of the outer membrane of bacteria in great detail. The cationic quaternary amine groups of P1 led to electrostatic interactions with negatively charged moieties within the outer membrane of bacteria. Using atomic force microscopy (AFM), high-resolution transmission electron microscopy (TEM), we showed that due to this treatment, the bacterial outer membrane became rougher, decreased in stiffness/elastic modulus (AFM nanoindentation), formed blebs, and released vesicles near the cells. These evidences, in addition to increased staining of the P1-treated cell membrane by lipophilic dye Nile Red (confocal laser scanning microscopy (CLSM)), suggested loosening/disruption of packing of the outer cell envelope and release and exposure of lipid-based components. Lipidomics and fatty acid analysis confirmed a significant loss of phosphate-based outer membrane lipids and fatty acids, some of which are critically needed to maintain cell wall integrity and mechanical strength. Lipidomics and UV-vis analysis also confirmed that the extracellular vesicles released upon treatment (AFM) are composed of lipids and cationic P1. Such surface alterations (vesicle/bleb formation) and release of lipids/fatty acids upon treatment were effective enough to inhibit further growth of cells without completely disintegrating the cells and have been known as a defense mechanism of the cells against cationic antimicrobial agents.
阳离子、π 共轭的低聚物/聚合物（CCOEs/CCPEs）作为一种对抗抗生素耐药性的抗菌材料具有很大的潜力。在这项工作中，我们用一种有前途的阳离子、π 共轭聚合物（P1）处理了野生型和氨苄青霉素耐药型（amp-resistant）（），该聚合物具有联苯骨架和带正电荷的季铵基团，详细研究了细菌外膜的形态、力学和组成变化。P1 的阳离子季铵基团与细菌外膜中带负电荷的部分发生静电相互作用。通过原子力显微镜（AFM）和高分辨率透射电子显微镜（TEM），我们表明，由于这种处理，细菌外膜变得更加粗糙，刚性/弹性模量（AFM 纳米压痕）降低，在细胞附近形成泡状突起和小泡。除了用亲脂性染料尼罗红（共聚焦激光扫描显微镜（CLSM））对 P1 处理后的细胞膜进行染色增加外，这些证据表明，细胞外膜的包装变得松散/破坏，脂质基成分释放和暴露。脂质组学和脂肪酸分析证实，基于磷酸盐的外膜脂质和脂肪酸大量损失，其中一些对于维持细胞壁完整性和机械强度是至关重要的。脂质组学和紫外-可见分析还证实，处理后释放的细胞外小泡（AFM）由脂质和阳离子 P1 组成。这种表面改变（泡状突起/小泡形成）和脂质/脂肪酸的释放足以抑制 细胞的进一步生长，而不会完全破坏细胞，并且这种现象被认为是细胞对抗阳离子抗菌剂的一种防御机制。
