Department of Pharmacy , Uppsala University , SE-75123 Uppsala , Sweden.
Division of Dermatology and Venereology, Department of Clinical Sciences , Lund University , SE-22184 Lund , Sweden.
ACS Appl Mater Interfaces. 2019 May 1;11(17):15389-15400. doi: 10.1021/acsami.9b03527. Epub 2019 Apr 17.
The antimicrobial effects of Laponite nanoparticles with or without loading of the antimicrobial peptide LL-37 was investigated along with their membrane interactions. The study combines data from ellipsometry, circular dichroism, fluorescence spectroscopy, particle size/ζ potential measurements, and confocal microscopy. As a result of the net negative charge of Laponite, loading of net positively charged LL-37 increases with increasing pH. The peptide was found to bind primarily to the outer surface of the Laponite nanoparticles in a predominantly helical conformation, leading to charge reversal. Despite their net positive charge, peptide-loaded Laponite nanoparticles did not kill Gram-negative Escherichia coli bacteria or disrupt anionic model liposomes. They did however cause bacteria flocculation, originating from the interaction of Laponite and bacterial lipopolysaccharide (LPS). Free LL-37, in contrast, is potently antimicrobial through membrane disruption but does not induce bacterial aggregation in the concentration range investigated. Through LL-37 loading of Laponite nanoparticles, the combined effects of bacterial flocculation and membrane lysis are observed. However, bacteria aggregation seems to be limited to Gram-negative bacteria as Laponite did not cause flocculation of Gram-positive Bacillus subtilis bacteria nor did it bind to lipoteichoic acid from bacterial envelopes. Taken together, the present investigation reports several novel phenomena by demonstrating that nanoparticle charge does not invariably control membrane destabilization and by identifying the ability of anionic Laponite nanoparticles to effectively flocculate Gram-negative bacteria through LPS binding. As demonstrated in cell experiments, such aggregation results in diminished LPS-induced cell activation, thus outlining a promising approach for confinement of infection and inflammation caused by such pathogens.
研究了载负抗菌肽 LL-37 的和未载负的 Laponite 纳米颗粒的抗菌效果及其与膜相互作用。该研究结合了来自于椭圆测量法、圆二色性、荧光光谱学、粒径/ζ 电势测量和共聚焦显微镜的数据。由于 Laponite 的净负电荷，净正电荷的 LL-37 的载负量随 pH 值的增加而增加。研究发现该肽主要结合到 Laponite 纳米颗粒的外表面，呈主要的螺旋构象，导致电荷反转。尽管载负肽的 Laponite 纳米颗粒带正电荷，但它们不能杀死革兰氏阴性的大肠杆菌或破坏阴离子模型脂质体。然而，它们确实引起细菌絮凝，起源于 Laponite 和细菌脂多糖 (LPS) 的相互作用。相比之下，自由 LL-37 通过膜破坏具有强大的抗菌作用，但在研究浓度范围内不会引起细菌聚集。通过 Laponite 纳米颗粒载负 LL-37，观察到细菌絮凝和膜裂解的联合效应。然而，细菌聚集似乎仅限于革兰氏阴性细菌，因为 Laponite 不会引起革兰氏阳性枯草芽孢杆菌的絮凝，也不会与来自细菌包膜的脂磷壁酸结合。总的来说，本研究报告了几个新现象，证明了纳米颗粒的电荷不一定控制膜不稳定，并确定了阴离子 Laponite 纳米颗粒通过 LPS 结合有效絮凝革兰氏阴性细菌的能力。如细胞实验所示，这种聚集导致 LPS 诱导的细胞激活减少，从而为限制此类病原体引起的感染和炎症提供了一种很有前景的方法。
