Madrid Institute for Advanced Studies in Nanoscience (IMDEA Nanociencia), C/Faraday 9, Madrid 28049, Spain.
Department of Applied Physics, University of Extremadura, Avda de Elvas s/n, Badajoz 06006, Spain.
ACS Appl Mater Interfaces. 2020 Jul 15;12(28):31235-31241. doi: 10.1021/acsami.0c08184. Epub 2020 Jun 12.
Mechano-bactericidal nanomaterials rely on their mechanical or physical interactions with bacteria and are promising antimicrobial strategies that overcome bacterial resistance. However, the real effect of mechanical versus chemical action on their activity is under debate. In this paper, we quantify the forces necessary to produce critical damage to the bacterial cell wall by performing simultaneous nanoindentation and fluorescence imaging of single bacterial cells. Our experimental setup allows puncturing the cell wall of an immobilized bacterium with the tip of an atomic force microscope (AFM) and following in real time the increase in the fluorescence signal from a cell membrane integrity marker. We correlate the forces exerted by the AFM tip with the fluorescence dynamics for tens of cells, and we find that forces above 20 nN are necessary to exert critical damage. Moreover, a similar experiment is performed in which bacterial viability is assessed through physiological activity, in order to gain a more complete view of the effect of mechanical forces on bacteria. Our results contribute to the quantitative understanding of the interaction between bacteria and nanomaterials.
力致杀菌纳米材料依赖于其与细菌的机械或物理相互作用，是一种有前途的克服细菌耐药性的抗菌策略。然而，机械作用与化学作用对其活性的实际影响仍存在争议。在本文中，我们通过对单个细菌细胞进行同步纳米压痕和荧光成像，定量确定了对细菌细胞壁产生临界损伤所需的力。我们的实验装置允许用原子力显微镜（AFM）的尖端刺穿固定细菌的细胞壁，并实时跟踪细胞膜完整性标记物的荧光信号增强。我们将 AFM 尖端施加的力与数十个细胞的荧光动力学相关联，发现需要超过 20 nN 的力才能产生临界损伤。此外，还进行了类似的实验，通过生理活性评估细菌的存活能力，以更全面地了解机械力对细菌的影响。我们的结果有助于定量理解细菌与纳米材料之间的相互作用。
