Effect of Flexibility and Size of Nanofabricated Topographies on the Mechanobactericidal Efficacy of Polymeric Surfaces

Abstract

Driven by the growing threat of antimicrobial resistance, the design of intrinsically bactericidal surfaces has been gaining significant attention. Proposed surface topography designs are often inspired by naturally occurring nanopatterns on insect wings that mechanically damage bacteria via membrane deformation. The stability of and the absence of chemicals in such surfaces support their facile and sustainable employment in avoiding surface-born pathogen transmission. Recently, the deflection of controllably nanofabricated pillar arrays has been shown to strongly affect bactericidal activity, with the limits of mechanical effectiveness of such structures remaining largely unexplored. Here, we examine the limits of softer, commonly used polymeric materials and investigate the interplay between pillar nanostructure sizing and flexibility for effective antibacterial functionality. A facile, scalable, UV nanoimprint lithography method was used to fabricate nanopillar array topographies of variable sizes and flexibilities. It was found that bacterial death on nanopillars in the range of diameters ≤100 nm and Young’s moduli ≥1.3 GPa is increased by 3.5- to 5.6-fold, while thicker or softer pillars did not reduce bacterial viability. To further support our findings, we performed a finite element analysis of pillar deformation. It revealed that differences in the amount of stress exerted on bacterial membranes, generated from the stored elastic energy in flexible pillars, contribute to the observed bactericidal performance.

PEGDMA-Based Pillar-Shape Nanostructured Antibacterial Films Having Mechanical Robustness

“…The stretching and damage of the bacterial membrane by the nanostructure causes the death of attached bacteria. In this process, low-stiffness nanostructures cannot deform and damage the bacterial membrane, whereas higher-stiffness nanostructures resist bacterial attraction and can effectively damage the bacterial membrane . Therefore, modeled nanostructures compared the bending of the previously reported nanocone and the proposed nanopillar structures.…”

“…In this process, low-stiffness nanostructures cannot deform and damage the bacterial membrane, whereas higherstiffness nanostructures resist bacterial attraction and can effectively damage the bacterial membrane. 31 Therefore, modeled nanostructures compared the bending of the previously reported nanocone and the proposed nanopillar structures. The results for each nanostructure deformation case are shown in Figure 6c.…”

“…Therefore, as shown in Figure , four cases were assessed numerically to determine the mechanical response to the horizontal force boundary condition. For the boundary conditions, we implement the horizontal forced boundary condition because the bacteria, which attached to the surface of the nanostructure, pull the nanostructure for reasons of migration and proliferation . Therefore, the boundary conditions for computational analysis are shown in Figure b.…”

“…For the boundary conditions, we implement the horizontal forced boundary condition because the bacteria, which attached to the surface of the nanostructure, pull the nanostructure for reasons of migration and proliferation. 31 Therefore, the boundary conditions for computational analysis are shown in Figure 6b. The numerical model was meshed using a linear solid tetrahedral element (C3D4 in ABAQUS).…”

Liquid-Repellent Surfaces

“…Images in a are reproduced with permission from ref , copyright 2021 AAAS and ref , copyright 2017 AAAS. Images in b are reproduced with permission from ref , copyright 2020 Wiley-VCH; ref , copyright 2012 Wiley-VCH; ref , copyright 2022 American Chemical Society; ref , copyright 2013 American Chemical Society; and ref , copyright 2017 American Chemical Society. Images in c are reproduced with permission from ref , copyright 2020 Elsevier and ref , copyright 2017 Elsevier.…”