School of Science, College of Science, Engineering and Health, RMIT University, Melbourne, VIC 3000, Australia;
Australian Research Council Research Hub for Australian Steel Manufacturing, Wollongong, NSW 2500, Australia.
Proc Natl Acad Sci U S A. 2020 Jun 9;117(23):12598-12605. doi: 10.1073/pnas.1916680117. Epub 2020 May 26.
The mechano-bactericidal activity of nanostructured surfaces has become the focus of intensive research toward the development of a new generation of antibacterial surfaces, particularly in the current era of emerging antibiotic resistance. This work demonstrates the effects of an incremental increase of nanopillar height on nanostructure-induced bacterial cell death. We propose that the mechanical lysis of bacterial cells can be influenced by the degree of elasticity and clustering of highly ordered silicon nanopillar arrays. Herein, silicon nanopillar arrays with diameter 35 nm, periodicity 90 nm and increasing heights of 220, 360, and 420 nm were fabricated using deep UV immersion lithography. Nanoarrays of 360-nm-height pillars exhibited the highest degree of bactericidal activity toward both Gram stain-negative and Gram stain-positive bacteria, inducing 95 ± 5% and 83 ± 12% cell death, respectively. At heights of 360 nm, increased nanopillar elasticity contributes to the onset of pillar deformation in response to bacterial adhesion to the surface. Theoretical analyses of pillar elasticity confirm that deflection, deformation force, and mechanical energies are more significant for the substrata possessing more flexible pillars. Increased storage and release of mechanical energy may explain the enhanced bactericidal action of these nanopillar arrays toward bacterial cells contacting the surface; however, with further increase of nanopillar height (420 nm), the forces (and tensions) can be partially compensated by irreversible interpillar adhesion that reduces their bactericidal effect. These findings can be used to inform the design of next-generation mechano-responsive surfaces with tuneable bactericidal characteristics for antimicrobial surface technologies.
纳米结构表面的力学杀菌活性已成为开发新一代抗菌表面的研究重点，尤其是在当前抗生素耐药性不断出现的时代。本工作研究了纳米突起高度的逐渐增加对纳米结构诱导细菌细胞死亡的影响。我们提出，细菌细胞的机械裂解可以受到高度有序硅纳米柱阵列的弹性和聚集程度的影响。在此，我们使用深紫外浸入光刻技术制造了直径为 35nm、周期为 90nm 且高度分别为 220nm、360nm 和 420nm 的硅纳米柱阵列。360nm 高的纳米柱阵列对革兰氏阴性菌和革兰氏阳性菌均表现出最高的杀菌活性，分别诱导 95±5%和 83±12%的细胞死亡。在 360nm 高度时，纳米柱弹性的增加有助于在细菌黏附在表面时引发柱的变形。对纳米柱弹性的理论分析证实，对于具有更柔韧的纳米柱的基底，挠度、变形力和机械能更为显著。机械能量的增加储存和释放可能解释了这些纳米柱阵列对接触表面的细菌细胞的增强杀菌作用；然而，随着纳米柱高度的进一步增加（420nm），力（和张力）可以通过不可逆的柱间粘附部分得到补偿，从而降低其杀菌效果。这些发现可用于为具有可调杀菌特性的下一代机械响应表面的设计提供信息，用于抗菌表面技术。
