Nanodarts, nanoblades, and nanospikes: Mechano-bactericidal nanostructures and where to find them (original) (raw)

Mechano-bactericidal nanopillars require external forces to effectively kill bacteria

Nanopillars are known to mechanically damage bacteria, suggesting a promising strategy for highly-effective anti-bacterial surfaces. However, the mechanisms underlying this phenomena remain unclear, which ultimately limits translational potential towards real-world applications. Using real-time and end-point analysis techniques, we demonstrate that in contrast to expectations, bacteria on multiple “mechano-bactericidal” surfaces remain viable, unless exposed to a moving air-liquid interface which caused considerable cell death. Reasoning that normal forces arising from surface tension may underlie mechano-bactericidal activity, we developed computational and experimental models to estimate, manipulate, and recreate the impact of these forces. Our experiments together demonstrate that nanopillar surfaces alone do not cause cell death, but require a critical level of external force to deform and rupture bacteria. These studies hence provide fundamental physical insight into the mechan...

Hydrophilic Mechano-Bactericidal Nanopillars Require External Forces to Rapidly Kill Bacteria

Recently, nanopillars have been shown to mechanically damage bacteria, suggesting a promising strategy for future antibacterial surfaces. However, the mechanisms underlying this phenomena remain unclear, which ultimately limits translational potential towards real-world applications. Using real-time and end-point analysis techniques, we demonstrate that in contrast to initial expectations, bacteria on multiple hydrophilic "mechano-bactericidal" surfaces remained viable, unless exposed to a moving air-liquid interface, which caused considerable cell death. Reasoning that normal forces arising from surface tension may underlie this mechano-bactericidal activity, we developed computational and experimental models to estimate, manipulate, and recreate the impact of these forces. Our experiments together demonstrate that a critical level of external force acting on cells attached to nanopillar surfaces can rapidly deform and rupture bacteria. These studies provide fundamental physical insight into how nanopillar surfaces can serve as effective antibacterial materials, and suggest use-conditions under which such nanotechnology approaches may provide practical value.

The multi-faceted mechano-bactericidal mechanism of nanostructured surfaces

Proceedings of the National Academy of Sciences

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-negativePseudomonas aeruginosaand Gram stain-positiveStaphylococcus aureusbacteria, inducing 95 ± 5% and 83 ± 12% cell death, respectively. At heights of 360 nm, increased nanopi...

High Aspect Ratio Nanostructures Kill Bacteria via Storage and Release of Mechanical Energy

ACS nano, 2018

The threat of a global rise in the number of untreatable infections caused by antibiotic-resistant bacteria calls for the design and fabrication of a new generation of bactericidal materials. Here, we report a concept for the design of antibacterial surfaces, whereby cell death results from the ability of the nanofeatures to deflect when in contact with attaching cells. We show, using three-dimensional transmission electron microscopy, that the exceptionally high aspect ratio (100-3000) of vertically aligned carbon nanotubes (VACNTs) imparts extreme flexibility, which enhances the elastic energy storage in CNTs as they bend in contact with bacteria. Our experimental and theoretical analyses demonstrate that, for high aspect ratio structures, the bending energy stored in the CNTs is a substantial factor for the physical rupturing of both Gram-positive and Gram-negative bacteria. The highest bactericidal rates (99.3% for Pseudomonas aeruginosa and 84.9% for Staphylococcus aureus) were...

Progress in Nanostructured Mechano-Bactericidal Polymeric Surfaces for Biomedical Applications

Nanomaterials

Bacterial infections and antibiotic resistance remain significant contributors to morbidity and mortality worldwide. Despite recent advances in biomedical research, a substantial number of medical devices and implants continue to be plagued by bacterial colonisation, resulting in severe consequences, including fatalities. The development of nanostructured surfaces with mechano-bactericidal properties has emerged as a promising solution to this problem. These surfaces employ a mechanical rupturing mechanism to lyse bacterial cells, effectively halting subsequent biofilm formation on various materials and, ultimately, thwarting bacterial infections. This review delves into the prevailing research progress within the realm of nanostructured mechano-bactericidal polymeric surfaces. It also investigates the diverse fabrication methods for developing nanostructured polymeric surfaces with mechano-bactericidal properties. We then discuss the significant challenges associated with each appr...

Bacterial envelope damage inflicted by bioinspired nanospikes grown in a hydrogel

Device-associated infections are one of the deadliest complications accompanying the use of biomaterials, and despite recent advances in the development of anti-biofouling strategies, biomaterials that exhibit both functional tissue restoration and antimicrobial activity have been challenging to achieve. Here, we report the fabrication of bio-inspired bactericidal nanospikes in bacterial cellulose and investigate the mechanism underlying this phenomenon. We demonstrate these structures affects preferentially stiff membranes like those in Gram-positive bacteria, but exhibit cytocompatibility towards mammalian cells, a requisite for tissue restoration. We also reveal the bactericidal activity of the nanospikes is due to a pressure-induced mechanism, which depends on the cell’s adherence time, nanospike’s geometry and spacing, cell shape, and mechanical properties of the cell wall. Our findings provide a better understanding of the mechanobiology of bacterial cells at the interface wit...

Death at the interface: Nanotechnology's challenging frontier against microbial surface colonization

Frontiers in Chemistry - Nanoscience, 2022

The emergence of antimicrobial-resistant bacterial strains has led to novel approaches for combating bacterial infections and surface contamination. More specifically, efforts in combining nanotechnology and biomimetics have led to the development of next-generation antimicrobial/antifouling nanomaterials. While nature-inspired nanoscale topographies are known for minimizing bacterial attachment through surface energy and physicochemical features, few studies have investigated the combined inhibitory effects of such features in combination with chemical alterations of these surfaces. Studies describing surface alterations, such as quaternary ammonium compounds (QACs), have also gained attention due to their broad spectrum of inhibitory activity against bacterial cells. Similarly, antimicrobial peptides (AMPs) have exhibited their capacity to reduce bacterial viability. To maximize the functionality of modified surfaces, the integration of patterned surfaces and functionalized exteriors, achieved through physical and chemical surface alterations, have recently been explored as viable alternatives. Nonetheless, these modifications are prone to challenges that can reduce their efficacy considerably in the long term. Their effectiveness against a wider array of microbial cells is still a subject of investigation. This review article will explore and discuss the emerging trends in biomimetics and other antimicrobials while raising possible concerns about their limitations and discussing future implications regarding their potential combined applications.

Mechano-bactericidal actions of nanostructured surfaces

Nature Reviews Microbiology, 2020

Describes specially designed materials and coatings to prevent or remove biofouling by any number of organisms on wetted surfaces. Hydrophobic The physical property of having no affinity with water (that is, water repellent).

Mechano-bactericidal mechanism of graphene nanomaterials

Interface focus, 2018

Growing interest in the bactericidal effect of graphene and graphene-derived nanomaterials has led to the investigation and effective publication of the bactericidal effects of the substratum, many of which present highly conflicting material. The nature of bacterial cell death on graphene bio-interfaces, therefore, remains poorly understood. Here, we review recent findings on the bactericidal effect of graphene and graphene-derived nanomaterials, and proposed mechanisms of cell inactivation, due to mechanical contact with graphene materials, including lipid extraction, physical damage to membranes and pore formation.

Antibacterial Action of Nanoparticles by Lethal Stretching of Bacterial Cell Membranes

Advanced Materials, 2020

It is commonly accepted that nanoparticles can kill bacteria; however, the mechanism of antimicrobial action remains obscure for nanoparticles that are unable to be translocated across the bacterial cell membrane by the passive or active processes that exist for mammalian cells. In this study, we demonstrate that the increase of membrane tension provoked by the adsorption of nanoparticles (NP) is responsible for mechanical deformation of the membrane that leads to cell rupture and consequent bacterial cell death. We present a biophysical model of the NPmembrane interactions. The theoretical model suggests that adsorbed NPs can lead to global stretching and squeezing of the membrane. This general phenomenon was revealed experimentally using both model membranes and bacterial cells. Hydrophilic and hydrophobic quasi-spherical and star shaped gold (Au)NPs were synthesised to explore the antibacterial mechanism of non-translocating AuNPs in vitro. Direct observation of nanoparticle-induced membrane tension and squeezing was realised by a custom-designed microfluidic device that revealed the contraction of the model membrane surface area that resulted in the eventual collapse of the lipid bilayer. Quasi-spherical nanoparticles exhibited a greater bactericidal action due to a higher interactive affinity that resulted in higher degrees of membrane stretching and rupturing, as confirmed by the theoretical model. Electron microscopy techniques were used to characterise the nanoparticle-bacterial-membrane interactions. This combination of experimental and theoretical results confirmed the proposed mechanism of membrane-tensioninduced (mechanical) killing of bacterial cells by non-translocating NPs.