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The scientific and industrial interest in antimicrobial surfaces has significantly increased in recent times. This interest is largely in response to the persistent microbial ...contamination of industrial and, importantly, medical implant surfaces. Bacterial contamination of implant surfaces often leads to infection at the implant-tissue interface, and with the prevalence of increasing levels of antimicrobial resistance, the treatment of these infections is becoming far more challenging. Recently, many naturally occurring, high-aspect-ratio surface topographies have been discovered that exhibit high levels of biocidal efficacy. These include epicuticular lipid nano-architectures that are formed on the surfaces of insect wings, such as cicadae and dragonflies. The antimicrobial activity of such surfaces has been found to be a consequence of the physical interactions between the nanoscale topography of the substrate and the attaching pathogenic cells, meaning that the activity is independent of biochemical surface functionality. Importantly, these desirable surface properties can be translated to synthetic biomimetic surfaces, which, when mimicked, lead to a substantial increase in the antimicrobial properties of such surfaces. This paper reviews the recent advances in understanding the basis of these mechanical antimicrobial mechanisms, and discusses the progress being made towards the fabrication of optimised, biocompatible, synthetic analogues.
Nature has endowed many of its living systems with functional structures with highly tuned wettability. Inspired by nature, scientists began to mimic these natural templates and as a result a wide ...spectrum of biomimetic superhydrophobic surfaces are fabricated. Fluorinated synthetic materials are currently used on an industrial scale to produce superhydrophobic surfaces. The negative impact of fluorinated substances on human health together with growing environmental concerns has prompted researchers to adopt safer routes with minimal use of fluorinated compounds. This has led to increased focus on bio-inspired studies. Current research on the fabrication and characterisation of superhydrophobic materials aims to use fluorine-free reagents such as siloxane polymers and long-chain fatty acids. In this context, this review attempts to highlight the recent progress in fluorine-free superhydrophobic surfaces and important features of their design, synthesis and fabrication that would potentially broaden their application in various fields. This review also aims to provide insights into technical breakthroughs in manufacturing of these materials with the aid of easy-to-understand illustrations. The current challenges regarding scale up, industrial production and marketing of these novel and natural polymer based superhydrophobic materials are also highlighted.
This review attempts to highlight the recent progress in the design, synthesis and fabrication of fluorine-free superhydrophobic surfaces.
In this review we attempt to clarify the notion of what is meant by the term antibacterial surfaces and categorise the approaches that are commonly used in the design of antibacterial surfaces. ...Application of surface coatings and the modification of the surface chemistry of substrata are generally considered to be a chemical approach to surface modification (as are surface polymerisation, functionalisation, and derivatisation), whereas, modification of the surface architecture of a substrate can be considered a physical approach. Here, the antifouling and bactericidal effects of antibacterial surfaces are briefly discussed. Finally, several recent efforts to design a new generation of antibacterial surfaces, which are based on mimicking the surface nanotopography of natural surfaces, are considered.
Antibiotic resistance is a global human health threat, causing routine treatments of bacterial infections to become increasingly difficult. The problem is exacerbated by biofilm formation by ...bacterial pathogens on the surfaces of indwelling medical and dental devices that facilitate high levels of tolerance to antibiotics. The development of new antibacterial nanostructured surfaces shows excellent prospects for application in medicine as next-generation biomaterials. The physico-mechanical interactions between these nanostructured surfaces and bacteria lead to bacterial killing or prevention of bacterial attachment and subsequent biofilm formation, and thus are promising in circumventing bacterial infections. This Review explores the impact of surface roughness on the nanoscale in preventing bacterial colonization of synthetic materials and categorizes the different mechanisms by which various surface nanopatterns exert the necessary physico-mechanical forces on the bacterial cell membrane that will ultimately result in cell death.
With increasing global consumption and their natural resistance to degradation, plastic materials and their accumulation in the environment is of increasing concern. This review aims to present a ...general overview of the current state of knowledge in areas that relate to biodegradation of polymers, especially poly(ethylene terephthalate) (PET). This includes an outline of the problems associated with plastic pollution in the marine environment, a description of the properties, commercial manufacturing and degradability of PET, an overview of the potential for biodegradation of conventional polymers and biodegradable polymers already in production.
Plasma-enhanced synthesis and modification of polymers is a field that continues to expand and become increasingly more sophisticated. The highly reactive processing environments afforded by the ...inherently dynamic nature of plasma media are often superior to ambient or thermal environments, offering substantial advantages over other processing methods. The fluxes of energy and matter toward the surface enable rapid and efficient processing, whereas the charged nature of plasma-generated particles provides a means for their control. The range of materials that can be treated by plasmas is incredibly broad, spanning pure polymers, polymer-metal, polymer-wood, polymer-nanocarbon composites, and others. In this review, we briefly outline some of the recent examples of the state-of-the-art in the plasma-based polymer treatment and functionalization techniques.
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•The various green routes applied for synthesizing NIPU precursors is reviewed.•Synthetic cyclic carbonates can be substituted with their bio-based equivalents.•Polyamines can be ...synthesized from their renewable analogous.•The challenges faced by industry to make use of NIPU materials are highlighted.
The synthesis of conventional polyurethanes (PUs) relies on isocyanate reactants as crucial starting materials. Toxicity, water-sensitivity and phosgene-based synthesis of isocyanates have made it necessary to undertake systematic and focused research to develop environment-friendly processes that use ecofriendly and non-hazardous materials. Among the numerous pathways that have been proposed, the reaction between cyclic carbonates and polyamines is shown to be the most promising route for the synthesis of non-isocyanates polyurethanes (NIPUs). The past decade has witnessed a consistent trend that seeks to take advantage of the vast reserve of renewable feedstocks such as vegetable oils, terpenes, lignin derivatives, and polyols as starting molecules for the synthesis of NIPU precursors. More recently, numerous strategies have come to the fore seeking to utilize the abovementioned renewable resources for the synthesis of NIPUs to meet the prerequisites of green chemistry. In this context, this review aims to shed light on recent progress that has been made in this direction. It also critically reviews the various green routes that have been pursued towards the synthesis of NIPU and their precursors to pave way for their applications in the PU industry. The challenges currently faced by industry in making use of these renewable (NIPUs and their precursors) materials into large-scale production is also highlighted.
The nanopattern on the surface of Clanger cicada (Psaltoda claripennis) wings represents the first example of a new class of biomaterials that can kill bacteria on contact based solely on their ...physical surface structure. The wings provide a model for the development of novel functional surfaces that possess an increased resistance to bacterial contamination and infection. We propose a biophysical model of the interactions between bacterial cells and cicada wing surface structures, and show that mechanical properties, in particular cell rigidity, are key factors in determining bacterial resistance/sensitivity to the bactericidal nature of the wing surface. We confirmed this experimentally by decreasing the rigidity of surface-resistant strains through microwave irradiation of the cells, which renders them susceptible to the wing effects. Our findings demonstrate the potential benefits of incorporating cicada wing nanopatterns into the design of antibacterial nanomaterials.
It is commonly accepted that nanoparticles (NPs) can kill bacteria; however, the mechanism of antimicrobial action remains obscure for large NPs that cannot translocate the bacterial cell wall. It is ...demonstrated that the increase in membrane tension caused by the adsorption of NPs is responsible for mechanical deformation, leading to cell rupture and death. A biophysical model of the NP–membrane interactions is presented which suggests that adsorbed NPs cause membrane stretching and squeezing. This general phenomenon is demonstrated experimentally using both model membranes and Pseudomonas aeruginosa and Staphylococcus aureus, representing Gram‐positive and Gram‐negative bacteria. Hydrophilic and hydrophobic quasi‐spherical and star‐shaped gold (Au)NPs are synthesized to explore the antibacterial mechanism of non‐translocating AuNPs. Direct observation of nanoparticle‐induced membrane tension and squeezing is demonstrated using a custom‐designed microfluidic device, which relieves contraction of the model membrane surface area and eventual lipid bilayer collapse. Quasi‐spherical nanoparticles exhibit a greater bactericidal action due to a higher interactive affinity, resulting in greater membrane stretching and rupturing, corroborating the theoretical model. Electron microscopy techniques are used to characterize the NP–bacterial‐membrane interactions. This combination of experimental and theoretical results confirm the proposed mechanism of membrane‐tension‐induced (mechanical) killing of bacterial cells by non‐translocating NPs.
The mechanism of antimicrobial action for nanoparticles that are unable to translocate across the bacterial cell wall remains obscure. In this work, it is demonstrated that the increase of membrane tension provoked by the adsorption of nanoparticles is responsible for mechanical deformation of the membrane, which leads to bacterial cell rupture and death.
An integrated approach is applied in the study to define the concept of ecosystems and features of their development in current conditions. Three groups of ecosystems are identified and a number of ...their types are defined, including industrial, agro-industrial, agrarian, entrepreneurial, social, innovative, national, university, regional, corporate, sectoral and business systems. The understanding of clusters as a transitional form of ecosystems is grounded, the author’s classification of them is proposed. The concept of a cluster is connected, first of all, with the phenomenon of spatial economy, therefore, the essential characteristics of spatial economy are defined in the paper. The systematization of the viewpoints of various scholars is presented along with the author’s approach to the classification of clusters according to different criteria. The problematic field of creation and development of innovative clusters in the field of agriculture is presented. The list of participants of innovative clusters in the agro-industrial complex and the system of relations between them in various functional areas are studied, and also promising trends in terms of digital economy are substantiated.
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