Search

The recent COVID‐19 pandemic and the accelerating rise of deaths associated with antibiotic‐resistant bacterial strains have highlighted the global health and economic threats caused by the super spreading of pathogens. A major route of transmission for pathogens is via surfaces contaminated by touch or droplets generated via sneezing and coughing. Current surface disinfection strategies are having diminishing efficacy, due to the increasing number of superbugs and the short‐lasting effect of disinfectants resulting in recontamination. New strategies for inhibiting surface‐mediated pathogen transmission are the focus of significant multi‐disciplinary efforts. Among those, the development of superhydrophobic surfaces (SHS) is increasingly regarded as a powerful alternative, or additive, to antimicrobial strategies. SHS provide a neutral/inert interface that can prevent viral and bacterial surface colonization. Here, the use of such water‐repellent coatings are critically reviewed to impede the surface‐mediated transmission of pathogens, addressing the challenges and future directions for their translation into real‐world settings. [ABSTRACT FROM AUTHOR]

Gallium-based liquid metals (LMs) have emerged as novel materials for biomedical applications. Gallium (Ga) is considered significantly less toxic than other LMs, such as mercury. However, Ga droplets have not been thoroughly assessed for their cytotoxicity. Here, we report the concentration-dependent cytotoxic effects of Ga nano- and microdroplets on HaCaT cells, a human keratinocyte cell line. We found that Ga droplets demonstrated substantial cytotoxic effects at 1000 μg/mL after 24 h exposure, while lower concentrations such as 500 μg/mL indicated only a slight reduction in cell viability at longer exposure times. At higher concentrations, it was observed that the cells were unable to form confluent layers and the cytoplasmic membrane became damaged. The formation of a protein corona on the Ga droplets in cell media is also described, which will be an important consideration for future research on Ga droplets for bio-applications. Importantly, this work provides an indication of the concentration at which Ga droplets become damaging to human cells, which will be useful information for a wide range of researchers and regulatory bodies. [ABSTRACT FROM AUTHOR]

In the fight against drug-resistant pathogenic bacterial and fungal cells, low-dimensional materials are emerging as a promising alternative treatment method. Specifically, few-layer black phosphorus (BP) has demonstrated its effectiveness against a wide range of pathogenic bacterial and fungal cells with studies suggesting low cytotoxicity towards healthy mammalian cells. However, the antimicrobial mechanism of action of BP is not well understood. Before new applications for this material can be realised, further in-depth investigations are required. In this work, the biochemical interaction between BP and a series of microbial cells is investigated using a variety of microscopy and spectroscopy techniques to provide a greater understanding of the antimicrobial mechanism. Synchrotron macro-attenuated total reflection-Fourier transform infrared (ATR-FTIR) micro-spectroscopy is used to elucidate the chemical changes occurring outside and within the cell of interest after exposure to BP nanoflakes. The ATR-FTIR data, coupled with high-resolution microscopy, reveals major physical and bio-chemical changes to the phospholipids and amide I and II proteins, as well as minor chemical changes to the structural polysaccharides and nucleic acids when compared to untreated cells. These changes can be attributed to the physical interaction of the BP nanoflakes with the cell membranes, combined with the oxidative stress induced by the degradation of the BP nanoflakes. This study provides insight into the biochemical interaction of BP nanoflakes with microbial cells, allowing for a better understanding of the antimicrobial mechanism of action that will be important for the next generation of applications such as implant coatings, wound dressings, or medical surfaces. [ABSTRACT FROM AUTHOR]

Liquid metals (LMs) have emerged as novel materials for biomedical applications. Here, the interactions taking place between cells and LMs are reported, presenting a unique opportunity to explore and understand the LM‐biological interface. Several high‐resolution imaging techniques are used to characterize the interaction between droplets of gallium LM and bacterial, fungal, and mammalian cells. Adhesive interactions between cells and LM droplets are observed, causing deformation of the LM droplet surface, resulting in surface wrinkling and in some cases, breakage of the native oxide layer present on the LM droplet surface. In many instances, the cell wall deforms to intimately contact the LM droplets. Single‐cell force spectroscopy is performed to quantify the adhesion forces between cells and LM and characterize the nature of the adhesion. It is proposed that the flexible nature of the cell enables multiple adhesion sites with the LM droplets, imparting tensile forces on the LM droplet surface, which results in surface wrinkling on the LM droplets due to their liquid nature. Molecular dynamics simulations also suggest that flexible biomolecules on the cell surface can disrupt the Ga2O3 layer formed at the LM droplet surface. This study reveals a unique biointerfacial interaction and provides insights into the mechanisms involved. [ABSTRACT FROM AUTHOR]

The formation and proliferation of bacterial biofilms on surfaces, particularly those on biomedical devices, is a significant issue that results in substantial economic losses, presenting severe health risks to patients. Furthermore, heterogeneous biofilms consisting of different bacterial species can induce the increase in pathogenicity, and the resistance to antimicrobial agents due to the synergistic interactions between the different species. Heterogeneous bacterial biofilms are notoriously difficult to treat due to the presence of extracellular polymeric substances (EPS) and, in conjunction with the rapid rise of multi-drug resistant pathogens, this means that new solutions for anti-biofilm treatment are required. In this study, we investigate the application of magneto-responsive gallium-based liquid metal (GLM-Fe) nanomaterials against a broad range of Gram-positive and Gram-negative bacterial mono-species and multi-species biofilms. The GLM-Fe particles exhibit a magneto-responsive characteristic, causing spherical particles to undergo a shape transformation to high-aspect-ratio nanoparticles with sharp asperities in the presence of a rotating magnetic field. These shape-transformed particles are capable of physically removing bacterial biofilms and rupturing individual cells. Following treatment, both mono-species and multi-species biofilms demonstrated significant reductions in their biomass and overall cell viability, demonstrating the broad-spectrum application of this antibacterial technology. Furthermore, the loss of integrity of the bacterial cell wall and membranes was visualized using a range of microscopy techniques, and the leakage of intracellular components (such as nucleic acids and protein) was observed. Insights gained from this study will impact the design of future liquid metal-based biofilm treatments, particularly those that rely on magneto-responsive properties. [ABSTRACT FROM AUTHOR]

The development of antimicrobial drug resistance among pathogenic bacteria and fungi is one of the most significant health issues of the 21st century. Recently, advances in nanotechnology have led to the development of nanomaterials, particularly metals that exhibit antimicrobial properties. These metal nanomaterials have emerged as promising alternatives to traditional antimicrobial therapies. In this review, a broad overview of metal nanomaterials, their synthesis, properties, and interactions with pathogenic micro‐organisms is first provided. Secondly, the range of nanomaterials that demonstrate passive antimicrobial properties are outlined and in‐depth analysis and comparison of stimuli‐responsive antimicrobial nanomaterials are provided, which represent the next generation of microbiocidal nanomaterials. The stimulus applied to activate such nanomaterials includes light (including photocatalytic and photothermal) and magnetic fields, which can induce magnetic hyperthermia and kinetically driven magnetic activation. Broadly, this review aims to summarize the currently available research and provide future scope for the development of metal nanomaterial‐based antimicrobial technologies, particularly those that can be activated through externally applied stimuli. [ABSTRACT FROM AUTHOR]

The colonisation of biomaterial surfaces by pathogenic bacteria is a significant issue of concern, particularly in light of the rapid rise of antibiotic resistance. Current strategies are proving ineffective as multi-drug resistant pathogenic bacteria emerge. Recently, it was discovered that surfaces with nanoscale features are capable of physically rupturing bacteria and hence displaying mechano-bactericidal activity. In this study, we investigated the interactions between methicillin- and gentamicin-susceptible and -resistant Staphylococcus aureus strains and nanostructured titanium surfaces, fabricated using a hydrothermal etching process. The nanostructured titanium surfaces proved to be equally effective and highly bactericidal against both the susceptible and resistant S. aureus strains, with killing efficiencies of 80.7% ± 12.0 and 86.8% ± 11.6, respectively. The mechano-bactericidal activity of these nanostructured titanium surfaces offers an innovative solution to establish medical device surfaces with antimicrobial activity in the context of increasing antibiotic resistance. [ABSTRACT FROM AUTHOR]

Biofilms are assemblages of microbial cells, extracellular polymeric substances (EPS), and other components extracted from the environment in which they develop. Within biofilms, the spatial distribution of these components can vary. Here we present a fundamental characterization study to show differences between biofilms formed by Gram-positive methicillin-resistant Staphylococcus aureus (MRSA), Gram-negative Pseudomonas aeruginosa, and the yeast-type Candida albicans using synchrotron macro attenuated total reflectance-Fourier transform infrared (ATR-FTIR) microspectroscopy. We were able to characterise the pathogenic biofilms' heterogeneous distribution, which is challenging to do using traditional techniques. Multivariate analyses revealed that the polysaccharides area (1200–950 cm−1) accounted for the most significant variance between biofilm samples, and other spectral regions corresponding to amides, lipids, and polysaccharides all contributed to sample variation. In general, this study will advance our understanding of microbial biofilms and serve as a model for future research on how to use synchrotron source ATR-FTIR microspectroscopy to analyse their variations and spatial arrangements. [ABSTRACT FROM AUTHOR]

Gastrointestinal (GIT) diseases have risen globally in recent years, and early detection of the host's gut microbiota, typically through fecal material, has become a crucial component for rapid diagnosis of such diseases. Human fecal material is a complex substance composed of undigested macromolecules and particles, and the processing of such matter is a challenge due to the unstable nature of its products and the complexity of the matrix. The identification of these products can be used as an indication for present and future diseases; however, many researchers focus on one variable or marker looking for specific biomarkers of disease. Therefore, the combination of genomics, transcriptomics, proteomics and metabonomics can give a detailed and complete insight into the gut environment. The proper sample collection, sample preparation and accurate analytical methods play a crucial role in generating precise microbial data and hypotheses in gut microbiome research, as well as multivariate data analysis in determining the gut microbiome functionality in regard to diseases. This review summarizes fecal sample protocols involved in profiling coeliac disease. [ABSTRACT FROM AUTHOR]

There is no doubt that the current knowledge in chemistry, biochemistry, biology, and mathematics have led to advances in our understanding about food and food systems. However, the so-called reductionist approach has dominated food research, hindering new developments and innovation in the field. In the last three decades, food science has moved into the digital and technological era, inducing several challenges resulting from the use of modern instrumental techniques, computing and algorithms incorporated to the exploration, mining, and description of data derived from this complexity. In this environment, food scientists need to be mindful of the issues (advantages and disadvantages) involved in the routine applications of chemometrics. The objective of this opinion paper is to give an overview of the key issues associated with the implementation of chemometrics in food research and development. Please note that specifics about the different methodologies and techniques are beyond the scope of this review. [ABSTRACT FROM AUTHOR]

High frequency (HF) electromagnetic fields (EMFs) have been widely used in many wireless communication devices, yet within the terahertz (THz) range, their effects on biological systems are poorly understood. In this study, electromagnetic radiation in the range of 0.3–19.5 × 1012 Hz, generated using a synchrotron light source, was used to investigate the response of PC 12 neuron-like pheochromocytoma cells to THz irradiation. The PC 12 cells remained viable and physiologically healthy, as confirmed by a panel of biological assays; however, exposure to THz radiation for 10 min at 25.2 ± 0.4 °C was sufficient to induce a temporary increase in their cell membrane permeability. High-resolution transmission electron microscopy (TEM) confirmed cell membrane permeabilization via visualisation of the translocation of silica nanospheres (d = 23.5 ± 0.2 nm) and their clusters (d = 63 nm) into the PC 12 cells. Analysis of scanning electron microscopy (SEM) micrographs revealed the formation of atypically large (up to 1 µm) blebs on the surface of PC 12 cells when exposed to THz radiation. Long-term analysis showed no substantial differences in metabolic activity between the PC 12 cells exposed to THz radiation and untreated cells; however, a higher population of the THz-treated PC 12 cells responded to the nerve growth factor (NGF) by extending longer neurites (up to 0–20 µm) compared to the untreated PC12 cells (up to 20 µm). These findings present implications for the development of nanoparticle-mediated drug delivery and gene therapy strategies since THz irradiation can promote nanoparticle uptake by cells without causing apoptosis, necrosis or physiological damage, as well as provide a deeper fundamental insight into the biological effects of environmental exposure of cells to electromagnetic radiation of super high frequencies. [ABSTRACT FROM AUTHOR]

Polymer contamination is a major pollutant in all waterways and a significant concern of the 21st Century, gaining extensive research, media, and public attention. The polymer pollution problem is so vast; plastics are now observed in some of the Earth's most remote regions such as the Mariana trench. These polymers enter the waterways, migrate, breakdown; albeit slowly, and then interact with the environment and the surrounding biodiversity. It is these biodiversity and ecosystem interactions that are causing the most nervousness, where health researchers have demonstrated that plastics have entered the human food chain, also showing that plastics are damaging organisms, animals, and plants. Many researchers have focused on reviewing the macro and micro-forms of these polymer contaminants, demonstrating a lack of scientific data and also a lack of investigation regarding nano-sized polymers. It is these nano-polymers that have the greatest potential to cause the most harm to our oceans, waterways, and wildlife. This review has been especially ruthless in discussing nano-sized polymers, their ability to interact with organisms, and the potential for these nano-polymers to cause environmental damage in the marine environment. This review details the breakdown of macro-, micro-, and nano-polymer contamination, examining the sources, the interactions, and the fates of all of these polymer sizes in the environment. The main focus of this review is to perform a comprehensive examination of the literature of the interaction of nanoplastics with organisms, soils, and waters; followed by the discussion of toxicological issues. A significant focus of the review is also on current analytical characterisation techniques for nanoplastics, which will enable researchers to develop protocols for nanopolymer analysis and enhance understanding of nanoplastics in the marine environment. Unlabelled Image • Polymer contamination has reached a breaking point. • Contamination has now been observed in the Earth's most remote oceans. • Macro and micro plastics have been discussed comprehensively. • Nanoplastics are an overlooked issue, this review focuses on nanoplastics. • Sources, breakdown, fates, uptake, and characterisation will be discussed. [ABSTRACT FROM AUTHOR]

Naturally occurring and synthetic nanostructured surfaces have been widely reported to resist microbial colonization. The majority of these studies have shown that both bacterial and fungal cells are killed upon contact and subsequent surface adhesion to such surfaces. This occurs because the presence of high-aspect-ratio structures can initiate a self-driven mechanical rupture of microbial cells during the surface adsorption process. While this technology has received a large amount of scientific and medical interest, one important question still remains: what factors drive microbial death on the surface? In this work, the interplay between microbial-surface adhesion, cell elasticity, cell membrane rupture forces, and cell lysis at the microbial-nanostructure biointerface during adsorptive processes was assessed using a combination of live confocal laser scanning microscopy, scanning electron microscopy, in situ amplitude atomic force microscopy, and single-cell force spectroscopy. Specifically, the adsorptive behavior and nanomechanical properties of live Gram-negative ( Pseudomonas aeruginosa ) and Gram-positive (methicillin-resistant Staphylococcus aureus ) bacterial cells, as well as the fungal species Candida albicans and Cryptococcus neoformans , were assessed on unmodified and nanostructured titanium surfaces. Unmodified titanium and titanium surfaces with nanostructures were used as model substrates for investigation. For all microbial species, cell elasticity, rupture force, maximum cell-surface adhesion force, the work of adhesion, and the cell-surface tether behavior were compared to the relative cell death observed for each surface examined. For cells with a lower elastic modulus, lower force to rupture through the cell, and higher work of adhesion, the surfaces had a higher antimicrobial activity, supporting the proposed biocidal mode of action for nanostructured surfaces. This study provides direct quantification of the differences observed in the efficacy of nanostructured antimicrobial surface as a function of microbial species indicating that a universal, antimicrobial surface architecture may be hard to achieve.

Antibiotic resistance has made the treatment of biofilm-related infections challenging. As such, the quest for next-generation antimicrobial technologies must focus on targeted therapies to which pathogenic bacteria cannot develop resistance. Stimuli-responsive therapies represent an alternative technological focus due to their capability of delivering targeted treatment. This study provides a proof-of-concept investigation into the use of magneto-responsive gallium-based liquid metal (LM) droplets as antibacterial materials, which can physically damage, disintegrate, and kill pathogens within a mature biofilm. Once exposed to a low-intensity rotating magnetic field, the LM droplets become physically actuated and transform their shape, developing sharp edges. When placed in contact with a bacterial biofilm, the movement of the particles resulting from the magnetic field, coupled with the presence of nanosharp edges, physically ruptures the bacterial cells and the dense biofilm matrix is broken down. The antibacterial efficacy of the magnetically activated LM particles was assessed against both Gram-positive and Gram-negative bacterial biofilms. After 90 min over 99% of both bacterial species became nonviable, and the destruction of the biofilms was observed. These results will impact the design of next-generation, LM-based biofilm treatments.

The waxy epicuticle of dragonfly wings contains a unique nanostructured pattern that exhibits bactericidal properties. In light of emerging concerns of antibiotic resistance, these mechano-bactericidal surfaces represent a particularly novel solution by which bacterial colonization and the formation of biofilms on biomedical devices can be prevented. Pathogenic bacterial biofilms on medical implant surfaces cause a significant number of human deaths every year. The proposed mechanism of bactericidal activity is through mechanical cell rupture; however, this is not yet well understood and has not been well characterized. In this study, we used giant unilamellar vesicles (GUVs) as a simplified cell membrane model to investigate the nature of their interaction with the surface of the wings of two dragonfly species, Austrothemis nigrescens and Trithemis annulata, sourced from Victoria, Australia, and the Baix Ebre and Terra Alta regions of Catalonia, Spain. Confocal laser scanning microscopy and cryo-scanning electron microscopy techniques were used to visualize the interactions between the GUVs and the wing surfaces. When exposed to both natural and gold-coated wing surfaces, the GUVs were adsorbed on the surface, exhibiting significant deformation, in the process of membrane rupture. Differences between the tensile rupture limit of GUVs composed of 1,2-dioleoyl- sn-glycero-3-phosphocholine and the isotropic tension generated from the internal osmotic pressure were used to indirectly determine the membrane tensions, generated by the nanostructures present on the wing surfaces. These were estimated as being in excess of 6.8 mN m -1 , the first experimental estimate of such mechano-bactericidal surfaces. This simple model provides a convenient bottom-up approach toward understanding and characterizing the bactericidal properties of nanostructured surfaces.

Dragonfly wings are of great interest to researchers investigating biomimetic designs for antiwetting and antibacterial surfaces. The waxy epicuticular layer on the membrane of dragonfly wings possesses a unique surface nanoarchitecture that consists of irregular arrays of nanoscale pillars. This architecture confers superhydrophobic, self-cleaning, antiwetting, and antibiofouling behaviors. There is some evidence available that suggests that lifestyle factors may have influenced the evolution of the wing nanostructures and, therefore, the resulting properties of the wings; however, it appears that no systematic studies have been performed that have compared the wing surface features across a range of dragonfly species. Here, we provided a comparison of relevant wing surface characteristics, including chemical composition, wettability, and nanoarchitecture, of seven species of dragonfly from three families including Libellulidae , Aeshnidae , and Gomphidae . The characteristic nanopillar arrays were found to be present, and the chemical composition and the resultant wing surface superhydrophobicity were found to be well-conserved across all of the species studied. However, subtle differences were observed between the height, width, and density of nanofeatures and water droplet bouncing behavior on the wing surfaces. The results of this research will contribute to an understanding of the physical and chemical surface features that are optimal for the design of antiwetting and antibacterial surfaces., Competing Interests: The authors declare no competing financial interest.