Gelatin emulsion gels loaded with host defence peptides for the treatment of antibiotic-resistant infections.

The surge in multidrug-resistant bacteria against conventional antibiotics is a rapidly developing global health crisis necessitating novel infection management strategies. Host defence peptides (HDPs), also known as antimicrobial peptides (AMPs), offer a promising alternative to traditional antibiotics, but their practical translation is limited by their susceptibility to proteases and potential off-site cytotoxicity. In this paper, we investigate the feasibility of using gelatin emulsion gels (GELs), prepared using a water-in-oil (W/O) method, for the delivery of HDPs DJK-5 and IDR-1018 to improve their clinical utility. DJK-5-loaded GELs exhibited complete eradication of planktonic Methicillin-resistant Staphylococcus aureus (MRSA) at 4 - and 24-h intervals. Similarly, IDR-1018-loaded GELs demonstrated almost complete killing of MRSA and Escherichia coli (E. coli) after 4 h. Importantly, none of the GEL formulations investigated exhibited in vitro cytotoxicity. Overall, these HDP loaded GELs are a promising solution for the treatment of antibiotic-resistant infections.

3D printable gelatin/nisin biomaterial inks for antimicrobial tissue engineering applications.

Modern regenerative medicine approaches can rely on the fabrication of personalised medical devices and implants; however, many of these can fail due to infections, requiring antibiotics and revision surgeries. Given the rise in multidrug resistant bacteria, developing implants with antimicrobial activity without the use of traditional antibiotics is crucial for successful implant integration and improving patient outcomes. 3D printed gelatin-based implants have a broad range of applications in regenerative medicine due to their biocompatibility, ease of modification and degradability. In this paper, we report on the development of gelatin biomaterial inks loaded with the antimicrobial peptide, nisin, for extrusion-based 3D printing to produce scaffolds with controlled porosity, high shape fidelity, and structural stability. Rheological properties were comprehensively studied to develop inks that had shear thinning behaviour and viscoelastic properties to ensure optimal printability and extrudability, and enable precise deposition and structural integrity during 3D printing. The 3D printed scaffolds fabricated from the gelatin/nisin inks demonstrated excellent antimicrobial efficacy (complete kill) against Gram positive bacteria methicillin-resistant Staphylococcus aureus (MRSA). Overall, this ink's high printability and antimicrobial efficacy with the model antimicrobial peptide, nisin, offers the potential to develop customisable regenerative medicine implants that can effectively combat infection without contributing to the development of multidrug resistant bacteria.

Interpreting the role of antioxidants in vivo: A cautionary tale.

Bacteria have a remarkable ability to sense environmental stresses and to respond to these stressors by adapting their metabolism and physiology. In recent publications, investigators have suggested that multiple stresses that cause cell death share the mechanistic feature of stimulating the formation of reactive oxygen species (ROS). A central piece of evidence cited in these claims is the ability of exogenous antioxidant compounds to mitigate stress-related cell death. The validity of attributing a positive effect of exogenous antioxidants to ROS-mediated stress is challenged by an important study by Korshunov and Imlay in this issue of Molecular Microbiology. This study reports biochemical data that convincingly show that some commonly used antioxidants quench oxidants orders of magnitude too slowly to have a significant effect on the concentration of ROS in the cell. Under conditions where antioxidants minimize cell death, they also slow growth. Significantly, slowing cell growth by other means has the same restorative effect as adding an antioxidant. Based on the solid biochemical and genetic data, Korshunov and Imlay make the case for discarding the use of antioxidants to diagnose conditions that generate increased internal ROS production.

The manganese carbonyl complex [Mn(CO)3(tqa-κ3N)]Br: A novel antimicrobial agent with the potential to treat avian pathogenic Escherichia coli (APEC) infections.

The development of alternatives to antibiotics is essential for the treatment of animal infections and as a measure to reduce the selective pressure on antibiotics that are critical for human medicine. Metal complexes have been highlighted for their antimicrobial activity against several bacterial pathogens. In particular, manganese carbonyl complexes have shown efficacy against multidrug-resistant Gram-negative pathogens, and relatively low cytotoxicity against avian macrophages and in wax moth larval models. They are thus potential candidates for deployment against Avian Pathogenic Escherichia coli (APEC), the aetiological agent of avian colibacillosis, which results in severe animal welfare issues and financial losses worldwide. This study aimed to determine the efficacy of [Mn(CO)3(tqa-κ3N)]Br in Galleria mellonella and chick models of infection against APEC. The results demonstrated in vitro and in vivo antibacterial activity against all antibiotic-resistant APEC test isolates screened in the study.

Social causes and outcomes of acute transient psychotic disorder: A review of recent evidence.

BACKGROUND: Reports of increasing presentations of new cases of acute psychosis both locally, nationally and internationally during the COVID-19 pandemic, warranted further investigation. International case reports almost exclusively reported only clinical outcome (e.g. remission of psychotic symptoms), and fail to report on social precipitants or social outcomes. This is a common omission when investigating new psychosis cases such as acute and transient psychotic disorder (ATPD). In order to assess social impacts and outcomes, we conducted a rapid review of recent evidence. AIMS: To conduct a rapid review of the recent evidence of social outcomes on new cases of psychosis emerging during the COVID-19 pandemic. METHOD: Four databases (Medline, Embase, Psychinfo and Cochrane COVID-19) were searched for ATPD, psychosis and social outcomes in adults aged 18+. Duplicates were removed. There were no language limitations. Results: There were 24 papers consisting of 18 original data research papers and 6 reviews. Additionally, 33 papers/letters, reporting on 60 individual cases of psychosis emerging during the COVID-19 pandemic. These two sets of papers were reviewed separately. Many original data research papers and reviews were sub optimal in their quality, with 44% online surveys, with the remainder being routinely collected data. CONCLUSION: There is a consensus that clinical outcomes of ATPD and other brief psychotic disorders (BPD) are good in the short term. The focus only on symptomatic clinical presentation and outcomes, leaves a gap in our understanding regarding social stressors and longer term social outcomes. ATPD and BPD often may not come to the attention of Early Intervention in Psychosis services, and if they do, are discharged following symptomatic remission. Without an understanding of the social stress factors and social outcomes, opportunities may be missed to prevent increased social disability and future relapse with these presentations.

Transferring Micellar Changes to Bulk Properties via Tunable Self-Assembly and Hierarchical Ordering.

Hierarchical self-assembly is an effective means of preparing useful materials. However, control over assembly across length scales is a difficult challenge, often confounded by the perceived need to redesign the molecular building blocks when new material properties are needed. Here, we show that we can treat a simple dipeptide building block as a polyelectrolyte and use polymer physics approaches to explain the self-assembly over a wide concentration range. This allows us to determine how entangled the system is and therefore how it might be best processed, enabling us to prepare interesting analogues to threads and webs, as well as films that lose order on heating and "noodles" which change dimensions on heating, showing that we can transfer micellar-level changes to bulk properties all from a single building block.

Surface Tension and Viscosity Dependence of Slip Length over Irregularly Structured Superhydrophobic Surfaces.

A comprehensive understanding of the slip phenomenon on liquid/solid interfaces is essential for multiple real-world applications of superhydrophobic materials, especially those involving drag reduction. In the current contribution, the so-called "slip-length" on an irregularly structured superhydrophobic surface was systematically evaluated, with respect to varying liquid surface tension and viscosity. The superhydrophobic polymer-nanoparticle composite (SPNC) material used exhibits a dual-scale surface roughness and was fabricated via coating a surface with a mixture of polydimethylsiloxane solution and functionalized silica particles. A cone-and-plate rheometric device was employed to quantify the slip length. To independently study the impact of surface tension and viscosity, three types of aqueous solutions were used: sodium dodecyl sulfate, ethanol, and polyethylene glycol. Our experimental results demonstrate that a decreasing surface tension results in a decreasing slip length when the fluid viscosity is held constant. Meanwhile, the slip length is shown to increase with increasing viscosity when the surface tension of the various liquids is matched to isolate effects. The study reveals a linear relationship between slip length and both capillary length and viscosity providing a reference to potentially predict the degree of achievable drag reduction for differing fluids on SPNC surfaces.

Charge screening wormlike micelles affects extensional relaxation time and noodle formation.

A functionalised dipeptide that self-assembles to form wormlike micelles at high pH can be treated as a surfactant. By varying salt concentration, the self-assembled structures and interactions between them change, resulting in solutions with very different shear and extensional viscosity. From these, gel noodles with different mechanical properties can be prepared.

The Evolution of Nitric Oxide Function: From Reactivity in the Prebiotic Earth to Examples of Biological Roles and Therapeutic Applications.

Nitric oxide was once considered to be of marginal interest to the biological sciences and medicine; however, there is now wide recognition, but not yet a comprehensive understanding, of its functions and effects. NO is a reactive, toxic free radical with numerous biological targets, especially metal ions. However, NO and its reaction products also play key roles as reductant and oxidant in biological redox processes, in signal transduction, immunity and infection, as well as other roles. Consequently, it can be sensed, metabolized and modified in biological systems. Here, we present a brief overview of the chemistry and biology of NO-in particular, its origins in geological time and in contemporary biology, its toxic consequences and its critical biological functions. Given that NO, with its intrinsic reactivity, appeared in the early Earth's atmosphere before the evolution of complex lifeforms, we speculate that the potential for toxicity preceded biological function. To examine this hypothesis, we consider the nature of non-biological and biological targets of NO, the evolution of biological mechanisms for NO detoxification, and how living organisms generate this multifunctional gas.

CORM-3 induces DNA damage through Ru(II) binding to DNA.

When the 'CO-releasing molecule-3', CORM-3 (Ru(CO)3Cl(glycinate)), is dissolved in water it forms a range of ruthenium complexes. These are taken up by cells and bind to intracellular ligands, notably thiols such as cysteine and glutathione, where the Ru(II) reaches high intracellular concentrations. Here, we show that the Ru(II) ion also binds to DNA, at exposed guanosine N7 positions. It therefore has a similar cellular target to the anticancer drug cisplatin, but not identical, because Ru(II) shows no evidence of forming intramolecular crossbridges in the DNA. The reaction is slow, and with excess Ru, intermolecular DNA crossbridges are formed. The addition of CORM-3 to human colorectal cancer cells leads to strand breaks in the DNA, as assessed by the alkaline comet assay. DNA damage is inhibited by growth media containing amino acids, which bind to extracellular Ru and prevent its entry into cells. We conclude that the cytotoxicity of Ru(II) is different from that of platinum, making it a promising development target for cancer therapeutics.

'Carbon-Monoxide-Releasing Molecule-2 (CORM-2)' Is a Misnomer: Ruthenium Toxicity, Not CO Release, Accounts for Its Antimicrobial Effects.

Carbon monoxide (CO)-releasing molecules (CORMs) are used to deliver CO, a biological 'gasotransmitter', in biological chemistry and biomedicine. CORMs kill bacteria in culture and in animal models, but are reportedly benign towards mammalian cells. CORM-2 (tricarbonyldichlororuthenium(II) dimer, Ru2Cl4(CO)6), the first widely used and commercially available CORM, displays numerous pharmacological, biochemical and microbiological activities, generally attributed to CO release. Here, we investigate the basis of its potent antibacterial activity against Escherichia coli and demonstrate, using three globin CO sensors, that CORM-2 releases negligible CO (<0.1 mol CO per mol CORM-2). A strong negative correlation between viability and cellular ruthenium accumulation implies that ruthenium toxicity underlies biocidal activity. Exogenous amino acids and thiols (especially cysteine, glutathione and N-acetyl cysteine) protected bacteria against inhibition of growth by CORM-2. Bacteria treated with 30 µM CORM-2, with added cysteine and histidine, exhibited no significant loss of viability, but were killed in the absence of these amino acids. Their prevention of toxicity correlates with their CORM-2-binding affinities (Cys, Kd 3 µM; His, Kd 130 µM) as determined by 1H-NMR. Glutathione is proposed to be an important intracellular target of CORM-2, with CORM-2 having a much higher affinity for reduced glutathione (GSH) than oxidised glutathione (GSSG) (GSH, Kd 2 µM; GSSG, Kd 25,000 µM). The toxicity of low, but potent, levels (15 µM) of CORM-2 was accompanied by cell lysis, as judged by the release of cytoplasmic ATP pools. The biological effects of CORM-2 and related CORMs, and the design of biological experiments, must be re-examined in the light of these data.

Bacterial Oxidases of the Cytochrome bd Family: Redox Enzymes of Unique Structure, Function, and Utility As Drug Targets.

Significance: Cytochrome bd is a ubiquinol:oxygen oxidoreductase of many prokaryotic respiratory chains with a unique structure and functional characteristics. Its primary role is to couple the reduction of molecular oxygen, even at submicromolar concentrations, to water with the generation of a proton motive force used for adenosine triphosphate production. Cytochrome bd is found in many bacterial pathogens and, surprisingly, in bacteria formally denoted as anaerobes. It endows bacteria with resistance to various stressors and is a potential drug target. Recent Advances: We summarize recent advances in the biochemistry, structure, and physiological functions of cytochrome bd in the light of exciting new three-dimensional structures of the oxidase. The newly discovered roles of cytochrome bd in contributing to bacterial protection against hydrogen peroxide, nitric oxide, peroxynitrite, and hydrogen sulfide are assessed. Critical Issues: Fundamental questions remain regarding the precise delineation of electron flow within this multihaem oxidase and how the extraordinarily high affinity for oxygen is accomplished, while endowing bacteria with resistance to other small ligands. Future Directions: It is clear that cytochrome bd is unique in its ability to confer resistance to toxic small molecules, a property that is significant for understanding the propensity of pathogens to possess this oxidase. Since cytochrome bd is a uniquely bacterial enzyme, future research should focus on harnessing fundamental knowledge of its structure and function to the development of novel and effective antibacterial agents.

Low- and High-Drag Intermittencies in Turbulent Channel Flows.

Recent direct numerical simulations (DNS) and experiments in turbulent channel flow have found intermittent low- and high-drag events in Newtonian fluid flows, at Reτ=uτh/ν between 70 and 100, where uτ, h and ν are the friction velocity, channel half-height and kinematic viscosity, respectively. These intervals of low-drag and high-drag have been termed "hibernating" and "hyperactive", respectively, and in this paper, a further investigation of these intermittent events is conducted using experimental and numerical techniques. For experiments, simultaneous measurements of wall shear stress and velocity are carried out in a channel flow facility using hot-film anemometry (HFA) and laser Doppler velocimetry (LDV), respectively, for Reτ between 70 and 250. For numerical simulations, DNS of a channel flow is performed in an extended domain at Reτ = 70 and 85. These intermittent events are selected by carrying out conditional sampling of the wall shear stress data based on a combined threshold magnitude and time-duration criteria. The use of three different scalings (so-called outer, inner and mixed) for the time-duration criterion for the conditional events is explored. It is found that if the time-duration criterion is kept constant in inner units, the frequency of occurrence of these conditional events remain insensitive to Reynolds number. There exists an exponential distribution of frequency of occurrence of the conditional events with respect to their duration, implying a potentially memoryless process. An explanation for the presence of a spike (or dip) in the ensemble-averaged wall shear stress data before and after the low-drag (or high-drag) events is investigated. During the low-drag events, the conditionally-averaged streamwise velocities get closer to Virk's maximum drag reduction (MDR) asymptote, near the wall, for all Reynolds numbers studied. Reynolds shear stress (RSS) characteristics during these conditional events are investigated for Reτ = 70 and 85. Except very close to the wall, the conditionally-averaged RSS is higher than the time-averaged value during the low-drag events.

Role of Carbon Monoxide in Host-Gut Microbiome Communication.

Nature is full of examples of symbiotic relationships. The critical symbiotic relation between host and mutualistic bacteria is attracting increasing attention to the degree that the gut microbiome is proposed by some as a new organ system. The microbiome exerts its systemic effect through a diverse range of metabolites, which include gaseous molecules such as H2, CO2, NH3, CH4, NO, H2S, and CO. In turn, the human host can influence the microbiome through these gaseous molecules as well in a reciprocal manner. Among these gaseous molecules, NO, H2S, and CO occupy a special place because of their widely known physiological functions in the host and their overlap and similarity in both targets and functions. The roles that NO and H2S play have been extensively examined by others. Herein, the roles of CO in host-gut microbiome communication are examined through a discussion of (1) host production and function of CO, (2) available CO donors as research tools, (3) CO production from diet and bacterial sources, (4) effect of CO on bacteria including CO sensing, and (5) gut microbiome production of CO. There is a large amount of literature suggesting the "messenger" role of CO in host-gut microbiome communication. However, much more work is needed to begin achieving a systematic understanding of this issue.

Antibacterial activity of Mn(I) and Re(I) tricarbonyl complexes conjugated to a bile acid carrier molecule.

A bifunctional cholic acid-bis(2-pyridylmethyl)amine (bpa) ligand featuring an amide linker was coordinated to a manganese(i) or rhenium(i) tricarbonyl moiety to give [M(bpacholamide)(CO)3] with M = Mn, Re in good yield and very high purity. Strong antibacterial activity was observed against four strains of methicillin-susceptible (MSSA) and methicillin-resistant (MRSA) Staphylococcus aureus, with minimum inhibitory concentrations (MICs) in the range of 2-3.5 µM. No difference in response was observed for the MSSA vs. MRSA strains. Activity was also independent of the nature of the metal center, as the Mn and Re complexes showed essentially identical MIC values. In contrast to some other metal carbonyl complexes, the activity seems to be unrelated to the release of carbon monoxide, as photoactivation of the Mn complex reduced the potency by a factor of 2-8. Both metal complexes were non-toxic in Galleria mellonella larvae at concentrations of up to 100× the MIC value. In vivo testing in Galleria larvae infected with MRSA/MSSA demonstrated a significant increase in overall survival rates from 46% in the control to 88% in the group treated with the metal complexes. ICP-MS analysis showed that the Mn and Re cholamide complexes are efficiently internalized by E. coli cells and do not interfere with membrane integrity, as evident from a lack of release of intracellular ATP. An increased sensitivity was observed in acrB, acrD, and mdt mutants that are defective in multidrug exporters, indicating that the compounds have an intracellular mechanism of action. Furthermore, E. coli mntP mutants defective in the gene encoding an Mn exporter were more sensitive than the wildtype, while inactivation of the regulator that controls expression of the Mn uptake proteins MntP and MntH slightly increased sensitivity to the compound. Single knockout mutants defective in genes linked to bile salt and oxidative stress response (dinF, yiaH, sodA, katE, and soxS) did not show increased sensitivity relative to the wild type. Overall, neither the cholic acid moiety nor the metal-carbonyl fragment alone appear to be responsible for the biological activity observed and thus the search for the primary intracellular target continues.

A microbubble-sparged yeast propagation-fermentation process for bioethanol production.

BACKGROUND: Industrial biotechnology will play an increasing role in creating a more sustainable global economy. For conventional aerobic bioprocesses supplying O2 can account for 15% of total production costs. Microbubbles (MBs) are micron-sized bubbles that are widely used in industry and medical imaging. Using a fluidic oscillator to generate energy-efficient MBs has the potential to decrease the costs associated with aeration. However, little is understood about the effect of MBs on microbial physiology. To address this gap, a laboratory-scale MB-based Saccharomyces cerevisiae Ethanol Red propagation-fermentation bioethanol process was developed and analysed. RESULTS: Aeration with MBs increased O2 transfer to the propagation cultures. Titres and yields of bioethanol in subsequent anaerobic fermentations were comparable for MB-propagated and conventional, regular bubble (RB)-propagated yeast. However, transcript profiling showed significant changes in gene expression in the MB-propagated yeast compared to those propagated using RB. These changes included up-regulation of genes required for ergosterol biosynthesis. Ergosterol contributes to ethanol tolerance, and so the performance of MB-propagated yeast in fed-batch fermentations sparged with 1% O2 as either RBs or MBs were tested. The MB-sparged yeast retained higher levels of ergosteryl esters during the fermentation phase, but this did not result in enhanced viability or ethanol production compared to ungassed or RB-sparged fermentations. CONCLUSIONS: The performance of yeast propagated using energy-efficient MB technology in bioethanol fermentations is comparable to that of those propagated conventionally. This should underpin the future development of MB-based commercial yeast propagation.