Postbiotics-peptidoglycan, lipoteichoic acid, exopolysaccharides, surface layer protein and pili proteins-Structure, activity in wounds and their delivery systems.

Chronic wound healing is a pressing global public health concern. Abuse and drug resistance of antibiotics are the key problems in the treatment of chronic wounds at present. Postbiotics are a novel promising strategy. Previous studies have reported that postbiotics have a wide range of biological activities including antimicrobial, immunomodulatory, antioxidant and anti-inflammatory abilities. However, several aspects related to these postbiotic activities remain unexplored or poorly known. Therefore, this work aims to outline general aspects and emerging trends in the use of postbiotics for wound healing, such as the production, characterization, biological activities and delivery strategies of postbiotics. In this review, a comprehensive overview of the physiological activities and structures of postbiotic biomolecules that contribute to wound healing is provided, such as peptidoglycan, lipoteichoic acid, bacteriocins, exopolysaccharides, surface layer proteins, pili proteins, and secretory proteins (p40 and p75 proteins). Considering the presence of readily degradable components in postbiotics, potential natural polymer delivery materials and delivery systems are emphasized, followed by the potential applications and commercialization prospects of postbiotics. These findings suggest that the treatment of chronic wounds with postbiotic ingredients will help provide new insights into wound healing and better guidance for the development of postbiotic products.

Modulation of Mouse Dendritic Cells In Vitro by Lactobacillus gasseri Postbiotic Proteins.

Different lactobacilli are probiotics for their beneficial effects that confer to the host. Recently, some of these effects were associated with released metabolic products/constituents (postbiotics). In the present study, the potential immunomodulatory capacity of the probiotic Lactobacillus gasseri OLL2809 cell-free supernatant (sup) was investigated in murine bone marrow-derived dendritic cells (DCs). Bacteria induced significantly higher expression of all examined cytokines than those induced by the stimulatory lipopolysaccharide (LPS) itself. On the contrary, sup only induced the anti-inflammatory IL-10 similarly to LPS, whereas IL-12 and IL-6 secretions were stimulated at a lower level. Moreover, sup reduced the surface expression of the analyzed co-stimulatory markers CD40, CD80, and CD86. Treatments of sup with different digestive enzymes indicated the proteinaceous nature of these immunomodulatory metabolites. Western blot and immunoadsorption analyzes revealed cross-reactivity of sup with the surface-layer proteins (SLPs) isolated from OLL2809. Therefore, we directly tested the ability of OLL2809 SLPs to stimulate specifically cytokine expression in iDCs. Interestingly, we found that all tested cytokines were induced by SLPs and in a dose-dependent manner. In conclusion, our results highlighted distinct immune properties between L. gasseri OLL2809 and its metabolites, supporting the concept that bacterial viability is not an essential prerequisite to exert immunomodulatory effects.

Growth of Size-Tunable Ag2O Polyhedra and Revelation of Their Bulk and Surface Lattices.

By primarily adjusting the reagent amounts, particularly the volume of AgNO3 solution introduced, Ag2O cubes with decreasing sizes from 440 to 79 nm, octahedra from 714 to 106 nm, and rhombic dodecahedra from 644 to 168 nm are synthesized. 733 nm cuboctahedra are also prepared for structural analysis. With in-house X-ray diffraction (XRD) peak calibration, shape-related peak shifts are recognizable. Synchrotron XRD measurements at 100 K reveal the presence of bulk and surface layer lattices. Bulk cell constants also deviate slightly. They show a negative thermal expansion behavior with shrinking cell constants at higher temperatures. The Ag2O crystals exhibit size- and facet-dependent optical properties. Bandgaps red-shift continuously with increasing particle sizes. Optical facet effect is also observable. Moreover, synchrotron XRD peaks of a mixture of Cu2O rhombicuboctahedra and edge- and corner-truncated cubes exposing all three crystal faces can be deconvoluted into three components with the bulk and the [111] microstrain phase as the major component. Interestingly, while the unheated Cu2O sample shows clear diffraction peak asymmetry, annealing the sample to 450 K yields nearly symmetric peaks even when returning the sample to room temperature, meaning even moderately high temperatures can permanently change the crystal lattice.

The effect of the endothelial surface layer on cell-cell interactions in microvessel bifurcations.

Red blood cells (RBCs) carry oxygen and make up 40-45% of blood by volume in large vessels down to 10% or less in smaller capillaries. Because of their finite size and large volume fraction, they are heterogeneously distributed throughout the body. This is partially because RBCs are distributed or partitioned nonuniformly at diverging vessel bifurcations where blood flows from one vessel into two. Despite its increased recognition as an important player in the microvasculature, few studies have explored how the endothelial surface layer (ESL; a vessel wall coating) may affect partitioning and RBC dynamics at diverging vessel bifurcations. Here, we use a mathematical and computational model to consider how altering ESL properties, as can occur in pathological scenarios, change RBC partitioning, deformation, and penetration of the ESL. The two-dimensional finite element model considers pairs of cells, represented by interconnected viscoelastic elements, passing through an ESL-lined diverging vessel bifurcation. The properties of the ESL include the hydraulic resistivity and an osmotic pressure difference modeling how easily fluid flows through the ESL and how easily the ESL is structurally compressed, respectively. We find that cell-cell interaction leads to more uniform partitioning and greatly enhances the effects of ESL properties, especially for deformation and penetration. This includes the trend that increased hydraulic resistivity leads to more uniform partitioning, increased deformation, and decreased penetration. It also includes the trend that decreased osmotic pressure increases penetration.

An ultrasensitive genosensor for detection of toxigenic and non-toxigenic Clostridioides difficile based on a conserved sequence in surface layer protein coding gene.

Clostridioides difficile (C. difficile) is the most common agent of antibiotic-associated diarrhea, leading to intestinal infection through the secretion of two major toxins. Not all strains of this bacterium are toxigenic, but some of them cause infection via their accessory virulence factors, such as surface layer protein (SlpA). SlpA is conserved in both toxigenic and non-toxigenic strains of C. difficile. In the present work, an amplification-free electrochemical genosensor was designed for the detection of the slpA gene. A glassy carbon electrode coated with gold nanoparticle-reduced graphene oxide nanocomposite was used as the working electrode, and its surface was modified using a simple thiolated linear oligonucleotide as the bioreceptor. Moreover, the hexaferrocenium tri[hexa(isothiocyanato) iron(III)] trihydroxonium (HxFc) complex was used as an intercalator, and its redox signal was recorded using differential pulse voltammetry. Scan rate studies indicated a quasi-reversible adsorption-controlled process for the HxFc complex. This genosensor showed high sensitivity with a limit of detection of 0.2 fM, a linear response range of 0.46-1900 fM, and a satisfactory specificity toward the synthetic slpA target gene. Also, the genosensor indicated responses in the mentioned linear range toward the genome extracted from either toxigenic or non-toxigenic strains of C. difficile.

Exopolysaccharides and Surface-Layer Proteins Expressed by Biofilm-State Lactiplantibacillus plantarum Y42 Play Crucial Role in Preventing Intestinal Barrier and Immunity Dysfunction of Balb/C Mice Infected by Listeria monocytogenes ATCC 19115.

Our previous study showed that Lactiplantibacillus plantarum Y42 in the biofilm state can produce more exopolysaccharides and surface-layer proteins and showed a stronger promoting effect on intestinal barrier function than that in the planktonic state. In this study, oral administration of the live/pasteurized planktonic or biofilm L. plantarum Y42 and its metabolites (exopolysaccharides and surface-layer proteins) increased the expression of Occludin, Claudin-1, ZO-1, and MUC2 in the gut of the Balb/C mice after exposure to Listeria monocytogenes ATCC 19115 and inhibited the activation of the NLRP3 inflammasome pathway, which in turn reduced the levels of inflammatory cytokines IL-1ß and IL-18 in the serum of the mice. Furthermore, oral administration of the live/pasteurized planktonic or biofilm L. plantarum Y42 and its metabolites increased the abundance of beneficial bacteria (e.g., Lachnospiraceae_NK4A136_group and Prevotellaceae_UCG-001) while reducing the abundance of harmful bacteria (e.g., norank_f__Muribaculaceae) in the gut of the mice, in line with the increase of short-chain fatty acids and indole derivatives in the feces of the mice. Notably, biofilm L. plantarum Y42 exerted a better preventing effect on the intestinal barrier dysfunction of the Balb/C mice due to the fact that biofilm L. plantarumY42 expressed more exopolysaccharides and surface-layer proteins than the planktonic state. These results provide data support for the use of exopolysaccharides and surface-layer proteins extracted from biofilm-state L. plantarum Y42 as functional food ingredients in preventing intestinal barrier dysfunction.

Tribological Properties of a Sliding Joint with an a-C:H:W Coating under Lubrication Conditions with PAO8 Oil and the Addition of 2% MoS2 Nanoparticles.

One of the promising methods for improving the durability and reliability of friction joints in combustion engines is the use of thin and hard coatings, including coatings based on amorphous DLC. The a-C:H:W coating was produced using the commercial PVD method. The tested tribological joints were made of AISI 4337 steel and SAE-48 bearing alloy (conformal contact) and AISI 4337 steel and valve shims (non-conformal contact). The contact area was lubricated with SAE 5W40 engine oil and PAO8 oil + 2 wt.% MoS2 nanoparticles. The objective of this work is to explore the influence of PAO8 + MoS2 on the tribological properties of a sliding joint with an a-C:H:W coating and the change in the properties of the oils. In the conformal contact, the lubrication of the a-C:H:W coating with PAO8 + MoS2 caused a significant increase in the friction resistance (than in) as compared to the joints with a quenching and tempering surface layer and lubricated SAE 5W40, while in the non-conformal contact, the lubrication of the a-C:H:W coating with PAO8 + MoS2 caused a decrease in the friction resistance and temperature of the contact area. The joints with the a-C:H:W coating were characterized by higher wear of the SAE-48 bearing alloy, as compared to the joints with the surface layer without coating (lubricated with SAE 5W40 oil-11-fold increase, PAO8 + MoS2-46-fold increase). The wear of valve shims with the a-C:H:W coating was significantly lower as compared to the wear of the commercial version of the valve shims (the difference between joints lubricated with SAE 5W40 oil and PAO8 + MoS2 was 12%, 36% and 29% for unit pressures of 10, 15 and 20 MPa). Lubrication of the a-C:H:W coating with PAO8 oil + MoS2 protected the sliding joints against seizing in non-conformal contact.

Effects of Lacticaseibacillus paracasei SNB-derived postbiotic components on intestinal barrier dysfunction and composition of gut microbiota.

The bacterial surface components are considered as effector molecules and show the potential to support intestinal health, but the detailed mechanism of how the gut microbiota changes after the intervention of surface molecules is still unknown. In the present study, capsular polysaccharide (B-CPS) and surface layer protein (B-SLP) were extracted from Lacticaseibacillus paracasei S-NB. The protective effect of direct administration of B-CPS (100 µg/mL) and B-SLP (100 µg/mL) on intestinal epithelial barrier dysfunction was verified based on the LPS-induced Caco-2 cell model. Additionally, the B-CPS and B-SLP could be utilized as carbon source and nitrogen source for the growth of several Lactobacillus strains, respectively. The postbiotic potential of B-CPS and B-SLP was further evaluated by in vitro fermentation with fecal cultures. The B-CPS and a combination of B-CPS and B-SLP regulated the composition of gut microbiota by increasing the relative abundances of Bacteroides, Bifidobacterium, Phascolarctobacterium, Parabacteroides, Subdoligranulum and Collinsella and decreasing the abundance of pathogenic bacteria like Escherichia-Shigella, Blautia, Citrobacter and Fusobacterium. Meanwhile, the total short-chain fatty acid production markedly increased after fermentation with either B-CPS individually or in combination with B-SLP. These results provided an important basis for the application of B-CPS and B-SLP as postbiotics to improve human intestinal health.

Nanocrystalline Composite Layer Realized by Simple Sintering Without Surface Treatment, Reducing Hydrophilicity and Increasing Thermal Conductivity.

The surface treatment for a polymer-ceramic composite is additionally performed in advanced material industries. To prepare the composite without a surface treatment, the simplest way to manufacture an advanced ceramic-particle is devised. The method is the formation of a nanocrystalline composite layer through the simple liquid-phase sintering. Using magnesia (MgO) which shows hydrophilicity, a nanocrystalline surface layer is realized by liquid-phase sintering. The amorphous matrix of nanocrystalline composite layer makes MgO hydrophobic and ensures miscibility with polymers, and the nanocrystalline MgO ensures high thermal conductivity. In addition, the liquid phase removes the open pores and makes the surface morphology smooth MgO with smooth surface (MgO-SM). Thermal interface materials (TIM) prepared with MgO-SM and epoxy show a high thermal conductivity of ≈7.5 W m-1 K-1 , which is significantly higher than 4.5 W m-1 K-1 of pure MgO TIM. Consequently, the formation process of a nanocrystalline surface layer utilizing simple liquid-phase sintering is proposed as a fabrication method for a next-generation ceramic-filler. In addition, it is fundamentally identified that the thermal conductivity of MgO depends on the Mg deficiency, and therefore a poly-crystal MgO-SM (produced at a low temperature) has a higher thermal conductivity than a single-crystal MgO (produced at a high temperature).

Analysis of Geometric Surface Structure and Surface Layer Microhardness of Ti6Al4V Titanium Alloy after Vibratory Shot Peening.

This article presents an analysis of the impact of vibratory shot peening on the surface roughness and physical properties of the Ti6Al4V titanium alloy surface layer after milling. The elements of machine parts and structures made of titanium alloys are often exposed to variable loads during operation. Therefore, it is advisable to apply methods that enhance functional properties and increase the durability of interacting components. Increasing the operational durability of such elements can be achieved by vibratory shot peening. Variable amplitudes A = 24; 33; 42; 51; 60 mm and times t = 1; 7; 13; 19; 25 min were applied. It has been demonstrated that it is possible to achieve a threefold reduction in the roughness parameter, Sa = 0.344 µm, compared with milling, Sa = 0.95 µm. An increase in Smr(c) areal material ratio was observed after vibratory shot peening compared with milling. It has been shown that amplitude has a greater impact on the increase in hardening of the surface layer gh compared with time. The highest rate of change in surface roughness and thickness of the hardened layer was achieved at a vibratory shot-peening time of t = 13 min. The greatest thickness of the hardened layer, exceeding 200 µm, was obtained after shot peening with an amplitude of A = 60 mm.

Application of surface-layer matrix-assisted laser desorption/ionization mass spectrometry imaging to pharmaceutical-loaded poly(ester urea) films.

Polymer thin films are often used in transdermal patches as a method of continuous drug administration for patients with chronic illness. Understanding the drug segregation and distribution within these films is important for monitoring proper drug release over time. Surface-layer matrix-assisted laser desorption/ionization mass spectrometry imaging (SL-MALDI-MSI) is a unique analytical technique that provides an optical representation of chemical compositions that exist at the surface of polymeric materials. Solvent-free sublimation is employed for application of matrix to the sample surface, so that only molecules in direct contact with the matrix layer are detected. Here, these methodologies are utilized to visualize variations in drug concentration at both the air and substrate interface in pharmaceutical-loaded polymer films.

Engineered Secretory Immunoglobulin A provides insights on antibody-based effector mechanisms targeting Clostridiodes difficile.

Secretory (S) Immunoglobin (Ig) A is the predominant mucosal antibody, which mediates host interactions with commensal and pathogenic microbes, including Clostridioides difficile. SIgA adopts a polymeric IgA structure that is bound by secretory component (SC). Despite significance, how SIgA supports diverse effector mechanisms is poorly characterized and SIgA-based therapies nonexistent. We engineered chimeric (c) SIgAs, in which we replaced SC domain D2 with a single domain antibody or a monomeric fluorescent protein, allowing us to investigate and enhance SIgA effector mechanisms. cSIgAs exhibited increased neutralization potency against C. difficile toxins, promoted bacterial clumping and cell rupture, and decreased cytotoxicity. cSIgA also allowed us to visualize and/or quantify C. difficile morphological changes and clumping events. Results reveal mechanisms by which SIgA combats C. difficile infection, demonstrate that cSIgA design can modulate these mechanisms, and demonstrate cSIgA's adaptability to modifications that might target a broad range of antigens and effector mechanisms.

Enhanced electrochemical performance of li-ion battery via ultrasonic-assisted inorganic-rich and thin SEI layer.

Lithium-ion batteries (LIBs) stand as a compelling solution to energy source transition in various applications such as the vehicle industry due to their energy and power density. However, the impact of mechanical factors on them remains understudied. Of particular interest is the effect of vibration, an inherent characteristic of vehicles, on battery performance. Ultrasound has been reported to improve mass transfer and surface cleaning, yet its effects on LIBs are still not thoroughly investigated. This study investigates the influence of ultrasound on the solid electrolyte interphase (SEI) layer, resulting in a thin, inorganic-rich layer. The induced SEI layer alteration improves charge transfer, showing enhanced kinetics. We also reveal that ultrasound application enhances cycling stability, maintains discharge capacity at high charging rates, and facilitates inorganic-rich SEI layer creation. This novel combination of ultrasound and LIBs presents a promising pathway for achieving high-performance batteries.

Analytical Models for Grain Size Determination of Metallic Coatings and Machined Surface Layers Using the Four-Point Probe Method.

The grain size of a metallic coating or the surface layer after the machining of metallic parts strongly impacts corrosion and wear properties along with fatigue behavior. By measuring the combined electrical resistance of this layer and the substrate using the four-point probe method, the grain size of the layer can be determined. For different grain shapes, models are derived based on an analytical approach. The parameters in the models can be determined by appropriate calibration measurements. As a result, the grain sizes can be determined quickly with a non-destructive method, which can be applied to ensure consistent coating or machining results as part of quality control routines in industrial processes.

Microstructural characterization of near-surface microstructures on rail wheels in service - an insight into "stratified surface layers".

Background: To decrease maintenance costs and improve safety in rail transportation, the understanding of rail and wheel defects is vital. Studies on "white etching layers" (WEL) on rails and wheels, prone to fatigue crack initiation, have been extensively studied. Recently, a relative named "brown etching layer" (BEL) and its combination, the so-called "stratified surface layer" (SSL), are observed in the field. This study presents an investigation on a rail wheel affected by mechanical and thermal loadings from service with focus on the different evolved layers in the near-surface region. Methods: Optical microscopy is performed on etched cross-sectional cuts to identify different evolved microstructures (WEL, BEL, SSL), further, specific regions are investigated in detail by scanning electron microscopy to evaluate the microstructural characteristics.  To analyze the change in mechanical properties, low-load Vickers hardness investigations are executed in distinctive zones. Results: This study highlights the broad variety of evolved microstructures, however, a rough classification of WEL (fine mesh-like microstructure, 900 - 1200 HV0.01) and BEL (globular cementite particles, 400 - 600 HV0.01) is given. Further, results indicate that the BEL is commonly accompanied by a WEL, representing an SSL. Conclusions: The complex loading situation in a wheel-rail contact can lead to the formation of WEL, BEL and SSL. The observation of numerous initiated fatigue cracks within these regions demonstrates the relevance of in-depth studies on evolved microstructures in wheel-rail contacts.

Investigation of the Impact of High-Speed Machining in the Milling Process of Titanium Alloy on Tool Wear, Surface Layer Properties, and Fatigue Life of the Machined Object.

This article presents the results of experimental research on the effect of high-speed machining (HSM) in the milling process on the tool wear, surface layer properties, and fatigue life of objects made of Ti-6Al-4V titanium alloy. Titanium alloys are widely used in many industries due to their high strength-to-density ratio, corrosion resistance, and resistance to dynamic loads. The experiment was conducted on a vertical three-axis machining centre, Avia VMC800HS. The influence of increased cutting speeds on the average values and amplitudes of the total cutting force components and the surface roughness of the machined workpiece was determined. Variable cutting speeds vc = 70; 130; 190; 250; 310 m/min were applied. The impact of HSM on machinability indicators, such as the microhardness of the surface layer, the distribution of residual stresses, and the fatigue life of the samples after milling, was analysed. The thickness of the hardened layer varied from 20 to 28 micrometres. The maximum compressive residual stress Ϭm = 190 MPa was achieved at the speed of vc = 190 m/min. A significant influence of increased cutting speeds on tool wear was demonstrated. The longest tool life (t = 70 min) was obtained for low cutting speeds (conventional) vc = 70 m/min.

Effect of De-Icing Chemicals on Concrete Scaling: The Role of Storage Water.

This paper deals with the effect of the character of the water used for the water storage of concrete test specimens on the results of tests for resistance to de-icing chemicals. Two experiments were conducted to investigate the effect of the content of free CO2 in water and leaching of calcium hydroxide from concrete on the test results. In the first experiment, the resistance of mortars to water and de-icing chemicals was investigated. It was found that the character of the water storage, i.e., fresh water vs. previously used water, can significantly affect the test results. The second experiment focused on investigating the effect of the content of free CO2 in water on the test results. It was found that the content of free CO2 in the water can statistically significantly influence the test results. In conclusion, the paper shows that the character of the water used for water storage of concrete test specimens and the content of free CO2 in water are essential factors that can significantly affect the results of concrete resistance tests to de-icing chemicals. Further research is needed to understand these influences and their potential use to improve the resistance of concrete.

The relationship between carbon dioxide flux and environmental parameters at a tropical coastal sea on different timescales.

This paper analyzes CO2 flux between the atmosphere and a tropical coastal sea using the eddy covariance technique. Coastal carbon dioxide flux studies are limited, particularly in tropical regions. Data was collected from the study site in Pulau Pinang, Malaysia, since 2015. The research found that the site is a moderate CO2 sink and experiences seasonal monsoonal changes that affect its carbon-sink or carbon-source capability. The analysis showed that the coastal sea systematically shifted from being a carbon-sink at night to a weak carbon-source during the day possibly due to cause by the synergistic influence of wind speed and seawater temperature. The CO2 flux are also influenced by small-scale, unpredictable winds, limited fetch, developing waves, and high-buoyancy conditions caused by low wind speeds and an unstable surface layer. Furthermore, it exhibited a linear relationship with wind speed. In stable conditions, the flux was influenced by wind speed and drag coefficient, while in unstable conditions, it was mostly controlled by friction velocity and atmospheric stability. These findings could improve our understanding of the critical factors that drive CO2 flux at the tropical coast.

Birefringent Glass-Engraved Tilted Pillar Metasurfaces for High Power Laser Applications.

Birefringent materials-which are highly needed in high power laser systems-may be limited in usage due to the laser-induced damage threshold of traditional birefringent materials. This work reports here on all-glass metasurfaces, fabricated by angled etching through sacrificial metal nanoparticle (NP) etching masks, for generation of effective birefringence in the formed layer. As a result, a fused silica metasurface, monolithic to the underlying substrate, is demonstrated to exhibit a birefringence of 6.57° under 375 nm illumination. Full-wave analysis shows a good agreement with the measurement and presents potential paths forward to increasing the effective metasurface birefringence. This is the first demonstration, to the best of knowledge, of an etching technique to obtain the resulting tilted pillar-like nanofeatures. The anisotropy of the metasurface nanoelements along the two window in-plane major axes presents different effective paths for the two polarizations and thus generates birefringence in a nonbirefringent material. Additionally, the imparted anisotropy lends itself to manipulation of physical properties of the surface as well, with metasurface feature orientation suppressing water flow along one principal axis and giving rise to water flow steering capabilities.

Experimental Revelation of Surface and Bulk Lattices in Faceted Cu2 O Crystals.

Semiconductor crystals have generally shown facet-dependent electrical, photocatalytic, and optical properties. These phenomena have been proposed to result from the presence of a surface layer with bond-level deviations. To provide experimental evidence of this structural feature, synchrotron X-ray sources are used to obtain X-ray diffraction (XRD) patterns of polyhedral cuprous oxide crystals. Cu2 O rhombic dodecahedra display two distinct cell constants from peak splitting. Peak disappearance during slow Cu2 O reduction to Cu with ammonia borane differentiates bulk and surface layer lattices. Cubes and octahedra also show two peak components, while diffraction peaks of cuboctahedra are comprised of three components. Temperature-varying lattice changes in the bulk and surface regions also show shape dependence. From transmission electron microscopy (TEM) images, slight plane spacing deviations in surface and inner crystal regions are measured. Image processing provides visualization of the surface layer with depths of about 1.5-4 nm giving dashed lattice points instead of dots from atomic position deviations. Close TEM examination reveals considerable variation in lattice spot size and shape for different particle morphologies, explaining why facet-dependent properties are emerged. Raman spectrum reflects the large bulk and surface lattice difference in rhombic dodecahedra. Surface lattice difference can change the particle bandgap.