Gel-like Layer Research Articles

Stable Zinc Anode Facilitated by Regenerated Silk Fibroin-modified Hydrogel Protective Layer.

Inherent dendrite growth and side reactions of zinc anode caused by its unstable interface in aqueous electrolytes severely limit the practical applications of zinc-ion batteries (ZIBs). To overcome these challenges, a protective layer for Zn anode inspired by cytomembrane structure is developed with PVA as framework and silk fibroin gel suspension (SFs) as modifier. This PVA/SFs gel-like layer exerts similar to the solid electrolyte interphase, optimizing the anode-electrolyte interface and Zn2+ solvation structure. Through interface improvement, controlled Zn2+ migration/diffusion, and desolvation, this buffer layer effectively inhibits dendrite growth and side reactions. The additional SFs provide functional improvement and better interaction with PVA by abundant functional groups, achieving a robust and durable Zn anode with high reversibility. Thus, the PVA/SFs@Zn symmetric cell exhibits an ultra-long lifespan of 3150 h compared to bare Zn (182 h) at 1.0 mAh cm-2-1.0 mAh cm-2, and excellent reversibility with an average Coulombic efficiency of 99.04% under a large plating capacity for 800 cycles. Moreover, the PVA/SFs@Zn||PANI/CC full cells maintain over 20 000 cycles with over 80% capacity retention under harsh conditions at 5 and 10 A g-1. This SF-modified protective layer for Zn anode suggests a promising strategy for reliable and high-performance ZIBs.

Target-Driven Annular DNA Walker Coupled with Electrochemiluminescent Silicon Quantum Dots for APE1 Bioanalysis.

Functional DNA walkers with substantial nanostructures have been extensively investigated; however, their stability still faces challenges when exposed to diverse nuclease in clinical biological samples, resulting in the unreliability of actual assessment. This work proposed a target-driven annular DNA walker with enhanced stability enabling the sensitive and reliable response to different concentrations of apurinic/apyrimidinic endonuclease 1 (APE1), by preparing silicon quantum dots (SiQDs) as electrochemiluminescence (ECL) emitters. Specifically, the SiQDs showed significant strong and stable ECL signals by purifying the microenvironment of SiQDs through the dialysis removal of the gel-like layers surrounding the SiQDs. The relative standard deviation (RSD) of their ECL signal had been improved 16.59 times under consecutive scanning compared to that of SiQDs without dialysis, demonstrating a significant improvement in ECL stability. Subsequently, in the presence of APE1, the designed annular DNA walker was activated to move along the numerous quenching probes within the continuous cross-based DNA orbits, which were immobilized to the SiQD-modified electrode, providing ECL readout signals. The linear range of this ECL biosensor was 1.0 × 10-13 U·μL-1 to 1.0 × 10-7 U·μL-1, and the limit of detection (LOD) was as low as 1.766 × 10-14 U·μL-1. This work provides a novel structure of a DNA walker with nuclease resistance for clinical sample detection and designs a new strategy for synthesizing SiQDs with favorable ECL performance, tremendously expanding the ECL application of SiQDs.

Core-shell tin pyrophosphate-based composite membrane for fuel cell with durability enhancement at elevated temperatures

Tin pyrophosphate has been employed as a proton conductor in polymer electrolyte membranes (PEMs) at temperatures over 200 °C. However, neither the aggregation of the SnP2O7 nanoparticles nor the proton conduction mechanism of the material has been clearly clarified in PEM. The present work reports a polybenzimidazole (PBI)/SnP2O7 composite membrane with homogeneous distribution of the inorganic phase. The membrane is successfully fabricated by in-situ transformation of SnO2 nanoparticles to core-shell SnP2O7 nanoparticles in the PBI matrix during fuel cell operation. Further in-depth analysis shows that the core-shell SnP2O7 contains a crystalline SnP2O7 core, an amorphous SnP2O7 intermediate layer and a gel-like outer layer mainly containing H4P2O7. In addition, the crystal growth of the SnP2O7 nucleus consumes ions from the amorphous SnP2O7 layer, where the reacted ions are compensated by the diffusion of Sn4+ and P2O74− ions from the gel-like outer layer. Also, the fuel cell with the composite membrane shows superior proton conductivity and durability compared to the pristine phosphoric acid-doped PBI membrane at 240 °C for over 50 h. That is due to the presence of H4P2O7 in the outer layer, which contributes to high and stable proton conductivity of the core-shell SnP2O7 at 220–260 °C.

Endothelial cell activation and glycocalyx shedding - potential as biomarkers in patients with lupus nephritis.

Lupus nephritis (LN) is a common and severe manifestation of systemic lupus erythematosus and an important cause of acute and chronic kidney injury. Early diagnosis of LN and preventing relapses are key to preserving renal reserve. However, due to the complexity and heterogeneity of the disease, clinical management remains challenging. Kidney biopsy remains the gold standard for confirming the diagnosis of LN and subsequent assessment of kidney histopathology, but it is invasive and cannot be repeated frequently. Current clinical indicators of kidney function such as proteinuria and serum creatinine level are non-specific and do not accurately reflect histopathological changes, while anti-dsDNA antibody and C3 levels reflect immunological status but not kidney injury. Identification of novel and specific biomarkers for LN is prerequisite to improve management. Renal function deterioration is associated with changes in the endothelial glycocalyx, a delicate gel-like layer located at the interface between the endothelium and bloodstream. Inflammation induces endothelial cell activation and shedding of glycocalyx constituents into the circulation. This review discusses the potential role of soluble glycocalyx components as biomarkers of active LN, especially in patients in whom conventional serological and biochemical markers do not appear helpful.

The impact of vascular endothelial glycocalyx on the pathogenesis and treatment of disseminated intravascular coagulation.

Disseminated intravascular coagulation (DIC) is a complex disorder characterized by widespread activation of blood clotting mechanisms throughout the body. Understanding the role of vascular endothelial glycocalyx in the pathogenesis and treatment of DIC is crucial for advancing our knowledge in this field. The vascular endothelial glycocalyx is a gel-like layer that coats the inner surface of blood vessels. It plays a significant role in maintaining vascular integrity, regulating fluid balance, and preventing excessive clotting. In the pathogenesis of DIC, the disruption of the vascular endothelial glycocalyx is a key factor. Pathological conditions trigger the activation of enzymes, including heparanase, hyaluronase, and matrix metalloproteinase. This activation leads to glycocalyx degradation, subsequently exposing endothelial cells to procoagulant stimuli. Additionally, the ANGPTs/Tie-2 signaling pathway plays a role in the imbalance between the synthesis and degradation of VEG, exacerbating endothelial dysfunction and DIC. Understanding the mechanisms behind glycocalyx degradation and its impact on DIC can provide valuable insights for the development of targeted therapies. Preservation of the glycocalyx integrity may help prevent the initiation and propagation of DIC. Strategies such as administration of exogenous glycocalyx components, anticoagulant agents, or Tie-2 antibody agents have shown promising results in experimental models. In conclusion, the vascular endothelial glycocalyx plays a crucial role in the pathogenesis and treatment of DIC. Further research in this field is warranted to unravel the complex interactions between the glycocalyx and DIC, ultimately leading to the development of novel therapies.

Reducing starch digestibility of white rice by structuring with hydrocolloids

Controlling starch digestion in high glycaemic index staple foods such as white rice is of interest as it has been associated with reduced risk for conditions such as obesity and type-2 diabetes mellitus. Addition of hydrocolloids has been proposed to reduce the rate of post-prandial glucose by controlling the rate of starch hydrolysis. In this work, the potential of a range of hydrocolloids to modify starch digestibility when added (at 1 % maximum concentration) during cooking of white rice was first investigated. Low acyl gellan gum (LAG) showed the highest potential (in-vitro estimated Glycaemic Index reduced by about 20 %, from 94 in the control to 78 in the LAG rice) and was investigated further. While the grains of rice control and rice with LAG appeared similar, SEM images revealed a gel-like layer (a few micrometers in thickness) on the surface of the treated samples. Addition of LAG appeared to also have an effect on the breakdown of a simulated cm-sized bolus. During gastric digestion, bolus breakdown of the rice control was completed after 30 min, while the rice LAG bolus appeared intact after 1 h of observation. This was attributed to strengthening of the LAG gel in the acidic environment of the stomach. During intestinal digestion, rice samples containing 1 % LAG appeared to be less susceptible to breakdown when seen under a microscope and in environmental SEM, while they showed larger rice particle aggregates, compared to rice control. Overall, LAG showed potential to control starch digestion kinetics of white rice with a mechanism that may involve formation of a protective layer on the rice grains (um) that reduces bolus break down (cm) and enzymatic hydrolysis (nm). Outcomes of this work will be used to identify conditions for further relevant in-vitro and in-vivo investigations.

EMERGENCY COOLING OF SUPERHEATED SURFACES BY NANOFLUIDS ADDITIVES IN STOP- AND NON-STOP MODES OF HEAT LOAD RISE

Early [Technical Physics Letters, 2016, Vol. 42, P. 677–681. — https://doi.org/10.1134/ S106378501607004X] we have shown the possibility of emergency cooling of an overheated Ni/Cr surface using additives of aluminosilicate nanofluids (AlSi-NF) at the time of developed film boiling of water (crisis), provided that the increase in thermal load is stopped and its fixation at the level of Q » 1.0 MW/m2, exceeding the critical heat flux (CHF) of water (0.7 MW/m2). However, in real operating conditions of cooling systems (especially for nuclear reactors), emergency situations sometimes arise in which it is very problematic to immediately turn off the heat load supply or maintain it at a certain predetermined level. In this regard, in this work, on a fully automated stand, the peculiarities of eliminating the water boiling crisis and emergency cooling of the overheated surface of the mini-reactor heater by injecting a portion of hot AlSi-NF in conditions of film boiling of water and a steady increase in heat load were studied, and the results were compared with previously obtained in the mode of stopping the rise of the thermal load. The test was carried out on an aqueous AlSi-NF nanofluid obtained on the basis of a natural mixture of aluminosilicates montmorillonite + palygorskite (Ukraine). The boiling-overheating-cooling curves, as well as the time dependences of the heat transfer coefficient and the heating surface temperature, were recorded in automatic real-time mode. Emergency cooling of the overheated surface (from 600 to 125 °C) after the introduction of a portion of hot AlSi-NF occurred in a matter of minutes due to a sharp increase in the heat transfer coefficient α up to 55,000 W/(m2.K). Such a phenomenon of a sharp intensification of heat transfer and a 3-fold increase in the specific heat flux (qsp) during boiling of AlSi-NF compared to the base liquid (water) is explained by the deposition on the heating surface of a gel-like layer of nanoparticles with high hydrophilicity and mobility, which can sharply increase nucleate boiling and convection. Regardless of the mode of supplying the heat load, the principal possibility of overcoming the boiling crisis and emergency cooling of the superheated surface with the addition of AlSi-NF nanofluid has been established, for a time sufficient to eliminate the accident. Bibl. 27, Fig. 4, Tab. 1.

Anion exchange resin/quartz sand bi-layer composite dynamic membranes in ultrafiltration for algae-laden water treatment

Ultrafiltration treatment of algae-laden water is the biggest challenge of membrane fouling. In this study, a bi-layer composite dynamic membrane was constructed by depositing anion exchange resin (AER) and quartz sand on the surface of UF membrane to enhance the separation performance and reduce membrane fouling. AER deposition layers improve contaminants removal and reduce membrane fouling based on retention and ion exchange effect, however, the large porosity results in less than optimal efficiency gains. Deposition of quartz sand on the AER deposit layer significantly enhanced pollutants removal rate and reduced the fouling resistance of the membrane. Compared to AER deposition alone, the bi-layer significantly improved the removal of DOC (20%), UV254 (22%), protein (18%), polysaccharide (13%), MC-LR (11%), GSM (18%) and 2-MIB (3%) and slowed down the development of fouling resistance when the amount of quartz sand deposited reached 68.6 g/m2. As the quartz sand deposition increased to 91.4 g/m2, the presence of a critical value was found, and although the pollutants retention rate increased further, reversible fouling appeared to increase. SEM image analysis of the dense sediment layer traps too much contaminants, resulting in a gel-like layer of contamination that increases membrane fouling.

Cerebrovascular glycocalyx damage and microcirculation impairment in patients with temporal lobe epilepsy

Temporal lobe epilepsy (TLE) is increasingly associated with blood-brain barrier dysfunction and microvascular alterations, yet the pathophysiological link is missing. An important barrier function is exerted by the glycocalyx, a gel-like layer coating the endothelium. To explore such associations, we used intraoperative videomicroscopy to quantify glycocalyx and microcirculation properties of the neocortex and hippocampus of 15 patients undergoing resective brain surgery as treatment for drug-resistant TLE, and 15 non-epileptic controls. Fluorescent lectin staining of neocortex and hippocampal tissue was used for blood vessel surface area quantification. Neocortical perfused boundary region, the thickness of the glycocalyx’ impaired layer, was higher in patients (2.64 ± 0.52 µm) compared to controls (1.31 ± 0.29 µm), P < 0.01, indicative of reduced glycocalyx integrity in patients. Moreover, erythrocyte flow velocity analysis revealed an impaired ability of TLE patients to (de-)recruit capillaries in response to changing metabolic demands (R2 = 0.75, P < 0.01), indicating failure of neurovascular coupling mechanisms. Blood vessel quantification comparison between intraoperative measurements and resected tissue showed strong correlation (R2 = 0.94, P < 0.01). This is the first report on in vivo assessment of glycocalyx and microcirculation properties in TLE patients, confirming the pivotal role of cerebrovascular changes. Further assessment of the cerebral microcirculation in relation to epileptogenesis might open avenues for new therapeutic targets for drug-resistant epilepsy.

Extraordinary Destabilization of Silica Nanocolloids by Filtration

After silica nanoparticles in solutions were filtered by a syringe filter with a much larger pore size than the particle diameter Dp, the filtrated effects on the rapid coagulation rate in 1 M KCl solution, the dynamic light scattering diameter, and the zeta potential at pH ∼ 6 were investigated by employing the particles of two different sizes: S particles (Dp ∼ 50 nm) of silica and latex and L particles (Dp ∼ 300 nm) of silica. It was found that the hydrodynamic diameters of silica particles became a little smaller and the absolute values of their zeta potentials decreased significantly by filtration, but that is not the case for latex particles. As for the rapid coagulation rate, the value of silica S particles increased more than 2 orders of magnitude by filtration, but no significant difference was found in the case of silica L and latex S particles. From these data, it was postulated that the gel-like layer was removed from the surface of silica S particles by filtration and the existence of the gel-like layer resulted into about 2 orders of magnitude reduction of the rapid coagulation rate. The extraordinary reduction of rapid coagulation of silica particles at Dp < 150 nm was successfully estimated by the revised Smoluchowski theory, which we call the Higashitani-Mori (HM) model. It was also found that the rapid coagulation rate of filtrated particles decreased slowly with a decreasing particle size at Dp < ca. 250 nm, which was also estimated properly by the HM model, neglecting the contribution of the redispersion of coagulated particles. Another finding in this study was that the gel-like layers were recovered with time even if they were removed by filtration, although the detailed mechanism of this recovering is not known at present and left as a future problem.

Acute pyelonephritis in pregnancy and plasma syndecan-1: evidence of glycocalyx involvement

Background Acute pyelonephritis, a risk factor for maternal sepsis, adult respiratory distress syndrome, and preterm labor, is a frequent cause of hospitalization. This condition is characterized by excessive intravascular inflammation and endothelial cell activation and dysfunction. Syndecan-1, a major component of the glycocalyx, is a gel-like layer that covers the luminal surface of healthy endothelial cells, preserving and mediating many endothelial functions. During pregnancy, there is an additional potential source of syndecan-1, the “syncytiotrophoblast glycocalyx,” which lines the intervillous space. Insults that damage the glycocalyx lead to a shedding of syndecan-1 into the circulation. Hence, syndecan-1 has been proposed as a marker of endothelial injury in conditions such as sepsis, trauma, cardiovascular disease, and diabetes mellitus. Objective The objective of this study was to determine whether the plasma syndecan-1 concentration changes in women with acute pyelonephritis in the presence or absence of bacteremia. Study design This cross-sectional study included three groups: (1) non-pregnant women (n = 25); (2) women with an uncomplicated pregnancy from whom samples were collected preterm (n = 61) or at term (n = 69); and (3) pregnant women diagnosed with acute pyelonephritis from whom samples were collected at the time of diagnosis during the second and third trimesters (n = 33). The diagnosis of acute pyelonephritis was based on clinical findings and a positive urine culture for bacteria. Blood culture results were available in 85% (28/33) of women with acute pyelonephritis. Plasma concentrations of syndecan-1 were determined by a validated immunoassay. Results (1) Women with an uncomplicated pregnancy had a higher plasma concentration of syndecan-1 than non-pregnant women. The geometric mean (95% confidence interval [CI]) of syndecan-1 concentration was 51.0 (12.1–216.1) ng/mL in non-pregnant controls; 1280 (365–4487) ng/mL in normal preterm gestations; and 1786 (546–5834) ng/mL in normal term gestations (adjusted p < .005 for all three between group comparisons); (2) plasma syndecan-1 concentrations increased with gestational age among women with a normal pregnancy (p < .001, R 2 = 0.27); (3) syndecan-1 multiple of the mean (MoM) values in pregnant patients with acute pyelonephritis were higher than those in normal pregnant women based on second- and third-trimester samples (p = .048, 1.26-fold change). The increase was driven primarily by cases with a positive blood culture (p = .009, 1.74-fold change); (4) when data from third-trimester samples were compared, overall differences in syndecan-1 MoM values between cases and controls were slightly larger (p = .03, 1.36- fold change), which were especially contributed to by cases with a positive blood culture (p = .023, fold change 1.79-fold change). Conclusions Plasma syndecan-1 concentration is higher in pregnant women and increases as a function of gestational age. Patients with acute pyelonephritis have a higher plasma concentration of syndecan-1, and this is particularly the case in the presence of bacteremia.

Endothelial glycocalyx in hepatopulmonary syndrome: An indispensable player mediating vascular changes.

Hepatopulmonary syndrome (HPS) is a serious pulmonary vascular complication that causes respiratory insufficiency in patients with chronic liver diseases. HPS is characterized by two central pathogenic features-intrapulmonary vascular dilatation (IPVD) and angiogenesis. Endothelial glycocalyx (eGCX) is a gel-like layer covering the luminal surface of blood vessels which is involved in a variety of physiological and pathophysiological processes including controlling vascular tone and angiogenesis. In terms of lung disorders, it has been well established that eGCX contributes to dysregulated vascular contraction and impaired blood-gas barrier and fluid clearance, and thus might underlie the pathogenesis of HPS. Additionally, pharmacological interventions targeting eGCX are dramatically on the rise. In this review, we aim to elucidate the potential role of eGCX in IPVD and angiogenesis and describe the possible degradation-reconstitution equilibrium of eGCX during HPS through a highlight of recent literature. These studies strongly underscore the therapeutic rationale in targeting eGCX for the treatment of HPS.

Mathematical Modeling of Wax Deposition in Field-Scale Crude Oil Pipeline Systems

The formation of solid wax crystals, which interlock and form a gel-like layer on the inner wall of the crude oil pipeline, influences the transportation of waxy crude oil. The deposited layer grows continuously and hardens during the oil transportation, reducing the effective inside diameter of the crude oil pipeline and the flow rate. In extreme cases, the deposited layer may block the crude oil pipeline leading to a loss of production and capital investment. In this paper, wax deposition from multiphase flow in field-scale oil pipeline transport systems has been studied. The novelty of this work is to develop a mathematical model that incorporates water-in-oil emulsions, wax precipitation kinetics, molecular diffusion, and shear dispersion to enable accurate predictions of both the wax deposit growth rate and aging of the deposit. The coupled nonlinear partial differential equations governing the flow are discretized in time by a second-order semi-implicit time discretization scheme based on the Adams-Bashforth and Crank-Nicolson methods, which completely decouples the computation of the governing equations. The resulting temporal schemes are discretized in space by the bivariate spectral collocation method based on Chebyshev-Gauss-Lobatto grid points and simulated in MATLAB software to obtain the profiles of the flow variables. The simulation results are presented in graphical and in tabular forms and discussed. This study found that the deposit thickness is directly proportional to the Reynolds number and inversely proportional to the mass Grashof number, Schmidt number, and Weber number. Deposit aging is rampant during the early stages of wax deposition, after which it stabilizes at a specific value as time elapses. A deposition model to predict the wax deposit thickness and aging is proposed in this study. The findings of this study will help in making informed decisions on the planning of pigging operations, thermal insulation, and other remediation techniques to be applied in controlling wax deposition in field-scale crude oil pipeline systems.

Detecting Early-Stage Cohesion Due to Calcium Silicate Hydration with Rheology and Surface Force Apparatus.

Extremely robust cohesion triggered by calcium silicate hydrate (C-S-H) precipitation during cement hardening makes concrete one of the most commonly used man-made materials. Here, in this proof-of-concept study, we seek an additional nanoscale understanding of early-stage cohesive forces acting between hydrating model tricalcium silicate (C3S) surfaces by combining rheological and surface force measurements. We first used time-resolved small oscillatory rheology measurements (SAOSs) to characterize the early-stage evolution of the cohesive properties of a C3S paste and a C-S-H gel. SAOS revealed the reactive and viscoelastic nature of C3S pastes, in contrast with the nonreactive but still viscoelastic nature of the C-S-H gel, which proves a temporal variation in the cohesion during microstructural physicochemical rearrangements in the C3S paste. We further prepared thin films of C3S by plasma laser deposition (PLD) and demonstrated that these films are suitable for force measurements in the surface force apparatus (SFA). We measured surface forces acting between two thin C3S films exposed to water and subsequent in situ calcium silicate hydrate precipitation. With the SFA and SFA-coupled interferometric measurements, we resolved that C3S surface reprecipitation in water was associated with both increasing film thickness and progressively stronger adhesion (pull-off force). The lasting adhesion developing between the growing surfaces depended on the applied load, pull-off rate, and time in contact. These properties indicated the viscoelastic character of the soft, gel-like reprecipitated layer, pointing to the formation of C-S-H. Our findings confirm the strong cohesive properties of hydrated calcium silicate surfaces that, based on our preliminary SFA measurements, are attributed to sharp changes in the surface microstructure. In contact with water, the brittle and rough C3S surfaces with little contact area weather into soft, gel-like C-S-H nanoparticles with a much larger surface area available for forming direct contacts between interacting surfaces.

Experimental Investigation of the Novel Periodic Feed Pressure Technique in Minimizing Fouling during the Filtration of Oily Water Systems Using Ceramic Membranes.

Fouling represents a bottleneck problem for promoting the use of membranes in filtration and separation applications. It becomes even more persistent when it comes to the filtration of fluid emulsions. In this case, a gel-like layer that combines droplets, impurities, salts, and other materials form at the membrane’s surface, blocking its pores. It is, therefore, a privilege to combat fouling by minimizing the accumulation of these droplets that work as seeds for other incoming droplets to cluster and coalesce with. In this work, we explore the use of the newly developed and novel periodic feed pressure technique (PFPT) in combating the fouling of ceramic membranes upon the filtration of oily water systems. The PFPT is based on alternating the applied transmembrane pressure (TMP) between the operating one and zero. A PFPT cycle is composed of a filtration half-cycle and a cleaning half-cycle. Permeation occurs when the TMP is set at its working value, while the cleaning occurs when it is zero. Three PFPT patterns were examined over two feeds of oily water systems with oil contents of 100 and 200 ppm, respectively. The results show that the PFPT is very effective in minimizing the problem of fouling compared to a non-PFPT normal filtration. Furthermore, the overall drops in permeate flux during the cleaning half-cycles are compensated by appreciable enhancement due to the significant elimination of fouling development such that the overall production of filtered water is even increased. Inspection of the internal surface of the membrane post rinsing at the end of the experiment proves that all PFPT cycles maintained the ceramic membranes as clean after a 2-h operation. This can ensure a prolonged lifespan of the ceramic membrane use and a continuous greater permeate volume production. The advantage of the PFPT is that it can be implemented on existing units with minimal modification, ease of operation, and saving energy.

Endothelial Glycocalyx Degradation in Critical Illness and Injury.

The endothelial glycocalyx is a gel-like layer on the luminal side of blood vessels that is composed of glycosaminoglycans and the proteins that tether them to the plasma membrane. Interest in its properties and function has grown, particularly in the last decade, as its importance to endothelial barrier function has come to light. Endothelial glycocalyx studies have revealed that many critical illnesses result in its degradation or removal, contributing to endothelial dysfunction and barrier break-down. Loss of the endothelial glycocalyx facilitates the direct access of immune cells and deleterious agents (e.g., proteases and reactive oxygen species) to the endothelium, that can then further endothelial cell injury and dysfunction leading to complications such as edema, and thrombosis. Here, we briefly describe the endothelial glycocalyx and the primary components thought to be directly responsible for its degradation. We review recent literature relevant to glycocalyx damage in several critical illnesses (sepsis, COVID-19, trauma and diabetes) that share inflammation as a common denominator with actions by several common agents (hyaluronidases, proteases, reactive oxygen species, etc.). Finally, we briefly cover strategies and therapies that show promise in protecting or helping to rebuild the endothelial glycocalyx such as steroids, protease inhibitors, anticoagulants and resuscitation strategies.

Analysis of a Gel-like State of Nickel Hydroxide Created By Electrochemical Aging

As global energy demands increase, the need for clean energy and energy storage is evident. Water electrolysis has shown promise as a clean energy storage solution and can be coupled with other clean energy techniques (e.g., wind, solar) to store chemical energy in the form of hydrogen. Alkaline systems are of particular interest as they are more cost effective compared to acidic systems that require precious metal-based catalysts. Alkaline water electrolysis suffers from inefficiencies that include the oxidative half reaction known as the oxygen evolution reaction (OER). Nickel-based electrocatalysts are being developed for the electrochemical transformations of organic species and used in gas evolution reactions, such as the OER. Nickel-based materials are sought after in part for their lower cost relative to precious metal catalysts (e.g., Pt, Ru, Ir), but they lack the higher electrochemical activity achieved by their precious metal counterparts. To develop more active and durable materials and to better understand the mechanisms involved in electrochemical transformations on nickel-based materials, it is essential to understand how these materials evolve and age as a result of electrocatalytic use.In this study, we have preserved the hydrated form of Ni electrocatalysts aged under alkaline conditions relevant to the OER. We prepared a series of electrocatalysts with nano- and micro-scale grains that were polished to a similar nano-scale roughness. First, we electrochemically aged Ni electrocatalysts with nanoscale and microscale grains by potential cycling techniques (i.e., cyclic voltammetry). Following electrochemical aging, the Ni electrocatalysts were preserved by immersion in liquid nitrogen and sublimed in a lyophilizer. After this freeze-drying process, the electrocatalysts were imaged under cryogenic conditions using scanning electron microscopy (SEM) techniques. A comparison was made to aged electrocatalysts where freeze-drying was implemented and those that were allowed to air dry. The surfaces of aged Ni electrocatalysts were all observed to contain an electrochemically active layer with a gel-like form. When the catalysts were air-dried, the layer appeared to have a collapsed, web-like texture. Through the use of transmission electron microscopy analyses, it was determined that these gel-like layers contained predominantly nanocrystalline β-phase nickel hydroxide (β-Ni(OH)2), which likely formed due to relaxation of the OER active beta-phase nickel oxyhydroxide [β-NiOOH] prior to the imaging process. The formation of the gel-like layer covering these electrocatalysts has implications for dynamic processes taking place at their interface with the electrolyte. Processes influenced by the gel-like form of this active layer include the rates of diffusion of electrolyte, the mechanism of O2 bubble nucleation, and the mechanics of bubble release. The results of these studies also have implications for the electrocatalytic activity and stability of other types of electrocatalysts. Further, this work can be extended for the design of new electrocatalysts for a variety of electrocatalytic processes, such as the hydrogen evolution reaction and other gas evolution reactions. Figure 1

Vascular Endothelial Glycocalyx Damage and Potential Targeted Therapy in COVID-19.

COVID-19 is a highly infectious respiratory disease caused by a new coronavirus known as SARS-CoV-2. COVID-19 is characterized by progressive respiratory failure resulting from diffuse alveolar damage, inflammatory infiltrates, endotheliitis, and pulmonary and systemic coagulopathy forming obstructive microthrombi with multi-organ dysfunction, indicating that endothelial cells (ECs) play a central role in the pathogenesis of COVID-19. The glycocalyx is defined as a complex gel-like layer of glycosylated lipid–protein mixtures, which surrounds all living cells and acts as a buffer between the cell and the extracellular matrix. The endothelial glycocalyx layer (EGL) plays an important role in vascular homeostasis via regulating vascular permeability, cell adhesion, mechanosensing for hemodynamic shear stresses, and antithrombotic and anti-inflammatory functions. Here, we review the new findings that described EGL damage in ARDS, coagulopathy, and the multisystem inflammatory disease associated with COVID-19. Mechanistically, the inflammatory mediators, reactive oxygen species (ROS), matrix metalloproteases (MMPs), the glycocalyx fragments, and the viral proteins may contribute to endothelial glycocalyx damage in COVID-19. In addition, the potential therapeutic strategies targeting the EGL for the treatment of severe COVID-19 are summarized and discussed.

Biophysical Properties of Endothelial Mechanotransduction Mediated by Glycocalyx

Endothelial surface glycocalyx (ESG) is a carbohydrate‐rich layer found on the endothelial cell (EC) surface lining all blood vessels' inner lumen. Composed of membrane glycoproteins, glycosaminoglycans (GAGs), such as hyaluronan and heparan sulfate (HS), and proteoglycans, the ESG forms a bulky, gel‐like layer serving critical functions in blood flow mechanotransduction, endothelial permeability maintenance, leukocyte adhesion, and inflammation control. ESG is known for sensing shear stress of blood flow and transducing the mechanical signal into nitric oxide (NO) production. NO is an essential signaling molecule to regulate vascular tone. To date, the molecular pathways of ESG‐mediated mechanotransduction have not been completely clear.We utilize a custom‐built AFM with fluorescence imaging capabilities to vertically stretch the ESG, which applies a pulling force to specific ESG components on the surface of a single live mouse brain endothelial cell (bEnd.3) and quantify the cell's NO production in real‐time. NO production is quantified by the fluorescent dye DAF‐FM. AFM probe is coated with monoclonal antibodies against HS or glypican‐1 (a major core protein for HS) to exert pulling forces onto the HS or glypican‐1 on bEnd.3. To ensure that DAF intensity is a signal of NO production, we treated the cells with L‐NAME (an inhibitor of endothelial nitric oxide synthase). The DAF intensity was greatly reduced, which confirms that the DAF intensity is representing NO production.The AFM anti‐glypican‐1 coated probe showed an increase in DAF intensity, while the anti‐HS probe is shown to have a slight rise in DAF intensity. Since HS may attach to other proteins besides glypican, the data suggest that glypican‐1 is a more critical mechanotransducer. Our prior study indicated cation‐permeable, transient receptor potential (TRP) ion channels mediate stretch‐induced NO production. Probes were coated in glypican‐1 while the cells were exposed to Amiloride or SKF96365, blockers of TRPP2 and TRPC1 channels, respectively. After the Amiloride‐treated cells were mechanically stimulated, there was a reduction of NO production. However, the amount of NO output was still significant over the basal levels observed in cells. When the SKF96365‐treated cells were mechanically stimulated, production was inhibited entirely, thus, demonstrating TRPC1 channels play a vital role in allowing the Ca2+ into the cell to begin NO production cascade.These findings confirm the critical roles of HS, glypican‐1, and TRP channels on the rapid NO production resulting from mechanical signaling and have important implications for ESG‐related cardiovascular diseases such as diabetes, strokes, cardiac arrest, and atherosclerosis. It has been shown that intracellular Ca2+regulates eNOS activity. In future studies, we will measure the Ca2+intake mediated by TRP channels and delineate the interplay among mechanical stretch, TRP channel activation, Ca2+intake and NO production.

Interfacial nano-engineering by graphene oxide to enable better utilization of silica fume in cementitious composite

As an industrial by-product, silica fume (SF) has been widely employed as supplementary cementitious material to develop high-performance concrete, and contribute to the sustainability goals of the concrete industry. However, with the typical size in the range of 50–300 nm, SF particles tend to form agglomerations when mixed with water and quickly become covered by a gel-like layer, thus retarding hydration. In this study, SF was coated with graphene oxide (GO) to nano-engineer the interface between SF and cement, aimed to allow better utilization of SF in cementitious composites. We report the concept of a nano/microhybrid via the electrostatic adsorption of negatively charged GO on positively charged modified SF (termed as MSF@GO), which aims to improve the dispersion quality of SF as well as the SF-cement interaction. The addition of 5 wt% modified SF (MSF) and 0.04 wt% GO (by mass of binder) result in a significant improvement of 3-d and 28-d compressive strengths of a cement paste by 56% and 29%, respectively, as compared to the sample incorporating 5 wt% SF. Additionally, the 5MSF@GO paste exhibits a greatly reduced initial sorptivity, by 33% (from 1.56 mm to 1.05 mm), along with the lowest secondary sorptivity. The noticeably higher strengths and lower water transport are primarily attributable to the increased polymerization of calcium silicate hydrates and the refinement of pore structure. This study demonstrates the great potential to improve the utilization efficiency of SF by interfacial nano-engineering with GO nanocoating and provide a new strategy to develop low-carbon cementitious composites for practical applications.