Elevated Ionic Strength Research Articles

High sensitivity capillary electrophoresis with fluorescent detection for glycan mapping

We present in this study a novel strategy to drastically improve the detection sensitivity and peak capacity for capillary electrophoresis with laser induced fluorescent detection (CE-LIF) of glucose oligomers and released glycans. This is based on a new approach exploiting a polymer-free background electrolyte (BGE) for CE-LIF of glycans. The best performance in terms of sample stacking and suppression of electroosmotic flow (EOF) was found for a BGE composed of triethanolamine/citric acid and triethanolamine/acetic acid at elevated ionic strengths (IS up to 200 mM). Compared to the conventional protocols for CE-LIF of glucose-oligosaccharides and released glycans, our polymer-free strategy offered up to 5-fold improvement of detection sensitivity and visualization of higher degree of polymerization (DP) of glucose oligomers (18 vs 15). To further improve the detection sensitivity, a new electrokinetic preconcentration strategy via large volume sample stacking with electroosmotic modulation without having recourse to neutrally coated capillaries is proposed, offering a 200-fold signal enhancement. This approach is based on variation of the buffer's IS, rather than pH adjustment as in conventional methods, for EOF modulation or quasi-total reduction. This strategy allows selecting with high flexibility the best pH conditions to perform efficient preconcentration and separation. The new approach was demonstrated to be applicable for the analysis of N-linked oligosaccharides released from a model glycoprotein (Human Immunoglobulin G) and applied to map N-glycans from human serum for congenital disorders of glycosylation (CDG) diagnosis.

DNA Interaction with a Polyelectrolyte Monolayer at Solution-Air Interface.

The formation of ordered 2D nanostructures of double stranded DNA molecules at various interfaces attracts more and more focus in medical and engineering research, but the underlying intermolecular interactions still require elucidation. Recently, it has been revealed that mixtures of DNA with a series of hydrophobic cationic polyelectrolytes including poly(N,N-diallyl-N-hexyl-N-methylammonium) chloride (PDAHMAC) form a network of ribbonlike or threadlike aggregates at the solution—air interface. In the present work, we adopt a novel approach to confine the same polyelectrolyte at the solution—air interface by spreading it on a subphase with elevated ionic strength. A suite of techniques–rheology, microscopy, ellipsometry, and spectroscopy–are applied to gain insight into main steps of the adsorption layer formation, which results in non-monotonic kinetic dependencies of various surface properties. A long induction period of the kinetic dependencies after DNA is exposed to the surface film results only if the initial surface pressure corresponds to a quasiplateau region of the compression isotherm of a PDAHMAC monolayer. Despite the different aggregation mechanisms, the micromorphology of the mixed PDAHMAC/DNA does not depend noticeably on the initial surface pressure. The results provide new perspective on nanostructure formation involving nucleic acids building blocks.

Unsaturated fatty acids augment protein transport via the SecA:SecYEG translocon.

The translocon SecYEG and the associated ATPase SecA form the primary protein secretion system in the cytoplasmic membrane of bacteria. The secretion is essentially dependent on the surrounding lipids, but the mechanistic understanding of their role in SecA:SecYEG activity is sparse. Here, we reveal that the unsaturated fatty acids (UFAs) of the membrane phospholipids, including tetraoleoyl-cardiolipin, stimulate SecA:SecYEG-mediated protein translocation up to ten-fold. Biophysical analysis and molecular dynamics simulations show that UFAs increase the area per lipid and cause loose packing of lipid head groups, where the N-terminal amphipathic helix of SecA docks. While UFAs do not affect the translocon folding, they promote SecA binding to the membrane, and the effect is enhanced up to fivefold at elevated ionic strength. Tight SecA:lipid interactions convert into the augmented translocation. Our results identify the fatty acid structure as a notable factor in SecA:SecYEG activity, which may be crucial for protein secretion in bacteria, which actively change their membrane composition in response to their habitat.

Passive sampler designed for per‐ and polyfluoroalkyl substances using polymer‐modified organosilica adsorbent

AbstractA passive sampler designed to measure per‐ and polyfluoroalkyl substances (PFAS) was evaluated to determine chemical uptake rates under a variety of conditions. The sampler design is simple and robust, using organosilica modified with cross‐linked amine polymer in an high density polyethylene housing retained with polypropylene mesh. The addition of amine groups as a weak ion‐exchange resin in combination with Cu2+ was designed to promote binding of short‐chain PFAS. A five‐fold improvement in perfluorobutanoic acid adsorption was measured when Cu2+ was added to the polyethylenimine polymer. The samplers showed an integrated response to all analytes tested except for short‐chain PFAS. Sampling rates of PFAS analytes from simulated groundwater were on average 10 mL/day at flow rates of 0.038–1.9 cm/min. Relatively low variability in sampling rate was observed over the range of laboratory tested conditions (representing common conditions in environmental waters) including elevated ionic strength, sulfate concentration, and humic acid content.Article Impact StatementMeasuring per‐ and polyfluoroalkyl substances in environmental samples is important for monitoring. Passive samplers can offer practical advantages for making measurements.

Impact of selected cement additives and model compounds on the solubility of Nd(III), Th(IV) and U(VI): screening experiments in alkaline NaCl, MgCl2 and CaCl2 solutions at elevated ionic strength

Abstract The solubility of Nd(III), Th(IV) and U(VI) was studied from undersaturation conditions in the presence of selected organic cement additives and model compounds: adipic acid, methyl acrylate, citric acid, melamine, ethylene glycol, phthalic acid and gluconic acid. Experiments were performed under Ar atmosphere in NaCl (2.5 and 5.0 M), MgCl2 (1.0 and 3.5 M) and CaCl2 (1.0 and 3.5 M) solutions with 9 ≤ pHm ≤ 13 (pHm = −log[H+]). Initial concentrations of organic ligands in solution were set constant in all systems to [L]0 = 0.025 M, except in specific cases (e.g. adipic acid, melamine and phthalic acid) where the ligand concentration in the matrix solutions was lower and controlled by solubility. Adipic acid, methyl acrylate, melamine, ethylene glycol and phthalic acid do not impact the solubility of Nd(III), Th(IV) and U(VI) in the investigated NaCl, MgCl2 and CaCl2 systems. Citrate significantly enhances the solubility of Nd(III), Th(IV) and U(VI) in NaCl systems. A similar effect was observed for Th(IV) and U(VI) in the presence of gluconate in NaCl systems. The impact of pH on the stability of the complexes is different for both ligands. Because of the larger number of alcohol groups in the gluconate molecule, this ligand is prone to form more stable complexes under hyperalkaline conditions that likely involve the deprotonation of several alcohol groups. The complexation of gluconate with U(VI) at pHm ≈ 13 is however weaker than at pHm ≈ 9 due to the competition with the highly hydrolysed moiety prevailing at pHm ≈ 13, i.e. UO2(OH)4 2−. The impact of citrate and gluconate in MgCl2 and CaCl2 systems is generally weaker than in NaCl systems, expectedly due to the competition with binary Mg-L and Ca-L complexes. However, the possible formation of ternary complexes further enhancing the solubility is hinted for the systems Mg/Ca-Th(IV)-GLU and Ca-U(VI)-GLU. These observations reflect again the differences in the complexation properties of citrate and gluconate, the key role of the alcohol groups present in the latter ligand, and the importances of interacting matrix cations. The screening experiments conducted within this study contribute to the identification of organic cement additives and model compounds potentially impacting the solution chemistry of An(III)/Ln(III), An(IV) and An(VI) under intermediate to high ionic strength conditions (2.5 ≤ I ≤ 10.5 M). This shows evident differences with respect to investigations conducted in dilute systems, and thus represents a very relevant input in the safety assessment of repositories for radioactive waste disposal where such elevated ionic strength conditions are expected.

Hydraulic Resistance and Protein Fouling Resistance of a Zirconia Membrane with a Tethered PVP Layer

The influence of surface modification of zirconia (ZrO2) membrane with tethered poly(vinyl pyrrolidone) (PVP) chains was evaluated with respect to the impact of pH and ionic strength on hydraulic resistance and fouling resistance in the filtration of bovine serum albumin (BSA) and lysozyme (Lys) as model protein foulants. The tethered PVP surface layer led to membrane permeability and fouling propensity that were responsive to both pH and ionic strength. The PVP-modified membrane (PVP-ZrO2) hydraulic resistance increased by up to ~48% over a pH range of 6–11, but with no discernible impact at lower pH. Membrane hydraulic resistance was virtually unaffected by ionic strength over the 0.001–1 M range. However, reversible foulant cake resistance in BSA and Lys solution filtration increased with elevated ionic strength, owing in part to the weakening of protein–protein repulsion. Irreversible BSA and Lys fouling was affected by the operational pH relative to the protein isoelectric point (IEP) and reduced under conditions of chain swelling. Irreversible membrane fouling resistance for both proteins was significantly lower, by ~11–49% and 18–74%, respectively, for the PVP-ZrO2 membrane relative to the unmodified ZrO2 membrane. The present results suggest the merit of further exploration of fouling reduction and improvement of membrane cleaning effectiveness via tuning pH and ionic strength triggered conformational responsiveness of the tethered target polymer layer.

Effects of polysaccharide charge density on the structure and stability of carboxymethylcellulose-casein nanocomplexes at pH 4.5 prepared with and without a pH-cycle

Carboxymethylcellulose (CMC) can stabilize acidic casein dispersions but the CMC charge density effect has not been studied. The objective of the present work was to study the structure and stability of CMC-casein nanocomplexes at pH 4.5 using CMC with the degree of substitution (DS) of 0.7, 0.9, and 1.2. Dispersions were prepared at 1%w/v casein and casein:CMC mass ratios from 5:1 to 1:1 with and without a pH-cycle. The calcium chelating capacity of CMC was strengthened as the DS increased, which enhanced the partial disassociation of casein micelles and therefore improved the dispersion clarity. The lowest dispersion turbidity was observed at a casein:CMC mass ratio of 3:1 for all three kinds of CMC, and the pH-cycle, by alkalizing dispersion pH to 11.3 followed by acidifying to pH 4.5, further lowered the dispersion turbidity. Electrostatic attraction was the mechanism of complex formation at pH 4.5, and the CMC on the complex surface was critical to the stability against aggregation. Furthermore, increasing the DS of CMC resulted in smaller complexes and clearer dispersions. Particularly, the dispersions with a CMC:casein mass ratio of 3:1 after the pH-cycle had the absorbance at 600 nm of 1.25, 0.85, and 0.57, and the mean hydrodynamic diameter of 379, 392, and 188 nm at the DS of 0.7, 0.9, and 1.2 respectively; the increased DS also increased the stability of complexes against aggregation and precipitation at elevated ionic strengths, from 50 mM to 200 mM NaCl. The present findings may broaden the application of caseins in acidic systems.

Virus-like particle preparation is improved by control over capsomere-DNA interactions during chromatographic purification.

Expression of viral capsomeres in bacterial systems and subsequent in vitro assembly into virus-like particles is a possible pathway for affordable future vaccines. However, purification is challenging as viral capsomeres show poor binding to chromatography media. In this study, the behavior of capsomeres in unfractionated bacterial lysate was compared with that for purified capsomeres, with or without added microbial DNA, to better understand reasons for poor bioprocess behavior. We show that aggregates or complexes form through the interaction between viral capsomeres and DNA, especially in bacterial lysates rich in contaminating DNA. The formation of these complexes prevents the target protein capsomeres from accessing the pores of chromatography media. We find that protein-DNA interactions can be modulated by controlling the ionic strength of the buffer and that at elevated ionic strengths the protein-DNA complexes dissociate. Capsomeres thus released show enhanced bind-elute behavior on salt-tolerant chromatography media. DNA could therefore be efficiently removed. We believe this is the first report of the use of an optimized salt concentration that dissociates capsomere-DNA complexes yet enables binding to salt-tolerant media. Post purification, assembly experiments indicate that DNA-protein interactions can play a negative role during in vitro assembly, as DNA-protein complexes could not be assembled into virus-like particles, but formed worm-like structures. This study reveals that the control over DNA-protein interaction is a critical consideration during downstream process development for viral vaccines.

Linking PFAS partitioning behavior in sewage solids to the solid characteristics, solution chemistry, and treatment processes

Per- and polyfluoroalkyl substances (PFAS) have gained increasing attention due to the potential health risks that they present. Secondary sludge and biosolids are known as notable PFAS emission routes to the environment. In this study, partitioning behavior of 14 PFAS were investigated across four secondary wastewater treatment types (activated sludge, trickling filter, biological nutrient removal, and rotating biological contactor; n = 10) and three sludge stabilization methods (composting, aerobic digestion, and anaerobic digestion; n = 6). Batch experiments were conducted to evaluate how PFAS sorption to secondary sludge and biosolid was affected by various treatment methods, solid properties, and solution chemistry parameters. Insignificant differences in compound-specific partitioning coefficients (Kd) were observed among the four secondary treatment methods. However, sludge stabilization resulted in significantly different partitioning behavior among biosolid samples, in which anaerobically digested biosolids generally had significantly higher Kd values compared to aerobically digested and composted biosolids (anaerobic digestion > aerobic digestion > composting). Multiple linear regression models were developed to explain analyte-specific Kd values across the biosolid samples and identified that solid-specific property significance was as follows: protein fraction > organic matter fraction > lipid fraction. Stabilization generally decreased the PFAS sorption capacity relative to the secondary sludge samples. Furthermore, PFAS Kd increased with elevated calcium concentrations and ionic strengths and decreased with increasing pH values in sludge and biosolid samples. These findings could inform the decision-making process to reduce the release of PFAS to the environment.

On the sensitivity of the evaporative pattern deposition of particulate mass to the ionic strength in kinetically stable suspensions

The deposition of particulate mass from a volatile suspension is a common process. Usually, the employed suspensions are designed to be kinetically stable, which is achieved by employing surface forces of molecular origin, e.g., the electrical double layer (EDL) or steric forces, to render high energy barriers to particle attachments. One may expect that a high energy barrier in the original suspension will render the deposit morphology solely connected to particle convection in the volatile liquid and, once most of the carrier liquid has evaporated, to capillary attraction between detached particles to each other and to the solid substrate. However, we show that variations in the magnitude of large energy barriers to particle attachments in our original suspensions are connected to variations in the deposit morphology following the evaporation of the carrier liquid. In our experiments, the different original EDL induced energy barriers are large and traverse tens and hundreds of KBT in magnitude. Nevertheless, the evaporation of the carrier liquid during the deposition process supports the convection of mass toward the three phase contact line between the suspension, substrate, and vapor phases. The convection of particle and ion mass dynamically increases particle concentration and ionic strength in the vicinity of the contact line. The elevated ionic strength reduces the energy barriers to particle attachments in that vicinity, which appears to locally support particle coagulation and adsorption effects and hence to alter the deposit morphology. Thus, the morphology of the deposit may show considerable sensitivity to the specific magnitude of energy barrier to particle attachments in the original, kinetically stable, suspension.

Physicochemical properties of skim milk powder dispersions prepared with calcium-chelating sodium tripolyphosphate, trisodium citrate, and sodium hexametaphosphate

Due to health benefits of proteins, the demand for protein beverages has grown rapidly. Translucent protein drinks with neutral pH may have advantages over acidic beverages that may cause dental erosion, and skim milk powder (SMP) is an affordable protein ingredient. Dissociating casein micelles by calcium chelators is a well-known method to reduce SMP dispersion turbidity, but much is to be studied for physicochemical properties as affected by chelator type and concentration. The objective of the present study was to characterize physicochemical properties of dispersions with 5% (wt/vol) SMP after addition of 0 to 30 mM sodium tripolyphosphate, trisodium citrate, or sodium hexametaphosphate. The turbidity was decreased with increasing chelator concentration, with the lowest turbidity observed in the SMP dispersions with sodium hexametaphosphate. The smallest hydrodynamic diameter was observed at an intermediate chelator concentration, resulting from the balance of casein micelle dissociation and aggregation of dissociated caseins induced at an elevated ionic strength. Heating at 90°C for 5 min increased turbidity but lowered hydrodynamic diameter of SMP dispersions, with some exceptions. The morphology of SMP dispersions differed for each chelator and was also affected by chelator concentration and heating. Trisodium citrate was the most effective to demineralize colloidal calcium phosphate in casein micelles, but the amount of dissolved calcium was not directly correlated with the decreased turbidity, indicating different chelating mechanisms by each chelator. Analysis of serum calcium and phosphorus concentrations also suggested that the type and concentration of soluble and insoluble calcium phosphates and their partitioning in the serum and casein micelles were dynamically changed by the studied parameters to affect dispersion turbidity and structures of casein micelles. Findings from the present study may be used to formulate translucent beverages incorporating SMP and other casein micelle ingredients.

Volume Transition and Phase Coexistence in Polyelectrolyte Gels Interacting with Amphiphiles and Proteins.

Polyelectrolyte gels have the capacity to absorb large amounts of multivalent species of opposite charge from aqueous solutions of low ionic strength, and release them at elevated ionic strengths. The reversibility offers the possibility to switch between “storage” and “release” modes, useful in applications such as drug delivery. The review focuses on systems where so-called volume phase transitions (VPT) of the gel network take place upon the absorption and release of proteins and self-assembling amphiphiles. We discuss the background in terms of thermodynamic driving forces behind complex formation in oppositely charged mixtures, the role played by cross-links in covalent gels, and general aspects of phase coexistence in networks in relation to Gibbs’ phase rule. We also briefly discuss a gel model frequently used in papers covered by the review. After that, we review papers dealing with collapse and swelling transitions of gels in contact with solution reservoirs of macroions and surfactants. Here we describe recent progress in our understanding of the conditions required for VPT, competing mechanisms, and hysteresis effects. We then review papers addressing equilibrium aspects of core–shell phase coexistence in gels in equilibrium. Here we first discuss early observations of phase separated gels and results showing how the phases affect each other. Then follows a review of recent theoretical and experimental studies providing evidence of thermodynamically stable core–shell phase separated states, and detailed analyses of the conditions under which they exist. Finally, we describe the results from investigations of mechanisms and kinetics of the collapse/swelling transitions induced by the loading/release of proteins, surfactants, and amphiphilic drug molecules.

Uptake of Sulfate from Ambient Water by Freshwater Animals.

To better understand how the sulfate (SO42−) anion may contribute to the adverse effects associated with elevated ionic strength or salinity in freshwaters, we measured the uptake and efflux of SO42− in four freshwater species: the fathead minnow (Pimephales promelas, Teleostei: Cyprinidae), paper pondshell (Utterbackia imbecillis, Bivalvia: Unionidae), red swamp crayfish (Procambarus clarkii, Crustacea: Cambaridae), and two-lined mayfly (Hexagenia bilineata, Insecta: Ephemeridae). Using δ(34S/32S) stable isotope ratios and the concentrations of S and SO42−, we measured the SO42− influx rate (Jin), net flux (Jnet), and efflux rate (Jout) during a 24 h exposure period. For all four species, the means of Jin for SO42− were positive, and Jin was significantly greater than 0 at both target SO42− concentrations in the fish and mollusk and at the lower SO42− concentration in the crayfish. The means of Jout and Jnet were much more variable than those for Jin, but several species by target SO42− concentration combinations for Jout and Jnet, were negative, which suggests the net excretion of SO42− by the animals. The results of our experiments suggest a greater regulation of SO42− in freshwater animals than has been previously reported.

Nanoformulation of fibrinogen by thermal stabilization of its electrostatic complexes with hyaluronic acid

The formulation of well-defined and stable fibrinogen-based nanoparticles (NPs) without the use of any chemical reaction or any toxic organic solvent is reported. Electrostatic interaction between hyaluronic acid (HA) and fibrinogen (Fbg) leads to well-defined complexes at acidic pH which however readily dissolve at neutral pH. On the other hand, when thermal treatment is applied on the pre-formed complexes NPs keep their integrity. Circular dichroism indicates that the protein's native secondary conformation in the final NPs is not affected by the formulation. The tendency of the complexes to aggregate at elevated ionic strengths is greatly suppressed after the application of the temperature treatment protocol. This characteristic is even more pronounced at neutral pH and it is connected to the enhanced surface charge of the NPs. The encapsulation of the hydrophobic compound curcumin causes only weak secondary aggregation. This work shows that the ability of Fbg to self-assemble upon thermal treatment can be effectively used to stabilize Fbg nanoformulations inside complexes with polysaccharides.

Adsorption of dissolved organic matter (DOM) on polystyrene microplastics in aquatic environments: Kinetic, isotherm and site energy distribution analysis.

Microplastics and dissolved organic matter (DOM) are ubiquitous in aquatic environments. The adsorption behavior of DOM on microplastics in aquatic environments is a prominent concern. In this study, the adsorption of two types of DOM, Suwannee River Humic Acid (HA) and Suwannee River Fulvic Acid (FA), on polystyrene microplastics (PSMPs, 10μm) in aquatic environments was investigated. The adsorption of both HA and FA on PSMPs could be well described by using pseudo second-order and Freundlich models. The adsorption of HA and FA on PSMPs was low pH-dependent, particularly for FA adsorption. However, the elevated ionic strength slightly increased the adsorption of HA and FA on PSMPs. Based on Freundlich model, the site energy distribution of HA and FA adsorption on PSMPs under the experimental conditions were estimated. HA and FA first occupied the high-energy adsorption sites and then diffused to the low-energy adsorption sites on PSMPs. With higher site energies, HA demonstrated a much stronger adsorption affinity to PSMPs than FA. The adsorption site heterogeneity (σe*) on PSMPs under the experimental conditions were close. Hydrophobic interaction and π-π electron donor acceptor interaction acted simultaneously in the HA and FA adsorption on PSMPs. The results of this study suggested that the environmental behaviors of microplastics would be influenced by the amount and the type of DOM as well as solution chemistry.

Interactions between gold, thiol and As(iii) for colorimetric sensing.

As(iii) or arsenite is extremely toxic, and various colorimetric sensors were reported for its on-site detection. A highly cited example was based on gold nanoparticles (AuNPs) modified with a few thiol-containing compounds including dithiothreitol (DTT), reduced glutathione (GSH), and cysteine (Cys). As(iii) was believed to crosslink these surface ligands to aggregate AuNPs and produce a red-to-blue color change. Since As(iii) can also adsorb on AuNPs, we herein carefully studied this effect on these ligand-capped AuNPs. For citrate-capped AuNPs, 10 mM free citrate resulted in a strong blue color in the presence of As(iii) attributable to the elevated ionic strength, while common divalent cations resulted in no color change due to the chelation effect of free citrate. For AuNPs capped with the three thiol compounds, more than 5 mM As(iii) was needed to produce a color change, which was very different from the previously reported color change with nanomolar concentration of As(iii). Our color change was attributed to the displacement of the surface ligands by As(iii) instead of crosslinking by it. This conclusion was made based on the irreversibility of the color change, kinetics of the reaction, and high As(iii) concentration needed. This work has revealed that any two species from AuNPs, thiol and As(iii) can react. It also calls for care in the interpretation of related colorimetric sensing mechanisms, and the need to consider the previously overlooked As(iii) adsorption onto AuNPs.

Utilization of L-serinyl derivate to preparing triple stimuli-responsive hydrogels for controlled drug delivery

Environmentally responsive hydrogels are widely used in various applications. Facile synthesis of multiply stimuli-responsive hydrogels is necessary. Herein, a triple pH-, thermo- and ion-sensitive hydrogel, shorted as HSP, was synthesized by aqueous radical polymerization using L-serinyl acrylate as a monomer and PEG180DMA as a crosslinker. The compositions and microstructures of HSP are characterized by FT-IR, 1H NMR and SEM. The swelling ratio of HSP is the lowest at pH = 3.0 while increases sharply far away from this pH value. Meanwhile, HSP expands with elevated temperatures or ionic strengths, and reaches a plateau when they above 60 °C or 3.0 mol/L, respectively. In addition, these swelling processes are reversible under alternative changing in extern stimuli, and these cycles can be repeated at least 5 times. Furthermore, the release of sodium salicylate can be easily mediated by pH values, temperatures and ion concentrations, all above indicating that HSP is a promising material for controlled drug delivery.

Formation, characterization, and application of chitosan/pectin-stabilized multilayer emulsions as astaxanthin delivery systems

Multilayer emulsions were formed by sequential electrostatic deposition of anionic (pectin) and cationic (chitosan) biopolymers onto anionic saponin-coated lipid droplets. These emulsions were then tested for their ability to encapsulate and protect a hydrophobic nutraceutical (astaxanthin). The impact of chitosan and pectin concentration, pH, and ionic strength on the formation and stability of the multilayer emulsions was examined. Multilayer emulsions containing small uniform particles were produced using 2.5% lipid droplets, 0.05% chitosan, and 0.0125% pectin. The physical stability of the astaxanthin-loaded emulsions after exposure to heating, pH, and NaCl was determined. The multilayer-coatings improved the chemical stability of the encapsulated astaxanthin, as well as the aggregation stability of the lipid droplets at elevated ionic strengths and temperatures. Astaxanthin degradation during storage was 3- to 4-fold slower in multilayer emulsions than conventional ones. The multilayer emulsions developed in this study may be useful for encapsulating, protecting, and delivering hydrophobic carotenoids, which may aid in the development of more efficacious functional foods, supplements, and medical foods.

The Lubricity of Mucin Solutions Is Robust toward Changes in Physiological Conditions.

Solutions of manually purified gastric mucins have been shown to be promising lubricants for biomedical purposes, where they can efficiently reduce friction and wear. However, so far, such mucin solutions have been mostly tested in specific tribological settings, i.e., in combination with different material pairings; variations in the composition of the lubricating fluid have not been systematically explored yet. We here fill this gap and determine the viscosity, adsorption behavior, and lubricity of porcine gastric mucin solutions on hydrophobic surfaces at different pH levels, mucin and salt concentrations, and in the presence of other proteins. We demonstrate that mucin solutions provide excellent lubricity even at very low concentrations of 0.01% (w/v), over a broad range of pH levels and even at an elevated ionic strength. Furthermore, we provide mechanistic insights into mucin lubricity, which help explain how certain variations in physiologically relevant parameters can limit the lubricating potential of mucin solutions. Our results show that solutions of manually purified mucin solutions can be powerful biomedical lubricants, e.g., serving as artificial joint fluids for viscosupplementation, as eye drops or mouth spray, or as a personal lubricant for intercourse.

Calpain silencing alleviates myocardial ischemia-reperfusion injury through the NLRP3/ASC/Caspase-1 axis in mice

AimsPrior to reperfusion, Calpains remain inactive due to the acidic pH and elevated ionic strength in the ischemic myocardium; but Calpain is activated during myocardial reperfusion. The underlying mechanism of Calpain activation in the ischemia-reperfusion (I/R) is yet to be determined. Therefore, the present study aims to investigate the mechanism of Calpain in I/R-induced mice. Main methodsIn order to detect the function of Calpain and the NLRP3/ASC/Caspase-1 axis in cardiomyocyte pyroptosis, endoplasmic reticulum (ER) stress and myocardial function, the cardiomyocytes were treated with hypoxia-reoxygenation (H/R), and NLRP3 were silenced, Calpain was overexpressed and Caspase-1 inhibitors were used to determine cardiomyocyte pyroptosis. The results obtained from the cell experiments were then verified with an animal experiment in I/R mice. Key findingsThere was an overexpression in Calpain, ASC, NLRP3, GRP78 and C/EBP homologous protein (CHOP) in cardiomyocytes following H/R. A significant increase was witnessed in lactic acid dehydrogenase (LDH) activity, cardiomyocyte pyroptosis rate, Calpain activity, reactive oxygen species (ROS) concentration, as well as activation of ER stress in cardiomyocytes after H/R. However, opposing results were observed in H/R cardiomyocytes that received siRNA Calpain, siRNA NLRP3 or Caspase-1 inhibitor treatment. Overall, the results obtained from the animal experiment were consistent with the results from the cell experiment. SignificanceThe silencing of Calpain suppresses the activation of the NLRP3/ASC/Caspase-1 axis, thus inhibiting ER stress in mice and improving myocardial dysfunction induced by I/R, providing a novel therapeutic pathway for I/R.