Influence of EDTA and citrate on physicochemical properties of whey protein-stabilized oil-in-water emulsions containing CaCl2

Investigating the thermal stability and calcium resistance of O/W emulsions prepared with glycosylated whey protein hydrolysates modified by different saccharides

The poor thermal stability and ion tolerance of whey protein hydrolysates (WPH) restrict its application in emulsions, while glycosylation shows potential benefits in improving WPH stability. However, the relationship between saccharides with different Mw and the glycosylation behavior of WPH rich in short peptides is unclear. In response, the effect of different saccharides on glycosylated WPH rich in short peptides and its emulsion stability were investigated. Grafted small Mw saccharides were more beneficial to the emulsion stability of WPH. Specifically, grafting xylose effectively inhibited 121 °C sterilization and 5 mM CaCl2-induced coalescence of WPH emulsion (687.50 nm) by comprehensively enhancing steric hindrance, conformational flexibility and electrostatic repulsion, and dissociating large aggregates into small aggregates. Conversely, grafting maltodextrin (30,590 Da) reduced thermal stability of WPH emulsion (4791.80 nm) by steric shielding and bridging flocculation. These findings provide new sights into glycosylation mechanism for WPH and achieving its application in nutritional emulsions.

Constructing myosin/high-density lipoprotein composite emulsions: Roles of pH on emulsification stability, rheological and structural properties

The emulsification activity of myosin plays a significant role in affecting quality of emulsified meat products. High-density lipoprotein (HDL) possesses strong emulsification activity and stability due to its structural characteristics, suggesting potential for its utilization in developing functional emulsified meat products. In order to explore the effect of HDL addition on emulsification stability, rheological properties and structural features of myosin (MS) emulsions, HDL-MS emulsion was prepared by mixing soybean oil with isolated HDL and MS, with pH adjustments ranging from 3.0 to 11.0. The results found that emulsification activity and stability in two emulsion groups consistently improved as pH increased. Under identical pH, HDL-MS emulsion exhibited superior emulsification behavior as compared to MS emulsion. The HDL-MS emulsion under pH of 7.0-11.0 formed a viscoelastic protein layer at the interface, adsorbing more proteins and retarding oil droplet diffusion, leading to enhanced oxidative stability, compared to the MS emulsion. Raman spectroscopy analysis showed more flexible conformational changes in the HDL-MS emulsion. Microstructural observations corroborated these findings, showing a more uniform distribution of droplet sizes in the HDL-MS emulsion with smaller particle sizes. Overall, these determinations suggested that the addition of HDL enhanced the emulsification behavior of MS emulsions, and the composite emulsions demonstrated heightened responsiveness under alkaline conditions. This establishes a theoretical basis for the practical utilization of HDL in emulsified meat products.

Correlationship between self-assembly behavior and emulsion stabilization of pea protein-high methoxyl pectin complexes treated with ultrasound at pH 2.0

This study investigated the effects of ultrasound on the self-assembly behavior of pea protein (PP)-high methoxyl pectin (HMP) complexes at pH 2.0 through transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and intrinsic fluorescence analysis. The emulsion stabilization mechanism of PP-HMP treated with ultrasound (PP-HMP-US) was also elucidated. The results indicated that ultrasound increased the emulsifying activity index (EAI) and emulsifying stability index (ESI) of PP-HMP. Moreover, PP-HMP-US-based emulsions formed small, dispersed oil drops, which were stable during storage. PP-HMP- and PP-HMP-US-based emulsions did not demonstrate any creaming. The TEM results revealed that ultrasound can regulate the self-assembly behavior of PP and HMP to form spherical particles with a core-shell structure. This structure possessed low turbidity, a small particle size, and high absolute zeta potential values. The FTIR and intrinsic fluorescence spectra demonstrated that ultrasound increased the α-helix and β-sheet contents and exposed the tryptophan groups to more hydrophilic environments. Ultrasound also promoted the PP-HMP self-assembly through electrostatic interaction and improved its oil-water interfacial behavior, as indicated by the EAI and ESI values of PP-HMP-US-based emulsions. The current results provide a reference for the development of an innovative emulsifier prepared by ultrasound-treated protein-pectin complexes at low pH.

Preanalytical conditions for multiparameter platelet flow cytometry

Background

Flow cytometry is an important technique for understanding multiple aspects of blood platelet biology. Despite the widespread use of the platform for assessing platelet function, the optimization and careful consideration of preanalytical conditions, sample processing techniques, and data analysis strategies should be regularly assessed. When set up and designed with optimal conditions, it can ensure the acquisition of robust and reproducible flow cytometry data. However, these parameters are rarely described despite their importance.

Objectives

We aimed to characterize the effects of several preanalytical variables on the analysis of blood platelets by multiparameter fluorescent flow cytometry.

Methods

We assessed anticoagulant choice, sample material, sample processing, and storage times on 4 distinct and commonly used markers of platelet activation, including fibrinogen binding, expression of CD62P and CD42b, and phosphatidylserine exposure.

Results

The use of suboptimal conditions led to increases in basal platelet activity and reduced sensitivities to stimulation; however, the use of optimal conditions protected the platelets from artifactual stimulation and preserved basal activity and sensitivity to activation.

Conclusion

The optimal preanalytical conditions identified here for the measurement of platelet phenotype by flow cytometry suggest a framework for future development of multiparameter platelet assays for high-quality data sets and advanced analysis.

The Impact of Ca2+ on Intracellular Distribution of Hemoglobin in Human Erythrocytes

The membrane-bound hemoglobin (Hb) fraction impacts red blood cell (RBC) rheology and metabolism. Therefore, Hb-RBC membrane interactions are precisely controlled. For instance, the signaling function of membrane-bound deoxy-Hb and the structure of the docking sites in the cytosolic domain of the anion exchanger 1 (AE-1) protein are well documented; however, much less is known about the interaction of Hb variants with the erythrocyte's membrane. Here, we identified factors other than O2 availability that control Hb abundance in the membrane-bound fraction and the possible variant-specific binding selectivity of Hb to the membrane. We show that depletion of extracellular Ca2+ by chelators, or its omission from the extracellular medium, leads to membrane-bound Hb release into the cytosol. The removal of extracellular Ca2+ further triggers the redistribution of HbA0 and HbA2 variants between the membrane and the cytosol in favor of membrane-bound HbA2. Both effects are reversible and are no longer observed upon reintroduction of Ca2+ into the extracellular medium. Fluctuations of cytosolic Ca2+ also impact the pre-membrane Hb pool, resulting in the massive transfer of Hb to the cellular cytosol. We hypothesize that AE-1 is the specific membrane target and discuss the physiological outcomes and possible clinical implications of the Ca2+ regulation of the intracellular Hb distribution.

Ethanol as a switch to induce soybean lipophilic protein self-assembly and resveratrol delivery

Protein-based nanoparticles or nanocarriers of emulsion systems have piqued the interest of nutrition and health care goods. As a result, this work examines the characterisation of ethanol-induced soybean lipophilic protein (LP) self-assembly for resveratrol (Res) encapsulation, particularly the influence on emulsification. By varying the ethanol content ([E]) in the range of 0-70% (v/v), the structure, size, and morphology of LP nanoparticles may be adjusted. Similarly, the self-assembled LPs have a strong [E] dependency on the encapsulation efficiency of Res. For [E] = 40% (v/v), Res had the highest encapsulation efficiency (EE) and load capacity (LC) of 97.1% and 141.0 μg/mg nanoparticles, respectively. Most of the Res was encapsulated by the hydrophobic core of LP. Moreover, for [E] = 40% (v/v), LP-Res showed significantly improved emulsifying properties, independent of low-oil or high-oil emulsion systems. Furthermore, the ethanol-induced production of appropriate aggregates increased emulsion system stability, hence increasing Res retention during storage.

Effects of casein phosphopeptides on thermal stability and sensory quality of whey protein emulsions containing calcium beta-hydroxy-beta-methylbutyrate

This study aimed to elucidate the effect of casein phosphopeptides (CPP) on the thermal stability and sensory quality of whey protein emulsions containing calcium beta-hydroxy-beta-methylbutyrate (WPEs-HMB-Ca). The interaction mechanism among CPP, HMBCa, and WP in the emulsions before and after autoclaving (121 °C, 15 min) was systematically investigated from macroscopic external and microscopic molecular perspectives. It was found that WPEs-HMB-Ca treated by autoclaving resulted in an increase in droplet size (d_4,3 = 24.09 μm) due to aggregation/flocculation of proteins, along with a stronger odor with higher viscosity, compared to those without autoclaving. When CPP:HMB-Ca = 1:25 (w/w) in the emulsion, the droplets exhibited a more uniform and consistent state in the emulsion. In addition, CPP was able to inhibit the formation of complex spatial network structures of proteins during autoclaving by binding with Ca²⁺, thus improving the thermal stability and storage stability of WPEs-HMB-Ca. This work might provide theoretical guidance for developing functional milk drinks with good thermal stability and flavor.

Effects of pH and Ionic Strength in Calcium on the Stability and Aeration Characteristics of Dairy Emulsion

The effects of different pH levels and ionic strength in calcium on the stability and aeration characteristics of dairy emulsions were investigated in this study. The results revealed that the stability and aeration characteristics of the emulsion were enhanced as the pH value increased from 6.5 to 7.0 and were optimal within the pH of 6.8~7.0, while the concentration of free calcium ions (Ca²⁺) was 2.94~3.22 mM. With the pH subsequently fixed at 6.8 and 7.0, when the addition of CaCl₂ was increased to 2.00 mM (free Ca²⁺ strength > 4.11 mM), stability and aeration characteristics reduced significantly, including the flocculation of fat globules, an increase in particle size, and a decrease in the zeta potential and viscosity of the O/W emulsion, all leading to an increase in interfacial protein mass and decreased overrun and foam firmness. Overall, the results indicated that pH changes and CaCl₂ addition significantly influenced the stability and aeration characteristics of dairy emulsions, by influencing free Ca²⁺ strength, which is an important factor in determining the quality of dairy emulsions.

Possibility of drug-distribution measurement in the hair of drowned bodies: evaluation of drug stability in water-soaked hair using micro-segmental analysis

In postmortem examinations, the drug analysis of hair is effective for revealing drug-use history. Additionally, a method to estimate the day of death using hair was previously developed by analyzing a single hair strand segmented at 0.4-mm intervals (micro-segmental hair analysis). However, for drowned bodies, drugs in the hair may be washed out due to soaking in water for extended periods. To evaluate the possibility of measuring drug distribution in the hair of drowned bodies, drug stability in hair samples soaked in various aqueous solutions was examined. First, reference hair strands of drug users containing specific drugs consistently along the hair shaft were prepared. The participants ingested 4 hay-fever medicines (fexofenadine, epinastine, cetirizine, and loratadine) every day for approximately 4 months before hair collection. Each reference strand was divided into regions, and each region was soaked in different solutions containing various solutes for extended periods up to approximately 2 months. In solutions without divalent ions (Ca²⁺ and Mg²⁺), the drug content in the hair decreased up to approximately 5 % with increasing salt concentration and soaking time. However, the decreased drug content was negligible in solutions containing divalent ions, implying that the divalent ions prevented drugs contained in hair from washing out. As natural river and sea waters contain divalent ions, the drugs in hair were hardly washed out even when the hair was soaked for 2 months. Thus, it was concluded that drug-distribution measurements using micro-segmental analysis can also be applied to the hairs of drowned bodies.

Degradation of hydrogel beads for the detection of serum bicarbonate levels for the diagnosis of metabolic alkalosis at the point of care

In this work, we present a novel point-of-care hydrogel-based diagnostic device for the rapid detection of elevated bicarbonate levels in serum for the diagnosis of mild to severe cases of metabolic alkalosis. Our system consists of hydrogel beads composed of calcium alginate and the nonionic polymer dextran. This assay utilizes the reaction of sodium bicarbonate and citric acid to produce citrate, a metal chelator capable of competitively binding to calcium cations in the gel matrix to trigger hydrogel degradation. This results in successful detection of elevated bicarbonate concentrations in less than one hour. Specifically, critically high bicarbonate concentrations of 50, 45, and 40 mmol L^-1 in human serum were detected in as little as 10, 15, and 20 min, respectively. To demonstrate the assay's feasibility for use in resource-limited settings, we developed a simple electronic device that achieved similar results and could be used by untrained individuals with no lab equipment and minimal power. To our knowledge, this is the first demonstration of the use of nonionic polymers to synthesize and improve the morphology of calcium alginate hydrogel beads using a simple processing method that involves minimal labor and equipment. The simplified bead synthesis protocol combined with the user-friendly device allows for the rapid detection of metabolic alkalosis at the point of care.

Reduction in the Migration Activity of Microglia Treated with Silica-Coated Magnetic Nanoparticles and their Recovery Using Citrate

Nanoparticles have garnered significant interest in neurological research in recent years owing to their efficient penetration of the blood–brain barrier (BBB). However, significant concerns are associated with their harmful effects, including those related to the immune response mediated by microglia, the resident immune cells in the brain, which are exposed to nanoparticles. We analysed the cytotoxic effects of silica-coated magnetic nanoparticles containing rhodamine B isothiocyanate dye [MNPs@SiO2(RITC)] in a BV2 microglial cell line using systems toxicological analysis. We performed the invasion assay and the exocytosis assay and transcriptomics, proteomics, metabolomics, and integrated triple-omics analysis, generating a single network using a machine learning algorithm. The results highlight alteration in the mechanisms of the nanotoxic effects of nanoparticles using integrated omics analysis.

Instability Mechanism of Osimertinib in Plasma and a Solving Strategy in the Pharmacokinetics Study

Osimertinib is a third-generation epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) and a star medication used to treat non-small-cell lung carcinomas (NSCLCs). It has caused broad public concern that osimertinib has relatively low stability in plasma. We explored why osimertinib and its primary metabolites AZ-5104 and AZ-7550 are unstable in rat plasma. Our results suggested that it is the main reason inducing their unstable phenomenon that the Michael addition reaction was putatively produced between the Michael acceptor of osimertinib and the cysteine in the plasma matrix. Consequently, we identified a method to stabilize osimertinib and its metabolite contents in plasma. The assay was observed to enhance the stability of osimertinib, AZ-5104, and AZ-7550 significantly. The validated method was subsequently applied to perform the pharmacokinetic study for osimertinib in rats with the newly established, elegant, and optimized ultra-performance liquid chromatography–tandem mass spectrometer (UPLC-MS/MS) strategy. The assay was assessed for accuracy, precision, matrix effects, recovery, and stability. This study can help understand the pharmacological effects of osimertinib and promote a solution for the similar problem of other Michael acceptor-contained third-generation EGFR-TKI.

Synchrotron radiation analysis of root dentin: the roles of fluoride and calcium ions in hydroxyapatite remineralization

Although the use of fluoride for root caries control is reported to be effective, the mechanism of maintaining hydroxyapatite is still unclear. This study elucidates the roles of fluoride in the recrystallization of hydroxyapatite, and the impact of calcium to maintain the abundance of hydroxyapatite on acid-challenged root dentin with a novel approach - using synchrotron radiation. Root dentin samples obtained from 40 extracted human premolars were subjected to pH challenge in combination with fluoride treatment. The effect of fluoride on hydroxyapatite regeneration on the root was investigated by using a range of fluoride concentrations (1000-5000 p.p.m.) and the EDTA-chelation technique in vitro. Synchrotron radiation X-ray micro-computed tomography and X-ray absorption spectroscopy were utilized to characterize the chemical composition of calcium species on the surface of prepared samples. The percentage of hydroxyapatite and the relative abundance of calcium species were subsequently compared between groups. The absence of calcium or fluoride prevented the complete remineralization of hydroxyapatite on the surface of early root caries. Different concentrations of fluoride exposure did not affect the relative abundance of hydroxyapatite. Sufficient potency of 1000 p.p.m. fluoride solution in promoting hydroxyapatite structural recrystallization on the root was demonstrated. Both calcium and fluoride ions are prerequisites in a caries-prone environment. Orchestration of F^- and Ca²⁺ is required for structural homeostasis of root dentin during acid attack. Sustainable levels of F^- and Ca²⁺ might thus be a strict requirement in the saliva of the population prone to root caries. Fluoride and calcium contribute to structural homeostasis of tooth root, highlighting that routine fluoride use in combination with calcium replenishment is recommended for maintaining dental health. This study also demonstrates that utilization of synchrotron radiation could provide a promising experimental platform for laboratory investigation especially in the dental material research field.

Pickering emulsions stabilized by carboxylated nanodiamonds over a broad pH range

HYPOTHESIS

Surfactants in emulsions sometimes do not provide adequate stability against coalescence, whereas Pickering emulsions often offer greater stability. In a search for stabilizers offering biocompatibility, we hypothesized that carboxylated nanodiamonds (ND) would impart stability to Pickering emulsions.

EXPERIMENTS

We successfully prepared Pickering emulsions of sunflower oil in water via two different methods: membrane emulsification and probe sonication. The first method was only possible when the pH of the aqueous ND suspension was ≤ 4.

FINDINGS

Pendant-drop tensiometry confirmed that carboxylated ND is adsorbed at the oil/water interface, with a greater decrease in interfacial tension found with increasing ND concentrations in the aqueous phase. The carboxylated ND become more hydrophilic with increasing pH, according to three-phase contact angle analysis, because of deprotonation of the carboxylic acid groups. Membrane emulsification yielded larger (about 30 µm) oil droplets, probe sonication produced smaller (sub-μm) oil droplets. The Pickering emulsions show high stability against mechanical vibration and long-term storage for one year. They remain stable against coalescence across a wide range of pH values. Sonicated emulsions show stability against creaming. In this first-ever systematic study of carboxylated ND-stabilized Pickering emulsions, we demonstrate a promising application in the delivery of β-carotene, as a model active ingredient.

Alginate-gelatin-Matrigel hydrogels enable the development and multigenerational passaging of patient-derived 3D bioprinted cancer spheroid models

Hydrogels consisting of controlled fractions of alginate, gelatin, and Matrigel enable the development of patient-derived bioprinted tissue models that support cancer spheroid growth and expansion. These engineered models can be dissociated to be then reintroduced to new hydrogel solutions and subsequently reprinted to generate multigenerational models. The process of harvesting cells from 3D bioprinted models is possible by chelating the ions that crosslink alginate, causing the gel to weaken. Inclusion of the gelatin and Matrigel fractions to the hydrogel increases the bioactivity by providing cell-matrix binding sites and promoting cross-talk between cancer cells and their microenvironment. Here we show that immortalized triple-negative breast cancer cells (MDA-MB-231) and patient-derived gastric adenocarcinoma cells can be reprinted for at least three 21 d culture cycles following bioprinting in the alginate/gelatin/Matrigel hydrogels. Our drug testing results suggest that our 3D bioprinted model can also be used to recapitulatein vivopatient drug response. Furthermore, our results show that iterative bioprinting techniques coupled with alginate biomaterials can be used to maintain and expand patient-derived cancer spheroid cultures for extended periods without compromising cell viability, altering division rates, or disrupting cancer spheroid formation.

Ultrasensitive circulating tumor DNA analysis enables precision medicine: experimental workflow considerations

Introduction: Circulating tumor DNA (ctDNA) has become a relevant biomarker in cancer management, allowing tumor assessment through analysis of minimally invasive liquid biopsies. Applications include screening, diagnostics, monitoring of treatment efficacy and detection of minimal residual disease as well as relapse. The potential of ctDNA analysis is significant, but several biological and technical challenges need to be addressed before widespread clinical implementation.Areas covered: Several clinical applications where ctDNA analysis may be beneficial require detection of individual DNA molecules. Consequently, to acquire accurate and informative data the entire workflow from sampling to final data interpretation needs to be optimized. In this review, we discuss the biological and technical challenges of ctDNA analysis and how preanalytical and analytical approaches affect different cancer applications.Expert opinion: While numerous studies have demonstrated the potential of using ctDNA in cancer applications, yet few reports about true clinical utility exist. Despite encouraging data, the sensitivity of ctDNA analyses, i.e. the probability to detect presence of cancer in liquid biopsies, is still an issue. Analysis of multiple mutations in combination with simultaneous assessment of other analytes is one solution. Improved standardization and guidelines will also facilitate the introduction of ctDNA analysis into clinical routine.

Calcium Chelation by Phosphate Ions and Its Influence on Fouling Mechanisms of Whey Protein Solutions in a Plate Heat Exchanger

Fouling of plate heat exchangers (PHEs) is a recurring problem when pasteurizing whey protein solutions. As Ca²⁺ is involved in denaturation/aggregation mechanisms of whey proteins, the use of calcium chelators seems to be a way to reduce the fouling of PHEs. Unfortunately, in depth studies investigating the changes of the whey protein fouling mechanism in the presence of calcium chelators are scarce. To improve our knowledge, reconstituted whey protein isolate (WPI) solutions were prepared with increasing amounts of phosphate, expressed in phosphorus (P). The fouling experiments were performed on a pilot-scale PHE, while monitoring the evolution of the pressure drop and heat transfer coefficient. The final deposit mass distribution and structure of the fouling layers were investigated, as well as the whey protein denaturation kinetics. Results suggest the existence of two different fouling mechanisms taking place, depending on the added P concentration in WPI solutions. For added P concentrations lower or equal to 20 mg/L, a spongy fouling layer consists of unfolded protein strands bound by available Ca²⁺. When the added P concentration is higher than 20 mg/L, a heterogeneously distributed fouling layer formed of calcium phosphate clusters covered by proteins in an arborescence structure is observed.

EDTA as a chelating agent in quantitative 1H-NMR of biologically important ions

Biologically important ions such as Ca, K, Mg, Fe, and Zn play major roles in numerous biological processes, and their homeostatic balance is necessary for the maintenance of cellular activities. Sudden and severe loss in homeostasis of just one biologically important ion can cause a cascade of negative effects. The ability to quickly, accurately, and reliably quantify biologically important ions in samples of human bio-fluids is something that has been sorely lacking within the field of metabolomics. ¹H-NMR spectra. The foundation of our investigation was the a-priori knowledge that free ethylenediaminetetraacetic acid (EDTA) produces two clear single peaks on ¹H-NMR spectra, and that EDTA chelated to different ions produces unique ¹H-NMR spectral patterns due to 3D conformational changes in the chemical structure of chelated-EDTA and varying degrees of electronegativity. The aim of this study was to develop and test a ¹H-NMR-based method, with application specifically to the field of metabolomics, to quantify biologically important ions within the physiological pH range of 6.50-7.50 using EDTA as a chelating agent. Our method produced linear, accurate, precise, and repeatable results for Ca, Mg, and Zn; however, K and Fe did not chelate with EDTA.

Growth differentiation factor-5-gelatin methacryloyl injectable microspheres laden with adipose-derived stem cells for repair of disc degeneration

Nucleus pulposus (NP) degeneration is the major cause of degenerative disc disease (DDD). This condition cannot be treated or attenuated by traditional open or minimally invasive surgical options. However, a combination of stem cells, growth factors (GFs) and biomaterials present a viable option for regeneration. Injectable biomaterials act as carriers for controlled release of GFs and deliver stem cells to target tissues through a minimally invasive approach. In this study, injectable gelatin methacryloyl microspheres (GMs) with controllable, uniform particle sizes were rapidly biosynthesized through a low-cost electrospraying method. The GMs were used as delivery vehicles for cells and GFs, and they exhibited good mechanical properties and biocompatibility and enhanced the in vitro differentiation of laden cells into NP-like phenotypes. Furthermore, this integrated system attenuated the in vivo degeneration of rat intervertebral discs, maintained NP tissue integrity and accelerated the synthesis of extracellular matrix. Therefore, this novel therapeutic system is a promising option for the treatment of DDD.

Highly selective Protein A resin allows for mild sodium chloride-mediated elution of antibodies

The manufacturability of therapeutic monoclonal antibodies is limited by the harsh conditions that antibodies are subjected to during the purification procedure, which in turn restricts the development of novel acid-sensitive antibodies. The gold standard for antibody purification, Protein A affinity chromatography, offers the selective capture of antibodies with great yields, but also poses a threat to the quality of the antibodies. Antibodies and Fc-fusion proteins risk forming aggregates as a consequence of the acidic elution from the Protein A ligands, compromising the potency and safety of the drug. Here, we present a novel, mild purification strategy based on a calcium-dependent ligand derived from Protein A, called Z_Ca. Antibodies captured on a high-capacity tetrameric Z_Ca resin in the presence of calcium can be eluted by removing the calcium ions through the addition of a chelator, and we describe the strive to find a sustainable alternative to the previously applied chelator EDTA. The naturally occurring chelator citrate is shown to seamlessly replace EDTA. Further buffer optimization reveals that the elution can be considerably improved by increasing the conductivity through the addition of 300 mM sodium chloride, leading to a very concentrated eluate. Remarkably, merely sodium chloride at a concentration of 50 mM is proven to be sufficient for calcium-dependent antibody release in a cost-efficient manner. Antibodies of subclasses IgG2 and IgG4 are eluted with sodium chloride at neutral pH and IgG1 at pH 6, due to varying affinities for the tetrameric Z_Ca, ranging between 90-780 nM. The mild elution of an IgG4 antibody eliminated the formation of aggregates, which constituted as much as 34% of all eluted antibody from MabSelect SuRe at pH 3. This novel purification strategy thus combines the valuable qualities of a Protein A resin, by providing high selectivity and a recovery of 88-99%, with an exceptionally mild elution step similar to ion-exchange chromatography, rendering considerably more functional antibody.

Identification and Characterization of a Novel Thermostable and Salt-Tolerant β-1,3 Xylanase from Flammeovirga pacifica Strain WPAGA1

β-1,3 xylanase is an important enzyme in the biorefinery process for some algae. The discovery and characterization of new β-1,3 xylanase is a hot research topic. In this paper, a novel β-1,3 xylanase (Xyl88) is revealed from the annotated genome of Flammeovirga pacifica strain WPAGA1. Bioinformatic analysis shows that Xyl88 belongs to the glycoside hydrolase 26 (GH26) with a suspected CBM (carbohydrate-binding module) sequence. The activity of rXyl88 is 75% of the highest enzyme activity (1.5 mol/L NaCl) in 3 mol/L NaCl buffer, which suggests good salt tolerance of rXy188. The optimum reaction temperature in the buffer without NaCl and with 1.5 mol/L NaCl is 45 °C and 55 °C, respectively. Notably, the catalytic efficiency of rXyl88 (k_cat/K_m) is approximately 20 higher than that of the thermophilic β-1,3 xylanase that has the highest catalytic efficiency. Xyl88 in this study becomes the most efficient enzyme ever found, and it is also the first reported moderately thermophilic and salt-tolerant β-1,3 xylanase. Results of molecular dynamics simulation further prove the excellent thermal stability of Xyl88. Moreover, according to the predicted 3D structure of the Xyl88, the surface of the enzyme is distributed with more negative charges, which is related to its salt tolerance, and significantly more hydrogen bonds and Van der Waals force between the intramolecular residues, which is related to its thermal stability.

Preparation of CaF2 Microspheres with Nanopetals for Water Vapor Adsorption

The hierarchically structured flower-like CaF₂ microspheres with nanopetals, named FL-CaF₂, were synthesized via a hydrothermal method using calcium acetate Ca(Ac)₂ and NaBF₄ as calcium and fluorine sources, respectively, assisted by the chelating reagent trisodium citrate (Na₃Cit) with the optimal pH of the synthesis solution. Meanwhile, a reference sample, named FL-CaF₂-R, was reproduced using ethylenediaminetetraacetic acid disodium salt (Na₂EDTA) as the chelating reagent, based on the recipe and synthesis procedure from the literature. Various techniques such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform-infrared spectroscopy, and N₂ adsorption-desorption at 77 K were then used to characterize the synthesized samples. The results show that FL-CaF₂ with a larger diameter has a much higher thermal stability than FL-CaF₂-R because the larger the nanocrystallite size, the higher the thermal stability. The adsorption of water vapor on CaF₂ is irreversible because CaF₂ can interact with the adsorbed water molecules strongly. The dual-site Langmuir model was used to describe the measured adsorption isotherms of water vapor on FL-CaF₂ at low water vapor pressures and 298, 308, and 318 K. FL-CaF₂ has a much higher water-adsorption capacity than those reported in the literature. Furthermore, the isosteric heat of adsorption as a function of loading, derived from the measured isotherms, varies from ca. 46 to 43 kJ mol^-1 in the whole loading range investigated. Finally, the applications of FL-CaF₂ are anticipated in the dehydration of hydrogen fluoride gas as well as in catalysis.

A Comparative Study of The Effects of Anticoagulants on Pure Platelet-Rich Plasma Quality and Potency

It is generally accepted that citrate or the A-form of acid-citrate-dextrose (ACD-A) are suitable for preparing platelet-rich plasma (PRP) for regenerative therapy. However, this is based on evidence from blood transfusions and not from regenerative medicine. Thus, we examined the effects of anticoagulants, such as ACD-A, ethylenediaminetetraacetic acid (EDTA), and heparin, on the regenerative quality of PRP to address this gap. The blood samples were collected in the presence of anticoagulants and were processed to prepare pure-PRP. Platelet size, activation status, and intra-platelet free Ca²⁺ concentration were determined while using a hematology analyzer and flow cytometer. Platelet-derived growth factor-BB (PDGF-BB) was quantified while using an ELISA. In pure-PRP samples, EDTA caused platelet swelling and activation, but yielded the highest number of platelets. Heparin aggregated platelets and disturbed the overall counting of blood cells. However, no significant differences in PDGF-BB levels were observed among the anticoagulants tested. Moreover, when considering the easy preparation of platelet suspensions, without the need for high-level pipetting skills, these findings suggest the comparable potency of EDTA-derived pure-PRP in tissue regeneration and support the use of EDTA in the preparation of pure-PRP. Further in vivo studies are required in animal models to exclude the possible negative effects of including EDTA in pure-PRP preparations.

Complement Activation and Thrombotic Microangiopathies

BACKGROUND AND OBJECTIVES

Atypical hemolytic uremic syndrome is a form of thrombotic microangiopathy caused by dysregulation of the alternative complement pathway. There is evidence showing complement activation in other thrombotic microangiopathies. The aim of this study was to evaluate complement activation in different thrombotic microangiopathies and to monitor treatment response.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Complement activation was assessed by exposing endothelial cells to sera or activated-patient plasma-citrated plasma mixed with a control sera pool (1:1)-to analyze C5b-9 deposits by immunofluorescence. Patients with atypical hemolytic uremic syndrome (n=34) at different stages of the disease, HELLP syndrome (a pregnancy complication characterized by hemolysis, elevated liver enzymes, and low platelet count) or severe preeclampsia (n=10), and malignant hypertension (n=5) were included.

RESULTS

Acute phase atypical hemolytic uremic syndrome-activated plasma induced an increased C5b-9 deposition on endothelial cells. Standard and lower doses of eculizumab inhibited C5b-9 deposition in all patients with atypical hemolytic uremic syndrome, except in two who showed partial remission and clinical relapse. Significant fibrin formation was observed together with C5b-9 deposition. Results obtained using activated-plasma samples were more marked and reproducible than those obtained with sera. C5b-9 deposition was also increased with samples from patients with HELLP (all cases) and preeclampsia (90%) at disease onset. This increase was sustained in those with HELLP after 40 days, and levels normalized in patients with both HELLP and preeclampsia after 6-9 months. Complement activation in those with malignant hypertension was at control levels.

CONCLUSIONS

The proposed methodology identifies complement overactivation in patients with atypical hemolytic uremic syndrome at acute phase and in other diseases such as HELLP syndrome and preeclampsia. Moreover, it is sensitive enough to individually assess the efficiency of the C5 inhibition treatment.

Gelatin-based micro-hydrogel carrying genetically engineered human endothelial cells for neovascularization

Cell delivery systems based on micro-hydrogels may facilitate the long-term survival of cells upon transplantation. Micro-hydrogels may effectively support cell proliferation, attachment, and migration in ischemic environments. In this study, we report the fabrication of a gelatin methacrylate (GelMA)-based micro-hydrogel for efficient in vivo delivery of genetically engineered endothelial cells. Micro-hydrogels were initially processed via electrospraying of GelMA and alginate (ALG) mixtures (at different ratios) on to calcium chloride (CaCl₂) solution. Electrospraying of the GelMA/ALG mixture resulted in the formation of a micro-hydrogel, owing to ALG crosslinking. Secondary crosslinking of GelMA with UV light and ALG hydrogel chelation using sodium citrate solution resulted in GelMA-based micro-hydrogel formation. We observed the angiogenic response of human umbilical vein endothelial cells (HUVECs) in GelMA concentration-dependent manner. The seeding of HUVECs engineered to express human vascular endothelial growth factor on to the GelMA micro-hydrogel and the subsequent transplantation of the micro-hydrogel into a hindlimb ischemia model effectively attenuated the ischemia condition. This facile and simple micro-hydrogel fabrication strategy may serve as a robust method to fabricate efficient cell carriers for various ischemic diseases. STATEMENT OF SIGNIFICANCE: For the therapeutic angiogenesis, it is important to provide the therapeutic cells with a carrier that could stabilize therapeutic cells and facilitate long-term survival of cells. Furthermore, it is also important to administer as many therapeutic cells as possible in a fixed volume. From these cues, we fabricated ECM-based micro-hydrogel produced by the high through-put system. And we intended to facilitate activation of therapeutic cells by coating the therapeutic cells onto the micro-hydrogel. In this manuscript, we fabricated methacrylate gelatin (GelMA) based micro-hydrogels using the electro-spraying method and coated HUVECs engineered to express hVEGF onto the micro-hydrogels. Then, we identified that GelMA concentration-dependent angiogenic response of HUVECs. Furthermore, we demonstrated that the VEGF secreting HUVEC-GelMA micro-hydrogels induced the restoration of blood flow and neovascularization in a hind-limb ischemia mouse model. These findings demonstrate that the high-throughput fabrication of ECM micro-hydrogels could be a novel platform to apply in neovascularization and tissue engineering.

Porous Alginate Scaffolds Assembled Using Vaterite CaCO3 Crystals

Formulation of multifunctional biopolymer-based scaffolds is one of the major focuses in modern tissue engineering and regenerative medicine. Besides proper mechanical/chemical properties, an ideal scaffold should: (i) possess a well-tuned porous internal structure for cell seeding/growth and (ii) host bioactive molecules to be protected against biodegradation and presented to cells when required. Alginate hydrogels were extensively developed to serve as scaffolds, and recent advances in the hydrogel formulation demonstrate their applicability as "ideal" soft scaffolds. This review focuses on advanced porous alginate scaffolds (PAS) fabricated using hard templating on vaterite CaCO3 crystals. These novel tailor-made soft structures can be prepared at physiologically relevant conditions offering a high level of control over their internal structure and high performance for loading/release of bioactive macromolecules. The novel approach to assemble PAS is compared with traditional methods used for fabrication of porous alginate hydrogels. Finally, future perspectives and applications of PAS for advanced cell culture, tissue engineering, and drug testing are discussed.

Platelet number in different anticoagulants as a diagnostic biomarker for increased intestinal permeability

The main pathological process associated to increased intestinal permeability is the translocation of toxic products, predominantly endotoxins/lipopolysaccharide (LPS), from the intestinal tract into the microcirculation. In blood, LPS binds to surface receptors on immune cells initiating an inflammatory response. LPS can also bind to platelets leading to preactivated platelets that have a lower threshold to be aggregated in presence heparin. The aim of this study was to validate a simple, fast and reliable test for screening LPS-loaded platelets. This test named PANDA (acronym for Platelet Number in Different Anticoagulants) consists in the measurement of the mean platelet number in blood samples collected into EDTA and heparin. We analyzed blood samples from 92 patients with gastrointestinal diseases and 23 healthy volunteers and found a markedly low number of platelets in heparinized blood compared to EDTA-anticoagulated blood in patients but not in healthy volunteers. Furthermore, ex vivo addition of endotoxin to blood samples induced a remarkable decrease in platelet count in heparinized blood of the volunteers but not in the patient's group, where platelets could be previously saturated by endotoxin circulating in blood. Platelet should be counted during the first hour after blood collection, in order to avoid false results due to a progressive platelet aggregation in heparinized blood in function of the time. Our results demonstrated that PANDA test can be used for screening LPS-loaded platelets as an indirect diagnostic biomarker for increased intestinal permeability and also for monitoring the gut barrier function during the treatment of gastrointestinal diseases.

A mutually induced conformational fit underlies Ca2+-directed interactions between calmodulin and the proximal C terminus of KCNQ4 K+ channels

Calmodulin (CaM) conveys intracellular Ca²⁺ signals to KCNQ (Kv7, "M-type") K⁺ channels and many other ion channels. Whether this "calmodulation" involves a dramatic structural rearrangement or only slight perturbations of the CaM/KCNQ complex is as yet unclear. A consensus structural model of conformational shifts occurring between low nanomolar and physiologically high intracellular [Ca²⁺] is still under debate. Here, we used various techniques of biophysical chemical analyses to investigate the interactions between CaM and synthetic peptides corresponding to the A and B domains of the KCNQ4 subtype. We found that in the absence of CaM, the peptides are disordered, whereas Ca²⁺/CaM imposed helical structure on both KCNQ A and B domains. Isothermal titration calorimetry revealed that Ca²⁺/CaM has higher affinity for the B domain than for the A domain of KCNQ2-4 and much higher affinity for the B domain when prebound with the A domain. X-ray crystallography confirmed that these discrete peptides spontaneously form a complex with Ca²⁺/CaM, similar to previous reports of CaM binding KCNQ-AB domains that are linked together. Microscale thermophoresis and heteronuclear single-quantum coherence NMR spectroscopy indicated the C-lobe of Ca²⁺-free CaM to interact with the KCNQ4 B domain (K_d ∼10-20 μm), with increasing Ca²⁺ molar ratios shifting the CaM-B domain interactions via only the CaM C-lobe to also include the N-lobe. Our findings suggest that in response to increased Ca²⁺, CaM undergoes lobe switching that imposes a dramatic mutually induced conformational fit to both the proximal C terminus of KCNQ4 channels and CaM, likely underlying Ca²⁺-dependent regulation of KCNQ gating.

Tunable activation of therapeutic platelet-rich plasma by pulse electric field: Differential effects on clot formation, growth factor release, and platelet morphology

BACKGROUND

Activation of platelet-rich plasma (PRP) by pulse electric field (PEF) releases growth factors which promote wound healing (e.g., PDGF, VEGF for granulation, EGF for epithelialization).

AIMS

To determine after PEF activation of therapeutic PRP: 1) platelet gel strength; 2) profile of released growth factors; 3) alpha- and T-granule release; 4) platelet morphology.

METHODS

Concentrated normal donor PRP was activated by 5 μsec (long) monopolar pulse, ~4000 V/cm (PEF A) or 150 nsec (short) bipolar pulse, ~3000 V/cm (PEF B) in the presence of 2.5 mM (low) or 20 mM (high) added CaCl2. Clot formation was evaluated by thromboelastography (TEG). Surface exposure of alpha granule (P-selectin) and T-granule (TLR9 and protein disulfide isomerase [PDI]) markers were assessed by flow cytometry. Factors in supernatants of activated PRP were measured by ELISA. Platelet morphology was evaluated by transmission electron microscopy (TEM).

RESULTS

Time to initial clot formation was shorter with thrombin (<1 min) than with PEF A and B (4.4-8.7 min) but clot strength (elastic modulus, derived from TEG maximum amplitude) was greater with PEF B than with either thrombin or PEF A (p<0.05). Supernatants of PRP activated with PEF A had higher EGF levels than supernatants from all other conditions. In contrast, levels of PF4, PDGF, and VEGF in supernatants were not significantly different after PEF A, PEF B, and thrombin activation. T-granule markers (TLR9 and PDI) were higher after thrombin than after PEF A or B with low or high CaCl2. By TEM, platelets in PEF-treated samples retained a subset of granules suggesting regulated granule release.

CONCLUSION

Pulse length and polarity can be modulated to produce therapeutic platelet gels as strong or stronger than those produced by thrombin, and this is tunable to produce growth factor profiles enhanced in specific factors important for different stages of wound healing.

Characterization of a novel psychrophilic and halophilic β-1, 3-xylanase from deep-sea bacterium, Flammeovirga pacifica strain WPAGA1

β-1, 3-Xylanase is one of the most important hydrolytic enzymes to prepare oligosaccharides as functional foods in seaweed industry. However, less than five β-1, 3-xylanases have been experimentally expressed and characterized; moreover, none of them is psychrophilic and salt tolerant. Here, we mined a novel β-1, 3-xylanase (Xyl512) from the genome of the deep-sea bacterium Flammeovirga pacifica strain WPAGA1 and biochemically characterized it in detail. The Xyl512 did not contain any carbohydrate-binding module; the catalytic domain of it belonged to the glycoside hydrolase family 26. The optimum temperature and pH of the purified β-1, 3-xylanase was 20 °C and pH 7.0 in the condition of no NaCl. However, they shifted to 30 °C and 7.5 with 1.5 mol/L NaCl, respectively. In this condition (1.5 mol/L NaCl), the overall activity was 2-fold as high as that without NaCl. Based on the residue interactions and the electrostatic surfaces, we addressed the possible mechanism of its adaption to low temperature and relative high NaCl concentration. The Xyl512 showed significantly reduced numbers of hydrogen bonds leading to a more flexible structure, which is likely to be responsible for its cold adaptation. While the negatively charged surface may contribute to its salt tolerance. The β-1, 3-xylanase we identified here was the first reported psychrophilic and halophilic one with functionally characterized. It could make new contributions to exploring and studying the β-1, 3-xylanase for further associated investigations.

Thallium Labeled Citrate-Coated Prussian Blue Nanoparticles as Potential Imaging Agent

Background

The aim of this study was to develop and characterize a nanoparticle-based image-contrast platform which is biocompatible, chemically stable, and accessible for radiolabeling with ²⁰¹Tl. We explored whether this nanoparticle enhanced the T1 signal which might make it an MRI contrast agent as well.

Methods

The physical properties of citrate-coated Prussian blue nanoparticles (PBNPs) (iron(II);iron(III);octadecacyanide) doped with ²⁰¹Tl isotope were characterized with atomic force microscopy, dynamic light scattering, and zeta potential measurement. PBNP biodistribution was determined by using SPECT and MRI following intravenous administration into C57BL6 mice. Activity concentrations (MBq/cm³) were calculated from the SPECT scans for each dedicated volume of interest (VOI) of liver, kidneys, salivary glands, heart, lungs, and brain.

Results

PBNP accumulation peaked at 2 hours after injection predominantly in the kidneys and the liver followed by a gradual decrease in activity in later time points.

Conclusion

We synthetized, characterized, and radiolabeled a Prussian blue-based nanoparticle platform for contrast material applications. Its in vivo radiochemical stability and biodistribution open up the way for further diagnostic applications.