•Salecan/chitosan polyelectrolyte complex hydrogel was prepared by self-assembly.•The electrostatic interactions between salecan and chitosan were thoroughly studied.•Hydrogels presented a controlled ...and pH-dependent release profile of Vitamin C (VC).•The amount of VC released in SIF was significantly higher than in SGF.•VC release was driven by Fickian diffusion in SGF and anomalous transport in SIF.
Vitamin C (VC) is an indispensable nutrient for human health. However, poor chemical stability in gastric environment restricts its full assimilation by intestine. It is important to construct a safe carrier that can protect VC from the gastric fluid and sustainably release it in intestine. Herein, we designed a novel polyelectrolyte complex (PEC) hydrogel through self-assembly of salecan and chitosan. PEC structure formed by electrostatic interactions was confirmed by FT-IR, XRD, XPS and TGA. Their swelling, morphology, rheology, cytocompatibility and biodegradation were well investigated. In particular, VC released in a controlled and pH-dependent manner. The release amount in simulated intestinal fluid (SIF) was significantly higher than simulated gastric fluid (SGF), and can be maintained at high level in blood after 6 h. Release mechanism agreed well with Ritger-Peppas model. The purpose of this study was to develop a smart nutrient delivery platform for targeted release of VC in intestinal condition.
SARS-CoV-2 is a global challenge due to its ability to spread much faster than the SARS-CoV, which was attributed to the mutations in the receptor binding domain (RBD). These mutations enhanced the ...electrostatic interactions. Recently, a new strain is reported in the UK that includes a mutation (N501Y) in the RBD, that is possibly increasing the infection rate. Here, using Molecular Dynamics simulations (MD) and Monte Carlo (MC) sampling, we show that the N501 mutation enhanced the electrostatic interactions due to the formation of a strong hydrogen bond between SARS-CoV-2-T500 and ACE2-D355 near the mutation site. In addition, we observed that the electrostatic interactions between the SARS-CoV-2 and ACE2 in the wild type and the mutant are dominated by salt-bridges formed between SARS-CoV-2-K417 and ACE2-D30, SARS-CoV-2-K458, ACE2-E23, and SARS-CoV-2-R403 and ACE2-E37. These interactions contributed more than 40% of the total binding energies.
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•The N501Y mutation enhance the binding affinity between SARS-CoV-2 and ACE2.•The interactions between the SARS-CoV-2 and ACE2 are dominated by electrostatic interactions•Stronger interaction between SARS-CoV-2-N501Y and ACE2 is due to shorter distances between SARS-CoV2-T500 and ACE2-D355.
•The PDB was investigated for protein structures with incorporated POMs.•POMs were analyzed with regard to their effects on protein crystallography.•POMs can stabilize and provide crystal contacts ...which facilitate crystal packing.
Polyoxometalates (POMs) are discrete polynuclear metal-oxo anions with a fascinating variety of structures and unique chemical and physical properties. Their application in various fields is well covered in the literature, however little information about their usage in protein crystallization is available. This review summarizes the impact of the vast class of POMs on the formation of protein crystals, a well-known (frustrating) bottleneck in macromolecular crystallography, with the associated structure elucidation and a particular emphasis focused on POM's potential as a powerful crystallization additive for future research. The Protein Data Bank (PDB) was scanned for protein structures with incorporated POMs which were assigned a PDB ligand ID resulting in 30 PDB entries. These structures have been analyzed with regard to (i) the structure of POM itself in the immediate protein environment, (ii) the kind of interaction and position of the POM within the protein structure and (iii) the beneficial effects of POM on protein crystallography apparent so far.
The Cover Feature shows the effect of the repulsive electrostatic interaction in the interlayer region of 2D ferrous nitroprussides with short pillar molecules on the spin transition kinetics. Wider ...hysteresis loops were observed for the lower scan rates. This is an effect opposite to that expected under conditions close to those corresponding to the thermodynamic equilibrium. The axial CN ligand and the NO group found in the interlayer region accumulate electron density, via π‐back donation, in their N and O ends. These charge centers result in a repulsive electrostatic interaction between adjacent layers, which opposes the HS→LS transition during the cooling of the sample and favors the inverse (LS→HS) transition. Since the spin transition is closely related to the nucleation and growth of the new structural phase, the observed effect of the scan rate value on the width of the hysteresis loop was discussed in terms of structural changes. More information can be found in the Research Article by M. González, E. Reguera and co‐workers.
•In situ injectable hydrogels based on polyelectrolyte complexes were prepared.•Chitosan oligosaccharide induced a two-stage gelling process and stronger hydrogels.•Chitosan oligosaccharide notably ...helped to accelerate the wound healing.
In situ injectable hydrogels for wound healing based on carboxymethyl chitosan (CMCS) and alginate were developed in this work. The liquid mixture of CMCS and alginate solutions formed a gel by polyelectrolyte complexation after addition of d-glucono-δ-lactone (GDL), which slowly hydrolyzed and donated protons. When chitosan oligosaccharide (COS) was added into the mixture, a two-stage gelling process occurred. The primary gelling process was similar to that of the hydrogel without COS, while the secondary gelling process appeared about 20 min later, and much stronger hydrogels with storage modulus G’ about 1 MPa, 104 times higher, were obtained. COS also significantly influenced the microstructure of hydrogels as well as their biological activities. The hydrogels with 0.5% of COS significantly promoted proliferation of human umbilical cord mesenchymal stem cells (HUMSCs). These injectable hydrogels, especially when COS was added, remarkably accelerated the wound healing process in a mouse skin defect model. Microscopic wound analysis showed an increase of the thickness and integrity of epidermal tissue, increased formation of collagen fibers, and enhanced expression of vascular endothelial growth factor as compared to the control group.
Interactions between positively charged amino-modified (APS) and negatively charged bare (BPS) polystyrene nanoplastics may cause heteroaggregation in aquatic environments. This study investigated ...the effects of particle concentration ratio, solution chemistry electrolytes, pH, and natural organic matter (NOM), and interaction sequence on their heteroaggregation kinetics. In the absence of electrolytes and NOM, the APS/BPS ratio for attaining maximum heteroaggregation rate (khetero) increased from APS/BPS= 3/7 to APS/BPS= 1/1 as pH increased from 4 to 10, indicating that electrostatic interactions dominated heteroaggregation. In the absence of NOM, khetero ranked APS/BPS= 2/3 > APS/BPS= 1/1 > APS/BPS= 3/2. Colloidal stability decreased linearly as pH increased from 4 to 8 at APS/BPS= 1/1, while diffusion-limited heteroaggregation persisted at pH 10. In NaCl solution, humic acid (HA) retarded heteroaggregation more effectively than sodium alginate (SA) via steric hindrance and weakening electrostatic interactions, following the modified Derjaguin-Landau-Verwey-Overbeek (MDLVO) theory. Compared with simultaneous interactions among APS, BPS, NaCl, and NOM, the NOM retardation effects on heteroaggregation weakened if delaying its interaction with others. In CaCl2 solution, the effects of NOM on heteroaggregation depended on counterbalance among charge screening, steric hindrance, and calcium bridging. These findings highlight the important role of heteroaggregation between oppositely charged nanoplastics on their fate and transport in aquatic environments.
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•Decreasing APS/BPS ratio and increasing solution pH mostly promote heteroaggregation.•NOM promotes aggregation at high CaCl2 concentration but retards it in NaCl solution.•HA retards aggregation more effectively than SA, which are explained by MDLVO theory.•NOM-stabilization effect weakens in NaCl solution with delayed interaction sequence.•Electrostatic interactions, steric hindrance and calcium bridging are key mechanisms.
This Review discusses ionic electrets: their preparation, their mechanisms of formation, tools for their characterization, and their applications. An electret is a material that has a permanent, ...macroscopic electric field at its surface; this field can arise from a net orientation of polar groups in the material, or from a net, macroscopic electrostatic charge on the material. An ionic electret is a material that has a net electrostatic charge due to a difference in the number of cationic and anionic charges in the material. Any material that has ions at its surface, or accessible in its interior, has the potential to become an ionic electret. When such a material is brought into contact with some other material, ions can transfer between them. If the anions and cations have different propensities to transfer, the unequal transfer of these ions can result in a net transfer of charge between the two materials. This Review focuses on the experimental evidence and theoretical models for the formation of ionic electrets through this ion-transfer mechanism, and proposes--as a still-unproved hypothesis--that this ion-transfer mechanism may also explain the ubiquitous contact electrification ("static electricity") of materials, such as organic polymers, that do not explicitly have ions at their surface.
Antimicrobial peptides (AMPs) are part of the innate immune defense mechanism of many organisms. Although AMPs have been essentially studied and developed as potential alternatives for fighting ...infectious diseases, their use as anticancer peptides (ACPs) in cancer therapy either alone or in combination with other conventional drugs has been regarded as a therapeutic strategy to explore. As human cancer remains a cause of high morbidity and mortality worldwide, an urgent need of new, selective, and more efficient drugs is evident. Even though ACPs are expected to be selective toward tumor cells without impairing the normal body physiological functions, the development of a selective ACP has been a challenge. It is not yet possible to predict antitumor activity based on ACPs structures. ACPs are unique molecules when compared to the actual chemotherapeutic arsenal available for cancer treatment and display a variety of modes of action which in some types of cancer seem to co-exist. Regardless the debate surrounding the definition of structure-activity relationships for ACPs, great effort has been invested in ACP design and the challenge of improving effective killing of tumor cells remains. As detailed studies on ACPs mechanisms of action are crucial for optimizing drug development, in this review we provide an overview of the literature concerning peptides' structure, modes of action, selectivity, and efficacy and also summarize some of the many ACPs studied and/or developed for targeting different solid and hematologic malignancies with special emphasis on the first group. Strategies described for drug development and for increasing peptide selectivity toward specific cells while reducing toxicity are also discussed.
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MXene has been considered as a promising two-dimensional material for supercapacitors owing to its large surface area, high conductivity, and excellent cycling stability. However, its ...low specific capacitance restricts its extensive applications. Therefore, to address the issue, we homogeneously deposited NiCo2S4 nanoflakes on the surface of MXene on conductive nickel foam (denoted as MXene-NiCo2S4@NF), which was used as a composite binder-free electrode for supercapacitor applications. The NiCo2S4 nanoflakes increased the surface area of the composite electrode, thereby increasing its specific capacity from 106.34Cg−1 to 596.69Cg−1 at 1Ag−1. Compared to the pristine MXene, MXene-NiCo2S4@NF maintained the high retention rate of pristine MXene and exhibited excellent cycling stability with 80.4% of its initial specific capacity after 3000 cycles. The composite electrode exhibited improved electrochemical performance for supercapacitors, owing to the combined merits of NiCo2S4 (high specific capacity) and MXene (high retention rate and good cycling stability. The fabricated asymmetric solid-state supercapacitor using MXene-NiCo2S4 as a positive electrode and active carbon as a negative electrode, exhibited an energy density of 27.24Whkg−1 at 0.48kWkg−1 of power density.
There is increasing interest in the food industry to develop plant-based emulsifiers for sustainability, ethical, and health reasons. In this study, we showed that stable Pickering emulsions could be ...fabricated using either cellulose or and chitin nanofibrils, as well as their physical mixtures. These emulsions were highly stable to droplet coalescence during storage, which we attributed to the ability of the nanofibers to adsorb to the oil droplet surfaces and form a thick particulate layer that protected them from coalescence. Moreover, the nanofibers formed a 3D-network in the aqueous phase that prevented the oil droplets from moving, thereby improving their creaming stability. We identified the optimum nanoparticle concentration and nanochitin-to-nanocellulose ratio required to formulate these emulsions. These nanofibers may be useful as edible particle-based emulsifiers for forming more sustainable plant-based food emulsions.
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•Pickering emulsions were formed from plant-based nanoparticles.•Cationic nanochitin and/or anionic nanocellulose were used.•The optimum nanoparticle concentration and ratio was identified.•The Pickering emulsions had good stability against coalescence during storage.
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