Charged Carboxylate Research Articles

Adhesive polyelectrolyte coating through UV-triggered polymerization on PLGA particles for enhanced drug delivery to inflammatory intestinal mucosa

Administering medication precisely to the inflamed intestinal sites to treat ulcerative colitis (UC), with minimized side effects, is of urgent need. In UC, the inflammation damaged mucosa contains a large number of amino groups which are positively charged, providing new opportunities for drug delivery system design. Here, we report an oral drug delivery system utilizing the tacrolimus-loaded poly (lactic-co-glycolic acid) (TAC/PLGA) particles with an adhesion coating by in situ UV-triggered polymerization of polyacrylic acid and N-hydroxysuccinimide (PAA-NHS). The negatively charged carboxyl groups effectively interact with the positively charged focal mucosa, and the NHS ester groups form the covalent bonds with the amino groups, thereby synergically enhancing the adhesion of the PLGA particles to the focal mucosa. Our findings reveal that, compared to the naked particles, the PAA-NHS coating increases the adhesion of particles to the inflammatory intestine. In a dextran sulfate sodium-induced acute colitis mouse model, the TAC/PLGA particles with PAA-NHS coating exhibits substantial retention of TAC within the inflammatory intestine, enhancing drug delivery efficiency and therapeutic effects. This approach holds promise for UC management, minimizing systemic side effects and optimizing therapeutic outcomes.Graphical abstract

Exploring Salts, Co‐crystals, Drug Nanoparticles, and Co‐Delivery in Formulation Development of Ciprofloxacin: A Review

AbstractBased on Biopharmaceutics Classification System, Ciprofloxacin (CIP) is class IV active pharmaceutical ingredient which exhibits poor solubility and permeability in water. It showed limited solubility due to formation of strong crystal lattice, as positive charged piperazine group interacts with negatively charged carboxylate group to form chains of molecules. Due to better performance, it is used very frequently for many infections treatment. Though, it is very useful antibiotic, but it is photo‐chemically unstable and development of antimicrobial resistance also reported in literature. Due to these serious concerns, the development of CIP formulation is a challenging task for pharmaceutical industries. Currently, several strategies are used to boost pharmaceutical properties of CIP such as solubility, dissolution and antibacterial activity. In this review we have discussed the approaches through which pharmaceutical properties of CIP can be improved such as solubility, dissolution rate and antibacterial activity and so forth. Salts, Co‐crystals, salt‐Co‐crystals, metal complexes, and nanoparticles formations are some prominent strategies for altering CIP pharmaceutical properties. Preliminary, this review is design for CIP, but it can also be helpful for other antibiotics (especially fluoroquinolones class).

A click chemistry-based biorthogonal approach for the detection and identification of protein lysine malonylation for osteoarthritis research.

Lysine malonylation is a post-translational modification where a malonyl group, characterized by a negatively charged carboxylate, is covalently attached to the ε-amino side chain of lysine, influencing protein structure and function. Our laboratory identified Mak upregulation in cartilage under aging and obesity, contributing to osteoarthritis (OA). Current antibody-based detection methods face limitations in identifying Mak targets. Here, we introduce an alkyne-functionalized probe, MA-diyne, which metabolically incorporates into proteins, enabling copper(I) ion-catalyzed click reactions to conjugate labeled proteins with azide-based fluorescent dyes or affinity purification tags. In-gel fluorescence confirms MA-diyne incorporation into proteins across various cell types and species, including mouse chondrocytes, adipocytes, Hek293T cells, and C. elegans . Pull-down experiments identified known Mak proteins such as GAPDH and Aldolase. The extent of MA-diyne modification was higher in Sirtuin 5-deficient cells suggesting these modified proteins are Sirtuin 5 substrates. Pulse-chase experiments confirmed the dynamic nature of protein malonylation. Quantitative proteomics identified 1136 proteins corresponding to 8903 peptides with 429 proteins showing 1-fold increase in labeled group. Sirtuin 5 regulated 374 of these proteins. Pull down of newly identified proteins such as β-actin and Stat3 was also done. This study highlights MA-diyne as a powerful chemical tool to investigate the molecular targets and functions of lysine malonylation in OA conditions.

A Novel Turn‐On Fluorescence Probe for Selective Picomolar Detection of Uric Acid Using Green Carbon Dots (G‐NCDs) from Waste Brachyura Shells

AbstractIn the current study, a Novel synthesis of fluorescent Green carbon dots (G‐NCDs) is reported from waste Brachyura shells using a simple, green technique. G‐NCDs function as a TURN‐ON fluorescent probe for the selective detection Uric Acid (UA) in presence of Dopamine (DA). The synthesized carbon dots are sand colored under visible light and exhibit pale green fluorescence under UV radiation. The G‐NCDs are characterized using UV–vis, FTIR, XPS, SEM‐EDAX, HR‐TEM, X‐ray diffraction, and PL spectroscopic technique. The SEM‐EDAX data of G‐NCDs shows a layered, fibrous morphology and confirms the presence of only Carbon, Nitrogen, and Oxygen in the matrix. FTIR and XPS response confirms the presence of functional groups like ─C≡N, ─C≡C─, CH, ═C─H, O─H on the surface of G‐NCDs. XRD data confirms G‐NCDs to be crystalline with a particle size of 4.51 nm. The quantum yield found to be 99.8%. PL response confirms a TURN OFF fluorescence with increased addition of DA. Fluorescence resonance energy transfer (FRET), a form of dynamic quenching is responsible for the DA quenching, confirmed through linear Stern‐ Volmer plot. With increase in addition of UA in presence of DA fluorescence TURNs ON with a minimum selective detection limit of UA as 0.23 × 10−12 M. Selective detection of UA in presence of DA is due to the following reasons i) decrease in bandgap of G‐NCDs in presence of UA ii) electrostatic attraction between negatively charged carboxyl group of G‐NCDs and positively charge secondary amine group of UA molecule ii) UA molecules near to the surface of G‐NCDs switches off the formation of polydopamine iv) formation of surface defects due to the formation of hydrogen bonds between the ketone/hydroxyl group in the UA molecule and the amino group on the surface of G‐NCD resulting in fluorescence. The first time the lowest detection limit of 0.23 × 10−12 M of UA is been reported in presence of DA using G‐NCDs. In future, G‐NCDs will be used for the detection of UA in biological fluids.

Studies on remediation of neutral red using water insoluble β-cyclodextrin (β-CD) polymers in aqueous solution

The increasing global contamination of dyes in natural waters has highlighted the need for versatile and effective cleanup methods. In this study, water-insoluble β-Cyclodextrin (β-CD) polymers, including CA/β-CD, MA/β-CD, and TA/β-CD, were synthesized by cross-linking β-cyclodextrin with three different organic acids: citric acid (CA), tartaric acid (TA), and malic acid (MA). This synthesis aimed to create polymers with distinct properties by incorporating these acids into the β-Cyclodextrin framework. The resulting polymers were characterized using various advanced analytical techniques, such as Fourier transform infrared spectroscopy, scanning electron microscopy, and UV–visible (UV–Vis) spectrophotometry. The synthesized polymers were then used to adsorb neutral red dye from aqueous solutions. The study explored various conditions for adsorption, including pH, adsorbent mass, dye concentration, temperature, and contact time, as well as adsorption isotherms, kinetics, and thermodynamics. Among the polymers, CA/β-CD, with its higher content of carboxyl groups, showed the highest efficiency in adsorbing neutral red dye under all tested conditions. The CA/β-CD adsorbent achieved 92% removal efficiency, with the dye being attracted to the negatively charged carboxyl ions through electrostatic forces, effectively removing it from water. These findings suggest that water-insoluble cyclodextrin-based polymers could be cost-effective adsorbents for removing dye from aqueous solutions.

Electrochemically induced release of a model dye from a pH-sensitive and electroactive microgel monolayer attached to an electrode surface

We present a novel electrochemically-induced release system featuring a pH-responsive and electroactive microgel monolayer specifically designed to enhance drug delivery mechanisms. This microgel, synthesized from acrylic acid and a ferrocene derivative, was formed on a conductive electrode surface, providing a robust platform for controlled release applications. The physical and chemical properties of the microgel were meticulously characterized using dynamic light scattering (DLS), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), nuclear magnetic resonance (NMR), and electrochemical techniques. The microgel particles modified the electrode surface by forming a monolayer through interactions between the sulfur present in the crosslinking agent and the gold surface of the electrode. Cyclic voltammetry was used to analyze the properties of the modified electrode, and the morphology of the monolayer was confirmed by scanning electron microscopy (SEM). Notably, we demonstrated that the incorporation of positively charged crystal violet (CV) dye molecules was facilitated through electrostatic interactions with the negatively charged carboxylic groups of the microgel, resulting in effective dye retention. Our investigation revealed that the electrochemical oxidation of the ferrocene groups significantly weakens the interactions between the crystal violet (CV) dye and the polymer chains within the microgel network, facilitating controlled dye release. The release process was successfully monitored using quartz crystal microbalance with dissipation monitoring (QCM-D), confirming the system's potential for innovative drug delivery platforms and implant construction.

Unveiling molecular mechanism underlying inhibition of human islet amyloid polypeptide fibrillation by benzene carboxylic acid-peptide conjugate

Type 2 diabetes (T2D) is linked to the apoptosis of insulin-producing β-cells due to the aberrant fibrillation of the human islet amyloid polypeptide (hIAPP or amylin) to cytotoxic aggregates. Profit et al. generated conjugates (C1–C7) by appending benzene carboxylic acids of varying charges to the N-terminal of hIAPP22-29 fragment peptide NFGAILSS to modulate hIAPP fibrillation and cytotoxicity. C5 (4 µM) derived by conjugating low-cost, commercially available benzene-1,2,4,5-tetracarboxylic acid known as pyromellitic acid to NFGAILSS completely abolishes the hIAPP (40 µM) self-assembly as noted in the thioflavin T (ThT) fluorescence assay. The circular dichroism (CD) spectra highlighted that C5 stabilized hIAPP in a distinctive conformation and blocked its conformational switching to amyloidogenic β-sheet structure. C5 possessing a charge-dense pyromellitic acid moiety appended on the N-terminal region of self-recognition hIAPP fragment sequence NFGAILSS created significant interest as it effectively inhibited hIAPP fibrillation and possessed lower molecular mass, smaller size, and charge as compared to hIAPP aggregation inhibitor EEEENFGAILSS (P10). However, it remains unclear how C5 traps hIAPP into a unique conformation that abolishes its self-aggregation propensity. Thus, molecular dynamics (MD) simulations have been employed to illuminate the conformational transitions and structural changes in hIAPP on the inclusion of C5. C5 displayed high-affinity binding interactions to hIAPP (ΔGbinding = −37.11 ± 3.72 kcal/mol) with major contributions from the van der Waals and electrostatic interactions. Furthermore, residue-specific binding free energy analysis depicted high-affinity binding interactions of C5 with Phe15, His18, Asn21, and Tyr37 of hIAPP that play a crucial role in hIAPP fibrillation. The negatively charged carboxylate groups of pyromellitic acid moiety of C5 displayed interactions with the key residues of hIAPP as noted in the conformational clustering analysis. Notably higher sampling of helix from 24.00 ± 0.84 % in hIAPP to 34.20 ± 1.92 % in hIAPP–C5 is consistent with the CD studies, which depicted that C5 trapped hIAPP monomer in a conformation that blocked its self-association. MD simulations illuminated the molecular mechanism and atomistic details of the C5 interactions with hIAPP, which are responsible for its inhibitory activity against hIAPP fibrillation and alleviating hIAPP aggregates-induced cytotoxicity.

Charged organic ligands inserting/supporting the nanolayer spacing of vanadium oxides for high-stability/efficiency zinc-ion batteries.

Given their high safety, environmental friendliness and low cost, aqueous zinc-ion batteries (AZIBs) have the potential for high-performance energy storage. However, issues with the structural stability and electrochemical kinetics during discharge/charge limit the development of AZIBs. In this study, vanadium oxide electrodes with organic molecular intercalation were designed based on intercalating 11 kinds of charged organic carboxylic acid ligands between 2D layers to regulate the interlayer spacing. The negatively charged carboxylic acid group can neutralize Zn2+, reduce electrostatic repulsion and enhance electrochemical kinetics. The intercalated organic molecules increased the interlayer spacing. Among them, the 0.028EDTA · 0.28NH4 + · V2O5 · 0.069H2O was employed as the cathode with a high specific capacity (464.6mAhg-1 at 0.5Ag-1) and excellent rate performance (324.4mAhg-1 at 10Ag-1). Even at a current density of 20Ag-1, the specific capacity after 2000 charge/discharge cycles was 215.2mAhg-1 (capacity retention of 78%). The results of this study demonstrate that modulation of the electrostatic repulsion and interlayer spacing through the intercalation of organic ligands can enhance the properties of vanadium-based materials.

Initiation of Medial Calcification: Revisiting Calcium Ion Binding to Elastin.

Pathological calcification of elastin, a key connective tissue protein in the medial layers of blood vessels, starts with the binding of calcium ions. This Mini-Review focuses on understanding how calcium ions interact with elastin to initiate calcification at a molecular level, and emphasizes water's critical role in mediating this interaction. In the past decade, great strides have been made in understanding and modeling ion-specific hydration and its effects on biomolecule interactions. However, these advances have been largely absent from our understanding of elastin calcification. Historically, charge-neutral backbone carbonyls and negatively charged carboxyl groups have been proposed as elastin's calcium binding sites. Recently, tropoelastin's only four carboxyl groups have been identified as binding sites from classical molecular dynamics (MD). While carboxyl groups have a much higher affinity for binding calcium ions than backbone carbonyls, conflicting evidence persists for both functional group's importance in elastin calcification. This can be attributed to the fact that divalent ions strongly polarize water, leading to a hydration shell that shields electrostatic forces. The hydration shell surrounding both a calcium ion and either of the proposed binding sites must be displaced to enable binding. Providing our own extended X-ray absorption fine structure (EXAFS) data and complementary simulations, we discuss the potential structures of calcium binding in elastin and review prior knowledge regarding the relative importance of the two proposed binding sites.

Creating High Yield Stress Particle-Laden Oil/Water Interfaces Using Charge Bidispersity.

Interfacial engineering has been increasingly used to stabilize Pickering emulsions in commercial products and biomedical applications. Pickering emulsion stabilization is aided by interfacial viscoelasticity; however, typically the primary means of stabilization are steric hindrances between high surface concentration shells of particles around the drops. In this work, the concept of creating large interfacial viscoelastic yield stresses with low particle surface concentrations (<50%) using bidisperse charged particle systems is tested to evaluate their potential efficacy in emulsion stabilization. To explore this hypothesis, interfacial rheology and visualization experiments are conducted at o/w interfaces using positively charged amidine, negatively charged carboxylate, and negatively charged sulfate-coated latex spheres and compared to a model based on interparticle forces. Bidisperse particle systems have been observed to create more networked structures than monodisperse systems. For surface concentrations of <50%, bidisperse interfaces created measurable viscoelastic moduli ∼1 order of magnitude larger than monodisperse interfaces. Furthermore, these interfaces have measurable yield stresses on the order of 10-4 Pa·m when monodisperse systems have none. Bidispersity impacts surface viscoelasticity primarily by increasing the overall magnitude of attraction between particles at the interface and not due to changes in the microstructure. The developed model predicts the relative surface fraction that creates the largest moduli and shows good agreement with the experimental data. The results demonstrate the ability to create large viscoelastic moduli for small surface fractions of particles, which may enable stabilization using fewer particles in future applications.

Fabrication of clickable bamboo-sourced cellulose nanofibrils for diverse surface modifications: Hydrophobicity and fluorescence functionalities

Surface functionalization of cellulose nanofibrils (CNF) is crucial for expanding their practical application. However, most functionalization processes are complicated and laborious. Herein, this work presents a facile surface engineering strategy to create a range of functionalized CNF via thiol-ene click reaction. Initially, clickable CNF was produced by grafting a compound with both carboxylate- and norbornene groups onto bamboo cellulose via norbornene-dicarboxylic anhydride esterification followed by homogenization. The introduction of negatively charged carboxylates facilitated nanofibrillation, resulting in CNF with a diameter of 3 nm and an aspect ratio of up to 600. The introduction of norbornenes enabled diverse functionalization of CNF through click reaction. Subsequently, hexadecanethiol successfully clicked with norbornene-grafting CNF, enhancing its hydrophobicity and dispersion in organic solvents. 7-mercapto-4-methyl coumarin was also able to click with norbornene-grafting CNF, yielding fluorescence-labeled CNF while maintaining excellent aqueous dispersibility. The fluorescence-labeled CNF was demonstrated to be utilized as an eco-friendly sensor for the detection of Fe3+ ions. Additionally, it could be converted into fluorescent films or intelligent inks suitable for anti-counterfeiting purposes. This study demonstrates that the proposed surface engineering strategy provides an effective approach for producing clickable CNF and fabricating cellulosic materials with diverse functionalities that meet the demands of various applications.

Novel peptides with calcium-binding capacity from antler bone hydrolysate, its bioactivity on MC3T3-E1 cells, and the possible chelating mode.

In this study, peptide-calcium chelate was screened from antler bone hydrolysate, and its bioactivity on MC3T3-E1 cells and its chelating mechanism were investigated. Invitro experiments showed that peptide-calcium chelate promoted the differentiation and mineralization of MC3T3-E1 cells. Subsequently, three novel calcium-chelating peptides were obtained from antler bone hydrolysate using hydroxyapatite chromatography (HAC), Sephadex G-25 gel filtration chromatography, and reversed-phase high-performance liquid chromatography (RP-HPLC). Meanwhile, this work determined peptides' amino acid sequences as TKLGTQLQL, LETVILGLLKT, and KMVFLMDLLK based on LC-MS/MS. Then the present work prepared the three peptides, with the corresponding calcium-chelating rates being verified as 87.68 ± 2.86%, 80.72 ± 0.93%, and 67.96 ± 0.98%, respectively. Fourier transform infrared (FTIR) spectroscopy, ultraviolet-visible absorption (UV-vis) spectroscopy, X-ray diffraction (XRD), circular dichroism (CD), zeta potential, and molecular dynamics (MD) simulations were adopted to investigate the chelating mode of peptides with calcium ions. As a result, oxygen in the carboxyl group and the nitrogen in the amino group were related to calcium binding. In addition, the chelation site preferred the negatively charged carboxylate groups of Leu or Thr. The present work revealed that antler bone might be the new calcium-chelating peptide source and elucidated their positive role in osteogenesis.

Formation of a Covalent Adduct in Retaining β‐Kdo Glycosyl‐Transferase WbbB via Substrate‐Mediated Proton Relay

AbstractThe GT99 domain of the membrane‐anchored WbbB glycosyltransferase (WbbBGT99) catalyzes the transfer of 3‐deoxy‐D‐manno‐oct‐2‐acid (β‐Kdo) to an O‐antigen saccharide acceptor with retention of stereochemistry. It has been proposed that the enzyme follows an unprecedented double‐displacement mechanism involving the formation of covalent adduct between the Kdo sugar and an active site residue (Asp232) that is properly oriented for nucleophilic attack. Here we use QM/MM metadynamics simulations on recently reported crystal structures to provide theoretical evidence for the formation of such adduct and unveil the atomic details of the chemical reaction. Our results support the interpretation made on the basis of X‐ray and mass spectrometry analyses. Moreover, we show that the formation of the β‐Kdo‐Asp232 adduct is assisted by the sugar Kdo‐carboxylate group, which mediates the transfer of a proton from Asp232 towards the phosphate leaving group, alleviating electrostatic repulsion between the two negatively charged carboxylate groups. The computed mechanism also explains why His265, previously proposed to act as a general acid, does not impair catalysis. This mechanism can be extended to other related enzymes, expanding the repertoire of GT mechanisms in Nature.

Effect of “corona-core” structuring of poly(1-vinyl-1,2,4-triazole)–poly(acrylic acid)-Ag(I) interpolymer complexes on the radiation-induced preparation and stability of silver nanoparticles

Interpolymer complexes (IPC) of water-soluble polymers can be promising matrices for the synthesis of metal colloids. In this work, silver nanoparticles were obtained via radiation-induced reduction (under X-ray irradiation) of complexes based on poly (1-vinyl-1,2,4-triazole) (PVT) and poly (acrylic acid) (PAA) containing Ag+ ions. Particular attention was paid to the role of the supramolecular structure in the formation of nanoparticles. Combined dynamic light scattering and electrophoretic mobility measurements have revealed that, in pH range 5.5–7, micro-scale aggregates of the initial PVT-PAA-Ag(I) IPC transform into nano-sized particles consisting of a PVT-Ag(I) core electrostatically stabilized by PAA loops and tails forming a corona. It was explicitly demonstrated for the first time that such transformation of IPC aggregates can significantly enhance the efficiency of AgNPs formation. In particular, using UV-VIS spectroscopy and transmission electron microscopy, we have shown that at pH 7.0 the core of the “corona-like” form of the PVT-PAA-Ag(I) complex ensures the radiation-induced generation of AgNPs with a narrow size distribution due to the strong affinity of triazole groups to the metal surface. At the same time, the localization of the excessive negatively charged carboxylate groups in the outer part of the complex provides a long-term colloidal stability of the prepared AgNPs.

Characterization of TEMPO-Oxidized Cellulose Nanofiber From Biowaste and Its Influence on Molecular Behavior of Fluorescent Rhodamine B Dye in Aqueous Suspensions

AbstractCellulose nanofiber (CNFs) obtained through TEMPO oxidation was structurally characterized using FT-IR (Fourier Transformed Infrared) and SEM (Scanning Electron Microscopy) spectroscopy. The molecular aggregation and spectroscopic properties of Rhodamine B (Rh-B) in CNFs suspension were investigated using molecular absorption and steady-state fluorescence spectroscopy techniques. The interaction between CNFs particles in the aqueous suspension and the cationic dye compound was examined in comparison to its behavior in deionized water. This interaction led to significant changes in the spectral features of Rh-B, resulting in an increase in the presence of H-dimer and H-aggregate in CNFs suspension. The H-type aggregates of Rh-B in CNFs suspensions were defined by the observation of a blue-shifted absorption band compared to that of the monomer. Even at diluted dye concentrations, the formation of Rh-B’s H-aggregate was observed in CNFs suspension. The pronounced aggregation in suspensions originated from the strong interaction between negatively charged carboxylate ions and the dye. The aggregation behavior was discussed with deconvoluted absorption spectra. Fluorescence spectroscopy studies revealed a significant reduction in the fluorescence intensity of the dye in CNFs suspension due to H-aggregates. Furthermore, the presence of H-aggregates in the suspensions caused a decrease in the quantum yield of Rh-B compared to that in deionized water.

Zwitterion Intercalated Manganese Dioxide Nanosheets as High-Performance Cathode Materials for Aqueous Zinc Ion Batteries.

In this study, a novel approach is introduced to address the challenges associated with structural instability and sluggish reaction kinetics of δ-MnO2 in aqueous zinc ion batteries. By leveraging zwitterionic betaine (Bet) for intercalation, a departure from traditional cation intercalation methods, Bet-intercalated MnO2 (MnO2-Bet) is synthesized. The positively charged quaternary ammonium groups in Bet form strong electrostatic interactions with the negatively charged oxygen atoms in the δ-MnO2 layers, enhancing structural stability and preventing layer collapse. Concurrently, the negatively charged carboxylate groups in Bet facilitate the rapid diffusion of H+/Zn2+ ions through their interactions, thus improving reaction kinetics. The resulting MnO2-Bet cathode demonstrates high specific capacity, excellent rate capability, fast reaction kinetics, and extended cycle life. This dual-function intercalation strategy significantly optimizes the electrochemical performance of δ-MnO2, establishing it as a promising cathode material for advanced aqueous zinc ion batteries.

Unlocking the Fluorine-Free Buoy Effect: Surface-Enriched Ruthenium Polypyridine Complexes in Ionic Liquids.

Controlling the local concentration of metal complexes at the surface of ionic liquids (ILs) is a highly sought-after objective due to its pivotal implications in supported ionic liquid phase (SILP) catalysis. Equally important is to avoid per- and polyfluorinated substances due to environmental concerns. Herein, we investigate the surface enrichment of Ru polypyridyl complexes with fluorine-free alkylic side groups of varying lengths and shapes, using the hydrophilic IL [C2C1Im][OAc] as solvent. Additional charged carboxylate groups are included into the polypyridyl ligands to increase the solubility of the complex in the IL. When the ligand system is functionalized with long and hydrophobic alkyl side chains, the complex predominantly localizes at the IL/vacuum interface, as deduced from angle-resolved X-ray photoelectron spectroscopy. Conversely, in the presence of short or more bulky substituents, no surface enrichment is observed. This buoy-like behaviour with fluorine-free side groups is explored for 0.05 %mol to 1 %mol solutions. Intriguingly, surface saturation occurs at approximately 0.5 %mol, which is beneficial to the efficient operation of catalytic systems featuring high surface areas, such as SILP catalysts.

Structural and tribological studies on the interaction of porcine gastric mucin with non- and cationic-modified β-lactoglobulins

β-lactoglobulin (BLG) is the major whey protein with negative charges at neutral pH in aqueous media. Thus, the interaction with mucins, the major polyanionic component of mucus, is very weak due to the electrostatic repulsion between them. The present study postulates that cationization of BLG molecules may reverse the interaction characteristics between BLG and mucin from repulsive to associative. To this end, cationic-modified BLGs were prepared by grafting positively charged ethylenediamine (EDA) moieties into the negatively charged carboxyl groups on the aspartic and glutamic acid residues and compared with non-modified BLG upon mixing with porcine gastric mucin (PGM). To characterize the structural and conformational features of PGM, non/cationized BLGs, and their mixtures, various spectroscopic approaches, including zeta potential, dynamic light scattering (DLS), and circular dichroism (CD) spectroscopy were employed. Importantly, we have taken surface adsorption with optical waveguide lightmode spectroscopy (OWLS), and tribological properties with pin-on-disk tribometry at the sliding interface as the key approaches to determine the interaction nature between them as mixing PGM with polycations can lead to synergistic lubrication at the nonpolar substrate in neutral aqueous media as a result of an electrostatic association. All the spectroscopic studies and a substantial improvement in lubricity collectively supported a tenacious and associative interaction between PGM and cationized BLGs, but not between PGM and non-modified BLG. This study demonstrates a unique and successful approach to intensify the interaction between BLG and mucins, which is meaningful for a broad range of disciplines, including food science, macromolecular interactions, and biolubrication etc.

Postbiotic characterization of a potential probiotic yeast isolate, and its microencapsulation in alginate beads coated layer-by-layer with chitosan

Considering biosafety concerns and survivability limitations of probiotics (PRO) under different stresses, application of postbiotics and encapsulated PRO has received considerable attentions. Accordingly, the objective of the present study was to investigate the postbiotic capabilities of a potential PRO yeast isolate and the effect of encapsulation with alginate (Alg) and chitosan (Ch) on its survival under SGI conditions. Sequencing results of the PCR products led to the identification of Saccharomyces cerevisiae as the selected potential PRO yeast isolated from wheat germ sourdough. High survival of the isolate under simulated gastrointestinal (SGI) conditions (95.74%), its proper adhesion abilities, as well as its potent inhibitory activity against Listeria monocytogenes (75.84%) and Aspergillus niger (77.35%) were approved. Interestingly, the yeast cell-free supernatant (CFS) showed the highest antioxidant (84.35%) and phytate-degrading (56.19%) activities compared to the viable and heat-dead cells of the isolate. According to the results of the HPLC-based assay, anti-ochratoxin A (OTA) capability of the dead cells was also significantly (P < 0.05) higher than that of the viable cell. Meanwhile, the yeast CFS had no anti-OTA and antimicrobial activities against the foodborne bacteria and fungi tested. Further, microencapsulation of the yeast isolate in Alg beads coated layer-by-layer with Ch (with 77.02% encapsulation efficacy and diameter of 1059 μm based on the field emission scanning electron microscopy analysis) significantly enhanced its survivability under SGI conditions in comparison with the free cells. In addition, electrostatic cross-linking between negatively charged carboxylic groups of Alg and positively charged amino groups of Ch was verified in accordance with Fourier transform infrared and zeta potential data. Human and/or industrial food trials in future are needed for practical applications of these emerging ingredients.

Tuning of ion current rectification and ion current saturation of multiple nanochannels in polymeric membrane

The present study gives an insight into ion flow dynamics of aqueous electrolytes via functionalized multiple nanochannels in polyethylene terephthalate (PET) membrane. The selectivity of certain ions (anions/cations) of various electrolyte combinations KCl- KClO4 (S1), KBr-KCl (S2), KBr-KClO4 (S3) over their counter-ions by the nanochannels (generated via swift heavy ion irradiation followed by chemical etching) has been studied. Tuning of the ion transport and ion current rectification has been done using different functionalized nanochannels (with charged carboxyl and protonated amino groups). The impact of ion selectivity of the nanochannels is reflected in the short circuit current and ion current saturation of different systems. The collection of counter ions outside the channels along with the in-built potential due to the flow of ions inside the channels play a crucial role in the ion transport behaviour of the collective system. The cation-selective channels (with charged carboxyl groups) show low rectification ratio compared to the anion-selective channels. The functionalized nanochannels with two -OH polar charge groups (generated through the amino-silane based reagent (3-aminopropyl) trimethoxysilane (APTMS)) exhibit higher current saturation values (S1AP∼31 μA, S2AP∼30 μA and S3AP ∼ 30.5 μA) and higher short circuit current values (S1AP ∼32.3μA, S2AP ∼ 29.6μA and S3AP ∼31.3μA) due to the overlapping of electric double layer (EDL). Systematic study of tuning of ion transport through nanochannels helps to understand the nanofluidic flow and has imminent application in the fabrication of nanoelectronic and bioinspired nanodevices.