Gelation Activity Research Articles

Click synthesis and self-assembly of novel dendritic ethylene glycol/alkyl-substituted diarylated triazoles into supramolecular nanofibers

Copper-catalyzed 1, 3-dipolar cycloaddition reaction between azides and alkynes under mild conditions has been known to exhibit high selectivity and good yields of 1, 2, 3-triazole. Additionally, 1, 2, 3-triazoles are used in various medical and pharmaceutical applications. Herein, we present novel low molecular weight organogelators from fluorescent ethylene glycol/alkyl-substituted 2, 6-diarylated pyridine 1, 2, 3-triazoles. Compact supramolecular architectures were created by the self-assembly of the synthesized gelators. The gel formation activity of the prepared ethylene glycol/alkyl-substituted 2, 6-diarylated pyridine triazoles were presented. The synthesis process was achieved by copper-catalyzed alkyne-azide cycloaddition (CuAAC) of ethylene glycol/alkyl-functionalized aromatic azide with aromatic alkyne bearing alkyl ester tails of various lengths. The ethylene glycol/alkyl-functionalized diaryl triazoles were investigated by 1H/13C NMR and FTIR spectroscopic methods. Triazoles with long ethylene glycol and/or alkyl ester tails showed an enhanced gelation activity as compared to those with shorter ethylene glycol and/or alkyl ester tails. The morphological features of the self-assembled ethylene glycol/alkyl-substituted arylated triazoles were studied by scanning electron microscopy (SEM), demonstrating supramolecular nanofibrous assemblies. Those supramolecular assemblies were forced by van der Waals and π-stacks interactions. Both antibacterial activity and cytotoxicity of the synthesized arylated triazole gelators were studied.

Synthesis and Self-assembly of Novel Nanofeather-like Fluorescent Alkyloxy-Containing Diphenyl Ether Organogelators.

In this study, novel fluorescent low molecular-weight organogelators are derived from diphenyl ethers and substituted with para-alkoxy groups of different aliphatic chain lengths. The present research promotes the preparation of innovative nanofeather-like assemblies from the synthesized diphenyl ether-derived organogelators. The gelation performance of the prepared alkoxy-substituted diphenyl ethers was reported. The synthesis procedure was achieved by using a base-catalyzed reaction of hydroxyl-substituted diphenyl with various alcohols of different aliphatic chain lengths. The chemical structures of the synthesized diphenyl ether derivatives were studied by 1H/13C NMR and infrared spectroscopy. Fluorescence and UV–vis absorption spectral analyses showed solvatochromism. The diphenyl ether derivatives with longer alkoxy terminal substituents showed enhanced thermoreversible gelation activity as compared to the diphenyl ether derivatives with shorter alkoxy terminal substituents. The morphological properties of the self-assembled diphenyl ethers were studied by transmission electron microscopy and scanning electron microscopy, which showed supramolecular architectures of highly ordered nanofeathers, enforced by van der Waals interactions and π-stacks. Depending on the length of the aliphatic tail, different morphologies were detected, including nanofeathers, nanofibers, and nanosheets. The antimicrobial and cytotoxic properties of the prepared diphenyl ether-derived organogelators were examined to confirm their possible use in various fields like drug delivery systems.

The dual effects of non-solvent on the sol-gel transition of polyacrylonitrile solution: The promotion in thermodynamics and hindrance in kinetics

The effects of non-solvent on the sol-gel transition of polyacrylonitrile (PAN) solution were investigated in thermodynamics and kinetics by the means of rheology method. The facilitating effects of non-solvent in thermodynamics was illustrated by the variety of viscoelasticity and gel transition temperature (Tgel). With the addition of non-solvent, the mobility of PAN molecular chains are limited due to its increased entanglement. As a result, the PAN solution with higher non-solvent content has lower conformation entropy to satisfy the occurrence of sol-gel transition at higher temperature. It means that less thermodynamic driving is demanded. The kinetical characteristics of PAN solution with different non-solvent content in sol-gel transition process were also discussed. The kinetic hindrance of non-solvent was proved by the gradually stronger time-dependence of loss tangent with the addition of non-solvent during sol-gel transition. This apparent extending of relaxation time is resulted from the more restriction of the mobility of PAN molecules. The gelation activation energy (Egel) was calculated according to Ozawa method. The results also indicated that the activity of PAN molecules in this transition became weaken with the addition of non-solvent since a relative tight connection between PAN molecules was there. Therefore, the formation of physical junction points for sol-gel transition was hindered due to the decreasing of the mobility of self-adjustment for PAN molecules. This is the fundamental reason for the kinetic hindrance role of non-solvent.

Synthesis and self-assembly of novel pH triggered smart organogelators from novel alkyl-substituted chalcone-based hydrazonotriazole derivatives

Chalcones have been known as a significant group of compounds used for treatment of parasitic infections, cardiovascular diseases, viral disorders, gastritis, pain, and stomach cancer. Additionally, they have been employed in cosmetic formulation ingredients and food additives. In the current study, a series of new 4-(1-(2-(2,4-dinitrophenyl)hydrazineylidene)ethyl)-5-methyl-1-aryl-1H-1, 2, 3-triazole derivatives with different terminal alkyl chains were synthesized to function as pH-induced and thermally reversible low molecular weight gelators (LMWG). The novel hydrazonotriazole derivatives were synthesized by a simple reaction of (2,4-dinitrophenyl)hydrazine with various derivatives of 1-(5-methyl-1-(4- alkoxyphenyl)-1H-1, 2, 3-triazol-4-yl)ethan-1-ones in absolute ethanol using hydrochloric acid as a catalyst. Elemental analysis, FTIR, and NMR spectroscopic techniques were used to prove the molecular structures of the synthesized chalcone-based gelators. The photophysical properties of the synthesized gelators were described. The chalcone-based gelators were found to efficiently gelate various organic solvents with reversible responsiveness ability to pH stimulus, demonstrating a sol–gel switching process in association with a colorimetric shift from yellow to purple. The optimum gelation activity was observed for the nonyloxy-substituted chalcone-based organogelator in various solvents with critical gel concentration (CGC) in the range of 2.05–9.28 mM, and thermal stability up to 46 °C. Various analytical techniques were utilized to examine the morphologies of xerogels, displaying nanofibrous assemblies (10–30 nm). Both cytotoxicity and antibacterial activities of the synthesized alkyl-substituted chalcone-based gelators were explored.

Study on Properties and Optimization of Ternary Auxiliary Cementing Materials for IOTs.

In order to control energy consumption and reduce pollution, the use of supplementary cementitious materials (SCMs) instead of cement to produce green cementitious materials can save energy, reduce emissions and achieve sustainable development. This study demonstrates the possibility of developing SCMs with iron tailings (IOTs), fly ash (FA) and ceramic powder (CP) ternary system, as well as the optimization and improvement scheme of gelation activation. The effects of activator dosage, mix ratio and substitution rate on mechanical properties of ternary SCMs system were investigated. The formation and evolution of hydration products were analyzed by differential thermogravimetric analysis (DTA) and scanning electron microscopy (SEM). The results of the study show that there is synergy in the system. The results show that there is synergy in the system and the hydration reaction is sufficient. At the substitution rate of 30%, the doping ratio of IOTs, CP and FA is 1:2:2 and the Ca(OH)2 is 0.6%, the strength reaches 39.9 MPa and the activity index is 91.5%, which can provide a basis for the application and more in-depth study of IOTs multi SCMs.

Stability improvement of emulsion gel fabricated by Artemisia sphaerocephala Krasch. polysaccharide fractions.

Artemisia sphaerocephala Krasch. polysaccharide (ASKP) contained two fractions of 60P and 60S with different molecular weight. It was found the potential performance of interface adsorption and gelation activities for the high molecular weight of 60P in comparison with low molecular weight of 60S. The emulsion stability and droplets filling in gel network was highly dependent on the medium chain triglyceride (MCT) concentrations. The emulsion gels fabricated through a complexation of 60P and gelatin or collagen peptides exhibited significantly improved emulsifying activity and gel strength at higher concentration of MCT. Gelatin or collagen peptide could be adsorbed on the droplets interface and interact with 60P in gel matrix, thus presenting an active filling. However, 60P based emulsion gel complexed with pullulan contributed to a lower strength than hydrogel, which was probably due to the existence of spaces between droplets and gel matrix, weakening the stability of gel network, considered as an inactive filling.

Study on Pretreatment of Phosphogypsum and Preparation of Non Burning Building Materials

Phosphogypsum has poor cementitious activity, which hinders its large consumption in the field of building materials. By studying the phase and microstructure of phosphogypsum pretreated by alkali activation, and the compressive strength, and microstructure of the non-sintering building materials prepared with the high content phosphogypsum, the process parameters of preparing high content and high compressive strength non-burning building materials with phosphogypsum were obtained. The result showed that, when 100 g phosphogypsum was added with 200 mL activator, after 24 hours of excitation under room temperature, the main crystalline phase CaSO4·2H2O of phosphogypsum have smaller grains and lower crystallinity. Microstructure analysis showed that the particles of tabular phosphogypsum were powdered, and the original plate-like crystal form became smaller plates. Thus, its gelation activity was improved. When the content of phosphogypsum was 80%, the compressive strength of non-burning building materials after maintenance for 7 days, 28 days and after immersion in water for 24h were 15.13 MPa, 16.4 MPa and 11.8 MPa, respectively. The micro morphology showed that the particle size gradient was appropriate and the density was very high, which was very beneficial to improve the strength of the material.

Preparation and microstructural characterization of a novel 3D printable building material composed of copper tailings and iron tailings

This paper proposes an environmentally friendly 3D printable building material composed of copper tailings and iron tailings that matches well with an extrusion-based printing process. The experimental results show that copper tailings and iron tailings have the best compounding effect on mechanical properties at a mass ratio of 1:4. The microstructure and gelation activities of 3D printable building material were characterized by XRD, FTIR and SEM techniques. The research results show that the hydration products of 3D printable building material composed of copper tailings and iron tailings are mainly ettringite and C-S-H gel, which contribute for the development of strength. It is found that the ettringite, C-S-H gels, and cemented crystals are closely connected to form a three-dimensional structure, which makes the matrix more compact, and importantly enhances the mechanical properties of 3D printable building material. Furthermore, the leaching toxicity and radioactivity of 3D printable building material were tested, and the results show that the 3D printable building material composed of copper tailings and iron tailings is environmentally friendly.

Potential of recovered proteins from invasive green crabs (Carcinus maenas) as a functional food ingredient

Invasive green crabs contain high-quality proteins that have potential as functional ingredients in formulated foods. This study evaluated the functional properties and compositional characteristics of green crab proteins recovered by isoelectric solubilization/precipitation (ISP). Mechanically separated green crab mince (control) was solubilized at pH 2 (PP2) and pH 10 (PP10), then proteins were precipitated at pH 5.5 and subsequently dried. Yield of recovered protein powder was approximately 1.5 times higher for PP2 than for PP10. Compared with the control (230 g kg-1 ), ash content was reduced in PP2 (54 g kg-1 ) and PP10 (23 g kg-1 ) samples. PP2 contained predominantly large-molecular-weight proteins, while small-molecular-weight proteins were distributed in PP10. With regard to functional properties, at pH 7 and 8, solubility of PP10 was significantly higher than that of PP2. At pH 7.5, PP10 exhibited significantly higher emulsifying activity (1482 m2 g-1 ) than PP2 (858 m2 g-1 ) and the control (958 m2 g-1 ). PP2 showed statistically higher gelation activity and had higher L* value than PP10 and the control. The results indicate that recovered green crab proteins have functional properties potentially useful for formulated foods, and that these functional properties can be modified by the solubilization pH during the recovery process. © 2018 Society of Chemical Industry.

Alkynyl-functionalized benzoxazine containing phthalide side group: Synthesis, characterization and curing mechanism

Alkynyl-functionalized benzoxazine (A-BZ) resin containing phthalide side group with excellent heat resistance has been successfully synthesized with phenolphthalein, meta-aminophenylacetylene and formaldehyde solution as starting materials. Its chemical structure was characterized and analyzed by Fourier transform infrared (FT-IR) spectroscopy and hydrogen nuclear magnetic resonance (1H-NMR) spectroscopy. A-BZ can easily dissolve in the common organic solvents including ethanol, acetone et al. The gelation time under different temperature of A-BZ resin was measured by dynamic mechanical analysis (DMA) according to the intersection time of the isothermal curves of the storage modulus and loss modulus. The gelation activation energy was determined by Arrhenius formula (Ea = 48.51 kJ/mol). The optimal curing procedure was established by combing non-isothermal differential scanning calorimetry (DSC) and isothermal DMA. The curing mechanism was analyzed in in-situ FT-IR method by monitoring the change of characteristic peaks under different temperature. The reaction temperatures of ring-opening reaction of benzoxazine (170 °C) and trimerization cyclization of alkynyl groups (170–200 °C) were determined. The glass transition temperature (Tg) of A-BZ cured product tested by DMA equals to 382 °C, which is much larger than those of counterparts (251–259 °C).

Techno-Functional Properties of Crude Extracts from the Green Microalga Tetraselmis suecica.

A mild fractionation process to extract functional biomolecules from green microalgae was implemented. The process includes bead milling, centrifugation, and filtration with several membrane cut-offs. For each fraction, the corresponding composition was measured, and the surface activity and gelation behavior were determined. A maximum protein yield of 12% was obtained in the supernatant after bead milling and between 3.2 and 11.7% after filtration. Compared to whey protein isolate, most of the algae fractions exhibited comparable or enhanced functionality. Surface activity for air–water and oil–water interfaces and gelation activities were notably superior for the retentate fractions compared to the permeates. It is proposed that such functionality in the retentates is due to the presence of hydrophobic compounds and molecular complexes exhibiting a similar behavior as Pickering particles. We demonstrated that excellent functionality can be obtained with crude fractions, requiring minimum processing and, thus, constituting an interesting option for commercial applications.

Performance of fly ash based polymer gels for water reduction in enhanced oil recovery: Gelation kinetics and dynamic rheological studies

The complexity of well and reservoir conditions demands frequent redesigning of water plugging polymer gels during enhanced oil recovery (EOR). In the present study, we developed coal fly ash (CFA) based gels from polyacrylamide (PAM) polymer and polyethyleneimine (PEI) crosslinker for water control in mature oil fields. The CFA acts as an inorganic additive to fine-tune gelation performance and rheological properties of PAM/PEI gel system. Hence, effects of various CFA (0.5 to 2 wt%), PAM (2 to 8.47 wt%) and PEI (0.3 to 1.04 wt%) concentrations on gelation kinetics and dynamic rheology of pure PAM/PEI gel and PAM/PEI-CFA composite gels were studied at a representative reservoir temperature of 90 oC. Experimental results reveal that gelation time of pure PAM/PEI gel increases with increasing CFA addition. Further observation demonstrates that increasing PAM and PEI concentrations decreases the gelation times of PAM/PEI-CFA composite gels. Gelation time was found to be within 3-120 hours. Understanding the property of reaction order enables better prediction of gelation time. Dynamic rheological data show that viscoelastic moduli (G′ and G″) of various PAM/PEI-CFA composite gels improved better as compared to the pure PAM/PEI gel across the strain-sweep and frequency-sweep tests. SEM analysis of selected samples at 72 hours and 720 hours of gelation activity consolidated gelation kinetics and dynamic rheological results. These polymer gels are excellent candidates for sealing water thief zones in oil and gas reservoirs.

Lipopolysaccharide of Marinobacter litoralis inhibits swarming motility and biofilm formation in Pseudomonas aeruginosa PA01

The lipopolysaccharide (LPS) was isolated from a marine bacterium identified as Marinobacter litoralis BK09 using 16S rRNA gene sequence similarity analysis. The GCMS analysis showed that the LPS contained 3-hydroxy-dodecanoic acid (C12:0 3OH) (49%), dodecanoic acid (C12:0) (24%) and decanoic acid (C10:0) (19%) as major fatty acids, and the polysaccharide constituents were fucose (53.79%), xylose (28.04%) and mannose (18.15%). The LPS almost completely inhibited swarming motility in Pseudomonas aeruginosa PA01. It also reduced biofilm formation by 50% with no adverse effect on cell growth. The production of virulence factor such as pyocyanin pigment was reduced (∼40%) by the LPS. The LPS did not show any limulus amoebocyte lysate (LAL) gelation activity. The repression of swarming motility, pyocyanin production and biofilm formation by the LPS suggests its potential application against P. aeruginosa infection. This is the first report on characterization and application of LPS from M. litoralis.

140 The importance of hydrophobic moieties in ice recrystallization inhibitors

Ice recrystallization during thawing after cryopreservation results in extensive cellular damage that ultimately leads to cell death and decreased cell viabilities. This is a significant problem particularly with cryopreserved cells utilized in various regenerative medicine therapies. Given the success of these therapies to treat spinal cord injury, cartilage lesions, and cardiac disease, the development of new and improved cryprotectants that minimize cell damage during freeze-thawing and improve cell viability post-cryopreservation are urgently required. Our laboratory has demonstrated that carbohydrate-based hydrogelators can be potent inhibitors of ice recrystallization. While our studies have indicated that a delicate balance between hydrophobic and hydrophilic interactions is crucial for ice recrystallization inhibition (IRI) activity, the essential structural features necessary for potent IRI activity remain unknown. To address this issue, we synthesized and assessed the IRI activity of structurally diverse amino acid-based surfactants/gelators and anti-ice nucleating using a splat-cooling assay. The results indicate that long alkyl chains and increased hydrophobicity are important for potent IRI activity and that the position of these alkyl chains is essential. Additionally, no correlation was found between IRI activity and critical micelle concentrations, gelation or anti-ice nucleation activity although the counterion of some surfactants did affect IRI activity. The results of our study will facilitate the design of improved ice recrystallization inhibitors for medical, commercial and industrial applications. Source of funding: None declared. Conflict of interest: None declared. abalcerzak@uottawa.ca

Colloidal and chemical aspects of nanosized hydrated zirconium dioxide synthesized via a sol–gel process

The processes of coagulation and gelation of sols in zirconium oxychloride aqueous solutions and the properties of hydrated zirconium dioxide sols (pH, particles size, dynamic viscosity) depending on the aging conditions of partially neutralized zirconium oxychloride feedstock solution–zirconyl hydroxychloride used for the synthesis and molar ratio of initial reagents (Zr/NaOH, Zr/CH 3COO −) were first studied in the paper. The concentration and temperature limits of hydrated zirconium dioxide sols stability were determined. The coagulation constant, gelation activation energy, and gelation thermal effect values were found.

Structure of Compositionally Simple Lipopolysaccharide from Marine Synechococcus

Lipopolysaccharide (LPS) is the first defense against changing environmental factors for many bacteria. Here, we report the first structure of the LPS from cyanobacteria based on two strains of marine Synechococcus, WH8102 and CC9311. While enteric LPS contains some of the most complex carbohydrate residues in nature, the full-length versions of these cyanobacterial LPSs have neither heptose nor 3-deoxy-D-manno-octulosonic acid (Kdo) but instead 4-linked glucose as their main saccharide component, with low levels of glucosamine and galacturonic acid also present. Matrix-assisted laser desorption ionization mass spectrometry of the intact minimal core LPS reveals triacylated and tetraacylated structures having a heterogeneous mix of both hydroxylated and nonhydroxylated fatty acids connected to the diglucosamine backbone and a predominantly glucose outer core-like region for both strains. WH8102 incorporated rhamnose in this region as well, contributing to differences in sugar composition and possibly nutritional differences between the strains. In contrast to enteric lipid A, which can be liberated from LPS by mild acid hydrolysis, lipid A from these organisms could be produced by only two novel procedures: triethylamine-assisted periodate oxidation and acetolysis. The lipid A contains odd-chain hydroxylated fatty acids, lacks phosphate, and contains a single galacturonic acid. The LPS lacks any limulus amoebocyte lysate gelation activity. The highly simplified nature of LPSs from these organisms leads us to believe that they may represent either a primordial structure or an adaptation to the relatively higher salt and potentially growth-limiting phosphate levels in marine environments.

Mechanism of Filamin A (FLNa) actin filament (F‐actin) crosslinking

FLNa is a scaffold with multiple binding partners and, by promoting orthogonal F-actin branching, is a potent F-actin gelation factor. Subunits composing this elongated homodimeric molecule have N-terminal F-actin-binding domains (ABDs) connected to 24 Ig-like repeats that dimerize at C-terminal repeat 24. We report that deletion of ABDs abolishes F-actin gelation activity, explaining how calcium-calmodulin, acting through this domain, dissociates FLNa from F-actin. FLNa repeats 1 to 15 enhance the affinity of FLNa subunits for F-actin 25-fold; adding repeats 16–23, where most FLNa binding partners interact, barely increases affinity. Dimerization, however, increases the avidity by 1000-fold. Electron- and videomicroscopy reveal that FLNa subunits bind F-actin laterally and interact perpendicularly at their C-termini. These findings ascribe firm F-actin tethering to the ABDs, repeats 1–15 and bivalency. Weak F-actin binding by repeats 16–23 accommodates crosslink flexibility that confers unique rheological properties to FLNa-F-actin gels and permits partner interactions. The self-association domains account for perpendicular F-actin branching.

Isolation and characterisation of the lipopolysaccharide from Acidiphilium strain GS18h/ATCC55963, a soil isolate of Indian copper mine

The lipopolysaccharide (LPS) of the Gram-negative Acidiphilium strain GS18h/ATCC55963, a new soil isolate, exhibited very low endotoxic activity as determined by Limulus gelation activity, lethal toxicity in galactosamine (GalN) sensitised mice, and level of tumor necrosis factor alpha (TNFα) in the blood serum of BALB/c mice. Analysis of the LPS, specially of lipid A which usually accounts for the toxicity, revealed the latter to contain glucosamine and phosphate besides fatty acids, of which 14:0(3-OH), 18:0(3-OH), 18:1 and 19:0(cyclo) are the major components, while 12:0, 16:0, 19:1, 20:0(3-OH) and 20:1(3-OH) are present in small amounts. The 14:0(3-OH) and 18:0(3-OH) fatty acids are amide-linked, whereas the rest are ester bound. Glucose, galactose, mannose, rhamnose, heptose, galacturonic acid and 3-deoxy- d- manno-oct-2-ulosonic acid (Kdo) were present in the polysaccharide part of this LPS. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE) of the LPS showed a macromolecular heterogeneity distinctly different from those of Escherichia coli or Salmonella. The toxicity of this LPS being extremely low attributed to fatty acid composition of its lipid A, promises potential therapeutic application.

Requirement of protein phosphatase 2A for recruitment of IQGAP1 to Rac‐bound β1 integrin

Serine/threonine protein phosphatase (PP) 2A is thought to dephosphorylate phosphorylated beta1 integrin to link with actin filaments (F-actin). However, whether PP2A participates in the regulation of F-actin assembly to which beta1 integrin is anchored is unclear. We report here that the core enzyme of PP2A (PP2A-AC), consisting of the regulatory subunit A (PP2A-A) and the catalytic subunit C (PP2A-C), forms a complex with beta1 integrin, a small GTPase Rac, and its effector IQGAP1 in non-malignant human mammary epithelial (HME) cells. Treatment of HME cells with okadaic acid (OA), an inhibitor of PP2A, caused cell rounding, reduction in F-actin assembly that links with beta1 integrin, and dissociation of IQGAP1-bound PP2A-AC from Rac-beta1 integrin. The dissociation of IQGAP1-PP2A-AC was accompanied by loss of F-actin gelating activity of Rac-beta1 integrin. In breast cancer MCF-7 cells, which possess PP2A-C but lack PP2A-A, IQGAP1 was not associated with Rac-beta1 integrin but with PP2A-C, with no distinct F-actin assembly that linked to Rac-beta1 integrin even before treatment with OA. We therefore propose that PP2A, especially PP2A-A, functions to maintain F-actin assembly to which beta1 integrin is anchored by recruitment of IQGAP1 to Rac-beta1 integrin.

Fast transient fluorescence technique for studying sol–gel phase transition in polymeric mixtures

Fast transient fluorescence (FTRF) technique was used to study the sol–gel phase transition in free-radical crosslinking copolymerization of methyl methacrylate (MMA), ethyl methacrylate (EMA) and their mixtures with ethylene glycol dimethacrylate (EGDM). Fluorescence lifetimes of pyrene (Py) from its decay traces were monitored during sol–gel phase transitions. Consumption of MMA and/or EMA in pregel solutions due to gel formation dramatically increased the Py fluorescence lifetimes, in which were used to study the gelation of MMA, EMA and their mixtures as a function of time, at various temperatures and monomer concentrations. Monomer consumption rates, k r were measured during sol–gel transition process by using Stern–Volmer model. Gelation activation energies Δ E G were determined and found to be 14 and 10 kcal mol −1 for MMA and EMA respectively.