High Anionic Charge Research Articles

Effect of PCE anionic charge density on fly ash cementitious system-PCE compatibility

In this study, the compatibility of polycarboxylate-based water-reducing admixtures (PCEs) with cementitious systems containing fly ash (FA) was investigated. For this purpose, PCEs with carboxylate, phosphate, and sulfonate anionic groups having different anionic charge densities were synthesized. The effects of PCEs on fresh properties and compressive strength of cementitious systems containing FA were investigated. The PCE with 9% phosphate substitution and high anionic charge density was found to be the most effective, requiring the least amount for the target flow. Similarly, in terms of the PCE requirement for the minimum Marsh funnel flow time and rheological parameters, the best performance was obtained with 5% sulfonate substituted PCE having high anionic charge density. While FA had a positive effect on the PCE requirement and consistency retention of the mixtures; it had a negative effect on Marsh funnel flow time, rheological properties, and compressive strength. However, the rheological properties of the mortar mixtures were not adversely affected by the FA substitution as much as that of the paste mixtures. Regarding the 28-day compressive strength of mortar mixtures, the optimum FA substitution ratio was 15%. Fly ash substitution above this level reduced the compressive strength at all ages including 28-day strength. Anionic charge density variation of PCE had no significant influence on the compressive strength of the mortars.

Tuning the surface charge of rice straw-derived cellulose nanofibril membrane separator for electrochemical performance enhancement of supercapacitors

The electrochemical performance of supercapacitors has often overlooked the effect of surface charge on cellulose-based separators. Cellulose nanofibrils (CNFs) produced by 2,2,6,6-tetramethylpipridine-1-oxyl (TEMPO) oxidation possess a high anionic surface charge due to the presence of carboxylate groups, which could affect the transport of electrolyte ions. In this work, the surface of CNFs is modified with a cationic polyelectrolyte, namely polydiallydimethylammonium chloride (PDADMAC), to yield a nearly-zero surface charge CNF membrane derived from rice straw. The surface modification of CNFs using 20 wt% PDADMAC results in CNF-M2, with a surface charge of +5.3 mV, notable porosity (64 %), excellent electrolyte uptake (225 %), and improved ionic conductivity (5.0 mS cm−1). A symmetric supercapacitor assembled with CNF-M2 as a separator, exhibits enhanced specific capacitance (185.3 F g−1 at 0.1 A g−1), energy density (37.1 Wh kg−1 at a power density of 0.24 kW kg−1), and is able to maintain 100 % capacitance retention over 10,000 cycles in 1.0 M Na2SO4 aqueous electrolyte solution. This surface modification leads to 1.2–1.4 times increase in energy and power densities compared to the unmodified CNF membrane. Thus, the nearly-zero surface charge of the modified CNF membrane holds promise as a separator that elevates the performance of supercapacitors.

Improving the Mechanical Strength of Paper Sheets Made from Phosphorylated Fibers Through the Use of Forming Agents

ABSTRACT The fabrication of paper or cardboards sheets with phosphorylated pulp fibers has proven to be a difficult task using traditional papermaking techniques. This problem is mainly attributed to the very high anionic charge of phosphorylated fibers. In the present work, we propose the use of cationic polymers as a neutralizing agent to attenuate the detrimental effect of the very high anionic charge of phosphorylated fibers and to promote the formation of microflocs that can be agglomerated into a uniform sheet with sufficient strength. The results obtained show that using positively charged retention agents significantly improves the sheet formation. The Kaptra formation index (KFI) was reduced from 133 to 17, which is a very good value when compared to unmodified kraft pulp fibers, which have a formation index of 35. The addition of cationic polymeric additives during the preparation of phosphorylated fiber sheets resulted in an improvement of mechanical properties over unmodified kraft pulp fibers, especially for tensile energy absorption and elongation. This study demonstrates that the use of cationic retention agents reduces the impact of the charge of the phosphorylated fibers on the overall sheet quality.

Preparation of nanodelivery systems for oral administration of low molecular weight heparin

Low molecular weight heparins (LMWHs) are only used parenterally. They have low oral absorption and bioavailability due to their high anionic charge density, exposure to enzymatic degradation and first-pass effect. The aim of this study was the development and evaluation of nanodelivery systems to increase the oral bioavailability of enoxaparin (low molecular weight heparin). In line with this goal, three nanosystems, such as three-layered nanofiber membrane (NF), enoxaparin loaded nanoparticles (NP) and three-layered nanofiber membrane loaded with enoxaparin nanoparticles (NP/NF) were prepared. As a result of the SEM images of nanofiber membranes, the surfaces of the fibers were found to be smooth and the fiber diameters were between 300 and 500 nm. Enoxaparin amount was found to be 390–400 μg/cm2 for nanofiber membranes. Porosity, specific surface area, contact angle, and work of mucoadhesion values were found to be 53.78%, 9.46 m2/g, 113.39°, 0.19 mJ/cm2 for NF formulation and 50.52%, 3.04 m2/g, 104.96°, 2.65 mJ/cm2 for NP/NF formulation, respectively. In vitro dissolution studies showed that less than 20% of the drug was released from the nanofibers at the end of 2 h in acidic pH. MTT studies showed that cell viability was more than 80%. Stability studies showed that there was no significant changes at three different storage conditions. In conclusion, nanodelivery systems were successfully prepared to increase the oral bioavailability of enoxaparin and to protect it from the acid pH of the stomach.

Use of Multi-Anionic Sodium Tripolyphosphate to Enhance Dispersion of Concentrated Kaolin Slurries in Seawater

This research aims to analyze the impact of sodium tripolyphosphate (STPP) as a rheological modifier of concentrated kaolin slurries in seawater at pH 8, which is characteristic of copper sulfide processing operations. The dispersion phenomenon was analyzed through chord length measurements using the focused beam reflectance measurement (FBRM) technique, complementing size distributions in unweighted and square-weighted modes. The reduction of the rheological properties was significant, decreasing from 231 Pa in a reagent-free environment to 80 Pa after the application of STPP. A frequency sweep in a linear viscoelastic regime indicated that by applying a characteristic dosage of 0.53 kg/t of STPP, the pulp before yielding increases its phase angle, which increases its liquid-like character. Measurements of the chord length verified the dispersion of particles, which showed an apparent increase in the proportion of fine particles and a reduction of the coarser aggregates when STPP was applied. Measurements of the zeta potential suggested that the high anionic charge of the reagent (pentavalent) increases the electrostatic repulsions between particles, overcoming the effect of cations in seawater. The results are relevant for the mining industry, especially when the deposits have high contents of complex gangues, such as clays, that increase the rheological properties. This increases the energy costs and water consumption needed for pumping the tailings from thickeners to the tailing storages facilities. The strategies that allow for the improvement of the fluidity and deformation of the tailings generate slack in order to maximize water recovery in the thickening stages.

Hydrothermal synthesis of zeolites from green container glass

Landfilling and stockpiling unrecycled colored container glass represents a considerable failure in sustainability with respect to the conservation of energy and mineral resources. In this study, the single-step hydrothermal synthesis of low-silica zeolites from a mixture of waste green container glass and aluminum foil (Al:Si = 1) in 4 M NaOH(aq) at 125 °C was followed at 1, 3, 7 and 14 days. The principal phases, sodalite and cancrinite, appeared within 1 day accompanied by minor quantities of hydrogarnet and tobermorite arising from a stoichiometric excess of calcium ions in the parent glass. Products of 63, 67, 71 and 72% crystallinity were obtained at 1, 3, 7 and 14 days, respectively, with partial successive conversion of sodalite to cancrinite over time. Ion-exchange and catalytic applications of sodalite and cancrinite arise from the high anionic charge of the 1:1 ratio of alternating SiO44- and AlO45- units within their aluminosilicate frameworks. In this respect, the uptake capacity of the 14-day zeolitic product for Cu2+ and Cd2+ ions (1.58 meq g-1 and 1.66 meq g-1, respectively) was within the expected range for zeolites and compared favorably with those reported for other inorganic sorbents derived from industrial and municipal wastes. The 14-day product was also found to be an effective basic heterogeneous catalyst for the Knoevenagel condensation reaction.

Generation of Multiply Charged Protein Anions from Multiply Charged Protein Cations via Gas-Phase Ion/Ion Reactions.

We report a novel charge inversion ion/ion reaction that converts multiply charged protein cations to multiply charged protein anions via a single ion/ion collision using highly charged anions derived from nanoelectrospray ionization (nESI) of hyaluronic acids (HAs). This type of charge inversion reaction is demonstrated with cations derived from cytochrome c, apo-myoglobin, and carbonic anhydrase (CA) cations. For example, the reaction has been demonstrated to convert the [CA+22H]22+ carbonic anhydrase cation to a distribution of anions as high in absolute charge as [CA-19H]19-. Ion/ion reactions involving multiply charged ions of opposite polarity have previously been observed to result predominantly in the attachment of the reactant ions. All mechanisms for ion/ion charge inversion involving low energy ions proceed via the formation of a long-lived complex. Factors that underlie the charge inversion of protein cations to high anionic charge states in reaction with HA anions are hypothesized to include: (i) the relatively high charge densities of the HA anions that facilitate the extraction of multiple protons from the protein leading to multiply charged protein anions, (ii) the relatively high sum of absolute charges of the reactants that leads to high initial energies in the ion/ion complex, and (iii) the relatively high charge of the ion/ion complex following the multiple proton transfers that tends to destabilize the complex.

Influence of the polymer structure of polycarboxylate-based superplasticizers on the intercalation behaviour in montmorillonite clays

The influence of polymeric structure of polycarboxylate-ether (PCE) based superplasticizers on the intercalation behavior in sodium montmorillonite clay (Na-MNT) is investigated by performing in-situ X-ray diffraction (XRPD) on fresh, unaltered clay pastes. The use of this technique reveals the real influence of the PCE structure and of the PCE/clay dosage ratio on the expansion profile of the clay. This is not observed with the traditional XRPD methodology performed on dried clay pastes, which shows the same values of d-spacing despite using polymers of diverse structures. It is observed that PCE polymers with long side chains and high side chain density result in larger expansion. Additionally, polymers with a high anionic charge saturate the interlaminar space of montmorillonite at a lower dosage. The experimental results also indicate that clay exfoliation is critical in the intercalation process and the exfoliation tendency of the clay is influenced by the structure of PCE polymers.

Supramolecular caging for cytosolic delivery of anionic probes.

The cytosolic delivery of hydrophilic, anionic molecular probes and therapeutics is a major challenge in chemical biology and medicine. Herein, we describe the design and synthesis of peptide-cage hybrids that allow an efficient supramolecular binding, cell membrane translocation and cytosolic delivery of a number of anionic dyes, including pyranine, carboxyfluorescein and several sulfonate-containing Alexa dyes. This supramolecular caging strategy is successful in different cell lines, and the dynamic carrier mechanism has been validated by U-tube experiments. The high efficiency of the reported approach allowed intracellular pH tracking by exploiting the ratiometric excitation of the pyranine fluorescent probe.

In situ formation of SERS hot spots by a bis-quaternized perylene dye: a simple strategy for highly sensitive detection of heparin over a wide concentration range.

A simple and ultrasensitive surface-enhanced Raman scattering (SERS) assay for heparin detection has been demonstrated based on an in situ hot spot assembly method using N,N'-bis[3,3'-(trimethylammonium)propylamine]-3,4,9,10-perylenediimide (bis-quaternized perylene dye, abbreviated as BQPER). In this assay, a BQPER probe with two positive charges is employed as both Raman reporter and electrostatic bridge to cause the aggregation of citrate-capped Ag nanoparticles (Ag NPs), resulting in a strong SERS signal due to the formation of numerous hot spots in the gaps of the aggregates. The SERS intensity of BQPER decreases in the presence of heparin, because BQPER binds primarily to heparin due to its high anionic charge to mass ratio compared to that of Ag NPs. Accordingly, a novel method for the detection of heparin has been developed based on SERS of the unbound BQPER probe. Two obvious advantages of the proposed heparin assay over other reported methods are: its much wider linear concentration range (10-5-10-10 g mL-1) and lower limit of detection (0.08 ng mL-1). Besides, our proposed heparin assay has been successfully applied to the detection of heparin in serum samples, indicating its great potential in the diagnosis of heparin-related diseases. This work provides a new Raman probe for the SERS analysis of heparin and opens a different perspective for SERS-based transducer design in charged analytes.

Conducting Organic Polymer Electrodes with Embedded Polyoxometalate Catalysts for Water Splitting

AbstractPolyoxometalates (POMs) from earth‐abundant metals are promising electrocatalysts to promote the oxygen evolution reaction in a green process to obtain hydrogen from water and a renewable energy source. Taking advantage of their high anionic charge, we have incorporated a cobalt‐based POM as dopant into an organic conducting polymer matrix (polypyrrole). This heterostructure combines the catalytic water oxidation features from the POM, together with the unique processability of polypyrrole. We have optimized the electrocatalytic performance by studying the effect of several parameters, such as the POM content, film thickness, counter anions, and so forth. It is remarkable that less than 6 % POM content in a polypyrrole film multiplies oxygen evolution reaction currents by one order of magnitude, reducing the required overpotentials by approximately 200 mV. Despite the moderate efficiency (ca. 65 %), this strategy, being based on inexpensive and readily available raw materials, may be useful for the preparation of water splitting anodes that can be adapted to any surface, geometry, or support.

Functionalized non-viral cationic vectors for effective siRNA induced cancer therapy.

RNA interference (RNAi) has been regarded as a vital asset in the field of therapeutics as it has the capability to silence various disease causing genes including those that cause cancer. Small non-coding RNA molecules such as short interfering RNAs (siRNAs) are one of the extensively studied RNAi inducers for gene modulations. However, the delivery of RNAi inducers including siRNAs is compromised due to the barriers imposed by the biological system such as degradation by nucleases, rapid clearance, high anionic charge, immunogenicity and off-target effects. Viral vectors, in general exhibit high transfection efficiencies but are expensive and likely to confer immunological and safety issues. Therefore, non-viral cationic vectors (NVCVs) have received considerable attention to not only address these issues but also for developing efficacious siRNA delivery vectors. In this review, we will first discuss the historical development of various NVCVs and then will discuss functionalized NVCVs with linkers that provide stability, as well as respond to the cancer cell environment and with cancer cell receptor specific ligands to explicitly target them for improved siRNA efficacy. Multifunctional NVCVs (MNVCVs) that employ multiple synergistically working components to aid siRNA delivery efficacy are also discussed.

Study on the effectiveness of PNS and LS superplasticizers in air lime-based mortars

Polynaphtalenesulfonate (PNS) and lignosulfonate (LS) were tested as superplasticizers in pastes and mortars of pure air lime and air lime with a pozzolanic additive, nanosilica (NS). LS showed a better plasticizing effect than PNS: the flowability of the samples with LS as well as the slump retention over time was larger. LS strongly hindered carbonation due to its ability to form Ca2+ complexes. In mortars with NS, PNS was seen to interfere with the C-S-H formation, resulting in lower mechanical strengths. Adsorption isotherms and zeta potential showed that PNS was more adsorbed than LS onto lime and C-S-H particles. PNS acted mainly through electrostatic repulsion owing to its high anionic charge density and flat adsorption. However, LS was more efficient as superplasticizer in air lime media, steric hindrance being the main mechanism responsible for avoiding flocculation. Furthermore, LS yielded high compressive strengths in mortars with NS.

Development and validation of a simple and sensitive size-exclusion chromatography method for quantitative determination of heparin in pharmaceuticals.

Heparin is widely used as an anticoagulant for the treatment and prevention of various thrombotic diseases. However, due to its high anionic charge, heterogeneity in size distribution and high polarity, its analysis is very challenging. In this paper, a novel method based on size-exclusion chromatography (SEC) for quantitative determination of intact heparin in pharmaceuticals is presented. Analyses were performed on a BioSep-SEC-S 2000 column with Larginine solution at pH 6.5 as mobile phase and UV detection at 210 nm. The proposed method was found to be selective, linear (R2>0.997) over the concentration range of 3.1 to 1222 μg mL(-1), with a limit of detection of 1.0 μg mL(-1). Intraday and inter-day precision were below 5.1% and inaccuracy expressed as bias did not exceed 6.5 %. The reported method is simple, selective, sensitive, and requires no laborious sample preparation, which makes it appropriate for routine quantitative analysis of heparin in pharmaceuticals.

FACE analysis as a fast and reliable methodology to monitor the sulfation and total amount of chondroitin sulfate in biological samples of clinical importance.

Glycosaminoglycans (GAGs) due to their hydrophilic character and high anionic charge densities play important roles in various (patho)physiological processes. The identification and quantification of GAGs in biological samples and tissues could be useful prognostic and diagnostic tools in pathological conditions. Despite the noteworthy progress in the development of sensitive and accurate methodologies for the determination of GAGs, there is a significant lack in methodologies regarding sample preparation and reliable fast analysis methods enabling the simultaneous analysis of several biological samples. In this report, developed protocols for the isolation of GAGs in biological samples were applied to analyze various sulfated chondroitin sulfate- and hyaluronan-derived disaccharides using fluorophore-assisted carbohydrate electrophoresis (FACE). Applications to biologic samples of clinical importance include blood serum, lens capsule tissue and urine. The sample preparation protocol followed by FACE analysis allows quantification with an optimal linearity over the concentration range 1.0–220.0 µg/mL, affording a limit of quantitation of 50 ng of disaccharides. Validation of FACE results was performed by capillary electrophoresis and high performance liquid chromatography techniques.

Porous thin film barrier layers from 2,3-dicarboxylic acid cellulose nanofibrils for membrane structures

To fabricate a strong hydrophilic barrier layer for ultrafiltration (UF) membranes, 2,3-dicarboxylic acid cellulose nanofibrils with high anionic surface charge density (1.2mekv/g at pH 7) and a width of 22±4nm were used. A simple vacuum filtration method combined with a solvent exchange procedure resulted in a porous layer with a thickness of ∼0.85μm. The fabricated membranes reached high rejection efficiencies (74–80%) when aqueous dextrans up to 35–45kDa were filtrated to evaluate the molecular weight cut-offs (MWCO). A linear correlation between the barrier layer thickness and the flux rate was observed in all tested cases. Further optimization of the barrier layer thickness can lead to an even more effective structure.

Glycosaminoglycans in biomedicine

Glycosaminoglycans (GAGs) compose one of four classes of mammalian biopolymers, and are arguably the most complex. The research areas of glycobiology, glycopolymers, and the use of GAGs within tissue engineering and regenerative medicine have grown exponentially during the past decade. Researchers are closing in on high throughput methods for GAG synthesis and sequencing, but our understanding of glycan sequence and the information contained in this sequence lags behind. Screening methods to identify key GAG-biopolymer interactions are providing insights into important targets for nanomedicine, regenerative medicine, and pharmaceutics. Importantly, GAGs are most often found in the form of glycolipids and proteoglycans. Several studies have shown that the clustering of GAGs, as is often the case in proteoglycans, increases the affinity between GAGs and other biopolymers. In addition, GAG clustering can create regions of high anionic charge, which leads to high osmotic pressure. Recent advances have led to proteoglycan mimics that exhibit many of the functions of proteoglycans including protection of the extracellular matrix from proteolytic activity, regulation of collagen fibril assembly on the nanoscale, alteration of matrix stiffness, and inhibition of platelet adhesion, among others. Collectively, these advances are stimulating possibilities for targeting of drugs, nanoparticles, and imaging agents, opening new avenues for mimicking nanoscale molecular interactions that allow for directed assembly of bulk materials, and providing avenues for the synthesis of proteoglycan mimics that enhance opportunities in regenerative medicine.

Investigation on the effect of zeolite precursor on the formation process of MCM-41 containing zeolite Y building units

The formation process of MCM-41 containing zeolite Y building units has been investigated by UV Raman spectroscopy, 29Si and 27Al MAS NMR spectroscopy, X-ray diffraction (XRD), N2 adsorption and electron microscopy (SEM and TEM). It is found that the precursor containing zeolite Y secondary building units promotes the formation of a metastable mesopore structure just after mixing the zeolite precursors with CTAB. In contrast, the low-polymerized aluminosilicates and well-crystallized zeolite crystals cannot be assembled with CTAB at this stage. The result supports that the zeolite secondary building units should promote to the formation of the mesopore wall. This has been ascribed to its high anionic charge density as well as the appropriate multidentate coordination. Lowering down the pH value to 9.3 facilitates the further polymerization of the aluminosilicate species to build up a stable mesoporous phase.

Cross-linked polyethylenimine-hexametaphosphate nanoparticles to deliver nucleic acids therapeutics

Branched polyethylenimine (PEI; 25 kDa) as a nonviral vector exhibits high transfection efficiency and is a potential candidate for efficient gene delivery. However, the cytotoxicity of PEI limits its application in vivo. PEI was ionically interacted with hexametaphosphate, a compact molecule with high anionic charge density, to obtain nanoparticles (PEI-HMP). Nanoparticles were assessed for their efficacy in protecting complexed DNA against nucleases. The intracellular trafficking of nanoparticles was monitored by confocal microscopy. The cytotoxicity and transfection efficiency of PEI-HMP nanoparticles were evaluated in vitro. In vitro transfection efficiency of PEI-HMP (7.7%) was ∼1.3- to 6.4-folds higher than that of the commercial reagents GenePORTER 2 TM, Fugene TM, and Superfect TM. Also, PEI-HMP (7.7%) delivered green fluorescent protein (GFP)-specific small interfering ribonucleic acid (siRNA) in culture cells leading to >80% suppression in GFP gene expression. PEI-HMP nanoparticles protected complexed DNA against DNase for at least 2 hours. A time-course uptake of PEI-HMP (7.7%) nanoparticles showed the internalization of nanoparticles inside the cell nucleus in 2 hours. Thus, PEI-HMP nanoparticles efficiently transfect cells with negligible cytotoxicity and show great promise as nonviral vectors for gene delivery. From the Clinical Editor Branched polyethylenimine (PEI) as a non-viral vector exhibits high transfection efficiency for gene delivery, but its cytotoxicity limits its applications. PEI hexametaphosphate nanoparticles (PEI-HMP) demonstrated a 1.3-6.4 folds higher transfection rate compared to commercial reagents. Overall, PEI-HMP nanoparticles efficiently transfect cells with negligible cytotoxicity and show great promise as non-viral vectors for gene delivery.

Use of GAC after enhanced coagulation for the removal of natural organic matter from water for purification

Filtration with granular activated carbon (GAC) after an enhanced coagulation (EC) process was evaluated in order to determine the effectiveness of GAC in the reduction of natural organic matter (NOM), which should result in much lower formation of trihalomethane in the disinfection step. The results show that a combination of EC and GAC considerably reduces the organic matter content, which is mainly fulvic acid. This type of organic matter is removed with high coagulant dosages which neutralize their high anionic charge. A further reduction of NOM is achieved due the adsorption of NOM by GAC. As a result, the average trihalomethane (THM) concentration was only 14.5±5 μg L−1. Enhanced coagulation alone decreased the NOM concentration by 50%, but the remaining NOM reacted in the chlorination step and a higher average THM concentration was found (38±23 μg L−1). An average THM concentration of 73.8±41.2 μg L−1 was found at the drinking water plant of Boaco when conventional treatment was used. This THM concentration sometimes exceeds the maximum contaminant level of 80 μg L−1 established by the United States Environmental Protection Agency (USEPA), but not the Nicaraguan threshold of 460 μg L−1.