orabase and phosphoric-acid

To investigate the effects of a sodium carboxymethyl cellulose (SCMC)-based extrafibrillar demineralization conditioner on dentin bonding durability and explore the possible mechanisms.. The SCMC-based extrafibrillar demineralization conditioner was facilely developed by dissolving SCMC into deionized water at an appropriate concentration. A single layer collagen mineralization/demineralization model was designed to visualize extrafibrillar demineralization in detail. Dentin surfaces of human third molars were conditioned with 3 % SCMC or 37 % phosphoric acid (PA). The morphology, composition, and mechanical properties of conditioned dentin from each group were characterized. To evaluate dentin bonding performance, SCMC- and PA- conditioned dentin were applied with adhesive restoration using the dry-bonding technique. The microtensile bond strength (MTBS), interface nanoleakage, and in situ zymography were measured after 24 h of water storage, 10,000 thermocycles, or one month of collagenase aging. The inhibitory effect of SCMC on recombinant human matrix metalloproteinase-2 (rhMMP-2) and cell toxicity were also investigated.. After SCMC conditioning, both demineralization of extrafibrillar minerals and retention of intrafibrillar minerals were observed in the single layer collagen model and the dentin ultrastructure. The mechanical properties of SCMC-conditioned dentin were largely preserved. Compared with PA, SCMC conditioning produced greater MTBS values and less nanoleakage expression after aging. Endogenous gelatinolytic activity was suppressed in SCMC-conditioned dentin. In addition to being nontoxic, the inhibition of rhMMP-2 by SCMC was confirmed to be dose-dependent.. From the perspective of minimal intervention, the SCMC-based extrafibrillar demineralization conditioner could improve dentin bonding durability, suggesting a promising strategy to extend the service life of adhesive restorations.

Topics: Carboxymethylcellulose Sodium; Dentin; Humans; Matrix Metalloproteinase 2; Sodium; Tooth Demineralization; Water

With the growing environmental concerns and an emergent demand, a growing attention is turned to eco-friendly superabsorbent hydrogels instead of synthetic counterparts. Hydrogels based on cellulose derivatives can absorb and retain a huge amount of water in the interstitial sites of their structures, stimulating their uses in various useful industrial purposes. In this work, cross-linked superabsorbent composite hydrogel films (CHF) were designed, manufactured and characterized, by taking advantage of the combination of carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC) and newly developed regenerated cellulose (RC) spheres. RC with sphere-like shape was successfully prepared using a green method based on cold phosphoric acid-mediated dissolution of microcrystalline cellulose (MCC) followed by regeneration process using water as anti-solvent. Prior to be used, the morphological and structural properties of RC spheres, with an average diameter of 477 ± 270 nm, were examined by SEM, AFM, XRD, FTIR and TGA techniques. CHF crosslinked with citric acid were, in fact, prepared by solvent casting method with different RC weight fractions (i.e. 0, 2.5, 5, 10 and 15 wt%), then the crosslinking reaction was triggered by thermal treatment at 80 °C during 8 h. Prepared CHF were then characterized in terms of their structural, thermal, tensile and transparency properties. Swelling tests were carried at three different aqueous media (i.e. with a pH = 3, 6.4 or 11) to evaluate the water retention capacity of hydrogel films, as well as, the pH effect on their swelling and hydrolytic degradation properties. Collected results reveal that CHF with low RC content (i.e. RC weight fraction of 2.5 or 5 wt%) have the best tensile and swelling properties, with a tensile strength and a swelling capacity (at pH = 6.4) up to 95 MPa and 4000%, respectively.

Topics: Carboxymethylcellulose Sodium; Cellulose; Hydrogels; Hydrogen-Ion Concentration; Hydrolysis; Microscopy, Atomic Force; Microscopy, Electron, Scanning; Phosphoric Acids; Phosphorus; Solvents; Spectroscopy, Fourier Transform Infrared; Tensile Strength; Water; X-Ray Diffraction

Increasing the environmental benignity of lithium-ion batteries is one of the greatest challenges for their large-scale deployment. Toward this end, we present herein a strategy to enable the aqueous processing of high-voltage LiNi

Topics: Carboxymethylcellulose Sodium; Citric Acid; Electric Power Supplies; Electrodes; Green Chemistry Technology; Lithium Compounds; Manganese; Microscopy, Electron, Scanning; Nickel; Phosphoric Acids; Powder Diffraction; Water

Endocellulase E2 from the thermophilic bacterium Thermomonospora fusca is a member of glycosyl-hydrolase family 6 and is active from pH 4 to 10. Enzymes in this family hydrolyze beta-1,4-glycosidic bonds with inversion of the stereochemistry at the anomeric carbon. The X-ray crystal structures of two family 6 enzymes have been determined, and four conserved aspartic acid residues are found in or near the active sites of both. These residues have been mutated in another family 6 enzyme, Cellulomonas fimi CenA, and evidence was found for both a catalytic acid and a catalytic base. The corresponding residues in E2 (D79, D117, D156, and D265) were mutated, and the mutant genes were expressed in Streptomyces lividans. The mutant enzymes were purified and assayed for activity on three cellulosic substrates and 2, 4-dinitrophenyl-beta-D-cellobioside. Activity on phosphoric acid-swollen cellulose was measured as a function of pH for selected mutant enzymes. Binding affinities for each mutant enzyme were measured for two fluorescent ligands and cellotriose, and circular dichroism spectra were recorded. The results show that the roles of D117 and D156 are the same as those for the corresponding residues in CenA; D117 is the catalytic acid, and D156 raises the pK(a) of D117. No specific function was assigned to the CenA residue corresponding to D79, but in E2, this residue also assists in raising the pK(a) of D117 and is important for catalytic activity. The D265N mutant retained 7% of the wild-type activity, indicating that this residue is not playing the role of the catalytic base. Experiments were conducted to rule out contamination of the D265 enzymes by either wild-type E2 or an endogenous S. lividans CMCase.

Topics: Actinomycetales; Binding Sites; Carboxymethylcellulose Sodium; Cellobiose; Cellulase; Circular Dichroism; Deuterium Oxide; Filtration; Glucosides; Hydrogen-Ion Concentration; Hymecromone; Mutagenesis, Site-Directed; Paper; Phosphoric Acids; Solvents; Trisaccharides