tempo and sodium-bromide

This study concerns the performance evaluation of 6-carboxyl chitin for its wound healing application. 6-Carboxyl chitins were prepared by the oxidation of chitin at C-6 with NaClO/TEMPO/NaBr after α-chitin was pretreated in NaOH/urea solution. The products with different molecular weights were obtained by changing reaction conditions. They all were completely oxidized at C-6 and N-acetylated at C-2 according to FT-IR and NMR results. 6-Carboxyl chitins could stimulate significantly the proliferation of human skin fibroblasts (HSF) and human keratinocytes (HaCaT), and the bioactivities were concentration and Mws dependent. Within the scope of the study, 10-40 kDa of Mws and 10-100 μg/mL of concentrations were most suitable for the HSF proliferation, but the proliferation of HaCaT increased with decreasing the concentration and Mw. In addition, 6-carboxyl chitins could also induce macrophages and fibroblasts to secrete growth factors. Therefore, 6-carboxyl chitins could be expected to be an active ingredient for wound healing.

Topics: Bromides; Cell Proliferation; Chitin; Chlorates; Cyclic N-Oxides; Fibroblasts; Humans; In Vitro Techniques; Keratinocytes; Molecular Weight; Oxygen; Sodium Compounds; THP-1 Cells; Wound Healing

C-6 oxidized chitosan is of great interest in obtaining a new moisture retention polymer like hyaluronic acid. The direct C-6 specific oxidation of chitosan mediated by the TEMPO/NaClO/NaBr system has proven to be difficult because of the high crystalline and high C-2 amino group content. In this work, the pre-modification of chitosan by

Topics: Bromides; Calorimetry, Differential Scanning; Catalysis; Chitosan; Cyclic N-Oxides; Magnetic Resonance Spectroscopy; Molecular Structure; Oxidation-Reduction; Sodium Compounds; Solubility; Spectroscopy, Fourier Transform Infrared; Water; X-Ray Diffraction

A xanthouronic acid sodium salt called xanthouronan was produced from xanthan by regioselective oxidation with NaOCl/NaBr using 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO) as catalyst. The efficiency of the one pot TEMPO-mediated oxidation was confirmed by HPAEC-PAD, (13)C NMR, and FT-IR. The oxidation degree was close to 98% and the mass yield of this new polyglucuronic acid was higher than 90% (w/w). The macromolecular characterization of xanthouronan using SEC-MALLS showed a molecular size reduced by a third due to the oxidation treatment and the degree of polymerization (DP) of the xanthouronan form was about 665. The evaluation of the enzymatic degradation of this C-6 carboxylated xanthan by various polysaccharide hydrolases and one polysaccharide lyase showed its high resistant to biodegradation. The antioxidant activity of xanthouronan was also tested by using the 2,2'-diphenyl-1-picrylhydrazyle (DPPH) and hydroxyl radical procedures. At 1 g/L, xanthouronan presented 75% of the ascorbic acid antioxidant activity.

Topics: Antioxidants; Biphenyl Compounds; Bromides; Catalysis; Cyclic N-Oxides; Oxidation-Reduction; Picrates; Polysaccharides; Polysaccharides, Bacterial; Sodium Compounds; Sodium Hydroxide; Sodium Hypochlorite; Uronic Acids

One-sided surface oxidation of lyocell type cellulose fabric can be achieved by use of a modified TEMPO-mediated oxidation system. A borate-based buffer was used to maintain stable pH conditions and screen printing was applied to achieve oxidation on the fabric surface only. To formulate an applicable procedure, the TEMPO/NaBr/NaOCl system was split into two treatment steps: firstly, the fabric was impregnated with a buffered TEMPO/NaBr solution and dried, then a thickened NaOCl paste was printed on the fabric. FTIR-ATR spectra and methylene blue sorption experiments demonstrated successful modification on the printed side of the fabric. Substantial increases in carboxylic group content and water retention value were observed. The higher concentration of carboxylic groups on the fabric surface also led to a localised increase in binding capacity for Ca(2+)-ions. This new concept permits controlled oxidation of cellulose surfaces by printing techniques.

Topics: Bromides; Cellulose; Cotton Fiber; Cyclic N-Oxides; Oxidants; Oxidation-Reduction; Printing; Sodium Compounds; Sodium Hypochlorite; Spectrophotometry, Atomic; Spectroscopy, Fourier Transform Infrared; Surface Properties; Textiles

Native hyaluronan (HA) has been oxidized to polyaldehyde polymers with a degree of substitution (DS) of up to 50%. Two different procedures enabling the control of the degree of substitution were followed in this study. Selective oxidation of primary hydroxyl groups of N-acetyl-D-glucosamine of hyaluronan was performed either in an aqueous solution containing AcNH-TEMPO/NaBr/NaOCl or in an aprotic solvent containing Dess-Martin periodinane (DMP). It was found that a change of reaction parameters (reaction time and temperature, type of catalyst, oxidant-to-HA ratio, presence of nitrogen, buffer type, and concentration) had an influence on the degree of substitution and molecular weight. The derivatives were characterized by MS, NMR spectroscopy, and SEC-MALLS. Degradation of hyaluronic acid by the oxidant was observed and confirmed by SEC. The effect of oxidized derivatives of hyaluronan on cells was studied by means of NIH 3T3 fibroblast viability, which indicates that prepared hyaluronan polyaldehydes are biocompatible and suitable for medical applications and tissue engineering. The function of polyaldehyde as precursor for other modification was illustrated in the reaction with lysine.

Topics: Acetylglucosamine; Aldehydes; Animals; Biocompatible Materials; Biopolymers; Bromides; Catalysis; Cell Survival; Cyclic N-Oxides; Hyaluronic Acid; Imino Pyranoses; Magnetic Resonance Spectroscopy; Mice; Molecular Weight; NIH 3T3 Cells; Nitrogen; Oxidation-Reduction; Sodium Compounds; Sodium Hypochlorite; Temperature

TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated 6-carboxy β-chitin derivatives (T-chitin) with different carboxylate content were successfully synthesized by controlling the addition level of NaClO as the primary oxidant. The structural and biochemical properties of the derivatives were investigated. The carboxylate contents of the derivatives calculated by electrical conductivity titration were 1.33, 1.68, 1.80, and 2.08 mmol/g, respectively. The yield of T-chitin with carboxylate content of 2.08 mmol/g reached 74.55%. T-chitin exhibited stronger bile acid binding capacities than that of β-chitin. The scavenging ability of T-chitin against hydroxyl radicals improved with increasing concentration, and EC(50) values were below 1.2 mg/mL. All T-chitin exhibited a strong ferrous ion chelating effect. At 8 mg/mL, the chelating effects of T-chitin with carboxylate content of 0.81 mmol/g reached 80.15%. These results showed that T-chitin had good bile acid binding capacity and antioxidant activities and it may be a potential antioxidant in vitro.

Topics: Animal Shells; Animals; Bile Acids and Salts; Biphenyl Compounds; Bromides; Carboxylic Acids; Chitin; Cyclic N-Oxides; Decapodiformes; Free Radical Scavengers; Hydroxyl Radical; Iron Chelating Agents; Oxidation-Reduction; Picrates; Sodium Compounds; Sodium Hypochlorite

Cellulose nanowhiskers as a kind of renewable and biocompatible nanomaterials evoke much interest because of its versatility in various applications. Herein, for the first time, a novel controllable fabrication of spider-web-like nanoporous networks based on jute cellulose nanowhiskers (JCNs) deposited on the electrospun (ES) nanofibrous membrane by simple directly immersion-drying method is reported. Jute cellulose nanowhiskers were extracted from jute fibers with a high yield (over 80%) via a 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)/NaBr/NaClO system selective oxidization combined with mechanical homogenization. The morphology of JCNs nanoporous networks/ES nanofibrous membrane architecture, including coverage rate, pore-width and layer-by-layer packing structure of the nanoporous networks, can be finely controlled by regulating the JCNs dispersions properties and drying conditions. The versatile nanoporous network composites based on jute cellulose nanowhiskers with ultrathin diameters (3-10 nm) and nanofibrous membrane supports with diameters of 100-300 nm, would be particularly useful for filter applications.

Topics: Animals; Biomimetics; Bromides; Cellulose; Cyclic N-Oxides; Mechanical Phenomena; Membranes, Artificial; Nanostructures; Oxidation-Reduction; Porosity; Quaternary Ammonium Compounds; Sodium Compounds; Sodium Hypochlorite; Spiders; Surface Tension; Vegetables

This study examined the characteristics of the oxidation reaction on the primary alcohol groups in cellulose involving the 2,2,6,6-tetramethyl-1-piperidinyl oxoammonium ion (TEMPO) and determined the optimum conditions for the preparation of oxidized cellulose (OC). The applicability of OC in polysaccharide systems was also investigated. The effects of TEMPO, sodium bromide (NaBr), and temperature on the oxidation reaction time, yield, and selectivity for primary alcohol groups were examined using response surface methodology (RSM). The reaction time decreased with increases in the temperature and the levels of TEMPO and NaBr. The yield increased with the level of NaBr and decreased as the temperature increased. Selectivity increased with the temperature and decreased as the levels of TEMPO and NaBr increased. The optimum levels of TEMPO and NaBr and the optimum temperature for the production of OC were determined as 0.3 mM/100 mM anhydroglucose unit (AGU), 50 mM/100 mM AGU, and 25 degrees C, respectively. The water and oil binding capacity and viscosity of cellulose increased with oxidation. Wheat starch containing OC exhibited a decreased initial pasting temperature and setback, but increased peak viscosity, gelatinization, and retrogradation enthalpy (DeltaH). The hardness of the wheat starch gel decreased significantly upon the addition of OC.

Topics: Antioxidants; Bromides; Cellulose; Cyclic N-Oxides; Dose-Response Relationship, Drug; Food Technology; Molecular Structure; Oxidation-Reduction; Sodium Compounds; Starch; Structure-Activity Relationship; Temperature; Time Factors; Viscosity

Chitosan was selectively oxidized at C-6 primary alcohol groups by TEMPO in the presence of sodium hypochlorite (NaOCl) and sodium bromide (NaBr), and also non-specifically oxidized only by NaOCl. Sequentially oxidized chitosan samples from 25 to 100% were produced by 25% increment, from both oxidation processes. By introducing carbonyl groups in chitosan structure with either oxidizing process, the water solubility was shown to be enhancing from all the oxidized sample groups. At the 25% of non-specific oxidation, 0.56% of solubility was detected but there was no proportional increase in solubility as the oxidation level increased. Moreover, the decreases in solubility were observed at 50%-oxidized (0.43%) and 100%-oxidized (0.45%) chitosan samples. During the specific oxidation process, 25%-oxidized 6-oxychitosan had the highest solubility, and the solubility decreased substantially from 0.72 to 0.15% as the degree of oxidation increased from 25 to 100%. Possibly, excessive incorporation of negative charges on chitosan resulted in the aggregation among 6-oxychitosan molecules by charge-charge interactions. The strongest cholic acid-retardation index (CRI, %) of highly soluble 25%-oxidized 6-oxychitosan was consistently observed until 24h of dialysis, which means the CRI is closely related to the water solubility of 6-oxychitosan. Therefore, the solubility improvement should be considered for enhancing the biological activity such as bile acid-binding capacity. Also, it was suggested that negative charge increase in chitosan structure above a certain level led to adverse effect on the binding capacity.

Topics: Alcohols; Bile Acids and Salts; Biocompatible Materials; Bromides; Chitosan; Cholic Acid; Cyclic N-Oxides; Dose-Response Relationship, Drug; Hydrogen-Ion Concentration; Macromolecular Substances; Oxygen; Polymers; Sodium Compounds; Sodium Hypochlorite; Solubility; Temperature; Water

Regiospecific oxidation of the primary hydroxyl groups in lacquer polysaccharide (LPL, Mw 6.85 x 10(4)) and its NaIO4 oxidation derivatives (LPLde) to C-6 carboxy groups was achieved with NaOCl in the presence of Tempo and NaBr. Sulfate groups were incorporated into the oxidated polysaccharides using Py.SO3 complex as a reagent. Reactivity of polysaccharide hydroxyl group was C-6 > C-2 > C-4. Sulfate groups were mainly linked to the second hydroxy at C-2 in the products. The results of APTT assay showed after incorporation of carboxyl groups into lacquer polysaccharides, the intrinsic coagulation pathway was promoted, and all sulfated polysaccharides had very weak anticoagulant activity within the scope of studied DS (0.39-1.11). These indicated that carboxyl groups and sulfate groups had the synergistic action. At the same time, the anticoagulant activity increased very slowly with the DS in the second hydroxy. This indicated that 6-O-SO3- in the side chains took an important role in the anticoagulant activity.

Topics: Anticoagulants; Blood Coagulation; Bromides; Carbon; Cyclic N-Oxides; Humans; Macromolecular Substances; Magnetic Resonance Spectroscopy; Oxygen; Partial Thromboplastin Time; Polysaccharides; Protein Structure, Tertiary; Sodium Compounds; Software; Spectroscopy, Fourier Transform Infrared; Structure-Activity Relationship; Sulfates; Trees

The side products formed in the TEMPO-mediated oxidation of glucose to glucaric acid were determined by GC. Next to glucaric acid, gluconic acid, the intermediate in the oxidation, the degradation products, oxalic acid, tartronic acid, meso- (erythraric) and DL-threaric (tartaric) acid were detected. Chiral GC determined the DL-tartaric acid to be non-racemic mixtures of L- and D-tartaric acids, with inverse D/L-ratios depending on the oxidation of D- or L-glucose. The origin of all degradation products is rationalized. This study details a fast screening method to optimize the reaction conditions toward minimal degradation.

Topics: Bromides; Chromatography, Gas; Cyclic N-Oxides; Glucaric Acid; Glucose; Magnetic Resonance Spectroscopy; Oxidation-Reduction; Sodium Compounds; Tartrates

Oxidation of sucrose by the NaOCl/TEMPO system provided sucrose tricarboxylate without the addition of sodium bromide as co-catalyst when high-frequency (500 kHz) ultrasound was applied, in contrast to very limited conversion without sonication. In the presence of sodium bromide, sonication also caused acceleration of the oxidation. The rate increase due to sonication of the oxidant system prior to sucrose addition suggests that ultrasound acts at the level of the formation of the nitrosonium ion, the active oxidising species in the catalytic cycle.

Topics: Antioxidants; Bromides; Catalysis; Cyclic N-Oxides; Molecular Structure; Oxidation-Reduction; Sodium Compounds; Sodium Hypochlorite; Sucrose; Tricarboxylic Acids; Ultrasonics