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121.
G. Panariello R. Favaloro M. Forbicioni E. Caputo R. Barbucci 《Macromolecular Symposia》2008,266(1):68-73
Summary: Guar gum (GG) polymer was crosslinked in order to obtain a new hydrogel. The GG hydrogel has been characterized by means of FT-IR spectroscopy, the determination of the water content, at different pH values, rheological measurements and in vitro release studies. The GG hydrogel shows a maximum water uptake at acid and basic pH values. The mechanical properties are investigated in order to verify the thixotropic behaviour of the material. In vitro release studies are conducted to evaluate the application of the GG hydrogel as a matrix for controlled drug release. 相似文献
122.
The semi‐IPN hydrogels consisting of poly(methacrylic acid) and guar gum (GG) are prepared at room temperature using water as solvent. 5‐aminosalicylic acid (5‐ASA) is entrapped in the hydrogel in the synthesis of hydrogel and all entrapment efficiencies are found above 85%. The hydrogel shows excellent pH‐sensitivity. It exhibited minimum swelling in an acidic pH medium through the formation of a complex hydrogen‐bonded structure and maximal swelling due to the electrostatic repulsion due to the ionization of the carboxylic groups in pH 7.4 medium. The degradation in vitro shows that the degree of degradation (R%) depended on the concentration of cross‐linking agent and content of GG. The hydrogel shows a minimum release of 5‐ASA due to the complex hydrogen bonded structure of the hydrogels in the medium of pH 2.2. The enzymatic degradation of hydrogels by cecal bacteria can accelerate the release of 5‐ASA entrapped in the hydrogel in pH 7.4 medium. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
123.
A new composite film of microbial exocellular polysaccharide‐gellan gum (GG) and hydrophilic room temperature ionic liquid 1‐butyl‐3‐methyl‐imidazolium tetrafluoroborate (BMIMBF4) was firstly used as an immobilization matrix to entrap horseradish peroxidase (HRP), and its properties were studied by UV/vis spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy. The results showed that BMIMBF4 could promote the electron transfer between HRP and electrode surface, and the existence of GG could successfully immobilize BMIMBF4 on the electrode surface with improved stability. HRP–BMIMBF4–GG/GCE exhibited a pair of well‐defined and quasireversible cyclic voltammetric peaks in 0.1 M pH 7.0 phosphate buffer solutions at 1.8 V/s, which was the characteristic of HRP Fe(III)/Fe(II) redox couples. The formal potentials (E°′) was ?0.368 V (vs. SCE) and the peak‐to‐peak potential separation (ΔEP) was 0.058 V. The peak currents were five times as large as those of HRP–GG/GCE. The average surface coverage (Γ*) and the apparent Michaelis‐Menten constant (Km) were 4.5×10?9 mol/cm2 and 0.67 μM, respectively. The electron transfer rate constant was estimated to be 15.8 s?1. The proposed electrode showed excellent electrocatalytic activity towards hydrogen peroxide (H2O2). The linear dynamic range for the detection of H2O2 was 0.05–0.5 μM with a correlation coefficient of 0.9945 and the detection limit was estimated at about 0.02 μM (S/N=3). BMIMBF4–GG composite film was promising to immobilize other redox enzymes or proteins and attain their direct electrochemistry. 相似文献
124.
铅(Ⅱ)-碘化钾-丁基罗丹明B-阿拉伯胶-TritonX-100体系分光光度法测定痕量铅 总被引：1，自引：0，他引：1
本文研究结果表明,水溶性大分子化合物阿拉伯胶和非离子表面活性剂Triton X-100共同存在下,铅碘络阴离子和丁基罗丹明B的显色反应具有很高的灵敏度,表观摩尔吸光系数ε=6.2×10~5L.mol~(-1)·cm~(-1)。拟定了用本法测定金属及其合金、工业废水中痕量铅的分析步骤,测定结果较满意。 相似文献
125.
Introduction of polyalkoxyalkyleneamide grafts to guar gum produces new water soluble guar derivatives as described in an earlier publication. 10 In this paper, the rhelogical behavior of these products was explored in more detail at 25 and 65°C. In addition, the viscosity was measured at high temperatures (90 and 120°C) and pressure (150 psi) to partially simulate the down hole conditions of oil wells. Upon treatment with zirconium lactate, the cross‐linked hydrophobically‐modified CMG derivatives exhibited better high‐temperature stability and higher gel viscosities than the corresponding CMHPG derivatives. The cross‐linked gel viscosities indicate that gels will be capable of supporting a high proppant carrying capacity. To facilitate removal of the gels from the formation, the hydrophobically modified derivatives were treated with an enzyme breaker system which produced fragments capable of producing stable emulsions when extracted with toluene. Thus, the clean up process will be enhanced by emulsification of the gel fragments produced by the gel hydrolysis. The low viscosities of the linear derivatives, the rapid formation of high viscosity gels upon cross‐linking and generation of emulsifiers during the gel removal suggest that these new derivatives are good candidates for fracturing fluid applications. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
126.
The aggregation and disaggregation of Aeromonas (A) gum, an acidic heteropolysaccharide, were investigated by viscometry, a fluorescent probe, and gel permeation chromatography combined with laser light scattering techniques in aqueous solutions containing desired NaCl at different temperatures. The A gum had a strong tendency of aggregation and high viscosity in the aqueous solutions. The weight‐average molecular weight, z‐average radius of gyration, weight‐average molar number (wag), and apparent aggregation number (Nap) of the aggregates were investigated and discussed. The results indicated that there were three regions that corresponded to three kinds of aggregates and two transition temperatures at about 35 and 75 °C in the disaggregation course. When the temperature was higher than 75 °C, the wag hardly changed, and there was still a certain amount of aggregates even at 100 °C, indicating that the aggregates were difficult to disrupt completely. Moreover, the aggregation was thermally irreversible. Decreasing polysaccharide concentration reduced the content of the aggregate. However, Nap remained constant around 20, independent of the polysaccharide concentration in a 0.5 M NaCl aqueous solution at 25 °C. At a salt concentration greater than or equal to 0.05 M, the aggregation was almost independent of the salt concentration used here. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2644–2651, 2000 相似文献
127.
Tatsuko Hatakeyama Sunao Naoi M. IIjima Hyoe Hatakeyama 《Macromolecular Symposia》2005,224(1):253-262
Locust bean gum (LBG) hydrogels were prepared by freezing and thawing. It was found that the junction zone of LBG hydrogels is tightly formed by repeating freezing and thawing. During this process, LBG molecules not connected with the junction zone are excluded from the gel portion and the remaining molecules gradually form densely packed hydrogels. Molecular conformation in the sol state affects the rate of the junction formation. Obtained LBG hydrogels are thermally stable and no gel-sol transition was observed in temperatures from 40 to 100 °C by the observation of differential scanning calorimetry (DSC). Non-freezing water content calculated from the DSC melting peak of water in the gel indicates that the junction zone became dense with increasing freezing and thawing. 相似文献
128.
Poly(2-(dimethylamino)ethylmethacrylate) was grafted on gellan gum (GG) in aqueous medium under microwave irradiation using ammonium persulfate and N,N,N′N′-tetramethylethylenediamine as the initiation system. Grafted copolymers were characterized by FT-IR, TGA, and SEM techniques. The influence of microwave power, exposure time, and composition of the reaction mixture on extent of grafting was studied. Conditions for obtaining the highest degree of grafting were optimized. The rate of grafting was determined from weight measurements. The overall activation energy for grafting is found to be 31.2 kJ/mol, indicating the occurrence of the grafting process with absorption of low thermal energy. 相似文献
129.
Hassan Beheshti Seresht;Mohamad Sadegh Aghajanzadeh;Rana Imani;Masoumeh Haghbin Nazarpak; 《先进技术聚合物》2024,35(4):e6402
Hydrogels hold immense promise in biomedical applications due to their biocompatibility, high water content, and versatile fabrication. This study focuses on the mechanical behavior of a novel polysaccharide/protein hybrid hydrogel, GEL-AXG, synthesized via a Schiff base reaction between aldehyde-modified xanthan gum (AXG) and gelatin (Gel). Hydrogel samples with varying AXG-to-Gel ratios were subjected to unconfined compression tests to assess their mechanical properties. The observed stress-relaxation mechanism in deformed hydrogels primarily involves water migration. To quantify these mechanical properties, we applied the linear poroelasticity theory. Our results highlight that Gel-AXG hydrogels with a 2:1 AXG-to-Gel ratio exhibit significantly higher peak and equilibrium stresses. This enhancement can be attributed to increased crosslink density and reduced dangling chain presence. Moreover, the linear poroelasticity formulation yielded a shear modulus of G = 44.91 ± 0.25 kPa for Gel-AXG hydrogels with a 1:2 AXG-to-Gel volume ratio, which we identified as our optimized hydrogel. 相似文献
130.
Karen Onofre-Rentería;Denis Aidée Cabrera-Munguía;Luis Enrique Cobos-Puc;Jesús Alejandro Claudio-Rizo;Lourdes Morales-Oyervides;Ernesto Oyervides-Muñoz; 《先进技术聚合物》2024,35(11):e70004
Biopolymers are molecules widely used in many industries because they are biodegradable and have a natural origin. Therefore, they can be obtained from renewable resources and organisms such as animals, plants, or microorganisms. Among the best-known biopolymers, xanthan gum is an anionic biopolymer composed of glucose, mannose, glucuronic acid, pyruvic acid, and acetyl groups. It can be obtained by fermentation with bacteria of the genus Xanthomonas, has good physicochemical properties, and it is biocompatible with human cells. However, it has disadvantages as it is very susceptible to microbial contamination. Therefore, various physical, chemical, or enzymatic modification methods have been developed to improve its physicochemical and biological properties. Modifications in the backbone of the xanthan gum chains have made it possible to create xanthan gum derivatives with new uses, such as drug delivery systems and improving absorption methods in the pharmaceutical industry to enhance the efficacy of several treatments or therapeutic processes, to promote cell proliferation for tissue engineering as biomedical applications when used in systems such as hydrogels or films. They are also used in food products, in cosmetics, to recover oil from water or ground, to treat wastewater, or granting soil with good conditions to promote plant and vegetables growth. Hence, it is important to know and develop new modification methods to improve and impart new properties to obtain novel applications of xanthan gum. 相似文献