Synthesis,characterization and swelling behaviors of sodium alginate-g-poly(acrylic acid)/sodium humate superabsorbent

A novel sodium alginate-g-poly(acrylic acid)/sodium humate superabsorbent was prepared by graft copolymerization with sodium alginate, acrylic acid and sodium humate in aqueous solution, using N,N’-methylenebisacrylamide as a crosslinker and ammonium persulfate as an initiator. The effects of crosslinker, sodium alginate and sodium humate content on water absorbency of the superabsorbent were studied. The swelling behavior in solutions of various pH and the swelling kinetics in saline solutions (5 mmol/L NaCl and CaCl₂) were also investigated. The results from IR analysis showed that both sodium alginate and sodium humate react with the acrylic acid monomer during the polymerization process. The introduction of sodium humate into the sodium alginate-g-poly(acrylic acid) system could enhance the water absorbency and the superabsorbent containing 10 wt% sodium humate acquired the highest water absorbency (1380 g/g in distilled water and 83 g/g in 0.9 wt% NaCl solution).     

Structure and characterization of amphoteric semi-IPN hydrogel based on cationic starch

A series of semi-interpenetrating polymer network (semi-IPN) materials were prepared by blending polymerization of acrylic acid (AA) in cationic starch (CS) and poly(methacryloyloxyethyl trimethylammonium chloride) (PDMC) solution. The crosslinker concentration, the feed ratio of the CS-g-AA to PDMC was discussed in term of the swelling capacity, and hydrogel properties were evaluated by network parameters M_c, morphological and compressive load tests. The semi-IPN hydrogels were also characterized by FT-IR spectroscopy to confirm the interactions between CS-g-AA and PDMC. Electron microscopy involved to staining of the anionic phases using CsF showed a transition from two-phase to compatible structure with the increasing content of PDMC, and further confirmed that the semi-IPN structure in hydrogels along with DSC. The resultant semi-IPN hydrogels were found to possess appreciable compatibility, good swellability and mechanical strength.     

pH响应型蔗渣木质素水凝胶的制备及其对蛋白质的控释性能

该研究以蔗渣木质素和甲基丙烯酸为原料合成了pH敏感型蔗渣木质素/聚甲基丙烯酸水凝胶,对其合成条件、pH敏感性、溶胀-退溶胀性能以及对牛血清蛋白的控释等性质进行研究,并采用红外光谱、扫描电镜等对凝胶进行表征。结果表明:(1)对凝胶溶胀比影响的因素由大到小依次为甲基丙烯酸用量、交联剂用量、催化剂用量、反应的温度、木质素用量。当甲基丙烯酸单体浓度为1.75 mol·L~(-1)、木质素浓度为25 g·L~(-1)、交联剂浓度为3.25×10~(-2)mol·L~(-1)、引发剂浓度为1.25×10~(-2)mol·L~(-1)、反应温度为65℃时,所得水凝胶在模拟肠液中的溶胀比最大(28.16 g·g~(-1))。与不加木质素的聚甲基丙烯酸水凝胶相比,蔗渣木质素/聚甲基丙烯酸水凝胶的溶胀比有所下降,但其敏感pH由4~5碱移至6~8。(2)蔗渣木质素/聚甲基丙烯酸水凝胶的溶胀—退溶胀可逆性受组成的影响较大,但相对于聚甲基丙烯酸水凝胶,蔗渣木质素/聚甲基丙烯酸水凝胶对pH值的敏感响应性更强、响应速率更快,同时能在更短时间内达到溶胀平衡。(3)加入木质素可以提高水凝胶对牛血清蛋白的负载量,所试验的蔗渣木质素/聚甲基丙烯酸水凝胶样品对牛血清蛋白的最大负载量可达577 mg·g~(-1)。(4)牛血清蛋白在12 h后基本可达释放平衡;在模拟胃液中,牛血清蛋白的释放率仅10%,而在模拟肠液中释放率达92%。pH响应型蔗渣木质素/聚甲基丙烯酸水凝胶可以作为口服型蛋白类药物的潜在载体。     

Rheological Characterization of Cataplasm Bases Composed of Cross-Linked Partially Neutralized Polyacrylate Hydrogel

Viscoelasticity is a useful parameter for characterizing the intrinsic properties of the cross-linked polyacrylate hydrogel used in cataplasm bases. The aim of this study was to investigate the effects of various formulation parameters on the rheological characteristics of polyacrylate hydrogel. The hydrogel layers were formed using a partially neutralized polyacrylate (Viscomate^™), which contained acrylic acid and sodium acrylate in different copolymerization ratios, as the cross-linked gel framework. Dihydroxyaluminum aminoacetate (DAAA), which produces aluminum ions, was used as the cross-linking agent. Rheological analyses were performed using a “stress amplitude sweep” and a “frequency sweep”. The results showed that greater amounts of acrylic acid in the structure of Viscomate as well as higher concentrations of DAAA and Viscomate led to an increase in the elastic modulus (G′). However, greater amounts of acrylic acid in the structure of Viscomate and higher concentrations of DAAA had an opposite on the viscous modulus (G″); this might be owing to higher steric hindrance. The results of this study can serve as guidelines for the optimization of formulations for cataplasms.KEY WORDS: cataplasm, hardness, rheology, viscoelasticity     

An Investigation and Characterization on Alginate Hydogel Dressing Loaded with Metronidazole Prepared by Combined Inotropic Gelation and Freeze-Thawing Cycles for Controlled Release

The purpose of this study was to investigate the effect of combined Ca²⁺ cross-linking and freeze-thawing cycle method on metronidazole (model drug) drug release and prepare a wound film dressing with improved swelling property. The hydrogel films were prepared with sodium alginate (SA) using the freeze-thawing method alone or in combination with ionotropic gelation with CaCl₂. The gel properties such as morphology, swelling, film thickness, and content uniformity and in vitro dissolution profiles using Franz diffusion cell were investigated. The cross-linking process was confirmed by differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy. In vitro protein adsorption test, in vivo wound-healing test, and histopathology were also performed. The hydrogel (F2) composed of 6% sodium alginate and 1% metronidazole prepared by combined Ca²⁺ cross-linking and freeze-thawing cycles showed good swelling. This will help to provide moist environment at the wound site. With the in vivo wound-healing and histological studies, F2 was found to improve the wound-healing effect compared with the hydrogel without the drug, and the conventional product.KEY WORDS: alginate, Ca²⁺ cross-linking, freeze-thawing, swelling, wound dressing     

A new amphoteric superabsorbent hydrogel based on sodium starch sulfate

A new amphoteric superabsorbent hydrogels were synthesized by graft copolymerization blending based on acrylamide (AM), diallydimethylammonium chloride (DMDAAC) and sodium starch sulfate (SSS). The effect of polymerization conditions on swelling capacity was investigated. The results showed that the swelling capacity was affected by various factors, such as polymerization temperature, concentration of initiator and crosslinker, and dose of AM. Additionally, the results testified that salt bond was a potential crosslinking factor in the amphoteric hydrogel. The maximum swelling capacity in distilled water and saline solution reached 1493.1 and 91.0 g/g, respectively. These results were compared with those obtained from original starch-based hydrogel.     

“Development and Evaluation of Sodium Alginate–Polyacrylamide Graft–Co-polymer-Based Stomach Targeted Hydrogels of Famotidine”

In the present study, grafting technology has been used to develop novel grafted hydrogel beads as controlled drug delivery carriers. The chemical crosslinking and grafting of polyacrylamide onto sodium alginate has been found to be efficient method for the development of new polymeric carrier. The successful crosslinking has been confirmed by Fourier transformed infrared spectroscopy, thermogravimetric analysis, and elemental analysis. The polymeric network of sodium alginate–co-polyacrylamide (NaAlg-g-PAM) has been interlinked by covalent and hydrogen bonds which also strength the gel network. Simple ionotropic gelation method has been used for the preparation of NaAlg-g-PAM hydrogel beads. Its swelling and gelation were dependent on monomer and crosslinker concentrations. Entrapment of the drug moiety (famotidine; an antiulcer drug) within the grafted beads has been confirmed by X-ray powder diffraction and differential scanning calorimetry. More than 75% of drug loading in beads occurred with the increase of monomer and crosslinker concentration. In vitro drug release was found to be sustained up to the 12 h with 80% drug release.Key words: crosslinking, grafting, hydrogel beads, mechanical strength, polyacrylamide     

Preparation and characterization of konjac glucomannan–poly(acrylic acid) IPN hydrogels for controlled release

In this paper, we reported the synthesis and properties of interpenetrating polymer network (IPN) hydrogel systems designed for colon targeted drug delivery. The gels were composed of konjac glucomannan (KGM) and cross-linked poly(acrylic acid) (PAA) by N,N-methylene-bis-(acrylamide) (MBAAm). It was possible to modulate the swelling degree of the gels. And the swelling ratio has sensitive respondence to the environmental pH value variation. The degradation tests show that the hydrogels retain the enzymatic degradation character of KGM. In vitro release of model drug VB₁₂ was studied in the presence of Cellulase E0240 in pH 7.4 phosphate buffer at 37 °C. The accumulative release percent of the model drug reached 85.6% after 48 h and the drug release was controlled by the swelling and the degradation of the hydrogels. The results indicated that the IPN hydrogels can be exploited as potential carriers for colon-specific drug delivery.     

Preparation, characterization and properties of superabsorbent nanocomposites based on natural guar gum and modified rectorite

Novel guar gum-g-poly(sodium acrylate)/rectorite (GG-g-PNaA/REC) superabsorbent nanocomposites were prepared in aqueous solution using guar gum (GG), partially neutralized acrylic acid (NaA), acidified rectorite (H⁺-REC) and organified rectorite (CTA⁺-REC) by cetyltrimethylammonium bromide (CTAB) as raw materials, ammonium persulfate (APS) as initiator and N,N′-methylenebisacrylamide (MBA) as crosslinker. FTIR spectra confirmed that NaA had been grafted onto GG chains and the OH groups of REC participated in polymerization reaction. Exfoliated nanocomposite was obtained for H⁺-REC and intercalated structure was formed for CTA⁺-REC as shown by XRD results. SEM observations show REC has been uniformly dispersed in polymeric matrix. Effects of HCl concentration, organification degree of CTA⁺-REC and content of REC on swelling capabilities were investigated and the swelling kinetics of nanocomposites was evaluated. Results indicate that modifying REC by acidification and organification can improve swelling properties of the resultant nanocomposites, and GG-g-PNaA/CTA⁺-REC exhibited higher swelling capability and swelling rate contrast to GG-g-PNaA/H⁺-REC.     

Preparation of pH- and ionic-strength responsive biodegradable fumaric acid crosslinked carboxymethyl cellulose

A novel biodegradable sodium carboxymethyl cellulose (NaCMC)-based hydrogel was synthesized by using fumaric acid (FA) as a crosslinking agent at various ratios. Hydrogels (CMCF) were characterized using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Swelling behaviors of hydrogels were investigated in distilled water, various salt, and pH solutions. The FTIR results indicated the crosslinking between carboxyl groups of FA with hydroxyl group of NaCMC through ester formation. AFM analyses showed that roughness of hydrogel surface decreased with increasing crosslinker concentration. The swelling capacity decreased with an increase in charge of the metal cation (Al(3+)相似文献   

Synthesis and properties of a novel biosuperabsorbent from alkali soluble <Emphasis Type="Italic">Rhizomucor pusillus</Emphasis> proteins

A novel biosuperabsorbent protein hydrogel was prepared from protein-rich alcoholic–alkali soluble parts of zygomycete Rhizomucor pusillus biomass. The fungal protein content was 46.8%, and the lipid content was 13.1%. Extraction of protein from this microorganism through the method applied prevents protein decomposition, resulting in maximum yield. After alcoholic–alkaline extraction, the proteins from the biomass were acylated using ethylenediaminetetraacetic dianhydride and subsequently treated with glutaraldehyde as a crosslinker for further experiments. Thermal consistency was investigated by means of two different methods: thermal denaturation via differential scanning calorimetry and thermal decomposition study via thermogravimetric analysis. The swelling behaviour of the crosslinked hydrogel was measured in deionised water, 0.9% NaCl solution and synthetic urine, which were 87.6, 43 and 38.6 g/g water after 24 h, respectively. Moreover, the isoelectric point (pI) of the hydrogel was determined as pH = 8 by studying swelling behaviour at different pHs. In addition, the dependencies of the swelling behaviour with regard to the chemical modification, the ionic strength, the degree of crosslinking, as well as water absorbency with or without load were studied.     

Enhanced efficacy of nitrifying biomass by modified PVA_SB entrapment technique

In this study, we developed a novel technique for preparing polyvinyl alcohol (PVA) hydrogel as an immobilizing matrix by the addition of sodium bicarbonate. This resulted in an increase in the specific surface area of PVA_sodium bicarbonate (PVA_SB) hydrogel beads to 65.23 m² g^?1 hydrogel beads, which was approximately 85 and 14 % higher than those of normal PVA and PVA_sodium alginate (PVA_SA) hydrogel beads, respectively. The D _e value of PVA_SB hydrogel beads was calculated as 7.49 × 10^?4 cm² s^?1, which was similar to the D _e of PVA_SA hydrogel beads but nearly 38 % higher than that of the normal PVA hydrogel beads. After immobilization with nitrifying biomass, the oxygen uptake rate and the ammonium oxidation rate of nitrifying biomass entrapped in PVA_SB hydrogel beads were determined to be 19.53 mg O₂ g MLVSS^?1 h^?1 and 10.59 mg N g MLVSS^?1 h^?1, which were 49 and 43 % higher than those of normal PVA hydrogel beads, respectively. Scanning electron microscopy observation of the PVA_SB hydrogel beads demonstrated relatively higher specific surface area and revealed loose microstructure that was considered to provide large spaces for microbial growth. This kind of structure was also considered beneficial for reducing mass transfer resistance and increasing pollutant uptake.     

Preparation and characterization of a novel pH-sensitive chitosan-g-poly (acrylic acid)/attapulgite/sodium alginate composite hydrogel bead for controlled release of diclofenac sodium

A series of pH-sensitive composite hydrogel beads composed of chitosan-g-poly (acrylic acid)/attapulgite/sodium alginate (CTS-g-PAA/APT/SA) was prepared as drug delivery matrices crosslinked by Ca²⁺ owing to the ionic gelation of SA. The structure and surface morphology of the composite hydrogel beads were characterized by FTIR and SEM, respectively. pH-sensitivity of these composite hydrogels beads and the release behaviors of drug from them were investigated. The results showed that the composite hydrogel beads had good pH-sensitivity. The cumulative release ratios of diclofenac sodium (DS) from the composite hydrogel beads were 3.76% in pH 2.1 solution and 100% in pH 6.8 solutions within 24 h, respectively. However, the cumulative release ratio of DS in pH 7.4 solution reached 100% within 2 h. The DS cumulative release ratio reduced with increasing APT content from 0 to 50 wt%. The drug release was swelling-controlled at pH 6.8.     

Using polyaspartic acid hydro-gel as water retaining agent and its effect on plants under drought stress

Polyaspartic acid (PASP) hydrogel is an important and widely applied water-retaining agent, thanks to its special space network structure which contains a carboxyl group attached on the side chain. In this study, the PASP hydrogel with high water absorption rate (300–350 g H₂O/g hydrogel) was developed and adopted to transplant Xanthoceras sorbifolia seedlings in the ecological restoration project of Mount Daqing National Nature Reserve. Transplantation experiments showed that the survival rate and leaf water content index for X. sorbifolia seedlings were increased by 8–12% and 4–16%, respectively. Additionally, compared with the counterpart without PASP hydrogel, the value of chlorophyll fluorescence that was considered as one of the most important indicators of plant physiology, was significantly improved with the addition of PASP hydrogel. The PASP hydrogel displays a promising future for the applications of increasing the survival rate and simultaneously alleviating the drought stress effects on the pioneer plants in arid and semi-arid areas.     

The Novelty in Fabrication of Poly Vinyl Alcohol/κ-Carrageenan Hydrogel with <Emphasis Type="Italic">Lactobacillus bulgaricus</Emphasis> Extract as Anti-inflammatory Wound Dressing Agent

Material barrier properties to microbes are an important issue in many pharmaceutical applications like wound dressings. A wide range of biomaterials has been used to manage the chronic inflamed wounds. Eight hydrogel membranes of poly vinyl alcohol (PVA) with κ-carrageenan (KC) and Lactobacillus bulgaricus extract (LAB) have been prepared by using freeze–thawing technique. To evaluate the membranes efficiency as wound dressing agents, various tests have been done like gel fraction, swelling behavior, mechanical properties, etc. The antibacterial activities of the prepared membranes were tested against the antibiotic-resistant bacterial isolates. In addition, the safety usage of the prepared hydrogel was checked on human dermal fibroblast cells. The anti-inflammatory properties of the prepared hydrogel on LPS-PBMC cell inflammatory model were quantified using enzyme-linked immunosorbent assay (ELISA) and real-time polymerase chain reaction (RT-qPCR). The analysis data of TGA, SEM, gel fraction, and swelling behavior showed changes in properties of prepared PVA\KC\LAB hydrogel membrane than pure PVA hydrogel membrane. The antibacterial activities of the prepared membranes augmented in LAB extract-prepared membranes. Out of the eight used hydrogel membranes, the PVAKC4 hydrogel membrane is the safest one on fibroblast cellular proliferation with a maximum proliferation percentage 97.3%. Also, all the used hydrogel membrane showed abilities to reduce the concentration of IL-2 and IL-8 compared with both negative and positive control. In addition, almost all the prepared hydrogel membrane showed variable abilities to downregulate the expression of TNF-α gene with superior effect of hydrogel membrane KC1. PVA/KC/LAB extract hydrogel membrane may be a promising material for wound dressing application and could accelerate the healing process of the chronic wound because of its antimicrobial and anti-inflammatory properties.     

Synthesis and antioxidant activity evaluation of a novel cellulose hydrogel containing trans-ferulic acid

In the present work, we report the synthesis of cellulose hydrogel containing ferulic moieties and the evaluation of its antioxidant and scavenger activity. Acrylic groups were inserted onto cellulose backbone by a heterogeneous synthesis to produce two cellulose monomers with different degree of substitution (DS). The radical copolymerization of acrylcellulose (AcrC) with N,N-dimethylacrylamide (DMAA) was carried out in NH₃/Urea aqueous solution, in a range of composition between 24 and 60 wt% of AcrC. The obtained hydrogels were characterized by infrared spectroscopy (FT-IR). Their equilibrium swelling degree (α%) was evaluated. They showed good swelling behavior in simulating gastric, intracellular and intestinal fluids and no more different at various pH. The ferulic moieties were directly grafted on the free hydroxylic groups of cellulose hydrogel by acylation, using dicyclohexylcarbodiimide (DCC) and 4-hydroxybenzotriazole (HBT) as condensation agents. Finally, the antioxidant activity in inhibiting the lipid peroxidation, in rat-liver microsomal membranes, induced in vitro by two different sources of free radicals, 2,2′-azobis (2-amidinopropane) (AAPH) and tert-butyl hydroperoxide (tert-BOOH), was evaluated. The effects of scavenging DPPH (1,1-diphenyl-2-picrylhydrazyl) radicals were also investigated. Hydrogel was found to be very efficient scavengers of DPPH radicals. The results strongly suggested that the antioxidant hydrogel neutralize free radicals. This biomaterial could be successfully applied in pharmaceutical field both as prodrug of trans-ferulic acid than as carrier for photo and thermo-degradable drugs to improve their stability.     

Nutritional study of Kapparazii powderTM as a food ingredient

Kappaphycus alvarezii is one of the most important commercial sources of carrageenan. Red seaweeds are found in tropical areas, and K. alvarezii is famous for its high growth rate among other tropical red seaweeds. This study was conducted to produce Kapparazii powder^TM, a product comprised of high amount of carrageenan with valuable nutrients from K. alvarezii found in Sabah, Malaysia. Spray drying and an environmentally friendly process without using chemicals were employed to produce Kapparazii powder^TM. Physicochemical properties of Kapparazii powder^TM such as proximate composition (moisture, protein, lipid, ash, and crude fiber), mineral content, heavy metals, vitamins, amino acid, color, viscosity, gel strength, swelling capacity, and water and oil holding capacity were evaluated. Kapparazii powder^TM contained moisture (4.69?±?0.03 %), protein (5.11?±?0.02 %), lipid (1.00?±?0.02 %), ash (14.52?±?0.01 %), and crude fiber (0.93?±?0.02 %). Color analysis of Kapparazii powder^TM showed that lightness (L ^*)?=?89.51?±?0.02, redness (a ^*)?=??1.27?±?0.03, and yellowness (b^*)?=?5.49?±?0.02. The value of viscosity, gel strength, swelling capacity, and water and oil holding capacity of the Kapparazii powder^TM were 0.06?±?0.00 Pa.s, 82.77?±?3.66 gf, 100?±?0.00 mL.g^?1, 4.67?±?0.58 g.g^?1, and 5.11?±?0.36 g.g^?1, respectively. Moreover, Kapparazii powder^TM did not inhibit proliferation of L929 cells after 24 h of exposure at the highest concentration (2 mg.mL^?1). In conclusion, the Kapparazii powder^TM as a source of high nutrient hydrocolloid suggested on the point of healthy ingredient for food industry application.     

Potential availability of anaerobic treatment with digester slurry of animal waste for the reclamation of acid mine water containing sulfate and heavy metals

The use of an anaerobic digester slurry of cattle waste for the reclamation of acid mine water was examined. When the digester slurry was mixed with acid mine water, anaerobic digestion, including sulfate reduction and methanogenesis, was enhanced. In the mixture of acid mine water and the digester slurry, sulfate reduction proceeded without diminishing methanogenesis. The digester slurry and its supernatant (SDF-sup) showed a significant capacity to act as a strong alkaline reagent, and the pH of the acid mine water was markedly elevated by the addition of the digester slurry of SDF-sup even at the low ratio of 1% (v/v). Precipitation of heavy metals in the acid mine water occurred as the pH was elevated by the addition of SDF-sup. When the digester slurry was added at the ratio of 5% (v/v) to acid mine water which had been pretreated with SDF-sup, the rate of sulfate reduction increased with increasing the concentration of sulfate in the mixture up to about 1,400 mg·l⁻¹. In acid mine water pretreated with SDF-sup and supplemented with the digester slurry at the ratio of 5% (v/v), the maximum amount of sulfate reduced within 20 d of incubation was about 1,000 mg·l⁻¹, and the maximum rate of sulfate reduction was about 120 mg SO₄²⁻·l⁻¹·d⁻¹.     

Synthesis and characterization of novel guar gum hydrogels and their use as Cu sorbents

To prepare novel hydrogels for use in water technologies, guar gum was subjected to acid hydrolysis. The depolymerized guar gum obtained there from and the native guar gum were oxidized to their respective polycarboxylic forms using NO_x as oxidant. All these polymers were crosslinked with N,N-methylenebisacrylamide, and were used as Cu²⁺ sorbents. The candidate hydrogel exhibiting the highest uptake was used further to investigate the effect of external stimuli on sorption. The sorption on hydrogels was fast as the highest sorption was observed after 2 h at 40 °C and 20 ppm of Cu²⁺ ions. The hydrogel prepared from the oxidized guar gum afforded the maximum sorption capacity of 125.893 mg g⁻¹. Langmuir and Freundlich isotherms, and pseudo second order kinetics matches the experimental data. The evidence of sorption was obtained by characterizing Cu²⁺-loaded hydrogels by FTIR spectroscopy.     

The swelling behavior and network parameters of guar gum/poly(acrylic acid) semi-interpenetrating polymer network hydrogels

Guar gum/poly(acrylic acid) semi-interpenetrating polymer network (IPN) hydrogels have been prepared via free radical polymerization in the presence of a crosslinker of N,N′-methylene bisacrylamide (MBA). The kinetics of swelling and the water transport mechanism were studied as a function of the composition of the hydrogels and the pH of the swelling medium. Hydrogels showed enormous swelling in aqueous medium and displayed swelling characteristics, which were highly dependent on the chemical composition of the hydrogels and pH of the medium in which hydrogels were immersed (ionic strength I = 0.15 mol/L). The semi-INP hydrogels were characterized by evaluating various network parameters such as average molecular weight between crosslinks (M_c) crosslink density (ρ) and mesh size ξ.