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Gel Network (gel + network)
Selected AbstractsGel immobilization of acrylamide-modified single-stranded DNA template for pyrosequencingELECTROPHORESIS, Issue 12 2007Pengfeng Xiao Dr. Abstract A novel two-step process was developed to prepare ssDNA templates for pyrosequencing. First, PCR-amplified DNA templates modified with an acrylamide group and acrylamide monomers were copolymerized in 0.1,M NaOH solution to form polyacrylamide gel spots. Second, ssDNA templates for pyrosequencing were prepared by removing electrophoretically unbound complementary strands, unmodified PCR primers, inorganic pyrophosphate (PPi), and excess deoxyribonucleotides under alkali conditions. The results show that the 3-D polyacrylamide gel network has a high immobilization capacity and the modified PCR fragments are efficiently captured. After electrophoresis, gel spots copolymerized from 10,,L of the crude PCR products and the acrylamide monomers contain template molecules on the order of pmol, which generate enough light to be detected by a regular photomultiplier tube. The porous structure of gel spots facilitated the fast transportation of the enzyme, dNTPs and other reagents, and the solution-mimicking microenvironment guaranteed polymerase efficiency for pyrosequencing. Successful genotyping from the crude PCR products was demonstrated. This method can be applied in any laboratory; it is cheap, fast, simple, and has the potential to be incorporated into a DNA-chip format for high-throughput pyrosequencing analysis. [source] Electroaddressing of Cell Populations by Co-Deposition with Calcium Alginate HydrogelsADVANCED FUNCTIONAL MATERIALS, Issue 13 2009Xiao-Wen Shi Abstract Electroaddressing of biological components at specific device addresses is attractive because it enlists the capabilities of electronics to provide spatiotemporally controlled electrical signals. Here, the electrodeposition of calcium alginate hydrogels at specific electrode addresses is reported. The method employs the low pH generated at the anode to locally solubilize calcium ions from insoluble calcium carbonate. The solubilized Ca2+ can then bind alginate to induce this polysaccharide to undergo a localized sol-gel transition. Calcium alginate gel formation is shown to be spatially controlled in the normal and lateral dimensions. The deposition method is sufficiently benign that it can be used to entrap the bacteria E. coli. The entrapped cells are able to grow and respond to chemical inducers in their environment. Also, the entrapped cells can be liberated from the gel network by adding sodium citrate that can compete with alginate for Ca2+ binding. The capabilities of calcium alginate electrodeposition is illustrated by entrapping reporter cells that can recognize the quorum sensing autoinducer 2 (AI-2) signaling molecule. These reporter cells were observed to recognize and respond to AI-2 generated from an external bacterial population. Thus, calcium alginate electrodeposition provides a programmable method for the spatiotemporally controllable assembly of cell populations for cell-based biosensing and for studying cell-cell signaling. [source] Calcite Growth in Hydrogels: Assessing the Mechanism of Polymer-Network Incorporation into Single CrystalsADVANCED MATERIALS, Issue 4 2009Hanying Li Calcite crystals grown in agarose hydrogels incorporate the gel network while retaining their single-crystal nature. The amount of gel network that is incorporated is determined by two competing factors: crystallization pressure promotes the exclusion of the gel network, while faster growth rates favor its incorporation. [source] Improved compatibility of EVOH/LDPE blends by ,-ray irradiationADVANCES IN POLYMER TECHNOLOGY, Issue 3 2009Haihong Li Abstract The change of compatibility of poly(ethylene- co -vinyl alcohol) (EVOH)/LDPE blends induced by,-ray radiation was studied. Gel extraction experiment results show that the gel fraction of blends increases linearly with the content of LDPE and reaches a maximum at 100 kGy, because neat EVOH is difficult to cross-link by irradiation. A comparison of theoretical and experimental gel contents indicates that some EVOH molecular chains enter the LDPE gel network. The peak at 3363 cm,1 on the Fourier transform infrared spectrum of pure blend gel is assigned to typical stretching of an OH bond, which indicates that a "graft" reaction occurs in the interface between EVOH and LDPE phases during the irradiation process. Mechanical property measurement results support such a structural change. The tensile strength of cross-linked blends increases with absorbed dose first, reaches a maximum value at 150 kGy, and then decreases with dose. A similar trend can also be observed in bending tests. © 2009 Wiley Periodicals, Inc. Adv Polym Techn 28:192,198, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20160 [source] Structure and drug release in a crosslinked poly(ethylene oxide) hydrogelJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 5 2007Boris Y. Shekunov Abstract Hydrogels are a continuously expanding class of pharmaceutical polymers designed for sustained or controlled drug release. The structure and intermolecular interactions in such systems define their macroscopic properties. The aim of this study was to investigate the mechanism of swelling, drug impregnation, and drug release from poly(ethylene oxide) (PEO) gel crosslinked by urethane bonds. A combination of SAXS/WAXS/SANS techniques enabled us to determine the phase transition between lamellar and extended gel network, and to apply different descriptions of crystallinity, based on lamellar and crystal lattice structures. It is shown that even low (1,7% w/w) loading of model drugs acetaminophen and caffeine, produced significant disorder in the polymer matrix. This effect was particularly pronounced for acetaminophen due to its specific ability to form complexes with PEO. The drug-release profiles were analyzed using a general cubic equation, proposed for this work, which allowed us to determine the gel hydration velocity. The results indicate that the release profiles correlate inversely with the polymer crystallinity. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96: 1320,1330, 2007 [source] RHEOLOGICAL PROPERTIES, WHEY SEPARATION, AND MICROSTRUCTURE IN SET-STYLE YOGURT: EFFECTS OF HEATING TEMPERATURE AND INCUBATION TEMPERATUREJOURNAL OF TEXTURE STUDIES, Issue 5-6 2003WON-JAE LEE The effects of heat treatment and incubation temperature on the rheological and microstructural properties of yogurt were studied. A central composite experimental design and response surface methodology were used for data analysis. The rheological properties were determined by dynamic low amplitude oscillation and the amount of spontaneous whey separation was quantified by the volumetric flask test. Confocal scanning laser microscopy was used to examine the gel structure. The storage moduli of yogurts increased with an increase in heating temperature and a decrease in incubation temperature. The maximum loss tangent value during gelation, permeability, and amount of spontaneous whey separation of yogurts increased with a decrease in heating temperature and with an increase in incubation temperature. These parameters indicated an increased possibility for rearrangements, which was confirmed by presence of large pores in the gel network. Second order polynomial models successfully predicted the effects of heating temperature and incubation temperature on the rheological properties, permeability, and whey separation of yogurts. Whey separation was negatively correlated with storage modulus (r= -0.66), and was positively correlated with the maximum loss tangent (r= 0.63) and permeability (r= 0.78). This study demonstrates that weak yogurt gels, which have high loss tangent values, favor rearrangements in the network and the resulting network has larger pores (high permeability) and exhibits greater whey separation. [source] Molecular Characteristics of Poly(N -isopropylacrylamide) Separated from Nanocomposite Gels by Removal of Clay from the Polymer/Clay NetworkMACROMOLECULAR RAPID COMMUNICATIONS, Issue 8 2010Kazutoshi Haraguchi Abstract The extraordinary mechanical and swelling/deswelling properties of nanocomposite (NC) gels are attributed to their unique organic (polymer)/inorganic (clay) network structure. In this study, poly(N -isopropylacrylamide) (PNIPA) was successfully separated from an NC gel network by decomposing the clay (hectorite) using hydrofluoric acid (HF). A very low HF concentration (0.2,wt.-%) was adequate for the decomposition of the clay without causing any damage to PNIPA. The separated PNIPA had a high (=5.5,×,106 g,·,mol,1). Also, was almost constant regardless of the clay concentration (Cclay,=,1,25,×,10,2 mol,·,l,1), even though the properties of the NC gel varied widely over this Cclay range. Comparisons of NC gels, PNIPA, and SiO2 -NC gels indicated that the clay platelets specifically play an important role in NC gels. [source] Pyroelectric investigations of a hydrogen bonded ferroelectric liquid crystal gel by LIMMPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 1 2005Jianjun Li Abstract The laser intensity modulation method (LIMM) is employed to determine spatially resolved polarization distributions in sandwich cells containing a hydrogen-bonded ferroelectric liquid crystal (FLC) gel. At no external electric fields, contributions to the distributions at the surface of the FLC layer are dominating in all the samples with different concentration of gel former. These are attributed to non-vanishing polarization due to surface interaction. In this case, the effect of hydrogen-bonded network on the polarization distribution is not visible. In external electric fields, additional contribution to the resulting distribution caused by the induced polarization due to unwinding the FLC helix has been observed. Furthermore, the influence of hydrogen-bonded network on the polarization distribution is also detected when the gel former content is increased up to 5.0,wt%. Therein the shape of the measured pyrospectra is completely different to other FLC gel samples with lower gel former concentration, where their maximum distributions still locate at the surface of FLC layer which is comparable to the initial field-free state. These result indicate that the helical structure and orientation director of FLC are able to be stabilized effectively by the gel network even under strong external electric field. Copyright © 2004 John Wiley & Sons, Ltd. [source] Physicochemical properties of the thermal gel of water-washed meat in the presence of the more soluble fraction of porcine sarcoplasmic proteinANIMAL SCIENCE JOURNAL, Issue 1 2007Yuji MIYAGUCHI ABSTRACT We investigated the physicochemical properties of the thermal gel of water-washed pork meat (WWM) in the presence of the soluble fraction of porcine sarcoplasmic protein (SP) obtained with ammonium sulfate at 75 percent saturation. Two precipitated fractions of SP were obtained at 0,50 percent and 50,75 percent saturation, named SP-f1 and SP-f2, respectively, and the soluble fraction obtained at 75 percent saturation, SP-f3, was used. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that SP-f3 contained mainly glyceraldehyde-3-phosphate dehydrogenase (GAPDH), while SP-f1 and SP-f2 had other SPs such as phosphorylase b, enolase, actin and phosphoglycerate mutase. The gel strength of WWM was greater when SP-f3 rather than one of various animal proteins such as bovine plasma (BP), egg white, or whey protein isolates (WPI), was added and SP-f3 had a gel-enhancing effect as good as that of polyphosphate (PP). The gel strength of WWM with added SP-f3 increased significantly with NaCl at 0.15 mol/L or more, but not in the absence of NaCl (0 mol/L). The effect of SP-f3 was evident at neutral pH and maximum gel strength was obtained at a pH above 6.0. Differential scanning calorimetric (DSC) analysis showed that an endothermic peak corresponding to myosin heads in WWM shifted to a lower temperature with the addition of SP-f3, as in the case of PP, though there was no such shift in the presence of other animal proteins (BP, egg white and WPI), suggesting that SP-f3 increases the gel strength of WWM through the dissociation of actomyosin similar to PP. Scanning electron microscopy (SEM) revealed wall-like structures among the protein strands in the WWM gel matrix in the presence of SP-f3. The results of DSC and SEM indicated that the formation of a gel network in meat products is reinforced with GAPDH in SP after the interaction between GAPDH and myofibrillar protein. [source] Self-Assembly of Two-Component Gels: Stoichiometric Control and Component SelectionCHEMISTRY - A EUROPEAN JOURNAL, Issue 2 2009Andrew Abstract Two-component systems capable of self-assembling into soft gel-phase materials are of considerable interest due to their tunability and versatility. This paper investigates two-component gels based on a combination of a L -lysine-based dendron and a rigid diamine spacer (1,4-diaminobenzene or 1,4-diaminocyclohexane). The networked gelator was investigated using thermal measurements, circular dichroism, NMR spectroscopy and small angle neutron scattering (SANS) giving insight into the macroscopic properties, nanostructure and molecular-scale organisation. Surprisingly, all of these techniques confirmed that irrespective of the molar ratio of the components employed, the "solid-like" gel network always consisted of a 1:1 mixture of dendron/diamine. Additionally, the gel network was able to tolerate a significant excess of diamine in the "liquid-like" phase before being disrupted. In the light of this observation, we investigated the ability of the gel network structure to evolve from mixtures of different aromatic diamines present in excess. We found that these two-component gels assembled in a component-selective manner, with the dendron preferentially recognising 1,4 - diaminobenzene (>70,%), when similar competitor diamines (1,2- and 1,3-diaminobenzene) are present. Furthermore, NMR relaxation measurements demonstrated that the gel based on 1,4-diaminobenzene was better able to form a selective ternary complex with pyrene than the gel based on 1,4-diaminocyclohexane, indicative of controlled and selective ,,, interactions within a three-component assembly. As such, the results in this paper demonstrate how component selection processes in two-component gel systems can control hierarchical self-assembly. [source] Kinetics of the volume phase transition in poly(n -isopropylacrylamide) gels prepared under high pressureJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2001Tadayosi Kitada Abstract New poly(N -isopropylacrylamide) gels were prepared under high pressure (ca. 200 MPa) during gelation. The preparation-pressure dependence of the deswelling speed of the gels was measured with a conventional T-jump method. The deswelling time of a gel rod 2.2 mm in diameter prepared at 193 MPa was about 200 s, 1000 times faster than that of a homogeneous poly(N -isopropylacrylamide) gel. Moreover, the collective diffusion coefficient, the thermal fluctuation, and the ensemble-average intensity of the swollen gel networks were obtained with dynamic light scattering measurements. Both the enthalpy and entropy of the gels were estimated from equilibrium swelling curves with the Flory,Huggins interaction parameter evaluated with mean field theory based on the Flory-type of the Gibbs free-energy formula. It was found that the networks of the gels had an inhomogeneous structure newly introduced by the preparation pressure. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2315,2325, 2001 [source] Increased plasma fibrin gel porosity in patients with Type I diabetes during continuous subcutaneous insulin infusionJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 6 2003G. Jörneskog Summary.,Background:,Patients with Type 1 diabetes have a tighter plasma fibrin gel structure, to which impaired glycemic control might contribute. Improved glycemic control can be achieved with continuous subcutaneous insulin infusion (CSII). Objectives:,The aim of the present study was to investigate the effect of CSII on plasma fibrin gel properties and circulating markers of inflammatory activity in patients with Type 1 diabetes. Patients and methods:,Twenty-eight patients were investigated before and after 4,6 months' treatment with CSII. Fibrin gel structure formed in vitro from plasma samples was investigated by liquid permeation of hydrated fibrin gel networks. P-fibrinogen was analyzed by a syneresis method. Comparisons were made between patients with improved (> 0.5%) and unchanged (< 0.5%) glucosylated hemoglobin (HbA1c) during CSII. Results:,Eighteen patients showed improved and 10 patients unchanged HbA1c during CSII. P-fibrinogen, high sensitive C-reactive protein and serum amyloid A-antigen were not significantly changed, while fibrin gel permeability (Ks) and fiber mass,length ratio (µ) increased in both groups (P < 0.02). P-insulin and triglycerides decreased (P < 0.05) in both groups, while reductions of total cholesterol and intercellular adhesion molecule-1 were seen only in patients with improved HbA1c (P < 0.05). Absolute changes in Ks were inversely correlated to changes in plasma fibrinogen (r = 0.50; P < 0.01) and in LDL-cholesterol (r = 0.46; P < 0.05). Conclusions:,Treatment with CSII in patients with Type 1 diabetes is associated with increased plasma fibrin gel porosity. Slight attenuation of the inflammatory activity was also observed. The changes in fibrin gel porosity seem to be mainly mediated by changes in plasma fibrinogen and blood lipids, and are probably secondary to improved insulin sensitivity. [source] Fabrication of Silver Nanoparticles in Hydrogel Networks,MACROMOLECULAR RAPID COMMUNICATIONS, Issue 16 2006Y. Murali Mohan Abstract Summary: This paper describes a simple and facile approach to fabricate well dispersed silver nanoparticles (AgNPs) in poly[N -isopropylacrylamide- co -(sodium acrylate)] hydrogels. The silver nanoparticles formed are spherical in shape with a narrow size distribution in the hydrogel networks in which the nanoparticles are stabilized by the polymer network. Uniformly dispersed silver nanoparticles were obtained with poly[N -isopropylacrylamide- co -[sodium acrylate)] hydrogels, whereas a poly(N -isopropylacrylamide)/poly(sodium acrylate) IPN gel showed aggregated nanoparticles. It is demonstrated that the hydrogel network structure determines the size and shape of the nanoparticles. These particles are more stable in the gel networks compared to other reduction methods. The hydrogel/silver nanohybrids were well characterized by XRD, UV-vis spectrometry, scanning electron microscopy and transmission electron microscopy. Schematic representation of the preparation of Ag nanoparticles in hydrogel networks. [source] Casein gelation under simultaneous action of transglutaminase and glucono-,-lactoneMOLECULAR NUTRITION & FOOD RESEARCH (FORMERLY NAHRUNG/FOOD), Issue 3 2004Orquídea Menéndez Abstract Casein solutions (5% w/v) were treated with microbial transglutaminase (MTG) and glucono-,-lactone (GDL) under varying conditions in order to obtain gels. Storage modulus (G ,) and gelation time of the gels were measured by oscillation rheometry, while protein cross-linking was determined by gel permeation chromatography. The addition of only GDL to milk resulted in very weak gels, while MTG on its own was not able to create gel networks. Simultaneous action of both ingredients led to gels, the firmness of which was linearly related to the added amount of MTG, but passed through a maximum with rising GDL concentrations. Using chromatographical analysis, increasing G , values were interrelated with the formation of MTG-induced oligomers. The gelation time was directly proportional to the GDL concentration but not influenced by the addition of MTG within the studied range of concentration. [source] Chromogenic polymer gels for reversible transparency and color control with temperature at a constant volumePOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 7 2002A. Seeboth Abstract The preparation and characterization of novel chromogenic materials has developed extremely rapid in the last years. Among them, thermotropic and thermochromic polymer gel networks have met with growing interest, because of their advanced properties. These novel polymer gels exhibit pronounced changes in transparency and/or color intensity in a practically relevant temperature range. For many future technical applications it is an essential condition, that the volume of the used gel materials is independent of temperature. A current overview of this field is given. Copyright © 2002 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||||||||