Distribution by Scientific Domains
Distribution within Polymers and Materials Science

Kinds of Hydrogels

  • alginate hydrogel
  • biodegradable hydrogel
  • chitosan hydrogel
  • composite hydrogel
  • copolymer hydrogel
  • gelatin hydrogel
  • hybrid hydrogel
  • injectable hydrogel
  • nanocomposite hydrogel
  • physical hydrogel
  • polymer hydrogel
  • polymeric hydrogel
  • responsive hydrogel
  • semi-ipn hydrogel
  • superabsorbent hydrogel
  • synthesized hydrogel
  • synthetic hydrogel
  • thermoresponsive hydrogel

  • Terms modified by Hydrogels

  • hydrogel bead
  • hydrogel composite
  • hydrogel film
  • hydrogel formation
  • hydrogel material
  • hydrogel matrix
  • hydrogel membrane
  • hydrogel nanofiber
  • hydrogel network
  • hydrogel particle
  • hydrogel scaffold
  • hydrogel surface
  • hydrogel system

  • Selected Abstracts

    Tissue Integration of Polyacrylamide Hydrogel: An Experimental Study of Periurethral, Perivesical, and Mammary Gland Tissue in the Pig

    BACKGROUND Polyacrylamide hydrogel (PAAG) is a nondegradable water-based polymer with high viscoelasticity. The gel is used as a tissue filler, the only risk being prolonged infection with anaerobic, contaminating microorganisms if not treated early with broad-spectrum antibiotics. OBJECTIVE With silicone gel as reference, PAAG tissue integration and migration was studied in a longitudinal study of the pig. MATERIALS AND METHODS Forty-one pigs were used. PAAG and silicone gel were injected into mammary tissue, and PAAG was injected into urethral or bladder wall or the anal canal. Tissues and regional lymph nodes were examined at 1, 1 1/2, 3, 3 1/2, 6, 12, and 14 months, and other lymph nodes and organs were examined at 1, 6, 12, and 14 months. RESULTS PAAG was invaded by macrophages and giant cells that were gradually replaced by a network of fibrous tissue. Silicone gel was seen inside these cells or as large vacuoles, surrounded by a fibrous capsule. Regional lymph nodes contained PAAG only at 1 1/2 months and silicone gel at 12 months. CONCLUSION PAAG is a stable, viscoelastic bulking agent, which unlike silicone gel is slowly integrated within its host tissue via a thin fibrous network. Long-term risk of fibrosis and migration is minimal. [source]

    Periodic Micropatterning of Polyethylene Glycol Diacrylate Hydrogel by Laser Interference Lithography Using Nano- and Femtosecond Pulsed Lasers,

    Andrés F. Lasagni
    In this article, we report on the fabrication of periodic arrays using multibeam laser interference patterning (MLI) with both nanosecond and femtosecond lasers on hydrogel materials. Configurations involving two, four, and five laser beams were utilized being able to produce a wide range of periodic arrays. [source]

    Integration of a Chemical-Responsive Hydrogel into a Porous Silicon Photonic Sensor for Visual Colorimetric Readout

    Lisa M. Bonanno
    Abstract The incorporation of a chemo-responsive hydrogel into a 1D photonic porous silicon (PSi) transducer is demonstrated. A versatile hydrogel backbone is designed via the synthesis of an amine-functionalized polyacrylamide copolymer where further amine-specific biochemical reactions can enable control of cross-links between copolymer chains based on complementary target,probe systems. As an initial demonstration, the incorporation of disulfide chemistry to control cross-linking of this hydrogel system within a PSi Bragg mirror sensor is reported. Direct optical monitoring of a characteristic peak in the white light reflectivity spectrum of the incorporated PSi Bragg mirror facilitates real-time detection of the hydrogel dissolution in response to the target analyte (reducing agent) over a timescale of minutes. The hybrid sensor response characteristics are shown to systematically depend on hydrogel cross-linking density and applied target analyte concentration. Additionally, effects due to responsive hydrogel confinement in a porous template are shown to depend on pore size and architecture of the PSi transducer substrate. Sufficient copolymer and water is removed from the PSi transducer upon dissolution and drying of the hydrogel to induce color changes that can be detected by the unaided eye. This highlights the potential for future development for point-of-care diagnostic biosensing. [source]

    Dual Stimuli-Responsive Supramolecular Polypeptide-Based Hydrogel and Reverse Micellar Hydrogel Mediated by Host,Guest Chemistry

    Yi Chen
    Abstract Versatile strategies are currently being discovered for the fabrication of synthetic polypeptide-based hybrid hydrogels, which have potential applications in polymer therapeutics and regenerative medicine. Herein, a new concept,the reverse micellar hydrogel,is introduced, and a versatile strategy is provided for fabricating supramolecular polypeptide-based normal micellar hydrogel and reverse micellar hydrogels from the same polypeptide-based copolymer via the cooperation of host,guest chemistry and hydrogen-bonding interactions. The supramolecular hydrogels are thoroughly characterized, and a mechanism for their self-assembly is proposed. These hydrogels can respond to dual stimuli,temperature and pH,and their mechanical and controlled drug-release properties can be tuned by the copolymer topology and the polypeptide composition. The reverse micellar hydrogel can load 10% of the anticancer drug doxorubicin hydrochloride (DOX) and sustain DOX release for 45 days, indicating that it could be useful as an injectable drug delivery system. [source]

    Modulation of Viscoelasticity and HIV Transport as a Function of pH in a Reversibly Crosslinked Hydrogel

    Julie I. Jay
    Abstract Materials that respond to physiological stimuli are important in developing advanced biomaterials for modern therapies. The reversibility of covalent crosslinks formed by phenylboronate (PBA) and salicylhydroxamate (SHA) has been exploited to provide a pH-responsive gel for application to the vaginal tract. Dynamic rheology reveals that the gel frequency-dependent viscoelastic properties are modulated by pH. At pH 4.8 the viscous component dominates throughout most of the frequency range. As the pH increases, the characteristic relaxation time continues to increase while the G,Plateau levels off above pH 6. At pH 7.5, the elastic component dominates throughout the frequency sweep and is predominately independent of frequency. Particle tracking assesses the transport of both fluorescently labeled HIV-1 and 100-nm latex particles in the PBA,SHA crosslinked gel as a function of pH. At pH 4.8 the ensemble-averaged mean squared displacement at lag times greater than three seconds reveals that transport of the HIV-1 and 100-nm particles becomes significantly impeded by the matrix, exhibiting diffusion coefficients less than 0.0002,µm2 s,1. This pH-responsive gel thus displays properties that have the potential to significantly reduce the transport of HIV-1 to susceptible tissues and thus prevent the first stage of male-to-female transmission of HIV-1. [source]

    Mesoscopic Network Structure of a Semi-Rigid Polyion Complex Nested in a Polycationic Hydrogel

    ADVANCED MATERIALS, Issue 46 2009
    Zi Liang Wu
    A dual network gel, consisting of a micrometer-scaled network-like structure of a semi-rigid polyion complex nested in a nanometer-scaled polycationic network, has been developed by polymerization of a cationic monomer in the presence of a small amount of semi-rigid polyanion as dopant. Self-assembly and viscoelastic phase separation (see figure) compete with each other during the polymerization and render the micrometer-scaled network structure, which is permanently frozen by the subsequent gelation. [source]

    Artifical Muscles: Nanocomposite Hydrogel with High Toughness for Bioactuators (Adv. Mater.

    ADVANCED MATERIALS, Issue 17 2009
    The inside cover shows a nanofibrous hydrogel based on ferritin for a bioinspired nanocomposite actuator, reported in work by Seon Jeong Kim and co-workers on p. 1712. The ferritin-based nanofibrous hydrogels demonstrate synergy between the ferritin protein and a synthetic polymer matrix, as the protein shell of ferritin behaves like an elastic nanospring in the polymer. The actuator is reversibly actuated by chemical energy under external tensile stress, showing improved response speed in comparison to bulk and microfiber hydrogels, coming closer to the goal of mimicking the performance of natural muscle. [source]

    Nanocomposite Hydrogel with High Toughness for Bioactuators

    ADVANCED MATERIALS, Issue 17 2009
    Min Kyoon Shin
    Ferritin-based nanofibrous hydrogels that demonstrate synergy between the ferritin protein and the synthetic polymer matrix are fabricated. The hybrid hydrogels showed enhanced mechanical properties and repeated expansion and contraction without showing severe creep during pH switching. The ferritin nanoparticles incorporated into the hydrogel nanofibers improved the actuation stability of a hydrogel actuator by acting as elastic nanosprings in a nanoscale polymer. [source]

    An Electro- and Thermochromic Hydrogel as a Full-Color Indicator,

    ADVANCED MATERIALS, Issue 19 2007
    K. Ueno
    Electric-field-triggered "two-state switching" between two arbitrary structural colors (see figure) in the entire visible region at certain temperatures is shown by a stimuli-responsive chromic hydrogel. The external rapid tuning in the structural color of this hydrogel is successfully achieved by introducing a periodically ordered interconnecting porous structure. [source]

    A Novel Hydrogel with High Mechanical Strength: A Macromolecular Microsphere Composite Hydrogel,

    ADVANCED MATERIALS, Issue 12 2007
    T. Huang
    A novel hydrogel with a new, well- defined network structure is prepared through a two-step method in which the radiation-peroxidized macromolecular microspheres act as both initiators and crosslinkers. The macromolecular microsphere composite hydrogel (see figure) can effectively dissipate applied mechanical stress and has extremely high mechanical strength. Some of the hydrogels can nearly completely recover their original shapes, even after an extremely high strain (99.7%) in compression tests. [source]

    Influence of Solute Charge and Hydrophobicity on Partitioning and Diffusion in a Genetically Engineered Silk-Elastin-Like Protein Polymer Hydrogel

    Adam A. Dinerman
    Abstract The influence of solute hydrophobicity and charge on partitioning and diffusion in physically crosslinked networks of a genetically engineered SELP polymer was investigated. A series of fluorescent dyes were used to assess the impact of solute charge and hydrophobicity on release behavior. The mechanism of solute release from the SELP hydrogel appeared to vary as a function of dye hydrophobicity. The extent of FITC attachment to amine-terminated G4 dendrimers influenced SELP hydrogel partitioning more than dendrimer diffusion properties. Results suggest the possibility of controlling solute release from SELP hydrogels by modifying the hydrophobicity and surface charge of drugs and drug/polymer conjugates as well as the possibility of "designing-in" solute-specific interactions. [source]

    Effect of Motif-Programmed Artificial Proteins on the Calcium Uptake in a Synthetic Hydrogel

    Traian V. Chirila
    Abstract Motif-programmed artificial proteins with mineralization-related activity were covalently immobilized onto the surface of a hydrogel, poly(2-hydroxyethyl methacrylate) (PHEMA). We investigated the influence of assaying conditions upon the ability of three selected proteins (PS64, PS382 and PS458) to modulate calcification in vitro. A long-term assay measuring the real amount of calcium phosphate phase in the protein-modified PHEMA showed that all proteins enhanced the uptake of calcium by the hydrogel. For PS382 and PS458, this is a behaviour opposite to that displayed when the same proteins were tested in a free state by a rapid solution assay. Such difference may be attributed to a restricted mobility of the proteins due to immobilization. [source]

    Bioadhesive Properties of a Polyaminoacidic Hydrogel: Evaluation by ATR FT-IR Spectroscopy

    Filippo Saiano
    Abstract Summary: The bioadhesive properties of a novel chemical hydrogel based on a polymer of protein-like structure, have been investigated by using ATR FT-IR spectroscopy. In particular, the copolymer PHG obtained by partial derivatization of PHEA with GMA was chemically crosslinked by UV irradiation at 313 nm. Crosslinked PHG was treated with water to obtain a swelled sample, named PHG-UV gel, that was brought into contact with a phosphate buffer/citric acid solution at pH 7.0 in the absence or in the presence of mucin at various concentrations (0.01, 0.1 and 1 wt.-%). Preliminary dynamic swelling studies have evidenced the occurrence of an interaction between the PHG-UV gel and the glycoprotein. This result was confirmed by ATR FT-IR measurements. A diffusion model using a solution of Ficks' second law was employed to determine the diffusion coefficient of water into PHG-UV gel as a consequence of adsorption and/or interdiffusion which occur at the PHG-UV gel/mucin solution interface. Experimental results suggest a potential use of PHG-UV gel to prepare bioadhesive devices. [source]

    Novel Biodegradable and Thermosensitive Dex-AI/PNIPAAm Hydrogel

    Xian-Zheng Zhang
    Abstract The dextran-allyl isocyanate/poly(N -isopropylacrylamide) (Dex-AI/PNIPAAm) hydrogel was designed and prepared by copolymerization of the modified dextran with N -isopropylacrylamide (NIPAAm). This novel Dex-AI/PNIPAAm hydrogel is biodegradable and intelligent due to its biodegradable dextran linkage and thermosensitive PNIPAAm moiety. With an increase in dextran content, it exhibits the increased lower critical solution temperature (LCST) and decreased porous microstructure. Also, the thermosensitivity of this hydrogel is also controllable and adjustable depending on the different compositions. SEM micrographs of the Dex-AI/PNIPAAm hydrogels. [source]

    Synthesis of Guanidinium-Modified Hyaluronic Acid Hydrogel

    Oommen P. Varghese
    Abstract In this report, a new guanidinylating reagent is presented, which was developed without any protection/deprotection strategy and was successfully employed for linking to hyaluronan in aqueous solution. The dually functionalised HA biopolymer bearing guanidinium and hydrazide groups was synthesised to form hydrogel in less than a minute when mixed with aldehyde-modified HA. This hydrogel exhibited higher storage modulus with enhanced stability in PBS when compared to the non-guanidine-containing gel. The gel shift assay showed that this biopolymer formed a stable complex with DNA as well as efficient gene transfection to cells that express HA-receptor CD44. The toxicity studies of this polymer with fibroblast cells revealed that the cells were almost 80% viable after 4,d of incubation at high HA concentration (2.5,×,10,3,M). [source]

    Color-Oscillating Photonic Crystal Hydrogel

    Entao Tian
    Abstract In this work, a color-oscillating system is first developed by combining the intrinsic peristaltic motion of a Landolt pH-oscillator with the structure color of a well-designed pH-sensitive photonic crystal hydrogel. As a result, the pH oscillation reaction procedure could be distinctly monitored by the distinct change of structure color/optic signal. The oscillation rhythm of the pH well coincides with that of the stopband/structure color. The oscillation detail of each cycle can also be clearly monitored by color change. This work would be of great significance for the promising applications of real-time monitoring of the microactuator by optical signal or structure color. [source]

    Thermo-Responsive Hydrogels with Nanodomains: Rapid Shrinking of a Nanogel-Crosslinking Hydrogel of Poly(N -isopropyl acrylamide)

    Nobuyuki Morimoto
    Abstract Rapidly shrinking poly(N -isopropyl acrylamide) (PNIPAM) hydrogels are prepared by crosslinking with self-assembled nanogels that consist of cholesteryl- and methacryloyl-substituted pullulan (CHPMA). The CHPMA nanogel (Rh,=,26.4 nm) was used as a crosslinker for a hydrophilic nanodomain. Transmission electron microscopy images of the nanogel-crosslinked PNIPAM hydrogel reveal a well-defined nanoporous structure. The nanogel-crosslinked PNIPAM hydrogel shows rapid shrinking based on its structure. The shrinking half-time was ,2 min, which is about 3,400 times faster than that of a PNIPAM hydrogel crosslinked by methylene(bisacrylamide). [source]

    Polymeric gels and hydrogels for biomedical and pharmaceutical applications

    Joseph Jagur-Grodzinski
    Abstract Hydrogels are formed when a three-dimensional polymeric network is loosely crosslinked. They are swollen by water but not dissolved in it. Hydrogels may display reversible sol,gel transitions, induced by changes in the environmental conditions such as temperature, pH, ionic strength, phase separation, wave length of light, crystallinity, etc. Hydrogel is described as smart or intelligent when sharp transition is induced by small change in such conditions. For the shape-memory hydrogels, reversible change in shape may also be induced by such stimuli. The preparation and applications of the molecularly imprinted polymeric hydrogels (MIPs) are illustrated by a few examples. The use of shape sensitive hydrogels in microfluidic is mentioned. Application of hydrogels for chronobiology and chronotherapy is outlined. The conversion of hydrogels into aerogels and their respective properties is discussed. Copyright © 2009 John Wiley & Sons, Ltd. [source]

    An Aptamer Cross-Linked Hydrogel as a Colorimetric Platform for Visual Detection,

    ANGEWANDTE CHEMIE, Issue 6 2010
    Zhi Zhu
    Der Gel-Sol-Übergang eines Hydrogels, in dem ein Enzym eingeschlossen ist, kann effizient durch die Bindung eines Substrats gesteuert werden. Das freigesetzte Enzym kann anschließend als Katalysator wirken und das Signal verstärken (siehe Bild). Schon 20,ng Kokain lassen sich binnen 10,min anhand eines Farbumschlags mit bloßem Auge nachweisen. [source]

    A pH-Triggered, Fast-Responding DNA Hydrogel,

    ANGEWANDTE CHEMIE, Issue 41 2009
    Enjun Cheng
    Wer schaltet am schnellsten? Ein schnelles, pH-responsives DNA-Hydrogel (rechts im Bild) wurde ausgehend von einer dreiarmigen DNA-Nanostruktur (links) unter Bildung von intermolekularen i-Strukturen (Mitte) erhalten. Eine Änderung des pH-Werts der Umgebung genügt, damit das Hydrogel binnen Minuten in den ungelierten Zustand wechselt. [source]

    Fluorescent Nanogel of Arsenic Sulfide Nanoclusters,

    ANGEWANDTE CHEMIE, Issue 34 2009
    Junzhong Wang Dr.
    Markieren und zerstören: Arsensulfidcluster, die mit Ethylendiaminderivaten passiviert wurden, bilden in Wasser ein fluoreszierendes und pH-responsives kolloidales Hydrogel (siehe Schema). Dieses AsS-Nanogel dient nicht nur als Fluoreszenzmarker, sondern wirkt darüber hinaus cytotoxisch auf die Krebszellen OVCAR-3 und HeLa. [source]

    Effect of Photocrosslinkable Chitosan Hydrogel and Its Sponges to Stop Bleeding in a Rat Liver Injury Model

    ARTIFICIAL ORGANS, Issue 4 2010
    Takuya Horio
    Abstract This study examined the hemostatic efficacy of photocrosslinkable chitosan hydrogel-mixed photocrosslinked chitosan sponges (PCM-S) after hepatic injury in rats. The left lobe of the liver was penetrated with a dermal punch to produce a penetrating wound in heparinized and nonheparinized rats. Treated rats either had PCM-S applied into the wound and then were immediately ultraviolet irradiated, or they had TachoComb (TC) inserted into the wound. Blood loss, hemostasis, and survival were quantified after the hepatic injury. Measurements on serum alanine aminotransferase in nonheparinized rats and hemoglobin concentrations and histologic examinations in heparinized rats were performed to assess hepatic function. Although the hemostatic effect in the PCM-S-treated nonheparinized rats was identical to that of the TC-treated group, PCM-S-treatment has higher hemostatic effect in heparinized rats. No adverse events related to the use of PCM-S were detected in blood and histologic examinations. [source]

    Hydrogel-Based Engineered Skeletal Muscle Grafts Normalize Heart Function Early After Myocardial Infarction

    ARTIFICIAL ORGANS, Issue 1 2009
    Sunil Kanwal MD
    No abstract is available for this article. [source]

    Tissue Integration of Polyacrylamide Hydrogel: An Experimental Study of Periurethral, Perivesical, and Mammary Gland Tissue in the Pig

    BACKGROUND Polyacrylamide hydrogel (PAAG) is a nondegradable water-based polymer with high viscoelasticity. The gel is used as a tissue filler, the only risk being prolonged infection with anaerobic, contaminating microorganisms if not treated early with broad-spectrum antibiotics. OBJECTIVE With silicone gel as reference, PAAG tissue integration and migration was studied in a longitudinal study of the pig. MATERIALS AND METHODS Forty-one pigs were used. PAAG and silicone gel were injected into mammary tissue, and PAAG was injected into urethral or bladder wall or the anal canal. Tissues and regional lymph nodes were examined at 1, 1 1/2, 3, 3 1/2, 6, 12, and 14 months, and other lymph nodes and organs were examined at 1, 6, 12, and 14 months. RESULTS PAAG was invaded by macrophages and giant cells that were gradually replaced by a network of fibrous tissue. Silicone gel was seen inside these cells or as large vacuoles, surrounded by a fibrous capsule. Regional lymph nodes contained PAAG only at 1 1/2 months and silicone gel at 12 months. CONCLUSION PAAG is a stable, viscoelastic bulking agent, which unlike silicone gel is slowly integrated within its host tissue via a thin fibrous network. Long-term risk of fibrosis and migration is minimal. [source]

    Complications from Injectable Polyacrylamide Gel, a New Nonbiodegradable Soft Tissue Filler

    DERMATOLOGIC SURGERY, Issue 12p2 2004
    Snehal P. Amin
    Background. Polyacrylamide gels, containing a hydrogel composed of polyacrylamide and water, are used for soft tissue augmentation and contour correction. There are no reports of significant complications after injection of this material into the face. Objective. We report an inflammatory reaction after injection of polyacrylamide gels for zygomatic facial augmentation. Methods. A retrospective chart review of single case is presented. Results. An inflammatory reaction at the sites of polyacrylamide gels injection was noted at 1 month after initial injection. Despite two ensuing courses of broad-spectrum antibiotics, the patient presented to us with persistent draining nodules. Intralesional steroid injections resulted in prompt resolution and no recurrence. Conclusion. Inflammatory reactions have been noted in patients receiving polyacrylamide gels for breast augmentation. Facial polyacrylamide gels injections may also be associated with an inflammatory reaction that responds to intralesional steroids. With increasing availability of a variety of soft tissue fillers, dermatologists should be aware of this delayed complication from polyacrylamide gels. [source]

    The value of debridement and Vacuum-Assisted Closure (V.A.C.) Therapy in diabetic foot ulcers

    Magnus Eneroth
    Abstract Background Treatment of diabetic foot ulcers includes a number of different regimes such as glycaemic control, re-vascularization, surgical, local wound treatment, offloading and other non-surgical treatments. Although considered the standard of care, the scientific evidence behind the various debridements used is scarce. This presentation will focus on debridement and V.A.C. Therapy, two treatments widely used in patients with diabetes and foot ulcers. Methods A review of existing literature on these treatments in diabetic foot ulcers, with focus on description of the various types of debridements used, the principles behind negative pressure wound therapy (NPWT) using the V.A.C. Therapy system and level of evidence. Results Five randomized controlled trials (RCT) of debridement were identified; three assessed the effectiveness of a hydrogel as a debridement method, one evaluated surgical debridement and one evaluated larval therapy. Pooling the three hydrogel RCTs suggested that hydrogels are significantly more effective than gauze or standard care in healing diabetic foot ulcers. Surgical debridement and larval therapy showed no significant benefit. Other debridement methods such as enzyme preparations or polysaccharide beads have not been evaluated in RCTs of people with diabetes. More than 300 articles have been published on negative pressure wound therapy, including several small RCTs and a larger multi-centre RCT of diabetic foot ulcers. Negative pressure wound therapy seems to be a safe and effective treatment for complex diabetic foot wounds, and could lead to a higher proportion of healed wounds, faster healing rates, and potentially fewer re-amputations than standard care. Conclusions Although debridement of the ulcer is considered a prerequisite for healing of diabetic foot ulcers, the grade of evidence is quite low. This may be due to a lack of studies rather than lack of effect. Negative pressure wound therapy seems to be safe and effective in the treatment of some diabetic foot ulcers, although there is still only one well-performed trial that evaluates the effect. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    Electroconductive Hydrogels: Electrical and Electrochemical Properties of Polypyrrole-Poly(HEMA) Composites

    ELECTROANALYSIS, Issue 7 2005
    Sean Brahim
    Abstract Composites of inherently conductive polypyrrole (PPy) within highly hydrophilic poly(2-hydroxyethyl methacrylate)-based hydrogels (p(HEMA)) have been fabricated and their electrochemical properties investigated. The electrochemical characteristics observed by cyclic voltammetry suggest less facile reduction of PPy within the composite hydrogel compared to electropolymerized PPy, as shown by the shift in the reduction peak potential from ,472,mV for electropolymerized polypyrrole to ,636,mV for the electroconductive composite gel. The network impedance magnitude for the electroconductive hydrogel remains quite low, ca. 100,,, even upon approach to DC, over all frequencies and at all offset potentials suggesting retained electronic (bipolaronic) conductivity within the composite. In contrast, sustained application of +0.7 V (vs. Ag/AgCl, 3,M Cl,) for typically 100,min. (conditioning) to reduce the background amperometric current to <1.0,,A, resulted in complete loss of electroactivity. Nyquist plots suggest that sustained application of such a modest potential to the composite hydrogel results in impedance characteristics that resembles p(HEMA) without evidence of the conducting polymer component. PPy composite gels supported a larger ferrocene monocarboxylate diffusivity (Dappt=7.97×10,5,cm2,s,1) compared to electropolymerized PPy (Dappt=5.56×10,5,cm2,s,1), however a marked reduction in diffusivity (Dappt=1.01×10,5,cm2,s,1) was observed with the conditioned hydrogel composite. Cyclic voltammograms in buffer containing H2O2 showed an absence of redox peaks for electrodes coated with PPy-containing membranes, suggesting possible chemical oxidation of polypyrrole by the oxidant [source]

    Competitive immunoassay by capillary electrophoresis with laser-induced fluorescence for the trace detection of chloramphenicol in animal-derived foods

    ELECTROPHORESIS, Issue 16 2008
    Can Zhang
    Abstract A competitive immunoassay using CE with an LIF detector was developed for the detection of chloramphenicol (CAP). The method was based on the competitive reactions between fluorescently labeled CAP hapten and free CAP, with a limited amount of anti-CAP antibody. The poly(N -isopropylacrylamide) (pNIPA) hydrogel was added in the separation buffer as a dynamic modifier to reduce adsorption and enhance reproducibility. The linear range and LOD for CAP were 0.008,5,,g/L and 0.0016,,g/L, respectively. An ELISA using the same immuno-reagents was also developed for the analysis of CAP, with an LOD of 0.03,,g/L. The sensitivity of this CE immunoassay (CEIA)-LIF was almost 20 times greater than that of the ELISA. Using CEIA-LIF, equilibrium was reached in 15,min and the analytical results were obtained within 5,min by CE separation. Sample preparation for CEIA-LIF was not time-consuming and the matrix effect was easy to remove. An LOD of 0.1,,g/kg CAP in food matrices was easily achieved. This method is thus proposed as a fast and sensitive means of detecting trace amounts of CAP residues in animal-derived foods. [source]

    Influence of Surface Chemistry on Dehydrogenation in Carbon Cryogel Ammonia Borane Nanocomposites

    Saghar Sepehri
    Abstract This paper reports the synthesis and characterization of boron- and nitrogen-modified carbon cryogel (CC) ammonia borane (AB) nanocomposites (BNCC-AB) for hydrogen storage. Resorcinol,formaldehyde (RF) derived CCs were modified by homogeneous dispersion of AB in RF hydrogel prior to pyrolysis. Nanocomposites were fabricated by immersing CC in the AB solution. Nitrogen sorption analysis, X-ray photoelectron spectroscopy, and differential scanning calorimetry at multiple heating rates were used to study the structure and dehydrogenation properties of the nanocomposites. The results demonstrated lower dehydrogenation temperatures and reduced activation energies for AB when confined inside pores of B- and N-modified CCs relative to AB when confined in the unmodified CC with the same pore size.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    Proteolytically Degradable Photo-Polymerized Hydrogels Made From PEG,Fibrinogen Adducts,

    Daniel Dikovsky
    Abstract We develop a biomaterial based on protein,polymer conjugates where poly(ethylene glycol) (PEG) polymer chains are covalently linked to multiple thiols on denatured fibrinogen. We hypothesize that conjugation of large diacrylate-functionalized linear PEG chains to fibrinogen could govern the molecular architecture of the polymer network via a unique protein,polymer interaction. The hypothesis is explored using carefully designed shear rheometry and swelling experiments of the hydrogels and their precursor PEG/fibrinogen conjugate solutions. The physical properties of non-cross-linked and UV cross-linked PEGylated fibrinogen having PEG molecular weights ranging from 10 to 20,kDa are specifically investigated. Attaching multiple hydrophilic, functionalized PEG chains to the denatured fibrinogen solubilizes the denatured protein and enables a rapid free-radical polymerization cross-linking reaction in the hydrogel precursor solution. As expected, the conjugated protein-polymer macromolecular complexes act to mediate the interactions between radicals and unsaturated bonds during the free-radical polymerization reaction, when compared to control PEG hydrogels. Accordingly, the cross-linking kinetics and stiffness of the cross-linked hydrogel are highly influenced by the protein,polymer conjugate architecture and molecular entanglements arising from hydrophobic/hydrophilic interactions and steric hindrances. The proteolytic degradation products of the protein,polymer conjugates proves to be were different from those of the non-conjugated denatured protein degradation products, indicating that steric hindrances may alter the proteolytic susceptibility of the PEG,protein adduct. A more complete understanding of the molecular complexities associated with this type of protein-polymer conjugation can help to identify the full potential of a biomaterial that combines the advantages of synthetic polymers and bioactive proteins. [source]