			Home About us Contact

Hydrogel System (hydrogel + system)

Distribution by Scientific Domains

Polymers and Materials Science	92%

Selected Abstracts

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

ADVANCED FUNCTIONAL MATERIALS, Issue 4 2010
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]

Protein-Release Behavior of Self-Assembled PEG,, -Cyclodextrin/PEG,Cholesterol Hydrogels

ADVANCED FUNCTIONAL MATERIALS, Issue 18 2009
Frank van de Manakker
Abstract This paper reports on the degradation and protein release behavior of a self-assembled hydrogel system composed of , -cyclodextrin- (,CD) and cholesterol-derivatized 8-arm star-shaped poly(ethylene glycol) (PEG8). By mixing ,CD- and cholesterol-derivatized PEG8 (molecular weights 10, 20 and 40 kDa) in aqueous solution, hydrogels with different rheological properties are formed. It is shown that hydrogel degradation is mainly the result of surface erosion, which depends on the network swelling stresses and initial crosslink density of the gels. This degradation mechanism, which is hardly observed for other water-absorbing polymer networks, leads to a quantitative and nearly zero-order release of entrapped proteins. This system therefore offers great potential for protein delivery. [source]

Preparation and characterization of infection-resistant antibiotics-releasing hydrogels rods of poly[hydroxyethyl methacrylate- co -(poly(ethylene glycol)-methacrylate]: Biomedical application in a novel rabbit penile prosthesis model

JOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2008
M. Yakup Ar
Abstract In this work, preparation and characterization of novel three different antibiotic loaded penile prosthesis in the rod form were investigated by copolymerization of 2-hydroxyethylmethacrylate (HEMA) with poly(ethylene glycol)-methacrylate, (PEG-MA). To achieve this goal, a series of novel copolymer hydrogels were prepared in rod form using HEMA and PEG-MA monomers via UV initiated photopolymerization. The thermal stability of the copolymer was found to be lowered by increase in the ratio of PEG-MA in the rod structure. Contact angle measurements on the surface of copolymer hydrogel demonstrated that the copolymer gave rise to a significant hydrophilic surface compared with pure poly(HEMA). The blood protein adsorption and platelet adhesion were significantly reduced on the surface of the copolymer hydrogels compared with control pure poly(HEMA). Poly(HEMA:PEG-MA;1:1)-1 formulation containing different antibiotics (20 mg antibiotic/g polymer) released about 90, 91, and 55% of the total loaded cephtriaxon, vancomycin, and gentamicin in 48 h at pH 7.4, respectively. Finally, antibiotics loaded biocompatible poly(HEMA:PEG-MA;1:1)-1 hydrogel compositions was used as a penile prosthesis in preventing cavernous tissue infections in a rabbit prosthesis model. The efficacy of the three different antibiotics loaded hydrogel system was evaluated in four different groups of rabbits, in which various infectious agents were inoculated. The animals were sacrificed after predetermined time periods, and clinical, histological and microbiological assessment on the implant side were carried out to detect infections. Eventually, we concluded that three different antibiotic loaded penile prostheses (i.e. poly(HEMA:PEG-MA;1:1)-1 hydrogel systems) were as effective as parenteral antibiotics applications. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008 [source]

Spatiotemporal control of vascular endothelial growth factor delivery from injectable hydrogels enhances angiogenesis

JOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 3 2007
E. A. SILVA
Summary. Therapeutic angiogenesis with vascular endothelial growth factor (VEGF) delivery may provide a new approach for the treatment of ischemic diseases, but current strategies to deliver VEGF rely on either bolus delivery or systemic administration, resulting in limited clinical utility, because of the short half-life of VEGF in vivo and its resultant low and transient levels at sites of ischemia. We hypothesize that an injectable hydrogel system can be utilized to provide temporal control and appropriate spatial biodistribution of VEGF in ischemic hindlimbs. A sustained local delivery of relatively low amounts of bioactive VEGF (3 ,g) with this system led to physiologic levels of bioactive VEGF in ischemic murine (ApoE,/,) hindlimbs for 15 days after injection of the gel, as contrasted with complete VEGF deprivation after 72 h with bolus injection. The gel delivery system resulted in significantly greater angiogenesis in these limbs as compared to bolus (266 vs. 161 blood vessels mm,2). Laser Doppler perfusion imaging showed return of tissue perfusion to normal levels by day 28 with the gel system, whereas normal levels of perfusion were never achieved with saline delivery of VEGF or in control mice. The system described in this article could represent an attractive new generation of therapeutic delivery vehicle for treatment of cardiovascular diseases, as it combines long-term in vivo therapeutic benefit (localized bioactive VEGF for 1,2 weeks) with minimally invasive delivery. [source]

Development of a robust hydrogel system based on agar and sodium alginate blend

POLYMER INTERNATIONAL, Issue 2 2008
Ramavatar Meena
Abstract BACKGROUND: As part of an ongoing research and development programme of our laboratory on functional modification of seaweed polysaccharides for preparing hydrogels with improved properties, we report herein the preparation of a robust hydrogel system based on grafting of agar and sodium alginate blend (Agar/Na-Alg) with acrylamide (AAm) to obtain the copolymer Agar/Na-Alg- graft -PAAm. RESULTS: A robust hydrogel system with superior absorbency and pH resistance has been developed based on a PAAm-grafted seaweed polysaccharide blend of Agar/Na-Alg. The blend (Agar/Na-Alg) and grafted product (Agar/Na-Alg- graft -PAAm) were evaluated using Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, swelling capacity, rheology and scanning electron microscopy. The swelling capacity of the grafted copolymer exhibited an enhancement over that of the blend from 14 to 24 g g,1 in acidic medium. The blend and grafted copolymer produced hydrogels with lower gelling points of 31 and 29 °C and gel strengths were 170 and 120 g cm,2, respectively. CONCLUSION: This study constitutes an example of value addition of seaweed polysaccharides targeting new applications. The copolymer hydrogel may be useful in health, personal care and agricultural applications. Copyright © 2007 Society of Chemical Industry [source]

Modulation of dynamic release of vitamin B2 from a model pH-sensitive terpolymeric hydrogel system

POLYMER INTERNATIONAL, Issue 12 2004
Dr SK Bajpai
Abstract Terpolymeric devices consisting of acrylamide, methacrylamide and acrylic acid were synthesized and the release of the model drug riboflavin from these devices was studied at the physiological temperature 37°C. The gels exhibit a sharp pH-dependent release behavior. The devices released nearly 42.2 ± 2.6% drug at pH 1.0 while nearly 95.3 ± 3.2% drug was released at pH 7.4. With increasing concentration of cross-linker in the gel, the drug released was found to decrease. Moreover, with low content of cross-linker a nearly zero-order profile was obtained. The size of the cylindrical devices also affected the release kinetics and a linear dependency was observed between t1/2 (ie, the time required for 50 % release) and the square of the diameter, thus supporting the Tanaka,Fillmore theory. The molar ratio of acrylamide and methacrylamide also affected the dynamic release of riboflavin. It was found that variation in transit time could also affect the drug-releasing capacity of the devices. Finally, the average and ,late-time' diffusion coefficients for the gels having different initial loads were also evaluated. Copyright © 2004 Society of Chemical Industry [source]

Mass transfer from theophylline hydrogels of a -PVA/H2O and a -PVA/NaCl/H2O system on heating

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 10 2003
Sharif M. Shaheen
Abstract Theophylline hydrogels of atactic -poly(vinyl alcohol) (a -PVA)/H2O and a -PVA/NaCl/H2O systems were prepared followed by cyclic freezing (,30°C for 16,hr),thawing (at room temperature for 8,hr) and one cycle gelation (at ,20°C for 24,hr) processes, respectively. In order to prepare xerogels (dried hydrogels) of these hydogel systems, an apparently first-order mass transfer phenomenon of water as evaporation was observed for a -PVA/H2O hydrogel system, while heating at 60°C. The rate of evaporation decreased with increasing time in hyperbolic fashion. The total surface area (both lateral and two end surfaces of hydrogel matrix disc) decreased linearly for the first 90,min and thereafter had a tendency towards the steady-state. The total mass flux showed time dependent linear reduction phenomenon, which is a characteristic physical behavior for these hydrogel systems on heat treatment. When NaCl was included in a -PVA/H2O system mass transfer of water followed fourth-order polynomial. But in consideration of a comparative study, sustained mass transfer was found from the hydrogel matrices of a -PVA/H2O/NaCl system (gelation at ,20°C). Copyright © 2003 John Wiley & Sons, Ltd. [source]

Biodegradable Polymer Crosslinker: Independent Control of Stiffness, Toughness, and Hydrogel Degradation Rate

ADVANCED FUNCTIONAL MATERIALS, Issue 19 2009
Chaenyung Cha
Abstract Hydrogels are being increasingly studied for use in various biomedical applications including drug delivery and tissue engineering. The successful use of a hydrogel in these applications greatly relies on a refined control of the mechanical properties including stiffness, toughness, and the degradation rate. However, it is still challenging to control the hydrogel properties in an independent manner due to the interdependency between hydrogel properties. Here it is hypothesized that a biodegradable polymeric crosslinker would allow for decoupling of the dependency between the properties of various hydrogel materials. This hypothesis is examined using oxidized methacrylic alginate (OMA). The OMA is synthesized by partially oxidizing alginate to generate hydrolytically labile units and conjugating methacrylic groups. It is used to crosslink poly(ethylene glycol) methacrylate and poly(N -hydroxymethyl acrylamide) to form three-dimensional hydrogel systems. OMA significantly improves rigidity and toughness of both hydrogels as compared with a small molecule crosslinker, and also controls the degradation rate of hydrogels depending on the oxidation degree, without altering their initial mechanical properties. The protein-release rate from a hydrogel and subsequent angiogenesis in vivo are thus regulated with the chemical structure of OMA. Overall, the results of this study suggests that the use of OMA as a crosslinker will allow the implantation of a hydrogel in tissue subject to an external mechanical loading with a desired protein-release profile. The OMA synthesized in this study will be, therefore, highly useful to independently control the mechanical properties and degradation rate of a wide array of hydrogels. [source]

Preparation and characterization of infection-resistant antibiotics-releasing hydrogels rods of poly[hydroxyethyl methacrylate- co -(poly(ethylene glycol)-methacrylate]: Biomedical application in a novel rabbit penile prosthesis model

Multi-Component Kinetic Modeling for Controlling Local Compositions in Thermosensitive Polymers

MACROMOLECULAR THEORY AND SIMULATIONS, Issue 8 2006
Todd Hoare
Abstract Summary: An explicit terminal copolymerization kinetic model accounting for the copolymerization of up to four different comonomers is developed and applied to model the conversion profiles and local compositional gradients in functionalized PNIPAM-based polymer and hydrogel systems. The kinetics of the functional comonomer(s) have a large influence on both the mole fraction and chain distribution of functional groups in polymers. Strategies are developed to synthesize polymers with uniform compositions by applying semi-batch techniques or via copolymerization of multiple monomers with the same target functionality but with divergent reactivities relative to NIPAM. Synthetic protocols are also designed to maximize the compositional uniformity and randomness of ampholytic polymers. Instantaneous mole fractions of monomers in polymers as a function of the overall monomer conversion for the copolymerizations of NIPAM, MBA, and two functional monomers: MMA and acrylamide. [source]

Chemical actuation in responsive hydrogels,

POLYMER INTERNATIONAL, Issue 3 2009
Joshua MG Swann
Abstract Chemically actuated hydrogels share a unique feature with living systems: they are both driven by their ability to convert chemical energy into a mechanical response. However, macroscopic applications of hydrogels are limited due to the slow response rate of these materials. This problem has been overcome by developing materials at micrometre length scales, as the diffusion kinetics are related to the square of the size of the smallest dimension of the gel. Herein, the progress in the field of chemical actuation in hydrogel systems is reviewed, with an emphasis on the ways in which new devices have been designed. Copyright © 2009 Society of Chemical Industry [source]