Showing papers on "Self-healing hydrogels published in 1990"
TL;DR: It is shown that pH-sensitive behaviour with a wide range of swelling ratios could be obtained using a range of compositional changes and was a function of the acidity of the buffered solution.
174 citations
Book•
01 Jul 1990
TL;DR: Low Voltage Scanning Electron Microscopy for Improved Surface Characterization of Ocular Implants and Other Prosthetic Devices and the Tissue-Protective Properties of Hydrophilic Surface Modified Intraocular Lens Implants are evaluated.
Abstract: Ophthalmic Polymer Applications.- Contact Lens Materials: Their Properties and Chemistries.- Characterization of Contact Lens Plastics.- Contact Lens Manufacture and Function: Material Related Issues.- Low Voltage Scanning Electron Microscopy (LVSEM) for Improved Surface Characterization of Ocular Implants and Other Prosthetic Devices.- Evaluation of the Tissue-Protective Properties of Hydrophilic Surface Modified Intraocular Lens Implants.- Development of a New Type of Artificial Cornea for Treatment of Endstage Corneal Diseases.- Surgical, Dental and Diagnostic Applications.- Methacrylate Oligomers with Pendant Isocyanate Groups as Tissue Adhesives.- Physical Modification of ?-Cyanoacrylate for Application as Surgical Adhesives.- A Polymeric Bone Replacement Material in Human Oral and Maxillofacial Surgery.- Ceramic Bone Composite Graft for Reconstruction of the Bony Defects of the Maxilla.- Evaluation of Collagen-Immobilized Percutaneous Implants.- Electrophysiological Study of Recovery of Peripheral Nerves Regenerated by a Collagen-Glycosaminoglycan Copolymer Matrix.- Synthesis and Properties of a Polyfluorinated Prepolymer Multifunctional Urethane Methacrylate.- Evaluation of Spiro Orthocarbonate Monomers Capable of Polymerization with Expansion as Ingredients in Dental Composite Materials.- Applications of the Weibull Method of Statistical Analysis of Strength Parameters of Dental Materials.- Polymer and Stability Considerations in Dry Reagent Diagnostic Chemistry.- Quantification of Steroids via a Polymer Linked Second Antibody Enzyme Immunoassay System: Methods of Linking Anti-Rabbit IgG to Poly(styrene).- Polymeric Biomaterials.- The Poly(nonapeptide) of Elastin: A New Elastomeric Polypeptide Biomaterial.- New Transparent and Low-Tensile Set Biocompatible Thermoplastic Elastomers: Poly(siloxane) Modified Poly(olefin) Block Copolymers.- The Poly(urethane) - Calcium Ion Interaction. I. Effect on the Mechanical and Thermal Properties.- Surface Modification of Poly(ether urethane) by Chemical Infusion and Graft Polymerization.- Plasma Techniques for Production of Permanent Hydrophilic Polymer Surfaces for Biomedical Applications.- Influence of Aqueous Environment on Surface Molecular Mobility and Surface Microphase Separated Structure of Segmented Poly(ether urethanes) and Segmented Poly(ether urethane ureas).- In Vitro Analysis of Plasma Protein Diffusion in Crosslinked Gelatin Coatings Used for Blood Pumps.- Development of Absorbable, Ultra High Strength Poly(lactides).- Biodegradable Polyamides Based on 4,4?-Spirobibutyrolactone.- Comparison of Bioabsorbable Poly(ester-amide) Monomers and Polymers In Vivo Using Radiolabeled Homologs.- Chitosan: A Biocompatible Material for Oral and Intravenous Administrations.- Synthetic Poly(phosphates) Related to Nucleic and Teichoic Acids.- Effect of Modification of Poly(vinyl alcohol) Hydrogels on Mouse Fibroblast Cell Growth in Culture.- Medical Applications for Extraction Resistant PVC Compounds.- Controlled Release and Bioactive Polymer Applications.- The Controlled Release of 5-Fluorouracil from Annealed Monolithic Systems.- Monomers and Polymers from Nalidixic Acid - Synthesis, Characterization and Hydrolysis Study.- Antibiotic-Containing Polyurethanes for the Prevention of Foreign-Body Infections.- The Ability of Norgestomet Impregnated Poly(dimethylsiloxane) Implants to Maintain Pregnancy Subsequent to Ovariectomy.- Biological Characterization of Selected Palladium (II) Poly(amides), Poly(thioamides) and Poly(hydrazides).- Platinum II Polyamines: Relationship of Chain Length to Biological Activity.- Contributors.
164 citations
TL;DR: The cross-linked gels were stable in neutral or strongly acidic aqueous media, but the cross-linking process was reversed in basic aqueously solutions of excess monovalent cations.
Abstract: Hexachlorocyclotriphosphazene and poly(dichlorophosphazene) react with the sodium salt of ethyl p-hydroxybenzoate to give small molecule cyclic and high polymeric phosphazenes with aryloxy ester side groups; reaction of these compounds with potassium tert-butoxide brings about complete hydrolysis of the ester groups to yielding aqueous media-soluble, carboxylic acid bearing cyclic and high polymeric phosphazenes; the carboxylic acid bearing high polymer formed ionic cross-links when treated in aqueous media with salts of di- or trivalent cations yield hydrogels and membranes. The cross-linked gels were stable in neutral or strongly acidic aqueous media, but the cross-linking process was reversed in basic aqueous solutions of excess monovalent cations.
156 citations
TL;DR: In this article, the authors studied the swelling kinetics of polyvinyl alcohol (PVA) hydrogels in water and found that the rate of swelling linearly increased with the square root of immersion time in water.
145 citations
TL;DR: Histopathological data indicated that the tissue reaction at the implant site progressed from an initial acute inflammatory response characterized by the presence of eosinophils and polymorphs to a chronic response marked by few macrophages, foreign body giant cells and fibroblasts.
121 citations
TL;DR: Thermal cycling of LCST hydrogels is both a novel and useful approach to minimizing Mass transfer resistance and product inhibition in immobilized biocatalyst technology.
Abstract: Arthrobacter simplex cells, which convert the steroid hydrocortisone to prednisolone, have been entrapped in a thermally reversible hydrogel. Such hydrogels exhibit a lower critical solution temperature (LCST) wherein the gel shrinks and deswells when it is warmed through its LCST, and then reversibly expands and reswells when it is cooled below the LCST. The immobilized cell-hydrogel system has been thermally cycled between two temperatures, each below the LCST. The upper temperature was selected to be just below the LCST, where the gel deswells but does not collapse, as it does at the LCST. The thermal cycling acts like a “hydraulic pump” which enhances mass transfer of the substrate (hydrocortisone) in and the product (prednisolone) out of the gel, thereby increasing steroid conversion dramatically relative to isothermal operation at either the upper or lower temperature. The increased conversion can also be due in part to reduced product inhibition. Mass transfer resistance and product inhibition are among the most serious problems in immobilized biocatalyst technology and thermal cycling of LCST hydrogels is both a novel and useful approach to minimizing these problems.
118 citations
01 Sep 1990
TL;DR: By using the composite structure of the natural material as a model a new family of hydrogels, based on interpenetrating polymer network (IPN) technology, has been developed that begin to mimic the properties of biological hydrogel composites.
Abstract: The relatively poor mechanical properties of conventional synthetic hydrogels are illustrated and compared with those of articular cartilage. By using the composite structure of the natural material as a model a new family of hydrogels, based on interpenetrating polymer network (IPN) technology, has been developed. The underlying synthetic strategies are discussed and the properties of a novel representative network presented. IPN formation produces networks that are stiffer and stronger than the hydrogel copolymers of similar water content. In this behaviour these simple IPNs begin to mimic the properties of biological hydrogel composites. Thus, these materials have exciting potential for demanding in vivo applications.
105 citations
TL;DR: In this article, the mechanical properties and the swelling behaviour of hydrogels based on sodium carmelcellulose and hydroxyethyl cellulose were investigated, and it was shown that the cellulosic gels are superior to the acrylic polyelectrolytes currently in use for superabsorbent products.
103 citations
TL;DR: The correlation between the macrophage spreading and fusion and surface charge of the hydrogel implant can be hypothetically explained by electrostatic interaction between macrophages cell membrane and implant.
Abstract: This study provides information on the behavior of macrophages on the surface of the subcutaneously implanted hydrogel strips. Hydrogel containing -OH, -CO-NH-, and (CH3)2N- groups induced a spreading of macrophages on the implants. The materials containing -SO3H groups slightly, and materials containing -COOH groups more intensively, inhibited spreading of the macrophages. The fusion of macrophages into multinucleate cells was inhibited on the surface of materials containing acidic groups (-SO3H, -COOH) and increased on the hydrogels containing 30 mol% of alkaline (CH3)2N- groups in comparison with hydrogels containing -OH or -CO -NH- groups. The differences of the behavior of macrophages on the surface of individual types of hydrogels are probably independent on the adsorption of plasma fibronectin onto the hydrogels. The correlation between the macrophages spreading and fusion and surface charge of the hydrogel implant can be hypothetically explained by electrostatic interaction between macrophages cell membrane and implant.
99 citations
96 citations
Patent•
30 Mar 1990
TL;DR: The non-stringy hydrogels of as discussed by the authors are comprised of a homogeneous uniform mixture of water and at least one water-soluble high molecular weight polymer, which are crosslinked by exposure to radiant energy.
Abstract: The non-stringy hydrogels of this invention are comprised of a homogeneous uniform mixture of water and at least one water-soluble high molecular weight polymer. Suitable mixtures may be derived from poly(ethylene oxide) and water or poly(vinyl pyrrolidone), a viscosity-enhancing hydrophilic polymer and water, and further, may optionally contain an effective amount of a water-soluble electrolyte to provide conductive non-stringy materials. These polymeric mixtures which are crosslinked by exposure to radiant energy provide gel-like solids which are sufficiently tacky and adhesive to adhere to the subjects' skin and yet are substantially non-stringy and non-aggressive such that contact with such hydrogels imparts less discomfort to the user. In addition, the consumer utilizing the products of this invention would not experience the objectionable sticky, stringy sensation associated with existing conductive adhesive gels.
TL;DR: In this paper, N-vinyl-2-pyrrolidone with methyl methacrylate was copolymerized to high conversion in both the presence and absence of ethyleneglycol dimethacrylated.
TL;DR: In this article, the transition temperature of a 50 wt% ethylene glycol-water solution in the PHEMA hydrogel is the same as in its pure state, but the distribution of structural relaxation times is broader in the former than in the latter.
Abstract: Water in PHEMA hydrogels unergoes a glass-to-liquid transition in two steps: the first at ∼132 K, which is caused by the nonfreezing water fraction, and the second at ∼162 K, which is caused by the freezable water fraction. The H-bonded structure of the latter water fraction in the hydrogel has a narrower distribution of relaxation times and/or higher activation enthalpy than in pure glassy water. The glass transition temperature of a 50 wt% ethylene glycol-water solution in the PHEMA hydrogel is the same as in its pure state, but the distribution of structural relaxation times is broader in the former than in the latter
TL;DR: In this paper, the properties of water in the wet membranes of a random copolymer of methyl methacrylate and methoxy poly(ethylene glycol)-monomethacrylated P(MMA-co-M100G) were studied by proton NMR spectroscopy, which revealed that most of the bound water in these copolymers does not exist in a rigid state as suggested for the other hydrogels.
Abstract: Properties of water in the wet membranes of a random copolymer of methyl methacrylate and methoxy poly(ethylene glycol)–monomethacrylate P(MMA-co-M100G) and of a graft copolymer of vinyl chloride and methoxy poly(ethylene glycol)–monomethacrylate P(VC-g-M100G) membranes were studied by proton NMR spectroscopy. Both polymers contain flexible polyoxyethylene side chains. Temperature and frequency dependences of relaxation times, changes of signal intensity of water protons on freezing and thawing, and saturation transfer were measured for both copolymers. These experimental results revealed that most of the bound water in these copolymers does not exist in a rigid state as suggested for the other hydrogels. The introduction of flexible hydrophilic side chains resulted in high mobility of the water molecules bound to the side chains (the apparent correlation time Tc ∼ 10−10 s). For the graft copolymer P(VC-g-M100G), hydrophilic polyoxyethylene side chains are contiguous to each other. Because of the interaction between the side chains, the mobility became more complex than that for the random copolymer P(MMA-co-M100G). The difference in the mode of mobility of water on the membrane surface may be related to the difference of the membrane characteristics of these copolymers.
TL;DR: A new approach to repair brain lesions consisting of loss of tissue volume is suggested, using poly (2-hydroxyethyl methacrylate)-collagen composite hydrogels implanted into the cortex of adult rat brains to provide mechanical guiding substrates for wound healing and tissue ingrowth.
TL;DR: Results of a 6 month implant study indicated no difference in reactions of the animal body on the silicone rubber-p( HEMA) composite and a non-toxic, non-irritant pure solid p(HEMA) control.
Journal Article•
TL;DR: An approach to the quantitative description of superabsorbent polymer hydrogels is examplified by partially hydrolyzed polyacrylamide gels obtained by three-dimensional radical copolymerization or radiation cross-linking of the polymer as discussed by the authors.
Abstract: An approach to the quantitative description of superabsorbent polymer hydrogels is examplified by partially hydrolyzed polyacrylamide gels obtained by three-dimensional radical copolymerization or radiation cross-linking of the polymer. The modified swelling theory has been used to develop a system of experimental and computational methods for the evaluation of the supergels network parameters. The possibility of applying these methods to the analysis of the network formation process is also discussed.
TL;DR: In this article, the physicochemical models utilized to analyze the equilibrium swelling behavior of neutral and ionic, porous and non-porous hydrogels are reviewed, with emphasis given to the determination of the molecular weight between crosslinks.
Abstract: SUMMARY The physicochemical models utilized to analyze the equilibrium swelling behavior of neutral and ionic, porous and non-porous hydrogels are reviewed. Emphasis is given to the determination of the molecular weight between crosslinks and the equilibrium swelling ratio, especially in relation to utilization of such materials in superabsorbent and controlled release technology.
TL;DR: Albumin-cross-linked hydrogels were prepared by free radical polymerization using 1-vinyl-2-pyrrolidinone as a monomer and functionalized albumin as a crosslinking agent to examine both the swelling and the mechanical properties in the absence and presence of pepsin.
Abstract: Albumin-cross-linked hydrogels were prepared by free radical polymerization using 1-vinyl-2-pyrrolidinone as a monomer and functionalized albumin as a crosslinking agent. The degree of chemical cross-linking was controlled by varying the degree of albumin functionality and the concentration of albumin. With emphasis placed on the potential use of these hydrogels for long-term oral drug delivery, gel characterization studies examined both the swelling and the mechanical properties in the absence and presence of pepsin. In the absence of pepsin, the equilibrium swelling ratio in simulated gastric fluid ranged from 17 to 55, depending on the degree of albumin functionality and the albumin concentration. Swelling was pH dependent at pH's greater than 7. The uptake of solvent into the dried hydrogels was determined to be Fickian. The integrity of swelling gels was dependent on the concentration of the functionalized albumin as well as on the degree of albumin functionality. In the presence of pepsin, a predominance of either surface or bulk degradation was observed, depending on the functionality of the albumin used as a cross-linker. Gel integrity during pepsin degradation also showed a marked dependence on the albumin functionality.
TL;DR: Grafted starch solutions were polymerized to produce hydrogels, with and without the addition of an unsaturated acid, and both are shown to be degraded by the enzyme alpha-amylase.
TL;DR: This model was shown to give an accurate prediction of phenylpropanolamine release from poly(hydroxyethy1 methacrylate-co-methacrylic acid) gels, and through a free volume relationship, the experimentally determined swelling kinetics are coupled to a diffusion mechanism for the drug molecules.
TL;DR: In this article, copolymers of acrylic acid and butyl acrylate crosslinked with 4,4′-bis(methacryloylamino)-azobenzene were synthesized by radical copolymerization with different amounts of acrylic acids and crosslinker.
Abstract: Copolymers of acrylic acid and butyl acrylate crosslinked with 4,4′-bis(methacryloylamino)-azobenzene were synthesized by radical copolymerization with different amounts of acrylic acid and crosslinker. They were characterized by equilibrium degree of swelling, modulus of elasticity in compression at pH 2 and 7, and effective network density. The acido-basic properties of crosslinked copolymers were compared with linear (soluble) ones of the same composition. The study of the dependence of the apparent dissociation constant (pKapp) on the degree of dissociation has shown that conformational transition from the compact to the random conformation of the polymeric chains occurs only in crosslinked copolymers. The high values of pKapp obtained indicate that strong Donnan effects and low polarity of environment of carboxy groups are operative in acido-basic equilibria.
TL;DR: In this paper, a helix model for the stable trihydrate is tentatively proposed, which is based on hydrogen bonding between the hydrogen of the water molecule and the ether oxygen of the network.
TL;DR: A series of polymeric hydrogels containing different oxyethylene oligomers has been prepared by radical polymerization of oligo(oxyethylene) methacrylate monomers in the presence of different amounts of N,N′-methylenebisacrylamide as crosslinking agent or acrylamides as hydrophilic comonomer as discussed by the authors.
Patent•
21 May 1990TL;DR: In this article, thermotropic hydrogel forming polymers are described, which are ramdom copolymers of N,N-dimethyacrylamide with methoxy-ethyl acrylate or methacrylate.
Abstract: Novel thermotropic hydrogel forming polymers are described, which are ramdom copolymers of N,N-dimethyacrylamide with methoxy-ethyl acrylate or methacrylate The linear polymers exhibit in water a lower-critical-solution-temperature (LCST) between 0° and 70° C The water swelling of the crosslinked polymers is extremely temperature dependent and the gels show sharply defined clear to opaque transitions The novel polymers are useful in drug delivery systems, absorption and extraction processes and as qualitative thermometers, thermosensors and self-activating sunscreens, for example for greenhouses
TL;DR: In this paper, the γ-ray initiated copolymerisation of N-vinyl-2-pyrrolidone with methyl methacrylate in the presence of crosslinker has been effected to high conversion.
Abstract: The γ-ray initiated copolymerisation of N-vinyl-2-pyrrolidone with methyl methacrylate in the presence of crosslinker has been effected to high conversion. At two fixed compositions of the principal monomers, the inclusion of different concentrations of the tetrafunctional crosslinkers ethylene dimethacrylate and a low molar mass poly(ethylene glycol) dimethacrylate produced crosslinked xerogels, which were subsequently swollen in water and 1,4-dioxane to yield hydrogels and organogels, respectively. These gels were characterised by determinations of sol fraction, equilibrium solvent content and uniaxial compression stress/strain measurements. Differences among the swelling and mechanical properties according to the nature and concentration of crosslinking agent and according to the nature of the swelling medium are noted and discussed.
Abstract: The diffusional behaviour of chloramphenicol1 (1) from poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogels is reported. The drug was trapped in the matrix cross-linked with various amounts of ethylene dimethacrylate (0,5–18 mol-%), and the diffusion was followed from disc-shaped slabs at swelling equilibrium in water (phosphate buffer, pH 7) at 37°C. The diffusion obeys the second Fick law and is rapid (D ≈ 10−8 cm2 s−1) in the case of the slightly crosslinked hydrogels used for corneal lenses. The diffusion coefficients decrease almost exponentially with increasing cross-linking ratio, and the process appears predominantly controlled by the free volume contribution of the diluent rather than by the sieving of the network.
TL;DR: In this article, the results compared with theory for the diffusion of four decapeptides (LHRH analogs) through glycerol methacrylate, hydroxyethyl methacylate, and co-methyl methacyrelate hydrogels was studied, and the results were found to vary exponentially with the reciprocal of the degree of hydration.
TL;DR: In this paper, a crosslinked poly(N-isopropyl-acrylamide) and its networks, modified with hydrophobic components by copolymerization or by interpenetrating polymer networks (IPNs) formation, were utilized as temperature sensitive hydrogels.
Abstract: Temperature sensitive and electric field sensitive hydrogels were prepared for use in modulated drug release systems. Crosslinked poly(N-isopropyl-acrylamide) and its networks, modified with hydrophobic components by copolymerization or by interpenetrating polymer networks (IPNs) formation, were utilized as temperature sensitive hydrogels. Indomethacin (a model solute)-release from polymer matrix and permeation through polymer membrane demonstrated “on-off” regulation with temperature fluctuation. This was the result of polymer surface properties rather than bulk swelling, as temperature was changed past the swelling transition temperature range of the polymer. The on-off regulation in an electric field was also obtained with a positively charged solute (Edrophonium chloride) release in distilled-deionized water from a matrix of crosslinked poly(2-acrylamido-2-methylpropanesulfonic acid-co-butyl methacrylate). This was attributed to the ion exchange between Edrophonium ion and protons produced at the anode. The swelling changes produced by local pH or ionic strength changes affected non-charged solute release.