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Results for “Polyhydroxyethyl Methacrylate”

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At least 217 records · Page 12Linked to original sources

PubMed1999

Artificial emboli based on poly(2-hydroxyethyl methacrylate) particles in animal experiments.

Spherical poly(2-hydroxyethyl methacrylate) particles 0.4-0.6 mm in diameter prepared by suspension polymerization were used for embolization of the internal thoracic artery in ten dogs and the renal artery in two dogs. No signs of toxic or irritating effect of poly(HEMA), either on the artery wall, or surrounding tissues were found in any animal in intervals of observation lasting two weeks, three months or one year. Possible neocapillarity, the presence of fibrous bundles among the particles of poly(HEMA) and, eventually, their slow degradation, were symptomatic of reparative processes.

Angiography↗

PubMed1991

Biological activity of urokinase immobilized to cross-linked poly(2-hydroxyethyl methacrylate).

The fibrinolytic enzyme urokinase was immobilized by encapsulation or cross-linking to poly(2-hydroxyethyl methacrylate) networks. The immobilized urokinase was more thermally stable, more stable against pH change and more resistant to inactivation by plasma protease inhibitors. These stabilities were improved with increasing degree of cross-linking. On the other hand, the enzymatic activity of immobilized urokinase decreased with increasing degree of cross-linking. A suitable degree of cross-linking is needed for the maintenance of high biological activity of immobilized urokinase over a long period.

Antithrombin III↗

PubMed1999

Conformal coating of small particles and cell aggregates at a liquid-liquid interface.

Polymer encapsulation of allogeneic or xenogeneic tissue is under active investigation as a means of isolating transplanted cells, such as pancreatic islets, from the immune system. We report here a method for coating small particles and cell aggregates with a very thin water insoluble hydroxyethyl methacrylate-methyl methacrylate (HEMA-MMA) membrane that conforms to the shape of the aggregate, and minimizes the polymer's contribution to the total transplant volume. Cell aggregates were coated at a liquid-liquid interface of a discontinuous density gradient composed of both aqueous and organic liquids. By increasing the viscosity difference and decreasing the density difference between the two liquids of the coating interface, coatings from approximately 1 to 15 microns thick were formed. Aggregates of HepG2 cells and pancreatic islets were coated and remained viable.

Biocompatible Materials↗

PubMed1983

Polymer analogs of 3-chloro-4-benzyloxyphenylacetic acid and their pharmacological activity.

Polymer analogs of 3-chloro-4-benzyloxy-phenylacetic acid (BPh) were prepared, representing esters of BPh with three polymer alcohols: poly(vinyl alcohol) (P-I), poly(2-hydroxyethyl methacrylate) (P-II), and poly(2,3-dihydroxypropyl methacrylate) (P-III). Their anti-inflammatory activity was determined by testing their inhibitory effect on the growth of edema in the hind legs of rats. The relative activities of the esters P-I-BPh and P-II-BPh with respect to that of BPh are 0.06 and 0.10, respectively. In the case of P-III-BPh the activity is stronger (0.37), probably owing to the easier release of BPh from P-III-BPh due to hydrolysis. No prolonged effect of BPh polymeric esters could be achieved.

Animals↗

PubMed1985

Poly(2-hydroxyethyl methacrylate)--collagen composites which promote muscle cell differentiation in vitro.

A new simple method has been developed which allows the mixing of poly(2-hydroxyethyl methacrylate)--polyHEMA--and fibrillar collagen in any desired ratio. PolyHEMA alone was shown to be an unsuitable cultivation substrate for primary cultures of chicken embryonic skeletal muscle cells. Composites containing polyHEMA and 50% (w/w) or more collagen supported myogenesis. Such layers, firmly adhered to the bottom of plastic Petri dishes, were mechanically stable and biologically active, thus favourably combining properties of both the original materials. It is suggested that polyHEMA-collagen composite layers may be used for cultivation of differentiating cells in vitro.

Animals↗

PubMed1982

Glycol methacrylate embedding of bone and cartilage for light microscopic staining.

A method is described for embedding bone and cartilage in glycol methacrylate (GMA) for light microscopy. Dehydration-infiltration of the hard tissue is with aqueous GMA solutions minimizing solvent and dehydration artefact, and polymerization is by UV light in the cold to minimize thermal damage. Over fifty stains, enzyme localizations and related histochemical methods for 0.5-3.0 micrometer thick sections of GMA embedded tissue are listed. The increased resolution plus the localization of cellular and extracellular chemical moieties is now easier and more accurate providing an improved method for the study of the musculo-skeletal system by light microscopy histochemistry.

Animals↗

PubMed2004

PHEMA as a fibrous capsule-resistant breast prosthesis.

The presence of a silicone (poly-dimethyl siloxane) breast prosthesis in a breast reconstruction patient typically leads to fibrous tissue encapsulation of the prosthesis. Fibrous capsular contracture forces the prosthesis into a hardened sphere. The initially satisfactory cosmetic result can thus be changed into a deformed mass of inappropriate compliance. It is the author's hope with the present study to identify a material for implantation with a diminished tendency to form fibrous encapsulation, to improve the long-term results of prosthetic implants. The purpose of this investigation was to compare the early capsule production quality of poly-2-hydroxyethyl methacrylate (PHEMA) and poly-dimethyl siloxane (silicone). Each of five rats subcutaneously underwent implantation with both a disk of poly-dimethyl siloxane (control) and a similar disk of PHEMA. In this study, the extent of fibrous encapsulation was assessed at 6 weeks after implantation of the two disk types. The five disks of poly-dimethyl siloxane were embedded in fibrous tissue, whereas there was no apparent fibrous tissue surrounding the implants of PHEMA. The author concludes that the results for PHEMA were superior to those for silicone at 6 weeks with regard to fibrous encapsulation (p = 0.0312).

Animals↗

PubMed1988

Irritation effects of residual products derived from poly(2-hydroxyethyl methacrylate) gels. I. Testing of some model compounds.

2-Hydroxyethyl methacrylate (HEMA) monomer and sodium benzoate, diluted with saline in the range 0-20%, were tested for intradermal irritation in rats. Radioactive indicator (113mIn) was used to quantify this biological response. At low concentrations (up to 1%) only a little irritation was recorded, while at higher levels (5% or more) a significant adverse reaction developed. The degree of irritation was dose dependent. In the concentration range 0-10%, the response was exponential. Model decomposition products derived from three different polymerization initiators were also tested. How the results obtained with the model irritants relate to real polymerization systems is discussed.

Animals↗

PubMed1990

Silicone rubber-hydrogel composites as polymeric biomaterials. I. Biological properties of the silicone rubber-p(HEMA) composite.

A composite material was prepared consisting of silicone rubber matrix and particulate lightly cross-linked poly(2-hydroxyethyl methacrylate) (p(HEMA] hydrogel. The material resembling common silicone rubber is hydrophilic and swells in water like hydrogels. The effects of the implanted composite on tissues of the living organism were tested in rats by methods assessing local acute and chronic inflammatory reactions and calcification by means of radioactive indicators and by histological examination. 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.

Animals↗

PubMed2006

Evaluation of surface roughness of hydrogels by fractal texture analysis during swelling.

The surface of a biomaterial reacts in contact with biological fluids. Hydrogels are used to prepare biomaterials. The surface roughness of materials can be explored by several techniques. However, when considering hydrogels, the surface examined in the dry state does not reflect the final conformation. How the surface roughness is affected by swelling has been little explored by quantitative methods. We have evaluated the surface roughness of poly(2-hydroxyethyl methacrylate) (i.e., pHEMA) by image analysis. Images of disks, prepared from linear pHEMA, were obtained on a light microscope after various incubation times in saline. Fractal texture analysis was done on images to determine the fractal dimension D. In this study, D exhibited a significant decrease during swelling and was highly correlated with the swelling ratio (r2 = 0.994, p < 0.00001). Water uptake by the surface of the polymer affected the surface roughness. Image analysis using fractal algorithms appears to be the most interesting technique for the quantitative exploration of surfaces of hydrated materials that cannot be measured by conventional methods.

Hydrogels↗

PubMed1988

Molecular design of materials for cell separation.

There has been a strong demand in biomedical sciences to isolate viable cell populations with high yield and purity. An important facet of this work was to develop new polymeric adsorbent for the separation of lymphocyte subpopulations. Based on our strategy of separating cells through their differential ionic affinity toward multiphase-structured adsorbent with ionically derivatized microdomains, a series of poly(2-hydroxyethyl methacrylate)/polyamine graft copolymers (HA copolymers) was prepared. HA copolymer columns were found to show specific adsorption affinity toward B lymphocytes, and allows for separation of B and T lymphocytes in high yield and purity with a short operating time. Separation mechanism involved in the resolution of B and T lymphocytes by HA copolymer column is discussed in this paper. Further, photo-induced desorption of cells from the adsorbent derivatized with photo-responsive functional group (azobenzene group) was demonstrated to emphasize the feasibility of photo-regulated chromatography as a novel tool in cell separation technology.

B-Lymphocytes↗

PubMed2004

Adsorption of a blood protein on to hydrophilic sponges based on poly(2-hydroxyethyl methacrylate).

Spongy materials of poly(2-hydroxyethyl methacrylate) were synthesized and the adsorption of bovine serum albumin was carried out onto their surfaces. The sponges were characterized by IR spectral analysis, and water sorption property. It was noticed that the chemical architecture of the sponge has a pronounced impact on both the water sorption capacity and adsorption affinity of the sponge surfaces. The adsorption was also studied kinetically and the effect of pH was also investigated. The synthesized sponges were evaluated for antithrombogenic property by performing blood-clot formation tests.

Absorption↗

PubMed1997

Inhibition of anchorage-independent growth of ras-transformed cells on polyHEMA surface by antisense oligodeoxynucleotides directed against K-ras.

We examined the effect of antisense oligodeoxynucleotides (AS ODNs) directed against v-Ki-ras on the anchorage-independent growth of v-Ki-ras-transformed rat fibroblasts using plates coated with an antiadhesive polymer, poly(2-hydroxyethyl methacrylate) (polyHEMA). Among AS ODNs tested, 17mer AS ODN centered around codon 12 of v-Ki-ras inhibited the v-Ki-Ras expression and v-Ki-Ras-induced anchorage-independent growth, while its sense sequence did not affect it. Using polyHEMA plates, the direct addition of AS ODNs to the cells growing anchorage-independently and various treatment schedules of AS ODNs are now available to identify the most desirable conditions for AS ODNs treatment.

Animals↗

PubMed2003

Histology of anterior capsule opacification with a polyHEMA/HOHEXMA hydrophilic hydrogel intraocular lens compared to poly(methyl methacrylate), silicone, and acrylic lenses.

To evaluate the biocompatibility of various materials including a poly(2-hydroxyethyl methacrylate [HEMA])/(6-hydroxyhexyl methacrylate [HOHEXMA]) hydrophilic hydrogel intraocular lens (IOL) (Hydroview, Bausch & Lomb). Department of Ophthalmology, Wakayama Medical University, Wakayama, Japan. Ten opacified anterior capsules were extracted, including 3 specimens with the Hydroview IOL. They were processed for light and electron microscopy. Immunohistochemistry for alpha-smooth muscle actin (alpha SMA) and collagen types was also done to evaluate mesenchymal transition in lens epithelial cells (LECs). Anterior capsule opacification (ACO) in the 3 specimens with a polyHEMA/HOHEXMA hydrogel IOL contained more LECs and less extracellular matrix (ECM) than in the specimens with IOLs of other materials. Ultrastructural observation showed a well-organized collagenous ECM in tissues with an IOL of poly(methyl methacrylate), silicone, or soft acrylic material; an immature matrix was seen in specimens with a hydrogel IOL. The alpha SMA-positive LECs and collagen I and III, both types related to capsular wound healing, were detected in ACO.A polyHEMA/HOHEXMA hydrogel IOL facilitated the proliferation of LECs on the anterior capsule compared with other IOLs of other materials but did not completely suppress mesenchymal transition of LECs. Extracellular matrix accumulation appeared immature and less with a polyHEMA/HOHEXMA hydrogel IOL.

Acrylic Resins↗

PubMed1987

Calcification of poly(2-hydroxyethyl methacrylate)-collagen composites implanted in rats.

Samples of the polyHEMA-collagen composites with varying collagen content have been implanted into the popliteal region of rats. Three, six and twelve months after the implantation, calcification of the implanted material was determined using a radioactive indicator. At the same time, the implants and surrounding tissue were examined histologically. The degree of calcification of the implants was dependent on the collagen content; it was more pronounced with a higher amount of collagen. The composites with 30% (w/w) or more collagen were biodegraded during the long-term implantation. It is suggested that the composites containing less than 20% (w/w) of fibrillar collagen are used for biomedical applications and that those with a higher collagen content for the in vitro studies.

Animals↗

PubMed1981

Physical characterization of microporous poly(2-hydroxyethyl methacrylate) gels.

Poly(2-hydroxyethyl methacrylate)-(PHEMA) has been prepared by polymerizing in presence of different types of water-soluble additives, at various amounts, which were removed by swelling in water. Mechanical properties of swollen samples have been measured and analyzed by using the classical theory of rubber elasticity. Water permeability measurements were also performed to detect the presence of micropores and to determine the type of water transport. It has been shown that it's possible, using different types and amounts of additives, to obtain a wide range of physical properties of swollen PHEMA as required for various biomedical applications.

Chemical Phenomena↗

PubMed1993

Preliminary report on use of a p(HEMA)-collagen composite in maxillo-facial surgery.

After being thoroughly tested on animals, a composite polymer material based on poly(2-hydroxyethyl methacrylate) and calf skin collagen has been allowed in a limited clinical trial in the Czech Republic. Up to now, the medical use of the biomaterial comprises implants for maxillo-facial surgery, i.e. augmentation of soft tissues (seven cases); reparation of fractured eye sockets (12 cases) and in special indications (two cases). The clinical results obtained so far are presented here as case reports. These preliminary results are very encouraging for a broader utilization of this type of biomaterial in the surgical fields of human medicine.

Adult↗

PubMed1998

Covalent bonding of PMMA, PBMA, and poly(HEMA)to hydroxyapatite particles.

In our earlier study, we showed that the surface hydroxyl groups of hydroxyapatite have the ability to react with organic isocyanate groups. In this study, the feasibility of grafting poly(methyl methacrylate) (PMMA), poly(n-butyl methacrylate) (PBMA), and Poly(hydroxyethyl methacrylate) [poly(HEMA)] by using the reaction of isocyanate groups with the hydroxyl groups on the surface of HA was investigated. Double bonds were introduced to the surface of HA via the coupling reaction of isocyanateoethyl methacrylate (ICEM) with HA, or through hexamethylene diisocyanate (HMDI) with hydroxyethyl methacrylate (HEMA) and HA, followed by radical polymerization in MMA, BMA, or HEMA. Infrared spectra indicated the existence of polymers on the surfaces of HA. Thermogravimetric analysis also confirmed the presence of grafted polymers on the surface of HA powder particles (20-26 wt%). The polymers gave typical PMMA, PBMA, or poly(HEMA) infrared spectra, with the exception of amide bands, a result of the coupling reaction of ICEM or HMDI with hydroxy groups of HA or HEMA. Therefore it is concluded that the polymers were chemically bonded to the surface of HA through the isocyanate groups of ICEM or HMDI.

Biocompatible Materials↗