PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Polyhydroxyethyl Methacrylate”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 523 records · Page 29Linked to original sources
PubMed1993

Imaging surfaces of hydrophilic contact lenses with the atomic force microscope.

Soft contact lens (SCL) surfaces were imaged with atomic force microscopy (AFM). High-resolution images of unworn SCL were obtained under nearly physiological medium. We present images of surfaces of collagen bandage lens under dry or aqueous conditions and of SCL of different water content and fabrication processes. Roughness parameters were determined. AFM studies of surfaces of SCL are expected to provide useful information on the hydrogel surfaces.

Buffers↗
PubMed1993

p(HEMA) composite as allografting material during therapy of periodontal disease: three case reports.

The p(HEMA) composite is shown to be a possibly effective allografting material for therapy of periodontal disease. Three cases from a clinical pilot study are presented in this report. The p(HEMA) composite may be used alone or as a part of more complex biomaterial, together with tricalcium phosphate ceramics. Further scientific and clinical work is needed for definitive judgement on the use of the p(HEMA) composite in periodontology.

Adult↗
PubMed1996

Synthesis and characterization of a new interpenetrated poly(2-hydroxyethylmethacrylate)-gelatin composite polymer.

Poly(2-hydroxyethylmethacrylate) [poly(HEMA)] is a widely used biomaterial which does not allow cell adhesion and growth on its surface, limiting its use in biomedical applications in which cell cohesion is detrimental. We have prepared a poly(HEMA)-gelatin composite hydrogel using a sequential interpenetrating polymer network technique. The properties of this material were compared with poly(HEMA) freeze-dried sponges in terms of morphology, mechanical properties and biocompatibility. Moreover, in vivo biocompatibility experiments highlighted the occurrence of cellular interactions on the surface of the poly(HEMA)-gelatin interpenetrating polymer network, which are usually absent when unmodified poly(HEMA) hydrogels are implanted in the same host organism. These tests also showed a progressive gelatin degradation from the surface to the bulk of the poly(HEMA)-gelatin specimens during short-term (7 d) implantation. Finally, in vitro tests confirmed an improved ability of this composite to scaffold for the cells.

3T3 Cells↗
PubMed1990

A ground-based model to study the effects of weightlessness on lymphocytes.

The mitogenic response of human lymphocytes was found to be markedly reduced in weightlessness conditions as compared to normal gravity. One possible explanation is that due to the non-existent sedimentation in space the lymphocytes could not adhere and spread on a substratum. Thus, we investigated the effect of substratum adhesiveness on lymphocyte responsiveness by reducing and blocking cell adhesion with poly-HEMA in a simple on-ground system. Lymphocyte adhesiveness was assessed by measuring the proportion of non-adhesive, slightly, and strongly adhesive 51Cr-radiolabelled cells on uncoated and poly-HEMA coated plastic. The amount of cell spreading on surfaces with varying adhesiveness was determined by measuring the area of cells. Cells grown on medium and thick poly-HEMA films were rounded in shape. By contrast, on tissue culture plastic, they showed clear signs of spreading. The mitogenic response of lymphocytes grown on thick poly-HEMA films was reduced by up to 68% of the control (tissue culture plastic). Interferon-gamma production was virtually nil when the cells were grown on the least adhesive substratum. These results show that activated lymphocytes need to anchor and spread prior to achieving an optimal proliferation response. We conclude that decreased lymphocyte adhesion could contribute to the depressed in vitro lymphocyte responsiveness found in the microgravity conditions of space flight.

Cell Adhesion↗
PubMed1993

Poly(HEMA)-collagen composite as a biomaterial for hard tissue replacement.

This article briefly reviews the possibilities for hard tissue replacement with a new biomaterial. The basic differences found experimentally for polymer (HEMA) and collagen composite at the biological environment are stressed. The influence of the collagen distribution and matrix porosity of composite material on biodegradation is also discussed.

Animals↗
PubMed1992

The ultrastructural architecture of the tissue/hard-tissue replacement interface.

This investigation examined the tissue response and interfacial bonding between bone and hard-tissue replacement (HTR) using scanning (SEM) and transmission (TEM) electron microscopy. Twenty adult male Sprague-Dawley rats were anesthetized and a hole (1.0 mm deep by 2.0 mm wide) was drilled in the calvarium. Subsequently, HTR was implanted and the wound closed. The implants and surrounding tissues were removed at 7, 14, 28, and 56 days and prepared for examination by SEM or TEM. Scanning electron microscopic analysis revealed a typical inflammatory response that subsided by day 14. At that time, a fine layer of collagen fibrils (fibrous envelope) was observed covering the polymeric surface. Energy dispersive x-ray analysis (EDXA) showed no sign of mineralization. Ultrastructural analysis demonstrated that the fibrous envelope was bilaminar; it consisted of a relatively undifferentiated cellular layer adjacent to the polymer and an outer fibrous region. Scanning electron microscopic analysis of 28-day implants showed that osteoblasts had migrated onto the outer surface of the fibrous envelope and that calcification had been initiated as judged by EDXA. Electron microscopic examination confirmed previous observations of an undifferentiated cellular layer along the interfacial boundary, but also showed both macrophages and foreign-body giant cells. At 56 days, bone was observed to contact and cover the fibrous envelope surrounding the polymeric bead; however, EDXA showed that the fibrous envelope remained noncalcified. Transmission electron microscopic analysis revealed that the inner cellular layer was beginning to mature, as indicated by the presence of numerous cellular organelles. This maturation was accompanied by an increased incidence of macrophages as well as foreign-body giant cells. Within the time constraints of the experimental design, it is apparent that a bilaminar layer of cells and fibers remains between the HTR and the bone. Additional studies will be necessary, over extended time periods, to determine whether the bilaminar layer remains a constant feature between the HTR and the surrounding bone or whether this region is gradually supplanted by the ingrowing bone.

Animals↗
PubMed1995

DNA-immobilized polyhydroxyethylmethacrylate microbeads for affinity sorption of human immunoglobulin G and anti-DNA antibodies.

Polyhydroxymethacrylate (PHEMA) microbeads were prepared by a suspension polymerization technique and activated by CNBr in an alkaline medium (pH 11.5). DNA molecules were immobilized onto CNBr-activated PHEMA beads. The amount of immobilized DNA was controlled by changing the medium pH and the initial concentrations of CNBr and DNA. The maximum DNA immobilization was observed at pH 5.0. Non-specific adsorption on the plain PHEMA microbeads was less than 0.1 mg/g. Much higher values, up to 2.75 mg/g, were achieved with the CNBr-activated PHEMA microbeads. Human immunoglobulin G (HIgG) adsorption onto PHEMA microbeads containing different amounts of DNA on their surfaces from aqueous solutions containing different amounts of HIgG at different pH values was investigated. The maximum HIgG adsorption was observed at pH 7.0. Non-specific HIgG adsorption onto the plain PHEMA microbeads was low (about 0.167 mg/g). Higher adsorption values, up to 7.5 mg/g, were obtained with the DNA-PHEMA beads. HIgG and anti-DNA antibody removal from the blood plasma obtained from a healthy donor and a patient with systemic lupus erythematosus (SLE) were also investigated. The maximum amounts of HIgG adsorbed from aqueous solution and human plasma onto the DNA-PHEMA microbeads were 7.35 and 23.46 mg/g, respectively. Anti-DNA antibody adsorption value was 40 mg/g.

Animals↗
PubMed1995

Protein A immobilized polyhydroxyethylmethacrylate beads for affinity sorption of human immunoglobulin G.

Protein A immobilized polyhydroxyethylmethacrylate (PHEMA) microbeads were investigated for the specific removal of HIgG from aqueous solutions and from human plasma. PHEMA microbeads were prepared by a suspension polymerization technique and activated by CNBr in an alkaline medium (pH 11.5). Protein A was then immobilized by covalent binding onto these microbeads. The amount of immobilized protein A was controlled by changing pH and the initial concentrations of CNBr and protein A. The maximum protein A immobilization was observed at pH 9.5. Up to 3.5 mg protein A/g PHEMA was immobilized on the CNBr activated PHEMA microbeads. The maximum HIgG adsorption on the protein A immobilized PHEMA microbeads was observed at pH 8.0. The non-specific HIgG adsorption onto the plain PHEMA microbeads was low (about 0.167 mg of HIgG/g PHEMA). Higher adsorption values (up to 6.0 mg of HIgG/g PHEMA) were obtained in which the protein A immobilized PHEMA microbeads were used. Much higher amounts of HIgG (up to 24.0 mg of HIgG/g PHEMA) were adsorbed from human plasma.

Chromatography, Affinity↗
PubMed1995

Heparin-immobilized polyhydroxyethylmethacrylate microbeads for cholesterol removal: a preliminary report.

Heparin-attached polyhydroxyethylmethacrylate (PHEMA) microbeads were investigated for specific removal of cholesterol from human and rabbit plasma. PHEMA microbeads were prepared by a suspension polymerization technique and activated by cyanogen bromide (CNBr) in an alkaline medium (pH 11.5). Heparin was then immobilized by covalent binding onto these microbeads. Cholesterol adsorption onto PHEMA microbeads containing two different amounts of immobilized heparin, i.e., 57.3 and 122.7 mg/g, from both hypercholesterolaemic human and rabbit plasma was investigated. The non-specific cholesterol adsorptions on the plain PHEMA microbeads were 0.47 mg/g and 0.30 mg/g from human and rabbit plasmas, respectively. About 35% and 32% of the cholesterol was removed from human and rabbit plasmas, respectively, when the heparin-immobilized PHEMA microbeads were used.

Adsorption↗
PubMed1988

The relationship between patency of the maxillary sinus and craniofacial growth in the rabbit.

Numerous researchers report the interaction between deviant respiratory patterns (airway obstruction) and craniofacial growth. Many of these studies consisted of cephalometric evaluations of children with enlarged adenoids, obstruction turbinates, or other nasal obstructions. Other experimental studies of the airway's influence on growth include studies that have induced nasal obstruction in animals by plugging the external nares. No investigations were found that examined the role of the paranasal sinuses in craniofacial growth by filling a sinus in growing animals. Furthermore, nothing appears in the literature that considers the paranasal sinuses in the oronasopharyngeal functional matrix theory. The purpose of this study was twofold: (1) to determine the effect of decreasing the pneumatization of the maxillary sinus on ultimate craniofacial growth and development, and (2) to determine the effect on future morphology by obturating a growing sinus. New Zealand white weaning rabbits were used as the experimental animals. Unilateral maxillary sinuses were injected in 18 animals--nine animals were injected on the right side and nine on the left. Eight rabbits served as controls: five received left-side and three right-side sham injections. Dorsal view cephalometric radiographs were taken at (1) the start, (2) at three progress intervals, and (3) at the end of the experiment. Dried skull direct measurements also were performed at the conclusion of the experiment. No statistical significance was found when comparing right and left sides within groups or when comparing any measurement between groups. This demonstrated that filling the maxillary sinuses had no effect on craniofacial growth; the sinuses grew normally in all animals.

Animals↗
PubMed2005

Removal of the intruding Miragel's scleral buckle by pars plana ultrasonic fragmentation.

PURPOSE: To introduce a surgical approach for removing intruded scleral buckle resulting from Miragel's implant. DESIGN: Interventional case report. METHODS: After cutting and releasing scleral band externally, a pars plana Fragmatome was used to break up and aspirate pieces of the Miragel's implant that had grown into the eye, filling the vitreous cavity. RESULTS: The intruding Miragel's buckle was shaved to the plane of the retina without any complication. The retina was completely attached. CONCLUSION: Use of ultrasonic fragmentation by a pars plana approach was effective in removing the intavitreally expanded buckling element without harming the retina.

Aged↗
PubMed2006

Evaluation of an integrated orbital tissue expander in an anophthalmic feline model.

PURPOSE: To evaluate the anatomical effects and tissue biocompatibility in a feline model of an integrated orbital tissue expander (OTE) designed to stimulate bone growth in an anophthalmic socket. DESIGN: An animal study was performed in cats to assess orbital bone growth with and without an OTE. METHODS: The OTE is an inflatable (0.5 to >6.0 cm(3)) polymeric globe sliding on a titanium T plate secured to the lateral orbital rim with screws. Eight cats had left eye enucleation at age two weeks, with five orbits receiving an OTE and the remaining three serving as nonimplanted controls. Serial transconjunctival implant inflation was performed by injecting normal saline solution into the OTE to a final volume of 3.5 ml. Serial computed tomographic scans were obtained to assess socket growth. All eight cats were euthanized at 18 weeks and dry skulls prepared. The effective orbital volume was measured by inflating an OTE in the orbit of a dry skull until it filled the cavity completely. RESULTS: Three cats periodically scratched open the tarsorrhaphy and conjunctiva to rupture the OTE, which resulted in implant exchanges. At 18 weeks, the OTE expanded orbital volume was approximately 18% smaller than the normal contralateral side. In the control animals, the anophthalmic orbital volume was approximately 66% smaller than the contralateral orbit. Histopathology of orbital tissues showed no evidence of foreign body reaction. CONCLUSIONS: This proof-of-concept pilot study demonstrated implant efficacy in cats, and no implant-related adverse effects were observed. OTE has the potential to stimulate bone growth in human anophthalmic orbits.

Animals↗
PubMed2004

Drug release characteristics of phase separation pHEMA sponge materials.

A number of phase separation pHEMA sponge hydrogels have been prepared based on variations in monomer contents, concentration of cross-linking agent, solvent mixture and temperature of polymerization. The loading levels and release profiles of the anti-inflammatory drug prednisolone were examined for each of the pHEMA sponge materials. An effective diffusion coefficient determined by an optimization approach based on the experimental data was used to measure their release characteristics. The effect of morphological variations, revealed by the environmental scanning electron microscopy, and polymer/solvent volume fractions on these properties were discussed.

Adhesives↗
PubMed2006

Surface energy components of a dye-ligand immobilized pHEMA membranes: effects of their molecular attracting forces for non-covalent interactions with IgG and HSA in aqueous media.

In the present paper, we report the study of the adsorption behaviour of human immunoglobulin G (IgG), human serum albumin (HSA) and polyethylenimine (PEI) onto surfaces of Procion Green HE-4BD (PG) immobilized poly(hydroxyethylmethacrylate) (pHEMA) membranes. The adsorption behaviour of the IgG and HSA onto surfaces of the PG-PEI complexed membrane was also studied. Surface wettability and hydrophilicity of all the membranes were investigated by static contact angle measurements. The measurements of the contact angle to various test liquids, i.e., water, glycerol, formamide, diiodomethane (DIM) and ethylene glycol on the investigated membranes were made by sessile drop method. In accordance to the Young equation, the smaller the surface tension of the test liquid, the smaller becomes the contact angles measured on all the investigated membranes surfaces. The highest contact angles were obtained with water, whereas ethylene glycol gave the lowest contact angles for all the tested membranes. Component and parameters of the surface free energy of all the investigated membranes were calculated from measured contact angle values using two methods (the geometric mean by Fowkes and acid-base by van Oss). HSA adsorption was enhanced after complexation of PEI with the immobilized dye-ligand. The adsorption of proteins and PEI significantly changed both the contact angles and component of surface free energies of the investigated membranes.

Adsorption↗
PubMed2006

Synthesis of tentacle-type magnetic beads as immobilized metal-chelate affinity support for cytochrome c adsorption.

Magnetic poly(2-hydroxyethylmethacrylate) (mPHEMA) beads with an average diameter of 100-140 microm were produced by suspension polymerization in the presence of magnetite particles (i.e. Fe3O4). Specific surface area and average pore size of the magnetic beads was found to be 50 m2/g and 819 nm, respectively. Ester groups in the mPHEMA structure were converted to imine groups by reacting with poly(ethyleneimine) (PEI) in the presence of NaH. Amino (-NH2) content of PEI-attached mPHEMA beads was determined as 102 mg PEI/g. Then, Cu2+ ions were chelated on the magnetic beads in the range of 20-793 micromol Cu2+/g. Cytochrome c (cyt c) adsorption was performed on the metal chelating beads from aqueous solutions containing different amounts of cyt c at different pHs, Cu2+ loadings and temperatures. Cyt c adsorption on the mPHEMA/PEI beads was 4.6 mg/g. Cu2+ chelation increased the cyt c adsorption significantly (40.1 mg/g). Adsorption capacity increased with Cu2+ loading and then reached a saturation value. Cyt c adsorption decreased with increasing temperature. Cyt c molecules could be reversibly adsorbed and eluted ten times with the magnetic adsorbents without noticeable loss in their cyt c adsorption capacity. The applicability of two kinetic models including pseudo-first order and pseudo-second order model was estimated on the basis of comparative analysis of the corresponding rate parameters, equilibrium capacity and correlation coefficients. Results suggest that chemisorption processes could be the rate-limiting step in the adsorption process. In the last part of this article, cyt c adsorption experiments were performed in a magnetically stabilized fluidized bed (MSFB) system at optimum conditions determined from the batch experiments. The adsorption capacity decreased significantly from 46.8 to 15.4 mg/g polymer with the increase of the flow-rate from 0.5 to 4.0 ml/min. The resulting magnetic chelator beads possessed excellent long-term storage stability.

Adsorption↗
PubMed2005

Folate-mediated targeting of polymeric conjugates of gemcitabine.

The synthesis of two new macromolecular prodrugs for active tumor targeting was set up. Gemcitabine (2'-deoxy-2',2'-difluorocytidine) was conjugated to alpha,beta-poly(N-2-hydroxyethyl)-DL-aspartamide (PHEA) through succinyl or diglycolyl hydrolysable spacers. The targeting agent folic acid was attached to the macromolecular backbone through the aminocaproic spacer. The two conjugates [PHEA-(5'-succinylgemcitabine)-1'-carboxypentyl-folamide and PHEA-(5'-diglycolyl-gemcitabine)-1'-carboxypentyl-folamide], were purified and extensively characterised by spectroscopic (UV, IR and NMR) and chromatographic analyses to determine the correct chemical structure, the purity degree and the reaction yield. In vitro studies demonstrated that the drug release depends on the spacer arm (diglycolyil or succinyl) and incubation pH. After 30 h incubation at pH 7.4, mimicking the plasma and extracellular compartments, the gemcitabine release from the succinyl and diglycolyl derivatives was 28 and 31%, respectively. After 30 h incubation at pH 5.5, mimicking the lisosomial compartment, the drug released from both bioconjugates was lower than 13%. In plasma, the polymer conjugation increased the drug stability and provided for a sustained drug release. In vitro citotoxicity studies performed using human nasopharyngeal epidermal carcinoma KB cells demonstrated that PHEA-(5'-succinylgemcitabine)-1'-carboxypentyl-folamide displays an higher dose dependent cytotoxic effect with respect to PHEA-(5'-diglycolyl-gemcitabine)-1'-carboxypentyl-folamide.

Antimetabolites, Antineoplastic↗
PubMed2004

Molecular recognition based cadmium removal from human plasma.

Molecularly imprinted polymers (MIPs) are easy to prepare, stable, inexpensive and capable of molecular recognition. MIPs can be considered as affinity separation media. Cadmium is a carcinogenic and mutagenic element. There is no specific treatment available for acute or chronic metal poisoning. Besides supportive therapy and hemodialysis, metal poisoning is often treated with commercially available chelating agents including EDTA and dimercaprol. However, there is histopathological evidence for increased toxicity in animals when these agents are utilized. The aim of this study is to prepare ion-imprinted polymers, which can be used for the selective removal of Cd2+ ions from Cd2+-overdosed human plasma. N-Methacryloly-(L)-cysteinemethylester (MAC) was chosen as the complexing monomer. In the first step, Cd2+ was complexed with MAC and the Cd2+ -imprinted p(HEMA-MAC) beads were synthesized by suspension polymerization. After that, the template (i.e., Cd2+ ions) were removed using 0.1 M thiourea solution. The specific surface area of the Cd2+ -imprinted poly(HEMA-MAC) beads was found to be 19.4 m2/g with a size range of 63-140 microm in diameter and the swelling ratio was 78%. According to the elemental analysis results, the beads contained 42.1 micromol MAC/g polymer. The maximum adsorption capacity was 32.5 micromol Cd2+/g beads. The relative selectivity coefficients of imprinted beads for Cd2+/Pb2+ and Cd2+/Zn2+ were 7.8 and 1683 times greater than non-imprinted matrix, respectively. The Cd2+-imprinted poly(HEMA-MAC) beads could be used many times without decreasing their adsorption capacities significantly.

Adsorption↗