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Results for “Polyhydroxyethyl Methacrylate”

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At least 19 recordsLinked to original sources
PubMed1992

Compatibility of intraocular lenses with blood and connective tissue cells measured by cellular deposition and inflammatory response in vitro.

Injection molded poly(methyl methacrylate) (IM-PMMA), lathe-cut PMMA (LC-PMMA), heparin surface modified PMMA (HSM-PMMA), silicone, and polyhydroxyethyl methacrylate (polyHEMA) intraocular lenses (IOLs) were incubated with platelets, granulocytes, mouse macrophage-like RAW 264.7 cells and mouse fibrosarcoma L929 cells to examine their compatibility. The number of cells attached to the IOL was counted after the central IOL area (0.04 mm2) was photographed with an inverted light microscope. Cell morphology was examined by scanning electron microscopy (SEM). More platelets and granulocytes were attached to the IM-PMMA and silicone IOLs than to the HSM-PMMA and polyHEMA IOLs (P less than .05). RAW 264.7 and L929 cells grew on PMMA-based and silicone IOLs, whereas HSM-PMMA and polyHEMA IOLs did not support an abundant growth of these cells. Granulocytes were incubated with the IOLs in the presence of Luminol and the generation of chemiluminescence was measured. Poly(methyl methacrylate)-based IOLs caused granulocytes to release significant amounts of oxygen radicals, while the polyHEMA IOL was almost inactive in stimulating granulocytes. Silicone and HSM-PMMA IOLs showed an intermediate level of stimulating activity. The light intensity reached a peak within 14 minutes with the IM-PMMA IOL, and in about 18 minutes with the other IOLs. Our results suggest that IOL hydrophilicity prevents attachment of cells and that a hydrophilic, soft surface can discourage granulocyte stimulation.

Animals↗
PubMed1990

Preparation of spherical encapsulation of activated carbons and their adsorption capacity of typical uremic toxins.

A method has been designed for making spherical microencapsulation of activated-carbon particles for use in the removal of metabolic wastes and/or toxins from blood. This bench-scale method was able to make better uniformity in particle size, and at a higher particle production rate. The material properties such as particle size, particle porosity, electromicroscopy of surface morphology, surface hardness, and pore-size distribution were characterized in order to conclude with their adsorption capacity for specific toxin solutes. The performance characteristics of these self-prepared particle encapsulation was also evaluated against the commercially available hemoperfusion particles, e.g., Kuraray's DHP (Japan). The encapsulation particles were also coated with polyhydroxyethyl methacrylate (PHEMA) for blood compatibility purpose.

Adsorption↗
PubMed1990

Evaluation of polyvinyl alcohol hydrogel as a soft contact lens material.

We prepared a transparent polyvinyl alcohol (PVA) hydrogel from a PVA solution in a mixed solvent consisting of water and a water-miscible organic solvent by cooling. The physical properties of the hydrogel were evaluated in various mixed solvents and compared with those of commercially available soft contact lens materials, such as polyhydroxyethyl methacrylate (PHEMA) and copolymers of methylmethycrylate (MMA) and N-vinyl pyrrolidone (N-VP). The PVA hydrogel showed higher tensile strength and elongation before breaking than did the other materials. Also, the PVA hydrogel was comparable in its high water content and its oxygen permeability with the MMA/VP copolymers. The protein adsorption of the PVA hydrogel was much lower than that of the other materials. Soft contact lenses of PVA hydrogel were applied to rabbit eyes for 12 weeks. The effects of the lenses on the cornea were studied by biomicroscopy, ultrasonic pachymetry, and histopathologic examination. No abnormal findings were noted, suggesting that the PVA hydrogel may be promising as a new material for use in soft contact lenses.

Animals↗
PubMed1991

In vitro testing of a simply constructed, highly stable glucose sensor suitable for implantation in diabetic patients.

We have constructed and tested in vitro a potentially implantable, needle-type amperometric enzyme electrode which is suitable for continuous monitoring of glucose concentrations in diabetic patients. The major requirements of stability during operation and ease of manufacture have been met with a sensor design which involves a simple dip-coating procedure for applying to a platinum base electrode an inner membrane of glucose oxidase immobilised in polyhydroxyethyl methacrylate (pHEMA), and an outer membrane composed of a pHEMA/polyurethane mixture. Sensors were operated at 700 mV for detection of hydrogen peroxide. Calibration curves for the sensor were linear to at least 20 mM glucose and were unaffected by a reduction in PO2 from 20 to 5 kPa. During continuous operation in 5 mM buffered glucose solutions in vitro, sensors suffered no significant loss of response over periods of up to 60 h. Such electrodes are, therefore, useful for development as in vivo glucose sensors.

Biosensing Techniques↗
PubMed1991

An electrically modulated drug delivery device: I.

A controlled drug delivery device based on the principle of electrophoresis is described. A model system using propranolol HCl and PHEMA films was used to demonstrate how control over the release of a model drug may be achieved using low constant electric currents. It was found that a linear relationship existed between electric current and drug delivery rate. Additionally, two main effects of applying an electric current during the lag period of delivery from the system were identified. First, the drug delivery rate was less when a current was applied before the lag period had expired, and second, the voltage-time profiles were found to be significantly different. The model shows the feasibility of using an electrophoretically controlled drug delivery device to provide truly controllable and predictable release rates.

Cross-Linking Reagents↗
PubMed1992

True and apparent oxygen permeabilities of contact lenses.

We studied the passage of oxygen through some commercially available contact lenses. Oxygen diffusion coefficients were determined by the time-lag method and a 201T Redher permeometer was used to measure the oxygen permeability and transmissibility by the polarographic method. The measurements were carried out at room temperature with 0.09% sodium chloride physiologic solution. The following types of lenses were tested: (1) 12 lenses of cellulose acetate butyrate (CAB) of a mean thickness of 0.194 mm (observed Dk approximately 6.3 barrers) (1 barrier is equivalent to 10(-11) cm3 of O2 (STP).cm2/cm3.s.mm Hg). (2) 13 lenses of a cross-linked polyhydroxyethyl methacrylate (2-HEMA), manufactured by Lenticon and Bausch & Lomb, with 40 and 38.6% water content, respectively. The mean thicknesses were 0.160 and 0.148 mm, respectively (observed Dk approximately 12 to 13.5 barrers). (3) Finally 10 lenses of a copolymer of 2 HEMA with N-2-vinylpyrrolidone (2-HEMA/VP), manufactured by Bausch & Lomb under the name Hydrocurve II, with 55% water content and a mean thickness of 0.138 mm (observed Dk approximately 24.5 barrers). For a given lens thickness, the transmissibility and permeability of lenses whose main material is 2-HEMA are found to be equivalent. This fact suggests the use of such material as a standard in the study of diffusion processes in contact lenses of low oxygen permeability (Dk approximately 12 to 13.5 barrers). We studied the boundary layer effects and found significant discrepancies between true and apparent oxygen permeabilities. The apparent transmissibility decreased with increasing lens thickness, this effect being more apparent for lenses with low water content. Oxygen permeability is found to be exponentially dependent on water content rather than on the chemical composition of the hydrogel.

Contact Lenses↗
PubMed1990

Towards an artificial cornea: surface modifications of optically clear, oxygen permeable soft contact lens materials by ammonia plasma modification technique for the enhanced attachment and growth of corneal epithelial cells.

The advent of high water content, oxygen permeable contact lens materials has made the intracorneal implants more feasible. A major obstacle encountered is the regrowth of a stable epithelium over the implant. Therefore, ammonia gaseous plasma modification technique was used to modify the surface chemical properties of soft contact lens material such as poly(2-hydroxyethyl methacrylate and methacrylic acid), PHEMA-MAA copolymer, in an attempt to enhance the cell attachment and growth of rabbit corneal epithelial cells.

Ammonia↗
PubMed1990

[A polyvinyl alcohol (PVA) hydrogel as a soft contact lens material].

A transparent polyvinyl alcohol (PVA) hydrogel was prepared from a PVA solution in a mixed solvent consisting of water and a water miscible organic solvent by cooling. The physical properties were evaluated in comparison with commercially available soft contact lens materials, such as polyhydroxyethyl methacrylate (PHEMA) and copolymers of methyl methacrylate (MMA) and N-vinyl pyrrolidone (VP). The PVA hydrogel showed higher tensile strength and elongation at break than the other materials, while it had high water content and oxygen permeability the latter being comparable to those of PMMA/VP copolymers. The protein adsorption of the PVA hydrogel was much less than those of the other materials. The PVA hydrogel soft contact lenses were applied on rabbit eyes for 12 weeks. The influence on the cornea was studied by biomicroscopy, ultrasonic corneal pachymetry and histopathological examination. These examinations revealed no abnormal findings in the cornea. These results suggest that the PVA hydrogel may be promising as a new soft contact lens material.

Adsorption↗
PubMed1978

Surface tension measurements on methacrylate monomer solutions, selected solvents, and gel extracts.

The surface tensions of selected methacrylate monomer and solvent solutions were measured, and calibration curves were generated. The curves were then used to deduce the amounts of water soluble extractables in methacrylate hydrogels by measuring the surface tension of the extractant. The detectability limit (parts per 10,000) and the overall sensitivity of the method suggests its possible use as an extraction monitor test for related biomaterials.

Acrylates↗
PubMedDate not supplied

Influence of physico-chemical parameters on the release kinetics of ketoprofen from Poly(HEMA) crosslinked microspheres.

This report analyses the release of Ketoprofen from Poly(HEMA) microspheres crosslinked with EGDMA at different crosslinking ratios and loaded by soaking in saturated solutions of the drug. Release appears to be influenced by the dissolution of Ketoprofen in the hydrogel and it is strictly correlated with the diffusibility of the drug in the gelled matrix. The release rate of the drug in the hydrogel rises with the increase in the diffusional conductance and the release kinetics approaches zero order particularly at the higher values of the diffusional conductance.

Cross-Linking Reagents↗
PubMedDate not supplied

A hydrogel pericardial patch.

Patients undergoing repeat cardiac operations are higher operative risks than those undergoing an initial cardiac procedure because adhesion formation can occur if the native pericardium is not closed. A unique composite patch that may be used to augment the pericardial tissue when primary closure is not possible has been developed. The patch is made of a hydrogel, poly (2-hydroxyethyl methacrylate), reinforced with an ethylene tetrafluoroethylene (ETFE) mesh. The mesh provides the needed mechanical properties, whereas the patch's surface properties are comparable to the hydrogel. Two types of patches were fabricated: one with the mesh weave at a perpendicular orientation and one at 45 degrees to the principle loading direction. The patches were mechanically tested and compared with canine pericardium. Ultimate tensile strength of the patches is not significantly different from canine pericardium (p less than 0.05), are the patch suture strength is nearly twice that of canine pericardium. The perpendicular patch is stiffer than canine pericardium, whereas the 45 degree patch is not (p less than 0.05). The 45 degree patch shows considerable promise as a pericardial substitute because it closely matches the properties native canine pericardium.

Animals↗
PubMed1992

Staining of semithin tissue sections embedded in HPMA, quetol 523 and MMA.

Various tissues fixed in a mixture of formaldehyde and glutaraldehyde, and embedded in an improved 2-hydroxypropyl methacrylate mixture were employed for studying the fine structures of cells and tissues by light microscopy. The embedding mixture contained Quetol 523 and methyl methacrylate as a plasticizer without a cross-linker. The catalyst was QCU-1. The mixture had a low viscosity, was easy to handle and penetrated readily and completely into the specimen, producing a homogeneous block from which it was easy to cut sections of 1-2 microns in thickness. A wide variety of stains have been employed with such sections and those reported here are hematoxylin-eosin, Azan and PAS. There was excellent preservation of alkaline phosphatase activity. A method of poststaining immunoperoxidase labeling was also applied to the mouse pancreas and examples of staining with insulin are included.

Aminosalicylic Acid↗
PubMed1991

Early deposition trends on group I (Polymacon and Tetrafilcon A) and group III (Bufilcon A) materials.

One of the problems with hydrophilic contact lenses is that they are susceptible to spoilage. This study investigated the degree of spoilage associate with lenses of various surface changes during the early stages of wear and the effect of surfactant cleaning of lenses at this stage. Ten patients wore a control HEMA lens on one eye and either an ionic (Bufilcon A) or non-ionic (Tetrafilcon A) lens on the other for one week and used a peroxide system for disinfection. The lenses were then replaced with identical lenses, which were also worn for 1 week, with surfactant cleaning added to the care regimen. The lenses then were examined by fluorescence spectroscopy in order that the extent of lipid and protein deposition could be assessed. The results indicate that protein accumulation is highly material dependent, whereas lipid deposition is primarily patient dependent. Also the term "ionic" does not necessarily indicate equally enhanced deposition in all lenses so termed. Surfactant cleaning appears to be of little benefit in reducing deposits during the early stages of wear, its benefit in the long-term being of much greater significance.

Adult↗
PubMed1990

Suspension polymerization of 2-hydroxyethyl methacrylate in the presence of polymeric diluents: a novel route to spherical highly porous beads for biomedical applications.

Spherical, highly porous beads of poly(2-hydroxyethyl methacrylate) (PHEMA) cross-linked with ethylene glycol dimethacrylate (EGDM) were prepared by suspension polymerization of HEMA in concentrated NaCl solutions in presence of toluene, poly(methyl methacrylate) (PMMA) in toluene, and poly(tetramethylene glycol) (PTMG). Magnesium hydroxide prepared in situ in the dispersion medium gave the best stabilization effect for the monomer droplets. In the presence of PTMG, beads having nearly 1.0 mm in diameter could be prepared, while toluene alone as the diluent produced beads of very small size. Removal of PMMA or PTMG from the beads after polymerization using suitable solvents gave rise to highly porous PHEMA microspsheres. Polymerization in the presence of PTMG produced microspsheres with better spherical geometry as compared to those generated in the presence of PMMA. The effect of various factors such as NaCl concentration, concentration of Mg(OH)2, and the concentration of PMMA or PTMG in the monomer phase on the stability of the suspension and the particle size distribution was investigated.

Cross-Linking Reagents↗
PubMed1989

The short-term blood biocompatibility of poly(hydroxyethyl methacrylate-co-methyl methacrylate) in an in vitro flow system measured by digital videomicroscopy.

An in vitro flow system for short-term blood biocompatibility testing of solution-castable polymeric biomaterials was developed. This system was relatively free of artefacts resulting from blood contact with materials other than the test material itself. In conjunction with epifluorescence videomicroscopy and digital image processing, this method provided a high resolution, quantitative, continuous analysis of platelet adhesion, aggregation, thrombus formation, and embolization on the biomaterial surface. This system was well suited for performing biochemical assays on post-contact blood for assessment of platelet activation and release as additional measures of the thrombogenicity of the test material. This method for biomaterials evaluation in vitro was demonstrated by a detailed examination of copolymers of hydroxyethyl methacrylate (HEMA) and methyl methacrylate (MMA). Videomicroscopic analysis of fluorescently labelled platelets adhering per unit area of the polymer surface after 5 min of flow at a wall shear rate of 500 s-1 showed a dramatic decrease with increasing HEMA fraction in the polymer. The release of serotonin and thromboxane A2 by platelets decreased with increasing HEMA fraction. Reflection interference contrast microscopy was used to examine focal contacts of platelets on the copolymer surfaces as a qualitative measure of the platelet-surface interaction. A polymer-dependent gradation in contact extent and morphology was observed, ranging from large contacts on P(MMA) to none on P(HEMA).

Biocompatible Materials↗
PubMed1988

Light and electron microscopic observation of specific atrial granules using water-miscible resin as an embedding medium.

A mixture of glycol methacrylate (GMA) and Quetol 523 was examined as an embedding medium for atrial tissue to be selectively stained for specific atrial granules. Semi-thin sections of rat atrial tissue embedded in this resin were stained with lead hematoxylin and observed under a light microscope. Atrial granules were found to be specifically stained blue black with lead hematoxylin. The same semithin sections stained with OsO4 vapor were examined electron microscopically and the atrial granules could be distinguised clearly from other cytoplasmic components. The GMA-Quetol 523 mixture is a useful embedding medium for studying the distribution of specific atrial granules by light and electron microscopy.

Animals↗
PubMed1990

Swelling of PHEMA based membranes in ethanol and their nitroglycerin permeabilities.

The aim of this study is to prepare PHEMA based polymeric membranes for a transdermal delivery system, which includes a skin permeation enhancer (i.e. ethanol) for nitroglycerin. Membranes were prepared by bulk polymerization of HEMA monomer. Polymerization was achieved in the presence of EGDMA, as the cross-linker, and AIBN as the initiator. MMA was used as a comonomer to improve the mechanical properties and to adjust the permeabilities of the resulting membranes. Water was also included in the polymerization mixture to control the matrix structure. Membranes with different chemical and physical structures were prepared. Swelling behaviour of these matrices in ethanol were observed. Nitroglycerin diffusion through swollen membranes (in ethanol) were investigated. It was obtained that the relative amounts of ingredients (i.e., HEMA, MMA, EGDMA and water) in the casting solutions affect both the equilibrium swelling values and the permeabilities. By increasing the water content and by decreasing the amounts of MMA and EGDMA both parameters can be increased. AIBN does not affect these parameters significantly.

Ethanol↗
PubMed1992

Hemocompatibility of human whole blood on polymers with a phospholipid polar group and its mechanism.

The hemocompatibility of a polymer containing a phospholipid polar group, poly(2-methacryloyloxyethyl phosphorylcholine (MPC)-co-n-butyl methacrylate(BMA)), with human whole blood was evaluated. When human whole blood without an anticoagulant was contacted with polymers, the blood cell adhesion and aggregation on the polymer without the MPC moiety was extensive, and considerable fibrin deposition was observed. This phenomenon was suppressed with an increase in the polymer MPC composition. Thus, the MPC moiety in the copolymer plays an important role in the nonthrombogenic behavior of the copolymer. These results were also confirmed by the whole blood coagulation time on the polymer surface which was determined by Lee-White method. The adsorption of phospholipids and proteins from human plasma on poly(MPC-co-BMA) was investigated to clarify the mechanism of the nonthrombogenicity observed with the polymer. The amount of phospholipids was increased; whereas, adsorbed proteins were decreased with an increase in the MPC composition. From these results, we concluded that the phospholipids adsorbed on poly(MPC-co-BMA) play the most important role in the nonthrombogenicity of the MPC copolymer.

Adsorption↗