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At least 685 records · Page 38Linked to original sources
PubMed2001

Preparation of magnetic dye affinity adsorbent and its use in the removal of aluminium ions.

Aluminium has recently been considered as a causative agent in dialysis encephalopathy, osteodystrophy, and anemia occuring in hemodialysis patients. The aim of this study is to prepare magnetic poly(2-hydroxyethylmethacrylate) (mPHEMA) adsorbent and to investigate it's useability for the removal of Al(III) ions from drinking and dialysis water. Magnetic PHEMA beads in a size range 80-120 microm were produced by a dispersion polymerization technique. Then Alizarin Red was covalenlty attached onto the mPHEMA beads. Al(III) adsorption from aqueous solutions was examined by batch system. mPHEMA beads were characterized by swelling tests, electron spin resonance (ESR), scanning electron microscopy (SEM), and elemental analysis. Important results obtained in this study are as follows: the swelling ratio of mPHEMA beads was 34%. The presence of magnetite in the polymeric structure was confirmed by ESR. The mPHEMA beads have a spherical shape and porous structure. Alizarin Red loading was 135.8 micromol g(-1) polymer. The maximum Al(III) adsorption was 722 micromol g(-1) polymer at pH 5.0. Non-specific Al(III) adsorption was about 23 micromol g(-1) polymer under the same conditions. High desorption ratios (98%) were achieved by using 0.1 M HNO3. It was possible to reuse the beads without significant loss of Al(III) adsorption capacity.

Adsorption↗
PubMed2003

Chemically-bound nerve growth factor for neural tissue engineering applications.

In order to promote regeneration after spinal cord injury, growth factors have been applied in vivo to rescue ailing neurons and provide a path finding signal for regenerating neurites. We previously demonstrated that soluble growth factor concentration gradients can guide axons over long distances, but this model is inherently limited to in vitro applications. To translate the use of growth factor gradients to an implantible device for in vivo studies, we developed a photochemical method to bind nerve growth factor (NGF) to microporous poly(2-hydroxyethylmethacrylate) (PHEMA) gels and tested bioactivity in vitro. A cell adhesive photoreactive poly(allylamine) (PAA) was synthesized and characterized. This photoreactive PAA was applied to the surface of the PHEMA gels to provide both a cell adhesive layer and a photoreactive handle for further NGF immobilization. Using a direct ELISA technique, the amount of NGF immobilized on the surface of PHEMA after UV exposure was determined to be 5.65 +/- 0.82 ng/cm2 or 3.4% of the originally applied NGF. A cell-based assay was performed to determine the bioactivity of the immobilized NGF. Using pheochromocytoma (PC-12) cells, 30 +/- 7% of the cell population responded to bound NGF, a response statistically similar to that of cells cultured on collagen in the presence of 40 ng/ml soluble NGF of 39 +/- 12%. These results demonstrate that PHEMA with photochemically bound NGF is bioactive. This photochemical technique may be useful to spatially control the amount of NGF bound to PHEMA using light and thus build a stable concentration gradient.

Animals↗
PubMed2003

Albumin and fibrinogen adsorption on cibacron blue F3G-A immobilised onto PU-PHEMA (polyurethane-poly(hydroxyethylmethacrylate)) surfaces.

In the present work, it is intended to study the effect of Cibacron blue F3G-A (CB) immobilised onto PU-PHEMA (polyurethane-poly(hydroxyethylmethacrylate)) surfaces on protein adsorption and bacterial adhesion. CB immobilisation was carried out by covalent binding between its triazine ring and the hydroxyl groups of the polymer. Characterisation of the films was carried out by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FT-IR), contact angle measurements. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). CB efficiency was evaluated using radiolabelled albumin and fibrinogen from pure solutions, mixtures of both and plasma. Bacterial adhesion tests before and after albumin pre-coating were also performed. The presence of CB increases albumin and fibrinogen adsorption to PU-PHEMA surfaces. The incorporation of CB onto the PU-PHEMA surface also increases bacterial adhesion. Although albumin pre-coating decreases bacterial adhesion onto PU (67% decrease) and PU-PHEMA-CB (80%), bacterial adhesion is always lower on PU and PU-PHEMA surfaces than on PU-PHEMA-CB. These results demonstrate that, in contrast to what has been described for CB bound to dextran, CB immobilisation on PU-PHEMA surfaces presents low selectivity to albumin and increased bacterial adhesion relatively to PU and PU-PHEMA surfaces.

Adsorption↗
PubMed1991

Adsorption of negatively charged microcapsules to a poly(2-hydroxyethylmethacrylate)/polyamine graft co-polymer surface.

The electrokinetic properties of artificial particles--microcapsules--were compared with those of the rat lymphocyte sub-populations, T and B cells, and similar results were obtained. The affinity of the microcapsules to the polyamine graft co-polymer, which was claimed to be capable of separating the cells efficiently, was measured and it revealed that not the magnitude of the surface negative charge and the kind of dissociable groups, but the balance of the anionic and cationic charges on the microcapsule surface played a key role in their adsorption to the co-polymer.

Adsorption↗
PubMed1993

The effect of plasma-induced graft copolymerization of PHEMA on silicone rubber towards improving corneal epithelial cells growth.

A PHEMA grafted polymer film was prepared by plasma induced graft copolymerization onto an elastic material, silicone rubber. The control, Ar plasma-treated, and PHEMA-grafted silicone rubber surfaces were characterized by ESCA, FTIR-ATR, and SEM techniques. ESCA verified the respective chemical shift of control and Ar plasma-treated films. The presence of the grafted PHEMA was also verified by ESCA. The amounts of grafted PHEMA did not monotonously increase with the plasma exposure conditions, but decreased after passing a maximum. The introduction of PHEMA onto a hydrophobic support provided an adequate surface for rabbit corneal epithelium cell attachment and growth. Cell attachment and growth onto these surfaces were examined by light microscopy. Cell attachment onto the control and Ar plasma-treated surface was negligible, while improved attachment and growth of rabbit corneal epithelium cells was demonstrated on the PHEMA-grafted polymer surface. The PHEMA-grafted silicone rubber surface demonstrated a confluent cell layer after 72 h.

Animals↗
PubMed1994

Protein adsorption behaviour of ionogenic poly(HEMA) membranes: a fluorescence study.

A series of ionogenic poly(HEMA) membranes which were prepared by bulk copolymerization of 2-hydroxyethylmethacrylate (HEMA) and anionic or cationic comonomers, acrylic acid (AA), and dimethylaminoethylmethacrylate (DMAEMA), were characterized by equilibrium swelling measurements, surface free energies, and protein adsorption studies. It was found that their equilibrium water content (EWC) values are greater than 40% which increases with increasing comonomer concentration. That is why the surface free energy is approximately the same (approximately 60 erg cm-2) for all surfaces and does not depend mainly on the composition of the polymer matrix. The adsorption of two plasma proteins that have received much attention, i.e. BSA and fibrinogen, on these membranes was followed by fluorimetric measurements as a function of time. The uptake of proteins from dilute solutions appeared to be directly related to the type and density of surface charge, and also structural properties of the proteins.

Adsorption↗
PubMed1999

Diamine-plasma treated and Cu(II)-incorporated poly(hydroxyethylmethacrylate) microbeads for albumin adsorption.

Poly(2-hydroxyethylmethacrylate) (PHEMA) microbeads prepared by suspension polymerization were treated with diamine-plasmas (i.e. ethylene-diamine (EDA) and hexamethylene diamine (HMDA)) in a glow-discharge reactor in which the exposure time and glow-discharge power were changed between 5 and 30 min and 5 and 20 W, respectively. The amount of nitrogen deposition increased both with increase in exposure time and glow-discharge power. The maximum amounts of nitrogen deposition on the microbeads were 22.3 and 23.4 micromol g(-1) with the EDA- and HMDA-plasmas. Then, Cu(II) ions were incorporated onto the PHEMA microbeads by chelating with the nitrogen-carrying functional groups. Different amounts of Cu(II) ions (2.4-6.8 mg g(-1)) were incorporated on the PHEMA microbeads by changing the initial concentration of Cu(II) ions. Bovine serum albumin (BSA) adsorption onto the unmodified PHEMA, diamine-plasma treated PHEMA, and diamine-plasma treated Cu(II)-incorporated PHEMA microbeads was investigated. The non-specific adsorption of BSA on the unmodified microbeads was very low (0.22 mg BSA g(-1)). Deposition of nitrogen increased the BSA adsorption (9.3 mg g(-1) for EDA-plasma and 12.7 mg g(-1) for HMDA-plasma). Cu(II)-incorporation significantly increased the BSA adsorption (154 mg g(-1) for EDA-plasma and 178 mg g(-1) for HMDA-plasma). Further increases in the albumin adsorption capacities of the polymer microbeads (185 mg g(-1) for EDA-plasma and 208 mg g(-1) for HMDA-plasma) were observed when human plasma was used. More than 92% of the adsorbed albumin molecules was desorbed in 1 h in the desorption medium containing 0.5 M NaSCN at pH 8.0. Repeated adsorption-desorption cycles showed the feasibility of these plasma-modified polymer microbeads.

Adsorption↗
PubMed1992

Covalently linking a peptidyl carbamate elastase inhibitor to a hydrophilic polymer increases its effectiveness in preventing emphysema and secretory cell metaplasia in the hamster.

A peptidyl carbamate, p-nitrophenyl N-(succinyl-L-alanyl-L-alanyl-L-prolyl-methyl)-N-isopropylcarbamate++ + (PCI) was tested for its ability to inhibit the elastolytic activity of human neutrophil elastase (HNE) and to prevent HNE-induced emphysema and secretory cell metaplasia in the hamster. In vitro, 50% of the elastolytic activity of 10 micrograms of HNE was inhibited by 0.9 micrograms of PCI, a molar ratio of PCI to HNE of 4.5. Bronchoalveolar lavage of hamsters receiving PCI intratracheally showed a rapid decrease in HNE inhibitory activity (4 min for 50% decrease), suggesting rapid clearance, binding, or inactivation of the PCI. Instillation of 300 micrograms of HNE combined with 100, 500, or 3,000 micrograms PCI, a 16-, 83-, and 503-fold molar excess of PCI, respectively (molar ratios of 17, 84, and 504), suppressed HNE-induced lung hemorrhage, but it did not moderate HNE-induced emphysema despite the large molar excess of inhibitor. When PCI was covalently bound to a linear hydrophilic polymer of alpha,beta-poly[N(2-hydroxyethyl)-D,L-aspartamide], producing a polymer-bound carbamate inhibitor (PPCI) of HNE, the time for a 50% decrease of PPCI functional activity from the hamster lung lavage was 421 min. Instillation of 100 micrograms of PPCI 1 h before instillation of 300 micrograms HNE resulted in significant amelioration of emphysema; 900 micrograms of PPCI was required to obtain amelioration of bronchial secretory cell metaplasia. The larger dose of PPCI also provided significant amelioration of emphysema when the interval between PPCI and HNE administration was 8 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1998

Structural integrity of resin-modified glass ionomers as affected by the delay or omission of light activation.

Since light activation of resin-modified glass ionomers as a means of polymerizing the HEMA is usually done shortly after mixing occurs, the acid-base reaction will proceed mainly within a formed HEMA-polymer matrix. Delaying or omitting light activation may alter the structure and consequently its integrity. The aim of this study was to investigate the effect on the structural integrity of Fuji II LC, Photac-Fil, and Vitremer by delaying or omitting light initiation as compared with the integrity when light activation is performed 2 min after mixing occurs. We evaluated integrity by three-body wear experiments, conducted 8 hrs after sample preparation, to establish the integrity in the early phase of hardening, as well as after 1 wk and after 4 mos, to follow the materials throughout the process of maturation. When light activation was delayed for 1 hr, the structural integrity of Fuji II LC and Photac-Fil improved significantly in the early stages of hardening. In the case of Vitremer, an hour's delay of light activation significantly decreased integrity, which declined further when light activation was omitted. Fuji II LC was not affected by the omission of light activation, while Photac-Fil was markedly weakened. After 4 mos of aging, most of the samples of each product which had been cured by the different methods attained equal integrity, with the exception of the non-light-activated Vitremer samples, which remained weaker. We concluded that the structural integrity of resin-modified glass-ionomer cements benefits from a chemical integration of the polyalkenoate and poly-HEMA networks, as in Vitremer. Improvement in the structural integrity in the early phase for cements with a mechanical entanglement of the matrices, as in Fuji II LC and Photac-Fil, requires an acid-base reaction, a considerable portion of which may take place before activation of the HEMA polymerization.

Composite Resins↗
PubMed1988

Hydron gel implants in vocal cords.

A new operation for the correction of insufficient closure of the glottis is described. A Hydron rod is implanted while the patient is under general anesthesia at direct laryngoscopy; the operative microscope is used for visualization and illumination. The implant was introduced into a submucosal tunnel made by special instruments after a transverse incision was made of the vocal mucosa, 1 or 2 mm in front of the insertion of the processus vocalis. A spindle-form implant made from dry Hydron gel was used. This swells in the tissue within a short time. The results of the operation, which was performed successfully on 40 patients, reflects an improvement in the quality of the voice, as demonstrated by sound analysis and a considerable subjective decrease in symptoms--especially voice fatiguability.

Adolescent↗
PubMed1993

Relationship of surface characteristics to cellular attachment in PU and PHEMA.

Adhesion characteristics of fibroblastic baby hamster kidney (BHK) cells and epithelial Madine Darby kidney (MDBK) cells on polyurethane (PU) and polyhydroxyethylmethacrylate (PHEMA) based surfaces have been studied. PU surfaces were prepared by a classical solvent-casting procedure of Pellethane solution that contains different types of solvents, i.e., THF, dioxane and their compositions. PHEMA based surfaces were obtained by bulk polymerization of respective comonomers (HEMA, acrylic acid, AA, and dimethylaminoethylmethacrylate, DMAEMA) in the presence of the crosslinker. Thus, a number of polymeric surfaces were obtained with different surface charges (COO- and NH+4) and with different surface free energies in a range between 60-82 ergs/cm2. Surface properties of these membranes were characterized by equilibrium water contents, air and octane contact angles, surface free energies, SEM photographs and ATR-FTIR spectra. Interactions of BHK and MDBK cells with the surfaces were examined in stationary culture conditions which were carried out in MEM supplemented with fetal calf serum. The observations strongly suggested that the chemical and/or physical properties of membrane surface and morphology of the cell control the degree of cell adhesion to the PU and PHEMA based membranes.

Animals↗
PubMed1993

Hydrogen grafted polymer surfaces: interaction and morphology of platelets.

Besides the quantification of platelet adhesion, the morphology of adherent platelets on a polymer surface seems to be important as far as thrombogenicity is concerned. It is suggested that such events usually take place on a layer of adsorbed proteins on the surface of the blood. In the present study, we observed the morphological variation of adherent calf platelets (in vitro under static conditions) on bare and hydrogel-grafted Angioflex sheets. Electron micrographs indicate the extent of deformation of the Angioflex sheets varying with modified substrates as compared to the bare sheets.

Animals↗
PubMed1995

Water and antimicrobial agent permation of PU and PHEMA membranes in relation to their surface and bulk properties.

Four types of polyurethane (PU) and two types of 2-polyhydroxyethylmethacrylate (PHEMA) membranes were prepared by convenient methods. Surface properties, water and antibacterial agent permeabilities of PU membranes were investigated. Water permeability values were determined in the region of 2000 g/m2.24 h. The membranes were found to have sufficient permeability toward antibacterial agents of 1% Silver Sulfadiazine and Bacitracin 10,000 UI-Neomycin sulphate 100 mg ointment.

Anti-Infective Agents, Local↗
PubMed1997

In vitro assessment of the biological activity of basic fibroblast growth factor released from various polymers and biomatrices.

The kinetics of controlled release of basic fibroblast growth factor (bFGF) from polymers (sutures, polycarbonate, Hydron, and Elvax), biopolymers (alginate), and biomatrices (lens capsules), and conditions for storage of bFGF (temperature, plastic type, heparin) were evaluated in vitro. Tissue culture proliferation bioassays with 3T3 fibroblasts, showed that only lens capsules with bFGF had a sustained release of bFGF for up to three weeks. The other materials released all of the 'bound' bFGF with two hours or produced an inflammatory response in vivo. Therefore, the lens tissue had the most potential for controlled long-term delivery of bFGF in vivo. These studies emphasise the importance of in vitro analysis of release kinetics of growth factors from a range of materials as a basis for potential in vivo applications.

3T3 Cells↗
PubMed1992

Hepatocyte immobilization on PHEMA microcarriers and its biologically modified forms.

Polyhydroxyethylmethacrylate (PHEMA) based microcarriers with different bulk structures were prepared by a phase inversion polymerization technique. PHEMA surfaces were further modified chemically by glow-discharge treatment, and biologically by covalent attachment of fibrinogen and collagen. Hepatocytes were isolated from young male Wistar rats using an in situ portal vein collagenase perfusion technique. Freshly isolated hepatocytes were seeded at 6 x 10(5) cells/mL and microcarrier concentration was 10 g/L. Stationary microcarrier cultures were carried out in standard (nontissue culture) polystyrene petri dishes in a humidified 5% CO2 incubator at 37 +/- 0.5 degrees C. Cell attachment was followed by light microscopy by taking samples from the culture medium every 30 min. Urea and protein syntheses by microcarrier-attached hepatocytes were determined by standard techniques. Nonswellable (highly cross-linked) hydrophilic PHEMA microcarriers did not support cell attachment and viability. However, swellable (low cross-linked) PHEMA microcarriers (pretreated in FBS) allowed high attachment and cell spreading. PHEMA microcarriers treated in dimethylaminoethylmethacrylate (DMAEMA) glow-discharge plasma also improved the cell attachment characteristics of the PHEMA microcarriers. The highest attachment efficiencies (immobilization yields) were observed with the biologically modified PHEMA microcarriers, especially modified with fibronectin. Metabolic activity, as estimated by urea and protein syntheses, was also higher in these microcarriers.

Animals↗
PubMedDate not supplied

Influence of optic and haptic materials on the adherence of Staphylococcus epidermidis to intraocular lenses: a pilot study.

To evaluate in vitro the adherence of Staphylococcus epidermidis to intraocular lenses (IOL) of different optic and haptic materials and design, we used a quantitative cultural method. Polymethylmethacrylate (PMMA), PMMA-prolene, polyHEMA, silicone and surface-modified PMMA (wet and dry) implants were tested. Adherence differed significantly in the various groups, with the best performance by all-PMMA IOL.

Bacterial Adhesion↗