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At least 379 records · Page 21Linked to original sources

PubMed1999

Neutrophil adhesion on polyurethanes preadsorbed with high molecular weight kininogen.

Interaction of biomaterials with blood components including neutrophils is responsible for some of the clinical complications that have occurred in cardiopulmonary bypass, hemodialysis, and ventricular assist procedures. The possibility of inhibiting the initial adhesion of neutrophils to biomaterials has been studied extensively, but the problem remains unsolved. In this study, we investigated the effect of HK adsorption on polyurethane, a widely used component of extracorporeal and intracorporeal devices. HK and HKa were allowed to adsorb on 4 different charged polyurethanes: noncharged (PU), cationic (NR(4)), anionic (SO(3)), and zwitterionic (GPC) polyurethanes. The effect of kininogen adsorption on neutrophil adhesion, the surface density of the adsorbed kininogen, and the exposure of HK domains 3 and 5 (D(3) and D(5H)), which are responsible for the binding of HK to the neutrophil integrin alpha(m)beta(2) or Mac-1, were examined. On PU, NR(4), and SO(3), kininogen adsorption reached 80% of monolayer coverage when 100 pmol/mL or higher concentration of protein solutions were used. The NR(4) surface adsorbed the most kininogen along with a high exposure of D(3) and D(5H). The availability of D(3) and D(5H) allowed neutrophils to bind to the surface via the Mac-1 receptor; thus, on the NR(4) surface, adsorbed kininogens lost their antiadhesive property, which resulted in a high degree of neutrophil adhesion. Increasing Mac-1 expression by exposure to fMLP increased the neutrophil adhesion on this surface. In contrast, exposure of D(3) and D(5H) on SO(3) was significantly less, because HK binds to anionic surfaces with similar protein sequences used for cell binding. This low binding site exposure preserved the antiadhesive property of HK. GPC was resistant to neutrophil adhesion even in the absence of adsorbed kininogens because of its phosphorylcholine moiety. Thus, both SO(3) coupled with kininogen (or kininogen peptides) and GPC have the potential to markedly reduce neutrophil adhesion to biomaterial devices.

Adsorption↗

PubMed2000

Self-expandable vascular stent covered with polyurethane membrane: an experimental preliminary study of a placement in the thoracic descending aorta of a rabbit using endovascular intervention.

The effectiveness of self-expandable vascular endoprosthesis covered with polyurethane membrane for arterial substitution was examined in the descending thoracic aorta of a rabbit, followed by an observation period of 937 days. In this model there was no evidence of thrombus, aneurysmal formation, and/or infection. The self-expandable vascular stent covered with a polyurethane membrane showed long-term patency as well as excellent function, and the histological evaluation revealed endothelial cells covering all of the surface of the endoprosthesis, as was expected. Minimal intimal hyperplasia and no calcifica-tion were demonstrated in any portions. This study suggests that our newly designed self-expandable vascular stent covered with a polyurethane membrane could serve as a satisfactory vascular endoprosthesis with a good long-term patency for substitution. Furthermore, stenting using our model is a safe, simple technique, and an effective treatment for vascular remodeling.

Animals↗

PubMed2003

[Synthesis, characterization and blood compatibility studies of biomedical aliphatic polyurethanes].

The one-step method was adopted in this study to synthesize aliphatic polyurethane with 4,4-methylene dicyclohexyl diisocyanate(HMDI), 1,4-butanediol (BDO) and poly (tetrahydrofuran) (PTMG). The tests conducted on this material were: FIR spectrum, mechanical properties test, water contact angles test, hemolysis test and platelet adhesion test. Results showed that this material has a good tensile strength up to 30 Mpa, similar to aromaphatic polyurethane. But its tensile elongation, tensile permanent change, hydrophility are better than those of aromaphatic polyurethane. The hemolysis test and platelet adhesion test showed that it has good blood compatibility.

Animals↗

PubMedDate not supplied

[Treatment of infected wounds and abscesses in bovine limbs with Ligasano-polyurethane-soft foam dressing material].

The objective of this report is to present the most important indications for the use of Ligasano-polyurethane-soft-foam dressing material in the treatment of infected wounds in cattle. For this study, 28 cattle were selected, which were treated at the clinic (2000-2003) for infected cut, puncture and laceration wounds on the limbs, purulent tarsal hygromas, large abscesses in the tarsal, crural and thigh regions, and purulent tenosynovitis of the digital flexor tendon sheath caused by penetrating puncture wounds. After routine wound cleansing, debridement or adequate surgery with wound lavage, Ligasano-polyurethane-soft-foam (Ligamed Medical Produkte, Cadolzburg-Wachendorf, Germany) was applied as a primary wound dressing instead of the conventional cotton gauze swabs or as drainage material in all these wounds. The porous surface structure of this material caused subtle wound debridement and mechanical stimulation of the wound surface increasing exudation and decreasing fibrinous adhesions. The pores ensured good drainage, reduced infection, avoided the accumulation of exudate and the following destruction of the wound surface. In all these indications, except abscesses and purulent hygromas, no or only slight purulent exudation of the treated wounds was observed. Especially in the treatment of purulent tenosynovitis of the digital flexor tendon sheath with tendon resection a rapid healing of these large surgical wounds--often within 2 weeks--was found. The therapeutic effect of Ligasano-polyurethane-soft-foam as a primary wound dressing was so convincing in these bovine patients, that it is now used exclusively as primary wound dressing material for treatment of infected wounds.

Abscess↗

PubMed2005

[Synthesis, characterization and blood compatibility studies of waterproof breathable polyurethanes].

Adopting the two-step method and changing the proportion between PEG (Polyethylene glycol) and PTMG (poly (tetrahydrofuran), we used the MDI (4,4'-diphenylmethane diisocyanate) and short chain extender BDO (1,4-butanediol) as hard segment, the PTMG and PEG as soft segment, and hence prepared a series of polyether-based thermoplastic polyurethanes. FTIR showed the structure character of these polyurethanes. The determination of mechanics property and water contact angles revealed their good mechanics properties and hydrophilicity. Blood compatibility was evaluated by hemolysis test and platelet adhesion test, which revealed their good hemocompatibility. So those polyurethanes may be of wide application in the future.

Animals↗

PubMed1991

[Polyurethane versus polyethylene: in vivo randomized study of infectious complications of central catheterization].

Polyurethane (PU) and polyethylene (PE) catheters were distributed by randomization among adult ICU patients to evaluate the impact of the catheter polymer on the rate of catheter-related sepsis (CRS). The two catheters were otherwise strictly identical. Three hundred central venous catheters were randomized and inserted in the subclavian or internal jugular vein, at the discretion of the clinician. Mean duration of insertion was 9.2 (+/- 3) days for both catheter types and mean number of line openings was 159 (+/- 60). A bacteriologic culture using a variant of Maki's technique was performed on the 205 catheters removed before patient discharge. No significant differences were found between the two catheters. Total number of tip infections was 33 and polyurethane and polyethylene prevalence ratio was 0.7. A clinical evaluation was performed for the 183 catheters inserted for a least 48 hours (in 142 patients). Patients were divided into four clinical categories according to previously reported definitions (Brun-Buisson et al., 1987). Clinical tip-infection rate was 4.4% and polyurethane and polyethylene ratio was 0.7. For three additional catheters (1.6%), only the Luer-lock was infected. These three catheters were made of polyethylene and were inserted into the internal jugular vein. The Luer-lock was made of polypropylene.

Bacterial Infections↗

PubMed1991

Antithrombotic mechanisms of urokinase immobilized polyurethane.

Urokinase immobilized polymer is highly antithrombotic, which cannot be explained only by fibrinolysis. We immobilized 10 IU/cm2 of urokinase to polyurethane by using maleic anhydride methylvinyl ether copolymer as a carrier. Then we incubated blood in circular tubes made of this material, measured the clotting factors and observed the surface of the tubes after incubation by scanning electronmicroscopy and immunofluorescence microscopy. After 5 min incubation, the relative activities of factors V, VIII, IX, X and XII, fibrinogen, plasminogen and alpha 2 plasmin inhibitor decreased, but the activity of factor VII increased. No platelet adhesion to the surface of the urokinase immobilized polyurethane was observed and there was no significant adsorption of serum proteins, including fibrinogen, fibronectin and vWF antigen, on the surface. Urokinase-immobilized polyurethane catalyzed the digestion of clotting factors as well as fibrinolysis and also inhibited platelet adhesion on its surface probably by inhibiting protein adsorption and its clinical application including vessel prosthesis should be developed further.

Blood Coagulation Factors↗

PubMed1991

Gas chromatographic-mass spectrometric analysis of urban-related aquatic and airborne volatile organic compounds. Study of the extracts obtained by water closed-loop stripping and air adsorption with charcoal and polyurethane foam.

The distribution of volatile organic compounds (VOC) in urban-influenced air and river waters was investigated. The aquatic VOC were extracted with the closed-loop stripping technique (CLST) and the airborne compounds were studied using two methods, charcoal and polyurethane foam adsorption. In both types of samples, C1-C5 alkylbenzenes and n-alkanes constitute the two major VOC groups, and the presence of these groups indicates a predominance of petroleum products in these two environmental compartments. Chlorinated compounds such as polychlorobenzenes, polychloronaphthalenes and hexachlorobutadiene are abundant in water samples, whereas tetrachloroethene is the predominant chlorinated airborne VOC. The compounds collected with each sampling system can be described in terms of ranges of volatility. These ranges (expressed as mmHg vapour pressure at 25 degrees C) can be defined approximately as 140 (methylcyclopentane)-0.65 (n-undecane) for charcoal, 5.1 (n-nonane)-0.000061 (n-docosane) for polyurethane foam and 29 (toluene)-0.000029 (n-eicosane) for the CLST. Parallel air sampling with charcoal and polyurethane foam is therefore needed to cover a VOC range similar to that afforded by the CLST in water.

Adsorption↗

PubMedDate not supplied

Effective endothelialization of polyurethane surfaces. Response to shear stress and platelet adhesion.

Biomer and Mitrathane are thromboresistant polyurethane ureas that are suitable for coating artificial valves. Degeneration of the surface coatings, however, does occur over time, and in experimental animal studies adherent thrombi have been observed as a complication. In this study, morphometric techniques applied to scanning electron microscopy were used to assess whether vascular endothelial cells harvested from jugular veins of fetal lambs could be grown to confluence on these polyurethane surfaces, whether the monolayer would remain intact under conditions of shear stress (104 dynes/cm2), and whether this would result in decreased platelet adherence of sheep platelets relative to nonendothelialized surfaces. The results have shown that both Biomer and Mitrathane could be endothelialized: 88.8 +/- 5.1% of the Biomer surface consisted of intact confluent endothelial cells, as did 95.45 +/- 1.7% of the Mitrathane surface. After 6 hr of shear stress, a significant reduction in this feature was observed (p = 0.02), but both materials still maintained a high percentage of confluent endothelial cells (78.65% for Biomer and 85.58% for Mitrathane). After 48 hr of shear stress, however, the percent confluence was similar to control values, which suggested new cell growth. Endothelialized Biomer compared with Mitrathane had fewer adherent single platelets, or small or large aggregates (p = 0.001, p = 0.01, and p = 0.05, respectively); this feature was not affected by shear stress. Whereas endothelialization of the surface clearly decreased platelet adherence on Mitrathane (p = 0.01), only a trend was seen with Biomer. These studies therefore show that endothelialization of these polyurethane surfaces is feasible.

Animals↗

PubMed1987

[Increased risk of bacterial colonization of intravenous catheters covered with transparent adhesive polyurethane bandages, compared to classical gauze bandages].

While transparent polyurethane dressings are increasingly used for the care of intravenous catheters, concern has recently been expressed regarding their microbiological safety. We have therefore compared the rate of intravenous catheter bacterial colonization after randomly assigning intensive care patients to transparent polyurethane (n = 21) or dry gauze (n = 20) dressings. Polyvinyl chloride catheters were inserted and maintained by the nurses. No antiseptic or antibiotic ointment was used. The two groups of patients were similar regarding risk factors for catheter colonization. Colonization rate was 48% (10/21) among patients with transparent dressings versus 10% (2/20) among patients with dry gauze dressings (p = 0.008). Colonizing bacterial species were Staphylococcus epidermidis (11 strains) and S. aureus (1 strain). No catheter-related bacteremia was observed. These data suggest that the colonization rate of intravenous catheters is increased by the use of polyurethane dressings, possibly increasing the risk of septic phlebitis and bacteremia.

Adult↗

PubMedDate not supplied

Biostability considerations for implantable polyurethanes.

Polyurethanes have become the most valuable implantable elastomers for uses requiring toughness, durability, biocompatibility and biostability. They are inherently stable in the body environment. However, physical and chemical changes may be effected by conditions of processing, fabrication, use or interactions with other device components. Most prominent modes of polyurethane degradation include mineralization, environmental stress-cracking and oxidation. While the mechanisms of these forms of degradation are not fully understood, an awareness of their causes and effects can lead to procedures that provide all of the long-term functionality required for the sophisticated polyurethane-based devices of today and tomorrow.

Animals↗

PubMed1987

Evaluation of explanted polyurethane trileaflet cardiac valve prostheses.

Morphologic, chemical, and hemodynamic studies were made of eight prototype polyurethane trileaflet cardiac valve prostheses that had been implanted in juvenile sheep for 17 to 21 weeks in the mitral position. Calcification of the polyurethane leaflet surfaces was the principal finding. Quantitative chemical analyses revealed calcium values with a mean of 42.7 +/- 21 mg/gm dry weight of leaflet. Morphologically, two distinct types of calcification were observed: One was associated with the polyurethane surface or the interface between the leaflet surface and microthrombi or fibrous sheaths; the other was characterized by calcification associated with degenerated cells within thrombotic material and the fibrous sheath. These morphologic findings were in accord with the results of hemodynamic performance studies indicating that these heart valve prostheses had become both stenotic and regurgitant.

Animals↗

PubMed1986

The acute thrombogenicity of a compliant polyurethane arterial graft compared with autologous vein. An experimental study in sheep.

The acute thrombogenicity of a new type of polyurethane urea graft was compared with that of autologous femoral vein graft in a sheep carotid artery interposition model. There was significantly more thrombus formation (as measured from thrombus weight and thrombus-free surface) and greater platelet accumulation in the polyurethane graft. Despite flow restriction to 25 ml/min, the patency rates after 4 hours were similar; all veins were patent and only one of the eight polyurethane grafts was occluded.

Animals↗

PubMed1977

[Skin wound granulation from contact with synthetic foil of teflon-polyurethane type].

When a plastic-foil consisting of teflon-polyurethan foam is applied to ulcer cruris and to polyurethan foam is applied to ulcera cruris and to combusted skin, pronounced granulation and formation of new capillaries and collagen fibers are observed in the contact area. The tightly adhering foils are tolerated by the wounds for more than 40 days with continous granulation. An adverse reaction against the foreign material and development of eosinophils and giant cells is not observed, though the polyurethan-foam of the foil was burst by the ingrowing granulation tissue. When the wound surface is clean, change of the dressing with this foil is necessary only every second or third day.

Bandages↗

PubMedDate not supplied

Polyurethane foam in postoperative casts.

One-half inch thick polyurethane foam is recommended for use in postoperative casts to avoid complications seen with postoperative swelling. The polyurethane is placed over the operative area, over the dorsum of the foot, and the anterior surface of the leg. The use of polyurethane foam in the postoperative cast not only avoids the necessity of having to split the cast in many instances but the foam also constitutes a compression dressing. If splitting of the postoperative cast should become necessary, the foam protects the skin.

Casts, Surgical↗

PubMed1980

[Chemical composition of linear polyurethanes and the rate of their destruction in physiological solution and animal body].

The examinations of biodestruction of segmental polyurethanes from hexamethylene diisocyanate ethylene glycol and polyesters with different chemical composition: polydiethylene glycol succinate, molecular mass 750 (formula A-19), polydiethylene glycol adypates, molecular mass 800 and 1500 (formula A-14 and A-10) were performed employing physico-chemical and histological methods. It was noted that in physiological liquids and animal organisms that polyurethanes containing more polyester bounds, which easily undergo hydrolytic decomposition, had decomposed in higher rate - A-10 > A-19 > A-14. Histological examination revealed the hydrolytic destruction of samples A-19 and A-10 during 24 weeks. However, the rate and biodestruction degree in sample A-10 (especially in ensuring period) was found to be higher than in sample A-19. This appears in its fragmentation and cell activation in connective tissue, surrounding the alloplastic material. These data are consistent to the results of physico-chemical examinations which revealed that sample A-10 after 24 weeks completely loose the durability and the molecular mass diminishes almost four times, while the sample A-19 maintains 37% of durability comparing to initial condition and molecular mass diminishes only two times. Sample A-14 undergoes destruction, at lower degree maintains 50% of durability and its molecular mass diminishes almost two times. The performed examinations show that the changes of ester groups concentration in polyurethanes give the possibility of regulation of the biodegradation rate.

Animals↗

PubMed1981

Toxicology of urea formaldehyde and polyurethane foam insulation.

Two types of foam insulation are in wide use. Urea formaldehyde foam is a relatively inexpensive, easily installed, and efficient insulation. Toxicity from this insulation is related to release of free formaldehyde into the home. Mild to incapacitating symptoms have been reported in occupants of urea formaldehyde-insulated homes. Airborne formaldehyde levels frequently have exceeded standards set for occupational exposure. The long-term consequences of such exposure are unknown. Because of publicity over the toxicity of urea formaldehyde foam, many physicians and patients have confused urea formaldehyde and polyurethane foam. Unlike urea formaldehyde, polyurethane foam is fully cured before construction. Toxicity occurs only during manufacture and curing. To date, there have been no reports to our knowledge of toxicity in occupants of polyurethane-insulated homes. However, toxicity caused by pyrolysis products may occur during combustion in homes insulated with either type of insulation. This report details 48 patients in whom complete medical data were obtained out of the first 100 patients contacting the Rocky Mountain Poison Center.

Construction Materials↗

PubMed1999

Role of Silicone Surfactant in Flexible Polyurethane Foam.

Grafted copolymers which consist of a polydimethylsiloxane backbone and polyethylene oxide-co-propylene oxide pendant groups are used as surfactants to stabilize the foam cells in the flexible polyurethane foaming process. The mechanical properties of the cured polyurethane foam such as air permeability and foam cell size are affected significantly by the structure of the silicone surfactant used in the formulation. It is shown that silicone surfactant has an important impact on both the bubble generation and the cell window stabilization stage. A series of silicone surfactants with different structures was tested. Surfactants with higher silicone content will provide lower surface tension and thus help increase the number of air bubbles introduced during mixing. These air bubbles serve as the starting point for foam cell growth. As a result, the cured polyurethane foam made with higher silicone content surfactant has a smaller bubble size. It is also shown that silicone surfactant can reduce the cell window drainage rate due to the surface tension gradient along the cell window. The Gibbs film elasticity, the dynamic film elasticity, and the film drainage rate were measured for the first time versus surfactant composition. Surfactants with longer siloxane backbones are shown to give higher film elasticity. Using the vertical film drainage and foam column tests, it is shown that surfactants with higher film elasticity will yield slower drainage rate and better foam cell stability. Copyright 1999 Academic Press.

Journal Article↗