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PubMedDate not supplied

A new microporous polyurethane vascular graft prepared by an excimer laser ablation technique.

Three types of polyurethane (PU) based tubes (internal diameter, 2 mm; wall thickness, 100 microns) with micropores of well controlled size and arrangement were fabricated using an excimer laser (KrF) ablation technique. The pore size (100 microns) and the longitudinal pore-to-pore distance (200 microns) were constant, and the circumferential pore-to-pore intervals were 60 degrees (type 1), 30 degrees (type 2), and 15 degrees (type 3). The surface of the fabricated tube was photochemically modified with photoreactive gelatin. Scanning electron microscopy showed that pore size and arrangement were precisely controlled as designed, and that a gelatinous layer thoroughly covered the luminal surface. The stiffness parameter (beta), inversely related to compliance, was determined from the change in external diameter against intraluminal pressure. An increase in the number of pores around the circumference decreased the beta value. The type 1 tubes implanted preliminarily in rats for 4 weeks showed good patency (80%). The combination of excimer laser-directed microporing and photochemical surface processing techniques enabled the development of a novel compliant small caliber vascular graft, which is expected to show enhanced transmural tissue ingrowth in vivo.

Animals↗

PubMedDate not supplied

Platelet adhesion and activation on polyethylene glycol modified polyurethane surfaces. Measurement of cytoplasmic calcium.

Polyurethane (PU) surfaces were modified by coupling polyethylene glycol (PEG; molecular weight, 1,000) chains carrying different terminal groups (PU-PEG1K-OH, PU-PEG1K-NH2, PU-PEG1K-SO3) and longer PEG chains (MW, 3,350; PU-PEG3.4K-OH). The modified PU surfaces have the same PEG (1K) chain density. Surface induced platelet activation was evaluated by measuring cytoplasmic free calcium concentration in platelets contacting modified surfaces, and platelet adhesion onto modified surfaces was investigated in vitro. Cytoplasmic free calcium levels in platelets contacting PU-PEG-SO3 remained relatively constant, in contrast to the significant increase observed for PU-PEG-NH2, PU-PEG-OH, and control PU surfaces. The degree of platelet adhesion clearly demonstrates that all PEG graft surfaces prevented platelet adhesion. Among PEG1K surfaces, PU-PEG-SO3 shows the lowest platelet adhesion. In the case of relatively longer PEG grafted surfaces (PU-PEG3.4K-OH and PU-PEG3.4K-Hep), both surfaces were found to prevent the increase in both cytoplasmic free calcium and platelet adhesion. These results suggest that longer PEG chain grafting is more effective than shorter grafting in preventing platelet activation and adhesion because of the highly dynamic movement of hydrated PEG chains at the interface. In addition, in vitro platelet interaction is dependent upon terminal groups of PEG chains on PEG1K series surfaces.

Biocompatible Materials↗

PubMedDate not supplied

Synthesis of a novel small diameter polyurethane vascular graft with reactive binding sites.

Development of a small diameter (4 mm inner diameter [ID]) prosthetic vascular graft with functional groups accessible for covalent binding of recombinant hirudin (a potent anticoagulant) should create a more hemocompatible surface. The purpose of this study was to develop a technique for generating carboxylic acid groups on the surface of precast 4 mm ID poly-(carbonate urea)-urethane vascular grafts and to evaluate the accessibility of these groups. A polycarbonate based urethane with the chain extender 2,2-bis(hydroxymethyl)propionic acid was synthesized. A precast 4 mm ID poly(carbonate urea)-urethane vascular graft (Chronoflex [CF]; CardioTech International, Woburn, MA) was then placed into a 4% carboxylated polyurethane (cPU) solution (in 1% dimethyl acetamide) and incubated for 30 minutes (cPU graft). To determine the accessibility of the carboxylic acid groups, a standard textile technique using methylene blue dye was used. Macroscopic cross-sections, which were cut and evaluated for dye penetration, showed greatest concentration of carboxylic acid groups at the luminal and capsule surfaces, with minimal penetration into the mid-portion of the graft. Analysis of dye baths for absorbance reduction resulted in the cPU grafts having 3.7-fold and 5.4-fold more accessible carboxylic acid groups compared with untreated and dimethyl acetamide dipped CF grafts. Thus, a novel small diameter vascular graft has been developed that contains reactive carboxylic acid groups accessible for protein binding.

Blood Vessel Prosthesis↗

PubMedDate not supplied

Bioengineering of a novel small diameter polyurethane vascular graft with covalently bound recombinant hirudin.

Development of a small diameter prosthetic vascular graft with surface based antithrombin properties should aid in maintaining early graft patency in small vessel reconstruction. The purpose of this study was to bind covalently a basecoat protein (canine serum albumin [CSAJ) and a potent antithrombin agent (recombinant hirudin [rHir]) to 4 mm inner diameter poly(carbonate urea) urethane grafts with reactive carboxylic acid groups (cPU). 125I-CSA was covalently bound to 1 cm length segments of cPU grafts using the carbodimide cross-linker, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC). To bind 125I-rHir covalently, CSA was modified with the heterobifunctional cross-linker sulfosuccinimidyl 4-(N-maleimidomethyl) cyclohexane-1-carboxylate (sulfo-SMCC) before linkage to the cPU surface with EDC (cPU-CSA-SMCC). 125I-rHir was modified with Traut's reagent and reacted with the cPU-CSA-SMCC surface, covalently linking 125I-rHir to surface bound CSA. 125I-CSA binding to the cPU graft surface (34,235 ng/segment) was ninefold, sevenfold, and 10-fold greater than controls with nonspecifically bound 125I-CSA. Covalent linkage of 125I-rHir to the cPU-CSA-SMCC surface (9,974 ng/segment) was 172, 192, and 142-fold greater than controls with nonspecifically bound 125I-rHir. Surface antithrombin properties were characterized using a chromogenic assay to measure residual thrombin activity. Evaluation of surface antithrombin activity showed significantly greater 131I-thrombin inhibition and binding by the cPU surface with covalently bound 125I-rHir, as compared with controls. Release of 125I-rHir from the cPU surface was minimal as compared with controls. Therefore, rHir can be covalently linked to a novel small diameter polyurethane vascular graft surface while maintaining its potent antithrombin properties.

Blood Vessel Prosthesis↗

PubMed1988

Thrombosis caused by polyurethane double-lumen subclavian superior vena cava catheter and hemodialysis.

During an 18-month period, 82 consecutive patients (37 women and 45 men), with a mean age of 50 yr (range 15 to 74), underwent hemodialysis with 91 polyurethane double-lumen subclavian superior vena cava catheters inserted via the right subclavian vein. Upon catheter removal, venograms were performed in 53 which revealed thrombosis in 13. Autopsy performed in 13 other patients revealed thrombosis in three. Mean catheter duration was 27 days (range 1 to 138). Catheter duration was significantly (p less than .01) longer in the 16 cases complicated by thrombosis. There was no significant difference in the frequency of thrombosis between men and women. Two patients developed symptoms of subclavian vein occlusion after the creation of an arteriovenous fistula on the same side as a previous hemodialysis catheter. Overall, thrombosis was found in 23% and increased with longer catheter duration. We recommend phlebography to exclude thrombosis before creating an arteriovenous fistula on the same side as the previous hemodialysis catheter. There was no case of clinical discernible pulmonary embolism.

Adolescent↗

PubMed1981

Use of semipermeable polyurethane membrane for skin graft dressings.

The use of semipermeable polyurethane membrane (Op-site) for skin graft donor-site dressings is now well-accepted. We have used Op-site for skin graft coverage in 25 patients with good results. The dressing modality is not only easy to do, even in anatomically difficult areas, but it also maintains a moist environment, allows daily graft observation, and provides a barrier for exogenous bacteria.

Humans↗

PubMed1986

Labeled leukocyte scans for detection of retained polyurethane foam.

Complete removal of an infected polyurethane-covered breast prosthesis is difficult, and retained tissue-embedded foam can form a nidus for persistent infection. Scanning the chest wall after administration of indium-111 oxine-labeled autogenous leukocytes will locate areas of infection around retained fragments of foam, thereby facilitating their removal and allowing eventual successful reconstruction. This technique may deserve wider application for locating infected foreign bodies in a variety of patient problems.

Adult↗

PubMed1990

Treatment of breast contractures with open capsulotomy and replacement of gel prostheses with polyurethane-covered implants.

Capsular contracture around gel and gel-saline implants is the most common complication following breast augmentation and reconstruction. Thirty-one patients with postaugmentation gel-implant contractures were treated with open capsulotomy and replacement with polyurethane-covered implants. Eighty-seven percent remain soft after a minimum follow-up of 14 months. Results of replacement after subcutaneous mastectomy and reconstruction are more varied and less successful. Results in 14 patients are presented.

Breast↗

PubMed2005

Novel method for training skin flap surgery: polyurethane foam dressing used as a skin equivalent.

BACKGROUND: With a substantial rise in the incidence of skin cancer, skin surgery has become an increasingly large part of dermatology. Skin surgery is best performed by dermatologists. This demands effective training in dermatologic surgery, including flap surgery. OBJECTIVE: To find a modern alternative to traditional training on pig's feet skin in teaching flap surgery to residents in dermatology. MATERIALS AND METHODS: A face with expression lines printed on a nonadhesive hydrocellular polyurethane dressing (Allevyn, #66007638, 20 x 20 cm, Smith & Nephew Medical Limited, Hull, England). Tumors were marked in suitable locations, necessitating the use of transposition, advancement, and rotation flaps. Twenty-two residents were trained in flap construction, excision, and closure. RESULTS: Training on Allevyn was rated high by participants. CONCLUSION: Allevyn has unlimited storing qualities and skinlike qualities when incised, extended, and sutured. Sutures stay tight without the help of an assistant. Training on Allevyn gives students a good understanding of the mechanics of skin flaps, including transposition, advancement, and rotational flaps. The Allevyn is kept by the student after the course and can be studied afterward. Skin surgery training on Allevyn is superior to traditional training in pig's feet skin.

Audiovisual Aids↗

PubMed1983

Ringworm resulting from swimming with a polyurethane cast.

A case of ringworm of the arm is described in a 6-year-old child, after swimming with a polyurethane cast. This report illustrates a potential problem when these casts are inadequately dried and worn for prolonged periods in warm climates. Accurate diagnosis depends on demonstration of fungus in the lesion by smear and culture. Topical antifungal therapy led to rapid resolution.

Casts, Surgical↗

PubMed2004

Multiple linear regression analysis of bacterial deposition to polyurethane coatings after conditioning film formation in the marine environment.

Many studies have shown relationships of substratum hydrophobicity, charge or roughness with bacterial adhesion, although bacterial adhesion is governed by interplay of different physico-chemical properties and multiple regression analysis would be more suitable to reveal mechanisms of bacterial adhesion. The formation of a conditioning film of organic compounds adsorbed from seawater affects the properties of substratum surfaces prior to bacterial adhesion, which is a complicating factor in studying the mechanism of bacterial adhesion. In this paper, the impact of conditioning films adsorbed from natural seawater to four polyurethane coatings with different hydrophobicity, elasticity and roughness was studied for three different marine bacterial strains in a multiple linear regression analysis. The water contact angle on hydrophobic coatings decreased on average by 8 degrees and increased on average by the same amount on hydrophilic coatings. These changes were accompanied by increased concentrations of oxygen and nitrogen on the surface as determined by X-ray photoelectron spectroscopy, indicative of adsorption of proteinaceous material. Furthermore, the mean surface roughness increased on average by 4 nm after conditioning film formation. Multiple linear regression analysis revealed that changes in deposition due to conditioning film formation of Marinobacter hydrocarbonoclasticus, Psychrobacter sp. SW5H and Halomonas pacifica in a stagnation-point flow chamber could be explained in a model comprising hydrophobicity and the prevalence of nitrogen-rich components on the surface for the most hydrophobic strain. For the two more hydrophilic strains, deposition was governed by a combination of surface roughness and hydrophobicity. Elasticity was not a factor in bacterial adhesion to conditioning films.

Bacterial Adhesion↗

PubMed2000

Studies on polyurethane potting compound based on isocyanurate of aliphatic diisocyanate for fabrication of a haemodialyser.

Polyurethane potting compounds based on multifunctional isocyanurate of aliphatic diisocyanate, hexamethylene diisocyanate (HDI-IC) as Component A and polypropylene glycol, polyethylene glycol and castor oil (Component B) were prepared as potential potting compounds for the fabrication of a haemodialyser. The setting characteristics of the potting compounds having isocyanate index 2.54 are better than those of the compounds having 1.77. The ageing stability of castor oil and PPG-based potting compounds having isocyanate index 2.54 is better than that of PEG oil-based potting compounds. Appreciable hydrolytic, oxidative and chemical stability could be observed with HDI-IC/PPG/2.54 potting compounds for development of haemodialyser, oxygenator, etc.

Cyanates↗

PubMed1991

Comparison of the effects of semi-occlusive polyurethane dressings and hydrocolloid dressings on dermal repair: 1. Cellular changes.

The effects on dermal repair of two wound dressings, one the semi-occlusive polyurethane sheet Opsite, the other the hydrocolloid Granuflex, were compared in full-thickness excised lesions on porcine skin during the period from 5 d to 6 months after injury. Quantitative studies were made of changes in the populations of polymorphonuclear leucocytes, macrophages, fibroblasts, and endothelial cells. The progress of repair in the wounds covered with the semi-occlusive dressing showed a decrease in the number of inflammatory cells (polymorphonuclear leukocytes and macrophages) from 5 to 60 d, whereas the number of proliferative phase cells (fibroblasts and endothelial cells) increased from 5 to 7 d. The total cellularity per unit area showed an increase between 5 and 7 d, that is, during the proliferative phase of repair, and then progressively decreased as the proliferative phase was succeeded by the remodeling phase. In contrast, the repair process in the hydrocolloid-dressed wounds was more complex. The number of inflammatory cells remained relatively high throughout and there were consistently fewer endothelial cells present throughout. Fibroblast number showed an initial fall from 5 to 14 d but then started to increase in number from 21 to 60 d. This chronic inflammatory reaction appeared to be in response to particulate matter that had been incorporated into the wound bed and hypodermis, and was still apparent 6 months after injury, when hydrocolloid particles were detectable microscopically in the hypodermis.

Animals↗

PubMed1994

The polyurethane nasotracheal tube.

An uncuffed nasotracheal tube for use in minor maxillofacial surgery has been developed using polyurethane. The suitability of this tube as an alternative to the existing soft red rubber and harder polyvinyl chloride materials has been assessed at four centres during anaesthesia for routine oral surgery. The tube was found to be satisfactory.

Anesthesia, General↗

PubMed1986

The effect of isoxicam-aspirin combinations on the polyurethane sponge implantation model in the rat.

1 Anti-inflammatory effects of isoxicam alone and in combination with aspirin were studied in rats using the polyurethane sponge implantation model of acute inflammation. 2 Dose-response studies were performed to delineate a suppressive (high) and non-suppressive (low) dose of isoxicam prior to studying these doses in combination with aspirin. 3 The results indicate that a combination of aspirin with isoxicam does not have an additive anti-inflammatory effect. 4 The interference demonstrated by aspirin with the anti-inflammatory effects of other NSAIDs such as indomethacin is also demonstrated with aspirin/isoxicam combinations.

Animals↗

PubMed1976

Banked blood microfiltration. I. Microfilter composed of five polyurethane foam layers with graded pore size.

Aggregates of amorphous material which develop with storage of banked blood may be a source of pulmonary microembolism in patients having massive transfusions. In order to remove such debris, blood microfilters have been developed and are in routine clinical use. This paper describes the evaluation of one such filter, the Bentley PF 127 model B, which is composed of five layers of polyurethane foam. The time of filtration as a function of the pressure applied, the number of particles removed, the observed changes in blood cells, and the results of scanning electron microscopy of the filter after filtration of human banked blood, are reported.

Blood Banks↗

PubMed1992

Safety and efficacy of percutaneous injection of polyurethane elastomer (MPU) plugs for vas occlusion in man.

This report describes the safety and efficacy of the procedure for percutaneous injection of medical-grade polyurethane elastomer (MPU) to form plugs in the vas deferens. The injection of 0.16-0.22 ml MPU in 53 men resulted in occlusion and azoospermia in 85% of the men after 12 months; 96% achieved azoospermia by 2 years. The success rate of the method and the rate of sperm suppression to azoospermia depended on the shapes of the plugs; this was determined by palpation after insertion. There were few complications and the results are discussed in terms of the reversibility potential of this method.

Adult↗

PubMed2005

In vitro degradation of polyurethane orthodontic elastomeric modules.

The objectives of this study were to investigate the structural characteristics of orthodontic polyurethane elastomeric modules and their changes produced by mechanical and chemical ageing. Three products were tested (Generation II, Dentaurum, Alastic). For each product four groups of modules were studied under the following conditions: as-received (A(0)); after 3 weeks stretching at 50% elongation in air (B(0)); after 3 weeks immersion in an ethanol/water solution (3:1 v/v) to induce accelerated ageing (A(1)); and after 3 weeks immersion in the ethanol/water solution at 50% elongation, as above (B(1)). The chains and the solution extracts were characterized by micro-MIR FTIR spectroscopy. Specimens of group B(0) exhibited changes in peak intensities relative to the control group (A(0)), attributed to molecular orientation of poly (methylene glycol) soft segments and chain extenders such as butanediol. Moreover, group B(0) showed differences in the omega(CH(2))b peak at 1364 cm(-1), attributed to oxidative degradation of alpha-methylene groups by formation of ester, carboxylic acid or aldehyde groups due to hydrogen abstraction. Comparison of A(1) and B(1) groups with the controls (A(0), B(0)) showed no major differences between their respective spectra, apart from the loss of the 1639 cm(-1) peak attributed to ethylene NN bis (stearamide) wax. However, comparison of the spectra of the extracts from the elongated modules with the extracts of the controls revealed differences in the concentration of alcohol and alkene groups. The structural changes identified were the same in all the products tested and may indicate degradation mechanisms that could potentially hold intraorally.

Elastomers↗