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PubMed1993

Comparative biological tests on segmented polyurethanes for cardio-vascular applications.

In order to select a candidate segmented polyurethane (SPU) elastomer for the preparation of cardio-vascular prostheses, a series of biological tests (namely haemolysis, aPTT and PT coagulation tests, cytotoxicity, human endothelial cells seeding) was carried out on five commercially available biomedical polyurethanes. The tests were performed on solvent cast samples, from THF (Cardiothane 51, Pellethane 2363 80A, Estane 5714 F1, and Estane 58810), or DMAC (Biomer). All the materials were sterilized by gamma-irradiation before being tested. From the results obtained all the polyurethanes used in this study were shown to be devoid of toxicity towards blood (as proved by haemolysis and coagulation time tests) or blood cells (as proved by cytotoxicity and cell adhesion assays). A clear difference among the tested copolymers didn't stand out under our test conditions, although Cardiothane, possibly due to its physico-chemical characteristics, was less effective in promoting endothelial cell adhesion.

Animals↗

PubMed1994

Polymeric stenting in the porcine coronary artery model: differential outcome of exogenous fibrin sleeves versus polyurethane-coated stents.

OBJECTIVES: In a porcine coronary model, fibrin film soaked for 3 h in heparin was used as a circumferential coating on a tantalum stent to assess the effect of this naturally occurring biopolymer on arterial healing. The results were compared with those obtained with medical grade polyurethane-coated stainless steel stents. BACKGROUND: Thrombus plays an important role in healing after arterial injury and may affect the development of neointimal hyperplasia. Manipulation of the initial thrombus may alter the healing response. To study this, we placed a template of fibrin in a porcine coronary artery restenosis model. METHODS: Thirty-four fibrin film stents were delivered in 20 swine. Oversizing was avoided, to prevent deep arterial injury, by placement of optimally sized stents. Initial patency of the stented vessel was confirmed by angiography. RESULTS: Three fibrin-stented swine died within 48 h; in each, the stent was occluded with a fibrin/red blood cell mass. In two of these three, a portion of the exogenous fibrin had become detached from the stent and partially occluded the lumen. Of the remaining 31 stents, all were patent at elective sacrifice at 28 days. Eighty-four percent had a diameter stenosis < 50%, and the mean (+/- SD) diameter stenosis was 32.3 +/- 13%. There was no evidence of significant foreign-body giant-cell reaction. These results contrasted with the medical grade polyurethane-coated stents placed according to the same protocol without oversizing. Twelve of these stents were placed; six swine died of thrombotic occlusion within the 1st 48 h. At elective sacrifice at 28 days, the remaining polyurethane-coated stents were occluded by marked neointimal hyperplasia. CONCLUSIONS: Fibrin film-coated stents seem promising as a template for modifying the local response to arterial injury and for potentially decreasing restenosis rates.

Animals↗

PubMed1986

Polyurethane and silver sulfadiazene dressings in treatment of partial-thickness burns and abrasions.

Epi-Lock, a 1-mm-thick semipermeable sheet of modified polyurethane dressing material, was compared with silver sulfadiazene cream (Silvadene) in a prospective, randomized, cross-over-controlled study in which 50 patients alternated changing antibiotic cream daily with leaving the polyurethane sheet in place for a week. Overall, patient and physician preference for Epi-Lock was statistically significant (P less than 0.004), based on less pain, easier care, and faster healing. The collection of fluid under the polyurethane dressing and the necessity of leaving the wound covered for a week were less well accepted. Epi-Lock represents a major advance in wound dressing materials and should eventually gain wide application in outpatient treatment of partial thickness burns and abrasions.

Adolescent↗

PubMed2004

Synthesis of metal incorporated low molecular weight polyurethanes from novel aromatic diols, their characterization and bactericidal properties.

Low molecular weight polyurethanes with sites for metal complexation were synthesized. The -SO(2) and the -COOH groups were incorporated into the polyurethane chain by the reactions of tri-functional monomers, 4,4'-bis(hydroxyphenyl)sulfone and 4,4'-bis(hydroxyphenyl) valeric acid with hexa-methylene di-isocyanate (HMDI) and 2,4 toluene di-isocyanate (TDI), respectively. The reaction was monitored from the disappearance of the -OH group and results show that the -NCO groups of the isocyanate reacted with the -OH group preferentially when compared to the other reactive groups. The pristine tri-functional monomers themselves formed stable complexes with the metals and so were chosen to be incorporated into the polyurethane chain. These polymers were characterized by IR and NMR spectroscopy. The free -SO(2) and the -COOH groups were used for metal complexation using non-toxic metals like zinc and silver. The anti-bacterial studies conducted on the six polymers in film form showed interesting results as elaborated in the paper.

Bacteria↗

PubMed2006

Polyurethanes with radiopaque properties.

An aliphatic, commercially available, medical grade polyurethane, Tecoflex 80A was made radiopaque by coupling a 5-iodine-containing molecule, N-(2,6- diiodocarboxyphenyl)-3,4,5-triiodo benzamide (DCPTB) onto the polymer backbone. DCPTB was synthesized by coupling 4-amino-3,5-diiodobenzoic acid and 3,4,5-triiodobenzoic acid using dicyclohexyl carbodiimide. Radiopaque polyurethane thus obtained was characterized by IR, TGA, DSC and X-radiography. By optimizing the reaction conditions, it was possible to incorporate about 8% iodine in the polymer (wt/wt) to achieve radiopacity almost equivalent to that of a 2mm thick aluminium wedge. However, the products differed from the starting polymer in thermal characteristics. The starting polymer showed two endothermic transitions, the first one due to glass transition of the soft segment and the second one due to disruption of the hard segments. After modification, the second transition shifted to a lower temperature, while the first transition remained unaltered. Also, the modified polymers showed reduced thermal stability compared to the starting polymer. These observations could be explained on the basis of the reduced extent of intermolecular hydrogen bonding among the hard segments of the end product. Radiopaque polyurethanes are expected to have significant advantage over their non-radiopaque counterparts in many medical and related applications.

Biocompatible Materials↗

PubMed2006

The effect of sterilisation on a poly(dimethylsiloxane)/poly(hexamethylene oxide) mixed macrodiol-based polyurethane elastomer.

The effect of various forms of sterilisation on a novel thermoplastic polyurethane elastomer synthesised using poly(hexamethylene oxide) (PHMO) and poly(dimethylsiloxane) (PDMS) macrodiols has been studied. The five sterilisation methods investigated were ethylene oxide (EtO) (single and multiple cycles), gas plasma, steam, vapour phase liquid chemical and gamma-irradiation (single and multiple cycles). Following sterilisation, scanning electron microscopy (SEM) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) were used to assess changes in the surface chemical structure and morphology, and gel permeation chromatography (GPC) and tensile testing were used to examine changes in bulk characteristics. Biostability was assessed using subcutaneous implantation of strained samples in sheep for 6 weeks. The results showed that the properties of the commercially available control material, Pellethane 2363-80A, were significantly affected by exposure to gamma-irradiation, steam and multiple cycles of EtO with aging and implantation compounding the effect. Exposure to a gas plasma sterilisation process resulted in significant degradation in both polyurethanes. A vapour phase liquid chemical sterilisation process caused minimal adverse effects. Sterilisation of the PDMS-based polyurethane using EtO, gamma-irradiation and autoclaving resulted in no significant changes in properties. The material's biostability was also unaffected by exposure to each of these sterilisation processes followed by short-term implantation suggesting that this material is a potential candidate for use in a wide range of implantable medical devices sterilised using commercially available processes. Further biostability studies should be performed to assess the longer-term in vivo biostability of the PDMS-based material sterilised using autoclaving and gamma-irradiation.

Chromatography, Gel↗

PubMed2005

A long-term flexible minimally-invasive implantable glucose biosensor based on an epoxy-enhanced polyurethane membrane.

This paper describes the preparation method as well as the in vitro and in vivo evaluation of a novel flexible glucose biosensor designed for long-term subcutaneous implantation. An epoxy-enhanced polyurethane membrane, which includes ca. 30-40% epoxy resin adhesive and 50-70% polyurethane, has been developed and used for the first time as the outer protective membrane of the sensor. This new membrane was developed to increase the in vivo durability and lifetime of implantable biosensors. This epoxy-polyurethane membrane was shown to be porous and is of excellent durability. A sensor with such a membrane shows excellent long-term stability and can last for 4-8 months in solutions at room temperature. To verify the in vivo performance of the sensor, nine sensors were implanted in three rats and tested regularly. Eight sensors kept functioning well in the rats for 10-56 days. The ninth sensor was damaged during implantation. All original sensitivity data as well as four response curves obtained at days 7, 17, 52 and 56, respectively are presented.

Animals↗

PubMed2006

Effect of surface charge and hydrophobicity of polyurethanes and silicone rubbers on L929 cells response.

Wettability and zeta potential studies were performed to characterize the hydrophobicity and surface charge of virgin and oxygen plasma irradiated silicone rubbers and polyurethane (polyether and polyesther) samples and evaluate the effect of hydrophobicity and surface charge on fibroblast cells attachment and growth. The surface properties of polyurethanes and silicones and plasma irradiated surfaces were compared by water drop contact angle and zeta potential measurement. Using SEM photomicrographs to study the morphology of virgin and plasma irradiated samples surfaces and light microscopy for study the behavior of cell attachment on these surfaces. Water drop contact angle measurements show that in despite of the silicones, the polyurethanes become more hydrophobic and have stable surface than silicones. Results show that wettability of plasma treated silicones increase and after 48 h recovery take place. Zeta potential measurements noticed that plasma treated polyetherurethane surface is more negatively charge, and consequently attachment of the L929 fibroblast cells decreased whereas on silicones surfaces, negatively charge surfaces show increase cells attachment.

Animals↗

PubMed2004

Synthesis and characterization of polyurethane and poly(ether urethane) nanocapsules using a new technique of interfacial polycondensation combined to spontaneous emulsification.

Polyurethane polymers and poly(ether urethane) copolymers were chosen as drug carriers for alpha-tocopherol. This active ingredient is widely used as a strong antioxidant in many medical and cosmetic applications, but is rapidly degraded, because of its light, heat and oxygen sensitivity. Polyurethane and poly(ether urethane)-based nanocapsules were synthesized by interfacial reaction between two monomers. Interfacial polycondensation combined with spontaneous emulsification is a new technique for nanoparticles formation. Nanocapsules were characterized by studying particle size (150-500 nm), pH, yield of encapsulation and morphologies. Polyurethanes (PUR) were obtained from the condensation of diisocyanate (isophorone diisocyanate: IPDI) and polyol: 1,2-ethanediol (EG), 1,4-butanediol (BD), 1,6-hexanediol (HD). Poly(ether urethane) copolymers were obtained by replacing diols by polyethylene glycol oligomers (PEG) M(w) 200, 300, 400 and 600. Molecular weights of di- and polyols have a considerable influence on nanocapsules characteristics cited above. The increase of molecular weight of polyols tends to increase the mean size of nanocapsules from (232+/-3)nm using EG to (615+/-39)nm using PEG 600, and led to the apparition of a population of agglomerate particles. We also noted that the yield of encapsulation increases with the increase of polyol length (from 85.6 to 92.2% w/w). Microscopic observations confirmed particle size analysis, but cannot predict the membrane structure owing the small size of the particles.

Administration, Topical↗

PubMed2001

Treatment of nasolacrimal duct obstruction in adults with polyurethane stent.

PURPOSE: To evaluate the efficacy of polyurethane nasolacrimal duct stents in the treatment of epiphora resulting from primary acquired nasolacrimal duct obstruction in adults. MATERIALS AND METHODS: In 25 patients (21 women and four men with mean age of 44 years, range 20 to 74 years) with nasolacrimal duct obstruction, 28 hollow polyurethane stents designed by Song and associates were placed under fluoroscopic guidance. The obstruction was complete in 20 lacrimal drainage systems and partial in eight. The lacrimal sac size was normal or large on dacryocystogram in all lacrimal drainage systems. A Ritleng probe was introduced through the upper punctum and advanced past the obstruction. A guide wire with a flexible tip was then introduced through the probe, over which the stent was advanced in retrograde fashion and placed into the lacrimal sac and nasolacrimal duct. Clinical success was defined by the demonstration of a completely patent lacrimal drainage pathway through saline irrigation and no or minimal complaint of epiphora. RESULTS: Stent placement was technically successful in 26 of 28 lacrimal drainage systems (93%). The mean time of fluoroscopy screening was 3.2 minutes (range, 1.4 to 5.8 minutes). The overall success rate was 82% (23 of 28 lacrimal drainage systems). Two stents were completely occluded. In one lacrimal drainage system with minimal epiphora, the stented drainage pathway was partially occluded. The patients were followed up from 4 to 22 months (mean, 7.2 months). CONCLUSIONS: Retrograde placement of a hollow polyurethane nasolacrimal duct stent is a technique that is simple and well tolerated by patients. This method achieves a high success rate and may be suggested as a nonsurgical procedure for adults with primary nasolacrimal duct obstruction and proper lacrimal sac size. The Ritleng probe facilitates the procedure.

Adult↗

PubMed2001

The effect of roughness, floor polish, water, oil and ice on underfoot friction: current safety footwear solings are less slip resistant than microcellular polyurethane.

Research over a period of about 18 years has shown that a microcellular polyurethane known as AP66033 is the most slip-resistant safety footwear soling material on oily and wet surfaces. In recent years it has been replaced in commercially available footwear by a dual density polyurethane (DDP) which has a dense outer layer and a soft microcellular backing. This research programme has compared the slip resistance of AP66033 with DDP and some rubber solings. In addition, data were obtained on the effects of soling and floor roughness, and floor polish on slip resistance. Some data were also obtained for walking on ice. The coefficient of friction (CoF) of the solings was measured on 19 water wet surfaces in three conditions: (I) when the solings were new, (II) following abrasion to create maximum roughness and (III) after polishing. The CoF was measured on four oily surfaces after each of 11 abrasion or polishing treatments. The profound effects of the roughening of all soles and of floor roughness on the CoF were demonstrated for both wet and oily surfaces. The superior slip resistance of AP66033 was confirmed for oily and wet conditions; however, some rubbers not suitable for safety footwear achieved higher CoF values on wet floors. All of the floor polishes reduced the CoF of all floors when contaminated with water. The mean CoF of DDP solings was lower than the mean for AP66033 on wet and oily surfaces. No safety footwear soling provided adequate grip on dry ice and the CoF was reduced by water on the ice. A rubber used for rock climbing footwear was one of the most slip-resistant solings on wet surfaces in the laboratory but recorded the lowest CoF on ice. It is concluded that the incidence of occupational injuries caused by slipping could be reduced by the following: (A) returning to safety footwear soled with the microcellular polyurethane AP66033; (B) abrading all new and smooth footwear solings with a belt sanding machine coated with P100 grit; (C) avoiding the use of floor polish; (D) informing the general public about the poor slip resistance of ordinary footwear on ice and the lowering of slip resistance in cold weather.

Accidental Falls↗

PubMed2003

Treatment of complete obstruction of the nasolacrimal system by temporary placement of nasolacrimal polyurethane stents: preliminary results.

AIM: To assess the efficacy of the temporary placement of polyurethane nasolacrimal stents as a treatment for complete post-saccal obstruction of the lacrimal apparatus. MATERIALS AND METHODS: Polyurethane nasolacrimal stents were inserted under radiological guidance in nine patients with grade IV epiphora due to complete obstruction of the lacrimal system, at the junction of the lacrimal sac and duct (eight patients) or in the lacrimal duct (one patient). On average, the stents were removed 4 months (range: 3-6 months) after insertion. Dacryocystography was performed immediately before and after each stent was removed. Subsequently, periodic clinical and radiological examinations were performed until recurrence of the epiphora, at which point follow-up concluded. RESULTS: All patients remained free of epiphora and clinical inflammation while the stents were in place, but re-obstruction of the lacrimal system occurred in all patients less than 2 months after the stents were removed. Adhesion of three stents to the lacrimal tract was observed upon removal. In seven cases the dacryocystography results at the end of follow-up revealed changes in the configuration of the lacrimal apparatus. CONCLUSION: Based on our preliminary experience, temporary placement of polyurethane stents would not appear to be an efficacious therapeutic option for treating epiphora caused by post-saccal obstruction.

Adult↗

PubMed1987

The prevalence of asthma among inhabitants in the vicinity of a polyurethane factory in Finland.

Because toluene diisocyanate (TDI) is a strong sensitizer for asthma among workers in polyurethane factories, it is mostly extracted from the factory premises. The influence of such emissions on the prevalence of asthma among the people living in the vicinity of a polyurethane factory in Kouvola, Southern Finland, was studied through a questionnaire survey sent to 6807 persons living around the factory and in a control area; of these 4182 (61%) responded. In the study area near the factory there were 68 cases of asthma out of 3153 respondents (2.2%). In the control area there were 25 cases out of 1029 respondents (2.4%). The difference is insignificant (chi 2 = 0.27). Among the middle-aged the prevalence was significantly higher in the control area (chi 2 = 6.8). There was some indication of a lower asthma prevalence in the zone nearest to the factory, possibly due to its psychologically repellent effect on asthmatics, causing them to move away. Serum samples from 62 asthma patients out of 68 contacted (91%) were received and analyzed for TDI, HDI, and MDI. A positive result for the isocyanates was observed in only one patient who had been exposed in his occupation outside the factory. It was concluded that the polyurethane factory did not have a noticeable influence upon the prevalence of asthma in its surroundings.

Adolescent↗

PubMedDate not supplied

Bacterial adherence to hydrophilic polymer-coated polyurethane stents.

Biliary stent blockage by adherence of bacteria and formation of biofilm is a major problem in endoscopic stenting procedures. We have investigated bacterial adherence to hydrophilic polymer (Hydromer)-coated polyurethane stents in stationary and perfusion experiments. Adherence of gram negative and gram positive organisms under stationary conditions was similar between Hydromer-coated and non-coated control polyurethane stents; however, a marked 1 to 3 log reduction in adherence to Hydromer-coated stents occurred when perfusion experiments in phosphate buffer solution or bile were performed. The results suggest that Hydromer-coated polyurethane stents could be useful in preventing complications caused by biliary stent blockage.

Bacterial Adhesion↗

PubMed1991

Removal of organic pollutants from aqueous solution. V. Comparative study of the extraction, recovery and chromatographic separation of some organic insecticides using unloaded polyurethane foam columns.

The concentration of dissolved insecticides in aqueous media was determined by chromatographic separation on polyurethane foam columns. The results of preliminary screening tests on the removal of insecticides by the unloaded polyurethane foam indicated that a reasonable percentage of the insecticides was retained on the foam. Therefore attempts were made to extract these compounds from aqueous media using foam columns. Various parameters affecting the retention and separation of these compounds were studied, including temperature, flow-rate, pH, insecticide concentration, shaking time, sample volume and eluting solvent. The complete separation and quantitative recovery of these compounds from the foam with acetone in a Soxhlet extractor were achieved. The method can be used to preconcentrate insecticides in tap water and modified to determine dissolved insecticides in industrial and natural waters. Polyurethane foam has a good capacity for use when large volume samples need to be handled and is an inexpensive sorbent compared to other known solid sorbents.

Chromatography, Liquid↗

PubMed1978

Physical and mechanical behavior of polyurethane elastomer formulations used for facial prostheses.

The initial results of this study of the physical and mechanical behavior of polyurethanes used for facial prostheses are presented. The parameters studied were surface hardness, modulus of elasticity (M), strength (S), percentage of elongation, and S/M ratio. Results showed that the physical and mechanical behavior of the polyurethanes can be altered by variations in the basic composition of the material accomplished through changes in the ratio of Part A to Part B and by the addition of catalysts. Properties of compositions with low quantities of Part B (isocyanate) and no catalyst reached or approximated those parameters proposed as ideal goals to simulate living tissue. When preparing polyurethane material, proper mixing is essential to avoid entrapment of air and phase separation of the catalyst. These conditions, which may render the prostheses less durable, are masked by the addition of colorants in the prearation of a sample for clinical application.

Chemical Phenomena↗

PubMed1998

Experimental right ventricle to pulmonary artery discontinuity: outcome of polyurethane valved conduits.

OBJECTIVE: The ideal substitute for the treatment of ventricle-pulmonary artery discontinuity remains a topic of controversy, because of calcifications and degeneration of biologic substitutes leading to subsequent reoperations. Because polyurethane valves used in ventricular assist devices show a satisfactory biocompatibility, the aim of this study was to evaluate a valved conduit composed of a Dacron graft incorporating a trileaflet 25 mm polyurethane valve. METHODS: The conduit was implanted between the right ventricle and the main pulmonary artery in adult sheep, with ligation of the proximal pulmonary artery. The animals received no medications. Serial hemodynamic data were collected at the time of implantation and at postoperative intervals of 6 and 12 months. RESULTS: The peak pressure gradient across the valve increased significantly between implantation (0.17 +/- 5.6 mm Hg) and 6 months after operation (7.3 +/- 3 mm Hg, p = 0.0007) and remained stable thereafter (6.7 +/- 3 mm Hg at 12 months), whereas the cardiac output remained unchanged (4.6 +/- 0.6 L/min at implantation, 4 +/- 0.6 L/min at 6 months, and 3.9 +/- 1.1 L/min at 12 months). At the completion of the study, valve samples were processed and vapor coated with carbon for microscopic examination. There was one instance of nonadherent thrombus formation inside a cusp but no structural failures. The other valves were free of calcium deposits and no significant amounts of phosphorus could be detected by scanning electron microscopy and energy dispersive spectrometry. CONCLUSIONS: These data demonstrate the good hemodynamic performance, low thrombogenicity, and acceptable durability of the polyurethane valves implanted in the right side of the heart in a chronic sheep model.

Animals↗

PubMed1996

Wound closure with human keratinocytes cultured on a polyurethane dressing overlaid on a cultured human dermal replacement.

BACKGROUND: Burn excision followed by immediate wound coverage has become the clinical standard for managing extensive burn injuries in much of the world. When sufficient autograft skin to achieve permanent wound closure is unavailable, cell culture technology has made the use of cultured human keratinocyte (HK) sheets clinically feasible. Whereas previous techniques have focused on development of multilayered, differentiated HK sheets, our attention has been drawn to using HK in a highly proliferative, less differentiated state. Time requirements for preparation of multistratified cultured HK are high, and preparatory steps may destroy important integrin adhesion molecules. METHODS: We describe the use of HK cultured to single layer confluence on a polyurethane membrane(HD), with serum-free medium. HK-HD grafts were transplanted to full-thickness wounds on athymic mice (n = 31). A second group of mice (DG-HK-HD), n = 28) received a living human dermal replacement containing cultured fibroblasts before placement of HK-HD. Control mice received HD alone (n = 4). Basement membrane proteins on healed wounds and surface integrins on cultured HK were identified by means of immunostaining and direct microscopic visualization. RESULTS: HK cultured just to the confluent state on polyurethane membrane were positive for integrins alpha(5) and alpha(6), major integrins on proliferating HK. Histologic analysis showed epithelialized wounds in all groups after 21 days. Using an anti-human involucrin antibody we demonstrated the presence of HK in 64.5% of the HK-HD group, 61% of the DG-HK-HD group, and 0% in the HD group. Mice that received the living human dermal replacement containing cultured fibroblasts in combination with HK-HD grafts developed a thick, well-vascularized neodermis. Strong laminin and collagen IV staining was observed in wound areas covered with HK. CONCLUSIONS: These data show that full-thickness wounds can be closed by application of a single layer of proliferating HK cultured on a biocompatible polyurethane membrane. This technique is an alternative to the use of multilayered, differentiated HK sheets. Preparation times for HK-HD grafts should be significantly shorter than required for multilayered HK sheets, technical efforts should be less, and more extensive wound areas could be covered.

Animals↗