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PubMed1990

Characterization of alkyl grafted polyurethane block copolymers by variable takeoff angle x-ray photoelectron spectroscopy.

Variable takeoff angle x-ray photoelectron spectroscopy was used to determine the surface composition of five polyurethane block copolymers. The high-resolution C1s spectra from all five polyurethane samples had peaks at binding energies of 285.0, 286.5, and 289.5 eV, which are consistent with the presence of hydrocarbon, ether, and urethane carbon species. Both the measured elemental compositions at the low takeoff angles (deepest sampling depths) and the calculated elemental compositions for depths greater than 15 A generally showed good agreement with the expected bulk compositions. The outer 15 A of the surface of all five samples was depleted in the nitrogen-containing hard segment. For the base polyurethane sample in this series, an enrichment of the poly(tetramethylene oxide) soft segment and the presence of an organic silicone impurity were detected. Doubling the chain length of both the hard and soft segments resulted in a further decrease of the hard segment concentration in the outer surface of the sample. The grafting of C2 and C18 alkyl groups onto 10 or 20% of the urethane linkages resulted in an increase in the percentage of aliphatic carbon species present on the surface. In the case of the C18-alkylated material, the presence of alkyl chains at the surface was inferred using contact angle measurements.

Biocompatible Materials↗

PubMed1992

Postadsorptive transitions in fibrinogen adsorbed to polyurethanes: changes in antibody binding and sodium dodecyl sulfate elutability.

Residence time-dependent changes in fibrinogen after adsorption to six different polyurethanes were examined by measuring polyclonal antifibrinogen binding to the adsorbed protein. The amount of adsorbed fibrinogen that could be eluted by sodium dodecyl sulfate (SDS) was also measured. Baboon fibrinogen was first adsorbed from dilute plasma to the polymers, which were then stored in either buffer or buffered albumin solution prior to testing. Subsequently, the amount of antifibrinogen bound by the adsorbed fibrinogen was measured using a direct enzyme linked immunosorbent assay (ELISA). Alternatively, the surface with the adsorbed fibrinogen was soaked in a 3% SDS solution, and the amount of retained 125I-radiolabeled fibrinogen was measured. With increasing residence time, decreases in both antibody binding and the SDS elutability of the adsorbed fibrinogen occurred, but the rate of change was dependent on the polyurethane to which the fibrinogen was adsorbed. In addition, the antibody binding per unit of adsorbed fibrinogen, when measured immediately after the adsorption step, varied by approximately a factor of 3 among the various polyurethanes. When the protein-coated surfaces were stored in buffered albumin solution rather than buffer, the decrease in the reactivity of fibrinogen with residence time did not occur on some of the surfaces. This study shows that the chemical properties of the adsorbing surface influence the rate at which adsorbed fibrinogen undergoes change. The significance of the polymer-dependent changes in adsorbed fibrinogen with respect to blood reactions with polymers is discussed.

Adsorption↗

PubMed1992

Theoretical analysis on cell size distribution and kinetics of foreign-body giant cell formation in vivo on polyurethane elastomers.

The nature of in vivo leukocyte adhesion and foreign-body giant cell (FBGC) formation on polyurethanes was studied through theoretical and statistical analyses in terms of cell size distribution, density changes, and kinetics of FBGC formation. The results showed that the size distribution of FBGCs followed a "most probable" distribution. During FBGC formation, the densities of FBGCs changed with time. At an early stage, the number of FBGCs increased with time to a maximum at the expense of macrophages. As more FBGCs were formed and less macrophages were present, the fusion of FBGCs among themselves became significant. This, in turn, caused a gradual decrease of FBGC density with time. The rate of FBGC formation was characterized by a rate constant that represented certain characteristics of cell fusion and FBGC formation and the density of initial FBGC-forming macrophages that were a small fraction of leukocytes adhering to the surface. The direct correlations of surface cracking and pitting and adherent FBGCs demonstrated the influence of phagocytic actions of FBGCs on the biostability of implanted polyurethanes. While the cracking was thought to be caused by oxidative degradation facilitated by oxygen ion/radical release of FBGCs, the pitting appeared to result from the Methacrol 2138F aggregates diffusing out of the polymer in an acidic microenvironment under FBGCs, which in turn could be enhanced by the surface degradation and cell phagocytosis. The added Santowhite powder in polyurethane had a significant influence on FBGC formation: It reduced FBGC density and rate of FBGC formation by reducing leukocyte adhesion and the number of macrophages participating in FBGC formation.

Amines↗

PubMed1993

Degradation of polyurethane foams used in the Même breast implant.

The release of toluene diisocyanate derivatives from polyurethane foam covers that were removed from the Même breast implant was studied. The polyurethane foam covers as retrieved from the implants were contaminated on average with 2,4- and 2,6-toluene diamine (TDA), 2,4- and 2,6-toluene diisocyanate (TDI), and toluene isocyanate amine (TIA) at the 1086 ppm level (combined TDA, TDI, and TIA). When cleaned foam was incubated in Ringer's solution at 37 degrees C for periods ranging from 6-35 days, 4.6 ppm/day of TDA, TDI, and TIA (combined) was formed; the projected annual degradation rate of the foam under these conditions was estimated to be about 0.8%. When cleaned foam was incubated dry at 37 degrees C, 1.5 ppm/day of TDA, TDI, and TIA (combined) was produced. Hence, the polyurethane foam covers used in the Même breast implants are susceptible to both thermal and hydrolytic degradation under simulated physiological conditions.

Biocompatible Materials↗

PubMed1993

Effect of polyol type on the physical properties and thrombogenicity of sulfonate-containing polyurethanes.

Polyetherurethanes (PEUs) based on polytetramethylene oxide (PTMO) as the polyol, and derivatized with propyl sulfonate functionality, have previously been shown to possess antithrombotic properties. In this article, the bulk physical properties of sulfonated and nonsulfonated polyurethanes containing either polyethylene oxide (PEO) or PTMO as the soft segment are studied. The in vitro shape-change of platelets in contact with these surfaces, and their ex vivo blood-contacting response are also investigated. It was found that PEO-base was physically weaker than PTMO-base, which is attributed to a lower degree or phase separation in the former. In the dry state, sulfonation enhanced the physical properties for PTMO-containing polyurethane (PTMO-SO3-0.20), but weakened the PEO-containing polyurethane (PEO-SO3-0.15). In vitro platelet spreading studies showed the lowest degree of platelet spreading and also the lowest platelet density on PEO-base, while platelet spreading and density on the other three materials and polyethylene (PE) was greater. The thromboresistance of these materials was evaluated using a canine arteriovenous series shunt ex vivo. It was determined that PTMO-SO3-0.20 was the least thrombogenic, followed by both PEO-base and PEO-SO3-0.15, and that PTMO-base was the most thrombogenic.

Alkanesulfonic Acids↗

PubMed1994

Antithrombogenicity of lumbrokinase-immobilized polyurethane.

Lumbrokinase is a potent fibrinolytic enzyme purified from the earthworm, Lumbricus rubellus. We immobilized 18 IU/cm2 of lumbrokinase to polyurethane using maleic anhydride methylvinyl ether copolymer (MAMEC) as an enzyme carrier, and the proteolytic and fibrinolytic activities of immobilized lumbrokinase were assayed. Immobilized lumbrokinase retained about 34% of its activity, compared with soluble lumbrokinase activity. Immobilized lumbrokinase showed stability against thermal inactivation and degradation and within a various pH range. The optimal pH of immobilized lumbrokinase shifted 1.0 pH unit upward compared with soluble enzyme. Upon exposure to the human whole blood, less amount of 125I-fibrinogen was adsorbed to lumbrokinase-immobilized surface than to the polyurethane control surface. The lumbrokinase-immobilized surface showed less platelet adhesion than did the MAMEC-grafted surface. At the early stage of platelet adhesion, the number of adhered platelets increased on the lumbrokinase-immobilized surface with increasing time; yet, the platelet number drastically decreased on the lumbrokinase-immobilized surface after 80 min incubation. This suggests that lumbrokinase-immobilized polyurethane digested the adsorbed fibrinogen and inhibited platelet adhesion on the surface, probably by inhibiting fibrinogen adsorption to be highly antithrombogenic. Clinical applications of this material to artificial organs should be developed in the near future.

Adsorption↗

PubMed2006

Urokinase-immobilization suppresses inflammatory responses to polyurethane tubes implanted in rabbit muscles.

Urokinase and plasmin appear to have antiinflammatory activity in some injury models, and urokinase immobilization has been clinically used to prevent thrombus formation in various implants, including intravenous indwelling catheters and subcutaneous drainage tubes. In the present study, polyurethane tubes were embedded in rabbit muscle for 3 months and the effect of urokinase immobilization on inflammatory responses to the implanted tubes was studied at 1 week, 1 month, and 3 months. Mononuclear leukocyte accumulation occurred around implanted polyurethane tubes and peaked after 1 month, but was reduced significantly by urokinase immobilization. The treatment also lessened as well as delayed eosinophil accumulation, but did not affect fibrosis caused by implanted tubes. These results indicate suppressive effects of urokinase immobilization on polyurethane-elicited inflammatory responses and suggest that an approach to develop persistently active urokinase immobilization is rational for successful long-term device implantation.

Animals↗

PubMed2006

Effect of molecular weight on the transfection efficiency of novel polyurethane as a biodegradable gene vector.

New polyurethane 2-diethylaminoethylamine-polyurethane (LGEA-PU) containing poly(ethylene glycol) segments and tertiary amines was synthesized. LGEA-PU self-assembled readily with the plasmid DNA (pCMV-betagal) in HEPES buffer and was characterized by dynamic light scattering, zeta potential, atomic force microscopy, and XTT cell viability assays. To examine the effect of molecular weight of LGEA-PU systems on transfection, LGEA-PU systems of four different molecular weights (LGEA-PU99, LGEA-PU59, LGEA-PU24, and LGEA-PU7) were prepared. This study found that LGEA-PU99, LGEA-PU59, and LGEA-PU24 were able to bind plasmid DNA and yielded positively charged complexes with a nano-sized transfection (<200 nm). The LGEA-PU59/DNA complexes were able to transfect COS-7 cells in vitro with higher transfection efficiency than the other LGEA-PU systems. These results demonstrated that molecular weights of LGEA-PU systems had a significant effect on transferring ability, except for LGEA-PU99, which showed the strongest DNA condensation. Examination of the cytotoxicity of PEI and LGEA-PU systems revealed that LGEA-PU systems had lower cytotoxicity. In this article, LGEA-PU59 seemed to be a novel cationic polyurethane for gene delivery and an interesting candidate for further study.

Animals↗

PubMed2006

Biodegradable polyurethane cytocompatibility to fibroblasts and staphylococci.

Biodegradable polyurethanes have potential for use as implantable devices (orthopedic, maxillofacial, cardiovascular, wound dressing and plastic surgery) because of their controllable elasticity, and the possibility of changing their chemistry and structure. Studying bacterial and cell adhesion to polyurethanes helps to determine surface cytocompatibility and suitability for in vivo trials. Staphylococcus aureus, Staphylococcus epidermidis and hTERT human fibroblast cells were used to determine the cytocompatibility of experimental biodegradable polyurethanes (PUs) with different hydrophobic-to-hydrophilic (pho:phi) content ratios (100% pho, 70% pho, and 30% pho). Poly(L/DL-lactide) 70/30% (PLDL) and Thermanox were used as control surfaces. Surface characterization using noncontact profilometry, contact angles, and scanning electron microscopy (SEM) showed that the three PU surfaces, PLDL, and Thermanox have different properties. On the 100% PU and 30% PU surfaces, hTERT cells spread less in comparison to the 70% PU, PLDL, and Thermanox surfaces. The adsorption of fibronectin to the surfaces had no effect on the adhesion and spreading of hTERT cells when compared to the uncoated surfaces. The trend for S. aureus was the most adhered on the 70% PU and 30% PU, then Thermanox, followed by 100% PU and PLDL, respectively. The amount of S. epidermidis adhesion followed the trend of the most on 70% PU, then 100% PU, then 30% PU and PLDL, and the least on Thermanox. These results suggest that the 70% PU surface is cytocompatible to hTERT fibroblasts, while the 100% PU and 30% PU were not. All surfaces encouraged S. aureus and S. epidermidis colonization, particularly the 70% PU.

Bacterial Adhesion↗

PubMed2006

In vivo biostability of polyether polyurethanes with fluoropolymer surface modifying endgroups: resistance to biologic oxidation and stress cracking.

A series of Shore 80A polyether polyurethanes were synthesized with from 0 to 6% fluoropolymer surface modifying endgroups (SME) to provide the bulk properties of the polyurethane with the surface properties of the fluoropolymer. It was theorized that the fluoropolymer would migrate to the surface, forming a monolayer barrier to the oxidants and crack-driving agents released by macrophages and foreign body giant cells in vivo. In a 12-week biostability screening test, samples strained to 400% elongation appeared to be highly stable. In a longer-term study, the fluoropolymer SME significantly delayed, but did not completely prevent the onset of microcracking and the development of environmental stress cracking in strained samples. Even so, the 4 and 6% SME polymers explanted at 2 years performed significantly better than the control. FTIR analysis did not correlate with SME concentration, but increased hydrogen-bonding index and loss of aliphatic ether (autoxidation) did correlate with the visual appearance and density of microcracks. Significant molecular weight reductions were seen for the SME-free control, but were small (within instrumental error) for the polymers with SME. The use of fluoropolymer as a SME does appear to be warranted as a means to improve polyether polyurethane biostability.

Animals↗

PubMed2007

Biodegradable polyurethane cancellous bone graft substitutes in the treatment of iliac crest defects.

Porous scaffolds were produced from newly designed biodegradable, segmented aliphatic polyurethanes of various chemical compositions and hydrophilic-to-hydrophobic segment ratios. The scaffolds were implanted into monocortical defects in the iliac crest of healthy sheep for 6 months. The resected cortex was not repositioned. The ilium defects, which were not implanted with polyurethane scaffolds, were used as controls. In none of the control defects was there bone regeneration at the time of euthanasia. The defects implanted with porous scaffolds from polyurethanes were healed to varying extents with cancellous bone. The structure of the regenerated cancellous bone was radiographically denser than the structure of native bone. New bone that was formed in the scaffolds with a higher amount of hydrophilic component contained more calcium phosphate deposit than the bone formed in the scaffolds with a lower amount of the hydrophilic component. There was no new cortex formed over the defect, but a thin layer of soft tissue covered the newly formed cancellous bone.

Animals↗

PubMed2007

In vivo biostability of polyether polyurethanes with fluoropolymer and polyethylene oxide surface modifying endgroups; resistance to metal ion oxidation.

Polyether polyurethanes are subject to oxidation catalyzed by, and through direct (redox) reaction with transition metal ions (metal ion oxidation, MIO). The source of the ions is corrosion of metallic parts within an implanted device. A Shore 80A polyether polyurethane was modified with fluoropolymer (E80AF) or polyethylene oxide (E80AP) surface modifying end groups (SME). The SME migrates to the surface to form a covalently bonded monolayer, while maintaining the bulk properties of the polyurethane. In vitro tests in H(2)O(2) solution indicated that both SME's accelerated MIO. Tubing samples containing cobalt mandrels were implanted in the subcutis of rabbits for up to 2 years. In vivo, E80AF significantly slowed the rate of visible degradation, but did not prevent MIO. E80AP had virtually identical visual performance to the unmodified control in vivo. Infrared spectroscopy and molecular weight correlated well with visual appearance. When cracks were seen, polyether soft segment oxidation was occurring. Both E80AP and the control developed severe loss of molecular weight in vivo. The changes were much less severe for E80AF. Thus, contrary to in vitro test results, the PEO SME had no effect at all on MIO resistance, while the fluoropolymer SME produced a significant improvement in biostability.

Animals↗

PubMed2007

Modification of HTPB-based polyurethane with temperature-sensitive poly(N-isopropyl acrylamide) for biomaterial usage.

Hydroxyl-terminated polybutadiene (HTPB)-based polyurethane with dimethyol propionic acid (DPA) as chain extender was synthesized by solution polymerization. The HTPB-based polyurethane was modified by UV radiation with N-isopropyl acrylamide monomer to get poly(N-isopropyl acrylamide)-modified polyurethane (PUDPANIPAAm). The cohesive energy (E(coh)), molar volume (V), solubility parameter (delta), molecular weight (W(M)), volume per gram (V(g)), and the density (1/V(g)) of PUDPANIPAAm were calculated by group contribution methods. To evaluate the application of PUDPANIPAAm for wound dressing and transplantation of cell sheet, the measurement of water content, water vapor transmission rate, and gas permeation on the PUDPANIPAAm membrane was evaluated. The biocompatibility of these membranes, cell adhesion, and proliferation assay were conducted in the cell culture. The effect of thermosensitivity of poly(N-isopropyl acrylamide) on cell detachment was also evaluated in the primary study. The results showed that these PUDPANIPAAm membranes are thermosensitive. The modification of PU with poly(N-isopropyl acrylamide) reduced the water vapor transmission rate and permeability of gas through PUDPANIPAAm membrane. PUDPANIPAAm membranes could support cell adhesion and growth. Owing to the thermosensitive nature of poly(N-isopropyl acrylamide), the relative cell numbers detached from PUDPANIPAAm membranes were larger than those detached from the polystyrene dish.

3T3 Cells↗

PubMed1995

Hydrophobic adsorption of aromatic compounds on polyurethane foam as a carbon source for Pseudomonas growth.

The use of polyurethane foam appears to be efficient to extract hydrophobic pollutants from aqueous media. Their adsorption is the result of spontaneous hydrophobic interactions with the foam, The rate of adsorption is a function of the diffusion of the molecules into the foam as well as their hydrophilic/lipophilic balance. A mixture of different molecules modifies the adsorption capacities of each type of molecule on the foam, probably resulting from stacking phenomena between the molecules. The Pseudomonas species can grow in the presence of the polyurethane foam and be adsorbed on it. Moreover, a strain of Pseudomonas pseudoalcaligenes tested in this study can use adsorbed biphenyl as the sole carbon source. Polyurethane foam therefore shows favorable characteristics for being chosen as a method of concentrating aromatic compounds and optimizing the rate of degradation of these molecules by bacteria.

Adsorption↗

PubMed1983

Applicability of liquid radiopaque polyurethane for transcatheter embolization.

Polyurethane Bayer was tested as an occlusive agent for experimental embolization in postmortem and postnephrectomy kidneys which served as a tumor model. Coaxial and balloon catheters were used for the embolization. To make polyurethane radiopaque, the material was labeled with different water-soluble, oily and solid contrast agents. Best results were achieved with oily contrast materials, e.g., Pantopaque. We found that polyurethane can easily be injected during a predetermined working time of 8-10 min. The embolization results in a complete, permanent, and homogeneous occlusion of the proximal arterial branches and small peripheral vessels.

Embolization, Therapeutic↗

PubMed1999

Determination of the silver ion release from polyurethanes enriched with silver.

The Erlanger silver catheter was developed in order to reduce the risk of infection from long-term catheters by means of silver ions, which are known to have antibacterial properties. This is achieved by incorporating silver into polyurethane catheters by means of a special procedure. The aim of this materials science study was to verify the release of silver ions from the polyurethanes. Static experiments were carried out following the usual norms. Clinically relevant dynamic experiments, which were designed and constructed at this institute, were also performed. The eluates from both experiments were analyzed by anodic stripping voltammetry. Polyurethanes filled with silver, as used in the Erlanger silver catheter, release silver in static as well as in dynamic experiments. If the experimentally determined releases are converted to the usual catheter length of 30 cm, the release is about 0.1 microgram/l. This lies in the order of concentrations that have been reported in the literature to be antibacterial.

Catheterization↗

PubMed2002

Polyurethane-covered self-expandable nitinol stent for malignant biliary obstruction: preliminary results.

PURPOSE: To evaluate the immediate and long-term results in ten patients with malignant biliary obstruction using a polyurethane-covered, self-expandable nitinol stent. METHODS: A nitinol stent, fully covered with high-elasticity polyurethane, with an unconstrained diameter of 10 mm and a total length of 60-80 mm, was placed transhepatically under fluoroscopic guidance in ten patients. The length of the biliary obstruction varied between 30-50 mm. The follow-up examination included a clinical assessment, serum bilirubin measurement, and ultrasound examinations at one-month intervals in all patients. RESULTS: Initial stent deployment was successful in eight patients. Two patients experienced proximal migration, which was solved by insertion of two, uncovered Wallstents. One patient had the stent removed after two weeks because of severe nausea and vomiting. One patient had delayed migration of the covered stent after 40 weeks. The follow-up duration was 3-40 weeks (Mean: 16.9 weeks). Seven patients died (3-26 weeks) and three patients survived (24-40 weeks). The bilirubin measurements in all patients had significantly decreased one week after stent insertion. The levels of amylase and lipase had did not increase after stent insertion. CONCLUSIONS: A polyurethane-covered, self-expandable nitinol stent can be used effectively and safely in the treatment of malignant biliary obstruction. The preliminary results are favorable, but there is a need for further large studies to determine both long-term survival and patency.

Adult↗

PubMedDate not supplied

Nasolacrimal polyurethane stent: complications with CT correlation.

PURPOSE: To evaluate initial results in patients with epiphora secondary to obstruction of the nasolacrimal duct treated by placement of a polyurethane stent, and to discuss the technical problems and complications arising during the procedure, with visualization of the anatomy of the drainage apparatus using computed tomography (CT). METHODS: We inserted 20 polyurethane Song stents under fluoroscopic guidance after dacryocystography in 19 patients with grade 3-4 epiphora caused by idiopathic obstruction of the nasolacrimal duct. CT scans were obtained following stent placement in all patients. RESULTS: We focus on the technical problems and complications that arose during these procedures. During negotiation of the guidewire past the obstruction at the level of the junction of the duct with the lacrimal sac, the guidewire created a false passage in a posterior suborbital direction in two cases and towards the posterior midline in another. In all cases the guidewire was withdrawn and reinserted through the proper anatomic route without further difficulty or complications. In two cases the stent was improperly positioned wholly or partially outside the nasolacrimal system (one medially, one posteriorly). In one case the stent was removed and reinserted; in the other it remains in place and functional. CT was performed in all these cases to ensure proper anatomic alignment and determine what had gone wrong. The epiphora was completely resolved in 13 cases and partially relieved in four; there were three cases of stent obstruction. Epistaxis of short duration (1 hr) occurred in seven patients and headache in one. CONCLUSIONS: Treatment of epiphora with polyurethane stents is a technique that is well tolerated by patients and achieves a high success rate, yet problems in placement may be encountered. Though no major consequences for patients are involved, cognizance of such difficulties is important to avoid incorrect positioning of stents.

Adult↗