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At least 109 records · Page 6Linked to original sources

PubMed1999

Experimental studies on application of small-caliber vascular prosthesis produced by polyurethane.

It has been suggested that a microporous structure enhances fast and complete endothelialization. For long-term patency, antithrombogenicity and microporous structure are very important factors. In this paper, we have developed a new technique to give a micro-porous structure to small-caliber vascular prosthesis produced by polyurethane which has favorable antithrombogenecity. A mixed solution (tetrahydrofuran: dimethylformamide = 1:1) containing 13 wt% of segmented polyurethane and a variable amount of calcium carbonate (mean particle size of 8 mm in diameter) was dip-coated on a glass mandril of 3 mm and 6 mm in diameter and placed into distilled water for 24 hours. After the glass mandrill was removed, this polyurethane tube was placed into 1 mmol hydrochloric acid for 1 hour, and a microporous polyurethane vascular prosthesis of 20 mm in length was completed. These prostheses of 3 mm and 6 mm in diameter were implanted into the femoral and the carotid arteries, and the abdominal aorta of the dogs, respectively. Patency was recognized by arteriography and Duplex scanning and the removed grafts were inspected macro- and microscopically. Greater hydraulic permeability of this graft was obtained with an increase in the quantity of calcium carbonate mixed with polyurethane. In elasticity, this graft was more similar to the canine jugular vein than the polytetrafluoroethylene graft. Patency was observed 8 weeks after implantation on the arteriogram, and neointima was observed microscopically on the smooth and lustrous lumen. The new polyurethane vascular prosthesis we developed might provide a potential prosthesis for small-caliber vascular reconstruction.

Animals↗

PubMed2003

Evaluation of two types of polyurethane for the immobilisation of Rhizopus oryzae for copper uptake.

Previous studies have shown that Rhizopus oryzae strain IM 057412 grown in reticulated polyurethane foam demonstrated the same heavy metal adsorption capacity as the free biomass. Immobilisation in other types of polymers was shown to reduce the biomass uptake capacity because of mass transfer limitations due to the restricted porosity of the immobilisation matrices. For practical purposes the growing of biomass in polyurethene support particles to use as a commercial adsorbent is not viable or financially sound. The current work describes a different approach in which dried non-viable cells of R. oryzae were incorporated into two types of polyurethane carrier matrix during the production process. The polymers used were a conventional hydrophobic polyurethane and a hydrophilic polyurethane, Hypol 2002. Oven-dried and powdered particles (D<150 microm) of R. oryzae were immobilised by mixing the biomass with each of the polymers prior to the reaction in which the polymer was expanded to form a foam; consequently the biomass was uniformly dispersed throughout the porous matrix. The resulting fungi-polyurethane matrices were then cut into cubes (approximately = 4-6 mm dimension) and their adsorptive properties studied with respect to copper. Experiments were conducted in shake flasks to establish the equilibrium time for the reaction for both free and immobilied biomass. The biomass immobilised in Hypol gave the same adsorptive capacity as that of free biomass when compared on a weight basis, but biomass immobilised in conventional polyurethane foam showed no adsorption. To assess fully the effect of pH on copper and to eliminate precipitation as a removal mechanism experiments were conducted at different pHs and different copper concentrations. In each case the solution pH was maintained by acid or base addition in response to measurements using a standard calomel electrode. It was shown that at pH 5 copper concentrations above 100 mg l(-1) were likely to precipitate. The amount of precipitation was accounted for within the high concentration adsorption isotherm experiments by using a mass balance approach. Results showed that the adsorption of the Hypol immobilised biomass followed the Langmuir adsorption isotherm model and showed the copper adsorption capacity of the matrix to be between 10 and 13 mg g(-1). The copper attached to the immobilised biomass could easily be desorbed by increasing the acidity, allowing the matrix to be used in repetitive sorption-desorption cycles. There was a small decrease in the adsorption capacity after the first desorption cycle that could be explained by a partial loss of biomass as detected by loss of total organic carbon (TOC).

Biomass↗

PubMedDate not supplied

Morphology of autogenous bone graft and castor oil polyurethane in the infraorbital rim of rabbits: a comparative study.

PURPOSE: Morphological study comparing castor oil polyurethane and autogenous bone graft to repair bone defect in zygomatic bone of rabbits. METHODS: Twenty-four adult, male New Zealand rabbits were randomly distributed between two groups of twelve. Bone defects of 5mm in diameter were cut through the zygomatic bone and filled with polyurethane discs in the experimental group or autogenous bone harvested from the tibia in the control group. Animals were sacrificed after 30, 60 or 90 days, and the zygomatic bones were macro- and microscopically analyzed. Student's, Fisher's, chi-squared and McNemar's tests were used for statistical analysis. RESULTS: Both the castor oil polyurethane and the autograft adapted well to the defect, with no need for fixation. Fibrous connective tissue encapsulated the polyurethane, but no inflammation or giant cell reaction was observed. Acidophilic and basophilic areas were observed inside the micropores of the polyurethane, suggesting cell nuclei. After 90 days, bone repair with a lamellar pattern of organization was observed in the control group. CONCLUSION: The castor oil polyurethane was biocompatible and did not cause inflammation. It may be considered an alternative to fill bone defects.

Animals↗

PubMed1989

Semipermeable polyurethane membrane as an artificial skin for the premature neonate.

A thin and semipermeable polyurethane membrane adherently applied to premature neonates as an artificial skin was investigated as an atraumatic surface barrier sufficient to reduce transepidermal water loss without inhibiting natural infant skin development during the first few days of life. A sample group of 18 neonates (birth weight [mean +/- SEM] 1.39 +/- 0.12 kg, gestation [mean +/- SEM] 31 +/- 1 weeks) received two 3 X 3-cm polyurethane patches adherent over the chest and abdomen. Transepidermal water loss was measured before and after application and after membrane removal. During longitudinal study, seven infants were treated day 1 through day 4 of life and were evaluated for skin integrity 24 hours after patch removal on day 5. Polyurethane membranes produced an acute and significant reduction in transepidermal water loss for the 18 subjects: 21.1 +/- 2.0 g/m2/h before application v 10.5 +/- 1.4 g/m2/h with membranes in place (P less than .001). Immediately after patch removal, transepidermal loss returned to 22.8 +/- 3.0 g/m2/h. Throughout the first four days of life, daily measurements of water loss were significantly less: 53% to as much as 72% reduction from polyurethane-covered sites when compared with adjacent naked skin. After polyurethane membrane removal, skin development of transepidermal barrier function was comparable over both sites. Dressings did not lose adhesive or plastic properties during an extended time in either radiant warmer or incubator environments, electronic monitoring through membranes was not impeded, and adhesive injuries were not observed. An adherent, semipermeable polyurethane membrane may be effective as an atraumatic artificial barrier to prevent large transepidermal water loss and protect the skin of the premature neonate.

Body Temperature Regulation↗

PubMed1995

[Tissue reaction to implanted polyurethane designed for parts of the artificial heart].

Experiments on producing polyurethane membranes which could be used for elements of an artificial heart have been carried out in Poland for several years. In the Institute of Biocybernetics and Biomedical Engineering PAN in Warsaw two kinds of polyurethanes with symbols PU 47 and PU 90 have been worked out. They differ in physicochemical properties and they were subjected to investigations of tissue reaction in the Institute of Experimental Surgery and of Biomaterials Investigations of the Medical Academy in Wrocław. The investigations were carried out on 70 rats of the Wistar breed and on 30 rabbits of the New Zealand breed. Polyurethane circles were implanted into subcutaneous tissue, to peritoneal cavity and into muscles of the back in rats; polyurethane oars were implanted into muscles of the back along the backbone of the rabbits. Sections of the animals were carried out 3, 7, 14, 28, 90 and 180 days after the surgery taking 5 animals in each term. Macroscopic and microscopic as well as physicomechanical investigations were carried out. The carried out experimental investigations of the both kinds of polyurethanes showed good tolerance of the animals' organisms on the implanted material. Summing up, we can say that the tested polyurethane foils with symbols PU 47 and PU 90 satisfy the basic requirements made on the materials designed for temporal contact with a living organism.

Abdominal Muscles↗

PubMed1998

Fine-bore cannulas for peripheral intravenous nutrition: polyurethane or silicone?

The peripheral intravenous route is being used more frequently for the administration of short- to medium-term parenteral nutritional support. Dedicated fine bore cannulas have significantly reduced the incidence of thrombophlebitis. Currently available cannulas are made of polyurethane or silicone. We present our experience with a 23G silicone cannula and a 22G polyurethane alternative. Fifty-four silicone cannulas were used with a median survival of only 3 days, compared with 7 days for 90 polyurethane cannulas (P < 0.0001). Only 22% of silicone cannulas were removed electively compared with 56% of polyurethane cannulas (P < 0.00005). The most common cause for silicone cannula removal was occlusion (48%), which occurred in only 8% of polyurethane cannulas (P < 0.00001). Polyurethane cannulas develop fewer complications and are more effective in the delivery of peripheral intravenous nutritional support.

Adult↗

PubMed1997

Quantitative comparison of shear-dependent Staphylococcus aureus adhesion to three polyurethane ionomer analogs with distinct surface properties.

Bacterial adhesion is a central step in infection on biomaterial surfaces; however, the relation between biomaterial surface properties and adhesion remains poorly understood. To quantitatively determine the relationship among polyurethane surface properties, protein coating, and adhesion, we have compared attachment and detachment kinetics of Staphylococcus aureus on three different novel polyurethanes with different protein coatings. Rate constants for attachment or detachment were measured as a function of shear rate in a well-defined laminar flow field. The tested polyurethanes included a relatively hydrophobic-base polyether urethane and hydrophilic anionomer and cationomer analogs of the base material. Materials were tested bare, or coated with human fibrinogen, plasma, or albumin. The results suggest that the presence of fibrinogen or plasma greatly enhance the attachment rate constants and decrease the detachment rate constants on all materials. The most extreme differences among the different materials were observed on the bare materials, with the base polyurethane being most resistant to both attachment and detachment. However, except for a reduced attachment rate constant on the plasma-coated sulfonated polyurethane, few differences in the rate constants were observed among protein-coated materials, suggesting the primary role of surface properties is masked by the presence of the adsorbed protein layer.

Bacterial Adhesion↗

PubMed2003

Spatially organized layers of cardiomyocytes on biodegradable polyurethane films for myocardial repair.

Tissue engineering constructs should match the physical and mechanical properties of the native tissue. This implies that pliable scaffolds might be better suited for soft-tissue applications than rigid polymeric materials. In this study, we examined spatially organized cardiomyocyte cultures on biodegradable, elastomeric polyurethane films patterned by microcontact printing of laminin lanes. The resulting cardiomyocyte patterns on polyurethane displayed a similar morphology to those previously achieved for up to 7-10 days on other substrates, such as polystyrene dishes. However, the integrity of the cardiomyocyte patterns on thin, spin-cast or solvent-cast polyurethane films was retained for up to 4 weeks in culture. When additional cardiomyocytes (labeled with Cell Tracker reagents) were seeded onto the patterned cultures, secondary and tertiary cell populations aligned between and on top of the primary patterned cells to form a multilayered, organized tissue construct approximately 2-3 cell layers thick. In addition, dense, highly aligned monolayers of patterned cardiomyocytes were able to contract the thin, solvent-cast polyurethane films. These results indicate that elastomeric, biodegradable polyurethane films can serve as an appropriate scaffold material to support stably the engineering of spatially organized layers of cardiomyocytes in vitro. This approach may serve as a novel method for transplantation of organized cardiac tissue constructs to the heart for myocardial repair.

Animals↗

PubMed2006

Examination of surface properties and in vitro biological performance of amorphous diamond-like carbon-coated polyurethane.

Despite the emerging use of diamond-like carbon (DLC) as a coating for medical devices, few studies have examined the resistance of DLC coatings onto medical polymers to both microbial adherence and encrustation. In this study, amorphous DLC of a range of refractive indexes (1.7-1.9) and thicknesses (100-600 nm) was deposited onto polyurethane, a model polymer, and the resistance to microbial adherence (Escherichia coli; clinical isolate) and encrustation examined using in vitro models. In comparison to the native polymer, the advancing and receding contact angles of DLC-coated polyurethane were lower, indicating greater hydrophilic properties. No relationship was observed between refractive index, thickness, and advancing contact angle, as determined using multiple correlation analysis. The resistances of the various DLC-coated polyurethane films to encrustation and microbial adherence were significantly greater than that to polyurethane; however, there were individual differences between the resistances of the various DLC coatings. In general, increasing the refractive index of the coatings (100 nm thickness) decreased the resistance of the films to both hydroxyapatite and struvite encrustation and to microbial adherence. Films of lower thicknesses (100 and 200 nm; of defined refractive index, 1.8), exhibited the greatest resistance to encrustation and to microbial adherence. In conclusion, this study has uniquely illustrated both the microbial antiadherence properties and resistance to urinary encrustation of DLC-coated polyurethane. The resistances to encrustation and microbial adherence were substantial, and in light of this, it is suggested that DLC coatings of low thickness and refractive index show particular promise as coatings of polymeric medical devices.

Bacterial Adhesion↗

PubMed1990

Polyurethane arterial prosthesis: experimental evaluation.

Two types of microporous polyurethanes have been evaluated both in vitro and in vivo. In vitro polyurethane disks have been seeded by endothelial cells from bovine aortic origin and from fresh human greater omentum. Various pretreatments permit comparison of six different experimental groups. The benefit of poly L lysine, laminin, fibronectin and previous astrocyte cell seeding is shown. The cell proliferation was assessed daily, using trypan blue in Malassez cells. Cell identification was performed by class I MHC antigen characterization and factor VIII staining. In vivo, 4 mm polyurethane arterial prostheses were implanted as carotid interpositions. Evaluation of polyurethane, both in vitro and in vivo, failed to demonstrate a satisfactory hemocompatibility of the material. However, previous treatment of polyurethane with laminin, fibronectin, and astrocyte cell seeding improves the biologic characteristics of the raw material.

Animals↗

PubMed1999

A new technology of microdispersed silver in polyurethane induces antimicrobial activity in central venous catheters.

Metal ions or metal ions in complexes or compounds have been used for centuries to disinfect fluids, solids and tissues. The biocidal effect of silver, with its broad spectrum of activity including bacterial, fungal and viral agents, is particularly well known and the term "oligodynamic activity" was coined for this phenomenon. Silver ions have an affinity to sulfhydryl groups in enzyme systems of the cell wall, through which they interfere with the transmembranous energy transfer and electron transport of bacterial microorganisms. Silver ions also block the respiratory chain of microorganisms reversibly in low concentrations and irreversibly in higher concentrations. Binding to the DNA of bacteria and fungi increases the stability of the bacterial double helix and thus inhibits proliferation. There is no cross resistance with antibiotics and also no induction of antimicrobial resistance by silver ions. The concentrations required for bactericidal activity are in the range 10(-9) mol/l. These concentrations can be achieved in solution by the interaction of metallic silver with electrolytes only if there is a large enough surface of silver. By a novel technology, metallic silver is distributed in submicron particles in polyurethane and results in a concentration of 0.8% in an active surface of 450 cm2/g polyurethane. Polyurethane is hygroscopic and rapidly attracts water; the interaction of electrolyte solutions with the extremely finely distributed silver throughout the polyurethane releases bactericidal concentrations of silver ions over a period of years to the surface of the material. The electronegatively charged surface of bacteria attracts the positively charged silver ions. The concentrations released from the polyurethane are far below the toxic concentrations for humans.

Animals↗

PubMed1992

Endothelial cell adhesion on polyurethanes containing covalently attached RGD-peptides.

Peptides based on cell-adhesive regions of fibronectin, Arg-Gly-Asp-Ser (RGDS), and vitronectin, Arg-Gly-Asp-Val (RGDV), were covalently bound to a polyurethane backbone via amide bonds. Nuclear magnetic resonance (NMR) and Fourier-transform infrared (FTIR) spectroscopies were used to monitor the reactions. The amount of grafted peptide was determined by amino acid analysis. X-ray photoelectron spectroscopy (XPS) suggested the presence of the grafted peptide at the polymer-air interface in vacuo. Dynamic contact angle analysis showed that, in water, the peptide-grafted polyurethane surfaces were more polar than the underivatized polyurethane indicating enrichment of peptide groups at the surface. The attachment and spreading of human umbilical vein endothelial cells (HUVECs) on the underivatized and peptide-grafted polyurethanes was investigated. The GRGDSY- and GRGDVY-grafted substrates supported cell adhesion and spreading even without serum in the culture medium. The GRGDVY-grafted substrate supported a larger number of adherent cells and a higher extent of cell spreading than the GRGDSY-grafted substrate. These RGD-containing peptide-grafted polyurethane copolymers may be useful in providing an easily prepared cell-adhesive substrate for various biomaterial applications.

Amino Acids↗

PubMed1996

New polyurethane heart valve prosthesis: design, manufacture and evaluation.

In light of the thrombogenicity of mechanical valves and the limited durability of bioprosthetic valves, alternative designs and materials are being considered for prosthetic heart valves. A new tri-leaflet valve, made entirely from polyurethane, has been developed. The valve comprises three thin polyurethane leaflets (approximately 100 microns thick) suspended from the inside of a flexible polyurethane frame. The closed leaflet geometry is elliptical in the radial direction and hyperbolic in the circumferential direction. Valve leaflets are formed and integrated with their support frame in a single dip coating operation. The dipping process consistently gives rise to tolerably uniform leaflet thickness distributions. In hydrodynamic tests, the polyurethane valve exhibits pressure gradients similar to those for a bioprosthetic valve (St Jude Bioimplant), and levels of regurgitation and leakage are considerably less than those for either a bi-leaflet mechanical valve (St Jude Medical) or the bioprosthetic valve. Six out of six consecutively manufactured polyurethane valves have exceeded the equivalent of 10 years function without failure in accelerated fatigue tests. The only failure to date occurred after the equivalent of approximately 12 years cycling, and three valves have reached 527 million cycles (approximately 13 years equivalent). The simplicity of valve manufacture, combined with promising results from in vitro testing, indicate that further evaluation is warranted.

Biocompatible Materials↗

PubMed2004

Long-term in vivo biostability of poly(dimethylsiloxane)/poly(hexamethylene oxide) mixed macrodiol-based polyurethane elastomers.

The long-term biostability of a novel thermoplastic polyurethane elastomer (Elast-Eon 2 80A) synthesized using poly(hexamethylene oxide) (PHMO) and poly(dimethylsiloxane) (PDMS) macrodiols has been studied using an in vivo ovine model. The material's biostability was compared with that of three commercially available control materials, Pellethane 2363-80A, Pellethane 2363-55D and Bionate 55D, after subcutaneous implantation of strained compression moulded flat sheet dumbbells in sheep for periods ranging from 3 to 24 months. Scanning electron microscopy, attenuated total reflectance-Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy were used to assess changes in the surface chemical structure and morphology of the materials. Gel permeation chromatography, differential scanning calorimetry and tensile testing were used to examine changes in bulk characteristics of the materials. The results showed that the biostability of the soft flexible PDMS-based test polyurethane was significantly better than the control material of similar softness, Pellethane 80A, and as good as or better than both of the harder commercially available negative control polyurethanes, Pellethane 55D and Bionate 55D. Changes observed in the surface of the Pellethane materials were consistent with oxidation of the aliphatic polyether soft segment and hydrolysis of the urethane bonds joining hard to soft segment with degradation in Pellethane 80A significantly more severe than that observed in Pellethane 55D. Very minor changes were seen on the surfaces of the Elast-Eon 2 80A and Bionate 55D materials. There was a general trend of molecular weight decreasing with time across all polymers and the molecular weights of all materials decreased at a similar relative rate. The polydispersity ratio, Mw/Mn, increased with time for all materials. Tensile tests indicated that UTS increased in Elast-Eon 2 80A and Bionate 55D following implantation under strained conditions. However, ultimate strain decreased and elastic modulus increased in the explanted specimens of all three materials when compared with their unimplanted unstrained counterparts. The results indicate that a soft, flexible PDMS-based polyurethane synthesized using 20% PHMO and 80% PDMS macrodiols has excellent long-term biostability compared with commercially available polyurethanes.

Absorptiometry, Photon↗

PubMed2004

Blood compatibility of polyurethane surface grafted copolymerization with sulfobetaine monomer.

Surface modification is an effective way to improve the hemocompatibility and remain bulk properties of biomaterials. Recently, polymer tailed with zwitterions was found having good blood compatibility. In this study, the grafting copolymerization of sulfobetaine onto polyurethane surface was obtained through two steps. In the first step, polyurethane film coupled with vinyl groups was obtained through the reaction between the carboxyl group of acrylic acid (AA) and the NH-urethane group of polyurethane by dicyclohexylcarbodiimide (DCC). In the second step, sulfobetaine was grafted copolymerization on the surface using AIBN as an initiator. The reaction process was monitored with ATR-IR spectra and X-ray photoelectron spectroscopy (XPS) spectra. The wettability of films was investigated by water contact angle measurement. The blood compatibility of the grafted films was evaluated by platelet adhesion in platelet rich plasma (PRP) and protein absorption in bovine fibrinogen (BFG). Low platelet adhesion was observed on the grafted films incubated in PRP for 1 and 3 h, respectively. The protein absorption was reduced on the grafted films after incubated in bovine fibrinogen for 2 h. All of these results revealed that the improved blood compatibility was obtained by grafting copolymerization with zwitterionic monomer of sulfobetaine onto polyurethane film. In addition, introducing vinyl groups onto surface through DCC and AA is a novel method to functionalize polyurethane for further modification.

Acrylates↗

PubMed2000

Acceptability evaluation of a natural rubber latex, a polyurethane, and a new non-latex condom.

After more than a century of reliance on latex condoms, male condoms fabricated from new materials are finally becoming commercially available to consumers. This study was an open label acceptability study that compared three lubricated condom products during vaginal intercourse: a natural rubber latex condom, a polyurethane condom, and a new non-latex (styrene ethylene butylene styrene, SEBS) condom. Fifty-four couples who were using condoms for birth control were enrolled in this three-way crossover study. Each couple tested three condoms of each type in a randomized sequence. Couples reported condom performance after each use and rated condom acceptability after use of three condoms of each type. At the completion of the study, participants selected their preferred condom type for overall acceptability, sensitivity, ease of use, appearance, and comfort. All three condom types had low clinical breakage and slippage rates (</= 3.3%) although the polyurethane condom did not perform as well in other measures of performance including unrolling, discomfort, stretching, bunching, and sliding along the penis during intercourse. None of the condom types were statistically preferred overall [males: natural rubber latex 37%, polyurethane 24%, new non-latex (SEBS) 37%, no preference 2%; females: natural rubber latex 33%, polyurethane 27%, new non-latex 37%, no preference 2%]. A statistically higher proportion of couples preferred both the natural rubber latex condom and the new non-latex condom above the polyurethane condom for ease of unrolling, and the natural rubber latex condom above the other condom types for perceived safety. Approximately two-thirds of both male and female participants preferred one of the two condoms made of synthetic materials suggesting that consumers will appreciate the availability of these products.

Adolescent↗

PubMed2002

Potential role of fire retardant-treated polyurethane foam as a source of brominated diphenyl ethers to the US environment.

Five tetra- to hexabrominated diphenyl ether (BDE) congeners (BDE-47, -99, -100, -153 and -154) are the most frequently reported in wildlife and humans. The commercial penta-BDE product, used predominantly to flame-retard polyurethane foam, consists primarily of these same congeners. In 1999, North American demand accounted for 98% of the total global penta-market of 8500 metric tons. Frogs, housed with flame retardant-treated polyurethane foam as a dry substrate, accumulated 10,100 microg/kg (wet weight) of the above BDEs. Crickets kept therein as food contained 14,400 microg/kg. The crickets are believed to have browsed directly on the foam and, in turn, were consumed by the frogs. BDE congener composition in all three matrices matched that of the penta-commercial product. Similar congeners were also observed in soil and stream sediments collected near a polyurethane foam manufacturing plant. Summed concentrations of BDE-47, -99 and -100, the dominant congeners observed in these samples, ranged from < 1 to 132 microg/kg (dry weight basis). Sunfish fillets obtained from a nearby, off-site pond contained a total of 624 microg/kg (lipid basis). Sewage treatment plant (STP) sludge exhibited these same congeners at 1370 microg/kg (dry weight). BDE-209, the fully brominated congener predominant in the commercial deca-BDE product, was also present at 1470 microg/kg. While no known polyurethane foam manufacturers discharged to this plant, the distribution pattern of the low brominated congeners in the sludge matched that of the penta-product. After four weeks of exposure to ambient outdoor conditions, the surface of flame-retarded polyurethane foam became brittle and began to disintegrate. Subsequent dispersal of these penta-containing foam fragments may be one mechanism by which these BDEs reach the environment.

Animals↗

PubMed1998

In vitro blood compatibility of surface-modified polyurethanes.

Polyurethanes have proven durable materials for the manufacture of flexible trileaflet heart valves, during in vitro tests. The response of two polyurethanes of differing primary structure to parameters of blood compatibility has now been investigated, using an in vitro test cell. Platelet (beta-thromboglobulin) release, complement (C3a) activation, the activation of free plasma and surface-bound factor XII were studied using fresh, human blood (no anticoagulant) or citrated plasma in control and surface-modified polyurethane. Surface modifications were designed to affect material thrombogenicity and included covalent attachment of heparin, taurine, a platelet membrane glycoprotein fragment, polyethylene oxide (PEO), 3-aminopropyltriethoxysilane, and glucose or glucosamine. Unmodified control polyurethanes caused platelet release and complement activation. High molecular weight (2000 D) polyethylene oxide reduced platelet release slightly but only glucose attachment to the surface produced a significant reduction in platelet activation. All modifications reduced C3 activation compared with controls, but the greatest reduction was achieved with polyethylene oxide attachment or glycosylation. Most surface modifications were more activating of factor XII, both in plasma and on the material surfaces, than the control polyurethanes. Heparin and high molecular weight PEO produced the greatest activation of factor XII in the free plasma form, but low molecular weight PEO and glucosamine produced the greatest activation of surface-bound factor XIIa. The least activating surfaces, affecting both free plasma and surface-bound factor XIIa, were those treated with platelet membrane glycoprotein fragment and glucose. PEO surfaces performed relatively well, compared with controls and most surface modifications. The best overall surface, however, was the glucose-modified surface which was least activating considering all parameters of blood compatibility.

Biocompatible Materials↗