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PubMed1995

Synthesis of phospholipid polymers having a urethane bond in the side chain as coating material on segmented polyurethane and their platelet adhesion-resistant properties.

Surface modification of segmented polyurethanes (SPUs) was carried out using new blood compatible polymers having both phospholipid polar groups and urethane bonds in the side chains. The polymers were composed of 2-methacryloyloxyethyl phosphorylcholine (MPC), n-butyl methacrylate (BMA) and methacrylate with a urethane bond (MU). The MPC copolymers were soluble in ethanol. The SPU membranes were immersed in an ethanol solution of MPC copolymers and dried in vacuo for coating. The surface formed was completely covered with the MPC copolymer which was confirmed by X-ray photoelectron spectroscopic analysis. The polymer coatings were hardly detached in water, ethanol and 40% aqueous solution of ethanol compared with poly(MPC-co-BMA) which did not have the MU moieties. Therefore, the MU moieties had affinity for the SPU. The surface modification of the SPUs suppressed platelet adhesion effectively after contact with platelet-rich plasma for 180 min.

Biocompatible Materials↗

PubMed1995

New polyurethane compositions able to bond high amounts of both albumin and heparin. Part I.

In order to prepare polymers provided with better haemocompatibility with respect both to the coagulative cascade and to platelet aggregation and activation, we have synthesized new polyurethanes containing in the chain-extender [di(2-hydroxyethyl)hexadecylamine] both a long chain alkyl group (able to bond albumin) and a tertiary ammonium group able, after suitable quaternization reaction, to bind ionically significant amounts of heparin. The amounts of heparin and albumin bonded to the polymer films were determined spectrophotometrically. A biological in vitro evaluation of the heparinized and albuminized films was also carried out with respect to blood coagulation factors (by activated partial thromboplastin time measurements) and to platelet adhesion and activation (by platelet count and scanning electron microscopy examination). It was seen that the type of adsorption sequence for albumin and heparin, respectively, onto the various homo- and copolymer films, plays an important role on their biological properties; the possible mechanisms involved are also discussed on the basis of X-ray photoelectron spectroscopy and attenuated transmission reflectance evaluation of the polymer surfaces.

Albumins↗

PubMed1995

Heparin-like anticoagulant activity of sulphonated poly(ethylene oxide) and sulphonated poly(ethylene oxide)-grafted polyurethane.

Sulphonated poly(ethylene oxide) (PEO-SO3) and PEO-SO3-grafted polyurethane (PU-PEO-SO3) were prepared by bulk modification and their anticoagulant and heparin-like activities were investigated. Anticoagulant activity measured by activated partial thromboplastin time of PU-PEO-SO3 displayed 2%, whereas that of PEO-SO3 itself reached 14% as compared to free heparin. In addition, the anticoagulant effects of these sulphonated polymers were not due to factor Xa inhibition but mainly thrombin inhibition. From the clotting time measurements using reptilase instead of thrombin and antithrombin III (AT III), PEO-SO3 and PU-PEO-SO3 indicated heparin-like activity which represents both prolonged thrombin time (TT) and normal reptilase time and increased TT in the presence of AT III. Thrombin was also neutralized by sulphonated polymers to a great extent. Therefore, the anticoagulant and heparin-like activities of PEO-SO3 and PU-PEO-SO3 seem to contribute to their improved blood compatibility.

Anticoagulants↗

PubMed1996

Biocompatibility of sulphonated polyurethane surfaces.

Surfaces of medical devices made of polymeric materials may promote thrombosis and inflammation. Therefore, in an attempt to produce surfaces which might diminish biomaterial-mediated thrombosis and inflammation, surface derivatization with 2-acrylamido-2-methylpropanesulphonic acid (AMPS) was carried out. The derivatization procedure generates free radicals which initiate the copolymerization of AMPS monomers directly to a polyurethane surface. In an in vitro blood loop study using non-anticoagulated human blood, the resulting AMPS-derivatized material completely abrogates the generation of fibrinopeptide A, decreases the production of beta-thromboglobulin and C3a, and decreases the adherence of platelets. The derivatized material also attracts fewer adherent neutrophils when implanted in mice. However, AMPS derivatization unexpectedly increases the recruitment of macrophages to implanted material and promotes the formation of adherent sleeve thrombi on central venous catheters indwelling in non-anticoagulated canine femoral veins. Thus, AMPS derivatization has highly variable effects on inflammatory and thrombotic systems. Further investigation is clearly required to determine the mechanisms underlying both desired and adverse effects.

Acrylamides↗

PubMed1996

Synthesis and characterization of segmented polyurethanes based on amphiphilic polyether diols.

Segmented polyurethanes (SPUs) based on polyethylene glycol (PEG), polypropylene glycol (PPG) and a series of Pluronics with different ethylene oxide/propylene oxide ratios (EO/PO) and molecular weights were prepared. Different diisocyanates were used for making SPUs: 4,4-diphenylmethane diisocyanate (MDI), 4,4-dicyclohexylmethane diisocyanate (MDCI), hexamethylene diisocyanate (HMDI) and isophorone diisocyanate (IPDI). 1,4-Butane diol (BD) and ethylene diamine (ED) were used as chain extenders. The polymers obtained were characterized by infrared spectroscopy (IR), nuclear magnetic resonance (NMR) and differential scanning calorimetry (DSC). The microphase morphology (phase separation and phase mixing) is discussed in more detail.

Biocompatible Materials↗

PubMed1996

Use of porous polyurethanes for meniscal reconstruction and meniscal prostheses.

In the past, porous materials made of an aromatic polyurethane (PU) were successfully used to meniscal reconstruction in dogs. Since aromatic PUs yield very toxic fragments upon degradation, a linear PU was synthesized by curing a poly(epsilon-caprolactone) and 1,4-trans-cyclohexane diisocyanate based prepolymer with cyclohexanedimethanol. Porous materials of this polymer were also implanted for meniscal reconstruction. The results were comparable with the most successful implant series so far. Additionally, a porous meniscal prosthesis was developed to replace a total meniscus. Due to the very high shear stresses to which the prosthesis would be exposed, the stress hysteresis phenomenon linear PUs are known to exhibit could be of great consequence. Therefore an aliphatic PU network, synthesized by cross-linking poly(epsilon-caprolactone) and 1,4-trans-cyclohexane diisocyanate with glycerol, was used. Dislocation caused by tearing out of the sutures was found to be a problem because the tear resistance of the material was relatively low. In this study the tearing problem has been partly circumvented by using a complex suturing technique. Meniscal prostheses turned out to induce fibrocartilage upon implantation, and degeneration of articular cartilage was less severe than after meniscectomy.

Animals↗

PubMed1996

Uptake of drugs by catheters: the influence of the drug molecule on sorption by polyurethane catheters.

The sorption of drugs by indwelling intravenous catheters may have clinical consequences both by alteration of the dose received by the patient and by physically affecting the catheter materials themselves which may lead to changes in mechanical properties and biocompatibility. Studies of drug sorption to new catheter materials are therefore important. Pellethane, a polyurethane increasingly used in vascular access catheters, is as yet little studied in terms of its capacity for drug sorption. In this work a range of drugs known to be sorbed by PVC infusion sets were studied with respect to their sorption by Pellethane catheters. Standard lengths of catheter were incubated with solutions of drugs and samples of the solution were taken at intervals, assayed spectrophotometrically and compared with control solutions incubated without catheter. Losses from solution of up to 93% were found after 24 h. A series of highly sorbing and clinically relevant drugs was identified and their uptake was studied until equilibrium had been reached. A correlation was evident between the octanol/water partition coefficient and the fraction of drug taken up from solution at equilibrium, with the more hydrophobic drugs being taken up to a greater extent by the catheter.

Adsorption↗

PubMed1992

Experimental pathology of intravenous polyurethane cannulae containing disinfectant.

Cannula tubing (1.6 mm external, 1 mm internal diameter) manufactured from medical grade polyurethane containing 2%, 2,4,4'-tri-chloro-2'-hydroxydiphenylether ('Irgasan', Ciba-Geigy) was found to have no effect other than that seen with control ('Irgasan'-free) tubing in the following test systems: (i) haemolysis, (ii) endothelial cell cultures, (iii) paravertebral muscle of rabbits, (iv) jugular vein of rabbits, (v) cannulation of baboons and (vi) clotting times of human platelet-rich plasma. However, the results from (iv) showed a significant amount of damage from both inpregnated and control cannulae and (v) showed that all detectable 'Irgasan' had been eluted from the portions of tubing retained within the animal before the end of the experiment, more rapidly than predicted from in-vitro studies. The rate of elution of 'Irgasan' in vivo needs to be further investigated, and consideration should be given to developing a plastic-disinfectant combination with a slower rate of loss of disinfectant.

Animals↗

PubMed1993

Effect of polyurethane catheters and bacterial biofilms on the in-vitro activity of antimicrobials against Staphylococcus epidermidis.

The effect of two polyurethane ['Cavafix Certo' (CAV); 'Viacath' (VIA)] catheters on the in-vitro activity of amikacin (AN), clindamycin (CM), cloxacillin (CX), ciprofloxacin (CIP), vancomycin (VA), teicoplanin (TEI) and daptomycin (DAP) against slime producing and non-producing Staphylococcus epidermidis strains was determined using a microdilution assay. None of the antimicrobial agents was significantly affected in the presence of the catheters. The susceptibility of S. epidermidis attached to CAV and VIA catheters was also evaluated. Minimum inhibitory concentration (MIC) values were similar when planktonic and attached bacteria were compared. Minimum bactericidal concentrations (MBCs) markedly increased in the presence of 6 and 48 h bacterial biofilms. These increases in MBC values occurred when either slime producing or non-producing strains were used, and in most cases were higher for CAV catheters than for VIA catheters. This phenomenon was shown not to be due to differences in bacterial adherence. It is concluded that the in-vitro bactericidal activity of certain antimicrobials markedly decreased when bacteria adhered to plastic catheters, but this effect could have been dependent partially on the nature of the catheters.

Anti-Bacterial Agents↗

PubMed1990

Structural and cellular characterization of solvent-casted polyurethane membranes.

Fibroblastic cell attachment and growth characteristics of different polyurethane (PU) films were tested. These films were prepared by a classical solvent-casting procedure. By changing the composition and the type of casting solution (i.e. tetrahydrofurane, dioxane, dimethyl formamide-tetrahydrofurane, tetrahydrofurane-dioxane, etc.) PU films with different physical and chemical bulk and surface structures were obtained. Structural properties of these films were investigated by scanning electron microscopy, equilibrium swelling experiments and contact-angle studies. In stationary cell culture tests, a model cell-line, i.e. baby hamster kidney (BHK) were used. Thus the effects of structural properties on the cell behaviour were investigated. The results demonstrate that it is possible to achieve different cell responses by changing the preparation conditions of the films. While the cell attachment is excellent on porous PU surfaces, the others showed similar adhesion. Better proliferation of BHK cells was obtained with PU films prepared from dioxane solution.

Animals↗

PubMed1993

Safety and intracardiac function of a silicone-polyurethane elastomer designed for vascular use.

No ideal prosthetic heart valve exists. While polyurethane copolymers possess excellent physical properties, thrombosis and embolism remain a problem and compounds designed to be less thrombogenic have been prone to biodegradation and failure ('cracking'). We tested a new material which has an elastomeric silicone applied to the polymer surface. A hydrophilic film of protamine and gelatin is covalently bonded to the silicone--this obviates the need for preclotting and should permit endothelial growth. The material was tested by implantation during cardiopulmonary bypass as patches in the mitral valve of six weanling sheep (weanling sheep provide a standard model of accelerated calcification for bioprosthetic heart valves). Prosthetic valves constructed from the material were implanted in an additional four animals, but all of these died within 30 days with heavily calcified valves. Four of the six animals with patches survived and were sacrificed 180 days after surgery when the patches were found to be well healed to native tissue, with collagenous ingrowth and partial endothelial covering. Scanning electron microscopy confirmed good healing, tissue ingrowth and good surface endothelium. The material functioned well as a patch in the mitral valve, allowing tissue ingrowth and endothelial growth on the surface of the patch. The material is not able to resist the strains experienced by a mitral valve prosthesis. Prospects for improved polymers for intravascular applications are good.

Animals↗

PubMed1989

Polyurethane-coated Dacron mesh tray for temporary mandibular reconstruction following resection of oral cancer: clinical results of 27 cases.

During a 3-year period from 1983 to 1986, a polyurethane-coated Dacron mesh tray (Xomed Inc, Jacksonville, FL) was used in 27 cases for temporary mandibular reconstruction in patients who had undergone jaw resection for oral carcinoma. Delayed mandibular reconstruction using the Dacron mesh tray combined with rib grafts was performed in three cases. The Dacron mesh tray technique provides good functional and esthetic results and offers several advantages when compared with metal trays. The success rate was 74%; intraoral perforation was the main reason for early removal of the tray.

Adult↗

PubMed1995

Exposure to toluenediamines from polyurethane-covered breast implants.

Toluenediamines (TDA) were monitored in blood, urine and redon drainage following implantation of polyurethane (PU)-covered breast prostheses. In the redon drainage TDAs showed an initial steep drop. The levels did not fall below detection limits but formed a plateau, which suggests a continued degradation of the PU foam. Urinary metabolite levels were above pre-operation background in all samples collected. In plasma there is an initial lag period of 20-30 days, where little above background TDA was found, after which levels rose to above 4.0 and 1.5 ng/ml plasma for 2,4-toluenediamine (24TDA) and 2,6-toluenediamine (26TDA), respectively. Elevated levels were found up to 2 years post-operation. Acid hydrolysis of precipitated plasma proteins released equivalent amounts of TDA as from total plasma, TDA being covalently bound to both albumin and globulin fractions. Urinary and plasma levels from these patients are in the same range detected from occupational exposure to toluene diisocyanate.

Breast Implants↗

PubMed2004

Decreased fibroblast cell density on chemically degraded poly-lactic-co-glycolic acid, polyurethane, and polycaprolactone.

Select prolonged functions of fibroblasts leading to extensive fibrous tissue encapsulation can be detrimental to numerous implant applications, including materials designed for the bladder, vasculature, and bone. Specifically, overextended functions of fibroblasts at the tissue-implant interface for orthopedic applications lead to callus formation, fibrous encapsulation events, and ultimately soft (not desirable hard-bony) tissue juxtaposition. Such events result in insufficient regeneration of bone and compromise the overall success of the implant. The objective of the present in vitro study was to determine, for the first time, fibroblast densities on NaOH-treated poly-lactic-co-glycolic acid co-polymers (PLGA), HNO(3)-treated polyurethane (PU), and NaOH-treated polycaprolactone (PCL). Previous studies have demonstrated increased bladder, vascular, and bone cell densities on chemically treated compared to unaltered PLGA, PU, and PCL films. Results of this study provided evidence of decreased fibroblast numbers on chemically treated PLGA, PU, and PCL after time periods of up to 5 days. Examination of these substrates revealed that all chemically modified polymers possessed a high degree of nanometer surface roughness compared to their respective unaltered polymers. In contrast, other material properties (such as chemistry and wettability) were different when comparing chemically treated PLGA, PU, and PCL films. Since fibroblasts are anchorage-dependent cells whose adhesion is a critical prerequisite to the prolonged, extensive formation of a fibrous-tissue containing extracellular matrix, the present in vitro results of decreased fibroblast densities on chemically degraded PLGA, PU, and PCL suggest that these materials may be suitable materials for numerous tissue-engineering applications and, thus, deserve further investigation.

Absorbable Implants↗

PubMed2004

Hemocompatibilty of new ionic polyurethanes: influence of carboxylic group insertion modes.

New segmented polyurethane (PU) anionomers based on hydroxytelechelic polybutadiene (HTPB) were synthesized via two environment-friendly chemical routes. The effects of carboxylic content and ion incorporation mode on the surface properties were investigated by mean of water absorption analysis and static contact angle measurements using water, diiodomethane, formamide and ethylene glycol. Blood compatibility of the PUs was evaluated by in vitro adhesion assay using 111In-radiolabeled platelet rich plasma and 125I-fibrinogen. The morphology of platelet adhesion was also observed by scanning electron microscopy (SEM). Results were compared with a biomedical-grade PU, Pellethane. Insertion of the carboxylic groups on the soft segments (S-alpha series), using thioglycolic acid (TGA), increases surface hydrophilicity, limits water uptake (5%, for an ion content of 3.6 wt%), and reduces platelet adhesion and fibrinogen adsorption on the PUs' surfaces. In contrast, the classical insertion onto the hard segment (H-alpha series), using dimethylolpropionate (DMPA) as chain extender, leads to high water uptake (18%, for an ion content of 3.6 wt%) and promotes platelet and fibrinogen adhesion. SEM analyses of the non-ionic PUs exhibited surfaces with adhered platelets which underwent morphological modification. Similarly, the H-alpha ionic PUs show adherent and activated platelets. On the contrary, no platelet morphology changes were observed on the S-alpha ionic surfaces. In conclusion, insertion of carboxyl groups on the soft segments of PUs reduces their thrombogenicity.

Absorption↗

PubMed2004

Nano-scale surface modification of a segmented polyurethane with a phospholipid polymer.

Nano-scale modification of a segmented polyurethane (SPU) with cross-linked 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer was performed to obtain a biocompatible elastomer. To control the domain size and the depth of the modified layer, various compositions of monomers, including MPC, 2-ethylhexyl methacrylate (EHMA), and glycerol 1,3-diglycerolate diacrylate, were examined. SPU film was immersed in the monomer solution and visible light irradiation was applied to initiate polymerization to the SPU film that was held by mica to condense MPC units at the surface. The surfaces of the obtained film were analyzed by X-ray photoelectron spectroscopy and water contact angle measurement. The surface density of MPC units changed with the monomer concentration, and the density was the highest when the ratio between MPC and EHMA was 7:3. In modified SPU films, 6- to 25-nm MPC unit-enriched domains were observed and the density of these domains gradually decreased with depth. The sizes of the domains depended on the MPC composition in the monomer solution. The mechanical properties of the modified films as evaluated by tensile strength measurement under wet conditions were not significantly different from those of SPU. With increase in the existence of MPC unit-enriched domains on the MEG film surface, platelet adhesion and activation were remarkably reduced compared to the SPU film. This nano-scale surface modification may be a useful technique for applying elastic polymer biomaterials.

Biocompatible Materials↗

PubMed2005

Extent of iron pick-up in deforoxamine-coupled polyurethane materials for therapy of chronic wounds.

Polyurethane net substrates (PNS) coupled with deferoxamine (DFO) have been studied to determine the extent of Fe2+ pick-up for use in chronic wound therapy. A m solution of ferrous sulphate (FeSO4) was used to generate ferrous ions similar to those found in chronic wounds. The concentration of Fe as a function of position through the dressings was evaluated using a variety of techniques. Atomic force microscopy (AFM) and energy-filtered transmission electron microscopy (EFTEM) revealed a rough precipitated layer at the surface of activated PNS exposed to FeSO4 solution. Optical microscopy (OM) and backscattered environmental scanning electron microscopy (ESEM) showed a clear layer of Fe(3+)-enriched material in the surface regions exposed to DFO. The penetration depth of DFO into activated dressings was found to be 20-30 microm. Energy-dispersive X-ray (EDX) analysis was used to approximate the distribution of bound- and unbound-Fe as a function of position within BPNS and DFO-activated dressings after immersing them in a FeSO4 solution for various times. These studies have shown the activity of iron with respect to ionic state in DFO-activated PNS for potential using as dressing for chronic wounds.

Adhesives↗

PubMed2005

Effect of isoliquiritigenin on viability and differentiated functions of human hepatocytes maintained on PEEK-WC-polyurethane membranes.

In this study, we tested the ability of microporous membranes synthesised from a polymeric blend of modified polyetheretherketone (PEEK-WC) and polyurethane (PU) to support long-term maintenance and differentiation of human liver cells. The effect of isoliquiritigenin (ISL), which is a component of liquorice extract, exhibiting growth stimulatory and antiproliferative dose-dependent effect was investigated by comparing cultures treated with ISL with those untreated. To this purpose, flat-sheet membranes were prepared by a blend of PEEK-WC and PU polymers by phase inverse technique. The morphological and physico-chemical properties were characterised, respectively, by scanning electron microscopy and water contact angle measurements. Human hepatocytes cultured on PEEK-WC-PU membranes were constant up to 1 month albumin production and urea synthesis as well as the synthesis of total proteins. The liver-specific functions were expressed at high levels when cells were cultured on membranes with respect to collagen. Also the biotransformation functions were maintained for all culture periods: the ISL elimination rate increased during the culture time and high values were measured up to 22 days. Thereafter, a decrease was observed. ISL stimulated the proliferation of hepatocytes cultured on both substrata but did not affect their liver-specific functions. Hepatocytes cultured on PEEK-WC-PU membranes responded very well to ISL and expressed high levels of P450 cytochrome. These results demonstrated that long-term maintenance of human liver differentiation can be achieved on PEEK-WC-PU membranes. The incubation with ISL at the investigated concentration could stimulate the proliferation of human hepatocytes in biohybrid systems.

Benzophenones↗