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At least 1,117 records · Page 62Linked to original sources
PubMed2006

[Compliance of small diameter polyurethane artificial vascular graft ].

The radical compliance of small diameter artificial vascular grafts was measured by a device made of laser micrometer, pressure transducer, A/D card, micro computer and pulsed circulation loop, the volumetric compliance was measured by a device made of micro-syringe and pressure transducer; the longitudinal compliance was calculated from volumetric compliance and radical compliance. The research results showed that the radical compliance, volumetric compliance and longitudinal compliance would rise not only with the increase in polyurethane (PU) elasticity and salt/polymer ratio (or porosity), but also with the decrease in dipping layers (or wall thickness). Circumferential moduli E zeta and longitudinal moduli E theta could be calculated from volumetric compliance and longitudinal compliance respectively; E theta and E zeta would decrease with the increase in PU elasticity and salt/polymer ratio, but was independent on number of dipping layers. Small diameter PU artificial vascular grafts with compliance close to natural vein or artery can be prepared by choosing of more elastic PU materials (Chro or PCU1500), optimization of salt/polymer ratio (6:1), and the number of dipping layers (4-6 layers).

Biocompatible Materials↗
PubMed2006

[Application of monoclonal antibody immobilized polyurethane film for site-specific gene therapy].

OBJECTIVE: To study the feasibility of delivering viral gene vector from a collagen-coated polyurethane (PU) film through a mechanism involving monoclonal antiviral antibody tethering. METHODS: Anti-adenoviral monoclonal antibodies were covalently bound to the collagen-coated PU surface. These antibodies enabled tethering of replication defective adenoviruses through highly specific antigen-antibody affinity. The PU film-based gene delivery using antibody-tethered adenovirus encoding green fluorescent protein (GEP) was tested in rat arterial smooth muscle cell (A10 cell) culture in vitro. The virus binding stability was studied by incubating the collagen-coated PU film in PBS solution at 37 degrees C for 20 days, followed with A10 cell cultures with the incubated films and the corresponding buffer solution. RESULTS: PU films with antibody-tethered adenovirus encoding GFP demonstrated efficient and highly localized gene delivery to A10 cells. Virus binding was stable for at least 10 days at physiological conditions, more than 77% of the originally bound virus remained in the film after 15 day's incubation. CONCLUSION: Gene delivery using PU film-based anti-viral antibody tethering of vectors exhibited potentials of applications in a wide array of single or multiple therapeutic gene strategies, and in further stent-based gene delivery therapeutic strategies.

Adenoviridae↗
PubMed2006

Endothelial cell attachment to the gamma irradiated small diameter polyurethane vascular grafts.

Previously we have fabricated the small diameter polyurethane (Pellethane 2363-80A, abbreviated PU) vascular grafts that were modified by epoxy-crosslinked gelatin (abbreviated gelatin) and an RGD-containing protein (abbreviated CBD-RGD) to facilitate the endothelial cell (EC) seeding on the surface. In this study, the biocompatibility of such surface after freeze-drying and gamma irradiation was evaluated. The contact angle of the irradiated PU dropped a little and the ESCA spectra revealed oxygen bonding. The increases in the amount of extractables as well as in the molecular weight distribution were observed. The mechanical properties decreased only slightly. The irradiated PU surface showed enhanced EC affinity that persisted after several months of storage. Gelatin, CBD-RGD (used with either gelatin or PU), and PU modified by gelatin and CBD-RGD all demonstrated higher EC affinity after freeze-drying and gamma irradiation (2.5 Mrad). The positive cellular effect remained after storage. Based on these results, freeze-drying followed by gamma irradiation at 2.5 Mrad is a proper way to process and store these vascular grafts.

Biocompatible Materials↗
PubMed1991

A method for assaying biofilm capacity on polyurethane-coated slides.

Isolates of coagulase-negative Staphylococci (CNS) were examined for their ability to form biofilms on polyurethane-coated slides. These slides provided a smooth plastic coating simulating polymeric plastic surfaces of medical grade catheter tubing. Slides were placed into plastic conical tubes containing tryptic soy broth inoculated with 10(6) bacteria per mL. The tubes were then incubated at 37 degrees for 48 hours. After incubation, 1 of the slides was stained with a fluorescent acridine orange stain and the other with a safranin stain. The incubation tubes were also stained with safranin. Forty-eight percent of the 65 CNS isolates were found to form a biofilm using acridine orange staining. Forty percent of the 65 CNS isolates were found to form a biofilm using the safranin stain on slides, whereas only 34% were found to adhere on sides of plastic tubes. Increased sensitivity of the fluorescent stain was probably due to enhanced visualization of smaller numbers of bacteria on the plastic. This method using fluorescent stained plastic-coated slides was easier to visualize and interpret than the tube method.

Acridine Orange↗
PubMedDate not supplied

Experimental evaluation of a new type of heparin-bonded polyurethane.

A new type of heparin bonding method using polyurethane (H-PU) in an ionically equivalent manner was examined experimentally. In vitro testing of polyvinylchloride tubes with this coating showed that the behavior of the heparin was attributed to the activation of retained heparin on the surface. After 4 hrs of heparinless arterio-arterial bypass in a canine model with a central shear rate of 25 sec-1 (inner diameter, 0.8 x 80 cm), macroscopic and scanning electron microscopic examinations showed that the H-PU coated tube had better antithrombogenicity than that of a conventional PU coated tube (Pellethane). These results suggest that this heparin bonding method with PU appears to have good antithrombogenicity with possible long durability.

Animals↗
PubMedDate not supplied

In vivo evaluation of porous versus skinned polyurethane-polydimethylsiloxane small diameter vascular grafts.

Two types of spongy polyurethane-polydimethylsiloxane (PU-PDMS) vascular grafts (1.5 mm ID, 450 microns wall thickness) were fabricated with either a skinned (SG) or a porous (PG) luminal surface and an open mesh filamentous external surface by a spraying, phase-inversion technique. Tubular membranes, 15-20 mm in length, were all implanted by the same surgeon as infrarenal aorta replacements in male Sprague-Dawley rats weighing 250-350 g (SG: n = 12, PG: n = 23). The patency rates at 2 weeks and 3 months were 0% (0/7) and 0% (0/1) for SG, 72% (8/11) and 8% (1/12) for PG. Because the wall structure of these grafts was relatively compact and did not provide enough communicating voids, another series of 15 highly porous luminal surface grafts was fabricated with a higher void to material ratio. These grafts (HPG) exhibited a 73% patency at 3 months, with a fully endothelialized surface. The authors conclude that a very open luminal surface structure, and a high wall porosity, are significant factors of graft patency in small diameter vascular prostheses made of a porous material.

Animals↗
PubMed1991

Breast reconstruction utilizing subcutaneous tissue expansion followed by polyurethane-covered silicone implants: a 6-year experience.

Reconstruction of the breast after modified radical mastectomy can be safely and adequately performed in the subcutaneous plane. Placement of a subcutaneous tissue expander (as either an immediate or a delayed procedure), rapid expansion over a 3- to 4-month period, capsulotomy, and placement of a polyurethane-coated implant have led to satisfactory results over a 6-year period. Breast reconstruction methods are well documented; however, the utilization of expanded subcutaneous chest wall skin has not been reported heretofore.

Breast↗
PubMed1991

[Use of polyurethane foil for wound covering].

The authors account of the application of the Omiderm folie in connection with 29 cases. The transparent polyurethan skin substitute was used in dermatological diseases when presenting extensive shortage of tissue or for covering the half-thick skin's donor areas and for the treatment of deep second degree burns. The advantages of the application of the wound covering folie is being valued and the authors are calling attention to the most common complications being noticed during the application. The Omiderm is being judged as a suitable alternative bandage and skin substitute.

Burns↗
PubMed1990

Polyurethane foam-covered implants and capsular contracture: a laboratory investigation.

Experiments were conducted in rabbits comparing polyurethane foam-covered implants with otherwise identical smooth silicone gel implants. Using five objective methods of measurement of capsular contracture, no significant difference could be identified. The foam-covered implants consistently developed capsular contracture, although in most cases this was of mild degree and would not have been clinically significant. In the two foam-covered implants with hard contractures, there was no evidence of hematoma or separation of the foam.

Animals↗
PubMed1990

Mineralization of polyurethane membranes in the total artificial heart (TAH): a retrospective study from long-term animal experiments.

The degree of mineralization of TAH membranes in animals is directly related to the survival time of animals with a TAH. Large differences in mineralization of the membranes among individual animals have been observed. These differences can be explained by the simultaneous presence of infection on biomaterials (polyurethane) as well as by different levels of natural inhibitors of mineralization. No positive influence of applying sodium warfarin for the inhibition of the mineralization was observed.

Animals↗
PubMedDate not supplied

Endothelialization on various segmented polyurethanes: cellular behavior and its substrate dependency.

Endothelialization on artificial substrates is essential for providing vital function to artificial and hybrid vascular prostheses. The authors studied fundamental behaviors of endothelial cells (EC), including adhesion, spreading, migration, and growth, on various segmented polyurethanes (SPU) with a wide variety of wettability. Endothelialization has a synergistic action on these cellular behaviors that was quantitatively evaluated by phase contrast microscopy. Surface characteristics of SPU were analyzed by contact angle measurement and X-ray photoelectron spectroscopy. Adhesion, spreading, migration, growth, and endothelialization in vitro of bovine aortic EC on relatively hydrophobic SPU exceeded those on both a hydrophilic SPU, and a very hydrophobic siliconized one. Minimal interaction with EC was found for hydrophilic SPU. Adherent cells tended to be delaminated from siliconized SPU in a later culture period. The addition of a peptidyl antagonist of adhesive protein receptor inhibited adhesion of EC on SPU. These results suggest that surface characteristics, possibly regulating adsorption of adhesive proteins, are important factors in the development of vascular SPU prostheses.

Animals↗
PubMedDate not supplied

In vitro ultrasound characterization of a polyurethane trileaflet valve.

Polyurethane synthetic trileaflet valves were compared with commercial prostheses in vitro, in a pulse duplicator using ultrasound to characterize the flow velocities and patterns. Flow-pressure drop behavior was in the middle range of other prosthetic valves. Diastolic regurgitant jets were located by color Doppler ultrasound, and there appeared to be some leakage through the leaflet fold at the commissure. Nevertheless, the closing volumes and closed valve leakage volumes were, on average, lower than other prosthetic valves. Systolic 20 Hz spectral oscillations detected with pulsed Doppler and continuous wave Doppler were attributed to leaflet flutter in the open valve.

Aortic Valve↗
PubMedDate not supplied

The dynamics of platelet thrombus formation rate, thrombus retention time, and rate of embolization on a control and heparin bonded polyurethane angio-catheter.

The dynamics of platelet deposition and embolization from control and heparin bonded polyurethane catheters (CPC and HBPC) was evaluated with In-111 labeled autologous platelets (IN-PLT) and a computerized gamma camera (CGC). Ten non-heparinized dogs (18-25 kg) were catheterized in both femoral arteries with 10 cm of CPC and HBPC (5 Fr., Cordis) 24 hr after injection of 300-420 microCi of In-PLT, and imaged for 3 hr with the computerized gamma camera. The regional platelet deposition curves (RPDC) indicated multiple peaks and valleys; the curves were analyzed for early rate of thrombus formation (upswing), thrombus retention time (full width at half maxima of the RPDC-peak), and rate of embolization (downswing) on both catheters. The four parameters (mean +/- SD) of thrombosis on catheters and integral of the radioactivity time curve for the 3 hr duration of imaging were calculated from normalized counts/sec. The rate of thrombus formation and rate of embolization are higher for the control than HBPC, suggesting that heparin-bonding decreases the early rate of thrombosis and embolization. The thrombus adhesivity and retention time appear shorter for the control catheter, indicating that the control thrombogenic catheter forms multiple thrombi and emboli than HBPC. The integral appears larger for the control catheter than HBPC. In vivo (dynamic) studies, in vitro studies, and critical analyses of the radioactivity time curve were essential for complete evaluation of thrombogenicity of catheters and other cardiovascular prostheses.

Animals↗
PubMed1990

Evaluation of mechanical loading of a trileaflet polyurethane blood pump valve by finite element analysis.

The mechanical loading of the leaflets of a polyurethane blood pump valve at closing pressure (max 300 mmHg) and during the opening phase can be numerically calculated by the finite element method. Geometrical and physical non-linearities, supporting forces by neighbouring leaflets and manufacturing-related thickness distribution are taken into account. The valve housing is assumed to be rigid. Volume forces are neglected. The calculations showed that the critical strain limit of 4.5% (long-term failure limit) was exceeded at closing pressure and during valve opening. During valve operation the connection between leaflet and valve housing and the central leaflet region seem to be the critical areas.

Biocompatible Materials↗
PubMed1989

[The effect on wound healing of venous leg ulcers of a two-layered polyurethane foam wound dressing].

To demonstrate the effect of a two-layered polyurethane foam wound dressing (Lyomousse) on the healing of venous leg ulcers a comparative study in 41 patients (24 treated, 17 controls) was performed. For a quantification of the process of healing a computer-assisted morphometric procedure was used. This method is based on a Polaroid-photograph of the ulceration which is transferred in digital form by means of a digitizing equipment. From the digital data the primary variables area, perimeter and maximal diameter of the ulceration are calculated. For quantitative comparison the relative changes as well as the rate of the changes of the primary variables were used. The statistical comparison of the treated group and the control group showed a highly significant (p less than 0.001) promotion of wound healing for the therapy with the synthetic foam dressing using the relative changes as an indicator, and a significant (p less than 0.05) increase in the rates of changes, indicating an acceleration of healing. This therapeutical advantage can be drawn back to specific characteristics of the synthetic material, assuring a water vapour saturated micro-environment at the surface of the wound and reducing this way the detrimental effect of heat loss due to evaporation onto the healing process.

Aged↗
PubMed1989

[Infectious complications caused by a hemodialysis catheter. Retrospective study of septicemia related to a dual lumen polyurethane hemodialysis catheter in the subclavian vein].

Of 52 patients started on hemodialysis during two years, 19 used a polyurethane subclavian dual lumen hemodialysis catheter for temporary or permanent vascular access. Three of them (15.8%) got catheter sepsis, and one died. The article discusses prevention of intravascular catheter-related infection, and methods for vascular access.

Adult↗
PubMed1989

Evaluation of blood compatibility of PEO grafted and heparin immobilized polyurethanes.

To develop better blood compatible polymer for long-term biomedical applications, poly(ethylene oxide) (PEO) grafted and/or heparin immobilized polyurethanes (PUs) were made by novel surface modification. Their blood compatibilities were investigated using in vitro platelet adhesion test, APTT, PT, immobilized heparin bioactivity measurement, and ex vivo rabbit A-A shunt test. In platelet adhesion tests, PEO grafted PU surfaces, compared to PU control, displayed very little platelet adhesion and activation, and this effect was more significant as the molecular weight of PEO increased from 200 to 2000. Also, the degree of platelet adhesion was lower in the heparinized PU surfaces than that of PU control. The immobilized heparin showed a greater effect on intrinsic blood coagulation factors than on extrinsic ones, whereas the PU-PEO surface was independent of blood coagulation factors. Lowering both in vitro platelet adhesion and activation led to a prolongation in the ex vivo occlusion time. In particular, the heparinized PU-PEO surfaces displayed enhanced blood compatibility due to the synergistic effects of PEO and heparin.

Animals↗