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At least 1,315 records · Page 73Linked to original sources
PubMed1989

Comparative study of the thromboresistance of Dacron combined with various polyurethanes.

In vitro tests were carried out on Dacron samples differently knitted and on Dacron vascular prostheses coated with various urethanes. All the materials were put in contact with human platelet-rich plasma; the subsequent assay of three platelet released substances, i.e. beta-thromboglobulin, platelet factor 4 and thromboxane B2, as well as the quantification of platelet retention, were used to establish the degree of thrombogenicity of the material itself. In some cases Dacron-urethanes composites showed better thromboresistance than any other materials conventionally used in vascular surgery.

Biocompatible Materials↗
PubMed1990

Albumin adsorption on to aluminium oxide and polyurethane surfaces.

The changes in protein adsorption onto aluminium surfaces coated with different thicknesses of oxide layers were examined. The oxide layers on aluminium substrates were derived by the anodizing technique. Protein adsorption studies were conducted using 125I-labelled albumin and the amount of albumin adsorbed was estimated with the help of a gamma counter. An increase in albumin adsorption was observed on oxide layer coated aluminium surfaces. The effect of anti-Hageman factor on albumin and fibrinogen adsorption on to bare aluminium, oxide layer coated aluminium and bare polyether urethane urea surfaces was also investigated. It was observed that the presence of anti-Hageman factor increased the adsorption of albumin and fibrinogen on to all these substrates.

Adsorption↗
PubMed1991

Synthesis and antithrombogenicity of heparinized polyurethanes with intervening spacer chains of various kinds.

Heparin was immobilized to polyetherurethaneurea membrane by covalent or ionic bondings with intervening spacer chains having different lengths and different terminal functional groups. The amount of immobilization of heparin and the release rate of immobilized heparin were controlled by the nature and the mode of bonding of spacer chains. The heparinized polyetherurethaneurea membranes became more in vitro antithrombogenic and suppressed more strongly the adhesion and activation of platelets, as the amount of immobilization increased. It was also shown that the membrane to which the low-molecular-weight fraction of heparin was immobilized was less stimulating to platelets.

Animals↗
PubMed1992

Degradation of five polyurethane gastric bubbles following in vivo use: SEC, ATR-IR and DSC studies.

Five Garren-Edwards Gastric Bubbles were characterized, following up to 4 months use in vivo, using size exclusion chromatography, differential scanning calorimetry and attenuated total reflectance infrared spectroscopy. These techniques show that the material used to construct the bubble is probably an aromatic polyester urethane and revealed a 39-55% decrease in number average molecular weight, a 9 degrees C decrease in glass transition temperature, the disappearance of soft segment crystallinity and a broadening of the hard segment melting region after exposure to highly acidic (approximately pH 1.2) gastric fluid. The results indicate that significant chemical and morphological changes have taken place in the bubble material, including loss in chemical functionality, phase separation and increased hard segment aggregation. A comparison of the decrease in glass transition temperature as a function of molecular weight suggests that glass transition temperature is a sensitive predictor of this material's stability. Additionally, evidence is provided that the broad infrared absorption at 1077-1067 cm-1 normally assigned to C-O-C hard segment may represent two types of C-O-C stretching: (1) C-O-C stretching of the free urethane carbonyl, and (2) C-O-C stretching of the hydrogen bonded urethane carbonyl.

Biodegradation, Environmental↗
PubMed1996

New polyurethane compositions able to bond high amounts of both albumin and heparin. II: Copolymers and polymer blends.

Haemocompatible new urethane copolymers and polymer blends containing, in the chain extender, a long chain alkyl group (able to bond albumin) or a tertiary ammonium group able, after suitable quaternization reaction, to bind ionically significant amounts of heparin, were prepared. The copolymers were characterized by differential scanning calorimetry, intrinsic viscosity determinations, infrared spectroscopy and nuclear magnetic resonance (1H and 13C). Biological in vitro evaluation has shown that the adsorption sequence for albumin and heparin, respectively, onto films of the various copolymers and blends, exerts a great influence. From scanning electron microscopy measurements it was seen that the bonding type of albumin to the polymer films plays a determining role on the platelet activation. A phase segregation occurring on the polymer blends surface was demonstrated by X-ray photoelectron spectroscopy measurements.

Biocompatible Materials↗
PubMed1993

Analysis of biomedical polymer surfaces: polyurethanes and plasma-deposited thin films.

The surface characterization of biomaterials is important for understanding the biological reactivity of surfaces and for monitoring surface reproducibility and contamination. Electron spectroscopy for chemical analysis (ESCA), secondary ion mass spectrometry (SIMS), contact-angle methods, vibrational spectroscopic methods, and scanning probe microscopies are briefly reviewed. Examples are presented using these methods to characterize RF plasma-deposited surfaces based upon acetone and oxygen for cell culture and Biomer¿ surfaces.

Biocompatible Materials↗
PubMed1993

Topical phenytoin in the treatment of split-thickness skin autograft donor sites: a comparative study with polyurethane membrane drape and conventional dressing.

The effectiveness of topical phenytoin as a wound healing agent was compared with that of OpSite (Smith & Nephew) and a conventional topical antibiotic dressing (Soframycin, Roussel) in a controlled study of 60 patients with partial-thickness skin autograft donor sites on the lower extremities. Mean time to complete healing (complete epithelialization) was 6.2 +/- 1.6 days in the phenytoin-treated group (30 patients), compared to 8.6 +/- 2.2 days with OpSite (15 patients), and 12.6 +/- 3.4 days in the 15 Soframycin-treated patients. The differences between the treatment groups were significant at P < 0.001. Mean pain scores were also lower in the phenytoin-treated group, 0.40 +/- 0.55 vs. 0.66 +/- 0.60 with OpSite (P < 0.05) and 1.4 +/- 0.50 with the conventional dressing (P < 0.001). Both phenytoin and OpSite were superior to the Soframycin dressing with respect to bacterial contamination and wound infection as measured by Gram stains of wound smears, swab and aspirate (OpSite) cultures, and clinical assessments (P < 0.001) carried out on the fifth day of treatment. No local or systemic adverse effects of the three agents used were noted. Phenytoin appears to be an effective, low-cost and safe method for the treatment of partial-thickness skin graft donor sites, comparing very favourably with, and in some aspects superior to, occlusive dressings. Further clinical use and evaluation of topical phenytoin are merited.

Administration, Topical↗
PubMed2005

Development of an RNA isolation procedure for the characterisation of human endothelial cell interactions with polyurethane cardiovascular bypass grafts.

To date no reliable method has been developed for the isolation of RNA from cells seeded onto cylindrical vascular grafts. This study was performed in order to develop a reliable methodology for isolating RNA from cylindrical conduits made from poly(carbonate-urea)urethane (PU). Human umbilical vein EC were seeded onto PU vascular grafts and an Alamar blue assay performed to assess cell viability. Cells were prepared for RNA extraction by trypsinisation, cell scraping and direct application of cell lysis buffer. In all cases RNA was extracted using a "Qiagen RNeasy" kit. Alamar blue showed viable cells were present on all of the seeded PU vascular grafts. Levels of RNA extracted from the cells removed from the graft by the trypsinisation yielded 0.130 microg/microl, by scraping 0.078 microg/microl and by direct lysing 0.093 microg/microl of RNA, respectively. RTPCR was conducted successfully for GAPDH and TGF-beta1. Trypsinisation prior to RNA extraction provided the highest RNA yield and attained near complete cell removal ensuring that gene expression obtained was representative.

Biocompatible Materials↗
PubMed2005

Preparation and characterization of highly porous, biodegradable polyurethane scaffolds for soft tissue applications.

In the engineering of soft tissues, scaffolds with high elastance and strength coupled with controllable biodegradable properties are necessary. To fulfill such design criteria we have previously synthesized two kinds of biodegradable polyurethaneureas, namely poly(ester urethane)urea (PEUU) and poly(ether ester urethane)urea (PEEUU) from polycaprolactone, polycaprolactone-b-polyethylene glycol-b-polycaprolactone, 1,4-diisocyanatobutane and putrescine. PEUU and PEEUU were further fabricated into scaffolds by thermally induced phase separation using dimethyl sulfoxide (DMSO) as a solvent. The effect of polymer solution concentration, quenching temperature and polymer type on pore morphology and porosity was investigated. Scaffolds were obtained with open and interconnected pores having sizes ranging from several mum to more than 150 microm and porosities of 80-97%. By changing the polymer solution concentration or quenching temperature, scaffolds with random or oriented tubular pores could be obtained. The PEUU scaffolds were flexible with breaking strains of 214% and higher, and tensile strengths of approximately 1.0 MPa, whereas the PEEUU scaffolds generally had lower strengths and breaking strains. Scaffold degradation in aqueous buffer was related to the porosity and polymer hydrophilicity. Smooth muscle cells were filtration seeded in the scaffolds and it was shown that both scaffolds supported cell adhesion and growth, with smooth muscle cells growing more extensively in the PEEUU scaffold. These biodegradable and flexible scaffolds demonstrate potential for future application as cell scaffolds in cardiovascular tissue engineering or other soft tissue applications.

Absorbable Implants↗
PubMed2006

Calibration of polyurethane foam (PUF) disk passive air samplers for quantitative measurement of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs): factors influencing sampling rates.

PUF disk passive air samplers are increasingly employed for monitoring of POPs in ambient air. In order to utilize them as quantitative sampling devices, a calibration experiment was conducted. Time integrated indoor air concentrations of PCBs and PBDEs were obtained from a low volume air sampler operated over a 50 d period alongside the PUF disk samplers in the same office microenvironment. Passive sampling rates for the fully-sheltered sampler design employed in our research were determined for the 51 PCB and 7 PBDE congeners detected in all calibration samples. These values varied from 0.57 to 1.55 m3 d(-1) for individual PCBs and from 1.1 to 1.9 m3 d(-1) for PBDEs. These values are appreciably lower than those reported elsewhere for different PUF disk sampler designs (e.g. partially sheltered) employed under different conditions (e.g. in outdoor air), and derived using different calibration experiment configurations. This suggests that sampling rates derived for a specific sampler configuration deployed under specific environmental conditions, should not be extrapolated to different sampler configurations. Furthermore, our observation of variable congener-specific sampling rates (consistent with other studies), implies that more research is required in order to understand fully the factors that influence sampling rates. Analysis of wipe samples taken from the inside of the sampler housing, revealed evidence that the housing surface scavenges particle bound PBDEs.

Air Pollutants↗
PubMed2005

Performance of the Reality polyurethane female condom and a synthetic latex prototype: a randomized crossover trial among South African women.

OBJECTIVE: This multisite, randomized, crossover trial comparing the performance of the Reality female condom (FC1) with a new synthetic latex prototype (FC2) was conducted in Durban, South Africa. METHOD: In total, 276 women were enrolled and 201 women completed the study. Altogether, 1910 FC1 condoms and 1,881 FC2 condoms were used. RESULTS: Total breakage was 0.73% in FC1 and 0.85% in FC2 (95% confidence interval, -0.64 to 0.87). The number of clinical breakages (those that could result in a pregnancy or sexually transmitted infection) was similar for each condom type (FC1, n=9; FC2, n=8). Incorrect penetration (penis between condom and vaginal wall) was 1.26% and 0.64% for FC1 and FC2, respectively. Outer ring displacements (outer ring pushed into the vagina partially or fully) were comparable for both condoms (FC1, 3.14%; FC2, 2.98%). Slippage (condom came out of the vagina) was rare and reported in 0.37% or less of devices used. Total clinical failure was 5.24% in FC1 and 4.3% in FC2. CONCLUSION: The FC1 and FC2 performed comparably within this trial.

Adult↗
PubMed2006

Short-term acceptability of the Reality polyurethane female condom and a synthetic latex prototype: a randomized crossover trial among South African women.

PURPOSE: This multisite, randomized, crossover trial comparing the acceptability of the Reality(R) female condom (FC1), with a new synthetic latex prototype (FC2) of similar design and appearance to FC1, was conducted in Durban, South Africa. METHODS: In total, 276 women were enrolled and 1910 FC1 condoms and 1881 FC2 condoms were used by 218 and 216 women, respectively. RESULTS: Overall experience of use was reported as good for over half the participants with both condom types (FC1=50.9%, FC2=55.1%). Similar acceptability issues were reported in like proportions for FC1 and FC2, with features such as the lubricant (FC1=36.7%, FC2=37.0%) and the material (FC1=36.2%, FC2=29.2%) most commonly viewed positively for both condom types. Negative aspects commonly reported for both female condoms were the lubricant (FC1=30.3%, FC2=31.5%) and the appearance (FC1=29.8%, FC2=34.0%). Preference for FC1 was 29.5% and was slightly higher for FC2 (36.6%). Some women felt that there was no real difference between the two devices (33.8%). CONCLUSION: The acceptability of FC1 and FC2 was comparable, and women who find FC1 acceptable to use should also find FC2 acceptable.

Adult↗
PubMed2004

Removal of copper from aqueous solution by Ascophyllum nodosum immobilised in hydrophilic polyurethane foam.

The seaweed Ascophyllum nodosum was pre-treated by successive washes in distilled water and dilute acid, dried, and pulverised to produce particles of <150 microm. These were immobilised during the manufacturing process of Hypol 2002 polymer to form a biomass/polymer matrix that was stable and easy to handle. In making the composite a mixing speed of 360 rpm for 20-30 s with 2% (w/w) addition of surfactant to pre-polymer was found to be ideal. The average pore sizes for different water polymer mixes (expressed as volume ratios) were 1.66 mm +/- 0.98 (ratio 0.75:1), 1.58 mm +/- 0.76 (ratio 1:1), 1.64 mm +/- 0.6 (ratio 1.5:1) and 1.11 mm +/- 0.615 (ratio 2:1). The biomass/polymer was used alongside free native biomass in an initial adsorption experiment using a 0.0315 mmol dm(-3) Cu (II) solution and gave a copper uptake capacity (q)(max) of 0.037 mmol Cu g(-1) dry weight seaweed in both cases which represented approximately 85% of total initially available copper. In later adsorption isotherm experiments using Cu concentrations between 0.0315 and 0.944 mmol dm(-3) at pH 5.0 and immobilized biomass over five consecutive adsorption/desorption cycles the biomass/polymer showed an initial lowering of adsorption capacity but stabilised at 0.23 mmol g(-1) dry weight by the third re-use. The q(max) of the immobilised biomass decreased from 0.55 and 0.416 mmol of Cu g(-1) dry weight when pH was lowered from 4.0 to 3.0, and increased from 0.576 mmol g(-1) dry weight (biomass) at 283 K to 0.636 mmol g(-1)(biomass) at 303 K.

Adsorption↗