Search results for "Polyurethanes"
showing 10 items of 21 documents
Prospective, randomized, single-center trial comparing 3 different 10F plastic stents in malignant mid and distal bile duct strictures.
2003
Abstract Background: The aim of this study was to determine whether patency rates differ with respect to the material, design, and surface texture of 3 different plastic stents. Methods: A total of 120 patients (median age 70.5 years; interquartile range 62-78 years) with malignant mid or distal bile duct strictures, seen between March 1996 and May 1999, were prospectively randomized to receive a 10F polyurethane stent, a Teflon Tannenbaum stent, or a hydrophilic hydromer-coated polyurethane stent. The primary study outcome measure was the interval between stent insertion and the first episode of clogging (or the presence of jaundice at death without stent exchange). All 3 types of stent we…
Elastomeric Electrospun Polyurethane Scaffolds: The Interrelationship Between Fabrication Conditions, Fiber Topology, and Mechanical Properties
2010
Electrospinning has been gaining increasing popularity in the fabrication of engineered tissue scaffolds due to its ability to produce nano to micro scale fibrous sheets. Many investigators have attempted to apply various degrees of control to this process in order to produce fiber meshes with more predictable patterns. These attempts have largely been limited to controlling fiber alignment and have fallen into two categories: physical manipulation of the fibers by pulling them into alignment using a rapidly spinning mandrel[1–3] or manipulation of the electric field during fabrication.[4, 5]
An asymmetric electrospun membrane for the controlled release of ciprofloxacin and FGF-2: Evaluation of antimicrobial and chemoattractant properties.
2021
Here, an asymmetric double-layer membrane has been designed and fabricated by electrospinning as a tool for a potential wound healing application. A hydrophobic layer has been produced by using a polyurethane-polycaprolactone (PU-PCL) copolymer and loaded with the antibacterial ciprofloxacin whereas an ion responsive hydrophilic layer has been produced by using an octyl derivative of gellan gum (GG-C8) and polyvinyl alcohol (PVA) and loaded with the growth factor FGF-2. This study investigated how the properties of this asymmetric membrane loaded with actives, were influenced by the ionotropic crosslinking of the hydrophilic layer. In particular, the treatment in DPBS and the crosslinking i…
Nonthrombogenic, Biodegradable Elastomeric Polyurethanes with Variable Sulfobetaine Content
2014
For applications where degradable polymers are likely to have extended blood contact, it is often important for these materials to exhibit high levels of thromboresistance. This can be achieved with surface modification approaches, but such modifications may be transient with degradation. Alternatively, polymer design can be altered such that the bulk polymer is thromboresistant and this is maintained with degradation. Toward this end a series of biodegradable, elastic polyurethanes (PESBUUs) containing different zwitterionic sulfobetaine (SB) content were synthesized from a polycaprolactone-diol (PCL-diol):SB-diol mixture (100:0, 75:25, 50:50, 25:75 and 0:100) reacted with diisocyanatobuta…
Synthesis and characterization of redox-sensitive polyurethanes based on L-glutathione oxidized and poly(ether ester) triblock copolymers
2021
Abstract Segmented polyurethanes, based on PCL-PEG-PCL copolymers, 1,4-diisocyanatobutane and l -glutathione oxidized, used as chain extender, were synthetized. Three different reactions conditions were investigated using three different copolymers having ɛ-CL/polyethylene glycol molar ratios equal to 12, 24 and 36 and three different reaction conditions. As investigated by size exclusion chromatography analyses and quantification of l -glutathione, the polymerization and the extension phase's efficiency depended on the ɛ-CL/PEG ratio and the extension phase's operating temperature. Three selected polyurethanes were characterized by spectroscopic, differential scanning calorimetry (DSC) and…
From single fiber to macro-level mechanics: A structural finite-element model for elastomeric fibrous biomaterials
2014
In the present work, we demonstrate that the mesoscopic in-plane mechanical behavior of membrane elastomeric scaffolds can be simulated by replication of actual quantified fibrous geometries. Elastomeric electrospun polyurethane (ES-PEUU) scaffolds, with and without particulate inclusions, were utilized. Simulations were developed from experimentally-derived fiber network geometries, based on a range of scaffold isotropic and anisotropic behaviors. These were chosen to evaluate the effects on macro-mechanics based on measurable geometric parameters such as fiber intersections, connectivity, orientation, and diameter. Simulations were conducted with only the fiber material model parameters a…
Characterization of the complete fiber network topology of planar fibrous tissues and scaffolds
2010
Understanding how engineered tissue scaffold architecture affects cell morphology, metabolism, phenotypic expression, as well as predicting material mechanical behavior has recently received increased attention. In the present study, an image-based analysis approach that provides an automated tool to characterize engineered tissue fiber network topology is presented. Micro-architectural features that fully defined fiber network topology were detected and quantified, which include fiber orientation, connectivity, intersection spatial density, and diameter. Algorithm performance was tested using scanning electron microscopy (SEM) images of electrospun poly(ester urethane)urea (ES-PEUU) scaffo…
Development of stimulus-sensitive electrospun membranes based on novel biodegradable segmented polyurethane as triggered delivery system for doxorubi…
2022
In this work, redox-sensitive polyurethane urea (PUU) based electrospun membranes have been exploited to chemically tether a pH-sensitive doxorubicin derivative achieved by linking a lipoyl hydrazide to the drug via a hydrazone linkage. First, the lipoyl-hydrazone-doxorubicin derivative labelled as LA-Hy-Doxo has been syn- thesized and characterized. Then, the molecule has been tethered, via a thiol-disulfide exchange reaction, to the redox-sensitive PUU (PolyCEGS) electrospun membrane. The redox-sensitive PolyCEGS PUU has been produced by using PCL-PEG-PCL polyol and glutathione-tetramethyl ester (GSSG-OMe)4 as a chain extender. The LA-Hy- Doxo tethered electrospun membrane has showed a du…
Use of new hydroxytelechelic cis-1,4-polyisoprene (HTPI) in the synthesis of polyurethanes (PUs): Influence of isocyanate and chain extender naturean…
2006
AbstractNew segmented polyurethanes (thermoplastic-elastomers) based on previously described hydroxytelechelic cis-1,4-polyisoprene (HTPI), miscellaneous isocyanates and chain extenders at various equivalent ratios were prepared by the classical one-shot method. The influence of the nature of isocyanate and chain extender, as well as their equivalent ratios, on the mechanical and thermal materials behavior was investigated. Thus, a comparative assessment of material properties was performed. Microphase separation of hard and soft segments was observed by DMTA, DSC and AFM. Moreover, according to Thermogravimetric Analysis (TGA), linear relationships depending on the isocyanate and chain ext…
Cell adhesion on UV-crosslinked polyurethane gels with adjustable mechanical strength and thermoresponsiveness
2021
Temperature-responsive polyurethane (PU) hydrogels represent a versatile material platform for modern tissue engineering and biomedical applications. However, besides intrinsic advantages such as high mechanical strength and a hydrolysable backbone composition, plain PU materials are generally lacking bio-adhesive properties. To overcome this shortcoming, the authors focus on the synthesis of thermoresponsive PU hydrogels with variable mechanical and cell adhesive properties obtained from linear precursor PUs based on poly(ethylene glycol)s (pEG) with different molar masses, isophorone diisocyanate, and a dimerizable dimethylmaleimide (DMMI)-diol. The cloud point temperatures of the dilute,…