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At least 397 records · Page 22Linked to original sources

PubMed1984

Albumin coating of a knitted polyester arterial prosthesis: an alternative to preclotting.

Coating a knitted polyester arterial prosthesis with cross-linked albumin fills the interstices of the graft and relieves the surgeon of the necessity to preclot . This is of particular value in patients whose blood clotting properties are hypercoagulable, or hypocoagulable . In addition, such prostheses require less handling, which can lower the risk of bacteremic colonization and shorten the operative time. The in vivo behavior of the implanted albuminated prosthesis in the thoracic aorta of dogs is similar to that of preclotted grafts, although the sequences of early healing are different. The preclotted graft develops a continuous, thick thrombotic matrix on its luminal surface during the first 4 hours of implantation. Following the initiation of the fibrinolytic mechanism 24 to 48 hours postoperatively, this thrombotic deposit quickly recedes , leaving blood cells and platelets adhering here and there to the prosthetic surface. In comparison, the albuminated coating is not associated with major early thrombotic deposits. The albumin remains visible between the filaments during the first 2 weeks of implantation. Both treated and control grafts contain numerous thrombi on their inner surface after 1 to 2 weeks. After 1, 3, and 6 months, both implants are well encapsulated and present a glistening and continuous luminal surface. This excellent healing, however, can be compromised should the graft adhere too closely to the animal's lungs.+2

Albumins↗

PubMed2001

Membrane perturbing properties of sucrose polyesters.

Sucrose polyester (SPE), in the form of sucrose octaesters and sucrose hexaesters of palmitic (16:0), stearic (18:0), oleic (18:1cis), and linoleic (18:2cis) acids, have many uses. Applications include: a non-caloric fat substitute, detoxification agent, and oral contrast agent for human abdominal (MRI) magnetic resonance imaging. However, it has been shown that the ingestion of SPE was shown to generate a depletion of physiologically important lipidic vitamins and other lipophilic molecules. In order to better understand, at the molecular level, the type of interaction between SPE and lipid membrane, we have, first synthesized different type of labelled and non-labelled SPEs. Secondly, we have studied the effect of SPEs on multilamellar dispersions of dielaidoylphosphatidylethanolamine (DEPE) and dipalmitoylphosphocholine (DPPC) as a function of temperature, SPE composition and concentration. The effects of SPEs were studied by differential scanning calorimetry (DSC), X-ray diffraction, 2H and 31P NMR spectroscopy. At low concentration (< 1 mol%) all of the SPEs lowered the bilayer to the inverted hexagonal phase transition temperature of DEPE and induced the formation of a cubic phase in a composition dependent manner. At the same low concentration, SPEs in DPPC induce the formation of a non-bilayer phase as seen by 31P NMR. Order parameter measurements of DPPC-d62/SPE mixtures show that the SPE effect on the DPPC monolayer thickness is dependent on the SPE, concentration, chains length and saturation level. At higher concentration (> or = 10 mol%) SPE are very potent DEPE bilayer to HII phase transition promoters, although at that concentration the SPE have lost the ability to form cubic phases. SPEs have profound effects on the phase behaviour of model membrane systems, and may be important to consider when developing current and potential industrial and medical applications.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed2002

Flow injection spectrophotometric determination of adrenaline in pharmaceutical formulations using a solid-phase reactor containing lead(IV) dioxide immobilized in a polyester resin.

A flow injection spectrophotometric procedure is proposed for determining adrenaline in pharmaceutical formulations. In this work, the adrenaline in acetate buffer reacts with a solid-phase reactor containing lead(IV) dioxide immobilized in a polyester resin and the adrenochrome yielded was continuously monitored at 486 nm. The analytical curve was linear in the adrenaline concentration range from 0.1 to 0.8 mmol l(-1) with a detection limit of 8 x 10(-3) mmol l(-1). Recoveries of 96.5-105% and relative standard deviation of 0.2% for a solution containing 0.4 mmol l(-1) adrenaline (n = 10) were obtained. The analytical frequency was 130 determinations per hour and the results obtained for adrenaline in pharmaceutical formulations using this procedure and those obtained using a pharmacopoeia procedure are in agreement at the 95% confidence level.

Adrenochrome↗

PubMed1999

Replacement of the proximal aorta and aortic valve using a composite bileaflet prosthesis and gelatin-impregnated polyester graft (Carbo-Seal): early results in 143 patients.

OBJECTIVE: We report the combined early results from two centers in the United Kingdom using a composite conduit consisting of a bileaflet mechanical valve incorporated into a gelatin-impregnated, ultra-low porosity, woven polyester graft (Carbo-Seal; Sulzer Carbomedics, Inc, Austin, Tex). METHODS: Between August 1992 and March 1997, 143 patients underwent aortic root replacement with the Carbo-Seal composite prosthesis. The indication for surgery was acute type A dissection in 31 (22%), chronic type A dissection in 9 (6%), ascending aortic aneurysm without dissection in 100 (70%), and false aneurysm of the ascending aorta in 3 (2%). Twenty-seven patients (19%) had undergone previous sternotomy, and 40 (28%) were seen as emergencies. Concomitant procedures were performed in 38 (27%), including 18 aortic arch or hemiarch replacements. Total follow-up is 270 patient-years. Follow-up is 100% complete. RESULTS: The early (30-day) mortality was 7% (10 patients). Permanent neurologic events occurred in 2%. At a mean follow-up of 23 months, 94% of survivors were in New York Heart Association functional class I. Freedom from reoperation was 97.2% +/- 1.6% (1 standard error [1 SE]) at 12 months and 95.7% +/- 2.2% at 48 months. Including early mortality, survival was 90.1% +/- 2.6% at 12 months and 83.1% +/- 3. 5% at 48 months. CONCLUSIONS: Aortic root replacement with use of the Carbo-Seal prosthesis can be undertaken with a relatively low early mortality and morbidity. A low reoperation rate and high intermediate-term survival can be expected, but continued follow-up is needed to determine the long-term efficacy of this prosthesis.

Aged↗

PubMedDate not supplied

Lipase-catalyzed ring-opening polymerization of lactones to polyesters and its mechanistic aspects.

Lipase catalysis induced a ring-opening polymerization of lactones with different ring-sizes. Small-size (four-membered) and medium-size lactones (six- and seven-membered) as well as macrolides (12-, 13-, 16-, and 17-membered) were subjected to lipase-catalyzed polymerization. The polymerization behaviors depended primarily on the lipase origin and the monomer structure. The macrolides showing much lower anionic polymerizability were enzymatically polymerized faster than epsilon-caprolactone. The granular immobilized lipase derived from Candida antartica showed extremely efficient catalysis in the polymerization of epsilon-caprolactone. Single-step terminal functionalization of the polyester was achieved by initiator and terminator methods. The enzymatic polymerizability of lactones was quantitatively evaluated by Michaelis-Menten kinetics.

Candida↗

PubMed2002

Biomodification of non-woven polyester fabrics by insulin and RGD for use in serum-free cultivation of tissue cells.

In this study, the development of a novel cell support material was purposed as due to the serum-free cultivation of tissue cells. This material was prepared by immobilizing RGD (Arg-Gly-Asp) sequence of cell-adhesion factor, fibronectin, and cell-growth factor, insulin, to the three-dimensional non-woven polyester fabric (briefly NWPF) discs that have been used successfully in our previous cell culture studies. At first these matrices were partially hydrolyzed and then the carboxyl groups were coupled with RGD or insulin in the presence of water-soluble carbodiimide. The effectiveness of immobilization process was checked with SEM, ATR-FTIR spectroscopy and swelling studies. The maximum amount of immobilized insulin was 6.96 micorgcm(-2) and it was obtained at 200 micorgml(-1) initial insulin concentration for 60 min immobilization period. The cell culture studies which were carried out with human skin fibroblasts (HS An1) showed that, percentage of adhesion on RGD modified NWPF discs is higher than that of other surfaces. i.e., unmodified discs, polystyrene Petri dishes and insulin-immobilized discs, in serum-free culture. According to the results of growth studies, highest cell yield was obtained in the case of insulin-modified discs.

Biocompatible Materials↗

PubMed2003

Biocompatibility and healing process of polyester meshes in the brain: in vivo examination in rats.

OBJECTIVES: To analyze the biocompatibility of multifilament polyester (PET) meshes used for the implantation of auditory brainstem implants in a standardized Wistar rat model (n=29). METHODS: The physical properties of the meshes were examined during surgery. Using a modified plastic embedding, the local tissue reaction and the stability of mesh position in the region of the fourth ventricle were evaluated in section series from day 3 to 64. The cellular reaction was further differentiated using transmission and scanning electron microscopy. RESULTS: PET meshes were stable for handling. However, sharp edges inevitably led to brainstem and cerebellar penetration in some cases. The meshes were preserved in situ in all section series. Positioning was stable with one exception. A sufficient fibroblast and collagen fiber encasement was reached after 14 days. In all cases, no further change was observed through day 64. The host-defense reaction was persistent and characterized by numerous macrophages and foreign-body giant cells. Bacterial infection occurred in three cases. CONCLUSIONS: PET meshes proved to have an acceptable biocompatibility regarding local-tissue reaction in the brain. Modified polymer structures should be developed to reduce risk of injury. Anti-inflammatory surface treatments and monofilament meshes could reduce the infection rate.

Animals↗

PubMed2002

Optimization of glycol methacrylate embedding of large specimens in neurological research. Study of rat skull-brain specimens after implantation of polyester meshes.

Advances in neuroscience require better anatomical knowledge of neuronal architecture and structural details. Optimal embedding techniques are the basis for precise morphometric studies in section series as well as for the evaluation of tissue specimens or implants of differing hardness. There are very few methods for preparing large specimens by resin embedding, although resins such as polyethylene glycol (PEG) and methyl methacrylate (MMA) are presently in use. However, these methods have proven to be laborious and sometimes unsatisfactory for serial sectioning. While glycol methacrylate embedding (GMA) is suitable for smaller specimens, it results in inadequate infiltration and polymerization in blocks larger than 1 x 1 x 0.2 cm. We present an improved technique using GMA, which permits both standardized embedding of 4 x 2 x 2 cm blocks and preparation of section series. This method was developed for preserving skull-brain specimens from rats with polyester-mesh implants. The excellent preservation of cellular details allowed the assessment of local tissue reaction to foreign-body material in situ. Advantages of this method are: (1) No toxic catalysts or solvents are used (as opposed to MMA and current GMA processes); (2) Laborious routines in stretching and mounting of sections are not necessary (in contrast to PEG and MMA); (3) No deplastination is required before staining (in contrast to PEG and MMA); (4) Excellent morphologic preservation of various tissue is achieved.

Animals↗

PubMed1997

In vitro evaluation of a novel bioreactor based on an integral oxygenator and a spirally wound nonwoven polyester matrix for hepatocyte culture as small aggregates.

BACKGROUND/AIMS: The development of custom-made bioreactors for use as a bioartificial liver (BAL) is considered to be one of the last challenges on the road to successful temporary extracorporeal liver support therapy. We devised a novel bioreactor (patent pending) which allows individual perfusion of high density cultured hepatocytes with low diffusional gradients, thereby more closely resembling the conditions in the intact liver lobuli. METHODS: The bioreactor consists of a spirally wound nonwoven polyester matrix, i.e. a sheet-shaped, three-dimensional framework for hepatocyte immobilization and aggregation, and of integrated hydrophobic hollow-fiber membranes for decentralized oxygen supply and CO2 removal. Medium (plasma in vivo) was perfused through the extrafiber space and therefore in direct hepatocyte contact. Various parameters were assessed over a period of 4 days including galactose elimination, urea synthesis, lidocaine elimination, lactate/pyruvate ratios, amino acid metabolism, pH, the last day being reserved exclusively for determination of protein secretion. RESULTS: Microscopic examination of the hepatocytes revealed cytoarchitectural characteristics as found in vivo. The biochemical performance of the bioreactor remained stable over the investigated period. The urea synthesizing capacity of hepatocytes in the bioreactor was twice that of hepatocytes in monolayer cultures. Flow sensitive magnetic resonance imaging (MRI) revealed that the bioreactor construction ensured medium flow through all parts of the device irrespective of its size. CONCLUSIONS: The novel bioreactor showed encouraging efficiency. The device is easy to manufacture with scale-up to the liver mass required for possible short-term support of patients in hepatic failure.

Amino Acids↗

PubMed2002

Polyether-polyester diblock copolymers for the preparation of paclitaxel loaded polymeric micelle formulations.

A number of hypersensitivity reactions have been attributed to the presence of Cremophor((R)) EL in the current formulation for paclitaxel. This has led to the development of formulations for paclitaxel employing polyether-polyester diblock copolymers as micelle forming carriers. Diblock copolymers of methoxypolyethylene glycol-block-poly(D,L-lactide) (MePEG:PDLLA) were synthesized from monomers of D,L-lactide and MePEG by a ring opening bulk polymerization in the presence of stannous octoate. Up to 25% paclitaxel could be loaded into matrices of MePEG:PDLLA (60:40, MePEG molecular weight of 2000) using the solution casting method. Dissolution of paclitaxel/copolymer matrices in aqueous media resulted in complete solubilization of paclitaxel within the hydrophobic PDLLA core of the micelles. This review article describes the synthetic reaction conditions influencing the degree of conversion of monomer to copolymer, thermal properties, critical micelle concentrations of copolymers, methods of incorporation of paclitaxel into copolymer matrices and subsequent constitution in aqueous media and biological evaluations of micellar paclitaxel.

Animals↗

PubMed2003

Polyesters based on diacid monomers.

Polymers with ester linkages in their main chain comprise a family of polymers with immense diversity and versatility. This review deals with the preparation of such polymers from dicarboxylic acid monomers, and the result in terms of properties and applicability. Polyesters alone, and their copolymers with amides, anhydrides, urethanes, imides, ethers or other functional groups, offer countless opportunities to tune the properties of the resulting material within a broad range. Of particular interest is the inherent biodegradability of the ester linkage. Biodegradability is sought after in a wide range of applications, above all in the preparation of environmentally friendly polymers and biomedical materials for temporary surgical use and in drug delivery.

Animals↗

PubMedDate not supplied

Subchronic inhalation toxicity study of a water-dispersible polyester in rats.

AQ55 is a high molecular weight, water-dispersible, amorphous polyester used in applications where the exclusion of solvents and conventional surfactants is desirable, such as water-based adhesives, coatings, emulsions, paint primers, cosmetics and detergents. Potential health effects were evaluated in rats exposed by inhalation for about 13 wk to mean concentrations of 0, 2.4, 19.6 or 199 mg/m3 AQ55 polymer. No mortality occurred and body weights were unaffected. Mean relative liver weights in all treated male groups were slightly higher than control weights, but were not judged to be treatment related. Absolute liver weights and all other organ weights except lung weights were normal. Haematology, clinical chemistries and gross pathology were unremarkable. Exposure-related changes in the 199 mg/m3 groups included increased mean absolute and relative lung weights, accumulations of macrophages and acute inflammatory cells in alveolar and bronchial lumina, and increased numbers of macrophages in sinusoids of peribronchial lymph nodes. Minor accumulation of macrophages in alveolar lumina was the only exposure-related change in the 19.6 mg/m3 group. No exposure-related effects were seen in the 2.4 mg/m3 group. AQ55 produced no systemic toxicity, and aerosols of AQ55 do not appear to be toxic to pulmonary tissues following subchronic inhalation exposure.

Administration, Inhalation↗

PubMed1987

[Complement activation in extracorporeal circulation. Comparison of nylon versus polyester bubble oxygenators].

Complement activation during cardiopulmonary bypass is well known and may influence postoperative morbidity. As nylon can particularly induce complement activation, its influence was assessed by measuring total haemolytic complement and B, C3 and C4 factors, during cardiopulmonary bypass with bubble oxygenators for coronary surgery, comparing "nylon" circuits (20 patients, Bentley BOS 10) versus "polyester" circuits (19 patients, Shiley S 100 A). Complement activation began with induction of anaesthesia and surgical procedures, B, C3 and C4 levels falling significantly (respectively 15, 17 and 20% from baseline values). The alternative pathway was activated before the classical pathway. Complement activation continued during cardiopulmonary bypass, with no more consumption of complement factors (slight variations of about 0 to 3% of the levels found after anaesthetic induction and surgical procedures). No statistically significant difference appeared between the two groups. This suggested that nylon did not significantly increase complement activation during cardiopulmonary bypass. The bubble oxygenator material cannot therefore be considered as a criterion for choosing the type of equipment.

Complement Activation↗

PubMed1986

Short-term in vivo stability of endothelial-lined polyester elastomer and polytetrafluoroethylene grafts.

A fibronectin substrate will significantly enhance the strength of endothelial cell attachment on grafts constructed of polyester elastomer (PE) and polytetrafluoroethylene (e-PTFE). This experiment was undertaken to determine the short-term in vivo stability of endothelium on these fibronectin coated surfaces. Eight mongrel dogs underwent bilateral carotid artery replacement with both graft materials. All grafts were inoculated with 2,000 cells/mm2 using cultured autogenous venous endothelium labelled with Indium-111-oxine. The Indium-111 label in the grafts was measured immediately prior to implantation, after 1 hour of in vivo perfusion, and at explantation after 24 hours. The percentage of inoculated cells attached to the grafts before perfusion was similar for both materials, 93.3 +/- 3.0% versus 92.2 +/- 7.2%, for PE and e-PTFE respectively. All grafts were patent at one hour after implantation. PE grafts were found to have 93.8 +/- 3.9% of the attached cells present at one hour while e-PTFE grafts had only 54.5 +/- 10.8% remaining, p less than .001. After 24 hours, 5/8 (62.5%) e-PTFE grafts and 2/8 (25.0%) PE grafts remained patent, p = .13. Of the patent grafts however, endothelial cell retention was still superior on the PE grafts with 78.0 +/- 0.6% of the attached cells remaining compared to only 24.5 +/- 6.1% on e-PTFE, p less than .001. Occluded PE grafts had fewer cells remaining at 24 hours than patent ones, 78.0 +/- 0.6% versus 31.1 +/- 32.8%, respectively, p = .13. Histologically, patent PE grafts demonstrated nearly confluent endothelial monolayers while e-PTFE had patches of endothelial cells surrounded by a platelet-fibrin carpet.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2002

Spray-dried indomethacin-loaded polyester nanocapsules and nanospheres: development, stability evaluation and nanostructure models.

The industrial development of polymeric nanoparticle suspensions, as drug delivery systems, is limited due to the problems in maintaining stability of suspensions. In this work, a spray-drying technique was applied to dry nanocapsule and nanosphere suspensions prepared by nanoprecipitation of polyesters using SiO(2) as adjuvant. Powders obtained from nanocapsules presented stable drug recoveries and morphological characteristics after 5 months. For nanocapsules, nanostructures around 200 nm were observed by scanning electron microscopy (SEM) on the surface of microparticles of SiO(2), whereas for the nanosphere formulation, nanostructures with a reduced diameter (60-90 nm) were observed, despite the particle sizes of each original suspension being similar, when measured by photon correlation spectroscopy (PCS). In order to investigate the morphological aspects of nanocapsule and nanosphere powders, several nanosphere formulations were spray-dried using different concentrations of SiO(2) and a comparative study of the different colloidal systems (nanocapsules, nanospheres, nanoemulsion or nanodispersion) was carried out by PCS. SEM analyses showed that nanostructures with reduced diameter are formed independently of the adjuvant concentration. The dynamic properties of these systems allowed to suggest that the structure of the nanosphere particle (polymer, sorbitan monostearate and polysorbate 80) was a polymeric matrix dispersing the sorbitan monostearate which, when submitted to the spray-drying process in the presence of SiO(2), gave nanostructures presenting diameters around 80 nm covering the microparticles due to the release of lipophilic surfactant from the polymeric matrix.

Capsules↗

PubMed2000

Scanning electron microscopy and X-ray diffraction studies in the analysis of medical materials: Gore-Tex versus braided polyester tape for repair of the incompetent cervix.

Cathodoluminescence in the scanning electron microscope and roentgenogram diffraction studies were applied to the analysis of two different medical materials used in cervical cerclage, the treatment of cervical incompetence. Braided polyester tape or Gore-Tex was used as suture material and was analyzed both before and after use in cerclage of the cervix. Results of SEM and X-ray diffraction studies showed distinct differences between the two materials, with the Gore-Tex demonstrating a superior morphological integrity and a decreased likelihood of phagocyte adhesion. These results correlated well with the clinical observations, which also showed Gore-Tex to be a superior medical material.

Female↗

PubMed2004

Rapid prototyping of thermoset polyester microfluidic devices.

This paper presents a simple procedure for the fabrication of thermoset polyester (TPE) microfluidic systems and discusses the properties of the final devices. TPE chips are fabricated in less than 3 h by casting TPE resin directly on a lithographically patterned (SU-8) silicon master. Thorough curing of the devices is obtained through the combined use of ultraviolet light and heat, as both an ultraviolet and a thermal initiator are employed in the resin mixture. Features on the order of micrometers and greater are routinely reproduced using the presented procedure, including complex designs and multilayer features. The surface of TPE was characterized using contact angle measurements and X-ray photoelectron spectroscopy (XPS). Following oxygen plasma treatment, the hydrophilicity of the surface of TPE increases (determined by contact angle measurements) and the proportion of oxygen-containing functional groups also increases (determined by XPS), which indicates a correlated increase in the charge density on the surface. Native TPE microchannels support electroosmotic flow (EOF) toward the cathode, with an average electroosmotic mobility of 1.3 x 10(-4) cm(2) V(-1) s(-1) for a 50-microm square channel (20 mM borate at pH 9); following plasma treatment (5 min at 30 W and 0.3 mbar), EOF is enhanced by a factor of 2. This enhancement of the EOF from plasma treatment is stable for days, with no significant decrease noted during the 5-day period that we monitored. Using plasma-treated TPE microchannels, we demonstrate the separation of a mixture of fluorescein-tagged amino acids (glycine, glutamic acid, aspartic acid). TPE devices are up to 90% transparent (for approximately 2-mm-thick sample) to visible light (400-800 nm). The compatibility of TPE with a wide range of solvents was tested over a 24-h period, and the material performed well with acids, bases, alcohols, cyclohexane, n-heptane, and toluene but not with chlorinated solvents (dichloromethane, chloroform).

Microfluidic Analytical Techniques↗

PubMedDate not supplied

Polyester dendritic systems for drug delivery applications: in vitro and in vivo evaluation.

High molecular weight polymers (> 20 000 Da) have been widely used as soluble drug carriers to improve drug targeting and therapeutic efficacy. Dendritic polymers are exceptional candidates for the preparation of near monodisperse drug carriers due to their well-defined structure, multivalency, and flexibility for tailored functionalization. We evaluated various dendritic architectures composed of a polyester dendritic scaffold based on the monomer unit 2,2-bis(hydroxymethyl)propanoic acid for their suitability as drug carriers both in vitro and in vivo. These systems are both water soluble and nontoxic. In addition, the potent anticancer drug, doxorubicin, was covalently bound via a hydrazone linkage to a high molecular weight 3-arm poly(ethylene oxide)-dendrimer hybrid. Drug release was a function of pH, and the release rate was more rapid at pH < 6. The cytotoxicity of the DOX-polymer conjugate measured on multiple cancer lines in vitro was reduced but not eliminated, indicating that some active doxorubicin was released from the drug polymer conjugate under physiological conditions. Furthermore, biodistribution experiments show little accumulation of the DOX-polymer conjugate in vital organs, and the serum half-life of doxorubicin attached to an appropriate high molecular weight polymer has been significantly increased when compared to the free drug. Thus, this new macromolecular system exhibits promising characteristics for the development of new polymeric drug carriers.

Animals↗