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PubMedDate not supplied

Endovascular packing of carotid bifurcation aneurysm with polyester fiber-coated platinum coils in a rabbit model.

PURPOSE: To assess the value of endovascular packing of intracranial bifurcation aneurysms with commercially available coils. METHODS: Carotid bifurcation aneurysms were surgically created in 12 New Zealand rabbits with subsequent assessment of the extent of aneurysm ablation following endovascular packing with polyester fiber-coated platinum coils. RESULTS: Follow-up angiograms obtained from 29 to 108 days postprocedures showed various degrees of aneurysm ablation. Complete obliteration of aneurysm dome occurred in seven out of eight rabbits, while ablation of aneurysm neck was successful in only one out of eight. No spontaneous thrombosis was observed in seven control animals over a 3-month period. Coils of various configurations used in this experiment all maintained stable intraaneurysmal position. Histologic examination of treated aneurysms consistently demonstrated extensive proliferation of spindle cells on the coil surface and in interstices between coils with channels lined by cells resembling endothelial cells. Organized thrombus was not a prominent feature. CONCLUSION: Endovascular packing of human bifurcation aneurysms with current commercially available polyester fiber-coated platinum coils may not result in complete obliteration of the aneurysm with reendothelialization occurring across the aneurysm neck.

Animals↗

PubMed1996

Albumin as a sealant for a polyester vascular prosthesis: its impact on the healing sequence in humans.

OBJECTIVE: Although the healing characteristics of albumin impregnated vascular prostheses have been extensively studied in animal models, they have never been studied in humans. We therefore examined the healing sequence and the albumin degradation rate of this type of prosthesis harvested from humans. We also addressed the possible relationship between the implantation of cross-linked albumin and a specific inflammatory reaction. METHODS: Thirty albumin-impregnated polyester vascular prostheses were collected in our institution from January 1991 to February 1993. The mean duration of implantation of the prostheses was 8.4+/-9.7 (SD) months (range: 1 hour to 26 months). Twenty two prostheses were patent at the time of explantation and 4 had been thrombosed for less than 24 hours. In 18 cases, the prostheses were surgically removed because of a complication or a reoperation, and during an autopsy in 12 cases. Each harvested specimen was submitted to histological and immunohistochemical studies in order to demonstrate the presence of human albumin sealant, and to determine the inflammatory cell constituents. RESULTS: The albumin-impregnated prostheses were poorly infiltrated by healing tissues after 2 years of implantation. An external capsule was constantly observed after 2 months of implantation with a nonspecific chronic inflammatory reaction localized between the capsule and the polyester yarns. We observed large amounts of albumin sealant after 2 months, a gradual degradation with time, and traces after 2 years of implantation in humans. The luminal surface of the explant was mainly covered with organized fibrin. No histological signs of a specific inflammatory reaction were observed. CONCLUSIONS: The healing of the albumin impregnated prosthesis was poor and the degradation rate of the albumin sealant was significantly delayed, when compared to animal models. This difference in degradation rate could be related to interspecies differences of phagocytic cells enzymatic machinery. Finally, implantation of glutaraldehyde cross-linked albumin in humans is safe, since we observed an aspecific chronic foreign body inflammatory reaction.

Aged↗

PubMed1997

Endogenic non-enzymatic antioxidative system of polyester grafts during their healing.

OBJECTIVE: Non-enzymatic low-molecular antioxidants are one of the important mechanisms which protect cells against the toxic effect of oxygen. The aim of the present study was to determine the content of glutathione, glutathione reductase, and ascorbic acid in the principal layers of polyester grafts. INTERVENTIONS AND MEASURES: The experiments were carried out on 24 mongrel dogs, in which polyester double velour DALLON grafts were implanted. Seven days, 1, 4, and 12 months after the operation the grafts were excised. The following were determined: glutathione content by use of a GSH-400 system, glutathione reductase activity by the method of Langdon and Mize, and ascorbic acid content by the Kyaw method. RESULTS: It was found that the glutathione content in the graft neointima was 33% lower, in the graft neomedia higher during the first 4 months, in the neoadventitia 50% lower after 4 months than in the corresponding layers of the aorta (p < 0.01). The activity of glutathione reductase was significantly higher in all the graft layers during 12 months' observation than in the normal aorta layers. The ascorbic acid content of the graft layers was lowest 7 days after the implantation, and then in time increased so that 12 months after the operation it reaches its highest values. CONCLUSIONS: Our study shows that low non-enzymatic antioxidative potential is not capable of proteoting the newly forming graft layers, particularly the neointima, against oxygen toxicity. Thus, it would be beneficial to administer antioxidants (vitamin C, vitamin E, and N-acetylcysteine).

Animals↗

PubMed1999

Chiral compounds from bacterial polyesters: sugars to plastics to fine chemicals.

A novel and efficient method for the production of enantiomerically pure (R)-(-)-hydroxycarboxylic acids by in vivo depolymerization of microbial polyester polyhydroxyalkanoates (PHAs) was developed. Using this method, several model compounds, (R)-(-)-3-hydroxyalkanoic acids, consisting of 4 to 12 carbon atoms, and (R)-(-)-3-hydroxy-5-phenylvaleric acid, could be prepared. In particular, (R)-(-)-3-hydroxybutyric acid could be efficiently prepared by this method. By providing the environmental condition in which cells possess high activity of intracellular PHA depolymerase and low activity of (R)-(-)-3-hydroxybutyric acid dehydrogenase, (R)-(-)-3-hydroxybutyric acid could be produced with a yield of 96% in only 30 min by in vivo depolymerization of polyhydroxybutyrate (PHB) accumulated in Alcaligenes latus.

Bacteria↗

PubMed1996

In vivo characterization of a fluoropassivated gelatin-impregnated polyester mesh for hernia repair.

The present study was undertaken to evaluate a new prototype mesh that consists of a knitted polyester structure treated with a fluoropolymer and impregnated with gelatin. The Fluoropassiv mesh, as well as two controls, the Surgipro polypropylene mesh and the Gore-Tex expanded polytetrafluoroethylene patch, were used for the repair of experimentally induced abdominal hernias in piglets and followed for scheduled implantation periods of 4, 15, and 60 days. At the sacrifice the mesh and surrounding tissue were excised for histological assessment of the healing sequence, for the identification of changes in hematologic and immunological characteristics, and for the measurement of the mechanical properties. After cleaning to remove the encroaching tissue, the explanted devices were monitored for biostability by infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The present study has demonstrated that the Fluoropassiv mesh provides adequate mechanical strength and compares favorably with the two controls. No exacerbated systemic or in situ hematologic or immunological reactions were observed with either the meshes of the patch material. Histological studies revealed that thick collagenous and vascularized tissue were well anchored to the three biomaterials as early as 15 days after implantation. The degree of tissue penetration differed depending on the device. Chemically, they proved stable over time.

Abdominal Muscles↗

PubMed1997

Development and characterization of an alginate-impregnated polyester vascular graft.

Alignate gels are known to be biocompatible, degradable, and nontoxic. In this study, sodium alginate was impregnated into a porous, knitted polyester graft (Microvel double velour graft) 6 mm in diameter. The alginate-impregnated graft was investigated in vitro and in vivo to evaluate its potential for use as a new vascular graft impervious to blood, while retaining high porosity for tissue ingrowth and biological healing. For in vitro investigation, the coating weight, water permeability, morphology, and mechanical properties of the alginate-impregnated grafts were compared to those of control or commercially available collagen-impregnated (Hemashield) grafts. The water permeability of the controls (1846 mL/min.cm2 at 120 mm Hg) was reduced > 99% by the alginate impregnation, rendering the graft impervious to blood. The coating weight of the alginate was 45 mg/g of graft, producing a much lower value than that of the collagen-impregnated model (310 mg/g). For in vivo investigation, the alginate-impregnated grafts were implanted in the aorta of mongrel dogs without preclotting for scheduled periods ranging from 4 h to 6 months. The control grafts after preclotting and the collagen-impregnated grafts without preclotting were also implanted for 3 and 6 months for comparison. Gross observation of the explanted grafts and histologic examination of the representative sections were conducted for three types of grafts using a light microscope after hematoxylin-eosin staining. No significant differences were observed between the histologic appearance of the alginate-impregnated grafts and that of the preclotted and collagen-impregnated grafts in terms of the degree of inflammation, foreign-body giant cell reaction, and intimal fibrosis. Endothelial-like cells were present on the midsections of all the grafts after 3 months of implantation. The resorption rate of alginate impregnated into the graft was also examined after staining the sections with periodic acid-Schiff reagent, Toluidine blue, and Alcian blue, which are specific for alginates. The staining alginate was partially visible between the graft fabrics up to 1 month after implantation, but was completely resorbed after 3 months. This preliminary study demonstrated that the use of an alginate as a biological sealant instead of proteins such as collagen, gelatin, and albumin may be a feasible approach to developing imprevious textile arterial prostheses, since the proteins have been reported to be generally unstable, hard to obtain in pure forms, not easy to crosslink and control resorption rate, and difficult to render compatible with standard storage and sterilization procedures.

Alginates↗

PubMed1999

Hydrolytic degradation characteristics of aliphatic polyesters derived from lactic and glycolic acids.

During the past decade, important advances have been made in the understanding of the hydrolytic degradation characteristics of aliphatic polyesters derived from lactic acid (LA) and glycolic acid (GA). Degradation of large poly(LAGA) (PLAGA) polymers is autocatalyzed by carboxyl end groups initially present or generated upon ester bond cleavage. Faster internal degradation and degradation-induced morphological and compositional changes are three of the most important findings deduced from the behaviors of various PLAGA polymers. This review presents the state of the art in this domain. The research efforts are focused on detailing the degradation mechanism and the effects of various factors on the degradation of PLAGA polymers. An attempt is also made to elaborate a scheme that can be used to predict degradation characteristics of these polymers from their initial composition and morphology.

Biocompatible Materials↗

PubMed2001

Combinatorial array-based enzymatic polyester synthesis.

A combinatorial strategy for biocatalytic polymer synthesis is demonstrated. A library of polymers was synthesized in 96 deep-well plates using AA-BB polycondensations of acyl donors and acceptors. The library was based on four straight-chain diesters as acyl donors (C(3)-C(10)) with aliphatic/aromatic diols as well as more diverse structures including carbohydrates, nucleic acids, and a natural steroid diol used as acyl acceptors. The lipase from Candida antarctica was active in acetonitrile and was capable of catalyzing the polycondensation of the aforementioned monomers to polymers with M(w)'s reaching as high as 20,000 Da, including the preparation of novel sugar-containing polyesters. The combinatorial approach to biocatalytic polymer synthesis described herein serves as a foundation for polymeric materials discovery by demonstrating that polymer arrays can be produced from structurally complex monomers.

Catalysis↗

PubMed1988

Application of Neuhoff's optimized Coomassie brilliant blue G-250/ammonium sulfate/phosphoric acid protein staining to ultrathin polyacrylamide gels on polyester films.

An optimized Coomassie staining procedure, utilizing Coomassie Brilliant Blue G-250 in phosphoric acid/ammonium sulfate, was applied to ultrathin-layer isoelectric focusing in 0.18 mm polyacrylamide gels, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis in 0.38 mm polyacrylamide gels, both backed to Gel-Fix polyester supporting films. After isoelectric focusing staining of gelatin and acidic proteins was better with the phosphoric acid/ammonium sulfate procedure than with conventional organic solvent methods. When applied to gels after sodium dodecyl sulfate-polyacrylamide gel electrophoresis the sensitivity of the phosphoric acid/ammonium sulfate method was equal to that on conventional staining but lower than on silver staining.

Acrylic Resins↗

PubMed2002

Biostability of electrically conductive polyester fabrics: an in vitro study.

The biostability of a series of polypyrrole (PPy)-coated polyester fabrics was investigated in an in vitro model. PPy-coated sample fabrics were incubated in saline at 37 degrees C for 1 and 2 weeks. After each period of incubation, the surface electrical resistivity of the sample fabrics was measured to monitor the changes caused by the incubation. Redoping was then performed by immersing the sample fabrics in a 1N HCl solution at room temperature for 30 min, which was followed by another measurement of the surface resistivity. The surface morphology of the sample fabrics was observed by scanning electron microscopy. The surface chemical composition of the fabrics and the oxidation of nitrogen in PPy were measured with X-ray photoelectron spectroscopy. The surface electrical resistivity of the PPy-coated fabrics was found to increase with the progress of incubation, which was mainly caused by dedoping and uptake of oxygen. This increase was nonlinear and accelerated with time. The surface resistivity of most of the samples was retained in the range of 10(3)-10(4) Omega/square after 1 week of incubation, which was considered suitable for short-term electrical stimulation applications. Physical deterioration represented by the cracking and delamination of the PPy coating was occasionally observed on the sample fabrics showing the most significant increase of resistivity. Further improvement of the stability of conductivity is highly desirable.

Chlorides↗

PubMed2002

Tissue response to microfibers of different polymers: polyester, polyethylene, polylactic acid, and polyurethane.

Tissue response to single polymer microfibers of polyester (PET), polyethylene (PE), poly(L-lactic acid) (PLA), and polyurethane (PU) was assessed using a rat subcutaneous model. Fibers of diameters ranging from 1 to 15 microm were aligned parallel to each other on polycarbonate frames and implanted in the subcutaneous dorsum in the subscapular region. After 5 weeks of implantation, fibrous capsule thickness was significantly less for fibers of diameters 1-5 than for those of 11-15 microm for all polymers tested. For PET and PU, 75.0 and 71.4% respectively of the 1-5 microm fibers had no capsule, while for PE and PLA only 45.5 and 56.3% respectively had no capsule. For 1-5 microm fibers, PE had significantly thicker capsules than PET and PU. Reducing fiber diameters from 6-10 to 1-5 microm induced a greater reduction in capsule thickness than changing polymers among PET, PE, and PLA. PU showed the least encapsulation of all polymers, demonstrating significantly thinner capsules than PET, PE, and PLA for 6-10 and 11-15 microm fibers.

Animals↗

PubMed1983

Polyester prostheses as substitutes in the thoracic aorta of dogs. I. Evaluation of commercial prostheses.

Using canine models, a representative selection of polyester or Dacron vascular prostheses, including woven, knitted, and velour types, were evaluated for their relative healing characteristics and for their structural changes during implantation. Following residence periods ranging from 4 h to 6 months at the site of the thoracic aorta, the dogs were sacraficed, and the grafts were excized for measurement of the thrombogenicity of the flow surface and for pathological examination by light microscopy and SEM. The kidneys were also removed and examined for infarcts caused by any trapped circulating emboli. The extent of healing, the presence of embolizing nuclei, and the thrombogenicity and morphology of the lumen surface were also assessed. The healing characteristics of each type of device proved similar. Velour fabrics exhibited more extensive encapsulation, but frequently their internal capsules failed to incorporate all the fibers. In all cases, cellular development on the lumen was limited to areas contiguous to the anastomoses. The initial porosity of the devices as measured by water permeability did not appear to influence the healing sequence to a significant extent. The grafts did exhibit differences in structural stability depending on whether they were of a knitted or woven construction. We suggest that users consider these different mechanical and structural properties when making their choice of a graft. Despite these differences, we believe that the healing process is far more host dependent than graft dependent.

Angiography↗

PubMed1994

Biodegradation evaluation of polyether and polyester-urethanes with oxidative and hydrolytic enzymes.

Enzyme-induced liberation of components from seven different radiolabeled polyurethanes was monitored by radiolabel counting of the incubation solutions and product isolation by high performance liquid chromatography (HPLC). The polyurethanes were selected to reflect variations in the hard-segment chemistry, soft-segment chemistry, and polyurethane hydrophilicity resulting from combinations of hydrophobic/hydrophilic soft segments. All materials were characterized using electron spectroscopy for chemical analysis, differential scanning calorimetry, size exclusion chromatography, and Fourier transform infrared spectroscopy. The material surfaces were examined both before and after incubation with enzyme and control solutions using scanning electron microscopy. Biodegradation assays were carried out at 37 degrees C using cholesterol esterase (CE) and horseradish peroxidase (HRP) under optimal pH conditions for each enzyme. The hydrolytic enzyme (CE) was effective in releasing degradation products that contained hard-segment components from some of the polyurethanes. HPLC analysis of products for a polyesterurethane synthesized with toluene diisocyanate (TDI) suggested that the bulk of the incorporated radiolabeled TDI was still covalently bonded within the cleaved chain segments of the original polymer and was not released as pure toluene diamine (TDA). The data suggest that urethane linkages in the soft-segment domains of phase separated polyetherurea-urethanes may be more prone to cleavage by CE than are the urea/urethane groups in the hard-segment domains. This could be related to the nature of the hard-segment domain structures. The oxidative enzyme (HRP) was not able to induce liberation of radiolabeled segments from either the polyether or polyester-based polyurethanes.

Biocompatible Materials↗

PubMed2003

The preparation of monodisperse biodegradable polyester nanoparticles with a controlled size.

In local drug delivery, nanoparticles based on biodegradable polymers can function as vehicles with controlled drug-release properties. To achieve a well-controlled drug-release profile, control over the particle size is of great importance. Therefore, biodegradable polyester nanoparticles were prepared by the salting-out method. Process variables were varied to study the effect on the particle size. The monodisperse particles obtained were between 100 and 400 nm in size and spherical in shape. It was found that the particle size could be adjusted by varying the preparation conditions upon which the polymer concentration had the most pronounced effect.

Chemistry, Pharmaceutical↗

PubMed1999

On the suitability of fiberglass reinforced polyester as building material for mesocosms.

Gel- and topcoat surface layers on fiberglass [glass-reinforced plastic (GRP)] made of unsaturated resin based on isophthalic acid polyester and neopentyl glycol (ISO-NPG) were tested for leaching, ecotoxicity of water eluates, and abrasion by river sediments at a current speed of 0.5 m * s-1. Leaching from topcoat tempered at low temperature was significant, whereas it was negligible from highly tempered gelcoat. Water eluates from both gel-and topcoat were nontoxic in routinely employed biotests (bacteria, algae, daphnids). No abrasion by river sediments was detectable. Based on these results, GRP with gelcoat made of ISO-NPG is considered a suitable building material for mesocosms.

Acetone↗

PubMed2001

Production of polyesters in transgenic plants.

Polyhydroxyalkanoates (PHAs) are bacterial polyesters having the properties of biodegradable thermoplastics and elastomers. Synthesis of PHAs has been demonstrated in transgenic plants. Both polyhydroxybutyrate and the co-polymer poly(hydroxybutyrate-co-hydroxyvalerate) have been synthesized in the plastids of Arabidopsis thaliana and Brassica napus. Furthermore, a range of medium-chain-length PHAs has also been produced in plant peroxisomes. Development of agricultural crops to produce PHA on a large scale and at low cost will be a challenging task requiring a coordinated and stable expression of several genes. Novel extraction methods designed to maximize the use of harvested plants for PHA, oil, carbohydrate, and feed production will be needed. In addition to their use as plastics, PHAs can also be used to modify fiber properties in plants such as cotton. Furthermore, PHA can be exploited as a novel tool to study the carbon flux through various metabolic pathways, such as the fatty acid beta-oxidation cycle.

Arabidopsis↗

PubMed1982

Human exposure to styrene. IV. Industrial hygiene investigations and biological monitoring in the polyester industry.

An industrial hygiene study of 10 glassfiber reinforced polyester plants (including 90 workers) was undertaken to investigate the styrene exposure in this industry and to estimate biological limit values (BLV's) for the urinary metabolites of styrene: mandelic (MA) and phenylglyoxylic acids (PGA). Time weighted average (TWA) styrene exposures were found ranging from 2 to 200 ppm. The urinary elimination of metabolites correlated well with exposure and the BLV's corresponding to an 8-h exposure at 100 ppm were consistent with earlier laboratory findings (end-of-shift sample: MA 1640, PGA 510, MA + PGA 2150; next-morning sample: MA 330, PGA 330, MA + PGA 660 mg/g creat.). Total metabolites (MA + PGA) in the next-morning sample or mandelic acid in the end-of-shift sample are recommended for routine monitoring of exposure to styrene. The study revealed the need for further research on how to reduce styrene exposure in this industry.

Air↗

PubMed1998

Endothelial cells lining polyester fabric express pro-coagulant phenotype in vitro.

The paper deals with the in vitro assessment of endothelial cell (EC) phenotype covering an albumin- and chitosan-coated polyester fabric and shows that resting ECs express a pro-coagulant phenotype by releasing a high von Willebrand factor level and expressing low thrombomodulin surface activity, despite maintaining an adequate response to stimulating agents.

Biocompatible Materials↗