Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Polyesters”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11Linked to original sources
PubMed1978

[Styrene migration into wine contained in polyester resin tanks].

The use of polyester resins in wine tanks manufacture or coating has widely spread during the past five years; this type of material has been and is still the source of organoleptic damage due to non polymerized sytrene migration into urine. Sytrene is a solvant often used in resin polymerization: it act as a reticulation agent of insaturated linear polyester. Polymerization at room temperature is allowed gy additives but has to be completed in warm air or in steam. An excess of styrene is often used for a polymerisation as complete as possible and remains on a free form. Then it migrates from the tank walls into the wine. For a better understanding of the styrene migration mechanism studies were performed on two levels: from small containers (4 l) kept in the laboratory and from tanks (30 hl) set up in an I.N.R.A. wine estate in all conditions usually realized in practice. Influence of time, temperature and alcohol content were studied. Styrene migration was interpreted as a diffusion phenomenom and styrene diffusion coefficients were calculated for several temperatures. Knowledge of these coefficients and of styrene content of the tank walls allow the prediction of a tank behaviour in time. Other substances that styrene were detected in wine and in tank walls, they are impurities either from resins like ethylbenzene, or from the catalyst like mesityl oxide. The lattest has never been mentioned in the litterature. From the results obtained it is possible to give some advices to manufacturers and users of polyester resin tanks, about the quality of raw materials, resins and additives along with the conditions carried and for their use and about the control of monomer styrene content in the walls of just manufactured tank.

Food Contamination↗
PubMed1997

In vitro and in vivo studies of a polyester arterial prosthesis with a warp-knitted sharkskin structure.

The present study was undertaken to assess the performance of a new knitted and gelatin-sealed polyester vascular graft that is believed to have greater dimensional stability than current commercial devices. Samples of the uncrimped, crimped, and sealed prosthesis were submitted to a series of in vitro and in vivo trials. Four commercial polyester knitted devices were included as controls for the in vitro tests, which included measurements of the textile and yarn structure and physical, chemical, and thermal properties of the graft, such as water permeability, dilatation, suture retention strength, melting point, and crystallinity index. The in vivo evaluation involved implanting the prototype device as a canine thoraco-abdominal bypass for periods ranging from 4 h to 1 year and assessing the biocompatibility, biofunctionality, and biostability of the explanted specimens. The warp-knitted structure of the prototype device has a unique sharkskin stitch that confers a superior dilatation resistance and suture retention strength to the prosthesis. The animal trial demonstrated that the gelatin ensures initial hemostasis without preclotting. The gelatin is bioresorbed during the first 2 weeks of implantation, which generates a temporary, moderate, acute inflammatory response. An external capsule of granulomatous tissue and an internal collagen capsule are formed between the first and third month. Analysis of the textile and physical properties of the explanted prostheses confirmed there was neither dilatation nor significant changes in structure or mechanical performance during implantation, thus confirming the biostability of this new prototype device and opening the way for clinical trials.

Anastomosis, Surgical↗
PubMed1998

In vitro cellular response to polypyrrole-coated woven polyester fabrics: potential benefits of electrical conductivity.

Electrically conducting polypyrrole-treated films have recently been shown to influence the morphology and function of mammalian cells in vitro. This type of polymer represents a possible alternative biomaterial for use in vascular implantation. The present study compared the in vitro biocompatibility of the five different polyester woven fabrics having increasing levels of electrical conductivity ranging from 4.5 x 10(4) to 123 omega/square with that of low density polyethylene and polydimethylsiloxane primary reference materials. Biocompatibility was measured in terms of four different types of in vitro cellular response, including (a) an indirect and (b) a direct control organotypic culture assay using endothelial cells, (c) a polymorphonuclear (PMN) cell activation study using flow-cytometric measurements of CD11/CD18 integrin molecule expression, and (d) a semiquantification of interleukin (IL)-6 mRNA expression on monocytes/macrophages using reverse-transcriptase polymerase chain reaction. The organotypic culture study revealed that the fabrics with high levels of conductivity exhibited lower cell migration, proliferation, and viability. The PMN activation study of blood from 10 healthy adult donors demonstrated that the two most conductive fabrics were able to identify the more reactive donors. The levels of IL-6 mRNA expression by monocytes/macrophages decreased as the conductivity level of the fabrics increased. The results of the present study therefore indicate that high levels of conductivity (< 200 omega/square) on polyester fabrics are detrimental to the growth, migration, and viability of endothelial cells; induce elevated PMN activation; and affect the intracellular metabolism of monocytes. They also point to a specific range of conductivity (10(3) < 10(4) omega/square) which is associated with an optimum in vitro cellular response.

Adult↗
PubMed2001

In vitro biocompatibility study of electrically conductive polypyrrole-coated polyester fabrics.

This study investigated the basic biocompatibility aspects of two types of polypyrrole (PPy)-coated polyester fabrics for possible use as vascular prostheses. These PPy-coated fabrics, PPy-Phos and PPy-Plas, were sterilized with ethylene oxide (EO) and the following characterizations were performed: surface morphology by scanning electron microscope, EO residuals analysis by the headspace method, acute systemic toxicity in the mouse model, hemolysis, blood coagulation time, viability and proliferation of endothelial cells measured with the WST-1 method, and activation of polymorphonuclear (PMN) cells indicated by the specific expression of interleukin 8 mRNA measured by reverse transcription polymerase chain reaction. Virgin polyester fabrics, expanded poly(tetrafluoroethylene) (ePTFE), and medical-grade Bionate 80A poly(carbonate urethane) were used as references in the cell culture experiments. The PPy-coated fabrics revealed different surface morphologies by showing more PPy lamina and clusters on the PPy-Plas. Neither of the PPy-coated fabrics had an adverse effect on hemolysis and coagulation time, and they did not cause any acute systemic toxicity. The EO residual level was as low as 5 ppm or less, which is considered quite acceptable. Although exhibiting a relatively low initial cell adhesion at 24 h, the two PPy-coated samples showed no cytotoxicity at 72 and 168 h. Bionate 80A and ePTFE recorded cytotoxicity at 72 and 168 h, respectively. The virgin fabrics also demonstrated a decrease of viable cells at 72 h that was not significant. The activation of PMN cells induced by both PPy-coated fabrics, the ePTFE, and the negative control was significantly lower than that induced by their respective tumor necrosis factor-alpha controls. These results therefore highlighted the potential of PPy-coated fabrics for use as cardiovascular prostheses. It was suggested that cell adhesion moieties should be incorporated into the PPy/fabric composite to increase cell adhesion and subsequent cell proliferation.

Animals↗
PubMed2006

Surface modification of metallic cardiovascular stents by strongly adhering aliphatic polyester coatings.

This article reports on a novel two-step strategy for the coating of cardiovascular stents by strongly adhering biocompatible and biodegradable aliphatic polyesters. First, a precoating of poly(ethylacrylate) (PEA) was electrografted onto the metallic substrate by cathodic reduction of the parent monomer in dimethylformamide (DMF). The electrodeposition of PEA, in a good solvent of it, was confirmed by both Infra-red and Raman spectroscopies. The pendant ester groups of PEA were then chemically reduced into aluminum alkoxides, able to initiate the ring-opening polymerization (ROP) of either D,L-lactide (LA) or epsilon-caprolactone (CL). Growth of biodegradable PLA or PCL coatings from the adhering precoating was confirmed by both Infra-red and Raman spectroscopies, and directly observed by scanning electron microscopy (SEM). This type of coating can act as an anchoring layer for the subsequent casting of drug-loaded polyester films allowing the controlled release of antiproliferative agents for the treatment of in-stent restenosis.

Biocompatible Materials↗
PubMed2006

"Wet-state" mechanical properties of three-dimensional polyester porous scaffolds.

Porous poly(D,L-lactic-co-glycolic acid) (PLGA) scaffolds under a simulated physiological environment were investigated to estimate their "true" mechanical properties, with emphasis on the effect of "wet-state" on the compressive behaviors. The effect of the history of ethanol sterilization was also investigated. The studies were focused upon the "wet-state" mechanical properties of polyester porous scaffolds, because the potential implants must be used under a wet environment. The measurements of three-dimensional porous scaffolds composed of amorphous PLGA with five polymer formulations including poly(D,L-lactic acid) (PDLLA) demonstrated that the mechanical properties of PLGA scaffolds significantly decreased in phosphate buffer saline solution (PBS) at 37 degrees C and/or with an ethanol sterilization history, even though PLGA is a hydrophobic material. The decrease extent depends on the copolymer composition: when the porosity is about 90%, a PDLLA scaffold remained about 75-80% of initial mechanical properties in the dry state at 25 degrees C, whereas PLGA 85:15, 75:25, and 65:35 scaffolds remained only about 10% or less, and the PLGA 50:50 scaffolds examined were not sufficiently strong for mechanical tests. If scaffolds were prewetted with ethanol ahead of prewetting with PBS, the mechanical properties further decreased compared with those merely prewetted with PBS. These phenomena were elucidated experimentally from plasticization of PLGA with water or ethanol, and the consequent reduction of glass transition temperature. The results might be helpful for designing polyester porous scaffolds for tissue engineering or in situ tissue induction applications.

Biocompatible Materials↗
PubMed2001

Use of rifampin-soaked gelatin-sealed polyester grafts for in situ treatment of primary aortic and vascular prosthetic infections.

BACKGROUND: In situ treatment of artery/graft infection has distinct advantages compared to vessel excision and extra-anatomic bypass procedures. Based on animal studies of a rifampin-soaked, gelatin-impregnated polyester graft that demonstrated prolonged in vivo antibacterial activity, this antibiotic-bonded graft was used selectively in patients for in situ treatment of low-grade Gram-positive prosthetic graft infections or primary aortic infections not amenable to excision and ex situ bypass. METHODS: In a 5-year period (1995-1999), 27 patients with prosthetic graft infection (aortofemoral, n = 18, femorofemoral, n = 3; axillofemoral, n = 1) or primary aortic infection (mycotic aneurysm, n = 3; infected AAA, n = 2) underwent excision of the infected vessel and in situ replacement with a rifampin soaked (45-60 mg/ml for 15 min) gelatin-impregnated polyester graft. All prosthetic graft infections were low grade in nature, caused Gram-positive bacteria (Staphylococcus epidermidis, 16; Staphylococcus aureus, 5; Streptococcus, 1), and were treated electively. Patients with mycotic aortic aneurysm presented with sepsis and underwent urgent or emergent surgery. RESULTS: Two (8%) patients died-1 as a result of a ruptured Salmonella mycotic aortic aneurysm and the other from methicillin-resistant S. aureus infection following deep vein replacement of an in situ replaced femorofemoral graft. No amputations or late deaths as the result of vascular infection occurred in the 25 surviving patients. Two patients developed recurrent infection caused by a rifampin-resistant S. epidermidis in a replaced aortofemoral graft limb and were successfully treated with graft excision and in situ autogenous vein replacement. Eighteen patients remain alive and clinically free of infection after a mean follow-up interval of 17 months. CONCLUSIONS: In situ replacement treatment using a rifampin-bonded prosthetic graft for low-grade staphylococcal arterial infection was safe, durable, and associated with eradication of clinical signs of infection. Failure of this therapy was the result of virulent and antibiotic-resistant bacterial strains.

Aged↗
PubMed2001

Microbial degradation of polyesters.

Polyesters, such as microbially produced poly[(R)-3-hydroxybutyric acid] [poly(3HB)], other poly[(R)-hydroxyalkanoic acids] [poly(HA)] and related biosynthetic or chemosynthetic polyesters are a class of polymers that have potential applications as thermoplastic elastomers. In contrast to poly(ethylene) and similar polymers with saturated, non-functionalized carbon backbones, poly(HA) can be biodegraded to water, methane, and/or carbon dioxide. This review provides an overview of the microbiology, biochemistry and molecular biology of poly(HA) biodegradation. In particular, the properties of extracellular and intracellular poly(HA) hydrolyzing enzymes [poly(HA) depolymerases] are described.

Air↗
PubMed2001

Polyesters from microorganisms.

Bacterial polyesters have been found to have useful properties for applications as thermoplastics, elastomers, and adhesives and are biodegradable and biocompatible. Poly(3-hydroxyalkanoates) (PHAs) and poly(beta-malate) are the most representative polyesters synthesized by microorganisms. PHAs containing a wide variety of repeating units can be produced by bacteria, including those containing many types of pendant functional groups which can be synthesized by microorganisms that are grown on unnatural organic substrates. Poly(beta-malate) is of interest primarily for medical applications, especially for drug delivery systems. In this chapter, the bacterial production and properties of poly(3-hydroxyalkanoates) and poly(beta-malate) are described with emphasis on the former.

Acyltransferases↗
PubMed2001

Production of microbial polyesters: fermentation and downstream processes.

Poly(3-hydroxyalkanoates) (PHAs) constitute a large and versatile family of polyesters produced by various bacteria. PHAs are receiving considerable attention because of their potential as renewable and biodegradable plastics, and as a source of chiral synthons since the monomers are chiral. Industrial PHA production processes have been developed for poly(3-hydroxybutyrate) (poly(3HB)) and poly(3-hydroxybutyrate-co-3-valerate) (poly(3HB-co-3HV). More than 100 other poly(3HAMCL)s, characterized by monomers of medium chain length, have been identified in the past two decades. These monomers typically contain 6-14 carbon atoms, are usually linked via-3-hydroxy ester linkages, but can occasionally also exhibit 2-, 4-, 5-, or 6-hydroxy ester linkages. Such polyesters are collectively referred to as medium chain length PHAs poly(3HAMCL)s. The vast majority of these interesting biopolyesters have been studied and produced only on the laboratory scale. However, there have been several attempts to develop pilot scale processes, and these provide some insight into the production economics of poly(3HAMCL)s other than poly(3HB) and poly(3HB-co-3HV). These processes utilize diverse fermentation strategies to control the monomer composition of the polymer, enabling the tailoring of polymer material properties to some extent. The best studied of these is poly(3-hydroxyoctanoate) (poly(3HO)), which contains about 90% 3-hydroxyoctanoate. This biopolyester has been produced on the pilot scale and is now being used in several experimental applications.

Chemical Engineering↗
PubMed2001

In vitro biosynthesis of polyesters.

In vitro synthesis of polyesters using isolated enzymes as catalyst via non-biosynthetic pathways is reviewed. In most cases, lipase was used as catalyst and various monomer combinations, typically oxyacids or their esters, dicarboxylic acids or their derivatives/glycols, and lactones, afforded the polyesters. The enzymatic polymerization often proceeded under mild reaction conditions in comparison with chemical processes. By utilizing characteristic properties of lipases, regio- and enantioselective polymerizations proceeded to give functional polymers, most of which are difficult to synthesize by conventional methodologies.

Chemical Engineering↗
PubMed1990

Plastics from bacteria and for bacteria: poly(beta-hydroxyalkanoates) as natural, biocompatible, and biodegradable polyesters.

Hence, PHB belongs to the family of poly(beta-hydroxyalkanoates), PHA, all of which are usually formed as intracellular inclusions under unbalanced growth conditions. Recently, it became of industrial interest to evaluate PHA polyesters as natural, biodegradable, and biocompatible plastics for a wide range of possible applications such as surgical sutures or packaging containers. For industrial applications, the controlled incorporation of repeating units with different chain lengths into a series of copolymers is desirable in order to produce polyesters with a range of material properties because physical and chemical characteristics depend strongly on the polymer composition. Such "tailormade" copolymers can be produced under controlled growth conditions, in that if a defined mixture of substrates for a certain type of microorganisms is supplied, a well defined and reproducible copolymer is formed.

Bacteria↗
PubMedDate not supplied

Primary implantation of polyester-covered stent-grafts for transjugular intrahepatic portosystemic stent shunts (TIPSS): A pilot study.

PURPOSE: To investigate whether placement of a polyester-covered stent-graft increases the primary patency of transjugular intrahepatic portosystemic stent shunts (TIPSS). METHODS: Between 1995 and 1997 Cragg Endopro or Passager MIBS stent-grafts were used for the creation of TIPSS in eight male patients, 35-59 years of age (mean 48 years). All patients suffered from recurrent variceal bleeding and/or refractory ascites due to liver cirrhosis. Seven stent-grafts were dilated to a diameter of 10 mm, one to 12 mm. Follow-up was performed with duplex ultrasound, clinical assessment, and angiography. RESULTS: The technical success rate for creation of a TIPSS was 100%. The mean portosystemic pressure gradient decreased from 25 mmHg to 12 mmHg. In seven of eight patients TIPSS dysfunction occurred between 2 days and 3 years after stent-graft placement. In one patient the TIPSS is still primarily patent (224 days after creation). The secondary patency rates are 31 days to 3 years. CONCLUSION: The primary use of polyester-covered stent-grafts for TIPSS did not increase primary patency rates in our small series.

Adult↗
PubMed2006

Laparoscopic ventral hernia repair using expanded polytetrafluoroethylene-polyester mesh compound.

BACKGROUND: Many biomaterials and composites have been used in clinical and experimental laparoscopic ventral hernia repair. The ideal prosthesis should allow firm binding to the abdominal wall without adhesion to the bowel. METHODS: A compound prosthesis was made by circumferentially suturing a Gore-Tex mesh as visceral interface to a smaller polyester mesh as parietal interface, and it was used in 46 laparoscopic ventral hernia repairs between January 2000 and December 2004. RESULTS: Average operative time was 65 min, with no intraoperative complications. Mean hospital stay was 2.2 days. Postoperative complications were five seromas, two hematomas, and one recurrence after a mean follow-up of 32.2 months. CONCLUSION: The prosthesis used was made of two biomaterials that have been tested and tried over the years. The polyester layer is known to induce sufficient tissue ingrowth, whereas Gore-Tex minimizes adhesion formation. The memory of the compound was high enough to allow easy laparoscopic unrolling and handling.

Adult↗
PubMed2001

Favorable histologic findings and tensile strength at 14 years in knitted polyester aortofemoral and femoropopliteal grafts in the same patient.

Patent right and left limbs of an aortobifemoral knitted polyester graft and a patent left femoropopliteal graft, both implanted for 14 years, were removed 40 hr postmortem from a 63-year-old man. Healing studies were performed, using routine and immunocytochemistry staining scanning electron microscopy (SEM), and transmission electron microscopy (TEM) on multiple samples taken from sites sufficiently far from the anastomoses to avoid pannus healing. Evaluation by weight-elongation comparison with a fresh graft demonstrated that structural stability and strength were well preserved. Anastomoses were patent with no remarkable intimal hyperplasia. There was no thrombus on the flow surface of either graft. Histologic studies of these grafts revealed uniform through-wall tissue ingrowth and extensive patches of endothelial cells scattered over the flow surface, confirmed by factor VIII, SEM, and TEM. These findings document that long-term stable tensile strength and healing with flow surface endothelialization can be attained with knitted polyester grafts in the human.

Aorta↗
PubMed2001

Evaluation of thrombogenicity of fluoropassivated polyester patches following carotid endarterectomy.

The use of a patch after carotid endarterectomy (CE) is recommended to reduce the incidence of restenosis. Most studies on this subject report the implantation of saphenous vein or PTFE patches, because polyester has always been considered to be a thrombogenic material. The purpose of this study was to evaluate the thrombogenicity of a knitted polyester patch passivated by fluoropolymer surface treatment (FPD patch), which experimental studies have demonstrated to be less thrombogenic than other materials. This prospective, randomized study was performed in 22 patients who underwent CE. In 11 patients the arteriotomy was sutured directly, while in the other 11 an FPD patch was applied. Patients' 111in-oxine labeled platelets were reinjected on the first postoperative day, and scintigraphies were performed after 4, 24, and 48 hr, respectively. The study confirmed that an FPD patch is no more thrombogenic than a simple carotid endarterectomy. The application of the patch, therefore, can be recommended to reduce restenosis without any adjunctive thromboembolic risk.

Aged↗
PubMed1986

Silver staining of proteins: standardized procedure for two-dimensional gels bound to polyester sheets.

A system for the simultaneous silver staining of numerous two-dimensional gels bound to polyester sheets is proposed. Under controlled conditions, a very good reproducibility of staining can be obtained, even between different experiments. Procedures to avoid artifacts due to polyester sheets (background, silver mirror, and vertical streaking) are described.

Electrophoresis, Polyacrylamide Gel↗
PubMed1993

Biosynthesis of polyesters from various amino acids by Alcaligenes eutrophus.

The possibilities of the biosynthesis of polyesters from 20 kinds of naturally occurring L-amino acids by Alcaligenes eutrophus were studied. It was found that several amino acids were used efficiently to synthesize copolyesters of 3-hydroxybutyrate (3HB) and 3-hydroxyvalerate (3 HV) by A. eutrophus under the 'loose nitrogen-limiting' condition, but the other amino acids were scarcely utilized as a carbon source for the synthesis of polyesters. When L-threonine or L-isoleucine were used as the sole carbon source, copolyesters with higher 3HV content were produced.

3-Hydroxybutyric Acid↗