SEARCH · PubMed Health

Results for “Polyesters”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 1,351 records · Page 75Linked to original sources

PubMedDate not supplied

In vitro adherence of bacteria to sutures in cardiac surgery.

The adherence of bacteria to sutures used in cardiac surgery was studied by in vitro quantitative determination with [3H]-leucine-labeled Staphylococcus epidermidis, Staphylococcus aureus and Streptococcus sanguis. The adherence per unit area for staphylococci was least for monofilament polypropylene (Prolene), 3 times higher (p less than 0.05) for braided polyester (Mersiline) and greatest (10 times, p less than 0.005) for braided polyester sutures coated with polybutylate (Ethibond). Mean values for the adherence of streptococci were low for all the sutures. Sutures pretreated with human plasma showed a 12-37% increase in bacterial adherence. The cell surface hydrophobicity, surface charge and the haemagglutinating property of bacteria did not correlate with their adherence property. In view of these observations, it is suggested that: (a) the preferential adherence of staphylococci to intra-cardiac sutures may be one of the explanations for its being the commonest cause of early prosthetic valve endocarditis, (b) there is a need for a careful selection of sutures used in cardiac surgery and (c) the described in vitro assay for bacterial adherence may be used for monitoring the development of better designed sutures and the effect of incorporation of antibiotics in the sutures.

Bacterial Adhesion↗

PubMed1979

The behavior of three different types of materials in vitro and in the dynamic physiological environment: review and analyses of critical parameters.

A comparative analysis of smooth-surfaced synthetic materials, gels, especially those based on polyacrylamide, and polyester flocked surfaces indicate profound differences between these three types of materials when in contact with blood. Although many smooth-surface materials adsorb fibrinogen in vitro, several of these perform well in vivo without polymerization of fibrinogen to fibrin leading to clot-formation apparently because of enzymatic reactions in the physiological environment. Polyacrylamide hydrogels adsorb little plasma proteins, show negligible platelet adhesion and activation. In contrast, polyester flocked (fibril) surface deposit large quantites of fibrinogen that polymerizes to fibrin with entrapped formed blood elements (clot). The thickness of this layer is difficult to control and the build-up continues to a thickness up to approximately 400 to 600 micron depending on the species. The danger of clot-fragmentation and flock-detachment especially during flexing makes these rough surfaces inferior in blood-contacting application, in comparison to the best current synthetic smooth-surfaced biomaterials, hydrogels, and chemically modified natural tissue components.

Acrylamides↗

PubMed1981

Clinical applications of magnetic rings in colorectal anastomosis.

Based upon experiments on animals, an anastomotic apparatus, consisting of two magnetic rings of polymer bonded, rare earth cobalt magnets embedded in polyester, was developed. There are three types of polyester device with diameters of 25, 28, and 30 millimeters, respectively. The force between the magnets varied between 2.5 Newtons at 4 centimer separation and 11.8 Newtons at union. For the low colorectal anastomosis, a magnet holder, connecting rod and spherical cap were developed. The aim of the technique is a quick restoration of the underbroken submucosal intestinal cylinder by optimal circular apposition of the submucosal layer. The working mechanism is based upon progressive compression, leading to necrosis of the intermediate mucosal and submucosal layers by increasing the magnetic force while intestinal healing takes place. After seven to 12 days, the magnets cut through the disappear from the anastomotic region by intestinal peristalsis. From the initial series of 21 patients, 11 resections of the sigmoid colon and nine low anterior resections were performed. Dehiscence of the suture line was noted in two instances. One patient required reoperation. The other patient had a small area of dehiscence at the suture line after evacuation of an infected hematoma with a further uncomplicated course. One patient died on the third postoperative day of recurrent myocardial infarction. In the other 18 patients, primary intestinal healing was demonstrated roentgenologically and sigmoidoscopically.

Aged↗

PubMed1995

[Analysis of the effects of selected polymers on morpho-dynamic features of rat hepatocytes].

The thesis shows the results of the research on the influence of the film-form polymers on the hepatocytes in rats. The polymers were composed of polyethylene (PE), polyvinyl chlorides (P-25, P-47), polyesters (A, B, E) and irradiated L7 collagen. The aim of the research was to establish whether the changes in the specific morpho-dynamic characteristics-which prove the changes in the hepatocyte metabolic activity in rats-could be used to assess the usability of the above mentioned polymers for medicine. The evaluation of the research findings was analysed on the basic of the stereometric methods and factor analysis. On the basic of the obtained results, polyvinyl chlorides P-25 and P-47 have been evaluated most favourably as far as their possible application in medicine is concerned, whereas polyester E shows the most negative characteristics for such an application.

Animals↗

PubMedDate not supplied

Small diameter vascular prostheses with incorporated bioabsorbable matrices. A preliminary study.

The authors have designed small diameter vascular prostheses with incorporated matrices that can be absorbed into a growing anastomotic neointima. First, a gelatin-heparin complex was coated on the inner surface of tubular ultrafine polyester fabrics presealed with heat denatured albumin. Second, to control the bioabsorption rate, the prepared grafts were cross-linked with polyepoxy compounds for 3 days (Group I; n = 14) or 5 days (Group II; n = 4). These grafts, 3 mm in diameter and 4 cm long, replaced the carotid arteries of nine mongrel dogs weighing 9.5-14 kg. Six of eight (75%) grafts in Group I were patent when the animals were killed 4 weeks after surgery. Doppler sound examination revealed that the remaining six were patent for 16 weeks. In Group II, three of four (75%) grafts were patent when the animals were killed 8 weeks after surgery. In both groups, scanning electron microscopic study showed neither platelet aggregation nor fibrin formation on the midportion. However, these two groups significantly differed in histology. In Group I, thin anastomotic neointima advanced over the mostly absorbed gelatin-heparin complex layer. Connective tissue was well formed around the polyester scaffold. In contrast, thick neointima advanced over the gelatin-heparin complex layer that still remained on the luminal surface in Group II. These results suggest that the gelatin-heparin complex, when cross-linked adequately, could simultaneously function as a temporary antithrombogenic surface and as an excellent substructure of an anastomotic neointima.

Anastomosis, Surgical↗

PubMed1996

[Texture of cruciate ligaments as a modifying factors of grafts].

In the last ten years hundreds of alloplastic prostheses of cruciate ligaments of knee (ACL) have been implanted. The remote results after surgeries of this kind were univocally bad. All the known synthetic fibres undergo the process of aging and of constant decrease of their mechanical properties. Research of graft fulfilling the conditions of resistance ACL and investigations over the ways of delaying its degradation are continued. The author investigated 5 kinds of polyester prostheses ACL made of homogeneous polyester fibres with the same mechanical properties only with different texture. To estimate biocompatibility he implanted them to piglets weighing 20-30 kg and to rabbits into dorsum muscles in the place of the cut out ACL. After 3 and 6 months a section of the piglets was made estimating the macroscopic, histological and radiological picture. For the rabbits a section was made after 14 days and 3 months. The investigations confirmed a high biocompatibility of the grafts. Large differences in hypertrophy of particular grafts with fibrous tissue were noticed.

Animals↗

PubMed1998

Evaluation of a novel bioprosthetic heart valve incorporating anticalcification and antimicrobial technology in a sheep model.

BACKGROUND AND AIM OF THE STUDY: The St. Jude Medical (SJM) Epic valve has been designed to diminish the risk of prosthetic valve endocarditis by the use of silver-coated polyester fabric, and to inhibit dystrophic calcification by the use of ethanol pretreatment. METHODS: A 20-week juvenile sheep mitral valve implant model was used to determine safety and efficacy of the device, as well as the rate of silver release and degree of dystrophic calcification. The SJM Epic valves were compared with SJM Biocor porcine valves (not ethanol-pretreated, not silver-modified polyester fabric) and Baxter Carpentier-EdwardsR standard valves. RESULTS: Blood concentrations of silver reached a maximum of 40 p.p.b. within 10 days of SJM Epic valve implantation, and were well below toxic levels (300 p.p.b.). Blood silver concentrations returned to baseline within 30 days after surgery. Maximal silver accumulation occurred in the liver (16.75 mg/g dry weight); concentrations in the brain, spleen, kidney and lung were similar to those reported for other silver-modified prosthetic valves. No statistically significant difference was found in calcium content between SJM Epic and Biocor valves. The fibrous response to the sewing cuff was similar among the three valve types. CONCLUSIONS: At all times tested, silver release from the SJM Epic valve led to blood concentrations well below toxic levels. Although calcification in the two SJM valve groups was extremely low, the 20-week sheep model may be insufficiently sensitive to detect differences in calcium accumulation in modern bioprosthetic valves.

Animals↗

PubMed1985

An evaluation of ultrastrong polyethylene fiber as an ophthalmic suture.

An ultrastrong polyethylene fiber was evaluated as an ophthalmic suture. Properties of this fiber and of nylon, polypropylene, and polyester sutures were measured by standard techniques for fiber testing and for testing knot characteristics of sutures. Their behavior in cataract and keratoplasty surgery was assessed qualitatively. The ultrastrong polyethylene fiber has great tensile strength, high flexibility, and is very inelastic. Its strength and knot security provide safe incision closure and it has good biocompatibility. Ultrastrong polyethylene fiber is potentially superior to nylon, polypropylene, and polyester in the most important characteristics of a non-absorbable monofilament polymer ophthalmic microsuture.

Biocompatible Materials↗

PubMed1994

Airway hyper-responsiveness and the prevalence of work-related symptoms in workers exposed to irritants.

The association between exposure to airway irritants and the presence of work-related symptoms and whether this association was modified by airway hyper-responsiveness, smoking, and allergy by history was studied in 668 workers of synthetic fiber plants. A Dutch version of the British Medical Research Council (BMRC) questionnaire with additional questions on allergy and work-related symptoms was used to assess symptoms, and a standardized histamine challenge test of airway hyper-responsiveness (AHR) was employed. Work-related symptoms were defined as having more than usual eye and respiratory symptoms during work. On the basis of job titles and working department, the exposure status of all workers was characterized into seven groups: (1) reference group; (2) white collars; (3) SO2, HCl, SO4(2-); (4) polyester vapor; (5) oil mist and oil vapor; (6) polyamide and polyester vapor; and (7) multiple exposure. The association between exposure groups and work-related symptom prevalence was estimated by means of multiple logistic regression. The overall prevalence of the work-related symptoms were: cough 9%; phlegm 6%; dyspnea 7%; wheeze 2%; eye symptoms 16%; nasal symptoms 15%. Exposure to airway irritants was significantly associated with work-related symptoms, independent of AHR, smoking, allergy by history, and chronic respiratory symptoms. The association of exposure group with work-related symptoms was stronger for subjects with AHR than for subjects with no AHR. The association with dyspnea and/or wheeze was also stronger for smokers than for nonsmokers and ex-smokers. In contrast, the association between exposure and a higher prevalence of work-related symptoms was stronger in subjects with no history of allergy than in subjects with history of allergy. This is most likely due to the relatively high prevalence of background symptoms in (nonexposed) allergic subjects. It is concluded that exposure to irritants in the working environment might lead to respiratory symptoms, even if exposure levels are relatively low.

Adult↗

PubMed1992

Plastic embedding procedure for 15 microns sections of large undecalcified tissue blocks.

A method is described that produces sections (15 microns) of large specimens (with dimensions up to 140 x 100 x 200 mm). They are suitable for comparison to CT images of that specimen and can be used as a basis for three-dimensional reconstructions. Frozen unfixed parts of the human body are embedded in polyurethane and scanned with CT. Undecalcified slices, 6 mm thick, of these specimens are cut with a bandsaw. These slices are successfully embedded in polyester resin by means of fixation, dehydration, and subsequent impregnation with this resin. Sections of 15 microns are obtained by cutting the trimmed and sandpapered polyester blocks with an LKB multirange microtome. They are collected on adhesive tape and stained according to Weigert-Azan, sealed between adhesive acetate sheets and photographed on colour slide film. As an example photographs of sections of the human elbow and lumbar spine region are presented.

Cryopreservation↗

PubMed2003

Mechanistic study of Bu2SnCl2-mediated ring-opening polymerization of epsilon-caprolactone by multinuclear NMR spectroscopy.

The ring-opening polymerization (ROP) of epsilon-caprolactone (CL) was carried out in toluene at 100 degrees C with n-propanol (nPrOH) in the presence of Bu(2)SnCl(2). It comes out that the molar mass of the polyester chains can be predicted from the initial monomer-to-alcohol molar ratio in accordance with a controlled ROP mechanism involving an O-acyl cleavage of the monomer to selectively form (alpha-propyloxy)(omega-hydroxy)poly(epsilon-caprolactone) chains. In order to gain fundamental understanding of the mechanistic factors governing the polyester chain growth, advanced (1)H, (13)C, and (119)Sn NMR investigations were performed in situ in [D(8)]toluene, as well as with model solutions that contained Bu(2)SnCl(2) and binary mixtures of the components at various concentrations and temperatures. This has enabled us to propose a mechanism in which Bu(2)SnCl(2) behaves as a catalyst, while nPrOH is the actual initiator. It involves non-aggregated, six-coordinate Bu(2)SnCl(2) complexes in which ligands exchange fast on the (119)Sn NMR observational timescale, and the simultaneous interactions of CL and alcohol function in such a way that it favors insertion/propagation reactions over transesterification ones, up to high monomer conversion.

Journal Article↗

PubMed1988

The use of ultrathin-layer polyacrylamide gel isoelectric focusing in two-dimensional analysis of plant and fungal proteins.

Although use of ultrathin polyacrylamide gel isoelectric focusing in the first dimension of two-dimensional analysis bestows a number of advantages, it has been little used by the plant science community. Nonstandardization along with problems unique to the format have probably delayed wider adoption. Relevant parameters were therefore tested in order to optimize resolution, reproducibility, economy and ease of use. Ultrathin-layer gels (200 microns in this study) used in the first dimension require a semirigid backing for support. Widely available matte-finished thin polyester film without chemical pretreatment was found to bind the gel adequately. The gel adheres to the film through all processing steps, yet, if desired, can be easily transferred to Whatman 3MM paper for special applications such as Western blotting. The ultrathin first-dimensional gels can be quickly dried on the polyester backing for convenient handling and long term storage. Strips cut from the dried gel for use in the second dimension are more easily manipulated than their tube format counterparts. The difficulty of disrupting and recovering microsamples of labeled leaf and root tissue prompted the invention of an efficient and simple communition device. An economical and efficient silver stain process is also described. This analytical technique was applied in an attempt to detect resistance gene products in different genetic backgrounds of maize. Although the ultrathin flatbed format provides as good as or better resolution than the tube gel system, the level of sensitivity was still inadequate to reveal the apparently rare resistance gene product.

Electrophoresis, Polyacrylamide Gel↗

PubMed1983

Structure-biocompatibility relationship of condensation polymers.

Various condensation polymers including polyamides, polyesters, polyethers, polysulfonamides, polysulfonate, polyphosphonate, polyimide, polyamide-imides, polyimide, polyamide-imides, polyester-amides, etc. have been prepared and evaluated for their biocompatibility by a cell culture method. Cell attachment and cell growth are influenced by the chemical structures of the tested polymers. Aliphatic polyamides exhibited considerably different cell growth behavior than aromatic polyamides.

Biocompatible Materials↗

PubMed1994

Photochemical conjugation of mammalian cells to polymeric supports and membranes: a kinetic study.

A commercial polyester acrylate prepolymer, to which a 2:3 wt/wt ratio of tripropyleneglycol diacrylate was added to increase photopolymerization rate, was employed as photochemical conjugating agent, through photografting. 1,2-Diphenyl,2,2-dimethoxyethanone was added as standard photoinitiator (7.0 wt/wt%), together with varying amounts (0.003-4.0 wt/wt%) of some proprietary photocatalytic systems, based on the following photocatalysts: mu-peroxo-bis[N,N'-ethylene-bis(salicylideneiminato)cobalt(I II) (I), vanadium(V) triethoxide (II), and a synergic mixture of vanadium(V) tri-t-butoxide and tri-i-propoxide (III). A homogeneous suspension containing (10 +/- 2) x 10(5) human thyroid follicular cells per milliliter of photochemically reacting medium was photografted, at a surface density of 6.5 +/- 0.7 mg.cm-2 of diacrylate prepolymer mixture, onto polystyrene plates or onto commercial microfiltration and ultrafiltration membranes consisting of nonwoven cellulose tissues with known porosities varying between 5 and 30 microns and in photografted polyester acrylate-based membranes with a cutoff of 50 +/- 5 KD. Bioconjugation yields, as a function of photografting time, were measured gravimetrically and by multiple internal reflection IR spectroscopy. Three series of experiments were performed: 1) measurements of graft yields of the prepolymer, and of the parallel disappearance of double bonds, in the absence of mammalian cells; 2) the same as 1), in the presence of thyroid follicular cells; 3) the same as 2), but with the photoinitiating system formed by the standard photoinitiator alone, with no photocatalyst. Results show that if a suitable photocatalyst is not added, no practical conjugation is possible. An appropriate choice of the photocatalytic system and of its concentration allows reduction of irradiation times (e.g., by a factor of about 2 x 10(4) calculated as the mean lifetime ratio, between the uncatalyzed system and that with 0.1 wt% of [III]), thus minimizing cell inactivation and/or improving responsiveness to the bioassay. From this point of view, photoactivity of (III) is outstanding. The very small, but clearly perceptible, influence of polymeric support on bioconjugation is also commented upon.

Animals↗

PubMed1995

Plasma protein adsorption to artificial ligament fibers.

The adsorption of plasma proteins onto biomedical polymers is an important factor in the biocompatibility of biomaterials. We identified the plasma proteins adsorbed onto four polymeric fibers used for synthetic ligament replacement: polyarylamide, polylactic acid, polyester, and polypropylene. The adsorbed proteins were eluted and analyzed by one-dimensional and two-dimensional gel electrophoresis. Fibrinogen, albumin, IgG, high molecular weight kininogen (HMWK), and lipoproteins ApoA-1 and ApoE were the major proteins adsorbed onto polyarylamide. The three others biomaterials bound albumin, fibrinogen, ApoA-1, and ApoE; however, the proportions of proteins bound to each polymer differed. There was an inverse relationship between ApoA-1 and fibrinogen binding for all four biomaterials; polyarylamide bound a high percentage of fibrinogen, but little ApoA-1; polylactic acid, polyester, and polypropylene bound a high percentage of ApoA-1, but little fibrinogen. These results support suggestions that low fibrinogen adsorption might be due to the preferential adsorption of Apo-1. High fibrinogen binding to polyarylamide ligaments may favor fibroblast adherence, growth, and tissue repair.

Adsorption↗

PubMed1995

Analysis of a vinyl pyrrolidone/poly(propylene fumarate) resorbable bone cement.

A resorbable bone cement was formulated from N-vinyl-2-pyrrolidinone (VP), the unsaturated polyester poly(propylene fumarate) (PPF), and the inorganic filler tribasic calcium phosphate (hydroxy apatite). Cure, initiated by benzoyl peroxide and accelerated by N,N-dimethyl-p-toluidine, resulted in the formation of VP crosslinks between polyester chains. During cure the cement hardened from a viscous moldable putty to a rigid structure with a shore D hardness of 50-60. The purpose of this study was to determine the fractions of PPF and VP incorporated into the crosslinked structure. Dissolution of the cured cement in water followed by extraction of the residue in tetrahydrofuran indicated that over 90% of the PPF was crosslinked over the range of PPF/VP ratios explored, but that the fraction of VP used in formation of crosslinks depended linearly on the PPF/VP ratio. Kinetic analysis of these data suggests that k'pp/kpf (the reactivity ratio) was approximately 2.0 where k'pp is the rate constant for the addition of VP radical to VP monomer leading to formation of poly(vinyl pyrrolidone), and kpf is for the addition of VP radical to PPF unsaturation.

Biocompatible Materials↗

PubMed2003

Polymer microfiber mechanical properties: a system for assessment and investigation of the link with fibrous capsule formation.

A novel microtensile testing instrument was developed to assess the mechanical properties of small-diameter polyethylene, polyurethane, and polyester microfibers. The instrument had a root-mean-square error of 2.96 microN for force measurement and 1.91 microm for displacement measurement. Microfibers ranging in diameter from 1.0 to 10.9 microm were strained at 2 mm/s in the device, and the slopes of their stress-strain curves (material moduli) were determined. Correlations between material modulus and previously published data on fibrous capsule presence and thickness for implanted polyethylene, polyurethane, and polyester microfibers were investigated. Results for the 1.0-5.9-microm microfiber diameter range showed that neither the percentage of unencapsulated fibers nor the capsule thickness correlated well with modulus. Correlation coefficients were 0.04 and 0.09, respectively. However, for the 6.0-10.9 microm diameter range the correlations were strong, 1.00 for both percentage of unencapsulated fibers and capsule thickness. It is suggested that the results reflect the greater attachment and mechanical interaction of cells with microfibers for the 6.0-10.9 microm-diameter range than for the 1.0-5.9 microm-diameter range.

Biocompatible Materials↗

PubMed2006

Novel sulfonated hydrogel composite with the ability to inhibit proteases and bacterial growth.

There is a growing interest in the development of wound dressings that possess functionality beyond providing physical protection and an optimal moisture environment for the wound. To this end, a novel dressing material based on a sulfonated triblock polymer has been developed. This versatile polymer possesses an ion-exchange capability that is amenable to binding and controlled release of a variety of therapeutic agents. This sulfonated polymer offers several advantages over existing commercial hydrogels used as wound dressings. These include (1) hydrophilicity that is proportional to sulfonation level, (2) easy preparation of fabric supported dressings (e.g., polyester, cotton, nylon), (3) excellent mechanical integrity of the materials when hydrated, (4) stability to a variety of chemistries, and (5) stability to a variety of sterilization methodologies. In this study, polymer was coated onto a polyester fabric and then modified by ion exchange to prepare the sodium, silver, or doxycycline salts. These sulfonated triblock polymer formulations were then evaluated for their capacity to sequester the neutrophil proteases, elastase, and collagenase-2 (MMP-8). Several of the formulations were found to sequester significant amounts of either elastase or collagenase. These formulations were demonstrated to be tested against a commercially available dressing that is currently marketed for its protease-inhibiting capability. The experimental dressing was statistically superior to the commercial dressing at inhibiting MMP-8 and elastase under the same conditions.

Anti-Bacterial Agents↗