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PubMed2006

Genetics and biochemistry of polyhydroxyalkanoate granule self-assembly: The key role of polyester synthases.

PHAs (polyhydroxyalkanoates = biopolyester) composed of hydroxy fatty acids represent a rather complex class of storage polymers synthesized by various bacteria and archaea and are deposited as water-insoluble cytoplasmic nano-sized inclusions. These spherical particles are composed of a polyester core surrounded by phospholipids and proteins. The key enzymes of polyester biosynthesis and polyester particle formation are the polyester synthases, which catalyze the formation of polyesters. Various metabolic routes have been identified and established in bacteria to provide substrate for polyester synthases. Although not essential for particle formation, non-covalently attached proteins, the so-called phasins, can be found at the particle surface and are considered as structural proteins. Protein engineering of polyester synthases and phasins was used to shed light into the topology of these granule attached proteins. Biopolyesters and the respective micro-/nano-structures are currently considered as biocompatible and biodegradable biomaterials with numerous potential applications particularly in the medical field.

Acyltransferases↗
PubMed1996

The effect of a non-absorbable fat substitute, sucrose polyester, on gastrointestinal function.

OBJECTIVES: To assess the effects of a single dose of a non-absorbable fat substitute, sucrose polyester, on gastrointestinal function. METHODS: The effects of 50 g of sucrose polyester taken as a single drink on gastric emptying, small bowel transit time (SBTT), whole gut transit time (WGTT) and faecal weight compared with a control fat were examined in double-blind studies. The effect of sucrose polyester on gallbladder ejection fraction and gastrointestinal hormones was also assessed. RESULTS: Sucrose polyester was found to accelerate gastric emptying significantly (98.33 +/- 71.0 vs. 112.92 +/- 82.0 min, P = 0.042) but to slow SBTT (153.75 +/- 36.25 vs. 128.75 +/- 47.39 min. P = 0.006). A trend to faster WGTT (37.47 +/- 15.61 vs. 46.63 +/- 20.65 h) and increased faecal weight was observed (453.33 +/- 122.05 vs. 395.0 +/- 107.85 g/48 h), but this did not reach statistical significance. There was a striking reduction in gallbladder ejection fraction with sucrose polyester (21.69 +/- 25.32 vs. 45.27 +/- 27.67%), P = 0.039) and a corresponding significant decrease in the release of cholecystokinin. Lower levels of motilin and enteroglucagon were also observed. CONCLUSIONS: Sucrose polyester has significant effects on gastrointestinal transit, gallbladder contraction and gastrointestinal hormones. These effects can be explained on the basis of decreased luminal products of digestion and may have implications for the widespread use of sucrose polyester as a fat substitute.

Administration, Oral↗
PubMed2007

Protein adsorption onto polyester surfaces: is there a need for surface activation?

Surface hydrolysis of polyester scaffolds is a convenient technique suggested to promote protein adsorption for improving cell attachment. We have, therefore, investigated the effect of hydrolysis of polyester surfaces for protein adsorption to clarify the conditions needed. Three polyesters, poly(ethylene terephthalate) (PET), poly(lactic acid) (PLA), and poly(glycolic acid) (PGA), were selected. Adsorption was investigated by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and quartz crystal microbalance (QCM). Hydrolyzed PET adsorbed significantly more proteins than nonhydrolyzed. Degradable polymers adsorbed at higher rates when the polymers were hydrolyzed prior to adsorption, but the same amount as nonhydrolyzed, suggesting spontaneous hydrolysis during the adsorption. XPS shows that hydrolysis prior to absorption for PET results in a surface nitrogen composition of approximately 14%, similar to pure protein (16%). Nonhydrolyzed PET surfaces showed only approximately 7% nitrogen, indicating protein layers thinner than approximately 10 nm. Adsorption to PLA and PGA shows nitrogen contents of 14-15% in both cases. SEM revealed striking differences in morphology of the protein coating. Hydrolyzed or spontaneously hydrolyzable surfaces display a pronounced fibrous structure while nonhydrolyzed surfaces give smooth structures. In combination, the results show that surface hydrolysis increase adsorption rate, but not the amount of proteins on polyesters that degrades in vivo. Surface treatment of nondegradable polyester increases the total amount of proteins and induces the formation of fibrous protein structures. Post hydrolysis treatment by acetic acid, replacing the counter-ion to a proton, further enhances protein attachment. Finally, cell attachment experiments verifies that protein adsorption increase the cell attachment to polyester surfaces.

3T3 Cells↗
PubMed2001

Polyesters in higher plants.

Polyesters occur in higher plants as the structural component of the cuticle that covers the aerial parts of plants. This insoluble polymer, called cutin, attached to the epidermal cell walls is composed of interesterified hydroxy and hydroxy epoxy fatty acids. The most common chief monomers are 10,16-dihydroxy C16 acid, 18-hydroxy-9,10 epoxy C18 acid, and 9,10,18-trihydroxy C18 acid. These monomers are produced in the epidermal cells by omega hydroxylation, in-chain hydroxylation, epoxidation catalyzed by P450-type mixed function oxidase, and epoxide hydration. The monomer acyl groups are transferred to hydroxyl groups in the growing polymer at the extracellular location. The other type of polyester found in the plants is suberin, a polymeric material deposited in the cell walls of a layer or two of cells when a plant needs to erect a barrier as a result of physical or biological stress from the environment, or during development. Suberin is composed of aromatic domains derived from cinnamic acid, and aliphatic polyester domains derived from C16 and C18 cellular fatty acids and their elongation products. The polyesters can be hydrolyzed by pancreatic lipase and cutinase, a polyesterase produced by bacteria and fungi. Catalysis by cutinase involves the active serine catalytic triad. The major function of the polyester in plants is as a protective barrier against physical, chemical, and biological factors in the environment, including pathogens. Transcriptional regulation of cutinase gene in fungal pathogens is being elucidated at a molecular level. The polyesters present in agricultural waste may be used to produce high value polymers, and genetic engineering might be used to produce large quantities of such polymers in plants.

Carboxylic Ester Hydrolases↗
PubMed1999

Remodeling of patellar tendon grafts augmented with woven polyester after anterior cruciate ligament reconstruction in humans.

Arthroscopic and histological evaluations of anterior cruciate ligament (ACL) grafts were made in 38 patients at various intervals after reconstruction was performed with patellar tendons (PTs) augmented with woven polyester. The interval between the surgery and the examinations ranged from 3 to 36 months (mean, 14.1 months). Biopsy specimens with woven polyester were removed from the anterior mid-portion of the graft 5 mm in depth from the graft surface. Arthroscopically, all 38 grafts showed thick ligamentous tissues, but some polyester fibers had ruptured in 9 grafts. The transplanted grafts were arthroscopically very similar to normal ACL 12 months after reconstruction. Histologically, a marked inflammatory response to the woven polyester was observed in the first 4 months after the operation, but this decreased with time. Five of 6 grafts obtained 18-36 months postoperatively showed decreased cellularity, with longitudinally oriented fibrous bundles, suggesting approaching ligament maturity. The appearance of the fibroblasts in the grafts varied from patient to patient, with 13 of 37 grafts (35.1%) showing spindling fibroblasts, and 24 grafts (64.9%) oval ones. (The remaining graft consisted of mesenchynal cells). Clinically, postoperative KT 1000 arthrometer measurements showed that the mean injured-to-uninjured difference in anterior knee laxity was 1.7 +/- 2.6 mm. There was no chronic synovitis or effusion during the study period. These results suggest that grafts with PT augmented with woven polyester transform arthroscopically and histologically into a structure similar to that of normal ligaments after reconstruction, and may act as a substitute for the ACL. The advantage of woven polyester for the augmentation of PT grafts was that it allowed earlier mobilization and weight-bearing after reconstruction, without adverse effects on graft integrity.

Adolescent↗
PubMed2004

Influence of hyperbranched polyesters on the surface tension of polyols.

The influence of hyperbranched polyesters with different functional end groups on the surface tension of mixtures with an oligo(ester diol) was investigated. The temperature dependence of the surface tension of the pure components and of the mixtures was measured by a modified Wilhelmy balance technique. The results indicate that the surface tension of the pure hyperbranched polyesters strongly depends on the functionality of the end groups. The functionalization of the hydroxyl end groups by short alkyl chains (methyl, tert-butyl) reduced the surface tension depending on the degree of substitution. The surface tension of the mixtures with the hydroxyl-terminated hyperbranched polyester was slightly increased at higher concentrations of the hyperbranched polymer compared to the surface tension of the pure ester diol. On the other hand, the surface tension of mixtures could be considerably decreased using 1% of hyperbranched polyester polyols partially substituted with short alkyl chains. In that case, the modified hyperbranched polyesters act as surface active agents. On the molecular level, the enrichment of the modified hyperbranched polyester in the surface region was proven by X-ray photoelectron spectroscopy measurements.

Molecular Structure↗
PubMed2003

Fabrication of thermoset polyester microfluidic devices and embossing masters using rapid prototyped polydimethylsiloxane molds.

Plastics are increasingly being used for the fabrication of Lab-on-a-Chip devices due to the variety of beneficial material properties, affordable cost, and straightforward fabrication methods available from a range of different types of plastics. Rapid prototyping of polydimethylsiloxane (PDMS) devices has become a well-known process for the quick and easy fabrication of microfluidic devices in the research laboratory; however, PDMS is not always an appropriate material for every application. This paper describes the fabrication of thermoset polyester microfluidic devices and masters for hot embossing using replica molding techniques. Rapid prototyped PDMS molds are convienently used for the production of non-PDMS polymeric devices. The recessed features in the cast polyester can be bonded to a second polyester piece to form an enclosed microchannel. Thermoset polyester can withstand moderate amounts of pressure and elevated temperature; therefore, the cast polyester piece also can be used as a master for embossing polymethylmethacrylate (PMMA) microfluidic systems. Examples of enclosed polyester and PMMA microchannels are presented, and we discuss the electroosmotic properties of both types of channels, which are important for analytical applications such as capillary electrophoresis.

Chemical Phenomena↗
PubMed2006

Polyester wax: a new embedding medium for the histopathologic study of human temporal bones.

BACKGROUND: Celloidin and paraffin are the two common embedding mediums used for histopathologic study of the human temporal bone by light microscopy. Although celloidin embedding permits excellent morphologic assessment, celloidin is difficult to remove, and there are significant restrictions on success with immunostaining. Embedding in paraffin allows immunostaining to be performed, but preservation of cellular detail within the membranous labyrinth is relatively poor. OBJECTIVES/HYPOTHESIS: Polyester wax is an embedding medium that has a low melting point (37 degrees C), is soluble in most organic solvents, is water tolerant, and sections easily. We hypothesized that embedding in polyester wax would permit good preservation of the morphology of the membranous labyrinth and, at the same time, allow the study of proteins by immunostaining. METHODS: Nine temporal bones from individuals aged 1 to 94 years removed 2 to 31 hours postmortem, from subjects who had no history of otologic disease, were used. The bones were fixed using 10% formalin, decalcified using EDTA, embedded in polyester wax, and serially sectioned at a thickness of 8 to 12 mum on a rotary microtome. The block and knife were cooled with frozen CO2 (dry ice) held in a funnel above the block. Sections were placed on glass slides coated with a solution of 1% fish gelatin and 1% bovine albumin, followed by staining of selected sections with hematoxylin and eosin (H&E). Immunostaining was also performed on selected sections using antibodies to 200 kD neurofilament and Na-K-ATPase. RESULTS: Polyester wax-embedded sections demonstrated good preservation of cellular detail of the organ of Corti and other structures of the membranous labyrinth, as well as the surrounding otic capsule. The protocol described in this paper was reliable and consistently yielded sections of good quality. Immunostaining was successful with both antibodies. CONCLUSION: The use of polyester wax as an embedding medium for human temporal bones offers the advantage of good preservation of morphology and ease of immunostaining. We anticipate that in the future, polyester wax embedding will also permit other molecular biologic assays on temporal bone sections such as the retrieval of nucleic acids and the study of proteins using mass spectrometry-based proteomic analysis.

Adolescent↗
PubMed2004

Strength and knot security of braided polyester and caprolactone/glycolide suture.

BACKGROUND: Appropriate suture selection is necessary in providing mechanical stability to soft tissue reconstructions. Caprolactone/glycolide (Panacryltrade mark) became a popular suture, possessing excellent handling properties; however, clinical observations questioned the knot security of caprolactone/glycolide. Caprolactone/glycolide is still available on many commercial suture anchor systems. This study compared the security of the knots and ultimate tensile strength of braided caprolactone/glycolide suture to that of a commonly used suture material, braided polyester (Ethibondtrade mark). MATERIALS: Suture knots of No. 2 braided polyester suture and No. 2 braided caprolactone/glycolide suture were submersed in a physiologic saline solution and stressed using a continuous (non-cyclic) load, simulating a single maximal loading event in a clinical setting. Continuous loading was done to achieve clinical suture knot failure (3-mm knot slippage), then continued until catastrophic suture failure (suture breakage) occurred. Ten trials of each suture were tested. RESULTS: Force required to cause knot slippage of 3 mm was greater for braided polyester than for braided caprolactone/glycolide (p <. 0001, unpaired Students' t-test). Forces resulting in catastrophic failure were greater for braided polyester than braided caprolactone/glycolide (p = .0284, unpaired Students' t-test). CONCLUSIONS: These data have important implications in the selection of suture materials for repair of soft tissue injuries. In the clinical setting, a single maximal loading event may result in suture failure. These data indicate that braided polyester possesses superior in-vitro mechanical properties and suggest that braided polyester may provide greater security in-vivo than braided caprolactone/glycolide suture.

Dioxanes↗
PubMed1980

[Inflammatory reaction to polyester threads in guinea pigs. III. Reduction of Nitroblue tetrazolium by peritoneal macrophages in vitro].

Peritoneal cells of guinea pigs treated or not by intraperitoneal injection of minced polyester threads have been tested by the NBT test. In phagocytic cells nitroblue tetrazolium (NBT) is reduced to formazan. This is deposited as a dark blue precipitate in the cytoplasm. Changes in reduction capacity have been quantitated by calculation of percentage of macrophages containing formazan deposits, (Tab. 1), and by extraction and photometric evaluation of formazan (Tab. 2). Peritoneal cells incubated with polyester show an increased NBT reduction, which is more apparent with the photometric evaluation. A statistically significant difference in NBT reduction has been found between the peritoneal cells of the guinea pigs treated "in vivo" with polyester and those of the untreated "in vivo" with polyester and those of the untreated animals, whether or not challenged in vitro with polyester threads. These results suggest a change in cell population following polyester treatment.

Animals↗
PubMed2002

Electrokinetic and thermodynamic analysis of the adsorption process of N-cetylpyridinium chloride on polyester fabric.

An electrokinetic and thermodynamic analysis of the adsorption process of N-cetylpyridinium chloride on polyester fabric is described in the present work. The electrokinetic study was performed by means of electrophoretic mobility measurements of the polyester-surfactant system. The most significant result is the increase in electrokinetic potential, zeta, toward more positive values as the surfactant concentration in the dispersion medium is raised. Given the molecular structure of N-cetylpyridinium chloride (N-CP-Cl), which contains a pyridinium group, positively charged, it is feasible that such increase in |zeta| is due to the electrostatic attraction between the carboxyl groups of polyester, ionized at pH 8.5, and the pyridinium group of the surfactant. The uptake of N-CP-Cl by the fiber is experimentally determined at four temperatures: the strong increase in the amount of the surfactant incorporated onto the fiber as the initial concentration of N-CP-Cl is larger shows that the electrostatic attraction between the fiber and the surfactant is the main mechanism of the adsorption of the surfactant onto the fiber. The obtained data on the kinetics and thermodynamics of adsorption of N-cetylpyridinium chloride onto the polyester, standard free energy, enthalpy, and entropy related to the process of adsorption are in accordance with our hypothesis on the mechanisms of adsorption. From a different point of view, the efficient coverage of polyester by N-CP-Cl is also demonstrated by the changes experienced by the surface free energy of polyester upon treatment with N-CP-Cl.

Journal Article↗
PubMed2006

Classical molecular dynamics study of [60]fullerene interactions with silica and polyester surfaces.

This study examines the interaction of neutral and charged fullerenes with model silica and polyester surfaces. Molecular dynamics simulations at 298 K indicate that van der Waals forces are sufficiently strong in most cases to cause physisorption of the neutral fullerene particle onto the surfaces. The fullerenes are unable to penetrate the rigid silica surface but are generally able to at least partially infiltrate the flexible polymer surface by opening surface cavities. The introduction of charge to the fullerene generally leads to an increase in both the separation distance and Work of Separation with silica. However, the charged fullerenes generally exhibit significantly closer and stronger interactions with polyester films, with a distinct tendency to absorb into the "bulk" of the polymer. The separation distance and Work of Separation of C60 with each of the surfaces also depend greatly on the sign, magnitude, and localization of the charge on the particle. Cross-linking of the polyester can improve resistance to the neutral fullerene. Functionalization of the polyester surface (F and OH substituents) has been shown to prevent the C60 from approaching as close to the polyester surface. Fluorination leads to improved resistance to positively charged fullerenes, compared to the unmodified polyester. However, hydroxylation generally enables greater adhesion of charged fullerenes to the surface due to H-bonding and electrostatic attraction.

Journal Article↗
PubMed1997

Sucrose polyester does not inhibit gastric acid secretion or stimulate cholecystokinin release in men.

Replacement of dietary fat by sucrose polyester reduces fat intake. However, little is known about the effects of sucrose polyester on gastrointestinal function. To investigate the effect on gastric acid secretion and on release of cholecystokinin into plasma, we perfused eight healthy male volunteers intraduodenally with sucrose polyester, digestible fat, or saline on separate days in random order. Intraduodenal perfusion of sucrose polyester did not suppress gastrin-stimulated gastric acid secretion (-1.8 +/- 6.8%) whereas digestible fat suppressed gastric acid secretion by 64 +/- 9% (P = 0.001) compared with saline. Sucrose polyester did not affect plasma cholecystokinin concentrations (-12.8 +/- 9.3 pmol.30 min/L) whereas perfusion with digestible fat resulted in a significant increase (31.7 +/- 9.3 pmol.30 min/L, P = 0.017) compared with saline. We conclude that sucrose polyester, in contrast with digestible fat, does not inhibit gastrin-stimulated gastric acid secretion or stimulate release of cholecystokinin.

Adult↗
PubMed1998

The nondigestible fat sucrose polyester does not stimulate gallbladder emptying in humans.

BACKGROUND: We determined the effect of oral ingestion of sucrose polyester, which was approved as a fat replacer in the United States, on gallbladder motility and on the release of cholecystokinin, the hormone that mediates gallbladder emptying. OBJECTIVE: Our objective was to measure effects of sucrose polyester on gallbladder emptying and cholecystokinin release. DESIGN: Eight healthy volunteers (3 men and 5 women) drank 60 mL sucrose polyester, digestible fat, or saline solution in a balanced crossover design on 3 separate days. RESULTS: Mean (+/-SEM) gallbladder emptying, when integrated over time, was low in response to both sucrose polyester (-150 +/- 214 mL x 120 min) and saline solution (-89 +/- 123 mL x 120 min). In contrast, there was marked emptying in response to digestible fat (1069 +/- 253 mL x 120 min). Sucrose polyester did not affect plasma cholecystokinin concentrations (-9.3 +/- 15.0 pmol x 120 min/L), whereas digestible fat resulted in a significant increase (89.5 +/- 44.8 pmol x 120 min/L, P = 0.014) compared with saline solution (-3.0 +/- 13.8 pmol x 120 min/L). CONCLUSIONS: Ingestion of sucrose polyester, in contrast with digestible fat, did not stimulate gallbladder emptying or release of cholecystokinin.

Adult↗
PubMed2003

Sustained off-resonance irradiation collision-induced dissociation of linear, substituted and cyclic polyesters using a 9.4 T Fourier transform ion cyclotron resonance mass spectrometer.

The fragment ions obtained from sustained off-resonance irradiation collision-induced dissociation of linear polyesters, substituted polyesters and cyclic polyesters have been characterized using a 9.4 T Fourier transform ion cyclotron resonance mass spectrometer. Charge-induced and charge-remote fragmentation channels, together with the participation of other nucleophilic groups, are proposed for the substituted polyesters. The linear polyesters were found to fragment at equivalent positions along the polymer chain whereas, under the experimental conditions employed, the cyclic polyester produced a single fragment.

Journal Article↗
PubMed1982

Sensitization capacity of polyester methacrylate in ultraviolet curing inks tested in the guinea pig.

One of the prepolymers used in Ultraviolet (UV) curing ink formulations is acrylated polyester. The prepolymer investigated is a dimethacrylated polyester, thus a saturated polyester terminated with methacrylic groups. In conventional UV-curing coatings the prepolymer commonly used is an unsaturated polyester. Three of six workers with dermatitis from UV-curing inks in printing plants had positive test results from the polyester methacrylate present in the inks used. The sensitizing capacity, performed with the "Guinea pig maximization test", shows polyester or methacrylate to be a moderate sensitizer.

Acrylates↗
PubMed1997

A novel method of tear collection: comparison of glass capillary micropipettes with porous polyester rods.

PURPOSE: To develop a rapid, user-friendly method of tear collection to facilitate tear-protein analysis. METHODS: Tears were collected from a total of 19 normal volunteers without evidence of ocular-surface disease with either porous polyester rods or glass-capillary micropipettes. Tear-collection rate and recovery of two tear proteins, epidermal growth factor (EGF, low abundance) and lactoferrin (LFR, high abundance) were compared between polyester rods and glass-capillary micropipettes. The recovery of LFR and EGF and the stability of these proteins after storage at -70 degrees C were quantitated by specific monoclonal enzyme-linked immunosorbent assay (ELISA). RESULTS: Polyester rods collected tears an average of 3.9-fold faster than glass-capillary micropipettes (p < 0.001). Both methods were comparable in efficacy of protein recovery. The polyester rods demonstrated a trend toward enhanced recovery, but this difference was not statistically significant (p = 0.12, LFR; p = 0.055, EGF). Analysis of the reliability and reproducibility of the tear-collection assay system revealed that ELISA analysis is highly reproducible, but there is significant day-to-day variation in tear-protein levels of both LFR and EGF for a given volunteer. Both LFR and EGF displayed a trend toward enhanced detection by ELISA shortly after freezing at -70 degrees C and slow decay after storage at -70 degrees C for up to 72 and 105 days, respectively. After stimulation of reflex tearing via the nasolacrimal reflex, LFR levels remained relatively constant, whereas EGF levels for most patients declined and then plateaued. CONCLUSIONS: Polyester rods provide a more rapid, user-friendly alternative to glass-capillary micropipettes for the collection and analysis of tear fluid and tear proteins. Polyester rods may have greater clinical utility, facilitating routine analysis of the preocular tear film.

Enzyme-Linked Immunosorbent Assay↗
PubMed2007

Co-immobilization of different enzyme activities to non-woven polyester surfaces.

Co-immobilization was applied to combine complementary enzyme reactions. Therefore, trypsin was co-immobilized together with both, lipase and alpha-amylase, onto the surface of non-woven polyester material. The progress of the immobilization reaction was directly monitored by investigating covalent fixation of the enzymes to the polyester flees using (1)H-MAS-NMR. Co-immobilization of the different types of enzymes to the polyester support showed retained enzymatic activity. However, a competition of binding to the support was observed. Increasing amounts of one type of enzyme reduced the degree of immobilization for the other type. In order to investigate the distribution of trypsin and alpha-amylase on the polyester support, the flees was treated with a mixture of rhodamine isothiocyanate labeled with anti-trypsin antibodies and fluorescein isothiocyanate labeled with anti-alpha-amylase antibodies. Using fluorescence microscopy, the co-immobilization was analyzed by selective excitation of both chromophores at 480 and 530 nm, respectively. In addition, fluorescence spectroscopy was applied by direct labeling of trypsin and lipase prior to co-immobilization to the polyester support. A special prism of plexiglass was constructed, which fit into a 10 x 10 mm fluorescence cuvette in that way that a diagonal plane was formed within the cuvette. The non-woven support was fixed in the cuvette and fluorescence spectra were obtained to characterize the amount of different enzymes linked to the support. Using FRET it was demonstrated that a uniform distribution of the various enzyme species was achieved, where the different enzyme activities are bound on the support in close neighborhood to one another.

Binding, Competitive↗