Water-soluble Polyethylene Glycol Research Articles

Solvent debinding kinetics and sintered properties of injection moulded 316L stainless steel powder

A stainless steel (316L) powder having a median particle size of ∼25 μm was injection moulded using binders composed of polyethylene glycols (PEG) and polymethylmethacrylate (PMMA). The PEG content was leached in water and debinding kinetics studied as a function temperature. At 40°C, the removal of PEG was controlled by dissolution of the polymer in water and by diffusion of water and PEG for leaching time <60 min and >60 min, respectively. Water soluble PEG was completely removed within 180 min and the diffusion mechanism controlled the de-binding process at 60 and 80°C. Sintered properties improved with increased sintering temperature and time. The improvement in mechanical properties was less pronounced for a longer soaking time owing to more grain coarsening.

Study on Elimination of Surface-Exfoliation and Crack of ZrO&lt;sub&gt;2&lt;/sub&gt; Green Body of Gelcasting with Water-Solubility Macromolecule

Ceramic gelcasting has to be performed in nitrogen to avoid surface-exfoliation and crack of the green body. The rapid drying of gelled bodies can cause nonuniform shrinkage. Non-uniform drying in various regions due to the solvent gradient, induces structural and residual stresses which cause defects, such as cracking, warpage and the other malformations. These malformations can be minimized or eliminated via adding a proper amount of water-soluble polymer polyethylene glycol(PEG).This study concentrates attention on dispersion, rheological property and gelation behavior in the new system, The flexural strength and microstructure of ZrO2 green bodies were measured and observed.

Solvent debinding mechanism for alumina injection molded compacts with water-soluble binders

The solvent debinding process has been widely accepted in the ceramic injection molding (CIM) industry process due to its short debinding cycle. However, the organic solvents most adopted in solvent debinding now are flammable, carcinogenic and not environmentally acceptable. For eliminating the use of unsound solvents, water-soluble polyethylene glycol (PEG) is used in this study to modify the pattern of debinding in CIM. The purpose of the investigation was to examine the binder behavior during solvent debinding based on water extraction for a multi-component PEG binder system. Based on the in situ evaluation results of dimensional variations, mercury intrusion data and scanning electron microscope (SEM) observations, possible solvent debinding mechanism for alumina injection molded compacts with water-soluble binders is proposed.

Synthesis and surface activity of polyethylene glycol–maleic anhydride–polydimethylsiloxane polyester surfactants

Abstract A novel series of water-soluble polyethylene glycol (PEG)–silicone polyester surfactants has been prepared by the polymerization of PEG, maleic anhydride, polydimethylsiloxane and fumaric acid. The unique structural features of these surfactants have been confirmed by FTIR, proton nuclear magnetic resonance and elemental analysis. Also, the influences of the PEG segment lengths of PEG–silicone polyesters on the surface tension, wetting power and dispersant properties were investigated. The experimental results indicated that the solution that contained the PEG–silicone polyester surfactants exhibits excellent surface active properties.

EFFECT OF CARRIER TYPES ON THE PHYSICOCHEMICAL AND DISSOLUTION CHARACTERISTICS OF OFLOXACIN SOLID DISPERSION

Solid dispersions of ofloxacin (OFX) and of a number of carriers including chitosan and the water soluble polymers polyethylene glycol (PEG) 4000, PEG 20000, and polyvinylpyrrolidone K- 90 were prepared by solvent evaporation method in order to increase the dissolution of the drug. The solid dispersions were subjected to X-ray diffraction, DSC, and dissolution to characterize their physicochemical and dissolution properties. The results demonstrated a decrease in drug crystallinity at higher amounts of carrier. Dissolution studies indicated that the dissolution rate of OFX was markedly increased in these solid dispersion systems compared with the pure drug. The results also showed that the increase in dissolution rate was higher when the weight fraction of carriers increased. An influence of molecular weight of PEG on OFX dissolution could also be observed. In solid dispersion with 1:9 ratio drug to carrier, PEG 4000 gave highest drug dissolution rate, whereas in 1:1 ratio, chitosan seems to be the best carrier for drug release. It was concluded that chitosan might be the carrier of choice for dissolution enhancement in solid dispersions with high content of drug.

Use of tannin-binding chemicals to assay for tannins and their negative postingestive effects in ruminants

Synthetic polymers such as water-soluble polyvinyl pyrrolidone (PVP), water-insoluble polyvinyl polypyrrolidone (PVPP), and water-soluble polyethylene glycol (PEG) contain sufficient oxygen molecules in a chain to form strong hydrogen bonds with the phenolic and hydroxyl groups in tannins. This review deals with the practical uses of tannin-binding agents, particularly PEG, in tannins assays and for determining the negative effects of tannins on feed intake and digestion in ruminants. A gravimetric method to assay tannins by precipitation with PVPP is specific for tannins and does not require standards. The extractability of tannins from plant tissues can be reduced by drying samples at temperatures above 50°C and is dependent on many other factors, such as content and types of plant proteins. Therefore, it is not feasible to recommend a single, optimal protocol for all plant samples. A method to assay tannins which is based on measuring the amount of binding of PEG to plant samples was shown to be simple and accurate. It can also overcome some of these extractability problems. The following biological effects of tannins were investigated in studies where tannin anti-nutritional effects were partially or completely neutralised by varying levels of PEG supplementation. (1) Effects on appetite: the negative effects of tannins on appetite can occur in the short-term (within 20–60 min) and the long-term (days and weeks). Astringency and adverse postingestive influences of tannins on the epithelium of the oral cavity and the foregut cause short-term effects on food intake. Long-term effects can be related to reduction in the concentration of ammonia and volatile fatty acids (VFA) in rumen fluids, which can in turn serve as metabolic cues for deficiency of nitrogen (ammonia), energy (VFA), or both. (2) Effects on digestion: increasing content of tannins in foliage can be associated with an increase in bound protein and with reduced degradation rate of the degradable matter in the rumen, but there is no corresponding increase of the non-degradable fraction. Consequently, organic matter, protein, and cell wall digestibility are inversely related to tannin concentrations. (3) Inducing digestive responses: if a significant amount of tannins reach the duodenum, they may markedly reduce the intestinal activity of pancreatic enzymes (trypsin and amylase) and amino acids absorption from the intestine. Condensed tannins can also reduce the content of fluid and particulate matter in the rumen, accelerate the passage of liquid from the abomasum, and delay the passage of digesta in the intestine. The overall effect is a delay in the passage of fluid and particulate matter throughout the entire gastrointestinal tract. It is hypothesised that these responses are largely the consequence of the interaction of tannins with digestive enzymes and the epithelium lining the digestive tract.

Effect of water-soluble polymers on the state of aggregation, vesicle size, and phase transformations in mixtures of phosphatidylcholine and sodium cholate

The state of aggregation and the steady-state size of mixed aggregates made of phospholipids and surfactants are both determined by the surfactant/lipid ratio in the mixed aggregates (Re). Water-soluble polymers, such as dextrans and polyethylene glycols (PEGs) of different molecular weights, induce reversible aggregation of phospholipid vesicles, mostly due to dehydration of the vesicle surface and depletion forces, and only at much higher concentrations, PEGs (but not dextran) also induce irreversible size growth of the vesicles. Here we show that the water-soluble polymers dextrans and PEGs do not affect the vesicle-micelle phase boundaries in mixtures of phosphatidylcholine and the anionic surfactant sodium cholate. By contrast, these polymers affect markedly the steady-state size of cholate-containing vesicles. As compared with pure phosphatidylcholine vesicles, the cholate-containing vesicles have a lower tendency to undergo polymer-induced aggregation, probably due to the electrostatic repulsion between the negatively charged vesicles, but a higher tendency to undergo irreversible size growth at relatively low polymer concentrations. Such irreversible size growth was observed not only for PEG but also for dextran, which in the absence of cholate is incapable of inducing vesicle size growth. These findings are consistent with the prevailing concept that the polymer-induced size growth is due to the effect of large structural fluctuations in the bilayers of deformed aggregated vesicles, the surface of which is dehydrated by the polymer. The presence of cholate in the bilayers at sufficiently high concentrations induces such fluctuations, yielding irreversible size growth within the clusters of dehydrated vesicles formed upon mixing with polymers.

Rectal absorption of omeprazole from suppositories in rabbits

Rectal absorption of omeprazole, a proton pump inhibitor, from suppositories was studied in rabbits. The suppositories were prepared by the conventional melting method with two types of bases, water-soluble polyethylene glycol (PEG) 4000 and oil-soluble Witepsol H15 bases, and administered intrarectally (ir) to rabbits at a dose of 10 mg omeprazole/kg. The plasma omeprazole concentration-time profiles of the two suppositories were compared with those following intravenous (iv) administration of the same dose. There were no significant differences between the two suppositories in bioavailabilities and peak plasma concentrations (Cmax). Bioavailabilities and Cmax of PEG- and Witepsol suppositories were 30.3 and 33.9%, and 7.0 and 5.6 μg/ml, respectively. However, PEG suppository showed significantly (P<0.05) shorter time to reach peak plasma concentration (Tmax), mean absorption time (MAT) and mean residence time in the plasma (MRT) than Witepsol suppository. The Tmax MRT and MAT were 25.0, 83.0 and 38.5 min for PEG suppository, but were 90.0, 122.5 and 78.0 min for Witepsol suppository, respectively. These differences between the two suppositories could be explained by the difference in the in vitro dissolution rates between the suppositories. The dissolution of omeprazole from PEG suppository was reportedly much faster than that from Witepsol suppository. It suggests that plasma profiles of omeprazole, especially Cmax, MAT and MRT, could be controlled by modifying thein vitro dissolution rate of the drug from the suppositories. Above results suggest that rectal suppository is worth developing as an alternative dosage form of omeprazole to the conventional oral preparations which need sophisticated treatments, such as enteric coating, to prevent acid degradation of the drug in the stomach fluid.

Probing alamethicin channels with water-soluble polymers. Size-modulated osmotic action

Contrary to expectations based on heightened solution viscosity, alamethicin channels appear to speed up in the presence of water soluble polyethylene glycols (PEGs) and dextrans. Specifically, added polymers reduce the probabilities of transition to higher-conductance states but do not change channel lifetimes. They thereby shorten the duration of current "bursts." These modified probabilities and kinetics reveal the action of polymer osmotic stress to suppress channel formation. The osmotic action of large, fully excluded polymers shows that some 3,000 A3 of water are taken up by the channel from the solution upon each transition to an adjacent higher-conductance state. The partial osmotic action of incompletely excluded polymers reveals the extent of exclusion for different-size polymers. The partial exclusion thus measured agrees remarkably well with estimates using data on reduction of single-channel conductance by current-impeding polymers. One can relate the degree of each polymer's exclusion to its size and to the radius of the channel pore.

Microwave-accelerated cytochemical stains for the image analysis and the electron microscopic examination of light microscopy diagnostic slides.

Recent studies in our laboratories have shown how microwave (MW) irradiation can accelerate a number of tissue-processing techniques, especially staining, to aid in the preparation of single specimens on glass microscope slides or coverslips for examination by light microscopy (and electron microscopy, if required) for diagnostic purposes. Techniques have been developed, which give permanently stained preparations, that can be studied initially by light microscopy, their areas of interest mapped, and computer-automated image analysis performed to obtain quantitative information. This is readily performed after MW-accelerated staining with silver methenamine by the Giammara-Hanker PATS or PATS-TS reaction. This variation of the PAS reaction gives excellent markers for specific infectious agents such as lipopolysaccharides for gram-negative bacteria or mannans for fungi. It is also an excellent stain for glycogen and basement membranes and an excellent marker for type III collagen or reticulin in the endoneurium or perineurium of peripheral nerve or in the capillary walls. Our improved MW-accelerated Feulgen reaction with silver methenamine for nuclear DNA is useful to show the nuclei of bacteria and fungi as well as of cells they are infecting. Improved coating and penetration of tissue surfaces by thiocarbohydrazide bridging of ruthenium red, applied under MW-acceleration, render biologic specimens sufficiently conductive for SEM so that sputter coating with gold is unnecessary. The specimens treated with these highly visible electron-opaque stains can be screened with the light microscope after mounting in polyethylene glycol (PEG) and the structures or areas selected for EM study are mapped with a Micro-Locator slide. After removal of the water soluble PEG the specimens are remounted in the usual EM media for scanning electron microscopy (SEM) or transmission electron microscopy (TEM) study of the mapped areas. By comparing duplicate smears from areas of infection, such as two coverslips of buffy coat smears of blood from a patient with septicemia, the microorganisms responsible can occasionally be classified for antimicrobial therapy long before culture results are available; gram-negative bacteria are positive with the Giammara-Hanker PATS-TS stain, and gram-positive bacteria are positive with the SIGMA HT40 Gram stain. The gram-positive as well as gram-negative bacteria are both initially stained by the crystal violet component of the Gram stain. The crystal violet stain is readily removed from the gram-negative (but not the gram-positive) bacteria when the specimens are rinsed with alcohol/acetone. If this rinse step is omitted, the crystal violet remains attached to both gram-negative and gram-positive bacteria. It can then be rendered insoluble, electron-opaque, and conductive by treatment with silver methenamine solution under MW-irradiation. This metallized crystal violet is a more effective silver stain than the PATS-TS stain for a number of gram-negative spirochetes such as Treponema pallidum, the microbe that causes syphilis.

Osmotically powered drug-delivery pump using semipermeable hollow fibre.

For the long-term continuous administration of drugs, a new osmotically powered infusion pump using semipermeable hollow fibres has been designed. Sufficient osmotic pressure, of about 980 mmHg, as a driving force the pump was obtained when hypertonic solution made of water-soluble polyethylene glycol (PEG) with 120 gl−1 was used. The prototype pump designed consist of: (i) a drug chamber; (ii) a chamber filled with PEG solution; (iii) a flow-control ring and clamps for flow-adjustment; (iv) a diaphragm bag filled with distilled water. In this pump eight values of the delivery rates ranging from 0 to 20 μl min−1 can be easily adjusted in 2·86 μl min−1 steps by choosing the combinations of three bundles of hollow fibres using the clamps. Fairly good pump charactersitics, including stability for long-term continuous infusion tested in vitro, were obtained. This pump seems to be practically useful for the infusion-therapy of diabetic and hypertensive patients and those with other diseases.

Characterization and molecular weight determination of water-soluble polyethylene glycol oligomers using open-tubing liquid chromatography—mass spectrometry

Characterization and molecular weight determination of water-soluble polyethylene glycol oligomers using open-tubing liquid chromatography—mass spectrometry

Separations of water soluble polyethylene glycol oligomers on phenyl‐bonded phase using low wavelength UV detection at 190 nm

Separations of water soluble polyethylene glycol oligomers on phenyl‐bonded phase using low wavelength UV detection at 190 nm

Synthesis, characterization, and in vivo disposition of iodinatable polyethylene glycol derivatives: Differences in vivo as a function of chain length

AbstractA series of iodinatable water soluble polyethylene glycol (PEG) derivatives were prepared for use as model hydrophilic drugs. Polyethylene glycol diamine 6000 was coupled to methyl p‐hydroxybenzimidate, and PEG 1900‐ and PEG 5000‐monomethyl ethers were coupled to tyramine and histamine. The derivatives underwent facile iodination with the chloramine‐T reaction and were stable under a wide range of conditions. The larger derivatives showed rapid renal clearance, but the 1900 MW compounds underwent significant clearance via the bile.

Infiltrating and Embedding Tissues with Mixtures of Polyethylene Glycols and Polyvinylacetate Resins

The use of water-soluble polyethylene glycol polymers (Carbowax, Hydrowax) as embedding media can be extended and facilitated by incorporating a water insoluble polyvinylacetate resin, AYAF (Union Carbide Co.). A combination of 7.5% resin added by heating to a 3:1 mixture of polyethylene glycols 1540 and 4000 gives blocks which may be cut at 2-3 μ. Sections can be floated and properly expanded on an ordinary water bath in a manner which may be impossible with Carbowax alone because of section fragility. This may require judicious adjustment of surface tension by the prior addition of minute quantities of the wax. On water, polyethylene glycol dissolves out of tissues, which remain supported by the resin. After attachment to albumen-coated slides, residual resin may, at option, be removed by a 1-2 min immersion in methyl alcohol without visible impairment of fat content. Abopon is used for mounting. The method appears suitable for the study of intracellular lipids, particularly in tissues which cannot be c...

Concurrent measurement, in unanaesthetized rats, of intestinal transport and fat absorption from the lumen.

A test meal containing emulsified coconut oil mixed with water soluble polyethyleneglycol (PEG) of high mol. wt. was given to rats by gastric intubation. At intervals up to 5 hr. after the meal, rats were killed and the amounts of PEG and fat recoverable from the stomach, small intestine and coæcum were measured. PEG was not absorbed from, nor broken down in, the intestine and left the stomach at the same rate as the emulsified fat. It was, therefore, a suitable reference substance. With a test meal of constant volume, 4 ml., increasing doses of fat, 0·25, 0·5 and 140 ml., decreased the rate of stomach emptying and of propulsion of PEG through the small intestine. The rate of fat absorption was limited by the decreasing rate of stomach emptying but there was no indication that the absorptive capacity of the small intestine had been saturated. The ratio of recovery of fat: PEG in successive segments of the small intestine indicated that fat was absorbed chiefly in the distal half. This was probably due to rapid propulsion of material through the proximal half rather than to any lack in capacity for fat absorption proximally.

Substances in the calf alimentary tract interfering in the determination of polyethylene glycol.

THE water-soluble polyethylene glycols of high molecular weight promise to be of great value as reference substances in the study of exchange processes in the alimentary canal. In particular, a mixture of such polymers with a molecular weight of about 4,000 appears to pass largely unchanged and unabsorbed through the alimentary tract in sheep, humans, hens, cows and calves1,2. Polyethylene glycol can readily be determined turbidimetrically, once interfering substances have been removed, after precipitation with trichloracetic acid solution containing barium chloride2,3. We found, in agreement with Hyden3, that an initial treatment with barium hydroxide, zinc sulphate and barium chloride sufficed to remove interfering substances (mainly protein and sulphate) from milk and from calf rumen contents, urine and faeces extracts. The method failed, however, in two respects when it was applied to samples from fistulas in the small intestines of milk-fed calves.

Water-soluble Embedding Materials for Botanical Microtechnique

A method employing water-soluble polyethylene glycols and solid materials of the same type of structure called “Carbowaxes” has been developed for the preparation of slides of plant materials. The specimens are killed and fixed in the usual manner and are then run up in dilutions of polyethylene glycol until they are completely dehydrated in 100 per cent glycol and are then embedded in the solid “Carbowax” matrix. Sectioning and mounting of the sections on glass slides is described and staining techniques are explained.