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At least 487 records · Page 27Linked to original sources
PubMed2001

Polyvinyl alcohol as an immobilization matrix--a case of gold biosorption.

The use of polyvinyl alcohol (PVA) as a matrix for cell immobilization has been extensively studied in various biological systems. However, its suitability has not been reported in biosorption studies where inactivated cells are used as biosorbents. In this work, PVA and alginate as immobilization matrices (for the biosorption of gold by a fungal biomass) were investigated by examining their physical and chemical properties. Compared to alginate gels, PVA gels were shown to be more resistant to mechanical abrasion, and more stable over a wide pH range. Although the PVA matrix did not affect the equilibrium uptake in gold biosorption studies, the time required to attain a removal of 80% of the initial metal concentration was 1.7 times that of the freely suspended biosorbent. This contrasts with the alginate immobilized biosorbent which required an increase of well over ten times the duration to attain the same removal efficiency. Results indicated that PVA gels conferred a lower mass transfer resistance than alginate gels. Gold biosorption by the PVA-immobilized fungi followed the commonly used Langmuir and Freundlich adsorption isotherm models although the former gave a better fit. The uptake of gold was dependent on the initial gold concentration and the biomass loading. Using a fungal biosorbent and gold ions as the model system, the results demonstrate the potential in the use of the PVA as a cell immobilisation matrix for biosorption studies.

Absorption↗
PubMedDate not supplied

Polyvinyl chloride-based membranes for flow injection analysis of quinine in beverages.

Potentiometric response characteristics were evaluated for quinine selective sensors based on a lipophilic ion-exchanger potassium tetrakis[3,5-bis(trifluoromethylphenyl)]borate (PTFB) immobilized together with plasticizing solvents in polyvinyl chloride membranes. The use of dioctyl phthalate (DOP), 2-nitrophenyl phenyl ether (NPPE), and bis(2-ethylhexyl)adipate (BEHA) plasticizers produced good quality quinine sensors that were sensitive and fast responding, and exhibited near Nernstian responses when used as batch-sensors. These membranes were further tested in a wall-jet flow-through potentiometric flow injection analysis (FIA) detector. Quinine sensors containing BEHA were the most suitable membrane, with no noticeable differences in sensitivity even after 5 h of continuous exposure to solutions. Interference by foreign species such as alkali, alkaline earth metal ions, sugars, and sodium benzoate was minimal in either the batch-mode (log selectivity coefficients <-2.60) or as FIA detector. When the FIA method was used, recoveries averaged 99.70% from mineral water samples spiked with 16.22 and 162.20 ppm quinine. Results for determination of quinine in other drinks such as carbonated (64.88 and 71.37 ppm) and bitter lemon drinks (55.15 ppm) agreed with those of the manufacturer's claimed values of <68, <81, and 51 ppm, respectively. With a sample throughput of 50 samples/h under optimized flow conditions, the method can be routinely used to monitor quinine in such samples.

Beverages↗
PubMed2001

Degradation of polyvinyl alcohol (PVA) by homogeneous and heterogeneous photocatalysis applied to the photochemically enhanced Fenton reaction.

The reaction mechanism of the oxidative degradation of polyvinyl alcohol (PVA) by the photochemically enhanced Fenton reaction was studied using a homogeneous (Fe2+(aq) + H2O2) and a heterogeneous reaction system (iron(III)-exchanged zeolite Y+ H2O2). In the homogeneous Fenton system, efficient degradation was observed in a batch reactor, equipped with a medium pressure mercury arc in a Pyrex envelope and employing 80% of the stoichiometric amount of H2O2 required for the total oxidation of PVA and a concentration ratio as low as I mole of iron(II) sulfate per 20 moles of PVA sub-units (C2H40). Model PVA polymers of three different molecular weights (15,000, 49,000 and 100,000 g mol(-1)) were found to follow identical degradation patterns. Strong experimental evidence supports the formation of supermacromolecules (MW: 1-5 x 10(6) g/mol) consisting of oxidized PVA and trapped iron(III) at an early reaction stage. Low molecular weight intermediates, such as oxalic acid, formic acid or formaldehyde were not found during PVA degradation in the homogeneous Fenton system, and we may deduce that the manifold of degradation reactions is mainly taking place within the super-macromolecules from which CO2 is directly released. However, in the heterogeneous Fenton system, the reaction behavior was found to be distinctly different: a decrease of the molecular weights of all three tested monodisperse PVA samples was observed by the broadening of the GPC-traces during irradiation, and oxalic acid was formed. The results lead to the mechanistic hypothesis that during the heterogeneous Fenton process, the cleavage of the PVA-chains may occur at random positions, the reactive centres being located inside the iron(III)-doped zeolite Y photocatalysts.

Hydrogen Peroxide↗
PubMed2001

The application of polyvinyl alcohol in the technology of modern drug form.

The following presentation is a review of literature related to application of nonionic polymer, polyvinyl alcohol, in the technology of modern drug form. The review contains the description of physical-chemical properties of this polymer, such as hydrolysis degree, solubility, swelling capacity. Each characteristic is followed by the description of its application as a therapeutical substance carrier in the pharmacy.

Administration, Cutaneous↗
PubMed1999

A prospective clinical evaluation of electronically mixed polyvinyl siloxane impression materials: results from the prosthetic "SuperStudy"--a consumer evaluation.

Polyvinyl siloxane (PVS) impression materials incorporating a polyether carbosilane wetting agent and mixed with an electronic mixing system (Pentamix) were clinically compared with traditionally delivered (i.e., automixed) PVS impression materials during routine use by 1,505 general and specialized dental practitioners evaluating more than 30,000 impressions. Each study participant selected 20 patients and used standard tooth-preparation procedures appropriate to the therapy required, supplied specific data on each case, and ultimately evaluated the marginal detail, fit, and success of the final restorations. The areas requiring evaluation upon completion of the final restorations were ranked between "excellent," "good," "poor," and "remake needed," among users of the PVS materials with the electronic mixing system. About 80% of the respondents rated the Pentamix system as easier to mix and deliver than the gun or hand-mixed systems and two thirds said it was faster to mix. The system also received high scores for hygienic delivery, ease of mixing, and clean-up.

Consumer Behavior↗
PubMed1975

[Prophylaxis of influenza with a clathrate of polyvinyl alcohol with iodine and boric acid].

Taking advantage of the viricdal and antimicrobial properties of the clathrate of polyvinyl alcohol with iodine and boric acid (PVAIB) and taking into account successful results obtained during the action in 1969, it was used again as a preventive measure during the epidemy of influenza in Poznań at the turn of 1971/1972. In this period, the prophylactic action included 1477 persons who recieved the drug as nasal drops in 30 gram bottles. After the extinction of influenza we checked 459 persons who had taken the drug regularly, according to medical prescription. Out of this group, only 23 persons or 5% fell ill with influenza. If compared with general morbidity, this rate proved to be four times smaller.

Administration, Intranasal↗
PubMed2002

Comparison among Op-site, polyvinyl chloride film and tulle gauze in the treatment of skin graft donor sitet.

A prospective analytic study was performed at the Division of Plastic and Reconstructive Surgery, Department of Surgery, King Chulalongkorn Memorial University Hospital and the Department of Surgery, Chiang Mai University Hospital to compare among Polyvinyl chloride film (PVC film), Op-site and tulle gauze in the treatment of skin graft donor site. From October 1998 to January 2000, 81 donor sites in the same number of patients were treated by three different methods; tulle gauze (26 patients), Op-site (27 patients) and PVC film (28 patients). Each wound was followed until it was completely healed and visual analogue scale was used for pain evaluation. Donor site dressed with PVC film had a healing time of 10.44 days which was not different from Op-site (10.54 days) but significantly faster (p<0.001) than tulle gauze (17.84 days). Pain as measured with visual analogue scale in the group of PVC film (1.48) was not different from Op-site (1.34) but significantly less than (p<0.001) tulle gauze (5.45). There was no difference in the rate of infection between each group. In conclusion, the authors found no difference between Op-site and PVC film in healing time and pain. Both of them were better than tulle gauze. The results demonstrate the usefulness of PVC film as a donor site dressing as it promises relatively rapid healing, less pain and is inexpensive.

Adolescent↗
PubMed2000

[Preparation and evaluation of polyvinyl pyrrolidone-coated columns based on sol-gel chemistry for capillary electrophoresis].

Polyvinyl pyrrolidone(PVP) coating techniques based on sol-gel chemistry was investigated in this article. Multiple-step coating and single-step coating methods were developed and the coating conditions(molar ratios of MAPS to 0.1 mol/L HCl, reaction times and concentration of PVP) were selected. Electroosmosis mobility and column efficiency were used as the evaluating parameters for coated capillary columns. For multiple-step coating, the optimal sublayer sol solution was obtained by adding 0.1 mol/L hydrochloric acid to MAPS(molar ratio, 1:1) and reacted at room temperature for 2 hours. The best PVP mass concentration was 40 g/L in alcohol. For single-step coating, the sol-gel solution was obtained by mixing the following ingredients: (a)MAPS, (b) 8% PVP alcohol solution and (c) 0.1 mol/L hydrochloric acid in 1:1 molar ratio to MAPS. The mixture was kept at room temperature for 2 hours. Proper amounts of 100 g/L ammonium persulfate and 10% (V/V) N, N, N', N'-tetramethylethylenediamine were then added. The mixture was mixed ultrasonically, then centrifuged at 4,000 r/min for 5 min. The upper clean sol-gel solution was transferred into another clean vial for coating capillary column. The reproducibility of migration times and efficiencies of single-step-coated capillary was better than that of multiple-step-coated capillary. Single-step-coating method was very effective and easy. It can fit the needs in experimental work. Coating techniques based on sol-gel chemistry are prospective but still need to be further developed.

Electrophoresis, Capillary↗
PubMed1992

Stability and sorption of FK 506 in 5% dextrose injection and 0.9% sodium chloride injection in glass, polyvinyl chloride, and polyolefin containers.

The effects of the diluent, the storage container, light, and infusion through various types of tubing on the stability and sorption of FK 506 were studied. Solutions of FK 506 in 0.9% sodium chloride injection or 5% dextrose injection were stored at room temperature (24 +/- 2 degrees C) in glass i.v. bottles, polyvinyl chloride (PVC) minibags, and polyolefin containers. FK 506 solution in 0.9% sodium chloride injection was stored in plastic syringes at room temperature and either exposed to normal room light or stored in the dark. FK 506 solution in 5% dextrose injection was placed in plastic syringes and infused through PVC anesthesia extension tubing, PVC i.v. administration set tubing, and fat emulsion tubing over a two-hour period. The infused samples and samples collected from the containers and syringes at intervals up to 48 hours were analyzed for FK 506 concentration by high-performance liquid chromatography. FK 506 concentrations remained greater than 90% of initial concentration for admixtures in 5% dextrose injection stored in glass bottles for 48 hours and for admixtures in 5% dextrose injection or 0.9% sodium chloride injection stored in polyolefin containers for 48 hours. No change in concentration was measured for admixtures in 0.9% sodium chloride injection stored in plastic syringes, and exposure to light did not affect the stability of FK 506 solution. No substantial change in concentration occurred in FK 506 solution in 5% dextrose injection infused through PVC anesthesia extension tubing, PVC i.v. administration set tubing, or fat emulsion tubing. FK 506 admixtures prepared with 5% dextrose injection or 0.9% sodium chloride injection should be stored in polyolefin containers. If polyolefin containers are not available, solutions should be prepared with 5% dextrose injection and stored in glass bottles.

Adsorption↗
PubMed1992

[Modification of drug mutagenicity by their immobilization. Effect of prostatilen immobilized in polyvinyl alcohol in mice].

Mutagenic drug effect of prostatilen and the possibility of modification were analysed in the sperm head anomalies (SHA) and the bone marrow cell aberrations (CA) tests in Mus musculus. It was found that intraperitoneal injection of 2.5 micrograms of prostatilen induced no significant increase in SHA and CA frequencies, the dose of 5 micrograms inducing both SHA and CA. Ultrafiltration of prostatilen led to decrease in its mutagenicity in the SHA test. Immobilization of the drug (5 and 10 micrograms) in polyvinyl alcohol reduced SHA and CA frequencies, the former decreasing to the control level.

Animals↗
PubMed2004

Ester synthesis catalyzed by Mucor miehei lipase immobilized on magnetic polysiloxane-polyvinyl alcohol particles.

Mucor miehei lipase was immobilized on magnetic polysiloxane-polyvinyl alcohol particles by covalent binding with high activity recovered. The performance of the resulting immobilized biocatalyst was evaluated in the synthesis of flavor esters using heptane as solvent. The impact on reaction rate was determined for enzyme concentration, molar ratio of the reactants, carbon chain length of the reactants, and alcohol structure. Ester synthesis was maximized for substrates containing excess acyl donor and lipase loading of 25 mg/mL. The biocatalyst selectivity for the carbon chain length was found to be different concerning the organic acids and alcohols. High reaction rates were achieved for organic acids with 8 or 10 carbons, whereas increasing the alcohol carbon chain length from 4 to 8 carbons gave much lower esterification yields. Optimal reaction rate was determined for the synthesis of butyl caprylate (12 carbons). Esterification performance was also dependent on the alcohol structure, with maximum activity occurring for primary alcohol. Secondary and tertiary alcohols decreased the reaction rates by more than 40%.

Alcohols↗
PubMedDate not supplied

[Immobilization of champagne yeasts by inclusion into cryogels of polyvinyl alcohol for preventing cell escape from carrier matrix].

Wine champagnizing, a process involving the use of champagne yeasts immobilized by inclusion into cryogels of polyvinyl alcohol, has been studied. Treatment of yeast cells with the autoregulatory factor d1 was proposed as a means of preventing the cell escape from the carrier matrix. Such a treatment inhibited growth and proliferation processes in yeasts cells, without affecting the activity of fermentation; the resulting champagne had the same organoleptic and chemical characteristics as its counterparts obtained using traditional techniques.

Blood Proteins↗
PubMed2003

Inhibition of membrane Na(+)-K+ Atpase of the brain, liver and RBC in rats administered di(2-ethyl hexyl) phthalate (DEHP) a plasticizer used in polyvinyl chloride (PVC) blood storage bags.

Significant amounts of di(2-ethylhexyl) phthalate (DEHP) leach out into blood stored in DEHP plasticized polyvinyl chloride (PVC) bags resulting in the exposure of recipients of blood transfusion to this compound. The aim of this study was to find out whether DEHP at these low levels has any effect on the activity of membrane Na(+)-K+ ATPase, since a decrease in this enzyme activity has been reported to take place in a number of disorders like neurodegenerative and psychiatric disorders, coronary artery disease and stroke, syndrome-X, tumours etc. DEHP was administered (ip) at a low dose of 750 microg/100 g body weight to rats and the activity of membrane Na(+)-K+ ATPase in liver, brain and RBC was estimated. Histopathology of brain, activity of HMG CoA reductase (a major rate limiting enzyme in the isoprenoid pathway of which digoxin, the physiological inhibitor of Na(+)-K+ ATPase is a product), intracellular concentration of Ca2+ and Mg2+ in RBC (which is altered as a result of inhibition of Na(+)-K+ ATPase) were also studied. (In the light of the observation of increase of intracellular Ca2+ load and intracellular depletion of Mg2+ when Na(+)-K+ ATPase is inhibited). Histopathology of brain revealed areas of degeneration in the rats administered DEHP. There was significant inhibition of membrane Na(+)-K+ ATPase in brain, liver and RBC. Intracellular Ca2+ increased in the RBC while intracellular Mg2+ decreased. However activity of hepatic HMG CoA reductase decreased. Activity of Na(+)-K+ ATPase and HMG CoA reductase, however returned to normal levels within 7 days of stopping administration of DEHP. The inhibition of membrane Na(+)-K+ ATPase activity by DEHP may indicate the possibility of predisposing recipients of transfusion of blood or hemodialysis to the various disorders mentioned above. However since this effect is reversed when DEHP administration is stopped, it may not be a serious problem in the case of a few transfusion; but in patients receiving repeated blood transfusion as in thalassemia patients or patients undergoing hemodialysis, possibility of this risk has to be considered. This inhibition is a direct effect of DEHP or its metabolites, since activity of HMG CoA reductase, (an enzyme which catalyses a major rate limiting step in the isoprenoid pathway by which digoxin, the physiological inhibitor of Na(+)-K+ ATPase is synthesized) showed a decrease.

Animals↗
PubMed2004

Preparation of naltrexone hydrochloride loaded poly (DL-lactide-co-glycolide) microspheres and the effect of polyvinyl alcohol (PVA) as surfactant on the characteristics of the microspheres.

The aim of this study was to investigate the effect of the surfactant properties of polyvinyl alcohol (PVA) in enhancing the yield of small size microspheres. Naltrexone microspheres were prepared by solvent-solvent extraction evaporation process. PVA of various concentrations were added into the aqueous phase prior to the mixing process. The addition of PVA was expected to influence the shape, size distribution, drug loading and drug release profile. The results indicated that it is desirable to increase the weight fraction of the microspheres with size range below 106 mm for the highest possible yield.

Delayed-Action Preparations↗
PubMed2004

A study of polyvinyl alcohol-hydrogel (PVA-H) artificial meniscus in vivo.

The importance of knee meniscus function is now recognized, and the treatment of meniscus injury has been changing from resection to repair. However, depending on the type of injury, meniscectomy sometimes cannot be avoided. In such case, it is important to anticipate the future problem of degenerative change or osteoarthrosis in knee joint. In future, auto-graph using regenerative meniscus will be developed by tissue engineering. However, even if it will be possible, considering the healing period, the young athlete with severe meniscus injury may select meniscectomy in order to return to sports life as early as possible avoiding the long immobilization or declining sports skill. In consideration of the prognosis and circumstances in such patients, we need a artificial meniscus for salvage. To assess further the use of polyvinyl alcohol-hydrogel (PVA-H) artificial meniscus, we performed some mechanical tests about PVA-H and animal experiment. In mechanical tests, we found that a high water content PVA-H showed viscoelastic behaviour similar to that of human meniscus. Moreover, the frictional coefficient of PVA-H against natural articular cartilage was also effective. In the animal experiment using rabbits, the lateral meniscus was replaced with an artificial meniscus in one knee side and lateral meniscectomy was performed in another knee side of each rabbit. We have already reported the results up to 1 year after operation, present study investigated the results in postoperative 1.5 years. In the results, the articular cartilage state of knee joint implanted PVA-H meniscus was good even after 1.5 years, while OA change progressed in meniscectomy knee joint. In addition, neither wear nor breakage of PVA-H was observed. These results proved that an artificial meniscus using a high water content PVA-H can compensate for meniscal function and might be clinically applicable.

Animals↗
PubMedDate not supplied

Embolic effects of superabsorbent polymer microspheres in rabbit renal model: comparison with tris-acryl gelatin microspheres and polyvinyl alcohol.

PURPOSE: We have developed a spherical embolic agent, superabsorbent polymer microspheres (SAP-MS). The aim of this study was to examine the embolic effects of SAP-MS in comparison with polyvinyl alcohol (PVA) particles and tris-acryl gelatin microsphere (Embosphere Microsphere; EM) in a rabbit renal model. MATERIALS AND METHODS: The right kidneys of nine rabbits were embolized with the given agents: PVA (180-300 microm) (n=3), EM (100-300 microm) (n=3), and SAP-MS (106-150 microm) (n=3). The embolized kidneys were evaluated by angiography and histology after one week. RESULTS: Renal artery occlusion and prominent coagulative necrosis were confirmed regardless of agent. PVA aggregated in the proximal vessels with tiny fragments migrating into glomeruli. Both EM and SAP-MS traveled distally up to the interlobular artery level, and a single particle achieved cross-sectional vessel occlusion. SAP-MS was markedly swollen, deformed, and conformed to the vessel lumen compared with the constantly spherical EM. Mild perivascular reaction was seen with both microspheres. CONCLUSION: SAP-MS resulted in targeted end-organ infarction in the rabbit renal model and showed different mechanical properties from other agents.

Acrylic Resins↗
PubMed1992

Modulation of angiotensin II binding affinity by allosteric interaction of polyvinyl sulfate with an intracellular domain of the DuP-753-sensitive angiotensin II receptor of bovine adrenal glomerulosa.

Angiotensin II (AII) is an important regulator of aldosterone secretion by adrenal glomerulosa cells. All interacts with a specific receptor coupled to a guanine nucleotide-binding protein that controls the activity of phospholipase C. Recently, novel All nonpeptide antagonists (DuP-753 and PD-123319) have been shown to discriminate between two subclasses of All receptors in many different tissues. Our studies confirmed that 125I-All specifically labeled two classes of binding sites for All in a membrane preparation of bovine adrenal glomerulosa cells. The first class (DuP-753 sensitive) represented approximately 85% of the total binding sites for All and possessed a high affinity (IC50 of 92.9 +/- 19.5 nM) for DuP-753. PD-123319 did not have any effect on 125I-All binding to this site. The second class of binding sites was more sensitive to PD-123319, with an IC50 of 6.9 +/- 3.7 nM, and had a much lower affinity for DuP-753 (IC50 around 10 microM). The two classes of receptors had different affinities for All. All showed an affinity around 2 nM for All type 1 receptor (AT1)(DuP-753 sensitive) and a higher affinity, around 0.3 nM, for All type 2 receptor (AT2) (PD-123319 sensitive). All-induced steroidogenesis was completely abolished in the presence of 3 microM DuP-753, indicating that this activity was mediated through a DuP-753-sensitive receptor. We also found that polyvinyl sulfate (PVS), a polyanion, could partly inhibit the binding of 125I-All to bovine adrenal glomerulosa cell membranes, with half-maximal efficiency at 17.3 +/- 8.2 nM. The inhibitory effect of PVS was selective for AT1. The inhibitory effect of PVS was due to a change in the affinity state of the receptor. Unexpectedly, PVS had no effect on All-induced steroidogenesis or on All binding to intact bovine adrenal glomerulosa cells. However, the inhibitory effect of PVS on All binding was recovered after permeabilization of cells. Direct interaction of polyanions with AT1 was suggested by the capacity of solubilized photoaffinity-labeled 125I-AT1 to adsorb to heparin-agarose gels. The adsorption of 125I-AT1 to heparin-agarose was inhibited by prior incubation of solubilized receptor with heparin or PVS. These results suggest that All-induced steroidogenesis is mediated by a DuP-753-sensitive receptor and that PVS decreases the affinity of this receptor by interacting with an intracellular domain (possibly the positively charged domain responsible for coupling with guanine nucleotide-binding proteins).

Allosteric Regulation↗
PubMed2004

[Applications of polyvinyl alcohol in modern preparations of TCM].

As a drug additive, polyvinyl alcohol(PVA) has merits of solubility, easy forming, strong conglutination, high thermal stability, low toxicity and no irritation. In these years, PVA has been applied wider and wider in medicine industry. In the study of modem preparations of TCM PVA, as film material of membrane and pellicles, is very promising owing to its easy forming and excellent toughness. PVA is good polymer matrix for suppositories and gel, because it can not only carry drug but also improve the properties of preparations on application and technology. It can be said that PVA is an excellent carrier. At the present, PVA is mainly applied in vitro preparations of TCM, but its applications will be spread with further research. The prospective applications of PVA in osmotic pump controlled release preparations, drug carried microspheres and swelling controlled release system are foreseen.

Delayed-Action Preparations↗