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PubMed2005

Electrochemical characteristics of a platinum electrode modified with a matrix of polyvinyl butyral and colloidal Ag containing immobilized horseradish peroxidase.

A new hydrogen peroxide biosensor was constructed, which consisted of a platinum electrode modified by a matrix of polyvinyl butyral (PVB) and nanometer-sized Ag colloid containing immobilized horseradish peroxidase (HRP), and using Co(bpy)3(3+) as mediator in the hydrogen peroxide solution. The electrochemical characteristics of the biosensor were studied by cyclic voltammetry and chronoamperometry. The modified process was characterized by electrochemical impedance spectroscopy and cyclic voltammetry. The HRP immobilized on colloidal Ag was stable and retained its biological activity. The sensor displays excellent electrocatalytic response to the reduction of H2O2. Analytical parameters such as pH and temperature were also studied. Linear calibration for H2O2 was obtained in the range of 1x10(-5) to 1x10(-2) M under optimized conditions. The sensor was highly sensitive to H2O2, with a detection limit of 2x10(-6) M, and the sensor achieved 95% of steady-state current within 10 s. The sensor exhibited high sensitivity, selectivity and stability.

Catalysis↗
PubMed1995

Delayed recanalization of a cerebral arteriovenous malformation following angiographic obliteration with polyvinyl alcohol embolization.

BACKGROUND: The efficacy of embolization of cerebral arteriovenous malformations (AVMs) is presently being evaluated. Embolization of single pedicle AVMs may produce complete angiographic obliteration and has been suggested as the sole therapy for treating these lesions. METHODS: A 17-year-old female presented with a left intraventricular and intraparenchymal cerebral hemorrhage resulting from a 1 cm left posterior choroidal AVM. She subsequently underwent polyvinyl alcohol (PVA) embolization of the AVM with complete angiographic obliteration. RESULTS: At 9 months follow-up, no evidence of recanalization of the AVM nidus was seen. Two years later, recanalization of the nidus was seen; and the patient received radiosurgical treatment. The natural history of previously embolized AVMs is reviewed and the mechanisms for recanalization are discussed. CONCLUSION: We recommend that patients with angiographic obliteration of AVMs receive further treatment, preferably resection, or be followed with serial angiography.

Adolescent↗
PubMed1982

The use of fibronectin-coated polyvinyl chloride microtest plates to detect monoclonal antibody-binding to adherent tumor cells.

This report describes the use of fibronectin-coated polyvinyl chloride (PVC) plates as a time-saving modification in an assay measuring antibody-binding to live adherent tumor cells. Three cell lines (A-431, Colo 16 and UCLA-SO-P3) derived from human squamous cell carcinomas (SCC) and forming monolayers in cultures were plated onto flexible PVC microtest plates rather than the commonly used rigid polystyrene plates. In PVC plates, two of the three cell lines (A-431 and Colo 16) grew as foci of clumped cells instead of monolayers. Coating of the plates with plasma fibronectin restored the monolayer morphology. [125I]Staphylococcal protein A radioimmunoassays measuring the binding of a monoclonal anti-beta 2 microglobulin antibody to the cells were slightly, but consistently, more sensitive in coated PVC plates than in polystyrene plates. In contrast, the sensitivity of the radioimmunoassay was remarkably constant when the assay was performed on the third cell line (UCLA-SO-P3), which formed monolayers in any of the conditions tested. Preliminary experiments suggested that the inability to form monolayers on uncoated PVC plates correlates with the amount of fibronectin associated with the cell surface.

Antibodies, Monoclonal↗
PubMed2004

Mechanism of growth of colloidal silver nanoparticles stabilized by polyvinyl pyrrolidone in gamma-irradiated silver nitrate solution.

Silver nanoparticles were prepared by using polyvinyl pyrrolidone (PVP) as a stabilizer and gamma-irradiation. Transmission electron microscopy (TEM) results showed that both the amount and the molecular weight of PVP in the irradiated solution considerably affect the average size of the silver nanoparticles. The average size of the silver nanoparticles decreases with increasing the amount of PVP in the solution, but increases with increasing its molecular weight. Further, TEM showed that the silver nanoparticles become disassembled into smaller nanoparticles after dilution with distilled water and sonication. Since the processes of dilution and sonication are not expected to result in chemical reactions or to split the silver nanoparticles, we conclude that each silver nanoparticle prepared by [Formula: see text] -irradiation consists of several smaller nanoparticles surrounded by PVP. Thus, based on these observations, we propose a three-step mechanism for the growth of the silver nanoparticles under the conditions considered here. In the first step, the silver ions interact with PVP, then in the second step the silver ions that are exposed to gamma-irradiation are reduced to silver atoms; nearby silver atoms then aggregate at close range. These aggregates are the primary nanoparticles. Finally, these primary nanoparticles coalesce with other nearby primary nanoparticles or interact with PVP to form larger aggregates which are the secondary (final) nanoparticles.

Journal Article↗
PubMed2005

Fundamental studies on the intermediate layer of a bipolar membrane part IV. Effect of polyvinyl alcohol (PVA) on water dissociation at the interface of a bipolar membrane.

This paper investigates the effect of polyvinyl alcohol (PVA) as the intermediate layer of bipolar membranes on water dissociation. The bipolar membranes are prepared by coating a solution of sulfonated polyphenylene oxide (SPPO) on the anion exchange layers, which had been immersed in PVA aqueous solutions with different concentrations in advance. The experimental results show that the effect of PVA on water dissociation is significantly affected by its concentration: at low concentration range PVA solution catalyzes water dissociation and at high concentration range PVA solution shows a retardant effect. The phenomenon is different from the situation where polyethylene glycol (PEG) is used as the intermediate layer. Based on the adsorption data and the measurements of X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy, it is found that (1) the effect of PVA concentration on water dissociation can be explained by the competition and compromise of two effects--the catalytic and hydrophilic effect of the PVA molecule and the steric effect of the enlargement of junction thickness; (2) the reason that at high concentration range PVA and PEG show different effects on water dissociation is that the junction thickness is enlarged excessively by PVA, which is based on the intrinsic characteristics of PVA molecules.

Journal Article↗
PubMed2004

DNA single strand breaks in peripheral lymphocytes associated with urinary thiodiglycolic acid levels in polyvinyl chloride workers.

The association between vinyl chloride monomer (VCM) exposure and DNA damage has been established. However, the relationship between individual exposure and DNA single strand breaks was limited. Since environmental monitoring may not reflect the actual exposure, a useful marker of exposure is needed to assess the individual exposure. In our previous study, we have found a high correlation between air VCM level and urinary thiodiglycolic acid (TdGA) at the commencement of the next shift. Here, we further used comet assay to evaluate the relationship between urinary TdGA levels and DNA single strand breaks in polyvinyl chloride monomer (PVC) workers. Urinary TdGA levels (n=26) at the commencement of the following shift were analyzed. Ten of the 26 workers also had personal air sampling for air VCM exposure. Questionnaires were administered to obtain epidemiological information including detailed history of occupation and lifestyles. Workers experiencing air VCM level greater than 5 ppm had higher tail moment and tail intensity (%) than those experiencing VCM exposure between 1 and 5, or <1 ppm, respectively (P < 0.05). The results also revealed that level of DNA single strand breaks, including tail moment and tail intensity, were increased with urinary TdGA level. The dose-response relationship of urinary TdGA level and DNA single strand breaks was particularly significant among the workers with 4 mg/g Cr of urinary TdGA level, which is equivalent to 5 ppm air VCM level. We concluded that air VCM exposure greater than 5 ppm could induce DNA damage. Further sensitive assay should be developed for the diction of DNA damage when air VCM exposure below 5 ppm.

Air Pollutants, Occupational↗
PubMed2001

Ultrasonic depolymerization of aqueous polyvinyl alcohol.

Ultrasonication has proved to be a highly advantageous method for depolymerizing macromolecules because it reduces their molecular weight simply by splitting the most susceptible chemical bond without causing any changes in the chemical nature of the polymer. Most of the effects involved in controlling molecular weight can be attributed to the large shear gradients and shock waves generated around collapsing cavitation bubbles. In general, for any polymer degradation process to become acceptable to industry, it is necessary to be able to specify the sonication conditions which lead to a particular relative molar mass distribution. This necessitates the identification of the appropriate irradiation power, temperature, concentration and irradiation time. According to the results of this study the reactors constructed worked well in depolymerization and it was possible to degrade aqueous polyvinyl alcohol (PVA) polymer with ultrasound. The most extensive degradation took place at the lowest frequency used in this study, i.e. 23 kHz, when the input power was above the cavitation threshold and at the lowest test concentration of PVA, i.e. 1% (w/w). Thus this study confirms the general assumption that the shear forces generated by the rapid motion of the solvent following cavitational collapse are responsible for the breakage of the chemical bonds within the polymer. The effect of polymer concentration can be interpreted in terms of the increase in viscosity with concentration, causing the molecules to become less mobile in solution and the velocity gradients around the collapsing bubbles to therefore become smaller.

Journal Article↗
PubMed2003

Calculation of the rate constant for the ultrasonic degradation of aqueous solutions of polyvinyl alcohol by viscometry.

Ultrasonic degradation of polyvinyl alcohol (PVA) was carried out in aqueous solution at 25 degrees C. In this experiment, the effect of solution concentration on the rate of degradation was investigated. Kinetics of degradation was studied by viscometry method. The calculated rate constants indicate that degradation rate of PVA solutions decreases with increasing of solution concentration (C= g lit(-1)). The calculated rate constants correlated in terms of reverse concentration and relative viscosity of PVA solutions. This behavior in the rate of degradation was interpreted in terms of viscosity and concentration of polymer solution. With increasing solution concentration, viscosity increases and it causes a reduction in the cavitation efficiency thus, the rate of degradation will be decreased.

Journal Article↗
PubMed1999

Treatment of aquarium water by denitrifying photosynthetic bacteria using immobilized polyvinyl alcohol beads.

During the purification of an aquarium for carp breeding, a relatively high level of chemical oxygen demand (COD) was removed by filtration systems packed with both alginate- and polyvinyl alcohol (PVA)-immobilized gel beads of Rhodobacter sphaeroides S. Low nitrate accumulation was observed in the alginate gel beads packed system due to denitrification, but high levels of nitrate and nitrite accumulation were observed in the PVA gel beads packed system. This phenomenon was caused by the inhibitory effect of PVA on nitrite reductase. The boric acid used for hardening gel beads of PVA slightly inhibited nitrate reductase. On the other hand, during the denitrifying growth experiments for this strain, boric acid inhibited cell growth, but PVA only partially inhibited cell growth. Based on electron equivalent (Y(eq.)), growth yields using various kinds of concentrations of PVA were almost identical. It was suggested that PVA might only limit the growth rate of this strain by the inhibition of nitrite reductase.

Journal Article↗
PubMed1981

The effect of Trichinella spiralis on the rate of clearance of 51Cr-labelled sheep red blood cells and 125I-polyvinyl pyrrolidone from the bloodstream of mice.

Mice infected for one to eight weeks with Trichinella spiralis cleared either 51Cr-labelled sheep red blood cells (SRBC) or 125I-polyvinyl pyrrolidone (PVP) given intravenously. PVP was cleared more rapidly from the blood of mice infected for one week than from uninfected mice with older infections which behaved in a similar manner to the controls. SRBC were consistently cleared faster from the blood of mice infected for one week than from normal mice. If the infections were older than this a more rapid clearance was also demonstrated as long as the infections were reasonably heavy.

Animals↗
PubMed2003

Release dynamics of tetracycline from a loaded semi-interpenetrating polymeric material of polyvinyl alcohol and poly(acrylamide-co-styrene).

A semi-interpenetrating polymer network (IPN) of polyvinyl alcohol (PVA) and poly(acrylamide-co-styrene) (PAMS) was prepared and its potential for controlled release of tetracycline was assessed. The IPN was characterized by IR spectral analysis and network parameters such as the average molecular weight between crosslinks (M(c)), crosslink density (q) and number of elastically effective chains (V(e)) were evaluated. The influence of various experimental conditions such as different percent loadings, composition of the IPNs, thickness of the loaded device, pH and nature of the release medium were investigated on the release profiles of the drug. Various kinetic constants such as the diffusional exponent (n), diffusion constant (D) and penetration velocity (v) were evaluated for different release processes and based on the dynamic release data, an analysis of transport mechanisms of tetracycline was made using Fick's equations.

Journal Article↗
PubMed2001

Properties of polyvinyl pyrrolidone/beta-chitosan hydrogel membranes and their biocompatibility evaluation by haemorheological method.

The semi-IPN hydrogel membranes of polyvinyl pyrrolidone (PVP) and beta-chitosan were synthesized by crosslinking beta-chitosan with glutaraldehyde. Hydrogel membranes were characterized by spectroscopic, swelling, thermal and mechanical properties. The in vitro biocompatibility of hydrogel membranes was studied by haemorheological method. These hydrogels have water contents in the range of 60-70% with a high fraction contributed by free water (> 45%). The gel composition, amount of cross-linking agent and swelling temperature plays an important role in swelling kinetics of these semi-IPN membranes. Melting temperature (Tm) of membranes increased with a decrease in endothermic peak with increasing beta-chitosan content. The tensile strength of membranes in the dry state was found to be high (29-43 MPa) and it increased with increasing beta-chitosan content. The in vitro haemorheological studies indicated the biocompatible nature of membranes with no significant changes in whole blood and plasma viscosity and red blood cell rigidity.

Journal Article↗
PubMed2001

Studies on the effect of polyvinyl pyrrolidone on the activity of chlorhexidine mouthrinses: plaque and stain.

BACKGROUND, AIMS: Polyvinyl pyrrolidone (PVP) was shown in vitro to reduce chlorhexidine induced, dietary staining without affecting the uptake of the antiseptic to the test substrate. The aim of these studies in vivo was to determine whether PVP affected plaque and dietary staining by a low concentration chlorhexidine rinse. METHODS: The plaque and stain studies used a double blind, randomised 6, treatment crossover design involving healthy subjects with a high standard of oral hygiene and gingival health. The rinse formulations under test were: (A) aqueous alcohol (placebo control), (B) 0.03% chlorhexidine, (C) 0.06% chlorhexidine, (D) 0.06% chlorhexidine+1.2% PVP, (E) 0.06% chlorhexidine+5% PVP, (F) 0.06% chlorhexidine+10% PVP. In the plaque study, on day 1 of each period, subjects were rendered plaque free and then rinsed with 15 ml of the test rinse for 60 s. No further tooth cleaning was performed and subjects returned 24 h later for plaque scoring by area. In the stain study, on day 1 of each period, the tongue and teeth of each subject were rendered stain free. Subjects then rinsed under supervision for 60 s with 15 ml of the allocated rinse 8 x a day between 09:00 h and 17:00 h for 3 days. Immediately after each rinse with the test formulation, subjects rinsed for 120 s with 15 ml of warm black tea. Subjects were requested to also drink at least 5 cups of tea or coffee per day. On day 4, stain was scored by area and intensity from designated teeth and dorsum of the tongue. Washout periods were at least 7 days in both studies. RESULTS: Plaque areas were greatest with placebo and least with 0.06% chlorhexidine. Plaque scores increased with increasing concentrations of PVP in the 0.06% chlorhexidine rinse and were significantly higher than 0.06% chlorhexidine without PVP rinse. Tooth stain areas were comparable for placebo, 0.03% and 0.06% chlorhexidine rinses, but significantly reduced with the PVP/chlorhexidine rinses compared to the 0.06% chlorhexidine rinse. Tooth stain intensity was significantly increased with 0.06% chlorhexidine rinses compared to placebo and chlorhexidine/PVP rinses. Tongue stain area and intensity were significantly reduced with 5% and 10% PVP/chlorhexidine rinses compared to 0.06% chlorhexidine rinse. CONCLUSION: PVP, at the concentrations tested, reduced the stain propensity of a 0.06% chlorhexidine rinse but at the expense of some loss of plaque inhibition.

Adolescent↗
PubMed2001

The effect of polyvinyl pyrrolidone on the clinical activity of 0.09% and 0.2% chlorhexidine mouthrinses.

BACKGROUND: Previous studies have shown that polyvinyl pyrrolidone (PVP) added to a chlorhexidine rinse reduced extrinsic dental stain but at the expense of a reduction in plaque inhibitory activity. This effect appeared due to a reduction in the effective chlorhexidine dose to levels where dose response studies show plaque inhibition falls off rapidly. The aim of these 2 clinical studies was to determine if PVP could be added to chlorhexidine rinses to maintain efficacy and reduce staining. METHOD: Study 1 involved 42 healthy dentate volunteers and was a blind, randomised, 7 treatment, crossover design balanced for residual effects. The rinses were: 1. 0.09% chlorhexidine to which was added, 2. 1% PVP, 3. 3% PVP, 4. 5% PVP, 5. 7% PVP, 6. Placebo, 7. Essential oil product. Rinses were used 2x on day one of each period after a prophylaxis. Subjects suspended tooth cleaning for 24 h and were then scored for plaque area. Study 2 used the experimental gingivitis model, involved 24 healthy dentate subjects and was a blind, randomised, 3 treatment, crossover design balanced for residual effects. The rinses were 1. 0.2% chlorhexidine, 2. 0.2% chlorhexidine/10% PVP, 3. Placebo. At baseline and the end of each study period subjects were rendered plaque, stain and calculus free, suspended oral hygiene and rinsed 2x per day. Plaque, gingivitis and stain were scored at baseline, 1, 2, and 3 weeks. Calculus was scored at baseline and 3 weeks. RESULTS: Study 1: Buccal plaque scores were significantly lower with all rinses compared to placebo. Also all buccal plaque scores were significantly lower with chlorhexidine and chlorhexidine/PVP rinses compared to the essential oil/phenolic rinse. There were no significant differences between the chlorhexidine rinse and the chlorhexidine/PVP rinses. Analyses for buccal and lingual plaque combined produced, with one exception, the same results for rinse comparisons as for buccal plaque alone. Thus the essential oil/phenolic rinse just failed to reach significance compared to placebo. Study 2: Plaque and gingivitis scores were significantly lower with positive control and test rinses compared to placebo but with no difference between these rinses. Tooth and tongue stain was significantly higher with the positive control and test rinses compared to placebo but not significantly different between these 2 rinses. Calculus scores were not significantly different between the three study rinses. CONCLUSION: Taken with previous data, the balance of evidence does not support PVP as an inhibitor of staining associated with chlorhexidine. These data are further evidence that chlorhexidine oral hygiene products, which, do not or claim not to cause staining, are most probably lacking efficacy.

Adult↗
PubMed1983

Immunological consequences of intestinal helminth infections in C57BL mice. Humoral responses to polyvinyl pyrrolidone.

Infection with Trichuris muris eggs or Nematospiroides dubius larvae (orally administered) did not affect IgG or IgM antibody responses to 0 X 2 micrograms polyvinyl pyrrolidone (PVP) (intravenously (i.v.) or intraperitoneally (i.p.)) or 20 micrograms PVP (i.p.) in C57BL mice. However, Nippostrongylus brasiliensis L3 subcutaneously (s.c.) and N. dubius L3 (i.v.) significantly increased responses to PVP (i.p.) so migrating larvae are probably responsible. Similar enhancement was obtained when extracts of N. brasiliensis worms or N. dubius larvae were administered i.p. The activity of N. brasiliensis extract was trypsin-insensitive and unaffected by heat (1 h, 60 degrees). Extracts of A. suum did not cause significant enhancement and BALB/c mice were not affected by N. brasiliensis extract. The possible roles of regulatory T-cells, non-specific mitogenesis and macrophage activation are discussed.

Animals↗
PubMedDate not supplied

Analysis of the effects of chitosan on inflammation, angiogenesis, fibroplasia, and collagen deposition in polyvinyl alcohol sponge implants in rat wounds.

Chitosan is a large molecular weight, positively charged polysaccharide extracted and purified from the chitin of crab shells. This compound has been shown to have hemostatic activity and has been suggested for use as a topical agent in tissue repair. The objective of this study was to analyze the effect of chitosan on the wound healing response to a standardized injury in the rat. The polyvinyl alcohol sponge implant model was used as a means to deliver either chitosan or its vehicle to a standardized subcutaneous wound on the backs of Sprague-Dawley rats. On days 8 and 14, the chitosan-treated implants contained primarily polymorphonuclear leukocytes compared with the vehicle controls which contained mainly macrophages, fibroblasts, collagen, and new blood vessels. High-performance liquid chromatography analysis for hydroxy-L-proline deposited in the sponge implants showed significantly lower amounts on both days 8 and 14 in the chitosan treatment group. These histologic and biochemical studies suggest that chitosan modulates wound healing by first reducing the influx of activated tissue macrophages, which in turn reduces the subsequent events of angiogenesis, fibroplasia, and connective tissue deposition.

Journal Article↗
PubMed1996

Stability of levofloxacin in intravenous solutions in polyvinyl chloride bags.

The stability of levofloxacin in 10 commonly used infusion fluids was studied. Levofloxacin 25-mg/mL injection was diluted to 0.5 and 5 mg/mL in each of the following i.v. infusion fluids: 0.9% sodium chloride injection, 5% dextrose injection, 5% dextrose and 0.9% sodium chloride injection, 5% dextrose and lactated Ringer's injection, 5% sodium bicarbonate injection, Plasma-Lyte 56 and 5% dextrose injection, 5% dextrose and 0.45% sodium chloride and 0.15% potassium chloride injection, 1/6 M sodium lactate injection, sterile water for injection, and 20% mannitol injection. Ten polyvinyl chloride bags were prepared for each solution; two were stored for 3 days at 25 degrees C, two for 7 days at 5 degrees C, two for 14 days at 5 degrees C, two for 13 weeks at -20 degrees C followed by 14 days at 5 degrees C, and two for 26 weeks at -20 degrees C, all in the dark. The solutions were visually examined, tested for turbidity and particulate matter, and subjected to stability-indicating high-performance liquid chromatography; solution pH was determined. Levofloxacin was stable in and compatible with all but two of the diluents tested. Precipitation occurred under all conditions in 20% mannitol injection for the 0.5-mg/mL levofloxacin concentration and after storage for 13 weeks at -20 degrees C for the 5-mg/mL concentration. Levofloxacin 0.5 mg/mL in 5% sodium bicarbonate injection formed a precipitate when stored at -20 degrees C for 13 weeks and beyond. Levofloxacin 0.5 and 5 mg/mL was compatible with and stable in 8 of the 10 infusion fluids studied.

Anti-Infective Agents↗
PubMed1996

Phenotype of B cells responding to the thymus-independent type-2 antigen polyvinyl pyrrolidinone.

We have determined the origin and cell surface phenotype of B cells producing antibody in response to immunization with the non-self TI-2 antigen polyvinyl pyrrolidinone (PVP). We report that the responding cells are derived from precursors in adult bone marrow and display the phenotype characteristic of B-1 cells. By use of allotype marked chimeric mice, constructed by reconstituting lethally irradiated recipients with adult bone marrow and peritoneal B-1 lymphocytes of recognizably different Ig allotypes, immunized with 1 microgram PVP, we found that although a substantial part of the total IgM produced in these chimeras bore the allotype of the transferred peritoneal B-1 cells, essentially all of the anti-PVP IgM expressed the allotype of the adult bone marrow. Fifteen of 16 hybridomas derived from a normal PVP-immune adult mouse bore N nucleotides at the V-D and D-J junctions of their heavy chain CDR3 regions, indicating their origin from precursors in the adult bone marrow. By use of ELISA spot analysis, we found the cells responding to PVP to be localized in the spleens of normal immunized mice. We then used multiparameter flow cytometric sorting to determine the cell surface phenotype of these cells. We found that the cells producing anti-PVP were greatly enriched in a small subpopulation with the phenotypic characteristics of B-1 cells; they were B220intermediate, CD5low, IgMhigh, IgDlow, CD43+ and CD23-. This subpopulation was also enriched for all cells producing IgM, regardless of specificity (the so-called 'spontaneous' antibody). We conclude that the B-1 phenotype is more likely a marker for a state of differentiation than for a discrete lineage of B cells.

Animals↗