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PubMed2005

Physicochemical and release properties of pellets coated with Kollicoat SR 30 D, a new aqueous polyvinyl acetate dispersion for extended release.

Kollicoat SR 30 D is a new aqueous colloidal polyvinyl acetate dispersion used for extended release coatings. Kollicoat SR 30 D is stable against sedimentation, has a low viscosity (54 mPas) and a negative zeta potential of -23.2 mV because of the presence of the anionic surfactant, sodium dodecyl sulfate. Because of its low minimum film formation temperature (MFT = 18 degrees C), plasticizer addition and a thermal after-treatment (curing) of coated pellets was not required. Coated pellets showed no aging or curing effect. The rate of release could be easily adjusted by varying the coating level. A subcoating layer of the hydrophilic polymer, polyvinyl alcohol, between an ibuprofen-containing core and the Kollicoat SR coating prevented the diffusion of the lipophilic, low melting ibuprofen into the polymer coating during storage. The drug release from Kollicoat SR 30 D coated pellets was almost independent of the pH and ionic strength of release medium.

Chemical Phenomena↗
PubMed2000

Accuracy of three polyvinyl siloxane putty-wash impression techniques.

STATEMENT OF PROBLEM: There is much discussion in the dental literature concerning the effect of the impression technique on the accuracy of cast restorations. PURPOSE: This study assessed the accuracy of 3 putty-wash impression techniques using the same impression material (polyvinyl siloxane) in a laboratory model. MATERIAL AND METHODS: The 3 putty-wash impression techniques used were (1) 1-step (putty and wash impression materials used simultaneously); (2) 2-step with 2-mm relief (putty first as a preliminary impression to create 2-mm wash space with prefabricated copings. In the second step, the wash stage was carried out); and (3) 2-step technique with a polyethylene spacer (plastic spacer used with the putty impression first and then the wash stage). For each technique, 15 impressions were made of a stainless steel master model that contained 3 complete crown abutment preparations, which were used as the positive control. Accuracy was assessed by measuring 6 dimensions (intraabutment and interabutment) on stone dies poured from impressions of the master model. RESULTS: One-way analysis of variance showed statistically significant differences among the 3 putty-wash impression techniques, for all intraabutment and interabutment measurements (P <.001). Overall discrepancies of the 2-step technique with 2-mm relief putty-wash impression technique were significantly smaller than that in the 1-step and polyethylene putty-wash impression techniques. CONCLUSION: The polyvinyl siloxane 2-step, 2-mm, relief putty-wash impression technique was the most accurate for fabricating stone dies.

Analysis of Variance↗
PubMed1998

Effect of frequency and amplitude of vibration on void formation in dies poured from polyvinyl siloxane impressions.

STATEMENT OF PROBLEM: Numerous factors are involved in making a void-free dental stone cast from a polyvinyl siloxane impression. PURPOSE: The aim of this study was to determine whether frequency and amplitude of vibration had any effect on the formation of voids on the cast surface poured from polyvinyl siloxane impression with a mechanical model vibrator. MATERIAL AND METHODS: Impressions were poured in dental stone with a mechanical model vibrator that was set at vibration frequency 3000 cycles/min (low) and 6000 cycles/min (high) by a knob. The amplitude of vibration is provided in 5 steps and remained constant for the step set on the instrument. A total of 240 casts were prepared. The vibrator was set at low frequency and 30 impressions were poured for each of the 5 steps of amplitude. The vibrator was then set at high frequency and 30 impressions were poured for each of the 5 steps of amplitude. The resultant casts were examined for the presence of surface voids under 10 x magnification. RESULTS: Means for voids in all cast groups calculated for low and high vibration frequencies indicated that an increase in the amplitude of vibration caused an increase in the number of voids on the die surface. CONCLUSION: Use of high frequency of vibration 6000 cycles/min and 0.40 mm amplitude produced significantly fewer voids (P < .0001) compared with steps 4 (0.45 mm) and 5 (0.80 mm) amplitude.

Analysis of Variance↗
PubMed2001

Sarcomas metastatic to the liver: response and survival after cisplatin, doxorubicin, mitomycin-C, Ethiodol, and polyvinyl alcohol chemoembolization.

PURPOSE: To evaluate the response to and survival after chemoembolization with cisplatin, doxorubicin, mitomycin-C, Ethiodol, and polyvinyl alcohol for patients with sarcomas metastatic to the liver that are surgically unresectable. MATERIALS AND METHODS: Sixteen patients were treated. Primary tumors included 11 gastrointestinal leiomyosarcomas, two splenic angiosarcomas, one leiomyosarcoma of the broad ligament, one leiomyosarcoma of the inferior vena cava, and one malignant fibrous histiocytoma of the colon. Chemoembolization with cisplatin, doxorubicin, mitomycin-C, Ethiodol, and polyvinyl alcohol particles was performed 1-5 times at approximately monthly intervals (mean, 2.8). Pre- and posttreatment cross-sectional imaging was performed 1 month after completion of treatment and then every 3 months. Thirty-day response was graded according to World Health Organization/Eastern Cooperative Oncology Group criteria. Survival was calculated with use of Kaplan-Meier analysis. RESULTS: Two patients (13%) exhibited partial morphologic response, 11 patients (69%) were morphologically stable, and three (19%) demonstrated progression of disease 30 days after completion of treatment. Among the 13 responders, two underwent partial hepatectomy after initial treatment. Seven developed intrahepatic progression at a mean of 10 months and a median time of 8 months. The remaining four patients had no documented intrahepatic progression at the time of last imaging follow-up. Nine patients developed extrahepatic progression at a mean time of 6.3 months and a median time of 6 months, of whom four underwent additional surgical resection. Response to therapy was based on time of first intervention. Cumulative survival from time of diagnosis with use of Kaplan-Meier analysis was 81% at 1 year, 54% at 2 years, and 40% at 3 years. Median survival time was 20 months. Cumulative survival from initial chemoembolization was 67% at 1 year, 50% at 2 years, and 40% at 3 years, with a median survival time of 13 months. The thirty-day mortality rate was zero. CONCLUSION: Durable tumor response with chemoembolization is possible in this form of metastatic disease, which is highly resistant to systemic chemotherapy.

Chemoembolization, Therapeutic↗
PubMed2002

Loading of tetanus toxoid to biodegradable nanoparticles from branched poly(sulfobutyl-polyvinyl alcohol)-g-(lactide-co-glycolide) nanoparticles by protein adsorption: a mechanistic study.

PURPOSE: Mucosal delivery of vaccine-loaded nanoparticles (NP) is an attractive proposition from an immunologic perspective. Although numerous NP preparation methods are known, sufficient antigen loading of NP remains a challenge. The aim of this study was to evaluate adsorptive loading of NP with a negatively charged surface structure using tetanus toxoid (TT) as a model vaccine. METHODS: Blank NP, consisting of poly(sulfobutyl-polyvinyl alcohol)-g-(lactide-co-glycolide), as well as poly(lactide-co-glycolide) NP were prepared by a solvent displacement technique. The use of polymers with different degrees of substitution resulted in NP with different negative surfaces charges. Adsorption of TT to NP was performed varying to NP surface properties, protein equilibrium concentration, and loading conditions. RESULTS: The protein adsorption was controlled by NP surface properties, and maximum TT adsorption occurred at highly negatively charged NP surfaces. Results from isothermal titration calorimetry and zeta-potential measurement suggest an adsorption process governed by electrostatic interactions. The adsorption followed the Langmuir isotherm in the concentration ranges studied. TT withstood this gentle loading procedure in a nonaggregated, enzyme-linked immunoabsorbant assay-active form. CONCLUSION: The results demonstrate that negatively charged NP consisting of poly(sulfobutyl-polyvinyl alcohol)-g-(lactide-co-glycolide) are suitable for adsorptive loading with TT and may have potential for mucosal vaccination.

Adsorption↗
PubMed2001

Functional T lymphocytes infiltrate implanted polyvinyl alcohol foams during surgical wound closure therapy.

Vacuum-assisted closure involving the implantation of polyvinyl alcohol foam is a technique recently developed for the treatment of patients suffering from either wound infection or chronic wounds. This method has been shown to improve and accelerate wound healing. However, little is known about the cell populations that infiltrate the foam, and their potential role in resolving the infection and promoting granulation tissue formation. Our study demonstrates that wound-implanted foams are mainly infiltrated with granulocytes, but that mononuclear cells, including macrophages and minor populations of T, B and natural killer lymphocytes, are also present. We show that foam-infiltrating T cells, especially CD4(+) T cells, constitute a phenotypically and functionally heterogeneous population influenced by wound-infecting bacteria. Thus, T lymphocytes could play a role in wound cleansing. In addition, our data indicate that implanted polyvinyl alcohol foams might be suitable microenvironments for manipulating T cell-mediated immune responses in patients.

Adult↗
PubMed2002

Laccase stabilization by covalent binding immobilization on activated polyvinyl alcohol carrier.

AIMS: Attempts were made to immobilize laccase from Panus conchatus. METHODS AND RESULTS: The laccase was immobilized on carboxylated polyvinyl alcohol (PVA) activated by N-hydroxysuccinimide (N-HSI) in aqueous solution at different pHs, temperatures, and with different reaction times. An optimum condition for laccase immobilization is at pH 3.2, 40 degrees C and 12 h, respectively. Immobilization of laccase increased optimal pH for reaction with 2, 2'-azinobis (3-ethylbenzthiazoline-6-solfonate) (ABTS) and pH stability. Immobilized laccase proved to be reacted consecutively 17 times with only a 50% decrease on activity and be used in removal of 2,4,6-trichlorophenol (TCP). CONCLUSIONS: It was possible to immobilize the laccase on carboxylated polyvinyl alcohol by activation with N-hydroxysuccinimide in HAc-NaAc buffer. The immobilized laccase is both stable and reusable. SIGNIFICANCE IMPACT OF THE STUDY: The results indicate that this immobilized laccase can be used in the removal of poisonous effluent from pulp bleaching mills.

Basidiomycota↗
PubMedDate not supplied

Increased fibrovascular invasion of subcutaneous polyvinyl alcohol sponges in SPARC-null mice.

The expression of SPARC (secreted protein acidic and rich in cysteine/osteonectin/BM-40) is elevated in endothelial cells participating in angiogenesis in vitro and in vivo. SPARC acts on endothelial cells to elicit changes in cell shape and to inhibit cell cycle progression. In addition, SPARC binds to and diminishes the mitotic activity of vascular endothelial growth factor. To determine the effect(s) of SPARC on angiogenic responses in vivo, we implanted polyvinyl alcohol sponges subcutaneously into wild-type and SPARC-null mice. On days 12 and 20 following implantation, SPARC-null mice showed increased cellular invasion of the sponges in comparison to wild-type mice. Areas of the sponge with the highest cell density exhibited the highest numbers of vascular profiles in both wild-type and SPARC-null animals. The endothelial component of the vessels was substantiated by immunoreactivity with three different markers specific for endothelial cells. Although sponges from SPARC-null relative to wild-type mice were populated by significantly more cells and blood vessels, an increase in the ratio of vascular to nonvascular cells was not apparent. No differences in the percentage of proliferating cells within the sponge were detected between wild-type and SPARC-null sections. However, elevated levels of vascular endothelial growth factor were associated with sponges from SPARC-null versus wild-type mice. An increase in vascular endothelial growth factor production was also observed in SPARC-null primary dermal fibroblasts relative to those of wild-type cells. In conclusion, we have shown that the fibrovascular invasion of polyvinyl alcohol sponges is enhanced in mice lacking SPARC, and we propose that increased levels of vascular endothelial growth factor account, at least in part, for this response.

Animals↗
PubMed1987

Stenosis of the external ear canal: prevention using hydroxylated polyvinyl acetal wicks.

Hydroxylated polyvinyl acetal wicks may be very helpful in preventing postsurgical stenosis of the external ear canal. The wick is inserted into the canal, wetted with Polysporin Otic, and changed periodically until scar tissue becomes stabilized. This method is simple, quick, and well tolerated by the patient. Polyvinyl wicks provide a useful adjunct in preventing stenosis of the external ear canal.

Acetals↗
PubMed1998

Polyvinyl siloxane impression materials: an update on clinical use.

Polyvinyl siloxane impression materials have applications in a variety of indirect procedures in prosthodontics and restorative dentistry. Favourable handling properties, good patient acceptance and excellent physical properties have resulted in their popularity in today's practice. In this review, the chemistry and important physical properties of polyvinyl siloxanes are summarized, and recent clinical questions of improved hydrophilics, tray adhesives, disinfection, and glove-induced polymerization inhibition are addressed.

Adhesives↗
PubMed1983

Comparison of polyvinyl alcohol- and formalin-preserved fecal specimens in the formalin-ether sedimentation technique for parasitological examination.

A total of 965 paired fecal specimens preserved in polyvinyl alcohol fixative and Formalin were processed by the Formalin-ether sedimentation technique. The effectiveness of the concentration procedures with material from each preservative was determined by comparing both diagnostic efficiency (percent identified) and quantitative egg and semiquantitative cyst counts. Of the 319 infections, 69.5% were detected in concentrates from both preservatives, 6.9% from polyvinyl alcohol only, and 23.5% from Formalin only. The egg and cyst counts were consistently higher from the specimens preserved in Formalin for most of the species of organisms recovered. These findings strongly support the use of Formalin-fixed specimens for the Formalin-ether concentration technique.

Ether↗
PubMed2006

Cell growth on tissue-engineering scaffolds prepared by gamma irradiation grafting of N-vinyl-2-pyrrolidone onto polyvinyl alcohol.

In the field of tissue engineering, promoting cell attachment and proliferation in polymer matrices is an attractive challenge for treating patients suffering from the loss or dysfunction of tissues or organs. In this study we have investigated the effect of grafting N-vinyl-2-pyrrolidone (NVP) by gamma irradiation onto polyvinyl alcohol (PVA), a highly hydrophilic and non-toxic material. PVA scaffolds were prepared by freeze-thaw and progen (glycerol) methods. In the first method, samples were freeze-thawed for three consecutive cycles at -25 degrees C (90 min) and room temperature (60 min); in the latter, 0-40% glycerol was used as progen. Gamma irradiation of the scaffolds in the presence of NVP was performed at different concentrations (2, 3, 4 and 6%) with 5, 10 and 15 kGy 60Co. The highest percentage of grafting was obtained at 4% NVP solution and 15 kGy. Cell attachment was optimal for the scaffolds prepared using freeze-thaw and glycerol methods with 3.8% and 2.7% polyvinyl pyrrolidone (PVP), respectively.

Animals↗
PubMed1983

A morphological study of ferritin synthesis in macrophages with ingested ferric hydroxide-potassium polyvinyl sulfate complexes.

A ferric hydroxide-polyvinyl sulfate colloidal solution (Fe-PVS), prepared by mixing potassium polyvinyl sulfate (PVSK) and ferric hydroxide colloidal solution was used to study ferritin synthesis in rat peritoneal macrophages. The colloidal particles had spherical electron opaque ferric hydroxide cores with diameters of about 250 nm surrounded by radially arranged fibrous PVS molecules. They also had strong negative electric charges. Fe-PVS particles injected into the peritoneal cavity were taken up by the macrophages then disintegrated rapidly. In the phagolysosomes the electron opaque ferric hydroxide cores of Fe-PVS were denuded of their PVS frames then decomposed into small 5-6 nm granules 24 to 48 h after injection. These small granules were released from the lysosomes into the hyaloplasm and the myelin figures were found in the lysosomal vacuoles. No reaccumulation of granules in lysosomes was found even 3 months later. The intracellular distribution of ferritin in macrophages demonstrated by the immunocytochemical method showed a pattern similar to that of the small granules formed by the disintegration of Fe-PVS. This means that in rat peritoneal macrophages that contain ingested Fe-PVS particles ferritin first is synthesized in phagolysosomes by the ferric hydroxide cores that conjugate with apoferritin or protein subunits then they are dispersed into the cytoplasm. Two possible pathways for the biosynthesis of ferritin are discussed.

Animals↗
PubMed1993

Pulmonary embolization and infarction. An iatrogenic complication of transcatheter embolization of a cerebral arteriovenous malformation with polyvinyl alcohol sponge.

Transcatheter embolization therapy of vascular abnormalities is a well-accepted technique. It is particularly useful in the preoperative management of cerebral arteriovenous malformations, in which the risk of significant hemorrhage at surgery would otherwise be unacceptably high. A patient developed symptomatic pulmonary emboli and infarction following an uneventful embolization using polyvinyl alcohol particles. The authors believe this to be the first reported case of this complication of embolic therapy using polyvinyl alcohol.

Adult↗
PubMed2000

The use of filter paper plasticized with polyvinyl alcohol-glutaraldehyde in ELISA.

F1-antigen purified from Yersinia pestis was covalently linked to 5-mm diameter filter paper discs plasticized with polyvinyl alcohol-glutaraldehyde. These discs were used both for ELISA and dot-ELISA for the detection of anti-F1 IgG in rabbits. The best conditions were achieved using 1.25 microg of F1 antigen/disc, 3% w/v skim milk in PBS as blocking agent, anti-IgG peroxidase conjugate diluted 12,000 times, and serum from rabbits immunized or not against Y. pestis, diluted 6,400 times. The absorbance values obtained from the comparative study between this procedure and conventional ELISA were not significantly different but the low cost of the reagents employed in ELISA using the filter paper discs plasticized with polyvinyl alcohol-glutaraldehyde makes this method economically attractive.

Animals↗
PubMed1993

Experimental investigations concerning a new liquid embolization method: combined administration of ethanol-estrogen and polyvinyl acetate.

A new embolization agent combining ethanol-estrogen and polyvinyl acetate was evaluated angiographically and histologically in 18 canine renal arterial systems. Peripheral vessels of less than 100 microns diameter were obliterated by thrombus induced by ethanol-estrogen, and larger vessels were obliterated by polyvinyl acetate casts and/or thrombus. This embolization method is easily controlled and has fewer adverse effects, so is suitable for intravascular applications, especially in the head and neck regions.

Animals↗
PubMed1987

Nonsuture microvascular anastomosis using an Nd-YAG laser and a water-soluble polyvinyl alcohol splint.

Anastomosis of rat common carotid artery was performed without sutures, using a neodymium (Nd)-YAG laser at 20 W for 100 msec; this power and exposure had been found optimal in preliminary experiments. An intraluminal intervascular splint made of water-soluble polyvinyl alcohol, which dissolved and disappeared within a few minutes after recirculation of blood, was used for precise "intima-to-intima" coaptation. No stay sutures or glue were required during the procedure. There was a 92% patency rate 24 hours after surgery, and the anastomosed vessels were still patent on the 7th and 30th postoperative days. Complications such as aneurysm formation or stenotic change were negligible. The fusion of the muscle layer and collagen fibers of the media in the anastomosis was confirmed histologically. A tensile strength test immediately following operation and 1 week later showed that this anastomosis was significantly better than that achieved with the usual manual suture method. The major advantages of this technique, combined with use of a water-soluble polyvinyl alcohol splint, are rapidity, consistency of results, and firm fusion with no residual foreign body.

Anastomosis, Surgical↗