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PubMed1991

Platelet consumption by polyvinyl alcohol coated tubing in canines.

Polyvinyl alcohol (PVA)-coated polyethylene tubing, with or without immobilized heparin, caused severe thrombocytopenia and enhanced the production of new platelets when inserted in a chronic arteriovenous shunt in canines. A similar length of uncoated polyethylene tubing neither lead to thrombocytopenia nor significantly enhanced platelet regeneration, relative to the shunt only without a test section. Platelet regeneration was monitored by the malondialdehyde assay, which was assumed to make a distinction between "new" and "old" platelets. This distinction was combined with the platelet count values to enable calculation of the cumulative consumption curve and the initial fractional consumption rate in the presence of a non constant platelet count. The resulting initial fractional consumption rates were: 34%/day for PVA, 20.5%/day for polyethylene, and 18%/day for the shunt only blank.

Animals↗

PubMed2006

Anisotropic polyvinyl alcohol hydrogel for cardiovascular applications.

Polyvinyl alcohol (PVA) is a hydrophilic polymer with various characteristics desired for biomedical applications and can be transformed into a solid hydrogel by physical crosslinking, using a low-temperature thermal cycling process. As with most polymeric materials, the mechanical properties of the resultant PVA are isotropic, as oppose to most soft tissues, which are anisotropic. The objective of this research is to develop a PVA-based hydrogel that not only mimics the nonlinear mechanical properties displayed by cardiovascular tissues, but also their anisotropic behavior. By applying a controlled strain to the PVA samples, while undergoing low-temperature thermal cycling, we were able to create oriented mechanical properties in PVA hydrogels. The oriented stress-strain properties of porcine aorta were matched simultaneously by a PVA hydrogel prepared (10% PVA, cycle 3, 75% initial strain). This novel technique allows the controlled introduction of anisotropy to PVA hydrogel, and gives a broad range of control of its mechanical properties, for specific medical device applications.

Animals↗

PubMed1990

Vaginal absorption of polyvinyl alcohol in Fischer 344 rats.

Polyvinyl alcohol (PVA) is a polymer with a wide range of molecular weights and uses. Recently, low molecular weight formulations of PVA have been used as components of contraceptive products designed for intravaginal administration in human females. Previous studies in animals have determined that little or no absorption of PVA occurs from the gastrointestinal (GI) tract. However, there is some concern that PVA of lower molecular weights might be absorbed across membranes of the reproductive tract. Consequently, this work has investigated the absorption of low molecular weight PVA across biological membranes of the reproductive and GI tracts of Fischer 344 rats. Oral administration of ten consecutive daily doses of 14C PVA resulted in little apparent absorption of the dose from the GI tract. In contrast, intravaginal administration of 14C PVA resulted in increasing concentrations of PVA-derived radioactivity in major tissues following one, three or ten daily doses of the estimated human dose of 3 mg/kg. PVA-derived radioactivity was concentrated mainly in the liver, reaching a peak greater than 1750 ng equivalents/g tissue 24 hours following ten daily doses. Over 300 ng equivalents/g tissue were still present in the liver 30 days following the last dose.

Absorption↗

PubMedDate not supplied

[Papain immobilization on a fibrous polymer of polyvinyl alcohol].

The paper discusses papain immobilization on modified polyvinyl alcohol fibers by the ion fixation technique. The effect of the chemical structure of polyvinyl alcohol fibers on the basic properties of the bound enzyme has been examined. The level of activity and tolerance to pH changes of the resultant immobilized enzymes have been shown to depend on the papain arrangement in the polymer molecule.

Enzymes, Immobilized↗

PubMedDate not supplied

Comparison of the polyvinyl alcohol sponge and expanded polytetrafluoroethylene subcutaneous implants as models to evaluate wound healing potential in human beings.

Our current understanding of the complex processes involved in wound healing is based mainly on studies of animal models. Although this information has been useful, it may not totally reflect the response found in human beings. For example, human beings have a tendency to either "overheal," as seen in keloids and hypertrophic scar formation, or have deficient healing, as seen in chronic ulcer formation. No animal models are available to analyze these human clinical pathologic conditions. Therefore the objective of this study was to analyze the wound healing response in a large population (n = 40) of normal healthy human beings as a first step to begin studies of abnormal human wound healing. Simultaneously, a comparison was made between the polyvinyl alcohol implant and the expanded polytetrafluoroethylene implant model. Under sterile conditions with the use of local anesthesia, two preweighed polyvinyl alcohol implants and two standard 6 cm expanded polytetrafluoroethylene implants were placed subcutaneously in the upper arm of each subject. High-performance liquid chromatography was used to quantitate isoleucine and hydroxy-l-proline in acid hydrolysates of each implant. Isoleucine was used as an indicator of protein content in the tissue sample, whereas hydroxyproline reflected collagen content. No infectious or hemorrhagic complications were found in the 40 volunteers included in the study. No significant difference was found in isoleucine or hydroxy-l-proline content between postoperative day 7 polyvinyl alcohol implants and day 14 polyvinyl alcohol implants. In contrast, both isoleucine and hydroxy-l-proline content were significantly increased in day 14 expanded polytetrafluoroethylene implants compared with day 7 implants (p < 0.005 and p < 0.001, respectively). In addition, the ratio of hydroxy-l-proline to isoleucine was significantly increased in day 14 expanded polytetrafluoroethylene implants compared with day 7 expanded polytetrafluoroethylene and both day 7 and day 14 polyvinyl alcohol implants (p < 0.001). This observation suggests that by 14 days implantation of expanded polytetrafluoroethylene stimulated an increased deposition of collagen. No significant differences were found in the hydroxy-l-proline to isoleucine ratios among day 7 expanded polytetrafluoroethylene, day 7 polyvinyl alcohol, and day 14 polyvinyl alcohol implants. Histologic analyses correlated with the biochemical findings. These results suggest that expanded polytetrafluoroethylene may be the preferred implant for studies designed to examine pathologic processes associated with retarded wound healing. In contrast, the polyvinyl alcohol implant may be better suited for studies where a low background response is required. Moreover, the extreme variability in normal healthy volunteers seen in this study correlates clinically with the finding that, among the normal adult human population, there is a heterogeneous wound healing response.

Journal Article↗

PubMedDate not supplied

[Immobilization of invertase in polyvinyl alcohol coatings].

A possibility of invertase immobilization in the polyvinyl alcohol coating formed directly on the electrode surface from water solution of polyvinyl alcohol and boric acid was being investigated. Conditions for obtaining the polymeric coating at the constant potential and at the constant current were compared. In order to obtain the polymeric coatings with a marked enzyme activity optimal conditions were found.

Electrochemistry↗

PubMed2005

Polyvinyl alcohol and gelatin sponge particle embolization of splenic artery pseudoaneurysm complicating chronic alcoholic pancreatitis.

AIM: To assess the effectiveness of and complications associated with polyvinyl alcohol (PVA) and gelatin sponge particles embolization of splenic artery pseudoaneurysm complicating chronic alcoholic pancreatitis. METHODS: A 42-year-old man with splenic artery pseudo-aneurysm formation secondary to chronic alcoholic pancreatitis was admitted. We used PVA and gelatin sponge particles embolization of splenic artery pseudoaneurysm by superselective embolization techniques. RESULTS: The splenic artery pseudoaneurysm was successfully controlled with splenic embolization. The patient was discharged in 9 d with complete recovery. CONCLUSION: This case confirms that superselective transcatheter embolization by PVA and gelatin sponge particles may represent an effective treatment for pseudoaneurysm caused by chronic alcoholic pancreatitis in the absence of other therapeutic alternatives.

Adult↗

PubMed1990

Preoperative embolization of cerebral arteriovenous malformations with polyvinyl alcohol particles: experience in 51 adults.

In order to determine possible risk factors and to assess the value of platinum microcoils added to polyvinyl alcohol particles in preoperative embolization of cerebral arteriovenous malformations in adults, we reviewed our experience with this procedure. Between September 1985 and June 1989, we performed embolizations in 54 patients with cerebral arteriovenous malformations. Of these, procedures in 51 adults involved the use of polyvinyl alcohol particles, either alone (n = 29) or in combination with platinum microcoils (n = 21). A complication during catheterization precluded embolization in another patient. Beginning as flow-directed embolizations via carotid artery catheterizations (n = 12), newer catheters allowed progression to superselective intracerebral catheterizations (n = 38). Embolization has led to shorter surgical procedures, more clearly defined operative margins, and less bloody operative fields. We have not found recanalization to significantly hinder embolization results with polyvinyl alcohol when resection is undertaken within 1-4 weeks of embolization. Its relative safety and ease of manipulation at surgery argue for its use. We found no significant increase in complications based on patient age, venous drainage of the arteriovenous malformation, or the circulation embolized. Embolization results in cerebral arteriovenous malformations were improved with superselective catheterization and most improved with the combined use of polyvinyl alcohol for nidus embolization followed by occlusion of the feeding vessel with microcoils.

Adolescent↗

PubMed2005

[A comparative study of 0.15% sodium hyaluronate versus polyvinyl alcohol in the treatment of dry eyes].

PURPOSE: To evaluate the efficacy of two artificial tears for the treatment of dry eyes: 0.15% sodium hyaluronate and polyvinyl alcohol. METHODS: The study included 60 dry eyes in 30 patients. Fifteen of the patients were treated with 0.15% sodium hyaluronate and 15 with polyvinyl alcohol. Five drops a day for one month was given in both groups. Visual acuity, Schirmer's test, tear clearance, dry eye symptoms questionnaire, fluorescein and rose bengal staining, corneal sensibility, bulbar hyperemia, tear detritus, meibomian gland plug, palpebral erythema and edema before and after treatment were evaluated. RESULTS: Symptoms as judged by the dry eye questionnaire, as well as both fluorescein and rose bengal staining, were significantly improved by 0.15% sodium hyaluronate. The polyvinyl alcohol treated patients did not show a significant improvement in any parameter. CONCLUSION: Sodium hyaluronate was more effective than polyvinyl alcohol in the treatment of patients with dry eyes (Arch Soc Esp Oftalmol 2005; 80: 387-394).

Adjuvants, Immunologic↗

PubMedDate not supplied

Histopathologic analysis of intraarterial polyvinyl alcohol microemboli in rat cerebral cortex.

Polyvinyl alcohol (PVA) foam particles have been used with success in both experimental and clinical embolization of vascular lesions. Cellular response to PVA has been well documented outside, but not within, the central nervous system. This study was directed specifically at the cellular response to PVA in rat brain vasculature. By using small numbers of microparticles, an effort was made to define the response to PVA alone, rather than associated occlusions or infarctions. It was determined that PVA elicited no significant inflammatory response in the embolized vessels nor in the surrounding tissue. The isolated fragments did not appear to alter the blood-brain barrier. The PVA microemboli were extremely adherent to vascular endothelium, lodging in vessels of larger diameter and in relatively high-flow locations without actually wedging within the vessel lumen. On the basis of this analysis, it was determined that PVA foam has properties suitable for an intracerebral vascular embolic agent.

Animals↗

PubMed1987

Effects of heat treatment on the permeability of polyvinyl alcohol films to a hydrophilic solute.

Polyvinyl alcohol (PVA) films may be useful as release-controlling membrane systems. Untreated, they are readily permeable to water and hydrophilic drugs. Because heating has been used to increase crystallinity and thus reduce the solubility and swelling in water of PVA films, we have studied the effects of heat on the permeability of PVA films to a water-soluble drug marker. Heat treatment was varied in the temperature range 100-200 degrees C for 1 h. The effect of time of heating was studied at 100 degrees C for 0.5-160 h. After pre-equilibration with water (heat-treated membranes remained intact, untreated ones dissolved), membrane permeabilities to methylene blue in aqueous solution (37 degrees C) were determined in a rotating diffusion cell. Permeabilities decreased with increased heating times (0.98-0.039 cm X min-1 for 0.5-160 h at 100 degrees C, respectively). Heating in air or N2 produced similar results. Further dramatic decreases in permeability occurred with increasing pretreatment temperatures; membrane permeability fell by a factor of approximately 500 with increasing temperature in the range 100-200 degrees C. There was no evidence of decomposition at temperatures less than or equal to 190 degrees C for 1 h. Results were consistent with literature reports of heat-induced increases in crystallinity. Membranes were simple to prepare and permeability could be controlled without recourse to chemical manipulation.

Diffusion↗

PubMed1995

Histologic long-term follow-up after embolization with polyvinyl alcohol particles.

A large facial vascular malformation was embolized with polyvinyl alcohol particles twice in 8 years. Resected tissue enabled long-term examination of this material, confirming its chemical inertness and revealing minimal tissue reaction to it apart from calcification. No particle migration, fragmentation, or absorption occurred. There was some recanalization of occluded vessels. Most vessels containing polyvinyl alcohol particles, and all of the larger vessels, were incompletely occluded, with particles becoming embedded in their walls.

Adult↗

PubMed1975

Ocular evaluation of polyvinyl alcohol vehicle in rabbits.

The flow properties and viscosity of the vehicle into which drugs are incorporated can be determining factors in the bioavailability of topically applied ophthalmic drugs. It is shown, in rabbits, that when polyvinyl alcohol and methylcellulose are compared on a viscosity basis, there is essentially no difference in the two vehicles with regard to their influence on ocular drug bioavailability. Moreover, the rate of drainage loss for polyvinyl alcohol solutions, as determined by the radioactive technetium technique, compares favorably to methylcellulose solutions of similar viscosity. The relationship between viscosity and contact time or drainage loss of a drug is not a direct one, but an optimum viscosity range exists for polyvinyl alcohol solutions. This optimum range of 12-15 cps in rabbits is identical to that found for methylcellulose and differs considerably from the commonly employed viscosity in commercial preparations. Based on the methylcellulose-polyvinyl alcohol comparison, it appears that vehicles exhibiting or approximating Newtonian flow properties show comparable effects as ophthalmic vehicles. Finally, a discussion of non-Newtonian vehicles and their expected behavior in the eye is presented.

Animals↗

PubMed1986

Small particle polyvinyl alcohol embolization of cranial lesions with minimal arteriolar-capillary barriers.

Polyvinyl alcohol foam, prepared as small particles measuring 70-150 micron when injected in intracerebral arteries of the rat, adhere to the vascular endothelium, allowing the particles to be captured without necessarily wedging intraluminally. Based on this observation, small particle microembolization was performed in a series of patients who had hypervascular cranial lesions, whose matrices angiographically appeared to have at best minimal arteriolar-capillary barriers. Each case was associated with intracranial dural sinus or cerebral venous drainage. In addition, several lesions had either venous ectasia or venous aneurysms. Symptomatic improvement occurred in all cases without apparent neurologic or pulmonary complications. These examples demonstrate the ability of very small polyvinyl alcohol foam particles to remain within the interstices of vascular lesions that display evidence of only minimal arteriolar-capillary barriers.

Adult↗

PubMed2006

Intrinsically radiopaque iodine-containing polyvinyl alcohol as a liquid embolic agent: evaluation in experimental wide-necked aneurysms.

OBJECT: To evaluate iodine-containing polyvinyl alcohol (I-PVA) as a precipitating liquid embolic agent, implant characteristics--including radiopacity, setting behavior, and biocompatibility--were studied in an aneurysm model in swine. METHODS: Twelve broad-based carotid artery (CA) sidewall aneurysms were surgically constructed in six pigs. Iodine-containing polyvinyl alcohol dissolved in dimethyl sulfoxide (DMSO) was injected during temporary balloon occlusion bridging the aneurysm neck. Control angiography as well as multidetector row computerized tomography (CT) angiography was performed after 4 weeks. Harvested aneurysms were investigated histopathologically and by 3-tesla high-field magnetic resonance (MR) imaging. The mean degree of aneurysm occlusion achieved was 96%. In two aneurysms a minimal protrusion of I-PVA into the CA lumen was observed. During one embolization, leakage of the liquid embolic agent due to DMSO-induced damage of the microcatheter resulted in CA occlusion. Aneurysms embolized with I-PVA could be discriminated clearly from the parent artery on CT angiograms because there was no beam-hardening artifact. High-field MR imaging allowed a detailed depiction of the liquid embolic distribution within the aneurysm. Histologically, a mild to moderate inflammatory response was found in successfully embolized aneurysms, and the polymer mass was frequently covered by a membrane of fibroblasts and endothelial cells. CONCLUSIONS: Iodine-containing polyvinyl alcohol is a ready-to-use liquid embolic agent clearly visible under fluoroscopy; additives are not required. The setting behavior allows for controlled delivery in aneurysm cavities. Histological studies performed 4 weeks after embolization revealed no sign of toxic tissue response to the liquid embolic agent. Overall, I-PVA exhibits interesting implant characteristics in that radiopaque admixtures are not necessary, thus allowing for artifact-free evaluation of treated aneurysms by using CT and MR angiography.

Aneurysm↗

PubMed1978

Effect of addition of inorganic acids or alkalis on gelation of polyvinyl alcohol aqueous solution by gamma-ray irradiation.--Color development with iodine--.

Below the critical concentration of polyvinyl alcohol, the effect of inorganic acids or alkalis on gelation of polyvinyl alcohol aqueous solution was investigated by color development with iodine after gamma-ray irradiation. The absorbances of the polyvinyl alcohol-iodine complex decreased remarkably in the presence of nitric or perchloric acid. These acids decompose and form oxygen or hydrogen peroxide which oxidize the polymer and leads to a fading of the color. On addition of sulfuric, phosphoric and hydrochloric acids, the absorbances decrease in the order that agrees with that of the acidity of these acids at the same molarity. In the alkaline solution the absorbances decrease by the addition of sodium hydroxide and aqueous ammonia in the order that agrees with that of the basicity of these alkalis. These results indicate that the gel formation is caused by the radiolysis of water. As a result of chemical analysis, these additives are considered not to be attached to the polymer.

Acids↗

PubMed1986

Radiolabeled polyvinyl alcohol particles: a potential agent to monitor embolization procedures.

Polyvinyl alcohol sponge (PVA) is a widely used angiographic embolic agent. The radiolabeling of PVA can accurately identify particle localization and may decrease the possibility of patient morbidity from embolization to distal sites. We incorporated 99mTc sulfur colloid (SC) into PVA by heating. Animal experiments demonstrated the in vivo stability of the 99mTc SC-PVA complex and the efficacy of external imaging. 99mTc SC-PVA biodistribution data and external NaI(T1) scintillation probe counts were performed, to assess anatomic localization. Embolization with this complex was performed in a patient.

Angiography↗

PubMed1992

Microparticles of polyvinyl alcohol for nasal delivery. I. Generation by spray-drying and spray-desolvation.

Spray-drying and spray-desolvation are described for the generation of polyvinyl alcohol microparticles intended for nasal administration. The spray-dried microparticles of polyvinyl alcohol were of an appropriate size distribution but consisted of hollow spheres, which made them unsuitable for nasal delivery, as rapid clearance and a varied deposition pattern would be expected. Microparticles were also produced by spraying polyvinyl alcohol (average molecular weight of 14,000) solution (12.5%, w/v) at 0.332 ml/min onto the surface of acetone (spray-desolvation). These microparticles were solid collapsed spheres with the desired size for nasal deposition (10-200 microns). This method can be applied to encapsulation of drugs that are heat labile such as peptides and proteins.

Administration, Intranasal↗