Science.gov

Sample records for agents polyvinyl alcohol

  1. Soy proteins as environmentally friendly sizing agents to replace poly(vinyl alcohol).

    PubMed

    Chen, Lihong; Reddy, Narendra; Yang, Yiqi

    2013-09-01

    An environmentally friendly and inexpensive substitute to the widely used poly(vinyl alcohol) (PVA) has been developed from soy proteins for textile warp sizing. Textile processing is the major source of industrial water pollution across the world, and sizing and desizing operations account for nearly 30 % of the water consumed in a textile plant. PVA is one of the most common sizing agents used for synthetic fibers and their blends due to PVA's easy water solubility and ability to provide desired sizing performance. However, PVA does not degrade and is a major contributor to pollution in textile effluent treatment plants. Although considerable efforts have been made to replace PVA with biodegradable sizing materials, the performance properties provided by PVA on synthetic fibers and their blends have been unmatched so far. Soy proteins are inexpensive, biodegradable, and have been widely studied for potential use in food packaging, as resins and adhesives. In this research, the potential of using soy proteins as textile sizing agents to replace PVA was studied. Polyester and polyester/cotton rovings, yarns, and fabrics sized with soy protein showed a considerably better improvement in strength and abrasion resistance compared to commercially available PVA-based size. Soy protein size had a 5-day biochemical oxygen demand /chemical oxygen demand ratio of 0.57 compared to 0.01 for PVA indicating that soy protein sizes were easily biodegradable in activated sludge. The total and ammonia nitrogen released from the proteins also did not adversely impact the biodegradability. Good sizing performance and easy biodegradability demonstrate that soy protein-based sizes have potential to replace PVA-based sizes leading to substantial benefits to the textile industry and the environment.

  2. Polyvinyl alcohol hydrogels for iontohporesis

    NASA Astrophysics Data System (ADS)

    Bera, Prasanta; Alam, Asif Ali; Arora, Neha; Tibarewala, Dewaki Nandan; Basak, Piyali

    2013-06-01

    Transdermal therapeutic systems propound controlled release of active ingredients through the skin into the systemic circulation in a predictive manner. Drugs administered through these systems escape first-pass metabolism and maintain a steady state scenario similar to a continuous intravenous infusion for up to several days. The iontophoresis deal with the systemic delivery of the bioactive agents (drug) by applying an electric current. It is basically an injection without the needle. The iontophoretic system requires a gel-based matrix to accommodate the bioactive agent. Hydrogels have been used by many investigators in controlled-release drug delivery systems because of their good tissue compatibility and easy manipulation of swelling level and, thereby, solute permeability. In this work we have prepared polyvinyl alcohol (PVA) hydrogel. We have cross linked polyvinyl alcohol chemically with Glutaraldehyde with different wt%. FTIR study reveals the chemical changes during cross linking. Swelling in water, is done to have an idea about drug loading and drug release from the membrane. After drug loading to the hydrogels, we have studied the drug release property of the hydrogels using salicylic acid as a model drug.

  3. 75 FR 61175 - Polyvinyl Alcohol From Taiwan

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-04

    ... COMMISSION Polyvinyl Alcohol From Taiwan AGENCY: United States International Trade Commission. ACTION... of polyvinyl alcohol, provided for in subheading 3905.30.00 of the Harmonized Tariff Schedule of the... of polyvinyl alcohol from Taiwan are being sold in the United States at less than fair value...

  4. 76 FR 13660 - Polyvinyl Alcohol From Taiwan

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-14

    ... COMMISSION Polyvinyl Alcohol From Taiwan Determination On the basis of the record \\1\\ developed in the... United States is materially injured by reason of imports from Taiwan of polyvinyl alcohol, provided for... of a preliminary determination by Commerce that imports of polyvinyl alcohol from Taiwan were...

  5. Poly(vinyl alcohol) as a water protecting agent for silver nanoparticles: the role of polymer size and structure.

    PubMed

    Kyrychenko, Alexander; Pasko, Dmitry A; Kalugin, Oleg N

    2017-02-20

    Chemical modification of silver nanoparticles (AgNPs) with a stabilizing agent, such as poly(vinyl alcohol) (PVA), plays an important role in shape-controlled seeded-growth and colloidal stability. However, theoretical aspects of the stabilizing mechanism of PVA are still poorly understood. To gain a better understanding of the role of PVA in water protecting effects for silver nanoparticles, we developed an atomistic model of a AgNP grafted with single-chain PVA of various lengths. Our model, designed for classical molecular dynamics (MD) simulations, approximates the AgNP as a quasi-spherical silver nanocrystal with 3.9 nm diameter and uses a united-atom representation for PVA with its polymer chain length varying from 220 up to 1540 repeating units. We found that PVA adsorbs onto the AgNP surface through multiple non-covalent interactions, among which non-covalent bonding of the hydroxyl groups plays a key role. The analysis of adsorption isotherms by using the Hill, Scatchard, and McGhee & von Hippel models exhibits evidence for positive binding cooperativity with the cooperativity parameter varying from 1.55 to 2.12. Our results indicate that the size of the PVA polymer rather than its structure plays a crucial role in providing water protecting effects for the AgNP core, varying from 40% up to 91%. The water-protecting efficiency was well approximated by the Langmuir-Freundlich equation, allowing us to predict that the saturated coverage of the nanoparticle of a given diameter of 3.9 nm should occur when the PVA molecular weight approaches 115 kDa, which corresponds to the number of vinyl alcohol monomers being equal to 3100 units.

  6. Polyvinyl alcohol cross-linked with two aldehydes

    NASA Technical Reports Server (NTRS)

    Sheibley, D. W.; Rieker, L. L.; Hsu, L. C.; Manzo, M. A. (Inventor)

    1982-01-01

    A film forming polyvinyl alcohol resin is admixed, in aqueous solution, with a dialdehyde crosslinking agent which is capable of crosslinking the polyvinyl alcohol resin and a water soluble acid aldehyde containing a reactive aldehyde group capable of reacting with hydroxyl groups in the polyvinyl alcohol resin and an ionizable acid hydrogen atom. The dialdehyde is present in an amount sufficient to react with from 1 to 20% by weight of the theoretical amount required to react with all of the hydroxyl groups of the polyvinyl alcohol. The amount of acid aldehyde is from 1 to 50% by weight, same basis, and is sufficient to reduce the pH of the aqueous admixture to 5 or less. The admixture is then formed into a desired physical shape, such as by casting a sheet or film, and the shaped material is then heated to simultaneously dry and crosslink the article.

  7. 21 CFR 177.1670 - Polyvinyl alcohol film.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Polyvinyl alcohol film. 177.1670 Section 177.1670... Contact Surfaces § 177.1670 Polyvinyl alcohol film. Polyvinyl alcohol film may be safely used in contact..., in accordance with the following prescribed conditions: (a) The polyvinyl alcohol film is...

  8. Polyvinyl alcohol gelation: A structural locking-up agent and carbon source for Si/CNT/C composites as high energy lithium ion battery anode

    NASA Astrophysics Data System (ADS)

    Chen, Dingqiong; Liao, Wenjuan; Yang, Yang; Zhao, Jinbao

    2016-05-01

    A novel polyvinyl alcohol (PVA) hydrogel method is developed to synthesize Si/CNT/C composites. The Si nanoparticles and CNTs are 'position' locked up by PVA hydrogel in a simple aqueous solution process, and then the Si-CNT-PVA hydrogel has pyrolyzed to form Si/CNT/C composites. In this unique structured Si/CNT/C composites, the CNTs form a porous network acting both as conductive agent for electron transfer and buffer space to accommodate huge Si volume change during lithiation/delithiation process, while the coating layer of carbon carbonized from polyvinyl alcohol (PVA) hydrogel is conducive to stabilize the interweaved composite structure. The complex structures of Si/CNT/C composites and their electrochemical properties are presented in this paper. The Si/CNT/C composites exhibit an initial reversible capacity of nearly 800 mAhg-1, an excellent capacity retention of 97.1% after 100 cycles at the rate of 0.1 C, and high capacity retention even at high current rate.

  9. 75 FR 15726 - Polyvinyl Alcohol From Taiwan; Determination

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-30

    ... COMMISSION Polyvinyl Alcohol From Taiwan; Determination On the basis of the record \\1\\ developed in the... Taiwan of polyvinyl alcohol provided for in subheading 3905.30.00 of the Harmonized Tariff Schedule of... threatened with material injury by reason of allegedly LTFV imports of polyvinyl alcohol from...

  10. 21 CFR 177.1670 - Polyvinyl alcohol film.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Polyvinyl alcohol film. 177.1670 Section 177.1670... Components of Single and Repeated Use Food Contact Surfaces § 177.1670 Polyvinyl alcohol film. Polyvinyl alcohol film may be safely used in contact with food of the types identified in § 176.170(c) of...

  11. 21 CFR 177.1670 - Polyvinyl alcohol film.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Polyvinyl alcohol film. 177.1670 Section 177.1670... Components of Single and Repeated Use Food Contact Surfaces § 177.1670 Polyvinyl alcohol film. Polyvinyl alcohol film may be safely used in contact with food of the types identified in § 176.170(c) of...

  12. 21 CFR 177.1670 - Polyvinyl alcohol film.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Polyvinyl alcohol film. 177.1670 Section 177.1670... Components of Single and Repeated Use Food Contact Surfaces § 177.1670 Polyvinyl alcohol film. Polyvinyl alcohol film may be safely used in contact with food of the types identified in § 176.170(c) of...

  13. 21 CFR 177.1670 - Polyvinyl alcohol film.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Polyvinyl alcohol film. 177.1670 Section 177.1670... Components of Single and Repeated Use Food Contact Surfaces § 177.1670 Polyvinyl alcohol film. Polyvinyl alcohol film may be safely used in contact with food of the types identified in § 176.170(c) of...

  14. 76 FR 13982 - Antidumping Duty Order: Polyvinyl Alcohol From Taiwan

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-15

    ... International Trade Administration Antidumping Duty Order: Polyvinyl Alcohol From Taiwan AGENCY: Import... Department is issuing an antidumping duty order on polyvinyl alcohol (PVA) from Taiwan. DATES: Effective Date... value in the antidumping duty investigation of PVA from Taiwan. See Polyvinyl Alcohol From Taiwan:...

  15. Cross-linked polyvinyl alcohol and method of making same

    NASA Technical Reports Server (NTRS)

    Hsu, L. C.; Sheibley, D. W.; Philipp, W. H. (Inventor)

    1981-01-01

    A film-forming polyvinyl alcohol polymer is mixed with a polyaldehyde-polysaccharide cross-linking agent having at least two monosaccharide units and a plurality of aldehyde groups per molecule, perferably an average of at least one aldehyde group per monosaccharide units. The cross-linking agent, such as a polydialdehyde starch, is used in an amount of about 2.5 to 20% of the theoretical amount required to cross-link all of the available hydroxyl groups of the polyvinyl alcohol polymer. Reaction between the polymer and cross-linking agent is effected in aqueous acidic solution to produce the cross-linked polymer. The polymer product has low electrical resistivity and other properties rendering it suitable for making separators for alkaline batteries.

  16. In situ self cross-linking of polyvinyl alcohol battery separators

    NASA Technical Reports Server (NTRS)

    Philipp, W. H.; Hsu, L. C.; Sheibley, D. W. (Inventor)

    1979-01-01

    A battery separator was produced from a polyvinyl alcohol sheet structure which was subjected to an in situ, self crosslinking process by selective oxidation of the 1,2 diol units present in the polyvinyl alcohol sheet structure. The 1,2 diol units were cleaved to form aldehyde end groups which subsequently crosslink through acetalization of the 1,3 diol units of the polyvinyl alcohol. Selective oxidation was achieved using a solution of a suitable oxidizing agent such as periodic acid or lead tetraacetate.

  17. Stability of polyvinyl alcohol-coated biochar nanoparticles in brine

    NASA Astrophysics Data System (ADS)

    Griffith, Christopher; Daigle, Hugh

    2017-01-01

    This paper reports on the dispersion stability of 150 nm polyvinyl alcohol coated biochar nanoparticles in brine water. Biochar is a renewable, carbon based material that is of significant interest for enhanced oil recovery operations primarily due to its wide ranging surface properties, low cost of synthesis, and low environmental toxicity. Nanoparticles used as stabilizing agents for foams (and emulsions) or in nanofluids have emerged as potential alternatives to surfactants for subsurface applications due to their improved stability at reservoir conditions. If, however, the particles are not properly designed, they are susceptible to aggregation because of the high salinity brines typical of oil and gas reservoirs. Attachment of polymers to the nanoparticle surface, through covalent bonds, provides steric stabilization, and is a necessary step. Our results show that as the graft density of polyvinyl alcohol increases, so too does the stability of nanoparticles in brine solutions. A maximum of 34 wt% of 50,000 Da polyvinyl alcohol was grafted to the particle surface, and the size of the particles was reduced from 3500 nm (no coating) to 350 nm in brine. After 24 h, the particles had a size of 500 nm, and after 48 h completely aggregated. 100,000 Da PVA coated at 24 wt% on the biochar particles were stable in brine for over 1 month with no change in mean particle size of 330 nm.

  18. Polyvinyl alcohol as photoluminescent conductive polymer

    NASA Astrophysics Data System (ADS)

    Ruiz-Limón, B.; Wetzel, G. B. J.; Olivares-Pérez, A.; Ponce-Lee, E. L.; Hernández-Garay, M. P.; Páez-Trujillo, G.; Toxqui-López, S.; Fuentes-Tapia, I.

    2007-02-01

    We synthesized a photoluminescent conductor polymer composed of polyvinyl alcohol, which was doped with nickel chloride to decrease its resistivity (300 Ωcm) and benzalkonium chloride to obtain photoluminescence properties, when it is radiated with a green laser beam (532 nm). We compared its absorbance curve and its energy emitted curve to observe the amount energy that is taken advantage of this process. Besides we research the photoluminescence behavior when an electric currant is applied in our conductor polymer, obtaining a modulation capacity.

  19. Complex compound polyvinyl alcohol-titanic acid/titanium dioxide

    NASA Astrophysics Data System (ADS)

    Prosanov, I. Yu.

    2013-02-01

    A complex compound polyvinyl alcohol-titanic acid has been produced and investigated by means of IR and Raman spectroscopy, X-ray diffraction, and synchronous thermal analysis. It is claimed that it represents an interpolymeric complex of polyvinyl alcohol and hydrated titanium oxide.

  20. High-flow priapism treated with superselective transcatheter embolization using polyvinyl alcohol particles

    PubMed Central

    Sánchez-López, Sebastián; González-Gómez, Silvia; Di lizio-Miele, Katyna; González-Gómez, Joaquín

    2017-01-01

    Objectives: Priapism is a persistent erection of the penis not associated with sexual stimulation. High-flow priapism is caused by unregulated arterial inflow, usually preceded by perineal or penile blunt trauma and formation of an arterial-lacunar fistula. We present a case of high-flow priapism in a 13-year-old patient managed with polyvinyl alcohol particles. Methods: After obtaining informed consent of the parents of the minor, diagnosis was made with penile Color Doppler Ultrasound and confirmed with flush angiography. Selective arterial embolization was performed with the use of polyvinyl alcohol particles. Results: Complete detumescence was achieved without compromising the patient’s erectile function. Conclusions: The use of permanent occlusive agents like polyvinyl alcohol particles for embolization shows good occlusion rates compared to temporary agents. More studies are needed to find the safer and better agent for the treatment of high flow priapism without compromising erectile function. PMID:28255447

  1. In Situ Cross-Linking of Polyvinyl Alcohol Films

    NASA Technical Reports Server (NTRS)

    Philipp, W. H.; Shu, L. C.; May, C. E.

    1984-01-01

    Films or impregnated matrices readily made from aqueous polyvinyl alcohol solution. Controlled thickness films made by casting precise quantities of aqueous polymer solution on smooth surface, allowing water to evaporate and then removing film. Composite separators formed in similar fashion by impregnating cloth matrix with polyvinyl alcohol solution and drying composite. Insoluble thin hydrophilic membranes made from aqueous systems, and use of undesirable organic solvents not required.

  2. Ultrasonic depolymerization of aqueous polyvinyl alcohol.

    PubMed

    Grönroos, A; Pirkonen, P; Heikkinen, J; Ihalainen, J; Mursunen, H; Sekki, H

    2001-07-01

    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.

  3. Preparation and properties of polyvinyl alcohol microspheres

    SciTech Connect

    Campbell, J.H.; Grens, J.Z.; Poco, J.F.; Ives, B.H.

    1986-06-01

    Polyvinyl alcohol (PVA) microspheres, having a size range of approx.150- to 250-..mu..m diameter with 1- to 5-..mu..m wall thickness, have been fabricated using a solution droplet technique. The spheres were developed for possible use on the Lawrence Livermore National Laboratory (LLNL) Inertial Confinement Fusion (ICF) Program. PVA, a polymer chosen based on earlier survey work carried out at KMS Fusion, Inc., has good strength, low hydrogen permeability, is optically transparent, and water soluble. The latter property makes it safe and easy to use in our droplet generator system. A unique dual-orifice droplet generator was used to prepare the spheres. The droplet generator operating conditions and the column processing parameters were chosen using results from our 1-D model calculations as a guide. The polymer microsphere model is an extension of the model we developed to support the glass sphere production. After preparation, the spheres were physically characterized for surface quality, sphericity, wall thickness (and uniformity), and size. We also determined the buckling pressure for both uncoated and CH-coated spheres. Radiation stability to beta decay (from tritium) was evaluated by exposing the spheres to a 7-keV electron beam. The results from these and other physical property measurements are presented in this report.

  4. Hybrid composite based on poly(vinyl alcohol) and fillers from renewable resources

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Hybrid composite laminates consisting of polyvinyl alcohol (PVA) as continuous phase (33% by weight) and lignocellulosic fillers, derived from sugarcane bagasse, apple and orange waste (22% by weight) were molded in a carver press in the presence of water and glycerol such as platicizers agents. Cor...

  5. Hybrid composite based on poly(vinyl alcohol) and fillers from renewable resources

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Hybrid composite laminates consisting of polyvinyl alcohol (PVA) as continuous phase and lignocellulosic fibres, derived from sugarcane bagasse, apple and orange waste were moulded in a carver press in the presence of water and glycerol such as platicizers agents. Corn starch was introduced as a bio...

  6. Radiation-chemical preparation of poly(vinyl alcohol) hydrogels

    NASA Astrophysics Data System (ADS)

    Duflot, Anastasia V.; Kitaeva, Natalia K.; Duflot, Vladimir R.

    2015-02-01

    This work reports the usage of method of radiation-chemical synthesis to prepare cross-linked hydrogels from poly(vinyl alcohol) modified with glycidyl methacrylate. Synthesis kinetics of modified poly(vinyl alcohol) and properties of hydrogels were studied. The gel fraction, swelling, mechanical properties, and water content of the hydrogels were measured. It was found that gel fraction increases with increasing radiation dose, concentration of modified poly(vinyl alcohol), and reaches 60%. It was established by differential scanning calorimetry that a fraction of the "bound" water in hydrogels is 50-70% and independent of gel fraction content. In addition to "bound" and "free" states, water in hydrogels is also present in the intermediate state.

  7. Polyvinyl alcohol battery separator containing inert filler. [alkaline batteries

    NASA Technical Reports Server (NTRS)

    Sheibley, D. W.; Hsu, L. C.; Manzo, M. A. (Inventor)

    1981-01-01

    A cross-linked polyvinyl alcohol battery separator is disclosed. A particulate filler, inert to alkaline electrolyte of an alkaline battery, is incorporated in the separator in an amount of 1-20% by weight, based on the weight of the polyvinyl alcohol, and is dispersed throughout the product. Incorporation of the filler enhances performance and increases cycle life of alkaline batteries when compared with batteries containing a similar separator not containing filler. Suitable fillers include titanates, silicates, zirconates, aluminates, wood floor, lignin, and titania. Particle size is not greater than about 50 microns.

  8. 75 FR 38079 - Postponement of Preliminary Determination of Antidumping Duty Investigation: Polyvinyl Alcohol...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-07-01

    ...: Polyvinyl Alcohol From Taiwan AGENCY: Import Administration, International Trade Administration, Department...) initiated the antidumping duty investigation on polyvinyl alcohol from Taiwan. See Initiation of Anti-Dumping Duty Investigation: Polyvinyl Alcohol From Taiwan, 69 FR 59204 (October 4, 2004). On October...

  9. 78 FR 39256 - Polyvinyl Alcohol From Taiwan: Rescission of Antidumping Duty Administrative Review; 2012-2013

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-01

    ...] Polyvinyl Alcohol From Taiwan: Rescission of Antidumping Duty Administrative Review; 2012-2013 AGENCY... on polyvinyl alcohol (PVA) from Taiwan for the period March 1, 2012, through February 28, 2013. DATES... administrative review.\\3\\ \\3\\ See letter from CCPC to the Department, ``Polyvinyl Alcohol from Taiwan:...

  10. In-situ cross linking of polyvinyl alcohol. [application to battery separator films

    NASA Technical Reports Server (NTRS)

    Philipp, W. H.; Hsu, L. C.; Sheibley, D. W. (Inventor)

    1981-01-01

    A method of producing a crosslinked polyvinyl alcohol structure, such as a battery separator membrane or electrode envelope is described. An aqueous solution of a film-forming polyvinyl alcohol is admixed with an aldehyde crosslinking agent a basic pH to inhibit crosslinking. The crosslinking agent, perferably a dialdehyde such as glutaraldehyde, is used in an amount of from about 1/2 to about 20% of the theoretical amount required to crosslink all of the hydroxyl groups of the polymer. The aqueous admixture is formed into a desired physical shape, such as by casting a sheet of the solution. The sheet is then dried to form a self-supporting film. Crosslinking is then effected by immersing the film in aqueous acid solution. The resultant product has excellent properties for use as a battery separator.

  11. Comparison of the Efficacy of the Embolic Agents Acrylamido Polyvinyl Alcohol Microspheres and Tris-Acryl Gelatin Microspheres for Uterine Artery Embolization for Leiomyomas: A Prospective Randomized Controlled Trial

    SciTech Connect

    Worthington-Kirsch, Robert L.; Chesnick, Richard

    2011-06-15

    Objective: To evaluate the efficacy of acrylamido polyvinyl alcohol microspheres (a-PVAM) as an embolic agent for uterine artery embolization (UAE) compared with Tris-acryl gelatin microspheres (TAGM).Design, Setting, ParticipantsProspective randomized double-blind noninferiority trial. Conducted at two sites both with regional UAE practices. Forty-six women with symptomatic leiomyomas.InterventionUAE procedure was performed with either of the two embolic agents. Either 700-900-{mu}m a-PVAM or 500-700-{mu}m TAGM was used.Main Outcome MeasuresChanges in leiomyoma perfusion, overall uterine volume, and dominant leiomyomas volume measured by contrast-enhanced magnetic resonance imaging at 1 week, 3 months, and 6 months after UAE by a reader blinded to the embolic agent used. Changes in Uterine Fibroid Symptoms and Quality of Life questionnaire scores were measured at 3, 6, and 12 months after UAE. Results: Forty-six patients were randomized and treated under the study protocol (a-PVAM n = 22, TAGM n = 24). There were no procedure-related complications. Two patients were excluded from analysis (one technical failure of the procedure, one withdrawal from study). Successful (>90%) leiomyoma devascularization was observed in 81% of subjects at 1 week after UAE, 97% at 3 months after UAE, and 95% at 6 months after UAE. No significant differences were observed in 14 of 15 outcome measurements, consistent with noninferiority. TAGM was slightly superior to a-PVAM on one comparison (overall quality of life at 3 months after UAE).

  12. Polyvinyl alcohol membranes as alkaline battery separators

    NASA Technical Reports Server (NTRS)

    Sheibley, D. W.; Gonzalez-Sanabria, O.; Manzo, M. A.

    1982-01-01

    Polyvinly alcohol (PVA) cross-linked with aldehyde reagents yields membranes that demonstrate properties that make them suitable for use as alkaline battery separators. Film properties can be controlled by the choice of cross-linker, cross-link density and the method of cross-linking. Three methods of cross-linking and their effects on film properties are discussed. Film properties can also be modified by using a copolymer of vinyl alcohol and acrylic acid as the base for the separator and cross-linking it similarly to the PVA. Fillers can be incorporated into the films to further modify film properties. Results of separator screening tests and cell tests for several variations of PBA films are discussed.

  13. Formation of Linear Polyenes in Thermal Dehydration of Polyvinyl Alcohol, Catalyzed by Phosphotungstic Acid

    NASA Astrophysics Data System (ADS)

    Tretinnikov, O. N.; Sushko, N. I.

    2015-01-01

    In order to obtain linear polyenes in polyvinyl alcohol films via acid-catalyzed thermal dehydration of the polyvinyl alcohol, we used phosphotungstic acid as the catalyst: a safe and heat-stable solid chemical compound. We established that phosphotungstic acid, introduced as solid nanoparticles into polyvinyl alcohol films, is a more effective dehydration catalyst than hydrochloric acid, since in contrast to HCl it does not evaporate from the film during heat treatment.

  14. Polyvinyl alcohol doped with nickel chloride hexahydrate as conductor polymer

    NASA Astrophysics Data System (ADS)

    Ruiz-Limon, B.; Olivares-Perez, Arturo; Silva-Andrade, F.; Fuentes-Tapia, I.; Ibarra-Torres, Juan Carlos

    2004-06-01

    Polyvinyl alcohol is a viscous solution, with blue clear appearance, not has odor, when is deposited, as a film dry the appearance is clear transparent and has high flexibility. This polymer no has double link and don not has p orbital that permit the conductivity. However, can be doped with salts as ammonium dichromate and nickel chloride hexahydrate NiCl26H2O constructing a good conductor polymer with a resistivity around 300 ohms cm. Conserving the high flexibility opened new possibilities and applications.

  15. 77 FR 14342 - Polyvinyl Alcohol From Taiwan: Correction to Notice of Opportunity To Request Administrative Review

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-09

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF COMMERCE International Trade Administration Polyvinyl Alcohol From Taiwan: Correction to Notice of Opportunity To Request... antidumping duty order on polyvinyl alcohol from Taiwan. See Antidumping or Countervailing Duty Order,...

  16. Mineralization of radiation-crosslinked polyvinyl alcohol/polyvinyl pyrrolidone hydrogels.

    PubMed

    Hill, David J T; Whittaker, Andrew K

    2007-11-01

    A study of the calcification of the polyvinyl alcohol/polyvinyl pyrrolidone (PVA/PVP) hydrogels during their exposure to a calcium chloride solution or a simulated body fluid has been carried out. On the basis of the experiments, using a two-compartment permeation cell, the diffusion of calcium ions and their subsequent deposition in the hydrogels were elucidated. Steady-batch experiments were also performed to further elaborate the deposition pattern and the types of calcium deposits. It was demonstrated that Fick's second law of diffusion can describe the diffusion of calcium ions through PVA/PVP hydrogels at 310 K. The diffusion coefficient was determined to be (4.4+/-0.1)x10(-10) m2/s and the partition coefficient for the hydrogels was 0.06. Formation of calcium deposits was noticed taking place both on the surface and inside the hydrogels. The deposits formed on the surface have flake morphology, while the deposits inside the hydrogels are more like globular aggregates. Both types of deposits have been characterized as being comprised calcium and hydroxyl ion deficient apatites with chloride ions the most likely substituting species at the hydroxyl sites.

  17. Electrospun nano-fibre mats with antibacterial properties from quaternised chitosan and poly(vinyl alcohol).

    PubMed

    Ignatova, Milena; Starbova, Kirilka; Markova, Nadya; Manolova, Nevena; Rashkov, Iliya

    2006-09-04

    Nano-fibres containing quaternised chitosan (QCh) have been successfully prepared by electrospinning of QCh solutions mixed with poly(vinyl alcohol) (PVA). The average fibre diameter is in the range of 60-200 nm. UV irradiation of the composite electrospun nano-fibrous mats containing triethylene glycol diacrylate as cross-linking agent has resulted in stabilising of the nano-fibres against disintegration in water or water vapours. Microbiological screening has demonstrated the antibacterial activity of the photo-cross-linked electrospun mats against Staphylococcus aureus and Escherichia coli. The obtained nano-fibrous electrospun mats are promising for wound-healing applications.

  18. 78 FR 37794 - Polyvinyl Alcohol from Taiwan: Final Results of Antidumping Duty Administrative Review; 2010-2012

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-24

    ... International Trade Administration Polyvinyl Alcohol from Taiwan: Final Results of Antidumping Duty... results of the administrative review of the antidumping duty order on polyvinyl alcohol (PVA) from Taiwan... February 29, 2012. \\1\\ See Polyvinyl Alcohol From Taiwan: Preliminary Results of Antidumping...

  19. Optical Fiber Relative-Humidity Sensor with Polyvinyl Alcohol Film

    NASA Astrophysics Data System (ADS)

    Gastón, Ainhoa; Pérez, Fátima; Sevilla, Joaquín

    2004-07-01

    We describe a fiber-optic relative-humidity (RH) sensor comprising a moisture-sensitive overlay on a single-mode side-polished fiber. The hygroscopic polymeric material deposited was polyvinyl alcohol (PVA), which proved to have good adherence and stability. The film reached a fast equilibrium with atmospheric moisture (in less than 1 min), inducing changes in the output optical power of ~10 dB for the 70%-90% RH range. To yield a low-cost device, single-mode standard communication fibers were used; therefore all the components of the sensor can be commercial, mass-produced telecommunication devices. The experimental results obtained are consistent with the expected behavior of the system; the output power decreases because of losses in the polished region of the fiber as the refractive index of its external medium approaches the fiber core value. Because the external medium is PVA film, its refractive index changes in response to its water content.

  20. Immobilization of enzyme into poly(vinyl alcohol) membrane

    SciTech Connect

    Imai, K.; Shiomi, T.; Uchida, K.; Miya, M.

    1986-11-01

    Glucoamylase, invertase, and cellulase were entrapped within poly(vinyl alcohol) (PVA) membrane cross-linked by means of irradiation of ultraviolet light. The conditions for immobilization of glucoamylase were examined with respect to enzyme concentration in PVA, sensitizer (sodium benzoate) concentration in PVA, irradiation time, and membrane thickness. Various characteristics of immobilized glucoamylase were evaluated. Among them, the pH activity curve for the immobilized enzyme was superior to that for the native one, and thermal stability was improved by immobilization with bovine albumin. The apparent Km was larger for immobilized glucoamylase than for the native one, while Vmax was smaller for the immobilized enzyme. Also, the apparent Km appeared to be affected by the molecular size of the substrate. Further, immobilized invertase and cellulase showed good stabilities in repeating usage. 9 references.

  1. End-of-life of starch-polyvinyl alcohol biopolymers.

    PubMed

    Guo, M; Stuckey, D C; Murphy, R J

    2013-01-01

    This study presents a life cycle assessment (LCA) model comparing the waste management options for starch-polyvinyl alcohol (PVOH) biopolymers including landfill, anaerobic digestion (AD), industrial composting and home composting. The ranking of biological treatment routes for starch-PVOH biopolymer wastes depended on their chemical compositions. AD represents the optimum choice for starch-PVOH biopolymer containing N and S elements in global warming potential (GWP(100)), acidification and eutrophication but not on the remaining impact categories, where home composting was shown to be a better option due to its low energy and resource inputs. For those starch-PVOH biopolymers with zero N and S contents home composting delivered the best environmental performance amongst biological treatment routes in most impact categories (except for GWP(100)). The landfill scenario performed generally well due largely to the 100-year time horizon and efficient energy recovery system modeled but this good performance is highly sensitive to assumptions adopted in landfill model.

  2. [Use of polyvinyl alcohol for preparing frozen histological sections].

    PubMed

    Serga, V A; Bykov, L A; Kasatonov, V G

    1982-01-01

    The authors developed a new method for preparation of frozen histological sections. It consists in the use of glycerin-plastified polymer, polyvinyl alcohol, and distilled water for impregnation of tissue pieces and subsequent freezing of them in the same medium. This produces histological sections of high quality. The frozen sections are sufficiently thin (3--5 micrometers). The method excludes cell structure destruction by ice crystals and overfreezing of blocks; the sections do not crumble. Losses of free cell elements, extraction of substances and other artifacts are minimized. The frozen histological sections are firmly glued to the glass without using protein with glycerin. The method saves time and reagents for the preparation of the sections and allows their wide use in morphological and histochemical studies.

  3. Cross-linked polyvinyl alcohol films as alkaline battery separators

    NASA Technical Reports Server (NTRS)

    Sheibley, D. W.; Manzo, M. A.; Gonzalez-Sanabria, O. D.

    1983-01-01

    Cross-linking methods have been investigated to determine their effect on the performance of polyvinyl alcohol (PVA) films as alkaline battery separators. The following types of cross-linked PVA films are discussed: (1) PVA-dialdehyde blends post-treated with an acid or acid periodate solution (two-step method) and (2) PVA-dialdehyde blends cross-linked during film formation (drying) by using a reagent with both aldehyde and acid functionality (one-step method). Laboratory samples of each cross-linked type of film were prepared and evaluated in standard separator screening tests. Then pilot-plant batches of films were prepared and compared to measure differences due to the cross-linking method. The pilot-plant materials were then tested in nickel oxide-zinc cells to compare the two methods with respect to performance characteristics and cycle life. Cell test results are compared with those from tests with Celgard.

  4. Polyvinyl alcohol coating of polystyrene inertial confinement fusion targets

    NASA Technical Reports Server (NTRS)

    Annamalai, P.; Lee, M. C.; Crawley, R. L.; Downs, R. L.

    1985-01-01

    An inertial confinement fusion (ICF) target made of polystyrene is first levitated in an acoustic field. The surface of the target is then etched using an appropriate solution (e.g., cyclohexane) to enhance the wetting characteristics. A specially prepared polyvinyl alcohol solution is atomized using an acoustic atomizer and deposited on the surface of the target. The solution is air dried to form a thin coating (2 microns) on the target (outside diameter of about 350-850 microns). Thicker coatings are obtained by repeated applications of the coating solutions. Preliminary results indicate that uniform coatings may be achievable on the targets with a background surface smoothness in the order of 1000 A.

  5. Cross-linked polyvinyl alcohol films as alkaline battery separators

    NASA Technical Reports Server (NTRS)

    Sheibley, D. W.; Manzo, M. A.; Gonzalez-Sanabria, O. D.

    1982-01-01

    Cross-linking methods were investigated to determine their effect on the performance of polyvinyl alcohol (PVA) films as alkaline battery separators. The following types of cross-linked PVA films are discussed: (1) PVA-dialdehyde blends post-treated with an acid or acid periodate solution (two-step method) and (2) PVA-dialdehyde blends cross-linked during film formation (drying) by using a reagent with both aldehyde and acid functionality (one-step method). Laboratory samples of each cross-linked type of film were prepared and evaluated in standard separator screening tests. The pilot-plant batches of films were prepared and compared to measure differences due to the cross-linking method. The pilot-plant materials were then tested in nickel oxide - zinc cells to compare the two methods with respect to performance characteristics and cycle life. Cell test results are compared with those from tests with Celgard.

  6. Analysis of polyvinyl alcohol microbubbles in human blood plasma using capillary electrophoresis.

    PubMed

    Josefsson, Leila; Larsson, Malin K; Bjällmark, Anna; Emmer, Åsa

    2016-04-01

    Recently, a new type of ultrasound contrast agent that consists of air-filled microbubbles stabilized with a shell of polyvinyl alcohol was developed. When superparamagnetic nanoparticles of iron oxide are incorporated in the polymer shell, a multimodal contrast agent can be obtained. The biodistribution and elimination pathways of the polyvinyl alcohol microbubbles are essential to investigate, which is limited with today's techniques. The aim of the present study was, therefore, to develop a method for qualitative and quantitative analysis of microbubbles in biological samples using capillary electrophoresis with ultraviolet detection. The analysis parameters were optimized to a wavelength at 260 nm and pH of the background electrolyte ranging between 11.9 and 12. Studies with high-intensity ultrasonication degraded microbubbles in water showed that degraded products and intact microbubbles could be distinguished, thus it was possible to quantify the intact microbubbles solely. Analysis of human blood plasma spiked with either plain microbubbles or microbubbles with nanoparticles demonstrated that it is possible to separate them from biological components like proteins in these kinds of samples.

  7. Thermal stability of polyvinyl alcohol/nanocrystalline cellulose composites.

    PubMed

    Voronova, Marina I; Surov, Oleg V; Guseinov, Sabir S; Barannikov, Vladimir P; Zakharov, Anatoly G

    2015-10-05

    Thermal stability of polyvinyl alcohol/cellulose nanocrystals (PVA/CNCs) composites prepared with solution casting technique was studied. The PVA/CNCs composites were characterized by Fourier transform infrared spectrometry, X-ray diffraction, differential scanning calorimeter (DSC) and thermogravimetric (TG) analysis. Due to the presence of CNCs nanoparticles, thermal degradation of the composites occurs at much higher temperatures compared to that of the neat PVA. Thermal stability of the PVA/CNCs composites is maximally enhanced with CNCs content of 8-12 wt%. Some thermal degradation products of the PVA/CNCs composites were identified by mass spectrometric analysis. TG measurements with synchronous recording of mass spectra revealed that the thermal degradation of both CNCs and PVA in the composites with CNCs content of 8-12 wt% occurs simultaneously at a much higher temperature than that of CNCs or the neat PVA. However, with increasing CNCs content more than 12 wt% the thermal stability of the composites decreases. In this case, the degradation of CNCs comes first followed by the degradation of PVA.

  8. UV-responsive polyvinyl alcohol nanofibers prepared by electrospinning

    NASA Astrophysics Data System (ADS)

    Khatri, Zeeshan; Ali, Shamshad; Khatri, Imran; Mayakrishnan, Gopiraman; Kim, Seong Hun; Kim, Ick-Soo

    2015-07-01

    We report UV-responsive polyvinyl alcohol (PVA) nanofibers for potential application for recording and erasing quick response (QR) codes. We incorporate 1‧-3‧-dihydro-8-methoxy-1‧,3‧,3‧-trimethyl-6-nitrospiro [2H-1-benzopyran-2,2‧-(2H)-indole] (indole) and,3-dihydro-1,3,3-trimethylspiro [2H-indole-2,3‧-[3H] phenanthr [9,10-b] (1,4) oxazine] (oxazine) into PVA polymer matrix via electrospinning technique. The resultant nanofibers were measured for recording-erasing, photo-coloration and thermal reversibility. The rate of photo-coloration of PVA-indole nanofibers was five times higher than the PVA-oxazine nanofibers, whereas the thermal reversibility found to be more than twice as fast as PVA-oxazine nanofibers. Results showed that the resultant nanofibers have very good capability of recording QR codes multiple times. The FTIR spectroscopy and SEM were employed to characterize the electrospun nanofibers. The UV-responsive PVA nanofibers have great potentials as a light-driven nanomaterials incorporated within sensors, sensitive displays and in optical devices such as erasable and rewritable optical storage.

  9. Electrospun chitosan/polyvinyl alcohol nanofibre mats for wound healing.

    PubMed

    Charernsriwilaiwat, Natthan; Rojanarata, Theerasak; Ngawhirunpat, Tanasait; Opanasopit, Praneet

    2014-04-01

    Chitosan (CS) aqueous salt blended with polyvinyl alcohol (PVA) nanofibre mats was prepared by electrospinning. CS was dissolved with hydroxybenzotriazole (HOBt), thiamine pyrophosphate (TPP) and ethylenediaminetetraacetic acid (EDTA) in distilled water without the use of toxic or hazardous solvents. The CS aqueous salts were blended with PVA at different weight ratios, and the effect of the solution ratios was investigated. The morphologies and mechanical and swelling properties of the generated fibres were analysed. Indirect cytotoxicity studies indicated that the CS/PVA nanofibre mats were non-toxic to normal human fibroblast cells. The CS-HOBt/PVA and CS-EDTA/PVA nanofibre mats demonstrated satisfactory antibacterial activity against both gram-positive and gram-negative bacteria, and an in vivo wound healing test showed that the CS-EDTA/PVA nanofibre mats performed better than gauze in decreasing acute wound size during the first week after tissue damage. In conclusion, the biodegradable, biocompatible and antibacterial CS-EDTA/PVA nanofibre mats have potential for use as wound dressing materials.

  10. Self Nucleation and Crystallization of Poly(vinyl alcohol)

    NASA Astrophysics Data System (ADS)

    Thomas, David; Cebe, Peggy

    Polyvinyl alcohol (PVA) is a hydrophilic, biodegradable, semi-crystalline polymer with uses ranging from textiles to medicine. Film samples of PVA were investigated to assess crystallization and melting behavior during self-nucleation experiments, and thermal degradation, using differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis, respectively. TG results show that degradation occurred at temperatures close to the observed peak melting temperature of 223 C. Using conventional DSC, PVA was heated at a rate of 10 C/min to various self-nucleation temperatures, Ts, within its melting range, briefly annealed, cooled and reheated. Three distinct crystallization regimes were observed upon cooling, depending upon self nucleation temperature. At low values of Ts, below 227 C, PVA only partially melts; residual crystal anneals while new, less perfect crystals form during cooling. Between 228 C and 234 C, PVA was found to crystallize exclusively by self-nucleation. For Ts above 235 C the PVA melts completely. Fast scanning chip-based calorimetry was used to heat and cool at 2000 K/s, to prevent degradation. Results of self nucleation experiments using fast scanning and conventional DSC will be compared. NSF DMR-1206010.

  11. Poly(vinyl alcohol) gels as photoacoustic breast phantoms revisited

    NASA Astrophysics Data System (ADS)

    Xia, Wenfeng; Piras, Daniele; Heijblom, Michelle; Steenbergen, Wiendelt; van Leeuwen, Ton G.; Manohar, Srirang

    2011-07-01

    A popular phantom in photoacoustic imaging is poly(vinyl alcohol) (PVA) hydrogel fabricated by freezing and thawing (F-T) aqueous solutions of PVA. The material possesses acoustic and optical properties similar to those of tissue. Earlier work characterized PVA gels in small test specimens where temperature distributions during F-T are relatively homogeneous. In this work, in breast-sized samples we observed substantial temperature differences between the shallow regions and the interior during the F-T procedure. We investigated whether spatial variations were also present in the acoustic and optical properties. The speed of sound, acoustic attenuation, and optical reduced scattering coefficients were measured on specimens sampled at various locations in a large phantom. In general, the properties matched values quoted for breast tissue. But while acoustic properties were relatively homogeneous, the reduced scattering was substantially different at the surface compared with the interior. We correlated these variations with gel microstructure inspected using scanning electron microscopy. Interestingly, the phantom's reduced scattering spatial distribution matches the optical properties of the standard two-layer breast model used in x ray dosimetry. We conclude that large PVA samples prepared using the standard recipe make excellent breast tissue phantoms.

  12. Nanofibrillated Cellulose and Copper Nanoparticles Embedded in Polyvinyl Alcohol Films for Antimicrobial Applications

    PubMed Central

    Zhong, Tuhua; Oporto, Gloria S.; Jaczynski, Jacek; Jiang, Changle

    2015-01-01

    Our long-term goal is to develop a hybrid cellulose-copper nanoparticle material as a functional nanofiller to be incorporated in thermoplastic resins for efficiently improving their antimicrobial properties. In this study, copper nanoparticles were first synthesized through chemical reduction of cupric ions on TEMPO nanofibrillated cellulose (TNFC) template using borohydride as a copper reducing agent. The resulting hybrid material was embedded into a polyvinyl alcohol (PVA) matrix using a solvent casting method. The morphology of TNFC-copper nanoparticles was analyzed by transmission electron microscopy (TEM); spherical copper nanoparticles with average size of 9.2 ± 2.0 nm were determined. Thermogravimetric analysis and antimicrobial performance of the films were evaluated. Slight variations in thermal properties between the nanocomposite films and PVA resin were observed. Antimicrobial analysis demonstrated that one-week exposure of nonpathogenic Escherichia coli DH5α to the nanocomposite films results in up to 5-log microbial reduction. PMID:26137482

  13. Copper-containing polyvinyl alcohol composite systems: Preparation, characterization and biological activity

    NASA Astrophysics Data System (ADS)

    Reza Hajipour, Abdol; Mohammadsaleh, Fatemeh; Reza Sabzalian, Mohammad

    2015-08-01

    The present investigation reports, the complex formation of Cu(II) with polyvinyl alcohol (PVA) and the synthesis of PVA-stabilized Cu2O particles. This PVA-Cu2O composite has been prepared via chemical reduction method using PVA-Cu(II) complex as precursor. At first, Cu(II) ions were stabilized in PVA matrix via complex formation with OH groups; subsequently, this PVA-Cu(II) macromolecular complex as precursor reacted with ascorbic acid as reducing agent at pH=12 to prepare PVA-Cu2O composite. The products were characterized by FTIR, XRD, FE-SEM, HRTEM, Visible Spectroscopy and atomic absorption. In the following, the antibacterial properties of as-prepared composites were examined against Gram-positive (Bacillus thuringiensis) and Gram-negative bacteria (Escherichia coli), and the results showed excellent antibacterial activity of these materials.

  14. Poly(vinyl alcohol) Physical Hydrogels: Matrix-Mediated Drug Delivery Using Spontaneously Eroding Substrate

    PubMed Central

    2016-01-01

    Poly(vinyl alcohol) hydrogels have a long and successful history of applications in biomedicine. Historically, these matrices were developed to be nondegradable—limiting their utility to applications as permanent implants. For tissue engineering and drug delivery, herein we develop spontaneously eroding physical hydrogels based on PVA. We characterize in detail a mild, noncryogenic method of producing PVA physical hydrogels using poly(ethylene glycol) as a gelating agent, and investigate PVA molar mass as a means to define the kinetics of erosion of these biomaterials. PVA hydrogels are characterized for associated inflammatory response in adhering macrophages, antiproliferative effects mediated through delivery of cytotoxic drugs to myoblasts, and pro-proliferative activity achieved via presentation of conjugated growth factors to endothelial cells. Together, these data present a multiangle characterization of these novel multifunctional matrices for applications in tissue engineering and drug delivery mediated by implantable biomaterials. PMID:26958864

  15. DIELECTRIC PROPERTIES OF POLYVINYL ALCOHOL, POLY(METHYL METHACRYLATE), POLYVINYL BUTYRAL RESIN AND POLYIMIDE AT LOW TEMPERATURES

    SciTech Connect

    Tuncer, Enis; Sauers, Isidor; James, David Randy; Ellis, Alvin R

    2008-01-01

    Performance of materials and their compatibility determine the size of the electrical insulation in power equipment. For this reason dielectric properties of electrical insulation materials are needed for low temperature power applications. In this work we report the dielectric properties of four polymers: polyvinyl alcohol (PVA), poly(methyl methacrylate) (PMMA), polyvinyl butyral resin (PVB), and polyimide (PI--Kapton\\textregistered). The dielectric measurements are performed with an electrical impedance analyzer in the frequency domain. The impedances are recorded in a cryocooler in the temperature range from 45K to 350K. The dielectric breakdown characteristics of the polymers are measured in a liquid nitrogen bath at atmospheric pressure. It is observed that PI and \\pmma\\ dissolved in toluene have the lowest dielectric losses for temperatures lower than $100\\ \\kelvin$. \\Blx\\ and PI have the smallest spread in their breakdown strength data.

  16. Preparing oxidized fractions of polyvinyl alcohol of a given molecular mass

    NASA Astrophysics Data System (ADS)

    Zimin, Yu. S.; Kutlugil'dina, G. G.; Mustafin, A. G.

    2016-10-01

    The effect of two oxidizers (an oxygen-ozone mixture and hydrogen peroxide) on the kinetics of the oxidative degradation of polyvinyl alcohol in aqueous solutions is studied. Degradation of the polymer is proved not only by a reduction in the weight of oxidized fractions, but in the intrinsic viscosity of their aqueous solutions as well (and thus the average molecular weight of the resulting fractions). It is shown that the degree of the destructive reactions of polyvinyl alcohol grows along with the duration of the process, increasing the initial concentrations of H2O2 and raising the temperature. These results can be used in obtaining oxidized fractions of polyvinyl alcohol that have predetermined molecular weights.

  17. Carboxyl-modified poly(vinyl alcohol)-crosslinked chitosan hydrogel films for potential wound dressing.

    PubMed

    Zhang, Di; Zhou, Wei; Wei, Bing; Wang, Xin; Tang, Rupei; Nie, Jiemin; Wang, Jun

    2015-07-10

    The objective of this study was to develop a novel carboxyl-modified poly(vinyl alcohol)-crosslinked chitosan hydrogel films for potential wound dressing. To prepare the crosslinked hydrogels, poly(vinyl alcohol) (PVA) was grafted with succinate acid to yield carboxyl-modified poly(vinyl alcohol) (PVA-COOH). Hydrogel films based on PVA-COOH and chitosan (CS) at different concentrations were crosslinked through the formation of amide linkages. The mechanical properties of these crosslinked hydrogel films in dry and swollen state were greatly improved with high swelling ratio. Water vapor and oxygen permeability evaluations indicated that crosslinked hydrogel films could maintain a moist environment over wound bed. Biocompatibility test showed the crosslinked hydrogels had no cytotoxicity and hemolytic potential. Gentamicin sulfate-loaded crosslinked hydrogel films showed sustained drug release profile, and could effectively suppress bacterial proliferation and protect wound from infection.

  18. Delayed spontaneous perforation of polyvinyl alcohol membrane-Covered atrial septal defect closure devices.

    PubMed

    Labombarda, Fabien; Roule, Vincent; Beygui, Farzin

    2017-03-01

    Percutaneous device closure has become the first choice for secundum atrial septal defect (ASD) closure when feasible in case of favorable anatomy. The Ultrasept II ASD occluder® device (Cardia Inc, Eagan, MN) is made of two nitinol disc frames covered with polyvinyl alcohol membranes, a synthetic polymer with a large application in the biomedical field. Four relatively early malfunctions of the polyvinyl alcohol membrane were observed in a series of six consecutive patients treated with ASD Ultrasept II closure device in our institution. Operators have to be aware of this apparently rare complication that is likely to be underestimated, associated with such devices. © 2016 Wiley Periodicals, Inc.

  19. Structural and electronic properties of poly(vinyl alcohol) using density functional theory

    SciTech Connect

    Dabhi, Shweta Jha, Prafulla K.

    2014-04-24

    The first principles calculations have been carried out to investigate the structural, electronic band structure density of states along with the projected density of states for poly(vinyl alcohol). Our structural calculation suggests that the poly(vinyl alcohol) exhibits monoclinic structure. The calculated structural lattice parameters are in excellent agreement with available experimental values. The band structure calculations reveal that the direct and indirect band gaps are 5.55 eV and 5.363 eV respectively in accordance with experimental values.

  20. Remediation of environmental pollution by substituting poly(vinyl alcohol) with biodegradable warp size from wheat gluten.

    PubMed

    Chen, Lihong; Reddy, Narendra; Yang, Yiqi

    2013-05-07

    We report the development of wheat gluten as an environmentally friendly sizing agent that can replace poly(vinyl alcohol) (PVA) and make the textile industry more environmentally friendly. Wheat gluten applied onto polyester/cotton (P/C) and polyester as warp sizing agent provided sizing performance and biodegradability in activated sludge necessary to substitute poly(vinyl alcohol) (PVA). PVA is one of the most widely used sizing agents and provides excellent sizing performance to synthetic fibers and their blends but is expensive and difficult to degrade in textile wastewater treatment plants. Although considerable efforts have been made to replace PVA, it has not been possible to develop a warp sizing chemical that can match the sizing performance of PVA and at the same time be cost-effective and biodegrade in effluent treatment plants. At similar % add-on, wheat gluten provided similar cohesion to P/C but much higher abrasion resistance to polyester fabrics compared to PVA. With a biochemical oxygen demand (BOD) to chemical oxygen demand (COD) ratio of 0.7 compared to 0.01 for PVA, wheat gluten was readily degradable in activated sludge. Wheat gluten has the ability to replace PVA for textile warp sizing applications.

  1. Compatibility of Polyvinyl Alcohol with the 241-F/H Tank Farm Liquid Waste

    SciTech Connect

    Oji, L.N.

    1998-11-25

    This report describes results from laboratory-scale oxidative mineralization of polyvinyl alcohol (PVA), and the evaluation of the F/H Tank Farms as a storage/disposal option for PVA waste solution generated in the Canyons and B-line decontamination operations.

  2. Oxidative Mineralization and Characterization of Polyvinyl Alcohol Solutions for Wastewater Treatment

    SciTech Connect

    Oji, L.N.

    1999-08-31

    The principal objectives of this study are to identify an appropriate polyvinyl alcohol (PVA) oxidative mineralization technique, perform compatibility and evaporation fate tests for neat and mineralized PVA, and determine potential for PVA chemical interferences which may affect ion exchange utilization for radioactive wastewater processing in the nuclear industry.

  3. Metronidazole loaded carboxymethyl tamarind kernel polysaccharide-polyvinyl alcohol cryogels: preparation and characterization.

    PubMed

    Meenakshi; Ahuja, Munish

    2015-01-01

    The purpose of present study was to prepare composite hydrogels of carboxymethyl tamarind kernel polysaccharide and polyvinyl alcohol employing freeze thaw-treatment and evaluate them for release behavior. The effect of concentrations of carboxymethyl tamarind kernel polysaccharide, polyvinyl alcohol, and freeze-thaw cycles on the % release of metronidazole was studied employing central composite experimental design. The result of the study revealed that the concentration of carboxymethyl tamarind kernel polysaccharide and interaction effect of concentrations of carboxymethyl tamarind kernel polysaccharide and polyvinyl alcohol influenced the release of metronidazole significantly. The optimal calculated parameters were concentration of carboxymethyl tamarind kernel polysaccharide-6.0% (w/v), concentration of polyvinyl alcohol-8.53% (w/v) and freeze-thaw cycles-4, which provided cryogels with a release of 75.77% over a period of 6h. The formation of cryogels was confirmed by Fourier-transformed infrared spectroscopy and X-ray diffraction studies. Thermal studies revealed higher thermal stability of cryogel.

  4. Electrospun nanofibers of poly(vinyl alcohol)reinforced with cellulose nanofibrils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In this work, nanofibers of poly(vinyl alcohol) (PVA) reinforced with cellulose nanofibrils (CnF) were produced by electrospinning. The effects of applied voltage, polymer concentration and injection rate, tip-to-collector distance (TCD), rotation speed of the collector, and relative humidity on mor...

  5. FOAMED ARTICLES BASED ON POTATO STARCH, CORN AND WHEAT FIBRE, AND POLY(VINYL ALCOHOL)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Continued research cooperation between USDA Laboratories (USA) and the University of Pisa, Italy, has yielded several composites based on blends of poly(vinyl alcohol) (PVA) and either corn or wheat fibres, co-product of the corn-wheat wet-milling process. Foam trays were prepared by baking the blen...

  6. Films from spruce galactoglucomannan blended with poly(vinyl alcohol), corn arabinoxylan and konjac glucomannan

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The improvement of mechanical properties of spruce galactoglucomannan (GGM)-based films was sought by blending GGM with each of poly(vinyl alcohol) (PVOH), corn arabinoxylan (cAX), and konjac glucomannan (KGM). The blend ratios were 3:1, 1:1, and 1:3(w/w), and in addition films were made from each o...

  7. Oxidative mineralization and characterization of polyvinyl alcohol for compatibility with tank farm processing chemistry

    SciTech Connect

    Oji, L.N.

    2000-01-04

    Polyvinyl alcohol (PVA) material has been evaluated for use as a cost-effective substitute for conventional cellulose-based disposal materials (decontamination mops and wipes), plastic bags, and disposable personal protection clothing, that are currently used at Savannah River Site. This study also provides process design criteria for ultraviolet/ultrasonic/hydrogen peroxide PVA reactor system.

  8. Mechanical properties and biocompatibility of co-axially electrospun polyvinyl alcohol/maghemite.

    PubMed

    Ngadiman, Nor Hasrul Akhmal; Mohd Yusof, Noordin; Idris, Ani; Kurniawan, Denni

    2016-08-01

    Electrospinning is a simple and efficient process in producing nanofibers. To fabricate nanofibers made of a blend of two constituent materials, co-axial electrospinning method is an option. In this method, the constituent materials contained in separate barrels are simultaneously injected using two syringe nozzles arranged co-axially and the materials mix during the spraying process forming core and shell of the nanofibers. In this study, co-axial electrospinning method is used to fabricate nanofibers made of polyvinyl alcohol and maghemite (γ-Fe2O3). The concentration of polyvinyl alcohol and amount of maghemite nanoparticle loading were varied, at 5 and 10 w/v% and at 1-10 v/v%, respectively. The mechanical properties (strength and Young's modulus), porosity, and biocompatibility properties (contact angle and cell viability) of the electrospun mats were evaluated, with the same mats fabricated by regular single-nozzle electrospinning method as the control. The co-axial electrospinning method is able to fabricate the expected polyvinyl alcohol/maghemite nanofiber mats. It was noticed that the polyvinyl alcohol/maghemite electrospun mats have lower mechanical properties (i.e. strength and stiffness) and porosity, more hydrophilicity (i.e. lower contact angle), and similar cell viability compared to the mats fabricated by single-nozzle electrospinning method.

  9. Magnetic Properties of Polyvinyl Alcohol and Doxorubicine Loaded Iron Oxide Nanoparticles for Anticancer Drug Delivery Applications

    PubMed Central

    Nadeem, Muhammad; Ahmad, Munir; Akhtar, Muhammad Saeed; Shaari, Amiruddin; Riaz, Saira; Naseem, Shahzad; Masood, Misbah; Saeed, M. A.

    2016-01-01

    The current study emphasizes the synthesis of iron oxide nanoparticles (IONPs) and impact of hydrophilic polymer polyvinyl alcohol (PVA) coating concentration as well as anticancer drug doxorubicin (DOX) loading on saturation magnetization for target drug delivery applications. Iron oxide nanoparticles particles were synthesized by a reformed version of the co-precipitation method. The coating of polyvinyl alcohol along with doxorubicin loading was carried out by the physical immobilization method. X-ray diffraction confirmed the magnetite (Fe3O4) structure of particles that remained unchanged before and after polyvinyl alcohol coating and drug loading. Microstructure and morphological analysis was carried out by transmission electron microscopy revealing the formation of nanoparticles with an average size of 10 nm with slight variation after coating and drug loading. Transmission electron microscopy, energy dispersive, and Fourier transform infrared spectra further confirmed the conjugation of polymer and doxorubicin with iron oxide nanoparticles. The room temperature superparamagnetic behavior of polymer-coated and drug-loaded magnetite nanoparticles were studied by vibrating sample magnetometer. The variation in saturation magnetization after coating evaluated that a sufficient amount of polyvinyl alcohol would be 3 wt. % regarding the externally controlled movement of IONPs in blood under the influence of applied magnetic field for in-vivo target drug delivery. PMID:27348436

  10. Controlling the color of Lippmann holograms recorded in dichromated gelatin polyvinyl alcohol

    NASA Astrophysics Data System (ADS)

    Cai, Tiequan; Tang, Yixing; Wang, Hui; Dai, Chaoming; Guo, Lurong

    1993-03-01

    The polyvinyl alcohol and several other organic materials are mixed into the aqueous gelatin while the film is coated. This thin solid film is sensitized by aqueous ammonium dichromate, so it is called a dichromated gelatin polyvinyl alcohol (DC-GPVA) holographic recording material. DC-GPVA not only possesses the same excellent holographic properties as the conventional dichromated gelatin (DCG) but also obviously improves its environmental stability. Experimental results have shown that the reconstruction wavelength of a Lippman hologram recorded in DC-GPVA can be shifted to longer or shorter wavelengths and freely controlled to a certain extent by varying the ratio of the gelatin and the polyvinyl alcohol and relative organic materials, or hardeners and its quantity, or heated temperature and heated time exerted on the drying films, or thickness of them. After the films are sensitized, they can be exposed by He-Cd or Ar+ laser (441.6 nm or 488.0 nm) and developed by the regular post processed method. Initial discussions are also presented about the functions and mechanisms of the polyvinyl alcohol and relative organic materials added into DC-GPVA.

  11. Linear Dichroism of Cyanine Dyes in Stretched Polyvinyl Alcohol Films: A Physical Chemistry Laboratory Experiment.

    ERIC Educational Resources Information Center

    Natarajan, L. V.; And Others

    1983-01-01

    Provides background information, procedures, and results of an undergraduate physical chemistry experiment on the polarization of absorption spectra of cyanine dyes in stretched polyvinyl alcohol films. The experiment gives a simple demonstration of the concept of linear dichromism and the validity of the TEM method used in the analyses. (JN)

  12. The Rheological Properties of Poly(Vinyl Alcohol) Gels from Rotational Viscometry

    ERIC Educational Resources Information Center

    Hurst, Glenn A.; Bella, Malika; Salzmann, Christoph G.

    2015-01-01

    A laboratory experiment was developed to follow the gelation of a polyvinyl alcohol (PVA) solution upon addition of borax by using rotational viscometry. The rheological properties of the gel were examined, measuring the dependence of viscosity and shear stress on the shear rate. Time-dependent studies were also conducted in which the viscosity of…

  13. Poly(vinyl alcohol)-based film potentially suitable for antimicrobial packaging applications.

    PubMed

    Musetti, Alessandro; Paderni, Katia; Fabbri, Paola; Pulvirenti, Andrea; Al-Moghazy, Marwa; Fava, Patrizia

    2014-04-01

    This work aimed at developing a thin and water-resistant food-grade poly(vinyl alcohol) (PVOH)-based matrix able to swell when in contact with high moisture content food products without rupturing to release antimicrobial agents onto the food surface. This film was prepared by blending PVOH and 7.20% (wt/wt of PVOH) of poly(ethylene glycol) (PEG) with citric acid as crosslinking agent. The film-forming solution was then casted onto a flat surface and the obtained film was 60 μm in thickness and showed a good transparency (close to T = 100%) in the visible region (400 to 700 nm). After immersion in water for 72 h at room temperature, the crosslinked matrix loses only 19.2% of its original weight (the percentage includes the amount of unreacted crosslinking agent, antimicrobial in itself). Water content, degree of swelling, and crosslinking density of the film prove that the presence of PEG diminishes the hydrophilic behavior of the material. Also the mechanical properties of the wet and dry film were assessed. Alongside this, 2.5% (wt/wt of dry film) of grapefruit seed extract (GSE), an antimicrobial agent, was added to the film-forming solution just before casting and the ability of the plastic matrix to release the additive was then evaluated in vitro against 2 GSE-susceptible microorganisms, Salmonella enteritidis and Listeria innocua. The results indicate that the developed matrix may be a promising food-grade material for the incorporation of active substances.

  14. [Preparation and clinical application of polyvinyl alcohol/drug-loaded chitosan microsphere composite wound dressing].

    PubMed

    Zhang, Xiuju; Lin, Zhidan; Chen, Wenbin; Song, Ying; Li, Zhizhong

    2011-04-01

    In order to prepare and apply the polyvinyl alcohol/drug-loaded chitosan microspheres composite wound dressing, we first prepared chitosan microspheres by emulsion cross-linking method, and then added chitosan microspheres into the reactants during the acetalization of polyvinyl alcohol and formaldehyde. We further studied the morphology, water absorption, swelling degree, mechanical properties and in vitro release of the sponge with different amount of chitosan microspheres. The results showed that polyvinyl alcohol/drug-loaded chitosan composite sponge has porous structure with connectionism. Increasing the amount of chitosan microspheres would make the apertures smaller, so that the water absorption and the swelling of sponge decreased, but the tensile strength and compressive strength increased. With the increase of the amount of chitosan microspheres, the drug absorption of cefradine and the release rate increase, and the release time become longer. With the results of toxicity grade of 0 to 1, this type of composite sponge is non-toxic and meets the requirement of biocompatibility. The observation of rabbit nasal cavity after surgical operation suggested that polyvinyl acetal sponge modified with the chitosan has antiphlogistic, hemostatic and non-adherent characteristic, and can promote the healing and recovering of the nasalmucosa. After using this composite material, best growing surroundings for patients' granulation tissue were provided. Exposed bone and tendon were covered well with granulation tissue.

  15. Synthesis of magnetic and multiferroic materials from polyvinyl alcohol-based gels

    NASA Astrophysics Data System (ADS)

    Lisnevskaya, I. V.; Bobrova, I. A.; Lupeiko, T. G.

    2016-01-01

    This review article summarizes results on the synthesis of the magnetic materials including modified nickel ferrite (Ni0.9Co0.1Cu0.1Fe1.9O4-δ), yttrium iron garnet (Y3Fe5O12), lanthanum-containing manganites (MxLa1-xMnO3 (M=Pb, Ba or Sr; x=0.3-0.35)), and multiferroics (BiFeO3 and BiFe0.5Mn0.5O3) from polyvinyl alcohol-based gels. It is shown that the ammonium nitrate accelerates destruction of organic components of xerogels and thus Ni0.9Co0.1Cu0.1Fe1.9O4-δ and BiFeO3 can be prepared at record low temperatures (100 and 250 °C, respectively) which are 200-300 °C lower compared to the process where air is used as an oxidizing agent. As for the synthesis of Y3Fe5O12, MxLa1-xMnO3 and BiFe0.5Mn0.5O3, the presence of NH4NO3 favors formation of foreign phases, which ultimately complicate reaction mechanisms and lead to the higher temperature to synthesize target products. Developed methods provide nanoscale magnetic and multiferroic materials with an average particle size of ∼20-50 nm.

  16. Electrospinning of porphyrin/polyvinyl alcohol (PVA) nanofibers and their acid vapor sensing capability.

    PubMed

    Jang, Kihun; Baek, Il Woong; Back, Sung Yul; Ahn, Heejoon

    2011-07-01

    Fluorescing 5,10,15,20-terakis(1-methyl-4-pyridinio)porphyrin tetra(p-toluenesulfonate) (TMPyP)-embedded and -coated polyvinyl alcohol (PVA) nanofibers were fabricated by using the electrospinning technique. To improve nonpolar solvent solubility of TMPyP/PVA nanofibers, tetraethyl orthosilicate (TEOS) was used as a cross-linking agent. UV-vis spectroscopy showed a strong Q band and two relatively weak Soret bands from the TMPyP/PVA nanofibers, and revealed that the TMPyP molecules were homogeneously loaded to the fibers. Scanning electron microscopy revealed that the electrospun nanofibers had ultrafine structures with an average diameter of ca. 250 nm. X-ray photoelectron spectroscopy confirmed the compositional structure of TMPyP/PVA/TEOS nanofibers and revealed the relative coverage of TMPyP molecules on the surface of TMPyP-embedded and TMPyP-coated PVA/TEOS fibers. For the comparison of the acid vapor sensitivity, TMPyP-embedded PVA/TEOS films, and TMPyP-embedded PVA/TEOS fibers, TMPyP-coated PVA/TEOS fibers were exposed to 1N nitric-acid vapor for 20-60 seconds. Fluorescence microscopy revealed that TMPyP-coated PVA/TEOS nanofibers exhibited better acid-sensing capability than TMPyP-embedded PVA/TEOS nanofibers and films.

  17. Mechanical properties and in vitro characterization of polyvinyl alcohol-nano-silver hydrogel wound dressings

    PubMed Central

    Oliveira, R. N.; Rouzé, R.; Quilty, B.; Alves, G. G.; Soares, G. D. A.; Thiré, R. M. S. M.; McGuinness, G. B.

    2014-01-01

    Polyvinyl alcohol (PVA) hydrogels are materials for potential use in burn healing. Silver nanoparticles can be synthesized within PVA hydrogels giving antimicrobial hydrogels. Hydrogels have to be swollen prior to their application, and the common medium available for that in hospitals is saline solution, but the hydrogel could also take up some of the wound's fluid. This work developed gamma-irradiated PVA/nano-Ag hydrogels for potential use in burn dressing applications. Silver nitrate (AgNO3) was used as nano-Ag precursor agent. Saline solution, phosphate-buffered solution (PBS) pH 7.4 and solution pH 4.0 were used as swelling media. Microstructural evaluation revealed an effect of the nanoparticles on PVA crystallization. The swelling of the PVA-Ag samples in solution pH 4.0 was low, as was their silver delivery, compared with the equivalent samples swollen in the other media. The highest swelling and silver delivery were related to samples prepared with 0.50% AgNO3, and they also presented lower strength in PBS pH 7.4 and solution pH 4.0. Both PVA-Ag samples were also non-toxic and presented antimicrobial activity, confirming that 0.25% AgNO3 concentration is sufficient to establish an antimicrobial effect. Both PVA-Ag samples presented suitable mechanical and swelling properties in all media, representative of potential burn site conditions. PMID:24501677

  18. Development of active polyvinyl alcohol/β-cyclodextrin composites to scavenge undesirable food components.

    PubMed

    López-de-Dicastillo, Carol; Jordá, María; Catalá, Ramón; Gavara, Rafael; Hernández-Muñoz, Pilar

    2011-10-26

    Active food packaging systems based on the incorporation of agents into polymeric package walls are being designed to purposely release or retain compounds to maintain or even increase food quality. The objective of this work was to develop polyvinyl alcohol (PVOH)/β-cyclodextrin (βCD) composite films that can be applied to reduce undesirable component content such as cholesterol in foods through active retention of the compounds in the package walls during storage. Cyclodextrins were added to PVOH in a proportion of 1:1 and cross-linked with glyoxal under acidic media to reduce its water-soluble character. Three different cross-linking procedures were used: cross-linking of the polymer/polysaccharide mixture in solution and film casting, PVOH. βCD*; cross-linking of the polymer, addition of βCD, and casting of the mixture, PVOH*.CD; and casting of a PVOH film, addition of a βCD/glyoxal solution onto the film, and cross-linking during drying, PVOH.CD*. Characterization studies showed that the PVOH*.CD and PVOH.CD* films provided the best physical characteristics with the lowest release values and the highest barrier properties. As a potential application, materials were tested as potential cholesterol-scavenging films. There was a significant reduction in the cholesterol concentration in milk samples when they were exposed to the materials developed.

  19. Investigation into the potential use of poly(vinyl alcohol)/methylglyoxal fibres as antibacterial wound dressing components.

    PubMed

    Bulman, Sophie E L; Goswami, Parikshit; Tronci, Giuseppe; Russell, Stephen J; Carr, Chris

    2015-03-01

    As problems of antibiotic resistance increase, a continuing need for effective bioactive wound dressings is anticipated for the treatment of infected chronic wounds. Naturally derived antibacterial agents, such as Manuka honey, consist of a mixture of compounds, more than one of which can influence antimicrobial potency. The non-peroxide bacteriostatic properties of Manuka honey have been previously linked to the presence of methylglyoxal. The incorporation of methylglyoxal as a functional antibacterial additive during fibre production was explored as a potential route for manufacturing wound dressing components. Synthetic methylglyoxal and poly(vinyl alcohol) were fabricated into webs of sub-micron fibres by means of electrostatic spinning of an aqueous spinning solution. Composite fabrics were also produced by direct deposition of the poly(vinyl alcohol)-methylglyoxal fibres onto a preformed spunbonded nonwoven substrate. Attenuated total reflectance fourier transform infrared and proton nuclear magnetic resonance spectroscopies confirmed the presence of methylglyoxal within the resulting fibre structure. The antibacterial activity of the fibres was studied using strains of Staphylococcus aureus and Escherichia coli. Strong antibacterial activity, as well as diffusion of methylglyoxal from the fibres was observed at a concentration of 1.55 mg/cm(2).

  20. Synthesis and characterization of polyvinyl alcohol based multiwalled carbon nanotube nanocomposites

    NASA Astrophysics Data System (ADS)

    Malikov, E. Y.; Muradov, M. B.; Akperov, O. H.; Eyvazova, G. M.; Puskás, R.; Madarász, D.; Nagy, L.; Kukovecz, Á.; Kónya, Z.

    2014-07-01

    Multiwalled carbon nanotubes were synthesized by chemical vapor deposition over an Fe-Co/alumina catalyst. Nanotubes were then oxidized and grafted with polyvinyl alcohol (PVA). The obtained nanostructure was characterized by Raman spectroscopy, XRD, FTIR, EDX, SEM, TEM and TGA methods. FTIR confirmed the presence of the characteristic peaks of the anticipated ester group. The formation of polymer nanocomposites based on polyvinyl alcohol and multiwalled carbon nanotubes was confirmed by SEM and TEM. High resolution electron micrographs revealed that the primary binding sites for PVA grafting are the sidewall defects of the nanotubes. The novelty of this work is the use of the Fischer esterification reaction for creating the permanent link between the nanotubes and the PVA matrix.

  1. Reversible energy transfer between monomers and fluorescent dimers of rhodamine S in polyvinyl alcohol films

    NASA Astrophysics Data System (ADS)

    Synak, A.; Kułak, L.; Rangełowa-Jankowska, S.; Grobelna, B.; Kubicki, A.; Bojarski, P.

    2011-04-01

    Nonradiative energy transfer and excitation trapping are studied for rhodamine S in polyvinyl alcohol (PVA) films. It occurs that fluorescent dimers of rhodamine S can play a role of imperfect traps for the excitation energy. At highest dye concentrations experimental data of fluorescence quantum yield and emission anisotropy cannot be described by the model of energy transfer neglecting the possibility of excitation return to the monomers. However, the agreement between experimental data and the results of computations can be much improved, if the reverse energy transfer is taken into account. Based on the quantitative analysis it is possible to estimate selected characteristics of rhodamine S dimer in polyvinyl alcohol matrix. The experiments and corresponding analysis are made both at room and elevated temperature.

  2. Edge-enhanced imaging with polyvinyl alcohol/acrylamide photopolymer gratings.

    PubMed

    Márquez, Andrés; Neipp, Cristian; Beléndez, Augusto; Gallego, Sergi; Ortuño, Manuel; Pascual, Inmaculada

    2003-09-01

    We demonstrate edge-enhanced imaging produced by volume phase gratings recorded on a polyvinyl alcohol/acrylamide photopolymer. Bragg diffraction, exhibited by volume gratings, modifies the impulse response of the imaging system, facilitating spatial filtering operations with no need for a physical Fourier plane. We demonstrate that Kogelnik's coupled-wave theory can be used to calculate the transfer function for the transmitted and the diffracted orders. The experimental and simulated results agree, and they demonstrate the feasibility of our proposal.

  3. Trisacryl Gelatin Microspheres Versus Polyvinyl Alcohol Particles in the Preoperative Embolization of Bone Neoplasms

    SciTech Connect

    Basile, Antonio; Rand, Thomas; Lomoschitz, Fritz; Toma, Cyril; Lupattelli, Tommaso; Kettenbach, Joachim; Lammer, Johannes

    2004-09-15

    The aim of this study was to compare the efficacy of trisacryl gelatin microspheres versus polyvinyl alcohol particles (PVA) in the preoperative embolization of bone neoplasms, on the basis of intraoperative blood loss quantified by the differences in preoperative and postoperative hematic levels of hemoglobin, hematocrit and erythrocytes count. From January 1997 to December 2002, preoperative embolization of bone tumors (either primary or secondary) was carried out in 49 patients (age range 12/78), 20 of whom were treated with trysacril gelatin microspheres (group A) and 29 with PVA particles (group B). The delay between embolization and surgery ranged from 1 to 13 days in group A and 1 to 4 days in group B. As used in international protocols, we considered hematic levels of hemoglobin, hematocrit and erythrocytes count for the measurement of intraoperative blood loss then the differences in pre- and postoperative levels were used as statistical comparative parameters. We compared the values of patients treated with embospheres (n = 10) and PVA (n = 18) alone, and patients treated with (group A = 10; group B = 11) versus patients treated without other additional embolic materials in each group (group A = 10; group B = 18). According to the Student's t-test (p < 0.05), the difference of hematic parameters between patients treated by embospheres and PVA alone were significant; otherwise there was no significant difference between patients treated with only one embolic material (embospheres and PVA) versus those treated with other additional embolic agents in each group. The patients treated with microspheres had a minor quantification of intraoperative blood loss compared to those who received PVA particles. Furthermore, they had a minor increase of bleeding related to the delay time between embolization and surgery. The use of additional embolic material did not improve the efficacy of the procedure in either group of patients.

  4. The impact of hot-melt extrusion on the tableting behaviour of polyvinyl alcohol.

    PubMed

    Grymonpré, W; De Jaeghere, W; Peeters, E; Adriaensens, P; Remon, J P; Vervaet, C

    2016-02-10

    There is evidence that processing techniques like hot-melt extrusion (HME) could alter the mechanical properties of pharmaceuticals, which may impede further processability (e.g. tableting). The purpose of this study was to evaluate if HME has an impact on the tableting behaviour of polyvinyl alcohol (PVA)-formulations. Mixtures of partially hydrolysed PVA grades (with a hydroxylation degree of 75 and 88%) and sorbitol (0, 10 and 40%) were extruded, (cryo-) milled and compressed into compacts of 350 ± 10 mg. Before compression all intermediate products were characterized for their solid-state (Tg, Tm, crystallinity) and material properties (particle size, moisture content, moisture sorption). Because both PVA-grades required higher extrusion temperatures (i.e. 180 °C), sorbitol was added to PVA as plasticizing agent to allow extrusion at 140 °C. Compaction experiments were performed on both physical mixtures and cryo-milled extrudates of PVA-sorbitol. By measuring tablet tensile strength and porosity in function of compaction pressure, tableting behaviour was compared before and after HME by means of the CTC-profiles (compressibility, tabletability, compactibility). A higher amorphous content in the formulation (as a result of HME) negatively influenced the tableting behaviour (i.e. lower tablet tensile strength). HME altered the mechanical properties towards more elastically deforming materials, thereby increasing tablet elastic recovery during decompression. The lower tensile strengths resulted from a combined effect of less interparticulate bonding areas (because of higher elastic recovery) and weaker bonding strengths per unit bonding area (between glassy particles).

  5. Poly(vinyl alcohol)/poly(vinyl chloride) composite polymer membranes for secondary zinc electrodes

    NASA Astrophysics Data System (ADS)

    Yang, Chun-Chen; Yang, Jen Ming; Wu, Cheng-Yeou

    A microporous composite polymer membrane composed of poly(vinyl alcohol) (PVA) and poly(vinyl chloride) (PVC), was prepared by a solution casting method and a partial dissolution process. The characteristic properties of microporous PVA/PVC composite polymer membranes containing 2.5-10 wt.% PVC polymers as fillers were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM), capillary flow porometry (CFP), micro-Raman spectroscopy, dynamic mechanical analyzer (DMA) and the AC impedance method. The electrochemical properties of a secondary Zn electrode with the PVA/PVC composite polymer membrane were studied using the galvanostatic charge/discharge method. The PVA/PVC composite polymer membrane showed good thermal, mechanical and electrochemical properties. As a result, the PVA/PVC composite polymer membrane appears to be a good candidate for use on the secondary Zn electrodes.

  6. Limonene and tetrahydrofurfuryl alcohol cleaning agent

    DOEpatents

    Bohnert, G.W.; Carter, R.D.; Hand, T.E.; Powers, M.T.

    1996-05-07

    The present invention is a tetrahydrofurfuryl alcohol and limonene or terpineol cleaning agent and method for formulating and/or using the cleaning agent. This cleaning agent effectively removes both polar and nonpolar contaminants from various electrical and mechanical parts and is readily used without surfactants, thereby reducing the need for additional cleaning operations. The cleaning agent is warm water rinsable without the use of surfactants. The cleaning agent can be azeotropic, enhancing ease of use in cleaning operations and ease of recycling.

  7. Limonene and tetrahydrofurfuryl alcohol cleaning agent

    DOEpatents

    Bohnert, G.W.; Carter, R.D.; Hand, T.E.; Powers, M.T.

    1997-10-21

    The present invention is a tetrahydrofurfuryl alcohol and limonene cleaning agent and method for formulating and/or using the cleaning agent. This cleaning agent effectively removes both polar and nonpolar contaminants from various electrical and mechanical parts and is readily used without surfactants, thereby reducing the need for additional cleaning operations. The cleaning agent is warm water rinsable without the use of surfactants. The cleaning agent can be azeotropic, enhancing ease of use in cleaning operations and ease of recycling.

  8. Limonene and tetrahydrofurfurly alcohol cleaning agent

    DOEpatents

    Bohnert, George W.; Carter, Richard D.; Hand, Thomas E.; Powers, Michael T.

    1997-10-21

    The present invention is a tetrahydrofurfuryl alcohol and limonene cleaning agent and method for formulating and/or using the cleaning agent. This cleaning agent effectively removes both polar and nonpolar contaminants from various electrical and mechanical parts and is readily used without surfactants, thereby reducing the need for additional cleaning operations. The cleaning agent is warm water rinsable without the use of surfactants. The cleaning agent can be azeotropic, enhancing ease of use in cleaning operations and ease of recycling.

  9. Supercritical water oxidation of polyvinyl alcohol and desizing wastewater: influence of NaOH on the organic decomposition.

    PubMed

    Zhang, Jie; Wang, Shuzhong; Guo, Yang; Xu, Donghai; Gong, Yanmeng; Tang, Xingying

    2013-08-01

    Polyvinyl alcohol is a refractory compound widely used in industry. Here we report supercritical water oxidation of polyvinyl alcohol solution and desizing wastewater with and without sodium hydroxide addition. However, it is difficult to implement complete degradation of organics even though polyvinyl alcohol can readily crack under supercritical water treatment. Sodium hydroxide had a significant catalytic effect during the supercritical water oxidation of polyvinyl alcohol. It appears that the OH- ion participated in the C-C bond cleavage of polyvinyl alcohol molecules, the CO2-capture reaction and the neutralization of intermediate organic acids, promoting the overall reactions moving in the forward direction. Acetaldehyde was a typical intermediate product during reaction. For supercritical water oxidation of desizing wastewater, a high destruction rate (98.25%) based on total organic carbon was achieved. In addition, cases where initial wastewater was alkaline were favorable for supercritical water oxidation treatment, but salt precipitation and blockage issues arising during the process need to be taken into account seriously.

  10. Poly/vinyl alcohol/ membranes for reverse osmosis

    NASA Technical Reports Server (NTRS)

    Katz, M. G.; Wydeven, T., Jr.

    1981-01-01

    A description is presented of the results of studies of the water and salt transport properties of PVA membranes, taking into account radiation crosslinked PVA membranes, diffusive salt permeability through PVA membranes, and heat treated PVA membranes. The experimental findings support an occurrence of independent water, and salt permeation processes. It is suggested that the salt permeation is governed by a solution-diffusion transport mechanism. The preparation of thin skinned, asymmetric PVA membranes is also discussed. The employed method has a certain similarity to the classical phase inversion method, which is widely applied in the casting of asymmetric reverse osmosis membranes. Instead of using a gelling bath composed of a nonsolvent for the membrane material and miscible with the solvent from which the membrane is cast, a 'complexing' bath is used, which is a solution of a complexing agent in water.

  11. Polyvinyl alcohol-cellulose nanofibrils-graphene oxide hybrid organic aerogels.

    PubMed

    Javadi, Alireza; Zheng, Qifeng; Payen, Francois; Javadi, Abdolreza; Altin, Yasin; Cai, Zhiyong; Sabo, Ronald; Gong, Shaoqin

    2013-07-10

    Hybrid organic aerogels consisting of polyvinyl alcohol (PVA), cellulose nanofibrils (CNFs), and graphene oxide nanosheets (GONSs) were prepared using an environmentally friendly freeze-drying process. The material properties of these fabricated aerogels were measured and analyzed using various characterization techniques including compression testing, scanning electron microscopy, thermogravimetric (TGA) analysis, Brunauer-Emmet-Teller (BET) surface area analysis, and contact angle measurements. These environmentally friendly, biobased hybrid organic aerogels exhibited a series of desirable properties including a high specific compressive strength and compressive failure strain, ultralow density and thermal conductivity, good thermal stability, and moisture resistance, making them potentially useful for a broad range of applications including thermal insulation.

  12. Suppression of instability by double ablation in tungsten doped polyvinyl alcohol foils

    NASA Astrophysics Data System (ADS)

    Peedikakkandy, Leshma; Chaurasia, S.

    2012-07-01

    In Inertial fusion Energy (IFE) research stable acceleration of fusion targets is a significant problem due to hydrodynamic instabilities. This paper presents the results of the experiments done to investigate the effects of doping 20% of Tungsten (W) (by weight) in Polyvinyl Alcohol (PVA) polymer foils for suppression of instability during laser ablative acceleration. A 20J, 1.060μm, 900ps, Nd: Glass laser system with a focusable intensity of 3 to 9.6×1013W/cm2 was used in the experiment. It is observed that the doped PVA targets yielded stable and enhanced foil acceleration as compared to the undoped PVA foils.

  13. Preparation and Characterization of Palm Leaf Incorporated Polyvinyl Alcohol Bio Composites

    NASA Astrophysics Data System (ADS)

    Patel, Arunendra Kumar; Bajpai, Rakesh; Keller, J. M.; Saha, Abhijit

    2011-12-01

    The Bio Composites of palm leaf (PL) incorporated polyvinyl alcohol (PVA) has been prepared using solution cast technique. Structural and microhardness properties of pure PVA and PL filled PVA Bio Composites has been determined by using FTIR and Vicker's indentation techniquque respectively. The FTIR analysis reveals the presence of PL moieties in PVA, which indicates the good compatibility between PL and PVA. The values of microhardness increases in all composition of PL incorporated PVA films as compared to the pure PVA. This increment in the microhardness is attributed to the excellent binding of PL into PVA.

  14. Preparation and characterization of poly(vinyl alcohol)/graphene nanofibers synthesized by electrospinning

    NASA Astrophysics Data System (ADS)

    Barzegar, Farshad; Bello, Abdulhakeem; Fabiane, Mopeli; Khamlich, Saleh; Momodu, Damilola; Taghizadeh, Fatemeh; Dangbegnon, Julien; Manyala, Ncholu

    2015-02-01

    We report on the synthesis and characterization of electrospun polyvinyl alcohol (PVA)/graphene nanofibers. The samples produced were characterized by Raman spectroscopy for structural and defect density analysis, scanning electron microscopy (SEM) for morphological analysis, and thermogravimetric (TGA) for thermal analysis. SEM measurements show uniform hollow PVA fibers formation and excellent graphene dispersion within the fibers, while TGA measurements show the improved thermal stability of PVA in the presence of graphene. The synthesized polymer reinforced nanofibers have potential to serve in many different applications such as thermal management, supercapacitor electrodes and biomedical materials for drug delivery.

  15. Effect of borax concentration on the structure of Poly(Vinyl Alcohol) gels

    NASA Astrophysics Data System (ADS)

    Lawrence, Mathias B.; Desa, J. A. E.; Aswal, V. K.

    2012-06-01

    Poly(Vinyl Alcohol) hydrogels cross-linked with varying concentrations of borax have been studied using Small-Angle Neutron Scattering and X-Ray Diffraction. The intensity of scattering increases with borax concentration from 1 mg/ml up to 2 mg/ml and falls thereafter for 4 mg/ml, increasing again for a concentration of 10 mg/ml. The mesoscopic structural changes that cause these trends in the SANS data are in keeping with the variations in the X-ray diffraction patterns pertaining to structures within the PVA chains.

  16. Monitoring of temperature fatigue failure mechanism for polyvinyl alcohol fiber concrete using acoustic emission sensors.

    PubMed

    Li, Dongsheng; Cao, Hai

    2012-01-01

    The applicability of acoustic emission (AE) techniques to monitor the mechanism of evolution of polyvinyl alcohol (PVA) fiber concrete damage under temperature fatigue loading is investigated. Using the temperature fatigue test, real-time AE monitoring data of PVA fiber concrete is achieved. Based on the AE signal characteristics of the whole test process and comparison of AE signals of PVA fiber concretes with different fiber contents, the damage evolution process of PVA fiber concrete is analyzed. Finally, a qualitative evaluation of the damage degree is obtained using the kurtosis index and b-value of AE characteristic parameters. The results obtained using both methods are discussed.

  17. Photochromic and microstructural properties of methyl orange doped poly(vinyl alcohol)

    NASA Astrophysics Data System (ADS)

    Bhajantri, R. F.; Sali, Renuka; Ravindrachary, V.; Pujari, P. K.; Sheela, T.; Rathod, Sunil G.

    2013-02-01

    The effect of Methyl Orange (MO) dye on microstructural, optical and fluorescence properties of the polymer Poly(vinyl alcohol) (PVA) is studied. The FTIR study shows the appearance of new peaks indicates the interaction of MO with PVA. The UV-Vis study shows three absorption regions with the first two shows red shift and the third one shows blue shift and hence correspondingly three optical energy band gaps. In fluorescence study, it is observed that the intensity increases with increasing wavelength. These results are understood by invoking the hydrogen bonding and hydrophobic interaction between PVA and MO, forms the charge transfer complex (CTC).

  18. Multiplexed holographic data page storage on a polyvinyl alcohol/acrylamide photopolymer memory.

    PubMed

    Fernández, Elena; Ortuño, Manuel; Gallego, Sergi; Márquez, Andrés; García, Celia; Beléndez, Augusto; Pascual, Inmaculada

    2008-09-01

    Holographic data pages were multiplexed in different thickness layers of a polyvinyl alcohol/acrylamide photopolymer. This material is formed of acrylamide photopolymers, which are considered interesting materials for recording holographic memories. A liquid crystal device was used to modify the object beam and store the data pages. A peristrophic multiplexing method is used to store a large number of data pages in the same spot in the material. The bit error rate was calculated fitting the histograms of the images to determine what parameters improve the quality of the images.

  19. Low voltage vertical organic field-effect transistor with polyvinyl alcohol as gate insulator

    NASA Astrophysics Data System (ADS)

    Rossi, Lucieli; Seidel, Keli F.; Machado, Wagner S.; Hümmelgen, Ivo A.

    2011-11-01

    We report the preparation of low gate leakage current organic field effect transistors in vertical architecture using polyvinyl alcohol as gate insulator and C60 fullerene as n-type semiconductor in devices with gate, source, and drain electrodes of Al. Intermediate electrode and top electrode operate, respectively, as source and drain, or vice-versa, depending on polarity. In these devices the intermediate electrode (source or drain) is permeable to the electric field produced by the gate so that increased drain current is obtained at either increasingly negative gate voltage when the source is the intermediate electrode or increasingly positive gate voltage when the drain is the intermediate electrode.

  20. Study of polyvinyl alcohol nanofibrous membrane by electrospinning as a magnetic nanoparticle delivery approach

    NASA Astrophysics Data System (ADS)

    Ger, Tzong-Rong; Huang, Hao-Ting; Huang, Chen-Yu; Hu, Keng-Shiang; Lai, Jun-Yang; Chen, Jiann-Yeu; Lai, Mei-Feng

    2014-05-01

    Electrospinning technique was used to fabricate polyvinyl alcohol (PVA)-based magnetic biodegradable nanofibers. PVA solution was mixed with ferrofluid or magnetic nanoparticles (MNPs) powder and formed two individual nanofibrous membranes (PVA/ferrofluid and PVA/MNPs powder) by electrospinning. The surface morphology of the nanofibrous membrane was characterized by scanning electron microscopy and the magnetic properties were measured by vibrating sample magnetometer. Macrophages (RAW 264.7) were co-cultured with the nanofibrous membranes for 12, 24, and 48 h and exhibited good cell viability (>95%). Results showed that the PVA fibers would be degraded and the embedded Fe3O4 nanoparticles would be released and delivered to cells.

  1. Catechol-derivatized poly(vinyl alcohol) as a coating molecule for magnetic nanoclusters

    NASA Astrophysics Data System (ADS)

    Burnand, David; Monnier, Christophe A.; Redjem, Anthony; Schaefer, Mark; Rothen-Rutishauser, Barbara; Kilbinger, Andreas; Petri-Fink, Alke

    2015-04-01

    Surface functionalization of superparamagnetic iron oxide nanoparticles (SPIONs) remains indispensable in promoting colloidal stability and biocompatibility. We propose a well-defined and characterized synthesis of a new catechol-functionalized RAFT (reversible addition-fragmentation chain transfer) poly(vinyl alcohol) polymer, which can be anchored onto hydrophobic SPIONs via a one-pot emulsion ligand exchange process. Both single and clustered nanoparticles are obtained and can be separated from each other. As clustered SPIONs are receiving increasing attention, this new macroligand might be of considerable interest for both basic and applied sciences.

  2. Characterization of nanocellulose reinforced semi-interpenetrating polymer network of poly(vinyl alcohol) & polyacrylamide composite films.

    PubMed

    Mandal, Arup; Chakrabarty, Debabrata

    2015-12-10

    Semi-interpenetrating polymer network (semi-IPN) of poly(vinyl alcohol)/polyacrylamide was reinforced with various doses of nanocellulose. The different composite films thus prepared were characterized with respect to their mechanical, thermal, morphological and barrier properties. The composite film containing 5 wt.% of nanocellulose showed the highest tensile strength. The semi-interpenetrating polymer network of poly(vinyl alcohol)/polyacrylamide; and its various composites with nanocellulose were almost identical in their thermal stability. Each of the composites however exhibited much superior stability with respect to the linear poly(vinyl alcohol) and crosslinked polyacrylamide. The scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies exhibited phase separated morphology where agglomerates of nanocellulose were found to be dispersed in the matrix of the semi-IPN. The moisture vapor transmission rate (MVTR) was the lowest for the film containing 5 wt.% of nanocellulose.

  3. Fabrication and characterization of methylene-blue-doped polyvinyl alcohol-polyacrylic acid blend for holographic recording.

    PubMed

    Ushamani, Mythili; Sreekumar, Krishnapillai; Kartha, Cheranellore S; Joseph, Rani

    2004-06-20

    A methylene-blue-sensitized polymer blend of polyvinyl alcohol and polyacrylic acid is fabricated and tested for holographic recording. It was found to have good characteristics such as high sensitivity, storage stability, ease of fabrication, and environmental stability. Optimization of the ratio of polyvinyl alcohol/polyacrylic acid, the sensitizer concentration, pH, energy, diffraction efficiency measurements, etc., have been done. pH is found to have a great influence on the recovery of the dye in this matrix. The results of experimental investigations into the properties of this new material are reported.

  4. Evaluation of the Antimicrobial Effect of Chitosan/Polyvinyl Alcohol Electrospun Nanofibers Containing Mafenide Acetate

    PubMed Central

    Abbaspour, Mohammadreza; Sharif Makhmalzadeh, Behzad; Rezaee, Behjat; Shoja, Saeed; Ahangari, Zohreh

    2015-01-01

    Background: Chitosan, an important biodegradable and biocompatible polymer, has demonstrated wound-healing and antimicrobial properties. Objectives: This study aimed to evaluate the antimicrobial properties of mafenide acetate-loaded nanofibrous films, prepared by the electrospinning technique, using chitosan and polyvinyl alcohol (PVA). Materials and Methods: A 32 full factorial design was used for formulating electrospinning solutions. The chitosan percentage in chitosan/PVA solutions (0%, 10%, and 30%) and the drug content (0%, 20%, and 40%) were chosen as independent variables. The release rate of mafenide acetate from nanofibrous films and their microbial penetration were evaluated. The antimicrobial activity of different nanofibrous film formulations against Staphylococcus aureus and Pseudomonas aeruginosa was studied. Results: The results indicated that all nanofibrous films, with and without drug, can prevent bacterial penetration. Incorporation of mafenide acetate into chitosan/PVA nanofibers enhanced their antimicrobial activity against P. aeruginosa and S. aureus. Conclusions: Overall, the results showed that chitosan/polyvinyl alcohol (PVA) nanofibrous films are applicable for use as a wound dressing with protective, healing, and antimicrobial effects. PMID:26587214

  5. Rheological and Performance Research on a Regenerable Polyvinyl Alcohol Fracturing Fluid.

    PubMed

    Shang, Xiaosen; Ding, Yunhong; Wang, Yonghui; Yang, Lifeng

    2015-01-01

    A regenerable polyvinyl alcohol/organic boron fracturing fluid system with 1.6 wt% polyvinyl alcohol (PVOH) and 1.2 wt% organic boron (OBT) was studied, and its main regeneration mechanism is the reversible cross-linking reaction between B(OH)4- and hydroxyl groups of PVOH as the change of pH. Results of rheology evaluations show that both the apparent viscosity and the thermal stability of the fracturing fluid decreased with the regeneration number of times increasing. In addition, the apparent viscosity of the fluid which was without regeneration was more sensitive to the shear action compared with that of the fluid with regeneration once or twice. When the fracturing fluid was without regeneration, the elasticity was dominating due to the three-dimensional network structure of the formed gel; the viscosity gradually occupied the advantage when the fracturing fluid was regenerated once or twice. The settling velocity of proppant was accelerated by both the regeneration process and the increasing temperature, but it was decelerated when the proppant ratio increased. Results of core damage tests indicate that less permeability damage was caused by the PVOH/OBT fracturing fluid compared with that caused by the guar gum fracturing fluid after gel breaking.

  6. Effects of nanoscale dispersion in the dielectric properties of poly(vinyl alcohol)-bentonite nanocomposites.

    PubMed

    Hernández, María C; Suárez, N; Martínez, Luis A; Feijoo, José L; Lo Mónaco, Salvador; Salazar, Norkys

    2008-05-01

    We investigate the effects of clay proportion and nanoscale dispersion in the dielectric response of poly(vinyl alcohol)-bentonite nanocomposites. The dielectric study was performed using the thermally stimulated depolarization current technique, covering the temperature range of the secondary and high-temperature relaxation processes. Important changes in the secondary relaxations are observed at low clay contents in comparison with neat poly(vinyl alcohol) (PVA). The high-temperature processes show a complex peak, which is a combination of the glass-rubber transition and the space-charge relaxations. The analysis of these processes shows the existence of two segmental relaxations for the nanocomposites. Dielectric results were complemented by calorimetric experiments using differential scanning calorimetry. Morphologic characterization was performed by x-ray diffraction (XRD) and transmission electron microscopy (TEM). TEM and XRD results show a mixture of intercalated and exfoliated clay dispersion in a trend that promotes the exfoliated phase as the bentonite content diminishes. Dielectric and morphological results indicate the existence of polymer-clay interactions through the formation of hydrogen bounds and promoted by the exfoliated dispersion of the clay. These interactions affect not only the segmental dynamics, but also the secondary local dynamics of PVA.

  7. Wound healing modulation by a latex protein-containing polyvinyl alcohol biomembrane.

    PubMed

    Ramos, Márcio V; de Alencar, Nylane Maria N; de Oliveira, Raquel S B; Freitas, Lyara B N; Aragão, Karoline S; de Andrade, Thiago Antônio M; Frade, Marco Andrey C; Brito, Gerly Anne C; de Figueiredo, Ingrid Samantha T

    2016-07-01

    In a previous study, we performed the chemical characterization of a polyvinyl alcohol (PVA) membrane supplemented with latex proteins (LP) displaying wound healing activity, and its efficacy as a delivery system was demonstrated. Here, we report on aspects of the mechanism underlying the performance of the PVA-latex protein biomembrane on wound healing. LP-PVA, but not PVA, induced more intense leukocyte (neutrophil) migration and mast cell degranulation during the inflammatory phase of the cicatricial process. Likewise, LP-PVA induced an increase in key markers and mediators of the inflammatory response (myeloperoxidase activity, nitric oxide, TNF, and IL-1β). These results demonstrated that LP-PVA significantly accelerates the early phase of the inflammatory process by upregulating cytokine release. This remarkable effect improves the subsequent phases of the healing process. The polyvinyl alcohol membrane was fully absorbed as an inert support while LP was shown to be active. It is therefore concluded that the LP-PVA is a suitable bioresource for biomedical engineering.

  8. Band gap energy and optical transitions in polyenes formed by thermal decomposition of polyvinyl alcohol

    NASA Astrophysics Data System (ADS)

    Kulak, A. I.; Bondarava, G. V.; Shchurevich, O. A.

    2013-07-01

    The band gap of the ensemble of oligoene clusters formed by thermocatalytic decomposition of polyvinyl alcohol is parametrized using optical absorption spectra. A band gap energy of E gm =1.53 ± 0.02 eV at the end of an infinite polyene chain is found by extrapolating the energies of π → π* transitions in clusters with a number of double bonds varying from 4 to 12. This value is close to the band gap of trans-polyacetylene and the lower bound for the Tauc energy E gT =1.50 eV, which characterizes the minimum interband transition energy. E gT is essentially independent of the concentration of oligoene clusters, which is determined by the concentration of the AlCl3 thermal decomposition catalyst. The Urbach energy determined from the long wavelength edge of the spectrum falls from 2.21 to 0.66 eV as the AlCl3 concentration is raised from 11.1 to 41.7 mmol per mol of polyvinyl alcohol structural units.

  9. Poly(vinyl alcohol) cryogel phantoms for use in ultrasound and MR imaging

    NASA Astrophysics Data System (ADS)

    Surry, K. J. M.; Austin, H. J. B.; Fenster, A.; Peters, T. M.

    2004-12-01

    Poly(vinyl alcohol) cryogel, PVA-C, is presented as a tissue-mimicking material, suitable for application in magnetic resonance (MR) imaging and ultrasound imaging. A 10% by weight poly(vinyl alcohol) in water solution was used to form PVA-C, which is solidified through a freeze-thaw process. The number of freeze-thaw cycles affects the properties of the material. The ultrasound and MR imaging characteristics were investigated using cylindrical samples of PVA-C. The speed of sound was found to range from 1520 to 1540 m s-1, and the attenuation coefficients were in the range of 0.075-0.28 dB (cm MHz)-1. T1 and T2 relaxation values were found to be 718-1034 ms and 108-175 ms, respectively. We also present applications of this material in an anthropomorphic brain phantom, a multi-volume stenosed vessel phantom and breast biopsy phantoms. Some suggestions are made for how best to handle this material in the phantom design and development process.

  10. Water resistance and thermal properties of polyvinyl alcohol-starch fiber blend film

    NASA Astrophysics Data System (ADS)

    Salleh, M. S. N.; Nor, N. N. Mohamed; Mohd, N.; Draman, S. F. Syed

    2017-02-01

    The growing attention of starch fiber (SF) has led to the innovation of Polyvinyl Alcohol-SF (PVA-SF) blends. This blend is regarded as the biodegradable material which aims to reduce the accumulation of synthetic polymer solid waste derived from petroleum. In this study, the thermal blending characterizations of PVA-SF were investigated by differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The water resistance of the blend was also evaluated to study the polarity of the blends. The blend was prepared by plasticizing the polyvinyl alcohol with glycerol and distilled water with the addition of starch fiber. The incorporation of SF to the blends was at 10 wt% to 50 wt% composition. Based on the thermal analysis, PVA-SF blends were suitable for processing at high temperatures, which can be seen by the shifted onset degradation temperature to a higher temperature. This is because cyclic hemiacetals which were provided by SF can act to prevent the thermal attacks. Conversely, increasing the starch fiber proportion to the film blend reduce the endothermic peak amplitude in the DSC thermogram. It was found that PVA-SF blend at the higher composition of SF had the highest water resistance. This may be attributed to the content of fibre in SF which is hydrophilic.

  11. Rheological and Performance Research on a Regenerable Polyvinyl Alcohol Fracturing Fluid

    PubMed Central

    Shang, Xiaosen; Ding, Yunhong; Wang, Yonghui; Yang, Lifeng

    2015-01-01

    A regenerable polyvinyl alcohol/organic boron fracturing fluid system with 1.6 wt% polyvinyl alcohol (PVOH) and 1.2 wt% organic boron (OBT) was studied, and its main regeneration mechanism is the reversible cross-linking reaction between B(OH)4- and hydroxyl groups of PVOH as the change of pH. Results of rheology evaluations show that both the apparent viscosity and the thermal stability of the fracturing fluid decreased with the regeneration number of times increasing. In addition, the apparent viscosity of the fluid which was without regeneration was more sensitive to the shear action compared with that of the fluid with regeneration once or twice. When the fracturing fluid was without regeneration, the elasticity was dominating due to the three-dimensional network structure of the formed gel; the viscosity gradually occupied the advantage when the fracturing fluid was regenerated once or twice. The settling velocity of proppant was accelerated by both the regeneration process and the increasing temperature, but it was decelerated when the proppant ratio increased. Results of core damage tests indicate that less permeability damage was caused by the PVOH/OBT fracturing fluid compared with that caused by the guar gum fracturing fluid after gel breaking. PMID:26641857

  12. A novel crosslinking strategy for preparing poly(vinyl alcohol)-based proton-conducting membranes with high sulfonation

    NASA Astrophysics Data System (ADS)

    Tsai, Chun-En; Lin, Chi-Wen; Hwang, Bing-Joe

    This study synthesizes poly(vinyl alcohol) (PVA)-based polymer electrolyte membranes by a two-step crosslinking process involving esterization and acetal ring formation reactions. This work also uses sulfosuccinic acid (SSA) as the first crosslinking agent to form an inter-crosslinked structure and a promoting sulfonating agent. Glutaraldehyde (GA) as the second crosslinking agent, reacts with the spare OH group of PVA and forms, not only a dense structure at the outer membrane surface, but also a hydrophobic protective layer. Compared with membranes prepared by a traditional one-step crosslinking process, membranes prepared by the two-step crosslinking process exhibit excellent dissolution resistance in water. The membranes become water-insoluble even at a molar ratio of SO 3H/PVA-OH as high as 0.45. Moreover, the synthesized membranes also exhibit high proton conductivities and high methanol permeability resistance. The current study measures highest proton conductivity of 5.3 × 10 -2 S cm -1 at room temperature from one of the synthesized membranes, higher than that of the Nafion ® membrane. Methanol permeability of the synthesized membranes measures about 1 × 10 -7 cm 2 S -1, about one order of magnitude lower than that of the Nafion ® membrane.

  13. Patterned cell arrays and patterned co-cultures on polydopamine-modified poly(vinyl alcohol) hydrogels.

    PubMed

    Beckwith, Kai M; Sikorski, Pawel

    2013-12-01

    Live cell arrays are an emerging tool that expand traditional 2D in vitro cell culture, increasing experimental precision and throughput. A patterned cell system was developed by combining the cell-repellent properties of polyvinyl alcohol hydrogels with the cell adhesive properties of self-assembled films of dopamine (polydopamine). It was shown that polydopamine could be patterned onto spin-cast polyvinyl alcohol hydrogels by microcontact printing, which in turn effectively patterned the growth of several cell types (HeLa, human embryonic kidney, human umbilical vein endothelial cells (HUVEC) and prostate cancer). The cells could be patterned in geometries down to single-cell confinement, and it was demonstrated that cell patterns could be maintained for at least 3 weeks. Furthermore, polydopamine could be used to modify poly(vinyl alcohol) in situ using a cell-compatible deposition buffer (1 mg mL(-1) dopamine in 25 mM tris with a physiological salt balance). The treatment switched the PVA hydrogel from cell repellent to cell adhesive. Finally, by combining microcontact printing and in situ deposition of polydopamine, patterned co-cultures of the same cell type (HeLa/HeLa) and dissimilar cell types (HeLa/HUVEC) were realized through simple chemistry and could be studied over time. The combination of polyvinyl alcohol and polydopamine was shown to be an attractive route to versatile, patterned cell culture experiments with minimal infrastructure requirements and low complexity.

  14. VALIDATION OF AN EPA METHOD FOR THE ION CHROMATOGRAPHIC DETERMINATION OF PERCHLORATE IN FERTILIZERS USING A POLYVINYL ALCOHOL GEL RESIN.

    EPA Science Inventory

    This paper summarizes the key points of a joint study between the EPA and Metrohm-Peak, Inc., on the use of polyvinyl alcohol [PVA] columns for the ion chromatographic determination of percholorate in aqueous leachates or solutions of fertilizers. A series of fertilizer samples ...

  15. Rheological characterization of solutions and thin films made from amylose-hexadecylammonium chloride inclusion complexes and polyvinyl alcohol

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The rheological properties of aqueous solutions and films made from blends of polyvinyl alcohol (PVOH) and amylose-hexadecylammonium chloride inclusion complexes (Hex-Am) were investigated to better understand the polymer interactions and processing parameters. Aqueous solutions of Hex-Am displayed ...

  16. Morphological influence of cellulose nanoparticles (CNs) from cottonseed hulls on rheological properties of polyvinyl alcohol/CN suspensions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This work aims to extract and characterize fibrous, rod-like and spherical cellulose nanoparticles (CNs) from cottonseed hull and to investigate the structure-morphology-rheology relationships. The rheological behavior of poly(vinyl alcohol) (PVA)/CNs suspensions was also examined to guide the solve...

  17. Poly(vinyl alcohol) composite films with high percent elongation prepared from amylose-fatty ammonium salt inclusion complexes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Amylose inclusion complexes prepared from cationic fatty ammonium salts and jet-cooked high amylose starch were combined with poly(vinyl alcohol) (PVOH) to form glycerol-plasticized films. Their tensile properties were compared with similar films prepared previously with analogous anionic fatty acid...

  18. Composite films based on biorelated agro-industrial waste and poly(vinyl alcohol). Preparation and mechanical properties characterization.

    PubMed

    Chiellini, E; Cinelli, P; Imam, S H; Mao, L

    2001-01-01

    As a part of an ongoing project on the production of composite materials based on poly(vinyl alcohol) (PVA) and polymeric materials from renewable resources, the present paper reports on the incorporation of agricultural waste materials as organic fillers in a film matrix based on PVA as continuous phase. In this study lignocellulosic fibers byproducts, derived from sugar cane (SC) and apple (AP) and orange (OR) fruit juice extraction, were cast from PVA aqueous solutions. The effect of fiber type and composition on the relative properties of cast films was evaluated and compared. OR resulted to be suitable for blending in higher amounts by weight than SC and AP. Glycerol and urea were added as plasticizing agents and were observed to be effective in giving flexible films. Additionally, cornstarch was added to further increase the composition of polymers from renewable resources in cost-effective and ecoefficient composite film formulations. The prepared films resulted sensitive to moisture and water. To reduce water sensitivity, hexamethoxymethylmelamine (HMMM) was tested as a cross-linking agent for the present composite formulations. Cross-linked films exhibited significant improvement in water-resistance that can be taken as a tuneable structural feature for customized applications. The mechanical properties of the prepared composite films (elongation at break, tensile strength, Young modulus) were found to be dependent upon the nature and content of the filler and on environmental conditions.

  19. How To Learn and Have Fun with Poly(Vinyl Alcohol) and White Glue

    NASA Astrophysics Data System (ADS)

    de Zea Bermudez, V.; Passos de Almeida, P.; Féria Seita, J.

    1998-11-01

    The general behavior of Newtonian, shear-thinning, shear-thickening, thixotropic, negative thixotropic, and viscoelastic fluids is characterized and briefly discussed in terms of existing theoretical models. Whenever possible, examples of these types of fluids taken from everyday life are given for better understanding. This theoretical introduction is the basis for same, simple, and inexpensive laboratory work employing no special glassware and generally done by pairs of students. The work involves the synthesis of two well-known viscoelastic materials displaying unique properties: poly(vinyl alcohol) (PVA) and white glue, a poly(vinyl acetate)-based emulsion. The students are asked to perform a series of representative mechanical tests on both gels and to describe their observations in full detail. In particular, they are expected to recognize and identify the origin of the intriguing behaviors found (elasticity, spinability, self-siphoning effect, die-swell effect, Weissenberg effect). The tests include the preparation of fibers by extrusion, introducing concepts such as water solubility, hydrogen bonding, and glass transition temperature. The long list of questions, which ideally should be answered at the end of the laboratory work, allows the students to apply the new concepts acquired.

  20. Chitosan functionalized poly(vinyl alcohol) for prospects biomedical and industrial applications: A review.

    PubMed

    Rafique, Ammara; Mahmood Zia, Khalid; Zuber, Mohammad; Tabasum, Shazia; Rehman, Saima

    2016-06-01

    Chitin and chitosan are amino polysaccharides having multidimensional properties, such as biocompatibility, biodegradability, antibacterial properties and non-toxicity, muco-adhesivity, adsorption properties, etc., and thus they can be widely used in variety of areas. Although human history mainly relies on the biopolymers, however synthetic materials like polyvinyl alcohol (PVA) have good mechanical, chemical and physical properties. Functionalization of PVA with chitin and chitosan is considered very appropriate for the development of well-designed biomaterials such as biodegradable films, for membrane separation, for tissue engineering, for food packaging, for wound healing and dressing, hydro gels formation, gels formation, etc. Considering versatile properties of the chitin and chitosan, and wide industrial and biomedical applications of PVA, this review sheds a light on chitin and chitosan based PVA materials with their potential applications especially focusing the bio-medical field. All the technical scientific issues have been addressed highlighting the recent advancement.

  1. Hybrid Polyvinyl Alcohol and Cellulose Fiber Pulp Instead of Asbestos Fibers in Cement-Based Composites

    NASA Astrophysics Data System (ADS)

    Shokrieh, M. M.; Mahmoudi, A.; Shadkam, H. R.

    2015-05-01

    The Taguchi method was used to determine the optimum content of a four-parameters cellulose fiber pulp, polyvinyl alcohol (PVA) fibers, a silica fume, and bentonite for cement-based composite sheets. Then cement composite sheets from the hybrid of PVA and the cellulose fiber pulp were manufactured, and their moduli of rapture were determined experimentally. The result obtained showed that cement composites with a hybrid of PVA and cellulose fiber pulp had a higher flexural strength than cellulose-fiber- reinforced cement ones, but this strength was rather similar to that of asbestos-fiber-reinforced cement composites. Also, using the results of flexural tests and an analytical method, the tensile and compressive moduli of the hybrid of PVA and cement sheet were calculated. The hybrid of PVA and cellulose fiber pulp is proposed as an appropriate alternative for substituting asbestos in the Hatschek process.

  2. Fabrication and Characterization of Graphene/Graphene Oxide-Based Poly(vinyl alcohol) Nanocomposite Membranes

    NASA Astrophysics Data System (ADS)

    Hieu, Nguyen Huu; Long, Nguyen Huynh Bach Son; Kieu, Dang Thi Minh; Nhiem, Ly Tan

    2016-05-01

    Graphene (GE)- or graphene oxide (GO)-based poly(vinyl alcohol) (PVA) nanocomposite membranes have been prepared by the solution blending method. Raman spectra and atomic force microscopy images confirmed that GE and GO were synthesized with average thickness of 0.901 nm and 0.997 nm, respectively. X-ray diffraction patterns indicated good exfoliation of GE or GO in the PVA matrix. Fourier-transform infrared spectra revealed the chemical fractions of the nanocomposite membranes. Differential scanning calorimetry results proved that the thermal stability of the nanocomposite membranes was enhanced compared with neat PVA membrane. Transmission electron microscopy images revealed good dispersion of GE or GO sheets in the PVA matrix with thickness in the range of 19 nm to 39 nm. As a result, good compatibility between GE or GO and PVA was obtained at 0.5 wt.% filler content.

  3. Simple but Strong: A Mussel-Inspired Hot Curing Adhesive Based on Polyvinyl Alcohol Backbone.

    PubMed

    Mu, Youbing; Wan, Xiaobo

    2016-03-01

    The strong adhesion ability of mussel foot-byssal proteins (Mfps) has inspired scientists to develop novel materials for strong and reversible adhesion, coating, antifouling, and many other applications. However, in many cases, the high costs and the tedious preparation steps of such bioinspired materials hamper the process to push them into practical application. Here a simple but effective way (one step) is presented to synthesize a mussel-inspired glue from two cheap commercially available materials: polyvinyl alcohol (PVA) and 3,4-dihydroxybenzaldehyde (DBA). This bioinspired hot curing adhesive exhibits a strong bonding ability as high as 17.3 MPa on stainless steel surfaces, which surpasses most of the commercially available adhesives.

  4. Improvement of polyvinyl alcohol properties by adding nanocrystalline cellulose isolated from banana pseudostems.

    PubMed

    Pereira, André Luís S; do Nascimento, Diego M; Souza Filho, Men de Sá M; Morais, João Paulo S; Vasconcelos, Niedja F; Feitosa, Judith P A; Brígida, Ana Iraidy S; Rosa, Morsyleide de F

    2014-11-04

    Cellulose nanocrystals (CNCs) isolated from banana pseudostems fibers (BPF) of the Pacovan variety were used as fillers in a polyvinyl alcohol (PVOH) matrix to yield a nanocomposite. The fibers from the external fractions of the BPF were alkaline bleached and hydrolyzed under acidic conditions (H2SO4 62% w/w, 70 min, 45 °C) to obtain CNCs with a length (L) of 135.0 ± 12.0 nm and a diameter (D) of 7.2 ± 1.9 nm to yield an aspect ratio (L/D) of 21.2. The CNCs were applied to PVOH films at different concentrations (0%, 1%, 3%, and 5% w/w, dry basis). With higher concentrations of CNCs, the water-vapor barrier of the films increased, while the optical properties changed very little. Increasing the concentration of the CNCs up to 3% significantly improved the mechanical properties of the nanocomposite.

  5. Anaerobic digestion of starch-polyvinyl alcohol biopolymer packaging: biodegradability and environmental impact assessment.

    PubMed

    Guo, M; Trzcinski, A P; Stuckey, D C; Murphy, R J

    2011-12-01

    The digestibility of a starch-polyvinyl alcohol (PVOH) biopolymer insulated cardboard coolbox was investigated under a defined anaerobic digestion (AD) system with key parameters characterized. Laboratory results were combined with industrial operational data to develop a site-specific life cycle assessment (LCA) model. Inoculated with active bacterial trophic groups, the anaerobic biodegradability of three starch-PVOH biopolymers achieved 58-62%. The LCA modeling showed that the environmental burdens of the starch-PVOH biopolymer packaging under AD conditions on acidification, eutrophication, global warming and photochemical oxidation potential were dominated by atmospheric emissions released from substrate degradation and fuel combustion, whereas energy consumption and infrastructure requirements were the causes of abiotic depletion, ozone depletion and toxic impacts. Nevertheless, for this bio-packaging, AD of the starch-PVOH biopolymer combined with recycling of the cardboard emerged as the environmentally superior option and optimization of the energy utilization system could bring further environmental benefits to the AD process.

  6. Structure-property relationships in Sterculia urens/polyvinyl alcohol electrospun composite nanofibres.

    PubMed

    Patra, Niranjan; Martinová, Lenka; Stuchlik, Martin; Černík, Miroslav

    2015-04-20

    Sterculia urens (Gum Karaya) based polyvinyl alcohol (PVA) composite nanofibres have been successfully electrospun after chemical modification of S. urens to increase its solubility. The effect of deacetylated S. urens (DGK) on the morphology, structure, crystallization behaviour and thermal stability was studied for spuned fibres before and after spinning post treatment. An apparent increase in the PVA crystallinity were observed in the PVA-DGK composite nanofibres indicating S. urens induced crystallization of PVA. The pure PVA nanofibre and the nanofibres of PVA-DGK composites were introduced to post electrospinning heat treatment at 150°C for 15 min. The presence of sterculia gum reduced the fibre diameter and distribution of the nanofibres due to the increased stretching of the fibres during spinning. Switching of the thermal behaviour occurs due to post spinning heat treatments.

  7. Characterization and application of zeolitic imidazolate framework-8@polyvinyl alcohol nanofibers mats prepared by electrospinning

    NASA Astrophysics Data System (ADS)

    Fan, Xiaoxiao; Yu, Linling; Li, Lianghao; Yang, Cao; Wen, Junjie; Ye, Xiaokun; Cheng, Jianhua; Hu, Yongyou

    2017-02-01

    In this study, Zeolitic imidazolate framework-8@polyvinyl alcohol (ZIF-8@PVA) nanofibers were creatively fabricated by electrospinning technique, and the nanofibers membranes were characterized by SEM, TEM, XRD, FTIR, TG, DSC, DTA, BET. Its thermal stability, mechanical property, water stability and adsorption nature were also performed. The optimized fabrication parameter of the ZIF-8@PVA was 10 wt% and the uniform diameters of the nanofibers has been obtained. In addition, the ZIF-8@PVA nanofibers displayed unique properties such as a water stable and flexible structure. The adsorption test for Congo red treatment revealed that the nanofibers had a great adsorption performance. The results indicated that the nonwoven fiber mats had a great potential as a new type of membrane adsorbents in wastewater purification. The possible mechanism of CR adsorption onto ZIF-8@PVA was researched.

  8. Tuning optical and three photon absorption properties in graphene oxide-polyvinyl alcohol free standing films

    NASA Astrophysics Data System (ADS)

    Karthikeyan, B.; Udayabhaskar, R.; Hariharan, S.

    2016-07-01

    We report the optical and nonlinear optical properties of graphene oxide (GO)-polyvinyl alcohol (PVA) free standing films. The composite polymer films were prepared in ex-situ method. The variation in optical absorption spectra and optical constants with the amount of GO loading was noteworthy from the optical absorption spectroscopic studies. Nonlinear optical studies done at 532 nm using 5 ns laser pulses show three photon absorption like behaviour. Both steady state and time resolved fluorescence studies reveal that the GO was functioning as a pathway for the decay of fluorescence from PVA. This is attributed to the energy level modifications of GO through hydroxyl groups with PVA. Raman spectroscopy also supports the interaction between GO and PVA ions through OH radicals.

  9. Activation of Ice Recrystallization Inhibition Activity of Poly(vinyl alcohol) using a Supramolecular Trigger†

    PubMed Central

    Phillips, Daniel J.; Congdon, Thomas R.; Gibson, Matthew I.

    2016-01-01

    Antifreeze (glyco)proteins (AF(G)Ps) have potent ice recrystallisation inhibition (IRI) activity – a desirable phenomenon in applications such as cryopreservation, frozen food and more. In Nature AF(G)P activity is regulated by protein expression levels in response to an environmental stimulus; temperature. However, this level of regulation is not possible in synthetic systems. Here, a synthetic macromolecular mimic is introduced, using supramolecular assembly to regulate activity. Catechol-terminated poly(vinyl alcohol) was synthesised by RAFT polymerization. Upon addition of Fe3+, larger supramolecular star polymers form by assembly with two or three catechols. This increase in molecular weight effectively ‘switches on’ the IRI activity and is the first example of external control over the function of AFP mimetics. This provides a simple but elegant solution to the challenge of external control of AFP-mimetic function. PMID:28003855

  10. PIXE investigation of in vitro release of chloramphenicol across polyvinyl alcohol/acrylamide hydrogel

    NASA Astrophysics Data System (ADS)

    Rihawy, M. S.; Alzier, A.; Allaf, A. W.

    2011-09-01

    Hydrogels based on polyvinyl alcohol and different amounts of acrylamide monomer were prepared by thermal cross-linking in the solid state. The hydrogels were investigated for drug delivery system applications. Chloramphenicol was adopted as a model drug to study its release behavior. Particle induced X-ray emission was utilized to study the drug release behavior across the hydrogels and a comparison study with ultraviolet measurements was performed. Fourier Transform Infrared measurements were carried out for molecular characterization. The releasing behavior of the drug exhibits a decrease and a subsequent increase in the release rate, as the acrylamide monomer increases. Characterization of the hydrogels has shown a competitive behavior between crosslinking with AAm acrylamide monomer or oligomerized version, depending on the amount added to prepare the hydrogels.

  11. Non-isothermal crystallization kinetics of eucalyptus lignosulfonate/polyvinyl alcohol composite.

    PubMed

    Ye, De-Zhan; Zhang, Xi; Gu, Shaojin; Zhou, Yingshan; Xu, Weilin

    2017-04-01

    The nonisothermal crystallinization kinetic was performed on Polyvinyl alcohol (PVA) mixed with eucalyptus lignosulfonate calcuim (HLS) as the biobased thermal stabilizer, which was systematically analyzed based on Jeziorny model, Ozawa equation and the Mo method. The results indicated that the entire crystallization process took place through two main stages involving the primary and secondary crystallization processes. The Mo method described nonisothermal crystallization behavior well. Based on the results of the half time for completing crystallization, kc value in Jeziorny model, F(T) value in Mo method and crystallization activation energy, it was concluded that low loading of HLS accelerated PVA crystallization process, however, the growth rate of PVA crystallization was impeded at high content of HLS.

  12. Radiolytic formation of Ag clusters in aqueous polyvinyl alcohol solution and hydrogel matrix

    NASA Astrophysics Data System (ADS)

    Kumar, Manmohan; Varshney, Lalit; Francis, Sanju

    2005-05-01

    Ag+ ions, in aqueous polyvinyl alcohol (PVA) solution and in PVA hydrogel matrix have been gamma radiolytically reduced to produce Ag clusters. UV-visible absorption spectral characteristics of Ag clusters obtained under different gamma dose, Ag+ concentration, PVA concentration and crosslinking density of the gel used have been studied. The effect of Ag+ ions on the radiation crosslinking of the PVA chains, have also been investigated by viscosity measurements. The radiation-induced Ag+ ion reduction was followed by crosslinking of the PVA chains. PVA was found to be a very efficient stabilizer to prevent aggregation of Ag clusters. The clusters produced in the hydrogel matrix were expected to be smaller than the pore size (∼2-20 nm) of the gels used in the study. These Ag clusters were unable to reduce methyl viologen (MV2+) chloride and were stable in air.

  13. A stimuli-responsive and bioactive film based on blended polyvinyl alcohol and cashew gum polysaccharide.

    PubMed

    Silva, Fábio E F; Batista, Karla A; Di-Medeiros, Maria C B; Silva, Cassio N S; Moreira, Bruna R; Fernandes, Kátia F

    2016-01-01

    In this study, a stimuli-responsive, biodegradable and bioactive film was produced by blending cashew gum polysaccharide (CGP) and polyvinyl alcohol (PVA). The film presented malleability and mechanical properties enabling an easy handling. Wetting the film changed the optical property from opacity to levels of transparency higher than 70% and resulted in up to 2-fold increase in its superficial area. Different swelling indexes were obtained varying the pH of solvent, which allows classifying the CGP/PVA film as pH sensitive stimuli-responsive material. The bioactivity was achieved through covalent immobilization of papain, which remained active after storage of CGP/PVA-papain film for 24h in the presence of buffer or in a dry form. These results evidenced that CGP/PVA-papain film is a very promising material for biomedical applications.

  14. Stability of latanoprost in an ophthalmic lipid emulsion using polyvinyl alcohol.

    PubMed

    Sakai, Yusuke; Yasueda, Shin-Ichi; Ohtori, Akira

    2005-11-23

    Latanoprost in water is not stable against heat stress due to hydrolysis of the isopropyl ester in the latanoprost molecule. Therefore, the storage condition of latanoprost ophthalmic solution, Xalatan brand, was in a low temperature (2-8 degrees C). We formulated a favorable ophthalmic lipid emulsion of latanoprost using polyvinyl alcohol as emulsifier which showed a good heat stability. The assays of the latanoprost ophthalmic lipid emulsions adjusted to pH 5.0, 6.0 and 7.0 were 100.4%, 100.7% and 99.2% after storage for 4 weeks at 60 degrees C, respectively. The possibility of room temperature storage for the latanoprost ophthalmic lipid emulsion was demonstrated.

  15. Effects of PVA(Polyvinyl Alcohol) on Supercooling Phenomena of Water

    NASA Astrophysics Data System (ADS)

    Kumano, Hiroyuki; Saito, Akio; Okawa, Seiji; Takizawa, Hiroshi

    In this paper, effects of polymer additive on supercooling of water were investigated experimentally. Poly-vinyl alcohol (PVA) were used as the polymer, and the samples were prepared by dissolving PVA in ultra pure water. Concentration, degree of polymerization and saponification of PVA were varied as the experimental parameters. The sample was cooled, and the temperature at the instant when ice appears was measured. Since freezing of supercooled water is statistical phenomenon, many experiments were carried out and average degrees of supercooling were obtained for each experimental condition. As the result, it was found that PVA affects nucleation of supercooling and the degree of supercooling increases by adding the PVA. Especially, it is found that the average degree of supercooling increases and the standard deviation of average degree of supercooling decreases with increase of degree of saponification of PVA. However, the average degree of supercooling are independent of the degree of polymerization of PVA in the range of this study.

  16. Novel polyvinyl alcohol-bioglass 45S5 based composite nanofibrous membranes as bone scaffolds.

    PubMed

    Shankhwar, Nisha; Kumar, Manishekhar; Mandal, Biman B; Srinivasan, A

    2016-12-01

    Composite nanofibrous membranes based on sol-gel derived 45SiO2 24.5CaO 24.5 Na2O 6 P2O5 (bioglass, BG) and 43SiO2 24.5CaO 24.5 Na2O 6 P2O5 2Fe2O3 (magnetic bioglass, MBG) blended with polyvinyl alcohol (PVA) have been electrospun. These low cost membranes were mostly amorphous in structure with minor crystalline (sodium calcium phosphate) precipitates. All membranes were biodegradable. Among these, the composites exhibited higher tensile strength, better proliferation of human osteosarcoma MG63 cells and higher alkaline phosphatase enzyme activity than the bare PVA membrane, indicating their potential in bone tissue engineering. The magnetic PVA-MBG scaffold was also found to be a promising candidate for magnetic hyperthermia application.

  17. Study of polyvinyl alcohol nanofibrous membrane by electrospinning as a magnetic nanoparticle delivery approach

    SciTech Connect

    Ger, Tzong-Rong; Huang, Hao-Ting; Hu, Keng-Shiang; Huang, Chen-Yu; Lai, Jun-Yang; Chen, Jiann-Yeu; Lai, Mei-Feng

    2014-05-07

    Electrospinning technique was used to fabricate polyvinyl alcohol (PVA)-based magnetic biodegradable nanofibers. PVA solution was mixed with ferrofluid or magnetic nanoparticles (MNPs) powder and formed two individual nanofibrous membranes (PVA/ferrofluid and PVA/MNPs powder) by electrospinning. The surface morphology of the nanofibrous membrane was characterized by scanning electron microscopy and the magnetic properties were measured by vibrating sample magnetometer. Macrophages (RAW 264.7) were co-cultured with the nanofibrous membranes for 12, 24, and 48 h and exhibited good cell viability (>95%). Results showed that the PVA fibers would be degraded and the embedded Fe{sub 3}O{sub 4} nanoparticles would be released and delivered to cells.

  18. Spectroelectrochemical Studies on Quinacridone by Using Poly(vinyl alcohol) Coating as Protection Layer

    PubMed Central

    Enengl, Sandra; Enengl, Christina; Stadler, Philipp; Neugebauer, Helmut; Sariciftci, Niyazi Serdar

    2015-01-01

    Spectroscopic measurements in the infrared range combined with electrochemistry are a powerful technique for investigation of organic semiconductors to track changes during oxidation and reduction (p- and n-doping) processes. For these measurements it is important that the studied material, mostly deposited as a thin film on an internal reflection element, does not dissolve during this characterization. In this study we introduce a technique that allows infrared spectroelectrochemical characterization of films of these materials for the first time. In many cases so far this has been impossible, due to solubility in the oxidized and/or reduced form. This novel technique is shown on thin films of quinacridone by adding a protection layer of poly(vinyl alcohol) (PVA). PMID:26013836

  19. Antimicrobial wound dressing nanofiber mats from multicomponent (chitosan/silver-NPs/polyvinyl alcohol) systems.

    PubMed

    Abdelgawad, Abdelrahman M; Hudson, Samuel M; Rojas, Orlando J

    2014-01-16

    Novel hybrid nanomaterials have been developed for antimicrobial applications. Here we introduce a green route to produce antibacterial nanofiber mats loaded with silver nanoparticles (Ag-NPs, 25 nm diameter) enveloped in chitosan after reduction with glucose. The nanofiber mats were obtained from colloidal dispersions of chitosan-based Ag-NPs blended with polyvinyl alcohol. Nanofibers (150 nm average diameter and narrow size distribution) were obtained by electrospinning and cross-linked with glutaraldhyde. The effect of crosslinking on the release of silver was studied by atomic absorption spectroscopy. Antimicrobial activity was studied by the viable cell-counting; mats loaded with silver and control samples (chitosan/PVA) with different degrees of cross-linking were compared for their effectiveness in reducing or halting the growth of aerobic bacteria. The results showed superior properties and synergistic antibacterial effects by combining chitosan with Ag-NPs.

  20. Lignosulfonate as reinforcement in polyvinyl alcohol film: Mechanical properties and interaction analysis.

    PubMed

    Ye, De-zhan; Jiang, Li; Hu, Xiao-qin; Zhang, Ming-hua; Zhang, Xi

    2016-02-01

    Recently, there has been a growing research interest on renewable composite due to sustainability concerns. This work demonstrated the possibility of using eucalyptus lignosulfonate calcium (HLS) particles as reinforcement in polyvinyl alcohol (PVA) matrix. 41% and 384.7% improvement of pure PVA tensile strength and Young's modulus were achieved with incorporation of 5 wt% HLS. The above results were ascribed to specific intermolecular interactions between HLS and PVA, suggested by the increasing PVA glass transition and crystalline relaxations temperature, depression of melting point with HLS incorporation. Moreover, this interaction was quantitatively determined by q value of -62.4±10.0 in Kwei equation. Additionally, the remarkable red shift of wavenumber corresponding to hydroxyl group also indicated the formation of strong hydrogen bond in HLS/PVA blend. SEM characterization confirmed that HLS/PVA blends are at least miscible.

  1. Method of cross-linking polyvinyl alcohol and other water soluble resins

    NASA Technical Reports Server (NTRS)

    Phillipp, W. H.; May, C. E.; Hsu, L. C.; Sheibley, D. W. (Inventor)

    1980-01-01

    A self supporting sheet structure comprising a water soluble, noncrosslinked polymer such as polyvinyl alcohol which is capable of being crosslinked by reaction with hydrogen atom radicals and hydroxyl molecule radicals is contacted with an aqueous solution having a pH of less than 8 and containing a dissolved salt in an amount sufficient to prevent substantial dissolution of the noncrosslinked polymer in the aqueous solution. The aqueous solution is then irradiated with ionizing radiation to form hydrogen atom radicals and hydroxyl molecule radicals and the irradiation is continued for a time sufficient to effect crosslinking of the water soluble polymer to produce a water insoluble polymer sheet structure. The method has particular application in the production of battery separators and electrode envelopes for alkaline batteries.

  2. Electrochemical properties of poly(vinyl alcohol) and graphene oxide composite for supercapacitor applications

    NASA Astrophysics Data System (ADS)

    Theophile, Niyitanga; Jeong, Hae Kyung

    2017-02-01

    Poly(vinyl alcohol), PVA, polymer was successfully combined with graphene oxide (GO) and thermally reduced graphene oxide (RGO), respectively, to make composites and characterized for supercapacitor applications. PVA-RGO composite shows excellent electrochemical properties compared to PVA-GO composite. The capacitance of 190 Fg-1 is obtained from PVA-RGO composite which is larger than that (13 Fg-1) of PVA-GO composite. Electrochemical impedance of PVA-RGO is more than ten times smaller than that of PVA-GO at 20 kHz, demonstrating that PVA-RGO composite has a great advantage for supercapacitor applications compared to PVA, GO, RGO, and PVA-GO composite.

  3. The effect of electron beam irradiation on preparation of sago starch/polyvinyl alcohol foams

    NASA Astrophysics Data System (ADS)

    Wongsuban, Benchamaporn; Muhammad, Kharidah; Ghazali, Zulkafli; Hashim, Kamaruddin; Ali Hassan, Muhammad

    2003-10-01

    Blends of sago starch (SS)/polyvinyl alcohol (PVA) were irradiated with doses ranging from 10 to 30 kGy. Foams were then produced from these irradiated blends using a microwave. Changes in the degree of crosslinking, gel strength, thermal stability morphology of blends and linear expansion of foam with increasing irradiation doses were subsequently investigated. It was observed that the degree of crosslinking was important in maximizing the positive effect on foams produced. The gel strength of SS/PVA blends was affected by the irradiation. The crosslinking by the irradiation enhanced the thermal stability of SS/PVA blends. The results also revealed that the highest linear expansion of foams could be produced by irradiation blends at 15 kGy. Changes in blend morphology were observed upon irradiation.

  4. Lipogels: surface-adherent composite hydrogels assembled from poly(vinyl alcohol) and liposomes.

    PubMed

    Jensen, Bettina E B; Hosta-Rigau, Leticia; Spycher, Philipp R; Reimhult, Erik; Städler, Brigitte; Zelikin, Alexander N

    2013-08-07

    Drug-eluting engineered surface coatings are of paramount importance for many biomedical applications from implantable devices to tissue engineering. Herein, we present the assembly of lipogels, composite physical hydrogels assembled from poly(vinyl alcohol) and liposomes using thiol-disulfide exchange between end group modified PVA and thiocholesterol containing liposomes, and the response of adhering cells to these coatings. We demonstrate the controlled loading of liposomes into the polymer matrix and the preserved mechanical properties of the lipogels. Furthermore, the lipogels are successfully rendered cell adhesive by incorporation of poly(l-lysine) into the PVA polymer matrix or by poly(dopamine) coating of the lipogels. The successful lipid uptake from the lipogels by macrophages, hepatocytes, and myoblasts was monitored by flow cytometry. Finally, the delivery of active cargo, paclitaxel, to adherent myoblasts is shown, thus illustrating the potential of the lipogels as a drug eluting interface for biomedical applications.

  5. Synthesis and characterization of polyvinyl alcohol- carboxymethyl tamarind gum based composite films.

    PubMed

    Yadav, Indu; Rathnam, V S Sharan; Yogalakshmi, Yamini; Chakraborty, Subhabrata; Banerjee, Indranil; Anis, Arfat; Pal, Kunal

    2017-06-01

    The present study delineates the synthesis of novel composite films using polyvinyl alcohol and carboxymethyl tamarind gum. The microscopic study results confirmed the formation of composite matrices. FTIR spectroscopy suggested the occurrence of hydrogen-bonding amongst the components of the films. The extent of hydrogen bonding was composition-dependent which reached a critical higher limit at a particular composition. At the critical composition, the instantaneous and the intermediate polymer relaxation time were longer. All the films were found to be viscoelastic in nature. The melting endotherm was also highest for the composition described above. Ciprofloxacin loaded films showed excellent antimicrobial property against E. coli, suggesting that the drug was released in its active form. Cell proliferation study using human keratinocytes suggested better cell proliferation in the CMT containing films as compared to the control (PVA only) film. In gist, the developed films can be explored for skin tissue engineering and drug delivery applications.

  6. Electrospun polyvinyl alcohol-collagen-hydroxyapatite nanofibers: a biomimetic extracellular matrix for osteoblastic cells

    NASA Astrophysics Data System (ADS)

    Song, Wei; Markel, David C.; Wang, Sunxi; Shi, Tong; Mao, Guangzhao; Ren, Weiping

    2012-03-01

    The failure of prosthesis after total joint replacement is due to the lack of early implant osseointegration. In this study polyvinyl alcohol-collagen-hydroxyapatite (PVA-Col-HA) electrospun nanofibrous meshes were fabricated as a biomimetic bone-like extracellular matrix for the modification of orthopedic prosthetic surfaces. In order to reinforce the PVA nanofibers, HA nanorods and Type I collagen were incorporated into the nanofibers. We investigated the morphology, biodegradability, mechanical properties and biocompatibility of the prepared nanofibers. Our results showed these inorganic-organic blended nanofibers to be degradable in vitro. The encapsulated nano-HA and collagen interacted with the PVA content, reinforcing the hydrolytic resistance and mechanical properties of nanofibers that provided longer lasting stability. The encapsulated nano-HA and collagen also enhanced the adhesion and proliferation of murine bone cells (MC3T3) in vitro. We propose the PVA-Col-HA nanofibers might be promising modifying materials on implant surfaces for orthopedic applications.

  7. Preparation of poly(vinyl alcohol)/kaolinite nanocomposites via in situ polymerization

    SciTech Connect

    Jia Xin; Li Yanfeng Zhang Bo; Cheng Qiong; Zhang Shujiang

    2008-03-04

    Poly(vinyl alcohol)/kaolinite intercalated nanocomposites (Kao-PVA) were prepared via in situ intercalation radical polymerization. Vinyl acetate (VAc) was intercalated into kaolinite by a displacement method using dimethyl sulfoxide/kaolinite (Kao-DMSO) as the intermediate. Then, PVAc/kaolinite (Kao-PVAc) was obtained via radical polymerization with benzoyl peroxide (BPO) as initiator. Last, PVAc/kaolinite was saponified via direct-hydrolysis with NaOH solution in order to obtain PVA/kaolinite nanocomposites, which was characterized by Fourier-Transformation spectroscopy (FTIR), wide X-ray diffraction (WXRD) and transmission electron microscopy (TEM). Their differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) results of the obtained PVA/kaolinite suggested that the thermal properties had an obvious improvement.

  8. Reverse osmosis performance of modified polyvinyl alcohol thin-film composite membranes

    SciTech Connect

    Lang, K.; Chowdhury, G.; Matsuura, T.; Sourirajan, S. )

    1994-08-01

    Membrane separation characteristics in the nanofiltration (NF) and reverse osmosis (RO) regions of the filtration spectrum are governed by a complex combination of both steric hindrance and surface force interactions. NF and RO membranes having surface charges show unusual selectivity behavior not predicted on the basis of physical pore size alone. Hence, practical characterizations should employ techniques to gain insight on membrane function. In this work, the separation characteristics of an anionically charged modified polyvinyl alcohol (PVA) thin-film composite membrane under different operating pressures were investigated. A qualitative measurement of the surface force interactions between solutes and membrane polymer was conducted using liquid chromatography technique. An attempt was also made to study the chlorine resistance of the composite membrane.

  9. Polyvinyl alcohol {gamma}-ray grafted nylon 4 membrane for pervaporation and evapomeation

    SciTech Connect

    Lai, J.Y.; Chen, R.Y.; Lee, K.R

    1993-05-01

    Nylon 4, which possesses high mechanical strength and good affinity for water, can be considered as a liquid separation membrane. To improve the hydrophilicity of a Nylon 4 membrane for pervaporation and evapomeation processes, and to overcome the hydrolysis of polyvinyl alcohol (PVA), this study attempts to prepare a PVA-g-Nylon 4 membrane by {gamma}-ray irradiation grafting of vinyl acetate (VAc) onto Nylon 4 membrane, followed by hydrolysis treatment. The effects of down-stream pressure, irradiation dose, VAc monomer concentration, degree of grafting, feed composition, and size of alcohols on the separation of water-alcohol mixtures were studied. The surface properties of the prepared membrane were characterized by FTIR, ESCA, and a contact angle meter. A separation factor of 13.8 and a permeation rate of 0.352 kg/m{sup 2}-h can be obtained for a PVA-g-Nylon 4 membrane with a degree of grafting of 21.2% for a 90-wt% ethanol feed concentration. Compared to the pervaporation process, the evapomeation process has a significantly increased separation factor with a decreased permeation rate for the same PVA-g-Nylon 4 membrane. 24 refs., 9 figs., 4 tabs.

  10. Properties of iopamidol-incorporated poly(vinyl alcohol) microparticle as an X-ray imaging flow tracer.

    PubMed

    Ahn, Sungsook; Jung, Sung Yong; Lee, Jin Pyung; Lee, Sang Joon

    2011-02-10

    We have recently reported on poly(vinyl alcohol) microparticles containing X-ray contrast agent, iopamidol, designed as a flow tracer working in synchrotron X-ray imaging ( Biosens. Bioelectron. 2010 , 25 , 1571 ). Although iopamidol is physically encapsulated in the microparticles, it displays a great contrast enhancement and stable feasibility in in vitro human blood pool. Nonetheless, a direct relation between the absolute amount of incorporated iopamidol and the enhancement in imaging efficiency was not observed. In this study, physical properties of the designed microparticle are systematically investigated experimentally with theoretical interpretation to correlate an enhancement in X-ray imaging efficiency. The compositional ratio of X-ray contrast agent in polymeric microparticle is controlled as 1/1 and 10/1 [contrast agent/polymer microparticle (w/w)] with changed degree of cross-linkings. Flory-Huggins interaction parameter (χ), retractive force (τ) and degree of swelling of the designed polymeric microparticles are investigated. In addition, the hydrodynamic size (D(H)) and ζ-potential are evaluated in terms of environment responsiveness. The physical properties of the designed flow tracer microparticles under a given condition are observed to be strongly related with the X-ray absorption efficiency, which are also supported by the Beer-Lambert-Bouguer law. The designed microparticles are almost nontoxic with a reasonable concentration and time period, enough to be utilized as a flow tracer in various biomedical applications. This study would contribute to the basic understanding on the physical property connected with the imaging efficiency of contrast agents.

  11. Amino-polyvinyl alcohol coated superparamagnetic iron oxide nanoparticles are suitable for monitoring of human mesenchymal stromal cells in vivo.

    PubMed

    Schulze, Frank; Dienelt, Anke; Geissler, Sven; Zaslansky, Paul; Schoon, Janosch; Henzler, Katja; Guttmann, Peter; Gramoun, Azza; Crowe, Lindsey A; Maurizi, Lionel; Vallée, Jean-Paul; Hofmann, Heinrich; Duda, Georg N; Ode, Andrea

    2014-11-12

    Mesenchymal stromal cells (MSCs) are promising candidates in regenerative cell-therapies. However, optimizing their number and route of delivery remains a critical issue, which can be addressed by monitoring the MSCs' bio-distribution in vivo using super-paramagnetic iron-oxide nanoparticles (SPIONs). In this study, amino-polyvinyl alcohol coated (A-PVA) SPIONs are introduced for cell-labeling and visualization by magnetic resonance imaging (MRI) of human MSCs. Size and surface charge of A-PVA-SPIONs differ depending on their solvent. Under MSC-labeling conditions, A-PVA-SPIONs have a hydrodynamic diameter of 42 ± 2 nm and a negative Zeta potential of 25 ± 5 mV, which enable efficient internalization by MSCs without the need to use transfection agents. Transmission X-ray microscopy localizes A-PVA-SPIONs in intracellular vesicles and as cytosolic single particles. After identifying non-interfering cell-assays and determining the delivered and cellular dose, in addition to the administered dose, A-PVA-SPIONs are found to be non-toxic to MSCs and non-destructive towards their multi-lineage differentiation potential. Surprisingly, MSC migration is increased. In MRI, A-PVA-SPION-labeled MSCs are successfully visualized in vitro and in vivo. In conclusion, A-PVA-SPIONs have no unfavorable influences on MSCs, although it becomes evident how sensitive their functional behavior is towards SPION-labeling. And A-PVA-SPIONs allow MSC-monitoring in vivo.

  12. Antimicrobial filtration with electrospun poly(vinyl alcohol) nanofibers containing benzyl triethylammonium chloride: Immersion, leaching, toxicity, and filtration tests.

    PubMed

    Park, Jeong-Ann; Kim, Song-Bae

    2017-01-01

    Antimicrobial electrospun poly(vinyl alcohol) (PVA) nanofibers were synthesized by impregnating benzyl triethylammonium chloride (BTEAC) as an antimicrobial agent into PVA nanofibers. The BTEAC-PVA nanofibers were heat-methanol treated during the preparation for various tests. The BTEAC-PVA nanofibers became more hydrophilic than the PVA nanofibers due to incorporation of BTEAC. Through heat-methanol treatment, thermal property, crystallinity, and water stability of BTEAC-PVA nanofibers were improved considerably. The immersion test shows that heat-methanol treatment has an advantage over heat treatment to maintain BTEAC content in BTEAC-PVA nanofibers. The acute toxicity test demonstrates that the 24-h EC50 and 48-h EC50 values (EC50 = median effective concentration) of BTEAC to Daphnia magna were 113 and 90 mg/L, respectively. The leaching test indicates that the BTEAC concentration leached from BTEAC-PVA nanofibers was far below the concentration affecting the immobilization of D. magna. For antimicrobial filtration tests, the BTEAC-PVA nanofibers were deposited onto glass fiber filter. The antimicrobial filtration test was conducted against bacteria (Escherichia coli, Staphylococcus aureus) and bacteriophages (MS2, PhiX174), demonstrating that the BTEAC-PVA nanofibers could enhance the removal of E. coli and S. aureus considerably but not the removal of MS2 and PhiX174 under dynamic flow conditions.

  13. Borax mediated layer-by-layer self-assembly of neutral poly(vinyl alcohol) and chitosan.

    PubMed

    Manna, Uttam; Patil, Satish

    2009-07-09

    We report a multilayer film of poly(vinyl alcohol) (PVA)-borate complex and chitosan by using a layer-by-layer approach. PVA is an uncharged polymer, but hydroxyl functional groups of PVA can be cross-linked by using borax as a cross-linking agent. As a result electrostatic charges and intra- and interchain cross-links are introduced in the PVA chain and provide physically cross-linked networks. The PVA-borate was then deposited on a flat substrate as well as on colloidal particles with chitosan as an oppositely charged polyelectrolyte. Quartz crystal microbalance, scanning electron microscopy, and atomic force microscopy were used to follow the growth of thin film on flat substrate. Analogous experiments were performed on melamine formaldehyde colloidal particles (3-3.5 microm) to quantify the process for the preparation of hollow microcapsules. Removal of the core in 0.1 N HCl results in hollow microcapsules. Characterization of microcapsules by transmission electron microscopy revealed formation of stable microcapsules. Further, self-assembly of PVA-borate/chitosan was loaded with the anticancer drug doxorubicin, and release rates were determined at different pH values to highlight the drug delivery potential of this system.

  14. A sustainable slashing industry using biodegradable sizes from modified soy protein to replace petro-based poly(vinyl alcohol).

    PubMed

    Zhao, Yi; Zhao, Yuzhu; Xu, Helan; Yang, Yiqi

    2015-02-17

    Biodegradable sizing agents from triethanolamine (TEA) modified soy protein could substitute poly(vinyl alcohol)(PVA) sizes for high-speed weaving of polyester and polyester/cotton yarns to substantially decrease environmental pollution and impel sustainability of textile industry. Nonbiodegradable PVA sizes are widely used and mainly contribute to high chemical oxygen demand (COD) in textile effluents. It has not been possible to effectively degrade, reuse or replace PVA sizes so far. Soy protein with good biodegradability showed potential as warp sizes in our previous studies. However, soy protein sizes lacked film flexibility and adhesion for required high-speed weaving. Additives with multiple hydroxyl groups, nonlinear molecule, and electric charge could physically modify secondary structure of soy protein and lead to about 23.6% and 43.3% improvement in size adhesion and ability of hair coverage comparing to unmodified soy protein. Industrial weaving results showed TEA-soy protein had relative weaving efficiency 3% and 10% higher than PVA and chemically modified starch sizes on polyester/cotton fabrics, and had relative weaving efficiency similar to PVA on polyester fabrics, although with 3- 6% lower add-on. In addition, TEA-soy sizes had a BOD5/COD ratio of 0.44, much higher than 0.03 for PVA, indicating that TEA-soy sizes were easily biodegradable in activated sludge.

  15. Synthesis of polyvinyl alcohol/cellulose nanofibril hybrid aerogel microspheres and their use as oil/solvent superabsorbents.

    PubMed

    Zhai, Tianliang; Zheng, Qifeng; Cai, Zhiyong; Xia, Hesheng; Gong, Shaoqin

    2016-09-05

    Superhydrophobic and crosslinked poly(vinyl alcohol) (PVA)/cellulose nanofibril (CNF) aerogel microspheres were prepared via a combination of the water-in-oil (W/O) emulsification process with the freeze-drying process, followed by thermal chemical vapor deposition of methyltrichlorosilane. The oil phase and the cooling agent were judiciously selected to ensure that the frozen ice microspheres can be easily separated from the emulsion system. The silanized microspheres were highly porous with a bulk density ranging from 4.66 to 16.54mg/cm(3). The effects of the solution pH, stirring rate, and emulsifier concentration on the morphology and microstructure of the aerogel microspheres were studied. The highly porous structure of the ultralight aerogel microspheres demonstrated an ultrahigh crude oil absorption capacity (up to 116 times its own weight). This study provides a novel approach for the large-scale preparation of polymeric aerogel microspheres with well-controlled particle sizes that can be used for various applications including oil and chemical spill/leak clean-up.

  16. Chloride ion addition for controlling shapes and properties of silver nanorods capped by polyvinyl alcohol synthesized by polyol method

    NASA Astrophysics Data System (ADS)

    Junaidi, Triyana, Kuwat; Harsojo, Suharyadi, Edi

    2016-04-01

    We report our investigation on the effect of chloride ions oncontrolling the shapes and properties of silver nanorods(AgNRs) synthesized using a polyol method. In this study, we used polyvinyl alcohol (PVA) as a capping agent and sodium chloride (NaCl) as asalt precursor and performed at the oilbath temperature of 140 °C. The chloride ions originating from the NaCl serve to control the growth of the silver nanorods. Furthermore, the synthesized silver nanorodswere characterized using UV-VIS, XRD, SEM and TEM. The results showed that besides being able to control the growth of AgCl atoms, the chloride ions were also able to control the growth of multi-twinned-particles into the single crystalline silver nanorods by micrometer-length. At an appropriate concentration of NaCl, the diameter of silver nanorodsdecreased significantly compared to that of without chloride ion addition. This technique may be useful since a particular diameter of silver nanorods affects a particular application in the future.

  17. Chloride ion addition for controlling shapes and properties of silver nanorods capped by polyvinyl alcohol synthesized using polyol method

    NASA Astrophysics Data System (ADS)

    Junaidi, Yunus, Muhammad; Triyana, Kuwat; Harsojo, Suharyadi, Edi

    2016-04-01

    We report our investigation on the effect of chloride ions on controlling the shapes and properties of silver nanorods (AgNRs) synthesized using a polyol method. In this study, we used polyvinyl alcohol (PVA) as a capping agent and sodium chloride (NaCl) as a salt precursor and performed at the oil bath temperature of 140°C. The chloride ions originating from the NaCl serve to control the growth of the silver nanorods. Furthermore, the synthesized silver nanorods were characterized using SEM and XRD. The results showed that besides being able to control the growth of AgCl atoms, the chloride ions were also able to control the growth of multi-twinned-particles into the single crystalline of silver nanorods by micrometer-length. At an appropriate concentration of NaCl, the diameter of silver nanorods decreased significantly compared to that of without chloride ion addition. This technique may be useful since a particular diameter of silver nanorods affects a particular application in the future.

  18. Unusual Morphologies of Poly(vinyl alcohol) Thin Films Adsorbed on Poly(dimethylsiloxane) Substrates.

    PubMed

    Karki, Akchheta; Nguyen, Lien; Sharma, Bhanushee; Yan, Yan; Chen, Wei

    2016-04-05

    Adsorption of poly(vinyl alcohol) (PVOH), 99% and 88% hydrolyzed poly(vinyl acetate), to poly(dimethylsiloxane) (PDMS) substrates was studied. The substrates were prepared by covalently attaching linear PDMS polymers of 2, 9, 17, 49, and 116 kDa onto silicon wafers. As the PDMS molecular weight/thickness increases, the adsorbed PVOH thin films progressively transition from continuous to discontinuous morphologies, including honeycomb and fractal/droplet. The structures are the result of thin film dewetting that occurs upon exposure to air. The PVOH film thickness does not vary significantly on these PDMS substrates, implicating the PDMS thickness as the cause for the morphology differences. The adsorbed PVOH thin films are less stable and have a stronger tendency to dewet on thicker, more liquid-like PDMS layers. When PVOH(99%) and PVOH(88%) thin films are compared, fractal and droplet morphologies are observed on high molecular weight PDMS substrates, respectively. The formation of the unique fractal features in the PVOH(99%) thin films as well as other crystalline and semicrystalline thin films is most likely driven by crystallization during the dehydration process in a diffusion-limited aggregation fashion. The only significant enhancement in hydrophilicity via PVOH adsorption was obtained on PDMS(2k), which is completely covered with a PVOH thin film. To mimic the lower receding contact angle and less liquid-like character of the PDMS(2k) substrate, light plasma treatment of the higher molecular weight PDMS substrates was carried out. On the treated PDMS substrates, the adsorbed PVOH thin films are in the more continuous honeycomb morphology, giving rise to significantly enhanced wettability. Furthermore, hydrophobic recovery of the hydrophilized PDMS substrates was not observed during a 1 week period. Thus, light plasma oxidation and subsequent PVOH adsorption can be utilized as a means to effectively hydrophilize conventional PDMS substrates. This study

  19. High-water-content mouldable polyvinyl alcohol-borax hydrogels reinforced by well-dispersed cellulose nanoparticles: dynamic rheological properties and hydrogel formation mechanism.

    PubMed

    Han, Jingquan; Lei, Tingzhou; Wu, Qinglin

    2014-02-15

    Cellulose nanoparticle (CNP) reinforced polyvinyl alcohol-borax (PB) hydrogels were produced via a facile approach in an aqueous system. The effects of particle size, aspect ratio, crystal structure, and surface charge of CNPs on the rheological properties of the composite hydrogels were investigated. The rheological measurements confirmed the incorporation of well-dispersed CNPs to PB system significantly enhanced the viscoelasticity and stiffness of hydrogels. The obtained free-standing, high elasticity and mouldable hydrogels exhibited self-recovery under continuous step strain and thermo-reversibility under temperature sweep. With the addition of cellulose I nanofibers, a 19-fold increase in the high-frequency plateau of storage modulus was obtained compared with that of the pure PB. CNPs acted as multifunctional crosslinking agents and nanofillers to physically and chemically bridge the 3D network hydrogel. The plausible mechanism for the multi-complexation between CNPs, polyvinyl alcohol and borax was proposed to understand the relationship between the 3D network and hydrogel properties.

  20. Novel hydrogels of chitosan and poly(vinyl alcohol)-g-glycolic acid copolymer with enhanced rheological properties.

    PubMed

    Lejardi, A; Hernández, R; Criado, M; Santos, Jose I; Etxeberria, A; Sarasua, J R; Mijangos, C

    2014-03-15

    Poly(vinyl alcohol) (PVA) has been grafted with glycolic acid (GL), a biodegradable hydroxyl acid to yield modified poly(vinyl alcohol) (PVAGL). The formation of hydrogels at pH = 6.8 and physiological temperature through blending chitosan (CS) and PVAGL at different concentrations has been investigated. FTIR, DOSY NMR and oscillatory rheology measurements have been carried out on CS/PVAGL hydrogels and the results have been compared to those obtained for CS/PVA hydrogels prepared under the same conditions. The experimental results point to an increase in the number of interactions between chitosan and PVAGL in polymer hydrogels prepared with modified PVA. The resulting materials with enhanced elastic properties and thixotropic behavior are potential candidates to be employed as injectable materials for biomedical applications.

  1. Lipogels: surface-adherent composite hydrogels assembled from poly(vinyl alcohol) and liposomes

    NASA Astrophysics Data System (ADS)

    Jensen, Bettina E. B.; Hosta-Rigau, Leticia; Spycher, Philipp R.; Reimhult, Erik; Städler, Brigitte; Zelikin, Alexander N.

    2013-07-01

    Drug-eluting engineered surface coatings are of paramount importance for many biomedical applications from implantable devices to tissue engineering. Herein, we present the assembly of lipogels, composite physical hydrogels assembled from poly(vinyl alcohol) and liposomes using thiol-disulfide exchange between end group modified PVA and thiocholesterol containing liposomes, and the response of adhering cells to these coatings. We demonstrate the controlled loading of liposomes into the polymer matrix and the preserved mechanical properties of the lipogels. Furthermore, the lipogels are successfully rendered cell adhesive by incorporation of poly(l-lysine) into the PVA polymer matrix or by poly(dopamine) coating of the lipogels. The successful lipid uptake from the lipogels by macrophages, hepatocytes, and myoblasts was monitored by flow cytometry. Finally, the delivery of active cargo, paclitaxel, to adherent myoblasts is shown, thus illustrating the potential of the lipogels as a drug eluting interface for biomedical applications.Drug-eluting engineered surface coatings are of paramount importance for many biomedical applications from implantable devices to tissue engineering. Herein, we present the assembly of lipogels, composite physical hydrogels assembled from poly(vinyl alcohol) and liposomes using thiol-disulfide exchange between end group modified PVA and thiocholesterol containing liposomes, and the response of adhering cells to these coatings. We demonstrate the controlled loading of liposomes into the polymer matrix and the preserved mechanical properties of the lipogels. Furthermore, the lipogels are successfully rendered cell adhesive by incorporation of poly(l-lysine) into the PVA polymer matrix or by poly(dopamine) coating of the lipogels. The successful lipid uptake from the lipogels by macrophages, hepatocytes, and myoblasts was monitored by flow cytometry. Finally, the delivery of active cargo, paclitaxel, to adherent myoblasts is shown, thus

  2. Development of structure in natural silk spinning and poly(vinyl alcohol) hydrogel formation

    NASA Astrophysics Data System (ADS)

    Willcox, Patricia Jeanene

    This research involves the characterization of structure and structure formation in aqueous systems. Particularly, these studies investigate the effect of various processing variables on the structure formation that occurs upon conversion from aqueous solution to fiber or hydrogel. The two processes studied include natural silk fiber spinning and physical gelation of poly(vinyl alcohol), PVOH, in water. The techniques employed combine cryogenic technology for sample preparation and direct observation by transmission electron microscopy with electron diffraction, atomic force microscopy, optical rheometry, X-ray scattering and optical microscopy. In order to explore the full range of structure formation in natural silk spinning, studies are conducted in vivo and in vitro. In vivo structural investigations are accomplished through the cryogenic quenching and subsequent microtoming of live silk-spinning animals, Nephila clavipes (spider) and Bombyx mori (silkworm). Observations made using transmission electron microscopy, electron diffraction and atomic force microscopy indicate a cholesteric liquid crystalline mesophase of aqueous silk fibroin in both species. The mechanism of structure formation in solution is studied in vitro using optical rheometry on aqueous solutions made from regenerated Bombyx mori cocoon silk. Concentrated solutions exhibit birefringence under flow, with a wormlike conformation of the silk molecules in concentrated salt solution. Changes in salt concentration and pH of the aqueous silk solutions result in differing degrees of alignment and aggregation. These results suggest that structural control in the natural silk spinning process is accomplished by chemical manipulation of the electrostatic interactions and hydrogen bonding between chains. Application of cryogenic methods in transmission electron microscopy also provides a unique look at hydration-dependent structures in gels of poly(vinyl alcohol) produced by freeze-thaw processing

  3. Influence of Block Copolymerization on the Antifreeze Protein Mimetic Ice Recrystallization Inhibition Activity of Poly(vinyl alcohol).

    PubMed

    Congdon, Thomas R; Notman, Rebecca; Gibson, Matthew I

    2016-09-12

    Antifreeze (glyco) proteins are produced by many cold-acclimatized species to enable them to survive subzero temperatures. These proteins have multiple macroscopic effects on ice crystal growth which makes them appealing for low-temperature applications-from cellular cryopreservation to food storage. Poly(vinyl alcohol) has remarkable ice recrystallization inhibition activity, but its mode of action is uncertain as is the extent at which it can be incorporated into other high-order structures. Here the synthesis and characterization of well-defined block copolymers containing poly(vinyl alcohol) and poly(vinylpyrrolidone) by RAFT/MADIX polymerization is reported, as new antifreeze protein mimetics. The effect of adding a large second hydrophilic block is studied across a range of compositions, and it is found to be a passive component in ice recrystallization inhibition assays, enabling retention of all activity. In the extreme case, a block copolymer with only 10% poly(vinyl alcohol) was found to retain all activity, where statistical copolymers of PVA lose all activity with very minor changes to composition. These findings present a new method to increase the complexity of antifreeze protein mimetic materials, while retaining activity, and also to help understand the underlying mechanisms of action.

  4. Enabling thermal processing of ritonavir-polyvinyl alcohol amorphous solid dispersions by KinetiSol® Dispersing.

    PubMed

    LaFountaine, Justin S; Jermain, Scott V; Prasad, Leena Kumari; Brough, Chris; Miller, Dave A; Lubda, Dieter; McGinity, James W; Williams, Robert O

    2016-04-01

    Polyvinyl alcohol has received little attention as a matrix polymer in amorphous solid dispersions (ASDs) due to its thermal and rheological limitations in extrusion processing and limited organic solubility in spray drying applications. Additionally, in extrusion processing, the high temperatures required to process often exclude thermally labile APIs. The purpose of this study was to evaluate the feasibility of processing polyvinyl alcohol amorphous solid dispersions utilizing the model compound ritonavir with KinetiSol® Dispersing (KSD) technology. The effects of KSD rotor speed and ejection temperature on the physicochemical properties of the processed material were evaluated. Powder X-ray diffraction and modulated differential scanning calorimetry were used to confirm amorphous conversion. Liquid chromatography-mass spectroscopy was used to characterize and identify degradation pathways of ritonavir during KSD processing and (13)C nuclear magnetic resonance spectroscopy was used to investigate polymer stability. An optimal range of processing conditions was found that resulted in amorphous product and minimal to no drug and polymer degradation. Drug release of the ASD produced from the optimal processing conditions was evaluated using a non-sink, pH-shift dissolution test. The ability to process amorphous solid dispersions with polyvinyl alcohol as a matrix polymer will enable further investigations of the polymer's performance in amorphous systems for poorly water-soluble compounds.

  5. Biomechanical analysis of a salt-modified polyvinyl alcohol hydrogel for knee meniscus applications, including comparison with human donor samples.

    PubMed

    Hayes, Jennifer C; Curley, Colin; Tierney, Paul; Kennedy, James E

    2016-03-01

    The primary objective of this research was the biomechanical analysis of a salt-modified polyvinyl alcohol hydrogel, in order to assess its potential for use as an artificial meniscal implant. Aqueous polyvinyl alcohol (PVA) was treated with a sodium sulphate (Na2SO4) solution to precipitate out the polyvinyl alcohol resulting in a pliable hydrogel. The freeze-thaw process, a strictly physical method of crosslinking, was employed to crosslink the hydrogel. Development of a meniscal shaped mould and sample housing unit allowed the production of meniscal shaped hydrogels for direct comparison to human meniscal tissue. Results obtained show that compressive responses were slightly higher in PVA/Na2SO4 menisci, displaying maximum compressive loads of 2472N, 2482N and 2476N for samples having undergone 1, 3 and 5 freeze-thaw cycles respectively. When compared to the human meniscal tissue tested under the same conditions, an average maximum load of 2467.5N was observed. This suggests that the PVA/Na2SO4 menisci are mechanically comparable to the human meniscus. Biocompatibility analysis of PVA/Na2SO4 hydrogels revealed no acute cytotoxicity. The work described herein has innovative potential in load bearing applications, specifically as an alternative to meniscectomy as replacement of critically damaged meniscal tissue in the knee joint where repair is not viable.

  6. Influence of Block Copolymerization on the Antifreeze Protein Mimetic Ice Recrystallization Inhibition Activity of Poly(vinyl alcohol)

    PubMed Central

    2016-01-01

    Antifreeze (glyco) proteins are produced by many cold-acclimatized species to enable them to survive subzero temperatures. These proteins have multiple macroscopic effects on ice crystal growth which makes them appealing for low-temperature applications—from cellular cryopreservation to food storage. Poly(vinyl alcohol) has remarkable ice recrystallization inhibition activity, but its mode of action is uncertain as is the extent at which it can be incorporated into other high-order structures. Here the synthesis and characterization of well-defined block copolymers containing poly(vinyl alcohol) and poly(vinylpyrrolidone) by RAFT/MADIX polymerization is reported, as new antifreeze protein mimetics. The effect of adding a large second hydrophilic block is studied across a range of compositions, and it is found to be a passive component in ice recrystallization inhibition assays, enabling retention of all activity. In the extreme case, a block copolymer with only 10% poly(vinyl alcohol) was found to retain all activity, where statistical copolymers of PVA lose all activity with very minor changes to composition. These findings present a new method to increase the complexity of antifreeze protein mimetic materials, while retaining activity, and also to help understand the underlying mechanisms of action. PMID:27476873

  7. Study of poly(3-hexylthiophene)/cross-linked poly(vinyl alcohol) as semiconductor/insulator for application in low voltage organic field effect transistors

    NASA Astrophysics Data System (ADS)

    Benvenho, Adriano R. V.; Machado, Wagner S.; Cruz-Cruz, Isidro; Hümmelgen, Ivo A.

    2013-06-01

    In this work we study the cross-linked poly(vinyl alcohol)/poly(3-hexylthiophene) interfacial properties of an organic field effect transistor. We use cross-linked poly(vinyl alcohol) prepared with different ammonium dichromate:poly(vinyl alcohol) proportions, ranging from 0% to 35%, as insulator. Using admittance spectroscopy, we show that the interfacial properties change when the ammonium dichromate concentration is altered. The interfacial properties and the better insulation are responsible for the improvement of the device performance in these organic field effect transistors, achieving best performance in the blend with ammonium dichromate:poly(vinyl alcohol) proportion of 0.25:1.

  8. Prediction of Thermal Properties and Effect of OH Substituent for Poly(vinyl alcohol)s by Molecular Dynamics Calculations

    NASA Astrophysics Data System (ADS)

    Tsuchiya, Yooko; Yoshii, Noriyuki; Iwatsubo, Tetsushiro

    2004-08-01

    Since heat storage technology contributes greatly to the effective use of energy, we are attempting to develop latent heat storage materials. If computer simulations enable the estimation of material properties prior to experiments, they will provide us with very effective tools for the development of new materials. We use molecular dynamics calculations to predict the melting points and latent heats of fusion, which are crucial thermal properties for evaluating the suitability of heat-storage materials. As the object of calculation, poly(vinyl alcohol) (PVA) was chosen, because polymer materials are effective in that they can be made to cover all temperature ranges by changing the molecular weight. The melting points were determined from the volume change, and the latent heats of fusion were determined from the internal energy. As for these calculations, it was ascertained that these thermal properties were suitable values in comparison with the results of actual calorimetry. From the comparative calculation of the polymer consistent force field (PCFF) and optimized potentials for liquid simulations (OPLS) force field, it was shown that the intermolecular potential could be simplified. Moreover, the stability of the structural isomer of PVA and the state of the hydrogen bond were evaluated, because a strong intermolecular bond leads to structural stability and a high melting temperature.

  9. Kinetics of desorption of KCL from polyvinyl alcohol-borate hydrogel in aqueous-alcoholic solvents at different temperatures

    NASA Astrophysics Data System (ADS)

    Saeed, Rehana; Abdeen, Zain Ul

    2015-11-01

    Desorption kinetics of adsorbed KCl from Polyvinyl alcohol borate hydrogel was studied by conductivity method in aqueous system and aqueous binary solvent system using 50% aqueous-methanol, aqueous- ethanol and aqueous-propanol at different temperature ranging from 293 to 313 K. Desorption process follows pseudo first order and intra particle diffusion kinetics was analyzed on the basis of linear regression coefficient R 2 and chi square test χ2 values. The process of desorption of KCl from hydrogel was favorable in aqueous system, the study reveals the fact that the polarity of solvent influenced the kinetics of desorption, on decrement of polarity of solvent rate, rate constant and intra particle rate constant decreases. Based on intra particle kinetic equation fitting it was concluded that desorption was initiated by removal of ions from surface of hydrogel later on ions interacted inside the cross linked unit was also become free. Temperature enhances the rate, rate constant and intra particle rate constant. Thermodynamic parameters attributed towards the fact that the process of desorption of KCl from hydrogel is non-spontaneous in nature.

  10. Development of ethyl alcohol-precipitated silk sericin/polyvinyl alcohol scaffolds for accelerated healing of full-thickness wounds.

    PubMed

    Siritienthong, Tippawan; Ratanavaraporn, Juthamas; Aramwit, Pornanong

    2012-12-15

    Silk sericin has been recently reported for its advantageous biological properties to promote wound healing. In this study, we established that the ethyl alcohol (EtOH) could be used to precipitate sericin and form the stable sericin/polyvinyl alcohol (PVA) scaffolds without the crosslinking. The sericin/PVA scaffolds were fabricated via freeze-drying and subsequently precipitating in various concentrations of EtOH. The EtOH-precipitated sericin/PVA scaffolds showed denser structure, higher compressive modulus, but lower water swelling ability than the non-precipitated scaffolds. Sericin could be released from the EtOH-precipitated sericin/PVA scaffolds in a sustained manner. After cultured with L929 mouse fibroblasts, the 70 vol% EtOH-precipitated sericin/PVA scaffolds showed the highest potential to promote cell proliferation. After applied to the full-thickness wounds of rats, the 70 vol% EtOH-precipitated sericin/PVA scaffolds showed significantly higher percentage of wound size reduction and higher extent of type III collagen formation and epithelialization, compared with the control scaffolds without sericin. The accelerated wound healing by the 70 vol% EtOH-precipitated sericin/PVA scaffolds was possibly due to (1) the bioactivity of sericin itself to promote wound healing, (2) the sustained release of precipitated sericin from the scaffolds, and (3) the activation and recruitment of wound healing-macrophages by sericin to the wounds. This finding suggested that the EtOH-precipitated sericin/PVA scaffolds were more effective for the wound healing, comparing with the EtOH-precipitated PVA scaffolds without sericin.

  11. [Characterization of collagen/polyvinyl alcohol complex membrane crosslinked by UV-riboflavin].

    PubMed

    Zhao, Hongbin; Ma, Hui; Zeng, Ping; Lin, Yang; Zhang, Quanwei

    2013-10-01

    The objective of this investigation was to study the characteristics and biocompatibility of collagen/polyvinyl alcohol (PVA) membrane crosslinked by UV-riboflavin. Membranes that were made into complex ones with different mass ratios of collagen to PVA (1:1 and 2:1) were synthesized, and crosslinked with UV-riboflavin. The surface characteristics were analyzed using the omnipotent materials instrument, IR, SEM, water absorption test, gas permeability test, and degradation test, respectively. The biocompatibility of membrane complex and rat bone marrow mesenchymal stem cells (BMSCs) was evaluated after 7 d and 14 d, respectively. The collagen/PVA complex membranes showed good homogeneity, mechanical property, degradation ratio, water absorption, gas permeability, etc. The biocompatibility of the collagen/PVA (2:1) complex membrane crosslinked with UV-Riboflavin was higher than that of without crosslinking and collagen/PVA (1:1) membrane. It could be well concluded that collagen/PVA complex membranes crosslinked with UV-riboflavin would have a potential application in biomedicine.

  12. Recording of diffraction gratings in polyvinyl alcohol/acrylamide photopolymers by pulsed laser irradiation

    NASA Astrophysics Data System (ADS)

    Garcia, Celia; Costela, Angel; Fimia, Antonio; Garcia-Moreno, Inmaculada; Pascual, Inmaculada V.; Sastre, Roberto

    2001-06-01

    In this communication we present the experimental results obtained when diffraction gratings are stored using pulsed exposure in polyvinyl alcohol/acrylamide photopolymer deposited in a dry film. The influence of the energy of the irradiation pulse was studied and the number of pulses needed to reach maximum diffraction efficiency was obtained. The recording was performed using a n holographic copying process. The original patten employed was a gratin of 1000 lines/mm processed according to sliver halide sensitized gelatin, with a beam ratio of 1:2 and transmittance of 75 percent. We exposed the samples by recording holograms with as collimated beam from a frequency-doubled Nd:YAG Q- switched laser. The pulse duration was approximately 8 ns and the frequency of repetition varied between 2 and 10 Hz. The pulse fluence was increased from 0.07 mJ/cm2 to 6.7 mJ/cm2. Our initial results show that it is possible to obtain diffraction gratings with a diffraction efficiency of 60 percent. The energetic sensitivities achieved are close to those obtained when working with the same material and continuous irradiation, without processing of the gratings.

  13. Mucus-penetrating nanoparticles made with "mucoadhesive" poly(vinyl alcohol).

    PubMed

    Popov, Alexey; Enlow, Elizabeth; Bourassa, James; Chen, Hongming

    2016-10-01

    Nanoparticles that readily penetrate mucosal layers are desirable for a variety of biomedical applications. Nevertheless, most nanoparticles tend to be immobilized in mucus via steric and/or adhesive interactions. Contrary to the established opinion that poly(vinyl alcohol) (PVA) is mucoadhesive, we discovered that coating otherwise mucoadhesive nanoparticles with certain partially hydrolyzed PVAs can aid particle mobility in mucus. We describe two approaches to producing such mucus-penetrating particles (non-covalent modification of pre-formed nanoparticles and emulsification in the presence of PVA) and provide mobility data in human cervicovaginal mucus ex vivo as measured by multiple particle tracking and bulk permeation. When coated with PVAs that are ≥95% hydrolyzed, nanoparticles as small as ~210nm were immobilized in mucus similarly to well-established mucoadhesive controls (P>0.05). However, nanoparticles coated with PVAs that are <95% hydrolyzed penetrated mucus with velocities significantly exceeding those for the mucoadhesive controls (P<0.001) and were mobile in the bulk permeation assay.

  14. Enlarged-taper tailored Fiber Bragg grating with polyvinyl alcohol coating for humidity sensing

    NASA Astrophysics Data System (ADS)

    Liang, Yanhong; Yan, Guofeng; He, Sailing

    2015-08-01

    In this paper, a novel optical fiber sensor based on an enlarged-taper tailored fiber Bragg grating (FBG) is proposed and experimentally demonstrated for the measurement of relative humidity. The enlarged-taper works as a multifunctional joint that not only excites cladding modes but also recouples the cladding modes reflected by the FBG back into the leading single mode fiber. Due to the fact that cladding modes have a strong evanescent field penetrating into the ambient medium, the intensity of the reflected cladding modes is greatly influenced by the refractive index (RI) of the ambient medium. Polyvinyl alcohol (PVA) film is plated on the fiber surface by dip-coating technique, as a humidity-to-refractive index transducer, whose RI variance from 1.49 to 1.34 when the ambient humidity increases from 20%RH to 95%RH. The relative humidity response of the sensing structure is investigated in our home-made humidity chamber with a commercial hygrometer. By monitoring the intensity of the reflected cladding modes, the RH variance can be demodulated. Experimental results show that RH sensitivity depends on the RH value, and a sensitivity up to 1.2 dB/%RH can be achieved within the RH range of 30-90%. A fast and reversible time response has also been investigated. Such a probe-type and reusable fiber-optic RH sensor is a very promising technology for biochemical sensing applications, e.g., breath analysis, chemical reaction monitoring.

  15. Structure and physical properties of high amorphous polyvinyl alcohol/clay composites

    NASA Astrophysics Data System (ADS)

    Russo, P.; Speranza, V.; Vignali, A.; Tescione, F.; Buonocore, G. G.; Lavorgna, M.

    2015-12-01

    Recently a high amorphous polyvinyl alcohol (HAVOH) which can be easily melt processed has been patented and commercialized with the trade name G-Polymer. In this work, we report on the characterization of clay-G-Polymer composites obtained by melt processing of HAVOH with two commercial chemically-modified organoclays, Cloisite 15A and Cloisite 30B. Results show that the extent of polymer intercalation in the layered clay structure as well as the thermal and mechanical properties of the obtained composites depend on the nature of clay organo-modifier, i.e a quaternary ammonium salt of dimethyl dehydrogenated tallow for Cloisite 15A and an alkyl ammonium salt of bis-(2-hydroxyethyl)methyl tallow for Cloisite 30B. In particular Cloisite 15A, which is only slightly intercalated by the polymer during melt compounding, contributes to enhance glass transition temperature and mechanical properties of the resulting composites. On the contrary, Cloisite 30B which is significantly intercalated by the interacting polymer macromolecules, disturbs to some extent the H-bonding network established within the polymeric matrix thus showing a reduction of thermal and mechanical properties.

  16. Treatment of desizing wastewater containing poly(vinyl alcohol) by wet air oxidation

    SciTech Connect

    Chen, G.; Lei, L.; Yue, P.L.; Cen, P.

    2000-05-01

    The effectiveness of wet air oxidation (WAO) is studied in a 2-L autoclave for the treatment of desizing wastewater from man-made fiber textile plants. At an oxygen pressure of less than 2 MPa, over 30-min, chemical oxygen demand (COD) removal was found to increase from 15 to 65% when the temperature was raised from 150 to 250 C. The biodegradability of the wastewater was also simultaneously increased. Up to 90% of the COD could be removed within 120 min. A simplified reaction mechanism is proposed which involves a direct mineralization step in parallel with a step in which an intermediate is formed prior to mineralization. A kinetic model for COD removal was developed based on this reaction mechanism. The model was tested with experimental COD results over the temperature range of the experiments. The dependence of the specific reaction rate constants was found to follow the Arrhenius type of equation. The direct oxidation of poly(vinyl alcohol) (PVA) to carbon dioxide and water is the dominant reaction step. The intermediates formed are not likely to be the acetic acid but may be short segments of PVA that are easily oxidized.

  17. Adsorption of Methylene Blue from Aqueous Solutions by Polyvinyl Alcohol/Graphene Oxide Composites.

    PubMed

    Yang, Xiaoxia; Li, Yanhui; Du, Qiuju; Wang, Xiaohui; Hu, Song; Chen, Long; Wang, Zonghua; Xia, Yanzhi; Xia, Linhua

    2016-02-01

    As a new member of the carbon family, graphene oxide (GO) has shown excellent adsorption ability to micro-pollutants in aqueous solutions. However, its tiny size makes it difficult to be removed from aqueous solutions using the conventional separation methods, which limits its practical application in the environmental protection. In this study, polyvinyl alcohol (PVA) was used as carrier immobilizing GO, and novel PVA/GO composites were prepared. The morphology and physicochemical properties of the composites were characterized by SEM, FTIR and TGA analysis. The adsorption properties of methylene blue (MB) onto the composites were studied through investigating the experimental parameters such as solution pH, adsorbent dosage, contact time and temperature. The isotherm data were analyzed using the Langmuir, Freundlich and Dubinin-Radushkevich models. The calculated maximum adsorption capacity reached 476.2 mg/g at 50% GO content. The pseudo-first-order kinetic, pseudo-second-order kinetic and intra-particle diffusion models were used to explore the adsorption kinetics. The results showed that the dynamic data were fitted to the pseudo-second-order kinetic model.

  18. TiO2 and polyvinyl alcohol (PVA) coated polyester filter in bioreactor for wastewater treatment.

    PubMed

    Liu, Lifen; Zhao, Chuanqi; Yang, Fenglin

    2012-04-15

    Prepared by coating TiO(2)/polyvinyl alcohol (PVA) on a low cost polyester filter cloth (22 μm), a composite membrane (10 μm pore size) was successfully used in an anoxic/oxic membrane bioreactor (A/O-MBR) for treating a simulate wastewater in removing nitrate/ammonium for water reuse in a polyester fiber production plant. Its permeate flux and the anti-fouling properties against extracellular polymeric substances (EPS) were studied. Comparing with a commercial (0.1 μm) PVDF (polyvinylidene fluoride) membrane, similar effluent qualities were achieved, meeting the basic COD requirements for reuse. Anti-EPS accumulation, the TiO(2)/PVA Polyester composite membrane had higher sustained permeability and required less frequent cleaning. Its filtration time was 4 times longer when operated at a higher flux than the PVDF membrane. The nano-TiO(2) enhances the interaction between PVA and polyester, forms a more hydrophilic surface, drastically reduces the contact angle with water and reduces EPS fouling. The slow (trans-membrane pressure) TMP rise, loose cake layer, the low filtration resistances, and the EPS, SEM analysis confirmed the advantage of the composite membrane. Potential in lowering the membrane cost, the operation and maintenance cost, and in enhancing MBR waste water treatment efficiency is expected by the use of this new composite membrane.

  19. Poly(vinyl alcohol)-coated microfluidic devices for high-performance microchip electrophoresis.

    PubMed

    Belder, Detlev; Deege, Alfred; Kohler, Frank; Ludwig, Martin

    2002-10-01

    The channels of microfluidic glass chips have been coated with poly(vinyl alcohol) (PVA). Applied for microchip electrophoresis, the coated devices exhibited a suppressed electroosmotic flow and improved separation performance. The superior performance of PVA-coated channels could be demonstrated by electrophoretic separations of labeled amines and by video microscopy. While a distorted sample zone is injected using uncoated channels the application of PVA-coated channels results in an improved shape of the sample zone with less band broadening. Applying PVA-coated microchips for the separation of amines labeled with Alexa Fluor 350 even sub-second separations, utilizing a separation length of only 650 microm, could be obtained, while this was not possible using uncoated devices. By using PVA-coated devices rather than an uncoated chip a threefold increase in separation efficiencies could be observed. As the electroosmotic flow (EOF) was suppressed, the anionic compounds were detected at the anode whereas the dominant EOF in uncoated devices resulted in an effective mobility to the cathode. Besides improved separation performance another important feature of the PVA-coated channels was the suppressed adsorption of fluorescent compounds in repetitive runs which results in an improved robustness and detection sensitivity. Applying PVA-coated channels, rinsing or etching steps could be omitted while this was necessary for a reliable operation of uncoated devices.

  20. Adsorption properties of polyvinyl-alcohol-grafted particles toward genistein driven by hydrogen-bond interaction.

    PubMed

    Zhang, Yanyan; Gao, Baojiao; Xu, Zeqing

    2013-05-09

    The adsorption properties of polyvinyl alcohol (PVA)-grafted silica gel particles PVA/SiO2 toward genistein are researched in this paper. The effects of the main factors on the adsorption properties are investigated, the adsorption mechanism is explored in depth, and the adsorption thermodynamics is researched. The experimental results show that the conventional hydrogen bond is formed between the hydroxyl groups with high density on the surfaces of PVA/SiO2 and the phenolic hydroxyl groups in genistein, while π-type hydrogen bond is formed between the hydroxyl groups of PVA/SiO2 and the conjugated aromatic rings. It is the two types of hydrogen bond that make the functional composite particles PVA/SiO2 produce very strong physical adsorption toward genistein. The competitive adsorption of the solvent can have severe negative impact on the adsorption capacity of genistein. Increasing temperature will weaken the hydrogen-bond interaction between PVA/SiO2 particles and genistein. The existence of electrolytes in the protic solvent will affect the adsorption negatively. The adsorption process of PVA/SiO2 particles toward genistein is exothermic and driven by enthalpy. The adsorption isotherm data matches the Langmuir model.

  1. Conductive, tough, hydrophilic poly(vinyl alcohol)/graphene hybrid fibers for wearable supercapacitors

    NASA Astrophysics Data System (ADS)

    Chen, Shaohua; Ma, Wujun; Xiang, Hengxue; Cheng, Yanhua; Yang, Shengyuan; Weng, Wei; Zhu, Meifang

    2016-07-01

    Graphene fibers based flexible supercapacitors have great potential as wearable power sources for textile electronics. However, their electrochemical performance is limited by the serious stacking of graphene sheets and their hydrophobicity in aqueous electrolytes. Meanwhile, their brittleness is unfavorable for practical application. Incorporation of nanofillers into graphene fibers has been proved effective for enhancing their capacitance, whereas often leading to deteriorated mechanical strength. Herein we demonstrate that the strength, toughness and capacitive performance of graphene-based fibers can be significantly enhanced simultaneously, simply by incorporating hydrophilic poly(vinyl alcohol) (PVA) into a non-liquid-crystalline graphene oxide (GO) dispersion before wet spinning and chemical reduction. The structure and properties of the resulted PVA/graphene hybrid fibers are systematically investigated, and the mechanism behind these enhancements is discussed in detail. The hybrid fiber with a PVA/GO weight ratio of 10/90 possesses a strength of 186 MPa, a toughness of 11.3 J cm-3, and a capacitance of 241 F cm-3 in 1 M H2SO4. A solid-state yarn supercapacitor assembled from these fibers exhibits a device energy of 5.97 mW h cm-3, and features excellent flexibility and bending stability. This device is robust enough to be integrated into textile and thus promising as wearable power supply for smart textiles.

  2. Melt-processed poly(vinyl alcohol) composites filled with microcrystalline cellulose from waste cotton fabrics.

    PubMed

    Sun, Xunwen; Lu, Canhui; Liu, Yong; Zhang, Wei; Zhang, Xinxing

    2014-01-30

    Waste cotton fabrics (WCFs), which are generated in a large volume from the textile industry, have caused serious disposal problem. Recycling WCFs into value-added products is one of the vital measures for both environmental and economic benefits. In this study, microcrystalline cellulose (MCC) was prepared by acid hydrolysis of WCFs, and used as reinforcement for melt-processed poly(vinyl alcohol) (PVA) with water and formamide as plasticizer. The microstructure and mechanical properties of the melt-processed PVA/MCC composites were characterized by Fourier transform infrared spectra, Raman spectra, differential scanning calorimetry, thermal gravimetric analysis, X-ray diffraction, tensile tests and dynamic mechanical analysis. The results indicated that MCC could establish strong interfacial interaction with PVA through hydrogen bonding. As a result, the crystallization of PVA was confined and its melting temperature was decreased, which was beneficial for the melt-processing of PVA. Compared with the unfilled PVA, the PVA/MCC composites exhibited remarkable improvement in modulus and tensile strength.

  3. Improvement of Starch Digestion Using α-Amylase Entrapped in Pectin-Polyvinyl Alcohol Blend

    PubMed Central

    Cruz, Maurício; Fernandes, Kátia; Cysneiros, Cristine; Nassar, Reginaldo; Caramori, Samantha

    2015-01-01

    Polyvinyl alcohol (PVA) and pectin blends were used to entrap α-amylase (Termamyl) using glutaraldehyde as a cross-linker. The effect of glutaraldehyde concentration (0.25, 0.5, 0.75, 1.0, and 1.25%) on the activity of the immobilized enzyme and rate of enzyme released was tested during a 24 h period. Characteristics of the material, such as scanning electron microscopy (SEM), tensile strength (TS), elongation, and rate of dissolution in water (pH 5.7), ruminal buffering solution (pH 7.0), and reactor containing 0.1 mol L−1 sodium phosphate buffer (pH 6.5), were also analyzed. SEM results showed that the surfaces of the pectin/PVA/amylase films were highly irregular and rough. TS values increased as a function of glutaraldehyde concentration, whereas percentage of elongation (%E) decreased. Pectin/PVA/amylase films presented similar values of solubility in the tested solvents. The material obtained with 0.25% glutaraldehyde performed best with repeated use (active for 24 h), in a phosphate buffer reactor. By contrast, the material obtained with 1.25% glutaraldehyde presented higher performance during in vitro testing using an artificial rumen. The results suggest that pectin/PVA/amylase is a highly promising material for biotechnological applications. PMID:25949991

  4. Coupled electron beam radiation and MBR treatment of textile wastewater containing polyvinyl alcohol.

    PubMed

    Sun, Weihua; Chen, Jun; Chen, Lujun; Wang, Jianlong; Zhang, Yongming

    2016-07-01

    Advanced oxidation processes (AOP) can be combined with biological treatments for recalcitrant organic pollutant decomposition. However, there has been no thorough investigation on the coupling of AOPs and membrane bioreactors (MBR) to treat polymer organic pollutants. This study proposes a new AOP that couples electron beam (EB) radiation and MBR treatment. This method was applied to treat real textile effluents containing polyvinyl alcohol (PVA). During the stable operation stage, 31 ± 7% (n = 28) COD was removed by the EB-MBR process. COD removal was enhanced to 45% at the end of the research period without process optimization. In addition, both the membrane flux and activated sludge system exhibited good stability. Only a 2% membrane flux decreased was observed after a 46 d operation period. PVA radiolysis and biofacies analysis mechanisms are also discussed. By contrast, PVA degradation using only the MBR treatment was ineffective in this study. This ineffectiveness was caused by membrane interception and floccule formation by PVA and activated sludge.

  5. Poly(vinyl alcohol) hydrogel coatings with tunable surface exposure of hydroxyapatite.

    PubMed

    Moreau, David; Villain, Arthur; Ku, David N; Corté, Laurent

    2014-01-01

    Insufficient bone anchoring is a major limitation of artificial substitutes for connective osteoarticular tissues. The use of coatings containing osseoconductive ceramic particles is one of the actively explored strategies to improve osseointegration and strengthen the bone-implant interface for general tissue engineering. Our hypothesis is that hydroxyapatite (HA) particles can be coated robustly on specific assemblies of PVA hydrogel fibers for the potential anchoring of ligament replacements. A simple dip-coating method is described to produce composite coatings made of microscopic hydroxyapatite (HA) particles dispersed in a poly(vinyl alcohol) (PVA) matrix. The materials are compatible with the requirements for implant Good Manufacturing Practices. They are applied to coat bundles of PVA hydrogel fibers used for the development of ligament implants. By means of optical and electronic microscopy, we show that the coating thickness and surface state can be adjusted by varying the composition of the dipping solution. Quantitative analysis based on backscattered electron microscopy show that the exposure of HA at the coating surface can be tuned from 0 to over 55% by decreasing the weight ratio of PVA over HA from 0.4 to 0.1. Abrasion experiments simulating bone-implant contact illustrate how the coating cohesion and wear resistance increase by increasing the content of PVA relative to HA. Using pullout experiments, we find that these coatings adhere well to the fiber bundles and detach by propagation of a crack inside the coating. These results provide a guide to select coated implants for anchoring artificial ligaments.

  6. Electrospun polylactic acid and polyvinyl alcohol fibers as efficient and stable nanomaterials for immobilization of lipases.

    PubMed

    Sóti, Péter Lajos; Weiser, Diana; Vigh, Tamás; Nagy, Zsombor Kristóf; Poppe, László; Marosi, György

    2016-03-01

    Electrospinning was applied to create easy-to-handle and high-surface-area membranes from continuous nanofibers of polyvinyl alcohol (PVA) or polylactic acid (PLA). Lipase PS from Burkholderia cepacia and Lipase B from Candida antarctica (CaLB) could be immobilized effectively by adsorption onto the fibrous material as well as by entrapment within the electrospun nanofibers. The biocatalytic performance of the resulting membrane biocatalysts was evaluated in the kinetic resolution of racemic 1-phenylethanol (rac-1) and 1-phenylethyl acetate (rac-2). Fine dispersion of the enzymes in the polymer matrix and large surface area of the nanofibers resulted in an enormous increase in the activity of the membrane biocatalyst compared to the non-immobilized crude powder forms of the lipases. PLA as fiber-forming polymer for lipase immobilization performed better than PVA in all aspects. Recycling studies with the various forms of electrospun membrane biocatalysts in ten cycles of the acylation and hydrolysis reactions indicated excellent stability of this forms of immobilized lipases. PLA-entrapped lipases could preserve lipase activity and enantiomer selectivity much better than the PVA-entrapped forms. The electrospun membrane forms of CaLB showed high mechanical stability in the repeated acylations and hydrolyses than commercial forms of CaLB immobilized on polyacrylamide beads (Novozyme 435 and IMMCALB-T2-150).

  7. Polyethylene glycol-polyvinyl alcohol grafted copolymer: study of the bioavailability after oral administration to rats.

    PubMed

    Heuschmid, Franziska F; Schuster, Paul; Lauer, Birthe; Fabian, Eric; Leibold, Edgar; van Ravenzwaay, Bennard

    2013-07-01

    The absorption, urinary excretion, and the biliary excretion of a single oral dose of 10 or 1000 mg/kg bw of (14)C-polyethylene glycol-polyvinyl alcohol (PEG-PVA) grafted copolymer were studied in adult male and female rats. In a balance/excretion experiment, the total excretion of ingested radioactivity was determined over a period of 168 h and residual radioactivity was detected in selected tissues and the carcass. In a biliary excretion experiment, excretion of radioactivity via the bile duct was determined over a period of 48 h after administration of the substance to cannulated rats. Most, if not all, of the radioactivity (>100%) was excreted within 48 h via the feces regardless of sex or dose. Urinary excretion was very limited: 0.45-0.50% of dose at the low dose and 0.22-0.27% of dose at the high dose. At both dose levels, residual radioactivity in the carcass and all organs and tissues after 168 h was ≤ 0.02% of dose. Biliary excretion was 0.01-0.02% of dose. Based on these findings, the bioavailability of PEG-PVA grafted copolymer was determined to be <1% demonstrating that absorption was virtually negligible following a single oral administration to male and female rats.

  8. Developmental toxicity of polyethylene glycol-g-polyvinyl alcohol grafted copolymer in rats and rabbits.

    PubMed

    Heuschmid, Franziska F; Schneider, Steffen; Schuster, Paul; Lauer, Birthe; van Ravenzwaay, Bennard

    2013-07-01

    Polyethylene glycol-g-polyvinyl alcohol (PEG-PVA) grafted copolymer was evaluated in developmental toxicity studies with Wistar rats and Himalayan rabbits. Pregnant Wistar rats were gavaged with 0 (vehicle control), 100, 300, or 1000 mg PEG-PVA grafted copolymer/kg bw/day from gestation day (GD) 6-15. Pregnant Himalayan rabbits received the same treatment from GD 6 to 19. On GD 20 and 29 for rats and rabbits, respectively, the animals were euthanized and were examined grossly. For each dam, corpora lutea were counted and number and distribution of implantation sites were determined. The fetuses were removed, sexed, weighed, and evaluated for any external, soft tissue, and skeletal findings. No significant findings were found that could be attributed to administration of PEG-PVA grafted copolymer. Under the conditions of these studies, the no-observed-adverse-effect level (NOAEL) for maternal and developmental toxicity in both species was the highest dose tested of 1000 mg/kg bw/day.

  9. Polyethylene glycol-g-polyvinyl alcohol grafted copolymer: reproductive toxicity study in Wistar rats.

    PubMed

    Heuschmid, Franziska F; Schneider, Steffen; Schuster, Paul; Lauer, Birthe; van Ravenzwaay, Bennard

    2013-07-01

    Polyethylene glycol-g-polyvinyl alcohol (PEG-PVA) grafted copolymer was administered by gavage to groups of 25 male and 25 female young Wistar rats at doses of 0 (vehicle control), 100, 300, or 1000 mg/kg bw/day for one generation (F0). The study followed the treated F0 generation through mating, gestation, lactation, and weaning of the F1 generation. F1 animals were mated and followed to gestation day (GD) 15-17 at which time F2 implants were evaluated. There were no indications from the various clinical and gross pathological examinations that the oral administration of PEG-PVA grafted copolymer to the F0-parental rats produced any signs of general, reproductive, or developmental toxicity in the F0 or F1 animals or F2 implants. Based on the lack of any dose-related or biologically relevant effects on fertility, reproduction, development, and overall health of rats gavaged with PEG-PVA grafted copolymer and their progeny, the no-observed-adverse effect level (NOAEL) was determined to be the highest dose tested of 1000 mg/kg bw/day.

  10. Subchronic toxicity of polyethylene glycol-g-polyvinyl alcohol grafted copolymer.

    PubMed

    Heuschmid, Franziska F; Schuster, Paul; Lauer, Birthe; Buesen, Roland; Mellert, Werner; Groeters, Sibylle; van Ravenzwaay, Bennard

    2013-07-01

    The safety of polyethylene glycol-g-polyvinyl alcohol (PEG-PVA) grafted copolymer was evaluated in a 13-week oral toxicity study in rats and in a 9-month oral toxicity study in dogs. Wistar rats were administered 600, 3000, or 15,000 ppm PEG-PVA grafted copolymer in their drinking water whereas beagle dogs were fed 3000, 10,000, or 30,000 ppm PEG-PVA grafted copolymer in the diet. There were no mortalities, no adverse clinical signs, no toxicologically adverse effects on body weight or body weight gain, feed consumption, hematological, clinical chemistry or urinary parameters, or histopathology in either species. In rats, no treatment-related effects were observed in the functional observational battery (FOB) or related measurements of motor activity. Increased water consumption observed in rats at the highest dose was the only test substance-induced effect noted. The no-observed-adverse-effect level (NOAEL) was the highest concentration tested in both species: 15,000 ppm in rats (corresponding to a daily intake of 1611 mg/kg bw for males and 2191 mg/kg bw for females) and 30,000 ppm in dogs (corresponding to a mean daily intake of 783 mg/kg bw for males and 811 mg/kg bw for females).

  11. Permanent hydrophilic modification of polypropylene and poly(vinyl alcohol) films by vacuum ultraviolet radiation

    NASA Astrophysics Data System (ADS)

    Belmonte, Guilherme Kretzmann; Charles, German; Strumia, Miriam Cristina; Weibel, Daniel Eduardo

    2016-09-01

    Polypropylene (PP) and Poly(vinyl alcohol) (PVA) both synthetics polymers but one of them biodegradable, were surface modified by vacuum ultraviolet (VUV) irradiation. After VUV irradiation in an inert nitrogen atmosphere, the films were exposed to oxygen gas. The treated films were characterized by water contact angle measurements (WCA), optical profilometry, FTIR-ATR, XPS, UPS and NEXAFS techniques. PP and PVA VUV-treated films reached superhydrophilic conditions (WCAs <10°) in about 30 min of irradiation under our experimental conditions. It was observed that when the WCAs reached about 35-40° the hydrophilicity was permanent in both polymers. These results contrasted with typical plasma treatments were a rapid hydrophobic recovery with aging time is usually observed. UPS and XPS data showed the presence of new functionalities on the PP and PVA surfaces that were assigned to COO, Cdbnd O, Csbnd O and Cdbnd C functional groups. Finally, grafting of styrene (ST) as a typical monomer was tested on PP films. It was confirmed that only in the VUV irradiated region an efficient grafting of ST or polymerized ST was found. Outside the irradiated regions no ST grafted was observed. Our results showed the potential use of VUV treatment for surface modification and processing of polymers which lack chromophores in the UV region.

  12. Poly(vinyl alcohol)-Tannic Acid Hydrogels with Excellent Mechanical Properties and Shape Memory Behaviors.

    PubMed

    Chen, Ya-Nan; Peng, Lufang; Liu, Tianqi; Wang, Yaxin; Shi, Shengjie; Wang, Huiliang

    2016-10-12

    Shape memory hydrogels have promising applications in a wide variety of fields. Here we report the facile fabrication of a novel type of shape memory hydrogels physically cross-linked with both stronger and weaker hydrogen bonding (H-bonding). Strong multiple H-bonding formed between poly(vinyl alcohol) (PVA) and tannic acid (TA) leads to their coagulation when they are physically mixed at an elevated temperature and easy gelation at room temperature. The amorphous structure and strong H-bonding endow the PVA-TA hydrogels with excellent mechanical properties, as indicated by their high tensile strengths (up to 2.88 MPa) and high elongations (up to 1100%). The stronger H-bonding between PVA and TA functions as the "permanent" cross-link and the weaker H-bonding between PVA chains as the "temporary" cross-link. The reversible breakage and formation of the weaker H-bonding imparts the PVA-TA hydrogels with excellent temperature-responsive shape memory. Wet and dried hydrogel samples with a deformed or elongated shape can recover to their original shapes when immersed in 60 °C water in a few seconds or at 125 °C in about 2.5 min, respectively.

  13. Fabrication and mechanical characterization of a polyvinyl alcohol sponge for tissue engineering applications.

    PubMed

    Karimi, A; Navidbakhsh, M; Faghihi, S

    2014-05-01

    Polyvinyl alcohol (PVA) sponges are widely used for clinical applications, including ophthalmic surgical treatments, wound healing and tissue engineering. There is, however, a lack of sufficient data on the mechanical properties of PVA sponges. In this study, a biomechanical method is used to characterize the elastic modulus, maximum stress and strain as well as the swelling ratio of a fabricated PVA sponge (P-sponge) and it is compared with two commercially available PVA sponges (CENEFOM and EYETEC). The results indicate that the elastic modulus of the P-sponge is 5.32% and 13.45% lower than that of the CENEFOM and EYETEC sponges, while it bears 4.11% more and 10.37% less stress compared to the CENEFOM and EYETEC sponges, respectively. The P-sponge shows a maximum strain of 32% more than the EYETEC sponge as well as a 26.78% higher swelling ratio, which is a significantly higher absorbency compared to the CENEFOM. It is believed that the results of this study would help for a better understanding of the extension, rupture and swelling mechanism of PVA sponges, which could lead to crucial improvement in the design and application of PVA-based materials in ophthalmic and plastic surgeries as well as wound healing and tissue engineering.

  14. Dual functions of polyvinyl alcohol (PVA): fabricating particles and electrospinning nanofibers applied in controlled drug release

    NASA Astrophysics Data System (ADS)

    Qin, Xiao-Hong; Wu, De-Qun; Chu, Chih-Chang

    2013-01-01

    The fabrication of submicron size microsphere from 8-Phe-4 poly(ester amide) (PEA) using polyvinyl alcohol (PVA) as the emulsion was reported. The biodegradable microspheres were prepared by an oil-in-water emulsion/solvent evaporation technique, and PVA was used as the emulsion. Furthermore, the emulsion PVA was electrospun into nanofibrous mats, and 8-Phe-4 PEA microspheres were entrapped in the resultant mats. The dual functions of PVA to fabricate ideal nanofibrous mats which can entrap microspheres in them and to obtain 8-Phe-4 microspheres as emulsion in their potential application were demonstrated. The anti-cancer drug doxorubicin (DOX) was encapsulated in the 8-Phe-4 amino acid-based PEA microspheres and the entrapment efficiency is almost 100 %. At the same time, the DOX can be controlled released in PBS solution and in α-chymotrypsin solution. The cytotoxicity of PVA, PVA mats-entrapped 8-Phe-4 microspheres and PVA mats-entrapped DOX-loaded 8-Phe-4 microspheres, was investigated. Hela cells were used to test the cytotoxicity of the DOX that released from the PVA mats-entrapped DOX-loaded 8-Phe-4 microspheres for 2 days, and the cell viability is below 30 % when the 8-Phe-4 microspheres concentration is 1 mg/mL. It demonstrated that the PVA mats-entrapped DOX-loaded 8-Phe-4 microspheres have a potential biomedical application.

  15. FAS Grafted Electrospun Poly(vinyl alcohol) Nanofiber Membranes with Robust Superhydrophobicity for Membrane Distillation.

    PubMed

    Dong, Zhe-Qin; Wang, Bao-Juan; Ma, Xiao-hua; Wei, Yong-Ming; Xu, Zhen-Liang

    2015-10-14

    This study develops a novel type of electrospun nanofiber membranes (ENMs) with high permeability and robust superhydrophobicity for membrane distillation (MD) process by mimicking the unique unitary microstructures of ramee leaves. The superhydrophobic ENMs were fabricated by the eletrospinning of poly(vinyl alcohol) (PVA), followed by chemical cross-linking with glutaraldehyde and surface modification via low surface energy fluoroalkylsilane (FAS). The resultant FAS grafted PVA (F-PVA) nanofiber membranes were endowed with self-cleaning properties with water contact angles of 158° and sliding angles of 4° via the modification process, while retaining their high porosities and interconnected open structures. For the first time, the robust superhydrophobicity of the ENMs for MD was confirmed by testing the F-PVA nanofiber membranes under violent ultrasonic treatment and harsh chemical conditions. Furthermore, vacuum membrane distillation experiments illustrated that the F-PVA membranes presented a high and stable permeate flux of 25.2 kg/m2 h, 70% higher than those of the commercial PTFE membranes, with satisfied permeate conductivity (<5 μm/cm) during a continuous test of 16 h (3.5 wt % NaCl as the feed solution, and feed temperature and permeate pressure were set as 333 K and 9 kPa, respectively), suggesting their great potentials in myriad MD processes such as high salinity water desalination and volatile organiccompounds removal.

  16. Dielectric relaxation and alternating current conductivity of lanthanum, gadolinium, and erbium-polyvinyl alcohol doped films

    NASA Astrophysics Data System (ADS)

    Hanafy, Taha A.

    2012-08-01

    Fourier transform infrared (FTIR) spectrum dielectric constant, ɛ', loss tangent, tan(δ), electric modulus, M*, and ac conductivity, σac, of pure polyvinyl alcohol (PVA) as well as La-, Gd-, and Er-PVA doped samples have been carried out. The dielectric properties have been studied in the temperature and frequency ranges; 300-450 K and 1 kHz-4 MHz, respectively. FTIR measurements reveal that La3+, Gd3+, and Er3+ ions form complex configuration within PVA structure. Two relaxation processes, namely, ρ and α were observed in pure PVA sample. The first process is due to the interfacial or Maxwell-Wagner-Sillers polarization. The second one is related to the micro-Brownian motion of the main chains. For doped PVA samples, α-relaxation process splits into αa and αc. This splitting is due to the segmental motion in the amorphous (αa) and crystalline (αc) phases of PVA matrix. Electric modulus analysis was discussed to understand the mechanism of the electrical transport process. The behavior of ac conductivity for all PVA samples indicates that the conduction mechanism is correlated barrier hopping.

  17. Sensitivity and Response of Polyvinyl Alcohol/Tin Oxide Nanocomposite Multilayer Thin Film Sensors.

    PubMed

    Sriram, G; Dhineshbabu, N R; Nithyavathy, N; Saminathan, K; Kaler, K V I S; Rajendran, V

    2016-01-01

    Nanocrystalline Tin Oxide (SnO₂) is Non-Stoichiometric in Nature with Functional Properties Suitable for gas sensing. In this study, SnO₂nanoparticles were prepared by the sol-gel technique, which were then characterised using X-ray diffraction. The nanoparticles showed tetragonal structure with an average crystallite size of 18 nm. The stretching and vibration modes of SnO₂were confirmed using Fourier transform infrared spectroscopy. The size of SnO₂ nanoparticles was determined using particle size analyser, which was found be 60 ± 10 nm on average. The surface morphology of the nanoparticles was investigated using scanning electron microscope, which showed irregular-sized agglomerated SnO₂nanostructures. In addition, primary particle size was evaluated using high-resolution transmission electron microscopy, which was found to be 50 nm on average. The polyvinyl alcohol/SnO₂ composite thin film was prepared on a glass substrate using spin-coating method. The values of band gap energy and electrical conductance of 13-layer thin film were found to be 2.96 eV and 0.0505 mho, respectively. Sulfur dioxide (SO₂) was suitably tailored to verify the sensor response over a concentration range of 10-70 ppm at room temperature. The performance, response, and recovery time of sensors were increased by increasing the layers of the thin film.

  18. Electrospun novel super-absorbent based on polysaccharide-polyvinyl alcohol-montmorillonite clay nanocomposites.

    PubMed

    Islam, Md Shahidul; Rahaman, Md Saifur; Yeum, Jeong Hyun

    2015-01-22

    A novel super-absorbent material was fabricated by electrospinning the natural polysaccharide pullulan (PULL) with polyvinyl alcohol (PVA) and montmorillonite (MMT) clay to form nonwoven webs, which were then heat treated. Transmission electron microscopy (TEM) micrographs, X-ray diffraction (XRD) patterns, and Fourier transform infrared (FTIR) analysis of the novel super-absorbent nanofibers suggest the coexistence of PULL, PVA, and MMT through the exfoliation of MMT layers in the super-absorbent nanofiber composite. The heat-treated PULL/PVA/MMT webs loaded with 5 wt% MMT electrospun nanofibers exhibited a water absorbency of 143.42 g g(-1) in distilled water and a water absorbency of 39.75 g g(-1) in a 0.9 wt% NaCl solution. Under extremely dry conditions, the PULL/PVA/MMT webs exhibited the ability to retain 43% distilled water and 38% saline water after being exposed to the atmosphere for one week. The heat treatment improved the crystallinity of the electrospun PULL/PVA/MMT super-absorbent webs and thus made the webs highly stable in aqueous environments. Overall, the addition of MMT resulted in improved thermal stability and mechanical properties and increased the water absorbency of the PULL/PVA/MMT composite.

  19. Gamma irradiation induced in situ synthesis of lead sulfide nanoparticles in poly(vinyl alcohol) hydrogel

    NASA Astrophysics Data System (ADS)

    Kuljanin-Jakovljević, Jadranka Ž.; Radosavljević, Aleksandra N.; Spasojević, Jelena P.; Carević, Milica V.; Mitrić, Miodrag N.; Kačarević-Popović, Zorica M.

    2017-01-01

    In this study, the nanocomposites based on semiconductor lead sulfide (PbS) nanoparticles and poly(vinyl alcohol) (PVA) were investigated. The gamma irradiation induced in situ incorporation of PbS nanoparticles in crosslinked polymer network i.e. PVA hydrogel was performed. PVA hydrogel was previously obtained also under the influence of gamma irradiation. UV-Vis absorption and X-ray diffraction measurements were employed to investigate optical and structural properties of PbS nanoparticles, respectively, and obtained results indicates the presence of nanoparticles with approximately 6 nm in diameter and face centered cubic rock-salt crystal structure. The porous morphology was confirmed by scanning electron microscopy. Swelling data revealed that investigated hydrogels (PVA and PbS-PVA nanocomposite) shows non-Fickian diffusion, indicating that both diffusion and polymer relaxation processes controlled the fluid transport. The values of diffusion coefficients have an order of magnitude 10-9 cm2/s (typical values for water diffusion in polymers) and the best fit with the experimental results showed the Etters approximation. Comparing the thermal properties of PbS-PVA xerogel nanocomposite with PVA xerogel it was observed that incorporation of PbS nanoparticles in crosslinked PVA matrix just slightly enhanced the thermal stability of nanocomposite.

  20. Improvement of starch digestion using α-amylase entrapped in pectin-polyvinyl alcohol blend.

    PubMed

    Cruz, Maurício; Fernandes, Kátia; Cysneiros, Cristine; Nassar, Reginaldo; Caramori, Samantha

    2015-01-01

    Polyvinyl alcohol (PVA) and pectin blends were used to entrap α-amylase (Termamyl) using glutaraldehyde as a cross-linker. The effect of glutaraldehyde concentration (0.25, 0.5, 0.75, 1.0, and 1.25%) on the activity of the immobilized enzyme and rate of enzyme released was tested during a 24 h period. Characteristics of the material, such as scanning electron microscopy (SEM), tensile strength (TS), elongation, and rate of dissolution in water (pH 5.7), ruminal buffering solution (pH 7.0), and reactor containing 0.1 mol L(-1) sodium phosphate buffer (pH 6.5), were also analyzed. SEM results showed that the surfaces of the pectin/PVA/amylase films were highly irregular and rough. TS values increased as a function of glutaraldehyde concentration, whereas percentage of elongation (%E) decreased. Pectin/PVA/amylase films presented similar values of solubility in the tested solvents. The material obtained with 0.25% glutaraldehyde performed best with repeated use (active for 24 h), in a phosphate buffer reactor. By contrast, the material obtained with 1.25% glutaraldehyde presented higher performance during in vitro testing using an artificial rumen. The results suggest that pectin/PVA/amylase is a highly promising material for biotechnological applications.

  1. Poly(vinyl alcohol)/sodium alginate/layered silicate based nanofibrous mats for bacterial inhibition.

    PubMed

    Li, Wei; Li, Xueyong; Chen, Yang; Li, Xiaoxia; Deng, Hongbing; Wang, Ting; Huang, Rong; Fan, Gang

    2013-02-15

    Poly(vinyl alcohol) (PVA)/sodium alginate (ALG)/organic rectorite (OREC) composite nanofibrous mats are fabricated by electrospinning aqueous solutions with different mixing ratios. Both good fiber shape and three-dimensional structure of nanofibrous mats can be observed by Field Emission Scanning Electron Microscopy. Energy-dispersive X-ray spectroscopy shows the existence of OREC in the as-spun composite mats. In addition, small-angle X-ray diffraction confirms that the interlayer of OREC is intercalated by ALG/PVA chains, and the distance between OREC interlayers is increased from 4.50 to 4.74 nm. Wide angle X-ray diffraction and Fourier transform infrared spectra further verify the intercalation is between polymers and layered silicate. Moreover, the thermal gravimetric analysis shows that the addition of OREC has only a small effect on the thermal stability of composites. Furthermore, the antibacterial experiments illustrate that OREC can enhance the bacterial inhibition ability of nanofibrous mats against Escherichia coli and Staphylococcus aureus.

  2. Controlled release of retinyl acetate from β-cyclodextrin functionalized poly(vinyl alcohol) electrospun nanofibers.

    PubMed

    Lemma, Solomon M; Scampicchio, Matteo; Mahon, Peter J; Sbarski, Igor; Wang, James; Kingshott, Peter

    2015-04-08

    Retinyl acetate (RA) was effectively incorporated into electrospun nanofibers of poly(vinyl alcohol) (PVA) containing β-cyclodextrin (β-CD) in order to form inclusion complexes for encapsulation to prolong shelf life and thermal stability. The physical and thermal properties of encapsulated RA were determined by scanning electron microscopy (SEM), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The nanofibers of PVA/RA and PVA/RA/β-CD exhibited bead free average fiber diameters of 264 ± 61 and 223 ± 49 nm, respectively. The surface chemistry of the functional nanofibers was investigated by X-ray photoelectron spectroscopy (XPS). Thermogravimetric analysis (TGA) demonstrated different thermal stabilities between the bioactive and the polymer, with and without β-CD. Square-wave voltammogram peak current changes were used to follow the release kinetics of RA from the nanofibers. Results indicate that RA coated inside PVA/β-CD nanofibers was protected against oxidation much better than RA in PVA nanofibers and should extend the shelf life. In addition, RA encapsulated in the PVA/β-CD had better thermal stability than PVA nanofibers.

  3. Polyaniline coated cellulose fiber / polyvinyl alcohol composites with high dielectric permittivity and low percolation threshold

    NASA Astrophysics Data System (ADS)

    Anju, V. P.; Narayanankutty, Sunil K.

    2016-01-01

    Cost effective, high performance dielectric composites based on polyvinyl alcohol, cellulose fibers and polyaniline were prepared and the dielectric properties were studied as a function of fiber content, fiber dimensions and polyaniline content over a frequency range of 40 Hz to 30 MHz. The short cellulose fibers were size-reduced to micro and nano levels prior to coating with polyaniline. Fiber surface was coated with Polyaniline (PANI) by an in situ polymerization technique in aqueous medium. The composites were then prepared by solution casting method. Short cellulose fiber composites showed a dielectric constant (DEC) of 2.3 x 105 at 40 Hz. For the micro- and nano- cellulose fiber composites the DEC was increased to 4.5 x 105 and 1.3 x 108, respectively. To gain insight into the inflection point of the dielectric data polynomial regression analysis was carried out. The loss tangent of all the composites remained at less than 1.5. Further, AC conductivity, real and imaginary electric moduli of all the composites were evaluated. PVA nanocomposite attained an AC conductivity of 3 S/m. These showed that by controlling the size of the fiber used, it was possible to tune the permittivity and dielectric loss to desired values over a wide range. These novel nanocomposites, combining high dielectric constant and low dielectric loss, can be effectively used in applications such as high-charge storage capacitors.

  4. A poly(vinyl alcohol)/sodium alginate blend monolith with nanoscale porous structure.

    PubMed

    Sun, Xiaoxia; Uyama, Hiroshi

    2013-10-04

    A stimuli-responsive poly(vinyl alcohol) (PVA)/sodium alginate (SA) blend monolith with nanoscale porous (mesoporous) structure is successfully fabricated by thermally impacted non-solvent induced phase separation (TINIPS) method. The PVA/SA blend monolith with different SA contents is conveniently fabricated in an aqueous methanol without any templates. The solvent suitable for the fabrication of the present blend monolith by TINIPS is different with that of the PVA monolith. The nanostructural control of the blend monolith is readily achieved by optimizing the fabrication conditions. Brunauer Emmett Teller measurement shows that the obtained blend monolith has a large surface area. Pore size distribution plot for the blend monolith obtained by the non-local density functional theory method reveals the existence of the nanoscale porous structure. Fourier transform infrared analysis reveals the strong interactions between PVA and SA. The pH-responsive property of the blend monolith is investigated on the basis of swelling ratio in different pH solutions. The present blend monolith of biocompatible and biodegradable PVA and SA with nanoscale porous structure has large potential for applications in biomedical and environmental fields.

  5. Rhizobia survival in seeds coated with polyvinyl alcohol (PVA) electrospun nanofibres.

    PubMed

    Damasceno, Raquel; Roggia, Isabel; Pereira, Claudio; de Sá, Enilson

    2013-11-01

    The electrospinning technique of rhizobia immobilization in nanofibres is an innovative and promising alternative for reducing the harmful effects of environmental stress on bacteria strains in a possible inoculant nanotechnology product for use in agriculture. The use of polyvinyl alcohol (PVA) shows up as an effective polymer in cell encapsulation because of its physical characteristics, such as viscosity and power of scattering. The aim of these studies has been to evaluate the survival of rhizobia incorporated in PVA nanofibres, which were applied to soybean seed and then subjected to different storage times and exposure to fungicide. The maintenance of the symbiotic characteristics of the incorporated bacterial strains was also evaluated, noting the formation of nodules in the soybean seedlings. No significant differences in the cell survival at 0 h and after 24 h of storage were observed. After 48 h, a significant difference in the bacterial cell concentration of the seeds affixed with PVA nanofibres was observed. Exposure to the fungicide decreased the viability of the bacteria strains even when coated with the nanofibres. A larger number of nodules formed in soybean seedlings from seeds inoculated with rhizobia incorporated in PVA nanofibres than from seeds inoculated with rhizobia without PVA. Thus, the electrospinning technique is a great alternative to the usual protector inoculants because of its unprecedented capacity to control the release of bacteria.

  6. A visco-hyperelastic constitutive approach for modeling polyvinyl alcohol sponge.

    PubMed

    Karimi, Alireza; Navidbakhsh, Mahdi; Beigzadeh, Borhan

    2014-02-01

    This study proposes the quasi-linear viscoelastic (QLV) model to characterize the time dependent mechanical behavior of poly(vinyl alcohol) (PVA) sponges. The PVA sponges have implications in many viscoelastic soft tissues, including cartilage, liver, and kidney as an implant. However, a critical barrier to the use of the PVA sponge as tissue replacement material is a lack of sufficient study on its viscoelastic mechanical properties. In this study, the nonlinear mechanical behavior of a fabricated PVA sponge is investigated experimentally and computationally using relaxation and stress failure tests as well as finite element (FE) modeling. Hyperelastic strain energy density functions, such as Yeoh and Neo-Hookean, are used to capture the mechanical behavior of PVA sponge at ramp part, and viscoelastic model is used to describe the viscose behavior at hold part. Hyperelastic material constants are obtained and their general prediction ability is verified using FE simulations of PVA tensile experiments. The results of relaxation and stress failure tests revealed that Yeoh material model can define the mechanical behavior of PVA sponge properly compared with Neo-Hookean one. FE modeling results are also affirmed the appropriateness of Yeoh model to characterize the mechanical behavior of PVA sponge. Thus, the Yeoh model can be used in future biomechanical simulations of the spongy biomaterials. These results can be utilized to understand the viscoelastic behavior of PVA sponges and has implications for tissue engineering as scaffold.

  7. Kinetic evaluation study on the bioactivity of silver doped hydroxyapatite-polyvinyl alcohol nanocomposites.

    PubMed

    Mostafa, Amany A; Oudadesse, Hassane; El Sayed, Mayyada M H; Kamal, Gehan; Kamel, Mohamed; Foad, Enas

    2014-12-01

    This work investigates the effect of adding silver nanoparticles (NPs) in ppm on the bioactivity of hydroxyapatite/polyvinyl alcohol nanocomposites (HAV). HAV prepared by an in situ biomimetic approach was doped with different concentrations of silver NPs (HAV-Ag), and the formed powder samples were characterized by different techniques such as Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-EOS), X-ray diffraction, transmission electron microscope, and Fourier Transform Infrared Spectroscopy. Bioactivity was evaluated in simulated body fluid through studying the kinetics of Ca and P uptake onto the different HAV-Ag nanocomposites. Uptake profiles of Ca and P were well described by a pseudo-second order kinetic model, and the obtained kinetic parameters confirmed that the highest uptake capacities were achieved by adding less than 0.001 ppm of silver NPs which is an amount not detectable by ICP. Furthermore, HAV-Ag nanocomposites were shown to be non-toxic as well as have a strong antibacterial effect. Silver NPs significantly enhanced the bioactivity of HAV nanocomposites and thus the developed nanocomposites promise to be excellent biomaterials for bone and reconstructive surgery applications.

  8. Effect of nanosilica on optical, electric modulus and AC conductivity of polyvinyl alcohol/polyaniline films

    NASA Astrophysics Data System (ADS)

    El-Sayed, Somyia; Abel-Baset, Tarob; Elfadl, Azza Abou; Hassen, Arafa

    2015-05-01

    Nanosilica (NS) was synthesized by a sol-gel method and mixed with 0.98 polyvinyl alcohol (PVA)/0.02 polyaniline (PANI) in different amounts to produce nanocomposite films. High-resolution transmission electron microscopy (HR-TEM) revealed the average particle size of the NS to be ca. 15 nm. Scanning electron microscopy (SEM) showed that the NS was well-dispersed on the surface of the PVA/PNAI films. The Fourier transform infrared (FTIR) spectra of the samples showed a significant change in the intensity of the characteristic peak of the functional groups in the composite films with the amount of NS added. The absorbance and refractive index (n) of the composites were studied in the UV-vis range, and the optical energy band gap, Eg, and different optical parameters were calculated. The dielectric loss modulus, M″ and ac conductivity, σac, of the samples were studied within 300-425 K and 0.1 kHz-5 MHz, respectively. Two relaxation peaks were observed in the frequency dependence of the dielectric loss modulus, M″. The behavior of σac(f) for the composite films indicated that the conduction mechanism was correlated barrier hopping (CBH). The results of this work are discussed and compared with those of previous studies of similar composites.

  9. Photochromic properties of the molecule Azure A chloride in polyvinyl alcohol matrix

    NASA Astrophysics Data System (ADS)

    Shahab, Siyamak; Filippovich, Liudmila; Kumar, Rakesh; Darroudi, Mahdieh; Borzehandani, Mostafa Yousefzadeh; Gomar, Maryam; Hajikolaee, Fatemeh Haji

    2015-12-01

    In the present work, isomerization, photophysical properties and heat conductivity of the substance Azure A chloride (AZAC): 3-amino-7-(dimethlamino)phenothiazin-5-ium chloride under the action of UV radiation in the presence of polyvinyl alcohol (PVA) matrix was studied using the Hartree-Fock (HF) and Density Functional Theory (DFT) methods. The electronic absorption spectra of AZAC in dimethylformamide (DMF) solution and in aqueous medium before and after UV radiation were calculated. The nature of absorption bands of AZAC and its tautomeric prototropic form with the transfer of the electron (AZAC1) in the visible and near UV spectral regions was interpreted. The solvent effect on the absorption spectrum of the AZAC has established. The comparison of measured FTIR, UV-Visible data allowed assignments of major special features of title molecules. The frontier molecular orbital HOMO-LUMO have been also presented that shows the charge transfer interactions taking place within these molecules. The excitation energies for both molecules AZAC and AZAC1 have also been calculated. The experimental as well as theoretical investigations of azure molecule have a close agreement and it gives other important clues about the properties of the system. Anisotropy of thermal conductivity in PVA-films containing AZAC and AZAC1 were also measured.

  10. Radiation sensitive indicator based on tetrabromophenol blue dyed poly(vinyl alcohol)

    NASA Astrophysics Data System (ADS)

    Beshir, W. B.

    2013-05-01

    Radiation sensitive indicators based on dyed polyvinyl alcohol (PVA) containing acid- sensitive dye (tetrabromophenol blue, TBPB) and chloral hydrate (CCl3·CH·(OH)2, 2,2,2-trichloroethane-1,1-diol) have been developed. These plastic film dosimeters undergo color change from blue (the alkaline form of TBPB) to yellow (the acidic form of TBPB), indicating acid formation. The concentration of radiation formed acids in the films containing different concentrations of chloral hydrate was calculated at different doses. These films can be used as dosimeters for food irradiation applications where the maximum of the useful dose ranges are between 1 and 8 kGy depending on chloral hydrate concentration in the film. The films have the advantage of negligible humidity effects on response in the intermediate range of relative humidity from 0 to 70% as good post irradiation stability when stored in the dark at room temperature. The overall combined uncertainty (at 2σ) associated with measurement of response (ΔA mm-1) at 623 nm for dose range 1-8 kGy is 4.53%.

  11. Arterial Distribution of Calibrated Tris-Acryl Gelatin and Polyvinyl Alcohol Embolization Microspheres in Sheep Uterus

    SciTech Connect

    Laurent, Alexandre; Wassef, Michel; Namur, Julien; Ghegediban, Homayra; Pelage, Jean-Pierre

    2010-10-15

    The purpose of this study was to compare, after embolization, the distribution in the uterine arterial vasculature of tris-acryl gelatin microspheres (TGMS) and polyvinyl alcohol microspheres (PVAMS). A limited bilateral uterine artery embolization was performed in six adult sheep under fluoroscopic control by injecting in each uterine artery 0.25 ml of 500- to 700-{mu}m TGMS of PVAMS suspended in 50/50 saline/contrast medium. Sacrifices were performed 1 week after embolization and uteri were analyzed histologically. The number and size of microspheres and vessels were measured, as well as the histological location according to a classification in four zones of the uterus. One hundred sixty-five vessels (69 vessels occluded with TGMS and 96 vessels occluded with PVAMS) were measured. The size of the occluded vessels decreased significantly from proximal to distal zones of the uterine vasculature (P < 0.0001). The location of TGMS and PVAMS within the vasculature was significantly different (P < 0.0001) since PVAMS blocked significantly more distally than TGMS. Deformation of the microspheres within the tissue was greater for PVAMS (18.0% {+-} 12.3%) than for TGMS (8.7% {+-} 9.2%) (P < 0.0001). In conclusion, PVAMS have a more distal distribution in the sheep uterine vasculature, compared to TGMS. Such differences in partition, already described in the kidney embolization model, can ultimately explain the different clinical outcome reported with these two types of microspheres in uterine fibroid embolization.

  12. Expression and fermentation optimization of oxidized polyvinyl alcohol hydrolase in E. coli.

    PubMed

    Yang, Yu; Zhang, Dongxu; Liu, Song; Jia, Dongxu; Du, Guocheng; Chen, Jian

    2012-01-01

    Oxidized polyvinyl alcohol (PVA) hydrolase (OPH) is a key enzyme in the degradation of PVA, suggesting that OPH has a great potential for application in textile desizing processes. In this study, the OPH gene from Sphingopyxis sp. 113P3 was modified, by artificial synthesis, for overexpression in Escherichia coli. The OPH gene, lacking the sequence encoding the original signal peptide, was inserted into pET-20b (+) expression vector, which was then used to transform E. coli BL21 (DE3). OPH expression was detected in culture medium in which the transformed E. coli BL21 (DE3) was grown. Nutritional and environmental conditions were investigated for improved production of OPH protein by the recombinant strain. The highest OPH activity measured was 47.54 U/mL and was reached after 84 h under optimal fermentation conditions; this level is 2.64-fold higher that obtained under sub-optimal conditions. The productivity of recombinant OPH reached 565.95 U/L/h. The effect of glycine on the secretion of recombinant OPH was examined by adding glycine to the culture medium to a final concentration of 200 mM. This concentration of glycine reduced the fermentation time by 24 h and increased the productivity of recombinant OPH to 733.17 U/L/h. Our results suggest that the recombinant strain reported here has great potential for use in industrial applications.

  13. Poly(vinyl alcohol) physical hydrogels: noncryogenic stabilization allows nano- and microscale materials design.

    PubMed

    Jensen, Bettina E B; Smith, Anton A A; Fejerskov, Betina; Postma, Almar; Senn, Philipp; Reimhult, Erik; Pla-Roca, Mateu; Isa, Lucio; Sutherland, Duncan S; Städler, Brigitte; Zelikin, Alexander N

    2011-08-16

    Physical hydrogels based on poly(vinyl alcohol), PVA, have an excellent safety profile and a successful history of biomedical applications. However, highly inhomogeneous and macroporous internal organization of these hydrogels as well as scant opportunities in bioconjugation with PVA have largely ruled out micro- and nanoscale control and precision in materials design and their use in (nano)biomedicine. To address these shortcomings, herein we report on the assembly of PVA physical hydrogels via "salting-out", a noncryogenic method. To facilitate sample visualization and analysis, we employ surface-adhered structured hydrogels created via microtransfer molding. The developed approach allows us to assemble physical hydrogels with dimensions across the length scales, from ∼100 nm to hundreds of micrometers and centimeter sized structures. We determine the effect of the PVA molecular weight, concentration, and "salting out" times on the hydrogel properties, i.e., stability in PBS, swelling, and Young's modulus using exemplary microstructures. We further report on RAFT-synthesized PVA and the functionalization of polymer terminal groups with RITC, a model fluorescent low molecular weight cargo. This conjugated PVA-RITC was then loaded into the PVA hydrogels and the cargo concentration was successfully varied across at least 3 orders of magnitude. The reported design of PVA physical hydrogels delivers methods of production of functionalized hydrogel materials toward diverse applications, specifically surface mediated drug delivery.

  14. Dye-sensitized solar cell using 4-chloro-7-nitrobenzofurazan incorporated polyvinyl alcohol polymer electrolyte

    NASA Astrophysics Data System (ADS)

    Senthil, R. A.; Theerthagiri, J.; Madhavan, J.; Arof, A. K.

    2016-11-01

    The influence of 4-chloro-7-nitrobenzofurazan (CNBF) on ionic conductivity of polyvinyl alcohol/KI/I2 (PVA/KI/I2) electrolytes was investigated in the present study. The pure and CNBF incorporated PVA/KI/I2 electrolyte films were prepared by solution casting method using dimethyl sulfoxide as a solvent. These polymer electrolyte films were characterized using Fourier transform infrared spectroscopy, X-ray diffractometer, UV-Vis spectrophotometer and impedance analysis. The ionic conductivities of polymer electrolyte films were calculated from impedance analysis. The pure PVA/KI/I2 electrolyte exhibited the ionic conductivity of 1.649 × 10-5 S cm-1 at room temperature and this value was significantly increased to 1.490 × 10-4 S cm-1 when CNBF was incorporated into the PVA/KI/I2 electrolyte. This might be due to the decrease in the crystallinity of the polymer and increase in the ionic mobility of charge carriers. The performance of the DSSCs using both pure and CNBF incorporated PVA/KI/I2 electrolytes were compared. A DSSC fabricated with CNBF incorporated PVA/KI/I2 electrolyte showed an improved power conversion efficiency of 3.89 % than that of the pure PVA/KI/I electrolyte (1.51 %). These results suggest that CNBF incorporated PVA/KI/I2 electrolyte could be used as a potential electrolyte for DSSC.

  15. Shock pressure measurements in Polyvinyl alcohol (PVA) films using multi-frame optical shadowgraphy

    NASA Astrophysics Data System (ADS)

    Chaurasia, S.; Tripathi, S.; Leshma, P.; Pasley, J.; Kumar, M.

    2012-07-01

    The knowledge of the equation of state (EOS) of materials at high pressures in excess of 10 Mbar is important in several branches of physics including astrophysics and inertial confinement fusion. It is possible to access this high pressure regime in the laboratory using shock waves launched by the interaction of a high power laser with a solid target. To study laser driven shock waves in plastic (Polyvinyl alcohol) (C2H4O)n targets, a multiframe optical shadowgraphy technique has been developed, with spatial and temporal resolution of 12 μm and 500 ps respectively. The experiments were performed using the 1064 nm 20 J /500 ps Nd: Glass laser at BARC. The focused laser intensity on target was varied between 6 × 1013 W/cm2 and 2.7 × 1014 W/cm2. The experimental data have been compared with the results of previous experimental and theoretical studies. The results are also found to be in agreement with SESAME data. The maximum pressure attained in the experiments was 30 Mbar, achieved with a laser intensity of 2.7 × 1014 W/cm2.

  16. In vitro release of metformin hydrochloride from sodium alginate/polyvinyl alcohol hydrogels.

    PubMed

    Martínez-Gómez, Fabián; Guerrero, Juan; Matsuhiro, Betty; Pavez, Jorge

    2017-01-02

    Hydrogels, based on polysaccharides have found a number of applications as drug delivery carriers. In this work, hydrogels of full characterized sodium alginate (Mn 87,400g/mol) and commercial poly(vinyl alcohol) (PVA) sensitive to pH and temperature stimuli were obtained using a simple, controlled, green, low cost method based on freeze-thaw cycles. Stable hydrogels of sodium alginate/PVA with 0.5:1.5 and 1.0:1.0w/v concentrations showed very good swelling ratio values in distilled water (14 and 20g/g, respectively). Encapsulation and release of metformin hydrochloride in hydrogels of 1.0:1.0w/v sodium alginate/PVA was followed by UV spectroscopy. The hydrogel released a very low amount of metformin hydrochloride at pH 1.2; the highest release value (55%) was obtained after 6h at pH 8.0. Also, the release of metformin hydrochloride was studied by (1)H NMR spectroscopy, the temporal evolution of methyl group signals of metformin showed 30% of drug release after 3h.

  17. Effect of salts on the electrospinning of poly(vinyl alcohol)

    NASA Astrophysics Data System (ADS)

    Stanger, Jonathan J.; Tucker, Nick; Staiger, Mark; Kirwan, Kerry; Coles, Stuart; Jacobs, Daniel; Larsen, Nigel

    2009-07-01

    Fibres with a diameter in the nanometer range were electrospun from aqueous poly(vinyl alcohol) (PVOH). In order to improve the mass deposition rate and decrease the final fibre diameter salts (NaCl, LiCl, LiBr and LiF) were added to the solution. The aim was to increase the charge density and hence increase the electrostatic forces on the fluid. It was found that with increasing salt concentration the charge density did increase. However the mass deposition rate was found to decrease and the final fibre diameter was found to increase. The decrease in mass deposition rate is explained by considering the concept of a virtual orifice. The increase in the final fibre diameter is explained by considering the charge distribution in the jet when it behaves like a conductor compared to when it behaves like an insulator. Both mechanisms result from the increase in conductivity of the PVOH solution without significantly modifying other solution properties when salt is added.

  18. Evaluation of polyvinyl alcohol composite membranes containing collagen and bone particles.

    PubMed

    Hameed, Nishar; Glattauer, Veronica; Ramshaw, John A M

    2015-08-01

    Composite biomaterials provide alternative materials that improve on the properties of the individual components and can be used to replace or restore damaged or diseased tissues. Typically, a composite biomaterial consists of a matrix, often a polymer, with one or more fillers that can be made up of particles, sheets or fibres. The polymer matrix can be chosen from a wide range of compositions and can be fabricated easily and rapidly into complex shapes and structures. In the present study we have examined three size fractions of collagen-containing particles embedded at up to 60% w/w in a poly(vinyl alcohol) (PVA) matrix. The particles used were bone particles, which are a mineral-collagen composite and demineralised bone, which gives naturally cross-linked collagen particles. SEM showed well dispersed particles in the PVA matrix for all concentrations and sizes of particles, with FTIR suggesting collagen to PVA hydrogen bonding. Tg of membranes shifted to a slightly lower temperature with increasing collagen content, along with a minor amount of melting point depression. The modulus and tensile strength of membranes were improved with the addition of both particles up to 10 wt%, and were clearly strengthened by the addition, although this effect decreased with higher collagen loadings. Elongation at break decreased with collagen content. Cell adhesion to the membranes was observed associated with the collagen particles, indicating a lack of cytotoxicity.

  19. Improved cellular response on multiwalled carbon nanotube-incorporated electrospun polyvinyl alcohol/chitosan nanofibrous scaffolds.

    PubMed

    Liao, Huihui; Qi, Ruiling; Shen, Mingwu; Cao, Xueyan; Guo, Rui; Zhang, Yanzhong; Shi, Xiangyang

    2011-06-01

    We report the fabrication of multiwalled carbon nanotube (MWCNT)-incorporated electrospun polyvinyl alcohol (PVA)/chitosan (CS) nanofibers with improved cellular response for potential tissue engineering applications. In this study, smooth and uniform PVA/CS and PVA/CS/MWCNTs nanofibers with water stability were formed by electrospinning, followed by crosslinking with glutaraldehyde vapor. The morphology, structure, and mechanical properties of the formed electrospun fibrous mats were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, and mechanical testing, respectively. We showed that the incorporation of MWCNTs did not appreciably affect the morphology of the PVA/CS nanofibers; importantly the protein adsorption ability of the nanofibers was significantly improved. In vitro cell culture of mouse fibroblasts (L929) seeded onto the electrospun scaffolds showed that the incorporation of MWCNTs into the PVA/CS nanofibers significantly promoted cell proliferation. Results from this study hence suggest that MWCNT-incorporated PVA/CS nanofibrous scaffolds with small diameters (around 160 nm) and high porosity can mimic the natural extracellular matrix well, and potentially provide many possibilities for applications in the fields of tissue engineering and regenerative medicine.

  20. Anomalous electrical transport properties of polyvinyl alcohol-multiwall carbon nanotubes composites below room temperature

    NASA Astrophysics Data System (ADS)

    Chakraborty, G.; Gupta, K.; Meikap, A. K.; Babu, R.; Blau, W. J.

    2011-02-01

    The dc and ac electrical transport property of polyvinyl alcohol-multiwall carbon nanotubes composites has been investigated within a temperature range 77≤T≤300 K and in the frequency range 20 Hz-1 MHz in presence as well as in absence of a transverse magnetic field up to 1 T. The dc conductivity follows variable range hopping model. The magnetoconductivity of the samples changes a sign from positive to negative with an increase in temperature which can be interpreted by the dominancy of the quantum interference effect over the wave function shrinkage effect. The ac conductivity follows a power law whereas the temperature dependence of frequency exponent s can be explained by correlated barrier hopping model. The dielectric behavior of the samples has been governed by the grain and grain boundary resistance and capacitance. The ac conductivity reduces with the application of magnetic field. Although the theoretical model to explain it, is still lacking, we may conclude that this is due to the increase in grain and grain boundary resistance by the application of magnetic field.

  1. Dye Adsorption Behavior of Polyvinyl Alcohol/Glutaraldehyde/β-Cyclodextrin Polymer Membranes

    NASA Astrophysics Data System (ADS)

    Ghemati, Dj.; Aliouche, Dj.

    2014-05-01

    Crosslinked polyvinyl alcohol/glutaraldehyde (PVA/GA) membranes were prepared, and attempts to obtain hydrophilic crosslinked PVA membranes were made by adding various amounts of β-cyclodexrin (β-CD), which is a typical cyclic oligosaccharide able to form inclusion complexes with organic host molecules (host-guest complexes). Thus, membranes of PVA/GA/β-CD were synthesized. The membranes were characterized by infrared spectroscopy (FTIR) and swelling measurements. The ability of cyclodextrin to include a wide variety of chemicals was also exploited for the dye adsorption to show the potentialities of the membranes in textile liquid waste processing. Adsorption of reactive methyl orange, and methylene blue dyes on PVA/GA/β-CD membranes was consequently studied using UV-Vis spectroscopy at wavelengths of 547, 463, and 660 nm. Adsorption reached equilibrium after 24 h. Results indicated that there is no covalent bond formation between PVA and β-CD; the β-CD is completely mixed into the PVA matrix polymer. The adsorption capacity increases with increasing amounts of cyclodextrin; the maximum adsorption capacity was obtained with 8% β-CD. Therefore, the change in adsorption capacities may be due to the dye structure effect, and the negative value of free energy indicated the spontaneous nature of adsorption.

  2. Nonlinear optical characterization of the Ag nanoparticles doped in polyvinyl alcohol films

    NASA Astrophysics Data System (ADS)

    Ghanipour, Mahshad; Dorranian, Davoud

    2015-06-01

    The effect of silver nanoparticles doped in polyvinyl alcohol (PVA) on the nonlinear optical properties of composite films is studied experimentally. Samples are PVA films of 0.14 mm thickness doped with different concentrations of silver nanoparticles. Nonlinear optical properties of doped polymer films are studied experimentally employing Z-scan techniques. Experiments are performed using the second harmonic of a continuous Nd-Yag laser beam at 532 nm wavelength and 45 mW power. The effect of nonlinear refractive index of samples is obtained by measuring the profile of propagated beam through the samples and their nonlinear refractive index is found to be negative. The nonlinear absorption coefficient is calculated using open aperture Z-scan data while its nonlinear refractive index is measured using the closed aperture Z-scan data, leads to measuring the third order susceptibility |χ(3)|. Real and imaginary parts of the third-order nonlinear optical susceptibility |χ(3)| are decrease with increasing the concentration of Ag nanoparticles in the films. The values of thermo-optic coefficient are determined at different concentrations of silver nanoparticles for samples.

  3. Characterization of a polyvinyl alcohol-hydrogel artificial articular cartilage prepared by injection molding.

    PubMed

    Kobayashi, Masanori; Oka, Masanori

    2004-01-01

    We have developed a hip hemi-arthroplasty using polyvinyl alcohol-hydrogel (PVA-H) as the treatment for hip joint disorders in which the lesion is limited to the joint surface. In previous studies, we characterized the biocompatibility and the mechanical properties of PVA-H as an arthroplasty material. To fix PVA-H firmly to the bone, we have devised an implant composed of PVA-H and porous titanium fiber mesh (TFM). However, because of poor infiltration of the PVA solution into the pores of the TFM when using the low temperature crystallization method, the strength of the PVA-H-TFM interface was insufficient. Consequently, the infiltration method was improved by adopting high-pressure injection molding. With this improved method, the bonding strength of the interface increased remarkably. However, as this injection molding requires high temperature, various mechanical properties of the PVA-H might change with this treatment in comparison with the previous method. The purpose of this study was to investigate the effect of high temperature treatment on the mechanical properties of PVA-H as artificial articular cartilage, the tensile test and friction test were performed about new PVA-H. The results showed no significant mechanical deterioration of the PVA-H. This certified that the injection-molding method did not induce the change of the mechanical properties of PVA-H and indicated the potential of hemi-arthroplasty using PVA-H by this method in the future.

  4. Dehydration of dioxane by pervaporation using filled blend membranes of polyvinyl alcohol and sodium alginate.

    PubMed

    Kuila, Sunil Baran; Ray, Samit Kumar

    2014-01-30

    Pervaporation membranes were made by solution blending of polyvinyl alcohol (PVA) and sodium alginate (SA). Accordingly, five different blends with PVA:SA weight ratio of 75:25, 50:50, 25:75, 20:80 and 10:90 designated as PS1, PS2, PS3, PS4 and PS5, respectively, were prepared. Each of these blends was crosslinked with 2, 4 and 6 wt% glutaraldehyde and the resulting fifteen (5 × 3) membranes were used for pervaporative separation of 90 wt% dioxane in water. The membranes made from PS4 and PS5 were not stable during pervaporation experiments. Among the stable membranes PS3 membrane crosslinked with 2 wt% glutaraldehyde showed the best results for flux and selectivity. Thus, it was filled with nano size sodium montmorillonite filler and used for separation of dioxane-water mixtures over the entire concentration range of 80-99.5 wt% dioxane in water. The membranes were also characterized by mechanical properties, FTIR, SEM, DTA-TGA and XRD.

  5. Surface stiffening and enhanced photoluminescence of ion implanted cellulose - polyvinyl alcohol - silica composite.

    PubMed

    Shanthini, G M; Sakthivel, N; Menon, Ranjini; Nabhiraj, P Y; Gómez-Tejedor, J A; Meseguer-Dueñas, J M; Gómez Ribelles, J L; Krishna, J B M; Kalkura, S Narayana

    2016-11-20

    Novel Cellulose (Cel) reinforced polyvinyl alcohol (PVA)-Silica (Si) composite which has good stability and in vitro degradation was prepared by lyophilization technique and implanted using N(3+) ions of energy 24keV in the fluences of 1×10(15), 5×10(15) and 1×10(16)ions/cm(2). SEM analysis revealed the formation of microstructures, and improved the surface roughness on ion implantation. In addition to these structural changes, the implantation significantly modified the luminescent, thermal and mechanical properties of the samples. The elastic modulus of the implanted samples has increased by about 50 times compared to the pristine which confirms that the stiffness of the sample surface has increased remarkably on ion implantation. The photoluminescence of the native cellulose has improved greatly due to defect site, dangling bonds and hydrogen passivation. Electric conductivity of the ion implanted samples was improved by about 25%. Hence, low energy ion implantation tunes the mechanical property, surface roughness and further induces the formation of nano structures. MG63 cells seeded onto the scaffolds reveals that with the increase in implantation fluence, the cell attachment, viability and proliferation have improved greatly compared to pristine. The enhancement of cell growth of about 59% was observed in the implanted samples compared to pristine. These properties will enable the scaffolds to be ideal for bone tissue engineering and imaging applications.

  6. Synthesis, characterization, optical and antimicrobial studies of polyvinyl alcohol-silver nanocomposites

    NASA Astrophysics Data System (ADS)

    Mahmoud, K. H.

    2015-03-01

    Silver nanoparticles (Ag NPs) were synthesized by chemical reduction of silver salt (AgNO3) through sodium borohydride. The characteristic surface plasmon resonance band located at around 400 nm in the UV-Visible absorption spectrum confirmed the formation of Ag nanoparticles. Polyvinyl alcohol-silver (PVA-Ag) nanocomposite films were prepared by the casting technique. The morphology and interaction of PVA with Ag NPs were examined by transmission electron microscopy and FTIR spectroscopy. Optical studies show that PVA exhibited indirect allowed optical transition with optical energy gap of 4.8 eV, which reduced to 4.45 eV under addition of Ag NPs. Optical parameters such as refractive index, complex dielectric constant and their dispersions have been analyzed using Wemple and DiDomenco model. Color properties of the nanocomposites are discussed in the framework of CIE L∗u∗v∗ color space. The antimicrobial activity of the nanocomposite samples was tested against Gram positive bacteria (Staphylococcus aureus NCTC 7447 &Bacillus subtillis NCIB 3610), Gram negative bacteria (Escherichia coli, NTC10416 &Pseudomonas aeruginosa NCIB 9016) and fungi (Aspergillus niger Ferm - BAM C-21) using the agar diffusion technique. The antimicrobial study showed that PVA has moderate antibacterial activity against B. subtillis and the 0.04 wt% Ag NPs composite sample effect was strong against S. aureus.

  7. A Study of Specific Heat Capacity Functions of Polyvinyl Alcohol- Cassava Starch Blends

    NASA Astrophysics Data System (ADS)

    Sin, Lee Tin; Rahman, W. A. W. A.; Rahmat, A. R.; Morad, N. A.; Salleh, M. S. N.

    2010-03-01

    The specific heat capacity ( C sp) of polyvinyl alcohol (PVOH) blends with cassava starch (CSS) was studied by the differential scanning calorimetry method. Specimens of PVOH-CSS blends: PPV37 (70 mass% CSS) and PPV46 (60 mass% CSS) were prepared by a melt blending method with glycerol added as a plasticizer. The results showed that the specific heat capacity of PPV37 and PPV46 at temperatures from 330 K to 530 K increased from (2.963 to 14.995) J· g-1 · K-1 and (2.517 to 14.727) J · g-1· K-1, respectively. The specific heat capacity of PVOH-CSS depends on the amount of starch. The specific heat capacity of the specimens can be approximated by polynomial equations with a curve fitting regression > 0.992. For instance, the specific heat capacity (in J · g-1 · K-1) of PPV37 can be expressed by C sp = -17.824 + 0.063 T and PPV46 by C sp = -18.047 + 0.061 T, where T is the temperature (in K).

  8. Vinyl monomers-induced synthesis of polyvinyl alcohol-stabilized selenium nanoparticles

    SciTech Connect

    Shah, Chetan P.; Singh, Krishan K.; Kumar, Manmohan; Bajaj, Parma N.

    2010-01-15

    A simple wet chemical method has been developed to synthesize selenium nanoparticles (size 100-200 nm), by reaction of sodium selenosulphate precursor with different vinyl monomers, such as acrylamide, N,N'-dimethylene bis acrylamide, methyl methacrylate, sodium acrylate, etc., in aqueous medium, under ambient conditions. Polyvinyl alcohol has been used to stabilize the selenium nanoparticles. Average size of the synthesized selenium nanoparticles can be controlled by adjusting concentration of both the precursors and the stabilizer. Rate of the reaction as well as size of the resultant selenium nanoparticles have been correlated with the functional groups of the different monomers. UV-vis optical absorption spectroscopy, X-ray diffraction, energy dispersive X-rays, differential scanning calorimetry, atomic force microscopy, scanning electron microscopy and transmission electron microscopy techniques have been employed to characterize the synthesized selenium nanoparticles. Gas chromatographic analysis of the reaction mixture established the non-catalytic role of the vinyl monomers, which were found to be consumed during the course of the reaction.

  9. Preparation and properties of nanometer silk fibroin peptide/polyvinyl alcohol blend films for cell growth.

    PubMed

    Luo, Qin; Chen, Zhongmin; Hao, Xuefei; Zhu, Qiangsong; Zhou, Yucheng

    2013-10-01

    Nanometer silk fibroin peptide (Nano-SFP) was prepared from silkworm cocoons through the process of dissolution, dialysis and enzymolysis. For comparison, silk fibroin was decomposed with α-chymotrypsin, trypsin and neutrase, respectively. From the SEM and particle size analysis results, the Nano-SFP prepared by neutrase was found to be the most desirable at about 50-200 nm. Nano-SFP/polyvinyl alcohol films (Nano-SFP/PVA) were prepared by blending Nano-SFP and PVA in water with different weight ratios of 10/90, 20/80, 30/70, and 40/60. The films were characterized by IR, SEM, TG, DSC and tensile strength test for investigating their structure, surface morphology, thermostability, and mechanical property. The results showed that Nano-SFP inserted in the PVA films with small linear particles, and Nano-SFP/PVA films exhibited smooth surface, good thermostability and tensile strength. The growth of Chinese hamster ovary (CHO) cells on films with and without Nano-SFP was investigated with MTT colorimetric assay to assess the films' ability to promote cell growth. It was observed that the Nano-SFP improved cell adhesion on the film surface, and the ability of promoting cell growth increased with the increasing content of Nano-SFP in the blend films. Nano-SFP/PVA film with the ratio of 30/70 was concluded to have the best properties.

  10. Voriconazole Composited Polyvinyl Alcohol/Hydroxypropyl-β-Cyclodextrin Nanofibers for Ophthalmic Delivery

    PubMed Central

    Sun, Xiaoyi; Cai, Zhengyuan; Yu, Lingyan; Lv, Yuanyuan

    2016-01-01

    Voriconazole (VRC) incorporated in composited polyvinyl alcohol (PVA)/hydroxypropyl-β-cyclodextrin (HPβCD) blended nanofibers were produced via electrospinning for efficient ophthalmic delivery. The VRC loading capacity increased with increasing HPβCD content. The optimal solution for electrospinning consisted of 8% (w/v) PVA, 4% (w/v) HPβCD and 0.5% (w/v) VRC. The nanofibers exhibited bead-free average fiber diameters of 307±31 nm and VRC was released in vitro in a sustained manner. The VRC nanofibers were characterized by infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The proton nuclear magnetic resonance (1H-NMR) was used to analyze the molar ratio of HPβCD/VRC in the nanofibers. Compared with a VRC solution, the nanofibers significantly prolonged the half life, and increased the bioavailability of VRC in rabbit tears. No obvious signs of irritation were observed after application in the conjunctival sac. VRC nanofibers are promising for ophthalmic drug delivery and further pharmacodynamics studies are needed. PMID:27974859

  11. Thermal, mechanical and dielectric properties of poly(vinyl alcohol)/graphene oxide composites

    NASA Astrophysics Data System (ADS)

    Rathod, Sunil G.; Bhajantri, R. F.; Ravindrachary, V.; Pujari, P. K.; Sheela, T.; Naik, Jagadish

    2014-04-01

    In this work the composite films of poly(vinyl alcohol) (PVA) doped with functionalized Graphene Oxide (GO) were prepared by solution casting method. The films were characterized using FT-IR, DSC, XRD, mechanical properties and dielectric studies at room temperature. FTIR spectra shows the formation of hydrogen bonds between hydroxyl groups of PVA and the hydroxy groups of GO. The DSC thermograms shows the addition of GO to PVA greatly improves the thermal stability of the composites. XRD patterns shows that the GO exfoliated and uniformly dispersed in PVA matrix. Mechanical properties are significantly improved in PVA/GO composites. The tensile strength increased from 8.2 to 13.7 MPa and the Young's modulus increased from 7.5 to 24.8 MPa for 5 wt% GO doped sample. Dielectric spectroscopy showed a highest dielectric constant for the 5 wt% GO doped PVA films. This work provides a potential design strategy on PVA/GO composite, which would lead to higher-performance, flexible dielectric materials, high charge-storage devices.

  12. Manipulating the morphologies of poly(vinyl alcohol) block copolymer surfactants

    NASA Astrophysics Data System (ADS)

    Repollet-Pedrosa, Milton H.

    Amphiphilic block copolymers (ABCs) are macromolecules containing well-defined hydrophilic and hydrophobic segments that self-assemble into nanoscale aggregates such as spherical and cylindrical micelles and vesicles, when dispersed in block-selective solvents. ABCs possess a miniscule critical micelle concentration, which results in kinetically trapped and persistent assemblies in solution with slow chain exchange between aggregates. This makes them useful as rheological modifiers for personal care products, enhanced oil recovery, and drug delivery formulations. Their utility in many of these applications is crucially dependent on the ability to control the micellar morphologies that they adopt in selective solvents. Triggering ABC micellar morphological transformations, i.e. from spherical to cylindrical micelles, is important for generating "on-demand" stimuli-responsive morphologies that control the aggregate morphology and the bulk solution properties in any given application. In this thesis, we develop the straightforward synthesis of biodegradable and biocompatible ABCs comprised of poly(vinyl acetate) (PVAc) and poly(vinyl alcohol) (PVA), with narrow molecular distributions and variable yet well-defined compositions. These block copolymer amphiphiles readily form spherical micelles in aqueous dispersions. We demonstrate that the addition of a water-soluble poly(ethylene oxide) (PEO) homopolymer to these dispersions results in a rapid transformation of these spherical micelles into cylindrical micelles. Dilution of these cylindrical micelles with water induces their reversion to spherical micelles. Our results indicate that the reversible morphology change depends sensitively on the PEO homopolymer concentration and molecular weight, as well as the length of the PVA corona block of the micelles. Through a series of quantitative 1H NMR studies, we found that the preferential partitioning of PEO homopolymer into the PVAc micellar core drives this morphological

  13. FTIR studies of plasticized poly(vinyl alcohol)-chitosan blend doped with NH 4NO 3 polymer electrolyte membrane

    NASA Astrophysics Data System (ADS)

    Kadir, M. F. Z.; Aspanut, Z.; Majid, S. R.; Arof, A. K.

    2011-03-01

    Fourier transform infrared (FTIR) spectroscopy studies of poly(vinyl alcohol) (PVA), and chitosan polymer blend doped with ammonium nitrate (NH 4NO 3) salt and plasticized with ethylene carbonate (EC) have been performed with emphasis on the shift of the carboxamide, amine and hydroxyl bands. 1% acetic acid solution was used as the solvent. It is observed from the chitosan film spectrum that evidence of polymer-solvent interaction can be observed from the shifting of the carboxamide band at 1660 cm -1 and the amine band at 1591 cm -1 to 1650 and 1557 cm -1 respectively and the shift of the hydroxyl band from 3377 to 3354 cm -1. The hydroxyl band in the spectrum of PVA powder is observed at 3354 cm -1 and is observed at 3343 cm -1 in the spectrum of the PVA film. On addition of NH 4NO 3 up to 30 wt.%, the carboxamide, amine and hydroxyl bands shifted from 1650, 1557 and 3354 cm -1 to 1642, 1541 and 3348 cm -1 indicating that the chitosan has complexed with the salt. In the PVA-NH 4NO 3 spectrum, the hydroxyl band has shifted from 3343 to 3272 cm -1 on addition of salt from 10 to 30 wt.%. EC acts as a plasticizing agent since there is no shift in the bands as observed in the spectrum of PVA-chitosan-EC films. The mechanism of ion migration is proposed for the plasticized and unplasticized PVA-chitosan-NH 4NO 3 systems. In the spectrum of PVA-chitosan-NH 4NO 3-EC complex, the doublet C dbnd O stretching in EC is observed in the vicinity 1800 and 1700. This indicates that there is some interaction between the salt and EC.

  14. MRI Assessment of Uterine Artery Patency and Fibroid Infarction Rates 6 Months after Uterine Artery Embolization with Nonspherical Polyvinyl Alcohol

    SciTech Connect

    Das, Raj Gonsalves, Michael; Vlahos, Ioannis; Manyonda, Issac; Belli, Anna-Maria

    2013-10-15

    Purpose: We have observed significant rates of uterine artery patency after uterine artery embolization (UAE) with nonspherical polyvinyl alcohol (nsPVA) on 6 month follow-up MR scanning. The study aim was to quantitatively assess uterine artery patency after UAE with nsPVA and to assess the effect of continued uterine artery patency on outcomes. Methods: A single centre, retrospective study of 50 patients undergoing bilateral UAE for uterine leiomyomata was undertaken. Pelvic MRI was performed before and 6 months after UAE. All embolizations were performed with nsPVA. Outcome measures included uterine artery patency, uterine and dominant fibroid volume, dominant fibroid percentage infarction, presence of ovarian arterial collaterals, and symptom scores assessed by the Uterine Fibroid Symptom and Quality of Life questionnaire (UFS-QOL). Results: Magnetic resonance angiographic evidence of uterine artery recanalization was demonstrated in 90 % of the patients (64 % bilateral, 26 % unilateral) at 6 months. Eighty percent of all dominant fibroids demonstrated >90 % infarction. The mean percentage reduction in dominant fibroid volume was 35 %. No significant difference was identified between nonpatent, unilateral, and bilateral recanalization of the uterine arteries with regard to percentage dominant fibroid infarction or dominant fibroid volume reduction. The presence of bilaterally or unilaterally patent uterine arteries was not associated with inferior clinical outcomes (symptom score or UFS-QOL scores) at 6 months. Conclusion: The high rates of uterine artery patency challenge the current paradigm that nsPVA is a permanent embolic agent and that permanent uterine artery occlusion is necessary to optimally treat uterine fibroids. Despite high rates of uterine artery recanalization in this cohort, satisfactory fibroid infarction rates and UFS-QOL scores were achieved.

  15. FTIR studies of plasticized poly(vinyl alcohol)-chitosan blend doped with NH4NO3 polymer electrolyte membrane.

    PubMed

    Kadir, M F Z; Aspanut, Z; Majid, S R; Arof, A K

    2011-03-01

    Fourier transform infrared (FTIR) spectroscopy studies of poly(vinyl alcohol) (PVA), and chitosan polymer blend doped with ammonium nitrate (NH(4)NO(3)) salt and plasticized with ethylene carbonate (EC) have been performed with emphasis on the shift of the carboxamide, amine and hydroxyl bands. 1% acetic acid solution was used as the solvent. It is observed from the chitosan film spectrum that evidence of polymer-solvent interaction can be observed from the shifting of the carboxamide band at 1660 cm(-1) and the amine band at 1591 cm(-1) to 1650 and 1557 cm(-1) respectively and the shift of the hydroxyl band from 3377 to 3354 cm(-1). The hydroxyl band in the spectrum of PVA powder is observed at 3354 cm(-1) and is observed at 3343 cm(-1) in the spectrum of the PVA film. On addition of NH(4)NO(3) up to 30 wt.%, the carboxamide, amine and hydroxyl bands shifted from 1650, 1557 and 3354 cm(-1) to 1642, 1541 and 3348 cm(-1) indicating that the chitosan has complexed with the salt. In the PVA-NH(4)NO(3) spectrum, the hydroxyl band has shifted from 3343 to 3272 cm(-1) on addition of salt from 10 to 30 wt.%. EC acts as a plasticizing agent since there is no shift in the bands as observed in the spectrum of PVA-chitosan-EC films. The mechanism of ion migration is proposed for the plasticized and unplasticized PVA-chitosan-NH(4)NO(3) systems. In the spectrum of PVA-chitosan-NH(4)NO(3)-EC complex, the doublet CO stretching in EC is observed in the vicinity 1800 and 1700. This indicates that there is some interaction between the salt and EC.

  16. Surface modified electrospun poly(vinyl alcohol) membranes for extracting nanoparticles from water

    NASA Astrophysics Data System (ADS)

    Mahanta, Narahari; Valiyaveettil, Suresh

    2011-11-01

    Contamination of water from nanomaterials will be an emerging problem in the future due to incorporation of nanomaterials in many commercial products and improper disposal of waste materials. In this report, electrospun polyvinyl alcohol nanofibers (PVA NFs) with diameters ranging between 300 and 500 nm were used for the extraction of nanosized contaminants from the aqueous environment. To obtain the best extraction efficiency, surface hydroxyl groups of PVA NFs were chemically modified with functional groups, such as thiols and amines. Two model nanoparticles (silver and gold) dissolved in water were used for adsorption studies. Depending on the nature of the surface functionalities, the fibers showed unique ability to adsorb nanoparticles. The extraction studies revealed that the amine and thiol modified PVA NFs showed 90% extraction efficiency for both silver and gold nanoparticles. The thiol and amine functionalized PVA NFs showed maximum adsorption capacities (Qt) towards Au NPs, which were around 79-84 mg g-1. Similarly for Ag NP extraction, amine functionalized PVA NFs showed a value for Qt at 56 mg g-1. Our results highlight that functionalized nanofibers have high extraction efficiency for dissolved nanoparticles in water and can be used for removal of the nanocontaminants from the aqueous environment.Contamination of water from nanomaterials will be an emerging problem in the future due to incorporation of nanomaterials in many commercial products and improper disposal of waste materials. In this report, electrospun polyvinyl alcohol nanofibers (PVA NFs) with diameters ranging between 300 and 500 nm were used for the extraction of nanosized contaminants from the aqueous environment. To obtain the best extraction efficiency, surface hydroxyl groups of PVA NFs were chemically modified with functional groups, such as thiols and amines. Two model nanoparticles (silver and gold) dissolved in water were used for adsorption studies. Depending on the nature of

  17. Analysis of isothiazolinone preservatives in polyvinyl alcohol cooling towels used in Japan.

    PubMed

    Kawakami, Tsuyoshi; Isama, Kazuo; Ikarashi, Yoshiaki

    2014-09-19

    Recently, cases of contact dermatitis that were related to the use of polyvinyl alcohol (PVA) cooling towels containing isothiazolinone preservatives were reported in Japan. The aim of this investigation was to analyze the concentrations of five different isothiazolinone compounds present in PVA towels and to assess the effectiveness of washing in removing the preservatives from new towels prior to being used for the first time. Twenty-seven PVA towels were used in this study. Two groups (i.e., laboratory-simulation and volunteer) of washing experiments were conducted to evaluate the effect of washing procedures. Qualitative and quantitative analyses were performed by LC/MS/MS, which detected 2-methyl-4-isothiazolin-3-one (MI) and 5-chloro-2-methyl-4-isothaizolin-3-one (CMI) in 23 samples (MI: 0.29-154 μg g-wet(-1), CMI: 2.2-467 μg g-wet(-1)), 2-n-octyl-4-isothiazolin-3-one (OIT) in one sample (478 μg g-wet(-1)). The compounds 4,5-Dichloro-2-n-octyl-4-isothiazolin-3-one (2Cl-OIT) and 1,2-benzisothiazolin-3-one (BIT) were not detected in all samples. We confirmed the presence of residual MI, CMI, and OIT in the washed towels, and the residual-to-original content ratio of OIT was higher than that of MI and CMI in PVA towels, due to the higher hydrophobicity of OIT than MI and CMI. A concern has been raised about the occurrence of contact dermatitis being caused by the use of PVA towels. It is suggested that a detailed description of isothiazolinone preservatives in PVA towels and an effective washing procedure for the removal of these preservatives should be provided by the manufacturer. Further, alternative non-sensitizing preservatives might be considered for the manufacture of PVA cooling towels in the future.

  18. Nanoparticle penetration of human cervicovaginal mucus: The effect of polyvinyl alcohol

    PubMed Central

    Yang, Ming; Lai, Samuel K.; Yu, Tao; Wang, Ying-Ying; Happe, Christina; Zhong, Weixi; Zhang, Michael; Anonuevo, Abraham; Fridley, Colleen; Hung, Amy; Fu, Jie; Hanes, Justin

    2014-01-01

    Therapeutic nanoparticles must rapidly penetrate the mucus secretions lining the surfaces of the respiratory, gastrointestinal and cervicovaginal tracts to efficiently reach the underlying tissues. Whereas most polymeric nanoparticles are highly mucoadhesive, we previously discovered that a dense layer of low MW polyethylene glycol (PEG) conferred a sufficiently hydrophilic and uncharged surface to effectively minimize mucin-nanoparticle adhesive interactions, allowing well-coated particles to rapidly diffuse through human mucus. Here, we sought to investigate the influence of surface coating by polyvinyl alcohol (PVA), a relatively hydrophilic and uncharged polymer routinely used as a surfactant to formulate drug carriers, on the transport of nanoparticles in fresh human cervicovaginal mucus. We found that PVA-coated polystyrene (PS) particles were immobilized, with speeds at least 4,000-fold lower in mucus than in water, regardless of the PVA molecular weight or incubation concentration tested. Nanoparticles composed of poly(lactide-co-glycolide) (PLGA) or diblock copolymers of PEG-PLGA were similarly immobilized when coated with PVA (slowed 29,000- and 2,500-fold, respectively). PVA coatings could not be adequately removed upon washing, and the residual PVA prevented sufficient coating with Pluronic F127 capable of reducing particle mucoadhesion. In contrast to PVA-coated particles, the similar sized PEG-coated formulations were slowed only ~6- to 10-fold in mucus compared to in water. Our results suggest incorporating PVA in the particle formulation process may lead to the formation of mucoadhesive particles for many nanoparticulate systems. Thus, alternative methods for particle formulation, based on novel surfactants or changes in the formulation process, should be identified and developed in order to produce mucus-penetrating particles for mucosal applications. PMID:25090196

  19. Elastic properties of thin poly(vinyl alcohol)-cellulose nanocrystal membranes.

    PubMed

    Pakzad, A; Simonsen, J; Yassar, R S

    2012-02-01

    In spite of extensive studies on the preparation and characterization of nanocomposite materials, the correlation of their properties at the nanoscale with those in bulk is a relatively unexplored area. This is of great importance, especially for materials with potential biomedical applications, where surface properties are as important in determining their applicability as bulk characteristics. In this study, the nanomechanical characteristics of thin poly(vinyl alcohol) (PVOH)-poly(acrylic acid) (PAA)-cellulose nanocrystal (CNC) membranes were studied using the nanoindentation module in an atomic force microscope (AFM) and the properties were compared with the macro-scale properties obtained by tensile tests. In general, the elastic properties measured by nanoindentation followed the same trend as macro-scale tensile tests except for the PVOH 85-PAA 0-CNC 15 sample. In comparison to the macro-scale elastic properties, the measured elastic moduli with AFM were higher. Macro-scale tensile test results indicated that, in the presence of PAA, incorporation of CNCs up to 20 wt% improved the elastic modulus of PVOH, but when no PAA was added, increasing the CNC content above 10 wt% resulted in their agglomeration and degradation in mechanical properties of PVOH. The discrepancy between macro-scale tensile tests and nanoindentation in the PVOH 85-PAA 0-CNC 15 sample was correlated to the high degree of inhomogeneity of CNC dispersion in the matrix. It was found that the composites reinforced with cellulose nanocrystals had smaller indentation imprints and the pile-up effect increased with the increase of cellulose nanocrystal content.

  20. Biomedical applications of stereoregular poly(vinyl alcohol) micro- and nanoparticles

    NASA Astrophysics Data System (ADS)

    Lyoo, Won Seok; Kim, Joon Ho; Kim, Sam Soo; Ghim, Han Do

    2002-11-01

    Syndiotactic poly(vinyl alcohol) (PVA)/poly(vinyl pivalate/vinyl acetate) (P(VPi/VAc)) and atactic PVA/PVAc micro- and nanoparticles with skin/core structure have been prepared by heterogeneous saponification of P(VPi/VAc) and PVAc micro- and nanoparticles. Especially, to prepare P(VPi/VAc) and PVAc microparticles having various particle sizes and uniform particle size distribution, vinyl pivalate (VPi)/vinyl acetate (VAc) and VAc were suspension-polymerized using a low-temperature initiator, 2,2"-azobis(2,4-dimethylvaleronitrile). P(VPi/VAc) particles are promising precursor of stereoregular PVA embolic materials which can be introduced through catheters in the management of gastrointestinal bleeders, arteriovenous malformations, hemangiomas, and traumatic rupture of blood vessels. Monodisperse and/or nearly monodisperse P(VPi/VAc) and PVAc microparticles with various particle diameters were obtained by controlling suspension polymerization conditions. Monodisperse P(VPi/VAc) and PVAc microparticles having various particle sizes were partially saponified in the heterogeneous system. PVA/P(VPi/VAc) and PVA/PVAc microparticles having various tacticity and degree of saponification were produced by controlling various polymerization and saponification conditions. The coating of stereoregular PVA micro- and nanoparticles for drug release experiments was conducted with the strepo-avidin-alkaline phosphatase conjugate in variable conditions of pH value, coating buffer, and reaction temperature. Protein-coated syndiotactic PVA micro- and nanoparticles, which does not crosslinking, were more superior to controllability of drug release, durability, and dimensional stability to water and blood than atactic one.

  1. Poly(vinyl alcohol)-heparin biosynthetic microspheres produced by microfluidics and ultraviolet photopolymerisation

    PubMed Central

    Young, Cara; Rozario, Kester; Serra, Christophe; Poole-Warren, Laura; Martens, Penny

    2013-01-01

    Biosynthetic microspheres have the potential to address some of the limitations in cell microencapsulation; however, the generation of biosynthetic hydrogel microspheres has not been investigated or applied to cell encapsulation. Droplet microfluidics has the potential to produce more uniform microspheres under conditions compatible with cell encapsulation. Therefore, the aim of this study was to understand the effect of process parameters on biosynthetic microsphere formation, size, and morphology with a co-flow microfluidic method. Poly(vinyl alcohol) (PVA), a synthetic hydrogel and heparin, a glycosaminoglycan were chosen as the hydrogels for this study. A capillary-based microfluidic droplet generation device was used, and by varying the flow rates of both the polymer and oil phases, the viscosity of the continuous oil phase, and the interfacial surface tension, monodisperse spheres were produced from ∼200 to 800 μm. The size and morphology were unaffected by the addition of heparin. The modulus of spheres was 397 and 335 kPa for PVA and PVA/heparin, respectively, and this was not different from the bulk gel modulus (312 and 365 for PVA and PVA/heparin, respectively). Mammalian cells encapsulated in the spheres had over 90% viability after 24 h in both PVA and PVA/heparin microspheres. After 28 days, viability was still over 90% for PVA-heparin spheres and was significantly higher than in PVA only spheres. The use of biosynthetic hydrogels with microfluidic and UV polymerisation methods offers an improved approach to long-term cell encapsulation. PMID:24404042

  2. Osteochondral defect repair using a polyvinyl alcohol-polyacrylic acid (PVA-PAAc) hydrogel.

    PubMed

    Bichara, David A; Bodugoz-Sentruk, Hatice; Ling, Doris; Malchau, Erik; Bragdon, Charles R; Muratoglu, Orhun K

    2014-08-01

    Poly(vinyl alcohol) (PVA) hydrogels can be candidates for articular cartilage repair due to their high water content. We synthesized a PVA-poly(acrylic acid) (PAAc) hydrogel formulation and determined its ability to function as a treatment option for condylar osteochondral (OC) defects in a New Zealand white rabbit (NZWR) model for 12 weeks and 24 weeks. In addition to hydrogel OC implants, tensile bar-shaped hydrogels were also implanted subcutaneously to evaluate changes in mechanical properties as a function of in vivo duration. There were no statistically significant differences (p > 0.05) in the water content measured in the OC hydrogel implant that was harvested after 12 weeks and 24 weeks, and non-implanted controls. There were no statistically significant differences (p > 0.05) in the break stress, strain at break or modulus of the tensile bars either between groups. Histological analysis of the OC defect, synovial capsule and fibrous tissue around the tensile bars determined hydrogel biocompatibility. Twelve-week hydrogels were found to be in situ flush with the articular cartilage; meniscal tissue demonstrated an intact surface. Twenty-four week hydrogels protruded from the defect site due to lack of integration with subchondral tissue, causing fibrillation to the meniscal surface. Condylar micro-CT scans ruled out osteolysis and bone cysts of the subchondral bone, and no PVA-PAAc hydrogel contents were found in the synovial fluid. The PVA-PAAc hydrogel was determined to be fully biocompatible, maintained its properties over time, and performed well at the 12 week time point. Physical fixation of the PVA-PAAc hydrogel to the subchondral bone is required to ensure long-term performance of hydrogel plugs for OC defect repair.

  3. Dressing liposomal particles with chitosan and poly(vinylic alcohol) for oral vaccine delivery.

    PubMed

    Rescia, Vanessa C; Takata, Célia S; de Araujo, Pedro S; Bueno da Costa, Maria H

    2011-03-01

    Liposomes have been used as adjuvants since 1974. One major limitation for the use of liposomes in oral vaccines is the lipid structure instability caused by enzyme activities. Our aim was to combine liposomes that could encapsulate antigens (i.e., Dtxd, diphtheria toxoid) with chitosan, which protects the particles and promotes mucoadhesibility. We employed physical techniques to understand the process by which liposomes (SPC: Cho, 3:1) can be sandwiched with chitosan (Chi) and stabilized by PVA (poly-vinylic alcohol), which are biodegradable, biocompatible polymers. Round, smooth-surfaced particles of REVs-Chi (reversed-phase vesicles sandwiched by Chi) stabilized by PVA were obtained. The REVs encapsulation efficiencies (Dtxd was used as the antigen) were directly dependent on the Chi and PVA present in the formulation. Chi adsorption on the REVs surface was accompanied by an increase of ζ-potential. In contrast, PVA adsorption on the REVs-Chi surface was accompanied by a decrease of ζ-potential. The presence of Dtxd increased the Chi surface-adsorption efficiency. The PVA affinity by mucine was 2,000 times higher than that observed with Chi alone and did not depend on the molecule being in solution or adsorbed on the liposomal surface. The liberation of encapsulated Dtxd was retarded by encapsulation within REVs-Chi-PVA. These results lead us to conclude that these new, stabilized particles were able to be adsorbed by intestinal surfaces, resisted degradation, and controlled antigen release. Therefore, REVs-Chi-PVA particles can be used as an oral delivery adjuvant.

  4. Influence of Cr2O3 nanoparticles on the physical properties of polyvinyl alcohol

    NASA Astrophysics Data System (ADS)

    Hassen, A.; El Sayed, A. M.; Morsi, W. M.; El-Sayed, S.

    2012-11-01

    Nano-sized chromium oxide (Cr2O3) was synthesized by sol-gel method and mixed with polyvinyl alcohol (PVA) to produce nanocomposite films. Scanning electron microscopy (SEM) was used to observe the morphology and dispersion of Cr2O3 on the surface of the PVA films. X-ray diffraction (XRD) was performed on nano-sized Cr2O3, pure PVA, and Cr2O3/PVA composites. Based on the results of both XRD and high-resolution transmission electron microscopy (HR-TEM), the average particle size of the Cr2O3 was ≈ 46 nm. Differential scanning calorimetry (DSC) showed that the thermal stability and degree of crystallinity of the PVA were reinforced by the addition of Cr2O3 nanoparticles. The absorbance and extinction coefficients of the composites were studied in the UV-vis range and compared with those of pure PVA. The optical energy band gap, Eg, was calculated. Dielectric constant, ɛ', dielectric loss modulus, M″, and ac conductivity, σac, of all samples were measured within temperature and frequency ranges of 300-468 K and 10 kHz-2 MHz, respectively. According to the frequency and temperature dependence of the dielectric loss modulus, M″, the observed α-relaxation peak was due to the micro-Brownian motion of the polymer main chains. The behavior of σac(f) for the composite films indicated that the conduction mechanism was correlated barrier hopping (CBH). The results of this work were discussed and compared with those of previous studies of PVA composites.

  5. Submillimeter Diameter Poly(Vinyl Alcohol) Vascular Graft Patency in Rabbit Model

    PubMed Central

    Cutiongco, Marie F. A.; Kukumberg, Marek; Peneyra, Jonnathan L.; Yeo, Matthew S.; Yao, Jia Y.; Rufaihah, Abdul Jalil; Le Visage, Catherine; Ho, Jackie Pei; Yim, Evelyn K. F.

    2016-01-01

    Microvascular surgery is becoming a prevalent surgical practice. Replantation, hand reconstruction, orthopedic, and free tissue transfer procedures all rely on microvascular surgery for the repair of venous and arterial defects at the millimeter and submillimeter levels. Often, a vascular graft is required for the procedure as a means to bridge the gap between native arteries. While autologous vessels are desired for their bioactivity and non-thrombogenicity, the tedious harvest process, lack of availability, and caliber or mechanical mismatch contribute to graft failure. Thus, there is a need for an off-the-shelf artificial vascular graft that has low thrombogenic properties and mechanical properties matching those of submillimeter vessels. Poly(vinyl alcohol) hydrogel (PVA) has excellent prospects as a vascular graft due to its bioinertness, low thrombogenicity, high water content, and tunable mechanical properties. Here, we fabricated PVA grafts with submillimeter diameter and mechanical properties that closely approximated those of the rabbit femoral artery. In vitro platelet adhesion and microparticle release assay verified the low thrombogenicity of PVA. A stringent proof-of-concept in vivo test was performed by implanting PVA grafts in rabbit femoral artery with multilevel arterial occlusion. Laser Doppler measurements indicated the improved perfusion of the distal limb after implantation with PVA grafts. Moreover, ultrasound Doppler and angiography verified that the submillimeter diameter PVA vascular grafts remained patent for 2 weeks without the aid of anticoagulant or antithrombotics. Endothelial cells were observed in the luminal surface of one patent PVA graft. The advantageous non-thrombogenic and tunable mechanical properties of PVA that are retained even in the submillimeter diameter dimensions support the application of this biomaterial for vascular replacement in microvascular surgery. PMID:27376059

  6. Pregnancy Following Uterine Artery Embolization with Polyvinyl Alcohol Particles for Patients with Uterine Fibroid or Adenomyosis

    SciTech Connect

    Kim, Man Deuk Kim, Nahk Keun; Kim, Hee Jin; Lee, Mee Hwa

    2005-06-15

    Purpose:To determine whether uterine fibroid embolization (UFE) with polyvinyl alcohol (PVA) particles affects fertility in women desiring future pregnancy.Methods:Of 288 patients managed with UFE with PVA particles for uterine myoma or adenomyosis between 1998 and 2001, 94 patients were enrolled in this study. The age range of participants was 20-40 years. The data were collected through review of medical records and telephone interviews. Mean duration of follow-up duration was 35 months (range 22-60 months). Patients using contraception and single women were excluded, and the chance of infertility caused by possible spousal infertility or other factors was disregarded. Contrast-enhanced magnetic resonance imaging was performed in all patients before and after UFE, and the size of PVA particles used was 255-700 {mu}m.Results:Among 94 patients who underwent UFE with PVA, 74 were on contraceptives, 6 had been single until the point of interview, and 8 were lost to follow-up. Of the remaining 6 patients who desired future pregnancy, 5 (83%) succeeded in becoming pregnant (1 patient became pregnant twice). Of a total of 8 pregnancies, 6 were planned pregnancies and 2 occurred after contraception failed. Five deliveries were vaginal, and 2 were by elective cesarean. Artificial abortion was performed in 1 case of unplanned pregnancy. There was 1 case of premature rupture of membrane (PROM) followed by preterm labor and delivery of an infant who was small-for-gestational-age. After UFE, mean volume reduction rates of the uterus and fibroid were 36.6% (range 0 to 62.6%) and 69.3% (range 36.3% to 93.3%), respectively.Conclusion:Although the absolute number of cases was small, UFE with PVA particles ultimately did not affect fertility in the women who underwent the procedure.

  7. Inhibition of nucleation and growth of ice by poly(vinyl alcohol) in vitrification solution.

    PubMed

    Wang, Hai-Yan; Inada, Takaaki; Funakoshi, Kunio; Lu, Shu-Shen

    2009-08-01

    Control of ice formation is crucial in cryopreservation of biological substances. Successful vitrification using several additives that inhibit ice nucleation in vitrification solutions has previously been reported. Among these additives, here we focused on a synthetic polymer, poly(vinyl alcohol) (PVA), and investigated the effects of PVA on nucleation and growth of ice in 35% (w/w) aqueous 1,2-propanediol solution by using a differential scanning calorimetry (DSC) system equipped with a cryomicroscope. First, the freezing temperature of the solution was measured using the DSC system, and then the change in ice fraction in the solution during cooling was evaluated based on images obtained using the cryomicroscope, at different concentrations of PVA between 0% and 3% (w/w). Based on the ice fraction, the change in residual solution concentration during cooling was also evaluated and then plotted on the state diagram of aqueous 1,2-propanediol solution. Results indicated that, when the partially glassy and partially frozen state was intentionally allowed, the addition of PVA effectively inhibited not only ice nucleation but also ice growth in the vitrification solution. The effect of PVA on ice growth in the vitrification solution was explained based on kinetic limitations mainly due to mass transport. The interfacial kinetics also might limit ice growth in the vitrification solution only when the ice growth rate decreased below a critical value. This coincides with the fact that PVA exhibits a unique antifreeze activity in the same manner as antifreeze proteins when ice growth rate is lower than a critical value.

  8. Solute retention and the states of water in polyethylene glycol and poly(vinyl alcohol) gels.

    PubMed

    Baba, Takayuki; Sakamoto, Ryosaku; Shibukawa, Masami; Oguma, Koichi

    2004-06-18

    The states of water sorbed in a cross-linked polyethylene glycol (PEG) gel, TSKgel Ether-250, and cross-linked poly(vinyl alcohol) (PVA) gels of different pore sizes, TSKgel Toyopearl HW-40S, 50S, 55S and 75S, were investigated by means of differential scanning calorimetry (DSC). It was found that there were three types of water in these hydrogels, non-freezing water, freezable bound water and free water. The amount of water that functions as the stationary phase in the column packed with the each gel was also estimated by a liquid chromatographic method. The estimated amount of the stationary phase water is in good agreement with the sum of the amount of non-freezing water and that of freezable bound water for HW-40S, 50S and 55S, while it agrees with the amount of only non-freezing water for HW-75S and Ether-250. This means that the stationary phase water consists of non-freezing water and freezable bound water for HW-40S, 50S and 55S, while only non-freezing water functions as the stationary phase in HW-75S and Ether-250 gels. This result can be attributed to the difference in the structure of the gels; the PVA gels containing PVA at relatively high concentrations, HW-40S, 50S and 55S, have a homogeneous gel phase, whereas HW-75S and Ether-250 have a heterogeneous gel phase consisting hydrated polymer domains and macropores with relatively hydrophobic surface. The freezable bound water in Toyopearl HW-40S, 50S and 55S can be regarded as a component of a homogeneous PVA solution phase, while that in HW-75S and Ether-250 may be water isolated in small pores of the hydrophobic domains. The results obtained by the investigation on the retention selectivity of these hydrogels in aqueous solutions supported our postulated view on the structures of the hydrogels.

  9. Morphology and thermal studies of zinc sulfide and cadmium sulfide nanoparticles in polyvinyl alcohol matrix

    NASA Astrophysics Data System (ADS)

    Osuntokun, Jejenija; Ajibade, Peter A.

    2016-09-01

    Zn(II) and Cd(II) metal complexes of 1-cyano-1-carboethoxyethylene-2,2-dithiolato-κS,S'-bis(N,N-dimethylthiourea-κS) have been synthesized and characterized with analytical and spectroscopic techniques. The complexes were thermolysed in hexadecylamine at 200 °C to prepare ZnS and CdS nanoparticles. The nanoparticles were characterized with scanning electron microscope (SEM), transmission electron microscope (TEM), and powder X-ray diffraction (p-XRD). TEM images showed spherically shaped nanoparticles, whose sizes are in the range 4.33-7.21 nm for ZnS and 4.95-7.7 nm CdS respectively and XRD confirmed cubic crystalline phases for the nanoparticles. The optical band gap energy evaluated from the absorption spectra are 2.88 eV (430 nm) and 2.81 eV (440 nm) for the ZnS and CdS nanoparticles respectively. The as-prepared metal sulfide nanoparticles were further incorporated into polyvinyl alcohol (PVA) to give ZnS/PVA and CdS/PVA composites. The polymer nanocomposites were studied to investigate their morphology and thermal properties relative to the pure PVA. XRD diffractions indicated that the crystalline phases of the nanoparticles and the sizes in PVA matrices remained unaltered. Infra-red spectra studies revealed interactions between the PVA and the metal sulfide nanoparticles and TGA studies show that the ZnS/PVA and CdS/PVA nanocomposites exhibit better thermal stability than the pure PVA.

  10. Unconfined compression properties of a porous poly(vinyl alcohol)-chitosan-based hydrogel after hydration.

    PubMed

    Lee, Si-Yuen; Pereira, Barry P; Yusof, N; Selvaratnam, L; Yu, Zou; Abbas, A A; Kamarul, T

    2009-07-01

    A poly(vinyl alcohol) (PVA) hydrogel composite scaffold containing N,O-carboxymethylated chitosan (NOCC) was tested to assess its potential as a scaffold for cartilage tissue engineering in a weight-bearing environment. The mechanical properties under unconfined compression for different hydration periods were investigated. The effect of supplementing PVA with NOCC (20wt.% PVA:5vol.% NOCC) produced a porosity of 43.3% and this was compared against a non-porous PVA hydrogel (20g PVA: 100ml of water, control). Under non-hydrated conditions, the porous PVA-NOCC hydrogel behaved in a similar way to the control non-porous PVA hydrogel, with similar non-linear stress-strain response under unconfined compression (0-30% strain). After 7days' hydration, the porous hydrogel demonstrated a reduced stiffness (0.002kPa, at 25% strain), resulting in a more linear stiffness relationship over a range of 0-30% strain. Poisson's ratio for the hydrated non-porous and porous hydrogels ranged between 0.73 and 1.18, and 0.76 and 1.33, respectively, suggesting a greater fluid flow when loaded. The stress relaxation function for the porous hydrogel was affected by the hydration period (from 0 to 600s); however the percentage stress relaxation regained by about 95%, after 1200s for all hydration periods assessed. No significant differences were found between the different hydration periods between the porous hydrogels and control. The calculated aggregate modulus, H(A), for the porous hydrogel reduced drastically from 10.99kPa in its non-hydrated state to about 0.001kPa after 7days' hydration, with the calculated shear modulus reducing from 30.92 to 0.14kPa, respectively. The porous PVA-NOCC hydrogel conformed to a biphasic, viscoelastic model, which has the desired properties required for any scaffold in cartilage tissue engineering.

  11. Composite Scaffold of Poly(Vinyl Alcohol) and Interfacial Polyelectrolyte Complexation Fibers for Controlled Biomolecule Delivery

    PubMed Central

    Cutiongco, Marie Francene A.; Choo, Royden K. T.; Shen, Nathaniel J. X.; Chua, Bryan M. X.; Sju, Ervi; Choo, Amanda W. L.; Le Visage, Catherine; Yim, Evelyn K. F.

    2015-01-01

    Controlled delivery of hydrophilic proteins is an important therapeutic strategy. However, widely used methods for protein delivery suffer from low incorporation efficiency and loss of bioactivity. The versatile interfacial polyelectrolyte complexation (IPC) fibers have the capacity for precise spatiotemporal release and protection of protein, growth factor, and cell bioactivity. Yet its weak mechanical properties limit its application and translation into a viable clinical solution. To overcome this limitation, IPC fibers can be incorporated into polymeric scaffolds such as the biocompatible poly(vinyl alcohol) hydrogel (PVA). Therefore, we explored the use of a composite scaffold of PVA and IPC fibers for controlled biomolecule release. We first observed that the permeability of biomolecules through PVA films were dependent on molecular weight. Next, IPC fibers were incorporated in between layers of PVA to produce PVA–IPC composite scaffolds with different IPC fiber orientation. The composite scaffold demonstrated excellent mechanical properties and efficient biomolecule incorporation. The rate of biomolecule release from PVA–IPC composite grafts exhibited dependence on molecular weight, with lysozyme showing near-linear release for 1 month. Angiogenic factors were also incorporated into the PVA–IPC grafts, as a potential biomedical application of the composite graft. While vascular endothelial growth factor only showed a maximum cumulative release of 3%, the smaller PEGylated-QK peptide showed maximum release of 33%. Notably, the released angiogenic biomolecules induced endothelial cell activity thus indicating retention of bioactivity. We also observed lack of significant macrophage response against PVA–IPC grafts in a rabbit model. Showing permeability, mechanical strength, precise temporal growth factor release, and bioinertness, PVA–IPC fibers composite scaffolds are excellent scaffolds for controlled biomolecule delivery in soft tissue

  12. Composite scaffold of poly(vinyl alcohol) and interfacial polyelectrolyte complexation fibers for controlled biomolecule delivery.

    PubMed

    Cutiongco, Marie Francene A; Choo, Royden K T; Shen, Nathaniel J X; Chua, Bryan M X; Sju, Ervi; Choo, Amanda W L; Le Visage, Catherine; Yim, Evelyn K F

    2015-01-01

    Controlled delivery of hydrophilic proteins is an important therapeutic strategy. However, widely used methods for protein delivery suffer from low incorporation efficiency and loss of bioactivity. The versatile interfacial polyelectrolyte complexation (IPC) fibers have the capacity for precise spatiotemporal release and protection of protein, growth factor, and cell bioactivity. Yet its weak mechanical properties limit its application and translation into a viable clinical solution. To overcome this limitation, IPC fibers can be incorporated into polymeric scaffolds such as the biocompatible poly(vinyl alcohol) hydrogel (PVA). Therefore, we explored the use of a composite scaffold of PVA and IPC fibers for controlled biomolecule release. We first observed that the permeability of biomolecules through PVA films were dependent on molecular weight. Next, IPC fibers were incorporated in between layers of PVA to produce PVA-IPC composite scaffolds with different IPC fiber orientation. The composite scaffold demonstrated excellent mechanical properties and efficient biomolecule incorporation. The rate of biomolecule release from PVA-IPC composite grafts exhibited dependence on molecular weight, with lysozyme showing near-linear release for 1 month. Angiogenic factors were also incorporated into the PVA-IPC grafts, as a potential biomedical application of the composite graft. While vascular endothelial growth factor only showed a maximum cumulative release of 3%, the smaller PEGylated-QK peptide showed maximum release of 33%. Notably, the released angiogenic biomolecules induced endothelial cell activity thus indicating retention of bioactivity. We also observed lack of significant macrophage response against PVA-IPC grafts in a rabbit model. Showing permeability, mechanical strength, precise temporal growth factor release, and bioinertness, PVA-IPC fibers composite scaffolds are excellent scaffolds for controlled biomolecule delivery in soft tissue engineering.

  13. Poly(vinyl alcohol) hydrogel coatings with tunable surface exposure of hydroxyapatite

    PubMed Central

    Moreau, David; Villain, Arthur; Ku, David N; Corté, Laurent

    2014-01-01

    Insufficient bone anchoring is a major limitation of artificial substitutes for connective osteoarticular tissues. The use of coatings containing osseoconductive ceramic particles is one of the actively explored strategies to improve osseointegration and strengthen the bone-implant interface for general tissue engineering. Our hypothesis is that hydroxyapatite (HA) particles can be coated robustly on specific assemblies of PVA hydrogel fibers for the potential anchoring of ligament replacements. A simple dip-coating method is described to produce composite coatings made of microscopic hydroxyapatite (HA) particles dispersed in a poly(vinyl alcohol) (PVA) matrix. The materials are compatible with the requirements for implant Good Manufacturing Practices. They are applied to coat bundles of PVA hydrogel fibers used for the development of ligament implants. By means of optical and electronic microscopy, we show that the coating thickness and surface state can be adjusted by varying the composition of the dipping solution. Quantitative analysis based on backscattered electron microscopy show that the exposure of HA at the coating surface can be tuned from 0 to over 55% by decreasing the weight ratio of PVA over HA from 0.4 to 0.1. Abrasion experiments simulating bone-implant contact illustrate how the coating cohesion and wear resistance increase by increasing the content of PVA relative to HA. Using pullout experiments, we find that these coatings adhere well to the fiber bundles and detach by propagation of a crack inside the coating. These results provide a guide to select coated implants for anchoring artificial ligaments. PMID:25482413

  14. Characterisation and in vitro stability of low-dose, lidocaine-loaded poly(vinyl alcohol)-tetrahydroxyborate hydrogels.

    PubMed

    Abdelkader, D H; Osman, M A; El-Gizawy, S A; Faheem, A M; McCarron, P A

    2016-03-16

    Poly(vinyl alcohol) hydrogels cross-linked with the tetrahydroxyborate anion possess textural and rheological properties that can be used as novel drug-loaded vehicles for application to traumatic wounds. However, addition of soluble drug substances causes concentration-dependent phase separation and rheological changes. The aim of this work was to investigate the effect of adding a local anaesthetic, but keeping the concentration low in an attempt to prevent these changes. Cross-linked hydrogels prepared from three grades of poly(vinyl alcohol) were characterised rheologically. Temperature sweep studies showed an elevated complex viscosity upon moving from 25°C to 80°C, which remained high for 48 h following completion of the cycle. Adhesion to model dermal surfaces achieved a maximum of 2.62 N cm(-2) and were greater than that observed to epidermal substrates, with a strong dependence on the rate of detachment used during testing. An optimised formulation (6% w/w PVA (31-50; 99) and 2% w/w THB) containing lidocaine hydrochloride loaded to an upper maximum concentration of 1.5% w/w was assessed for phase separation and drug crystallisation. After six months, crystallisation was present in formulations containing 0.7% and 1.5% lidocaine HCl. Changes in pH in response to increases in lidocaine loading were low. Drug release was shown to operate via a non-Fickian process for all three concentrations, with 60% occurring after approximately 24h. It can be concluded that using a low concentration of lidocaine hydrochloride in hydrogels based on poly(vinyl alcohol) will result in crystallisation. Furthermore, these hydrogels are unlikely to induce rapid anaesthesia due to the low loading and slow release kinetics.

  15. A Study of Cross-linked Regions of Poly(Vinyl Alcohol) Gels by Small-Angle Neutron Scattering

    NASA Astrophysics Data System (ADS)

    Lawrence, Mathias B.; Desa, J. A. E.; Aswal, V. K.

    2011-07-01

    A poly(vinyl alcohol)-borax cross-linked hydrogel has been studied by Small Angle Neutron Scattering as a function of borax concentration in the wave-vector transfer (Q) range of 0.017 Å-1 to 0.36 Å-1. It is found that as the concentration of borax increases, so does the intensity of scattering in this range. Beyond a borax concentration of 2 mg/ml, the increase in cross-linked PVA chains leads to cross-linked units larger than 150 Å as evidenced by a reduction in intensity in the lower Q region.

  16. Effects of Saponification Rate on Electrooptical Properties and Morphology of Poly(vinyl alcohol)/Liquid Crystal Composite Films

    NASA Astrophysics Data System (ADS)

    Ono, Hiroshi; Kawatsuki, Nobuhiro

    1995-03-01

    The relationship between the saponification rate of poly(vinyl alcohol) (PVA), and the electrooptical properties and morphology of the PVA/liquid crystal (LC) composite films was investigated. Light transmission clazing and the LC droplet size were varied by changing the saponification rate or the blend ratio of two kinds of PVA with different saponification rates because the refractive index and surface tension could be controlled by the saponification rate of PVA. The threshold voltage decreased with increasing saponification rate though the extrapolation length was decreased. It was suggested that the electrooptical properties were strongly dependent on the droplet size.

  17. Three methods for in situ cross-linking of polyvinyl alcohol films for application as ion-conducting membranes in potassium hydroxide electrolyte. [battery separators

    NASA Technical Reports Server (NTRS)

    Philipp, W. H.; Hsu, L. C.

    1979-01-01

    Three methods of in situ cross-linking polyvinyl alcohol films are presented. They are: (1) acetalization with a dialdehyde such as glutaraldehyde, (2) acetalization with aldehyde groups formed by selective oxidative cleaving of the few percent of 1,2 diol units present in polyvinyl alcohol, and (3) cross-linking by hydrogen abstraction by reaction with hydrogen atoms and hydroxyl radicals from irradiated water. For the third method, improvement in film conductivity in KOH solution at the expense of mechanical strength is obtained by the presence of polyacrylic acid in the polyvinyl alcohol films. Resistivities in 45 percent KOH are given for in situ cross-linked films prepared by each of the three methods.

  18. Preparation of novel carbon microfiber/carbon nanofiber-dispersed polyvinyl alcohol-based nanocomposite material for lithium-ion electrolyte battery separator.

    PubMed

    Sharma, Ajit K; Khare, Prateek; Singh, Jayant K; Verma, Nishith

    2013-04-01

    A novel nanocomposite polyvinyl alcohol precursor-based material dispersed with the web of carbon microfibers and carbon nanofibers is developed as lithium (Li)-ion electrolyte battery separator. The primary synthesis steps of the separator material consist of esterification of polyvinyl acetate to produce polyvinyl alcohol gel, ball-milling of the surfactant dispersed carbon micro-nanofibers, mixing of the milled micron size (~500 nm) fibers to the reactant mixture at the incipience of the polyvinyl alcohol gel formation, and the mixing of hydrophobic reagents along with polyethylene glycol as a plasticizer, to produce a thin film of ~25 μm. The produced film, uniformly dispersed with carbon micro-nanofibers, has dramatically improved performance as a battery separator, with the ion conductivity of the electrolytes (LiPF6) saturated film measured as 0.119 S-cm(-1), approximately two orders of magnitude higher than that of polyvinyl alcohol. The other primary characteristics of the produced film, such as tensile strength, contact angle, and thermal stability, are also found to be superior to the materials made of other precursors, including polypropylene and polyethylene, discussed in the literature. The method of producing the films in this study is novel, simple, environmentally benign, and economically viable.

  19. Effect of polyvinyl alcohol (PVA) concentration during vitrification of in vitro matured bovine oocytes.

    PubMed

    Asada, Masatsugu; Ishibashi, Satomi; Ikumi, Sachiko; Fukui, Yutaka

    2002-10-01

    Polyvinyl alcohol (PVA) was used as a substitute for serum in a vitrification solution for in vitro matured bovine oocytes. In vitro matured bovine oocytes were cryopreserved in various vitrification solutions (VS) supplemented with different concentrations (0.05, 0.1, 0.5, and 1%) of PVA, 20% fetal calf serum (FCS) or without macromolecule supplementation in a gel-loading tip (GL-tip). After warming, vitrified oocytes were examined for effects on survivability, fertilizability, and embryonic development in vitro. At 18 h in vitro fertilization after vitrifying and warming, the number of surviving mature oocytes vitrified in VS without macromolecule supplementation was significantly (P < 0.05) lower than those with macromolecule supplementation. For fertilizability after vitrification, there was no significant difference in the penetration rate of oocytes among fresh oocytes (98.7%); oocytes vitrified in VS supplemented with 0.1 (76.8%), 0.5 (70.2%), or 1% (80.3%) PVA; 20% (84.1%) FCS; or without supplementation (61.7%). Also, the normal fertilization rate was not significantly different in oocytes vitrified with 0.1 (56.5%), 0.5 (43.5%), or 1% (49.7%) PVA and 20% (60.6%) FCS, compared with fresh oocytes (84.0%). Subsequently, vitrified oocytes were examined for embryonic development effects in vitro. The highest proportion of cleaved oocytes after vitrification was obtained in VS supplemented with 0.1% (18.8%) PVA. Additionally, the proportion of development to morula stage (7.7%) in the oocytes vitrified in a VS supplemented with 0.1% PVA was significantly (P < 0.05) superior to that of the 0, 0.5, and 1% PVA-vitrified groups. However, the beneficial effect of PVA addition was not found in blastocyst development. Embryonic development of vitrified oocytes was significantly lower than that of fresh oocytes. In conclusion, the present results indicate that 0.1% PVA supplementation in VS results in a significantly higher rate of morula stage embryos than 0, 0.5, and

  20. Enzymatic removal of flatulence-inducing sugars in chickpea milk using free and polyvinyl alcohol immobilized alpha-galactosidase from Aspergillus oryzae.

    PubMed

    Patil, Aravind Goud G; Kote, Naganagoud V; Mulimani, Veerappa

    2009-01-01

    The treatment of chickpea milk was carried out in batch, repeated batch and continuous reaction by soluble and polyvinyl alcohol (PVA) immobilized Aspergillus oryzae alpha-galactosidase for the removal of raffinose family oligosaccharides (RFOs). In the batch mode of treatment 96 and 92% of RFOs hydrolysis was observed by soluble and immobilized enzyme, respectively. In repeated batch experiments, immobilized enzyme showed 70% RFOs hydrolysis up to sixth cycle. Polyvinyl alcohol immobilized alpha-galactosidase in fluidized bed reactor showed highest reduction of 94% at a flow rate of 30 ml/h. The results obtained from the present study are very interesting for industrial use of PVA-immobilized enzyme.

  1. Antifreeze (glyco)protein mimetic behavior of poly(vinyl alcohol): detailed structure ice recrystallization inhibition activity study.

    PubMed

    Congdon, Thomas; Notman, Rebecca; Gibson, Matthew I

    2013-05-13

    This manuscript reports a detailed study on the ability of poly(vinyl alcohol) to act as a biomimetic surrogate for antifreeze(glyco)proteins, with a focus on the specific property of ice-recrystallization inhibition (IRI). Despite over 40 years of study, the underlying mechanisms that govern the action of biological antifreezes are still poorly understood, which is in part due to their limited availability and challenging synthesis. Poly(vinyl alcohol) (PVA) has been shown to display remarkable ice recrystallization inhibition activity despite its major structural differences to native antifreeze proteins. Here, controlled radical polymerization is used to synthesize well-defined PVA, which has enabled us to obtain the first quantitative structure-activity relationships, to probe the role of molecular weight and comonomers on IRI activity. Crucially, it was found that IRI activity is "switched on" when the polymer chain length increases from 10 and 20 repeat units. Substitution of the polymer side chains with hydrophilic or hydrophobic units was found to diminish activity. Hydrophobic modifications to the backbone were slightly more tolerated than side chain modifications, which implies an unbroken sequence of hydroxyl units is necessary for activity. These results highlight that, although hydrophobic domains are key components of IRI activity, the random inclusion of addition hydrophobic units does not guarantee an increase in activity and that the actual polymer conformation is important.

  2. Clinical Long-Term Outcome and Reinterventional Rate After Uterine Fibroid Embolization with Nonspherical Versus Spherical Polyvinyl Alcohol Particles

    SciTech Connect

    Duvnjak, Stevo; Ravn, Pernille; Green, Anders; Andersen, Poul Erik

    2016-02-15

    PurposeThis study was designed to evaluate the long-term clinical outcome and frequency of reinterventions in patients with uterine fibroids treated with embolization at a single center using polyvinyl alcohol microparticles.MethodsThe study included all patients with symptomatic uterine fibroids treated with uterine fibroid embolization (UFE) with spherical (s-PVA) and nonspherical (ns-PVA) polyvinyl alcohol microparticles during the period January 2001 to January 2011. Clinical success and secondary interventions were examined. Hospital records were reviewed during follow-up, and symptom-specific questionnaires were sent to all patients.ResultsIn total, 515 patients were treated with UFE and 350 patients (67 %) were available for long-term clinical follow-up. Median time of follow-up was 93 (range 76–120.2) months. Eighty-five patients (72 %) had no reinterventions during follow-up in the group embolized with ns-PVA compared with 134 patients (58 %) treated with s-PVA. Thirty-three patients (28 %) underwent secondary interventions in the ns-PVA group compared with 98 patients (42 %) in s-PVA group (χ{sup 2} test, p < 0.01).ConclusionsSpherical PVA particles 500–700 µm showed high reintervention rate at long-term follow-up, and almost one quarter of the patients underwent secondary interventions, suggesting that this type of particle is inappropriate for UFE.

  3. Luminescence study of ZnSe/PVA (polyvinyl alcohol) composite film

    NASA Astrophysics Data System (ADS)

    Lahariya, Vikas

    2016-05-01

    The ZnSe nanocrystals have been prepared into poly vinyl alcohol(PVA) polymer matrix on glass using ZnCl2 and Na2SeSO3 as zinc and selenium source respectively. Poly vinyl Alcohol (PVA) used as polymer matrix cum capping agent due to their high viscosity and water solubility. It is transparent for visible region and prevents Se- ions to photo oxidation. The ZnSe/PVA composite film was deposited on glass substrate. The film was characterized by X Ray Diffraction (XRD) and UV-Visible absorption Spectroscopy and Photoluminescence. The X Ray Diffraction (XRD) study confirms the nanometer size (10 nm) particle formation within PVA matrix with cubic zinc blend crystal structure. The UV-Visible Absorption spectrum of ZnSe/PVA composite film shown blue shift in absorption edge indicating increased band gap due to quantum confinement. The calculated energy band gap from the absorption edge using Tauc relation is 3.4eV. From the Photoluminescence study a broad peak at 435 nm has been observed in violet blue region due to recombination of surface states.

  4. Poly(vinyl alcohol)-coated chitosan microparticles act as an effective oral vaccine delivery system for hepatitis B vaccine in rat model.

    PubMed

    Shrestha, Bijaya; Rath, Jyoti Prakash

    2014-12-01

    The present study focused on the development of an effective oral vaccine delivery system of poly(vinyl alcohol)-coated chitosan microparticles-based recombinant hepatitis B vaccine. Chitosan microparticles were prepared by ionotropic gelation technique; they were loaded with recombinant hepatitis B vaccine and coated with poly(vinyl alcohol). The average sizes of the microparticles were measured in the range of 100-410 nm. The optimal loading capacity and loading efficiency were recorded around 3.4 and 74%, respectively. In vitro release study shows that the prepared microparticles release the antigen in a sustained manner. Moreover, the microparticles were resistant to simulated gastric environment and release the antigen in the targeted intestinal milieu. Furthermore, oral immunisation of rats with poly(vinyl alcohol)-coated chitosan hepatitis-B microparticles vaccine shows comparable seroprotective immune response to presently practiced intramuscular vaccination. The results demonstrated that poly(vinyl alcohol)-coated chitosan microparticles have the potential for being used as an oral vaccine delivery system for hepatitis B vaccine and may be a suitable alternative for needle-based vaccination.

  5. Films prepared from poly(vinyl alcohol) and amylose-fatty acid salt inclusion complexes with increased surface hydrophobicity and high elongation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In this study, water-soluble amylose-inclusion complexes were prepared from high amylose corn starch and sodium salts of lauric, palmitic, and stearic acid by steam jet cooking. Cast films were prepared by combining the amylose complexes with poly(vinyl alcohol)(PVOH) solution at ratios varying from...

  6. Development of poly(vinyl acetate-methylacrylic acid)/chitosan/Fe3O4 nanoparticles for the diagnosis of non-alcoholic steatohepatitis with magnetic resonance imaging.

    PubMed

    Luo, Xiadan; Song, Xiaoli; Zhu, Aiping; Si, Yunfeng; Ji, Lijun; Ma, Zhanrong; Jiao, Zhiyun; Wu, Jingtao

    2012-12-01

    Non-alcoholic steatohepatitis is a burgeoning health problem. To diagnose NASH with magnetic resonance imaging (MRI), an effective contrast agent, a stable suspension of superparamagnetic Fe(3)O(4) nanoparticles, were newly developed. The negatively charged Fe(3)O(4) nanoparticles were coated with positive chitosan (CS) firstly, and then assembled with poly(vinyl acetate-methylacrylic acid) (P(VAc-MAA)). Transmission electron microscope and dynamic light scattering confirmed that the obtained P(VAc-MAA)/CS/Fe(3)O(4) nanoparticles had a spherical or ellipsoidal morphology with an average diameter in the range of 14-20 nm. The superparamagnetic property and spinel structure of the Fe(3)O(4) nanoparticles were well preserved due to the protection of the P(VAc-MAA)/CS layers on the surface of the Fe(3)O(4) nanoparticles. The in vivo rat experiments confirmed that the P(VAc-MAA)/CS/Fe(3)O(4) nanoparticles were an effective contrast agent for MRI to diagnose NASH.

  7. Coating gigaporous polystyrene microspheres with cross-linked poly(vinyl alcohol) hydrogel as a rapid protein chromatography matrix.

    PubMed

    Qu, Jian-Bo; Huan, Guan-Sheng; Chen, Yan-Li; Zhou, Wei-Qing; Liu, Jian-Guo; Huang, Fang

    2014-08-13

    Gigaporous polystyrene (PS) microspheres were hydrophilized by in situ polymerization to give a stable cross-linked poly(vinyl alcohol) (PVA) hydrogel coating, which can shield proteins from the hydrophobic PS surface underneath. The amination of microspheres (PS-NH2) was first carried out through acetylization, oximation and reduction, and then 4,4'-azobis (4-cyanovaleric acid) (ACV), a polymerization initiator, was covalently immobilized on PS-NH2 through amide bond formation, and the cross-linked poly(vinyl acetate) (PVAc) was prepared by radical polymerization at the surfaces of ACV-immobilized PS microspheres (PS-ACV). Finally, the cross-linked PVA hydrogel coated gigaporous PS microspheres (PS-PVA) was easily achieved through alcoholysis of PVAc. Results suggested that the PS microspheres were effectively coated with cross-linked PVA hydrogel, where the gigaporrous structure remained under optimal conditions. After hydrophilic modification (PS-PVA), the protein-resistant ability of microspheres was greatly improved. The hydroxyl-rich PS-PVA surface can be easily derivatized by classical chemical methods. Performance advantages of the PS-PVA column in flow experiment include good permeability, low backpressure, and mechanical stability. These results indicated that PS-PVA should be promising in rapid protein chromatography.

  8. In situ formation of poly(vinyl alcohol)–heparin hydrogels for mild encapsulation and prolonged release of basic fibroblast growth factor and vascular endothelial growth factor

    PubMed Central

    Roberts, Justine J; Farrugia, Brooke L; Green, Rylie A; Rnjak-Kovacina, Jelena; Martens, Penny J

    2016-01-01

    Heparin-based hydrogels are attractive for controlled growth factor delivery, due to the native ability of heparin to bind and stabilize growth factors. Basic fibroblast growth factor and vascular endothelial growth factor are heparin-binding growth factors that synergistically enhance angiogenesis. Mild, in situ encapsulation of both basic fibroblast growth factor and vascular endothelial growth factor and subsequent bioactive dual release has not been demonstrated from heparin-crosslinked hydrogels, and the combined long-term delivery of both growth factors from biomaterials is still a major challenge. Both basic fibroblast growth factor and vascular endothelial growth factor were encapsulated in poly(vinyl alcohol)-heparin hydrogels and demonstrated controlled release. A model cell line, BaF32, was used to show bioactivity of heparin and basic fibroblast growth factor released from the gels over multiple days. Released basic fibroblast growth factor promoted higher human umbilical vein endothelial cell outgrowth over 24 h and proliferation for 3 days than the poly(vinyl alcohol)-heparin hydrogels alone. The release of vascular endothelial growth factor from poly(vinyl alcohol)-heparin hydrogels promoted human umbilical vein endothelial cell outgrowth but not significant proliferation. Dual-growth factor release of basic fibroblast growth factor and vascular endothelial growth factor from poly(vinyl alcohol)-heparin hydrogels resulted in a synergistic effect with significantly higher human umbilical vein endothelial cell outgrowth compared to basic fibroblast growth factor or vascular endothelial growth factor alone. Poly(vinyl alcohol)-heparin hydrogels allowed bioactive growth factor encapsulation and provided controlled release of multiple growth factors which is beneficial toward tissue regeneration applications. PMID:27895888

  9. Polydopamine-coated electrospun poly(vinyl alcohol)/poly(acrylic acid) membranes as efficient dye adsorbent with good recyclability.

    PubMed

    Yan, Jiajie; Huang, Yunpeng; Miao, Yue-E; Tjiu, Weng Weei; Liu, Tianxi

    2015-01-01

    Free-standing poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) membranes with polydopamine (PDA) coating were prepared based on the combination of electrospinning and self-polymerization of dopamine. This is a facile, mild, controllable, and low-energy consumption process without any rigorous restriction to reactive conditions. Benefiting from the high specific surface area of electrospun membranes and the abundant "adhesive" functional groups of polydopamine, the as-prepared membranes exhibit efficient adsorption performance towards methyl blue with the adsorption capacity reaching up to 1147.6 mg g(-1). Moreover, compared to other nanoparticle adsorbents, the as-prepared self-standing membrane is highly flexible, easy to operate and retrieve, and most importantly, easy to elute, and regenerate, which enable its potential applications in wastewater treatment.

  10. Cell-compatible properties of calcium carbonates and hydroxyapatite deposited on ultrathin poly(vinyl alcohol)-coated polyethylene films.

    PubMed

    Serizawa, Takeshi; Tateishi, Taishi; Akashi, Mitsuru

    2003-01-01

    Poly(vinyl alcohol) (PVA) was coated onto polyethylene (PE) films by a repetitive adsorption and drying process, and then the PVA-coated PE films were alternately immersed into aqueous solutions of Ca2+ and CO3(2-) ions (alternate soaking cycles), to deposit calcium carbonate (CaCO3) onto the films. The PVA coating was essential for the CaCO3 deposition. The amount of CaCO3 deposited increased with an increasing number of cycles. Scanning electron microscopic observations and attenuated total reflection spectra revealed the presence of both calcite and aragonite as the crystal structures of CaCO3 on the film. L929 fibroblast cells adhered and proliferated on these CaCO3-deposited PE films, as well as the hydroxyapatite-coated PE films previously prepared. It was found that the PVA coating and the subsequent deposition of calcium salts on certain films facilitated cell compatibility.

  11. Passively Q-switched erbium doped fiber laser based on double walled carbon nanotubes-polyvinyl alcohol saturable absorber

    NASA Astrophysics Data System (ADS)

    Mohammed, D. Z.; Al-Janabi, A. H.

    2016-11-01

    A passively Q-switched Er-doped fiber laser with a ring cavity operating at 1568.6 nm is demonstrated using a saturable absorber based on a double walled carbon nanotubes film, which is prepared using polyvinyl alcohol as a host polymer. The Q-switching operation is achieved at a low pump threshold of 40 mW. The proposed fiber laser produces stable pulses train of repetition rate ranging from 14.7 KHz to 47 KHz as the pump power increases from threshold to 203 mW. The minimum recorded pulse width was 4.6 µs at 203 mW, while the highest energy obtained was 102.1 nJ.

  12. A new approach to immobilize poly(vinyl alcohol) on poly(dimethylsiloxane) resulting in low protein adsorption

    NASA Astrophysics Data System (ADS)

    Carneiro, Leandro B.; Ferreira, Jacqueline; Santos, Marcos J. L.; Monteiro, Johny P.; Girotto, Emerson M.

    2011-10-01

    The hydrophobic characteristics of PDMS and non-specific protein adsorption are major drawbacks for its application in biosensing. Here we have combined surface oxidation by plasma and chemical binding of polyvinyl alcohol (PVA) to obtain long-term stability of hydrophilic PDMS surfaces. Mercaptopropyltrimethoxisilane and aminopropyltrimethoxisilane were used as adhesives between the plasma-oxidized PDMS surface and the PVA, immobilized at room temperature. This approach has allowed for fast, uniform, and very stable modification of the PDMS surface, which maintained a hydrophilic character for as long as 30 days. In addition, the modified hydrophilic surface presented minimized protein adsorption when compared to pristine PDMS. The results obtained in this work are important contributions to the growing field of integrated microfluidic biosensors.

  13. Photoinduced crystallization of calcium carbonate from a homogeneous precursor solution in the presence of partially hydrolyzed poly(vinyl alcohol)

    NASA Astrophysics Data System (ADS)

    Nishio, Takashi; Naka, Kensuke

    2015-04-01

    Photoinduced crystallization of calcium carbonate (CaCO3) was demonstrated by the photodecarboxylation of ketoprofen (KP, 2-(3-benzoylphenyl)propionic acid) under alkaline conditions (pH 10). In this method, a homogeneous solution comprising KP, calcium chloride, ammonia, and partially hydrolyzed poly(vinyl alcohol) (PVAPS, degree of saponification: 86.5-89.0 mol %) was used as the precursor solution and was exposed to ultraviolet (UV) irradiation for different time periods. Thermogravimetric analysis of the obtained xerogels showed that increasing the UV irradiation time increased the amount of CaCO3 formed and the complete conversion of calcium ions to calcite was achieved after 50 min of UV irradiation. Furthermore, solid phase analyses suggested that nanometer-to-micron-sized calcite crystals were formed and dispersed in the obtained PVAPS matrix.

  14. Polyvinyl Alcohol Hydrogel Irradiated and Acetalized for Osteochondral Defect Repair: Mechanical, Chemical, and Histological Evaluation after Implantation in Rat Knees

    PubMed Central

    Batista, N. A.; Rodrigues, A. A.; Bavaresco, V. P.; Mariolani, J. R. L.; Belangero, W. D.

    2012-01-01

    Polyvinyl Alcohol (PVA) hydrogel plugs were implanted in artificial osteochondral defects on the trochlear groove of rat knees. After 0, 3, 6, 12, and 24 weeks of followup, samples containing the implants were mechanically evaluated by creep indentation test, chemically, and histologically by optical microscopy. The mechanical test pointed towards an increase of the implant creep modulus and the chemical analysis exhibited an increasing concentration of calcium and phosphorus within the implants over time. Optical microscopy showed no foreign body reaction and revealed formation, differentiation, and maintenance of new tissue at the defect/implant interface. The absence of implant wear indicated that the natural articular lubrication process was not disturbed by the implant. The performance of the irradiated and acetalized PVA was considered satisfactory for the proposed application. PMID:23197982

  15. Modifying theophylline microparticle surfaces via the sequential deposition of poly(vinyl alcohol-co-vinyl acetate) copolymers.

    PubMed

    Zhao, Yanjun; Alas'ad, Mannar A; Jones, Stuart A

    2014-03-10

    The aim of this study was to investigate the manner in which amphiphilic poly(vinyl alcohol-co-vinyl acetate) copolymers (PVA-Ac) assembled on drug surfaces and use this information to generate a novel bi-layer polymer coating for a theophylline microparticle. Three grades of PVA-Ac, differing in hydrolysis degree and monomer distribution, were synthesised, characterised by nuclear magnetic resonance and shown to interact with theophylline when suspended in water. PVA-Ac deposition at the solid/liquid interface was driven by polymer hydrogen bond formation in a process that induced consequential structural changes in the macromolecule architecture. The most hydrophobic grades of the copolymer appeared to adsorb in a multistage process that passed through a series of equilibrium points. The PVA-Ac surface allowed two grades of the copolymer to be sequentially adsorbed and this resulted in the fabrication of a microparticle with desirable characteristics for pharmaceutical formulation production.

  16. Design and simulation of a poly(vinyl alcohol)-bacterial cellulose nanocomposite mechanical aortic heart valve prosthesis.

    PubMed

    Mohammadi, H; Boughner, D; Millon, L E; Wan, W K

    2009-08-01

    In this study, a polymeric aortic heart valve made of poly(vinyl alcohol) (PVA)-bacterial cellulose (BC) nanocomposite is simulated and designed using a hyperelastic non-linear anisotropic material model. A novel nanocomposite biomaterial combination of 15 wt % PVA and 0.5 wt % BC is developed in this study. The mechanical properties of the synthesized PVA-BC are similar to those of the porcine heart valve in both the principal directions. To design the geometry of the leaflets an advance surfacing technique is employed. A Galerkin-based non-linear finite element method is applied to analyse the mechanical behaviour of the leaflet in the closing and opening phases under physiological conditions. The model used in this study can be implemented in mechanical models for any soft tissues such as articular cartilage, tendon, and ligament.

  17. Neutron spin-echo studies on dynamic and static fluctuations in two types of poly(vinyl alcohol) gels

    SciTech Connect

    Kanaya, T.; Takahashi, N.; Nishida, K.; Seto, H.; Nagao, M.; Takeda, T.

    2005-01-01

    We report neutron spin-echo measurements on two types of poly(vinyl alcohol) (PVA) gels. The first is PVA gel in a mixture of dimethyl sulfoxide (DMSO) and water with volume ratio 60/40, and the second is PVA gel in an aqueous borax solution. The observed normalized intermediate scattering functions I(Q,t)/I(Q,0) are very different between them. The former I(Q,t)/I(Q,0) shows a nondecaying component in addition to a fast decay, but the latter does not have the nondecaying one. This clearly indicates that the fluctuations in the former PVA gel consist of static and dynamic fluctuations whereas the latter PVA gel does include only the dynamic fluctuations. The dynamic fluctuations of the former and latter gels have been analyzed in terms of a restricted motion in the network and Zimm motion, respectively, and the origins of these motions will be discussed.

  18. Neutron spin-echo studies on dynamic and static fluctuations in two types of poly(vinyl alcohol) gels

    NASA Astrophysics Data System (ADS)

    Kanaya, T.; Takahashi, N.; Nishida, K.; Seto, H.; Nagao, M.; Takeda, T.

    2005-01-01

    We report neutron spin-echo measurements on two types of poly(vinyl alcohol) (PVA) gels. The first is PVA gel in a mixture of dimethyl sulfoxide (DMSO) and water with volume ratio 60/40 , and the second is PVA gel in an aqueous borax solution. The observed normalized intermediate scattering functions I(Q,t)/I(Q,0) are very different between them. The former I(Q,t)/I(Q,0) shows a nondecaying component in addition to a fast decay, but the latter does not have the nondecaying one. This clearly indicates that the fluctuations in the former PVA gel consist of static and dynamic fluctuations whereas the latter PVA gel does include only the dynamic fluctuations. The dynamic fluctuations of the former and latter gels have been analyzed in terms of a restricted motion in the network and Zimm motion, respectively, and the origins of these motions will be discussed.

  19. Graphene functionalized with poly(vinyl alcohol) as a Pickering stabilizer for suspension polymerization of poly(methyl methacrylate).

    PubMed

    Erdenedelger, Gansukh; Dao, Trung Dung; Jeong, Han Mo

    2016-08-15

    Two types of thermally reduced graphenes (TRGs) having different lateral sizes were non-covalently modified with poly(vinyl alcohol) to endow water-dispersibility. The modified TRGs were examined as Pickering stabilizers for the suspension polymerization of methyl methacrylate (MMA). They were effective graphene-based Pickering stabilizers for the system with almost all of the polymerized composite microparticles having a regular spherical shape. The particle size of the composite microparticles was tunable by the size or the amount of modified TRG used as stabilizer. The almost perfect core-shell structure of the composite microparticles effectively enhanced the thermal stability of the core PMMA. In addition, when the core-shell microparticles were compression molded into a monolith, the obtained composite exhibited an ultra-low percolation threshold of electrical conductivity of around 0.04vol%.

  20. Michael-type addition reactions for the in situ formation of poly(vinyl alcohol)-based hydrogels.

    PubMed

    Tortora, Mariarosaria; Cavalieri, Francesca; Chiessi, Ester; Paradossi, Gaio

    2007-01-01

    Michael-type addition reactions offer the possibility to obtain in situ formation of polymeric hydrogels in the absence of a radical mechanism for the networking process. We explored such a synthetic route for obtaining a poly(vinyl alcohol) (PVA)-based hydrogel as a potential biomaterial for applications in vitro-retinal replacement surgery. The presence of radicals in the reaction medium can represent a risk for in situ surgical treatment. To circumvent this problem we have applied nucleophilic addition to ad hoc modified PVA macromers. The gel formation has been studied with respect to the timing required in this surgery and in terms of the structural characteristics of the obtained network.

  1. Effect of Salt Concentration on the Structure of Poly(Vinyl Alcohol) Cryogels Obtained from Aqueous Salt Solutions

    NASA Astrophysics Data System (ADS)

    Tretinnikov, O. N.; Sushko, N. I.; Zagorskaya, S. A.

    2015-03-01

    The degree of polymer crystallinity and water content on the surfaces and in the bulk of poly(vinyl alcohol) (PVA) cryogels prepared from aqueous salt solutions were determined as functions of KCl concentration using FTIR-ATR spectroscopy. It was found that the degree of PVA crystallinity increased with increasing KCl concentration and was much greater in the cryogel bulk than on its surfaces. Addition of salt at a concentration of 1.3 M increased the degree of polymer crystallinity on the cryogel surfaces by 1.6-2.3 times whereas the crystallinity in the bulk increased by 3.3-4 times. The cryogel water contents on the surfaces and in the bulk were approximately equal and were practically independent of the salt concentration.

  2. Polyene Formation Catalyzed by Phosphotungstic Acid and Aluminum Chloride in Thin Films of Poly(Vinyl Alcohol)

    NASA Astrophysics Data System (ADS)

    Tretinnikov, O. N.; Sushko, N. I.; Maly, A. B.

    2016-01-01

    Formation of linear polyenes -(CH=CH) n - during thermal dehydration of thin layers (9-20 μm) of poly(vinyl alcohol) containing phosphotungstic-acid and aluminum-chloride catalysts was investigated. It was found that the concentration of long-chain ( n ≥ 8) polyenes in films containing phosphotungstic acid increased smoothly with increasing annealing time although the kinetics of the dehydration were independent of the film thickness. The polyene ( n ≥ 8) formation rate in films containing aluminum chloride dropped quickly with decreasing film thickness and increasing annealing time. As a result, long-chain polyenes practically did not form regardless of the annealing time for a film thickness of 11 μm.

  3. Effect of the PVA (polyvinyl alcohol) concentration on the optical properties of Eu-doped YAG phosphors

    NASA Astrophysics Data System (ADS)

    Hora, Daniela A.; Andrade, Adriano B.; Ferreira, Nilson S.; Teixeira, Verônica C.; dos S. Rezende, Marcos V.

    2016-10-01

    The influence of the polyvinyl alcohol (PVA) concentration on the synthesis and structural, morphological and optical properties of Y3Al5O13: Eu (Eu-doped YAG) was systematically investigated in this work. The final concentration of PVA in the preparation step influenced the crystallite size and also the degree of particle agglomeration in Eu-doped YAG phosphors. X-ray excited optical luminescence (XEOL) emission spectra results indicated typical Eu3+ emission lines and an abnormally intense 5D0 → 7F4. The intensity parameters Ω2 and Ω4 were calculated and indicated the PVA concentration affects the ratio Ω2:Ω4. X-ray absorption spectroscopy (XAS) results showed Eu valence did not change and the symmetry around the Eu3+ is influenced by the PVA concentration. XEOL-XAS showed the luminescence increases as a function of energy.

  4. Negative giant magnetoresistance effect in single layered superparamagnetic polymer nanocomposite structures of poly(vinyl alcohol)-polyaniline/bismuth ferrite

    NASA Astrophysics Data System (ADS)

    Prabhakaran, T.; Hemalatha, J.

    2012-08-01

    Superparamagnetic polyaniline/bismuth ferrite (PANI/BFO) nanocomposite powder is synthesized through an in situ sol-gel polymerization method and it is embedded in non-magnetic poly(vinyl alcohol) (PVA) matrix to fabricate high performance flexible films. The interaction between PANI/BFO filler and PVA matrix and hence the formation of composite is identified through XRD and it is further confirmed through FTIR spectra. Vibration sample magnetometry (VSM) studies ensure the superparamagnetic nature of the composite films. The magnetoresistance measurements are made at room temperature for various current values from which it is observed that the samples exhibit a negative giant magnetoresistance (GMR) effect. The variation of GMR from 21% to 66% with filler concentration and also the non-ohmic V-I characteristics of the composite films are reported.

  5. Comparison of Chain Conformation of Poly(vinyl alcohol) in Solutions and Melts from Quantum Chemistry Based Molecular Dynamics Simulations

    NASA Technical Reports Server (NTRS)

    Jaffe, Richard; Han, Jie; Matsuda, Tsunetoshi; Yoon, Do; Langhoff, Stephen R. (Technical Monitor)

    1997-01-01

    Confirmations of 2,4-dihydroxypentane (DHP), a model molecule for poly(vinyl alcohol), have been studied by quantum chemistry (QC) calculations and molecular dynamics (MD) simulations. QC calculations at the 6-311G MP2 level show the meso tt conformer to be lowest in energy followed by the racemic tg, due to intramolecular hydrogen bond between the hydroxy groups. The Dreiding force field has been modified to reproduce the QC conformer energies for DHP. MD simulations using this force field have been carried out for DHP molecules in the gas phase, melt, and CHCl3 and water solutions. Extensive intramolecular hydrogen bonding is observed for the gas phase and CHCl3 solution, but not for the melt or aqueous solution, Such a condensed phase effect due to intermolecular interactions results in a drastic change in chain conformations, in agreement with experiments.

  6. Synthesis and characterization of alkaline polyvinyl alcohol and poly(epichlorohydrin) blend polymer electrolytes and performance in electrochemical cells

    NASA Astrophysics Data System (ADS)

    Yang, Chun-Chen; Lin, Sheng-Jen; Hsu, Sung-Ting

    Alkaline SPE was obtained from a blend of polyvinyl alcohol (PVA) and poly(epichlorohydrin) (PECH), PVA-PECH, by a solution-cast technique. The PVA host polymer is blended with PECH polymer to provide a polymer electrolyte with improved chemical and mechanical properties. The ionic conductivity of the PVA-PECH polymer electrolytes is between 10 -2 and 10 -3 S cm -1 at room temperature when the blend ratio is varied from 1:0.2 to 1:1. The PVA-PECH polymer was characterized by means of scanning electron microscopy, X-ray diffraction, stress-strain test, cyclic voltammetry, and a.c. impedance spectroscopy. It is found that the polymer electrolytes exhibit good mechanical strength and excellent chemical stability. The electrochemical performance of solid-state Zn-air batteries with various types of the blended polymer electrolyte films is examined by a galvanostatic discharge method.

  7. Modification of poly(vinylidene fluoride) ultrafiltration membranes with poly(vinyl alcohol) for fouling control in drinking water treatment.

    PubMed

    Du, Jennifer R; Peldszus, Sigrid; Huck, Peter M; Feng, Xianshe

    2009-10-01

    A commercial poly(vinylidene fluoride) flat sheet membrane was modified by surface coating with a dilute poly(vinyl alcohol) (PVA) aqueous solution followed by solid-vapor interfacial crosslinking. The resulting PVA layer increased membrane smoothness and hydrophilicity and resulted in comparable pure water permeation between the modified and unmodified membranes. Fouling tests using a 5 mg/L protein solution showed that a short period of coating and crosslinking improved the anti-fouling performance. After 18 h ultrafiltration of a surface water with a TOC of approximately 7 mg C/L, the flux of the modified membrane was twice as high as that of the unmodified membrane. The improved fouling resistance of the modified membrane was related to the membrane physiochemical properties, which were confirmed by pure water permeation, X-ray photoelectron spectroscopy, and contact angle, zeta potential and roughness measurements.

  8. Surface modification of polyvinyl alcohol/malonic acid nanofibers by gaseous dielectric barrier discharge plasma for glucose oxidase immobilization

    NASA Astrophysics Data System (ADS)

    Afshari, Esmail; Mazinani, Saeedeh; Ranaei-Siadat, Seyed-Omid; Ghomi, Hamid

    2016-11-01

    Polymeric nanofiber prepares a suitable situation for enzyme immobilization for variety of applications. In this research, we have fabricated polyvinyl alcohol (PVA)/malonic acid nanofibers using electrospinning. After fabrication of nanofibers, the effect of air, nitrogen, CO2, and argon DBD (dielectric barrier discharge) plasmas on PVA/malonic acid nanofibers were analysed. Among them, air plasma had the most significant effect on glucose oxidase (GOx) immobilization. Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectrum analysis and X-ray photoelectron spectroscopy (XPS) results revealed that in case of air plasma modified nanofibers, the carboxyl groups on the surface are increased. The scanning electron microscopy (SEM) images showed that, after GOx immobilization, the modified nanofibers with plasma has retained its nanofiber structure. Finally, we analysed reusability and storage stability of GOx immobilized on plasma modified and unmodified nanofibers. The results were more satisfactory for modified nanofibers with respect to unmodified ones.

  9. Preparation and properties of a hydrogel of maleated poly(vinyl alcohol) (PVAM) grafted with cassava starch.

    PubMed

    Riyajan, Sa-Ad; Sukhlaaied, Wattana; Keawmang, Woranut

    2015-05-20

    A novel pH-sensitive graft copolymer (PVAM-g-CSt) was synthesized from maleated poly(vinyl alcohol) (PVAM) and cassava starch (CSt) through a grafting reaction using potassium persulfate as a thermal initiator. The chemical structure of the PVAM-g-CSt was revealed by FTIR and ether linkage of the graft copolymer was observed at 1089 cm(-1). The degree of grafting of the copolymer was found to range between 40 and 82%, depending on the PVAM/CSt ratio. The highest tensile strength was found at a ratio of 9:1 PVAM/CSt. In addition, the swelling ratio in water increased with increasing proportions of CSt in the PVAM-g-CSt due to the decrease in the degree of grafting. The resulting hydrogel exhibits good pH sensitivity in different pH mediums. The graft copolymer easily degraded in natural soil, especially at high proportions of CSt in the blend.

  10. The Gelation of Poly(Vinyl Alcohol) with Na2B4O7 10H2O: Killing Slime

    NASA Astrophysics Data System (ADS)

    McLaughlin, K. W.; Wyffels, N. K.; Jentz, A. B.; Keenan, M. V.

    1997-01-01

    The gelation of poly(vinyl alcohol), PVA, with sodium tetraborate decahydrate (borax) to produce "slime" is a popular chemistry demonstration (1). Since the borate serves to cross-link the PVA, the degree of cross-linking can be varied by changing the borate concentration (2). One way of changing the concentration of borate available to hold the PVA chains together is to "disable" the borate by protonation with a strong acid (3, 4). The titration of slime with sulfuric acid (eq 1) allows students to examine the relationship between cross-linking, viscosity, and the onset of gelation. This modification to a popular chemistry demonstration produces an interesting chemistry laboratory experiment designed to introduce students to the relationship between molecular structure and the bulk properties of macromolecules.

  11. A novel electrochemical biosensor based on Fe3O4 nanoparticles-polyvinyl alcohol composite for sensitive detection of glucose.

    PubMed

    Sanaeifar, Niuosha; Rabiee, Mohammad; Abdolrahim, Mojgan; Tahriri, Mohammadreza; Vashaee, Daryoosh; Tayebi, Lobat

    2017-02-15

    In this research, a new electrochemical biosensor was constructed for the glucose detection. Iron oxide nanoparticles (Fe3O4) were synthesized through co-precipitation method. Polyvinyl alcohol-Fe3O4 nanocomposite was prepared by dispersing synthesized nanoparticles in the polyvinyl alcohol (PVA) solution. Glucose oxidase (GOx) was immobilized on the PVA-Fe3O4 nanocomposite via physical adsorption. The mixture of PVA, Fe3O4 nanoparticles and GOx was drop cast on a tin (Sn) electrode surface (GOx/PVA-Fe3O4/Sn). The Fe3O4 nanoparticles were characterized by X-ray diffraction (XRD). Also, Fourier transform infrared (FTIR) spectroscopy and field emission scanning electron microscopy (FE-SEM) techniques were utilized to evaluate the PVA-Fe3O4 and GOx/PVA-Fe3O4 nanocomposites. The electrochemical performance of the modified biosensor was investigated using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Presence of Fe3O4 nanoparticles in the PVA matrix enhanced the electron transfer between enzyme and electrode surface and the immobilized GOx showed excellent catalytic characteristic toward glucose. The GOx/PVA-Fe3O4/Sn bioelectrode could measure glucose in the range from 5 × 10(-3) to 30 mM with a sensitivity of 9.36 μA mM(-1) and exhibited a lower detection limit of 8 μM at a signal-to-noise ratio of 3. The value of Michaelis-Menten constant (KM) was calculated as 1.42 mM. The modified biosensor also has good anti-interfering ability during the glucose detection, fast response (10 s), good reproducibility and satisfactory stability. Finally, the results demonstrated that the GOx/PVA-Fe3O4/Sn bioelectrode is promising in biosensor construction.

  12. Fabrication of silver nanoparticles embedded into polyvinyl alcohol (Ag/PVA) composite nanofibrous films through electrospinning for antibacterial and surface-enhanced Raman scattering (SERS) activities.

    PubMed

    Zhang, Zhijie; Wu, Yunping; Wang, Zhihua; Zou, Xueyan; Zhao, Yanbao; Sun, Lei

    2016-12-01

    Silver nanoparticle-embedded polyvinyl alcohol (PVA) nanofibers were prepared through electrospinning technique, using as antimicrobial agents and surface-enhanced Raman scattering (SERS) substrates. Ag nanoparticles (NPs) were synthesized in liquid phase, followed by evenly dispersing in PVA solution. After electrospinning of the mixed solution at room temperature, the PVA embedded with Ag NPs (Ag/PVA) composite nanofibers were obtained. The morphologies and structures of the as-synthesized Ag nanoparticles and Ag/PVA fibers were characterized by the techniques of transmission electron microscopy (TEM), X-ray diffraction (XRD), ultraviolet-visible absorption spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Ag NPs have an average diameter of 13.8nm, were found to be uniformly dispersed in PVA nanofibers. The Ag/PVA nanofibers provided robust antibacterial activities against both Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli) microorganisms. It's also found that Ag/PVA nanofibers make a significant contribution to the high sensitivity of SERS to 4-mercaptophenol (4-MPh) molecules.

  13. Polyvinyl alcohol as a useful indicator on iodometry: volumetric and spectrophotometric studies on iodine-PVA and iodine-starch complexes.

    PubMed

    Yoshinaga, T; Shirakata, T; Dohtsu, H; Hiratsuka, H; Hasegawa, M; Kobayashi, M; Hoshi, T

    2001-02-01

    Iodometry is one of the easiest, most rapid and accurate methods for the determination of a relatively small amount of oxidizing agent, such as residual chlorine. Starch has long been used as a useful color indicator in iodometry. However, we found that PVA (polyvinyl alcohol with partially saponificated; e.g., saponification degree of 88%) is a more useful color indicator than starch. For example, at 20 degrees C, the PVA indicator gave similar profiles of iodine concentration vs. titration efficiencies (percent recoveries) to those of starch at 0 degrees C. At 0 degrees C, the PVA indicator detected 1.1 mg I2/L (11 microg I2: with 10 mL sample volume) with a high percentage of recovery (=95%). Furthermore, at 20 degrees C an iodine concentration of 0.36 mg/L (which corresponds to a residual chlorine concentration of 0.1 mg Cl2/L) could be detected using PVA color indicator assuming an appropriate correction.

  14. Microencapsulation of lobster carotenoids within poly(vinyl alcohol) and poly(D,L-lactic acid) membranes.

    PubMed

    Sun, Z M; Poncelet, D; Conway, J; Neufeld, R J

    1995-01-01

    The use of natural pigments such as lobster carotenoids in fish feed formulations offers advantages over the use of the synthetic alternatives. Microencapsulation of the pigments, with or without the addition of antioxidants to the formulation, may be of benefit in terms of stabilizing pigment colour. In the present study, lobster carotenoids were extracted from lobster shell into petroleum ether and microencapsulated by phase separation and salt coacervation within (poly vinyl alcohol) and poly(vinyl alcohol)/poly(D,L-lactic acid) membranes. Spherical microcapsules, with smooth, thin and resilient membranes were obtained with mean diameters ranging from 50 to 150 microns, depending on the membrane material, and source of pigment. The microcapsules were pink-orange in colour, and colour stability was followed spectrophotometrically. Enhanced stability was observed in both membrane materials, in comparison to the non-encapsulated control. Rates of discoloration were determined under a variety of storage conditions, including the absence of light, reduced temperatures and under nitrogen atmosphere. The best stability of lobster carotenoids was observed under a nitrogen atmosphere within PVA/PLA membranes, representing an 11-fold enhancement of pigment stability in comparison to the controls. Under ambient conditions, the enhancement in pigment stability was approximately 6-fold. The optimum concentration of PVA during microencapsulation was 3-4%, and the microencapsulated pigments appeared most stable under acidic conditions. The rate of discoloration appeared independent of pigment concentration.

  15. Photo-triggered release from liposomes without membrane solubilization, based on binding to poly(vinyl alcohol) carrying a malachite green moiety.

    PubMed

    Uda, Ryoko M; Kato, Yutaka; Takei, Michiko

    2016-10-01

    When working with liposomes analogous to cell membranes, it is important to develop substrates that can regulate interactions with the liposome surface in response to light. We achieved a photo-triggered release from liposomes by using a copolymer of poly(vinyl alcohol) carrying a malachite green moiety (PVAMG). Although PVAMG is a neutral polymer under dark conditions, it is photoionized upon exposure to UV light, resulting in the formation of a cationic site for binding to liposomes with a negatively charged surface. Under UV irradiation, PVAMG showed effective interaction with liposomes, releasing the encapsulated compound; however, this release was negligible under dark conditions. The poly(vinyl alcohol) moiety of PVAMG played an important role in the photo-triggered release. This release was caused by membrane destabilization without lipid solubilization. We also investigated different aspects of liposome/PVAMG interactions, including PVAMG-induced fusion between the liposomes and the change in the liposome morphologies.

  16. Electron spin resonance of the phosphorescent triplet states of p-phenylphenol and p-phenylphenolate ion in stretched polyvinyl alcohol films

    NASA Astrophysics Data System (ADS)

    Yagi, Mikio; Higuchi, Jiro

    1980-05-01

    Using a stretched polyvinyl alcohol film as a host, electron spin resonance (ESR) of the phosphorescent triplet states of p-phenylphenol and p-phenylphenolate ion has been studied by changing the pH of the medium as an example of the application of ESR to an acid-base equilibrium. In assigning ESR spectra of aromatic acid and conjugated base, the present method is demonstrated to be most convenient and useful.

  17. The Surface Structure and Thermal Properties of Novel Polymer Composite Films Based on Partially Phosphorylated Poly(vinyl alcohol) with Aluminum Phosphate

    PubMed Central

    Mohamed Saat, Asmalina

    2014-01-01

    Partially phosphorylated polyvinyl alcohol (PPVA) with aluminum phosphate (ALPO4) composites was synthesized by solution casting technique to produce (PPVA)100−y − (ALPO4)y (y = 0, 1, and 2). The surface structure and thermal properties of the films were characterized using Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). The results showed that the films have higher thermal stability with strong bonding between PPVA and ALPO4. PMID:25506069

  18. 76 FR 5562 - Polyvinyl Alcohol From Taiwan: Final Determination of Sales at Less Than Fair Value

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-01

    ... questionnaire responses submitted by the sole respondent, Chang Chun Petrochemical Co., Ltd. (CCPC). We used... Alcohol from Taiwan: Sales Verification of Chang Chun Petrochemical Co., Ltd.,'' dated October 12, 2010... Value Data Submitted by Chang Chun Petrochemical Co., Ltd., in the Antidumping Duty Investigation...

  19. Development, mechanical evaluation and surface characteristics of chitosan/polyvinyl alcohol based polymer composite coatings on titanium metal.

    PubMed

    Mishra, Sandeep K; Kannan, S

    2014-12-01

    Mechanical properties of orthopedic implants play important role in the regeneration and cell growth of the diseased body part. The present investigation was aimed at the development of a biocompatible, biodegradable and mechanically stable coating of chitosan (CS)-polyvinyl alcohol (PVA) polymer composite on Titanium (Ti) metal by employing a simple methodology at ambient conditions. The PVA to CS concentrations were maintained in fixed ratios of 1:4 weight/weight (w/w) for the development of all the coatings on Ti metal. Four different concentrations of the polymers ranging in the order of 5%, 10%, 15% and 20% weight/volume (w/v) solution of CS were selected in an aim to test their efficacy on mechanical stability. The results obtained from the analysis confirmed considerable improvement in mechanical properties of the composite polymer film comprising CS and PVA on Ti metal with the four different concentrations showing variable elastic modulus and hardness. The difference in mechanical properties of both dehydrated and hydrated coatings demonstrates the effective and efficient shielding of high mechanical properties of Ti metal in physiological conditions. The scratch tests performed on the coated specimens also indicated a good adhesion of the polymer on the Ti metal surface.

  20. Thermodynamic and spectroscopic analysis of the conformational transition of poly(vinyl alcohol) by temperature-dependent FTIR

    NASA Astrophysics Data System (ADS)

    Han, Shan; Luan, Ye-Mei; Pang, Shu-Feng; Zhang, Yun-Hong

    2015-03-01

    The conformational change of poly(vinyl alcohol) has been studied by Fourier transform infrared spectroscopy at various temperatures in the 4000-400 cm-1 region. The molecular motion and the trans/gauche content are sensitive to the Csbnd H, Csbnd C stretching modes. FTIR spectra show that the I2920/I2849 decreases from 1.84 to 1.0 with increasing temperature, companying the decrease in I1047/I1095 from 0.78 to 0.58, implying the conformational transition from trans to gauche in alkyl chain. Based on the van't Hoff relation, the enthalpies and entropies have been calculated in different temperatures, which are 4.61 kJ mol-1 and 15.23 J mol-1 K-1, respectively, in the region of 80-140 °C. From the Cdbnd O stretching mode and Osbnd H band, it can be concluded that the intermolecular hydrogen bonds decrease owing to elevating temperature, which leads to more gauche conformers.

  1. Luminescence properties of Sm, Tb(Sal)3Phen complex in polyvinyl alcohol: an approach for white-light emission

    NASA Astrophysics Data System (ADS)

    Kaur, Gagandeep; Rai, S. B.

    2011-10-01

    Polyvinyl alcohol polymer films doped with Sm,Tb(Sal)3Phen complexes have been synthesized using solution casting technique. An enhancement in absorption intensity is observed revealing the encapsulation of rare earth ions by salicylic acid (Sal)/1,10 phenanthroline (Phen) complex. Photoluminescence spectra of the co-doped samples were examined by varying the concentration of Tb3+ keeping concentration of Sm3+ ions fixed and vice-versa. It is found that the polymer samples emit a combination of blue, green and orange-red wavelengths tunable to white light when excited with 355 nm radiation. The emission spectra also show a self-quenching effect at higher concentration of Sm3+ ions. An efficient energy transfer was observed from Tb3+ : 5D4 → Sm3+ : 4G9/2. The reason for the enhancement in fluorescence intensities of Sm3+ in the co-doped polymer sample is the intermolecular as well as the intramolecular energy transfer.

  2. Influence of dynamic load on friction behavior of human articular cartilage, stainless steel and polyvinyl alcohol hydrogel as artificial cartilage.

    PubMed

    Li, Feng; Su, Yonglin; Wang, Jianping; Wu, Gang; Wang, Chengtao

    2010-01-01

    Many biomaterials are being developed to be used for cartilage substitution and hemiarthroplasty implants. The lubrication property is a key feature of the artificial cartilage. The frictional behavior of human articular cartilage, stainless steel and polyvinyl alcohol (PVA) hydrogel were investigated under cartilage-on-PVA hydrogel contact, cartilage-on-cartilage contact and cartilage-on-stainless steel contact using pin-on-plate method. Tests under static load, cyclic load and 1 min load change were used to evaluate friction variations in reciprocating motion. The results showed that the lubrication property of cartilage-on-PVA hydrogel contact and cartilage-on-stainless steel contact were restored in both 1 min load change and cyclic load tests. The friction coefficient of PVA hydrogel decreased from 0.178 to 0.076 in 60 min, which was almost one-third of the value under static load in continuous sliding tests. In each test, the friction coefficient of cartilage-on-cartilage contact maintained far lower value than other contacts. It is indicated that a key feature of artificial cartilage is the biphasic lubrication properties.

  3. Influence of the covalent immobilization of graphene oxide in poly(vinyl alcohol) on human osteoblast response.

    PubMed

    Linares, Javier; Matesanz, María Concepción; Feito, María José; Salavagione, Horacio Javier; Martínez, Gerardo; Gómez-Fatou, Marián; Portolés, María Teresa

    2016-02-01

    The differences in the response of human Saos-2 osteoblasts to nanocomposites of poly(vinyl alcohol) (PVA) and 1.5wt.% graphene oxide (GO) prepared by covalent linking (PVA/GO-c) and simple blending (PVA/GO-m) have been evaluated through different biocompatibility parameters. The effects produced on osteoblasts by these two nanocomposites were analysed in parallel and compared with the direct action of GO and with the effect of PVA films without GO. The intracellular content of reactive oxygen species (ROS) and the levels of interleukin-6 (IL-6) were measured to evaluate oxidative stress induction and protective response, respectively. The results demonstrate that the combination of GO with PVA reduces both the proliferation delay and the internal cell complexity alterations induced by GO on human osteoblasts. Moreover, the covalent attachment of GO to the PVA chains increases both cell viability and IL-6 levels, reducing both apoptosis and intracellular ROS content when compared to simple blending of both materials. The use of this strategy to modulate the biointerface reduces the toxic effects of graphene while preserving the reinforcement characteristics for application in tissue engineering scaffolds, and has enormous interest for polymer/graphene biomaterials development.

  4. Rheological characterization of solutions and thin films made from amylose-hexadecylammonium chloride inclusion complexes and polyvinyl alcohol.

    PubMed

    Hay, William T; Byars, Jeffrey A; Fanta, George F; Selling, Gordon W

    2017-04-01

    The rheological properties of aqueous solutions and films made from blends of polyvinyl alcohol (PVOH) and amylose-hexadecylammonium chloride inclusion complexes (Hex-Am) were investigated to better understand the polymer interactions and processing parameters. Aqueous solutions of Hex-Am displayed non-Newtonian shear thinning characteristics, becoming highly viscous at 4.2% solids and forming a strong mechanical gel at 10% solids. Cationic Hex-Am was observed to have dramatically different rheological temperature response profiles from anionic amylose-sodium palmitate inclusion complexes, displaying a precipitous increase in viscosity upon cooling from 95°C to 50°C. Aqueous solution blends of 1:1 PVOH/Hex-Am lack this precipitous increase in viscosity, indicating that PVOH reduces amylose-chain entanglement. Films cast from varying blends of Hex-Am and PVOH were thermostable to 200°C, and displayed decreasing storage modulus with increasing concentrations of PVOH in film blends. Films cast from Hex-Am/PVOH absorb water vapor at lower rates than their constitutive polymers.

  5. Facile and green fabrication of electrospun poly(vinyl alcohol) nanofibrous mats doped with narrowly dispersed silver nanoparticles

    PubMed Central

    Lin, Song; Wang, Run-Ze; Yi, Ying; Wang, Zheng; Hao, Li-Mei; Wu, Jin-Hui; Hu, Guo-Han; He, Hua

    2014-01-01

    Submicrometer-scale poly(vinyl alcohol) (PVA) nanofibrous mats loaded with aligned and narrowly dispersed silver nanoparticles (AgNPs) are obtained via the electrospinning process from pure water. This facile and green procedure did not need any other chemicals or organic solvents. The doped AgNPs are narrowly distributed, 4.3±0.7 nm and their contents on the nanofabric mats can be easily tuned via in situ ultraviolet light irradiation or under preheating conditions, but with different particle sizes and size distributions. The morphology, loading concentrations, and dispersities of AgNPs embedded within PVA nanofiber mats are characterized by transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, ultraviolet-visible spectra, X-ray photoelectron spectroscopy, and X-ray diffraction, respectively. Moreover, the biocidal activities and cytotoxicity of the electrospun nanofiber mats are determined by zone of inhibition, dynamic shaking method, and cell counting kit (CCK)-8 assay tests. PMID:25170264

  6. Poly(vinyl alcohol)/poly(acrylic acid) hydrogel coatings for improving electrode-neural tissue interface.

    PubMed

    Lu, Yi; Wang, Dingfang; Li, Tao; Zhao, Xueqing; Cao, Yuliang; Yang, Hanxi; Duan, Yanwen Y

    2009-09-01

    A major problem which hinders the applications of neural prostheses is the inconsistent performance caused by tissue responses during long-term implantation. The study investigated a new approach for improving the electrode-neural tissue interface. Hydrogel poly(vinyl alcohol)/poly(acrylic acid) interpenetrating polymer networks (PVA/PAA IPNs) were synthesized and tailored as coatings for poly(dimethylsiloxane) (PDMS) based neural electrodes with the aid of plasma pretreatment. Changes in the electrochemical impedance and maximum charge injection (Q(inj)) limits of the coated iridium oxide microelectrodes were negligible. Protein adsorption on PDMS was reduced by approximately 85% after coating. In the presence of nerve growth factor (NGF), neurite extension of rat pheochromocytoma (PC12) cells was clearly greater on PVA/PAA IPN films than on PDMS substrates. Furthermore, the tissue responses of PDMS implants coated with PVA/PAA IPN films were studied by 6-week implantation in the cortex of rats, which found that the glial fibrillary acidic protein (GFAP) immunoreactivity in animals (n=8) receiving coated implants was significantly lower (p<0.05) compared to that of uncoated implants (n=7) along the entire distance of 150 microm from the outer skirt to the implant interface. The coated film remained on the surface of the explanted implants, confirmed by scanning electron microscopy (SEM). All of these suggest the hydrogel coating is feasible and favorable to neural electrode applications.

  7. Application of response surface methodology in optimization of electrospinning process to fabricate (ferrofluid/polyvinyl alcohol) magnetic nanofibers.

    PubMed

    Ahmadipourroudposht, Mohaddeseh; Fallahiarezoudar, Ehsan; Yusof, Noordin Mohd; Idris, Ani

    2015-05-01

    Magnetic nanofibers are composed of good dispersion of magnetic nanoparticles along an organic material. Magnetic nanofibers are potentially useful for composite reinforcement, bio-medical and tissue engineering. Nanofibers with the thinner diameter have to result in higher rigidity and tensile strength due to better alignments of lamellae along the fiber axis. In this study, the performance of electrospinning process was explained using response surface methodology (RSM) during fabrication of magnetic nanofibers using polyvinyl alcohol (PVA) as a shelter for (γ-Fe2O3) nanoparticles where the parameters investigated were flow rate, applied voltage, distance between needle and collector and collector rotating speed. The response variable was diameter distribution. The two parameters flow rate and applied voltage in primary evaluation were distinguished as significant factors. Central composite design was applied to optimize the variable of diameter distribution. Quadratic estimated model developed for diameter distribution indicated the optimum conditions to be flow rate of 0.25 ml/h at voltage of 45 kV while the distance and rotating speed are at 8 cm and 1500 rps respectively. The obtained model was verified successfully by the confirmation experiments.

  8. Gentamicin-loaded wound dressing with polyvinyl alcohol/dextran hydrogel: gel characterization and in vivo healing evaluation.

    PubMed

    Hwang, Ma-Ro; Kim, Jong Oh; Lee, Jeong Hoon; Kim, Yong Il; Kim, Jeong Hoon; Chang, Sun Woo; Jin, Sung Gju; Kim, Jung Ae; Lyoo, Won Seok; Han, Sung Soo; Ku, Sae Kwang; Yong, Chul Soon; Choi, Han-Gon

    2010-09-01

    To develop a gentamicin-loaded wound dressing, cross-linked hydrogel films were prepared with polyvinyl alcohol (PVA) and dextran using the freezing-thawing method. Their gel properties such as gel fraction, swelling, water vapor transmission test, morphology, tensile strength, and thermal property were investigated. In vitro protein adsorption test, in vivo wound healing test, and histopathology were performed. Dextran decreased the gel fraction, maximum strength, and thermal stability of hydrogels. However, it increased the swelling ability, water vapor transmission rate, elasticity, porosity, and protein adsorption. The drug gave a little positive effect on the gel properties of hydrogels. The gentamicin-loaded wound dressing composed of 2.5% PVA, 1.13% dextran, and 0.1% drug was more swellable, flexible, and elastic than that with only PVA because of its cross-linking interaction with PVA. In particular, it could provide an adequate level of moisture and build up the exudates on the wound area. From the in vivo wound healing and histological results, this gentamicin-loaded wound dressing enhanced the healing effect more compared to conventional product because of the potential healing effect of gentamicin. Thus, this gentamicin-loaded wound dressing would be used as a potential wound dressing with excellent forming and improved healing effect in wound care.

  9. Effect of partial atomic charges on the calculated free energy of solvation of poly(vinyl alcohol) in selected solvents.

    PubMed

    Noorjahan, Abolfazl; Choi, Phillip

    2015-03-01

    It is well-known that properties of poly(vinyl alcohol) (PVA) in the pure and solution states depend largely on the hydrogen bonding networks formed. In the context of molecular simulation, such networks are handled through the Coulombic interactions. Therefore, a good set of partial atom charges (PACs) for simulations involving PVA is highly desirable. In this work, we calculated the PACs for PVA using a few commonly used population analysis schemes with a hope to identify an accurate set of PACs for PVA monomers. To evaluate the quality of the calculated parameters, we have benchmarked their predictions for free energy of solvation (FES) in selected solvents by molecular dynamics simulations against the ab initio calculated values. Selected solvents were water, ethanol and benzene as they covered a range of size and polarity. Also, PVA with different tacticities were used to capture their effect on the calculated FESs. Based on our results, neither PACs nor FESs are affected by the chain tacticity. While PACs predicted by the Merz-Singh-Kollman scheme were close to original values in the OPLS-AA force field in way that no significant difference in properties of pure PVA was observed, free energy of solvation calculated using such PACs showed greater agreement with ab initio calculated values than those calculated by OPLS-AA (and all other schemes used in this work) in all three solvents considered.

  10. Use of Polyvinyl Alcohol as a Solubility-Enhancing Polymer for Poorly Water Soluble Drug Delivery (Part 1).

    PubMed

    Brough, Chris; Miller, Dave A; Keen, Justin M; Kucera, Shawn A; Lubda, Dieter; Williams, Robert O

    2016-02-01

    Polyvinyl alcohol (PVAL) has not been investigated in a binary formulation as a concentration-enhancing polymer owing to its high melting point/high viscosity and poor organic solubility. Due to the unique attributes of the KinetiSol® dispersing (KSD) technology, PVAL has been enabled for this application and it is the aim of this paper to investigate various grades for improvement of the solubility and bioavailability of poorly water soluble active pharmaceutical ingredients. Solid amorphous dispersions were created with the model drug, itraconazole (ITZ), at a selected drug loading of 20%. Polymer grades were chosen with variation in molecular weight and degree of hydroxylation to determine the effects on performance. Differential scanning calorimetry, powder X-ray diffraction, polarized light microscopy, size exclusion chromatography, and dissolution testing were used to characterize the amorphous dispersions. An in vivo pharmacokinetic study in rats was also conducted to compare the selected formulation to current market formulations of ITZ. The 4-88 grade of PVAL was determined to be effective at enhancing solubility and bioavailability of itraconazole.

  11. Development of an anti-insect sachet using a polyvinyl alcohol-cinnamon oil polymer strip against Plodia interpunctella.

    PubMed

    Jo, Heon-Joo; Park, Ki-Moon; Min, Sea C; Na, Ja Hyun; Park, Ki Hwan; Han, Jaejoon

    2013-11-01

    Plodia interpunctella is a major storage pest that penetrates into food packaging and causes serious economic losses, as well as posing health risks. The goal of this study was to develop effective anti-insect polymer strips against P. interpunctella by using plant essential oil (EO) and polyvinyl alcohol (PVA). The EO of cinnamon (Cinnamomum zeylanicum, CO) bark was used as an insect repellent, and fumigant mortality and the repellent activity of CO were measured to evaluate subsistent anti-insect properties through newly designed traps. Repellent activity was also examined with several foods to simulate the storage environment. The mortality rate with CO after fumigation for 120 h was 63%. In the repellent assay, CO-treated strips, but not control strips, effectively repelled P. interpunctella in both "with foods" and "without foods" groups. A PVA-CO strip sachet (PCO sachet) was developed to control the volatility of CO, and the PCO sachet demonstrated robust repellent activity. The loading contents of CO at the center and edges of strips were 39.41% and 39.59%, respectively, and through the results of FT-IR, it inferred that CO was physically diffused in the PVA polymer matrix, not forming chemical bonds. In a release test using a gas chromatography, the PCO sachet showed remarkable controlled release of CO. These results demonstrate that the anti-insect effects of CO can be maintained throughout the distribution and storage periods of foods using PCO sachets.

  12. Novel Knob-integrated fiber Bragg grating sensor with polyvinyl alcohol coating for simultaneous relative humidity and temperature measurement.

    PubMed

    Yan, Guofeng; Liang, Yanhong; Lee, El-Hang; He, Sailing

    2015-06-15

    A novel high performance optical fiber sensor for simultaneous measurement of relative humidity (RH) and temperature based on our newly designed knob-integrated fiber Bragg grating (FBG) is proposed and experimentally demonstrated. The knob-shaped taper followed by an FBG works as a multifunctional joint that not only excites the cladding modes but also recouples the cladding modes reflected by the FBG back into the leading single mode fiber. Polyvinyl alcohol (PVA) film is plated on the fiber surface by dip-coating technique as a humidity-to-refractive index (RI) transducer, and affects the intensity of reflected cladding modes by way of evanescent fields. By monitoring the intensity and wavelength of the reflected cladding modes, the RH and temperature variance can be determined simultaneously. Experimental results show an RH sensitivity of up to 1.2 dB/%RH within an RH range of 30-95%, which is significantly better than previously reported values. And the temperature sensitivity of 8.2 pm/°Ccould be achieved in the temperature range of 25-60°C. A fast and reversible time response has also been demonstrated, enabling to pick up a humidity change as fast as 630 ms. The capability of simultaneous measurement of RH and temperature, the fast response, the reusability and the simple fabrication process make this structure a highly promising sensor for real-time practical RH monitoring applications.

  13. Synthesis and characterization of electrospun polyvinyl alcohol nanofibrous scaffolds modified by blending with chitosan for neural tissue engineering.

    PubMed

    Alhosseini, Sanaz Naghavi; Moztarzadeh, Fathollah; Mozafari, Masoud; Asgari, Shadnaz; Dodel, Masumeh; Samadikuchaksaraei, Ali; Kargozar, Saeid; Jalali, Newsha

    2012-01-01

    Among several attempts to integrate tissue engineering concepts into strategies to repair different parts of the human body, neuronal repair stands as a challenging area due to the complexity of the structure and function of the nervous system and the low efficiency of conventional repair approaches. Herein, electrospun polyvinyl alcohol (PVA)/chitosan nanofibrous scaffolds have been synthesized with large pore sizes as potential matrices for nervous tissue engineering and repair. PVA fibers were modified through blending with chitosan and porosity of scaffolds was measured at various levels of their depth through an image analysis method. In addition, the structural, physicochemical, biodegradability, and swelling of the chitosan nanofibrous scaffolds were evaluated. The chitosan-containing scaffolds were used for in vitro cell culture in contact with PC12 nerve cells, and they were found to exhibit the most balanced properties to meet the basic required specifications for nerve cells. It could be concluded that addition of chitosan to the PVA scaffolds enhances viability and proliferation of nerve cells, which increases the biocompatibility of the scaffolds. In fact, addition of a small percentage of chitosan to the PVA scaffolds proved to be a promising approach for synthesis of a neural-friendly polymeric blend.

  14. Preparation and transdermal diffusion evaluation of the prazosin hydrochloride-loaded electrospun poly(vinyl alcohol) fiber mats.

    PubMed

    Shen, Xiaobing; Xu, Qian; Xu, Shi; Li, Jie; Zhang, Niping; Zhang, Ling

    2014-07-01

    This study reports on the use of electrospun polyvinyl alcohol (PVA) nanofiber mats loaded with prazosin hydrochloride (PRH) as a transdermal drug delivery system, investigating the morphology of electrospun PVA nanofibers, the in vitro release characteristics of the drug from the as-spun fibers, and the influence of permeation enhancer (water-resoluble azone, WSA) on transdermal diffusion of PRH through a rat skin. The same was also conducted on the PRH -loaded as-cast PVA films for comparison. Results indicated that the morphology of PRH-loaded PVA fibers observed by scanning electron microscopy (SEM) relied on the electrospinning processing parameters, and the addition of WSA had obvious effects on the diameter and morphology of electrospun PVA fibers. The PRH-loaded electrospun PVA fiber mats exhibited much higher accumulated release dose and release rate of PRH than as-cast PVA films. And WAS can improve the release amount and rate of PRH from drug-loaded samples. The content of PRH in receiver was more than that in the stratum corneum and in the dermis. It was concluded that the PRH-loaded electropun PVA fiber mats as a transdermal patches can be a promising candidate for the conventional preparation.

  15. Biodegradation of high concentration of nitrobenzene by Pseudomonas corrugata embedded in peat-phosphate esterified polyvinyl alcohol.

    PubMed

    Liu, Na; Li, Hai-Jun; Shi, Yue-E; Zhu, Bo-Lin; Gao, Song

    2013-10-01

    Efficiency on biodegradation of high concentration of nitrobenzene (NB) by peat-phosphate esterified polyvinyl alcohol-embedded NB-degrading bacteria Pseudomonas corrugata was conducted compared to free bacteria cells. Its biodegradation kinetics, reuse ability, degradation effect in the absence of the essential element needed for the growth of bacteria and degradation efficiency of the raw water from the contaminated site were also invested. Results show that the degradation rate when the concentration of NB was at 600, 750, and 900 mg/L reached 91.02, 83.23, and 55.9 %, which was higher than that observed in free bacteria at the same concentration levels. Biodegradation kinetics of the material could be well described by first- and zero-order kinetics when the concentration of NB was at 300, 450 mg/L and 600, 750, 900 mg/L, respectively. Stable degradation activity (stayed at a level of approximately 70 %) was displayed during the 11th repeat-batch experiment. The affect of absence of phosphorus in the medium can be abated ascribed to the addition of peat, which contributes with organic matter and other elements such as nitrogen and phosphorus necessary to maintain metabolically active the microorganisms. Effective biodegradation of the raw water from the experimental site revealed that the material can be a potential candidate for treating NB-contaminated wastewater in the practical setting.

  16. Combined nitric oxide-releasing poly(vinyl alcohol) film/F127 hydrogel for accelerating wound healing.

    PubMed

    Schanuel, Fernanda Seabra; Raggio Santos, Karen Slis; Monte-Alto-Costa, Andréa; de Oliveira, Marcelo G

    2015-06-01

    Nitric oxide (NO) releasing biomaterials represent a potential strategy for use as active wound dressings capable of accelerating wound healing. Topical NO-releasing poly(vinyl alcohol) (PVA) films and Pluronic F127 hydrogels (F127) have already exhibited effective skin vasodilation and wound healing actions. In this study, we functionalized PVA films with SNO groups via esterification with a mixture of mercaptosucinic acid (MSA) and thiolactic acid (TLA) followed by S-nitrosation of the SH moieties. These films were combined with an underlying layer of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide), i.e., PEO-PPO-PEO (Pluronic F127) hydrogel and used for the topical treatment of skin lesions in an animal model. The mixed esterification of PVA with MSA and TLA led to chemically crosslinked PVA-SNO films with a high swelling capacity capable of spontaneously releasing NO. Real time NO-release measurements revealed that the hydrogel layer reduces the initial NO burst from the PVA-SNO films. We demonstrate that the combination of PVA-SNO films with F127 hydrogel accelerates wound contraction, decreases wound gap and cellular density and accelerates the inflammatory phase of the lesion. These results were reflected in an increase in myofibroblastic differentiation and collagen type III expression in the cicatricial tissue. Therefore, PVA-SNO films combined with F127 hydrogel may represent a new approach for active wound dressings capable of accelerating wound healing.

  17. Property-based design: optimization and characterization of polyvinyl alcohol (PVA) hydrogel and PVA-matrix composite for artificial cornea.

    PubMed

    Jiang, Hong; Zuo, Yi; Zhang, Li; Li, Jidong; Zhang, Aiming; Li, Yubao; Yang, Xiaochao

    2014-03-01

    Each approach for artificial cornea design is toward the same goal: to develop a material that best mimics the important properties of natural cornea. Accordingly, the selection and optimization of corneal substitute should be based on their physicochemical properties. In this study, three types of polyvinyl alcohol (PVA) hydrogels with different polymerization degree (PVA1799, PVA2499 and PVA2699) were prepared by freeze-thawing techniques. After characterization in terms of transparency, water content, water contact angle, mechanical property, root-mean-square roughness and protein adsorption behavior, the optimized PVA2499 hydrogel with similar properties of natural cornea was selected as a matrix material for artificial cornea. Based on this, a biomimetic artificial cornea was fabricated with core-and-skirt structure: a transparent PVA hydrogel core, surrounding by a ringed PVA-matrix composite skirt that composed of graphite, Fe-doped nano hydroxyapatite (n-Fe-HA) and PVA hydrogel. Different ratio of graphite/n-Fe-HA can tune the skirt color from dark brown to light brown, which well simulates the iris color of Oriental eyes. Moreover, morphologic and mechanical examination showed that an integrated core-and-skirt artificial cornea was formed from an interpenetrating polymer network, no phase separation appeared on the interface between the core and the skirt.

  18. Synthesis and characterization of electrospun polyvinyl alcohol nanofibrous scaffolds modified by blending with chitosan for neural tissue engineering

    PubMed Central

    Alhosseini, Sanaz Naghavi; Moztarzadeh, Fathollah; Mozafari, Masoud; Asgari, Shadnaz; Dodel, Masumeh; Samadikuchaksaraei, Ali; Kargozar, Saeid; Jalali, Newsha

    2012-01-01

    Among several attempts to integrate tissue engineering concepts into strategies to repair different parts of the human body, neuronal repair stands as a challenging area due to the complexity of the structure and function of the nervous system and the low efficiency of conventional repair approaches. Herein, electrospun polyvinyl alcohol (PVA)/chitosan nano-fibrous scaffolds have been synthesized with large pore sizes as potential matrices for nervous tissue engineering and repair. PVA fibers were modified through blending with chitosan and porosity of scaffolds was measured at various levels of their depth through an image analysis method. In addition, the structural, physicochemical, biodegradability, and swelling of the chitosan nanofibrous scaffolds were evaluated. The chitosan-containing scaffolds were used for in vitro cell culture in contact with PC12 nerve cells, and they were found to exhibit the most balanced properties to meet the basic required specifications for nerve cells. It could be concluded that addition of chitosan to the PVA scaffolds enhances viability and proliferation of nerve cells, which increases the biocompatibility of the scaffolds. In fact, addition of a small percentage of chitosan to the PVA scaffolds proved to be a promising approach for synthesis of a neural-friendly polymeric blend. PMID:22275820

  19. Synchronous Improvement of Dispersibility and Electrical Property of Antimony Doped Tin Oxide Nanoparticles Processed by Polyvinyl Alcohol

    NASA Astrophysics Data System (ADS)

    Liu, Shimin; Wen, Bin; Jiang, Weiwei; Liu, Chaoqian; Ding, Wanyu; Wang, Nan; Chai, Weiping

    2015-08-01

    Antimony doped tin oxide (ATO) nanoparticles were prepared by wet chemical coprecipitation method with different contents of polyvinyl alcohol (PVA) dispersant. The prepared ATO nanoparticles have been characterized by means of XRD, SEM, HRTEM, SAED, EDS, bulk density and electrical resistivity measurement. Results indicated that the approach functionalized by PVA dispersant enables a synchronous improvement of two important properties namely the dispersibility and electrical conductivity due to the mechanism of avoiding the formation of agglomeration of nanoparticles, which could be regarded as primary factors for the enhanced electron transfer of powders: The surface area over which are crucial for the interfacial arrangement and electron charge scattering/transfer processes. The bulk density and electrical resistivity decreased to a minimum of 0.90 g/cm3 and 1.44 Ωṡcm at PVA dispersant content of 5%, and increased rapidly at higher PVA contents. The prepared ATO nanoparticles can serve as a kind of effective conductive filler in insulating species such as plastics, textile and rubber.

  20. Poly(vinyl alcohol) gel sublayers for reverse osmosis membranes. I. Insolubilization by acid-catalyzed dehydration

    SciTech Connect

    Immelman, E.; Sanderson, R.D.; Jacobs, E.P.; Van Reenan, A.J. . Inst. of Polymer Science)

    1993-11-10

    Both flat-sheet and tubular composite reverse osmosis (RO) membranes were prepared by depositing aqueous solutions of poly(vinyl alcohol) (PVA) and a dehydration catalyst on asymmetric poly(arylether sulfone) (PES) substrate membranes. The PVA coatings were insolubilized by heat treatment to create stable hydrophilic gel-layer membranes. The influence of variables such as PVA concentration, catalyst concentration, curing time, and curing temperature was investigated. It was shown that a simple manipulation of one or two variables could lead to membranes with widely differing salt retention and water permeability characteristics. The insolubilized PVA coatings were intended to serve as hydrophilic gel sublayers on which ultra thin salt-retention barriers could ultimately be formed by interfacial polycondensation. For this purpose, high-flux gel layers were required, whereas salt-retention capabilities were not regarded as important. However, the promising salt retentions obtained as 2 MPa (up to 85% NaCl retention and 92% MgSO[sub 4] retention) showed that some of these PES-PVA composite membranes could function as medium-retention, medium-flux RO membranes, even in the absence of an interfacially formed salt-retention barrier.

  1. Wound healing potential of a polyvinyl alcohol-blended pectin hydrogel containing Hippophae rahmnoides L. extract in a rat model.

    PubMed

    Kim, Jin; Lee, Chang-Moon

    2017-06-01

    In this study, we investigated the effect of a polyvinyl alcohol-blended pectin hydrogel (PVA-PT HG) containing the extracts of Hippophae rhamnoides L. (H. rhamnoides L.) leaves on wound healing in a rat model. The total phenolic content in the extract solution was 40.64±2.7 GAE mg/g and that of flavonoids was 13.15±1.8 QE mg/g. Of the total flavonoids in HGs, 61.6 and 50.0% were released at pH 5.5 and 7.4 after 60min. In rat acute wound models, the wound size was reduced significantly and the recovery rate was significantly higher after treatment with HG containing the extracts, compared with treatment with the control and HG only. The wound healing effects of the HG containing the extracts were confirmed by histological evaluation of the wound tissue. Therefore, HG containing extracts from H. rhamnoides L. leaves enhanced wound healing effectively, and so may be developed as a cover to promote wound healing.

  2. Horseradish peroxidase-catalyzed formation of hydrogels from chitosan and poly(vinyl alcohol) derivatives both possessing phenolic hydroxyl groups.

    PubMed

    Sakai, Shinji; Khanmohammadi, Mehdi; Khoshfetrat, Ali Baradar; Taya, Masahito

    2014-10-13

    Horseradish peroxidase-catalyzed cross-linking was applied to prepare hydrogels from aqueous solutions containing chitosan and poly(vinyl alcohol) derivatives both possessing phenolic hydroxyl groups (denoted as Ph-chitosan and Ph-PVA, respectively). Comparing the hydrogels prepared from the solution of 1.0% (w/v) Ph-chitosan and 3.0% (w/v) Ph-PVA and that of 3.0% (w/v) Ph-chitosan and 1.0% (w/v) Ph-PVA, the gelation time of the former hydrogel was 47 s, while was 10s longer than that of the latter one. The breaking point for the former hydrogel under stretching (114% strain) was approximately twice larger than that for the latter one. The swelling ratio of the former hydrogel in saline was about half of the latter one. Fibroblastic cells did not adhere on the former hydrogel but adhered and spread on the latter one. The growth of Escherichia coli cells was fully suppressed on the latter hydrogel during 48 h cultivation.

  3. Alkaline direct ethanol fuel cell performance using alkali-impregnated polyvinyl alcohol/functionalized carbon nano-tube solid electrolytes

    NASA Astrophysics Data System (ADS)

    Huang, Chien-Yi; Lin, Jia-Shiun; Pan, Wen-Han; Shih, Chao-Ming; Liu, Ying-Ling; Lue, Shingjiang Jessie

    2016-01-01

    This study investigates the application of a polyvinyl alcohol (PVA)/functionalized carbon nano-tubes (m-CNTs) composite in alkaline direct ethanol fuel cells (ADEFC). The m-CNTs are functionalized with PVA using the ozone mediation method, and the PVA composite containing the modified CNTs is prepared. Adding m-CNT into the PVA matrix enhances the alkaline uptake and the ionic conductivity of the KOH-doped electrolyte. Meanwhile, the m-CNT-containing membrane exhibited a lower swelling ratio and suppressed ethanol permeability compared to the pristine PVA film. The optimal condition for the ADEFC is determined to be under operation at an anode feed of 3 M ethanol in a 5 M KOH solution (at a flow rate of 5 cm3 min-1) with a cathode feed of moisturized oxygen (with a flow rate of 100 cm3 min-1) and the KOH-doped PVA/m-CNT electrolyte. We achieved a peak power density value of 65 mW cm-2 at 60 °C, which is the highest among the ADEFC literature data and several times higher than the proton-exchange direct ethanol fuel cells using sulfonated membrane electrolytes. Therefore, the KOH-doped PVA/m-CNT electrolyte is a suitable solid electrolyte for ADEFCs and has potential for commercialization in alkaline fuel cell applications.

  4. Highly conductive quasi-coaxial electrospun quaternized polyvinyl alcohol nanofibers and composite as high-performance solid electrolytes

    NASA Astrophysics Data System (ADS)

    Liao, Guan-Ming; Li, Pin-Chieh; Lin, Jia-Shiun; Ma, Wei-Ting; Yu, Bor-Chern; Li, Hsieh-Yu; Liu, Ying-Ling; Yang, Chun-Chen; Shih, Chao-Ming; Lue, Shingjiang Jessie

    2016-02-01

    Electrospun quaternized polyvinyl alcohol (Q-PVA) nanofibers are prepared, and a potassium hydroxide (KOH)-doped nanofiber mat demonstrates enhanced ionic conductivity compared with a dense Q-PVA film with KOH doping. The Q-PVA composite containing 5.98% electrospun Q-PVA nanofibers exhibits suppressed methanol permeability. Both the high conductivity and suppressed methanol permeability are attributed to the quasi-coaxial structure of the electrospun nanofibers. The core of the fibers exhibits a more amorphous region that forms highly conductive paths, while the outer shell of the nanofibers contains more polymer crystals that serve as a hard sheath surrounding the soft core. This shell induces mass transfer resistance and creates a tortuous fuel pathway that suppresses methanol permeation. Such a Q-PVA composite is an effective solid electrolyte that makes the use of alkaline fuel cells viable. In a direct methanol alkaline fuel cell operated at 60 °C, a peak power density of 54 mW cm-2 is obtained using the electrospun Q-PVA composite, a 36.4% increase compared with a cell employing a pristine Q-PVA film. These results demonstrate that highly conductive coaxial electrospun nanofibers can be prepared through a single-opening spinneret and provide a possible approach for high-performance electrolyte fabrication.

  5. Performance properties and antibacterial activity of crosslinked films of quaternary ammonium modified starch and poly(vinyl alcohol).

    PubMed

    Sekhavat Pour, Zahra; Makvandi, Pooyan; Ghaemy, Mousa

    2015-09-01

    There has been a growing interest in developing antibacterial polymeric materials. In the present work, novel antibacterial cross-linked blend films were prepared based on polyvinyl alcohol (PVA) and quaternary ammonium starch (ST-GTMAC) using citric acid (CA) as plasticizer and glutaraldehyde (GA) as cross-linker. The ST-GTMAC was successfully synthesized from reaction between water-soluble oxidized starch and glycidyltrimethylammonium chloride (GTMAC). The effect of ST-GTMAC, CA and GA contents on the swelling, solubility, mechanical and thermal properties of the films was investigated. It was found that incorporation of ST-GTMAC reduced UV-transmittance and provided antibacterial properties, increasing GA content increased tensile strength and decreased solubility and swelling degree of the films, while CA acted as plasticizer when its concentration was above 10 wt%. The results showed that ST-GTMAC/PVA/CA/GA film has fair antibacterial activity against Gram-positive (Staphylococcus aureus and Bacillus subtilis) and Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria. These results suggest that the prepared film might be used as potential antibacterial material in medical and packaging applications.

  6. Sharp beveled tip hollow microneedle arrays fabricated by LIGA and 3D soft lithography with polyvinyl alcohol

    NASA Astrophysics Data System (ADS)

    Pérennès, F.; Marmiroli, B.; Matteucci, M.; Tormen, M.; Vaccari, L.; Di Fabrizio, E.

    2006-03-01

    This paper describes a fabrication process of hollow microneedle arrays with a sharp beveled tip for transdermal drug delivery. A master is fabricated through a double deep x-ray lithography process. First, a polymethylmethacrylate (PMMA) sheet is exposed to produce single PMMA parts with a sawtooth profile. The tip angle of each tooth determines the final tip angle of the microneedles. The PMMA parts are assembled and glued on a conductive substrate and then exposed through a second x-ray mask containing an array of hollow triangles as absorbing structures. A metal layer is then electrodeposited around the needles in order to form the future base of the array. A polyvinyl alcohol (PVA) solution is cast on top of the master to form a negative mold of the microneedle array after a low temperature curing and peel-off steps. A liquid PMMA solution is cast on top of the PVA negative mold and after the full PMMA polymerization the PVA is dissolved in water. This fabrication method can be performed in a non-clean room environment and requires little instrumentation. It is therefore compatible with a low-cost mass-fabrication scheme.

  7. Probing the Biomimetic Ice Nucleation Inhibition Activity of Poly(vinyl alcohol) and Comparison to Synthetic and Biological Polymers

    PubMed Central

    2015-01-01

    Nature has evolved many elegant solutions to enable life to flourish at low temperatures by either allowing (tolerance) or preventing (avoidance) ice formation. These processes are typically controlled by ice nucleating proteins or antifreeze proteins, which act to either promote nucleation, prevent nucleation or inhibit ice growth depending on the specific need, respectively. These proteins can be expensive and their mechanisms of action are not understood, limiting their translation, especially into biomedical cryopreservation applications. Here well-defined poly(vinyl alcohol), synthesized by RAFT/MADIX polymerization, is investigated for its ice nucleation inhibition (INI) activity, in contrast to its established ice growth inhibitory properties and compared to other synthetic polymers. It is shown that ice nucleation inhibition activity of PVA has a strong molecular weight dependence; polymers with a degree of polymerization below 200 being an effective inhibitor at just 1 mg.mL–1. Other synthetic and natural polymers, both with and without hydroxyl-functional side chains, showed negligible activity, highlighting the unique ice/water interacting properties of PVA. These findings both aid our understanding of ice nucleation but demonstrate the potential of engineering synthetic polymers as new biomimetics to control ice formation/growth processes PMID:26258729

  8. Graphite oxide incorporated crosslinked polyvinyl alcohol and sulfonated styrene nanocomposite membrane as separating barrier in single chambered microbial fuel cell

    NASA Astrophysics Data System (ADS)

    Rudra, Ruchira; Kumar, Vikash; Pramanik, Nilkamal; Kundu, Patit Paban

    2017-02-01

    Different membranes with varied molar concentrations of graphite oxide (GO), 'in situ' polymerized sulfonated polystyrene (SS) and glutaraldehyde (GA) cross linked polyvinyl alcohol (PVA), have been analyzed as an effective and low cost nanocomposite barrier in single chambered microbial fuel cells (MFCs). The synthesized composite membranes, namely GO0.2, GO0.4 and GO0.6 exhibited comparatively better results with reduced water uptake (WU) and swelling ratios (SR) over the native PVA. The variation in properties is illustrated with membrane analyses, where GO0.4 showed an increased proton conductivity (PC) and ion exchange capacity (IEC) of 0.128 S cm-1 and 0.33 meq g-1 amongst all of the used membranes. In comparison, reduced oxygen diffusivity with lower water uptake showed a two-fold decrease in GO0.4 over pure PVA membrane (∼2.09 × 10-4 cm s-1). A maximum power density of 193.6 mW m-2 (773.33 mW m-3) with a current density of 803.33 mA m-2 were observed with GO0.4 fitted MFC, where ∼81.89% of chemical oxygen demand (COD) was removed using mixed firmicutes, as biocatalyst, in 25 days operation. In effect, the efficacy of GO incorporated crosslinked PVA and SS nanocomposite membrane has been evaluated as a polymer electrolyte membrane for harnessing bio-energy from single chambered MFCs.

  9. Formation of linear polyenes in poly(vinyl alcohol) films catalyzed by phosphotungstic acid, aluminum chloride, and hydrochloric acid

    NASA Astrophysics Data System (ADS)

    Tretinnikov, O. N.; Sushko, N. I.; Malyi, A. B.

    2016-07-01

    Formation of linear polyenes-(CH=CH)n-via acid-catalyzed thermal dehydration of polyvinyl alcohol in 9- to 40-µm-thick films of this polymer containing hydrochloric acid, aluminum chloride, and phosphotungstic acid as dehydration catalysts was studied by electronic absorption spectroscopy. The concentration of long-chain ( n ≥ 8) polyenes in films containing phosphotungstic acid is found to monotonically increase with the duration of thermal treatment of films, although the kinetics of this process is independent of film thickness. In films containing hydrochloric acid and aluminum chloride, the formation rate of polyenes with n ≥ 8 rapidly drops as film thickness decreases and the annealing time increases. As a result, at a film thickness of less than 10-12 µm, long-chain polyenes are not formed at all in these films no matter how long thermal duration is. The reason for this behavior is that hydrochloric acid catalyzing polymer dehydration in these films evaporates from the films during thermal treatment, the evaporation rate inversely depending on film thickness.

  10. Extraordinarily large swelling energy of iodine-treated poly(vinyl alcohol) demonstrated by jump of a film.

    PubMed

    Takamura, Tatsuro; Nozawa, Kazuya; Sugimoto, Yoshiki; Shioya, Masatoshi

    2014-10-15

    Organic material characteristics of volume change and stress generation have attracted the attention of many researchers aiming to develop chemomechanical systems such as artificial muscles and polymer engines having the advantages of high energy density and silent operation. Although polymer gels offer a relatively large actuator stroke, their mechanical properties are relatively poor and the working temperature is relatively low, often limited by the evaporation of liquid if contained. We have developed an iodine-treated poly(vinyl alcohol) having extraordinarily large vapor-induced deswelling stress reaching 59 MPa, which is one to two orders of magnitude greater than those of ordinary polymer gels. Furthermore, this material has extremely large volumetric and gravimetric energy densities reaching 1.3 × 10(6) J m(-3) and 9.6 × 10(2) J kg(-1), respectively, and an elastic modulus of a few GPa and is heat-resistant to at least 200 °C. The high performance of this material can be demonstrated by a jump of a film. © 2014 The Authors. Journal of Polymer Science Part B: Polymer Physics published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 1357-1365.

  11. Ferromagnetism in LaMnO3 Nanoparticles Prepared by Sol-Gel Method Combined with Polyvinyl Alcohol

    NASA Astrophysics Data System (ADS)

    Tola, Pardi S.; Kim, D. H.; Liu, Chunli; Phan, T. L.; Lee, B. W.

    2016-07-01

    This work presents the synthesis of rhombohedral LaMnO3 nanoparticles (NPs) by using a sol-gel method with the assistance of polyvinyl alcohol (PVA), followed with annealing at 700°C for 2 h in air. By changing the PVA amount from 0 ml to 15 ml, we have synthesized LaMnO3 NPs so that their ferromagnetic-paramagnetic phase-transition temperature ( T C) can be tuned in the range between 228 K and 305 K. At 15 K, saturation magnetization ( M s) and coercivity ( H c) values are tunable in the ranges of 32-52 emu/g and 200-258 Oe, respectively, if varying PVA amount from 0 ml to 15 ml. X-ray photoelectron analyses revealed a large amount of La deficiency and oxygen excess in the NPs, particularly for the NPs synthesized with the presence of PVA at a suitable amount (≤10 ml). This leads to a coexistence of Mn3+ and Mn4+ ions, and changes the geometrical structure of nanocrystalline LaMnO3 NPs, as confirmed by x-ray absorption data. We believe that the variation of PVA changed the concentration ratio of Mn3+/Mn4+, enriching a magnetic-phase diagram of LaMnO3 nanoparticles.

  12. Protein aggregation with poly(vinyl) alcohol surfactant reduces double emulsion-encapsulated mammalian cell-free expression

    PubMed Central

    Ho, Kenneth K. Y.; Lee, Jin Woo; Durand, Grégory; Majumder, Sagardip

    2017-01-01

    Development of artificial cell models requires encapsulation of biomolecules within membrane-bound compartments. There have been limited studies of using mammalian cell-free expression (CFE) system as the ‘cytosol’ of artificial cells. We exploit glass capillary droplet microfluidics for the encapsulation of mammalian CFE within double emulsion templated vesicles. The complexity of the physicochemical properties of HeLa cell-free lysate poses a challenge compared with encapsulating simple buffer solutions. In particular, we discovered the formation of aggregates in double emulsion templated vesicles encapsulating mammalian HeLa CFE, but not with bacterial CFE. The aggregates did not arise from insolubility of the proteins made from CFE nor due to the interaction of mammalian CFE with the organic solvents in the middle phase of the double emulsions. We found that aggregation is dependent on the concentration of poly(vinyl) alcohol (PVA) surfactant, a critical double emulsion-stabilizing surfactant, and the lysate concentration in mammalian CFE. Despite vesicle instability and reduced protein expression, we demonstrate protein expression by encapsulating mammalian CFE system. Using mass spectrometry and Western blot, we identified and verified that actin is one of the proteins inside the mammalian CFE that aggregated with PVA surfactant. Our work establishes a baseline description of mammalian CFE system encapsulated in double emulsion templated vesicles as a platform for building artificial cells. PMID:28358875

  13. Enhanced absorption of microwave radiations through flexible polyvinyl alcohol-carbon black/barium hexaferrite composite films

    NASA Astrophysics Data System (ADS)

    Kumar, Sushil; Datt, Gopal; Santhosh Kumar, A.; Abhyankar, A. C.

    2016-10-01

    Flexible microwave absorber composite films of carbon black (CB)/barium hexaferrite nano-discs (BaF) in polyvinyl alcohol (PVA) matrix, fabricated by gel casting, exhibit ˜99.5% attenuation of electromagnetic waves in the entire 8-18 GHz (X and Ku-band) range. The X-ray diffraction and Raman spectroscopy studies confirm the formation of CB-BaF-PVA composite films. The electromagnetic absorption properties of composite films are found to be enhanced with CB content due to the synergetic effect of multiple dielectric and magnetic losses. The 25 wt. % CB grafted PVA-BaF flexible composite films with a thickness of ˜ 2 mm exhibit effective electromagnetic shielding of 23.6 dB with a dominant contribution from absorption mechanism (SEA ˜ 21 dB). The dielectric properties of composite films are further discussed by using the Debye model. The detailed analysis reveals that major contribution to dielectric losses is from dipolar and interfacial polarizations, whereas magnetic losses are predominantly from domain wall displacement.

  14. Characterizing p-channel thin film transistors using ZnO/hydrated polyvinyl alcohol as the conducting channel

    NASA Astrophysics Data System (ADS)

    Liau, Leo Chau-Kuang; Hsu, Tzu-Hsien; Lo, Pei-Hsuan

    2014-08-01

    We report the characteristics of p-channel thin film transistors (p-TFTs) with ZnO/hydrated polyvinyl alcohol (PVA) (ZnO/PVA) conducting channels. The metal-oxide-semiconductor structure of the p-TFTs was composed of indium tin oxide (ITO)/SiO2/ZnO/PVA layers. The TFT was assembled using PVA gel, which was glued to ITO substrates patterned to form source and drain electrodes. The ZnO/PVA composite film acted as an effective conducting film because of the chemisorption reaction at the film interface where free electrons can be generated. The formation of the conducting channel was also affected by VG applied to the TFT. The ZnO/PVA-based TFTs demonstrated p-channel transistor performance, shown by current-voltage (I-V) data analysis. The electrical parameters of the device were evaluated, including the on/off ratio (˜103), threshold voltage (Vth, -1 V), and subthreshold swing (-2.2 V/dec). The PVA/ZnO-based p-TFTs were fabricated using simple and cost-effective approaches instead of doping methods.

  15. Effect of Copper Sulfide Nanoparticles on the Optical and Electrical Behavior of Poly(vinyl alcohol) Films

    NASA Astrophysics Data System (ADS)

    Abdullah, Omed Gh.; Saleem, Salwan A.

    2016-11-01

    Polymer nanocomposite films based on poly(vinyl alcohol) (PVA) containing copper sulfide nanoparticles (CuS) were prepared using in situ chemical reduction and casting techniques. The synthesized nanocomposites were analyzed using x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope, and ultraviolet-visible spectroscopy. The XRD pattern reveals that the CuS nanoparticles incorporated in the PVA showed a crystalline nature. The observed FTIR band shifts indicate the intermolecular interaction between the CuS nanoparticles and the PVA matrix. The absorbance of nanocomposite samples increased with increasing CuS concentration. The optical band gap energy was estimated using Tauc's formula and it decreased with increasing dopant concentration. The conductivity and dielectric behavior of the samples were studied over the frequency range of 300 Hz to 1 MHz in the temperature range of 30-110°C. The ac conductivity was found to increase with the increase of dopant concentration as well as frequency. Moreover, the variation of frequency exponent ( s) indicated that the conduction mechanism was the correlated barrier hopping model. The experimental results reveal that the optical and electrical performance of PVA can be enhanced dramatically by the addition of a small amount of CuS nanoparticles. This improved properties of the PVA/CuS nanocomposite suggest uses in optoelectronic devices.

  16. Influence of absorbed moisture on desizing of poly(vinyl alcohol) on cotton fabrics during atmospheric pressure plasma jet treatment

    NASA Astrophysics Data System (ADS)

    Peng, Shujing; Liu, Xiulan; Sun, Jie; Gao, Zhiqiang; Yao, Lan; Qiu, Yiping

    2010-04-01

    This paper studies the influence of moisture absorption of cotton fabrics on the effectiveness of atmospheric pressure plasma jet (APPJ) on desizing of polyvinyl alcohol (PVA). Cotton fabrics with three different moisture regains (MR), namely 1.8%, 7.3%, and 28.4% corresponding to 10%, 65%, and 98% of relative humidity respectively, are treated for 16 s, 32 s, 48 s, and 64 s. X-ray photoelectron spectroscopy analysis indicates that the plasma treated PVA has higher oxygen concentration than the control. Mass loss results show that the fabric with the highest MR has the largest mass loss after 64 s plasma exposure. Solubility measurement reveals that the sample with the lowest MR has the highest desizing efficacy and the percent desizing ratio reaches 96% after 64 s exposure plus a 20 min hot wash, which is shown as clean as the unsized sample through scanning electron microscopy analysis. The yarn tensile strength test results show that APPJ has no negative effect on fabric tensile strength.

  17. Characterizing p-channel thin film transistors using ZnO/hydrated polyvinyl alcohol as the conducting channel

    SciTech Connect

    Liau, Leo Chau-Kuang Hsu, Tzu-Hsien; Lo, Pei-Hsuan

    2014-08-11

    We report the characteristics of p-channel thin film transistors (p-TFTs) with ZnO/hydrated polyvinyl alcohol (PVA) (ZnO/PVA) conducting channels. The metal-oxide-semiconductor structure of the p-TFTs was composed of indium tin oxide (ITO)/SiO{sub 2}/ZnO/PVA layers. The TFT was assembled using PVA gel, which was glued to ITO substrates patterned to form source and drain electrodes. The ZnO/PVA composite film acted as an effective conducting film because of the chemisorption reaction at the film interface where free electrons can be generated. The formation of the conducting channel was also affected by V{sub G} applied to the TFT. The ZnO/PVA-based TFTs demonstrated p-channel transistor performance, shown by current-voltage (I-V) data analysis. The electrical parameters of the device were evaluated, including the on/off ratio (∼10{sup 3}), threshold voltage (V{sub th}, −1 V), and subthreshold swing (−2.2 V/dec). The PVA/ZnO-based p-TFTs were fabricated using simple and cost-effective approaches instead of doping methods.

  18. Effect of electron beam irradiation on the structural, thermal and optical properties of poly(vinyl alcohol) thin film

    NASA Astrophysics Data System (ADS)

    Nouh, S. A.; Bahareth, Radiyah A.

    2013-04-01

    Poly(vinyl alcohol) (PVA) polymer was prepared using the casting technique. The obtained PVA thin films have been irradiated with electron beam doses ranging from 20 to 300 kGy. The resultant effect of electron beam irradiation on the structural properties of PVA has been investigated using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), while the thermal properties have been investigated using thermo-gravimetric analysis and differential thermal analysis (DTA). The onset temperature of decomposition T 0 and activation energy of thermal decomposition E a were calculated, results indicate that the PVA thin film decomposes in one main weight loss stage. Also, the electron beam irradiation in dose range 95-210 kGy led to a more compact structure of the PVA polymer, which resulted in an improvement in its thermal stability with an increase in the activation energy of thermal decomposition. The variation of transition temperatures with electron beam dose has been determined using DTA. The PVA thermograms were characterized by the appearance of an endothermic peak due to melting. In addition, the transmission of the PVA samples and any color changes were studied. The color intensity Δ E was greatly increased with increasing electron beam dose, and was accompanied by a significant increase in the blue color component.

  19. Improved biocomposite development of poly(vinyl alcohol) and hydroxyapatite for tissue engineering scaffold fabrication using selective laser sintering.

    PubMed

    Wiria, Florencia Edith; Chua, Chee Kai; Leong, Kah Fai; Quah, Zai Yan; Chandrasekaran, Margam; Lee, Mun Wai

    2008-03-01

    In scaffold guided tissue engineering (TE), temporary three-dimensional scaffolds are essential to guide and support cell proliferation. Selective Laser Sintering (SLS) is studied for the development of such scaffolds by eliminating pore spatial control problems faced in conventional scaffolds fabrication methods. SLS offers good user control over the scaffold's microstructures by adjusting its main processing parameters, namely the laser power, scan speed and part bed temperature. This research focuses on the improvements in the fabrication of TE scaffolds using SLS with powder biomaterials, namely hydroxyapatite (HA) and poly(vinyl alcohol) (PVA). Grinding of as-received PVA powder to varying particle sizes and two methods of mixing are investigated as the preparation process to determine a better mixing method that would enhance the mixture homogeneity. Suitable sintering conditions for the improved biocomposite are then achieved by varying the important process parameters such as laser power, scan speed and part bed temperature.SLS fabricated samples are characterized using Fourier Transform Infrared Spectrometer (FTIR) and Scanning Electron Microscope (SEM). FTIR results show that the grinding and sintering processes neither compromise the chemical composition of the PVA nor cause undue degradation. Visual analysis of the grinding, powder mixing and sintering effect are carried out with SEM. The SEM observations show improvements in the sintering effects. The favorable outcome ascertains PVA/HA biocomposite as a suitable material to be processed by SLS for TE scaffolds.

  20. Spatial-phase-modulation-based study of polyvinyl-alcohol/acrylamide photopolymers in the low spatial frequency range.

    PubMed

    Gallego, Sergi; Márquez, André; Méndez, David; Marini, Stephan; Beléndez, Augusto; Pascual, Inmaculada

    2009-08-01

    Photopolymers are appealing materials for the fabrication of diffractive optical elements (DOEs). We evaluate the possibilities of polyvinyl-alcohol/acrylamide-based photopolymers to store diffractive elements with low spatial frequencies. We record gratings with different spatial frequencies in the material and analyze the material behavior measuring the transmitted and the reflected orders as a function of exposition. We study two different compositions for the photopolymer, with and without a cross-linker. The values of diffraction efficiency achieved for both compositions make the material suitable to record DOEs with long spatial periods. Assuming a Fermi-Dirac-function-based profile, we fitted the diffracted intensities (up to the eighth order) to obtain the phase profile of the recorded gratings. This analysis shows that it is possible to achieve a phase shift larger than 2pi rad with steep edges in the periodic phase profile. In the case of the measurements in reflection, we have obtained information dealing with the surface profile, which show that it has a smooth shape with an extremely large phase-modulation depth.

  1. Recycled Poly(vinyl alcohol) Sponge for Carbon Encapsulation of Size-Tunable Tin Dioxide Nanocrystalline Composites.

    PubMed

    Ma, Yue; Tai, Cheuk-Wai; Gustafsson, Torbjörn; Edström, Kristina

    2015-06-22

    The recycling of industrial materials could reduce their environmental impact and waste haulage fees and result in sustainable manufacturing. In this work, commercial poly(vinyl alcohol) (PVA) sponges are recycled into a macroporous carbon matrix to encapsulate size-tunable SnO2 nanocrystals as anode materials for lithium-ion batteries (LIBs) through a scalable, flash-combustion method. The hydroxyl groups present copiously in the recycled PVA sponges guarantee a uniform chemical coupling with a tin(IV) citrate complex through intermolecular hydrogen bonds. Then, a scalable, ultrafast combustion process (30 s) carbonizes the PVA sponge into a 3D carbon matrix. This PVA-sponge-derived carbon could not only buffer the volume fluctuations upon the Li-Sn alloying and dealloying processes but also afford a mixed conductive network, that is, a continuous carbon framework for electrical transport and macropores for facile electrolyte percolation. The best-performing electrode based on this composite delivers a rate performance up to 9.72 C (4 A g(-1) ) and long-term cyclability (500 cycles) for Li(+) ion storage. Moreover, cyclic voltammograms demonstrate the coexistence of alloying and dealloying processes and non-diffusion-controlled pseudocapacitive behavior, which collectively contribute to the high-rate Li(+) ion storage.

  2. Anisotropic polyvinyl alcohol hydrogel phantom for shear wave elastography in fibrous biological soft tissue: a multimodality characterization

    NASA Astrophysics Data System (ADS)

    Chatelin, Simon; Bernal, Miguel; Deffieux, Thomas; Papadacci, Clément; Flaud, Patrice; Nahas, Amir; Boccara, Claude; Gennisson, Jean-Luc; Tanter, Mickael; Pernot, Mathieu

    2014-11-01

    Shear wave elastography imaging techniques provide quantitative measurement of soft tissues elastic properties. Tendons, muscles and cerebral tissues are composed of fibers, which induce a strong anisotropic effect on the mechanical behavior. Currently, these tissues cannot be accurately represented by existing elastography phantoms. Recently, a novel approach for orthotropic hydrogel mimicking soft tissues has been developed (Millon et al 2006 J. Biomed. Mater. Res. B 305-11). The mechanical anisotropy is induced in a polyvinyl alcohol (PVA) cryogel by stretching the physical crosslinks of the polymeric chains while undergoing freeze/thaw cycles. In the present study we propose an original multimodality imaging characterization of this new transverse isotropic (TI) PVA hydrogel. Multiple properties were investigated using a large variety of techniques at different scales compared with an isotropic PVA hydrogel undergoing similar imaging and rheology protocols. The anisotropic mechanical (dynamic and static) properties were studied using supersonic shear wave imaging technique, full-field optical coherence tomography (FFOCT) strain imaging and classical linear rheometry using dynamic mechanical analysis. The anisotropic optical and ultrasonic spatial coherence properties were measured by FFOCT volumetric imaging and backscatter tensor imaging, respectively. Correlation of mechanical and optical properties demonstrates the complementarity of these techniques for the study of anisotropy on a multi-scale range as well as the potential of this TI phantom as fibrous tissue-mimicking phantom for shear wave elastographic applications.

  3. Changes induced by UV radiation in the presence of sodium benzoate in films formulated with polyvinyl alcohol and carboxymethyl cellulose.

    PubMed

    Villarruel, S; Giannuzzi, L; Rivero, S; Pinotti, A

    2015-11-01

    This work was focused on: i) developing single and blend films based on carboxymethyl cellulose (CMC) and polyvinyl alcohol (PVOH) studying their properties, ii) analyzing the interactions between CMC and PVOH and their modifications UV-induced in the presence of sodium benzoate (SB), and iii) evaluating the antimicrobial capacity of blend films containing SB with and without UV treatment. Once the blend films with SB were exposed to UV radiation, they exhibited lower moisture content as well as a greater elongation at break and rougher surfaces compared to those without treatment. Considering oxygen barrier properties, the low values obtained would allow their application as packaging with selective oxygen permeability. Moreover, the characteristics of the amorphous phase of the matrix prevailed with a rearrangement of the structure of the polymer chain, causing a decrease of the crystallinity degree. These results were supported by X-rays and DSC analysis. FT-IR spectra reflected some degree of polymer-polymer interaction at a molecular level in the amorphous regions. The incorporation of sodium benzoate combined with UV treatment in blend films was positive from the microbial point of view because of the growth inhibition of a wide spectrum of microorganisms. From a physicochemical perspective, the UV treatment of films also changed their morphology rendering them more insoluble in water, turning the functionalized blend films into a potential material to be applied as food packaging.

  4. Biodegradation behaviors and water adsorption of poly(vinyl alcohol)/starch/carboxymethyl cellulose/clay nanocomposites

    NASA Astrophysics Data System (ADS)

    Taghizadeh, Mohammad Taghi; Sabouri, Narges

    2013-09-01

    The focus of this work is to study the effect of sodium montmorillonite (MMT-Na) clay content on the rate and extent of enzymatic hydrolysis polyvinyl alcohol (PVA)/starch (S)/carboxymethyl cellulose (CMC) blends using enzyme cellulase. The rate of glucose production from each nanocomposite substrates was most rapid for the substrate without MMT-Na and decreased with the addition of MMT-Na for PVA/S/CMC blend (51.5 μg/ml h), PVA/S/CMC/1% MMT (45.4 μg/ml h), PVA/S/CMC/3% MMT (42.8 μg/ml h), and PVA/S/CMC/5% MMT (39.2 μg/ml h). The results of this study have revealed that films with MMT-Na content at 5 wt.% exhibited a significantly reduced rate and extent of hydrolysis. Enzymatic degradation behavior of MMT-Na containing nanocomposites of PVA/S/CMC was based on the determinations of weight loss and the reducing sugars. The degraded residues have been characterized by various analytical techniques, such as Fourier transform infrared spectroscopy, scanning electronic microscopy, and UV-vis spectroscopy.

  5. Degradation of dimethyl-sulfoxide-containing wastewater using airlift bioreactor by polyvinyl-alcohol-immobilized cell beads.

    PubMed

    He, Sin-Yi; Lin, Yun-Huin; Hou, Kuan-Yun; Hwang, Sz-Chwun John

    2011-05-01

    Airlift bioreactor containing polyvinyl-alcohol-immobilized cell beads was investigated for its capability of biodegradation of dimethyl sulfoxide (DMSO) in term of sludge characteristics including the strategy of acclimation with sucrose and the protection of microorganism from poisoning of DMSO by PVA cell beads. Media condition with sucrose at 50 mg L(-1) was beneficial to the biodegradation of DMSO in the fresh PVA entrapped-sludge, but became insignificant in the acclimated one as for tolerance of DMSO toxicity. The removal efficiency of DMSO had the highest rate at 1.42-kg DMSO per kilogram of suspended solid per day after series acclimation batches in the oxygen-enriched airlift bioreactor treated with the 1187.4 mg L(-1) of DMSO. Microbial consortium was required for the complete biodegradation of DMSO without any dimethyl sulfide produced. Pseudomonas sp. W1, excreting extracellular monooxygenase identified by indole, was isolated to be one of the most effective DMSO-degrading microorganism in our airlift bioreactor.

  6. Effects of Molecular Weight upon Irradiation-Cross-Linked Poly(vinyl alcohol)/Clay Aerogel Properties.

    PubMed

    Chen, Hong-Bing; Zhao, Yan; Shen, Peng; Wang, Jun-Sheng; Huang, Wei; Schiraldi, David A

    2015-09-16

    Facile fabrication of mechanically strong poly(vinyl alcohol) (PVOH)/clay aerogel composites through a combination of increasing polymer molecular weights and gamma irradiation-cross-linking is reported herein. The aerogels produced from high polymer molecular weights exhibit significantly increased compressive moduli, similar to the effect of irradiation-induced cross-linking. The required irradiation dose for fabricating strong PVOH composite aerogels with dense microstructure decreased with increasing polymer molecular weight. Neither thermal stability nor flammability was significantly changed by altering the polymer molecular weight or by modest gamma irradiation, but they were highly dependent upon the polymer/clay ratio in the aerogel. Optimization of the mechanical, thermal, and flammability properties of these composite aerogels could therefore be obtained by using relatively low levels of polymer, with very high polymer molecular weight, or lower molecular weight coupled with moderate gamma irradiation. The facile preparation of strong, low flammability aerogels is an alternative to traditional polymer foams in applications where fire safety is important.

  7. Dynamic modification of poly(methyl methacrylate) chips using poly(vinyl alcohol) for glycosaminoglycan disaccharide isomer separation.

    PubMed

    Zhang, Yong; Ping, Guichen; Kaji, Noritada; Tokeshi, Manabu; Baba, Yoshinobu

    2007-09-01

    We describe a microchip electrophoresis (MCE) method for the assay of unsaturated disaccharides of chondroitin sulfates, dermatan sulfates, and hyaluronic acid (HA). Poly(vinyl alcohol) (PVA) could be irreversibly adsorbed onto poly(methyl methacrylate) (PMMA) substrates and this approach was applicable for dynamic coating. The characteristics of the PMMA surface with PVA coating were evaluated in terms of the wettability, EOF, and adsorption of 2-aminoacridone (AMAC)-labeled disaccharide. The water contact angle decreased from 73 degrees on a pristine PMMA surface to 37.5 degrees on a PVA-coated surface, indicating that the PVA coating increased hydrophilicity. EOF was reduced approximately twofold and was relatively stable. Scanning electron microscopy and fluorescence microscopy images showed that adsorption of AMAC-labeled disaccharides was dramatically suppressed. Using the PVA coating, baseline separation of two pairs of glycosaminoglycan (GAG) disaccharide isomers, DeltaDi-diS(B)/DeltaDi-diS(D) and DeltaDi-0S/DeltaDi-HA, was achieved in Tris-borate buffer within 130 s by MCE.

  8. Enhanced cellular delivery of idarubicin by surface modification of propyl starch nanoparticles employing pteroic acid conjugated polyvinyl alcohol.

    PubMed

    Jain, Ratnesh; Dandekar, Prajakta; Loretz, Brigitta; Melero, Ana; Stauner, Thomas; Wenz, Gerhard; Koch, Marcus; Lehr, Claus-Michael

    2011-11-25

    Enhanced intracellular internalization of the anti-cancer active idarubicin (IDA) was achieved through appropriate surface modification of IDA loaded propyl starch nanoparticles. This was conducted by synthesizing pteroic acid modified polyvinyl alcohol (ptPVA) and employing this stabilizer for formulating the said nanoparticles. Pteroic acid attached at the nanoparticles improved the surface protein adsorption of the nanoparticle, a condition which the nanoparticles would largely experience in vitro and in vivo and hence improve their cellular internalization. Spherical, homogenous IDA nanoparticles (214 ± 5 nm) with surface modified by ptPVA were formulated using the solvent emulsification-diffusion technique. The encapsulation efficiency and drug loading amounted around 85%. In vitro release studies indicated a controlled release of IDA. Safety and efficacy of the nanoparticles was confirmed by suitable cellular cytotoxicity assays. Protein binding studies indicated a higher adsorption of the model protein on nanoparticles formulated with ptPVA as compared to PVA. Cellular uptake studies by confocal laser scanning microscopy revealed a higher cellular uptake of ptPVA stabilized nanoparticles thus confirming the proposed hypothesis of higher protein adsorption being responsible for higher cellular internalization.

  9. Extraordinarily large swelling energy of iodine-treated poly(vinyl alcohol) demonstrated by jump of a film

    PubMed Central

    Takamura, Tatsuro; Nozawa, Kazuya; Sugimoto, Yoshiki; Shioya, Masatoshi

    2014-01-01

    Organic material characteristics of volume change and stress generation have attracted the attention of many researchers aiming to develop chemomechanical systems such as artificial muscles and polymer engines having the advantages of high energy density and silent operation. Although polymer gels offer a relatively large actuator stroke, their mechanical properties are relatively poor and the working temperature is relatively low, often limited by the evaporation of liquid if contained. We have developed an iodine-treated poly(vinyl alcohol) having extraordinarily large vapor-induced deswelling stress reaching 59 MPa, which is one to two orders of magnitude greater than those of ordinary polymer gels. Furthermore, this material has extremely large volumetric and gravimetric energy densities reaching 1.3 × 106 J m−3 and 9.6 × 102 J kg−1, respectively, and an elastic modulus of a few GPa and is heat-resistant to at least 200 °C. The high performance of this material can be demonstrated by a jump of a film. © 2014 The Authors. Journal of Polymer Science Part B: Polymer Physics published by Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 1357–1365 PMID:25678738

  10. Roles of tryptophan residue and disulfide bond in the variable lid region of oxidized polyvinyl alcohol hydrolase.

    PubMed

    Yang, Yu; Ko, Tzu-Ping; Liu, Long; Li, Jianghua; Huang, Chun-Hsiang; Chen, Jian; Guo, Rey-Ting; Du, Guocheng

    2014-09-26

    Oxidized polyvinyl alcohol hydrolase (OPH) catalyzes the cleavage of C-C bond in β-diketone. It belongs to the α/β-hydrolase family and contains a unique lid region that covers the active site. The lid is the most variable region when pOPH from Pseudomonas sp. VM15C and sOPH from Sphingopyxis sp. 113P3 are compared. The wild-type enzymes and the pOPH mutants W255A, W255Y and W255F were analyzed for lipase activity by using p-nitrophenyl (pNP) esters as the substrates. The wild-type enzymes showed increased Km and decreased kcat/Km with the acyl chain length, and the mutants showed reduced kcat/Km for pNP acetate, indicating the importance of Trp255 in sequestering the active site from solvent. The significantly lower activity for pNP butyrate can be a result of product inhibition, as suggested by the complex crystal structures, in which butyric acid, DMSO or PEG occupied the same substrate-binding cleft. The mutant activity was retained with pNP caprylate and pNP laurate as the substrates, reflecting the amphipathic nature of the cleft. Moreover, the disulfide bond formation of Cys257/267 is important for the activity of pOPH, but it is not essential for sOPH, which has a shorter lid structure.

  11. Therapeutic-Ultrasound-Triggered Shape Memory of a Melamine-Enhanced Poly(vinyl alcohol) Physical Hydrogel.

    PubMed

    Li, Guo; Yan, Qiang; Xia, Hesheng; Zhao, Yue

    2015-06-10

    Therapeutic-ultrasound-triggered shape memory was demonstrated for the first time with a melamine-enhanced poly(vinyl alcohol) (PVA) physical hydrogel. The addition of a small amount of melamine (up to 1.5 wt %) in PVA results in a strong hydrogel due to the multiple H-bonding between the two constituents. A temporary shape of the hydrogel can be obtained by deformation of the hydrogel (∼65 wt % water) at room temperature, followed by fixation of the deformation by freezing/thawing the hydrogel under strain, which induces crystallization of PVA. We show that the ultrasound delivered by a commercially available device designed for the patient's pain relief could trigger the shape recovery process as a result of ultrasound-induced local heating in the hydrogel that melts the crystallized PVA cross-linking. This hydrogel is thus interesting for potential applications because it combines many desirable properties, being mechanically strong, biocompatible, and self-healable and displaying the shape memory capability triggered by a physiological stimulus.

  12. Preparation and properties of graphene oxide-regenerated cellulose/polyvinyl alcohol hydrogel with pH-sensitive behavior.

    PubMed

    Rui-Hong, Xie; Peng-Gang, Ren; Jian, Hui; Fang, Ren; Lian-Zhen, Ren; Zhen-Feng, Sun

    2016-03-15

    In this study, graphene oxide reinforced regenerated cellulose/polyvinyl alcohol (GO-RCE/PVA) ternary hydrogels were successfully prepared via a repeated freezing and thawing method in NaOH/urea aqueous solution. The effect of GO content on the mechanical properties, swelling behavior, water content of composite hydrogels was investigated. It was found that the mechanical properties of GO-RCE/PVA ternary hydrogels were largely enhanced relative to RCE/PVA hydrogels. With the addition of 1.0wt% GO, the tensile strength was increased by 40.4% from 0.52MPa to 0.73MPa, accompanied by the increase of the elongation at break (from 103% to 238%). Meanwhile, GO-RCE/PVA ternary hydrogels performed the excellent pH-sensitivity, and the higher pH leaded to higher swelling ratio. With 0.8wt% GO loading, the swelling ratio of GO-RCE/PVA ternary hydrogel was improved from 150% (pH=2) to 310% (pH=14). In addition, a slight increase in the water content of the ternary hydrogel was achieved with increasing concentrations of GO. It is believed that this novel ternary hydrogels is a promising material in the application of biomedical engineering and intelligent devices.

  13. Poly(vinyl alcohol)-borate hydro/cosolvent gels: viscoelastic properties, solubilizing power, and application to art conservation.

    PubMed

    Carretti, Emiliano; Grassi, Scilla; Cossalter, Manuela; Natali, Irene; Caminati, Gabriella; Weiss, Richard G; Baglioni, Piero; Dei, Luigi

    2009-08-04

    We report the development of a new type of hydrogel in which a cosolvent has been added to the water component. The gel networks are based on the well-known poly(vinyl alcohol)-borate systems (PVA-borate). However, it is shown that the rheological and solubilizing properties of the hydrogels can be modified drastically by the addition of a cosolvent. The studies have focused on 1-propanol as the added liquid, although it is shown that others (propylene carbonate, 1-pentanol, cyclohexanone, and 2-butanol) are amenable to making modified hydrogels as well. In addition to the rheological measurements, the gels have been investigated by differential scanning calorimetry (free water index) and determination of their solubilizing power. Finally, the gels have been applied to clean and oxidized varnish (patina) from the surface of a XVI-XVII century oil-on-wood painting by Ludovico Cardi detto il Cigoli. The mode of cleaning by and removal of the PVA-borate water/1-propanol gel from the painted surface demonstrate several advantages over other gels used in art conservation.

  14. Controlled release of theophylline from poly(vinyl alcohol) hydrogels/porous silicon nanostructured systems

    NASA Astrophysics Data System (ADS)

    Cervantes-Rincón, N.; Medellín-Rodríguez, F. J.; Escobar-Barrios, V. A.; Palestino, G.

    2013-03-01

    In this research, hybrid hydrogels of poly (vinyl alcohol)/ porous silicon (PSi)/theophylline were synthesized by the freezing and thawing method. We evaluated the influence of the synthesis parameters of the poly (vinyl alcohol) (PVA) hydrogels in relation to their ability to swell and drug released. The parameters studied (using an experimental design developed in Minitab 16) were the polymer concentration, the freezing temperature and the number of freezing/thawing (f/t) cycles. Nanostructured porous silicon particles (NsPSi) and theophylline were added within the polymer matrix to increase the drug charge and the polymer mechanical strength. The hybrid hydrogels were characterized by Infrared Spectroscopy Fourier Transform (FTIR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Differential Scanning Calorimetry (DSC), drug delivery kinetics were engineered according to the desired drug release schedule.

  15. Evaluation of hydrophobic polyvinyl-alcohol formaldehyde sponges as absorbents for oil spill.

    PubMed

    Pan, Yanxiong; Shi, Kai; Peng, Chao; Wang, Weicai; Liu, Zhi; Ji, Xiangling

    2014-06-11

    Macroporous materials are a class of absorbents used for oil spill cleanup. In this article, novel macroporous and hydrophobic polyvinyl formaldehyde (PVF-H) sponges were prepared by the reaction of stearoyl chloride with hydroxyl groups of hydrophilic PVF sponge at different temperatures. Attenuated total reflectance-infrared (ATR-IR) spectroscopy confirmed the successfully anchoring of hydrophobic stearoyl groups on the PVF networks. Scanning electron microscopy (SEM) images demonstrated that the as-prepared PVF-H had interconnected open-cell structures, and mercury intrusion porosimetry indicated that the average pore size ranged from 60 to 90 μm and porosity was greater than 94.8%. Such PVF-H sponges can absorb oil products effectively, such as toluene, n-hexane, kerosene, soybean oil, hydraulic oil, and crude oil up to 13.7 g·g(-1) to 56.6 g·g(-1), and this level of absorption was approximately 2-4 times higher than that absorbed by commercial polypropylene nonwoven mat. In low-viscosity oils, the samples can reach the saturated absorption amount only in 1 min, but in higher-viscosity oils, absorption equilibrium can be reached in 10 min. In a simulated oil slick system, these macroporous and hydrophobic sponges can still maintain high oil absorption capacities within the range of 14.4 g·g(-1) to 57.6 g·g(-1), whereas a relatively low absorption rate (approximately 20 min) indicated high absorption performance and excellent selectivity in the oil-water mixture. In addition, the absorbed oils were collected effectively only through a simple squeeze. The PVF-H sponges were subjected to 35 absorption-squeeze cycles and exhibited good reusability and 90% recovery for oils. The samples prepared at different temperatures differed in their absorption capacities to some extent. However, this new kind of macroporous and PVF-H sponges had excellent absorption performance on oil products.

  16. Synergistic toughening of bioinspired poly(vinyl alcohol)-clay-nanofibrillar cellulose artificial nacre.

    PubMed

    Wang, Jianfeng; Cheng, Qunfeng; Lin, Ling; Jiang, Lei

    2014-03-25

    Inspired by the layered aragonite platelet/nanofibrillar chitin/protein ternary structure and integration of extraordinary strength and toughness of natural nacre, artificial nacre based on clay platelet/nanofibrillar cellulose/poly(vinyl alcohol) is constructed through an evaporation-induced self-assembly technique. The synergistic toughening effect from clay platelets and nanofibrillar cellulose is successfully demonstrated. The artificial nacre achieves an excellent balance of strength and toughness and a fatigue-resistant property, superior to natural nacre and other conventional layered clay/polymer binary composites.

  17. Viscometric Studies in Dilute Solution Mixtures of Chitosan and Microcrystalline Chitosan with Poly(vinyl alcohol).

    PubMed

    Lewandowska, Katarzyna

    2013-01-01

    The viscosity behavior of aqueous mixtures formed by a polyelectrolyte (A) and a neutral polymer (B), such as chitosan/poly(vinyl alcohol) (Ch/PVA) and microcrystalline chitosan/poly(vinyl alcohol) (MCCh/PVA), have been investigated at 25 °C. The intrinsic viscosity and the viscosity interaction parameter of each polymer in 0.1 mol·dm(-3) CH3COOH/0.2 mol·dm(-3) NaCl solution as well as the ternary systems (polymer A/polymer B/solvent) have been determined and have served for estimation of the miscibility of different polymer mixtures by means of the method of classical dilution. By comparing the experimental and ideal viscosity data it is clearly seen that the satisfaction of the miscibility criterion depends on the definition of the ideal parameter [Formula: see text]. If the [Formula: see text] parameter is defined according to the Krigbaum-Wall criterion and Garcia criterion, the investigated blends of Ch/PVA satisfy the miscibility criterion. In the case of MCCh/PVA blends, the polymeric components show poor miscibility. Additionally, the viscosity results show that the degree of miscibility depends on the molecular weight of chitosan and on the degree of PVA hydrolysis.

  18. Fabrication of Poly (methyl methacrylate) and Poly(vinyl alcohol) Thin Film Capacitors on Flexible Substrates

    NASA Astrophysics Data System (ADS)

    Salim, Bindu; Meenaa Pria KNJ, Jaisree; Alagappan, M.; Kandaswamy, A.

    2015-11-01

    Flexible electronics is becoming more popular with introduction of more and more organic conducting materials and processes for making thin films. The use of polymers as gate dielectric has over ruled the usage of conventional inorganic oxides in Organic Thin Film Transistors (OTFTs) on account of its solution process ability and ease of making highly insulating thin film. In this work Capacitance is fabricated with polymeric dielectrics namely poly (methyl methacrylate) - PMMA and poly (vinyl alcohol) - PVA. The electrodes used for these capacitors are Indium Tin Oxide (ITO) and Aluminium. Capacitance value of 9.5nF/cm2 and 33.12nF/cm2 is achieved for thickness of 510 nm of PMMA and 80 nm of PVA respectively. This study on capacitance can be used for assessing the suitability of these polymers as gate insulators in OTFTs.

  19. A novel polyvinyl alcohol hydrogel functionalized with organic boundary lubricant for use as low-friction cartilage substitute: synthesis, physical/chemical, mechanical, and friction characterization.

    PubMed

    Blum, Michelle M; Ovaert, Timothy C

    2012-10-01

    A novel material design was developed by functionalizing polyvinyl alcohol hydrogel with an organic low-friction boundary lubricant (molar ratios of 0.2, 0.5, and 1.0 moles of lauroyl chloride). The hydrogels were fabricated using two different techniques. First, the boundary lubricant was initially functionalized to the polymer, then the hydrogels were created by physically crosslinking the reacted polymer. Second, hydrogels were initially created by crosslinking pure polyvinyl alcohol, with the functionalization reaction performed on the fully formed gel. After the reaction, Fourier transform infrared spectroscopy and attenuated total reflectance spectra revealed a clear ester peak, the diminishment of the alcohol peak, and the amplification of the alkyl peaks, which confirmed attachment of the hydrocarbon chains to the polymer. Additional chemical characterization occurred through elemental analysis where an average increase of 22% carbon and 40% hydrogen provided further confirmation of attachment. Physical characterization of the boundary lubricant functionalized hydrogels was performed by water content and contact angle measurements. Water content dependency showed that method 1 had a direct relationship with boundary lubricant concentration, and method 2 displayed an inverse relationship. The contact angle increased as boundary lubricant concentration increased for the pure matrix material for both processing methods, suggesting that the hydrocarbons produced surface properties that mimic natural cartilage, and contact behavior of the biphasic system was dependent on processing method. Friction tests demonstrated a significant decrease in friction coefficient, with a maximum decrease of 70% and a minimum decrease of 24% for boundary lubricant functionalized hydrogels compared with nonfunctionalized polyvinyl alcohol hydrogels.

  20. Bioinspired design and macroscopic assembly of poly(vinyl alcohol)-coated graphene into kilometers-long fibers

    NASA Astrophysics Data System (ADS)

    Kou, Liang; Gao, Chao

    2013-05-01

    Nacre is characterized by its excellent mechanical performance due to the well-recognized ``brick and mortar'' structure. Many efforts have been applied to make nacre-mimicking materials, but it is still a big challenge to realize their continuous production. Here, we prepared sandwich-like building blocks of poly(vinyl alcohol) (PVA)-coated graphene, and achieved high-nanofiller-content kilometers-long fibers by continuous wet-spinning assembly technology. The fibers have a strict ``brick and mortar'' layered structure, with graphene sheet as rigid brick and PVA as soft mortar. The mortar thickness can be precisely tuned from 2.01 to 3.31 nm by the weight feed ratio of PVA to graphene, as demonstrated by both atomic force microscopy and X-ray diffraction measurements. The mechanical strength of the nacre-mimicking fibers increases with increasing the content of PVA, and it rises gradually from 81 MPa for the fiber with 53.1 wt% PVA to 161 MPa for the fiber with 65.8 wt% PVA. The mechanical performance of our fibers was independent of the molecular weight (MW) of PVA in the wide range of 2-100 kDa, indicating that low MW polymers can also be used to make strong nanocomposites. The tensile stress of fibers immersed in PVA 5 wt% solution reached ca. 200 MPa, surpassing the values of nacre and most of other nacre-mimicking materials. The nacre-mimicking fibers are highly electrically conductive (~350 S m-1) after immersing in hydroiodic acid, enabling them to connect a circuit to illuminate an LED lamp.Nacre is characterized by its excellent mechanical performance due to the well-recognized ``brick and mortar'' structure. Many efforts have been applied to make nacre-mimicking materials, but it is still a big challenge to realize their continuous production. Here, we prepared sandwich-like building blocks of poly(vinyl alcohol) (PVA)-coated graphene, and achieved high-nanofiller-content kilometers-long fibers by continuous wet-spinning assembly technology. The fibers

  1. Optimal design and characterization of superparamagnetic iron oxide nanoparticles coated with polyvinyl alcohol for targeted delivery and imaging.

    PubMed

    Mahmoudi, Morteza; Simchi, Abdolreza; Imani, Mohammad; Milani, Abbas S; Stroeve, Pieter

    2008-11-20

    Superparamagnetic iron oxide nanoparticles (SPION) with narrow size distribution and stabilized by polyvinyl alcohol (PVA) were synthesized. The particles were prepared by a coprecipitation technique using ferric and ferrous salts with a molar Fe3+/Fe2+ ratio of 2. Using a design of experiments (DOE) approach, the effect of different synthesis parameters (stirring rate and base molarity) on the structure, morphology, saturation magnetization, purity, size, and size distribution of the synthesized magnetite nanoparticles was studied by various analysis techniques including X-ray powder diffraction (XRD), thermogravimetric analysis (TGA) with differential scanning calorimetry (DSC) measurements, vibrating-sample magnetometer (VSM), transmission electron microscopy (TEM), UV-visible, and Fourier transform infrared (FT-IR) spectrometer. PVA not only stabilized the colloid but also played a role in preventing further growth of SPION followed by the formation of large agglomerates by chemisorption on the surface of particles. A rich behavior in particle size, particle formation, and super paramagnetic properties is observed as a function of molarity and stirring conditions. The particle size and the magnetic properties as well as particle shape and aggregation (individual nanoparticles, magnetic beads, and magnetite colloidal nanocrystal clusters (CNCs) are found to be influenced by changes in the stirring rate and the base molarity. The formation of magnetic beads results in a decrease in the saturation magnetization, while CNCs lead to an increase in saturation magnetization. On the basis of the DOE methodology and the resulting 3-D response surfaces for particle size and magnetic properties, it is shown that optimum regions for stirring rate and molarity can be obtained to achieve coated SPION with desirable size, purity, magnetization, and shape.

  2. Development of a novel alginate-polyvinyl alcohol-hydroxyapatite hydrogel for 3D bioprinting bone tissue engineered scaffolds.

    PubMed

    Bendtsen, Stephanie T; Quinnell, Sean P; Wei, Mei

    2017-05-01

    Three-dimensional printed biomaterials used as personalized tissue substitutes have the ability to promote and enhance regeneration in areas of defected tissue. The challenge with 3D printing for bone tissue engineering remains the selection of a material with optimal rheological properties for printing in addition to biocompatibility and capacity for uniform cell incorporation. Hydrogel biomaterials may provide sufficient printability to allow cell encapsulation and bioprinting of scaffolds with uniform cell distribution. In this study, a novel alginate-polyvinyl alcohol (PVA)-hydroxyapatite (HA) hydrogel formulation with optimal rheological properties for 3D bioprinting of mouse calvaria 3T3-E1 (MC3T3) cells into scaffolds of high shape fidelity has been developed. A systematic investigation was conducted to determine the effect of varying concentrations of alginate, phosphate, calcium, and the PVA-HA suspension in the formulation on the resulting viscosity and thus printability of the hydrogel. HA, the main mineral component in natural bone, was incorporated into the hydrogel formulation to create a favorable bone-forming environment due to its excellent osteoconductivity. Degradation studies in α-MEM cell culture media showed that the 3D printed alginate-PVA-HA scaffolds remained in-tact for 14 days. MC3T3 cells were well distributed and encapsulated throughout the optimal hydrogel formulation and expressed high viability through the completion of the 3D printing process. Thus, the development of this novel, osteoconductive, biodegradable, alginate-PVA-HA formulation and its ability to 3D bioprint tissue engineered scaffolds make it a promising candidate for treating personalized bone defects. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1457-1468, 2017.

  3. Preparation and characterization of urease-encapsulated biosensors in poly(vinyl alcohol)-modified silica sol-gel materials.

    PubMed

    Tsai, Hsiao-chung; Doong, Ruey-an

    2007-08-30

    The microenvironments of the sol-gel-derived urease biosensors in terms of elemental ratio, surface morphology, specific surface area and pore size were investigated to characterize the physicochemical properties of poly(vinyl alcohol) (PVA)-modified sol-gel materials. X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and surface area analyzer were used to identify the surface species, topography and pore distribution of the organically doped sol-gel network. XPS results showed that stoichiometric ratios of oxygen-to-silicon in sol-gel materials were in the range 2.08-2.11. The sol-gel materials were partially dried and negatively charged, which retained 6-8% water content to maintain urease activity. The surface morphology of the sol-gel altered obviously when macromolecules were encapsulated, resulting in the increase in surface mean roughness from 0.207 to 2.636 nm. The specific surface area decreased dramatically after the immobilization of biomolecules and organic additives, which clearly depicts that PVA and urease were co-encapsulated into the sol-gel network. However, there still exist enough pore volumes for analytes to mass transport. The apparent Michaelis-Menten constant value (Km) of the encapsulated urease was similar to that in solution and the overall catalytic efficiency in PVA-doped sol-gel-derived glasses only decreased by a factor of 3.2 relative to the value in solution. In addition, the analytical performance of the entrapped urease in PVA-doped sol-gel materials was examined by determining the Cu(II) concentration in aqueous solution. The analytical range of Cu(II) was in the range 2x10(-6) to 2x10(-2) M with a detection limit of 1.5 microg L(-1). Results obtained in this study demonstrate a strategy for maintaining urease activity for biomedical and environmental applications.

  4. Poly(Vinyl Alcohol)/Poly(Acrylic Acid) Hydrogel in a dc Electric Field: Swelling, Shape Change, and Actuation Characteristics

    PubMed Central

    2014-01-01

    Poly(vinyl alcohol) (PVA)/Poly(acrylic acid) (PAA) hydrogel can be utilized as a biomimetic actuator and coating material for tissue-implant interface, when employing an electrical stimulus. The swelling, shape change, and actuation characteristics of PVA/PAA hydrogel in a range of dc electrical fields were determined to find the optimal electric field for the hydrogel application as biomimetic actuator and coating materials. The hydrogel samples were prepared by dissolving PVA and PAA in deionized water at 4 wt% and mixed together at 1:1 ratio. Two custom made experimental setups were fabricated; one used for the measurement of swelling ratio of the hydrogels; and the other used for the shape changes or actuation characteristics of the hydrogels. Swelling experiments show increased swelling ratios of the hydrogel due to 10 V, 20 V, and 30 V electric fields. The rate of increment of the swelling ratio of hydrogel samples under 10V was higher compare to those samples under 20 V and 30 V. The width and height changes of rectangular shapes and maximum deflection along the length of hydrogel sample due to a range of electric fields (0-30V) were measured using an optical microscope. Incremental shape change up to a specific threshold value (around 10V) was observed due to electric stimulus. Electrostatic actuation pressure of hydrogel samples under 10V was higher compare to those samples under 20 V and 30 V. These results suggested that optimal performance of PVA/PAA hydrogel can be achieved around 10V. PMID:25478321

  5. In vitro and in vivo evaluation of blood coagulation activation of polyvinyl alcohol hydrogel plus dextran-based vascular grafts.

    PubMed

    Alexandre, Nuno; Costa, Elísio; Coimbra, Susana; Silva, Alice; Lopes, Ascensão; Rodrigues, Miguel; Santos, Marta; Maurício, Ana Colette; Santos, José Domingos; Luís, Ana Lúcia

    2015-04-01

    Polyvinyl alcohol hydrogel (PVA) is a water-soluble synthetic polymer that is commonly used in biomedical applications including vascular grafting. It was argued that the copolymerization of PVA with dextran (Dx) can result in improvement of blood-biomaterial interactions. The focus of this experimental study was to assess that interaction through an in vivo and in vitro evaluation of the coagulation system activation. The thrombogenicity of the copolymer was determined by quantification of platelet adhesion through the lactate dehydrogenase assay, determination of whole blood clotting time, and by quantification of platelet activation by flow cytometry. The thrombin-antithrombin complex blood levels were also determined. The obtained results for the in vitro assays suggested a non-thrombogenic profile for PVA/Dx. Additionally in vivo coagulation and hematological parameters were determined in an animal model after PVA/Dx vascular graft implantation. For coagulation homeostasis assessment, the intrinsic and extrinsic pathway's activation was determined by measuring prothrombin time (PT) and activated partial thromboplastin time (aPTT). Other markers of coagulation and inflammation activation including d-dimers, interleukin-6, and C-reactive protein were also assessed. The PVA/Dx copolymer tended to inhibit platelet adhesion/activation process and the contact activation process for coagulation. These results were also confirmed with the in vivo experiments where the measurements for APTT, interleukin-6, and C-reactive protein parameters were normal considering the species normal range of values. The response to those events is an indicator of the in vitro and in vivo hemocompatibility of PVA/Dx and it allows us to select this biomaterial for further preclinical trials in vascular reconstruction.

  6. Comparison of polyvinyl alcohol fixative with three less hazardous fixatives for detection and identification of intestinal parasites.

    PubMed

    Jensen, B; Kepley, W; Guarner, J; Anderson, K; Anderson, D; Clairmont, J; De L'aune, W; Austin, E H; Austin, G E

    2000-04-01

    Polyvinyl alcohol (PVA) containing the fixative mercuric chloride is considered the "gold standard" for the fixation of ova and parasites in the preparation of permanently stained smears of stool specimens. However, mercuric chloride is potentially hazardous to laboratory personnel and presents disposal problems. We compared three new alternative, nontoxic fixatives with PVA, analyzing ease of sample preparation and quality of smears. Sixty-eight fresh stool specimens were divided into aliquots and placed in each of four different fixatives: PARASAFE (PS) (Scientific Devices Laboratory, Inc., Des Plaines, Ill.), ECOFIX (EC) (Meridian Diagnostics, Inc., Cincinnati, Ohio), Proto-Fix (PF) (Alpha-Tec Systems, Inc., Vancouver, Wash.), and low-viscosity PVA fixative (PVA) (Meridian). Specimens were processed and stained according to each manufacturer's directions. Parasites were found in 31 of 68 slide preparations with PVA, 31 with PF, 30 with EC, and 30 with PS. Blastocystis hominis and Iodamoeba bütschlii were preserved in a readily identifiable state by all methods of fixation. However, some parasites were more easily identified with some of the fixatives because of differences in parasite distortion. For example, Entamoeba histolytica (Entamoeba dispar) was detected in 13 stools fixed with PF, 7 with PVA, and 6 with EC but none with PS. Likewise, Chilomastix mesnili was identified in 13 specimens fixed with PF, 8 with EC, and 5 with PVA but only 1 with PS, while Entamoeba coli was seen much less frequently with PS than with the other three fixatives. A dirty background was observed in 41% of specimens prepared with PS, whereas background quality was acceptable with other fixatives. Sample preparation was most rapid with PS, although the EC method involved the fewest steps. In conclusion, PVA and PF produced the least parasite distortion, while PS proved unsatisfactory for the identification of E. histolytica, E. coli, and C. mesnili. Both PF and EC appear to be

  7. A comparative study on the elastic modulus of polyvinyl alcohol sponge using different stress-strain definitions.

    PubMed

    Karimi, Alireza; Navidbakhsh, Mahdi; Alizadeh, Mansour; Razaghi, Reza

    2014-10-01

    There have been different stress-strain definitions to measure the elastic modulus of spongy materials, especially polyvinyl alcohol (PVA) sponge. However, there is no agreement as to which stress-strain definition should be implemented. This study was aimed to show how different results are given by the various definitions of stress-strain used, and to recommend a specific definition when testing spongy materials. A fabricated PVA sponge was subjected to a series of tensile tests in order to measure its mechanical properties. Three stress definitions (second Piola-Kichhoff stress, engineering stress, and true stress) and four strain definitions (Almansi-Hamel strain, Green-St. Venant strain, engineering strain, and true strain) were used to determine the elastic modulus. The results revealed that the Almansi-Hamel strain definition exhibited the highest non-linear stress-strain relation and, as a result, may overestimate the elastic modulus at different stress definitions (second Piola-Kichhoff stress, engineering stress, and true stress). The Green-St. Venant strain definition failed to address the non-linear stress-strain relation using different definitions of stress and invoked an underestimation of the elastic modulus values. Engineering stress and strain definitions were only valid for small strains and displacements, which make them impractical when analyzing spongy materials. The results showed that the effect of varying the stress definition on the maximum stress measurements was significant but not when calculating the elastic modulus. It is important to consider which stress-strain definition is employed when characterizing the mechanical properties of spongy materials. Although the true stress-true strain definition exhibits a non-linear relation, we favor it in spongy materials mechanics as it gives more accurate measurements of the material's response using the instantaneous values.

  8. Polyvinyl alcohol nanofiber formulation of the designer antimicrobial peptide APO sterilizes Acinetobacter baumannii-infected skin wounds in mice.

    PubMed

    Sebe, Istvan; Ostorhazi, Eszter; Fekete, Aron; Kovacs, Krisztian N; Zelko, Romana; Kovalszky, Ilona; Li, Wenyi; Wade, John D; Szabo, Dora; Otvos, Laszlo

    2016-01-01

    Native and designer cationic antimicrobial peptides are increasingly acknowledged as host defense molecules rather than true antimicrobials. Due to their ability to activate the innate immune system, these structures are used to treat uninfected and bacterially-infected wounds, including those harboring Acinetobacter baumannii. Previously we documented that when administered intramuscularly or topically in liquid formulations, the proline-rich host defense peptide dimer A3-APO accelerates uninfected wound re-epithelization and eliminates systemic and local A. baumannii, methicillin-resistant Staphylococcus aureus and other pathogen load from infected lesions better than conventional antibiotics. In the current study we sought to produce and characterize a novel delivery system, suitable for immediate and convenient application in non-hospital environments. The APO monomer was incorporated into polyvinyl alcohol nanofibers and the complex was polymerized into a solid patch dressing. Mice were subjected to skin abrasion where the wounds were either left uninfected or were inoculated with a near lethal dose of multidrug resistant A. baumannii strain. Analyzed after 3 days, APO monomer-containing patches improved wound appearance significantly better than polymer patches without antibiotics. When compared to colistin, the APO patches accelerated wound healing, and statistically significantly reduced wound size and wound bacterial load. The in vivo antimicrobial effect was more extensive than after intramuscular administration of the peptide drug, by using only one tenth of the active pharmaceutical ingredient. These data suggest that the APO monomer-impregnated nanofiber dressing can be developed as an economical first-line treatment option to skin injuries in general and battlefield burn and blast injuries in particular.

  9. Airborne polyvinyl alcohol (PVA) and cellulose fibre levels in fibre-cement factories in seven European countries.

    PubMed

    De Raeve, H; Van Cleemput, J; Nemery, B

    2001-11-01

    Because of their relatively high diameter, polyvinyl alcohol (PVA) fibres, as used in fibre-cement, are not fibres as defined by WHO (or other) regulations. Nevertheless, as with all particulate raw materials, it can be questioned if and to what extent particles with critical fibrous dimensions might be generated by the handling or machining of this material. In order to investigate any tendency of PVA fibres to release airborne particles with critical fibrous dimensions (WHO fibres), static and/or personal samples were taken in eight fibre-cement factories at locations where potential exposures to PVA fibres were expected to be the highest. The following locations were surveyed: the PVA fibre weighing station, where PVA bales are opened mechanically and the PVA fibres are dispersed and weighed in a dry state; the fibre-cement slate punching machine; the slate 'riven edge' cutting machine or sheet sawing machine, whichever was present in the respective factories. Since cellulose fibres are an important constituent of fibre-cement, the organic fibre concentrations observed at the machining operations include cellulose. At each factory a control sample was taken in open air. Sampling, sample preparation and sample analysis by scanning electron microscopy (SEM) were performed according to standard German procedures. Only very low number concentrations of organic WHO fibres, ranging from below detection limit to 0.006 f/ml, were found. These levels are lower than the typical levels of organic fibres commonly found in the normal personal environment (0.009-0.02 f/ml), stemming from the release of particles by a person's activities and from clothing and other textiles (bed sheets, blankets, pillow,.). We conclude that the handling of PVA fibres as well as the machining of PVA and cellulose fibre containing cement products in the fibre-cement factories surveyed have a low potential to release fibres with critical fibrous (WHO) dimensions.

  10. Temperature dependent dielectric and conductivity studies of polyvinyl alcohol-ZnO nanocomposite films by impedance spectroscopy

    NASA Astrophysics Data System (ADS)

    Hemalatha, K. S.; Sriprakash, G.; Ambika Prasad, M. V. N.; Damle, R.; Rukmani, K.

    2015-10-01

    Dielectric and conductivity behaviors of nano ZnO doped polyvinyl alcohol (PVA) composites for various concentrations of dopant were investigated using impedance spectroscopy for a wide range of temperatures (303 K-423 K) and frequencies (5 Hz-30 MHZ). The dielectric properties of host polymer matrix have been improved by the addition of nano ZnO and are found to be highly temperature dependent. Anomalous dielectric behavior was observed in the frequency range of 2.5 MHz-5 MHz. Increase in dielectric permittivity and dielectric loss was observed with respect to temperature. The Cole-Cole plot could be modeled by low resistance regions in a high resistance matrix and the lowest resistance was observed for the 10 mol. % films. The imaginary part of the electric modulus showed asymmetric peaks with the relaxation following Debye nature below and non-Debye nature above the peaks. The ac conductivity is found to obey Jonscher's power law, whereas the variation of dc conductivity with temperature was found to follow Arrhenius behavior. Two different activation energy values were obtained from Arrhenius plot indicating that two conduction mechanisms are involved in the composite films. Fitting the ac conductivity data to Jonscher's law indicates that large polaron assisted tunneling is the most likely conduction mechanism in the composites. Maximum conductivity is observed at 423 K for all the samples and it is optimum for 10 mol. % ZnO doped PVA composite film. Significant increase in dc and ac conductivities in these composite films makes them a potential candidate for application in electronic devices.

  11. Development of sulfonated poly(vinyl alcohol)/polpyrrole based ionic polymer metal composite (IPMC) actuator and its characterization

    NASA Astrophysics Data System (ADS)

    Inamuddin; Khan, Ajahar; Jain, R. K.; Naushad, Mu

    2015-09-01

    In the present study, a novel sulfonated poly(vinyl alcohol)/polypyrrole polymer membrane sandwiched between platinum (SPVA-Py-Pt) is fabricated for a bending actuator which can be used in microrobotic applications. To examine the suitability of SPVA-Py-Pt based ionic polymer metal composite (IPMC) for microrobotic applications, ion exchange capacity (IEC), water uptake, proton conductivity, water loss, cyclic voltammetry (CV), linear sweep voltammetry (LSV), Fourier transform infrared spectroscopy (FTIR), thermal stability, and tip displacement studies are performed. The water holding capacity of the IPMC membrane is found to be 82.23% at room temperature for 8 h of immersion time. The IEC and proton conductivity of the IPMC membrane is found to be 1.2 meq g-1 and 1.6 × 10-3 S cm-1, respectively. Maximum water loss from IPMC is achieved as 31% at 5 V for a time period of 16 min. Based on electromechanical characterization, the maximum tip displacement of SPVA-Py-Pt IPMC (size 30 mm length, 10 mm width, 0.08 mm thickness) is 18.5 mm at 5.25 V. The major advantages of this new type of IPMC are good film-forming capability, short processing time, low cost of fabrication, good flexibility, high thermo-mechanical stabilities, good ion exchange and water holding capacities and proton conductivity as compared to other types of IPMC actuators. The comparison with other type of IPMC actuators is also summarized. A multi SPVA-Py-Pt IPMC based micro-gripping system is developed that shows the potential of microrobotic applications.

  12. Radiation-crosslinking of shape memory polymers based on poly(vinyl alcohol) in the presence of carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Basfar, A. A.; Lotfy, S.

    2015-01-01

    Shape memory polymers based on poly(vinyl alcohol) (SM-PVA) in the presence of 2-carboxyethyl acrylate oligomers (CEA) and multi-wall carbon nanotubes (MWCNTs) crosslinked by ionizing radiation were investigated. Chemical-crosslinking of PVA by glutaraldehyde in the presence of CEA and MWCNTs was also studied. The swelling and gel fraction of the radiation-crosslinked SM-PVA and chemically crosslinked systems were evaluated. Analysis of the swelling and gel fraction revealed a significant reduction in swelling and an increase in the gel fraction of the material that was chemically crosslinked with glutaraldehyde. The radiation-crosslinked SM-PVA demonstrated 100% gelation at an irradiation dose of 50 kGy. In addition, radiation-crosslinked SM-PVA exhibited good temperature responsive shape-memory behavior. A scanning electron microscopy (SEM) analysis was performed. The thermal properties of radiation-crosslinked SM-PVA were investigated by a thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). The ability of the material to return or store energy (E‧), to its ability to lose energy (E″), and the ratio of these effects (Tanδ), which is called damping were examined via DMA. The temperature of Tanδ in the radiation-crosslinked SM-PVA decreased significantly by 6 and 13 °C as a result of the addition of MWCNTs. In addition, the temperature of Tanδ for SM-PVA increased as the irradiation dose increased. These radiation-crosslinked SM-PVA materials show promising shape-memory behavior based on the range of temperatures at which Tanδ appears.

  13. Temperature dependent dielectric and conductivity studies of polyvinyl alcohol-ZnO nanocomposite films by impedance spectroscopy

    SciTech Connect

    Hemalatha, K. S.; Damle, R.; Rukmani, K.; Sriprakash, G.; Ambika Prasad, M. V. N.

    2015-10-21

    Dielectric and conductivity behaviors of nano ZnO doped polyvinyl alcohol (PVA) composites for various concentrations of dopant were investigated using impedance spectroscopy for a wide range of temperatures (303 K–423 K) and frequencies (5 Hz–30 MHZ). The dielectric properties of host polymer matrix have been improved by the addition of nano ZnO and are found to be highly temperature dependent. Anomalous dielectric behavior was observed in the frequency range of 2.5 MHz–5 MHz. Increase in dielectric permittivity and dielectric loss was observed with respect to temperature. The Cole-Cole plot could be modeled by low resistance regions in a high resistance matrix and the lowest resistance was observed for the 10 mol. % films. The imaginary part of the electric modulus showed asymmetric peaks with the relaxation following Debye nature below and non-Debye nature above the peaks. The ac conductivity is found to obey Jonscher's power law, whereas the variation of dc conductivity with temperature was found to follow Arrhenius behavior. Two different activation energy values were obtained from Arrhenius plot indicating that two conduction mechanisms are involved in the composite films. Fitting the ac conductivity data to Jonscher's law indicates that large polaron assisted tunneling is the most likely conduction mechanism in the composites. Maximum conductivity is observed at 423 K for all the samples and it is optimum for 10 mol. % ZnO doped PVA composite film. Significant increase in dc and ac conductivities in these composite films makes them a potential candidate for application in electronic devices.

  14. Time-dependence of pervaporation performance for the separation of ethanol/water mixtures through poly(vinyl alcohol) membrane.

    PubMed

    Li, Gewei; Zhang, Wei; Yang, Juping; Wang, Xinping

    2007-02-15

    To clarify the cause of time-dependent separation behavior, the pervaporation performance with operating time through pure poly(vinyl alcohol) (PVA) membrane and glutaraldehyde (GA) cross-linked PVA membranes was investigated. The results showed that the water concentration in the permeate for the air-side surface of the PVA membrane increased dramatically from 92.2 to 95.7% in about 110 min and then remained almost unchanged. However, the water selectivity for the glass-side surface did not change with operating time. Similar results were observed for the GA cross-linked PVA membranes. Furthermore, the contact angle of water on the air-side surfaces of those membranes decreased with the time of contact with the feed. These results revealed that this dynamic pervaporation process was mainly attributable to the reconstruction of hydroxyl groups at the air-side surfaces of PVA membranes in response to the change of their surrounding medium during pervaporation. The reconstruction at the glass-side surface of the membrane did not occur because of the preferential localization of hydroxyl groups at the interface between the membrane and the glass plate during film formation of PVA solution. The above conclusion was further confirmed by the following results. The water concentration in the permeate through PVA membranes with the air-side surface facing the feed reached equilibrium more quickly with increasing operation temperature or decreasing degree of cross-linking, which was consistent with the fact that the rate of surface reconstruction accelerated with the increase of temperature or the decrease of the degree of cross-linking.

  15. Carbonized properties of iodine-incorporated poly(vinyl alcohol) composite films prepared by gelation/crystallization from solution.

    PubMed

    Nakano, Yumiko; Matsuo, Masaru

    2010-02-16

    Poly(vinyl alcohol) (PVA) and titanium dioxide (TiO(2)) composite films were prepared by gelation/crystallization from a dispersed solution containing different TiO(2) contents against PVA. Iodine was incorporated into the composites, and the iodine-incorporated composites were carbonized under argon gas in the temperature range of 700-1600 degrees C. Under the carbonization process, the incorporation of iodine into composites ensured tough films without cracks. This indicated that iodine incorporation played an important role as a catalyst to promote the formation of cross links between amorphous carbon chains through the resultant Ti-C structure that occurs by hydration. Surprisingly, X-ray diffraction intensity measurements revealed that the coagulated TiO(2) powders in the composite film carbonized at 1200 degrees C remained predominantly anatase type, which has generally been known as photocatalytic activity. The perfect transition to the rutile-type structure dramatically occurred at 1600 degrees C. Judging from the carbon coating on the TiO(2) particle surface as detected by ESCA, no disruption of the composite was found to be due to the appearances of Ti(2)O(3) groups and the Ti-C structure performing cross linking between neighboring amorphous carbon chains. The characteristics of anatase-type TiO(2) crystallites and amorphous carbon structures were analyzed using the para-crystalline theory concerning the distance fluctuation between graphene sheets. The electrical conductivity of the carbonized composite was ca. 0.01 S/cm and was independent of the TiO(2) admixed in the carbon matrix.

  16. Electrospun poly(vinyl alcohol) fiber mats as carriers for extracts from the fruit hull of mangosteen.

    PubMed

    Opanasopit, Praneet; Ruktanonchai, Uracha; Suwantong, Orawan; Panomsuk, Suwannee; Ngawhirunpat, Tanasait; Sittisombut, Chavalit; Suksamran, Tittaya; Supaphol, Pitt

    2008-01-01

    Electrospinning is a process used to produce ultrafine fibers with diameters in the nanometer range. Electrospun fiber mats have high potentials for biomedical uses, due to their high surface area and ease of drug incorporation into the fibers. They can be used as carriers for drug delivery and can enhance drug release and skin permeability. The aim of this study was to prepare electrospun fiber mats and to incorporate extracts from the fruit hull of mangosteen. Antioxidant activity and extract release were determined and compared between the extract incorporated in the electrospun fiber mats and in the cast films. Poly(vinyl alcohol) (PVA) was selected as the polymer matrix. Extracts in the amount of 2.5%, 5%, and 10% w/w, based on the weight of PVA, were incorporated with 10% w/w PVA to finally obtain electrospun fiber mats and cast films. The extract content was evaluated by antioxidative activity using the 2,2-diphenyl-1-picryhydrazyl (DPPH) method. The morphology of the electrospun fiber mats was analyzed using a scanning electron microscope (SEM). The results showed that the diameters of the fibers were in nanoscales and that no crystal of the extract was found at any concentration of the extract. The extract contents in the electrospun fiber mats prepared at 2.5%, 5%, and 10% w/w of the extract were 9.6%, 9.7%, and 10.8% of the initial loading concentration, respectively, whereas, those in the cast films were 23.9%, 14.5%, and 21.0%, respectively. The release of the extract from the electrospun fiber mats prepared at 2.5%, 5%, and 10% w/w of the extract at 120 min were 73.2%, 83.6%, and 81.3% w/w, respectively. However, much slower release from the cast films was observed (i.e., 4.3%, 29.1%, and 40.8% w/w, respectively).

  17. Translucent poly(vinyl alcohol) cryogel dosimeters for simultaneous dose buildup and monitoring during chest wall radiation therapy.

    PubMed

    Eyadeh, Molham M; Weston, Mark A; Juhasz, Janos; Diamond, Kevin R

    2016-09-01

    Chest wall radiation therapy treatment delivery was monitored using a 5 mm thick radiochromic poly(vinyl alcohol) cryogel that also provided buildup material. The cryogels were used to detect positioning errors and measure the impact of shifts for a chest wall treatment that was delivered to a RANDO phantom. The phantom was shifted by ±2,±3, and ±5 mm from the planned position in the anterior/posterior (A/P) direction; these shifts represent setup errors and the uncertainty associated with lung filling during breath-hold. The two-dimensional absolute dose distributions measured in the cryogel at the planned position were compared with the distributions at all shifts from this position using gamma analysis (3%/3 mm, 10% threshold). For shifts of ±2,±3, and ±5 mm the passing rates ranged from 94.3% to 95.6%, 74.0% to 78.8%, and 17.5% to 22.5%, respectively. These results are consistent with the same gamma analysis performed on dose planes calculated in the middle of the cryogel and on the phantom surface using our treatment planning system, which ranged from 94.3% to 95.0%, 76.8% to 77.9%, and 23.5% to 24.3%, respectively. The Pinnacle dose planes were then scaled empirically and compared to the cryogel measurements. Using the same gamma metric, the pass rates ranged from 97.0% to 98.4%. The results of this study suggest that cryogels may be used as both a buildup material and to evaluate errors in chest wall treatment positioning during deep-inspiration breath-hold delivery. The cryogels are sensitive to A/P chest wall shifts of less than 3 mm, which potentially allows for the detection of clinically relevant errors. PACS number(s): 87.55.km, 87.57.uq.

  18. Translucent poly(vinyl alcohol) cryogel dosimeters for simultaneous dose buildup and monitoring during chest wall radiation therapy.

    PubMed

    Eyadeh, Molham M; Weston, Mark A; Juhasz, Janos; Diamond, Kevin R

    2016-09-08

    Chest wall radiation therapy treatment delivery was monitored using a 5 mm thick radiochromic poly(vinyl alcohol) cryogel that also provided buildup material. The cryogels were used to detect positioning errors and measure the impact of shifts for a chest wall treatment that was delivered to a RANDO phantom. The phantom was shifted by ± 2, ± 3, and ± 5 mm from the planned position in the anterior/posterior (A/P) direction; these shifts represent setup errors and the uncertainty associated with lung filling during breath-hold. The two-dimensional absolute dose distributions measured in the cryogel at the planned position were compared with the distributions at all shifts from this position using gamma analysis (3%/3 mm, 10% threshold). For shifts of ± 2, ± 3, and ± 5 mm the passing rates ranged from 94.3% to 95.6%, 74.0% to 78.8%, and 17.5% to 22.5%, respectively. These results are consistent with the same gamma analysis performed on dose planes calculated in the middle of the cryogel and on the phantom surface using our treatment plan-ning system, which ranged from 94.3% to 95.0%, 76.8% to 77.9%, and 23.5% to 24.3%, respectively. The Pinnacle dose planes were then scaled empirically and compared to the cryogel measurements. Using the same gamma metric, the pass rates ranged from 97.0% to 98.4%. The results of this study suggest that cryogels may be used as both a buildup material and to evaluate errors in chest wall treat-ment positioning during deep-inspiration breath-hold delivery. The cryogels are sensitive to A/P chest wall shifts of less than 3 mm, which potentially allows for the detection of clinically relevant errors.

  19. Improved dielectric properties of nanocomposites based on poly(vinylidene fluoride) and poly(vinyl alcohol)-functionalized graphene.

    PubMed

    Wang, Dongrui; Bao, Yaru; Zha, Jun-Wei; Zhao, Jun; Dang, Zhi-Min; Hu, Guo-Hua

    2012-11-01

    In this work, two series of nanocomposites of poly(vinylidene fluoride) (PVDF) incorporated with reduced graphene oxide (rGO) and poly(vinyl alcohol)-modified rGO (rGO-PVA) were fabricated using solution-cast method and their dielectric properties were carefully characterized. Infrared spectroscopy and atom force microscope analysis indicated that PVA chains were successfully grafted onto graphene through ester linkage. The PVA functionalization of graphene surface can not only prevent the agglomeration of original rGO but also enhance the interaction between PVDF and rGO-PVA. Strong hydrogen bonds and charge transfer effect between rGO-PVA and PVDF were determined by infrared and Raman spectroscopies. The dielectric properties of rGO-PVA/PVDF and rGO/PVDF nanocomposites were investigated in a frequency range from 10² Hz to 10⁷ Hz. Both composite systems exhibited an insulator-to-conductor percolating transition as the increase of the filler content. The percolation thresholds were estimated to be 2.24 vol % for rGO-PVA/PVDF composites and 0.61 vol % for rGO/PVDF composites, respectively. Near the percolation threshold, the dielectric permittivity of the nanocomposites was significantly promoted, which can be well explained by interfacial polarization effect and microcapacitor model. Compared to rGO/PVDF composites, higher dielectric constant and lower loss factor were simultaneously achieved in rGO-PVA/PVDF nanocomposites at a frequency range lower than 1 × 10³ Hz. This work provides a potential design strategy based on graphene interface engineering, which would lead to higher-performance flexible dielectric materials.

  20. Comparison of Polyvinyl Alcohol Fixative with Three Less Hazardous Fixatives for Detection and Identification of Intestinal Parasites

    PubMed Central

    Jensen, B.; Kepley, W.; Guarner, J.; Anderson, K.; Anderson, D.; Clairmont, J.; De l'aune, William; Austin, E. H.; Austin, G. E.

    2000-01-01

    Polyvinyl alcohol (PVA) containing the fixative mercuric chloride is considered the “gold standard” for the fixation of ova and parasites in the preparation of permanently stained smears of stool specimens. However, mercuric chloride is potentially hazardous to laboratory personnel and presents disposal problems. We compared three new alternative, nontoxic fixatives with PVA, analyzing ease of sample preparation and quality of smears. Sixty-eight fresh stool specimens were divided into aliquots and placed in each of four different fixatives: PARASAFE (PS) (Scientific Devices Laboratory, Inc., Des Plaines, Ill.), ECOFIX (EC) (Meridian Diagnostics, Inc., Cincinnati, Ohio), Proto-Fix (PF) (Alpha-Tec Systems, Inc., Vancouver, Wash.), and low-viscosity PVA fixative (PVA) (Meridian). Specimens were processed and stained according to each manufacturer's directions. Parasites were found in 31 of 68 slide preparations with PVA, 31 with PF, 30 with EC, and 30 with PS. Blastocystis hominis and Iodamoeba bütschlii were preserved in a readily identifiable state by all methods of fixation. However, some parasites were more easily identified with some of the fixatives because of differences in parasite distortion. For example, Entamoeba histolytica (Entamoeba dispar) was detected in 13 stools fixed with PF, 7 with PVA, and 6 with EC but none with PS. Likewise, Chilomastix mesnili was identified in 13 specimens fixed with PF, 8 with EC, and 5 with PVA but only 1 with PS, while Entamoeba coli was seen much less frequently with PS than with the other three fixatives. A dirty background was observed in 41% of specimens prepared with PS, whereas background quality was acceptable with other fixatives. Sample preparation was most rapid with PS, although the EC method involved the fewest steps. In conclusion, PVA and PF produced the least parasite distortion, while PS proved unsatisfactory for the identification of E. histolytica, E. coli, and C. mesnili. Both PF and EC appear to be

  1. Estimation of polyvinyl alcohol cryogel mechanical properties with four ultrasound elastography methods and comparison with gold standard testings.

    PubMed

    Fromageau, Jérémie; Gennisson, Jean-Luc; Schmitt, Cédric; Maurice, Roch L; Mongrain, Rosaire; Cloutier, Guy

    2007-03-01

    Tissue-mimicking phantoms are very useful in the field of tissue characterization and essential in elastography for the purpose of validating motion estimators. This study is dedicated to the characterization of polyvinyl alcohol cryogel (PVA-C) for these types of applications. A strict fabrication procedure was defined to optimize the reproducibility of phantoms having a similar elasticity. Following mechanical stretching tests, the phantoms were used to compare the accuracy of four different elastography methods. The four methods were based on a one-dimensional (1-D) scaling factor estimation, on two different implementations of a 2-D Lagrangian speckle model estimator (quasistatic elastography methods), and on a 1-D shear wave transient elastography technique (dynamic method). Young's modulus was investigated as a function of the number of freeze-thaw cycles of PVA-C, and of the concentration of acoustic scatterers. Other mechanical and acoustic parameters-such as the speed of sound, shear wave velocity, mass density, and Poisson's ratio-also were assessed. The Poisson's ratio was estimated with good precision at 0.499 for all samples, and the Young's moduli varied in a range of 20 kPa for one freeze-thaw cycle to 600 kPa for 10 cycles. Nevertheless, above six freeze-thaw cycles, the results were less reliable because of sample geometry artifacts. However, for the samples that underwent less than seven freeze-thaw cycles, the Young's moduli estimated with the four elastography methods showed good matching with the mechanical tensile tests with a regression coefficient varying from 0.97 to 1.07, and correlations R2 varying from 0.93 to 0.99, depending on the method.

  2. Sulfoacetic acid modifying poly(vinyl alcohol) hydrogel and its electroresponsive behavior under DC electric field

    NASA Astrophysics Data System (ADS)

    Xiang, Yu; Liu, Genqi; Zhang, Cheng; Liao, Jiae

    2013-01-01

    A strong electrolyte hydrogel was prepared by modifying poly (vinyl alcohol) hydrogel with sulfoacetic acid (SA-PVA). Its swelling properties, mechanical properties, and electroresponsive behavior in Na2SO4 solutions were studied. The results indicated that the water take-up ability of the hydrogel decreased with the increasing ionic strength of Na2SO4 solution. The Young’s modulus, elongation at break and tensile strength of the hydrogel swollen in deionized water are 1.247 MPa, 187% and 2.2 MPa, respectively. The hydrogel swollen in a Na2SO4 solution bent towards the cathode under non-contact dc electric fields, and its bending speed and equilibrium strain increased with increasing applied voltage. There is a critical ionic strength of 0.03 at which the maximum equilibrium strain of the hydrogel occurs. Also the bending behavior of hydrogel was not affected by the pH changes. By altering the direction of the applied potential cyclically, the hydrogel exhibited good reversible bending behavior. On this basis, a gel-worm was designed. Under a cyclically varying electric field (the period was 8 s, and the voltage ranged from -10 to 10 V), the walking speed was up to 15 cm min-1 in Na2SO4 solution with an ionic strength of 0.03.

  3. Rheological properties of poly(vinyl alcohol) (PVA) derived composite membranes for fuel cells

    NASA Astrophysics Data System (ADS)

    Remiš, T.

    2017-01-01

    Rheological properties of new anhydrous proton conducting membrane based on PVA, tetraethyl orthosilicate (TEOS),sulfosuccinic acid (SSA), titanium dioxide (TiO2)was examined at various stoichiometric ratios. SSA was used as sulfonating agents to form a crosslinked structure and as proton source, whereas TEO Sand TiO2were utilized to improve the thermal and mechanical properties of the membrane. In order to verify that all the substances were immobilized into the matrix, the membranes were analysed by means of FT-IR. The rheological, mechanical and thermal properties of the membranes were investigated using rheometer ARES G2 and thermogravimetic analyser (TGA).The analysis of mixed PVA solutions exhibited a unique behaviour of viscosity with increased crosslink density. The dynamic storage modulus G´ of dried composite membranes shows better mechanical resistance and increased tolerance to pressure applied during membrane electrode assembly (MEA).

  4. Alcohols as alkylating agents in heteroarene C–H functionalization

    PubMed Central

    Jin, Jian; MacMillan, David W. C.

    2015-01-01

    Redox processes and radical intermediates are found in many biochemical processes, including deoxyribonucleotide synthesis and oxidative DNA damage1. One of the core principles that underlies DNA biosynthesis is the radical-mediated elimnation of H2O to deoxygenate ribonucleotides, an example of ‘spin-center shift’ (SCS)2, during which an alcohol C–O bond is cleaved, resulting in a carbon-centered radical intermediate. While SCS is a well-understood biochemical process, it is underutilized by the synthetic organic chemistry community. We wondered whether it would be possible to take advantage of this naturally occurring process to accomplish mild, non-traditional alkylations using alcohols as radical precursors. Considering traditional radical-based alkylation methods require the use of stoichiometric oxidants, elevated temperatures, or peroxides3–7, the development of a mild protocol using simple and abundant alkylating agents would have significant utility in the synthesis of diversely functionalized pharmacophores. In this manuscript, we describe the successful execution of this idea via the development of a dual catalytic alkylation of heteroarenes using alcohols as mild alkylating reagents. This method represents the first broadly applicable use of unactivated alcohols as latent alkylating reagents, achieved via the successful merger of photoredox and hydrogen atom transfer (HAT) catalysis. The utility of this multi-catalytic protocol has been demonstrated through the late-stage functionalization of the medicinal agents, fasudil and milrinone. PMID:26308895

  5. Alcohols as alkylating agents in heteroarene C-H functionalization

    NASA Astrophysics Data System (ADS)

    Jin, Jian; MacMillan, David W. C.

    2015-09-01

    Redox processes and radical intermediates are found in many biochemical processes, including deoxyribonucleotide synthesis and oxidative DNA damage. One of the core principles underlying DNA biosynthesis is the radical-mediated elimination of H2O to deoxygenate ribonucleotides, an example of `spin-centre shift', during which an alcohol C-O bond is cleaved, resulting in a carbon-centred radical intermediate. Although spin-centre shift is a well-understood biochemical process, it is underused by the synthetic organic chemistry community. We wondered whether it would be possible to take advantage of this naturally occurring process to accomplish mild, non-traditional alkylation reactions using alcohols as radical precursors. Because conventional radical-based alkylation methods require the use of stoichiometric oxidants, increased temperatures or peroxides, a mild protocol using simple and abundant alkylating agents would have considerable use in the synthesis of diversely functionalized pharmacophores. Here we describe the development of a dual catalytic alkylation of heteroarenes, using alcohols as mild alkylating reagents. This method represents the first, to our knowledge, broadly applicable use of unactivated alcohols as latent alkylating reagents, achieved via the successful merger of photoredox and hydrogen atom transfer catalysis. The value of this multi-catalytic protocol has been demonstrated through the late-stage functionalization of the medicinal agents, fasudil and milrinone.

  6. Hybrid monolith sorbent of polypyrrole-coated graphene oxide incorporated into a polyvinyl alcohol cryogel for extraction and enrichment of sulfonamides from water samples.

    PubMed

    Chullasat, Kochaporn; Nurerk, Piyaluk; Kanatharana, Proespichaya; Kueseng, Pamornrat; Sukchuay, Thanyaporn; Bunkoed, Opas

    2017-04-08

    A hybrid monolith sorbent of polypyrrole-coated graphene oxide embedded in polyvinyl alcohol cryogel was prepared and used as an effective solid phase extraction sorbent for the determination of trace sulfonamides. The large surface areas with many adsorption sites of polypyrrole and graphene oxide facilitated the high adsorption of sulfonamides via hydrogen bonding, π-π and hydrophobic interactions. The high porosity of the polyvinyl alcohol cryogel helped to reduce the back pressure that occurs in a conventional packed solid phase extraction cartridge. The effecting parameters on the extraction efficiency including the type of sorbent, the polymerization time, desorption conditions, the sample pH, the sample volume, the sample flow rate, and ionic strength were investigated and optimized. Under the optimum conditions, the developed method provided a wide linear range from 0.20 to 100.0 μg L(-1) for sulfadiazine, sulfathiazole and sulfamerazine; and from 0.10 to 100 μg L(-1) for sulfamethazine, sulfamonomethoxine and sulfadimethoxine. The limits of detection were 0.20 μg L(-1) for sulfadiazine, sulfathiazole and sulfamerazine; and 0.10 μg L(-1) for sulfamethazine, sulfamonomethoxine and sulfadimethoxine. The developed hybrid monolith polypyrrole-coated graphene oxide embedded in the polyvinyl alcohol cryogel sorbent provided good recoveries in the range of 85.5-99.0% with RSDs of less than 5.0%. The sorbent offered a good reproducibility, was robust and can be reused at least 10 times. It was successfully applied for the extraction and enrichment of sulfonamides from normal and supplemented water samples.

  7. Fabrication, biocompatibility, and tissue engineering substrate analysis of polyvinyl alcohol-gelatin core-shell electrospun nanofibers

    NASA Astrophysics Data System (ADS)

    Merkle, Valerie Marie

    Cardiovascular disease is the leading cause of death in the United States with approximately 49% of the cardiovascular related deaths attributed to coronary heart disease (CHD). CHD is the accumulation of plaque resulting in the narrowing of the vessel lumen and a decrease in blood flow to the downstream heart muscle. In order to restore blood flow, arterial by-pass procedures can be undertaken. However, the patient's own arteries/veins may not be suitable for use as a vessel replacement, and synthetic grafts lack the compliancy and durability needed for these small diameter locations (< 5 mm). Therefore, the goal of this research is to develop a nanofibrous material that can be used in vascular applications such as this. In this study, we fabricate coaxial electrospun nanofibers with gelatin in the shell and polyvinyl alcohol (PVA) in the core using 1 Gelatin: 1 PVA and 3 Gelatin: 1 PVA mass ratios. Gelatin, derived from collagen, is highly bioactive while PVA, a synthetic polymer, has appealing mechanical properties. Therefore, by combining these materials in a core-shell structure, we hypothesize that the resulting nanofibers will have enhanced mechanical properties, cellular growth and migration, as well as minimal platelet deposition and activation compared to scaffolds composed solely of gelatin or PVA. First, the coaxial scaffolds exhibited an enhanced Young's modulus and ultimate strength compared to scaffolds composed of PVA or gelatin alone. Endothelial cells had high proliferation and migration on the coaxial electrospun scaffolds with higher migration seen on the stiffer, coaxial scaffolds. The smooth muscle cells had less proliferation and lower migration rates on the coaxial scaffolds than the endothelial cells. Using a modified prothrombinase assay, the coaxial scaffolds had minimal platelet activation. Lastly, when pre-seeding the coaxial scaffolds with endothelial cells or smooth muscle cells, the platelet deposition decreased in comparison to

  8. Comparison of Pain After Uterine Artery Embolization Using Tris-Acryl Gelatin Microspheres Versus Polyvinyl Alcohol Particles

    SciTech Connect

    Ryu, Robert K. Omary, Reed A.; Sichlau, Michael J.; Siddiqi, Aheed; Chrisman, Howard B.; Nemcek, Albert A.; Vogelzang, Robert L.

    2003-08-15

    When compared in a uterine artery embolization(UAE) animal model, Embospheres (ES) (Biosphere Medical, Rockland, MA)were found to induce less uterine ischemia than polyvinyl alcohol (PVA)particles. Given this finding, we aimed to test the hypothesis that ESis associated with less pain after UAE than PVA in human patients. We performed retrospective analysis on data from 72 consecutive UAE patients, collected from a prospectively acquired database.Patient-controlled analgesia (PCA) pump-delivered morphine sulfate (MS)dosages were compared between patients who received ES versus PVA.Subjective pain scores (SPS) were also compared between the two groups.Secondary outcome measures, including embolic volume and clinical outcome data, were also collected. Linear regression and t-test statistical analyses were performed. Null hypotheses were rejected at the p < 0.05 level. Mean follow-up period in the PVS population was 178 days (range 28-426), versus 96 days (range 24-197)in the ES population. The mean MS doses used by ES and PVA patients were 37.2 (s.d. 23.5) versus 47.1 (s.d. 26.8), respectively. This difference was not significant (p > 0.15).Utilizing a standard 0-10 pain scale, the mean peak SPS for the ES and PVA groups were 5.58 (s.d. 2.77) and 5.07 (s.d. 2.99), respectively.The difference was not significant. The mean amount of embolic material used in each ES and PVA patient was 4.86 cc (s.d. 3.01) and 3.52 cc(s.d. 1.63), respectively. The difference revealed a strong trend toward statistical significance (p = 0.05). There was one treatment failure in each group of patients. Within both patient samples, no significant correlation was found when comparing the volume of embolic used and subsequent MS dose. Despite a strong trend toward a significantly higher volume of ES used per patient, there is no subjective or objective difference in pain after UAE with ES when compared to PVA.

  9. Development of highly porous biodegradable γ-Fe2O3/polyvinyl alcohol nanofiber mats using electrospinning process for biomedical application.

    PubMed

    Ngadiman, Nor Hasrul Akhmal; Yusof, Noordin Mohd; Idris, Ani; Misran, Effaliza; Kurniawan, Denni

    2017-01-01

    The use of electrospinning process in fabricating tissue engineering scaffolds has received great attention in recent years due to its simplicity. The nanofibers produced via electrospinning possessed morphological characteristics similar to extracellular matrix of most tissue components. Porosity plays a vital role in developing tissue engineering scaffolds because it influences the biocompatibility performance of the scaffolds. In this study, maghemite (γ-Fe2O3) was mixed with polyvinyl alcohol (PVA) and subsequently electrospun to produce nanofibers. Five factors; nanoparticles content, voltage, flow rate, spinning distance, and rotating speed were varied to produce the electrospun nanofibrous mats with high porosity value. Empirical model was developed using response surface methodology to analyze the effect of these factors to the porosity. The results revealed that the optimum porosity (90.85%) was obtained using 5% w/v nanoparticle content, 35kV of voltage, 1.1ml/h volume flow rate of solution, 8cm spinning distance and 2455rpm of rotating speed. The empirical model was verified successfully by performing confirmation experiments. The properties of optimum PVA/γ-Fe2O3 nanofiber mats such as fiber diameter, mechanical properties, and contact angle were investigated. In addition, cytocompatibility test, in vitro degradation rate, and MTT assay were also performed. Results revealed that high porosity biodegradable γ-Fe2O3/polyvinyl alcohol nanofiber mats have low mechanical properties but good degradation rates and cytocompatibility properties. Thus, they are suitable for low load bearing biomedical application or soft tissue engineering scaffold.

  10. A novel hierarchically structured and highly hydrophilic poly(vinyl alcohol-co-ethylene)/poly(ethylene terephthalate) nanoporous membrane for lithium-ion battery separator

    NASA Astrophysics Data System (ADS)

    Xia, Ming; Liu, Qiongzhen; Zhou, Zhou; Tao, Yifei; Li, MuFang; Liu, Ke; Wu, Zhihong; Wang, Dong

    2014-11-01

    A novel hierarchically structured and highly hydrophilic poly(vinyl alcohol-co-ethylene)/poly(ethylene terephthalate) nanoporous separator (referred to NFs/PET/NFs) composed of a poly(ethylene terephthalate) (PET) nonwoven sandwiched between two interconnected poly(vinyl alcohol-co-ethylene) (PVA-co-PE) nanofibrous membranes is successfully developed for lithium-ion battery. Systematical investigations including structural characterization, porosity measurement, water contact angle testing, electrolyte uptake, and thermal shrinkage testing demonstrate that the notable feature of this NFs/PET/NFs nanofibrous separator is an electrolyte-philic, highly porous and hierarchically nanoscaled structure, thus resulting in superior electrolyte wettability, lower thermal shrinkage, and higher ion conductivity, in comparison to the commercial Polypropylene (PP) separator. These structural characteristics enable the NFs/PET/NFs separator to offer an excellent cell performance including outstanding C-rate capability, high capacity and excellent cycling performance. This suggests that the NFs/PET/NFs separator is a promising material for practical application in lithium-ion battery due to it low cost production and high performance.

  11. In vitro mechanical fatigue behavior of poly-ɛ-caprolactone macroporous scaffolds for cartilage tissue engineering: Influence of pore filling by a poly(vinyl alcohol) gel.

    PubMed

    Panadero, J A; Vikingsson, L; Gomez Ribelles, J L; Lanceros-Mendez, S; Sencadas, V

    2015-07-01

    Polymeric scaffolds used in regenerative therapies are implanted in the damaged tissue and submitted to repeated loading cycles. In the case of articular cartilage engineering, an implanted scaffold is typically subjected to long-term dynamic compression. The evolution of the mechanical properties of the scaffold during bioresorption has been deeply studied in the past, but the possibility of failure due to mechanical fatigue has not been properly addressed. Nevertheless, the macroporous scaffold is susceptible to failure after repeated loading-unloading cycles. In this work fatigue studies of polycaprolactone scaffolds were carried by subjecting the scaffold to repeated compression cycles in conditions simulating the scaffold implanted in the articular cartilage. The behavior of the polycaprolactone sponge with the pores filled with a poly(vinyl alcohol) gel simulating the new formed tissue within the pores was compared with that of the material immersed in water. Results were analyzed with Morrow's criteria for failure and accurate fittings are obtained just up to 200 loading cycles. It is also shown that the presence of poly(vinyl alcohol) increases the elastic modulus of the scaffolds, the effect being more pronounced with increasing the number of freeze/thawing cycles.

  12. Programmable Laser-Assisted Surface Microfabrication on a Poly(Vinyl Alcohol)-Coated Glass Chip with Self-Changing Cell Adhesivity for Heterotypic Cell Patterning.

    PubMed

    Li, Yi-Chen; Lin, Meng-Wei; Yen, Meng-Hua; Fan, Sabrina Mai-Yi; Wu, June-Tai; Young, Tai-Horng; Cheng, Ji-Yen; Lin, Sung-Jan

    2015-10-14

    Organs are composed of heterotypic cells with patterned architecture that enables intercellular interaction to perform specific functions. In tissue engineering, the ability to pattern heterotypic cells into desired arrangement will allow us to model complex tissues in vitro and to create tissue equivalents for regeneration. This study was aimed at developing a method for fast heterotypic cell patterning with controllable topological manipulation on a glass chip. We found that poly(vinyl alcohol)-coated glass showed a biphasic change in adhesivity to cells in vitro: low adhesivity in the first 24 h and higher adhesivity at later hours due to increased serum protein adsorption. Combining programmable CO2 laser ablation to remove poly(vinyl alcohol) and glass, we were able to create arrays of adhesive microwells of adjustable patterns. We tested whether controllable patterns of epithelial-mesenchymal interaction could be created. When skin dermal papilla cells and fibroblasts were seeded respectively 24 h apart, we were able to pattern these two cells into aggregates of dermal papilla cells in arrays of microwells in a background of fibroblasts sheet. Seeded later, keratinocytes attached to these mesenchymal cells. Keratinocytes contacting dermal papilla cells started to differentiate toward a hair follicle fate, demonstrating patternable epithelial-mesenchymal interaction. This method allows fast adjustable heterotypic cell patterning and surface topology control and can be applied to the investigation of heterotypic cellular interaction and creation of tissue equivalent in vitro.

  13. Double-layer poly(vinyl alcohol)-coated capillary for highly sensitive and stable capillary electrophoresis and capillary electrophoresis with mass spectrometry glycan analysis.

    PubMed

    Zhang, Yi-Wei; Zhao, Ming-Zhe; Liu, Jing-Xin; Zhou, Ying-Lin; Zhang, Xin-Xiang

    2015-02-01

    Glycosylation plays an important role in protein conformations and functions as well as many biological activities. Capillary electrophoresis combined with various detection methods provided remarkable developments for high-sensitivity glycan profiling. The coating of the capillary is needed for highly polar molecules from complex biosamples. A poly(vinyl alcohol)-coated capillary is commonly utilized in the capillary electrophoresis separation of saccharides sample due to the high-hydrophilicity properties. A modified facile coating workflow was carried out to acquire a novel multiple-layer poly(vinyl alcohol)-coated capillary for highly sensitive and stable analysis of glycans. The migration time fluctuation was used as index in the optimization of layers and a double layer was finally chosen, considering both the effects and simplicity in fabrication. With migration time relative standard deviation less than 1% and theoretical plates kept stable during 100 consecutive separations, the method was presented to be suitable for the analysis of glycosylation with wide linear dynamic range and good reproducibility. The glycan profiling of enzymatically released N-glycans from human serum was obtained by the presented capillary electrophoresis method combined with mass spectrometry detection with acceptable results.

  14. 49 CFR 40.341 - Must service agents comply with DOT drug and alcohol testing requirements?

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... Transportation PROCEDURES FOR TRANSPORTATION WORKPLACE DRUG AND ALCOHOL TESTING PROGRAMS Roles and Responsibilities of Service Agents § 40.341 Must service agents comply with DOT drug and alcohol testing... requirements of this part and the DOT agency drug and alcohol testing regulations. (b) If you do not...

  15. 49 CFR 40.341 - Must service agents comply with DOT drug and alcohol testing requirements?

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Transportation PROCEDURES FOR TRANSPORTATION WORKPLACE DRUG AND ALCOHOL TESTING PROGRAMS Roles and Responsibilities of Service Agents § 40.341 Must service agents comply with DOT drug and alcohol testing... requirements of this part and the DOT agency drug and alcohol testing regulations. (b) If you do not...

  16. 49 CFR 40.341 - Must service agents comply with DOT drug and alcohol testing requirements?

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Transportation PROCEDURES FOR TRANSPORTATION WORKPLACE DRUG AND ALCOHOL TESTING PROGRAMS Roles and Responsibilities of Service Agents § 40.341 Must service agents comply with DOT drug and alcohol testing... requirements of this part and the DOT agency drug and alcohol testing regulations. (b) If you do not...

  17. 49 CFR 40.341 - Must service agents comply with DOT drug and alcohol testing requirements?

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... Transportation PROCEDURES FOR TRANSPORTATION WORKPLACE DRUG AND ALCOHOL TESTING PROGRAMS Roles and Responsibilities of Service Agents § 40.341 Must service agents comply with DOT drug and alcohol testing... requirements of this part and the DOT agency drug and alcohol testing regulations. (b) If you do not...

  18. 49 CFR 40.341 - Must service agents comply with DOT drug and alcohol testing requirements?

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... Transportation PROCEDURES FOR TRANSPORTATION WORKPLACE DRUG AND ALCOHOL TESTING PROGRAMS Roles and Responsibilities of Service Agents § 40.341 Must service agents comply with DOT drug and alcohol testing... requirements of this part and the DOT agency drug and alcohol testing regulations. (b) If you do not...

  19. Composite poly(vinyl alcohol)/poly(vinyl acetate) electrospun nanofibrous mats as a novel wound dressing matrix for controlled release of drugs.

    PubMed

    Jannesari, Marziyeh; Varshosaz, Jaleh; Morshed, Mohammad; Zamani, Maedeh

    2011-01-01

    The aim of this study was to develop novel biomedicated nanofiber electrospun mats for controlled drug release, especially drug release directly to an injury site to accelerate wound healing. Nanofibers of poly(vinyl alcohol) (PVA), poly(vinyl acetate) (PVAc), and a 50:50 composite blend, loaded with ciprofloxacin HCl (CipHCl), were successfully prepared by an electrospinning technique for the first time. The morphology and average diameter of the electrospun nanofibers were investigated by scanning electron microscopy. X-ray diffraction studies indicated an amorphous distribution of the drug inside the nanofiber blend. Introducing the drug into polymeric solutions significantly decreased solution viscosities as well as nanofiber diameter. In vitro drug release evaluations showed that both the kind of polymer and the amount of drug loaded greatly affected the degree of swelling, weight loss, and initial burst and rate of drug release. Blending PVA and PVAc exhibited a useful and convenient method for electrospinning in order to control the rate and period of drug release in wound healing applications. Also, the thickness of the blend nanofiber mats strongly influenced the initial release and rate of drug release.

  20. Coexistence of Write Once Read Many Memory and Memristor in blend of Poly(3,4-ethylenedioxythiophene): polystyrene sulfonate and Polyvinyl Alcohol

    NASA Astrophysics Data System (ADS)

    Nguyen, Viet Cuong; Lee, Pooi See

    2016-12-01

    In this work, the coexistence of Write Once Read Many Memory (WORM) and memristor can be achieved in a single device of Poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT: PSS) and Polyvinyl Alcohol (PVA) blend organic memory system. In memristor mode, the bistable resistance states of the device can be cycled for more than 1000 times. Once a large negative bias of ‑8V was applied to the device, it was switched to permanent high resistance state that cannot be restored back to lower resistance states. The mechanism of the memristor effect can be attributed to the charge trapping behaviour in PVA while the WORM effect can be explained as the electrochemical characteristic of PEDOT: PSS which harnesses the percolative conduction pathways. The results may facilitate multipurpose memory device with active tunability.

  1. Preparation and properties of films cast from mixtures of poly(vinyl alcohol) and submicron particles prepared from amylose-palmitic acid inclusion complexes.

    PubMed

    Fanta, George F; Selling, Gordon W; Felker, Frederick C; Kenar, James A

    2015-05-05

    The use of starch in polymer composites for film production has been studied for increasing biodegradability, improving film properties and reducing cost. In this study, submicron particles were prepared from amylose-sodium palmitate complexes both by rapidly cooling jet-cooked starch-palmitic acid mixtures and by acidifying solutions of starch-sodium palmitate complexes. Films were cast containing poly(vinyl alcohol) (PVOH) with up to 50% starch particles. Tensile strength decreased and Young's modulus increased with starch concentration, but percent elongations remained similar to controls regardless of preparation method or starch content. Microscopy showed particulate starch distribution in films made with rapidly cooled starch-palmitic acid particles but smooth, diffuse starch staining with acidified sodium palmitate complexes. The mild effects on tensile properties suggest that submicron starch particles prepared from amylose-palmitic acid complexes provide a useful, commercially viable approach for PVOH film modification.

  2. Magnetic properties of the Fe{sup II} spin crossover complex in emulsion polymerization of trifluoroethylmethacrylate using poly(vinyl alcohol)

    SciTech Connect

    Suzuki, Atsushi; Iguchi, Motoi; Oku, Takeo; Fujiwara, Motoyasu

    2010-04-15

    Influence of chemical substitution in the Fe{sup II} spin crossover complex on magnetic properties in emulsion polymerization of trifluoroethylmethacrylate using poly(vinyl alcohol) as a protective colloid was investigated near its high spin/low spin (HS/LS) phase transition. The obvious bi-stability of the HS/LS phase transition was considered by the identification of multiple spin states between the quintet (S=2) states to single state (S=0) across the excited triplet state (S=1). Magnetic parameters of gradual shifts of anisotropy g-tensor supported by the molecular distortion of the spin crossover complex would arise from a Jahn-Teller effect regarding ligand field theory on the basis of a B3LYP density functional theory using electron spin resonance (ESR) spectrum and X-ray powder diffraction. - Graphical abstract: AFM surface image of the emulsion particles with the spin crossover complex.

  3. Short-range order and fractal cluster structure of aggregates of barium titanate microparticles in a composite based on cyano-ethyl ester of polyvinyl alcohol

    NASA Astrophysics Data System (ADS)

    Krasovskii, A. N.; Novikov, D. V.; Vasina, E. S.; Matveichikova, P. V.; Sychev, M. M.; Rozhkova, N. N.

    2015-12-01

    The distribution of barium titanate (BaTiO3) microparticles in the matrix of cyano-ethyl ester of polyvinyl alcohol and the change in the surface energy upon introduction of shungite carbon nanoclusters into the dielectric composite have been investigated using the methods of scanning electron microscopy and contact angles. The computer processing of the electron microscopy data has demonstrated that the introduction of 0.04% shungite carbon nanoparticles into the composite leads to a decrease in the spatial homogeneity of the quasi-lattice and to an increase in the local density distribution of BaTiO3 microparticles, as well as in the correlation length corresponding to the formation of an infinite cluster of BaTiO3 particles. It has been found that, in this case, the surface energy and dielectric permittivity of the composite extremely increase.

  4. A novel multicompartimental system based on aminated poly(vinyl alcohol) microspheres/succinoylated pullulan microspheres for oral delivery of anionic drugs.

    PubMed

    Constantin, M; Fundueanu, G; Bortolotti, F; Cortesi, R; Ascenzi, P; Menegatti, E

    2007-02-07

    Poly(vinyl alcohol) (PVA) microspheres were prepared by dispersion reticulation with glutaraldehyde and further aminated. These microspheres were firstly loaded with diclofenac (DF) and then entrapped in cellulose acetate butyrate (CAB) microcapsules by an o/w solvent evaporation technique for intestinal delivery of drug. The encapsulated PVA microspheres due to their low swelling degree in intestinal fluids, do not have enough force to produce the disruption of CAB shell, therefore different amounts of succinoylated pullulan microspheres (SP-Ms) (exchange capacity up to 5.2 meq/g) were co-encapsulated. The SP-Ms do not swell in acidic pH, but swell up to 20-times in intestinal fluids causing the rupture of CAB shell and facilitating the escape of loaded PVA microspheres.

  5. Coexistence of Write Once Read Many Memory and Memristor in blend of Poly(3,4-ethylenedioxythiophene): polystyrene sulfonate and Polyvinyl Alcohol

    PubMed Central

    Nguyen, Viet Cuong; Lee, Pooi See

    2016-01-01

    In this work, the coexistence of Write Once Read Many Memory (WORM) and memristor can be achieved in a single device of Poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT: PSS) and Polyvinyl Alcohol (PVA) blend organic memory system. In memristor mode, the bistable resistance states of the device can be cycled for more than 1000 times. Once a large negative bias of −8V was applied to the device, it was switched to permanent high resistance state that cannot be restored back to lower resistance states. The mechanism of the memristor effect can be attributed to the charge trapping behaviour in PVA while the WORM effect can be explained as the electrochemical characteristic of PEDOT: PSS which harnesses the percolative conduction pathways. The results may facilitate multipurpose memory device with active tunability. PMID:27941830

  6. PMMA-Etching-Free Transfer of Wafer-scale Chemical Vapor Deposition Two-dimensional Atomic Crystal by a Water Soluble Polyvinyl Alcohol Polymer Method

    PubMed Central

    Van Ngoc, Huynh; Qian, Yongteng; Han, Suk Kil; Kang, Dae Joon

    2016-01-01

    We have explored a facile technique to transfer large area 2-Dimensional (2D) materials grown by chemical vapor deposition method onto various substrates by adding a water-soluble Polyvinyl Alcohol (PVA) layer between the polymethyl-methacrylate (PMMA) and the 2D material film. This technique not only allows the effective transfer to an arbitrary target substrate with a high degree of freedom, but also avoids PMMA etching thereby maintaining the high quality of the transferred 2D materials with minimum contamination. We applied this method to transfer various 2D materials grown on different rigid substrates of general interest, such as graphene on copper foil, h-BN on platinum and MoS2 on SiO2/Si. This facile transfer technique has great potential for future research towards the application of 2D materials in high performance optical, mechanical and electronic devices. PMID:27616038

  7. Effect of electron beam irradiation on the structural properties of poly(vinyl alcohol) formulations with triphenyl tetrazolium chloride dye (TTC)

    NASA Astrophysics Data System (ADS)

    Ali, Z. I.; Said, Hossam M.; Ali, H. E.

    2006-01-01

    Films of poly(vinyl alcohol) (PVA) composites with triphenyl tetrazolium chloride (TTC) dye were prepared and exposed to various radiation doses delivered by accelerated electrons. The results showed that at a low dose of 50 kGy, the colour difference (Δ E*) of PVA/TTC films was increased by ˜10 times of the initial value. However, the change in colour differences did not go systematically with increasing the TTC content, in which the composite with 1.5 wt% displayed higher value than that with 3.5 wt%. The differential scanning calorimetry (DSC) showed that the presence of the TTC dye caused a depression in the melting point ( Tm) and heat of fusion (Δ Hf) of the PVA bulk polymer. However, the thermogravimetric analysis (TGA) showed that the presence of the TTC dye improved the thermal stability of PVA. Also, the tensile strength at break of PVA/TTC composites was improved after electron beam irradiation.

  8. Coexistence of Write Once Read Many Memory and Memristor in blend of Poly(3,4-ethylenedioxythiophene): polystyrene sulfonate and Polyvinyl Alcohol.

    PubMed

    Nguyen, Viet Cuong; Lee, Pooi See

    2016-12-12

    In this work, the coexistence of Write Once Read Many Memory (WORM) and memristor can be achieved in a single device of Poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT: PSS) and Polyvinyl Alcohol (PVA) blend organic memory system. In memristor mode, the bistable resistance states of the device can be cycled for more than 1000 times. Once a large negative bias of -8V was applied to the device, it was switched to permanent high resistance state that cannot be restored back to lower resistance states. The mechanism of the memristor effect can be attributed to the charge trapping behaviour in PVA while the WORM effect can be explained as the electrochemical characteristic of PEDOT: PSS which harnesses the percolative conduction pathways. The results may facilitate multipurpose memory device with active tunability.

  9. Poly(vinyl alcohol) and alginate cross-linked matrix with immobilized Prussian blue and ion exchange resin for cesium removal from waters.

    PubMed

    Lai, Yu-Chen; Chang, Yin-Ru; Chen, Man-Li; Lo, Yu-Kuo; Lai, Juin-Yih; Lee, Duu-Jong

    2016-08-01

    Cesium (Cs) removal from contaminated water bodies is an emerging issue after the disaster at the Fukushima Daiichi Nuclear Power Plant. The Prussian blue (PB) is an effective Cs adsorbent but will release hexacyanoferrate fragments from the adsorbent matrix during adsorption. Alginate is an affordable biopolymer for PB particles immobilization. This study synthesized poly(vinyl alcohol) (PVA) and alginate cross-linked matrix for immobilization of PB nano-sized particles and a surface-modified styrene-ethyl styrene divinyl benzene resin and tested their swelling stability and Cs adsorption performance in fresh water and in seawater. The PVA-alginate granules have high structural stability in both fresh water and seawater, with the Cs adsorption capability higher for the former than the latter. The adopted resin effectively remove released PB fragments from the tested granules. The transport and reaction parameters for the granules and for the sand filter bed were estimated.

  10. Effect of polyvinyl alcohol hydrogel as a biocarrier on volatile fatty acids production of a two-stage thermophilic anaerobic membrane bioreactor.

    PubMed

    Chaikasem, Supawat; Abeynayaka, Amila; Visvanathan, Chettiyappan

    2014-09-01

    This work studied the effect of polyvinyl alcohol hydrogel (PVA-gel) beads, as an effective biocarrier for volatile fatty acid (VFA) production in hydrolytic reactor of a two-stage thermophilic anaerobic membrane bioreactor (TAnMBR). The two-stage TAnMBR, treating synthetic high strength particulate wastewater with influent chemical oxygen demand (COD) [16.4±0.8 g/L], was operated at 55 °C. Under steady state conditions, the reactor was operated at an organic loading rate of 8.2±0.4 kg COD/m(3) d. Operational performance of the system was monitored by assessing VFA composition and quantity, methane production and COD removal efficiency. Increment of VFA production was observed with PVA-gel addition. Hydrolytic effluent contained large amount of acetic acid and n-butyric acid. However, increase in VFA production adversely affected the methanogenic reactor performance due to lack of methanogenic archaea.

  11. Preparation of poly(vinyl alcohol)-grafted graphene oxide/poly(vinyl alcohol) nanocomposites via in-situ low-temperature emulsion polymerization and their thermal and mechanical characterization

    NASA Astrophysics Data System (ADS)

    Zhang, Shengchang; Liu, Pengqing; Zhao, Xiangsen; Xu, Jianjun

    2017-02-01

    An in-situ polymerization combined with chemical grafting modification method for preparing Poly(vinyl alcohol)-grafted graphene oxide/Poly(vinyl alcohol) (PVA-g-GO/PVA) nanocomposites was reported. Firstly, Poly(vinyl acetate)-grafted graphene oxide/Poly(vinyl acetate) nanocomposites were prepared, and then the PVA-g-GO/PVA nanocomposites could be obtained through alcoholysis reaction. X-ray photoelectron spectrometer and fourier-transform infrared spectrometer confirmed that the PVAc or PVA chains were successfully grafted to GO sheets during in-situ polymerization and alcoholysis. And the results from transmission electron microscopy, scanning electron microscopy and X-ray diffraction showed that the well compatibility and homogenous dispersion of PVA-g-GO in PVA matrix could be achieved. Differential scanning calorimetric, thermogravimetry analysis and tensile test were employed to study the thermal and mechanical properties of the PVA-g-GO/PVA nanocomposites. The results indicated that a 53% improvement of tensile strength and a 36% improvement of Young's modulus were achieved by addition of 0.5 wt% of GO sheets. And the glass transition temperature of PVA-g-GO/PVA nanocomposites was increased, and their thermal stability and crystallization degree were both decreased. Due to well dispersion of fillers and strong interfacial interactions at the filler-matrix interface, in-situ polymerization combined with chemical grafting modification was a good choice to prepare graphene/PVA nanocomposite with excellent mechanical properties.

  12. Cell culture and characterization of cross-linked poly(vinyl alcohol)-g-starch 3D scaffold for tissue engineering.

    PubMed

    Hsieh, Wen-Chuan; Liau, Jiun-Jia

    2013-10-15

    The research goal of this experiment is chemically to cross-link poly(vinyl alcohol) (PVA) and starch to form a 3D scaffold that is effective water absorbent, has a stable structure, and supports cell growth. PVA and starch can be chemically cross-linked to form a PVA-g-starch 3D scaffold polymer, as observed by Fourier transform infrared spectroscopy (FTIR), with an absorbency of up to 800%. Tensile testing reveals that, as the amount of starch increases, the strength of the 3D scaffold strength reaches 4×10(-2) MPa. Scanning electron microscope (SEM) observations of the material reveal that the 3D scaffold is highly porous formed using a homogenizer at 500 rpm. In an enzymatic degradation, the 3D scaffold was degraded by various enzymes at a rate of up to approximately 30-60% in 28 days. In vitro tests revealed that cells proliferate and grow in the 3D scaffold material. Energy dispersive spectrometer (EDS) analysis further verified that the bio-compatibility of this scaffold.

  13. Modifying Poly(Vinyl Alcohol) (PVA) from Insulator to Small-Bandgap Polymer: A Novel Approach for Organic Solar Cells and Optoelectronic Devices

    NASA Astrophysics Data System (ADS)

    Aziz, Shujahadeen B.

    2016-01-01

    An innovative method has been used to reduce the bandgap of poly(vinyl alcohol) (PVA) polymer by addition of a nontoxic, inexpensive, and environmentally friendly material. The resulting materials are small-bandgap polymers, hence opening new frontiers in green chemistry. The doped PVA films showed a wide range of light absorption of the solar spectrum from 200 nm to above 800 nm. Nonsharp absorption behavior versus wavelength was observed for the samples. The refractive index exhibited a wide range of dispersion. Shift of the absorption edge from 6.2 eV to 1.5 eV was observed. The energy bandgap of PVA was diminished to 1.85 eV upon addition of black tea extract solution, lying in the range of small-bandgap polymers. Increase of the optical dielectric constant was observed with increasing tea solution addition. The results indicate that small-bandgap PVA with good film-forming ability could be useful in terms of cost-performance tradeoff, solving problems of short lifetime, cost, and flexibility associated with conjugated polymers. The decrease of the Urbach energy upon addition of black tea extract solution indicates modification of PVA from a disordered to ordered material. X-ray diffraction results confirm an increase of the crystalline fraction in the doped samples.

  14. Mechanical and structural response of a hybrid hydrogel based on chitosan and poly(vinyl alcohol) cross-linked with epichlorohydrin for potential use in tissue engineering.

    PubMed

    Garnica-Palafox, I M; Sánchez-Arévalo, F M; Velasquillo, C; García-Carvajal, Z Y; García-López, J; Ortega-Sánchez, C; Ibarra, C; Luna-Bárcenas, G; Solís-Arrieta, L

    2014-01-01

    The development and characterization of a hybrid hydrogel based on chitosan (CS) and poly(vinyl alcohol) (PVA) chemically cross-linked with epichlorohydrin (ECH) is presented. The mechanical response of these hydrogels was evaluated by uniaxial tensile tests; in addition, their structural properties such as average molecular weight between cross-link points (Mcrl), mesh size (DN), and volume fraction (v(s)) were determined. This was done using the equivalent polymer network theory in combination with the obtained results from tensile and swelling tests. The films showed Young's modulus values of 11 ± 2 MPa and 9 ± 1 MPa for none irradiated and ultraviolet (UV) irradiated hydrogels, respectively. The cell viability was assessed using Calcein AM and Ethidium homodimer-1 assay and environmental scanning electron microscopy. The 1-(4,5-dimethylthiazol-2-yl)-3,5-diphenylformazan thiazolyl blue formazan (MTT Formazan assay) results did not show cytotoxic effects; this was in good agreement with nuclear magnetic resonance and fourier transform infrared spectroscopies; their results did not show traces of ECH. This indicated that after the crosslinking process, there was no free ECH; furthermore, any possibility of ECH release in the construct during cell culture was discarded. The CS-PVA-ECH hybrid hydrogel allowed cell growth and extracellular matrix formation and showed adequate mechanical, structural, and biological properties for potential use in tissue engineering applications.

  15. Physicochemical characterization and biocompatibility in vitro of biphasic calcium phosphate/polyvinyl alcohol scaffolds prepared by freeze-drying method for bone tissue engineering applications.

    PubMed

    Nie, Lei; Chen, Dong; Suo, Jinping; Zou, Peng; Feng, Shuibin; Yang, Qi; Yang, Shuhua; Ye, Shunan

    2012-12-01

    In this study, a well developed porous biphasic calcium phosphate (BCP)/polyvinyl alcohol (PVA) scaffold was prepared by emulsion foam freeze-drying method possessed moderate inter-connected pores and porosity. The SEM analysis showed that BCP nano-particles could disperse uniformly in the scaffolds, and the pore size, porosity, and compressive strength could be controlled by the weight ratio of BCP/PVA. The in vitro degradation and cytocompatibility of scaffolds were examined in this study. The degradation analysis showed the prepared scaffolds have a low variation of pH values (approximately 7.18-7.36) in SBF solution, and have the biodegradation rate of BCP/PVA scaffolds decreased with the increase of PVA concentration. Moreover, MTT assay indicated that the BCP/PVA porous scaffold has no negative effects on cells growth and proliferation, and the hBMSCs possessed a favorable spreading morphology on the BCP/PVA scaffold surface. The inter-connected pore structure, mechanical strength, biodegradation rate and cytocompatibility of the prepared BCP/PVA scaffold can meet essential requirements for blame bearing bone tissue engineering and regeneration.

  16. Photoinduced synthesis of single-digit micrometer-size spheroidal calcite composites in the presence of partially hydrolyzed poly(vinyl alcohol)

    NASA Astrophysics Data System (ADS)

    Nishio, Takashi; Naka, Kensuke

    2015-06-01

    Photoinduced crystallization of calcium carbonate (CaCO3), which was based on the photodecarboxylation of ketoprofen (KP, 2-(3-benzoylphyenyl)propionic acid) under alkaline conditions of pH 8.4 and 10 was studied for preparation of CaCO3 composite particles in single-digit micrometer-sizes. In this method, a homogeneous solution comprising KP, calcium chloride, ammonia, and partially hydrolyzed poly(vinyl alcohol) (PVAPS, degree of saponification: 86.5-89.0 mol%) was used as a precursor solution and was exposed to ultraviolet (UV) irradiation for different time periods. After the UV irradiation for 50 min, calcite spheroids in single-digit micrometer-sizes were obtained as major products at pH 8.4. The obtained calcite spheroids contained organic components of about 10 wt%. The comparison of the characteristics of the CaCO3 obtained at pH 8.4 and 10 suggests that the nucleation and crystallization of both vaterite and calcite continuously took place in a moderated supersaturation owing to the CO2 hydration equilibrium as long as the photodecarboxylation of KP continued. Consequently, the aggregation-based crystal growth in the presence of PVAPS seemed to enable the formation of the spheroidal composites of calcite in single-digit micrometer-sizes.

  17. An animal model of peripheral nerve regeneration after the application of a collagen-polyvinyl alcohol scaffold and mesenchymal stem cells.

    PubMed

    Marinescu, Silviu Adrian; Zărnescu, Otilia; Mihai, Ioana Ruxandra; Giuglea, Carmen; Sinescu, Ruxandra Diana

    2014-01-01

    Extensive nerve injuries often leading to nerve gaps can benefit, besides the gold standard represented by autologous nerve grafts, by the inciting field of tissue engineering. To enhance the role of biomaterials in nerve regeneration, the nerve conduits are associated with Schwann or Schwann-like cells. In this study, we evaluated rat sciatic nerve regeneration, by using a biodegradable nerve guide composed of Collagen (COL) and Polyvinyl Alcohol (PVA), associated with mesenchymal stem cells (MSC). After the exposure of the rat sciatic nerve, a nerve gap was created by excising 1 cm of the nerve. Three experimental groups were used for nerve gap bridging: autografts, nerve conduits filled with medium culture and nerve conduits filled with MSC. The methods of sensory and motor assessment consisted of the functional evaluation of sciatic nerve recovery - toe-spread, pinprick tests and gastrocnemius muscle index (GMI). The histological and immunocytochemical analysis of the probes that were harvested from the repair site was performed at 12 weeks. Successful nerve regeneration was noted in all three groups at the end of the 12th week. The functional and immunocytochemical results suggested that COL-PVA tubes supported with mesenchymal stem cells could be considered similar to autologous nerve grafts in peripheral nerve regeneration, without the drawbacks of the last ones. The functional results were better for the autografts and the ultrastructural data were better for the nerve conduits, but there were not noticed any statistical differences.

  18. Formulation and in vitro characterization of novel sildenafil citrate-loaded polyvinyl alcohol-polyethylene glycol graft copolymer-based orally dissolving films.

    PubMed

    Xu, Li-Li; Shi, Li-Li; Cao, Qing-Ri; Xu, Wei-Juan; Cao, Yue; Zhu, Xiao-Yin; Cui, Jing-Hao

    2014-10-01

    This work was aimed to develop novel sildenafil citrate (SC)-loaded polyvinyl alcohol (PVA)-polyethylene glycol (PEG) graft copolymer (Kollicoat(®) IR)-based orally dissolving films (ODFs) using a solvent casting method. Formulation factors such as plasticizers and disintegrants were optimized on the basis of characteristics of blank ODFs. The SC-loaded ODF with a loading capacity up to 6.25mg in an area of 6 cm(2) was prepared and evaluated in terms of mechanical properties, disintegration time and dissolution rate. The physicochemical properties of drug-loaded ODF were also investigated using the scanning electron microscope (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FT-IR). The blank ODF composed of Kollicoat(®) IR, sodium alginate (ALG-Na) and glycerol (10:2:1.5, w/w) had a remarkably short disintegration time of about 20s. The SC-loaded ODF showed a delayed disintegration time (about 25s), but exhibited improved mechanical properties when compared to the blank ODF. SC was homogeneously dispersed throughout the ODF and the crystalline form of drug had been partly changed, existing strong hydrogen bonding between the drug and carriers. The Kollicoat(®) IR/ALG-Na based ODFs containing SC might be an alternative to conventional tablet for the treatment of male erectile dysfunction.

  19. Electrochemically driven biocatalysis of the oxygenase domain of neuronal nitric oxide synthase in indium tin oxide nanoparticles/polyvinyl alcohol nanocomposite.

    PubMed

    Xu, Xuan; Wollenberger, Ulla; Qian, Jing; Lettau, Katrin; Jung, Christiane; Liu, Songqin

    2013-12-01

    Nitric oxide synthase (NOS) plays a critical role in a number of key physiological and pathological processes. Investigation of electron-transfer reactions in NOS would contribute to a better understanding of the nitric oxide (NO) synthesis mechanism. Herein, we describe an electrochemically driven catalytic strategy, using a nanocomposite that consisted of the oxygenase domain of neuronal NOS (D290nNOSoxy), indium tin oxide (ITO) nanoparticles and polyvinyl alcohol (PVA). Fast direct electron transfer between electrodes and D290nNOSoxy was observed with the heterogeneous electron transfer rate constant (ket) of 154.8 ± 0.1s(-1) at the scan rate of 5 Vs(-1). Moreover, the substrate N(ω)-hydroxy-L-arginine (NHA) was used to prove the concept of electrochemically driven biocatalysis of D290nNOSoxy. In the presence of the oxygen cosubstrate and tetrahydrobiopterin (BH4) cofactor, the addition of NHA caused the decreases of both oxidation current at +0.1 V and reduction current at potentials ranging from -0.149 V to -0.549 V vs Ag/AgCl. Thereafter, a series of control experiments such as in the absence of BH4 or D290nNOSoxy were performed. All the results demonstrated that D290nNOSoxy biocatalysis was successfully driven by electrodes in the presence of BH4 and oxygen. This novel bioelectronic system showed potential for further investigation of NOS and biosensor applications.

  20. Effect of monomer sequence distribution in poly(vinyl alcohol-co-vinyl acetate) on the hydrogen bonding structure and physical properties

    NASA Astrophysics Data System (ADS)

    Tasaka, Shun; Urakawa, Osamu; Inoue, Tadashi

    2015-03-01

    It has been well known that hydrogen (H-) bonding interaction in polymer materials strongly affects their properties. For example, glass transition temperature (Tg) and terminal relaxation time increase by introducing H-bonding sites. This is because the molecular motion is restricted due to the formation of inter- and intra-chain H-bonds. For H-bonding copolymers in which H-bonding monomer and non- bonding one are incorporated, the fraction dependence of their properties has been examined so far. However, the influence of sequence distribution on their properties has not been studied in detail. In this work, we investigated the H-bonding structure and physical properties of molten poly(vinyl alcohol-co-vinyl acetate) with different monomer sequences to clarify the effect of the sequence distribution. We found that, with increasing the randomness in monomer sequences, the number of H-bonds between carbonyl group and hydroxyl (OH) group increased. Moreover, OH groups form linearly connected structure (OH-OH-OH) and its number also increases with the sequence randomness. Tg for the samples with higher sequence randomness are higher than those with lower randomness for high VOH copolymers. These results indicate that formation of larger number of H-bonds makes Tg higher.

  1. Luminescent Poly(vinyl alcohol)/Carbon Quantum Dots Composites with Tunable Water-Induced Shape Memory Behavior in Different pH and Temperature Environments.

    PubMed

    Yang, Guanghui; Wan, Xuejuan; Liu, Yijin; Li, Rui; Su, Yikun; Zeng, Xierong; Tang, Jiaoning

    2016-12-21

    Luminescent water-induced shape memory polymer (SMP) composites with tunable shape recovery rate are developed by blending poly(vinyl alcohol) (PVA) and carbon quantum dots (CQDs). The oxygen and active hydrogen-rich CQDs can serve as extra physical cross-linking points in PVA via strong hydrogen bonding interaction, which largely improves the shape memory performances of PVA. At room temperature, water can successfully actuate the shape recovery of deformed PVA/CQDs composite. It is demonstrated that this water-induced shape recovery is mainly attributed to the plasticizing effect of water and its competitive hydrogen bonding. Furthermore, a quantitative bending test suggests that the shape recovery time of this water-induced SMP is tunable by altering the environmental pH value and temperature, and a relatively large shape recovery time window (from 20 to 200 s) can be achieved. In addition, the introduction of CQDs endows the PVA/CQDs SMP composites with excellent luminescent property, which makes the shape change of SMP visible under UV light. It should be noted that the mild stimulus condition and tunable shape recovery performances make the luminescent visible PVA/CQDs SMP feasible for diverse biological applications in smart medical devices, stimuli-responsive drug-release, and intelligent sensors in vivo and in vitro.

  2. Solution spinning of a high-? oxide superconductor: the effect of poly(vinyl alcohol) spinning medium on the critical current density of melt-processed ? superconducting filaments

    NASA Astrophysics Data System (ADS)

    Tomita, Hisayo; Sunohara, Makoto; Goto, Tomoko; Takahashi, Kiyohisa

    1996-12-01

    The precursor 0953-2048/9/12/014/img9 filament was prepared by solution spinning through a homogeneous aqueous poly(vinyl alcohol) (PVA) solution of Y, Ba and Cu acetates. The solution spinning was successfully performed using PVA with degrees of polymerization (DP) of 1700 and 2450 and a degree of saponification of 85 mol%. The as-drawn filament was heated to remove volatile components and partially melted to generate a superconducting phase. The effects of the DP of PVA and a content of mixed acetates in the precursor filament on the critical current density 0953-2048/9/12/014/img10 of the melt-processed filament were examined. The higher 0953-2048/9/12/014/img11 was obtained for the filament spun from PVA solution of higher DP and lower acetate content. The highest 0953-2048/9/12/014/img11 value of 0953-2048/9/12/014/img13 at 77 K and 0 T was achieved for the filament spun from the DP 2450 PVA with an acetate to PVA ratio of two.

  3. Evaluation of the effect of V2O5 on the electrical and thermoelectric properties of poly(vinyl alcohol)/graphene nanoplatelets nanocomposite

    NASA Astrophysics Data System (ADS)

    Morad, M.; Fadlallah, M. M.; Hassan, M. A.; Sheha, E.

    2016-03-01

    The aim of this contribution is to introduce high performance materials for thermoelectric devices. A nanopolymer composite of PVAGNP ((polyvinyl alcohol ((PVA)0.6/graphene nanoplatelets (GNP)0.4))1-x(V2O5)x where x = 0, 2.5, 5, 7.5 and 10 wt% has been prepared using a solution cast technique. The influence of V2O5 additives on the morphology, structure, thermal and electrical properties of PVA has been examined by FTIR, XRD, TGA, DC and IV techniques. The disassociation of V2O5 to (V4+) and (V5+) in the composites acts as a co-bridge which can facilitate the translational electronic motion, which enhances the charge carrier mobility and the electrical conductivity. A prototype cell was constructed using (PVAGNP)1-x(GNP)x nanocomposites with constantan wire. The addition of V2O5 improves the thermoelectric properties of the (PVA)0.6(GNP)0.4 nanocomposite, where the Seebeck coefficient is increased from 23.1 to 45.8 μV K-1 from 0 to 10 wt% V2O5, respectively. The power factor is increased from 1.17 × 10-2 to 36.30 × 10-2 μWm-1 K-2 from 0 to 10 wt% V2O5, respectively, and the ZT is increased from 4.47 × 10-9 to 1.46 × 10-7.

  4. Modification of Novel Conductive PEDOT:Sulfonated Polyimide Nano-Thin Films by Anionic Surfactant and Poly(vinyl alcohol) for Electronic Applications

    NASA Astrophysics Data System (ADS)

    Romyen, Nathavat; Thongyai, Supakanok; Praserthdam, Piyasan; Sotzing, Gregory A.

    2013-12-01

    Conductive poly(3,4-ethylenedioxythiophene):sulfonated polyimide (PEDOT: SPI) nanoscale thin films were successfully developed by addition of anionic surfactant and poly(vinyl alcohol) (PVA) for potential application in electronic devices. In this work, sodium dodecyl sulfate (SDS) surfactant was introduced into PEDOT:SPI aqueous suspensions to improve the dispersion stability of the particles in water, leading to high transparency and low contact angle of PEDOT:SPI thin films. All of the conducting polymer thin films showed high transparency of more than 85% transmission. Conductivity enhancement and good film-formation properties of PEDOT:SPI were achieved by adding various amounts of PVA to each polymer aqueous suspension because of the resulting conformational changes. The highest conductivity of 0.134 S/cm was achieved at 0.08 wt.% PVA in PEDOT:SPI2/SDS/PVA film, increased by a factor of 3.5 compared with the original material. In addition, PVA also improved the thermal stability of the conductive films, as verified by thermogravimetric analysis (TGA). The interactions between conducting polymers, PVA, and SDS surfactant affecting nano-thin film properties were revealed and investigated. Moreover, the interactions between SDS and SPI were proven to be different from those between SDS and poly(styrenesulfonate) (PSS) in conventional PEDOT:PSS solutions.

  5. Synergistic and competitive aspects of the adsorption of poly(ethylene glycol) and poly(vinyl alcohol) onto Na-bentonite.

    PubMed

    Clegg, Francis; Breen, Chris; Khairuddin

    2014-11-20

    The competitive adsorption of poly(ethylene glycol) (PEG) and poly(vinyl alcohol) (PVOH) onto Na-bentonite has been assessed quantitatively. Particular emphasis was focused on the amount of organic located within the bentonite interlayer and any subsequent effects on the extent of layer expansion. The individual isotherms showed strong adsorption for both PVOH and PEG at amounts lower than the quantities required to produce a fully loaded bilayer (0.33 g of PVOH/g of clay) and single layered structures (0.10 g of PEG/g of clay), respectively. Above these concentrations, the incremental amounts adsorbed were smaller, and the concentration of adsorbates in solution gradually increased. Na-bentonite adsorbed more PVOH than PEG at any given concentration. In the competitive study, the amount of PVOH adsorbed was enhanced in the presence of PEG (0.10 and 0.30 g/g of clay), but less PEG was adsorbed. At low loadings of PVOH (0.02-0.10 g/g of clay), the amount of adsorbed PEG was increased but at higher PVOH levels PEG adsorption was reduced. The XRD data showed stepped changes in the d-spacing as the adsorbed amounts of both PEG and PVOH increased. The PEG-bentonite samples did not expand beyond a bilayer structure (18 Å), but the XRD data for PVOH-treated samples indicated the formation of multilayer structures (d ≥ 44 Å).

  6. Passive approach for the improved dispersion of polyvinyl alcohol-based functionalized multi-walled carbon nanotubes/Nafion membranes for polymer electrolyte membrane fuel cells.

    PubMed

    Abu Sayeed, M D; Talukdar, Krishan; Kim, Hee Jin; Park, Younjin; Gopalan, A I; Kim, Young Ho; Lee, Kwang-Pill; Choi, Sang-June

    2014-12-01

    Multi-walled carbon nanotubes (MWCNTs) are regarded as ideal fillers for Nafion polymer electrolyte membranes (PEMs) for fuel cell applications. The highly aggregated properties of MWCNTs can be overcome by the successful cross-linking with polyvinyl alcohol (PVA) into the MWCNTs/Nafion membrane. In this study, a series of nanocomposite membranes were fabricated with the PVA-influenced functionalized MWCNTs reinforced into the Nafion polymer matrix by a solution casting method. Several different PVA contents were blended to f-MWCNTs/Nafion nanocomposite membranes followed by successful cross-linking by annealing. The surface morphologies and the inner structures of the resulting PVA-MWCNTs/Nafion nanocomposite membranes were then observed by optical microscopy and scanning electron microscopy (SEM) to investigate the dispersion of MWCNTs into the PVA/Nafion composite membranes. After that, the nanocomposite membranes were characterized by thermo-gravimetric analysis (TGA) to observe the thermal enhancement caused by effective cross-linking between the f-MWCNTs with the composite polymer matrixes. Improved water uptake with reduced methanol uptake revealed the successful fabrication of PVA-blended f-MWCNTs/Nafion membranes. In addition, the ion exchange capacity (IEC) was evaluated for PEM fuel cell (PEMFC) applications.

  7. Real-time tracking the Li+-ion transition behavior and dynamics in solid Poly(vinyl alcohol)/LiClO4 electrolytes

    PubMed Central

    Bao, Lixia; Zou, Xin; Luo, Xin; Pu, Yanlei; Wang, Jiliang; Lei, Jingxin

    2017-01-01

    To delicately track the Li-ion transport in SPEs under an external electric field (EF) is a big challenge, considering the limitation of most spectroscopic methods to monitor the real-time conformational changes and track the dynamic process. Herein, real-time Li-ion transition behavior and transport dynamics in typical poly(vinyl alcohol)/LiClO4 electrolytes under an external EF have been studied by combining time-resolved Fourier transform infrared (FTIR) with two-dimensional correlation FTIR spectroscopy. Results show that no migration of Li-ions has been detected when the time scale of the EF loading is at nanosecond (less than 200 ns). However, for the first time, Li-ions have been found to significantly transfer along the EF direction as the time scale enhances to microsecond order of magnitude and the migration period is less than 10 microseconds. The Li+ migration in the SPEs under an EF is a complicated process including quasi-periodic dissociation and coordination effects between Li-ion carriers and polymeric chains. PMID:28378837

  8. Aqueous Boron Removal by Using Electrospun Poly(vinyl alcohol) (PVA) Mats: A Combined Study of IR/Raman Spectroscopy and Computational Chemistry.

    PubMed

    Lee, Kwan Sik; Eom, Ki Heon; Lim, Jun-Heok; Ryu, Hyunwook; Kim, Suhan; Lee, Dong-Kyu; Won, Yong Sun

    2017-03-23

    We report the use of a novel and efficient method to remove aqueous boron by using electrospun, water-resistant poly(vinyl alcohol) (PVA) mats stabilized in methanol. The removal of the primary aqueous boron species as (B(OH)3), was accomplished by chemical adsorption in reactions with -OH (hydroxyl) groups on the PVA mat surface. The chemical adsorption of B(OH)3 was qualitatively confirmed by the analysis of IR and Raman spectra. The bands, corresponding to the molecular vibration modes of chemically bonded boron in PVA, were identified by using the frequency calculation from the computational chemistry for the first time. The adsorption capacities of PVA mats for aqueous boron were then quantitated at a low boron concentration (range: 0.0010 to 0.0025 g of aqueous boron per g of PVA mats) by the Carmine method. The PVA mats were prepared by a well-established electrospinning technique, which make these substrates promising potential candidates for use as boron-selective sorbent media in applications such as reverse osmosis desalination processes.

  9. Photoinduced conformational changes in DNA by poly(vinyl alcohol) carrying a malachite green moiety for protecting DNA against attack by nuclease.

    PubMed

    Uda, Ryoko M; Matsui, Takashi

    2015-11-14

    Light is a highly advantageous means of specific cell targeting. Though targeted gene delivery is an important characteristic of an ideal delivery vehicle, there has been little effort to develop a photoresponsive vector. Among nonviral vectors, cationic substances interact effectively with negatively charged DNA. With this property in mind, we designed copolymers of poly(vinyl alcohol) carrying a malachite green moiety (PVAMG) with different molecular weights. Though PVAMG has no affinity for DNA in the absence of light, it undergoes photoionization in the presence of light to afford cationic DNA binding sites. The DNA-PVAMG complex was investigated with respect to DNA conformational changes and its protective nature, which are important properties for nonviral vectors. PVAMG irradiation promoted DNA conformational transitions from coils to partial globules to compacted globules. The complex had a protective effect against DNase I after PVAMG irradiation, while DNA was degraded under dark conditions. The effect on DNA transition and the protective nature were sensitive to the molecular weight of PVAMG. The data regarding binding constants and binding mode provided insight into the structure of the DNA-PVAMG complex. To withstand DNase I attacks, complexation results in the compaction of DNA, which is further covered with PVAMG.

  10. On-line sample enrichment for the determination of proteins by capillary zone electrophoresis with poly(vinyl alcohol)-coated bubble cell capillaries.

    PubMed

    Law, Wai S; Zhao, Jian H; Li, Sam F Y

    2005-09-01

    Field-amplified sample stacking (FASS) is used to separate basic proteins in a poly-(vinyl alcohol)-coated bubble cell capillary. To our knowledge, this is the first paper describing the on-column stacking of proteins (as cations) using FASS in bubble cell capillary. The bubble cell capillary is fabricated using a one-step method. Cetyltrimethylammonium chloride is added into the running buffer to reverse the EOF and, thus, to pump the water plug out during the sample stacking step. The effect of the water plug lengths and sample injection durations were investigated and optimized. The results obtained were compared with those for the normal capillary without bubble cell in terms of resolution and sensitivity enhancement. Under the optimal condition, this method can improve the sensitivity of the peak areas ranging from 5000- to 26 000-fold. The RSDs (n = 5) of the migration time and peak area are satisfactory (less than 0.6 and 12%, respectively). Application of the capillary electrophoresis method with bubble cell, FASS, and UV detection thereby leads to the determination of these proteins at concentrations ranging from 3 to 10 ng/mL, based on a signal-to-noise ratio of 3:1.

  11. Quality control of fruit juices by using organic acids determined by capillary zone electrophoresis with poly(vinyl alcohol)-coated bubble cell capillaries.

    PubMed

    Navarro-Pascual-Ahuir, María; Lerma-García, María Jesús; Simó-Alfonso, Ernesto F; Herrero-Martínez, José Manuel

    2015-12-01

    An enhanced method for the determination of organic acids in several fruit juices by capillary zone electrophoresis (CZE) with direct UV-Vis detection has been developed in this work. First, a study with simulated real juice samples was done to find the best separation conditions. Next, several commercial fruit juices were analyzed, and the organic acid contents were quantified in less than 12 min using a poly(vinyl alcohol)-coated fused-silica 'bubble cell' capillary. The present method is reliable, fast and provides detection limits comprised between 0.1 and 2.5 μg mL(-1). Moreover, different chemometric techniques, based on CZE data, were examined. Linear discriminant analysis allowed the differentiation of fruit juices according to the fruit type, whereas multiple linear regression models predicted the percentages of orange and pineapple juices in binary blends with grape. Thus, the present methodology is of utmost interest for routine and quality control purposes in food industries.

  12. Preparation and properties of poly(vinyl alcohol)/chitosan blend bionanocomposites reinforced with cellulose nanocrystals/ZnO-Ag multifunctional nanosized filler

    PubMed Central

    Azizi, Susan; Ahmad, Mansor Bin; Hussein, Mohd Zobir; Ibrahim, Nor Azowa; Namvar, Farideh

    2014-01-01

    A series of novel bionanocomposites were cast using different contents of zinc oxide-silver nanoparticles (ZnO-AgNPs) stabilized by cellulose nanocrystals (CNC) as multifunctional nanosized fillers in poly(vinyl alcohol)/chitosan (PVA/Cs) matrices. The morphological structure, mechanical properties, ultraviolet-visible absorption, and antimicrobial properties of the prepared films were investigated as a function of their CNC/ZnO-AgNP content and compared with PVA/chitosan/CNC bionanocomposite films. X-ray diffraction and field emission scanning electron microscopic analyses showed that the CNC/ZnO-AgNPs were homogeneously dispersed in the PVA/Cs matrix and the crystallinity increased with increasing nanosized filler content. Compared with pure PVA/Cs, the tensile strength and modulus in the films increased from 0.055 to 0.205 GPa and from 0.395 to 1.20 GPa, respectively. Ultraviolet and visible light can be efficiently absorbed by incorporating ZnO-AgNPs into a PVA/Cs matrix, suggesting that these bionanocomposite films show good visibility and ultraviolet-shielding effects. The bionanocomposite films had excellent antimicrobial properties, killing both Gram-negative Salmonella choleraesuis and Gram-positive Staphylococcus aureus. The enhanced physical properties achieved by incorporating CNC/ZnO-AgNPs could be beneficial in various applications. PMID:24790433

  13. Inorganic-organic polymer electrolytes based on poly(vinyl alcohol) and borane/poly(ethylene glycol) monomethyl ether for Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Aydın, Hamide; Şenel, Mehmet; Erdemi, Hamit; Baykal, Abdülhadi; Tülü, Metin; Ata, Ali; Bozkurt, Ayhan

    In this study, poly(vinyl alcohol) (PVA) was modified with poly(ethylene glycol) monomethyl ether (PEGME) using borane-tetrahydrofuran (BH 3/THF) complex. Molecular weights of both PVA and PEGME were varied prior to reaction. Boron containing comb-branched copolymers were produced and abbreviated as PVA1PEGMEX and PVA2PEGMEX. Then polymer electrolytes were successfully prepared by doping of the host matrix with CF 3SO 3Li at several stoichiomeric ratios with respect to EO to Li. The materials were characterized via nuclear magnetic resonance (1H NMR and 11B NMR), Fourier transform infrared spectroscopy (FT-IR), Thermogravimetry (TG) and differential scanning calorimeter (DSC). The ionic conductivity of these novel polymer electrolytes were studied by dielectric-impedance spectroscopy. Li-ion conductivity of these polymer electrolytes depends on the length of the side units as well as the doping ratio. Such electrolytes possess satisfactory ambient temperature ionic conductivity (>10 -4 S cm -1). Cyclic voltammetry results illustrated that the electrochemical stability domain extends over 4 V.

  14. Topological insulator: Bi{sub 2}Se{sub 3}/polyvinyl alcohol film-assisted multi-wavelength ultrafast erbium-doped fiber laser

    SciTech Connect

    Guo, Bo; Yao, Yong Yang, Yan-Fu; Yuan, Yi-Jun; Wang, Rui-Lai; Wang, Shu-Guang; Ren, Zhong-Hua; Yan, Bo

    2015-02-14

    We experimentally demonstrate a multi-wavelength ultrafast erbium-doped fiber laser incorporating a μm-scale topological insulator: Bi{sub 2}Se{sub 3}/Polyvinyl Alcohol film as both an excellent saturable absorber for mode-locking and a high-nonlinear medium to induce a giant third order optical nonlinear effect for mitigating the mode competition of erbium-doped fiber laser and stabilizing the multi-wavelength oscillation. By properly adjusting the pump power and the polarization state, the single-, dual-, triple-, four-wavelength mode-locking pulse could be stably initiated. For the four-wavelength operation, we obtain its pulse width of ∼22 ps and a fundamental repetition rate of 8.83 MHz. The fiber laser exhibits the maximum output power of 9.7 mW with the pulse energy of 1.1 nJ and peak power of 50 W at the pump power of 155 mW. Our study shows that the simple, stable, low-cost multi-wavelength ultrafast fiber laser could be applied in various potential fields, such as optical communication, biomedical research, and radar system.

  15. Real-time tracking the Li(+)-ion transition behavior and dynamics in solid Poly(vinyl alcohol)/LiClO4 electrolytes.

    PubMed

    Bao, Lixia; Zou, Xin; Luo, Xin; Pu, Yanlei; Wang, Jiliang; Lei, Jingxin

    2017-04-05

    To delicately track the Li-ion transport in SPEs under an external electric field (EF) is a big challenge, considering the limitation of most spectroscopic methods to monitor the real-time conformational changes and track the dynamic process. Herein, real-time Li-ion transition behavior and transport dynamics in typical poly(vinyl alcohol)/LiClO4 electrolytes under an external EF have been studied by combining time-resolved Fourier transform infrared (FTIR) with two-dimensional correlation FTIR spectroscopy. Results show that no migration of Li-ions has been detected when the time scale of the EF loading is at nanosecond (less than 200 ns). However, for the first time, Li-ions have been found to significantly transfer along the EF direction as the time scale enhances to microsecond order of magnitude and the migration period is less than 10 microseconds. The Li(+) migration in the SPEs under an EF is a complicated process including quasi-periodic dissociation and coordination effects between Li-ion carriers and polymeric chains.

  16. Multipoint relative humidity measurement by polyvinyl alcohol-coated Fresnel reflection-based optical fiber sensors with an array-waveguide grating.

    PubMed

    Wang, Xueping; Zhao, Chun-Liu; Li, Jihui; Jin, Yongxing; Jin, Shangzhong

    2013-04-01

    A simple multipoint humidity measurement by polyvinyl alcohol (PVA)-coated Fresnel reflection-based optical fiber sensors with an Array-Waveguide Grating (AWG) is proposed and demonstrated. Every channel end of the AWG is split as a vertical planar surface, and then is coated with a layer of a PVA whose refractive index is sensitive to moisture. The reflection intensity for each channel will change with its surrounding humidity, since the optical fiber interface's Fresnel reflection is affected strongly by the refractive index difference of the interface two sides. Multiplexing is achieved by the AWG with 16 channels, in which 15 channels can be used as sensing heads when they are coated with a layer of PVA and the left one is used as a reference channel. The experimental setup is simple and easy to handle. Experimental results show that the proposed Fresnel reflection-based optical fiber sensor for multipoint humidity measurement works well and the average sensitivity is 0.135 dB∕% relative humidity (RH) within the measurement range of 30%-80% RH.

  17. Effect of iron(III) sulphate on radiation-induced reduction of methyl viologen incorporated in poly(vinyl alcohol) film

    NASA Astrophysics Data System (ADS)

    Ohtani, Bunsho; Ye, Mu; Nishimoto, Sei-Ichi; Kagiya, Tsutomu

    Addition of iron(III) sulfate (Fe 2(SO 4) 3) to the methyl viologen (MV 2+)-poly(vinyl alcohol) (PVA) film dosimeter led to the induction dose ( Di) before appearance of blue-colored cation radical (MV +.) and reduction of G-value of MV +.. As a result, the measurable range for ionizing radiation (200 kV electron beam) was expanded to the higher dose >400 kGy, which was >25 times larger than that of base MV 2+-PVA film (<14 kGy). In the MV 2+-Fe 2(SO 4) 3-PVA film, iron(II) ion (Fe 2+) was also accumulated without any induction dose. The Fe 2+ still increased after Di, with the G-value relatively smaller than that before Di. Increase in pH ((pH) i) of the source aqueous PVA solution, subjected to casting into films, led to the decrease in Di and increase in G-value of MV +. ( G(MV +.)). The ratio of initial concentration of Fe 3+ (( CFe) i) to Di was apparently independent of ( CFe) i at given (pH) i. These results suggest the mechanism that radiation-induced electrons in the PVA matrix reduce both MV 2+ and Fe 3+, and the resulting MV +. successively reacts with neighboring Fe 3+ to regenerate MV 2+ in the initial stage of irradiation (within Di). At the dose of Di, such neighboring Fe 3+ is consumed entirely and substantial formation of MV +. can be observed.

  18. Synthesis, characterization and fuel cell performance tests of boric acid and boron phosphate doped, sulphonated and phosphonated poly(vinyl alcohol) based composite membranes

    NASA Astrophysics Data System (ADS)

    Şahin, Alpay; Ar, İrfan

    2015-08-01

    The aim of this study is to synthesize a composite membrane having high proton conductivity, ion exchange capacity and chemical stability. In order to achieve this aim, poly(vinyl alcohol) (PVA) based composite membranes are synthesized by using classic sol-gel method. Boric acid (H3BO3) and boron phosphate (BPO4) are added to the membrane matrix in different ratios in order to enhance the membrane properties. Characterization tests, i.e; FT-IR analysis, mechanical strength tests, water hold-up capacities, swelling properties, ion exchange capacities, proton conductivities and fuel cell performance tests of synthesized membranes are carried out. As a result of performance experiments highest performance values are obtained for the membrane containing 15% boron phosphate at 0.6 V and 750 mA/cm2. Water hold-up capacity, swelling ratio, ion exchange capacity and proton conductivity of this membrane are found as 56%, 8%, 1.36 meq/g and 0.37 S/cm, respectively. These values are close to the values obtained ones for perfluorosulphonic acid membranes. Therefore this membrane can be regarded as a promising candidate for usage in fuel cells.

  19. Cellulose Nanocrystals/ZnO as a Bifunctional Reinforcing Nanocomposite for Poly(vinyl alcohol)/Chitosan Blend Films: Fabrication, Characterization and Properties

    PubMed Central

    Azizi, Susan; Ahmad, Mansor B.; Ibrahim, Nor Azowa; Hussein, Mohd Zobir; Namvar, Farideh

    2014-01-01

    In this study, cellulose nanocrystals/zinc oxide (CNCs/ZnO) nanocomposites were dispersed as bifunctional nano-sized fillers into poly(vinyl alcohol) (PVA) and chitosan (Cs) blend by a solvent casting method to prepare PVA/Cs/CNCs/ZnO bio-nanocomposites films. The morphology, thermal, mechanical and UV-vis absorption properties, as well antimicrobial effects of the bio-nanocomposite films were investigated. It demonstrated that CNCs/ZnO were compatible with PVA/Cs and dispersed homogeneously in the polymer blend matrix. CNCs/ZnO improved tensile strength and modulus of PVA/Cs significantly. Tensile strength and modulus of bio-nanocomposite films increased from 55.0 to 153.2 MPa and from 395 to 932 MPa, respectively with increasing nano-sized filler amount from 0 to 5.0 wt %. The thermal stability of PVA/Cs was also enhanced at 1.0 wt % CNCs/ZnO loading. UV light can be efficiently absorbed by incorporating ZnO nanoparticles into a PVA/Cs matrix, signifying that these bio-nanocomposite films show good UV-shielding effects. Moreover, the biocomposites films showed antibacterial activity toward the bacterial species Salmonella choleraesuis and Staphylococcus aureus. The improved physical properties obtained by incorporating CNCs/ZnO can be useful in variety uses. PMID:24945313

  20. Gel characterisation and in vivo evaluation of minocycline-loaded wound dressing with enhanced wound healing using polyvinyl alcohol and chitosan.

    PubMed

    Sung, Jung Hoon; Hwang, Ma-Ro; Kim, Jong Oh; Lee, Jeong Hoon; Kim, Yong Il; Kim, Jeong Hoon; Chang, Sun Woo; Jin, Sung Giu; Kim, Jung Ae; Lyoo, Won Seok; Han, Sung Soo; Ku, Sae Kwang; Yong, Chul Soon; Choi, Han-Gon

    2010-06-15

    The purpose of this study was to develop a minocycline-loaded wound dressing with an enhanced healing effect. The cross-linked hydrogel films were prepared with polyvinyl alcohol (PVA) and chitosan using the freeze-thawing method. Their gel properties, in vitro protein adsorption, release, in vivo wound healing effect and histopathology were then evaluated. Chitosan decreased the gel fraction, maximum strength and thermal stability of PVA hydrogel, while it increased the swelling ability, water vapour transmission rate, elasticity and porosity of PVA hydrogel. Incorporation of minocycline (0.25%) did not affect the gel properties, and chitosan hardly affected drug release and protein adsorption. Furthermore, the minocycline-loaded wound dressing composed of 5% PVA, 0.75% chitosan and 0.25% drug was more swellable, flexible and elastic than PVA alone because of relatively weak cross-linking interaction of chitosan with PVA. In wound healing test, this minocycline-loaded PVA-chitosan hydrogel showed faster healing of the wound made in rat dorsum than the conventional product or the control (sterile gauze) due to antifungal activity of chitosan. In particular, from the histological examination, the healing effect of minocycline-loaded hydrogel was greater than that of the drug-loaded hydrogel, indicating the potential healing effect of minocycline. Thus, the minocycline-loaded wound dressing composed of 5% PVA, 0.75% chitosan and 0.25% drug is a potential wound dressing with excellent forming and enhanced wound healing.

  1. Preparation and formation mechanism of porous carbon nanosheets by thermal decomposition of polyvinyl alcohol films impregnated with zinc (II) and nitrate ions

    NASA Astrophysics Data System (ADS)

    Hattori, Yoshiyuki; Kojima, Rikio; Sagisaka, Kento; Umeda, Motoki; Tanaka, Toshihisa; Kondo, Atsushi; Iiyama, Taku; Kimura, Mutsumi; Fujimoto, Hiroyuki; Touhara, Hidekazu

    2017-03-01

    Porous carbon nanosheets (PCNS) with high surface areas were prepared by thermal decomposition of polyvinyl alcohol (PVA) films impregnated with Zn2+ and NO3-. Through this simple preparation method that required no additional activation processes, curved carbon nanosheets (<30 nm thick) were assembled into novel carbon materials. Detailed thermogravimetry-differential thermal analyses of the PVA films impregnated with Zn2+ and NO3- indicated that the sheet-like structures originated from exothermic pyrolysis of NO3- associated with the thermal decomposition of PVA. According to the nitrogen adsorption isotherm analyses at 77 K, the PCNS had a high specific surface area (>1600 m2 g-1) and bimodal pore structure consisting of micropores and mesopores. Because of their unique structural properties, the PCNS are attractive for use as electrode materials. The electrode performance of the PCNS was investigated in 1-M tetraethylammonium tetrafluoroborate ((C2H5)4NBF4) in propylene carbonate. The PCNS electrodes displayed high specific capacitance (86 F g-1 for cations and 115 F g-1 for anions). They also showed exceptionally high rate performance with ∼90% capacitance retention at current densities up to 2 A g-1 because their nanosheet structure allowed the rapid diffusion of ions inside the electrode.

  2. [The effect of long-term preservation of microbial cells immobilized in poly(vinyl alcohol) cryogel on their viability and biosynthesis of target metabolites].

    PubMed

    Efremenko, E N; Tatarinova, N Iu

    2007-01-01

    The effect of cell storage at -18 degrees C for 18-24 months on reproductive capacity was investigated for various microorganisms (gram-positive and gram-negative bacteria, yeasts, and filamentous fungi) immobilized in poly(vinyl alcohol) cryogel. To examine the viability of immobilized cells after defrosting, the bioluminescent method of intracellular ATP determination was used. A high level of metabolic activity of immobilized cells after various periods of storage was recorded for Streptomyces anulatus, Rhizopus orvzae, and Escherichia coli, which are producers of the antibiotic aurantin, L(+)-lactic acid, and the recombinant enzyme organophosphate hydrolase, respectively. It was shown that the initial concentration of immobilized cells in cryogel granules plays an important role in the survival of Str. anulatus and Pseudomonas putida after 1.5 years of storage. It was found that, after slow defrosting in the storage medium at 50C for 18 h of immobilized cells of the yeast Saccharomvces cerevisiae that had been stored for nine months, the number of reproductive cells increased due to the formation of ascospores.

  3. Synthesis of chitosan/polyvinyl alcohol/zeolite composite for removal of methyl orange, Congo red and chromium(VI) by flocculation/adsorption.

    PubMed

    Habiba, Umma; Siddique, Tawsif A; Joo, Tan Chin; Salleh, Areisman; Ang, Bee Chin; Afifi, Amalina M

    2017-02-10

    A chitosan/polyvinyl alcohol (PVA)/zeolite composite was fabricated in this study. The composite was analyzed through field emission scanning electron microscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis, and weight loss test. FTIR and XRD results revealed a strong interaction among chitosan, PVA, and zeolite. Weight loss test results indicated that the composite was stable in acidic and basic media. Congo red was removed through flocculation, and the removal rate was 94% at an initial concentration of 100mg/L for a dose of 1g/L. The removal rate of methyl orange was controlled by adsorption at an initial concentration of less than 100mg/L. Flocculation occurred at high concentrations. The removal rate was also 94% at an initial concentration of 500mg/L for a dose of 5g/L. The adsorption behavior of the composite for the removal of methyl orange and Cr(VI) was described by using a pseudo-second-order kinetic model. The adsorption capacity of the composite for Cr(VI) was 450mg/g. Therefore, the synthesized composite exhibited versatility during the removal of dyes and heavy metals.

  4. Cellulose nanocrystals/ZnO as a bifunctional reinforcing nanocomposite for poly(vinyl alcohol)/chitosan blend films: fabrication, characterization and properties.

    PubMed

    Azizi, Susan; Ahmad, Mansor B; Ibrahim, Nor Azowa; Hussein, Mohd Zobir; Namvar, Farideh

    2014-06-18

    In this study, cellulose nanocrystals/zinc oxide (CNCs/ZnO) nanocomposites were dispersed as bifunctional nano-sized fillers into poly(vinyl alcohol) (PVA) and chitosan (Cs) blend by a solvent casting method to prepare PVA/Cs/CNCs/ZnO bio-nanocomposites films. The morphology, thermal, mechanical and UV-vis absorption properties, as well antimicrobial effects of the bio-nanocomposite films were investigated. It demonstrated that CNCs/ZnO were compatible with PVA/Cs and dispersed homogeneously in the polymer blend matrix. CNCs/ZnO improved tensile strength and modulus of PVA/Cs significantly. Tensile strength and modulus of bio-nanocomposite films increased from 55.0 to 153.2 MPa and from 395 to 932 MPa, respectively with increasing nano-sized filler amount from 0 to 5.0 wt %. The thermal stability of PVA/Cs was also enhanced at 1.0 wt % CNCs/ZnO loading. UV light can be efficiently absorbed by incorporating ZnO nanoparticles into a PVA/Cs matrix, signifying that these bio-nanocomposite films show good UV-shielding effects. Moreover, the biocomposites films showed antibacterial activity toward the bacterial species Salmonella choleraesuis and Staphylococcus aureus. The improved physical properties obtained by incorporating CNCs/ZnO can be useful in variety uses.

  5. Preparation and properties of poly(vinyl alcohol)/chitosan blend bionanocomposites reinforced with cellulose nanocrystals/ZnO-Ag multifunctional nanosized filler.

    PubMed

    Azizi, Susan; Ahmad, Mansor Bin; Hussein, Mohd Zobir; Ibrahim, Nor Azowa; Namvar, Farideh

    2014-01-01

    A series of novel bionanocomposites were cast using different contents of zinc oxide-silver nanoparticles (ZnO-AgNPs) stabilized by cellulose nanocrystals (CNC) as multifunctional nanosized fillers in poly(vinyl alcohol)/chitosan (PVA/Cs) matrices. The morphological structure, mechanical properties, ultraviolet-visible absorption, and antimicrobial properties of the prepared films were investigated as a function of their CNC/ZnO-AgNP content and compared with PVA/chitosan/CNC bionanocomposite films. X-ray diffraction and field emission scanning electron microscopic analyses showed that the CNC/ZnO-AgNPs were homogeneously dispersed in the PVA/Cs matrix and the crystallinity increased with increasing nanosized filler content. Compared with pure PVA/Cs, the tensile strength and modulus in the films increased from 0.055 to 0.205 GPa and from 0.395 to 1.20 GPa, respectively. Ultraviolet and visible light can be efficiently absorbed by incorporating ZnO-AgNPs into a PVA/Cs matrix, suggesting that these bionanocomposite films show good visibility and ultraviolet-shielding effects. The bionanocomposite films had excellent antimicrobial properties, killing both Gram-negative Salmonella choleraesuis and Gram-positive Staphylococcus aureus. The enhanced physical properties achieved by incorporating CNC/ZnO-AgNPs could be beneficial in various applications.

  6. Simultaneous species-specific PCR detection and viability testing of poly(vinyl alcohol) cryogel-entrapped Rhodococcus spp. after their exposure to petroleum hydrocarbons.

    PubMed

    Kuyukina, Maria S; Ivshina, Irena B; Serebrennikova, Marina K; Rubtsova, Ekaterina V; Krivoruchko, Anastasiya V

    2013-08-01

    A method of simultaneous species-specific PCR detection and viability testing of poly(vinyl alcohol) cryogel-entrapped Rhodococcus spp. was developed that allowed the estimation of immobilized Rhodococcus opacus and Rhodococcus ruber survival after their exposure to petroleum hydrocarbon mixture. Spectrophotometric INT assay revealed high tolerance of gel-immobilized rhodococci to petroleum hydrocarbons, while among two Rhodococcus strains studied, R. ruber tolerated better to hydrocarbons compared to R. opacus. These findings were confirmed by respirometry results that showed increased respiratory activity of gel-immobilized Rhodococcus strains after 10-day incubation with 3% (v/v) petroleum hydrocarbon mixture. Moreover, jointly incubated rhodococcal strains demonstrated higher oxidative activities toward petroleum hydrocarbons than individual strains. Both Rhodococcus species were recovered successfully in cryogel granules using 16S rDNA-targeted PCR, even though the granules were previously stained with INT and extracted with ethanol. The method developed can be used for rapid detection and monitoring of gel-immobilized bacterial inocula in bioreactors or contaminated soil systems.

  7. Solvent Stability Study with Thermodynamic Analysis and Superior Biocatalytic Activity of Burkholderia cepacia Lipase Immobilized on Biocompatible Hybrid Matrix of Poly(vinyl alcohol) and Hypromellose.

    PubMed

    Badgujar, Kirtikumar C; Bhanage, Bhalchandra M

    2014-12-26

    In the present study, we have synthesized a biocompatible hybrid carrier of hypromellose (HY) and poly(vinyl alcohol) (PVA) for immobilization of Burkholderia cepacia lipase (BCL). The immobilized biocatalyst HY:PVA:BCL was subjected to determination of half-life time (τ) and deactivation rate constant (K(D)) in various organic solvents. Biocatalyst showed higher τ-value in a nonpolar solvent like cyclohexane (822 h) as compared to that of a polar solvent such as acetone (347 h), which signifies better compatibility of biocatalyst in the nonpolar solvents. Furthermore, the K(D)-value was found to be less in cyclohexane (0.843 × 10(-3)) as compared to acetone (1.997 × 10(-3)), indicating better stability in the nonpolar solvents. Immobilized-BCL (35 mg) was sufficient to achieve 99% conversion of phenethyl butyrate (natural constituent of essential oils and has wide industrial applications) using phenethyl alcohol (2 mmol) and vinyl butyrate (6 mmol) at 44 °C in 3 h. The activation energy (E(a)) was found to be lower for immobilized-BCL than crude-BCL, indicating better catalytic efficiency of immobilized lipase BCL. The immobilized-BCL reported 6-fold superior biocatalytic activity and 8 times recyclability as compared to crude-BCL. Improved catalytic activity of immobilized enzyme in nonpolar media was also supported by thermodynamic activation parameters such as enthalpy (ΔH(⧧)), entropy (ΔS(⧧)) and Gibb's free energy (ΔG(⧧)) study, which showed that phenethyl butyrate synthesis catalyzed by immobilized-BCL was feasible as compared to crude-BCL. The present work explains a thermodynamic investigation and superior biocatalytic activity for phenethyl butyrate synthesis using biocompatible immobilized HY:PVA:BCL in nonaqueous media for the first time.

  8. Reactive extrusion of epsilon-caprolactone polymers and application of poly(lauryl lactam-b-caprolactone) as a compatibilizing agent in blends containing poly(vinyl chloride)

    NASA Astrophysics Data System (ADS)

    Kim, Byong Jun

    In this dissertation, we investigate the continuous polymerization of epsilon-caprolactone (CL) and copolymerization of CL with epsilon-caprolactam (CA), o-lauryl lactam (LA), and styrene (ST) in a modular intermeshing co-rotating twin screw extruder. We consider the variables of temperature profile, screw speed, monomer feed rate, the ratio of monomer to initiator, and feeding order of co-monomers on reactive extrusion of CL polymers. Associated with the reactive extrusion of CL, we also perform the engineering analysis of molecular weight increase and shear-induced molecular weight reduction after polymerization of CL during the reactive extrusion process. Specially designed block copolymers have played a role as compatibilizing agents in the system of immiscible polymer blends. We apply the LA-CL block copolymer (P(LA-b-CL)) produced by reactive extrusion as a compatibilizing agent in immiscible polymer blend systems: (i) poly(vinyl chloride) (PVC)/polyamide 12(PA12), (ii) PVC/polypropylene (PP), and (iii) PVC/maleic anhydride (MA)-modified ethylene-propylene-non-conjugated diene elastomer (MA-EPDM). We investigate the mechanical and thermal properties of (i) PVC/PA12 blend compatibilized with P(LA-b-CL), (ii) PVC/PP blend compatibilized with P(LA-b-CL)/PA12/MA-PP, and (iii) PVC/MA-EPDM blend compatibilized with P(LA-b-CL)/PA12.

  9. Morphological influence of cellulose nanoparticles (CNs) from cottonseed hulls on rheological properties of polyvinyl alcohol/CN suspensions.

    PubMed

    Zhou, Ling; He, Hui; Li, Mei-Chun; Song, Kunlin; Cheng, H N; Wu, Qinglin

    2016-11-20

    The present work describes the isolation of cellulose nanoparticles (CNs) with different morphologies and their influence on rheological properties of CN and CN-poly (vinyl alcohol) (PVA) suspensions. Cottonseed hulls were used for the first time to extract three types of CNs, including fibrous cellulose nanofibers, rod-like cellulose nanocrystals and spherical cellulose nanoparticles through mechanical and chemical methods. Rheology results showed that the rheological behavior of the CN suspensions was strongly dependent on CN concentration and particle morphology. For PVA/CN systems, concentration of PVA/CN suspension, morphology of CNs, and weight ratio of CN to PVA were three main factors that influenced their rheology behaviors. This research reveals the importance of CN morphology and composition concentration on the rheological properties of PVA/CN, providing new insight in preparing high performance hydrogels, fibers and films base on PVA/CN suspension systems.

  10. Poly(vinyl alcohol) reinforced and toughened with poly(dopamine)-treated graphene oxide, and its use for humidity sensing.

    PubMed

    Hwang, Sang-Ha; Kang, Dongwoo; Ruoff, Rodney S; Shin, Hyeon Suk; Park, Young-Bin

    2014-07-22

    Poly(dopamine)-treated graphene oxide/poly(vinyl alcohol) ("dG-O/PVA") composite films were made and characterized. G-O was modified with poly(dopamine) in aqueous solution and then chemically reduced to yield poly(dopamine)-treated reduced G-O. A combination of hydrogen bonding, strong adhesion of poly(dopamine) at the interface of PVA and G-O sheets, and reinforcement by G-O resulted in increases in tensile modulus, ultimate tensile strength, and strain-to-failure by 39, 100, and 89%, respectively, at 0.5 wt % dG-O loading of the PVA. The dG-O serves as a moisture barrier for water-soluble PVA, and the dG-O/PVA composite films were shown to be effective humidity sensors over the relative humidity range 40-100%.

  11. Polyvinyl Alcohol-derived carbon nanofibers/carbon nanotubes/sulfur electrode with honeycomb-like hierarchical porous structure for the stable-capacity lithium/sulfur batteries

    NASA Astrophysics Data System (ADS)

    Deng, Nanping; Kang, Weimin; Ju, Jingge; Fan, Lanlan; Zhuang, Xupin; Ma, Xiaomin; He, Hongsheng; Zhao, Yixia; Cheng, Bowen

    2017-04-01

    The honeycomb-like hierarchical porous carbon nanofibers (PCNFs)-carbon nanotubes (CNTs)-sulfur(S) composite electrode is successfully desgined and prepared through ball-milling and heating method, in which the PCNFs are carbonized from fibers in the membrane composed of Polyvinyl Alcohol and Polytetrafluoroethylene by electro-blown spinning technology. The prepared PCNFs-CNTs-S composite are regarded as cathode for lithium-sulfur battery. The tailored porous structure and CNTs in the composite facilitate construction of a high electrical conductive pathway and store more S/polysulfides, and the dissoluble loss of intermediate S species in electrolyte can also be restrained because of acidized PVA-based porous carbon nanofibers. Meanwhile, the porous strcucture and CNTs can effectively alleviate volume changes in battery cycling process. Moreover, the presence of LiNO3 in electrolyte helps the electrochemical oxidation of Li2S and LiNO3-derived surface film effectively suppresses the migration of soluble polysulfide to the Li anode surface. Therefore, the obtained PCNFs-CNTs-S cathode exhibits excellent performance in Li-S battery with a high initial discharge capacity as high as 1302.9 mAh g-1, and super stable capacity retention with 809.1 mAh g-1 after 300 cycles at the current density of 837.5 mA g-1 (0.5 C). And the rate capability of PCNFs-CNTs-S electrode is much better than those of CNTs-S and PCNFs-S electrodes.

  12. A novel nonenzymatic amperometric hydrogen peroxide sensor based on CuO@Cu2O nanowires embedded into poly(vinyl alcohol).

    PubMed

    Chirizzi, Daniela; Guascito, Maria Rachele; Filippo, Emanuela; Tepore, Antonio

    2016-01-15

    A new, very simple, rapid and inexpensive nonenzymatic amperometric sensor for hydrogen peroxide (H2O2) detection is proposed. It is based on the immobilization of cupric/cuprous oxide core shell nanowires (CuO@Cu2O-NWs) in a poly(vinyl alcohol) (PVA) matrix directly drop casted on a glassy carbon electrode surface to make a CuO@Cu2O core shell like NWs PVA embedded (CuO@Cu2O-NWs/PVA) sensor. CuO nanowires with mean diameters of 120-170nm and length in the range 2-5μm were grown by a simple catalyst-free thermal oxidation process based on resistive heating of pure copper wires at ambient conditions. The oxidation process of the copper wire surface led to the formation of a three layered structure: a thick Cu2O bottom layer, a CuO thin intermediate layer and CuO nanowires. CuO nanowires were carefully scratched from Cu2O layer with a sharp knife, dispersed into ethanol and sonicated. Then, the NWs were embedded in PVA matrix. The morphological and spectroscopic characterization of synthesized CuO-NWs and CuO@Cu2O-NWs/PVA were performed by transmission electron microscopy (TEM), selected area diffraction pattern (SAD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analysis. Moreover a complete electrochemical characterization of these new CuO@Cu2O-NWs/PVA modified glassy carbon electrodes was performed by Cyclic Voltammetry (CV) and Cronoamperometry (CA) in phosphate buffer (pH=7; I=0.2) to investigate the sensing properties of this material against H2O2. The electrochemical performances of proposed sensors as high sensitivity, fast response, reproducibility and selectivity make them suitable for the quantitative determination of hydrogen peroxide substrate in batch analysis.

  13. Papain wound dressings obtained from poly(vinyl alcohol)/calcium alginate blends as new pharmaceutical dosage form: Preparation and preliminary evaluation.

    PubMed

    Dutra, J A P; Carvalho, S G; Zampirolli, A C D; Daltoé, R D; Teixeira, R M; Careta, F P; Cotrim, M A P; Oréfice, R L; Villanova, J C O

    2017-04-01

    Transparent, soft, flexible, mechanically resistant films, which are ideal for use as wound dressings were prepared in the presence of 2% papain, a proteolytic enzyme that can play a role in the chemical debridement of the skin and can accelerate the healing process. The films, based on poly(vinyl alcohol):calcium alginate blends with increasing concentrations of polysaccharide (10, 20, and 30% v/v), were obtained by casting method. FTIR and DSC analyses were performed to assess the composition and miscibility of blends. Mechanical properties such as tensile strength, elasticity modulus, and elongation at breakpoint were evaluated. The influence of different concentrations of calcium alginate on physical attributes of films like wettability, swelling capacity and mechanical properties was determined. The stability of papain in the films was assessed indirectly by hemolytic activity assay employing direct contact method and confirmed by technique based on blood agar diffusion. Preliminary cytotoxicity was evaluated with the XTT method. The results showed that at the polymer concentrations tested, the blends were miscible. The increase in the content of the calcium alginate increased the wettability and swelling capacity of the films, which is desirable in wound dressings. On the other hand, mechanical resistance decreased without causing breakage of the films during the swelling tests. The hemolytic activity of the films was maintained during the studied period, suggesting the stability of papain in the proposed formulations. Cellular viability indicated that the films were non-toxic. The analysis of the results showed that it is possible to prepare interactive and bioactive wound dressing containing papain from blends of PVA and calcium alginate polymers.

  14. Effect of Polyvinyl Alcohol (PVA) Containing Artemether in Treatment of Cutaneous Leishmaniasis Caused by Leishmania major in BALB/c Mice

    PubMed Central

    Ebrahimisadr, Parisa; Ghaffarifar, Fatemeh; Hassan, Zuhir Mohammad; Sirousazar, Mohammad; Mohammadnejad, Fatemeh

    2014-01-01

    Background: Polyvinyl alcohol (PVA) is one of the well-known polymers, which has been used in numerous biomedical applications because of its good biocompatibility. Objectives: Due to problems made by the therapeutics already used for leishmaniasis, the aim of this study was to evaluate the effect of PVA containing artemether in treating cutaneous leishmaniasis in BALB/c mice. Materials and Methods: Aqueous solution of PVA was prepared by mixing with Double Distilled Water. After preparation of PVA, 4.33 mg of each drug (main drug artemether and control drug 14% glucantime) was added to 100 g of prepared PVA-honey solution. The solution was incubated at 37°C and the release of artemether was evaluated by measuring absorbance at 260 nm wave length. In this study for treatment of mice lesion, we used PVA containing artemether and glucantime and this method was compared with ointment treatment. Results: Mean diameters of lesions in mice treated with artemether were smaller than the control group and the differences were significant (P < 0.05). The mean lesion size of mice treated with PVA containing artemether in comparison with the group treated with ointment of artemether were smaller and the differences were significant (P < 0.05). Conclusions: PVA containing artemether is a new method for treatment of cutaneous leishmaniasis and according to the obtained results, artemether is an appropriate and effective drug, especially when used with PVA as a lesion dressing; thus we suggest that this method can be applied for the treatment of cutaneous leishmaniasis. PMID:25147717

  15. Fabrication of novel high performance ductile poly(lactic acid) nanofiber scaffold coated with poly(vinyl alcohol) for tissue engineering applications.

    PubMed

    Abdal-Hay, Abdalla; Hussein, Kamal Hany; Casettari, Luca; Khalil, Khalil Abdelrazek; Hamdy, Abdel Salam

    2016-03-01

    Poly(lactic acid) (PLA) nanofiber scaffold has received increasing interest as a promising material for potential application in the field of regenerative medicine. However, the low hydrophilicity and poor ductility restrict its practical application. Integration of hydrophilic elastic polymer onto the surface of the nanofiber scaffold may help to overcome the drawbacks of PLA material. Herein, we successfully optimized the parameters for in situ deposition of poly(vinyl alcohol), (PVA) onto post-electrospun PLA nanofibers using a simple hydrothermal approach. Our results showed that the average fiber diameter of coated nanofiber mat is about 1265±222 nm, which is remarkably higher than its pristine counterpart (650±180 nm). The hydrophilicity of PLA nanofiber scaffold coated with a PVA thin layer improved dramatically (36.11±1.5°) compared to that of pristine PLA (119.7±1.5°) scaffold. The mechanical testing showed that the PLA nanofiber scaffold could be converted from rigid to ductile with enhanced tensile strength, due to maximizing the hydrogen bond interaction during the heat treatment and in the presence of PVA. Cytocompatibility performance of the pristine and coated PLA fibers with PVA was observed through an in vitro experiment based on cell attachment and the MTT assay by EA.hy926 human endothelial cells. The cytocompatibility results showed that human cells induced more favorable attachment and proliferation behavior on hydrophilic PLA composite scaffold than that of pristine PLA. Hence, PVA coating resulted in an increase in initial human cell attachment and proliferation. We believe that the novel PVA-coated PLA nanofiber scaffold developed in this study, could be a promising high performance biomaterial in regeneration medicine.

  16. Efficient approach to improving the flame retardancy of poly(vinyl alcohol)/clay aerogels: incorporating piperazine-modified ammonium polyphosphate.

    PubMed

    Wang, Yu-Tao; Liao, Shi-Fu; Shang, Ke; Chen, Ming-Jun; Huang, Jian-Qian; Wang, Yu-Zhong; Schiraldi, David A

    2015-01-28

    Ammonium polyphosphates (APP) modified with piperazine (PA-APP) was used to improve the flame retardancy of poly(vinyl alcohol) (PVA)/montmorillonite (MMT) aerogels, which were prepared via an environmentally friendly freeze-drying method. The thermal stabilities of the samples were evaluated by thermogravimetric analysis (TG); the flammability behaviors of samples were investigated by limiting oxygen index (LOI), vertical burning test (UL-94) and cone calorimeter (CC) tests. TG test results showed that the 5% weight loss temperature (T5%) of PVA/MMT/PA-APP was 10 °C higher than that of PVA/MMT/APP. In combustion testing, all of PVA/MMT/PA-APP aerogels achieved V-0 ratings and have a higher LOI values than the unmodified PVA/MMT aerogel. Moreover, the aerogel with 1% PA-APP5, which means that the content of piperazine is 5% in PA-APP, decreased the cone calorimetry THR value to 5.71 MJ/m(2), and increased the char residue to 52%. The compressive modulus of PVA/MMT/PA-APP was increased by 93.4% compared with PVA/MMT/APP because of the increase in interfacial adhesion between matrix and PA-APP fillers. The densities of the PVA/MMT/PA-APP samples were slightly lower than those of the unmodified aerogels because of reduced shrinkage in the presence of PA-APP. All the tests results indicated that the incorporation of PA-APP not only improved the thermal stability and flame retardancy of aerogels but also maintained their mechanical properties.

  17. Mechanical properties, biological activity and protein controlled release by poly(vinyl alcohol)-bioglass/chitosan-collagen composite scaffolds: a bone tissue engineering applications.

    PubMed

    Pon-On, Weeraphat; Charoenphandhu, Narattaphol; Teerapornpuntakit, Jarinthorn; Thongbunchoo, Jirawan; Krishnamra, Nateetip; Tang, I-Ming

    2014-05-01

    In the present study, composite scaffolds made with different weight ratios (0.5:1, 1:1 and 2:1) of bioactive glass (15Ca:80Si:5P) (BG)/polyvinyl alcohol (PVA) (PVABG) and chitosan (Chi)/collagen (Col) (ChiCol) were prepared by three mechanical freeze-thaw followed by freeze-drying to obtain the porous scaffolds. The mechanical properties and the in vitro biocompatibility of the composite scaffolds to simulated body fluid (SBF) and to rat osteoblast-like UMR-106 cells were investigated. The results from the studies indicated that the porosity and compressive strength were controlled by the weight ratio of PVABG:ChiCol. The highest compressive modulus of the composites made was 214.64 MPa which was for the 1:1 weight ratio PVABG:ChiCol. Mineralization study in SBF showed the formation of apatite crystals on the PVABG:ChiCol surface after 7 days of incubation. In vitro cell availability and proliferation tests confirmed the osteoblast attachment and growth on the PVABG:ChiCol surface. MTT and ALP tests on the 1:1 weight ratio PVABG:ChiCol composite indicated that the UMR-106 cells were viable. Alkaline phosphatase activity was found to increase with increasing culturing time. In addition, we showed the potential of PVABG:ChiCol drug delivery through PBS solution studies. 81.14% of BSA loading had been achieved and controlled release for over four weeks was observed. Our results indicated that the PVABG:ChiCol composites, especially the 1:1 weight ratio composite exhibited significantly improved mechanical, mineral deposition, biological properties and controlled release. This made them potential candidates for bone tissue engineering applications.

  18. Induction of angiogenesis via topical delivery of basic-fibroblast growth factor from polyvinyl alcohol-dextran blend hydrogel in an ovine model of acute myocardial infarction.

    PubMed

    Fathi, Ezzatollah; Nassiri, Seyed Mahdi; Atyabi, Nahid; Ahmadi, Seyed Hossein; Imani, Mohammad; Farahzadi, Raheleh; Rabbani, Shahram; Akhlaghpour, Shahram; Sahebjam, Mohammad; Taheri, Mohammad

    2013-09-01

    Hydrogels are currently used as interesting constructs for the delivery of proteins. In this study, a novel polyvinyl alcohol-dextran (PVA-Dex) blend hydrogel was used for controlled delivery of basic-fibroblast growth factor (bFGF). These biocompatible constructs were sutured to the epicardium as patches on the heart surface to provide slow release of bFGF to the infarcted site in an ovine model of myocardial infarction (MI). Eighteen sheep were randomly divided into three groups (n = 6 each), including group I (control without any patch and bFGF), group II (patch without bFGF) and group III (patch incorporating 100 µg bFGF). They were subjected to coronary artery ligation after lateral thoracotomy, and then in groups II and III the patches were implanted 20-30 min after MI. Cardiac function was assessed by both echocardiography and magnetic resonance imaging (MRI) 2 months after implantation. Then the animals were sacrificed and the hearts subjected to histopathological examination, immunohistochemistry and electron microscopy. Heart lysates were subject to protein expression analysis through western blotting. The results showed that sustained release of bFGF using PVA-Dex blend hydrogel strongly stimulated angiogenesis and increased wall thickness index in the infarcted myocardium. The patch also significantly attenuated the increase in left ventricular end-systolic diameter, but it did not improve cardiac function within 2 months of myocardial infarction. In conclusion, PVA-Dex gel incorporating bFGF can be used as a sustained release construct for therapeutic angiogenesis in ischaemic heart disease.

  19. Accelerated wound healing and anti-inflammatory effects of physically cross linked polyvinyl alcohol-chitosan hydrogel containing honey bee venom in diabetic rats.

    PubMed

    Amin, Mohamed A; Abdel-Raheem, Ihab T

    2014-08-01

    Diabetes is one of the leading causes of impaired wound healing. The objective of this study was to develop a bee venom-loaded wound dressing with an enhanced healing and anti-inflammatory effects to be examined in diabetic rats. Different preparations of polyvinyl alcohol (PVA), chitosan (Chit) hydrogel matrix-based wound dressing containing bee venom (BV) were developed using freeze-thawing method. The mechanical properties such as gel fraction, swelling ratio, tensile strength, percentage of elongation and surface pH were determined. The pharmacological activities including wound healing and anti-inflammatory effects in addition to primary skin irritation and microbial penetration tests were evaluated. Moreover, hydroxyproline, glutathione and IL-6 levels were measured in the wound tissues of diabetic rats. The bee venom-loaded wound dressing composed of 10 % PVA, 0.6 % Chit and 4 % BV was more swellable, flexible and elastic than other formulations. Pharmacologically, the bee venom-loaded wound dressing that has the same previous composition showed accelerated healing of wounds made in diabetic rats compared to the control. Moreover, this bee venom-loaded wound dressing exhibited anti-inflammatory effect that is comparable to that of diclofenac gel, the standard anti-inflammatory drug. Simultaneously, wound tissues covered with this preparation displayed higher hydroxyproline and glutathione levels and lower IL-6 levels compared to control. Thus, the bee venom-loaded hydrogel composed of 10 % PVA, 0.6 % Chit and 4 % BV is a promising wound dressing with excellent forming and enhanced wound healing as well as anti-inflammatory activities.

  20. Portal Vein Embolization with Radiolabeled Polyvinyl Alcohol Particles in a Swine Model: Hepatic Distribution and Implications for Pancreatic Islet Cell Transplantation

    SciTech Connect

    Owen, Richard J.; Mercer, John R.; Al-Saif, Faisal; Molinari, Michele; Ashforth, Robert A.; Rajotte, Ray V.; Conner-Spady, Barbara; Shapiro, A. M. James

    2009-05-15

    The distribution of radiolabeled polyvinyl alcohol microspheres (PVAMs) when infused into the portal vein of domestic swine was investigated, with the purpose of assessing implications for pancreatic islet cell transplantation. PVAMs measuring 100-300 {mu}m (Contour SE) and labeled with {sup 99m}Tc were infused into the main portal vein of 12 swine, with intermittent portal venous pressure measurements. The infusion catheter was introduced antegradely via direct or indirect cannulation of the portal vein. The liver was subsequently divided into anatomical segments. Radioactivity (decay corrected) was measured for {sup 99m}Tc microsphere synthesis, dose preparation, gross organ activities, tissue samples, and blood. Particulate labeling, catheter positioning, and infusion were successful in all cases. The number of particles used was (185,000 {+-} 24,000) with a volume of 1 ml. Mean portal pressure at 5 min was significantly higher than baseline, but without a significant difference at 15 min. Extrahepatic tissue and serum radioactivity was negligible. A significant difference in number of radioactive particles per gram was detected between segments 6/7 and segments 5/8. Intrasegmental activity was analyzed, and for segments 2/3 a significant difference in the percentage dose per gram across samples was demonstrated (P = 0.001). Effective and stable radiolabeling of PVAMs with {sup 99m}Tc-sulfur colloid was demonstrated. Portal venous infusion of 100- to 300-{mu}m particles showed entrapment in the sinusoidal hepatic system with transient portal pressure elevation. Preferential embolization into the right lateral and posterior segments occurs, suggesting that flow dynamics/catheter tip position plays a role in particle distribution.

  1. Characterization of Hybrid Bioactive Glass-polyvinyl Alcohol Scaffolds Containing a PTHrP-derived Pentapeptide as Implants for Tissue Engineering Applications

    PubMed Central

    Coletta, D.J.; Lozano, D.; Rocha-Oliveira, A.A.; Mortarino, P.; Bumaguin, G.E.; Vitelli, E.; Vena, R.; Missana, L.; Jammal, M. V.; Portal-Núñez, S.; Pereira, M.; Esbrit, P.; Feldman, S.

    2014-01-01

    Hybrid foam (BG-PVA) with 50 % Bioactive glass (BG) and 50 % polyvinyl alcohol (PVA) was prepared by sol-gel process to produce scaffolds for bone tissue engineering. The pore structure of hydrated foams was evaluated by 3-D confocal microscopy, confirming 70% porosity and interconnected macroporous network. In this study, we assessed the putative advantage of coating with osteostatin pentapeptide into BG-PVA hybrid scaffolds to improve their bioactivity. In vitro cell culture experiments were performed using mouse pre-osteoblastic MC3T3-E1 cell line. The exposure to osteostatin loaded-BG-PVA scaffolds increase cell proliferation in contrast with the unloaded scaffolds. An in vivo study was selected to implant BG-PVA scaffolds, non-coated (Group A) or coated (Group B) with osteostatin into non critical bone defect at rabbit femur. Both groups showed new compact bone formation on implant surface, with lamellae disposed around a haversian canal forming osteons-like structure. We observed signs of inflammation around the implanted unloaded scaffold at one month, but resolved at 3 months. This early inflammation did not occur in Group B; supporting the notion that osteostatin may act as anti-inflammatory inhibitor. On the other hand, Group B showed increased bone formation, as depicted by many new trabeculae partly mineralized in the implant regenerating area, incipient at 1 month and more evident at 3 months after implantation. PVA/BG hybrid scaffolds present a porous structure suitable to support osteoblast proliferation and differentiation. Our in vitro and in vivo findings indicate that osteostatin coating improves the osteogenic features of these scaffolds PMID:24772196

  2. Cellulose acetate butyrate-pH/thermosensitive polymer microcapsules containing aminated poly(vinyl alcohol) microspheres for oral administration of DNA.

    PubMed

    Fundueanu, Gheorghe; Constantin, Marieta; Bortolotti, Fabrizio; Cortesi, Rita; Ascenzi, Paolo; Menegatti, Enea

    2007-04-01

    The aim of this work is to safely transport bioadhesive microspheres loaded with DNA to intestine and to test their bioadhesive properties. Poly(vinyl alcohol) (PVA) microspheres were prepared by dispersion reticulation with glutaraldehyde and further aminated. These microspheres were firstly loaded with plasmid DNA by electrostatic interactions and then entrapped in cellulose acetate butyrate (CAB) microcapsules for gastric protection. The entrapped PVA microspheres do not have enough force by swelling to produce the rupture of CAB shell, therefore the resistance of microcapsules was weakened by incorporating different amount of the pH/thermosensitive polymer (SP) based on poly(N-isopropylacrylamide-co-methyl methacrylate-co-methacrylic acid) (NIPAAm-co-MM-co-MA). This polymer is insoluble in gastric juice at pH 1.2 and 37 degrees C, but quickly solubilized in intestinal fluids (pH 6.8 and pH 7.4). Therefore, DNA loaded PVA microspheres were not expelled in acidic media but were almost entirely discharged in small intestine or colon. The integrity of DNA after entrapment was tested by agarose gel electrophoresis indicating that no DNA degradation occurs during encapsulation. The percentage of adhered microspheres on the mucus surface of everted intestinal tissue was 65+/-18% for aminated PVA microspheres without DNA and almost 50+/-15% for those loaded with DNA. Non-aminated PVA microspheres display the lowest adhesive properties (33+/-12%). In conclusion DNA loaded microspheres were progressively discharged in intestine. The integrity of DNA was not modified after entrapment and release, as proved by agarose gel electrophoresis. Both loaded and un-loaded aminated microspheres display good bioadhesive properties.

  3. Design of freeze-dried Soluplus/polyvinyl alcohol-based film for the oral delivery of an insoluble drug for the pediatric use.

    PubMed

    Shamma, Rehab; Elkasabgy, Nermeen

    2016-01-01

    Spironolactone (SL) is a poorly water-soluble drug. Being poorly soluble affects its dissolution rate which in turn affects its oral bioavailability. This work aimed to prepare freeze-dried SL-Soluplus/polyvinyl alcohol (PVA) oral thin film in an attempt to enhance the drug solubility on one hand and at the same time prepare a solid dosage form convenient for the pediatric use. SL-Soluplus/PVA films were prepared using polyethylene glycol 400 (PEG 400) as a plasticizer applying the solvent-casting technique. The prepared films were evaluated for their thickness, tensile strength, and in vitro dissolution studies. Box-Behnken design (17 runs) was applied to optimize the effects of the formulation variables on the film properties. The optimized film formulation was freeze-dried after casting so as to enhance the drug dissolution. Moreover, the optimized freeze-dried film was re-characterized in vitro and evaluated in vivo in human volunteers to investigate its palatability and satisfaction. The results showed that the optimized formulation composed of 10% polymer concentration containing Soluplus:PVA (0.33:0.66) and plasticized with 30% PEG 400 possessed the highest desirability value (0.836). Freeze-drying of the optimized formulation succeeded to improve SL in vitro dissolution due to the preparation of a more porous film compared to the non-freeze-dried one. In vivo evaluation of the optimized freeze-dried film showed high satisfaction among the participating volunteers concerning the ease of administration and sensation thereafter, where all the film specimens dissolved without the need for water and no film residues remained in the mouth following film dissolution. In conclusion, freeze-dried Soluplus®/PVA-based oral thin film proved to be a successful carrier for the oral delivery of insoluble drugs like SL for pediatrics.

  4. Co-immobilization of Pseudomonas stutzeri YHA-13 and Alcaligenes sp. ZGED-12 with polyvinyl alcohol-alginate for removal of nitrogen and phosphorus from synthetic wastewater.

    PubMed

    Han, Yonghe; Zhang, Wenxian; Lu, Wenxian; Zhou, Zhihua; Zhuang, Zhigang; Li, Min

    2014-01-01

    Nitrogen (N) and phosphorus (P) are the two main factors causing water eutrophication. Immobilized micro-organisms have been widely studied in N and P removal. However, the effects of various immobilizing conditions on the removal efficiency of N and P using immobilized micro-organism beads (IMOBs) remain unclear. Polyvinyl alcohol (PVA) and alginate, as the two frequently immobilizing-used matrixes, were used for co-immobilizing Pseudomonas stutzeri YHA-13 and Alcaligenes sp. ZGED-12. PVA, alginate and CaCl₂contents, immobilization time and different wet biomass ratios of P. stutzeri to Alcaligenes sp. were conducted to elucidate their roles in and influences on the removal efficiency of N and P from synthetic wastewater. The application potential of IMOBs was estimated as well. Results showed that IMOBs prepared by cross-link of 4% PVA and 2-3% alginate with 5% CaCl₂and saturated boric acid solution for 10-15 min are the best ones in removal of N and P. Though IMOBs containing P. stutzeri and/or Alcaligenes sp. were capable of removal of the two nutrients, the highest removal efficiency was observed when the wet biomass ratio of P. stutzeri to Alcaligenes sp. was adjusted to 2:2. In addition, the IMOBs were of good ability to remove chemical oxygen demand (COD), NO(3)(-), NO(2)(-), NH(4)(+)- N, total nitrogen (TN) and total phosphorus (TP) from artificial wastewater. Of which, micro-organisms immobilized in matrixes were mainly responsible for NO(3)(-) and TP removal. Therefore, P. stutzeri YHA-13 and Alcaligenes sp. ZGED-12 are reliable bioresources to remove N and P from wastewater.

  5. Definition and validation of operating equations for poly(vinyl alcohol)-poly(lactide-co-glycolide) microfiltration membrane-scaffold bioreactors.

    PubMed

    Shipley, R J; Waters, S L; Ellis, M J

    2010-10-01

    The aim of this work is to provide operating data for biodegradable hollow fiber membrane bioreactors. The physicochemical cell culture environment can be controlled with the permeate flowrate, so this aim necessitates the provision of operating equations that enable end-users to set the pressures and feed flowrates to obtain their desired culture environment. In this paper, theoretical expressions for the pure water retentate and permeate flowrates, derived using lubrication theory, are compared against experimental data for a single fiber poly(vinyl alcohol)-poly(lactide-co-glycolide) crossflow module to give values for the membrane permeability and slip. Analysis of the width of the boundary layer region where slip effects are important, together with the sensitivity of the retentate and permeate equations to the slip parameter, show that slip is insignificant for these membranes, which have a mean pore diameter of 1.1 microm. The experimental data is used to determine a membrane permeability, of k = 1.86 x 10(-16) m(2), and to validate the model. It was concluded that the operating equation that relates the permeate to feed ratio, c, lumen inlet flowrate, Q (l,in), lumen outlet pressure, P (1), and ECS outlet pressure, P (0), is P(1) - P(0) = Q(l),in (Ac + B) where A and B are constants that depend on the membrane permeability and geometry (and are given explicitly). Finally, two worked examples are presented to demonstrate how a tissue engineer can use Equation (1) to specify operating conditions for their bioreactor.

  6. Optical properties of polyvinyl alcohol doped (Se80Te20)100-xAgx (0 ≤ x ≤ 4) composites

    NASA Astrophysics Data System (ADS)

    Singh, D.; Kumar, S.; Thangaraj, R.

    2014-02-01

    Polyvinyl alcohol (PVA) doped (Se80Te20)100-xAgx (0 ≤ x ≤ 4) thin films were prepared by the spin-coating technique on a quartz substrate. The optical parameters of PVA-doped (Se80Te20)100-xAgx (0 ≤ x ≤ 4) composites at the same chalcogen concentration (S0 = 0.1 mg ml-1) and PVA/(Se80Te20)96Ag4 composites at three different chalcogen concentrations viz. S1 = 0.3 mg ml-1, S2 = 0.6 mg ml-1 and S3 = 1 mg ml-1 have been studied. The semi-crystalline nature of the as-deposited thin filmsisdetermined by X-ray diffraction. The transmission and reflection spectra of PVA-doped Se-Te-Ag thin films were obtained in a 350-650 nm spectral region. The optical-band gap has been calculated from the transmission and reflection data. The refractive index has been calculated by the measured reflection data. It has been found that the optical-band gap increases, but the refractive index, extinction coefficient, and the real and imaginary parts of the dielectric constant decrease, with increase in Agcontent in PVA-doped (Se80Te20)100-xAgx (0 ≤ x ≤ 4) thin films. Such type of behavior is explained on the basis of decrease in density of the defect states. However, the optical-band gap has been found to be decreased and all other optical parameters show increase in their values with increase in concentration of (Se80Te20)96Ag4 glass in PVA-doped composites. The results have been explained on the basis of cluster-size formation at the time of dissolution. This study shows that the optical properties of new composites are affected by the change in silver and chalcogen concentration.

  7. Zirconium/polyvinyl alcohol modified flat-sheet polyvinyldene fluoride membrane for decontamination of arsenic: Material design and optimization, study of mechanisms, and application prospects.

    PubMed

    Zhao, Dandan; Yu, Yang; Chen, J Paul

    2016-07-01

    Arsenic contamination in industrial wastewater and groundwater has become an important environmental issue. In this study, a novel zirconium/polyvinyl alcohol (PVA) modified polyvinyldene fluoride (PVDF) membrane was developed for arsenate removal from simulated contaminated water. A PVDF flat-sheet membrane was first fabricated; it was then soaked in a zirconium-PVA solution and dried, and finally reacted with a glutaraldehyde solution, by which the zirconium ions were impregnated onto the PVDF surface through the ether and hydroxyl groups according to the cross-linkage mechanism. The fabrication procedure was optimized by the Box-Behnken experimental design approach. The adsorption kinetics study showed that most of uptake occurred in 5 h and the equilibrium was established in 24 h. The acidic condition was beneficial for the arsenate removal and the optimal removal efficiency can be obtained at pH 2.0. The experimental data of the adsorption isotherm was better described by Langmuir equation than Freundlich equation. The maximum adsorption capacity of 128 mg-As/g was achieved at pH 2.0. In the filtration study, the modified membrane with an area of 12.56 cm(2) could treat 15.6 L arsenate solution (equivalent to 75,150 bed volumes) with an influent concentration of 98.6 μg/L to meet the maximum contaminate level of 10 μg/L. Several instrumental studies revealed that the removal was mainly associated with ion exchange between chloride and arsenate ions.

  8. An ultrasound tomography system with polyvinyl alcohol (PVA) moldings for coupling: in vivo results for 3-D pulse-echo imaging of the female breast.

    PubMed

    Koch, Andreas; Stiller, Florian; Lerch, Reinhard; Ermert, Helmut

    2015-02-01

    Full-angle spatial compounding (FASC) is a concept for pulse-echo imaging using an ultrasound tomography (UST) system. With FASC, resolution is increased and speckles are suppressed by averaging pulse-echo data from 360°. In vivo investigations have already shown a great potential for 2-D FASC in the female breast as well as for finger-joint imaging. However, providing a small number of images of parallel cross-sectional planes with enhanced image quality is not sufficient for diagnosis. Therefore, volume data (3-D) is needed. For this purpose, we further developed our UST add-on system to automatically rotate a motorized array (3-D probe) around the object of investigation. Full integration of external motor and ultrasound electronics control in a custom-made program allows acquisition of 3-D pulse-echo RF datasets within 10 min. In case of breast cancer imaging, this concept also enables imaging of near-thorax tissue regions which cannot be achieved by 2-D FASC. Furthermore, moldings made of polyvinyl alcohol hydrogel (PVA-H) have been developed as a new acoustic coupling concept. It has a great potential to replace the water bath technique in UST, which is a critical concept with respect to clinical investigations. In this contribution, we present in vivo results for 3-D FASC applied to imaging a female breast which has been placed in a PVA-H molding during data acquisition. An algorithm is described to compensate time-of-flight and consider refraction at the water-PVA-H molding and molding-tissue interfaces. Therefore, the mean speed of sound (SOS) for the breast tissue is estimated with an image-based method. Our results show that the PVA-H molding concept is applicable and feasible and delivers good results. 3-D FASC is superior to 2-D FASC and provides 3-D volume data at increased image quality.

  9. Separator Membrane from Crosslinked Poly(Vinyl Alcohol) and Poly(Methyl Vinyl Ether-alt-Maleic Anhydride)

    PubMed Central

    Rohatgi, Charu Vashisth; Dutta, Naba K.; Choudhury, Namita Roy

    2015-01-01

    In this work, we report separator membranes from crosslinking of two polymers, such as poly vinyl alcohol (PVA) with an ionic polymer poly(methyl vinyl ether-alt-maleic anhydride) (PMVE-MA). Such interpolymer-networked systems were extensively used for biomedical and desalination applications but they were not examined for their potential use as membranes or separators for batteries. Therefore, the chemical interactions between these two polymers and the influence of such crosslinking on physicochemical properties of the membrane are systematically investigated through rheology and by critical gel point study. The hydrogen bonding and the chemical interaction between PMVE-MA and PVA resulted in highly cross-linked membranes. Effect of the molecular weight of PVA on the membrane properties was also examined. The developed membranes were extensively characterized by studying their physicochemical properties (water uptake, swelling ratio, and conductivity), thermal and electrochemical properties using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermo-gravimetric analysis (TGA) and electrochemical impedance spectroscopy (EIS). The DSC study shows the presence of a single Tg in the membranes indicating compatibility of the two polymers in flexible and transparent films. The membranes show good stability and ion conductivity suitable for separator applications. PMID:28347019

  10. Novel covalently coated diazoresin/polyvinyl alcohol capillary column for the analysis of proteins by capillary electrophoresis.

    PubMed

    Yu, Bing; Liu, Peng; Cong, Hailin; Tang, Jianguo; Zhang, Lixin

    2012-10-01

    A novel method for the preparation of covalently linked capillary coatings of PVA was demonstrated using photosensitive diazoresin (DR) as coupling agents. Layer-by-layer self-assembly film of DR and PVA based on hydrogen bonding was first fabricated on the inner wall of capillary, then the hydrogen bonding was converted into covalent bonding after treatment with UV light through the unique photochemistry reaction of DR. The covalently bonded coatings suppressed basic protein adsorption on the inner surface of capillary, and thus a baseline separation of lysozyme, cytochrome c and BSA was achieved using CE. Compared with bare capillary or noncovalently bonded DR/PVA coatings, the covalently linked DR/PVA capillary coatings not only improved the CE separation performance for proteins, but also exhibited good stability and repeatability. Due to the replacement of highly toxic and moisture-sensitive silane coupling agent by DR in the covalent coating preparation, this method may provide a green and easy way to make the covalently coated capillaries for CE.

  11. Absorption and luminescence spectroscopic analysis of tautomeric forms of protonatedN,N-dimethyl-N'-(1-nitro-9-acridinyl)-1,3-propanediamine (nitracrine) and its nitro isomers in poly(vinyl alcohol) films.

    PubMed

    Rak, J; Nowaczyk, K; Blazejowski, J; Kawski, A

    1991-03-01

    The electronic absorption, fluorescence, and phosphorescence excitation spectra, as well as the fluorescence and phosphorescence spectra, at either room or liquid nitrogen temperatures, were measured forN,N-dimethyl-N'-(1-nitro-9-acridinyl)-1,3-propanediamine and its three nitro isomers in acidified poly(vinyl alcohol) (PVA) film. The spectral characteristics obtained reveal the existence of the compounds studied in at least two structural forms. The results are interpreted in terms of the tautomeric phenomena which originate due to the migration of the hydrogen atom, which is bound to the nitrogen atom attached to the carbon atom (9), to the acridine ring nitrogen.

  12. Effect of cross-linking on properties and release characteristics of sodium salicylate-loaded electrospun poly(vinyl alcohol) fibre mats

    NASA Astrophysics Data System (ADS)

    Taepaiboon, Pattama; Rungsardthong, Uracha; Supaphol, Pitt

    2007-05-01

    Cross-linking of electrospun (e-spun) fibre mats (beaded fibre morphology with the average diameter of the fibre segments between beads being ~108 nm) of poly(vinyl alcohol) (PVA) containing sodium salicylate (SS), used as the model drug, was achieved by exposing the fibre mats to the vapour from 5.6 M aqueous solution of either glutaraldehyde or glyoxal for various exposure time intervals, followed by a heat treatment in a vacuum oven. With increasing the exposure time in the cross-linking chamber, the morphology of the e-spun fibre mats gradually changed from a porous to dense structure. Both the degree of swelling and the percentage of weight loss of the cross-linked fibre mats (i.e. ~200-530% and ~15-57%, respectively) were lower than those of the untreated ones (i.e. ~610% and ~67%, respectively). Cross-linking was also responsible for the monotonic increase in the storage moduli of the cross-linked SS-loaded e-spun PVA fibre mats with increasing exposure time in the cross-linking chamber. The release characteristic of the model drug from the SS-loaded e-spun PVA fibre mats both before and after cross-linking was assessed by the transdermal diffusion through a pig skin method. The cumulative release of the drug from these matrices could be divided into two stages: 0-4 and 4-72 h, in which the amount of SS released in the first stage increased very rapidly, while it was much slower in the second stage. Cross-linking slowed down the release of SS from the drug-loaded fibre mats appreciably and both the rate of release and the total amount of the drug released were decreasing functions of the exposure time interval in the cross-linking chamber. Lastly, the cross-linked SS-loaded e-spun PVA fibre mats were non-toxic to normal human dermal fibroblasts.

  13. Perifusion culture system for bovine embryos: improvement of embryo development by use of bovine oviduct epithelial cells, an antioxidant and polyvinyl alcohol.

    PubMed

    Lim, J M; Reggio, B C; Godke, R A; Hansel, W

    1997-01-01

    Three experiments were conducted in an attempt to improve a continuous flow-perifusion system capable of maintaining embryo development for long periods of time. Bovine embryos (8-16 cells) obtained from static co-culture with cumulus cells in a serum-free medium were perifused in an ACUSYST-S cell culture incubator. Culture chambers of the incubator consisted of a 0.2-mL unit (Chamber 1) connected to a 1.5-mL unit (Chamber 2), with the outflow from Chamber 1 routed to the inlet to Chamber 2. A bovine embryo culture medium supplemented with 3 mg mL-1 bovine serum albumin (BSA) and 25 mM HEPES was used as a perifusion culture medium (PCM). Embryos were perifused in Chamber 2 for 24, 48 and 72 h and further co-cultured in a static system up to 216 h after insemination. In Experiment 1, conditioning PCM with frozen-thawed bovine oviduct epithelial cells (BOEC) placed in Chamber 1 enhanced (P < 0.05) blastocyst formation of embryos in Chamber 2, after 24, 48 and 72 h of perifusion culture. The proportion of blastocysts was not further increased by placing BOEC in Chamber 2 along with the embryos. In Experiment 2, embryos were perifused with PCM conditioned with BOEC in Chamber 1 for 48 h or 72 h. A higher proportion of perifused embryos developed to the blastocyst stage after addition of 25 U mL-1 or 50 U mL-1 of superoxide dismutase (SOD) to PCM than in its absence. However, blastocyst formation of embryos perifused for 72 h was not increased after addition of 50 U mL-1 SOD compared with its absence. In Experiment 3, the proportions of morulae and blastocysts were not decreased by replacement of 3 mg mL-1 BSA with 1 mg mL-1 polyvinyl alcohol (PVA) in a BOEC-conditioned medium containing 50 U mL-1 SOD after perifusion for 48 h. In conclusion, PCM conditioning with BOEC and addition of an antioxidant to the perifusion medium improved the developmental capacity of perifused embryos. PVA is an adequate replacement for BSA in the perifusion medium.

  14. Water properties in a novel thermoswelling poly(vinyl alcohol) derivative hydrogel as studied by nuclear magnetic resonance and Fourier transform infrared spectroscopy.

    PubMed

    Wang, Jianquan; Satoh, Mitsuru

    2010-08-17

    Water properties in a novel thermoswelling hydrogel, which was prepared from poly(vinyl alcohol)-trimellitate (PVA-T) by a simple chemical cross-linking and swollen in 0.1-1.0 M Li(2)SO(4) solutions, were investigated through nuclear magnetic resonance and Fourier transform infrared (FTIR) spectroscopies. The spin-spin relaxation of the water proton in the hydrogel was measured at 5-35 degrees C, and the results were analyzed with a two-component model to obtain a long T(2) and a short T(2) as well as their fractions (f(short) = 1 - f(long)). The f(short) values thus obtained proved to be a linear function of the gel swelling ratio, and all of the data, except for an upper deviation at 1.0 M Li(2)SO(4), were found to be on an almost same line irrespective of the temperature and the salt concentration. This dependency of f(short) on the swelling degree strongly suggests that the temperature increment has an equivalent effect as that of the SO(4)(2-) concentration; namely, scission of inter(intra-)molecular hydrogen bonding (HB) between the COOHs on the side group must be responsible for the observed thermoswelling in the sulfate salt solutions. The upper deviation of f(short) at 1.0 M from the "master line" was reasonably interpreted in terms of the salting-out effect by the concentrated sulfate anion. On the other hand, attenuated total reflection-FTIR measurements for a gel plate revealed that an appreciable dissociation of the carboxyl group occurred only in the 1.0 M Li(2)SO(4) system. This finding, in turn, means that gel swelling with an increase in the salt concentration up to 0.5 M is not caused by the ionization of the gel and supports the scission of the intermolecular HB. Hydrophobic hydration around the main chain was investigated via a peak shift of the stretching vibration of -CH(2)-, and the slight red shift observed only at 1.0 M suggested that the salting-out effect onto the hydrophobic hydration is rather limited and the hydration around the main

  15. Capillary ion electrophoresis of inorganic anions and uric acid in human saliva using a polyvinyl alcohol coated capillary column and hexamethonium chloride as additive of background electrolyte.

    PubMed

    Mori, Masanobu; Yamamoto, Tsukasa; Kaseda, Maki; Yamada, Sachiko; Itabashi, Hideyuki

    2012-03-01

    A combination of polyvinyl alcohol chemically coated capillary (PVA capillary) and background electrolyte (BGE) with ion-pair reagent (hexamethonium dichloride, HMC) was used on capillary ion electrophoresis-UV detection (CIE-UV) for analysis of Br⁻, I⁻, NO₂⁻, NO₃⁻, SCN⁻ and uric acid in human saliva. The PVA capillary prepared in our laboratory minimized electro-osmotic flow (EOF) at the BGE in pH 3-10, and did not affect the UV detection at 210 nm by the PVA-layer on capillary wall. Therefore, use of the PVA capillary was suitable for sensitive UV detection for analyte anions, as well as suppression of protein adsorption. In this study, we optimized the BGE of 10 mM phosphate plus 10 mM HMC with applying a voltage of -15 kV. HMC as an additive to BGE could manipulate the electrophoretic mobility of anions, without electrostatic adsorption to the PVA capillary. The CIE-UV could separate and determine analyte anions in human saliva containing proteins by the direct injection without pretreatments such as dilution or deproteinization within 13 min. The relative standard deviations (n=10) were ranged of 0.5-1.6% in migration times, 2.2-6.8% in peak heights and 2.8-8.4% in peak areas. The limits of detection (S/N=3) were ranged of 3.42-6.87 μM. The peak height of anions in this system was gradually decreased through the successive injections of saliva samples, but the problem was successfully solved by periodically conditioning the PVA capillary. The quantifiability of anions in human saliva samples by the CIE-UV was evaluated through the recoveries by standard addition methods and comparison of other representative analytical methods, as well as identification by ion chromatography (IC). From the anion analyses in 12 different saliva samples, the CIE-UV demonstrated that can obtain obvious differences in concentrations of SCN⁻ between of smoker and non-smoker and those of uric acid between male and female with satisfactory results.

  16. 49 CFR 40.15 - May an employer use a service agent to meet DOT drug and alcohol testing requirements?

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... drug and alcohol testing requirements? 40.15 Section 40.15 Transportation Office of the Secretary of Transportation PROCEDURES FOR TRANSPORTATION WORKPLACE DRUG AND ALCOHOL TESTING PROGRAMS Employer Responsibilities § 40.15 May an employer use a service agent to meet DOT drug and alcohol testing requirements?...

  17. 49 CFR 40.15 - May an employer use a service agent to meet DOT drug and alcohol testing requirements?

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... drug and alcohol testing requirements? 40.15 Section 40.15 Transportation Office of the Secretary of Transportation PROCEDURES FOR TRANSPORTATION WORKPLACE DRUG AND ALCOHOL TESTING PROGRAMS Employer Responsibilities § 40.15 May an employer use a service agent to meet DOT drug and alcohol testing requirements?...

  18. 49 CFR 40.15 - May an employer use a service agent to meet DOT drug and alcohol testing requirements?

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... drug and alcohol testing requirements? 40.15 Section 40.15 Transportation Office of the Secretary of Transportation PROCEDURES FOR TRANSPORTATION WORKPLACE DRUG AND ALCOHOL TESTING PROGRAMS Employer Responsibilities § 40.15 May an employer use a service agent to meet DOT drug and alcohol testing requirements?...

  19. 49 CFR 40.15 - May an employer use a service agent to meet DOT drug and alcohol testing requirements?

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... drug and alcohol testing requirements? 40.15 Section 40.15 Transportation Office of the Secretary of Transportation PROCEDURES FOR TRANSPORTATION WORKPLACE DRUG AND ALCOHOL TESTING PROGRAMS Employer Responsibilities § 40.15 May an employer use a service agent to meet DOT drug and alcohol testing requirements?...

  20. 49 CFR 40.15 - May an employer use a service agent to meet DOT drug and alcohol testing requirements?

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... drug and alcohol testing requirements? 40.15 Section 40.15 Transportation Office of the Secretary of Transportation PROCEDURES FOR TRANSPORTATION WORKPLACE DRUG AND ALCOHOL TESTING PROGRAMS Employer Responsibilities § 40.15 May an employer use a service agent to meet DOT drug and alcohol testing requirements?...

  1. Synthesis of daidzin analogues as potential agents for alcohol abuse.

    PubMed

    Gao, Guang-Yao; Li, Dian-Jun; Keung, Wing Ming

    2003-09-01

    Daidzin, the active principle of an herbal remedy for 'alcohol addiction', has been shown to reduce alcohol consumption in all laboratory animals tested to date. Correlation studies using structural analogues of daidzin suggests that it acts by raising the monoamine oxidase (MAO)/mitochondrial aldehyde dehydrogenase (ALDH-2) activity ratio (J. Med. Chem. 2000, 43, 4169). Structure-activity relationship (SAR) studies on the 7-O-substituted analogues of daidzin have revealed structural features important for ALDH-2 and MAO inhibition (J. Med. Chem. 2001, 44, 3320). We here evaluated effects of substitutions at 2, 5, 6, 8, 3' and 4' positions of daidzin on its potencies for ALDH-2 and MAO inhibition. Results show that analogues with 4'-substituents that are small, polar and with hydrogen bonding capacities are most potent ALDH-2 inhibitors, whereas those that are non-polar and with electron withdrawing capacities are potent MAO inhibitors. Analogues with a 5-OH group are less potent ALDH-2 inhibitors but are more potent MAO inhibitors. All the 2-, 6-, 8- and 3'-substituted analogues tested so far do not inhibit ALDH-2 and/or have decreased potencies for MAO inhibition. This, together with the results obtained from previous studies, suggests that a potent antidipsotropic analogue would be a 4',7-disubstituted isoflavone. The 4'-substituent should be small, polar, and with hydrogen bonding capacities such as, -OH and -NH(2); whereas the 7-substituent should be a straight-chain alkyl with a terminal polar function such as -(CH(2))(n)-OH with 2< or =n < or =6, -(CH(2))(n)-COOH with 5< or =n < or =10, or -(CH(2))(n)-NH(2) with n > or =4.

  2. Influence of refractive index and molecular weight of alcohol agents on skin optical clearing effect

    NASA Astrophysics Data System (ADS)

    Mao, Zhongzhen; Zheng, Ying; Hu, Yating; Lu, Wei; Luo, Qingming; Zhu, Dan

    2007-02-01

    In order to discuss the relative factors affecting the optical clearing effect of agents on skin tissues, six hydroxy-terminated and saturated alcohols with different refractive index and molecular weight were chosen as the optical clearing agents (OCAs). After being treated by different OCAs, the change of transmitted intensity of porcine skins in vitro was measured by single integrating sphere system. The results showed the optical clearing effects of six OCAs, i.e., glycerol, PEG400, PEG200, 1,3-propylene glycol, 1,4-butanediol and 1-butanol, arranged in the descending order. Based on the above results, the refractive index and molecular weight was further discussed. The optical clearing effect of alcohols has been deduced to have negative correlation with refractive index (r=-0.608), but no correlation with molecular weight (r= 0.008).

  3. Preparation of Syndiotactic Poly(vinyl alcohol)/Poly(vinyl pivalate/vinyl acetate) Microspheres with Radiopacity Using Suspension Copolymerization and Saponification

    NASA Astrophysics Data System (ADS)

    Seok Lyoo, Won; Wook Cha, Jin; Young Kwak, Kun; Jae Lee, Young; Yong Jeon, Han; Sik Chung, Yong; Kyun Noh, Seok

    2010-06-01

    To prepare Poly(vinyl pivalate/vinyl acetate) [P(VPi/VAc)] microspheres with radiopacity, the suspension copolymerization approach in the presence of aqueous radiopaque nanoparticles was used. After, The P(VPi/VAc) microspheres with radiopacity were saponified in heterogeneous system, and then P(VPi/VAc) microspheres without aggregates were converted to s-PVA/P(VPi/VAc) microspheres of skin/core structure through the heterogeneous surface saponification. Radiopacity of microspheres was confirmed with Computed tomography (CT).

  4. Maltol, a Food Flavoring Agent, Attenuates Acute Alcohol-Induced Oxidative Damage in Mice

    PubMed Central

    Han, Ye; Xu, Qi; Hu, Jiang-ning; Han, Xin-yue; Li, Wei; Zhao, Li-chun

    2015-01-01

    The purpose of this study was to evaluate the hepatoprotective effect of maltol, a food-flavoring agent, on alcohol-induced acute oxidative damage in mice. Maltol used in this study was isolated from red ginseng (Panax ginseng C.A Meyer) and analyzed by high performance liquid chromatography (HPLC) and mass spectrometry. For hepatoprotective activity in vivo, pretreatment with maltol (12.5, 25 and 50 mg/kg; 15 days) drastically prevented the elevated activities of aspartate transaminase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP) and triglyceride (TG) in serum and the levels of malondialdehyde (MDA), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) in liver tissue (p < 0.05). Meanwhile, the levels of hepatic antioxidant, such as catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) were elevated by maltol pretreatment, compared to the alcohol group (p < 0.05). Histopathological examination revealed that maltol pretreatment significantly inhibited alcohol-induced hepatocyte apoptosis and fatty degeneration. Interestingly, pretreatment of maltol effectively relieved alcohol-induced oxidative damage in a dose-dependent manner. Maltol appeared to possess promising anti-oxidative and anti-inflammatory capacities. It was suggested that the hepatoprotective effect exhibited by maltol on alcohol-induced liver oxidative injury may be due to its potent antioxidant properties. PMID:25608939

  5. Investigation of the polyvinyl alcohol stabilization mechanism and adsorption properties on the surface of ternary mixed nanooxide AST 50 (Al2O3-SiO2-TiO2).

    PubMed

    Wiśniewska, Małgorzata; Ostolska, Iwona; Szewczuk-Karpisz, Katarzyna; Chibowski, Stanisław; Terpiłowski, Konrad; Gun'ko, Vladimir Moiseevich; Zarko, Vladimir Iljich

    A new adsorbent consisting of fumed, mixed alumina, silica, and titania in various proportions (AST 50) was investigated. The studied material was prepared by chemical vapor deposition method. The diameter of AST 50 primary particles was equal to about 51 nm which denotes that it can be classified as a nanomaterial. In the presented paper, the adsorption properties of polyvinyl alcohol on the ternary oxide were investigated. The polymer macromolecules were characterized by two different molecular weights and degree of hydrolysis. The polymer adsorption reaches the maximum at pH 3 and decreases with the solution pH rise. The reduction of the adsorbed PVA macromolecules is related to the electrostatic repulsion forces occurring in the studied system. The AST 50 point of zero charge (pHpzc) obtained from the potentiometric titration is equal to 4.7. Due to the nonionic character of the analyzed macromolecular compound, the polymer attendance has an insignificant effect on the AST 50 surface charge density. In the case of the adsorbent particles zeta potential, the obtained dependencies are different in the absence and presence of PVA. The shift of the slipping plane and displacement of the counter-ions from Stern layer by the adsorbed polymer chains have the greatest effect on the ζ potential value. The stability measurements indicate that the AST 50 suspensions in the presence of the background electrolyte at pH 3 and 6 are unstable. In turn, in an alkaline medium the mixed oxide suspensions exhibit the highest durability, which is a result of a large number of the negative charges on the AST 50 surface. The addition of PVA 100 significantly improves the suspension stability at pH 3 and 6; at higher pH value, the polymer presence does not influence the system durability. It is related to the steric and electrosteric stabilization of the colloidal particles by the adsorbed polyvinyl alcohol macromolecules.

  6. Investigation of the polyvinyl alcohol stabilization mechanism and adsorption properties on the surface of ternary mixed nanooxide AST 50 (Al2O3-SiO2-TiO2)

    NASA Astrophysics Data System (ADS)

    Wiśniewska, Małgorzata; Ostolska, Iwona; Szewczuk-Karpisz, Katarzyna; Chibowski, Stanisław; Terpiłowski, Konrad; Gun'ko, Vladimir Moiseevich; Zarko, Vladimir Iljich

    2015-01-01

    A new adsorbent consisting of fumed, mixed alumina, silica, and titania in various proportions (AST 50) was investigated. The studied material was prepared by chemical vapor deposition method. The diameter of AST 50 primary particles was equal to about 51 nm which denotes that it can be classified as a nanomaterial. In the presented paper, the adsorption properties of polyvinyl alcohol on the ternary oxide were investigated. The polymer macromolecules were characterized by two different molecular weights and degree of hydrolysis. The polymer adsorption reaches the maximum at pH 3 and decreases with the solution pH rise. The reduction of the adsorbed PVA macromolecules is related to the electrostatic repulsion forces occurring in the studied system. The AST 50 point of zero charge (pHpzc) obtained from the potentiometric titration is equal to 4.7. Due to the nonionic character of the analyzed macromolecular compound, the polymer attendance has an insignificant effect on the AST 50 surface charge density. In the case of the adsorbent particles zeta potential, the obtained dependencies are different in the absence and presence of PVA. The shift of the slipping plane and displacement of the counter-ions from Stern layer by the adsorbed polymer chains have the greatest effect on the ζ potential value. The stability measurements indicate that the AST 50 suspensions in the presence of the background electrolyte at pH 3 and 6 are unstable. In turn, in an alkaline medium the mixed oxide suspensions exhibit the highest durability, which is a result of a large number of the negative charges on the AST 50 surface. The addition of PVA 100 significantly improves the suspension stability at pH 3 and 6; at higher pH value, the polymer presence does not influence the system durability. It is related to the steric and electrosteric stabilization of the colloidal particles by the adsorbed polyvinyl alcohol macromolecules.

  7. Effect of poly(vinyl alcohol-co-vinyl acetate) copolymer blockiness on the dynamic interfacial tension and dilational viscoelasticity of polymer-anionic surfactant complex at the water-1-chlorobutane interface.

    PubMed

    Atanase, Leonard Ionut; Bistac, Sophie; Riess, Gérard

    2015-04-07

    Poly(vinyl alcohol-co-vinyl acetate) (PVA) copolymers obtained by partial hydrolysis of poly(vinyl acetate) (PVAc) are of practical importance for many applications, including emulsion and suspension polymerization processes. Their molecular characteristics have a major influence on the colloidal and interfacial properties. The most significant characteristics are represented by the average degree of hydrolysis D̅H̅, average degree of polymerization D̅P̅w̅ but also by the average acetate sequence length n(VAc)(0) which designates the so-called blockiness. Colloidal aggregates were observed in the aqueous PVA solutions having a D̅H̅ value of 73 mol%. The volume fraction of these aggregates at a given D̅H̅ value is directly correlated to the blockiness. Three PVA samples with identical D̅H̅ and D̅P̅w̅ but different blockiness were examined. By pendant drop and oscillating pendant drop techniques it was shown that the PVA sample having the lowest blockiness and thus the lowest volume fraction of colloidal aggregates has lower interfacial tension and elastic modulus E' values. On the contrary, the corresponding values are highest for PVA sample of higher blockiness. In the presence of sodium dodecyl sulfate (SDS), the colloidal aggregates are disaggregated by complex formation due to the hydrophobic-hydrophobic interactions. The PVA-SDS complex acts as a partial polyelectrolyte that induces the stretching of the chains and thus a reduction of the interface thickness. In this case, the interfacial tension and the elastic modulus both increase with increasing SDS concentration for all three PVA samples and the most significant effect was noticed for the most "blocky" copolymer sample.

  8. Alcohol

    MedlinePlus

    ... that's how many accidents occur. continue What Is Alcoholism? What can be confusing about alcohol is that ... develop a problem with it. Sometimes, that's called alcoholism (say: al-kuh-HOL - ism) or being an ...

  9. Alcohol

    MedlinePlus

    If you are like many Americans, you drink alcohol at least occasionally. For many people, moderate drinking ... risky. Heavy drinking can lead to alcoholism and alcohol abuse, as well as injuries, liver disease, heart ...

  10. Alcohol

    MedlinePlus

    ... de los dientes Video: Getting an X-ray Alcohol KidsHealth > For Kids > Alcohol Print A A A What's in this article? ... What Is Alcoholism? Say No en español El alcohol Getting the Right Message "Hey, who wants a ...

  11. MICROWAVE-ASSISTED SYNTHESIS OF CROSSLINKED POLY(VINYL ALCOHOL) NANOCOMPOSITES COMPRISING SINGLE-WALLED CARBON NANOTUBES, MULTI-WALLED CARBON NANOTUBES AND BUCKMINSTERFULLERENE

    EPA Science Inventory

    We report a facile method to accomplish cross-linking reaction of poly (vinyl alcohol) (PVA) with single-wall carbon nanotubes (SWNT), multi-wall carbon nanotubes (MWNT), and Buckminsterfullerene (C-60) using microwave (MW) irradiation. Nanocomposites of PVA cross-linked with SW...

  12. Long term performance evaluation of small-diameter vascular grafts based on polyvinyl alcohol hydrogel and dextran and MSCs-based therapies using the ovine pre-clinical animal model.

    PubMed

    Alexandre, Nuno; Amorim, Irina; Caseiro, Ana Rita; Pereira, Tiago; Alvites, Rui; Rêma, Alexandra; Gonçalves, Ana; Valadares, Guilherme; Costa, Elísio; Santos-Silva, Alice; Rodrigues, Miguel; Lopes, Maria Ascensão; Almeida, André; Santos, José Domingos; Maurício, Ana Colette; Luís, Ana Lúcia

    2017-03-07

    The functional and structural performance of a 5cm synthetic small diameter vascular graft (SDVG) produced by the copolymerization of polyvinyl alcohol hydrogel with low molecular weight dextran (PVA/Dx graft) associated to mesenchymal stem cells (MSCs)-based therapies and anticoagulant treatment with heparin, clopidogrel and warfarin was tested using the ovine model during the healing period of 24 weeks. The results were compared to the ones obtained with standard expanded polyetetrafluoroethylene grafts (ePTFE graft). Blood flow, vessel and graft diameter measurements, graft appearance and patency rate (PR), thrombus, stenosis and collateral vessel formation were evaluated by B-mode ultrasound, audio and color flow Doppler. Graft and regenerated vessels morphologic evaluation was performed by scanning electronic microscopy (SEM), histopathological and immunohistochemical analysis. All PVA/Dx grafts could maintain a similar or higher PR and systolic/diastolic laminar blood flow velocities were similar to ePTFE grafts. CD14 (macrophages) and α-actin (smooth muscle) staining presented similar results in PVA/Dx/MSCs and ePTFE graft groups. Fibrosis layer was lower and endothelial cells were only detected at graft-artery transitions where it was added the MSCs. In conclusion, PVA/Dx graft can be an excellent scaffold candidate for vascular reconstruction, including clinic mechanically challenging applications, such as SDVGs, especially when associated to MSCs-based therapies to promote higher endothelialization and lower fibrosis of the vascular prosthesis, but also higher PR values.

  13. A comparative study of nano-SiO2 and nano-TiO2 fillers on proton conductivity and dielectric response of a silicotungstic acid-H3PO4-poly(vinyl alcohol) polymer electrolyte.

    PubMed

    Gao, Han; Lian, Keryn

    2014-01-08

    The effects of nano-SiO2 and nano-TiO2 fillers on a thin film silicotungstic acid (SiWA)-H3PO4-poly(vinyl alcohol) (PVA) proton conducting polymer electrolyte were studied and compared with respect to their proton conductivity, environmental stability, and dielectric properties, across a temperature range from 243 to 323 K. Three major effects of these fillers have been identified: (a) barrier effect; (b) intrinsic dielectric constant effect; and (c) water retention effect. Dielectric analyses were used to differentiate these effects on polymer electrolyte-enabled capacitors. Capacitor performance was correlated to electrolyte properties through dielectric constant and dielectric loss spectra. Using a single-ion approach, proton density and proton mobility of each polymer electrolyte were derived as a function of temperature. The results allow us to deconvolute the different contributions to proton conductivity in SiWA-H3PO4-PVA-based electrolytes, especially in terms of the effects of fillers on the dynamic equilibrium of free protons and protonated water in the electrolytes.

  14. Long term performance evaluation of small-diameter vascular grafts based on polyvinyl alcohol hydrogel and dextran and MSCs-based therapies using the ovine pre-clinical animal model.

    PubMed

    Alexandre, Nuno; Amorim, Irina; Caseiro, Ana Rita; Pereira, Tiago; Alvites, Rui; Rêma, Alexandra; Gonçalves, Ana; Valadares, Guilherme; Costa, Elísio; Santos-Silva, Alice; Rodrigues, Miguel; Lopes, Maria Ascensão; Almeida, André; Santos, José Domingos; Maurício, Ana Colette; Luís, Ana Lúcia

    2016-11-20

    The functional and structural performance of a 5cm synthetic small diameter vascular graft (SDVG) produced by the copolymerization of polyvinyl alcohol hydrogel with low molecular weight dextran (PVA/Dx graft) associated to mesenchymal stem cells (MSCs)-based therapies and anticoagulant treatment with heparin, clopidogrel and warfarin was tested using the ovine model during the healing period of 24 weeks. The results were compared to the ones obtained with standard expanded polyetetrafluoroethylene grafts (ePTFE graft). Blood flow, vessel and graft diameter measurements, graft appearance and patency rate (PR), thrombus, stenosis and collateral vessel formation were evaluated by B-mode ultrasound, audio and color flow Doppler. Graft and regenerated vessels morphologic evaluation was performed by scanning electronic microscopy (SEM), histopathological and immunohistochemical analysis. All PVA/Dx grafts could maintain a similar or higher PR and systolic/diastolic laminar blood flow velocities were similar to ePTFE grafts. CD14 (macrophages) and α-actin (smooth muscle) staining presented similar results in PVA/Dx/MSCs and ePTFE graft groups. Fibrosis layer was lower and endothelial cells were only detected at graft-artery transitions where it was added the MSCs. In conclusion, PVA/Dx graft can be an excellent scaffold candidate for vascular reconstruction, including clinic mechanically challenging applications, such as SDVGs, especially when associated to MSCs-based therapies to promote higher endothelialization and lower fibrosis of the vascular prosthesis, but also higher PR values.

  15. Study of Dielectric Behavior and Charge Conduction Mechanism of Poly(Vinyl Alcohol) (PVA)-Copper (Cu) and Gold (Au) Nanocomposites as a Bio-resorbable Material for Organic Electronics

    NASA Astrophysics Data System (ADS)

    Mahendia, Suman; Goyal, Parveen Kumar; Tomar, Anil Kumar; Chahal, Rishi Pal; Kumar, Shyam

    2016-10-01

    Poly(vinyl alcohol) (PVA) embedded with varying concentrations of chemically synthesized copper (Cu) and gold (Au) nanoparticles (NPs) were prepared using ex situ sol-gel casting method. The addition of almost the same concentration of CuNPs in PVA improves the conducting properties, while that of AuNPs improves the dielectric nature of composite films. It has been found that addition of AuNPs up to ˜0.4 wt.% concentration enhaneces the capacitive nature due to the formation of small Coulomb tunneling knots as internal capacitors. The dielectric studies suggest the Maxwell-Wagner interfacial polarization as the dominant dielectric relaxation process, whereas the I- V characteristics indicate bulk limited Poole-Frenkel emission at high voltages as the dominant charge transport mechanism operating at room temperature in all specimens. These novel features lead to the conclusion that addition of a small quantity of metal nanoparticles can help tune the properties of PVA for desired applications in bio-compatible polymer-based organic electronic devices.

  16. A novel organic/inorganic polymer membrane based on poly(vinyl alcohol)/poly(2-acrylamido-2-methyl-1-propanesulfonic acid/3-glycidyloxypropyl trimethoxysilane polymer electrolyte membrane for direct methanol fuel cells

    NASA Astrophysics Data System (ADS)

    Yang, Chun-Chen; Lue, Shingjiang Jessie; Shih, Jeng-Ywan

    2011-05-01

    Poly(vinyl alcohol)/poly(2-acrylamido-2-methyl-1-propanesulfonic acid (PAMPS)/3-glycidyloxypropyl)trimethoxysilane (PVA/PAMPS/GPTMS) organic/inorganic proton-conducting polymer membranes are prepared by a solution casting method. PAMPS is a polymeric acid commonly used as a primary proton donor, while 3-(glycidyloxypropyl)trimethoxysilane (GPTMS) is an inorganic precursor forming a semi-interpenetrating network (SIPN). Varying amounts of sulfosuccinic acid (SSA) are used as the cross-linker and secondary proton source. The characteristic properties of PVA/PAMPS/GPTMS composite membranes are investigated by thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), micro-Raman spectroscopy and the AC impedance method. Direct methanol fuel cells (DMFCs) made of PVA/PAMPS/GPTMS composite membranes are assembled and examined. Experimental results indicate that DMFCs employing an inexpensive, non-perfluorinated, organic/inorganic SIPN membrane achieve good electrochemical performance. The highest peak power density of a DMFC using PVA/PAMPS/GPTMS composite membrane with 2 M CH3OH solution fuel at ambient temperature is 23.63 mW cm-2. The proposed organic/inorganic proton-conducting membrane based on PVA/PAMPS/GPTMS appears to be a viable candidate for future DMFC applications.

  17. The effect of polyvinyl alcohol (PVA) coating on structural, magnetic properties and spin dynamics of Ni0.3Zn0.7Fe2O4 ferrite nanoparticles

    NASA Astrophysics Data System (ADS)

    Rahimi, M.; Kameli, P.; Ranjbar, M.; Salamati, H.

    2013-12-01

    In this study, the structural and magnetic properties of uncoated and polyvinyl alcohol (PVA) coated Ni0.3Zn0.7Fe2O4 ferrite nanoparticles were studied using powder X-ray diffraction (XRD), Field Emission Scanning Electron Microscope (FE-SEM), Transmission Electron Microscope (TEM), Fourier Transform Infrared spectroscopy (FTIR) and magnetic measurements. The XRD patterns indicate that the crystalline structure is single phase cubic spinel and the spinel structure is retained after PVA coating. Also, after PVA coating, the crystallite size (from Scherrer formula) increases from 17 to 24 nm. The dc magnetization measurements revealed that both samples exhibit no hysteretic behavior at room temperature, symptomatic of the superparamagnetic behavior. The estimated values of zυ, τ0 and T0, using the critical slowing down model, confirm the observed variation of freezing temperatures. AC susceptibility measurements showed the magnetic responses are frequency dependent, as an applicable potential in cancer therapy. The relative sensitivity of samples to the variation of applied frequency, as an important parameter in hyperthermia based therapy, increases by coating Ni0.3Zn0.7Fe2O4 nanoparticles with PVA.

  18. Flexible all-solid-state supercapacitors based on graphene/carbon black nanoparticle film electrodes and cross-linked poly(vinyl alcohol)-H2SO4 porous gel electrolytes

    NASA Astrophysics Data System (ADS)

    Fei, Haojie; Yang, Chongyang; Bao, Hua; Wang, Gengchao

    2014-11-01

    Flexible all-solid-state supercapacitors (SCs) are fabricated using graphene/carbon black nanoparticle (GCB) film electrodes and cross-linked poly(vinyl alcohol)-H2SO4 porous gel electrolytes (gPVAP-H2SO4). The GCB composite films, with carbon black (CB) nanoparticles uniformly distributed in the graphene nanosheets, greatly improve the active surface areas and ion transportation of pristine graphene film. The porous structure of as-prepared gPVAP-H2SO4 membrane improves the equilibrium swelling ratio in electrolyte and provides interconnected ion transport channels. The chemical crosslinking solves the fluidity problem of PVA-H2SO4 gel electrolyte at high temperature. As-fabricated GCB//gPVAP(20)-H2SO4//GCB flexible SC displays an increased specific capacitance (144.5 F g-1 at 0.5 A g-1) and a higher specific capacitance retention (67.9% from 0.2 to 4 A g-1). More importantly, the flexible SC possesses good electrochemical performance at high temperature (capacitance retention of 78.3% after 1000 cycles at 70 °C).

  19. Preparation of La 0.8Sr 0.2Ga 0.83Mg 0.17O 2.815 powders by microwave-induced poly(vinyl alcohol) solution polymerization

    NASA Astrophysics Data System (ADS)

    Zhai, Yuling; Ye, Chang; Xia, Feng; Xiao, Jianzhong; Dai, Lei; Yang, Yifan; Wang, Yongqian

    A new and simple chemical route, named microwave-induced poly(vinyl alcohol) (PVA) solution polymerization, has been used to prepare fine, homogeneous and high-density pellets of purer La 0.8Sr 0.2Ga 0.83Mg 0.17O 2.815 (denoted as LS 0.2GM 0.17). The effect of different contents of PVA as the polymeric carrier, was studied and we obtained an optimal amount of PVA (1.65:1 ratio of positively charged valences of the cations (Me n+) to negatively charged hydroxyl (-OH -) groups of the organics), which could ensure homogenous distribution of the metal ions in the polymeric network structure and inhibit segregation. The behavior of the powder after calcination at different temperatures was studied. The PVA solution process consumed less organic material compared with the Pechini process, and consequently PVA was a more effective carrier in the preparation of LSGM. Higher heating rate and a more homogenous heating manner without thermal gradients in the microwave oven resulted in fewer secondary phases in the LS 0.2GM 0.17 powder after calcination at 1400 °C for 9 h and a smaller pellet grain size (2-3 μm) without segregation. The density of LS 0.2GM 0.17 pellet sintered at 1400 °C for 9 h was 6.19 g cm -3.

  20. Drug release behaviors of a pH sensitive semi-interpenetrating polymer network hydrogel composed of poly(vinyl alcohol) and star poly[2-(dimethylamino)ethyl methacrylate].

    PubMed

    Wu, Wei; Liu, Jing; Cao, Shuqin; Tan, Hong; Li, Jianshu; Xu, Fujian; Zhang, Xiao

    2011-09-15

    A series of pH sensitive semi-interpenetrating polymer network (semi-IPN) structural hydrogels composed of poly(vinyl alcohol) (PVA) and 21-arm star poly[2-(dimethylamino)ethyl methacrylate] (star PDMAEMA) with different molecular weight were prepared. Riboflavin was used as a model drug to evaluate the drug loading capacities and drug release behaviors of the semi-IPN structural hydrogels. The molecular weight of the star PDMAEMA polymers was calculated by GPC, and the formation of semi-IPN structure was confirmed by FTIR and SEM. It was found that the molecular weight of star PDMAEMA has significant effect on the structure, swelling ratio and drug release behaviors of the semi-IPN hydrogel at different pH conditions. The results suggested that the PVA/star PDMAEMA-50,000 hydrogel exhibited highest swelling ratio and drug loading capacity. The pH-sensitive semi-IPN hydrogel based on star PDMAEMA could be a promising drug delivery system due to the controllable porous structure.