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Sample records for acid pla films

  1. Antibacterial poly(lactic acid) (PLA) films grafting electrospun PLA/Ally isothioscyanate (AITC) fibers for food packaging

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Poly(lactic acid) (PLA) fibers of submicron sizes encapsulating allyl isothiocyanate (AITC) (PfA) were made and electrospun onto the surfaces of PLA films (PfA-g-film). SEM examination confirmed that the fibers were grafted to the PLA film after the (PfA-g-film) underwent air blowing and water washi...

  2. Improved thermal stability of polylactic acid (PLA) composite film via PLA-β-cyclodextrin-inclusion complex systems.

    PubMed

    Byun, Youngjae; Rodriguez, Katia; Han, Jung H; Kim, Young Teck

    2015-11-01

    The effects of the incorporation of PLA-β-cyclodextrin-inclusion complex (IC) and β-cyclodextrin (β-CD) on biopolyester PLA films were investigated. Thermal stability, surface morphology, barrier, and mechanical properties of the films were measured at varying IC (1, 3, 5, and 7%) and β-CD (1 and 5%) concentrations. The PLA-IC-composite films (IC-PLA-CFs) showed uniform morphological structure, while samples containing β-CD (β-CD-PLA-CFs) showed high agglomeration of β-CD due to poor interfacial interaction between β-CD and PLA moieties. According to the thermal property analysis, the 5% IC-PLA-CFs showed 6.6 times lower dimensional changes (6.5%) at the temperature range of 20-80°C than that of pure PLA film (43.0%). The increase of IC or β-CD content in the PLA-composite films shifted the glass transition and crystallization temperature to higher temperature regions. The crystallinity of both composite films improved by increasing IC or β-CD content. Both composite films had higher oxygen and water vapor permeability as IC or β-CD content increased in comparison to pure PLA film. All the composite films had less flexibility and lower tensile strength than the pure PLA film. In conclusion, this study shows that the IC technique is valuable to improve the thermal expansion stability of PLA-based films.

  3. Polymer Film-Based Screening and Isolation of Polylactic Acid (PLA)-Degrading Microorganisms.

    PubMed

    Kim, Mi Yeon; Kim, Changman; Moon, Jungheun; Heo, Jinhee; Jung, Sokhee P; Kim, Jung Rae

    2017-02-28

    Polylactic acid (PLA) has been highlighted as an alternative renewable polymer for the replacement of petroleum-based plastic materials, and is considered to be biodegradable. On the other hand, the biodegradation of PLA by terminal degraders, such as microorganisms, requires a lengthy period in the natural environment, and its mechanism is not completely understood. PLA biodegradation studies have been conducted using mainly undefined mixed cultures, but only a few bacterial strains have been isolated and examined. For further characterization of PLA biodegradation, in this study, the PLA-degrading bacteria from digester sludge were isolated and identified using a polymer film-based screening method. The enrichment of sludge on PLA granules was conducted with the serial transference of a subculture into fresh media for 40 days, and the attached biofilm was inoculated on a PLA film on an agar plate. 3D optical microscopy showed that the isolates physically degraded the PLA film due to bacterial degradation. 16S rRNA gene sequencing identified the microbial colonies to be Pseudomonas sp. MYK1 and Bacillus sp. MYK2. The two isolates exhibited significantly higher specific gas production rates from PLA biodegradation compared with that of the initial sludge inoculum.

  4. Processing-structure-properties relationships in PLA nanocomposite films

    NASA Astrophysics Data System (ADS)

    Di Maio, L.; Scarfato, P.; Garofalo, E.; Galdi, M. R.; D'Arienzo, L.; Incarnato, L.

    2014-05-01

    This work deals on the possibility to improve performances of PLA-based nanocomposite films, for packaging applications, through conveniently tuning materials and processing conditions in melt compounding technology. In particular, two types of polylactic acid and different types of filler selected from montmorillonites and bentonites families were used to prepare the hybrid systems by using a twin-screw extruder. The effect of biaxial drawing on morphology and properties of the nanocomposites, produced by film blowing, was investigated.

  5. Behaviors of keratinocytes and fibroblasts on films of PLA50-PEO-PLA50 triblock copolymers with various PLA segment lengths.

    PubMed

    Garric, Xavier; Garreau, Henri; Vert, Michel; Molès, Jean-Pierre

    2008-04-01

    The growth of human primary keratinocytes and fibroblasts on PLA-PEO-PLA copolymer films was investigated as an intermediate stage of a strategy aimed at making implantable dermo-epidermal substitutes. Four PLA-PEO-PLA triblock copolymers with the same PEO block and different DL-lactic acid/ethylene oxide molar ratios (LA/EO) (0.8, 1.4, 1.8 and 2), were synthesized and characterized by 1H-nuclear magnetic resonance and infrared spectroscopy. The films made of these copolymers were more hydrophilic than PLA50 and than tissue culture polystyrene controls according to contact angles with water. Proliferation and adhesion of human skin cells were evaluated by MTT assay and by scanning electron microscopy. The presence of PEO in the triblock copolymers influenced cell adhesion and proliferation of fibroblasts, whereas keratinocyte adhesion and proliferation were not affected. These features emphasize the interest of PLA-PEO-PLA triblock copolymers to serve as better compounds than the racemic PLA previously investigated to make supports for human skin primary cells and scaffolds for skin engineering.

  6. PLA/CS/Nifedipine Nanocomposite Films: Properties and the In Vitro Release of Nifedipine

    NASA Astrophysics Data System (ADS)

    Trang, Nguyen Thi Thu; Chinh, Nguyen Thuy; Giang, Nguyen Vu; Thanh, Dinh Thi Mai; Lam, Tran Dai; Hoang, Thai

    2016-07-01

    The polylactic acid (PLA)/chitosan (CS) films containing a drug, nifedipine (NIF), in the presence of polyethylene oxide (PEO) as a compatibilizer were prepared by the solution method. This method has not been used to form films containing four components (PLA, CS, NIF, PEO) up to now. The CS, PEO, and NIF contents are 25 wt.%, 6-8 wt.%, and 10-50 wt.% in comparison with PLA weight, respectively. Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TGA), differential scanning calorimetry (DSC), and field emission scanning electron microscopy (FESEM) were used to characterize the interactions, properties, and morphology of the PLA/CS/PEO/NIF films. The FTIR, TGA, and DSC results show that NIF carried by PLA/CS/PEO films and PLA, CS, NIF had better interaction and were more compatible when using PEO. The surface morphology of PLA/CS/PEO/NIF films was similar to that of PLA/CS/PEO films. Moreover, this was the first time drug loading and NIF release content from PLA/CS/PEO films were determined by the ultraviolet-visible (UV-Vis) spectroscopy method. The drug loading of PLA/CS/PEO/NIF films was from 80.99% to 93.61%. The in vitro NIF release studies were carried out in pH 2, 6.8, and 7.4 solutions corresponding to the pH of stomach, colon, and duodenum regions in the human body, respectively. The NIF release content in different pH solutions is in the order: pH 2 > pH 6.8 > pH 7.4 and increases when there is increasing NIF loading. The PLA/CS/PEO films are potential materials to apply for long-circulating systems for NIF delivery.

  7. Multifunctional PLA-PHB/cellulose nanocrystal films: processing, structural and thermal properties.

    PubMed

    Arrieta, M P; Fortunati, E; Dominici, F; Rayón, E; López, J; Kenny, J M

    2014-07-17

    Cellulose nanocrystals (CNCs) synthesized from microcrystalline cellulose by acid hydrolysis were added into poly(lactic acid)-poly(hydroxybutyrate) (PLA-PHB) blends to improve the final properties of the multifunctional systems. CNC were also modified with a surfactant (CNCs) to increase the interfacial adhesion in the systems maintaining the thermal stability. Firstly, masterbatch pellets were obtained for each formulation to improve the dispersion of the cellulose structures in the PLA-PHB and then nanocomposite films were processed. The thermal stability as well as the morphological and structural properties of nanocomposites was investigated. While PHB increased the PLA crystallinity due to its nucleation effect, well dispersed CNC and CNCs not only increased the crystallinity but also improved the processability, the thermal stability and the interaction between both polymers especially in the case of the modified CNCs based PLA-PHB formulation. Likewise, CNCs were better dispersed in PLA-CNCs and PLA-PHB-CNCs, than CNC.

  8. Bionanocomposite films based on plasticized PLA-PHB/cellulose nanocrystal blends.

    PubMed

    Arrieta, M P; Fortunati, E; Dominici, F; López, J; Kenny, J M

    2015-05-05

    Optically transparent plasticized poly(lactic acid) (PLA) based bionanocomposite films intended for food packaging were prepared by melt blending. Materials were plasticized with 15wt% of acetyl(tributyl citrate) (ATBC) to improve the material processability and to obtain flexibile films. Poly(hydroxybutyrate) (PHB) was used to increase PLA crystallinity. The thermal stability of the PLA-PHB blends was improved by the addition of 5 wt% of cellulose nanocrystals (CNC) or modified cellulose nanocrystals (CNCs) synthesized from microcrystalline cellulose. The combination of ATBC and cellulose nanocrystals, mainly the better dispersed CNCs, improved the interaction between PLA and PHB. Thus, an improvement on the oxygen barrier and stretchability was achieved in PLA-PHB-CNCs-ATBC which also displayed somewhat UV light blocking effect. All bionanocomposite films presented appropriate disintegration in compost suggesting their possible applications as biodegradable packaging materials.

  9. Polymer blends of polylactic acid (PLA) and polybutylene succinate-adipate

    NASA Astrophysics Data System (ADS)

    Ma, Wenguang

    A series of blends consisting of polylactic acid (PLA) and aliphatic succinate polyester (BionolleRTM #3000) had been prepared and investigated. The results of mechanical property investigations showed that using 20 wt% Bionolle#3000 can significantly increase the toughness of PLA. BionolleRTM #3000 also reduces the physical aging rate of PLA so blends remain tough longer. Conversely, the stiffness of BionolleRTM #3000 can be significantly increased by blending in PLA. DMA and DSC results show that PLA/BionolleRTM 3000 blends are not thermodynamically miscible, but are compatible blends. Studies have also been performed to determine the amount and rate of aerobic biodegradation of PLA/aliphatic succinate polyester blends in biologically active composting, enzymatic, and soil environments. The changes in molecular weight, molecular structure and thermal properties in the composting environment were also studied by GPC, NMR and DSC analyses. The research results showed BionolleRTM #3000 had a high degradation rate, while PLA had a low degradation rate. PLA/BionolleRTM #3000 blends had moderate degradation rates that increased with BionolleRTM #3000 content. The melt flow behavior of PLA/BionolleRTM #3000 blends has been studied by capillary rheometry. The relationship of the blends' viscosity with their composition, shear stress, shear rate, and temperature has been investigated. Power law index and activation energy of PLA, BionolleRTM #3000 and their blends have been calculated. The experimental and theoretical data can let us understand the processability of PLA/BionolleRTM #3000 blends. A scanning electron microscope (SEM) was used to investigate the morphological structure of the PLA/BionolleRTM #3000 blends. Micrographs of the samples made from different methods (blown film, extrudate and compression molding sheet) were taken; their differences in morphology were compared. For comparison, the micrographs of blend PLA/BionolleRTM #6000 was also studied. The

  10. Polylactic acid (PLA) controlled delivery carriers for biomedical applications.

    PubMed

    Tyler, Betty; Gullotti, David; Mangraviti, Antonella; Utsuki, Tadanobu; Brem, Henry

    2016-12-15

    Polylactic acid (PLA) and its copolymers have a long history of safety in humans and an extensive range of applications. PLA is biocompatible, biodegradable by hydrolysis and enzymatic activity, has a large range of mechanical and physical properties that can be engineered appropriately to suit multiple applications, and has low immunogenicity. Formulations containing PLA have also been Food and Drug Administration (FDA)-approved for multiple applications making PLA suitable for expedited clinical translatability. These biomaterials can be fashioned into sutures, scaffolds, cell carriers, drug delivery systems, and a myriad of fabrications. PLA has been the focus of a multitude of preclinical and clinical testing. Three-dimensional printing has expanded the possibilities of biomedical engineering and has enabled the fabrication of a myriad of platforms for an extensive variety of applications. PLA has been widely used as temporary extracellular matrices in tissue engineering. At the other end of the spectrum, PLA's application as drug-loaded nanoparticle drug carriers, such as liposomes, polymeric nanoparticles, dendrimers, and micelles, can encapsulate otherwise toxic hydrophobic anti-tumor drugs and evade systemic toxicities. The clinical translation of these technologies from preclinical experimental settings is an ever-evolving field with incremental advancements. In this review, some of the biomedical applications of PLA and its copolymers are highlighted and briefly summarized.

  11. Surface characteristics of PLA and PLGA films

    NASA Astrophysics Data System (ADS)

    Paragkumar N, Thanki; Edith, Dellacherie; Six, Jean-Luc

    2006-12-01

    Surface segregation and restructuring in polylactides (poly( D, L-lactide) and poly( L-lactide)) and poly( D,L-lactide-co-glycolide) (PLGA) films of various thicknesses were investigated using both attenuated total reflection FTIR (ATR-FTIR) and contact angle relaxation measurements. In case of poly( D,L-lactide) (DLPLA), it was observed that the surface segregation and the surface restructuring of methyl side groups are influenced by the polymer film thickness. This result has been confirmed by X-ray photoelectron spectroscopy (XPS). In the same way, PLGA thick films were also characterized by an extensive surface segregation of methyl side groups. Finally, surface restructuring was investigated by dynamic contact angle measurements and it was observed when film surface comes into contact with water. In parallel, we also found that poly( L-lactide) (PLLA) thin and clear films with thickness ˜15 μm undergo conformational changes on the surface upon solvent treatment with certain solvents. The solvent treated surface of PLLA becomes hazy and milky white and its hydrophobicity increases compared to untreated surface. FTIR spectroscopic analysis indicated that polymer chains at the surface undergo certain conformational changes upon solvent treatment. These changes are identified as the restricted motions of C-O-C segments and more intense and specific vibrations of methyl side groups. During solvent treatment, the change in water contact angle and FTIR spectrum of PLLA is well correlated.

  12. The effect of the stretching of PLA extruded films on their crystallinity and gas barrier properties

    NASA Astrophysics Data System (ADS)

    Guinault, A.; Menary, G. H.; Courgneau, C.; Griffith, D.; Ducruet, V.; Miri, V.; Sollogoub, C.

    2011-05-01

    Driven by environmental concerns, new polymers based on renewable resources are arriving on the market to replace conventional polymers, obtained from petroleum, for different applications like food packaging. One of the most prominent polymers among these materials is poly(lactic acid) (PLA), a biodegradable, thermoplastic, aliphatic polyester derived from renewable resources, such as corn starch (in the USA) or sugarcanes (in the rest of the world). However this polymer presents different disadvantages and especially low gas barrier properties [1]. Thermal crystallization can be used to increase its gas barrier properties but long times are necessary [2] and are not compatible with an industrial process. Another way to increase the gas barrier properties consists in stretching the film in order to increase its crystallinity and so its diffusion coefficient. We have prepared stretched PLA films with different stretch ratio and we have studied the effect of the stretching parameters on the gas barrier properties of PLA films. Finally we compared this process with the isothermal crystallization process by taking into account the crystallinity degree and the crystalline morphology.

  13. Development of PLA films containing oregano essential oil (Origanum vulgare L. virens) intended for use in food packaging.

    PubMed

    Llana-Ruiz-Cabello, M; Pichardo, S; Bermúdez, J M; Baños, A; Núñez, C; Guillamón, E; Aucejo, S; Cameán, A M

    2016-08-01

    Consumers' concerns about the environment and health have led to the development of new food packaging materials avoiding petroleum-based matrices and synthetic additives. The present study has developed polylactic acid (PLA) films containing different concentrations of essential oil from Origanum vulgare L. virens (OEO). The effectiveness of this new active packaging was checked for use in ready-to-eat salads. A plasticising effect was observed when OEO was incorporated in PLA films. The rest of the mechanical and physical properties of developed films did not show much change when OEO was included in the film. An antioxidant effect was recorded only for films containing the highest percentages of the active agent (5% and 10%). In addition, films exhibited in vitro antibacterial activity against Staphylococcus aureus, Yersinia enterocolitica, Listeria monocytogenes, Enterococcus faecalis and Staphylococcus carnosus. Moreover, in ready-to-eat salads, antimicrobial activity was only observed against yeast and moulds, where 5% and 10% of OEO was the most effective.

  14. A study on properties of PLA/PBAT from blown film process

    NASA Astrophysics Data System (ADS)

    Hongdilokkul, P.; Keeratipinit, K.; Chawthai, S.; Hararak, B.; Seadan, M.; Suttiruengwong, S.

    2015-07-01

    The aim of this work was to study the properties of films based on PLA/PBAT blend prepared by the reactive compounding. PLA/PBAT blends were prepared at the weight ratio of 80:20 together with peroxide as a reactive agent in a twin screw extruder with temperature profile of 160/170/180/210/220/190/175/150°C from feed to die zone. All blended samples, neat PLA, and neat PBAT were characterized for morphology, mechanical and rheological properties. SEM micrographs showed finely dispersed phases of PBAT in PLA in all cases. The particle sizes of PBAT were around 1 μm. The results indicated that the drawability and toughness properties of PLA were greatly improved when blended with 20%wt PBAT. The interface adhesion, and mechanical properties of PLA/PBAT blends were also improved when adding a very small quantity of peroxide. PLA/PBAT blends were then used to produce films. The film characteristics and mechanical properties were examined. Tensile strength of films was significantly improved in the machine direction in PLA/PBAT/peroxide blends whereas the good optical transparent property were remained the same compared with neat PLA.

  15. Biodegradable packaging materials conception based on starch and polylactic acid (PLA) reinforced with cellulose.

    PubMed

    Masmoudi, Fatma; Bessadok, Atef; Dammak, Mohamed; Jaziri, Mohamed; Ammar, Emna

    2016-10-01

    The plastic materials used for packaging are increasing leading to a considerable amount of undegradable solid wastes. This work deals with the reduction of conventional plastics waste and the natural resources preservation by using cellulosic polymers from renewable resources (alfa and luffa). Plasticized starch films syntheses were achieved at a laboratory scale. These natural films showed some very attractive mechanical properties at relatively low plasticizers levels (12 to 17 % by weight). Furthermore, mixtures including polylactic acid polymer (PLA) and cellulose fibers extracted from alfa and luffa were investigated by melt extrusion technique. When used at a rate of 10 %, these fibers improved the mixture mechanical properties. Both developed materials were biodegradable, but the plasticized starch exhibited a faster biodegradation kinetic compared to the PLA/cellulose fibers. These new materials would contribute to a sustainable development and a waste reduction.

  16. Potential of a newly developed high-speed near-infrared (NIR) camera (Compovision) in polymer industrial analyses: monitoring crystallinity and crystal evolution of polylactic acid (PLA) and concentration of PLA in PLA/Poly-(R)-3-hydroxybutyrate (PHB) blends.

    PubMed

    Ishikawa, Daitaro; Nishii, Takashi; Mizuno, Fumiaki; Sato, Harumi; Kazarian, Sergei G; Ozaki, Yukihiro

    2013-12-01

    This study was carried out to evaluate a new high-speed hyperspectral near-infrared (NIR) camera named Compovision. Quantitative analyses of the crystallinity and crystal evolution of biodegradable polymer, polylactic acid (PLA), and its concentration in PLA/poly-(R)-3-hydroxybutyrate (PHB) blends were investigated using near-infrared (NIR) imaging. This NIR camera can measure two-dimensional NIR spectral data in the 1000-2350 nm region obtaining images with wide field of view of 150 × 250 mm(2) (approximately 100  000 pixels) at high speeds (in less than 5 s). PLA with differing crystallinities between 0 and 50% blended samples with PHB in ratios of 80/20, 60/40, 40/60, 20/80, and pure films of 100% PLA and PHB were prepared. Compovision was used to collect respective NIR spectra in the 1000-2350 nm region and investigate the crystallinity of PLA and its concentration in the blends. The partial least squares (PLS) regression models for the crystallinity of PLA were developed using absorbance, second derivative, and standard normal variate (SNV) spectra from the most informative region of the spectra, between 1600 and 2000 nm. The predicted results of PLS models achieved using the absorbance and second derivative spectra were fairly good with a root mean square error (RMSE) of less than 6.1% and a determination of coefficient (R(2)) of more than 0.88 for PLS factor 1. The results obtained using the SNV spectra yielded the best prediction with the smallest RMSE of 2.93% and the highest R(2) of 0.976. Moreover, PLS models developed for estimating the concentration of PLA in the blend polymers using SNV spectra gave good predicted results where the RMSE was 4.94% and R(2) was 0.98. The SNV-based models provided the best-predicted results, since it can reduce the effects of the spectral changes induced by the inhomogeneity and the thickness of the samples. Wide area crystal evolution of PLA on a plate where a temperature slope of 70-105 °C had occurred was also

  17. Preparation and Characterization of an Olive Flounder (Paralichthys olivaceus) Skin Gelatin and Polylactic Acid Bilayer Film.

    PubMed

    Lee, Ka-Yeon; Song, Kyung Bin

    2017-03-01

    Olive flounder skin gelatin (OSG) was used as a film base material. A bilayer film of OSG and polylactic acid (PLA) was prepared using solvent casting method to enhance the film properties. Physical properties of the OSG-PLA film were increased compared with the nonaugmented OSG film. In particular, the PLA lamination decreased water vapor permeability from 2.17 to 0.92 × 10(-9) g·m/m(2) ·s·Pa, as well as of the water solubility from 16.62% to 9.27%, in the bilayer film relative to the OSG film. The oxygen permeability of the OSG-PLA bilayer film was held low by the OSG film, compensating for the high oxygen permeability of the PLA layer. Therefore, the OSG-PLA bilayer film with its enhanced physical properties and high water and oxygen barrier properties can be applied as a food packaging material.

  18. Preparation of hydrophilic poly(lactic acid) tissue engineering scaffold via (PLA)-(PLA-b-PEG)-(PEG) solution casting and thermal-induced surface structural transformation.

    PubMed

    Zhu, Xiaomin; Zhong, Tian; Huang, Ran; Wan, Ajun

    2015-01-01

    Porous poly(lactic acid) (PLA) tissue engineering scaffolds with a hydrophilic surface assembled by polyethylene glycol aggregations were prepared by the solvent casting/particulate leaching method from (PLA)-(PLA-b-PEG)-(PEG) blend solution, where the PLA-b-PEG block polymer serves as an amphiphilic glue between two phases. A thermal recrystallization process was inserted before leaching to induce a phase separation, which subsequently squeezes out PEG to form a hydrophilic shell. Characterizations of XRD and DSC indicated the composition and mixing states of materials. The water contact angle test qualitatively presented the excellent hydrophilicity compared to the pure PLA or PLA-PEG simple blend scaffold. The scanning electron microscope results confirmed the formation of porous structure of [Formula: see text] pore size, with an observable phase separation on the surface. The scaffold was degraded in PBS at [Formula: see text], and the degradation exhibits a three-stage behavior, which evidenced the amphiphilically glued phase separations.

  19. Additive Manufacturing and Characterization of Polylactic Acid (PLA) Composites Containing Metal Reinforcements

    NASA Technical Reports Server (NTRS)

    Kuentz, Lily; Salem, Anton; Singh, M.; Halbig, M. C.; Salem, J. A.

    2016-01-01

    Additive manufacturing of polymeric systems using 3D printing has become quite popular recently due to rapid growth and availability of low cost and open source 3D printers. Two widely used 3D printing filaments are based on polylactic acid (PLA) and acrylonitrile butadiene styrene (ABS) systems. PLA is much more environmentally friendly in comparison to ABS since it is made from renewable resources such as corn, sugarcane, and other starches as precursors. Recently, polylactic acid-based metal powder containing composite filaments have emerged which could be utilized for multifunctional applications. The composite filaments have higher density than pure PLA, and the majority of the materials volume is made up of polylactic acid. In order to utilize functionalities of composite filaments, printing behavior and properties of 3-D printed composites need to be characterized and compared with the pure PLA materials. In this study, pure PLA and composite specimens with different metallic reinforcements (Copper, Bronze, Tungsten, Iron, etc) were 3D printed at various layer heights and resulting microstructures and properties were characterized. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) behavior of filaments with different reinforcements were studied. The microscopy results show an increase in porosity between 3-D printed regular PLA and the metal composite PLA samples, which could produce weaker mechanical properties in the metal composite materials. Tensile strength and fracture toughness behavior of specimens as a function of print layer height will be presented.

  20. Mechanical and moisture barrier properties of titanium dioxide nanoparticles and halloysite nanotubes reinforced polylactic acid (PLA)

    NASA Astrophysics Data System (ADS)

    Alberton, J.; Martelli, S. M.; Fakhouri, F. M.; Soldi, V.

    2014-08-01

    Polylactic acid (PLA) has been larger used in biomedical field due to its low toxicity and biodegradability. The aim of this study was to produce PLLA nanocomposites, by melt extrusion, containing Halloysite nanotubes (HNT) and/or titanium dioxide (TiO2) nanoparticles. Immediately after drying, PLLA was mechanically homogenized with the nanofillers and then melt blended using a single screw extruder (L/D = 30) at a speed of 110 rpm, with three heating zones in which the following temperatures were maintained: 150, 150 and 160°C (AX Plasticos model AX14 LD30). The film samples were obtained by compression molding in a press with a temperature profile of 235 ± 5°C for 2.5 min, after pressing, films were cooled up to room temperature. The mechanical tests were performed according to ASTM D882-09 and the water vapor permeability (WVP) was measured according to ASTM E-96, in triplicate. The tensile properties indicated that the modulus was improved with increased TiO2 content up to 1g/100g PLLA. The Young's modulus (YM) of the PLA was increased from 3047 MPa to 3222 MPa with the addition of 1g TiO2/100g PLLA. The tensile strength (TS) of films increases with the TiO2 content. In both cases, the YM and TS are achieved at the 1% content of TiO2 and is due to the reinforcing effect of nanoparticles. Pristine PLA showed a strain at break (SB) of 3.56%, while the SB of nanocomposites were significant lower, for instance the SB of composite containing 7.5 g HNT/100g PLLA was around 1.90 %. The WVP of samples was increased by increasing the nano filler content. It should be expected that an increase of nanofiller content would decrease the mass transfer of water molecules throughout the samples due to the increase in the way water molecules will have to cross to permeate the material. However, this was not observed. Therefore, this result can be explained considering the molecular structure of both fillers, which contain several hydroxyl groups in the surface, making the

  1. Effect of an acid filler on hydrolysis and biodegradation of poly-lactic acid (PLA)

    NASA Astrophysics Data System (ADS)

    Iozzino, Valentina; Speranza, Vito; Pantani, Roberto

    2015-12-01

    The use of biodegradable polymers is certainly an excellent strategy to solve many of the problems related to the disposal of the traditional polymers, whose accumulation in the environment is harmful and damaging. In order to optimize the use of biodegradable polymers, it is very important to understand and control the transformation processes, the structures and the morphologies resulting from the process conditions used to produce the articles and, not least, the biodegradation. The latter is strictly dependent on the just mentioned variables. The poly-lactic acid, PLA, is a biodegradable polymer. Many studies have been carried out on the degradation process of this polymer. In the course of this work we performed degradation tests on the PLA, with a specific D-isomer content, having amorphous structure, and in particular of biodegradation and hydrolysis. An acid chemical, fumaric acid, was added to PLA with the objective of controlling the rate of hydrolysis and of biodegradation. The hydrolysis process was followed, as function of time, by means of different techniques: pH variation, variation of weight of samples and variation of crystallinity degree and glass transition temperature using DSC analysis. The samples were also analyzed in terms of biodegradability by means of a homemade respirometer apparatus, in controlled composting conditions.

  2. Development and characterisation of HPMC films containing PLA nanoparticles loaded with green tea extract for food packaging applications.

    PubMed

    Wrona, Magdalena; Cran, Marlene J; Nerín, Cristina; Bigger, Stephen W

    2017-01-20

    A novel active film material based on hydroxypropyl-methylcellulose (HPMC) containing poly(lactic acid) (PLA) nanoparticles (NPs) loaded with antioxidant (AO) green tea extract (GTE) was successfully developed. The PLA NPs were fabricated using an emulsification-solvent evaporation technique and the sizes were varied to enable a controlled release of the AO from the HPMC matrix. A statistical experimental design was used to optimise the synthesis of the NPs in order to obtain different sizes of nanoparticles and the loading of these into the HPMC matrix was also varied. The physico-chemical properties of the composite films were investigated and the release of the AO was confirmed by migration studies in 50% v/v ethanol/water food simulant. The AO capacity of the GTE released from the active films was studied using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical method and the results suggest that the material could potentially be used for extending the shelf-life of food products with high fat content.

  3. Influence of Filler on the Mechanical Properties and Kinetic Crystallization Behavior of Polylactic Acid (PLA)

    NASA Astrophysics Data System (ADS)

    Mitsuta, Ryo; Inoue, Ryohei; Hara, Ryosuke; Sato, Sadao

    The kinetic crystallization behavior of PLA (polylactic acid) and PLA/MMT nanocomposites containing 3 wt% montmorillonite (MMT) was examined in order to develop a new technique for obtaining the relative crystallization degree of a material from the spherulite occupation area based on images obtained using a charge-coupled device (CCD) camera. In addition, the relative crystallization degree is discussed in terms of the Ozawa theory. The effect of MMT filler on the mechanical properties of PLA/MMT nanocomposites, the number of spherulites generated in the nanocomposites, and the linear growth rate of these spherulites were also examined experimentally. The relative crystallization curves obtained by CCD and by DSC measurement were found to be approximately the same. Moreover, it was found that the Ozawa theory could be applied not only to PLA but also to PLA/MMT nanocomposites. In these nanocomposites, the number of spherulites decreased and the linear growth rate slightly increased ; moreover, the rate of crystallization also increased. The tensile and flexural modulus of the PLA/MMT nanocomposites containing 3 wt% MMT were 5.2-14.3% greater than those of PLA, and annealing resulted in a further increase of about 4.0-20.7%. However, the Izod impact value decreased due to the increase in rigidity caused by annealing and the addition of filler.

  4. Poly(lactic acid) and Osage Orange Wood Fiber Composites for Agricultural Mulch Films

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Osage orange wood(OO)was combined with poly(lactic acid)(PLA)to form a polymer composite intended for use as an agricultural mulch film. The PLA-OO mechanical properties were comparable to existing mulch film products and had the advantage of being completely biodegradable through a single growing ...

  5. Application of Lemongrass Oil-Containing Polylactic Acid Films to the Packaging of Pork Sausages.

    PubMed

    Yang, Hyun-Ju; Song, Kyung Bin

    2016-01-01

    Polylactic acid (PLA) is a biodegradable and renewable polymer, which represents a valuable alternative to plastic packaging films, often associated with environmental problems. In this study, we tested the suitability of PLA as a biodegradable packaging film and assessed the antimicrobial activity of lemongrass oil (LO), incorporated into the PLA film in different concentrations. To obtain the optimal physical properties for PLA films, tensile strength, elongation at break, and water vapor permeability were measured under different preparation conditions. In addition, the antimicrobial activity of the LO contained in the PLA film against Listeria monocytogenes was investigated by disc diffusion and viable cell count. Among all concentrations tested, 2% LO was the most suitable in terms of antimicrobial activity and physical properties of the PLA film. Based on these results, we used the PLA film containing 2% LO to pack pork sausages; after 12 d of storage at 4℃, the population of inoculated L. monocytogenes in the sausage samples wrapped with the PLA film containing 2% LO was reduced by 1.47 Log CFU/g compared with the control samples. Our data indicate that PLA films containing 2% LO represent a valuable means for antimicrobial sausage packaging.

  6. Application of Lemongrass Oil-Containing Polylactic Acid Films to the Packaging of Pork Sausages

    PubMed Central

    2016-01-01

    Polylactic acid (PLA) is a biodegradable and renewable polymer, which represents a valuable alternative to plastic packaging films, often associated with environmental problems. In this study, we tested the suitability of PLA as a biodegradable packaging film and assessed the antimicrobial activity of lemongrass oil (LO), incorporated into the PLA film in different concentrations. To obtain the optimal physical properties for PLA films, tensile strength, elongation at break, and water vapor permeability were measured under different preparation conditions. In addition, the antimicrobial activity of the LO contained in the PLA film against Listeria monocytogenes was investigated by disc diffusion and viable cell count. Among all concentrations tested, 2% LO was the most suitable in terms of antimicrobial activity and physical properties of the PLA film. Based on these results, we used the PLA film containing 2% LO to pack pork sausages; after 12 d of storage at 4℃, the population of inoculated L. monocytogenes in the sausage samples wrapped with the PLA film containing 2% LO was reduced by 1.47 Log CFU/g compared with the control samples. Our data indicate that PLA films containing 2% LO represent a valuable means for antimicrobial sausage packaging. PMID:27433114

  7. Thermal and mechanical properties of polylactic acid (PLA) and bagasse carboxymethyl cellulose (CMCB) composite by adding isosorbide diesters

    NASA Astrophysics Data System (ADS)

    Kamthai, Suthaphat; Magaraphan, Rathanawan

    2015-05-01

    An isosorbide diesters is one of isororbide types used as a plasticizer. The influence of this plasticizer on thermal and mechanical properties of polylactic acid and bagasse carboxymethyl cellulose (PLA/CMCB) composites was studied. PLA was blended with CMCB at 1%wt using various contents of isosorbide diesters (5, 10, 15 and 20%wt of PLA). The differential scanning calorimetric (DSC) and thermogravimetric (TGA) analyses indicated that the increment of isosorbide diesters concentration resulted in decreasing glass transition, melting and decomposition temperatures, as well as the reduction of storage modulus of PLA/CMCB composites. Moreover, the elongation of PLA/CMCB composites was significantly improved with increasing plasticizer content.

  8. Biodegradable PLA (polylactic acid) hinged trays keep quality of fresh-cut and cooked spinach.

    PubMed

    Botondi, Rinaldo; Bartoloni, Serena; Baccelloni, Simone; Mencarelli, Fabio

    2015-09-01

    This work examines the effects of packaging using two different polymeric trays with hinged lids, polyethylene terephthalate (PET) and polylactic acid (PLA), on fresh-cut and cooked spinach (Spinacia oleracea). Samples were stored in a cold room for 16 days at 4 °C. Chemical (total pigments, total polyphenols, ascorbic acid, antioxidant activity), physical (water activity), technological (colour evaluation), sensorial (aroma, visual appearance and water accumulation) and microbial (total aerobic mesophilic and psychrotrophic counts) parameters were tested. Both polymeric trays maintained the overall quality of fresh spinach for 6 days but spinach stored in PLA trays maintained its flavour longer. A significant increase in total polyphenols, antiradical activity, total carotenoids as well as a decrease in ascorbic acid in fresh spinach was observed in the first 3 days of storage in both samples. Unfortunately, the PLA package accumulated condensed water. The total microbial load of fresh-cut spinach reached about 6.3-7.3 log CFU g(-1) within 8 days. Cooked spinach packed in PLA and PET polymeric hinged trays showed the same behaviour as fresh spinach in terms of quality and shelf life. In conclusion, PLA plastic hinged trays can be used for packaging fresh-cut and cooked cut spinach, but the problem of condensed water must be solved.

  9. Polylactic acid (PLA)/Silver-NP/VitaminE bionanocomposite electrospun nanofibers with antibacterial and antioxidant activity

    NASA Astrophysics Data System (ADS)

    Munteanu, Bogdanel Silvestru; Aytac, Zeynep; Pricope, Gina M.; Uyar, Tamer; Vasile, Cornelia

    2014-10-01

    The antibacterial property of silver nanoparticles (Ag-NPs) and the antioxidant activity of Vitamin E have been combined by incorporation of these two active components within polylactic acid (PLA) nanofibers via electrospinning (PLA/Ag-NP/VitaminE nanofibers). The morphological and structural characterizations of PLA/Ag-NP/VitaminE nanofibers were performed by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy and X-ray diffraction. The average fiber diameter was 140 ± 60 nm, and the size of the Ag-NP was 2.7 ± 1.5 nm. PLA/Ag-NP/VitaminE nanofibers inhibited growth of Escherichia coli, Listeria monocytogenes and Salmonella typhymurium up to 100 %. The amount of released Ag ions from the nanofibers immersed in aqueous solution was determined by Inductively Coupled Plasma Mass Spectrometry, and it has been observed that the release of Ag ions was kept approximately constant after 10 days of immersion. The antioxidant activity of PLA/Ag-NP/VitaminE nanofibers was evaluated according to DPPH (2,2-diphenyl-1-picrylhydrazyl) method and determined as 94 %. The results of the tests on fresh apple and apple juice indicated that the PLA/Ag/VitaminE nanofiber membrane actively reduced the polyphenol oxidase activity. The multifunctional electrospun PLA nanofibers incorporating Ag-NP and Vitamin E may be quite applicable in food packaging due to the extremely large surface area of nanofibers along with antibacterial and antioxidant activities. These materials could find application in food industry as a potential preservative packaging for fruits and juices.

  10. Study of the free volume fraction in polylactic acid (PLA) by thermal analysis

    NASA Astrophysics Data System (ADS)

    Abdallah, A.; Benrekaa, N.

    2015-10-01

    The poly (lactic acid) or polylactide (PLA) is a biodegradable polymer with high modulus, strength and thermoplastic properties. In this work, the evolution of various properties of PLA is studied, such as glass transition temperature, mechanical modules and elongation percentage with the aim of investigating the free volume fraction. To do so, two thermal techniques have been used: the dynamic mechanical analysis (DMA) and dilatometry. The results obtained by these techniques are combined to go back to the structural properties of the studied material.

  11. Modification of cellulose nanocrystals with lactic acid for direct melt blending with PLA

    NASA Astrophysics Data System (ADS)

    Spinella, Stephen; Re, Giada Lo; Liu, Bo; Dorgan, John; Habibi, Youssef; Raquez, Jean-Marie; Dubois, Philippe; Gross, Richard A.

    2015-05-01

    Polylactide (PLA) is a commercially produced bio-based thermoplastic with unique properties such as high strength, biocompatibility and biodegradability. However, the low heat deflection temperature (HDT) of PLA significantly impedes its industrial implementation for high-performance applications, requiring the design of PLA-based nanocomposites. Cellulose nanocrystals (CNCs) are derived from cellulose which is highly abundant in nature, non-toxic, biodegradable, and has a low density. CNCs possess many attractive features for use in nano-composites. The main problem of adding hydrophilic CNCs into hydrophobic matrixes is their lack of affinity, leading to phase separation and a decrease in mechanical properties. A one-step method based on both Fischer esterification and acid hydrolysis was used in this work to obtain functionalized and ready-to-use CNCs, with the aim to improve the filler dispersion into the polymeric matrix. The study assesses the reinforcing effect of CNCs on PLA-based materials. CNCs functionalized with acetate (AA-CNCs), lactic acid (LA-CNCs) and unfunctionalized CNCs were synthesized and blends of PLA and these CNCs were prepared by direct melt blending. The corresponding thermomechanical properties were investigated by DMTA. Blends with LA-CNCs possessed the highest storage modulus. Based on these results, blends with up to 20 % LA-CNCs were prepared by direct melt blending and an increase of up to 20°C in the HDT resulted. A decrease in oxygen permeability also resulted from increasing the nano-filler content. This increase in materials properties can potentially expand the applications of PLA based materials.

  12. Synthesis and characterization of L-lactide and polylactic acid (PLA) from L-lactic acid for biomedical applications

    NASA Astrophysics Data System (ADS)

    Rahmayetty, Sukirno, Prasetya, Bambang; Gozan, Misri

    2017-02-01

    Lactide is the monomer for the polymer polylactic acid (PLA) from lactic acid through polycondensation and depolymerization process. The properties of PLA strongly depend on the quality of the lactide monomer from which it is synthesized. Optical purity of lactide produced in depolymerization process confirmed to be L-lactide. The highest yield of crude lactide was 38.5% at temperature 210 °C with average molecular weight (Mn) of oligomer was 2389. Ring opening polymerization of lactide using Candida rugosa lipase as biocatalyst to PLLA synthesis has been achieved to generate useful biomedical materials free from heavy metal.

  13. SKELETAL MUSCLE GROUP VIA PHOSPHOLIPASE A2 (iPLA2β): EXPRESSION AND ROLE IN FATTY ACID OXIDATION†

    PubMed Central

    Carper, Michael J.; Zhang, Sheng; Turk, John; Ramanadham, Sasanka

    2009-01-01

    Among the phospholipases A2 (PLA2s) are the Group VI Ca2+-independent PLA2s (iPLA2s) and expression of multiple transcripts of iPLA2 in skeletal muscle has been reported. In the present study, phospholipase activity and sequential ATP and calmodulin affinity column chromatography analyses reveal that skeletal muscle iPLA2 exhibits properties characteristic of the iPLA2β isoform. The phospholipase activity of iPLA2β has been demonstrated to participate in signal transduction, cell proliferation, and apoptosis. We also report here that skeletal muscle from iPLA2β-null mice, relative to wild type muscle, exhibits a reduced capacity to oxidize palmitate but not palmitoyl-CoA or acetyl-CoA in the absence of changes in fatty acid transporters CD36 and CPT1 or β-hydroxyacyl-CoA dehydrogenase activity. Recently, purified iPLA2β was demonstrated to manifest a thioesterase activity which catalyzes hydrolysis of fatty acyl-CoAs. The liberated CoA-SH facilitates fatty acid transport into the mitochondria. In this regard, we find that fractions eluted from the ATP column and containing iPLA2β phospholipase activity also contained acyl-CoA thioesterase activity that was inhibited by the bromoenol lactone (BEL) suicide inhibitor of iPLA2β. We further find that acyl-CoA thioesterase activity in skeletal muscle preparations from iPLA2β-null mice is significantly reduced, relative to WT activity. These findings suggest that the absence of acyl-CoA thioesterase activity of iPLA2β can lead to reduced fatty acyl-CoA generation and impair fatty acid oxidation in iPLA2β-null mice. Our findings therefore reveal a novel function of iPLA2β, related not to its phospholipase activity but to its thioesterase activity, which contributes to optimal fatty acid oxidation in skeletal muscle. PMID:18937505

  14. Cold Oxygen Plasma Treatments for the Improvement of the Physicochemical and Biodegradable Properties of Polylactic Acid Films for Food Packaging.

    PubMed

    Song, Ah Young; Oh, Yoon Ah; Roh, Si Hyeon; Kim, Ji Hyeon; Min, Sea C

    2016-01-01

    The effects of cold plasma (CP) treatment on the physicochemical and biodegradable properties of polylactic acid (PLA) films were studied. The PLA films were exposed to CP for 40 min at 900 W and 667 Pa using oxygen as the plasma-forming gas. The tensile, optical, and dynamic mechanical thermal properties, surface morphology, printability, water contact angle, chemical structure, weight change, and biodegradability properties of the films were evaluated during storage for up to 56 d. The tensile and optical properties of the PLA films were not significantly affected by CP treatment (CPT; P > 0.05). The surface roughness and water contact angle of PLA films increased by CPT and further increased during storage for 56 d. The printability of the PLA films increased following CPT and remained stable throughout the storage period. CP-induced hydrophilicity was also sustained during the storage period. The PLA films lost 1.9% of their weight after CPT, but recovered 99.5% of this loss after 14 d in storage. Photodegradation, thermal, and microbial biodegradable properties of the films were significantly improved by CPT (P < 0.05). Accelerated biodegradation of CP-treated PLA sachets with and without cheese was observed in compost. These results demonstrate the potential of CPT for modifying the stiffness, water contact angle, and chemical structure of PLA films and improving the printability and biodegradability of the films for food packaging.

  15. Degradation of PVC/rPLA Thick Films in Soil Burial Experiment

    NASA Astrophysics Data System (ADS)

    Nowak, Bożena; Rusinowski, Szymon; Chmielnicki, Blazej; Kamińska-Bach, Grażyna; Bortel, Krzysztof

    2016-10-01

    Some of the biodegradable polymers can be blended with a synthetic polymer to facilitate their biodegradation in the environment. The objective of the study was to investigate the biodegradation of thick films of poly(vinyl chloride)/recycled polylactide (PVC/rPLA). The experiments were carried out in the garden soil or in the mixture of garden soil and hydrocarbon-contaminated soil under laboratory conditions. Since it is widely accepted that the biosurfactants secreted by microorganisms enable biotransformation of various hydrophobic substances in the environment, it was assumed that the use of contaminated soil, rich in biosurfactant producing bacteria, may accelerate biodegradation of plastics. After the experimental period, the more noticeable weight loss of polymer films was observed after incubation in the garden soil. However, more pronounced changes in the film surface morphology and chemical structure as well as decrease of tensile strength were observed after incubation of films in the mixture of garden and contaminated soil. It turned out that as a result of competition between two distinct groups of microorganisms present in the mixture of garden and hydrocarbon-contaminated soils the number of microorganisms and their activity were lower than the activity of indigenous microflora of garden soil as well as the amount of secreted biosurfactants towards plastics.

  16. Mechanical, thermal, and biodegradable properties of polylactic acid (PLA)/coir fibre biocomposites

    NASA Astrophysics Data System (ADS)

    Dong, Y.; Ghataura, A.; Haroosh, H. J.

    2013-08-01

    Polylactic acid (PLA)/coir fibre biocomposites were fabricated using a compression moulding technique. The effects of fibre content (5-30 wt%) and fibre treatment on mechanical, thermal and biodegradable properties of biocomposites were holistically investigated via mechanical testing, scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and soil burial method to understand the applicability of manufacturing eco-efficient and sustainable "green composites".

  17. Improve the Strength of PLA/HA Composite Through the Use of Surface Initiated Polymerization and Phosphonic Acid Coupling Agent

    PubMed Central

    Wang, Tongxin; Chow, Laurence C.; Frukhtbeyn, Stanislav A.; Ting, Andy Hai; Dong, Quanxiao; Yang, Mingshu; Mitchell, James W.

    2011-01-01

    Bioresorbable composite made from degradable polymers, e.g., polylactide (PLA), and bioactive calcium phosphates, e.g., hydroxyapatite (HA), are clinically desirable for bone fixation, repair and tissue engineering because they do not need to be removed by surgery after the bone heals. However, preparation of PLA/HA composite from non-modified HA usually results in mechanical strength reductions due to a weak interface between PLA and HA. In this study, a calcium-phosphate/phosphonate hybrid shell was developed to introduce a greater amount of reactive hydroxyl groups onto the HA particles. Then, PLA was successfully grafted on HA by surface-initiated polymerization through the non-ionic surface hydroxyl groups. Thermogravimetric analysis indiated that the amount of grafted PLA on HA can be up to 7 %, which is about 50 % greater than that from the literature. PLA grafted HA shows significantly different pH dependent ζ-potential and particle size profiles from those of uncoated HA. By combining the phosphonic acid coupling agent and surface initiated polymerization, PLA could directly link to HA through covalent bond so that the interfacial interaction in the PLA/HA composite can be significantly improved. The diametral tensile strength of PLA/HA composite prepared from PLA-grafted HA was found to be over twice that of the composite prepared from the non-modified HA. Moreover, the tensile strength of the improved composite was 23 % higher than that of PLA alone. By varying additional variables, this approach has the potential to produce bioresorbable composites with improved mechanical properties that are in the range of natural bones, and can have wide applications for bone fixation and repair in load-bearing areas. PMID:22399838

  18. Morphology control in thin films of PS:PLA homopolymer blends by dip-coating deposition

    NASA Astrophysics Data System (ADS)

    Vital, Alexane; Vayer, Marylène; Tillocher, Thomas; Dussart, Rémi; Boufnichel, Mohamed; Sinturel, Christophe

    2017-01-01

    In this work, smooth polymer films of PS, PLA and their blends, with thicknesses ranging from 20 nm up to 400 nm and very few defects on the surface were obtained by dip-coating. In contrast to the process of spin-coating which is conventionally used to prepare thin films of polymer blends, we showed that depending on the deposition parameters (withdrawal speed and geometry of the reservoir), various morphologies such as layered films and laterally phase-separated domains could be formed for a given blend/solvent pair, offering much more opportunities compared to the spin-coating process. This diversity of morphologies was explained by considering the superposition of different phenomena such as phase separation process, dewetting and vitrification in which parameters such as the drying time, the compatibility of the polymer/solvent pairs and the affinity of the polymer towards the interfaces were suspected to play a significant role. For that purpose, the process of dip-coating was examined within the capillary and the draining regimes (for low and high withdrawal speed respectively) in order to get a full description of the thickness variation and evaporation rate as a function of the deposition parameters.

  19. Antimicrobial activity of nisin incorporated in pectin and polylactic acid composite films against Listeria monocytogenes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Extruded composite films from 20% pectin and 80% polylactic acids (PLA) were developed and nisin was loaded into films by a diffusion post extrusion. Inhibitory activities of the films against Listeria monocytogenes were evaluated in brain heart infusion (BHI) broth, liquid egg white and orange juic...

  20. Effect of Sterilization Methods on Electrospun Poly(lactic acid) (PLA) Fiber Alignment for Biomedical Applications.

    PubMed

    Valente, T A M; Silva, D M; Gomes, P S; Fernandes, M H; Santos, J D; Sencadas, V

    2016-02-10

    Medically approved sterility methods should be a major concern when developing a polymeric scaffold, mainly when commercialization is envisaged. In the present work, poly(lactic acid) (PLA) fiber membranes were processed by electrospinning with random and aligned fiber alignment and sterilized under UV, ethylene oxide (EO), and γ-radiation, the most common ones for clinical applications. It was observed that UV light and γ-radiation do not influence fiber morphology or alignment, while electrospun samples treated with EO lead to fiber orientation loss and morphology changing from cylindrical fibers to ribbon-like structures, accompanied to an increase of polymer crystallinity up to 28%. UV light and γ-radiation sterilization methods showed to be less harmful to polymer morphology, without significant changes in polymer thermal and mechanical properties, but a slight increase of polymer wettability was detected, especially for the samples treated with UV radiation. In vitro results indicate that both UV and γ-radiation treatments of PLA membranes allow the adhesion and proliferation of MG 63 osteoblastic cells in a close interaction with the fiber meshes and with a growth pattern highly sensitive to the underlying random or aligned fiber orientation. These results are suggestive of the potential of both γ-radiation sterilized PLA membranes for clinical applications in regenerative medicine, especially those where customized membrane morphology and fiber alignment is an important issue.

  1. Cold atmospheric plasma (CAP) surface nanomodified 3D printed polylactic acid (PLA) scaffolds for bone regeneration.

    PubMed

    Wang, Mian; Favi, Pelagie; Cheng, Xiaoqian; Golshan, Negar H; Ziemer, Katherine S; Keidar, Michael; Webster, Thomas J

    2016-12-01

    Three-dimensional (3D) printing is a new fabrication method for tissue engineering which can precisely control scaffold architecture at the micron-scale. However, scaffolds not only need 3D biocompatible structures that mimic the micron structure of natural tissues, they also require mimicking of the nano-scale extracellular matrix properties of the tissue they intend to replace. In order to achieve this, the objective of the present in vitro study was to use cold atmospheric plasma (CAP) as a quick and inexpensive way to modify the nano-scale roughness and chemical composition of a 3D printed scaffold surface. Water contact angles of a normal 3D printed poly-lactic-acid (PLA) scaffold dramatically dropped after CAP treatment from 70±2° to 24±2°. In addition, the nano-scale surface roughness (Rq) of the untreated 3D PLA scaffolds drastically increased (up to 250%) after 1, 3, and 5min of CAP treatment from 1.20nm to 10.50nm, 22.90nm, and 27.60nm, respectively. X-ray photoelectron spectroscopy (XPS) analysis showed that the ratio of oxygen to carbon significantly increased after CAP treatment, which indicated that the CAP treatment of PLA not only changed nano-scale roughness but also chemistry. Both changes in hydrophilicity and nano-scale roughness demonstrated a very efficient plasma treatment, which in turn significantly promoted both osteoblast (bone forming cells) and mesenchymal stem cell attachment and proliferation. These promising results suggest that CAP surface modification may have potential applications for enhancing 3D printed PLA bone tissue engineering materials (and all 3D printed materials) in a quick and an inexpensive manner and, thus, should be further studied.

  2. Preparation and characterization of microporous poly(D,L-lactic acid) film for tissue engineering scaffold.

    PubMed

    Shi, Shuai; Wang, Xiu Hong; Guo, Gang; Fan, Min; Huang, Mei Juan; Qian, Zhi Yong

    2010-11-24

    We prepared a series of microporous films based on poly(d,l-lactic acid) (PLA) via phase separation. According to scanning electron microscopy (SEM), a 3-dimensional foamy structure with multimicrometer scale pores on the air surface of film could be observed. As the morphology of PLA film could not be stabilized using solvent-nonsolvent phase separation, we investigated the effect of temperature, air movement, and concentration on the properties of microporous PLA films. The results show that when the temperature was 25°C in a vacuum, it was easy to prepare PLA film with micropores, and it was stable. As the relationship between the morphology and formation factors was clear and the morphology of the PLA film was controllable, we studied the PLA film's potential use for cell culture. SEM results showed that NIH3T3 cell could be adhered on the surface of film well after incubation for 2 days. Meanwhile, in vitro culture experiments revealed the great biocompatibility of the scaffold for adsorption and proliferation of fibroblasts.

  3. Three-dimensional printing with polylactic acid (PLA) thermoplastic offers new opportunities for cryobiology.

    PubMed

    Tiersch, Terrence R; Monroe, William T

    2016-12-01

    Development of devices through design, prototyping, testing, and fabrication is especially necessary for enhancement of research and eventual application in cryobiology. The advent of 3-dimensional printing offers unique opportunities for this process, given that the materials involved are suitable for use in cryogenic temperatures. We report herein that 3-D printing with polylactic acid (PLA) thermoplastic is ideally suited for cryobiology device development. Devices that are designed and standardized in open-source fashion can be electronically distributed and created locally on increasingly affordable 3-D printers, and can accelerate cryobiology findings and improve reproducibility of results.

  4. Paclitaxel-loaded nanoparticles of star-shaped cholic acid-core PLA-TPGS copolymer for breast cancer treatment

    PubMed Central

    2013-01-01

    A system of novel nanoparticles of star-shaped cholic acid-core polylactide-d-α-tocopheryl polyethylene glycol 1000 succinate (CA-PLA-TPGS) block copolymer was developed for paclitaxel delivery for breast cancer treatment, which demonstrated superior in vitro and in vivo performance in comparison with paclitaxel-loaded poly(d,l-lactide-co-glycolide) (PLGA) nanoparticles and linear PLA-TPGS nanoparticles. The paclitaxel- or couramin 6-loaded nanoparticles were fabricated by a modified nanoprecipitation method and then characterized in terms of size, surface charge, surface morphology, drug encapsulation efficiency, and in vitro drug release. The CA-PLA-TPGS nanoparticles were found to be spherical in shape with an average size of around 120 nm. The nanoparticles were found to be stable, showing no change in the particle size and surface charge during 90-day storage of the aqueous solution. The release profiles of the paclitaxel-loaded nanoparticles exhibited typically biphasic release patterns. The results also showed that the CA-PLA-TPGS nanoparticles have higher antitumor efficacy than the PLA-TPGS nanoparticles and PLGA nanoparticles in vitro and in vivo. In conclusion, such nanoparticles of star-shaped cholic acid-core PLA-TPGS block copolymer could be considered as a potentially promising and effective strategy for breast cancer treatment. PMID:24134303

  5. Investigation of Ultrasonics as a tool for energy efficient recycling of Lactic acid from postconsumer PLA products

    NASA Astrophysics Data System (ADS)

    Srinivasan, Gowrishankar

    The growing use of "ecofriendly," biodegradable polymers have created a need for a suitable recycling technique because, unlike petroleum derived plastics, their properties deteriorate during conventional recycling. These new techniques must be cost efficient and yield material properties same as virgin polymer. This research investigates the effectiveness of high-power ultrasonics as an efficient technique to recover lactic acid from postconsumer polylactic acid (PLA) products. Polylactic acid is a commercially available bioplastic derived from corn starch and/or sugar cane that is biorenewable and compostable (biodegradable). The various ongoing researches to recover lactic acid from PLA employ a common platform of high temperature, high pressure (HTHP) to effect polymer hydrolysis. The energy intensiveness of these HTHP processes prompted this work to investigate ultrasonics as an low energy alternative process to cause PLA depolymerization. The energy consumption and the time required for depolymerization were utilized as the metrics to quantify and compare depolymerization enhanced by ultrasonics with hot-bath technique. The coupled effect of catalysts concentration and different solvents, along with ultrasonic were studied based on preliminary trial results. In addition, the correlation between the rates of de-polymerization was analyzed for ultrasonic amplitude, treatment time, and catalyst concentration and types. The results indicate that depolymerization of PLA was largely effected by heating caused by ultrasonic-induced cavitations. Other effects of ultrasonics, namely cavitations and acoustic streaming, were shown to have minimal effects in enhancing depolymerization. In fact, thermal energy predominately affected the reaction kinetics; the heat introduced by conventional method (i.e., electrical heaters) was more efficient than ultrasonic heating in terms of energy (for depolymerization) per unit mass of PLA and depolymerizing time. The degree of

  6. Characterization of thermoplastic polyurethane/polylactic acid (TPU/PLA) tissue engineering scaffolds fabricated by microcellular injection molding.

    PubMed

    Mi, Hao-Yang; Salick, Max R; Jing, Xin; Jacques, Brianna R; Crone, Wendy C; Peng, Xiang-Fang; Turng, Lih-Sheng

    2013-12-01

    Polylactic acid (PLA) and thermoplastic polyurethane (TPU) are two kinds of biocompatible and biodegradable polymers that can be used in biomedical applications. PLA has rigid mechanical properties while TPU possesses flexible mechanical properties. Blended TPU/PLA tissue engineering scaffolds at different ratios for tunable properties were fabricated via twin screw extrusion and microcellular injection molding techniques for the first time. Multiple test methods were used to characterize these materials. Fourier transform infrared spectroscopy (FTIR) confirmed the existence of the two components in the blends; differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) confirmed the immiscibility between the TPU and PLA. Scanning electron microscopy (SEM) images verified that, at the composition ratios studied, PLA was dispersed as spheres or islands inside the TPU matrix and that this phase morphology further influenced the scaffold's microstructure and surface roughness. The blends exhibited a large range of mechanical properties that covered several human tissue requirements. 3T3 fibroblast cell culture showed that the scaffolds supported cell proliferation and migration properly. Most importantly, this study demonstrated the feasibility of mass producing biocompatible PLA/TPU scaffolds with tunable microstructures, surface roughnesses, and mechanical properties that have the potential to be used as artificial scaffolds in multiple tissue engineering applications.

  7. Characterization of thermoplastic polyurethane/polylactic acid (TPU/PLA) tissue engineering scaffolds fabricated by microcellular injection molding

    PubMed Central

    Mi, Hao-Yang; Salick, Max R.; Jing, Xin; Jacques, Brianna R.; Crone, Wendy C.; Peng, Xiang-Fang; Turng, Lih-Sheng

    2015-01-01

    Polylactic acid (PLA) and thermoplastic polyurethane (TPU) are two kinds of biocompatible and biodegradable polymers that can be used in biomedical applications. PLA has rigid mechanical properties while TPU possesses flexible mechanical properties. Blended TPU/PLA tissue engineering scaffolds at different ratios for tunable properties were fabricated via twin screw extrusion and microcellular injection molding techniques for the first time. Multiple test methods were used to characterize these materials. Fourier transform infrared spectroscopy (FTIR) confirmed the existence of the two components in the blends; differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) confirmed the immiscibility between the TPU and PLA. Scanning electron microscopy (SEM) images verified that, at the composition ratios studied, PLA was dispersed as spheres or islands inside the TPU matrix and that this phase morphology further influenced the scaffold’s microstructure and surface roughness. The blends exhibited a large range of mechanical properties that covered several human tissue requirements. 3T3 fibroblast cell culture showed that the scaffolds supported cell proliferation and migration properly. Most importantly, this study demonstrated the feasibility of mass producing biocompatible PLA/TPU scaffolds with tunable microstructures, surface roughnesses, and mechanical properties that have the potential to be used as artificial scaffolds in multiple tissue engineering applications. PMID:24094186

  8. UV protective poly(lactic acid)/rosin films for sustainable packaging.

    PubMed

    Narayanan, Meenu; Loganathan, Sravanthi; Valapa, Ravi Babu; Thomas, Sabu; Varghese, T O

    2017-06-01

    Recently, biopolymer based plastic materials are regarded as potential alternative for conventional plastics of fossil fuel origin in order to compensate depleting petroleum resources and address environmental pollution issues. Poly(lactic acid) (PLA) is one among the biopolymers which is rapidly commercialized for food packaging application. However, the demerits accompanied with PLA like brittle nature, slower crystallization rate, poor gas barrier and high ultraviolet radiation transmission properties confines its commercial application in food packaging sector. Studies on the improvement of ductility, crystallization rate and gas barrier properties are markedly reported. Much emphasis is not given in the literature on improving UV shielding properties which plays important role in preventing oxidation degradation of PLA. Therefore, the current work is focused on fabrication of eco-friendly poly(lactic acid)/rosin (RS) based biocomposite films with improved UV shielding along with ductility and oxygen barrier properties. The PLA-RS biocomposite films containing different loadings (1, 3, 5, 10 and 20wt%) of RS with an average thickness of 50μm are fabricated via solution casting technique. The PLA-RS film demonstrated noteworthy light barrier feature by shielding the passage of ∼98%, 92% and 53% in UV-B, UV-A and visible light regime, respectively. In case of UV-C region, complete blockage of UV transmission through the PLA-RS biocomposite film is noticed. In addition to this, the presence of RS in the PLA matrix brought considerable improvement in terms of ductility and oxygen barrier characteristics. This in turn indicates PLA-RS biocomposite films hold significant potential for sustainable food packaging application.

  9. Sandwich-Architectured Poly(lactic acid)-Graphene Composite Food Packaging Films.

    PubMed

    Goh, Kunli; Heising, Jenneke K; Yuan, Yang; Karahan, Huseyin E; Wei, Li; Zhai, Shengli; Koh, Jia-Xuan; Htin, Nanda M; Zhang, Feimo; Wang, Rong; Fane, Anthony G; Dekker, Matthijs; Dehghani, Fariba; Chen, Yuan

    2016-04-20

    Biodegradable food packaging promises a more sustainable future. Among the many different biopolymers used, poly(lactic acid) (PLA) possesses the good mechanical property and cost-effectiveness necessary of a biodegradable food packaging. However, PLA food packaging suffers from poor water vapor and oxygen barrier properties compared to many petroleum-derived ones. A key challenge is, therefore, to simultaneously enhance both the water vapor and oxygen barrier properties of the PLA food packaging. To address this issue, we design a sandwich-architectured PLA-graphene composite film, which utilizes an impermeable reduced graphene oxide (rGO) as the core barrier and commercial PLA films as the outer protective encapsulation. The synergy between the barrier and the protective encapsulation results in a significant 87.6% reduction in the water vapor permeability. At the same time, the oxygen permeability is reduced by two orders of magnitude when evaluated under both dry and humid conditions. The excellent barrier properties can be attributed to the compact lamellar microstructure and the hydrophobicity of the rGO core barrier. Mechanistic analysis shows that the large rGO lateral dimension and the small interlayer spacing between the rGO sheets have created an extensive and tortuous diffusion pathway, which is up to 1450-times the thickness of the rGO barrier. In addition, the sandwiched architecture has imbued the PLA-rGO composite film with good processability, which increases the manageability of the film and its competency to be tailored. Simulations using the PLA-rGO composite food packaging film for edible oil and potato chips also exhibit at least eight-fold extension in the shelf life of these oxygen and moisture sensitive food products. Overall, these qualities have demonstrated the high potential of a sandwich-architectured PLA-graphene composite film for food packaging applications.

  10. Improved wettability and adhesion of polylactic acid/chitosan coating for bio-based multilayer film development

    NASA Astrophysics Data System (ADS)

    Gartner, Hunter; Li, Yana; Almenar, Eva

    2015-03-01

    The objective of this study was to investigate the effect of methyldiphenyl diisocyanate (MDI) concentration (0, 0.2, 1, 2, and 3%) on the wettability and adhesion of blend solutions of poly(lactic acid) (PLA) and chitosan (CS) when coated on PLA film for development of a bio-based multi-layer film suitable for food packaging and other applications. Characterization was carried out by attenuated total reflectance infrared spectrometry (ATR-FTIR), contact angle (θ), mechanical adhesion pull-off testing, and scanning electron microscopy (SEM). The θ of the PLA/CS blend shifted to a lower value (41-35°) with increasing MDI concentration showing that the surface tension was modified between the PLA/CS blend solution and PLA film and better wettability was achieved. The increase in MDI also resulted in an increased breaking strength (228-303 kPa) due to the increased H-bonding resulting from the more urethane groups formed within the PLA/CS blend as shown by ATR-FTIR. The improved adhesion was also shown by the increased number of physical entanglements observed by SEM. It can be concluded that MDI can be used to improve wettability and adhesion between PLA/CS coating and PLA film.

  11. Biodegradable blends of poly (lactic acid) (PLA) / polyhydroxybutrate (PHB) copolymer and its effects on rheological, thermal and mechanical properties

    NASA Astrophysics Data System (ADS)

    Sood, Nitin K.

    Poly (Lactic acid) is the most important plastic derived from the renewable resources. PLA based products have extensively been used in the medical industry. However, PLA has a few disadvantages such as inherent brittleness and low toughness despite a high modulus. A focus of this experiment was to study the improvement in toughness of PLA and to study the changes in thermal and rheological properties by blending PLA with a PHB copolymer. Where, PLA and PHB copolymer were melt blended using a twin screw Brabender extruder in the ratios of 100/0, 70/30, 50/50, 30/70, 0/100. Further, the blends were injection molded into tensile bar and impact bars for mechanical testing. Rheological properties were studied using a Galaxy capillary rheometer for melt viscosities and temperature dependence indicated a shear-thinning behavior along with power law model and consistency index. Blends were characterized to study the phase model using a differential scanning calorimetric (DSC), showed two separate phases. Mechanical properties were analyzed using a Tensile and Izod impact test indicating decrease in elastic modulus with increase in toughness and elongation as the PHB copolymer content was increased in the blend.

  12. Thermoplastic starch/polyester films: effects of extrusion process and poly (lactic acid) addition.

    PubMed

    Shirai, Marianne Ayumi; Olivato, Juliana Bonametti; Garcia, Patrícia Salomão; Müller, Carmen Maria Olivera; Grossmann, Maria Victória Eiras; Yamashita, Fabio

    2013-10-01

    Biodegradable films were produced using the blown extrusion method from blends that contained cassava thermoplastic starch (TPS), poly(butylene adipate-co-terephthalate) (PBAT) and poly(lactic acid) (PLA) with two different extrusion processes. The choice of extrusion process did not have a significant effect on the mechanical properties, water vapor permeability (WVP) or viscoelasticity of the films, but the addition of PLA decreased the elongation, blow-up ratio (BUR) and opacity and increased the elastic modulus, tensile strength and viscoelastic parameters of the films. The films with 20% PLA exhibited a lower WVP due to the hydrophobic nature of this polymer. Morphological analyses revealed the incompatibility between the polymers used.

  13. Drastic Attenuation of Pseudomonas aeruginosa Pathogenicity in a Holoxenic Mouse Experimental Model Induced by Subinhibitory Concentrations of Phenyllactic acid (PLA)

    PubMed Central

    Chifiriuc, Mariana–Carmen; Veronica, Lazar; Dracea, Olguta; Ditu, Lia-Mara; Smarandache, Diana; Bucur, Marcela; Larion, Cristina; Cernat, Ramona; Sasarman, Elena

    2007-01-01

    The discovery of communication systems regulating bacterial virulence has afforded a novel opportunity to control infectious bacteria without interfering with growth. In this paper we describe the effect of subinhibitory concentrations of phenyllactic acid (PLA) on the pathogenicity of Pseudomonas aeruginosa in mice. The animals were inoculated by oral (p.o.), intranasal (i.n.), intravenous (i.v.) and intraperitoneal (i.p.) routes with P. aeruginoasa wild and PLA-treated cultures. The mice were followed up during 16 days after infection and the body weight, mortality and morbidity rate were measured every day. The microbial charge was studied by viable cell counts in lungs, spleen, intestinal mucosa and blood. The mice batches infected with wild P. aeruginosa bacterial cultures exhibited high mortality rates (100 % after i.v. and i.p. route) and very high cell counts in blood, lungs, intestine and spleen. In contrast, the animal batches infected with PLA treated bacterial cultures exhibited good survival rates (0 % mortality) and the viable cell counts in the internal organs revealed with one exception the complete abolition of the invasive capacity of the tested strains. In this study, using a mouse infection model we show that D-3-phenyllactic acid (PLA) can act as a potent antagonist of Pseudomonas (P.) aeruginosa pathogenicity, without interfering with the bacterial growth, as demonstrated by the improvement of the survival rates as well as the clearance of bacterial strains from the body.

  14. Cytocompatibility and Mechanical Properties of Short Phosphate Glass Fibre Reinforced Polylactic Acid (PLA) Composites: Effect of Coupling Agent Mediated Interface

    PubMed Central

    Hasan, Muhammad Sami; Ahmed, Ifty; Parsons, Andrew; Walker, Gavin; Scotchford, Colin

    2012-01-01

    In this study three chemical agents Amino-propyl-triethoxy-silane (APS), sorbitol ended PLA oligomer (SPLA) and Hexamethylene diisocyanate (HDI) were identified to be used as coupling agents to react with the phosphate glass fibre (PGF) reinforcement and the polylactic acid (PLA) polymer matrix of the composite. Composites were prepared with short chopped strand fibres (l = 20 mm, ϕ = 20 µm) in a random arrangement within PLA matrix. Improved, initial composite flexural strength (~20 MPa) was observed for APS treated fibres, which was suggested to be due to enhanced bonding between the fibres and polymer matrix. Both APS and HDI treated fibres were suggested to be covalently linked with the PLA matrix. The hydrophobicity induced by these coupling agents (HDI, APS) helped to resist hydrolysis of the interface and thus retained their mechanical properties for an extended period of time as compared to non-treated control. Approximately 70% of initial strength and 65% of initial modulus was retained by HDI treated fibre composites in contrast to the control, where only ~50% of strength and modulus was retained after 28 days of immersion in PBS at 37 °C. All coupling agent treated and control composites demonstrated good cytocompatibility which was comparable to the tissue culture polystyrene (TCP) control, supporting the use of these materials as coupling agent’s within medical implant devices. PMID:24955744

  15. Effects of ultraviolet light (315 nm), temperature and relative humidity on the degradation of polylactic acid plastic films.

    PubMed

    Copinet, Alain; Bertrand, Celine; Govindin, Stephanie; Coma, Veronique; Couturier, Yves

    2004-05-01

    The influence of temperature (30, 45 and 60 degrees C) and relative humidity (RH) (30%, 50% and 100%) on the degradation of poly(l-lactic acid) (PLA) films were studied. In addition, the effects of ultraviolet (UV) light (315 nm) on the degradation of PLA films were also analyzed. Various analytical techniques were applied to observe changes in the properties of PLA polymer films. FTIR spectroscopy was used as semi-quantitative method to get information about the chemistry of the degradative process. The degradation rate of PLA was enhanced by increasing temperature and RH, factors responsible for a faster reduction of the weight-average molecular weight (M(W)), of the glass transition temperature (Tg) and of the percentage of elongation at break. Moreover, UV treatment accelerated these phenomena.

  16. Poly(lactic acid) and Osage Orange Wood Fiber Composites for Agricultural Mulch Films

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Osage orange wood was combined with poly(lactic acid) to form a polymer composite intendedfor use as an agricultural mulch film. The mechanical properties were comparable to existing products and had the advantage of being completely biodegradable through a single growing season. PLA-OO composites...

  17. Efficient gas barrier properties of multi-layer films based on poly(lactic acid) and fish gelatin.

    PubMed

    Hosseini, Seyed Fakhreddin; Javidi, Zahra; Rezaei, Masoud

    2016-11-01

    Multi-layer film structures of poly(lactic acid) (PLA) and fish gelatin (FG), prepared using the solvent casting technique, were studied in an effort to produce bio-based films with low oxygen (OP) and water vapor permeability (WVP). The scanning electron microscopy (SEM) images of triple-layer film showed that the outer PLA layers are being closely attached to the inner FG layer to make continuous film. The OP of multi-layer film (5.02cm(3)/m(2)daybar) decreased more than 8-fold compared with that of the PLA film, and the WVP of multi-layer film (0.125gmm/kPah m(2)) also decreased 11-fold compared with that of the FG film. Lamination with PLA profoundly increased the water resistance of the bare gelatin film. Meanwhile, the tensile strength of the triple-layer film (25±2.13MPa) was greater than that of FG film (7.48±1.70MPa). At the same time, the resulting film maintains high optical clarity. Differential scanning calorimetry (DSC) analysis also revealed that the materials were compatible showing only one Tg which decreased with FG deposition. This material exhibits an environmental-friendliness potential and a high versatility in food packaging.

  18. Effect of PLA films containing propolis ethanolic extract, cellulose nanoparticle and Ziziphora clinopodioides essential oil on chemical, microbial and sensory properties of minced beef.

    PubMed

    Shavisi, Nassim; Khanjari, Ali; Basti, Afshin Akhondzadeh; Misaghi, Ali; Shahbazi, Yasser

    2017-02-01

    This study was conducted to examine the effects of polylactic acid (PLA) film containing propolis ethanolic extract (PE), cellulose nanoparticle (CN) and Ziziphora clinopodioides essential oil (ZEO) on chemical, microbial and sensory properties of minced beef during storage at refrigerated temperature for 11days. The initial total volatile base nitrogen (TVB-N) was 8.2mg/100g and after 7days reached to 29.1mg/100g in control, while it was lower than 25mg/100g for treated samples. At the end of storage time in control samples peroxide value (PV) reached to 2.01meqperoxide/1000g lipid, while the values for the treated samples remained lower than 2meqperoxide/1000g lipid. Final microbial population decreased approximately 1-3logCFU/g in treated samples compared to control (P<0.05). Films containing 2% ZEO alone and in combination with different concentrations of PE and CN extended the shelf life of minced beef during storage in refrigerated condition for at least 11days without any unfavorable organoleptic properties.

  19. Etude des melanges co-continus d'acide polylactique et d'amidon thermoplastique (PLA/TPS)

    NASA Astrophysics Data System (ADS)

    Chavez Garcia, Maria Graciela

    Les melanges co-continus sont des melanges polymeriques ou chaque composant se trouve dans une phase continue. Pour cette raison, les caracteristiques de chacun des composants se combinent et il en resulte un materiau avec une morphologie et des proprietes particulieres. L'acide polylactique (PLA) et l'amidon thermoplastique (TPS) sont des biopolymeres qui proviennent de ressources renouvelables et qui sont biodegradables. Dans ce projet, differents melanges de PLA et TPS a une haute concentration de TPS ont ete prepares dans une extrudeuse bi-vis afin de generer des structures co-continues. Grace a la technique de lixiviation selective, le TPS est enleve pour creer une structure poreuse de PLA qui a pu etre analysee au moyen de la microtomographie R-X et de la microscopie electronique a balayage MEB. L'analyse des images 2D et 3D confirme la presence de la structure co-continue dans les melanges dont la concentration en TPS. se situe entre 66% et 80%. L'effet de deux plastifiants, le glycerol seul et le melange de glycerol et de sorbitol, dans la formulation de TPS est etudie dans ce travail. De plus, nous avons evalue l'effet du PLA greffe a l'anhydride maleique (PLAg) en tant que compatibilisant. On a trouve que la phase de TPS obtenue avec le glycerol est plus grande. L'effet de recuit sur la taille de phases est aussi analyse. Grace aux memes techniques d'analyse, on a etudie l'effet du procede de moulage par injection sur la morphologie. On a constate que les pieces injectees presentent une microstructure heterogene et differente entre la surface et le centre de la piece. Pres de la surface, une peau plus riche en PLA est presente et les phases de TPS y sont allongees sous forme de lamelles. Plus au centre de la piece, une morphologie plus cellulaire est observee pour chaque phase continue. L'effet des formulations sur les proprietes mecaniques a aussi ete etudie. Les pieces injectees dont la concentration de TPS est plus grande presentent une moindre

  20. Structural and Functional Studies of a Bothropic Myotoxin Complexed to Rosmarinic Acid: New Insights into Lys49-PLA2 Inhibition

    PubMed Central

    dos Santos, Juliana I.; Cardoso, Fábio F.; Soares, Andreimar M.; dal Pai Silva, Maeli; Gallacci, Márcia; Fontes, Marcos R. M.

    2011-01-01

    Snakebite envenoming is an important public health problem in many tropical and subtropical countries, and is considered a neglected tropical disease by the World Health Organization. Most severe cases are inflicted by species of the families Elapidae and Viperidae, and lead to a number of systemic and local effects in the victim. One of the main problems regarding viperidic accidents is prominent local tissue damage whose pathogenesis is complex and involves the combined actions of a variety of venom components. Phospholipases A2 (PLA2s) are the most abundant muscle-damaging components of these venoms. Herein, we report functional and structural studies of PrTX-I, a Lys49-PLA2 from Bothops pirajai snake venom, and the influence of rosmarinic acid (RA) upon this toxin's activities. RA is a known active component of some plant extracts and has been reported as presenting anti-myotoxic properties related to bothopic envenomation. The myotoxic activity of Lys49-PLA2s is well established in the literature and although no in vivo neurotoxicity has been observed among these toxins, in vitro neuromuscular blockade has been reported for some of these proteins. Our in vitro studies show that RA drastically reduces both the muscle damage and the neuromuscular blockade exerted by PrTX-I on mice neuromuscular preparations (by ∼80% and ∼90%, respectively). These results support the hypothesis that the two effects are closely related and lead us to suggest that they are consequences of the muscle membrane-destabilizing activity of the Lys49-PLA2. Although the C-terminal region of these proteins has been reported to comprise the myotoxic site, we demonstrate by X-ray crystallographic studies that RA interacts with PrTX-I in a different region. Consequently, a new mode of Lys49-PLA2 inhibition is proposed. Comparison of our results with others in the literature suggests possible new ways to inhibit bothropic snake venom myotoxins and improve serum therapy. PMID:22205953

  1. Patterned poly(lactic acid) films support growth and spontaneous multilineage gene expression of adipose-derived stem cells.

    PubMed

    Foldberg, Steffan; Petersen, Morten; Fojan, Peter; Gurevich, Leonid; Fink, Trine; Pennisi, Cristian P; Zachar, Vladimir

    2012-05-01

    Conventional culture surfaces do not provide optimal environmental cues for expansion or differentiation of adult stem cells. Aiming to increase the efficiency of the in vitro culture conditions, biocompatible and biodegradable biomaterials such as poly(lactic acid) (PLA) have been proposed to engineer the stem cell microenvironment. In this study, we explored the feasibility of using PLA substrates to control the responses of adipose-derived stem cells (ASCs). The substrates consisted of flat and patterned PLA films fabricated by casting a chloroform-PLA solution on a glass surface. Patterning was achieved through the condensation of nano-sized water droplets during chloroform evaporation, which resulted in films displaying irregularly distributed circular indentations with a mean diameter of 248±65 nm. Both types of PLA substrates were assessed for protein adsorption using fibronectin and in vitro cell culturing. Tissue-culture polystyrene (TCPS) plates were used as control surfaces. The experiments demonstrated that the patterned PLA substrates had a significantly higher fibronectin adsorption capacity when compared with the flat counterparts. For the entire duration of the culture period, there was no significant difference in cell growth rate on the PLA surfaces with respect to TCPS despite signs of reduced adhesion. In addition, the semi-quantitative real-time RT-PCR analysis of a set of 14 lineage-specific genes revealed that the PLA-related transcriptional activity significantly surpassed that of TCPS. Remarkably, when assessing the effect of patterning, the patterned films proved superior regarding the activation of genes involved in the skeletal myogenic, cardiomyogenic, chondrogenic, and adipogenic pathways. Taken together, our data provide evidence that the surface patterning can exert such an influence on the stem cell microenvironment that the differentiation process can be effectively modulated. Consequently, the patterned PLA surfaces could

  2. Feasibility study of prestressed natural fiber-reinforced polylactic acid (pla) composite materials

    NASA Astrophysics Data System (ADS)

    Hinchcliffe, Sean A.

    The feasibility of manufacturing prestressed natural-fiber reinforced biopolymer composites is demonstrated in this work. The objective of this study was to illustrate that the specific mechanical properties of biopolymers can be enhanced by leveraging a combination of additive manufacturing (3D printing) and post-tensioning of continuous natural fiber reinforcement. Tensile and flexural PLA specimens were 3D-printed with and without post-tensioning ducts. The mechanical properties of reinforcing fibers jute and flax were characterized prior to post-tensioning. The effect of matrix cross-sectional geometry and post-tensioning on the specific mechanical properties of PLA were investigated using mechanical testing. Numerical and analytical models were developed to predict the experimental results, which confirm that 3D-printed matrices improve the specific mechanical properties of PLA composites and are further improved via initial fiber prestressing. The results suggest that both additive manufacturing and fiber prestressing represent viable new methods for improving the mechanical performance of natural fiber-reinforced polymeric composites.

  3. Biodegradable polylactic acid polymer with nisin for use in antimicrobial food packaging

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biodegradable polylactic acid (PLA) polymer was evaluated for its application as a material for antimicrobial food packaging. PLA films were incorporated with nisin to provide slow release of the encapsulated antimicrobial for control of foodborne pathogens. Antimicrobial activity of PLA/nisin films...

  4. Functionalized antibiofilm thin coatings based on PLA-PVA microspheres loaded with usnic acid natural compounds fabricated by MAPLE

    NASA Astrophysics Data System (ADS)

    Grumezescu, Valentina; Socol, Gabriel; Grumezescu, Alexandru Mihai; Holban, Alina Maria; Ficai, Anton; Truşcǎ, Roxana; Bleotu, Coralia; Balaure, Paul Cǎtǎlin; Cristescu, Rodica; Chifiriuc, Mariana Carmen

    2014-05-01

    We report the fabrication of thin coatings of PLA-PVA microspheres loaded with usnic acid by matrix assisted pulsed laser evaporation (MAPLE) onto Ti substrate. The obtained coatings have been physico-chemically characterized by scanning electron microscopy (SEM) and infrared microscopy (IRM). In vitro biological assays have been performed in order to evaluate the influence of fabricated microsphere thin coatings on the Staphylococcus aureus biofilm development as well as their biocompatibility. SEM micrographs have revealed a uniform morphology of thin coatings, while IRM investigations have proved both the homogeneity and functional groups integrity of prepared thin coatings. The obtained microsphere-based thin coatings have proved to be efficient vehicles for usnic acid natural compound with antibiofilm activity, as demonstrated by the inhibitory activity on S. aureus mature biofilm development, opening new perspectives for the prevention and therapy associated to biofilm related infections.

  5. Novel genipin-collagen immobilization of polylactic acid (PLA) fibers for use as tissue engineering scaffolds.

    PubMed

    Tambe, Nisarg; Di, Jin; Zhang, Ze; Bernacki, Susan; El-Shafei, Ahmed; King, Martin W

    2015-08-01

    The material surface plays an important role in the case of biomaterials used as tissue engineering scaffolds. On exposure to a biological environment, extra cellular matrix (ECM) proteins are adsorbed non-specifically onto the surface and cells interact indirectly with the surface through the adsorbed proteins. Most synthetic polymeric biomaterials lack the desirable surface properties for cells as well as have poor cellular adhesion due to their hydrophobic nature. The main objective of this study was to harness surface functionalization technologies to fabricate scaffolds that would be biocompatible and support the adhesion and proliferation of fibroblast cells. The collagen was immobilized on the surface of functionalized PLA via a novel natural cross-linking molecule genipin which resulted in improved cell proliferation of human dermal fibroblasts as compared to the PLA surface coated with collagen without genipin. It is believed that genipin helps reduce steric problems between the functional groups and large protein molecules, and enables immobilized peptide to move more freely in a biological environment.

  6. Effect of gamma ray on poly(lactic acid)/poly(vinyl acetate-co-vinyl alcohol) blends as biodegradable food packaging films

    NASA Astrophysics Data System (ADS)

    Razavi, Seyed Mohammad; Dadbin, Susan; Frounchi, Masoud

    2014-03-01

    Poly(lactic acid) (PLA)/poly(vinyl acetate-co-vinyl alcohol) [P(VAc-co-VA)] blends as new transparent film packaging materials were prepared at various blend compositions and different vinyl alcohol contents. The blends and pure PLA were irradiated by gamma rays to investigate the extent of changes in the packaging material during gamma ray sterilization process. The miscibility of the blends was dependent on the blend composition and vinyl alcohol content; gamma irradiation had little effect on the extent of miscibility. The glass transition temperature of pure PLA and PLA/P(VAc-co-VA) miscible blends reduced after irradiation. On the other hand in PLA/P(VAc-co-VA) immiscible blends, while the glass transition temperature of the PLA phase decreased; that of the copolymer phase slightly increased. The reduction in the glass transition was about 10 percent for samples irradiated with 50 kGy indicating dominance of chain scission of PLA molecules at high irradiation dose. The latter was verified by drop in mechanical properties of pure PLA after exposing to gamma irradiation at 50 kGy. Blending of PLA with the copolymer P(VAc-co-VA) compensated greatly the adverse effects of irradiation on PLA. The oxygen-barrier property of the blend was superior to the neat PLA and remained almost intact with irradiation. The un-irradiated and irradiated blends had excellent transparency. Gamma ray doses used for sterilization purposes are usually less than 20 kGy. It was shown that gamma irradiation at 20 kGy had no or little adverse effects on PLA/P(VAc-co-VA) blends mechanical and gas barrier properties.

  7. Fabrication and characterization of a foamed polylactic acid (PLA)/ thermoplastic polyurethane (TPU) shape memory polymer (SMP) blend for biomedical and clinical applications

    NASA Astrophysics Data System (ADS)

    Song, Janice J.; Srivastava, Ijya; Kowalski, Jennifer; Naguib, Hani E.

    2014-03-01

    Shape memory polymers (SMP) are a class of stimuli-responsive materials that are able to respond to external stimulus such as heat by altering their shape. Bio-compatible SMPs have a number of advantages over static materials and are being studied extensively for biomedical and clinical applications (such as tissue stents and scaffolds). A previous study has demonstrated that the bio-compatible polymer blend of polylactic acid (PLA)/ thermoplastic polyurethane (TPU) (50/50 and 70/30) exhibit good shape memory properties. In this study, the mechanical and thermo-mechanical (shape memory) properties of TPU/PLA SMP blends were characterized; the compositions studied were 80/20, 65/35, and 50/50 TPU/PLA. In addition, porous TPU/PLA SMP blends were fabricated with a gas-foaming technique; and the morphology of the porous structure of these SMPs foams were characterized with scanning electron microscopy (SEM). The TPU/PLA bio-compatible SMP blend was fabricated with melt-blending and compression molding. The glass transition temperature (Tg) of the SMP blends was determined with a differential scanning calorimeter (DSC). The mechanical properties studied were the stress-strain behavior, tensile strength, and elastic modulus; and the thermomechanical (or shape memory) properties studied were the shape fixity rate (Rf), shape recovery rate (Rr), response time, and the effect of recovery temperature on Rr. The porous 80/20 PLA/TPU SMP blend was found to have the highest tensile strength, toughness and percentage extension, as well as the lowest density and uniform pore structure in the micron and submicron scale. The porous 80/20 TPU/PLA SMP blend may be further developed for specific biomedical and clinical applications where a combination of tensile strength, toughness, and low density are required.

  8. A novel calcium-independent cellular PLA2 acts in insect immunity and larval growth

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Phospholipase A2 (PLA2) catalyzes the position-specific hydrolysis of fatty acids linked to the sn-2 position of phospholipids (PLs). PLA2s make up a very large superfamily, with more than known 15 groups, classified into secretory PLA2 (sPLA2), Ca2+-dependent cellular PLA2 (sPLA2), and Ca2+-indepen...

  9. Anti-listeria activity of poly(lactic acid)/sawdust particle biocomposite film impregnated with pediocin PA-1/AcH and its use in raw sliced pork.

    PubMed

    Woraprayote, Weerapong; Kingcha, Yutthana; Amonphanpokin, Pannawit; Kruenate, Jittiporn; Zendo, Takeshi; Sonomoto, Kenji; Benjakul, Soottawat; Visessanguan, Wonnop

    2013-10-15

    A novel poly(lactic acid) (PLA)/sawdust particle (SP) biocomposite film with anti-listeria activity was developed by incorporation of pediocin PA-1/AcH (Ped) using diffusion coating method. Sawdust particle played an important role in embedding pediocin into the hydrophobic PLA film. The anti-listeria activity of the PLA/SP biocomposite film incorporated with Ped (PLA/SP+Ped) was detected, while no activity against the tested pathogen was observed for the control PLA films (without SP and/or Ped). Dry-heat treatment of film before coating with Ped resulted in the highest Ped adsorption (11.63 ± 3.07 μg protein/cm(2)) and the highest anti-listeria activity. A model study of PLA/SP+Ped as a food-contact antimicrobial packaging on raw sliced pork suggests a potential inhibition of Listeria monocytogenes (99% of total listerial population) on raw sliced pork during the chilled storage. This study supports the feasibility of using PLA/SP+Ped film to reduce the initial load of L. monocytogenes on the surface of raw pork.

  10. Cloning and Sequence Analysis of cDNAs Encoding Two Acidic PLA(2) from venom of Ophiophagus hannah(King Cobra), Guangxi Species.

    PubMed

    Wang, Qiu-Yan; Shu, Yu-Yan; Zhuang, Mao-Xing; Lin, Zheng-Jiong

    2001-01-01

    Total RNA was extracted from venom glands of Ophiophagus hannah, Guangxi species. The cDNAs encoding PLA(2) were amplified by RT-PCR and cloned into the PUCm-T vector. The positive clones encoding two acidic PLA(2) (APLA(2)-1 and APLA(2)-2) were selected and bidirectionally sequenced. Their complete amino acid sequences were deduced and found to be identical to the known amino acid sequences. Their isoelectric points calculated by computer agreed with the values determined with their protein. Homology analysis indicated that the mature peptide of APLA(2)-1 had high homology with PLA(2) from venoms of Ophiophagus hannah, Fujian and Taiwan species, but APLA(2)-2 had lower homology. The most striking difference between APLA(2)-2 and other PLA(2) from Ophiophagus hannah venoms is the missing of a extra "pancreatic loop" at residues 62--66 in APLA(2)-2, and it may be related to their species evolution and biological activity.

  11. Photothermal and morphological characterization of PLA/PCL polymer blends

    NASA Astrophysics Data System (ADS)

    Correa-Pacheco, Z. N.; Jiménez-Pérez, J. L.; Sabino, M. A.; Cruz-Orea, A.; Loaiza, M.

    2015-09-01

    Nowadays, some synthetic polymers have been replaced by biodegradable polymers in order to avoid environmental contamination. Among these biodegradables polymers, aliphatic polyesters such as polylactic acid (PLA) and polycaprolactone (PCL) have been widely used. In the present study, solvent-casting films of PLA, PCL and polymer blends with and without compatibilizer (PLA grafted with maleic anhydride) were prepared. The thermal diffusivity ( α) of each sample was obtained by using the open photoacoustic cell technique. Morphology and thermal properties were determined by using scanning electron microscopy, transmission electron microscopy and differential scanning calorimetry (DSC), respectively. The blends showed lower thermal diffusivity compared to pure polymers. However, when the compatibilizer was used, the highest value of thermal diffusivity was obtained. Also, cold crystallization with the highest value of enthalpy of fusion was observed for the compatibilized sample, which was revealed by DSC. To our knowledge, this is the first time that the thermal diffusivity of these biodegradable polymer blends is reported.

  12. Kinetics and mechanism of the biodegradation of PLA/clay nanocomposites during thermophilic phase of composting process.

    PubMed

    Stloukal, Petr; Pekařová, Silvie; Kalendova, Alena; Mattausch, Hannelore; Laske, Stephan; Holzer, Clemens; Chitu, Livia; Bodner, Sabine; Maier, Guenther; Slouf, Miroslav; Koutny, Marek

    2015-08-01

    The degradation mechanism and kinetics of polylactic acid (PLA) nanocomposite films, containing various commercially available native or organo-modified montmorillonites (MMT) prepared by melt blending, were studied under composting conditions in thermophilic phase of process and during abiotic hydrolysis and compared to the pure polymer. Described first order kinetic models were applied on the data from individual experiments by using non-linear regression procedures to calculate parameters characterizing aerobic composting and abiotic hydrolysis, such as carbon mineralization, hydrolysis rate constants and the length of lag phase. The study showed that the addition of nanoclay enhanced the biodegradation of PLA nanocomposites under composting conditions, when compared with pure PLA, particularly by shortening the lag phase at the beginning of the process. Whereas the lag phase of pure PLA was observed within 27days, the onset of CO2 evolution for PLA with native MMT was detected after just 20days, and from 13 to 16days for PLA with organo-modified MMT. Similarly, the hydrolysis rate constants determined tended to be higher for PLA with organo-modified MMT, particularly for the sample PLA-10A with fastest degradation, in comparison with pure PLA. The acceleration of chain scission in PLA with nanoclays was confirmed by determining the resultant rate constants for the hydrolytical chain scission. The critical molecular weight for the hydrolysis of PLA was observed to be higher than the critical molecular weight for onset of PLA mineralization, suggesting that PLA chains must be further shortened so as to be assimilated by microorganisms. In conclusion, MMT fillers do not represent an obstacle to acceptance of the investigated materials in composting facilities.

  13. Lipase-catalyzed enantioselective synthesis of (R,R)-lactide from alkyl lactate to produce PDLA (poly D-lactic acid) and stereocomplex PLA (poly lactic acid).

    PubMed

    Jeon, Byoung Wook; Lee, Jumin; Kim, Hyun Sook; Cho, Dae Haeng; Lee, Hyuk; Chang, Rakwoo; Kim, Yong Hwan

    2013-10-20

    R-lactide, a pivotal monomer for the production of poly (D-lactic acid) (PDLA) or stereocomplex poly (lactic acid) (PLA) was synthesized from alkyl (R)-lactate through a lipase-catalyzed reaction without racemization. From among several types of lipase, only lipase B from Candida antarctica (Novozym 435; CAL-B) was effective in the reaction that synthesized (R,R)-lactide. Enantiopure (R,R)-lactide, which consisted of over 99% enantiomeric excess, was synthesized from methyl (R)-lactate through CAL-B catalysis. Removal of the methanol by-product was critical to obtain a high level of lactide conversion. The (R,R)-lactide yield was 56% in a reaction containing 100 mg of Novozym 435, 10 mM methyl (R)-lactate and 1500 mg of molecular sieve 5A in methyl tert-butyl ether (MTBE). The important monomer (R,R)-lactide that is required for the production of the widely recognized bio-plastic PDLA and the PLA stereocomplex can be obtained using this novel synthetic method.

  14. Development of chlorine dioxide releasing film and its application in decontaminating fresh produce

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A feasibility study was conducted to develop chlorine dioxide releasing packaging films for decontaminating fresh produce. Sodium chlorite and citric acid powder were incorporated into polylactic acid (PLA) polymer. Films made with different amount of PLA (100 & 300 mg), percentage of reactant (5-60...

  15. Growth, structural, spectral, mechanical, thermal and dielectric characterization of phosphoric acid admixtured L-alanine (PLA) single crystals

    NASA Astrophysics Data System (ADS)

    Rose, A. S. J. Lucia; Selvarajan, P.; Perumal, S.

    2011-10-01

    Phosphoric acid admixtured L-alanine (PLA) single crystals were grown successfully by solution method with slow evaporation technique at room temperature. Crystals of size 18 mm × 12 mm × 8 mm have been obtained in 28 days. The grown crystals were colorless and transparent. The solubility of the grown samples has been found out at various temperatures. The lattice parameters of the grown crystals were determined by X-ray diffraction technique. The reflection planes of the sample were confirmed by the powder X-ray diffraction study and diffraction peaks were indexed. Fourier transform infrared (FTIR) studies were used to confirm the presence of various functional groups in the crystals. UV-visible transmittance spectrum was recorded to study the optical transparency of grown crystal. The nonlinear optical (NLO) property of the grown crystal was confirmed by Kurtz-Perry powder technique and a study of its second harmonic generation efficiency in comparison with potassium dihydrogen phosphate (KDP) has been made. The mechanical strength of the crystal was estimated by Vickers hardness test. The grown crystals were subjected to thermo gravimetric and differential thermal analysis (TG/DTA). The dielectric behavior of the sample was also studied.

  16. Growth, structural, spectral, mechanical, thermal and dielectric characterization of phosphoric acid admixtured L-alanine (PLA) single crystals.

    PubMed

    Rose, A S J Lucia; Selvarajan, P; Perumal, S

    2011-10-15

    Phosphoric acid admixtured L-alanine (PLA) single crystals were grown successfully by solution method with slow evaporation technique at room temperature. Crystals of size 18 mm×12 mm×8 mm have been obtained in 28 days. The grown crystals were colorless and transparent. The solubility of the grown samples has been found out at various temperatures. The lattice parameters of the grown crystals were determined by X-ray diffraction technique. The reflection planes of the sample were confirmed by the powder X-ray diffraction study and diffraction peaks were indexed. Fourier transform infrared (FTIR) studies were used to confirm the presence of various functional groups in the crystals. UV-visible transmittance spectrum was recorded to study the optical transparency of grown crystal. The nonlinear optical (NLO) property of the grown crystal was confirmed by Kurtz-Perry powder technique and a study of its second harmonic generation efficiency in comparison with potassium dihydrogen phosphate (KDP) has been made. The mechanical strength of the crystal was estimated by Vickers hardness test. The grown crystals were subjected to thermo gravimetric and differential thermal analysis (TG/DTA). The dielectric behavior of the sample was also studied.

  17. Electrospun membranes of poly(lactic acid) (PLA) used as scaffold in drug delivery of extract of Sedum dendroideum.

    PubMed

    Santos, Larissa G; Oliveira, Daniel C; Santos, Michele S L; Neves, Lia Mara G; de Gaspi, Fernanda O G; Mendonça, Fernanda A S; Esquisatto, Marcelo A M; Santos, Gláucia M T; d'Avila, M A; Mei, Lucia H Innocentini

    2013-07-01

    Biomaterials nanofibrous electrospun with biodegradable polymers have the advantage of the similarity to natural extracellular matrices, showing promising as scaffolds for application in tissue engineering. Sedum dendroideum is a phytotherapic drug that stands out for its healing properties and anti-inflammatory. This study presents the efficacy of PLA electrospun membranes used as support S. dendroideum extract releasing on excisional skin lesions of Wistar rats. The PLA porous membranes, which are nonwoven fibrous mats, were obtained by electrospinning using a conventional apparatus with a flat collector. The animals were randomly divided into nine groups: control (C), animals treated with electrospun membranes of PLA (M), animals treated with extract of S. dendroideum dissolved in saline (F), animals treated with membranes of PLA with 10% S. dendroideum (MF10), animals treated with membranes of PLA with 25% S. dendroideum (MF25). Tissue samples were taken after 2, 6 and 10 days after surgery and were subjected to structural analysis and morphology. The experimental observations showed the application of the phytotherapic incorporated in the membrane promoted a significant response regarding the number of inflammatory cells, percentage of mature collagen fibers and epithelium birrefringent in thickness excisional skin lesions in Wistar rats. It was also demonstrated that the application of the PLA membranes without the extract promoted similar responses tissues.

  18. Circulating n-3 fatty acids and trans-fatty acids, PLA2G2A gene variation and sudden cardiac arrest.

    PubMed

    Lemaitre, Rozenn N; Bartz, Traci M; King, Irena B; Brody, Jennifer A; McKnight, Barbara; Sotoodehnia, Nona; Rea, Thomas D; Johnson, Catherine O; Mozaffarian, Dariush; Hesselson, Stephanie; Kwok, Pui-Yan; Siscovick, David S

    2016-01-01

    Whether genetic factors influence the associations of fatty acids with the risk of sudden cardiac arrest (SCA) is largely unknown. To investigate possible gene-fatty acid interactions on SCA risk, we used a case-only approach and measured fatty acids in erythrocyte samples from 1869 SCA cases in a population-based repository with genetic data. We selected 191 SNP in ENCODE-identified regulatory regions of fifty-five candidate genes in fatty acid metabolic pathways. Using linear regression and additive genetic models, we investigated the association of the selected SNP with erythrocyte levels of fatty acids, including DHA, EPA and trans-fatty acids among the SCA cases. The assumption of no association in non-cases was supported by analysis of publicly available datasets containing over 8000 samples. None of the SNP-fatty acid associations tested among the cases reached statistical significance after correction for multiple comparisons. One SNP, rs4654990 near PLA2G2A, with an allele frequency of 0·33, was nominally associated with lower levels of DHA and EPA and higher levels of trans-fatty acids. The strongest association was with DHA levels (exponentiated coefficient for one unit (1 % of total fatty acids), 0·90, 95 % CI 0·85, 0·97; P = 0·003), indicating that for subjects with a coded allele, the OR of SCA associated with one unit higher DHA is about 90 % what it is for subjects with one fewer coded allele. These findings suggest that the associations of circulating n-3 and trans-fatty acids with SCA risk may be more pronounced in carriers of the rs4654990 G allele.

  19. PLA composites: From production to properties.

    PubMed

    Murariu, Marius; Dubois, Philippe

    2016-12-15

    Poly(lactic acid) or polylactide (PLA), a biodegradable polyester produced from renewable resources, is used for various applications (biomedical, packaging, textile fibers and technical items). Due to its inherent properties, PLA has a key-position in the market of biopolymers, being one of the most promising candidates for further developments. Unfortunately, PLA suffers from some shortcomings, whereas for the different applications specific end-use properties are required. Therefore, the addition of reinforcing fibers, micro- and/or nanofillers, and selected additives within PLA matrix is considered as a powerful method for obtaining specific end-use characteristics and major improvements of properties. This review highlights recent developments, current results and trends in the field of composites based on PLA. It presents the main advances in PLA properties and reports selected results in relation to the preparation and characterization of the most representative PLA composites. To illustrate the possibility to design the properties of composites, a section is devoted to the production and characterization of innovative PLA-based products filled with thermally-treated calcium sulfate, a by-product from the lactic acid production process. Moreover, are emphasized the last tendencies strongly evidenced in the case of PLA, i.e., the high interest to diversify its uses by moving from biomedical and packaging (biodegradation properties, "disposables") to technical applications ("durables").

  20. Plasticized poly(lactic acid)-poly(hydroxybutyrate) (PLA-PHB) blends incorporated with catechin intended for active food-packaging applications.

    PubMed

    Arrieta, Marina Patricia; Castro-López, María del Mar; Rayón, Emilio; Barral-Losada, Luis Fernando; López-Vilariño, José Manuel; López, Juan; González-Rodríguez, María Victoria

    2014-10-15

    Active biobased packaging materials based on poly(lactic acid)-poly(hydroxybutyrate) (PLA-PHB) blends were prepared by melt blending and fully characterized. Catechin incorporation, as antioxidant compound, enhanced the thermal stability, whereas its release was improved by the addition of acetyl(tributyl citrate) (ATBC) as plasticizer. Whereas the incorporation of ATBC resulted in a reduction of elastic modulus and hardness, catechin addition produced more rigid materials due to hydrogen-bonding interactions between catechin hydroxyl groups and carbonyl groups of PLA and PHB. The quantification of catechin released into a fatty food simulant and the antioxidant effectiveness after the release process were demonstrated. The effect of the materials' exposure to a food simulant was also investigated. PHB-added materials maintained their structural and mechanical properties after 10 days in a test medium that represents the worst foreseeable conditions of the intended use. Thus, plasticized PLA-PHB blends with catechin show their potential as biobased active packaging for fatty food.

  1. Growth of nitric acid hydrates on thin sulfuric acid films

    NASA Technical Reports Server (NTRS)

    Iraci, Laura T.; Middlebrook, Ann M.; Wilson, Margaret A.; Tolbert, Margaret A.

    1994-01-01

    Type I polar stratospheric clouds (PSCs) are thought to nucleate and grow on stratospheric sulfate aerosols (SSAs). To model this system, thin sulfuric acid films were exposed to water and nitric acid vapors (1-3 x 10(exp -4) Torr H2O and 1-2.5 x 10(exp -6) Torr HNO3) and subjected to cooling and heating cycles. Fourier Transform Infrared (FTIR) spectroscopy was used to probe the phase of the sulfuric acid and to identify the HNO3/H2O films that condensed. Nitric acid trihydrate (NAT) was observed to grow on crystalline sulfuric acid tetrahydrate (SAT) films. NAT also condensed in/on supercooled H2SO4 films without causing crystallization of the sulfuric acid. This growth is consistent with NAT nucleation from ternary solutions as the first step in PSC formation.

  2. In-situ formation of silver nanoparticles on poly (lactic acid) film by γ-radiation induced grafting of N-vinyl pyrrolidone.

    PubMed

    Wang, Jingxia; Chen, Hao; Chen, Zhuping; Chen, Yuheng; Guo, Dan; Ni, Maojun; Liu, Siyang; Peng, Chaorong

    2016-06-01

    A fast, easy and novel method for preparing biodegradable polymer films with silver nanoparticles was investigated to endow the material with excellent biocompatibility and antibacterial property. Silver nanoparticles (Ag NPs) were immobilized on the surface of polylactic acid (PLA) film by gamma radiation induced grafting of N-vinyl pyrrolidone (NVP). In this method, poly (N-vinyl pyrrolidone) (PVP) was produced and grafted onto the surface of PLA film by gamma radiation polymerization of NVP. PVP acted as both a bridge to connect the Ag NPs with the PLA film, and a stabilizer to protect the Ag NPs from agglomeration. The effect of various reaction parameters, including NVP/Ag mole ratio and radiation dose, on the fabrication of PLA-g-NVP/Ag film was demonstrated. Moreover, the interaction between PVP and Ag NPs was studied by X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy, that revealed the Ag NPs coordinated through the oxygen atom on the carbonyl group of PVP at 15 kGy radiation dose, but through the nitrogen atom and the oxygen atom of the amide group of PVP at 1 kGy dose.

  3. From Nanofibrillar to Nanolaminar Poly(butylene succinate): Paving the Way to Robust Barrier and Mechanical Properties for Full-Biodegradable Poly(lactic acid) Films.

    PubMed

    Xie, Lan; Xu, Huan; Chen, Jing-Bin; Zhang, Zi-Jing; Hsiao, Benjamin S; Zhong, Gan-Ji; Chen, Jun; Li, Zhong-Ming

    2015-04-22

    The traditional approach toward barrier property enhancement of poly(lactic acid) (PLA) is the incorporation of sheet-like fillers such as nanoclay and graphene, unfortunately leading to the sacrificed biocompatibility and degradability. Here we unveil the first application of a confined flaking technique to establish the degradable nanolaminar poly(butylene succinate) (PBS) in PLA films based on PLA/PBS in situ nanofibrillar composites. The combination of high pressure (10 MPa) and appropriate temperature (160 °C) during the flaking process desirably enabled sufficient deformation of PBS nanofibrils and retention of ordered PLA channels. Particularly, interlinked and individual nanosheets were created in composite films containing 10 and 20 wt % PBS, respectively, both of which presented desirable alignment and large width/thickness ratio (nanoscale thickness with a width of 428±13.1 and 76.9±8.2 μm, respectively). With the creation of compact polymer "nano-barrier walls", a dramatic decrease of 86% and 67% in the oxygen permeability coefficient was observed for the film incorporated with well-organized 20 wt % PBS nanosheets compared to pure PLA and pure PBS (1.4 and 0.6×10(-14) cm3·cm·cm(-2)·s(-1)·Pa(-1)), respectively. Unexpectedly, prominent increases of 21% and 28% were achieved in the tensile strength and modulus of composite films loaded 20 wt % PBS nanosheets compared to pure PLA films, although PBS intrinsically presents poor strength and stiffness. The unusual combination of barrier and mechanical performances established in the fully degradable system represent specific properties required in packaging beverages, food and medicine.

  4. High melt strength, tear resistant blown film based on poly(lactic acid)

    NASA Astrophysics Data System (ADS)

    Edmonds, Neil R.; Plimmer, Peter N.; Tanner, Chris

    2015-05-01

    A major problem associated with the commercial manufacture of thin films from PLA is inferior processing characteristics on blown film lines compared to low density polyethylene. PLA has poor melt strength (leading to bubble instability) and develops a permanent crease in the flattened film as it exits the tower of the film line. In addition, the thin film product has poor tear strength and an unacceptable `noise' level when converted into flexible packaging. Furthermore, fabricated articles based on PLA are known to show an unattractive tendency toward dimensional instability. This behaviour is associated with `cold crystallization', a phenomenon which also causes exudation of any plasticizer added for improving flexibility. Blow moulded articles based on PLA also exhibit dimensional sensitivity above 60°C. All of these issues have been overcome by the technology described in this paper. This has been accomplished without loss of the valuable compostability characteristic of PLA; this was confirmed by evaluation of film in a commercial composting operation. These results have been achieved through novel reactive compounding technology which: (a) Creates a PLA-rich structure containing long chain crosslinks, (b) generates a low glass transition temperature phase covalently bonded to the PLA structure, and (c) provides a material which performs like LDPE in a blown film manufacturing operation. The technology developed is covered by NZ Patent 580231 (3). The patent is held by UniServices Ltd, The University of Auckland, New Zealand.

  5. Silver/poly (lactic acid) nanocomposites: preparation, characterization, and antibacterial activity

    PubMed Central

    Shameli, Kamyar; Ahmad, Mansor Bin; Yunus, Wan Md Zin Wan; Ibrahim, Nor Azowa; Rahman, Russly Abdul; Jokar, Maryam; Darroudi, Majid

    2010-01-01

    In this study, antibacterial characteristic of silver/poly (lactic acid) nanocomposite (Ag/PLA-NC) films was investigated, while silver nanoparticles (Ag-NPs) were synthesized into biodegradable PLA via chemical reduction method in diphase solvent. Silver nitrate and sodium borohydride were respectively used as a silver precursor and reducing agent in the PLA, which acted as a polymeric matrix and stabilizer. Meanwhile, the properties of Ag/PLA-NCs were studied as a function of the Ag-NP weight percentages (8, 16, and 32 wt% respectively), in relation to the use of PLA. The morphology of the Ag/PLA-NC films and the distribution of the Ag-NPs were also characterized. The silver ions released from the Ag/PLA-NC films and their antibacterial activities were scrutinized. The antibacterial activities of the Ag/PLA-NC films were examined against Gram-negative bacteria (Escherichia coli and Vibrio parahaemolyticus) and Gram-positive bacteria (Staphylococcus aureus) by diffusion method using Muller–Hinton agar. The results indicated that Ag/PLA-NC films possessed a strong antibacterial activity with the increase in the percentage of Ag-NPs in the PLA. Thus, Ag/PLA-NC films can be used as an antibacterial scaffold for tissue engineering and medical application. PMID:20856832

  6. Poly(lactic acid) microparticles coated with insulin-containing layer-by-layer films and their pH-dependent insulin release.

    PubMed

    Hashide, Ryosuke; Yoshida, Kentaro; Hasebe, Yasushi; Seno, Masaru; Takahashi, Shigehiro; Sato, Katsuhiko; Anzai, Jun-Ichi

    2014-04-01

    Poly(lactic acid) (PLA) microparticles were coated with layer-by-layer (LbL) films containing insulin and the pH-dependent release of insulin was studied. The LbL films were prepared on the surface of PLA microparticles by the alternate deposition of insulin and poly(allylamine hydrochloride) (PAH) through the electrostatic attraction between insulin and PAH. The insulin loading on the PLA microparticles depended on the film thickness, which corresponded to the number of insulin layers, and on the pH of the solution used to deposit insulin. The insulin loading increased with the film thickness and when the film was prepared at pH 7.4. The LbL films decomposed upon exposure to acidic solutions because the electrostatic attraction between the insulin and the PAH in the films disappeared when the charge on insulin changed from negative to positive at an acidic pH, which resulted in the release of insulin. The temperature and salt concentration did not affect the pH stability of the LbL films. The pH threshold for insulin release was pH 5.0-6.0, which corresponds to isoelectric point of insulin, 5.4. The release of insulin from the microparticles was rapid, and was almost complete within a few minutes. The circular dichroism spectra showed that the released insulin retained its original secondary structure. Our insulin-loaded PLA microparticles may be useful for the controlled release of insulin.

  7. Thermal degradation behaviour of nanoamphiphilic chitosan dispersed poly (lactic acid) bionanocomposite films.

    PubMed

    Pal, Akhilesh Kumar; Katiyar, Vimal

    2017-02-01

    In the present study, nano-amphiphilic chitosan termed as chitosan-grafted-oligo l-lactic acid (CH-g-OLLA), is synthesized by microwave initiated insitu condensation polymerization. The synthesized CH-g-OLLA becomes hydrophobic in nature due to chemical bond formation between chitosan backbone and OLLA chains. Further, CH-g-OLLA (30%) bionanocomposite is used as a nanofiller in poly (lactic acid)/chitosan-grafted-oligo l-lactic acid (PLA/CH-g-OLLA) bionanocomposite films. Surface morphology shows a homogeneous dispersion of CH-g-OLLA in the form of spherical aggregates, which vary in the range of ∼20 to 150nm. Non-isothermal degradation kinetics, proposed by Kissinger, Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa and Augis & Bennett models, are utilized to estimate the activation energies (Ea) for PLA, which are 254.1, 260.2, 257.0 and 259.1kJmol(-1) respectively. The reduction in Ea values of bionanocomposite films may be elucidated by intermolecular distance and enrichment in chain mobility. The evolved gaseous products like hydrocarbons, carbon dioxide, carbon monoxide and cyclic oligomers are successfully identified with TG-FTIR analysis.

  8. Coating of poly(p-xylylene) by PLA-PEO-PLA triblock copolymers with excellent polymer-polymer adhesion for stent applications.

    PubMed

    Hanefeld, Phillip; Westedt, Ullrich; Wombacher, Ralf; Kissel, Thomas; Schaper, Andreas; Wendorff, Joachim H; Greiner, Andreas

    2006-07-01

    Poly(p-xylylene) (PPX) was deposited by chemical vapor deposition (CVD) on stainless steel substrates. These PPX films were coated by solution casting of poly(lactide)-poly(ethylene oxide)-poly(lactide) triblock copolymers (PLA-PEO-PLA) loaded with 14C-labeled paclitaxel. Adhesion of PLA-PEO-PLA on PPX substrate coatings was measured using the blister test method. Excellent adhesion of the block copolymers on PPX substrates was found. Stress behavior and film integrity of PLA-PEO-PLA was compared to pure PLA on unexpanded and expanded stent bodies and was found to be superior for the block copolymers. The release of paclitaxel from the biodegradable coatings was studied under physiological conditions using the scintillation counter method. Burst release of paclitaxel was observed from PLA-PEO-PLA layers regardless of composition, but an increase in paclitaxel loading was observed with increasing content of PEO.

  9. Polylactide-based renewable composites from natural products residues by encapsulated film bag: characterization and biodegradability.

    PubMed

    Wu, Chin-San

    2012-09-01

    In the present study, the biodegradability, morphology, and mechanical properties of composite materials consisting of acrylic acid-grafted polylactide (PLA-g-AA) and natural products residues (corn starch, CS) were evaluated. Composites containing acrylic acid-grafted PLA (PLA-g-AA/CS) exhibited noticeably superior mechanical properties due to their greater compatibility with CS compared with PLA/CS. The feasibility of using PLA-g-AA/CS as a film bag material to facilitate the controlled release of an encapsulated phosphate-solubilizing bacterium (PSB) Burkholderia cepacia as a fertilizer use promoter was then evaluated. For purposes of comparison and accurate characterization, a PLA film bag was also assessed. The results showed that the bacterium completely degraded both the PLA and the PLA-g-AA/CS composite film bags, resulting in cell release. The PLA-g-AA/CS (20 wt%) film bags were more biodegradable than those made of PLA, and displayed a higher loss of molecular weight and intrinsic viscosity, indicating a strong connection between these characteristics and biodegradability.

  10. In vitro degradation kinetics of pure PLA and Mg/PLA composite: Effects of immersion temperature and compression stress.

    PubMed

    Li, Xuan; Chu, Chenglin; Wei, Yalin; Qi, Chenxi; Bai, Jing; Guo, Chao; Xue, Feng; Lin, Pinghua; Chu, Paul K

    2017-01-15

    The effects of the immersion temperature and compression stress on the in vitro degradation behavior of pure poly-lactic acid (pure-PLA) and PLA-based composite unidirectionally reinforced with micro-arc oxidized magnesium alloy wires (Mg/PLA or MAO-MAWs/PLA) are investigated. The degradation kinetics of pure-PLA and the PLA matrix in MAO-MAWs/PLA exhibit an Arrhenius-type behavior. For the composite, the synergic degradation of MAO-MAWs maintains a steady pH and mitigates the degradation of PLA matrix during immersion. However, the external compression stress decreases the activation energy (Ea) and pre-exponential factor (k0) consequently increasing the degradation rate of PLA. Under a compression stress of 1MPa, Ea and k0 of pure PLA are 57.54kJ/mol and 9.74×10(7)day(-1), respectively, but 65.5kJ/mol and 9.81×10(8)day(-1) for the PLA matrix in the composite. Accelerated tests are conducted in rising immersion temperature in order to shorten the experimental time. Our analysis indicates there are well-defined relationships between the bending strength of the specimens and the PLA molecular weight during immersion, which are independent of the degradation temperature and external compression stress. Finally, a numerical model is established to elucidate the relationship of bending strength, the PLA molecular weight, activation energy, immersion time and temperature.

  11. Extra-hepatic metabolism of 7-ketocholesterol occurs by esterification to fatty acids via cPLA2α and SOAT1 followed by selective efflux to HDL.

    PubMed

    Lee, Jung Wha; Huang, Jiahn-Dar; Rodriguez, Ignacio R

    2015-05-01

    Accumulation of 7-ketocholesterol (7KCh) in tissues has been previously associated with various chronic aging diseases. Orally ingested 7KCh is readily metabolized by the liver and does not pose a toxicity threat. However, 7KCh formed in situ, usually associated with lipoprotein deposits, can adversely affect surrounding tissues by causing inflammation and cytotoxicity. In this study we have investigated various mechanisms for extra-hepatic metabolism of 7KCh (e.g. hydroxylation, sulfation) and found only esterification to fatty acids. The esterification of 7KCh to fatty acids involves the combined action of cytosolic phospholipase A2 alpha (cPLA2α) and sterol O-acyltransferase (SOAT1). Inhibition of either one of these enzymes ablates 7KCh-fatty acid ester (7KFAE) formation. The 7KFAEs are not toxic and do not induce inflammatory responses. However, they can be unstable and re-release 7KCh. The higher the degree of unsaturation, the more unstable the 7KFAE (e.g. 18:0>18:1>18:2>18:3≫20:4). Biochemical inhibition and siRNA knockdown of SOAT1 and cPLA2α ablated the 7KFAE synthesis in cultured ARPE19 cells, but had little effect on the 7KCh-induced inflammatory response. Overexpression of SOAT1 reduced the 7KCh-induced inflammatory response and provided some protection from cell death. This effect is likely due to the increased conversion of 7KCh to 7KFAEs, which reduced the intracellular 7KCh levels. Addition of HDL selectively increased the efflux of 7KFAEs and enhanced the effect of SOAT1 overexpression. Our data suggests an additional function for HDL in aiding extra-hepatic tissues to eliminate 7KCh by returning 7KFAEs to the liver for bile acid formation.

  12. Adhesion and proliferation of skeletal muscle cells on single layer poly(lactic acid) ultra-thin films.

    PubMed

    Ricotti, Leonardo; Taccola, Silvia; Pensabene, Virginia; Mattoli, Virgilio; Fujie, Toshinori; Takeoka, Shinji; Menciassi, Arianna; Dario, Paolo

    2010-10-01

    An increasing interest in bio-hybrid systems and cell-material interactions is evident in the last years. This leads towards the development of new nano-structured devices and the assessment of their biocompatibility. In the present study, the development of free-standing single layer poly(lactic acid) (PLA) ultra-thin films is described, together with the analysis of topography and roughness properties. The biocompatibility of the PLA films has been tested in vitro, by seeding C2C12 skeletal muscle cells, and thus assessing cells shape, density and viability after 24, 48 and 72 h. The results show that free-standing flexible PLA nanofilms represent a good matrix for C2C12 cells adhesion, spreading and proliferation. Early differentiation into myotubes is also allowed. The biocompatibility of the novel ultra-thin films as substrates for cell growth promotes their application in the fields of regenerative medicine, muscle tissue engineering, drug delivery, and-in general-in the field of bio-hybrid devices.

  13. PLA micro- and nano-particles.

    PubMed

    Lee, Byung Kook; Yun, Yeonhee; Park, Kinam

    2016-12-15

    Poly(d,l-lactic acid) (PLA) has been widely used for various biomedical applications for its biodegradable, biocompatible, and nontoxic properties. Various methods, such as emulsion, salting out, and precipitation, have been used to make better PLA micro- and nano-particle formulations. They are widely used as controlled drug delivery systems of therapeutic molecules, including proteins, genes, vaccines, and anticancer drugs. Even though PLA-based particles have challenges to overcome, such as low drug loading capacity, low encapsulation efficiency, and terminal sterilization, continuous innovations in particulate formulations will lead to development of clinically useful formulations.

  14. Effect of the photoreaction solvent on surface and bulk properties of poly(lactic acid) and poly(hydroxyalkanoate) films.

    PubMed

    Rasal, Rahul M; Bohannon, Bradley G; Hirt, Douglas E

    2008-05-01

    The major objective of this research was to modify the surface properties of poly(lactic acid) (PLA) and poly(hydroxyalkanoate) (PHA) films by using a sequential two-step photografting approach. In step 1, benzophenone was photografted on the film surface and in step 2, hydrophilic monomers acrylamide and acrylic acid were photopolymerized from the film surfaces. Another objective was to study the effect of the reaction solvent in step 2 on surface and bulk properties of these films. ATR-FTIR spectroscopy and water contact angle goniometry were used to characterize the resultant film surfaces. When ethanol was used as the solvent in step 2, there was significant penetration of the monomers into the films, and bulk properties such as toughness and percent elongation at break were drastically affected. The penetration of these monomers into the bulk was characterized using transmission FTIR microspectroscopy. Microtomed sections of the surface-modified films were placed in a diamond compression cell to perform the FTIR microspectroscopic analyses. The observed monomer penetration into the films was successfully reduced by using water instead of ethanol in step 2, and resultant films showed higher toughness and percent elongation at break than films surface-modified using ethanol as a solvent in step 2.

  15. Polylactic acid/zinc oxide biocomposite films for food packaging application.

    PubMed

    Marra, Antonella; Silvestre, Clara; Duraccio, Donatella; Cimmino, Sossio

    2016-07-01

    Although PLA is much more expensive than polyolefins, such as PP and PE, there is a great interest to propose PLA based material as alternative films for food packaging being PLA derivable from natural source, compostable and biodegradable. For this purpose the research has the task to investigate and propose PLA materials with enhanced properties to be effectively and efficiently alternative to polyolefin films for food packaging application. In this contribution, biocomposite films of PLA with 1, 3 and 5wt% of ZnO have been investigated to determine mechanical, barrier and antimicrobial (against Escherichia coli) properties. It is found that the biocomposite films are characterized by a good dispersion of the ZnO particles in PLA matrix, although no previous treatment was performed on ZnO particles, such as silanization, to decrease its incompatibility with the polymer. The biocomposite films have shown good mechanical properties, decrease of permeability to CO2 and O2, and only a slight increase to water vapour. Particularly important is that, for the biocomposite with 5wt% of ZnO, the % Reduction for E. Coli test reached the value of 99.99 already after 24h.

  16. Photo-initiated grafting of gelatin/N-maleic acyl-chitosan to enhance endothelial cell adhesion, proliferation and function on PLA surface.

    PubMed

    Zhu, Aiping; Zhao, Feng; Ma, Teng

    2009-07-01

    Vascular graft surface properties significantly affect adhesion, growth and function of endothelial cells (ECs). The bulk degradation property of poly(lactic acid) (PLA) makes it possible for it to be replaced by cellular materials and PLA is desirable as a scaffold material for vascular grafts. However, PLA has an unfavorable surface property for EC adhesion and proliferation due to the lack of a selective cell adhesion motif. Photo-initiated surface-grafting polymerization is a promising method for immobilizing certain biomacromolecules on material surfaces without compromising bulk properties. N-Maleic acyl-chitosan (NMCS) is a novel biocompatible amphiphilic derivative of chitosan with double bonds and can be initiated by ultraviolet light. In this study, gelatin was complexed with NMCS via hydrophobic interaction, and gel/NMCS complex thus formed was then grafted on the PLA surface to improve EC biocompatibility. X-ray photoelectron and Fourier transform infrared spectroscopy, and water contact angle measurement confirmed immobilization of the gel/NMCS complex on PLA surface. Moreover, the gel/NMCS modified PLA enhanced human umbilical vein endothelial cell (HUVEC) spreading and flattening, and promoted the expression of more structured CD31 and vWF compared to unmodified PLA film. Compared to the unmodified PLA surface, the HUVECs on the modified PLA surface had elevated uptake of acetylated low-density lipoprotein, and maintained the ability to modulate metabolic activity upon exposure to shear stress at 5dyncm(-2) by up-regulating nitric oxide and prostacyclin production. Cell retention was 1.6 times higher on the gel/NMCS-PLA surface, demonstrating its improved potential for hemocompatibility. These results indicate that photo-initiated surface-grafting of the biomimetic gel/NMCS complex is an effective method to modify material surfaces as vascular grafts.

  17. Softened and flexible biodegradable poly(lactic acid) and its electromechanical properties for actuator application.

    PubMed

    Thummarungsan, Natlita; Pattavarakorn, Datchanee; Sirivat, Anuvat

    2016-12-01

    Poly (lactic acid) (PLA) is a biodegradable polymer with high stiffness presenting a limitation for using in actuator applications. Adding a plasticizer is one way to solve this problem to enhance flexibility and improve electromechanical properties of pristine PLA. In this work, the PLA films were prepared via a simple solvent casting method. The influences of plasticizer type and electric field strength on electromechanical behavior of PLA films were investigated by the melt rheometer and bending measurement. For the PLA films filled with dibutyl phthalate (DBP), the storage modulus, G', immediately increased towards its steady state and rapidly recovered to its original value with and without electric field, respectively, which can be referred to a reversible system. On the other hand, the PLA film with Tween 20 processed the highest ∆G׳/G׳0 of 1.34 due to the available amount of polarized groups. In the bending measurement, the dielectrophoresis forces of plasticized PLA films were found to increase with increasing electric field where the deflections occurred towards anode side as the polarized groups generated negative charges. The DBP_PLA1.5D film exhibited the greatest bending and dielectrophoresis force. Thus, the biodegradable PLA along with DBP combine to have a great potential towards actuator application.

  18. Effects of modified cellulose nanocrystals on the barrier and migration properties of PLA nano-biocomposites.

    PubMed

    Fortunati, E; Peltzer, M; Armentano, I; Torre, L; Jiménez, A; Kenny, J M

    2012-10-01

    The aim of this paper is to report the impact of the addition of cellulose nanocrystals on the barrier properties and on the migration behaviour of poly(lactic acid), PLA, based nano-biocomposites prepared by the solvent casting method. Their microstructure, crystallinity, barrier and overall migration properties were investigated. Pristine (CNC) and surfactant-modified cellulose nanocrystals (s-CNC) were used, and the effect of the cellulose modification and content in the nano-biocomposites was investigated. The presence of surfactant on the nanocrystal surface favours the dispersion of CNC in the PLA matrix. Electron microscopy analysis shows the good dispersion of s-CNC in the nanoscale with well-defined single crystals indicating that the surfactant allowed a better interaction between the cellulose structures and the PLA matrix. Reductions of 34% in water permeability were obtained for the cast films containing 1 wt.% of s-CNC while good oxygen barrier properties were detected for nano-biocomposites with both 1 wt.% and 5 wt.% of modified and un-modified cellulose nanocrystals, underlining the improvement provided by cellulose on the PLA films. Moreover, the migration level of the studied nano-biocomposites was below the overall migration limits required by the current normative for food packaging materials in both non-polar and polar simulants.

  19. An overview of the recent developments in polylactide (PLA) research.

    PubMed

    Madhavan Nampoothiri, K; Nair, Nimisha Rajendran; John, Rojan Pappy

    2010-11-01

    The concept of biodegradable plastics is of considerable interest with respect to solid waste accumulation. Greater efforts have been made in developing degradable biological materials without any environmental pollution to replace oil-based traditional plastics. Among numerous kinds of degradable polymers, polylactic acid sometimes called polylactide, an aliphatic polyester and biocompatible thermoplastic, is currently a most promising and popular material with the brightest development prospect and was considered as the 'green' eco friendly material. Biodegradable plastics like polyglycolic acid, polylactic acid, polycaprolactone, polyhydroxybutyrate, etc. are commercially available for controlled drug releases, implantable composites, bone fixation parts, packaging and paper coatings, sustained release systems for pesticides and fertilizers and compost bags etc. This review will provide information on current PLA market, brief account on recent developments in the synthesis of lactic acid (monomer of PLA) through biological route, PLA synthesis, unique material properties of PLA and modification of those by making copolymers and composites, PLA degradation and its wide spectrum applications.

  20. Augmentation of a Microbial Consortium for Enhanced Polylactide (PLA) Degradation.

    PubMed

    Nair, Nimisha R; Sekhar, Vini C; Nampoothiri, K Madhavan

    2016-03-01

    Bioplastics are eco-friendly and derived from renewable biomass sources. Innovation in recycling methods will tackle some of the critical issues facing the acceptance of bioplastics. Polylactic acid (PLA) is the commonly used and well-studied bioplastic that is presumed to be biodegradable. Considering their demand and use in near future, exploration for microbes capable of bioplastic degradation has high potential. Four PLA degrading strains were isolated and identified as Penicillium chrysogenum, Cladosporium sphaerospermum, Serratia marcescens and Rhodotorula mucilaginosa. A consortium of above strains degraded 44 % (w/w) PLA in 30 days time in laboratory conditions. Subsequently, the microbial consortium employed effectively for PLA composting.

  1. Biological nitrate removal using wheat straw and PLA as substrate.

    PubMed

    Fan, Zhenxing; Hu, Jun; Wang, Jianlong

    2012-01-01

    Biological nitrate removal using wheat straw and polylactic acid (PLA) as both carbon source and biofilm support was investigated. The results showed that biofilm could develop on the surface of wheat straw within 15 d, the denitrification rate was 0.067 mg-N/(g-wheat straw x h) and nitrate removal efficiency was about 100%. For PLA, the time required for biofilm development was 40 d, the denitrification rate was 0.0026 mg-N/(g-PLA x h) and nitrate removal efficiency could also reach 100%. Temperature had a substantial influence on the denitrification performance of both wheat straw and PLA. The FTIR analysis and SEM observation confirmed that wheat straw and PLA were used for denitrification, and explained some reasons for the differences between the two substrates. The wheat straw was superior to PLA when used as carbon source for nitrate removal, in terms of the denitrification rate.

  2. Synthesis and wound healing of alternating block polyurethanes based on poly(lactic acid) (PLA) and poly(ethylene glycol) (PEG).

    PubMed

    Li, Linjing; Liu, Xiangyu; Niu, Yuqing; Ye, Jianfu; Huang, Shuiwen; Liu, Chao; Xu, Kaitian

    2016-04-05

    Alternating block polyurethanes (abbreviated as PULA-alt-PEG) and random block polyurethanes (abbreviated as PULA-ran-PEG) based on biodegradable poly(lactic acid) (PLA) and poly(ethylene glycol) (PEG) were prepared. Results showed that alternating block polyurethane gives higher crystal degree, higher mechanical properties, more patterned and rougher surface than the random counterpart, due to the regular and controlled structure. Water absorptions of the polyurethanes were in the range of 620 to 780%. Cytocompatibility of the amphiphilic block polyurethanes (PU) (water static angle 41.4°-61.8°) was assessed by CCK-8 assay using human embryonic kidney (HEK293) cells. Wound healing evaluation of the PU foam scaffolds was carried out by full-thickness SD rat model experiment, with medical gauze as control. It was found that the skin of rat in PU groups was fully covered with new epithelium without any significant adverse reactions and PU dressings give much rapid and better healing than medical gauze. Histological examination revealed that PU dressings suppress the infiltration of inflammatory cells and accelerate fibroblast proliferation. It was also demonstrated that PULA-alt-PEG exhibits obvious better healing effect than PULA-ran-PEG does. This study has demonstrated that without further modification, plain alternating block polyurethane scaffold would help wound recovery efficiently. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2016.

  3. Mechanical, structural and thermal properties of Ag-Cu and ZnO reinforced polylactide nanocomposite films.

    PubMed

    Ahmed, Jasim; Arfat, Yasir Ali; Castro-Aguirre, Edgar; Auras, Rafael

    2016-05-01

    Plasticized polylactic acid (PLA) based nanocomposite films were prepared by incorporating polyethylene glycol (PEG) and two selected nanoparticles (NPs) [silver-copper (Ag-Cu) alloy (<100 nm) and zinc oxide (ZnO) (<50 and <100 nm)] through solvent casting method. Incorporation of Ag-Cu alloy into the PLA/PEG matrix increased the glass transition temperature (Tg) significantly. The crystallinity of the nanocomposites (NCs) was significantly influenced by NP incorporation as evidenced from differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analysis. The PLA nanocomposite reinforced with NPs exhibited much higher tensile strength than that of PLA/PEG blend. Melt rheology of NCs exhibited a shear-thinning behavior. The mechanical property drastically reduced with a loading of NPs, which is associated with degradation of PLA. SEM micrographs exhibited that both Ag-Cu alloy and ZnO NPs were dispersed well in the PLA film matrix.

  4. Production of PLA-Starch Fibers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Composites of polylactic acid (PLA) with starch have been prepared previously in an effort to reduce cost as well as to modify other properties such as biodegradation rate. However, strength and elongation both decrease on addition of starch due to poor adhesion and stress concentration at the inte...

  5. Fabrication and surface modification of poly lactic acid (PLA) scaffolds with epidermal growth factor for neural tissue engineering

    PubMed Central

    Haddad, Tanit; Noel, Samantha; Liberelle, Benoît; El Ayoubi, Rouwayda; Ajji, Abdellah

    2016-01-01

    ABSTRACT In an effort to design biomaterials that may promote repair of the central nervous system, 3-dimensional scaffolds made of electrospun poly lactic acid nanofibers with interconnected pores were fabricated. These scaffolds were functionalized with polyallylamine to introduce amine groups by wet chemistry. Experimental conditions of the amination protocol were thoroughly studied and selected to introduce a high amount of amine group while preserving the mechanical and structural properties of the scaffold. Subsequent covalent grafting of epidermal growth factor was then performed to further tailor these aminated structures. The scaffolds were then tested for their ability to support Neural Stem-Like Cells (NSLCs) culture. Of interest, NSLCs were able to proliferate on these EGF-grafted substrates and remained viable up to 14 d even in the absence of soluble growth factors in the medium. PMID:27740881

  6. Biocompatibility of poly(lactic acid) with incorporated graphene-based materials.

    PubMed

    Pinto, Artur M; Moreira, Susana; Gonçalves, Inês C; Gama, Francisco M; Mendes, Adélio M; Magalhães, Fernão D

    2013-04-01

    The incorporation of graphene-based materials has been shown to improve mechanical properties of poly(lactic acid) (PLA). In this work, PLA films and composite PLA films incorporating two graphene-based materials - graphene oxide (GO) and graphene nanoplatelets (GNP) - were prepared and characterized regarding not only biocompatibility, but also surface topography, chemistry and wettability. The presence of both fillers changed the films surface topography, increasing the roughness, and modified the wettability - the polar component of surface free energy increased 59% with GO and decreased 56% with GNP. Mouse embryo fibroblasts incubated with both fillers exceeded the IC(50) in both cases with a concentration of 10 μg mL(-1). No variations in cell proliferation at the surface of the composite films were observed, except for those containing GO after 24 h incubation, which presented higher cell proliferation than pristine PLA films. Platelet adhesion to PLA and PLA/GNP films was lower in the presence of plasma proteins than when no proteins were present. Furthermore, incorporation of GNP into PLA reduced platelet activation in the presence of plasma proteins. The results indicated that low concentrations of GO and GNP may be incorporated safely in PLA to improve aspects relevant for biomedical applications, such as mechanical properties.

  7. Recent advances in PEG-PLA block copolymer nanoparticles.

    PubMed

    Xiao, Ren Zhong; Zeng, Zhao Wu; Zhou, Guang Lin; Wang, Jun Jie; Li, Fan Zhu; Wang, An Ming

    2010-11-26

    Due to their small particle size and large and modifiable surface, nanoparticles have unique advantages compared with other drug carriers. As a research focus in recent years, polyethylene glycol-polylactic acid (PEG-PLA) block copolymer and its end-group derivative nanoparticles can enhance the drug loading of hydrophobic drugs, reduce the burst effect, avoid being engulfed by phagocytes, increase the circulation time of drugs in blood, and improve bioavailability. Additionally, due to their smaller particle size and modified surface, these nanoparticles can accumulate in inflammation or target locations to enhance drug efficacy and reduce toxicity. Recent advances in PEG-PLA block copolymer nanoparticles, including the synthesis of PEG-PLA and the preparation of PEG-PLA nanoparticles, were introduced in this study, in particular the drug release and modifiable characteristics of PEG-PLA nanoparticles and their application in pharmaceutical preparations.

  8. Conjugation of bioactive groups to poly(lactic acid) and poly[(lactic acid)-co-(glycolic acid)] films.

    PubMed

    Prime, Emma L; Cooper-White, Justin J; Qiao, Greg G

    2007-12-06

    A novel PLA-based polymer containing reactive pendent ketone or hydroxyl groups was synthesized by the copolymerization of L-lactide with epsilon-caprolactone-based monomers. The polymer was activated with NPC, resulting in an amine-reactive polymer which was then cast into thin polymeric films, either alone or as part of a blend with PLGA, before immersion into a solution of the cell adhesion peptide GRGDS in PBS buffer allowed for conjugation of GRGDS to the film surfaces. Subsequent 3T3 fibroblast cell adhesion studies demonstrated an increase in cellular adhesion and spreading over films cast from unmodified PLGA. Hence the new polymer can be used to obtain covalent linkage of amine-containing molecules to polymer surfaces.

  9. Zinc Metalloproteinase ProA Directly Activates Legionella pneumophila PlaC Glycerophospholipid:cholesterol Acyltransferase*

    PubMed Central

    Lang, Christina; Rastew, Elena; Hermes, Björn; Siegbrecht, Enrico; Ahrends, Robert; Banerji, Sangeeta; Flieger, Antje

    2012-01-01

    Enzymes secreted by Legionella pneumophila, such as phospholipases A (PLAs) and glycerophospholipid:cholesterol acyltransferases (GCATs), may target host cell lipids and therefore contribute to the establishment of Legionnaires disease. L. pneumophila possesses three proteins, PlaA, PlaC, and PlaD, belonging to the GDSL family of lipases/acyltransferases. We have shown previously that PlaC is the major GCAT secreted by L. pneumophila and that the zinc metalloproteinase ProA is essential for GCAT activity. Here we characterized the mode of PlaC GCAT activation and determined that ProA directly processes PlaC. We further found that not only cholesterol but also ergosterol present in protozoa was palmitoylated by PlaC. Such ester formations were not induced by either PlaA or PlaD. PlaD was shown here to possess lysophospholipase A activity, and interestingly, all three GDSL enzymes transferred short chain fatty acids to sterols. The three single putative catalytic amino acids (Ser-37, Asp-398, and His-401) proved essential for all PlaC-associated PLA, lysophospholipase A, and GCAT activities. A further four cysteine residues are important for the PLA/GCAT activities as well as their oxidized state, and we therefore conclude that PlaC likely forms at least one disulfide loop. Analysis of cleavage site and loop deletion mutants suggested that for GCAT activation deletion of several amino acids within the loop is necessary rather than cleavage at a single site. Our data therefore suggest a novel enzyme inhibition/activation mechanism where a disulfide loop inhibits PlaC GCAT activity until the protein is exported to the external space where it is ProA-activated. PMID:22582391

  10. sPLA2 IB induces human podocyte apoptosis via the M-type phospholipase A2 receptor.

    PubMed

    Pan, Yangbin; Wan, Jianxin; Liu, Yipeng; Yang, Qian; Liang, Wei; Singhal, Pravin C; Saleem, Moin A; Ding, Guohua

    2014-10-22

    The M-type phospholipase A2 receptor (PLA2R) is expressed in podocytes in human glomeruli. Group IB secretory phospholipase A2 (sPLA2 IB), which is one of the ligands of the PLA2R, is more highly expressed in chronic renal failure patients than in controls. However, the roles of the PLA2R and sPLA2 IB in the pathogenesis of glomerular diseases are unknown. In the present study, we found that more podocyte apoptosis occurs in the kidneys of patients with higher PLA2R and serum sPLA2 IB levels. In vitro, we demonstrated that human podocyte cells expressed the PLA2R in the cell membrane. After binding with the PLA2R, sPLA2 IB induced podocyte apoptosis in a time- and concentration-dependent manner. sPLA2 IB-induced podocyte PLA2R upregulation was not only associated with increased ERK1/2 and cPLA2α phosphorylation but also displayed enhanced apoptosis. In contrast, PLA2R-silenced human podocytes displayed attenuated apoptosis. sPLA2 IB enhanced podocyte arachidonic acid (AA) content in a dose-dependent manner. These data indicate that sPLA2 IB has the potential to induce human podocyte apoptosis via binding to the PLA2R. The sPLA2 IB-PLA2R interaction stimulated podocyte apoptosis through activating ERK1/2 and cPLA2α and through increasing the podocyte AA content.

  11. Antimicrobial activity of allyl isothiocyanate used to coat biodegradable composite films as affected by storage and handling conditions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We evaluated the effects of storage and handling conditions on the antimicrobial activity of biodegradable composite films (polylactic acid and sugar beet pulp) coated with allyl isothiocyanate (AIT). Polylactic acid (PLA) and chitosan were incorporated with AIT and coated on one side of the film. T...

  12. Biodegradable polylactic acid polymer with nisin for use in antimicrobial food packaging.

    PubMed

    Jin, T; Zhang, H

    2008-04-01

    Biodegradable polylactic acid (PLA) polymer was evaluated for its application as a material for antimicrobial food packaging. PLA films were incorporated with nisin to for control of foodborne pathogens. Antimicrobial activity of PLA/nisin films against Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella Enteritidis were evaluated in culture media and liquid foods (orange juice and liquid egg white). Scanned electron micrograph and confocal laser microscopy revealed that nisin particles were evenly distributed in PLA polymer matrix on the surface and inside of the PLA/nisin films. PLA/nisin significantly inhibited growth of L. monocytogenes in culture medium and liquid egg white. The greatest inhibition occurred at 24 h when the cell counts of L. monocytogenes in the PLA/nisin samples were 4.5 log CFU/mL less than the controls. PLA/nisin reduced the cell population of E. coli O157:H7 in orange juice from 7.5 to 3.5 log at 72 h whereas the control remained at about 6 log CFU/mL. PLA/nisin treatment resulted in a 2 log reduction of S. Enteritidis in liquid egg white at 24 degrees C. After 21 d at 4 degrees C the S. Enteritidis population from PLA/nisin treated liquid egg white (3.5 log CFU/mL) was significantly less than the control (6.8 log CFU/mL). E. coli O157:H7 in orange juice was more sensitive to PLA/nisin treatments than in culture medium. The results of this research demonstrated the retention of nisin activity when incorporated into the PLA polymer and its antimicrobial effectiveness against foodborne pathogens. The combination of a biopolymer and natural bacteriocin has potential for use in antimicrobial food packaging.

  13. Growth and characterization of organic ferroelectric croconic acid thin films

    NASA Astrophysics Data System (ADS)

    Jiang, Xuanyuan; Lu, Haidong; Yin, Yuewei; Enders, Axel; Gruverman, Alexei; Xu, Xiaoshan

    Using vapor phase evaporation, we have studied the growth of the croconic acid (CCA) thin films, at various conditions such as temperature, thickness, growth speed, and substrates. The morphology of thin film was measured by atomic force microscopy (AFM); the ferroelectric property was confirmed by piezoresponse force microscopy (PFM). A critical thickness of 40 nm and optimal temperature of -30 celsius were found for continuous films, while the substrate and growth speed are found to play a minimal role. According to the reflection high energy electron diffraction (RHEED), the CCA films are polycrystalline. For a 40 nm continuous film, the roughness is about 3 nm, while the coercive voltage for the ferroelectric domain switching is approximately 7V. This is the first molecule ferroelectric thin film. The successful growth of continuous CCA films enhances the applications potential of CCA, which is a molecular crystal of ferroelectricity. Supported by NSF through UNL MRSEC (DMR-1420645).

  14. Magnetic Cellulose Nanocrystal Based Anisotropic Polylactic Acid Nanocomposite Films: Influence on Electrical, Magnetic, Thermal, and Mechanical Properties.

    PubMed

    Dhar, Prodyut; Kumar, Amit; Katiyar, Vimal

    2016-07-20

    This paper reports a single-step co-precipitation method for the fabrication of magnetic cellulose nanocrystals (MGCNCs) with high iron oxide nanoparticle content (∼51 wt % loading) adsorbed onto cellulose nanocrystals (CNCs). X-ray diffraction (XRD), Fourier transform infrared (FTIR), and Raman spectroscopic studies confirmed that the hydroxyl groups on the surface of CNCs (derived from the bamboo pulp) acted as anchor points for the adsorption of Fe3O4 nanoparticles. The fabricated MGCNCs have a high magnetic moment, which is utilized to orient the magnetoresponsive nanofillers in parallel or perpendicular orientations inside the polylactic acid (PLA) matrix. Magnetic-field-assisted directional alignment of MGCNCs led to the incorporation of anisotropic mechanical, thermal, and electrical properties in the fabricated PLA-MGCNC nanocomposites. Thermomechanical studies showed significant improvement in the elastic modulus and glass-transition temperature for the magnetically oriented samples. Differential scanning calorimetry (DSC) and XRD studies confirmed that the alignment of MGCNCs led to the improvement in the percentage crystallinity and, with the absence of the cold-crystallization phenomenon, finds a potential application in polymer processing in the presence of magnetic field. The tensile strength and percentage elongation for the parallel-oriented samples improved by ∼70 and 240%, respectively, and for perpendicular-oriented samples, by ∼58 and 172%, respectively, in comparison to the unoriented samples. Furthermore, its anisotropically induced electrical and magnetic properties are desirable for fabricating self-biased electronics products. We also demonstrate that the fabricated anisotropic PLA-MGCNC nanocomposites could be laminated into films with the incorporation of directionally tunable mechanical properties. Therefore, the current study provides a novel noninvasive approach of orienting nontoxic bioderived CNCs in the presence of low

  15. Cell responses and hemocompatibility of g-HA/PLA composites.

    PubMed

    Li, Jia; Zheng, Wei; Zheng, Yufeng; Lou, Xia

    2011-04-01

    The objective of this study was to investigate the hemocompatibility and cell responses to some novel poly(L-lactide) (PLA) composites containing surface modified hydroxyapatite particles for potential applications as a bone substitute material. The surface of hydroxyapatite (HA) particles was first grafted with L-lactic acid oligomers to form grafted HA (g-HA) particles. The g-HA particles were further blended with PLA to prepare g-HA/PLA composites. Our previous study has shown significant improvement in tensile properties of these materials due to the enhanced interfacial adhesion between the polymer matrix and HA particles. To further investigate the potential applications of these composites in bone repair and other orthopedic surgeries, a series of in vitro and in vivo experiments were conducted to examine the cell responses and hemocompatibility of the materials. In vitro experiments showed that the g-HA/PLA composites were well tolerated by the L-929 cells. Hemolysis of the composites was lower than that of pure PLA. Subcutaneous implantation demonstrated that the g-HA/PLA composites were more favorable than the control materials for soft tissue responses. The results suggested that the g-HA/PLA composites are promising and safe materials with potential applications in tissue engineering.

  16. Fabrication of multifunctional cellulose nanocrystals/poly(lactic acid) nanocomposites with silver nanoparticles by spraying method.

    PubMed

    Yu, Hou-Yong; Yang, Xing-Yuan; Lu, Fang-Fang; Chen, Guo-Yin; Yao, Ju-Ming

    2016-04-20

    The poly (lactic acid) (PLA)/functionalized cellulose nanocrystals formates (CNFs) were prepared by solution casting and then the binary films were sprayed with silver ammonia aqueous solution to fabricate PLA/CNF/Ag ternary nanocomposites. It was found that both deposited silver (Ag) nanoparticles and CNFs showed efficient reinforcing effect on the thermal, mechanical, barrier properties and antibacterial activity of PLA matrix. Especially, the maximum decomposition temperature (Tmax) and Young's modulus of PLA/CNF/Ag(6) nanocomposite film increased by 15.5°C and 48.7%, respectively. Meanwhile an obvious reduction in the water vapor permeability was detected. Furthermore, the migration levels of the ternary nanocomposite films were well below the permitted limits in both non-polar and polar food simulants (60mgkg(-1)), and they showed a significant antibacterial activity influenced by the Ag contents. This study reveals that the novel nanocomposite films will offer a good perspective for food packaging applications.

  17. Development of novel nano-biocomposite antioxidant films based on poly (lactic acid) and thymol for active packaging.

    PubMed

    Ramos, Marina; Jiménez, Alfonso; Peltzer, Mercedes; Garrigós, María C

    2014-11-01

    Novel nano-biocomposite films based on poly (lactic acid) (PLA) were prepared by incorporating thymol, as the active additive, and modified montmorillonite (D43B) at two different concentrations. A complete thermal, structural, mechanical and functional characterization of all nano-biocomposites was carried out. Thermal stability was not significantly affected by the addition of thymol, but the incorporation of D43B improved mechanical properties and reduced the oxygen transmission rate by the formation of intercalated structures, as suggested by wide angle X-ray scattering patterns and transmission electron microscopy images. The addition of thymol decreased the PLA glass transition temperature, as the result of the polymer plasticization, and led to modification of the elastic modulus and elongation at break. Finally, the amount of thymol remaining in these formulations was determined by liquid chromatography (HPLC-UV) and the antioxidant activity by the DPPH spectroscopic method, suggesting that the formulated nano-biocomposites could be considered a promising antioxidant active packaging material.

  18. Differential hydrolysis of erythrocyte and mitochondrial membrane phospholipids by two phospholipase A2 isoenzymes (NK-PLA2-I and NK-PLA2-II) from the venom of the Indian monocled cobra Naja kaouthia.

    PubMed

    Doley, Robin; King, Glenn F; Mukherjee, Ashis K

    2004-05-01

    We previously demonstrated that venom from the Indian monocled cobra Naja kaouthia is a rich source of phospholipase A2 enzymes, and we purified and characterized a major PLA2 isoenzyme (NK-PLA2-I) from N. kaouthia venom. In the present study, we report the purification and biochemical characterization of a second PLA2 isoenzyme (NK-PLA2-II) from the same venom. A comparison of the membrane phospholipid hydrolysis patterns by these two PLA2s has revealed that they cause significantly more damage to mitochondrial membranes (NK-PLA2-I > NK-PLA2-II) as compared to erythrocyte membranes due to more efficient binding of the enzymes to mitochondrial membranes. Fatty acid release patterns by these PLA2s from the membrane phospholipid PC-pools indicate that NK-PLA2-I does not discriminate between saturated and unsaturated fatty acids whereas NK-PLA2-II shows a preference for unsaturated fatty acids during the initial phase of attack. The current investigation provides new insight into the molecular arrangement of NK-PLA2-sensitive domains in erythrocyte and mitochondrial membranes and highlights the contribution of polar, but uncharged, amino acids such as serine and cysteine in NK-PLA2 induced membrane damage.

  19. Lactic Acid and Biosurfactants Production from Residual Cellulose Films.

    PubMed

    Portilla Rivera, Oscar Manuel; Arzate Martínez, Guillermo; Jarquín Enríquez, Lorenzo; Vázquez Landaverde, Pedro Alberto; Domínguez González, José Manuel

    2015-11-01

    The increasing amounts of residual cellulose films generated as wastes all over the world represent a big scale problem for the meat industry regarding to environmental and economic issues. The use of residual cellulose films as a feedstock of glucose-containing solutions by acid hydrolysis and further fermentation into lactic acid and biosurfactants was evaluated as a method to diminish and revalorize these wastes. Under a treatment consisting in sulfuric acid 6% (v/v); reaction time 2 h; solid liquid ratio 9 g of film/100 mL of acid solution, and temperature 130 °C, 35 g/L of glucose and 49% of solubilized film was obtained. From five lactic acid strains, Lactobacillus plantarum was the most suitable for metabolizing the glucose generated. The process was scaled up under optimized conditions in a 2-L bioreactor, producing 3.4 g/L of biomass, 18 g/L of lactic acid, and 15 units of surface tension reduction of a buffer phosphate solution. Around 50% of the cellulose was degraded by the treatment applied, and the liqueurs generated were useful for an efficient production of lactic acid and biosurfactants using L. plantarum. Lactobacillus bacteria can efficiently utilize glucose from cellulose films hydrolysis without the need of clarification of the liqueurs.

  20. sPLA2 and the epidermal barrier

    PubMed Central

    Ilic, Dusko; Bollinger, James M.; Gelb, Michael; Mauro, Theodora M.

    2015-01-01

    The mammalian epidermis provides both an interface and a protective barrier between the organism and its environment. Lipid, processed into water-impermeable bilayers between the outermost layers of the epidermal cells, forms the major barrier that prevents water from exiting the organism, and also prevents toxins and infectious agents from entering. The secretory phospholipase 2 (sPLA2) enzymes control important processes in skin and other organs, including inflammation and differentiation. sPLA2 activity contributes to epidermal barrier formation and homeostasis by generating free fatty acids, which are required both for formation of lamellar membranes and also for acidification of the stratum corneum (SC). sPLA2 is especially important in controlling SC acidification and establishment of an optimum epidermal barrier during the first postnatal week. Several sPLA2 isoforms are present in the epidermis. We find that two of these isoforms, sPLA2 IIA and sPLA2 IIF, localize to the upper stratum granulosum and increase in response to experimental barrier perturbation. sPLA2F−/− mice also demonstrate a more neutral SC pH than do their normal littermates, and their initial recovery from barrier perturbation is delayed. These findings confirm that sPLA2 enzymes perform important roles in epidermal development, and suggest that the sPLA2IIF isoform may be central to SC acidification and barrier function. This article is part of a Special Issue entitled The Important Role of Lipids in the Epidermis and their Role in the Formation and Maintenance of the Cutaneous Barrier. Guest Editors: Kenneth R. Feingold and Peter Elias. PMID:24269828

  1. The Adipocyte-Inducible Secreted Phospholipases PLA2G5 and PLA2G2E Play Distinct Roles in Obesity

    PubMed Central

    Sato, Hiroyasu; Taketomi, Yoshitaka; Ushida, Ayako; Isogai, Yuki; Kojima, Takumi; Hirabayashi, Tetsuya; Miki, Yoshimi; Yamamoto, Kei; Nishito, Yasumasa; Kobayashi, Tetsuyuki; Ikeda, Kazutaka; Taguchi, Ryo; Hara, Shuntaro; Ida, Satoshi; Miyamoto, Yuji; Watanabe, Masayuki; Baba, Hideo; Miyata, Keishi; Oike, Yuichi; Gelb, Michael H.; Murakami, Makoto

    2014-01-01

    Summary Metabolic disorders including obesity and insulin resistance have their basis in dysregulated lipid metabolism and low-grade inflammation. In a microarray search of unique lipase-related genes whose expressions are associated with obesity, we found that two secreted phospholipase A2s (sPLA2s), PLA2G5 and PLA2G2E, were robustly induced in adipocytes of obese mice. Analyses of Pla2g5−/− and Pla2g2e−/− mice revealed distinct and previously unrecognized roles of these sPLA2s in diet-induced obesity. PLA2G5 hydrolyzed phosphatidylcholine in fat-overladen low-density lipoprotein to release unsaturated fatty acids, which prevented palmitate-induced M1 macrophage polarization. As such, PLA2G5 tipped the immune balance toward an M2 state, thereby counteracting adipose tissue inflammation, insulin resistance, hyperlipidemia and obesiy. PLA2G2E altered minor lipoprotein phospholipids, phosphatidylserine and phosphatidylethanolamine, and moderately facilitated lipid accumulation in adipose tissue and liver. Collectively, the identification of “metabolic sPLA2s” adds this gene family to a growing list of lipolytic enzymes that act as metabolic coordinators. PMID:24910243

  2. Thermochemical study of amino acid imprinted polymer films.

    PubMed

    Chai, Ziyi; BelBruno, Joseph J

    2015-11-01

    Molecularly imprinted polymers provide an alternative to traditional methods of amino acid analysis. The imprinted polymers are more robust and significantly less expensive than, for example, ELISA analysis. Amino acid imprinted nylon-6 thin films were studied by differential scanning calorimetry and scanning electron microscopy. Endothermic peaks were observed for imprinted films at temperatures higher than that for pure nylon, indicating the formation of a more-ordered, hydrogen bonded polymer. Removal of the amino acid from the imprinted film resulted in reversion to the peak observed for pure nylon-6. Additives, β-cyclodextrin and multiwalled carbon nanotubes, were added to the imprinted polymer solutions as a means to increase the porosity of the films. These studies resulted in alternative morphologies and calorimetric results that provide additional functionalities and applications for imprinted polymers.

  3. Nano-biocomposite films with modified cellulose nanocrystals and synthesized silver nanoparticles.

    PubMed

    Fortunati, E; Rinaldi, S; Peltzer, M; Bloise, N; Visai, L; Armentano, I; Jiménez, A; Latterini, L; Kenny, J M

    2014-01-30

    Ternary nano-biocomposite films based on poly(lactic acid) (PLA) with modified cellulose nanocrystals (s-CNC) and synthesized silver nanoparticles (Ag) have been prepared and characterized. The functionalization of the CNC surface with an acid phosphate ester of ethoxylated nonylphenol favoured its dispersion in the PLA matrix. The positive effects of the addition of cellulose and silver on the PLA barrier properties were confirmed by reductions in the water permeability (WVP) and oxygen transmission rate (OTR) of the films tested. The migration level of all nano-biocomposites in contact with food simulants were below the permitted limits in both non-polar and polar simulants. PLA nano-biocomposites showed a significant antibacterial activity influenced by the Ag content, while composting tests showed that the materials were visibly disintegrated after 15 days with the ternary systems showing the highest rate of disintegration under composting conditions.

  4. Electrospun PCL/PLA/HA based nanofibers as scaffold for osteoblast-like cells.

    PubMed

    Fang, Rui; Zhang, Enwei; Xu, Ling; Wei, Shicheng

    2010-11-01

    Polycaprolactone (PCL), poly (lactic acid) (PLA) and hydroxyapatite (HA) are frequently used as materials for tissue engineering. In this study, PCL/PLA/HA nanofiber mats with different weight ratio were prepared using electrospinning. Their structure and morphology were studied by FTIR and FESEM. FTIR results demonstrated that the HA particles were successfully incorporated into the PCL/PLA nanofibers. The FESEM images showed that the surface of fibers became coarser with the introduction of HA nanoparticles into PCL/PLA system. Furthermore, the addition of HA led to the decreasing of fiber diameter. The average diameters of PCL/PLA/HA nanofiber were in the range of 300-600 nm, while that of PCL/PLA was 776 +/- 15.4 nm. The effect of nanofiber composition on the osteoblast-like MC3T3-E1 cell adhesion and proliferation were investigated as the preliminary biological evaluation of the scaffold. The MC3T3-E1 cell could be attached actively on all the scaffolds. The MTT assay revealed that PCL/PLA/HA scaffold shows significantly higher cell proliferation than PCL/PLA scaffolds. After 15 days of culture, mineral particles on the surface of the cells was appeared on PCL/PLA/HA nanofibers while normal cell spreading morphology on PCL/PLA nanofibers. These results manifested that electrospun PCL/PLA/HA scaffolds could enhance bone regeneration, showing their marvelous prospect as scaffolds for bone tissue engineering.

  5. In-situ lamination of starch-based baked foam articles with degradable films

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A technique for making biodegradable food service packaging comprised of a starch/fiber core and a biodegradable film laminate is described. The biodegradable films were made of polylactic acid (PLA), polybutylenesuccinate/terephthalate (PBST), rubber latex and polybutyleneadipate/terephthalate (PB...

  6. Self-lubricating boric acid films for tribological applications

    SciTech Connect

    Erdemir, A.; Fenske, G.R.; Nichols, F.A.; Erck, R.A.; Busch, D.E.

    1990-01-01

    Because of its layered crystal structure, boric acid, has been found to be lubricious. Its self-lubricating mechanism is related to the easy shear of atomic layers over one another. Moreover, laser-Raman spectroscopy and electron microscopy analyses have confirmed that thin boric acid films can form on surfaces containing boron and boric oxides. To study the lubricity and self lubricating mechanism of boric acid, pin-on-disk tests were performed on pairs of boric acid compacts and steel disks, boric oxide films and steel pins, boron films and steel pins, and boron-implanted steel disks and steel pins. The mean steady-state friction coefficients of these tribosystems ranged from 0.04 to 0.12. 22 refs., 4 figs., 4 tabs.

  7. Preparation and evaluation of biodegradable films containing the potent osteogenic compound BFB0261 for localized delivery.

    PubMed

    Umeki, Nobuo; Sato, Takayuki; Harada, Masahiro; Takeda, Junko; Saito, Shuji; Iwao, Yasunori; Itai, Shigeru

    2011-02-14

    To achieve sustained release of 3-ethyl-4-(4-methylisoxazol-5-yl)-5-(methylthio) thiophene-2-carboxamide (BFB0261), a new potent osteogenic compound for treating bone disorders, we prepared film formulations containing BFB0261 and the following newly synthesized biodegradable polymers by a solvent casting technique: poly(D,L-lactic acid) (PLA), poly(D,L-lactic acid-co-glycolic acid) (PLGA), poly(D,L-lactic acid)-block-poly(ethylene glycol) (PLA-PEG), and poly(D,L-lactic acid-co-trimethylene carbonate) (PLA-TMC) polymers or copolymers. Powder X-ray diffractometry (PXRD), differential thermal analysis (DTA), scanning electron microscopy (SEM), and tensile testing were performed to examine the physicochemical properties of these films. Almost all the films exhibited a smooth and homogeneous surface, as observed by SEM. In addition, PXRD and DTA revealed that BFB0261 existed in an amorphous state in the films. The in vitro release of BFB0261 from PLA100 (M(w): 251 kDa), PLAPEG9604H (PLA/PEG ratio: 96:4; M(w): 181 kDa), PLAPEG8515H (PLA/PEG ratio: 85:15; M(w): 51.5 kDa), or PLAPEG8020 (PLA/PEG ratio: 80:20; M(w): 33.7 kDa) films followed zero-order kinetics with slow release up to 12 weeks following incubation. Although release of BFB0261 from PLA-TMC films followed first-order kinetics, sustained release of BFB0261 for 12 weeks was still observed for PLATMC8416 (PLA/TMC ratio: 84:16; M(w): 170 kDa) films. Furthermore, when the BFB0261-loaded films constructed from various polymers were implanted subcutaneously on rat backs, the PLAPEG8515H and PLATMC8416 films were capable of achieving sustained release of BFB0261 at the administrated site for 12 weeks. Therefore, the present data indicate that films constructed from PLAPEG8515H or PLATMC8416 may be applicable to bone or tissue engineering.

  8. ATR-IR spectroscopy as applied to nucleic acid films

    NASA Astrophysics Data System (ADS)

    Stepanyugin, Andriy V.; Samijlenko, Svitlana P.; Martynenko, Olena I.; Hovorun, Dmytro M.

    2005-07-01

    For the first time the ATR technique was applied to obtain IR absorption spectra of DNA and RNA dry films. There was worked out procedure of the nucleic acid removal from germanium plate, which obviously was a main obstacle to application of ATR-IR spectroscopy to nucleic acids. This technique of IR spectroscopy was applied to confirmation of RNA tropism of aurin tricarboxylic acid observed by molecular biological methods.

  9. [Preparation and spectroscopic properties of terbium polypropenic acid film].

    PubMed

    Wang, Xi-gui; Wu, Hong-ying; Weng, Shi-fu; Wu, Jin-guang

    2002-12-01

    The bonding-type rare earth polymers-polypropenic-acid terbium film was prepared through the bonding way. Three-dimension fluorescence spectra showed that the optimum excitation wavelength was 306 nm, the strongest emission wavelength was 544 nm. The terbium polypropenic-acid film showed the characteristic Tb3+ emission when excited at 306 nm due to 5D4-7FJ transition (J = 6, 5, 4 and 3). The emission maximum at 544 nm was ascribed to 5D4-7F5 transition of Tb3+ and presented strong green emission. The luminescent properties of Tb3+ were not affected by polymerism of propenic-acid and the transparency of polypropenic-acid in visible light region was not affected by the dopping Tb3+. The fluorescence properties and spectroscopic properties of the terbium polypropenic-acid were investigated by excitation spectrum, emission spectrum, IR, far-IR, and Raman spectrum.

  10. Growth and osteogenic differentiation of adipose stem cells on PLA/bioactive glass and PLA/beta-TCP scaffolds.

    PubMed

    Haimi, Suvi; Suuriniemi, Niina; Haaparanta, Anne-Marie; Ellä, Ville; Lindroos, Bettina; Huhtala, Heini; Räty, Sari; Kuokkanen, Hannu; Sándor, George K; Kellomäki, Minna; Miettinen, Susanna; Suuronen, Riitta

    2009-07-01

    The aim of this study was to compare the effects of novel three-dimensional composite scaffolds consisting of a bioactive phase (bioactive glass or beta-tricalcium phosphate [beta-TCP] 10 and 20 wt%) incorporated within a polylactic acid (PLA) matrix on viability, distribution, proliferation, and osteogenic differentiation of human adipose stem cells (ASCs). The viability and distribution of ASCs on the bioactive composite scaffolds was evaluated using Live/Dead fluorescence staining, environmental scanning electron microscopy, and scanning electron microscopy. There were no differences between the two concentrations of bioactive glass and beta-TCP in PLA scaffolds on proliferation and osteogenic differentiation of ASCs. After 2 weeks of culture, DNA content and alkaline phosphatase (ALP) activity of ASCs cultured on PLA/beta-TCP composite scaffolds were higher relative to other scaffold types. Interestingly, the cell number was significantly lower, but the relative ALP/DNA ratio of ASCs was significantly higher in PLA/bioactive glass scaffolds than in other three scaffold types. These results indicate that the PLA/beta-TCP composite scaffolds significantly enhance ASC proliferation and total ALP activity compared to other scaffold types. This supports the potential future use of PLA/beta-TCP composites as effective scaffolds for tissue engineering and as bone replacement materials.

  11. Homocomposites of Polylactide (PLA) with Induced Interfacial Stereocomplex Crystallites

    PubMed Central

    2015-01-01

    The demand for “green” degradable composite materials increases with growing environmental awareness. The key challenge is achieving the preferred physical properties and maintaining their eco-attributes in terms of the degradability of the matrix and the filler. Herein, we have designed a series of “green” homocomposites materials based purely on polylactide (PLA) polymers with different structures. Film-extruded homocomposites were prepared by melt-blending PLA matrixes (which had different degrees of crystallinity) with PLLA and PLA stereocomplex (SC) particles. The PLLA and SC particles were spherical and with 300–500 nm size. Interfacial crystalline structures in the form of stereocomplexes were obtained for certain particulate-homocomposite formulations. These SC crystallites were found at the particle/matrix interface when adding PLLA particles to a PLA matrix with d-lactide units, as confirmed by XRD and DSC data analyses. For all homocomposites, the PLLA and SC particles acted as nucleating agents and enhanced the crystallization of the PLA matrixes. The SC particles were more rigid and had a higher Young’s modulus compared with the PLLA particles. The mechanical properties of the homocomposites varied with particle size, rigidity, and the interfacial adhesion between the particles and the matrix. An improved tensile strength in the homocomposites was achieved from the interfacial stereocomplex formation. Hereafter, homocomposites with tunable crystalline arrangements and subsequently physical properties, are promising alternatives in strive for eco-composites and by this, creating materials that are completely degradable and sustainable. PMID:26523245

  12. Investigation on thermoformability of PLA by rheological and hot tensile tests

    NASA Astrophysics Data System (ADS)

    Garofalo, Emilia; Iannaccone, Giovanni; Scarfato, Paola; Di Maio, Luciano; Incarnato, Loredana

    2012-07-01

    In this work the correlation between the thermoformability of different grades of polylactide acid (PLA 4032D, PLA 4042D and PLA 2003D) and their mechanical, thermal, and rheological properties was explored. In particular, hot tensile tests, at different stretching temperatures and crosshead speeds, were performed in order to identify an optimum windows of temperature and strain rate for improved thermoforming performance. The properties measured from the creep experiments were correlated with the propensity of PLA sheet to sag, while the unrecovered strains by the creep recovery tests were associated to mold replication attitude of the materials investigated.

  13. Reinforcement of a porous collagen scaffold with surface-activated PLA fibers.

    PubMed

    Liu, Xi; Huang, Changbin; Feng, Yujie; Liang, Jie; Fan, Yujiang; Gu, Zhongwei; Zhang, Xingdong

    2010-01-01

    A hybrid porous collagen scaffold mechanically reinforced with surface-activated poly(lactic acid) (PLA) fiber was prepared. PLA fibers, 20 mum in diameter and 1 mm in length, were aminolyzed with hexanediamine to introduce free amino groups on the surfaces. After the amino groups were transferred to aldehyde groups by treatment with glutaraldehyde, different amounts (1.5, 3, 5 and 8 mg) of surface-activated PLA fibers were homogeneously mixed with 2 ml type-I collagen solution (pH 2.8, 0.6 wt%). This mixture solution was then freeze-dried and cross-linked to obtain collagen sponges with surface-activated PLA fiber. Scanning electron microscopy observation indicated that the collagen sponges had a highly interconnected porous structure with an average pore size of 170 mum, irrespective of PLA fiber incorporation. The dispersion of surface-activated PLA fibers was homogeneous in collagen sponge, in contrast to unactivated PLA fibers. The compression modulus test results showed that, compared with unactivated PLA fibers, the surface-activated PLA fibers enhanced the resistance of collagen sponge to compression more significantly. Cytotoxicity assay by MTT test showed no cytotoxicity of these collagen sponges. L929 mouse fibroblast cell-culture studies in vitro revealed that the number of L929 cells attached to the collagen sponge with surface-activated PLA fibers, both 6 h and 24 h after seeding, was higher than that in pure collagen sponge and sponge with unactivated PLA fibers. In addition, a better distribution of cells infiltrated in collagen sponge with surface-activated PLA fibers was observed by histological staining. These results indicated that the collagen sponge reinforced with surface-activated PLA fibers is a promising biocompatible scaffold for tissue engineering.

  14. Antibacterial performance of alginic acid coating on polyethylene film.

    PubMed

    Karbassi, Elika; Asadinezhad, Ahmad; Lehocký, Marian; Humpolíček, Petr; Vesel, Alenka; Novák, Igor; Sáha, Petr

    2014-08-21

    Alginic acid coated polyethylene films were examined in terms of surface properties and bacteriostatic performance against two most representative bacterial strains, that is, Escherichia coli and Staphylococcus aureus. Microwave plasma treatment followed by brush formation in vapor state from three distinguished precursors (allylalcohol, allylamine, hydroxyethyl methacrylate) was carried out to deposit alginic acid on the substrate. Surface analyses via various techniques established that alginic acid was immobilized onto the surface where grafting (brush) chemistry influenced the amount of alginic acid coated. Moreover, alginic acid was found to be capable of bacterial growth inhibition which itself was significantly affected by the brush type. The polyanionic character of alginic acid as a carbohydrate polymer was assumed to play the pivotal role in antibacterial activity. The cell wall composition of two bacterial strains along with the substrates physicochemical properties accounted for different levels of bacteriostatic performance.

  15. Modeling acid transport in chemically amplified resist films

    NASA Astrophysics Data System (ADS)

    Patil, Abhijit A.; Doxastakis, Manolis; Stein, Gila E.

    2014-03-01

    The acid-catalyzed deprotection of glassy poly(4-hydroxystyrene-co-tert butyl acrylate) films was studied with infrared absorbance spectroscopy and stochastic simulations. Experimental data were interpreted with a simple description of subdiffusive acid transport coupled to second-order acid loss. This model predicts key attributes of observed deprotection rates, such as fast reaction at short times, slow reaction at long times, and a non-linear dependence on acid loading. The degree of anomalous character is reduced by increasing the post-exposure bake temperature or adding plasticizing agents to the polymer resin. These findings indicate that the acid mobility and overall deprotection kinetics are coupled to glassy matrix dynamics. Furthermore, the acid diffusion lengths were calculated from the anomalous transport model and compared with nanopattern line widths. The consistent scaling between experiments and simulations suggests that the anomalous diffusion model could be further developed into a predictive lithography tool.

  16. Influence of the acid type in the production of chitosan films reinforced with bacterial nanocellulose.

    PubMed

    Velásquez-Cock, J; Ramírez, E; Betancourt, S; Putaux, J-L; Osorio, M; Castro, C; Gañán, P; Zuluaga, R

    2014-08-01

    Chitosan films reinforced with bacterial cellulose (BC) nanoribbons were studied to understand the influence of acid (acetic and lactic acids) on the reinforcing effect. For both acids, the maximum concentration of the reinforcing constituent was 5wt% with respect to the dry weight of chitosan. The infrared spectra, mechanical properties, morphology and antimicrobial activity of the films were analyzed. The results showed a difference between the acids in their behavior and effect on the reinforcement, with a tensile strength of 12.3MPa for the acetic acid films and 3.3MPa for the lactic acid films. Additionally, the bacterial inhibition tests were shown to be positive for the lactic acid films and negative for the acetic acid films. Therefore, exchanging the acid used in these films may be desirable for certain applications.

  17. Structure and blood compatibility of highly oriented PLA/MWNTs composites produced by solid hot drawing.

    PubMed

    Li, Zhengqiu; Zhao, Xiaowen; Ye, Lin; Coates, Phil; Caton-Rose, Fin; Martyn, Michasel

    2014-03-01

    Highly oriented poly(lactic acid) (PLA)/multi-walled carbon nanotubes (MWNTs) composites were fabricated through solid hot drawing technology in an effort to improve the mechanical properties and blood biocompatibility of PLA as blood-contacting medical devices. It was found that proper MWNTs content and drawing orientation can improve the tensile strength and modulus of PLA dramatically. With the increase in draw ratio, the cold crystallization peak became smaller, and the glass transition and the melting peak of PLA moved to high temperature, while the crystallinity increased, and the grain size decreased, indicating the stress-induced crystallization of PLA during drawing. MWNTs showed a nucleation effect on PLA, leading to the rise in the melting temperature, increase in crystallinity and reduction of spherulite size for the composites. Moreover, the intensity of (002) diffraction of MWNTs increased with draw ratio, indicating that MWNTs were preferentially aligned and oriented during drawing. Microstructure observation demonstrated that PLA matrix had an ordered fibrillar bundle structure, and MWNTs in the composite tended to align parallel to the drawing direction. In addition, the dispersion of MWNTs in PLA was also improved by orientation. Introduction of MWNTs and drawing orientation could significantly enhance the blood compatibility of PLA by prolonging kinetic clotting time, reducing hemolysis ratio and platelet activation.

  18. Stabilization of PS/PLA cocontinuous blends by interfacial graphene

    NASA Astrophysics Data System (ADS)

    Bai, Lian; He, Siyao; Fruehwirth, John; Stein, Andreas; Cheng, Xiang; Macosko, Christopher

    Reduced graphene oxide (r-GO) is known to be effective in increasing the conductivity of cocontinuous polymer blends with a lower electrical percolation threshold. However, little is known regarding the localization and dynamics of r-GO along with morphology change during annealing. In this study, we develop a facile method to stabilize the polystyrene (PS)/polylactic acid (PLA) cocontinuous blends with r-GO jammed at interface. In this method, the non-functionalized GO is premixed with PLA via solvent method, and then reduced in-situ at 210oC to obtain a PLA/r-GO polymer composite. This composite is further mixed with PS via batch melt compounding. We observe the migration of r-GO from the PLA phase to the interface during annealing. The interfacial r-GO suppresses the coarsening of cocontinuous morphology and increases the conductivity of the filled polymer blend. Moreover, we systematically investigate the relationship between r-GO localization, rheological and conductivity change during annealing of r-GO filled PLA/PS blends. University of Minnesota Industrial Partnership for Research in Interfacial and Materials Engineering (IPRIME).

  19. Electropolymerized Molecularly Imprinted Polypyrrole Film for Sensing of Clofibric Acid

    PubMed Central

    Schweiger, Bianca; Kim, Jungtae; Kim, Young Jun; Ulbricht, Mathias

    2015-01-01

    Piezoelectric quartz crystals and analogous gold substrates were electrochemically coated with molecularly imprinted polypyrrole films for pulsed amperometric detection (PAD) of clofibric acid, a metabolite of clofibrate. Cyclic voltammetry data obtained during polymerization and deposited weight estimations revealed a decrease of the polymerization rate with increasing clofibric acid concentration. XPS measurements indicated that clofibric acid could be removed after imprinting with an aqueous ethanol solution, which was further optimized by using PAD. Zeta potential and contact angle measurements revealed differences between molecularly imprinted (MIP) and non-imprinted polymer (NIP) layers. Binding experiments with clofibric acid and other substances showed a pronounced selectivity of the MIP for clofibric acid vs. carbamazepine, but the response of MIP and NIP to 2,4-dichlorophenoxyacetic acid was higher than that for clofibric acid. A smooth surface, revealed by AFM measurements, with roughness of 6–8 nm for imprinted and non-imprinted layers, might be a reason for an excessively low density of specific binding sites for clofibric acid. Furthermore, the decreased polymerization rate in the presence of clofibric acid might not result in well-defined polymer structures, which could be the reason for the lower sensitivity. PMID:25730487

  20. 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.

  1. Wettability Effect of PECVD-SiOx Films on Poly(lactic acid) Induced by Oxygen Plasma on Protein Adsorption and Cell Attachment

    NASA Astrophysics Data System (ADS)

    Sarapirom, S.; Lee, J. S.; Jin, S. B.; Song, D. H.; Yu, L. D.; Han, J. G.; Chaiwong, C.

    2013-04-01

    Surface wettability is an important property of biomaterials. Silicon oxide films have a wide range of applications due to a range of the properties such as the mechanical strength and surface wettability. This paper reports effect of the surface wettability of silicon oxide (SiOx) films on protein adsorption and cell attachment and proliferation. SiOx films were deposited onto poly(lactic acid) (PLA) substrate using plasma enhanced chemical vapor deposition (PECVD). Octamethylcyclotetrasiloxane (OMCTS:Si4O4C8H24) was used as a precursor with O2 as a carrier gas. After deposition, the films were treated with O2-plasma to adapt wettability. It was found that O2-plasma enhanced the wettability of the films without changing the film thickness, while made the surface morphology slightly smoother. The polar component increased after O2-plasma treatment as observed in the contact angle measurements. The surface energy of the films was calculated by means of the Owens-Wendt method to resolve the contributions of polar and dispersive components. The chemical structure was characterized using attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy. The films were dense with a high Si-network structure. The reduced carbon content (-CHn, Si-CH3) and increased hydrogen content (-OH) of the O2-plasma treated SiOx films led to the polar components enhancing the SiOx wettability. Adsorption of bovine serum albumin (BSA) on the films was investigated by using x-ray photoelectron spectroscopy (XPS). More BSA was adsorbed onto the O2-plasma treated SiOx films. Attachment and proliferation of MC3T3-E1 mouse pre-osteoblasts and L929 mouse fibroblasts cells on the SiOx films were evaluated via MTT assay. The cells were attached more to the untreated SiOx films but proliferated more on the surface of the O2-plasma treated SiOx films depending on the cell types.

  2. Effect of Heat Sealing Temperature on Mechanical Properties and Molecular Structure at Heat-Sealed Parts of Polylactic Acid Film —Part II

    NASA Astrophysics Data System (ADS)

    Hashimoto, Yumi; Hashimoto, Yasuo; Tsujii, Tetsuya; Morimoto, Mitsuhiko; Kotaki, Masaya; Hamada, Hiroyuki

    Actual failure accidents of plastic bags often occur at the pin-hole and/or the crack, and also the edge that is just outside of the heat-sealed part becomes the failure initiation point. In this study, fracture mechanics tests and tear tests were performed to understand the resistance of heat-sealed parts and edge parts to introduced cracks. The fracture resistance and tear strength of the edge part was lower than that of the heat-sealed part, which was more obvious at higher heat sealing temperature. The optimum heat sealing temperature to obtain the balanced properties of heat-sealed polylactic acid (PLA) films was found to be 130°C.

  3. Poly(L-lactic acid) membranes: absence of genotoxic hazard and potential for drug delivery.

    PubMed

    Uzun, Nelson; Martins, Thomás Duzzi; Teixeira, Gabriella Machado; Cunha, Nayanne Larissa; Oliveira, Rogério Belle; Nassar, Eduardo José; Dos Santos, Raquel Alves

    2015-01-22

    The use of poly(L-lactic acid) (PLA) has been considered an important alternative for medical devices once this polyester presents biomechanical, optical and biodegradable properties. Moreover, the use of PLA results in less inflammatory reactions and more recently it has been proposed its application in drug delivery systems. Genotoxicological evaluations are considered part of the battery assays in toxicological analysis. Considering the wide applications of PLA, the present work evaluated the potential cytotoxic and genotoxic effects of PLA in CHO-K1 cells, as well as its physicochemical properties. No cytotoxic effects of PLA were detected by colorimetric tetrazolium assay (XTT) analysis, and the clonogenic survival assay showed that PLA did not disrupt the replicative cell homeostasis, neither exhibited genotoxic effects as evidenced by comet and micronucleus assays. Thermogravimetric properties of PLA were not altered after contact with cells and this film exhibited ability in absorb and release Europium(III) complex. All these data suggest genotoxicological safety of PLA for further applications in drug delivery systems.

  4. Mechanical, thermal and morphological properties of poly(lactic acid)/epoxidized palm olein blend.

    PubMed

    Silverajah, V S Giita; Ibrahim, Nor Azowa; Zainuddin, Norhazlin; Yunus, Wan Md Zin Wan; Hassan, Hazimah Abu

    2012-10-08

    Poly(lactic acid) (PLA) is known to be a useful material in substituting the conventional petroleum-based polymer used in packaging, due to its biodegradability and high mechanical strength. Despite the excellent properties of PLA, low flexibility has limited the application of this material. Thus, epoxidized palm olein (EPO) was incorporated into PLA at different loadings (1, 2, 3, 4 and 5 wt%) through the melt blending technique and the product was characterized. The addition of EPO resulted in a decrease in glass transition temperature and an increase of elongation-at-break, which indicates an increase in the PLA chain mobility. PLA/EPO blends also exhibited higher thermal stability than neat PLA. Further, the PLA/1 wt% EPO blend showed enhancement in the tensile, flexural and impact properties. This is due to improved interaction in the blend producing good compatible morphologies, which can be revealed by Scanning Electron Microscopy (SEM) analysis. Therefore, PLA can be efficiently plasticized by EPO and the feasibility of its use as flexible film for food packaging should be considered.

  5. Photoresponsive Wettability in Monolayer Films from Sinapinic Acid

    PubMed Central

    Moura, Cleverson A. S.; Gomes, Douglas J. C.; de Souza, Nara C.; Silva, Josmary R.

    2013-01-01

    Sinapinic acid is an interesting material because it is both antioxidant and antibacterial agent. In addition, when illuminated with ultraviolet light, it can exhibit the so-called photodimerization process. In this paper, we report on the investigation of monolayer films from 3,5-dimethoxy-4-hydroxycinnamic acid (sinapinic acid, SinA) deposited onto poly(allylamine hydrochloride), PAH, films. SinA monolayers were prepared by using the layer-by-layer (LbL) self-assembly technique. Adsorption kinetics curves were well fitted by a biexponential function suggesting that the adsorption process is determined by two mechanisms: nucleation and growth of aggregates. By using wetting contact angle analysis, we have found that SinA monolayers exhibit photoresponsive wettability under UV irradiation (365 nm); that is, wettability decreases with increasing UV irradiation time. The photoresponse of wettability was attributed to photodimerization process. This hypothesis was supported by the dependence of surface morphological structure and absorption on UV irradiation time. The mechanism found in the well-known transcinnamic acid crystals is used to explain the photodimerization process in SinA monolayers. PMID:24302879

  6. Synthesis, characterization, and biocompatibility of alternating block polyurethanes based on PLA and PEG.

    PubMed

    Mei, Tingzhen; Zhu, Yonghe; Ma, Tongcui; He, Tao; Li, Linjing; Wei, Chiju; Xu, Kaitian

    2014-09-01

    A series of alternating block polyurethanes (abbreviated as PULA-alt-PEG) and random block polyurethanes (abbreviated as PULA-ran-PEG) based on poly(L-lactic acid) (PLA) and poly(ethylene glycol) (PEG) were synthesized. The differences of PULA-alt/ran-PEG chemical structure, molecular weight, distribution, thermal properties, mechanical properties and static contact angle were systematically investigated. The PULA-alt/ran-PEG polyurethanes exhibited low T(g) (-47.3 ∼ -34.4°C), wide mechanical properties (stress σ(t): 4.6-32.6 MPa, modulus E: 11.4-323.9 MPa and strain ε: 468-1530%) and low water contact angle (35.4-51.4°). Scanning electron microscope (SEM) observation showed that PULA-alt-PEG film displays rougher and more patterned surface morphology than PULA-ran-PEG does, due to more regular structures of PULA-alt-PEG. Hydrolytic degradation shows that degradation rate of random block polyurethane series PULA-ran-PEG is higher than the alternating counterpart PULA-alt-PEG. PLA segment degradation is faster than urethane linkage and PEG segment almost does not degrade in the buffer solution. Platelet adhesion study showed that all the polyurethanes possess excellent hemocompatibility. The cell culture assay revealed that PULA-alt/ran-PEG polyurethanes were cell inert and unfavorable for the attachment of rat glial cell due to the hydrophilic characters of the materials.

  7. Interaction between a high purity magnesium surface and PCL and PLA coatings during dynamic degradation.

    PubMed

    Chen, Ying; Song, Yang; Zhang, Shaoxiang; Li, Jianan; Zhao, Changli; Zhang, Xiaonong

    2011-04-01

    In this study, polycaprolactone (PCL) and polylactic acid (PLA) coatings were prepared on the surface of high purity magnesium (HPMs), respectively, and electrochemical and dynamic degradation tests were used to investigate the degradation behaviors of these polymer-coated HPMs. The experimental results indicated that two uniform and smooth polymer films with thicknesses between 15 and 20 µm were successfully prepared on the HPMs. Electrochemical tests showed that both PCL-coated and PLA-coated HPMs had higher free corrosion potentials (E(corr)) and smaller corrosion currents (I(corr)) in the modified simulated body fluid (m-SBF) at 37 °C, compared to those of the uncoated HPMs. Dynamic degradation tests simulating the flow conditions in coronary arteries were carried out on a specific test platform. The weight of the specimens and the pH over the tests were recorded to characterize the corrosion performance of those samples. The surfaces of the specimens after the dynamic degradation tests were also examined. The data implied that there was a special interaction between HPM and its polymer coatings during the dynamic degradation tests, which undermined the corrosion resistance of the coated HPMs. A model was proposed to illustrate the interaction between the polymer coatings and HPM. This study also suggested that this reciprocity may also exist on the implanted magnesium stents coated with biodegradable polymers, which is a potential obstacle for the further development of drug-eluting magnesium stents.

  8. Electrophoretic deposition of tannic acid-polypyrrolidone films and composites.

    PubMed

    Luo, Dan; Zhang, Tianshi; Zhitomirsky, Igor

    2016-05-01

    Thin films of polyvinylpyrrolidone (PVP)-tannic acid (TA) complexes were prepared by a conceptually new strategy, based on electrophoretic deposition (EPD). Proof of concept investigations involved the analysis of the deposition yield, FTIR and UV-vis spectroscopy of the deposited material, and electron microscopy studies. The analysis of the deposition mechanism indicated that the limitations of the EPD in the deposition of small phenolic molecules, such as TA, and electrically neutral polymers, similar to PVP, containing hydrogen-accepting carbonyl groups, can be avoided. The remarkable adsorption properties of TA and film forming properties of the PVP-TA complexes allowed for the EPD of materials of different types, such as huntite mineral platelets and hydrotalcite clay particles, TiO2 and MnO2 oxide nanoparticles, multiwalled carbon nanotubes, TiN and Pd nanoparticles. Moreover, PVP-TA complexes were used for the co-deposition of different materials and formation of composite films. In another approach, TA was used as a capping agent for the hydrothermal synthesis of ZnO nanorods, which were then deposited by EPD using PVP-TA complexes. The fundamental adsorption and interaction mechanisms of TA involved chelation of metal atoms on particle surfaces with galloyl groups, π-π interactions and hydrogen bonding. The films prepared by EPD can be used for various applications, utilizing functional properties of TA, PVP, inorganic and organic materials of different types and their composites.

  9. Development of pectin films with pomegranate juice and citric acid.

    PubMed

    Azeredo, Henriette M C; Morrugares-Carmona, Rosario; Wellner, Nikolaus; Cross, Kathryn; Bajka, Balazs; Waldron, Keith W

    2016-05-01

    The influence of pomegranate juice (PJ, replacing water as solvent) and citric acid (CA) on properties of pectin films was studied. PJ provided the films with a bright red color, and acted as a plasticizer. Increasing PJ/water ratio from 0/100 to 100/0 resulted in enhanced elongation (from 2% to 20%), decreased strength (from 10 to <2 MPa) and modulus (from 93 to <10 MPa), increased water vapor permeability (WVP, from 3 to 9 g.mm.kPa(-1).h(-1).m(-2)), and decreased insoluble matter (IM, from 35% to 24%). Although a crosslinking effect by CA was not confirmed, it has been suggested to occur from its effects on films. CA noticeably increased IM (from <10% to almost 40%); moreover, when measured on a dry film basis, the CA effects presented a noticeable tendency to increases strength and modulus, and to decrease WVP. The red color density was decreased by CA, suggesting a destabilization of anthocyanins.

  10. Effect of Gallic acid on mechanical and water barrier properties of zein-oleic acid composite films.

    PubMed

    Masamba, Kingsley; Li, Yue; Hategekimana, Joseph; Liu, Fei; Ma, Jianguo; Zhong, Fang

    2016-05-01

    In this study, the effect of gallic acid on mechanical and water barrier properties of zein-oleic acid 0-4 % composite films was investigated. Molecular weight distribution analysis was carried out to confirm gallic acid induced cross linking through change in molecular weight in fraction containing zein proteins. Results revealed that gallic acid treatment increased tensile strength from 17.9 MPa to 26.0 MPa, decreased water vapour permeability from 0.60 (g mm m(-2) h(-1) kPa(-1)) to 0.41 (g mm m(-2) h(-1) kPa(-1)), increased solubility from 6.3 % to 10.2 % and marginally increased elongation at break from 3.7 % to 4.2 % in zein films only. However, gallic acid treatment in zein-oleic composite films did not significantly influence mechanical and water barrier properties and in most instances irrespective of oleic acid concentration, the properties were negatively affected. Results from scanning electron microscopy showed that both gallic acid treated and untreated zein films and composite films containing 3 % oleic acid had a compact and homogeneous structure while those containing 4 % oleic acid had inhomogeneous structure. The findings have demonstrated that gallic acid treatment can significantly improve mechanical and water barrier properties especially in zein films only as opposed to when used in composite films using zein and oleic acid.

  11. Fabrication of novel PLA/CDHA bionanocomposite fibers for tissue engineering applications via electrospinning.

    PubMed

    Zhou, Huan; Touny, Ahmed H; Bhaduri, Sarit B

    2011-05-01

    The main theme here is to fabricate PLA (poly lactic-acid)/CDHA (carbonated calcium deficient hydroxyapatite) bionanocomposites, where both the constituents are biocompatible and biodegradable with one dimension in nanometer scale. Such materials are important in tissue engineering applications. The bionanocomposite fibers were fabricated via electrospinning. There are two important signatures of this paper. First, CDHA, rather than HA, is added to PLA as the second phase. As opposed to HA, CDHA mimics the bone mineral composition better and is biodegradable. Therefore, PLA/CDHA fibers should have better biodegradability while maintaining a physiological pH during degradation. To the best of our knowledge, this is the first attempt of electrospinning of such a composite. Second, the CDHA nanoparticles were synthesized using the benign low temperature biomimetic technique, the only route available for the retention of carbonate ions in the HA lattice. The structural properties, degradation behavior, bioactivity, cell adhesion, and growth capability of as-fabricated PLA/CDHA bionanocomposites were investigated. The results show that the incorporation of CDHA decreased PLA fiber diameters, accelerated PLA degradation, buffered pH decrease caused by PLA degradation, improved the bioactivity and biocompatibility of the scaffold. These results prove that PLA/CDHA bionanocomposites have the potential in tissue regeneration applications.

  12. Loss of PLA2G6 leads to elevated mitochondrial lipid peroxidation and mitochondrial dysfunction

    PubMed Central

    Castillo-Quan, Jorge Iván; Bartolome, Fernando; Angelova, Plamena R.; Li, Li; Pope, Simon; Cochemé, Helena M.; Khan, Shabana; Asghari, Shabnam; Bhatia, Kailash P.; Hardy, John; Abramov, Andrey Y.; Partridge, Linda

    2015-01-01

    The PLA2G6 gene encodes a group VIA calcium-independent phospholipase A2 beta enzyme that selectively hydrolyses glycerophospholipids to release free fatty acids. Mutations in PLA2G6 have been associated with disorders such as infantile neuroaxonal dystrophy, neurodegeneration with brain iron accumulation type II and Karak syndrome. More recently, PLA2G6 was identified as the causative gene in a subgroup of patients with autosomal recessive early-onset dystonia-parkinsonism. Neuropathological examination revealed widespread Lewy body pathology and the accumulation of hyperphosphorylated tau, supporting a link between PLA2G6 mutations and parkinsonian disorders. Here we show that knockout of the Drosophila homologue of the PLA2G6 gene, iPLA2-VIA, results in reduced survival, locomotor deficits and organismal hypersensitivity to oxidative stress. Furthermore, we demonstrate that loss of iPLA2-VIA function leads to a number of mitochondrial abnormalities, including mitochondrial respiratory chain dysfunction, reduced ATP synthesis and abnormal mitochondrial morphology. Moreover, we show that loss of iPLA2-VIA is strongly associated with increased lipid peroxidation levels. We confirmed our findings using cultured fibroblasts taken from two patients with mutations in the PLA2G6 gene. Similar abnormalities were seen including elevated mitochondrial lipid peroxidation and mitochondrial membrane defects, as well as raised levels of cytoplasmic and mitochondrial reactive oxygen species. Finally, we demonstrated that deuterated polyunsaturated fatty acids, which inhibit lipid peroxidation, were able to partially rescue the locomotor abnormalities seen in aged flies lacking iPLA2-VIA gene function, and restore mitochondrial membrane potential in fibroblasts from patients with PLA2G6 mutations. Taken together, our findings demonstrate that loss of normal PLA2G6 gene activity leads to lipid peroxidation, mitochondrial dysfunction and subsequent mitochondrial membrane

  13. Cell patterning on polylactic acid through surface-tethered oligonucleotides.

    PubMed

    Matsui, Toshiki; Arima, Yusuke; Takemoto, Naohiro; Iwata, Hiroo

    2015-02-01

    Polylactic acid (PLA) is a candidate material to prepare scaffolds for 3-D tissue regeneration. However, cells do not adhere or proliferate well on the surface of PLA because it is hydrophobic. We report a simple and rapid method for inducing cell adhesion to PLA through DNA hybridization. Single-stranded DNA (ssDNA) conjugated to poly(ethylene glycol) (PEG) and to a terminal phospholipid (ssDNA-PEG-lipid) was used for cell surface modification. Through DNA hybridization, modified cells were able to attach to PLA surfaces modified with complementary sequence (ssDNA'). Different cell types can be attached to PLA fibers and films in a spatially controlled manner by using ssDNAs with different sequences. In addition, they proliferate well in a culture medium supplemented with fetal bovine serum. The coexisting modes of cell adhesion through DNA hybridization and natural cytoskeletal adhesion machinery revealed no serious effects on cell growth. The combination of a 3-D scaffold made of PLA and cell immobilization on the PLA scaffold through DNA hybridization will be useful for the preparation of 3-D tissue and organs.

  14. Effect of carboxylic acid on sintering of inkjet-printed copper nanoparticulate films.

    PubMed

    Woo, Kyoohee; Kim, Youngwoo; Lee, Byungyoon; Kim, Jonghee; Moon, Jooho

    2011-07-01

    The reduction effect of various carboxylic acids on inkjet-printed copper film was investigated. Carboxylic acids were exposed to the film by nitrogen gas that was bubbled through the liquid acids during the annealing process. It was observed that in the case of saturated monocarboxylic acid (formic, acetic, propionic, butyric), the acids with shorter hydrocarbon chains perform better in reducing the surface copper oxides in the printed copper conductive film. The printed films exposed to formic acid vapor exhibited the lowest resistivity (3.10 and 2.30 μΩ cm when annealed at 200 and 250 °C, respectively). In addition, the oxalic acid more effectively reduces copper oxide than formic acid and its usage can shorten the annealing time for highly conductive printed copper film. This reductive annealing process allows fabrication of copper patterns with low resistivity, (3.82 μΩ cm annealed at 250 °C) comparable to the resistivity of bulk copper.

  15. Protection of NdFeB magnets by corrosion resistance phytic acid conversion film

    NASA Astrophysics Data System (ADS)

    Nan, Haiyang; Zhu, Liqun; Liu, Huicong; Li, Weiping

    2015-11-01

    Phytic acid conversion film was prepared on NdFeB magnets by dipping the NdFeB into phytic acid solution. The morphology, composition, structure and corrosion resistance of the film were systematically investigated. The results showed that the phytic acid film was effective in improving the corrosion resistance of NdFeB magnets. XRD, TEM and FT-IR analyses revealed that the film was amorphous and had a strong peak of phosphate radical (PO43-). The formation mechanism of the film was also explored by XPS and the potential of zero charge (Epzc) measurement at the solution-metal interface.

  16. Use of Gallic Acid to Enhance the Antioxidant and Mechanical Properties of Active Fish Gelatin Film.

    PubMed

    Limpisophon, Kanokrat; Schleining, Gerhard

    2017-01-01

    This study explores the potential roles of gallic acid in fish gelatin film for improving mechanical properties, UV barrier, and providing antioxidant activities. Glycerol, a common used plasticizer, also impacts on mechanical properties of the film. A factorial design was used to investigate the effects of gallic acid and glycerol concentrations on antioxidant activities and mechanical properties of fish gelatin film. Increasing the amount of gallic acid increased the antioxidant capacities of the film measured by radical scavenging assay and the ferric reducing ability of plasma assay. The released antioxidant power of gallic acid from the film was not reduced by glycerol. The presence of gallic acid not only increased the antioxidant capacity of the film, but also increased the tensile strength, elongation at break, and reduced UV absorption due to interaction between gallic acid and protein by hydrogen bonding. Glycerol did not affect the antioxidant capacities of the film, but increased the elasticity of the films. Overall, this study revealed that gallic acid entrapped in the fish gelatin film provided antioxidant activities and improved film characteristics, namely UV barrier, strength, and elasticity of the film.

  17. P9a(Cdt-PLA2) from Crotalus durissus terrificus as good immunogen to be employed in the production of crotalic anti-PLA2 IgG.

    PubMed

    Fusco, Luciano S; Rodríguez, Juan Pablo; Torres-Huaco, Frank; Huancahuire-Vega, Salomón; Teibler, Pamela; Acosta, Ofelia; Marangoni, Sergio; Ponce-Soto, Luis Alberto; Leiva, Laura C

    2015-10-01

    Four proteins with phospholipase A2 (PLA2) activity, designated P9a(Cdt-PLA2), P9b(Cdt-PLA2), P10a(Cdt-PLA2) and P10b(Cdt-PLA2) were purified from the venom of Crotalus durissus terrificus by two chromatographic steps: a gel filtration and reversed phase HPLC. The profile obtained clearly shows that three of them have a similar abundance. The molecular mass, 14193.8340Da for P9a(Cdt-PLA2), 14134.9102Da for P9b(Cdt-PLA2), 14242.6289Da for P10a(Cdt-PLA2) and 14183.8730Da for P10b(Cdt-PLA2), were initially evaluated by SDS-PAGE and confirmed by ESI-Q-TOF spectrometry, and all of them displayed a monomeric conformation. Also, partial amino acid sequence of each protein was obtained and their alignments with other crotalic PLA2 revealed a high degree of identity among them. Additionally, we studied some pharmacological activities like neurotoxicity, myotoxicity and lethality, which prompted us to pick two of them, P9a(Cdt-PLA2) and P10a(Cdt-PLA2) that resulted to be less toxic that the others, and further characterize them to be used as immunogen. We next injected these last proteins in mice to produce antitoxins against them and ELISA and dot blots reveled that both toxins do not show immunogenic differences, unlike those other pharmacologic activities tested. Furthermore, the antibodies produced cross-reacted with all the isoforms purified demonstrating the feasibility of using only one of them and ensuring the cross-reaction of all. The results obtained show that P9a(Cdt-PLA2) isoform has the lowest toxicity and also a good purification performance; thus this protein may be a promising candidate to be employed in the production of crotalic antitoxins.

  18. Synthesis and characterization of mPEG-PLA prodrug micelles.

    PubMed

    Hans, Meredith; Shimoni, Karin; Danino, Dganit; Siegel, Steven J; Lowman, Anthony

    2005-01-01

    Polymeric prodrugs of mPEG-PLA-haloperidol (methoxypoly(ethylene glycol)-b-poly(lactic acid)) can self-assemble into nanoscale micelle-like structures in aqueous solutions. mPEG-PLA-haloperidol was prepared and characterized using 1H and 13C NMR. The conjugation efficiency was found to be 64.8 +/- 21%. Micelles that form spontaneously upon solubilization of the mPEG-PLA and the polymeric prodrugs in water were characterized using a variety of techniques. The mPEG-PLA and prodrug micelles were found to have diameters of 28.73 +/- 1.45 and 49.67 +/- 4.29 nm, respectively, using dynamic light scattering (DLS). The micelle size and polydispersity were also evaluated with cryogenic transmission electron microscopy (cryo-TEM) and were consistent with the DLS results. Cryo-TEM and proton NMR confirmed that the micelles were spherical in shape. DLS was also used to determine the aggregation numbers of the micelles. The aggregation numbers ranged from 351 to 603. The change in aggregation number was dependent on the total drug incorporation into the micelle core. Critical micelle concentrations were determined for the various micelle/drug formulations and found to range from 3 to 14 microg/mL. Finally, drug was incorporated into the micelle core using the conjugate, free drug with a saturated aqueous phase during production, or a combination of both techniques. Drug incorporation could be increased from 3% to 20% (w/w) using the different formulations.

  19. Effect of hydrolysed cellulose nanowhiskers on properties of montmorillonite/polylactic acid nanocomposites.

    PubMed

    Arjmandi, Reza; Hassan, Azman; Haafiz, M K M; Zakaria, Zainoha; Islam, Md Saiful

    2016-01-01

    Polylactic acid (PLA) nanocomposites reinforced with hybrid montmorillonite/cellulose nanowhiskers [MMT/CNW(SO4)] were prepared by solution casting. The CNW(SO4) nanofiller was first isolated from microcrystalline cellulose using acid hydrolysis treatment. PLA/MMT/CNW(SO4) hybrid nanocomposites were prepared by the addition of various amounts of CNW(SO4) [1-9 parts per hundred parts of polymer (phr)] into PLA/MMT nanocomposite at 5 phr MMT content, based on highest tensile strength values as reported previously. The biodegradability, thermal, tensile, morphological, water absorption and transparency properties of PLA/MMT/CNW(SO4) hybrid nanocomposites were investigated. The Biodegradability, thermal stability and crystallinity of hybrid nanocomposites increased compared to PLA/MMT nanocomposite and neat PLA. The highest tensile strength of hybrid nanocomposites was obtained by incorporating 1 phr CNW(SO4) [∼ 36 MPa]. Interestingly, the ductility of hybrid nanocomposites increased significantly by 87% at this formulation. The Young's modulus increased linearly with increasing CNW(SO4) content. This is due to the relatively good dispersion of nanofillers in the hybrid nanocomposites, as revealed by transmission electron microscopy. Fourier transform infrared spectroscopy indicated the formation of some polar interactions. In addition, water resistance of the hybrid nanocomposites improved and the visual transparency of neat PLA film did not affect by addition of CNW(SO4).

  20. Preparation of flexible PLA/PEG-POSS nanocomposites by melt blending and radiation crosslinking

    NASA Astrophysics Data System (ADS)

    Jung, Chang-Hee; Hwang, In-Tae; Jung, Chan-Hee; Choi, Jae-Hak

    2014-09-01

    In this study, poly(lactic acid) (PLA)/poly(ethylene glycol)-functionalized polyhedral oligomeric silsesquioxane (PEG-POSS) nanocomposites with or without triallyl isocyanurate (TAIC) were investigated by melt blending and electron beam irradiation to enhance the flexibility of PLA. Based on the results of the crosslinking degree measurements, the PLA/PEG-POSS nanocomposites were crosslinked by electron beam irradiation in the presence of triallyl isocyanurate (TAIC) and their crosslinking degree reached up to 80% based on the absorbed dose and their compositions. From the results of the FE-SEM and EDX Si-mapping, the crosslinked PLA/PEG-POSS nanocomposites were homogenous without a micro-phase separation or radiation-induced morphological change. Based on the results of the tensile test, the PLA/PEG-POSS nanocomposites containing 15 wt% PEG-POSS exhibited the highest flexibility, and their tensile strength showed a maximum value of 44.5 MPa after electron beam irradiation at an absorbed dose of 100 kGy in the presence of TAIC, which is comparable to non-biodegradable polypropylene. The results of the dynamic mechanical analysis revealed that the crosslinked PLA/PEG-POSS nanocomposites exhibited a higher thermal resistance above their melting temperature in comparison to that of the neat PLA, although their glass transition temperature was lower than that of the neat PLA. The enzymatic biodegradation test revealed that the PLA/PEG-POSS nanocomposites were biodegradable even though their biodegradability was deteriorated in comparison to that of the neat PLA.

  1. Heterologous expression, and biochemical and cellular characterization of CaPLA1 encoding a hot pepper phospholipase A1 homolog.

    PubMed

    Seo, Young Sam; Kim, Eun Yu; Mang, Hyung Gon; Kim, Woo Taek

    2008-03-01

    Phospholipid signaling has been recently implicated in diverse cellular processes in higher plants. We identified a cDNA encoding the phospholipase A1 homolog (CaPLA1) from 5-day-old early roots of hot pepper. The deduced amino acid sequence showed that the lipase-specific catalytic triad is well conserved in CaPLA1. In vitro lipase assays and site-directed mutagenesis revealed that CaPLA1 possesses PLA1 activity, which catalyzes the hydrolysis of phospholipids at the sn-1 position. CaPLA1 was selectively expressed in young roots, at days 4-5 after germination, and rapidly declined thereafter, suggesting that the expression of CaPLA1 is subject to control by a development-specific mechanism in roots. Because transgenic work was extremely difficult in hot peppers, in this study we overexpressed CaPLA1 in Arabidopsis so as to provide cellular information on the function of this gene. CaPLA1 overexpressors had significantly longer roots, leaves and petioles, and grew more rapidly than the wild-type plants, leading to an early bolting phenotype with prolonged inflorescence. Microscopic analysis showed that the vegetative tissues of 35S:CaPLA1 plants contained an increased number of small-sized cells, which resulted in highly populated cell layers. In addition, mRNAs for cell cycle-controlled proteins and fatty acid catabolizing enzymes were coordinately upregulated in CaPLA1-overexpressing plants. These results suggest that CaPLA1 is functionally relevant in heterologous Arabidopsis cells, and hence might participate in a subset of positive control mechanisms of cell and tissue growth in transgenic lines. We discuss possible biochemical and cellular functions of CaPLA1 in relation to the phospholipid signaling pathway in hot pepper and transgenic Arabidopsis plants.

  2. The Effects of plasticizers and palmitic acid toward the properties of the carrageenan Film

    NASA Astrophysics Data System (ADS)

    Heru Wibowo, Atmanto; Listiyawati, Oktaviana; Purnawan, Candra

    2016-02-01

    Varied plasticizers and palmitic acid additive have been added in the carrageenan film. The film was made by mixing of the carrageenan and plasticizers (glycerol, polyethylene glycol, polyvinyl alcohol) with composition of 92:3, 90:6, 87:9, 84:12, 81:15(%w/w) and in the presence of palmitic acid as additive with 1%, 2%, 3%, 4%, 5% of total weight. Casting method was used for the film molding and drying at 60oC with the oven for 12 hours. To investigate the effects of plasticizers and additive, some mechanical tests on film were performed. The test result concludes that plasticizers in the film decreased the tensile strength and increased the elongation break of the carrageenan film. The additive of palmitic acid decreased the tensile strength of the carrageenan film and also decreased the-the water absorbance of the film. The highest tensile strength of films made was with the formulation of carrageenan: PEG with composition of 92:3 (% w/w). The highest elongation break of the film was for carrageenan:PVA with the composition of 81: 15 (%w/w) and carrageenan:palmitic acid:PEG with the composition of 92: 3: 1 (%w/w). The lowest water absorption of the film was achieved for carrageenan:PVA:palmitic acid with the composition of 87: 3: 5 (%w/w).

  3. Synthesis of protein-coated biocompatible methotrexate-loaded PLA-PEG-PLA nanoparticles for breast cancer treatment

    PubMed Central

    Massadeh, Salam; Alaamery, Manal; Al-Qatanani, Shatha; Alarifi, Saqer; Bawazeer, Shahad; Alyafee, Yusra

    2016-01-01

    Background PLA-PEG-PLA triblock polymer nanoparticles are promising tools for targeted dug delivery. The main aim in designing polymeric nanoparticles for drug delivery is achieving a controlled and targeted release of a specific drug at the therapeutically optimal rate and choosing a suitable preparation method to encapsulate the drug efficiently, which depends mainly on the nature of the drug (hydrophilic or hydrophobic). In this study, methotrexate (MTX)-loaded nanoparticles were prepared by the double emulsion method. Method Biodegradable polymer polyethylene glycol-polylactide acid tri-block was used with poly(vinyl alcohol) as emulsifier. The resulting methotrexate polymer nanoparticles were coated with bovine serum albumin in order to improve their biocompatibility. This study focused on particle size distribution, zeta potential, encapsulation efficiency, loading capacity, and in vitro drug release at various concentrations of PVA (0.5%, 1%, 2%, and 3%). Results Reduced particle size of methotrexate-loaded nanoparticles was obtained using lower PVA concentrations. Enhanced encapsulation efficiency and loading capacity was obtained using 1% PVA. FT-IR characterization was conducted for the void polymer nanoparticles and for drug-loaded nanoparticles with methotrexate, and the protein-coated nanoparticles in solid state showed the structure of the plain PEG-PLA and the drug-loaded nanoparticles with methotrexate. The methotrexate-loaded PLA-PEG-PLA nanoparticles have been studied in vitro; the drug release, drug loading, and yield are reported. Conclusion The drug release profile was monitored over a period of 168 hours, and was free of burst effect before the protein coating. The results obtained from this work are promising; this work can be taken further to develop MTX based therapies.

  4. Effects of swelling on the viscoelastic properties of polyester films made from glycerol and glutaric acid

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Viscoelastic properties have been determined for poly(glycerol-co-glutaric acid) films synthesized from Lewis acid-catalyzed polyesterifications. The polymers were prepared by synthesizing polymer gels that were subsequently cured at 125 degrees C to form polymer films. The polymers were evaluated ...

  5. A multivariant study of the absorption properties of poly(glutaric-acid-glycerol) films

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The solvent absorption into the matrix of poly(glutaric acid-glycerol) films made with or without either iminodiacetic acid, sugarcane bagasse, pectin, corn fiber gum or microcrystalline cellulose have been evaluated. The films were incubated in various solvent systems for 24h. The amounts of solve...

  6. Effect of composition ratio on the thermal and physical properties of semicrystalline PLA/PHB-HHx composites.

    PubMed

    Lim, Jung Seop; Park, Ku-il; Chung, Gun Soo; Kim, Jong Hoon

    2013-05-01

    In this study, composites of semicrystalline, biodegradable polylactide (PLA) and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHB-HHx) were prepared by direct melt compounding. The physical and thermal properties of the composites were investigated as a function of the composition ratio. Differential scanning calorimetry analysis indicated that PLA and PHB-HHx formed immiscible composites over the observed range of composition. The crystallization of PLA was gradually suppressed by increasing proportions of PHB-HHx. Dynamic mechanical analysis results confirmed that the innate ductility of PHB-HHX and its inhibiting effect on PLA crystallization improved the stiffness of the composite compared to those of neat PLA. The infrared spectra of the immiscible PLA/PHB-HHx composites at two crystallization temperatures (30 °C, 130 °C) were obtained and presented. At 30 °C, PHB-HHx existed as crystalline domains in the PLA matrix, while, amorphous phase of molten PHB-HHx was diffused within the crystalline phase of PLA at 130 °C. The interaction between PHB-HHX and PLA could not be elucidated from the temperature data. Mechanical tests showed that the addition of PHB-HHx improves ductility of PLA/PHB-HHx composite. Morphological analysis revealed that small proportions of PHB-HHx exhibited less tendency to aggregate, which resulted in greater plastic deformation and improved toughness. From this study, PLA blended with small portions of PHB-HHx may further expand the use of bio-friendly resources in a variety of applications such as flexible films, food packaging and something like that.

  7. Impact of acid and oxidative modifications, single or dual, of sorghum starch on biodegradable films.

    PubMed

    Biduski, Bárbara; Silva, Francine Tavares da; Silva, Wyller Max da; Halal, Shanise Lisie de Mello El; Pinto, Vania Zanella; Dias, Alvaro Renato Guerra; Zavareze, Elessandra da Rosa

    2017-01-01

    The objective of this study was to evaluate the effects of acid and oxidation modifications on sorghum starch, as well as the effect of dual modification of starch on the physical, morphological, mechanical, and barrier properties of biodegradable films. The acid modification was performed with 3% lactic acid and the oxidation was performed with 1.5% active chlorine. For dual modification, the acid modification was performed first, followed by oxidation under the same conditions as above. Both films of the oxidized starches, single and dual, had increased stiffness, providing a higher tensile strength and lower elongation when compared to films based on native and single acid modified starches. However, the dual modification increased the water vapor permeability of the films without changing their solubility. The increase in sorghum starch concentration in the filmogenic solution increased the thickness, water vapor permeability, and elongation of the films.

  8. Characterization of rice starch-ι-carrageenan biodegradable edible film. Effect of stearic acid on the film properties.

    PubMed

    Thakur, Rahul; Saberi, Bahareh; Pristijono, Penta; Golding, John; Stathopoulos, Costas; Scarlett, Christopher; Bowyer, Michael; Vuong, Quan

    2016-12-01

    The main aim of this study was to develop rice starch (RS), ι-carrageenan (ι-car) based film. Different formulations of RS (1-4%, w/w), ι-car (0.5-2%, w/w) was blended with stearic acid (SA; 0.3-0.9%, w/w) and glycerol (1%, w/w) as a plasticizer. The effect of film ingredients on the thickness, water vapour permeability (WVP), film solubility (FS), moisture content (MC), colour, film opacity (FO), tensile strength (TS), elongation-at-break (EAB) of film was examined. Interactions and miscibility of partaking components was studied by using Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). Hydrocolloid suspension solution of mix polysaccharides imparted a significant impact (p<0.05) on the important attributes of resulting edible film. TS and EAB of film were improved significantly (p<0.05) when ι-car was increased in the film matrix. Formulation F1 comprising 2% ι-car, 2% RS, 0.3% SA, Gly 30% w/w and 0.2% surfactant (tween(®)20) provided film with good physical, mechanical and barrier properties. FT-IR and XRD results reveal that molecular interactions between RS-ι-car have a great impact on the film properties confining the compatibility and miscibility of mixed polysaccharide. Results of the study offers new biodegradable formulation for application on fruit and vegetables.

  9. Effect of reactive agent and transesterification catalyst on properties of PLA/PBAT blends

    NASA Astrophysics Data System (ADS)

    Pitivut, S.; Suttiruengwong, S.; Seadan, M.

    2015-07-01

    This research aimed to study the properties of poly (lactic acid) (PLA)/poly (butylene adipate-co-terephthalate) (PBAT) blends with two different reactive systems: free radical reaction through peroxide (Perkadox) and transesterification catalyst (tetrabutyl titanate; TBT). Two blends composed of PLA as a matrix phase with the composition of 80 and 70 percent by weight. PLA/PBAT blends with Perkadox were prepared in twin screw extruder, whereas PLA/PBAT blends with TBT were prepared in an internal mixer. The morphology of the blends was investigated by scanning electron microscope (SEM). Tensile and impact testingsof the blends were reported. In case of the blends with Perkadox, SEM micrographs revealed that the size of particles was substantially reduced when adding more Perkadox. Young's modulus and the tensile strength of all blend ratios were insignificantly changed, whereas the elongation at break was decreased when compared to non-reactive blends due to the possible crosslinking reaction as observed from melt flow index (MFI) values. When adding Perkadox, the impact strength of PLA/PBAT (80/20) remained almost unchanged. However, the impact strength of PLA/PBAT (70/30) was enhanced, increasing to 110% for 0.05 phr Perkadox. In case of the blends with TBT, SEM micrographs showed the decrease in the particle size of PBAT phase when adding TBT. Young's modulus and the tensile strength of all blend ratios were not different, but the elongation at break was improved when adding TBT owing to the transesterification reaction. For PLA/PBAT (80/20), the elongation at break was increased by 39%, whereas the elongation at break was increased by 15% for PLA/PLA (70/30). The impact strength of all blend ratios unaffected.

  10. Production and characterization of thermoplastic cassava starch, functionalized poly(lactic acid), and their reactive compatibilized blends

    NASA Astrophysics Data System (ADS)

    Detyothin, Sukeewan

    Cassava starch was blended with glycerol using a co-rotating twin-screw extruder (TSE). Thermoplastic cassava starch (TPCS) at a ratio of 70/30 by weight of cassava/glycerol was selected and further blended with other polymers. TPCS sheets made from compression molding had low tensile strength (0.45 +/- 0.05 MPa) and Young's modulus (1.24 +/- 0.58 MPa), but moderate elongation at break (83.0 +/- 0.18.6%), medium level of oxygen permeability, and high water vapor permeability with a very high rate of water absorption. TPCS was blended with poly(lactic acid) (PLA) at various ratios by using a TSE. The blend resins exhibited good properties such as increased thermal stability (Tmax) and crystallinity of PLA, and improved water sensitivity and processability of TPCS. PLA and TPCS exhibited a high interfacial tension between the two phases of 7.9 mJ·m -2, indicating the formation of an incompatible, immiscible blend. SEM micrographs showed a non-homogeneous distribution of TPCS droplets in the PLA continuous phase. TEM micrographs of the blend films made by cast-film extrusion showed coalescence of the TPCS droplets in the PLA continuous phase of the blend, indicating that the compatibility between the polymer pair needs to be improved. A response surface methodology (RSM) design was used to analyze the effects of maleic anhydride (MA) and 2,5-bis(tert-butylperoxy)-2,5-dimethylhexane (Luperox or L101) contents, and TSE screw speed on the degree of grafted MA and number average molecular weight (Mn) of functionalized PLA (PLA-g-MA), a reactive compatibilizer. PLA-g- MA made by reactive extrusion had an array of colors depending on the content of L101 and MA used. New FTIR peaks suggested that MA was grafted onto the PLA backbone and oligomeric MA may occur. Increasing L101 increased the degree of grafting and decreased Mn, but the Mn of the PLA-g-MA's produced with a high amount of L101 was stable during storage. MA exhibited an optimum concentration for maximizing the

  11. iPLA2• Knockout Mouse, a Genetic Model for Progressive Human Motor Disorders, Develops Age-Related Neuropathology

    PubMed Central

    Blanchard, Helene; Taha, Ameer Y.; Cheon, Yewon; Kim, Hyung-Wook; Turk, John; Rapoport, Stanley I.

    2015-01-01

    Calcium-independent phospholipase A2 group VIa (iPLA2β) preferentially releases docosahexaenoic acid (DHA) from the sn-2 position of phospholipids. Mutations of its gene, PLA2G6, are found in patients with several progressive motor disorders, including Parkinson disease. At 4 months, PLA2G6 knockout mice (iPLA2β−/−) show minimal neuropathology but altered brain DHA metabolism. By 1 year, they develop motor disturbances, cerebellar neuronal loss, and striatal α-synuclein accumulation. We hypothesized that older iPLA2β−/− mice also would exhibit inflammatory and other neuropathological changes. Real-time polymerase chain reaction and Western blotting were performed on whole brain homogenate from 15 to 20-month old male iPLA2β−/− or wild-type (WT) mice. These older iPLA2β−/− mice compared with WT showed molecular evidence of microglial (CD-11b, iNOS) and astrocytic (glial fibrillary acidic protein) activation, disturbed expression of enzymes involved in arachidonic acid metabolism, loss of neuroprotective brain derived neurotrophic factor, and accumulation of cytokine TNF-α messenger ribonucleic acid, consistent with neuroinflammatory pathology. There was no evidence of synaptic loss, of reduced expression of dopamine active reuptake transporter, or of accumulation of the Parkinson disease markers Parkin or Pink1. iPLA2γ expression was unchanged. iPLA2β deficient mice show evidence of neuroinflammation and associated neuropathology with motor dysfunction in later life. These pathological biomarkers could be used to assess efficacy of dietary intervention, antioxidants or other therapies on disease progression in this mouse model of progressive human motor diseases associated with a PLA2G6 mutation. PMID:24919816

  12. Recycling of Poly (Lactic Acid)/Silk based Bionanocomposites Films and its Influence on Thermal Stability, Crystallization Kinetics, Solution and Melt Rheology.

    PubMed

    Tesfaye, Melakuu; Patwa, Rahul; Gupta, Arvind; Kashyap, Manash Jyoti; Katiyar, Vimal

    2017-03-17

    In this study, the effect of silk nanocrystals (SNCs) on the thermal and rheological properties of poly (lactic acid) (PLA) under repetitive extrusion process is investigated. The presence of SNCs facilitates the crystallization process and delaying the thermal degradation of PLA matrix. This leads to the reduction in cold crystallization peak temperature with lower crystallization half-time and higher growth rate. The substantial improvement in nucleation density observed through Polarized Optical Microscope (POM) proves the nucleating effect of SNC in all processing cycles. Moreover, the rheological investigation (complex viscosity, storage and loss modules values) revealed the stabilizing effect of SNC and the drastic degradation of neat PLA (NPLA) in third and fourth cycle is observed to be fortified by the presence of SNC. Cole-Cole plot and cross over frequencies have been correlated with the molar mass distribution of PLA and PLA-Silk composite during processing, which is further supported by the intrinsic viscosity measurement and acid value analysis. This investigation suggests that the melt viscosity and thermal properties of PLA can be stabilized by addition of silk nanocrystals.

  13. Fabrication of nanofibrous scaffold using a PLA and hagfish thread keratin composite; its effect on cell adherence, growth, and osteoblast differentiation.

    PubMed

    Kim, Beom-Su; Park, Ko Eun; Park, Won Ho; Lee, Jun

    2013-08-01

    Electrospinning is a useful method for the production of nanofibrous scaffolds in the field of tissue engineering. Keratin has been used as a biomaterial for electrospinning and can be used in a variety of biomedical applications because it is a natural protein, giving it the ability to improve cell affinity of scaffolds. In this study, keratin was extracted from hagfish slime thread (H-keratin) and blended with polylactic acid (PLA) polymer solution to construct a nanofibrous scaffold. Wool keratin (W-keratin) was used as a control for the comparison of morphological, physical, and biological properties. The results of Fourier transform infrared spectroscopy showed the presence of both W-keratin and H-keratin in the electrospun PLA/keratin. Observations with a scanning electron microscope revealed that PLA, PLA/W-keratin, and PLA/H-keratin had similar average diameters (~800 nm). Cell attachment experiments showed that MG-63 cells adhered more rapidly and spread better onto PLA/H-keratin than onto the pure PLA or PLA/W-keratin. Cell proliferation assay, DNA content, live/dead, and alkaline phosphatase activity assays showed that PLA/H-keratin scaffolds could accelerate the viability, proliferation, and osteogenesis of MG-63 cells relative to pure PLA or PLA/W-keratin nanofibrous scaffolds. These findings suggest that H-keratin can improve cellular attraction and has great potential to be used as a biomaterial in bone tissue engineering.

  14. Effects of heat treatment on chitosan nanocomposite film reinforced with nanocrystalline cellulose and tannic acid.

    PubMed

    Rubentheren, V; Ward, Thomas A; Chee, Ching Yern; Nair, Praveena; Salami, Erfan; Fearday, Christopher

    2016-04-20

    This article presents an analysis of the influence of heat treatment on chitosan nanocomposite film. A series of samples comprising: pure chitosan film, chitosan film embedded with nanocrystalline cellulose (NCC), chitosan film crosslinked with tannic acid and chitosan film with a blend of NCC and tannic acid were heat treated using a convection oven. Fourier-transform-infrared spectroscopy (FTIR) and X-ray diffraction test (XRD) shows the changes in chemical interaction of the heat treated films. The heat treated films show significant improvements in moisture absorption. Tensile strength and Young's Modulus were increased up to 7MPa and 259MPa, respectively when the samples were subjected to heat treatment. For the NCC particles, a transmission electron microscope (TEM) was used to inspect the structural properties of cellulose particle in suspension form.

  15. Surface proton transport of fully protonated poly(aspartic acid) thin films on quartz substrates

    NASA Astrophysics Data System (ADS)

    Nagao, Yuki; Kubo, Takahiro

    2014-12-01

    Thin film structure and the proton transport property of fully protonated poly(aspartic acid) (P-Asp100) have been investigated. An earlier study assessed partially protonated poly(aspartic acid), highly oriented thin film structure and enhancement of the internal proton transport. In this study of P-Asp100, IR p-polarized multiple-angle incidence resolution (P-MAIR) spectra were measured to investigate the thin film structure. The obtained thin films, with thicknesses of 120-670 nm, had no oriented structure. Relative humidity dependence of the resistance, proton conductivity, and normalized resistance were examined to ascertain the proton transport property of P-Asp100 thin films. The obtained data showed that the proton transport of P-Asp100 thin films might occur on the surface, not inside of the thin film. This phenomenon might be related with the proton transport of the biological system.

  16. [Degradable performance and bio-mineralization function of PLA-PEG-PLA/PLA tissue engineering scaffold in vitro and in vivo].

    PubMed

    Ge, Jianhua; Wang, Yingjun; Min, Shaoxiong

    2010-10-01

    The degradable performance and bio-mineralization function of PLA-PEG-PLA/PLA tissue engineering scaffolds in vitro and in vivo were systematically studied. The X-ray diffraction and Fourier transform infrared spectra showed that there was the deposition of bone-like carbonate hydroxyapatite on the surface of scaffolds. We found that the weight of scaffolds did not always decrease with the prolongation of time in vitro. At the same time, we found that after the PLA-PEG-PLA/PLA tissue engineering scaffolds were embedded in skulls of rhesus monkeys, the new bone area reached 75% at the 12th week. Histological observation showed that the new bones were rebuilt and knitted bones were formed at the 12th week. These findings meant that the PLA-PEG-PLA/PLA tissue engineering scaffolds were potential in clinical use.

  17. Development of polylactic acid-based materials through reactive modification

    NASA Astrophysics Data System (ADS)

    Fowlks, Alison Camille

    2009-12-01

    Polylactic acid (PLA)-based systems have shown to be of great potential for the development of materials requiring biobased content, biodegradation, and sufficient properties. The efforts in this study are directed toward addressing the current research need to overcome some of the inherent drawbacks of PLA. To meet this need, reactive extrusion was employed to develop new materials based on PLA by grafting, compounding, and polymer blending. In the first part of this work, maleic anhydride (MA) was grafted onto PLA by reactive extrusion. Two structurally different peroxides were used to initiate grafting and results were reported on the basis of grafting, molecular weight, and thermal behavior. An inverse relationship between degree of grafting and molecular weight was established. It was also found that, regardless of peroxide type, there is an optimum peroxid-to-MA ratio of 0.5:2 that promotes maximum grafting, beyond which degradation reactions become predominant. Overall, it was found that the maleated copolymer (MAPLA) could be used as an interfacial modifier in PLA-based composites. Therefore, MAPLA was incorporated into PLA-talc composites in varying concentrations. The influence of the MAPLA addition on the mechanical and thermal behavior was investigated. When added in an optimum concentration, MAPLA improved the tensile strength and crystallization of the composite. Furthermore, microscopic observation confirmed the compatibilization effect of MAPLA in PLA-talc composites. Vinyltrimethoxysilane was free-radically grafted onto the backbone of PLA and subsequently moisture crosslinked. The effects of monomer, initiator, and catalyst concentration on the degree of crosslinking and the mechanical and thermal properties were investigated. The presence of a small amount of catalyst showed to be a major contributor to the crosslinking formation in the time frame investigated, shown by an increase in gel content and decrease in crystallinity. Furthermore

  18. Effect of polymer/clay composition on processability of polylactide nanocomposites by film blowing

    NASA Astrophysics Data System (ADS)

    Garofalo, E.; Galdi, M. R.; D'Arienzo, L.; Di Maio, L.; Incarnato, L.

    2015-12-01

    The blown extrusion of poly(lactic acid) presents several challenges mainly due to its poor elongation properties. This work deals on the possibility to enhance the processabiliy of PLA by film blowing by functionalizing the polymer with nanosilicates. In particular, two types of polylactic acid (PLA 4032D and PLA 4042D) and different types of filler, selected from montmorillonites (Cloisite 30B) and bentonites (Nanofil SE3010) families, were used to prepare the hybrid systems by using a twin-screw extruder. The interaction between the polymer and the clay was evaluated by FTIR analysis and correlated to the structure of the obtained nanocomposites in terms of clay dispersion. All the samples were then submitted to rheological measurements both in shear and elongational mode.

  19. Pb"1"-"xFe"xS nanoparticle films grown from acidic chemical bath [rapid communication

    NASA Astrophysics Data System (ADS)

    Joshi, Rakesh K.; Subbaraju, G. V.; Sharma, Renu; Sehgal, H. K.

    2004-12-01

    Pb 1- xFe xS ( x=0.25, 0.50, 0.75) films were grown from an acidic chemical bath. Nanoparticle films were structurally characterized by XRD and TEM. Optical band gap of films is observed to vary from 1.65 to 1.42 eV with increase in their iron concentration from x=0.25 to 0.75 in the films. Increased optical band gap of the ternary films compared to the estimated bulk value is attributed to quantum confinement in the nanocrystals deposited on solid substrates.

  20. Physical properties of edible emulsified films based on carboxymethyl cellulose and oleic acid.

    PubMed

    Ghanbarzadeh, Babak; Almasi, Hadi

    2011-01-01

    Glycerol and oleic acid (OA) were incorporated into carboxymethyl cellulose (CMC) films by an emulsification method. Films containing different amounts of glycerol and OA were examined for mechanical properties, water vapor permeability (WVP), and moisture uptake, optical and thermal properties. Addition of OA to the CMC films significantly improved the barrier property. However, the effect of OA on the mechanical properties was lower than glycerol. By increasing of OA content, the cloudiness of the CMC films was intensified and Hunter value (b) of the films increased (by ca. 35.8%).

  1. Rapidly stopping hemorrhage by enhancing blood clotting at an opened wound using chitosan/polylactic acid/polycaprolactone wound dressing device.

    PubMed

    Boonkong, Wasinee; Petsom, Amorn; Thongchul, Nuttha

    2013-06-01

    Doxycycline and monosodium glutamate (MSG) loaded chitosan (CHI)/polylactic acid (PLA)/polycaprolactone (PCL) blend film was studied as a model device to deliver drug to targeted human organ which in this case was the skin with opened wound. The CHI/PLA/PCL blend film containing 60 % CHI, 28 % PLA, and 12 % PCL exhibited the good properties for making the dressing device. It was observed that doxycycline/MSG loaded CHI/PLA/PCL blend film could rapidly deliver both doxycycline and MSG at the high release percentage approaching 100 % loaded. MSG accelerated blood clotting and fibrin formation; thus, it exhibited the good hemostatic activity. The antibacterial activity of doxycycline loaded CHI/PLA/PCL blend film against Staphylococcus aureus and Escherichia coli as model bacteria was investigated. Doxycycline release played the crucial role in bacterial inhibition as observed from the lowest bacterial cell dry weight observed when compared with the control bacterial culture or the bacterial cultures with the presence of other films studied.

  2. Assessing Technology Innovation in the PLA

    DTIC Science & Technology

    2015-03-01

    TECHNOLOGY INNOVATION IN THE PLA by Gary L. Pembleton March 2015 Thesis Co-Advisors: Wade Huntley Michael Glosny THIS PAGE INTENTIONALLY LEFT...SUBTITLE 5. FUNDING NUMBERS ASSESSING TECHNOLOGY INNOVATION IN THE PLA 6. AUTHOR(S) Gaty L. Pembleton 7. PERFORMING ORGANIZATION NA:iVIE(S) AND ADDRESS(ES...standard for identifying innovation, and applies this standard to the PLAN and PLAAF. Historically, technological innovat ion is either overlooked or

  3. Curcumin-Loaded PLA Nanoparticles: Formulation and Physical Evaluation

    PubMed Central

    Rachmawati, Heni; Yanda, Yulia L.; Rahma, Annisa; Mase, Nobuyuki

    2016-01-01

    Curcumin is a polyphenolic compound derived from Curcuma domestica (Zingiberaceae) that possesses diverse pharmacological effects including anti-inflammatory, antioxidant, antimicrobial, and anticarcinogenic activities. Although phase I clinical trials have shown curcumin as a safe drug even at high doses (12 g/day) in humans, poor bioavaibility largely limits its pharmacological activity. Nanoencapsulation in biodegradable polymers is a promising alternative to improve curcumin bioavaibility. In this study, curcumin was encapsulated in biodegradable polymer poly-(lactic acid) (PLA) nanoparticles via the emulsification-solvent evaporation method. Optimization of selected parameters of this method including the type of solvent, surfactant concentration, drug loading, sonication time, and centrifugation speed, were performed to obtain polymeric nano-carriers with optimum characteristics. Dichloromethane was used as the solvent and vitamin E polyethylene glycol succinate (TPGS) was used as the surfactant. Four minutes of sonication time and centrifugation at 10500 rpm were able to produce spherical nanoparticles with average size below 300 nm. The highest encapsulation efficiency was found on PLA nanoparticles containing 5% of curcumin at 89.42 ± 1.04%. The particle size, polydispersity index, zeta potential of 5% curcumin-PLA nanoparticles were 387.50 ± 58.60 nm, 0.289 ± 0.047, and −1.12 mV, respectively. Differential Scanning Calorimetry (DSC) and X-Ray Diffraction (XRD) studies showed partial interaction between the drug and polymer. PMID:27110509

  4. Preparation of porous PLA/DBM composite biomaterials and experimental research of repair rabbit radius segmental bone defect.

    PubMed

    Zhang, Yumin; Wang, Jianru; Wang, Jue; Niu, Xiaojun; Liu, Jianchun; Gao, Lan; Zhai, Xiaoyan; Chu, Kaibo

    2015-12-01

    Bone substitutes are used in wide range of orthopaedic application. An ideal bone substitute should exhibit superior osteoinductive and osteoconductive properties. Neither bio-derived materials nor synthetic materials can meet the needs of an ideal bone substitute. Preparation of composite materials is a promising way to improve properties of biomaterial. In this study, the porous poly lactic acid (PLA)/demineralized bone matrix (DBM) composite biomaterials prepared by supercritical CO2 technique were implanted to repair rabbit radius segmental bone defect. By comparing with PLA and bone autograft, the X-ray result and histological analysis showed the repair effect of PLA/DBM porous composite materials is significantly better than that of the PLA group and the blank control group, and is similar to autologous bone. The PLA/DBM can promote the healing of bone defects and can be used as a kind of ideal alternative materials to repair bone defects.

  5. Polymorphisms in PLA2G6 and PLA2G4C genes for calcium-independent phospholipase A2 do not contribute to attenuated niacin skin flush response in schizophrenia patients.

    PubMed

    Nadalin, S; Radović, I; Buretić-Tomljanović, A

    2015-09-01

    We hypothesized that attenuated niacin skin flushing in schizophrenia patients might be associated with polymorphic variants in PLA2G6 and PLA2G4C genes (rs4375 and rs1549637 variations) which encode calcium-independent phospholipase A2 beta (iPLA2β) and cytosolic phospholipase A2 gamma (cPLA2γ) enzymes. The iPLA2β and cPLA2γ may play an important role in niacin-mediated signaling; in addition to their major role - mediating phospholipids remodeling, which alters membrane receptors and signal transduction, they regulate the reservoir of arachidonic acid for prostaglandins synthesis. Skin response to topical niacin of 0.1M, 0.01M, 0.001M and 0.0001M concentrations in 75 schizophrenia patients was rated using the method of volumetric niacin response (VNR). Neither PLA2G6 nor PLA2G4C gene polymorphisms were significantly associated with VNR values. Furthermore, polymorphisms׳ synergy on niacin skin flushing was also not detected.

  6. Improving the engineering properties of PLA for 3D printing and beyond

    NASA Astrophysics Data System (ADS)

    Rocha Gutierrez, Carmen Raquel

    Additive manufacturing (AM), now more commonly known as 3D printing, has been classified as efficient, fast, and practical in the prototyping sector of product development. In the work presented here, we will use one of the AM techniques known as Material extrusion 3D printing (ME3DP), which has all the advantages of AM. However, one of the biggest challenges facing ME3DP technologies is the limitation of the range of materials used by this technique. Acrylonitrile butadiene styrene (ABS) and poly-lactic acid (PLA) are currently the most common thermoplastics materials used in ME3DP because of their ability to melt and be reprocessed. PLA is a biodegradable polymer derived from renewable sources such as corn, and sugarcane. The expanded use of this polymer over traditional petroleum-based plastics (ABS) will decrease the demand on petrochemicals, and also lead to less non-biodegradable polymeric waste. While PLA offers an eco-friendly solution for polymeric 3D printing, the mechanical performance is limited by PLA's inherent characteristics (such as moisture absorbance) that may degrade the plastic during processing. PLA novel systems were used through this research maintaining the compatibility with material extrusion 3D printers. The purpose of this investigation is to alter the physical properties of PLA with sustainable additives in order to improve the end use products from this material.

  7. Tuning the properties of polyhydroxybutyrate films using acetic acid via solvent casting

    PubMed Central

    Anbukarasu, Preetam; Sauvageau, Dominic; Elias, Anastasia

    2015-01-01

    Biodegradable polyhydroxybutyrate (PHB) films were fabricated using acetic acid as an alternative to common solvents such as chloroform. The PHB films were prepared using a solvent casting process at temperatures ranging from 80 °C to 160 °C. The crystallinity, mechanical properties and surface morphology of the films cast at different temperatures were characterized and compared to PHB films cast using chloroform as a solvent. Results revealed that the properties of the PHB film varied considerably with solvent casting temperature. In general, samples processed with acetic acid at low temperatures had comparable mechanical properties to PHB cast using chloroform. This acetic acid based method is environmentally friendly, cost efficient and allows more flexible processing conditions and broader ranges of polymer properties than traditional methods. PMID:26640089

  8. Wheat straw hemicelluloses added with cellulose nanocrystals and citric acid. Effect on film physical properties.

    PubMed

    Pereira, Paulo H F; Waldron, Keith W; Wilson, David R; Cunha, Arcelina P; Brito, Edy S de; Rodrigues, Tigressa H S; Rosa, Morsyleide F; Azeredo, Henriette M C

    2017-05-15

    Wheat straw has been used as a source of hemicelluloses (WSH) and cellulose nanocrystals (CNC) for the elaboration of biodegradable films. Different films have been formed by using WSH as a matrix and different contents of CNC and citric acid. The predominant hemicelluloses were arabinoxylans. CNC reinforced the films, improving tensile strength and modulus, water resistance and water vapor barrier. Citric acid, on the other hand, presented concomitant plasticizing and crosslinking effects (the latter also evidenced by FTIR), probably due to a crosslinking extension by glycerol. The use of 5.9wt% CNC and 30wt% citric acid was defined as optimal conditions, resulting in minimum water sensitivity and permeability, while maintaining a good combination of tensile properties. Under those conditions, the films presented enhanced modulus, elongation, water resistance, and barrier to water vapor when compared to the control WSH film, and might be used for wrapping or coating a variety of foods.

  9. Tuning the properties of polyhydroxybutyrate films using acetic acid via solvent casting

    NASA Astrophysics Data System (ADS)

    Anbukarasu, Preetam; Sauvageau, Dominic; Elias, Anastasia

    2015-12-01

    Biodegradable polyhydroxybutyrate (PHB) films were fabricated using acetic acid as an alternative to common solvents such as chloroform. The PHB films were prepared using a solvent casting process at temperatures ranging from 80 °C to 160 °C. The crystallinity, mechanical properties and surface morphology of the films cast at different temperatures were characterized and compared to PHB films cast using chloroform as a solvent. Results revealed that the properties of the PHB film varied considerably with solvent casting temperature. In general, samples processed with acetic acid at low temperatures had comparable mechanical properties to PHB cast using chloroform. This acetic acid based method is environmentally friendly, cost efficient and allows more flexible processing conditions and broader ranges of polymer properties than traditional methods.

  10. Neutralisation of the pharmacological activities of Bothrops alternatus venom by anti-PLA2 IgGs.

    PubMed

    Garcia Denegri, María E; Maruñak, Silvana; Todaro, Juan S; Ponce-Soto, Luis A; Acosta, Ofelia; Leiva, Laura

    2014-08-01

    Basic phospholipases A2 (PLA2) are toxic and induce a wide spectrum of pharmacological effects, although the acidic enzyme types are not lethal or cause low lethality. Therefore, it is challenging to elucidate the mechanism of action of acidic phospholipases. This study used the acidic non-toxic Ba SpII RP4 PLA2 from Bothrops alternatus as an antigen to develop anti-PLA2 IgG antibodies in rabbits and used in vivo assays to examine the changes in crude venom when pre-incubated with these antibodies. Using Ouchterlony and western blot analyses on B. alternatus venom, we examined the specificity and sensitivity of phospholipase A2 recognition by the specific antibodies (anti-PLA2 IgG). Neutralisation assays using a non-toxic PLA2 antigen revealed unexpected results. The (indirect) haemolytic activity of whole venom was completely inhibited, and all catalytically active phospholipases A2 were blocked. Myotoxicity and lethality were reduced when the crude venom was pre-incubated with anti-PLA2 immunoglobulins. CK levels in the skeletal muscle were significantly reduced at 6 h, and the muscular damage was more significant at this time-point compared to 3 and 12 h. When four times the LD50 was used (224 μg), half the animals treated with the venom-anti PLA2 IgG mixture survived after 48 h. All assays performed with the specific antibodies revealed that Ba SpII RP4 PLA2 had a synergistic effect on whole-venom toxicity. IgG antibodies against the venom of the Argentinean species B. alternatus represent a valuable tool for elucidation of the roles of acidic PLA2 that appear to have purely digestive roles and for further studies on immunotherapy and snake envenoming in affected areas in Argentina and Brazil.

  11. All Biomass and UV Protective Composite Composed of Compatibilized Lignin and Poly (Lactic-acid)

    PubMed Central

    Kim, Youngjun; Suhr, Jonghwan; Seo, Hee-Won; Sun, Hanna; Kim, Sanghoon; Park, In-Kyung; Kim, Soo-Hyun; Lee, Youngkwan; Kim, Kwang-Jin; Nam, Jae-Do

    2017-01-01

    Utilization of carbon-neutral biomass became increasingly important due to a desperate need for carbon reduction in the issue of global warming in light of replacing petroleum-based materials. We used lignin, which was an abundant, low cost, and non-food based biomass, for the development of all biomass-based films and composites through reactive compatibilization with poly (lactic-acid) (PLA). Using a facile and practical route, the hydrophilic hydroxyl groups of lignin were acetylated to impose the compatibility with PLA. The solubility parameter of the pristine lignin at 26.3 (J/cm3)0.5 was altered to 20.9 (J/cm3)0.5 by acetylation allowing the good compatibility with PLA at 20.2 (J/cm3)0.5. The improved compatibility of lignin and PLA provided substantially decreased lignin domain size in composites (12.7 μm), which subsequently gave transparent and UV-protection films (visual transmittance at 76% and UV protection factor over 40). The tensile strength and elongation of the developed composite films were increased by 22% and 76%, respectively, and the biobased carbon content was confirmed as 96 ± 3%. The developed PLA/lignin composites provided 100% all-biomass contents and balanced optical and mechanical properties that could broaden its eco-friendly applications in various industries.

  12. All Biomass and UV Protective Composite Composed of Compatibilized Lignin and Poly (Lactic-acid)

    NASA Astrophysics Data System (ADS)

    Kim, Youngjun; Suhr, Jonghwan; Seo, Hee-Won; Sun, Hanna; Kim, Sanghoon; Park, In-Kyung; Kim, Soo-Hyun; Lee, Youngkwan; Kim, Kwang-Jin; Nam, Jae-Do

    2017-03-01

    Utilization of carbon-neutral biomass became increasingly important due to a desperate need for carbon reduction in the issue of global warming in light of replacing petroleum-based materials. We used lignin, which was an abundant, low cost, and non-food based biomass, for the development of all biomass-based films and composites through reactive compatibilization with poly (lactic-acid) (PLA). Using a facile and practical route, the hydrophilic hydroxyl groups of lignin were acetylated to impose the compatibility with PLA. The solubility parameter of the pristine lignin at 26.3 (J/cm3)0.5 was altered to 20.9 (J/cm3)0.5 by acetylation allowing the good compatibility with PLA at 20.2 (J/cm3)0.5. The improved compatibility of lignin and PLA provided substantially decreased lignin domain size in composites (12.7 μm), which subsequently gave transparent and UV-protection films (visual transmittance at 76% and UV protection factor over 40). The tensile strength and elongation of the developed composite films were increased by 22% and 76%, respectively, and the biobased carbon content was confirmed as 96 ± 3%. The developed PLA/lignin composites provided 100% all-biomass contents and balanced optical and mechanical properties that could broaden its eco-friendly applications in various industries.

  13. Grafting of poly (lactic acid) with maleic anhydride using supercritical carbon dioxide

    NASA Astrophysics Data System (ADS)

    Khankrua, R.; Pivsa-Art, S.; Hiroyuki, H.; Suttiruengwong, S.

    2015-07-01

    The aim of this work was to modify poly lactic acid (PLA) via free radical grafting with maleic anhydride (MA) by using supercritical carbon dioxide (SCCO2). Benzoyl peroxide (BPO) was used as an initiator. The solubility of MA in SCCO2 was first determined to estimate the suitable grafting conditions and equilibrium. From the solubility study of MA in SCCO2, it was found that the solubility of MA in SCCO2 increased with the increasing pressure and dissolution time. PLA films were first prepared by compression molding. The ratio of MA to BPO was 2:1. The reaction temperature and pressure were 70°C and 100 bar respectively. The grafting reaction and the degree of grafting were characterized by nuclear magnetic resonance (NMR) spectroscopy and titration, respectively. Scanning electron microscope (SEM) technique and contact angle were used to confirm the changes in physical properties of PLA film grafted MA. NMR spectrum indicated that the grafting of MA onto PLA was successively achieved. Degree of grafting by using SCCO2 was as high as 0.98%. This provided rather high grafting degree compared with other processes. SEM pictures showed the rough surface structure on modified PLA film. In addition, contact angle results showed an improvement of the hydrophilicity by maleic anhydride grafting onto polymers.

  14. Chemical modification of chitosan film via surface grafting of citric acid molecular to promote the biomineralization

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Shen, Xin; Zhou, Huan; Wang, Yingjun; Deng, Linhong

    2016-05-01

    We develop a novel chitosan-citric acid film (abbreviated as CS-CA) suitable for biomedical applications in this study. In this CS-CA film, the citric acid, which is a harmless organic acid has been extensively investigated as a modifying agent on carbohydrate polymers, was cross-linked by 1-Ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC) and N-hydroxysuccinimide (NHS) onto the surface of chitosan (CS) film. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) confirms the graft copolymerization of the modified chitosan film (CS-CA). Surface wettability, moisturizing performance, the capacity of mineralization in vitro and biocompatibility of the films were characterized. After modification, this CS-CA film has good hydrophilicity. It is very evident that the citric acid grafting treatment significantly promotes the biomineralization of the chitosan based substrates. Cell experiments show that the MC3T3-E1 osteoblasts can adhere and proliferate well on the surface of CS-CA film. This CS-CA film, which can be prepared in large quantities and at low cost, should have potential application in bone tissue engineering.

  15. Physicochemical and Mechanical Properties of Bambara Groundnut Starch Films Modified with Stearic Acid.

    PubMed

    Oyeyinka, Samson A; Singh, Suren; Amonsou, Eric O

    2017-01-01

    The physicochemical and mechanical properties of biofilm prepared from bambara starch modified with varying concentrations of stearic acid (0%, 2.5%, 3.5%, 5%, 7%, and 10%) were studied. By scanning electron microscopy, bambara starch films modified with stearic acid (≥3.5%) showed a progressively rough surface compared to those with 2.5% stearic acid and the control. Fourier transform infrared spectroscopy spectra revealed a peak shift of approximately 31 cm(-1) , suggesting the promotion of hydrogen bond formation between hydroxyl groups of starch and stearic acid. The addition of 2.5% stearic acid to bambara starch film reduced water vapor permeability by approximately 17%. Bambara starch films modified with higher concentration of stearic acid were more opaque and showed significantly high melting temperatures. However, mechanical properties of starch films were generally negatively affected by stearic acid. Bambara starch film may be modified with 2.5% stearic acid for improved water vapor permeability and thermal stability with minimal effect on tensile strength.

  16. Radiation-induced grafting of acrylic acid onto polypropylene film and its biodegradability

    NASA Astrophysics Data System (ADS)

    Mandal, Dev K.; Bhunia, Haripada; Bajpai, Pramod K.; Chaudhari, C. V.; Dubey, K. A.; Varshney, L.

    2016-06-01

    Polypropylene based commodity polyolefins are widely used in packaging, manufacturing, electrical, pharmaceutical and other applications. The aim of the present work is to study the effect of grafting of acrylic acid on the biodegradability of acrylic acid grafted polypropylene. The effect of different conditions showed that grafting percentage increased with increase in monomer concentration, radiation dose and inhibitor concentration but decreased with increase in radiation dose rate. The maximum grafting of 159.4% could be achieved at optimum conditions. The structure of grafted polypropylene films at different degree of grafting was characterized by EDS, FTIR, TGA, DSC, SEM and XRD. EDS studies showed that the increase in acrylic acid grafting percentage increased the hydrophilicity of the grafted films. FTIR studies indicated the presence of acrylic acid on the surface of polypropylene film. TGA studies revealed that thermal stability decreased with increase in grafting percentage. DSC studies showed that melting temperature and crystallinity of the grafted polypropylene films lower than polypropylene film. SEM studies indicated that increase in acrylic acid grafting percentage increased the wrinkles in the grafted films. The maximum biodegradability could be achieved to 6.85% for 90.5% grafting. This suggested that microorganisms present in the compost could biodegrade acrylic acid grafted polypropylene.

  17. Synthesis of CuFeS2 thin films from acidic chemical baths

    NASA Astrophysics Data System (ADS)

    Tonpe, Dipak; Gattu, Ketan; More, Ganesh; Upadhye, Deepak; Mahajan, Sandip; Sharma, Ramphal

    2016-05-01

    The growth of Copper iron sulfide nanocrystalline thin films onto glass substrates has been achieved by chemical bath deposition at acidic values of pH. The deposited thin films were characterized for their optoelectronic properties using Raman, UV-Vis spectroscopy. The Raman analysis confirms the formation of CuFeS2 thin film. The thin film with nanosized crystallites of CuFeS2 showed a bandgap of 0.7eV from UV-vis absorption spectroscopy.

  18. Impurity effects on orientation of lysozyme crystals nucleated on fatty acid thin films

    NASA Astrophysics Data System (ADS)

    Kubo, T.; Hondoh, H.; Nakada, T.

    2008-04-01

    Commercially available lysozyme samples that have different lot numbers (E02Z04 and E05802) were crystallized on fatty acid thin films. The orientation of lysozyme crystals nucleated on the films was investigated by atomic force microscopy and optical microscopy. The numbers of lysozyme crystals with specific planes parallel to the films are different. In other words, the impurities contained in commercial lysozyme significantly affect the orientation of lysozyme crystals. Detailed analysis of the orientation distribution of the lysozyme crystals nucleated from the purified sample showed that acetic acid is one of the substances promote the epitaxy.

  19. Inhibition of phospholipase A2 (PLA2) activity by nifedipine and nisoldipine is independent of their calcium-channel-blocking activity

    SciTech Connect

    Chang, J.; Blazek, E.; Carlson, R.P.

    1987-09-01

    The effects of several calcium antagonists on phospholipase A2 (PLA2) activity were examined. Nifedipine and nisoldipine inhibited a cell-free preparation of PLA2 in a dose-dependent manner with maximal inhibition of 71-77% observed at 100 microM. More potent or equipotent dihydropyridine calcium antagonists such as nitrendipine and felodipine did not inhibit PLA2 activity. In addition, nondihydropyridine calcium antagonists such as diltiazem, verapamil, and cinnarazine failed to reduce PLA2 activity markedly. Nifedipine and nisoldipine also reduced PLA2 activity in intact mouse peritoneal macrophages where PLA2 activity was monitored by free (/sup 14/C)arachidonic acid release from (/sup 14/C)arachidonic acid-prelabeled cells. When levels of PGE2 and LTC4 were measured by radioimmunoassay, it was found that the synthesis of these two metabolites was concomitantly inhibited by nifedipine and nisoldipine. In vivo, nifedipine and nisoldipine inhibited tetradecanoylphorbol acetate (TPA) induced ear edema. UV irradiation of nifedipine and nisoldipine (which destroys the slow calcium-channel-blocking activity of these compounds) did not result in a loss of PLA2 inhibitory activity. In fact, in both instances the UV-irradiated forms of nifedipine and nisoldipine were slightly more potent PLA2 inhibitors than the parent compound alone. We therefore conclude that the ability of nifedipine and nisoldipine to inhibit PLA2 was direct and unrelated to their actions on slow calcium channels.

  20. Controlled release properties of zein-fatty acid blend films for multiple bioactive compounds.

    PubMed

    Arcan, Iskender; Yemenicioğlu, Ahmet

    2014-08-13

    To develop edible films having controlled release properties for multiple bioactive compounds, hydrophobicity and morphology of zein films were modified by blending zein with oleic (C18:1)Δ⁹, linoleic (C18:2)Δ(9,12), or lauric (C₁₂) acids in the presence of lecithin. The blend zein films showed 2-8.5- and 1.6-2.9-fold lower initial release rates for the model active compounds, lysozyme (LYS) and (+)-catechin (CAT), than the zein control films, respectively. The change of fatty acid chain length affected both CAT and LYS release rates while the change of fatty acid double bond number affected only the CAT release rate. The film morphologies suggested that the blend films owe their controlled release properties mainly to the microspheres formed within their matrix and encapsulation of active compounds. The blend films showed antilisterial activity and antioxidant activity up to 81 μmol Trolox/cm². The controlled release of multiple bioactive compounds from a single film showed the possibility of combining application of active and bioactive packaging technologies and improving not only safety and quality but also health benefits of packed food.

  1. Mechanical characterization of commercial biodegradable plastic films

    NASA Astrophysics Data System (ADS)

    Vanstrom, Joseph R.

    Polylactic acid (PLA) is a biodegradable plastic that is relatively new compared to other plastics in use throughout industry. The material is produced by the polymerization of lactic acid which is produced by the fermentation of starches derived from renewable feedstocks such as corn. Polylactic acid can be manufactured to fit a wide variety of applications. This study details the mechanical and morphological properties of selected commercially available PLA film products. Testing was conducted at Iowa State University and in conjunction with the United States Department of Agriculture (USDA) BioPreferred ProgramRTM. Results acquired by Iowa State were compared to a similar study performed by the Cortec Corporation in 2006. The PLA films tested at Iowa State were acquired in 2009 and 2010. In addition to these two studies at ISU, the films that were acquired in 2009 were aged for a year in a controlled environment and then re-tested to determine effects of time (ageing) on the mechanical properties. All films displayed anisotropic properties which were confirmed by inspection of the films with polarized light. The mechanical testing of the films followed American Society for Testing and Materials (ASTM) standards. Mechanical characteristics included: tensile strength (ASTM D882), elongation of material at failure (ASTM D882), impact resistance (ASTM D1922), and tear resistance (ASTM D4272). The observed values amongst all the films ranged as followed: tensile strength 33.65--8.54 MPa; elongation at failure 1,665.1%--47.2%; tear resistance 3.61--0.46 N; and puncture resistance 2.22--0.28 J. There were significant differences between the observed data for a number of films and the reported data published by the Cortec Corp. In addition, there were significant differences between the newly acquired material from 2009 and 2010, as well as the newly acquired materials in 2009 and the aged 2009 materials, suggesting that ageing and manufacturing date had an effect on

  2. Thermally driven stability of octadecylphosphonic acid thin films grown on SS316L.

    PubMed

    Lim, Min Soo; Smiley, Katelyn J; Gawalt, Ellen S

    2010-01-01

    Stainless steel 316L is widely used as a biomedical implant material; however, there is concern about the corrosion of metallic implants in the physiological environment. The corrosion process can cause mechanical failure due to resulting cracks and cavities in the implant. Alkyl phosphonic acid forms a thin film by self-assembly on the stainless steel surface and this report conclusively shows that thermal treatment of the octadecylphosphonic acid (ODPA) film greatly enhances the stability of the ODPA molecules on the substrate surface. AFM images taken from the modified substrates revealed that thermally treated films remain intact after methanol, THF, and water flushes, whereas untreated films suffer substantial loss. Water contact angles also show that the hydrophobicity of thermally treated films does not diminish after being incubated in a dynamic flow of water for a 3-hour period, whereas the untreated film becomes increasingly hydrophilic due to loss of ODPA. IR spectra taken of both treated and untreated films after water and THF flushes show that the remaining film retains its initial crystallinity. A model is suggested to explain the stability of ODPA film enhanced by thermal treatment. An ODPA molecule is physisorbed to the surface weakly by hydrogen bonding. Heating drives away water molecules leading to the formation of strong monodentate or mixed mono/bi-dentate bonds of ODPA molecule to the surface.

  3. Thermally Driven Stability of Octadecylphosphonic Acid Thin Films Grown on SS316L

    PubMed Central

    Lim, Min Soo; Smiley, Katelyn J.; Gawalt, Ellen S.

    2010-01-01

    Stainless steel 316L is widely used as a biomedical implant material; however, there is concern about the corrosion of metallic implants in the physiological environment. The corrosion process can cause mechanical failure due to resulting cracks and cavities in the implant. Alkyl phosphonic acid forms a thin film by self-assembly on the stainless steel surface and this report conclusively shows that thermal treatment of the octadecylphosphonic acid (ODPA) film greatly enhances the stability of the ODPA molecules on the substrate surface. AFM images taken from the modified substrates revealed that thermally treated films remain intact after methanol, THF and water flushes while untreated films suffer substantial loss. Water contact angles also show that the hydrophobicity of thermally treated films does not diminish after being incubated in a dynamic flow of water for a three hour period while the untreated film becomes increasingly hydrophilic due to loss of ODPA. IR spectra taken of both treated and untreated films after water and THF flushes show that the remaining film retains its initial crystallinity. A model is suggested to explain the stability of ODPA film enhanced by thermal treatment. An ODPA molecule is physisorbed to the surface weakly by hydrogen bonding. Heating drives away water molecules leading to the formation of strong monodentate or mixed mono/bi-dentate bonds of ODPA molecule to the surface. PMID:20648546

  4. Electrodeposited nanostructured lead dioxide as a thin film electrode for a lightweight lead-acid battery

    NASA Astrophysics Data System (ADS)

    Egan, D. R. P.; Low, C. T. J.; Walsh, F. C.

    Thin films of nanostructured lead dioxide are investigated as a positive electrode material for a lightweight lead-acid battery. The films are obtained by constant current deposition from electrolytes of lead methanesulfonate in methanesulfonic acid. The films are tested in two conditions namely (a) cyclic voltammetry and (b) constant current battery cycling in sulfuric acid. The charge and discharge current density, charge density and charge efficiency are measured as a function of cycle number. The effect of deposition conditions, such as solution temperature (295 and 333 K), type of substrate and electrolyte additive (hexadecyltrimethylammonium hydroxide), on the electrochemical performance of the PbO 2 in sulfuric acid is investigated. It is found that the as-deposited lead dioxide film is compact and nanostructured β-phase structure. Following successive cycling in sulfuric acid, the compact thin film gradually transforms into a porous microstructure consisting of positive active material (PbO 2 and PbSO 4), several tens of nanometres size. The charge density, discharge density and peak discharge current density of the PbO 2 improve with cycling of the thin film electrode.

  5. Electrophoretic deposition of polyacrylic acid and composite films containing nanotubes and oxide particles.

    PubMed

    Wang, Y; Deen, I; Zhitomirsky, I

    2011-10-15

    Electrophoretic deposition (EPD) method has been developed for the deposition of thin films of polyacrylic acid (PAA). This method allowed the formation of uniform films of controlled thickness on conductive substrates. It was shown that PAA can be used as a common dispersing agent suitable for charging and EPD of various materials, such as multiwalled carbon nanotubes, halloysite nanotubes, MnO(2), NiO, TiO(2) and SiO(2). The feasibility of EPD of composite films containing the nanotubes and oxide particles in a PAA matrix has been demonstrated. The kinetics of deposition and deposition mechanisms were investigated and discussed. The films were studied by thermogravimetric analysis, differential thermal analysis, X-ray diffraction and scanning electron microscopy. The results indicated that film thickness and composition can be varied. Obtained results pave the way for the fabrication of PAA and composite films for biomedical, electrochemical and other applications.

  6. Ultrafine nanoporous palladium-aluminum film fabricated by citric acid-assisted hot-water-treatment of aluminum-palladium alloy film

    SciTech Connect

    Harumoto, Takashi; Tamura, Yohei; Ishiguro, Takashi

    2015-01-15

    Hot-water-treatment has been adapted to fabricate ultrafine nanoporous palladium-aluminum film from aluminum-palladium alloy film. Using citric acid as a chelating agent, a precipitation of boehmite (aluminum oxide hydroxide, AlOOH) on the nanoporous palladium-aluminum film was suppressed. According to cross-sectional scanning transmission electron microscopy observations, the ligament/pore sizes of the prepared nanoporous film were considerably small (on the order of 10 nm). Since this fabrication method only requires aluminum alloy film and hot-water with chelating agent, the ultrafine nanoporous film can be prepared simply and environmentally friendly.

  7. Forensic engineering of advanced polymeric materials. Part III - Biodegradation of thermoformed rigid PLA packaging under industrial composting conditions.

    PubMed

    Musioł, Marta; Sikorska, Wanda; Adamus, Grazyna; Janeczek, Henryk; Richert, Jozef; Malinowski, Rafal; Jiang, Guozhan; Kowalczuk, Marek

    2016-06-01

    This paper presents a forensic engineering study on the biodegradation behaviour of prototype packaging thermoformed from PLA-extruded film and plain PLA film under industrial composting conditions. Hydrolytic degradation in water was conducted for reference. The effects of composting duration on changes in molar mass, glass transition temperature and degree of crystallinity of the polymeric material were monitored using gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). The chemical structure of water soluble degradation products of the polymeric material was determined using nuclear magnetic resonance (NMR) and electrospray ionization mass spectrometry (ESI-MS). The results show that the biodegradation process is less dependent on the thermoforming process of PLA and more dependent on the composting/degradation conditions that are applied. The increase in the dispersity index, leading to the bimodal molar mass distribution profile, suggests an autocatalytic hydrolysis effect at the early stage of the composting process, during which the bulk hydrolysis mechanism dominantly operates. Both the prototype PLA-packaging and PLA rigid film samples were shown to have a gradual increase in opacity due to an increase in the degree of crystallinity.

  8. Uptake of formic acid on thin ice films and on ice doped with nitric acid between 195 and 211 K.

    PubMed

    Romanias, Manolis N; Zogka, Antonia G; Stefanopoulos, Vassileios G; Papadimitriou, Vassileios C; Papagiannakopoulos, Panos

    2010-12-17

    The adsorption of formic acid on thin ice films and on ice doped with nitric acid (1.96, 7.69 and 53.8 wt%) is studied as a function of temperature T=195-211 K and gas concentration (0.33-10.6)×10(11) molecule cm(-3). Experiments are performed in a Knudsen flow reactor coupled with a quadrupole mass spectrometer. The initial uptake coefficients γ are strongly and inversely dependent on the ice temperature. Initial uptake is determined at low surface coverages and ranges from (0.65-3.78)×10(-3). The adsorption uptake of formic acid on pure ice films and on ice lightly doped with HNO(3) is a reversible process, and the adsorption isotherms exhibit Langmuir behaviour. N(max)(1) is (2.94±0.67)×10(14) molecule cm(-2), in good agreement with previous measurements. The temperature dependence of K(Lin) is very well represented by the expression: K(Lin)(1)=(1.43±0.32)×10(-8) exp[(4720±520)/T] cm(3) molecule(-1); the quoted uncertainty is at the 95% level of confidence and includes systematic uncertainties. Formic acid uptakes on ice films highly doped with HNO(3) (53.8 wt%) are two orders of magnitude higher than those measured on pure ice films and irreversible, thus indicating the formation of a supercooled liquid layer on the ice films upon which dissolution of formic acid occurs. Finally, the atmospheric lifetime of formic acid due to heterogeneous loss on cirrus cloud ice particles and the removal of formic acid by adsorption are estimated under conditions related to the upper troposphere.

  9. Biodegradation of poly(hydroxy butanoic acid) copolymer mulch films in soil

    NASA Astrophysics Data System (ADS)

    Kukade, Pranav

    Agricultural mulch films that are used to cover soil of crop rows contribute to earlier maturation of crops and higher yield. Incineration and landfill disposals are the most common means of disposal of the incumbent polyethylene (PE) mulch films; however, these are not environment friendly options. Biodegradable mulch films that can be rototilled into the soil after crop harvest are a promising alternative to offset problems such as landfill disposal, film retrieval and disposal costs. In this study, an in-house laboratory scale test method was developed in which the rate of disintegration, as a result of biodegradation of films based on polyhydroxybutanoic acid (PHB) copolymers was investigated in a soil environment using the residual weight loss method. The influence of soil composition, moisture levels in the soil, and industry-standard anti-microbial additive in the film composition on the rate of disintegration of PHB copolymer films was investigated. The soil composition has significant effect on the disintegration kinetics of PHB copolymer films, since the increasing compost levels in the soil lowered the rate of disintegration of the film. Also, with the increase in moisture level up to a threshold limit, the microbial activity and, hence, the rate of disintegration increased. Lastly, the developed lab-scale test protocol was found to be sensitive to even small concentrations of industry-standard antimicrobial additive in the film composition.

  10. Low-velocity impact behavior of woven jute/poly(lactic acid) composites

    NASA Astrophysics Data System (ADS)

    Russo, Pietro; Simeoli, Giorgio; Papa, Ilaria; Acierno, Domenico; Lopresto, Valentina; Langella, Antonio

    2016-05-01

    Biocomposite laminates based on poly(lactic acid) (PLA) and woven jute fabric were obtained by film stacking and compression molding techniques. Sample laminates were systematically characterized by impact tests with a falling dart at impact energies equal to 5, 10 and 20 J. Tests showed that, investigated PLA/jute fabric plates suffer only barely visible damages at the first two levels of impact energy while they result to be perforated at 20 J as highlighted by photographic images taken on low and back side of impacted surfaces.

  11. Functionalization of Biodegradable PLA Nonwoven Fabric as Superoleophilic and Superhydrophobic Material for Efficient Oil Absorption and Oil/Water Separation.

    PubMed

    Gu, Jincui; Xiao, Peng; Chen, Peng; Zhang, Lei; Wang, Hanlin; Dai, Liwei; Song, Liping; Huang, Youju; Zhang, Jiawei; Chen, Tao

    2017-02-22

    Although the construction of superwettability materials for oil/water separation has been developed rapidly, the postprocess of the used separation materials themselves is still a thorny problem due to their nondegradation in the natural environment. In this work, we reported the functionalization of polylactic acid (PLA) nonwoven fabric as superoleophilic and superhydrophobic material for efficient treatment of oily wastewater with eco-friendly post-treatment due to the well-known biodegradable nature of PLA matrix.

  12. Surface modification of biomaterials based on high-molecular polylactic acid and their effect on inflammatory reactions of primary human monocyte-derived macrophages: perspective for personalized therapy.

    PubMed

    Stankevich, Ksenia S; Gudima, Alexandru; Filimonov, Victor D; Klüter, Harald; Mamontova, Evgeniya M; Tverdokhlebov, Sergei I; Kzhyshkowska, Julia

    2015-06-01

    Polylactic acid (PLA) based implants can cause inflammatory complications. Macrophages are key innate immune cells that control inflammation. To provide higher biocompatibility of PLA-based implants with local innate immune cells their surface properties have to be improved. In our study surface modification technique for high-molecular PLA (MW=1,646,600g/mol) based biomaterials was originally developed and successfully applied. Optimal modification conditions were determined. Treatment of PLA films with toluene/ethanol=3/7 mixture for 10min with subsequent exposure in 0.001M brilliant green dye (BGD) solution allows to entrap approximately 10(-9)mol/cm(2) model biomolecules. The modified PLA film surface was characterized by optical microscopy, SERS, FT-IR, UV and TG/DTA/DSC analysis. Tensile strain of modified films was determined as well. The effect of PLA films modified with BGD on the inflammatory reactions of primary human monocyte-derived macrophages was investigated. We developed in vitro test-system by differentiating primary monocyte-derived macrophages on a coating material. Type 1 and type 2 inflammatory cytokines (TNFα, CCL18) secretion and histological biomarkers (CD206, stabilin-1) expression were analyzed by ELISA and confocal microscopy respectively. BGD-modified materials have improved thermal stability and good mechanical properties. However, BGD modifications induced additional donor-specific inflammatory reactions and suppressed tolerogenic phenotype of macrophages. Therefore, our test-system successfully demonstrated specific immunomodulatory effects of original and modified PLA-based biomaterials, and can be further applied for the examination of improved coatings for implants and identification of patient-specific reactions to implants.

  13. Effect of platy and tubular nanoclays on behaviour of biodegradable PCL/PLA blend and related microfibrillar composites

    NASA Astrophysics Data System (ADS)

    Kelnar, Ivan; Kratochvíl, Jaroslav

    2016-05-01

    Blending of ductile poly(ɛ-caprolactone) (PCL) and rigid polylactic acid (PLA) is a promising way to tailor biodegradable materials with broad range of properties. But the mutual incompatibility of both polyesters leads to compromised behaviour only. Alternative to PCL/PLA blends is application of PLA in the form of short fibres, however, difficult dispergation of flexible fibres including their poor adhesion and limited processing is a significant restriction. More effective is in situ formation of polymeric fibre-reinforced materials using microfibrillar composites (MFC) concept based on melt- or cold-drawing of a polymer blend. Important advantage of MFC is efficient dispersion and bonding of in-situ formed reinforcing fibres This work deals with combination of structure-directing and reinforcing effects of montmorillonite (oMMT) and halloysite nanotubes (HNT) in the PCL/PLA 80/20 blend with in-situ formation of PLA fibrils in the PCL matrix. In the resulting microfibrillar composite, reinforcement by rigid PLA fibrils is combined with strengthening of both components by the nanofiller (NF). Moreover, PLA fibrils formation via melt-drawing is only possible after nanofiller addition due to favourable affecting of rheological parameters of the polymer components. The structure-properties relationship and complex effect of NF on microfibrillar composite performance, causing e.g., quite comparable parameters of both microfibrillar composites in spite of lower reinforcing effect of halloysite nanotubes on components, are discussed.

  14. Preparation of Nanocellulose Reinforced Chitosan Films, Cross-Linked by Adipic Acid

    PubMed Central

    Falamarzpour, Pouria; Behzad, Tayebeh; Zamani, Akram

    2017-01-01

    Adipic acid, an abundant and nontoxic compound, was used to dissolve and cross-link chitosan. After the preparation of chitosan films through casting technique, the in situ amidation reaction was performed at 80–100 °C as verified by Fourier transform infrared (FT-IR). The reaction was accompanied by the release of water which was employed to investigate the reaction kinetics. Accordingly, the reaction rate followed the first-order model and Arrhenius equation, and the activation energy was calculated to be 18 kJ/mol. Furthermore, the mechanical properties of the chitosan films were comprehensively studied. First, optimal curing conditions (84 °C, 93 min) were introduced through a central composite design. In order to evaluate the effects of adipic acid, the mechanical properties of physically cross-linked (uncured), chemically cross-linked (cured), and uncross-linked (prepared by acetic acid) films were compared. The use of adipic acid improved the tensile strength of uncured and chemically cross-linked films more than 60% and 113%, respectively. Finally, the effect of cellulose nanofibrils (CNFs) on the mechanical performance of cured films, in the presence of glycerol as a plasticizer, was investigated. The plasticized chitosan films reinforced by 5 wt % CNFs showed superior properties as a promising material for the development of chitosan-based biomaterials. PMID:28208822

  15. Preparation of Nanocellulose Reinforced Chitosan Films, Cross-Linked by Adipic Acid.

    PubMed

    Falamarzpour, Pouria; Behzad, Tayebeh; Zamani, Akram

    2017-02-13

    Adipic acid, an abundant and nontoxic compound, was used to dissolve and cross-link chitosan. After the preparation of chitosan films through casting technique, the in situ amidation reaction was performed at 80-100 °C as verified by Fourier transform infrared (FT-IR). The reaction was accompanied by the release of water which was employed to investigate the reaction kinetics. Accordingly, the reaction rate followed the first-order model and Arrhenius equation, and the activation energy was calculated to be 18 kJ/mol. Furthermore, the mechanical properties of the chitosan films were comprehensively studied. First, optimal curing conditions (84 °C, 93 min) were introduced through a central composite design. In order to evaluate the effects of adipic acid, the mechanical properties of physically cross-linked (uncured), chemically cross-linked (cured), and uncross-linked (prepared by acetic acid) films were compared. The use of adipic acid improved the tensile strength of uncured and chemically cross-linked films more than 60% and 113%, respectively. Finally, the effect of cellulose nanofibrils (CNFs) on the mechanical performance of cured films, in the presence of glycerol as a plasticizer, was investigated. The plasticized chitosan films reinforced by 5 wt % CNFs showed superior properties as a promising material for the development of chitosan-based biomaterials.

  16. Comparative study of electroless nickel film on different organic acids modified cuprammonium fabric (CF)

    NASA Astrophysics Data System (ADS)

    Zhao, Hang; Lu, Yinxiang

    2016-01-01

    Nickel films were grown on citric acid (CA), malic acid (MA) and oxalic acid (OA) modified cuprammonium fabric (CF) substrates via electroless nickel deposition. The nickel films were examined using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Their individual deposition rate and electromagnetic interference (EMI) shielding effectiveness (SE) were also investigated to compare the properties of electroless nickel films. SEM images illustrated that the nickel film on MA modified CF substrate was smooth and uniform, and the density of nickel nuclei was much higher. Compared with that of CA modified CF, the coverage of nickel nuclei on OA and MA modified CF substrate was very limited and the nickel particles size was too big. XRD analysis showed that the nickel films deposited on the different modified CF substrates had a structure with Ni (1 1 1) preferred orientation. All the nickel coatings via different acid modification were firmly adhered to the CF substrates, as demonstrated by an ultrasonic washing test. The result of tensile test indicated that the electroless nickel plating on CF has ability to strengthen the CF substrate while causes limited effect on tensile elongation. Moreover, the nickel film deposited on MA modified CF substrate showed more predominant in EMI SE than that deposited on CA or OA modified CF.

  17. Crystallization and preliminary X-ray diffraction studies of BmooPLA2-I, a platelet-aggregation inhibitor and hypotensive phospholipase A2 from Bothrops moojeni venom

    PubMed Central

    Salvador, Guilherme H. M.; Marchi-Salvador, Daniela P.; Silveira, Lucas B.; Soares, Andreimar M.; Fontes, Marcos R. M.

    2011-01-01

    Phospholipases A2 (PLA2s) are enzymes that cause the liberation of fatty acids and lysophospholipids by the hydrolysis of membrane phospholipids. In addition to their catalytic action, a wide variety of pharmacological activities have been described for snake-venom PLA2s. BmooPLA2-I is an acidic, nontoxic and catalytic PLA2 isolated from Bothrops moojeni snake venom which exhibits an inhibitory effect on platelet aggregation, an immediate decrease in blood pressure, inducing oedema at a low concentration, and an effective bactericidal effect. BmooPLA2-I has been crystallized and X-ray diffraction data have been collected to 1.6 Å resolution using a synchrotron-radiation source. The crystals belonged to space group C2221, with unit-cell parameters a = 39.7, b = 53.2, c = 89.2 Å. The molecular-replacement solution of BmooPLA2-I indicated a monomeric conformation, which is in agreement with nondenaturing electrophoresis and dynamic light-scattering experiments. A comparative study of this enzyme with the acidic PLA2 from B. jararacussu (BthA-I) and other toxic and nontoxic PLA2s may provide important insights into the functional aspects of this class of proteins. PMID:21821890

  18. PLA 2010 Conference: Plenty for the Price

    ERIC Educational Resources Information Center

    Miller, Rebecca

    2010-01-01

    This article outlines Public Library Association (PLA) 2010 annual conference to be held in Oregon Convention Center, Portland on March 23-27. The days quickly fill up with the picks of over 100 programs as well as valuable "talk tables" and special events. The well-organized schedule, divided into eight broad tracks (e.g., technology,…

  19. Thermal, mechanical and morphological characterization of plasticized PLA-PHB blends

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A blend of poly(lactic acid) (PLA) (75% by weight) and poly(3-hydroxybutyrate) (PHB) (25% by weight) with a polyester plasticizer (Lapol 108) at two different concentrations (5 and 7% by weight per 100 parts of the blends) were investigated by TGA, DSC, XRD, SEM, mechanical testing and biodegradatio...

  20. Fabrication of biodegradable PEG-PLA nanospheres for solubility, stabilization, and delivery of curcumin.

    PubMed

    Liang, Hongying; Friedman, Joel M; Nacharaju, Parimala

    2017-03-01

    Curcumin is an effective and safe anticancer agent, and also known to induce vasodilation, but its hydrophobicity limits its clinical application. In this study, a simple emulsion method was developed to prepare biodegradable poly (ethylene glycol)-poly (lactic acid) (PEG-PLA) nanospheres to encapsulate curcumin to improve its solubility and stability. The nanoparticle size was around 150 nm with a narrow size distribution. Fluorescence microscopy showed that curcumin encapsulated PEG-PLA nanospheres were taken up rapidly by Hela and MDA-MB-231 cancer cells. This novel nanoparticulate carrier may improve the bioavailability of curcumin without affecting its anticancer properties.

  1. Preparation and characterization of electrospun alginate/PLA nanofibers as tissue engineering material by emulsion eletrospinning.

    PubMed

    Xu, Weihong; Shen, Renzhe; Yan, Yurong; Gao, Jie

    2017-01-01

    Scaffolds made by biomaterials offer favorite environment for cell grow and show a wide potential application in tissue engineering. Novel biocompatibility materials polylatic acid (PLA) nanofiber membranes with favorable biocompatibility and good mechanical strength could serve as an innovative tissue engineering scaffold. Sodium alginate (SA) could be used in biomedical areas because of its anti-bacterial property, hydrophilicity and biocompatibility. In this article, we chose PLA as continuous phase and SA as dispersion phase to prepare a W/O emulsion and then electrospun it to get a SA/PLA composite nanofiber membranes. The CLSM images illustrated that the existence of SA was located on the surface of composite fibers and the FTIR results confirmed the result. A calcium ion replacement step was used as an after-treatment for SA/PLA nanofiber membranes in order to anchor the alginic ion in a form of gelated calcium alginate (CA). The single fiber tensile test shows a good mechanical property of CA/PLA nanofiber membranes, and the nanofiber membranes are beneficial for cell proliferation and differentiation owing to MTT array as well as Alizarin red S (ARS) staining test.

  2. Effect of filler loading of nickel zinc ferrite on the tensile properties of PLA nanocomposites

    NASA Astrophysics Data System (ADS)

    Shahdan, Dalila; Ahmad, Sahrim Hj

    2013-05-01

    The mechanical strength of magnetic polymer nanocomposite (MPNC) of nickel zinc (NiZn) ferrite nanoparticles incorporated with polylactic acid (PLA) and liquid natural rubber (LNR) as compatibilizer is reported. The matrix was prepared from PLA and LNR in the ratio of 90:10. The MPNC were prepared at constant mixing temperature at 180°C, mixing time of 15 min. and mixing speed of 100 rpm. In order to achieve a good dispersion of NiZn ferrite in the matrix, firstly an ultrasonic treatment had been employed to mix the LNR and NiZn ferrite for 1 hour. The MPNC of PLA/LNR/NiZn ferrite then were prepared via Thermo Haake internal mixer using melt-blending method from different filler loading from 1-5 wt% NiZn ferrite. The result of tensile tests showed that as the filler loading increases the tensile strength also increases until an optimum value of filler loading was reached. The Young's modulus, tensile strength and elongation at break have also increased. The study proves that NiZn ferrite is excellent reinforcement filler in PLA matrix. Scanning electron micrograph (SEM) and energy dispersive X-ray spectroscopy (EDX) were meant to show the homogeneity dispersion of nanoparticles within the matrix and to confirm the elemental composition of NiZn ferrites-PLA/LNR nanocomposites respectively.

  3. PlaMoM: a comprehensive database compiles plant mobile macromolecules

    PubMed Central

    Guan, Daogang; Yan, Bin; Thieme, Christoph; Hua, Jingmin; Zhu, Hailong; Boheler, Kenneth R.; Zhao, Zhongying; Kragler, Friedrich; Xia, Yiji; Zhang, Shoudong

    2017-01-01

    In plants, various phloem-mobile macromolecules including noncoding RNAs, mRNAs and proteins are suggested to act as important long-distance signals in regulating crucial physiological and morphological transition processes such as flowering, plant growth and stress responses. Given recent advances in high-throughput sequencing technologies, numerous mobile macromolecules have been identified in diverse plant species from different plant families. However, most of the identified mobile macromolecules are not annotated in current versions of species-specific databases and are only available as non-searchable datasheets. To facilitate study of the mobile signaling macromolecules, we compiled the PlaMoM (Plant Mobile Macromolecules) database, a resource that provides convenient and interactive search tools allowing users to retrieve, to analyze and also to predict mobile RNAs/proteins. Each entry in the PlaMoM contains detailed information such as nucleotide/amino acid sequences, ortholog partners, related experiments, gene functions and literature. For the model plant Arabidopsis thaliana, protein–protein interactions of mobile transcripts are presented as interactive molecular networks. Furthermore, PlaMoM provides a built-in tool to identify potential RNA mobility signals such as tRNA-like structures. The current version of PlaMoM compiles a total of 17 991 mobile macromolecules from 14 plant species/ecotypes from published data and literature. PlaMoM is available at http://www.systembioinfo.org/plamom/. PMID:27924044

  4. Effects of screw speed on the properties of plasticized PLA/POSS composites

    NASA Astrophysics Data System (ADS)

    Kodal, M.; Sirin, H.; Ozkoc, G.

    2014-05-01

    The effect of screw speed on the flow behavior, mechanical, thermal and morphological properties of the melt compounded plasticized poly(lactic acid) (PLA)/polyhedral oligomeric silsesquioxanes (POSS) composites were investigated. Two types of POSS-aminopropylisobutyl-POSS (A-POSS) as the reactive one and the octaisobutyl-POSS (O-POSS) as the non-reactive one, were used at 1-10 wt% filler loadings. Poly(ethylene glycol) (PEG-8000 g/moles) was utilized as a plasticizer. PEG amount was kept constant at 10 wt% with respect to PLA. To investigate the compounding conditions on the properties of the composites, two different screw speeds (100 and 200 rpm) were used. It was found that incorporation of POSS particles to the PLA decreased the melt viscosity of the composites due to the slip-agent behavior of POSS molecules. The mechanical test results showed that composites compounded at 100 rpm have higher yield strength and modulus values. Moreover, a significant improvement in Izod impact strength of plasticized PLA composites compounded at 100 rpm was obtained (regardless of POSS type). SEM analysis showed that POSS particles dispersed homogeneously in polymer matrix at all loadings regardless of screw speed. It was revealed from DSC that POSS particles acted as a nucleating agent for PLA/PEG independently from mixing conditions. Moreover, the percent crystallinity was found to be higher in the presence of POSS.

  5. Extruded films of blended chitosan, low density polyethylene and ethylene acrylic acid.

    PubMed

    Martínez-Camacho, A P; Cortez-Rocha, M O; Graciano-Verdugo, A Z; Rodríguez-Félix, F; Castillo-Ortega, M M; Burgos-Hernández, A; Ezquerra-Brauer, J M; Plascencia-Jatomea, M

    2013-01-16

    The obtaining of chitosan extruded films was possible by using low density polyethylene (LDPE) as a matrix polymer and ethylene-acrylic acid copolymer as an adhesive, in order to ensure adhesion in the interphase of the immiscible polymers. The obtained blend films were resistant; however, a reduction in the mechanical resistance was observed as chitosan concentration increased. The thermal stability of the films showed a certain grade of interaction between polymers as seen in FTIR spectra. The antifungal activity of the extruded films was assessed against Aspergillus niger and high inhibition percentages were observed, which may be mainly attributed to barrier properties of the extruded films and the limited oxygen availability, resulting in the inability of the fungi to grow. A low adherence of fungal spores to the material surface was observed, mainly in areas with chitosan clumps, which can serve as starting points for material degradation.

  6. Electrodeposited Films from Aqueous Tungstic Acid-Hydrogen Peroxide Solutions for Electrochromic Display Devices

    NASA Astrophysics Data System (ADS)

    Yamanaka, Kazusuke

    1987-11-01

    Electrodeposited tungsten oxide films from aqueous tungstic acid-hydrogen peroxide solutions were investigated for applications to electrochromic devices. These films exhibited electrochromism in aprotic electrolyte solutions containing Li-salts. When the films were heat-treated for an hour at temperatures between 100 and 200°C, the electrochromic reactions were rich in reversibility. The coloring efficiency and response rate for the films were favorable and comparable to those for tungsten trioxide evaporated films. A cell life-test was performed on several clock-size cells by applying a 1.2-V, 1-Hz, continuous square wave. The typical amount of charge required for coloration was about 50 C / m2 and remained unchanged even after 107 coloration-bleaching cycles.

  7. Unusual effects of monocarboxylic acids on the structure and on the transport and mechanical properties of chitosan films.

    PubMed

    Chen, Fei; Gällstedt, Mikael; Olsson, Richard T; Gedde, Ulf W; Hedenqvist, Mikael S

    2015-11-05

    The purpose of this study was to study the transport of monocarboxylic acids in chitosan films, since this is important for understanding and predicting the drying kinetics of chitosan from aqueous solutions. Despite the wealth of data on chitosan films prepared from aqueous monocarboxylic acid solutions, this transport has not been reported. Chitosan films were exposed to formic, acetic, propionic and butyric acid vapours, it was found that the rate of uptake decreased with increasing molecular size. The equilibration time was unexpectedly long, especially for propionic and butyric acid, nine months. A clear two-stage uptake curve was observed for propionic acid. Evidently, the rate of uptake was determined by acid-induced changes in the material. X-ray diffraction and infrared spectroscopy indicated that the structure of the chitosan acetate and buffered chitosan films changed during exposure to acid and during the subsequent drying. The dried films previously exposed to the acid showed less crystalline features than the original material and a novel repeating structure possibly involving acid molecules. The molar mass of the chitosan decreased on exposure to acid but tensile tests revealed that the films were always ductile. The films exposed to acid vapour (propionic and butyric acid) for the longest period of time were insoluble in the size-exclusion chromatography eluent, and they were also the most ductile/extensible of all samples studied.

  8. Vapor sensing mechanism of acid on copper phthalocyanine thin films studied by electrical conductivity

    NASA Astrophysics Data System (ADS)

    Singh, Sukhwinder; Saini, G. S. S.; Tripathi, S. K.

    2013-06-01

    The electrical conductivity of thin films of iron phthalocyanine on glass substrates by thermal evaporation technique have been investigated. The electrical conductivity of thin films of these complexes changes when exposed to oxidizing and reducing gases such as halogens, ammonia, water and NOX. Thermal activation energy in the intrinsic region and impurity scattering region can be calculated by using Arrhenius plot. The dark conductivity and photoconductivity have been taken at different temperatures in the range 312-389 K. These films have been studied as chemical sensors for dilute sulphuric acid.

  9. Rapid amplification/detection of nucleic acid targets utilizing a HDA/thin film biosensor.

    PubMed

    Jenison, Robert; Jaeckel, Heidi; Klonoski, Joshua; Latorra, David; Wiens, Jacinta

    2014-08-07

    Thin film biosensors exploit a flat, optically coated silicon-based surface whereupon formation of nucleic acid hybrids are enzymatically transduced in a molecular thin film that can be detected by the unaided human eye under white light. While the limit of sensitivity for detection of nucleic acid targets is at sub-attomole levels (60 000 copies) many clinical specimens containing bacterial pathogens have much lower levels of analyte present. Herein, we describe a platform, termed HDA/thin film biosensor, which performs helicase-dependant nucleic acid amplification on a thin film biosensor surface to improve the limit of sensitivity to 10 copies of the mecA gene present in methicillin-resistant strains of Staphylococcus. As double-stranded DNA is unwound by helicase it was either bound by solution-phase DNA primers to be copied by DNA polymerase or hybridized to surface immobilized probe on the thin film biosensor surface to be detected. Herein, we show that amplification reactions on the thin film biosensor are equivalent to in standard thin wall tubes, with detection at the limit of sensitivity of the assay occurring after 30 minutes of incubation time. Further we validate the approach by detecting the presence of the mecA gene in methicillin-resistant Staphylococcus aureus (MRSA) from positive blood culture aliquots with high specificity (signal/noise ratio of 105).

  10. Photoenhanced nitrous acid formation upon NO2 uptake on tannic and gentisic acid films

    NASA Astrophysics Data System (ADS)

    Sosedova, Yulia; Rouvière, Aurélie; Ammann, Markus

    2010-05-01

    The heterogeneous chemistry of nitrogen dioxide (NO2) is a potential source of nitrous acid (HONO). Hydroxy and methoxy substituted phenols may play a significant role in the aqueous-phase chemistry occurring on the ground or within aerosol particles in air masses affected by biomass burning. It is well established that electron transfer between phenols and NO2 in alkaline aqueous solutions is fast and could be a source of nitrite in the aqueous phase and HONO in the gas phase. However its kinetics is very slow under atmospheric conditions. The role of phenolic species as electron donors has also been suspected to be responsible for the photoenhanced transformation of NO2 to HONO over humic acids [1]. In this study we used tannic (TA) and gentisic (GA) as another proxy for atmospheric phenolic compounds. TA was shown to easily decompose under near UV light irradiation [2] resulting in oxidized products that might change the hygroscopic properties of the original material or have some potential photosensitizing effect. It was interesting to check the hypothesis that the presence of such products could lead to photoenhanced HONO formation upon NO2 uptake to aqueous surfaces containing TA. Experiments were performed in a horizontal coated wall flow tube (40 cm × 5.9 cm i.d.) circularly surrounded by 7 fluorescence lamps (UV: 300-420 nm, or visible: 400-750 nm), in an air cooled lamp housing. The inner surface coating was containing ~0.5 mg/cm-2 of either TA or GA, and was operated under RH 20-80%, 21-23 °C and ambient pressure. Concentration of HONO in the gas phase at the flow tube exit was measured with a LOPAP (Long Path Absorption Spectrometer). The uptake coefficient (γ) leading to NO2 to HONO conversion above aqueous films containing GA or TA in the dark was in the range 4×10-7 - 2×10-6. The photochemically enhanced HONO production was demonstrated by UV irradiation of the GA or TA coatings being in contact with gaseous NO2. In this case γ was 3-10 times

  11. PLA-grafting of collagen chains leading to a biomaterial with mechanical performances useful in tendon regeneration.

    PubMed

    Bellini, Davide; Cencetti, Claudia; Sacchetta, Anna Cristina; Battista, Angela Maria; Martinelli, Andrea; Mazzucco, Laura; Scotto D'Abusco, Anna; Matricardi, Pietro

    2016-12-01

    With the aim to obtain a scaffold with improved mechanical properties with respect to collagen for tendon augmentation and regeneration, a novel collagen-based material was prepared via heterogeneous phase derivatization of type I collagen sponges using polylactic acid. Compared to the untreated collagen, the functionalized sponge (Coll-PLA) was characterized by higher tensile properties and lower swelling capability; the degradation rate of Coll-PLA, in the presence of collagenase, was lower than that of the untreated collagen sponge. These results are related to an increased hydrophobic character of the collagen matrix due to the presence of PLA chains. In vitro tests, performed with human primary fibroblasts, showed that cell adhesion and proliferation rate on Coll-PLA were comparable to those obtained with the non-functionalized collagen. These findings suggest that the new biomaterial could be suitable as scaffold in tendon augmentation and regeneration.

  12. Collagen-Based Films Containing Liposome-Loaded Usnic Acid as Dressing for Dermal Burn Healing

    PubMed Central

    Nunes, Paula S.; Albuquerque-Júnior, Ricardo L. C.; Cavalcante, Danielle R. R.; Dantas, Marx D. M.; Cardoso, Juliana C.; Bezerra, Marília S.; Souza, Jamille C. C.; Serafini, Mairim Russo; Quitans-Jr, Lucindo J.; Bonjardim, Leonardo R.; Araújo, Adriano A. S.

    2011-01-01

    The aim of this study was assess the effect of collagen-based films containing usnic acid as a wound dressing for dermal burn healing. Second-degree burn wounds were performed in forty-five Wistar rats, assigned into nine groups: COL—animals treated with collagen-based films; PHO—animals treated with collagen films containing empty liposomes; UAL—animals treated with collagen-based films containing usnic acid incorporated into liposomes. After 7, 14, and 21 days the animals were euthanized. On 7th day there was a moderate infiltration of neutrophils, in UAL, distributed throughout the burn wounds, whereas in COL and PHO, the severity of the reaction was slighter and still limited to the margins of the burn wounds. On the 14th day, the inflammatory reaction was less intense in UAL, with remarkable plasma cells infiltration. On the 21st day, there was reduction of the inflammation, which was predominantly composed of plasma cells in all groups, particularly in UAL. The use of the usnic acid provided more rapid substitution of type-III for type-I collagen on the 14th day, and improved the collagenization density on the 21st day. It was concluded that the use of reconstituted bovine type-I collagen-based films containing usnic acid improved burn healing process in rats. PMID:21274404

  13. Partial characterization of chayotextle starch-based films added with ascorbic acid encapsulated in resistant starch.

    PubMed

    Martínez-Ortiz, Miguel A; Vargas-Torres, Apolonio; Román-Gutiérrez, Alma D; Chavarría-Hernández, Norberto; Zamudio-Flores, Paul B; Meza-Nieto, Martín; Palma-Rodríguez, Heidi M

    2017-05-01

    Chayotextle starch was modified by subjecting it to a dual treatment with acid and heating-cooling cycles. This caused a decrease in the content of amylose, which showed values of 30.22%, 4.80%, 3.27% and 3.57% for native chayotextle starch (NCS), starch modified by acid hydrolysis (CMS), and CMS with one (CMS1AC) and three autoclave cycles (CMS3AC), respectively. The percentage of crystallinity showed an increase of 36.9%-62% for NCS and CMS3AC. The highest content of resistant starch (RS) was observed in CMS3AC (37.05%). The microcapsules were made with CMS3AC due to its higher RS content; the total content of ascorbic acid of the microcapsules was 82.3%. The addition of different concentrations of CMS3AC microcapsules (0%, 2.5%, 6.255% and 12.5%) to chayotextle starch-based films (CSF) increased their tensile strength and elastic modulus. The content of ascorbic acid and RS in CSF was ranged from 0% to 59.4% and from 4.84% to 37.05% in the control film and in the film mixed with CMS3AC microcapsules, respectively. Water vapor permeability (WVP) values decreased with increasing concentrations of microcapsules in the films. Microscopy observations showed that higher concentrations of microcapsules caused agglomerations due their poor distribution in the matrix of the films.

  14. Doping Polypyrrole Films with 4-N-Pentylphenylboronic Acid to Enhance Affinity towards Bacteria and Dopamine

    PubMed Central

    Padiolleau, Laurence; Chen, Xi; Jafari, Mohammad Javad; Sheikhzadeh, Elham; Turner, Anthony P. F.; Jager, Edwin W. H.; Beni, Valerio

    2016-01-01

    Here we demonstrate the use of a functional dopant as a fast and simple way to tune the chemical affinity and selectivity of polypyrrole films. More specifically, a boronic-functionalised dopant, 4-N-Pentylphenylboronic Acid (PBA), was used to provide to polypyrrole films with enhanced affinity towards diols. In order to prove the proposed concept, two model systems were explored: (i) the capture and the electrochemical detection of dopamine and (ii) the adhesion of bacteria onto surfaces. The chemisensor, based on overoxidised polypyrrole boronic doped film, was shown to have the ability to capture and retain dopamine, thus improving its detection; furthermore the chemisensor showed better sensitivity in comparison with overoxidised perchlorate doped films. The adhesion of bacteria, Deinococcus proteolyticus, Escherichia coli, Streptococcus pneumoniae and Klebsiella pneumoniae, onto the boric doped polypyrrole film was also tested. The presence of the boronic group in the polypyrrole film was shown to favour the adhesion of sugar-rich bacterial cells when compared with a control film (Dodecyl benzenesulfonate (DBS) doped film) with similar morphological and physical properties. The presented single step synthesis approach is simple and fast, does not require the development and synthesis of functional monomers, and can be easily expanded to the electrochemical, and possibly chemical, fabrication of novel functional surfaces and interfaces with inherent pre-defined sensing and chemical properties. PMID:27875555

  15. Doping Polypyrrole Films with 4-N-Pentylphenylboronic Acid to Enhance Affinity towards Bacteria and Dopamine.

    PubMed

    Golabi, Mohsen; Padiolleau, Laurence; Chen, Xi; Jafari, Mohammad Javad; Sheikhzadeh, Elham; Turner, Anthony P F; Jager, Edwin W H; Beni, Valerio

    2016-01-01

    Here we demonstrate the use of a functional dopant as a fast and simple way to tune the chemical affinity and selectivity of polypyrrole films. More specifically, a boronic-functionalised dopant, 4-N-Pentylphenylboronic Acid (PBA), was used to provide to polypyrrole films with enhanced affinity towards diols. In order to prove the proposed concept, two model systems were explored: (i) the capture and the electrochemical detection of dopamine and (ii) the adhesion of bacteria onto surfaces. The chemisensor, based on overoxidised polypyrrole boronic doped film, was shown to have the ability to capture and retain dopamine, thus improving its detection; furthermore the chemisensor showed better sensitivity in comparison with overoxidised perchlorate doped films. The adhesion of bacteria, Deinococcus proteolyticus, Escherichia coli, Streptococcus pneumoniae and Klebsiella pneumoniae, onto the boric doped polypyrrole film was also tested. The presence of the boronic group in the polypyrrole film was shown to favour the adhesion of sugar-rich bacterial cells when compared with a control film (Dodecyl benzenesulfonate (DBS) doped film) with similar morphological and physical properties. The presented single step synthesis approach is simple and fast, does not require the development and synthesis of functional monomers, and can be easily expanded to the electrochemical, and possibly chemical, fabrication of novel functional surfaces and interfaces with inherent pre-defined sensing and chemical properties.

  16. Refractive index modulation in polymer film doped with diazo Meldrum's acid

    NASA Astrophysics Data System (ADS)

    Zanutta, Alessio; Villa, Filippo; Bertarelli, Chiara; Bianco, Andrea

    2016-08-01

    Diazo Meldrum's acid undergoes a photoreaction induced by UV light and it is used as photosensitizer in photoresists. Upon photoreaction, a change in refractive index occurs, which makes this system interesting for volume holography. We report on the sublimation effect at room temperature and the effect of photoirradiation on the refractive index in thin films of CAB (Cellulose acetate butyrate) doped with different amount of diazo Meldrum's acid. A net modulation of the refractive index of 0.01 is achieved with 40% of doping ratio together with a reduction of the film thickness.

  17. A PLA1-2 Punch Regulates the Golgi Complex

    PubMed Central

    Bechler, Marie E.; de Figueiredo, Paul; Brown, William J.

    2011-01-01

    The mammalian Golgi complex, trans Golgi network (TGN) and ER-Golgi-Intermediate Compartment (ERGIC) are comprised of membrane cisternae, coated vesicles and membrane tubules, all of which contribute to membrane trafficking and maintenance of their unique architectures. Recently, a new cast of players was discovered to regulate the Golgi and ERGIC: four unrelated cytoplasmic phospholipase A (PLA) enzymes, cPLA2α (GIVA cPLA2), PAFAH Ib (GVIII PLA2), iPLA2-β (GVIA-2 iPLA2), and iPLA1γ. These ubiquitously expressed enzymes regulate membrane trafficking from specific Golgi subcompartments, although there is evidence for some functional redundancy between PAFAH Ib and cPLA2α. Three of these enzymes, PAFAH Ib, cPLA2α, and iPLA2-β, exert effects on Golgi structure and function by inducing the formation of membrane tubules. Here, we review our current understanding of how PLA enzymes regulate Golgi and ERGIC morphology and function. PMID:22130221

  18. Combined effect of cellulose nanocrystal and reduced graphene oxide into poly-lactic acid matrix nanocomposite as a scaffold and its anti-bacterial activity.

    PubMed

    Pal, Nidhi; Dubey, Poornima; Gopinath, P; Pal, Kaushik

    2017-02-01

    In the present study, cellulose nanocrystals (CNCs) and reduced graphene oxide (rGO) were successfully synthesized via acid hydrolysis and modified Hummer's method, respectively. Further, the synthesized CNCs and rGO were incorporated into poly-lactic acid (PLA) matrix using solution casting method utilizing different weight (wt.) % of CNCs (nanofiller) and rGO. The successful synthesis of various nanoformulations were confirmed by several characterization techniques including Transmission Electron Microscopy (TEM), Field-Emission Scanning Electron Microscopy (FE-SEM) and Fourier Transform Infrared Spectroscopy (FTIR) analysis. Hydrophilicity measurement of the film was done by wettability analysis. The mechanical property evaluation of scaffold showed considerable increased tensile strength of PLA/CNC/rGO nanocomposite upto 23%, with increase in elongation at break (εb) indicating the ductile behavior of nanocomposite as compare to pristine PLA. The distinct anti-bacterial efficacy of PLA/CNC/rGO nanocomposite film was found against both Gram positive Staphylococcus aureus (S.aureus) and Gram negative Escherichia coli. (E. coli) bacterial strains respectively. Furthermore the in-vitro cell based cytotoxicity assay showed negligible cytotoxicity of fibroblast cell line (NIH-3T3) upon treatment with nanocomposite film. Therefore, the as fabricated nanocomposite film possesses considerable potential in biomedical as well as in food packaging applications.

  19. Boric/sulfuric acid anodizing of aluminum alloys 2024 and 7075: Film growth and corrosion resistance

    SciTech Connect

    Thompson, G.E.; Zhang, L.; Smith, C.J.E.; Skeldon, P.

    1999-11-01

    The influence of boric acid (H{sub 3}BO{sub 3}) additions to sulfuric acid (H{sub 2}SO{sub 4}) were examined for the anodizing of Al 2024-T3 (UNS A92024) and Al 7075-T6 (UNS A97075) alloys at constant voltage. Alloys were pretreated by electropolishing, by sodium dichromate (Na{sub 2}Cr{sub 2}O{sub 7})/H{sub 2}SO{sub 4} (CSA) etching, or by alkaline etching. Current-time responses revealed insignificant dependence on the concentration of H{sub 3}BO{sub 3} to 50 g/L. Pretreatments affected the initial film development prior to the establishment of the steady-state morphology of the porous film, which was related to the different compositions and morphologies of pretreated surfaces. More detailed studies of the Al 7075-T6 alloy indicated negligible effects of H{sub 3}BO{sub 3} on the coating weight, morphology of the anodic film, and thickening rate of the film, or corrosion resistance provided by the film. In salt spray tests, unsealed films formed in H{sub 2}SO{sub 4} or mixed acid yielded similar poor corrosion resistances, which were inferior to that provided by anodizing in chromic acid (H{sub 2}CrO{sub 4}). Sealing of films in deionized water, or preferably in chromate solution, improved corrosion resistance, although not matching the far superior performance provided by H{sub 2}CrO{sub 4} anodizing and sealing.

  20. PLA Reforms and Chinas Nuclear Forces

    DTIC Science & Technology

    2016-10-01

    will affect the force structure , adminis- tration, and command and control mechanisms of the People’s Liberation Army (PLA). The reforms have the...Army (PLAA) headquarters and the Strategic Support Force. Establishment of a separate headquarters will move the PLAA to a bureaucratic structure and...commands and the re- structured Central Military Commission (CMC), however, are staffed by PLAA officers, so the effectiveness of this change remains to

  1. Exceptionally crystalline and conducting acid doped polyaniline films by level surface assisted solution casting approach

    NASA Astrophysics Data System (ADS)

    Puthirath, Anand B.; Methattel Raman, Shijeesh; Varma, Sreekanth J.; Jayalekshmi, S.

    2016-04-01

    Emeraldine salt form of polyaniline (PANI) was synthesized by chemical oxidative polymerisation method using ammonium persulfate as oxidant. Resultant emeraldine salt form of PANI was dedoped using ammonia solution and then re-doped with camphor sulphonic acid (CSA), naphthaline sulphonic acid (NSA), hydrochloric acid (HCl), and m-cresol. Thin films of these doped PANI samples were deposited on glass substrates using solution casting method with m-cresol as solvent. A level surface was employed to get homogeneous thin films of uniform thickness. Detailed X-ray diffraction studies have shown that the films are exceptionally crystalline. The crystalline peaks observed in the XRD spectra can be indexed to simple monoclinic structure. FTIR and Raman spectroscopy studies provide convincing explanation for the exceptional crystallinity observed in these polymer films. FESEM and AFM images give better details of surface morphology of doped PANI films. The DC electrical conductivity of the samples was measured using four point probe technique. It is seen that the samples also exhibit quite high DC electrical conductivity, about 287 S/cm for CSA doped PANI, 67 S/cm for NSA doped PANI 65 S/cm for HCl doped PANI, and just below 1 S/cm for m-cresol doped PANI. Effect of using the level surface for solution casting is studied and correlated with the observed crystallinity.

  2. Enhanced charge transport in highly conducting PEDOT-PSS films after acid treatment

    NASA Astrophysics Data System (ADS)

    Shiva, V. Akshaya; Bhatia, Ravi; Menon, Reghu

    The high electrical conductivity, good stability, high strength, flexibility and good transparency of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS), make it useful for many applications including polymeric anodes for organic photovoltaics, light-emitting diodes, flexible electrodes, supercapacitors, electrochromic devices, field-effect transistors and antistatic-coatings. However, the electrical conductivity of PEDOT-PSS has to be increased significantly for replacement of indium tin oxide (ITO) as the transparent electrode in optoelectronic devices. The as prepared (pristine) PEDOT-PSS film prepared from the PEDOT-PSS aqueous solution usually has conductivity below 1Scm-1, remarkably lower than ITO. Significant conductivity enhancement has been observed on transparent and conductive PEDOT-PSS films after a treatment with inorganic acids. Our study investigates the charge transport in pristine and H2SO4, HNO3, HCl treated PEDOT-PSS films. We have treated the films with various concentrations of acids to probe the effect of the acid treatment on the conduction mechanism. The study includes the measurement of dc and electric field dependent conductivity of films in the temperature range of 4.2K-300K. We have also performed magneto-resistance measurements in the range of 0-5T. An enhancement by a factor of~103 has been observed in the room temperature conductivity. The detailed magneto-transport studies explain the various mechanisms for the conductivity enhancement observed.

  3. A comparative in vitro evaluation of self-assembled PTX-PLA and PTX-MPEG-PLA nanoparticles

    NASA Astrophysics Data System (ADS)

    Cui, Fei; Li, Yang; Zhou, Shuifan; Jia, Mengmeng; Yang, Xiangrui; Yu, Fei; Ye, Shefang; Hou, Zhenqing; Xie, Liya

    2013-06-01

    We present a dialysis technique to direct the self-assembly of paclitaxel (PTX)-loaded nanoparticles (NPs) using methoxypolyethylene glycol-poly( d, l-lactide) (MPEG-PLA) and PLA, respectively. The composition, morphology, particle size and zeta potential, drug loading content, and drug encapsulation efficiency of both PTX-PLA NPs and PTX-MPEG-PLA NPs were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, dynamic light scattering, electrophoretic light scattering, and high-performance liquid chromatography. The passive targeting effect and in vitro cell viability of the PTX-MPEG-PLA NPs on HeLa cells were demonstrated by comparative cellular uptake and MTT assay of the PTX-PLA NPs. The results showed that the PTX-MPEG-PLA NPs and PTX-PLA NPs presented a hydrodynamic particle size of 179.5 and 441.9 nm, with a polydispersity index of 0.172 and 0.189, a zeta potential of -24.3 and -42.0 mV, drug encapsulation efficiency of 18.3% and 20.0%, and drug-loaded content of 1.83% and 2.00%, respectively. The PTX-MPEG-PLA NPs presented faster release rate with minor initial burst compared to the PTX-PLA NPs. The PTX-MPEG-PLA NPs presented superior cell cytotoxicity and excellent cellular uptake compared to the PTX-PLA NPs. These results suggested that the PTX-MPEG-PLA NPs presented more desirable characteristics for sustained drug delivery compared to PTX-PLA NPs.

  4. Synthesis and film formation of furfuryl- and maleimido carbonic acid derivatives of dextran.

    PubMed

    Elschner, Thomas; Obst, Franziska; Stana-Kleinschek, Karin; Kargl, Rupert; Heinze, Thomas

    2017-04-01

    Carbonic acid derivatives of dextran possessing furfuryl- and maleimido moieties were synthesized and processed into thin films by spin coating. First, products with different degrees of substitution (DS) of up to 3.0 and substitution patterns were obtained and characterized by NMR- and FTIR spectroscopy, as well as elemental analysis. Thin films possessing maleimide groups were obtained by spin coating of maleimido dextran (furan-protected) and dextran furfuryl carbamate that was converted with bismaleimide. The removal of the protecting group (furan) on the thin film was monitored by QCM-D and compared with gravimetric analysis of the bulk material. Film morphology and wettability were determined by means of AFM and contact angle measurements.

  5. Electrodeposition of copper selenide films from acidic bath and their properties

    NASA Astrophysics Data System (ADS)

    Mane, Rajaram S.; Shaikh, Arif V.; Joo, Oh-Shim; Han, Sung-Hwan; Pathan, Habib M.

    2012-06-01

    Copper selenide thin films are successfully deposited using electrodeposition method by combining copper sulfate and sodiumseleno sulfate precursors at room temperature in acidic bath. The chemical composition was a key factor in preparing high-quality uniform and smooth thin films of the copper selenide. We present indium-tin-oxide as a substrate for depositing copper selenide films which usually exists as copper (I) selenide or copper (II) selenide. Obtained brownish films of copper selenide are examined for their structural, morphological, compositional and optical properties by means of X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis and optical absorption measurement techniques, respectively for the structural, morphological and optical analysis.

  6. Development and Characterization of Novel Polyurethane Films Impregnated with Tolfenamic Acid for Therapeutic Applications

    PubMed Central

    Sheraz, Muhammad Ali; Rehman, Ihtesham ur

    2013-01-01

    The present study deals with the preparation of polyurethane (PU) films impregnated with a nonsteroidal anti-inflammatory drug, tolfenamic acid (TA). Solvent evaporation technique has been employed for the preparation of TA-PU films in two different ratios of 1 : 2 and 1 : 5 in Tetrahydrofuran (THF) or THF-ethanol mixtures. The prepared films were characterized using X-Ray Diffraction (XRD), Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and release studies. The results indicate transformation of crystalline TA to its amorphous form. The degree of crystallinity changes both by increasing the polymer concentration and solvent used for the film preparations. The release profiles of TA were also found to be affected, showing a decrease from approximately 50% to 25% from 1 : 2 to 1 : 5 ratios, respectively. PMID:24073394

  7. Gemini amphiphiles regulated photopolymerization of diacetylene acid in organized molecular films.

    PubMed

    Zhong, Ling; Jiao, Tifeng; Liu, Minghua

    2009-07-02

    In this paper, we have investigated the photopolymerization of an amphiphilic diacetylene, 10,12-pentacosadiynoic acid (PCDA), in organized molecular films in the presence of a series of gemini amphiphiles with different spacer lengths. It has been found that, when gemini amphiphiles were mixed with the diacetylene, the film-forming properties were greatly improved and the photopolymerization could be regulated by the gemini amphiphiles. Miscibility and Fourier transform infrared spectroscopy (FT-IR) investigations revealed that the polymerization of PCDA in a mixed film was regulated by the mixing ratio and spacer length of the gemini amphiphiles. Although a slight amount of gemini amphiphile did not make the PCDA polymerize into blue films, the increment of the gemini amphiphile with the short spacer length in the mixed film caused the formation of a red film, and the intensity of red phase to blue phase can be modulated by changing the mixing ratios. When gemini amphiphiles with longer spacer lengths were mixed, blue films were predominantly obtained in all mixing ratios. A mechanism including the interaction between the headgroup of the gemini amphiphiles and the diacetylene and the regulation of the spacer was proposed.

  8. Nanomechanical properties of poly(lactic-co-glycolic) acid film during degradation.

    PubMed

    Shirazi, Reyhaneh Neghabat; Aldabbagh, Fawaz; Erxleben, Andrea; Rochev, Yury; McHugh, Peter

    2014-11-01

    Despite the potential applications of poly(lactic-co-glycolic) acid (PLGA) coatings in medical devices, the mechanical properties of this material during degradation are poorly understood. In the present work, the nanomechanical properties and degradation of PLGA film were investigated. Hydrolysis of solvent-cast PLGA film was studied in buffer solution at 37 °C. The mass loss, water uptake, molecular weight, crystallinity and surface morphology of the film were tracked during degradation over 20 days. Characterization of the surface hardness and Young's modulus was performed using the nanoindentation technique for different indentation loads. The initially amorphous films were found to remain amorphous during degradation. The molecular weight of the film decreased quickly during the initial days of degradation. Diffusion of water into the film resulted in a reduction in surface hardness during the first few days, followed by an increase that was due to the surface roughness. There was a significant delay between the decrease in the mechanical properties of the film and the decrease in the molecular weight. A sudden decline in mechanical properties indicated that significant bulk degradation had occurred.

  9. Effects of Ethylenediamine Tetraacetic Acid on the Texture and Magnetic Properties of Barium Ferrite Films

    NASA Astrophysics Data System (ADS)

    Li, Fang; Zhang, Wanli; Peng, Bin; Zhang, Wenxu

    2012-08-01

    M-type barium ferrite thin films with hexagonal platelets on sapphire were fabricated by spin-coating of precursors. Fourier-transform infrared spectra indicated that bonds between the metal and oxygen were formed at about 500°C. X-ray diffraction showed that the films had preferred c-axis orientation. Surface morphology of the film was investigated by scanning electron microscopy. Textures of the films were influenced by the amount of ethylenediamine tetraacetic acid (EDTA). The film with the least pores and the most c-axis-textured platelet hexagonal grains was obtained when the ratio of EDTA to metal ions was 1.0. At the same time, the magnetic hysteresis loops in directions parallel and perpendicular to the film plane demonstrated that the films were almost isotropic. The maximum coercive forces of 43.23 kA/m in plane and 54.70 kA/m out of plane were achieved when the ratio of the amount of EDTA to metal ions was 0.5. The highest in-plane remanence ratio was 0.32 when the ratio of EDTA to metal ions was 1.5, while the highest out-of-plane value was 0.28 in the other two cases.

  10. Development of polylactide (PLA) and PLA nanocomposite foams in injection molding for automotive applications

    NASA Astrophysics Data System (ADS)

    Najafi Chaloupli, Naqi

    Plastic materials are extensively used in automotive structures since they make cars more energy efficient. Recently, the automotive industry is searching for bio-based and renewable alternatives to petroleum-based plastics to reduce the dependence on fossil fuels. Among polymers originating from renewable sources, polylactide (PLA) has attracted significant interest. The use of this polymer in durable industries is promising. Fuel-efficient automobiles are nowadays demanded due to the increasing concerns about environmental and fuel issues. The automobile fuel efficiency can be improved by using a lightweight material and, thereby, reducing the automobile weight. A potential method to achieve this objective is the use of the foaming technology. Foam is a material where a gas phase is encapsulated by a solid phase. Foaming technology helps to manufacture lightweight parts with superior properties in comparison with their solid counterparts. The basic mechanisms of foaming process normally consists of gas implementation, formation of uniform polymer-gas solution, cell nucleation, cell growth and, finally, cell stabilization. PLA foaming has, however, proved to be difficult mainly due to poor rheological properties, small processing window, and slow crystallization kinetics. The ultimate purpose of this work is to reduce by 30 % the weight of polylactide (PLA)-clay based nanocomposites by manufacturing injection-molded foamed parts. To use standard processing equipment, a chemical blowing agent (CBA) was employed. The injection molding technique was utilized in this project because it is the most widely used fabrication process in industry that can produce complex shaped articles. This process, however, is more challenging than other foaming processes since it deals with many additional controlling parameters. In the first part of this project, we illustrated how long chain branching (LCB) and molecular structure impact the melt rheology, crystallization and batch

  11. Significant enhancement of PEDOT thin film adhesion to inorganic solid substrates with EDOT-acid.

    PubMed

    Wei, Bin; Liu, Jinglin; Ouyang, Liangqi; Kuo, Chin-Chen; Martin, David C

    2015-07-22

    With its high conductivity, tunable surface morphology, relatively soft mechanical response, high chemical stability, and excellent biocompatibility, poly(3,4-ethylenedioxythiophene) (PEDOT) has become a promising coating material for a variety of electronic biomedical devices. However, the relatively poor adhesion of PEDOT to inorganic metallic and semiconducting substrates still poses challenges for long-term applications. Here, we report that 2,3-dihydrothieno(3,4-b)(1,4)dioxine-2-carboxylic acid (EDOT-acid) significantly improves the adhesion between PEDOT thin films and inorganic solid electrodes. EDOT-acid molecules were chemically bonded onto activated oxide substrates via the chemisorption of the carboxylic groups. PEDOT was then polymerized onto the EDOT-acid modified substrates, forming covalently bonded coatings. The adsorption of EDOT-acid onto the electrode surfaces was characterized by cyclic voltammetry (CV), contact angle measurements, atomic force microscopy, and X-ray photoelectron spectroscopy. The electrical properties of the subsequently coated PEDOT films were studied by electrochemical impedance spectroscopy and CV. An aggressive ultrasonication test confirmed the significantly improved adhesion and mechanical stability of the PEDOT films on electrodes with EDOT-acid treatment over those without treatment.

  12. Photoconductivity study of acid on Zinc phthalocyanine pyridine thin films

    NASA Astrophysics Data System (ADS)

    Singh, Sukhwinder; Saini, G. S. S.; Tripathi, S. K.

    2016-05-01

    The Metal Phthalocyanine (MPc) have attracted much interest because of chemical and high thermal stability. Molecules forming a crystal of MPc are held together by weak attractive Vander Waals forces. Organic semiconductors have π conjugate bonds which allow electrons to move via π-electron cloud overlaps. Conduction mechanisms for organic semiconductor are mainly through tunneling; hopping between localized states, mobility gaps, and phonon assisted hopping. The photo conductivity of thin films of these complexes changes when exposed to oxidizing and reducing gases. Arrhenius plot is used to find the thermal activation energy in the intrinsic region and impurity scattering region. Arrhenius plotsare used to find the thermal activation energy.

  13. Electrospraying and Electrospinning of Polymers for Biomedical Applications. Poly(Lactic-Co-Glycolic Acid) and Poly(Ethylene-Co-Vinylacetate). Appendix 2

    NASA Technical Reports Server (NTRS)

    Stitzel, Joel D.; Bowlin, Gary L.; Mansfield, Kevin; Wnek, Gary E.; Simpson, David G.

    2000-01-01

    Significant opportunities exist for the processing of polymers (homopolymers and blends) using electric fields. Specific attention is given here to electrospinning, but we note that electroaerosol formation and field-modulated film casting represent additional processing options. Of particular interest is the ability to generate polymer fibers of sub-micron dimensions using electrospinning, down to about 0.05 microns (50 nm), a size range that has been traditionally difficult to access. In our work, poly(lactic-co-glycolic acid), PLA/PGA, poly(lactic acid) PLA, and poly(ethylene-co-vinylacetate) (PEVA) have been deposited from solutions in methylene chloride or chloroform by electrospraying or electrospinning to afford morphologically tailored materials for tissue engineering and related applications. Low solution concentrations tend to favor electrostatic spraying ('electro-aerosolization') while higher concentrations lead to spinning on fibrous mats. Preliminary observations of muscle cell growth on PLA electrospun mats are reported.

  14. Biomimetic niche for neural stem cell differentiation using poly-L-lysine/hyaluronic acid multilayer films.

    PubMed

    Lee, I-Chi; Wu, Yu-Chieh; Cheng, En-Ming; Yang, Wen-Ting

    2015-05-01

    Polyelectrolyte multilayer films have been suggested as tunable substrates with flexible surface properties that can modulate cell behavior. However, these films' biological effects on neural stem/progenitor cells have rarely been studied. Herein, biomimetic multilayer films composed of hyaluronic acid and poly-L-lysine were chosen to mimic the native extracellular matrix niche of brain tissue and were evaluated for their inductive effects, without the addition of chemical factors. Because neural stem/progenitor cells are sensitive to substrate properties, it is important that this system provides control over the surface charge, and slight stiffness variations are also possible. Both of these factors affect neural stem/progenitor cell differentiation. The results showed that neural stem/progenitor cells were induced to differentiate on the poly-L-lysine/hyaluronic acid multilayer films with 0.5-4 alternating layers. In addition, the neurite outgrowth length was regulated by the surface charge of the terminal layer but did not increase with the layer number. In contrast, the quantity of differentiated neurons was enhanced slightly as the number of layers increased but was not affected by the surface charge of the terminal layer. In sum, material pairs in the form of native poly-L-lysine/hyaluronic acid films achieved important targets for neural regenerative medicine, including enhancement of the neurite outgrowth length, regulation of neuron differentiation, and the formation of a network. These extracellular matrix-mimetic poly-L-lysine/hyaluronic acid multilayer films may provide a versatile platform that could be useful for surface modification for applications in neural engineering.

  15. Investigation of crystallinity, molecular weight change, and mechanical properties of PLA/PBG bioresorbable composites as bone fracture fixation plates.

    PubMed

    Felfel, Reda M; Ahmed, Ifty; Parsons, Andrew J; Haque, Papia; Walker, Gavin S; Rudd, Chris D

    2012-03-01

    In this study, bioresorbable phosphate-based glass (PBG) fibers were used to reinforce poly(lactic acid) (PLA). PLA/PBG random mat (RM) and unidirectional (UD) composites were prepared via laminate stacking and compression molding with fiber volume fractions between 14% and 18%, respectively. The percentage of water uptake and mass change for UD composites were higher than the RM composites and unreinforced PLA. The crystallinity of the unreinforced PLA and composites increased during the first few weeks and then a plateau was seen. XRD analysis detected a crystalline peak at 16.6° in the unreinforced PLA sample after 42 days of immersion in phosphate buffer solution (PBS) at 37°C. The initial flexural strength of RM and UD composites was ∼106 and ∼115 MPa, whilst the modulus was ∼6.7 and ∼9 GPa, respectively. After 95 days immersion in PBS at 37°C, the strength decreased to 48 and 52 MPa, respectively as a result of fiber-matrix interface degradation. There was no significant change in flexural modulus for the UD composites, whilst the RM composites saw a decrease of ∼45%. The molecular weight of PLA alone, RM, and UD composites decreased linearly with time during degradation due to chain scission of the matrix. Short fiber pull-out was seen from SEM micrographs for both RM and UD composites.

  16. BmPLA2 containing conserved domain WD40 affects the metabolic functions of fat body tissue in silkworm, Bombyx mori.

    PubMed

    Orville Singh, Chabungbam; Xin, Hu-Hu; Chen, Rui-Ting; Wang, Mei-Xian; Liang, Shuang; Lu, Yan; Cai, Zi-Zheng; Miao, Yun-Gen

    2016-02-01

    PLA2 enzyme hydrolyzes arachidonic acid, and other polyunsaturated fatty acids, from the sn-2 position to release free arachidonic acid and a lysophospholipid. Previous studies reported that the PLA2 in invertebrate organisms participates in lipid signaling molecules like arachidonic acid release in immune-associated tissues like hemocytes and fat bodies. In the present study, we cloned the BmPLA2 gene from fat body tissue of silkworm Bombyx mori, which has a total sequence of 1.031 kb with a 31.90 kDa protein. In silico results of BmPLA2 indicated that the protein has a putative WD40 conserved domain and its phylogeny tree clustered with Danaus plexippus species. We investigated the transcriptional expression in development stages and tissues. The highest expression of BmPLA2 was screened in fat body among the studied tissues of third day fifth instar larva, with a high expression on third day fifth instar larva followed by a depression of expression in the wandering stage of the fifth instar larva. The expression of BmPLA2 in female pupa was higher than that of male pupa. Our RNAi-mediated gene silencing results showed highest reduction of BmPLA2 expression in post-24 h followed by post-48 and post-72 h. The BmPLA2-RNAi larvae and pupa could be characterized by pharate adult lethality and underdevelopment. The phenotypic characters of fat body cells in RNAi-induced larva implied that BmPLA2 affects the metabolic functions of fat body tissue in silkworm Bombyx mori.

  17. Real refractive indices of infrared-characterized nitric-acid/ice films: Implications for optical measurements of polar stratospheric clouds

    NASA Technical Reports Server (NTRS)

    Middlebrook, Ann M.; Berland, Brian S.; George, Steven M.; Tolbert, Margaret A.; Toon, Owen B.

    1994-01-01

    The infrared spectra of nitric-acid/ice films representative of polar stratospheric clouds (PSCs) were collected with simultaneous optical interference measurements to determine the real refractive indices at lambda = 632 nm. Ice and amphorous nitric-acid/ice films were prepared by condensation of water and nitric acid vapors onto a wedged Al2O3 substrate. The real refractive indices of these films were determined from the optical interference of a reflected helium-neon laser during film growth. The indices of the amphorous films varied smoothly from n = 1.30 for ice to n = 1.49 for nitric acid, similar to observations in previous work. We were unable to obtain the refractive index of crystlline films during adsorption because of optical scattering caused by surface roughness. Therefore crystlline nitric acid hydrate films were prepared by annealing amphorous nitric-acid/ice films. Further heating caused desorption of the crystalline hydrate films. During desorption, the refractive indices for ice, NAM (nitric acid monohydrate), alpha- and beta-NAT (nitric acid trihydrate) films were measured using the optical interference technique. In agreement with earlier data, the real refractive indices for ice and NAM determined in desorption were n = 1.30 +/- 0.01 and n = 1.53 +/- 0.03, respectively. The real refractive indices for alpha- and beta-NAT were found to be n = 1.51 +/- 0.01 and n greater than or equal to 1.46, respectively. Our measurements also suggest that the shape of crystalline nitric acid particles may depend on whether they nucleate from the liquid or by vapor deposition. If confirmed by future studies, this observation may provide a means of distinguishing the nucleation mechanism of crystalline PSCs.

  18. Indirect potentiometric titration of ascorbic acid in pharmaceutical preparations using copper based mercury film electrode.

    PubMed

    Abdul Kamal Nazer, Meeran Mohideen; Hameed, Abdul Rahman Shahul; Riyazuddin, Patel

    2004-01-01

    A simple and rapid potentiometric method for the estimation of ascorbic acid in pharmaceutical dosage forms has been developed. The method is based on treating ascorbic acid with iodine and titration of the iodide produced equivalent to ascorbic acid with silver nitrate using Copper Based Mercury Film Electrode (CBMFE) as an indicator electrode. Interference study was carried to check possible interference of usual excipients and other vitamins. The precision and accuracy of the method was assessed by the application of lack-of-fit test and other statistical methods. The results of the proposed method and British Pharmacopoeia method were compared using F and t-statistical tests of significance.

  19. PLA branching with anhydrides and tri-functional aziridine

    NASA Astrophysics Data System (ADS)

    Gu, Liangliang; Xu, Yuewen; Naredla, Rajasekhar; Hoye, Thomas; Macosko, Christopher

    Branched PLA was prepared by melt blending with tri-functional aziridine (T-Az) and pyromellitic dianhydride (PMDA). 1HNMR, gel permeation chromatography (GPC) and rheology were used to characterize the topological structures of branched PLA. Fast reaction between PLA carboxyl end group and T-Az resulted in 3-arm stars and increased the molecular weight. However, the 3-arm stars did not show strain hardening behavior under extensional flow. After modifying PLA hydroxyl end group with PMDA, PLA can react with T-Az on both chain ends and form long chain branched structure, which showed strain hardening in extension. It was found that that only 10% of the PLA hydroxyl end groups reacted with PMDA. This work is supported by Center for Sustainable Polymers.

  20. Thin-film technology for direct visual detection of nucleic acid sequences: applications in clinical research.

    PubMed

    Jenison, Robert D; Bucala, Richard; Maul, Diana; Ward, David C

    2006-01-01

    Certain optical conditions permit the unaided eye to detect thickness changes on surfaces on the order of 20 A, which are of similar dimensions to monomolecular interactions between proteins or hybridization of complementary nucleic acid sequences. Such detection exploits specific interference of reflected white light, wherein thickness changes are perceived as surface color changes. This technology, termed thin-film detection, allows for the visualization of subattomole amounts of nucleic acid targets, even in complex clinical samples. Thin-film technology has been applied to a broad range of clinically relevant indications, including the detection of pathogenic bacterial and viral nucleic acid sequences and the discrimination of sequence variations in human genes causally related to susceptibility or severity of disease.

  1. Preliminary characterization of dexamethasone-loaded cross-linked hyaluronic acid films for topical ocular therapy.

    PubMed

    Calles, J A; López-García, A; Vallés, E M; Palma, S D; Diebold, Y

    2016-07-25

    The aim of this work was to design and characterize cross-linked hyaluronic acid (HA)-itaconic acid (IT) films loaded with dexamethasone sodium phosphate salt (DEX) for topical therapy of inflammatory ocular surface diseases. Films were chemically cross-linked with polyethylene glycol diglycidyl ether (PEGDE), then physical and mechanical characterization by stress-strain, X-ray diffraction, X-ray fluorescence spectrometry and swelling assays was conducted. A sequential in vitro therapeutic efficacy model was designed to assess changes in interleukin (IL)-6 production in an inflamed human corneal epithelial (HCE) cell line after film exposure. Changes in cell proliferation after film exposure were assessed using the alamarBlue(®) proliferation assay. Experimental findings showed desirable mechanical properties and in vitro efficacy to reduce cell inflammation. A moderately decreased proliferation rate was induced in HCE cells by DEX-loaded films, compared to commercial DEX eye drops. These results suggest that DEX and HA have opposite effects. The sequential in vitro therapeutic efficacy model arises as an efficient tool to study drug release from delivery systems by indirect measurement of a biological response.

  2. Influence of HF acid catalyst concentration on properties of aerogel low-k thin films

    NASA Astrophysics Data System (ADS)

    Gaikwad, A. S.; Gupta, S. A.; Mahajan, A. M.

    2016-08-01

    The effect of hydrofluoric acid (HF) catalyst concentration in coating solution on chemical, physical and structural properties of silica aerogel thin films was investigated. The aerogel films were synthesized by using a sol-gel spin coating method followed by aging in ethanol and CO2 supercritical drying. The refractive index (RI) is observed to be reduced from 1.32 to 1.13 and porosity percentage increased from 30.21% to 71.64% in accordance with increasing HF concentration. Deposition of silica aerogel was confirmed from Fourier transform infrared spectroscopy measurement. The nanoporous nature of deposited films was confirmed from field effect scanning electron microscopy and observed pore diameter is in the range of 3.33 to 6.69 nm. The nanoporous nature of the film was also validated from atomic force microscopy and root mean square roughness was observed to be increased from 2.31 nm to 3.2 nm with increasing acid catalyst concentration in the coating solution. The calculated dielectric constant from CV measurement of fabricated metal-insulator-semiconductor structure for the silica aerogel formed at 0.8 ml HF concentration is observed to be 1.73. These deposited nanoporous silica aerogel low-k films with lower k value and smaller pore size have application as interlayer dielectric materials to minimize the disadvantages of porous materials.

  3. Photoactive layer-by-layer films of cellulose phosphate and titanium dioxide containing phosphotungstic acid

    NASA Astrophysics Data System (ADS)

    Ullah, Sajjad; Acuña, José Javier Sáez; Pasa, André Avelino; Bilmes, Sara A.; Vela, Maria Elena; Benitez, Guillermo; Rodrigues-Filho, Ubirajara Pereira

    2013-07-01

    A versatile layer-by-layer (LbL) procedure for the preparation of highly dispersed, adherent and porous multilayer films of TiO2 nanoparticles (NPs) and phosphotungstic acid (HPW) on a variety of substrates at room temperature was developed based on the use of cellulose phosphate (CP) as an efficient and non-conventional polyelectrolyte. UV/vis absorption spectroscopy confirmed the linear and regular growth of the films with the number of immersion cycles and a strong adsorption ability of CP towards TiO2 NPs. FTIR spectroscopy showed that HPW binds to the surface of TiO2 through the oxygen atom at the corner of the Keggin structure. XPS results showed that the interaction between TiO2 and CP is through Ti-O-P linkage. A model is proposed for the TiO2-HPW interaction based on XPS and FTIR results. FEG/SEM study of the surface morphology revealed a porous film structure with a homogenous distribution of the TiO2 NPs induced by CP. HRTEM studies showed that the resulting composite films consist of crystalline anatase and rutile phases and poly-nano-crystalline HPW with a semi-crystalline TiO2-HPW interface. These CP/TiO2 and CP/TiO2/HPW LbL films showed good photoactivity against both saturated and unsaturated species, for instance, stearic acid (SA), crystal violet (CV) and methylene blue (MB) under UV irradiation. The CP/HPW films formed on bacterial cellulose (BC) showed good photochromic response which is enhanced in presence of TiO2 due to an interfacial electron transfer from TiO2 to HPW. This simple and environmentally safe method can be used to form coatings on a variety of surfaces with photoactive TiO2 and TiO2/HPW films.

  4. Formation of calcium carbonate films on chitosan substrates in the presence of polyacrylic acid

    SciTech Connect

    He, Linghao; Xue, Rui; Song, Rui

    2009-05-15

    In this investigation, chitosan membranes with different surface average degrees of deacetylation (DA) are prepared and then are employed as the support matrix to culture calcium carbonate (CaCO{sub 3}). In the presence of high concentration of polyacrylic acid (PAA), the CaCO{sub 3} films obtained on the surface of all chitosan films mainly consisted of vaterite, which suggests the presence of bulk PAA plays an overwhelming part in stabilizing the vaterite. As a comparison, the influences of active groups indicate that only in case of low concentration PAA the thin CaCO{sub 3} films grown on chitosan with 8% DA mainly consisted of vaterite owing to the strong nucleation ability of -NH{sub 2} group, whereas, for those grown on chitosan with 80% DA the CaCO{sub 3} films mainly consisted of aragonite. A more complex scenario revealed that in the case of intermediate concentration of PAA the formed polymorphs behave as mixtures of vaterite and aragonite. - Graphical abstract: Chitosan membranes with different degrees of deacetylation (DA) are employed as support to culture calcium carbonate (CaCO{sub 3}). In high concentration of polyacrylic acid (PAA), the CaCO{sub 3} films obtained consisted of vaterite. However, the CaCO{sub 3} film grown on chitosan with 8% DA mainly consisted of vaterite as opposed to aragonite for chitosan with 8% DA. The schematic presentation of the formation of calcium carbonate on chitosan films with different degrees of acetylation in the presence of PAA with low-, mid- and high concentrations.

  5. Bulk organisation and alignment in Langmuir and Langmuir-Blodgett films of tetrachloroperylene tetracarboxylic acid esters

    NASA Astrophysics Data System (ADS)

    Modlińska, Anna; Filipowicz, Marek; Martyński, Tomasz

    2016-12-01

    Perylene derivatives with chlorine atoms attached at the bay position to the dye core are expected to affect organisation and tendency to aggregation in Langmuir and Langmuir-Blodgett (LB) films. Therefore, newly synthesized core-twisted homologous series of tetrachloroperylene tetracarboxylic acid esters with n = 1,4,5,6,9 carbon atoms in terminal alkyl chains were studied. Phase transitions and crystalline structures were specified by differential scanning calorimetry (DSC) and single crystal X-ray diffraction (XRD), respectively. Intermolecular interactions and organisation of the dyes in monomolecular films were investigated by means of Brewster angle microscope (BAM), UV-Vis absorption and emission spectroscopy, fluorescence microscopy and atomic force microscopy (AFM). The dyes investigated do not form thermotropic mesogenic phases in bulk. The crystalline triclinic elementary cell with P-1 symmetry is revealed from X-ray experiments. In Langmuir and Langmuir-Blodgett films molecular tilted head-on alignment is postulated. Spectroscopic research confirmed by AFM texture images of the LB films show that in the Langmuir and LB films the dyes, depending on length of terminal chains, have a tendency to create H or I molecular aggregates. The impact of the twisted core on the molecular behavior in a bulk and thin films is discussed.

  6. Blend-modification of soy protein/lauric acid edible films using polysaccharides.

    PubMed

    Pan, Hongyang; Jiang, Bo; Chen, Jie; Jin, Zhengyu

    2014-05-15

    Different types of polysaccharides (propyleneglycol alginate (PGA), pectin, carrageenan and aloe polysaccharide) were incorporated into soy protein isolate (SPI)/lauric acid (La) films using a co-drying process or by direct addition to form biodegradable composite films with modified water vapour permeability (WVP) and mechanical properties. The WVP of SPI/La/polysaccharide films decreased when polysaccharides were added using the co-drying process, regardless of the type of polysaccharide. The tensile strength of SPI/La film was increased by the addition of polysaccharides, and the percentage elongation at break was increased by incorporating PGA using the co-drying process. Regarding oxygen-barrier performance, no notable differences were observed between the SPI/La and SPI/La/polysaccharide films. The most significant improvement was observed by blending PGA, with the co-dried preparation exhibiting better properties than the direct-addition preparation. Scanning electron microscopy (SEM) revealed that the microstructures of the films are the basis for the differences in the barrier and mechanical properties of the modified blends of SPI, polysaccharides and La.

  7. Photoelectrocatalytic degradation of benzoic acid using Au doped TiO2 thin films.

    PubMed

    Mohite, V S; Mahadik, M A; Kumbhar, S S; Hunge, Y M; Kim, J H; Moholkar, A V; Rajpure, K Y; Bhosale, C H

    2015-01-01

    Highly transparent pure and Au doped TiO2 thin films are successfully deposited by using simple chemical spray pyrolysis technique. The effect of Au doping onto the structural and physicochemical properties has been investigated. The PEC study shows that, both short circuit current (Isc) and open circuit voltage (Voc) are (Isc=1.81mA and Voc=890mV) relatively higher at 3at.% Au doping percentage. XRD study shows that the films are nanocrystalline in nature with tetragonal crystal structure. FESEM images show that the film surface covered with a smooth, uniform, compact and rice shaped nanoparticles. The Au doped thin films exhibit indirect band gap, decreases from 3.23 to 3.09eV with increase in Au doping. The chemical composition and valence states of pure and Au doped TiO2 films are studied by using X-ray photoelectron spectroscopy. The photocatalytic degradation effect is 49% higher in case 3at.% Au doped TiO2 than the pure TiO2 thin film photoelectrodes in the degradation of benzoic acid. It is revealed that Au doped TiO2 can be reused for five cycles of experiments without a requirement of post-treatment while the degradation efficiency was retained.

  8. Improving the physical and moisture barrier properties of Lepidium perfoliatum seed gum biodegradable film with stearic and palmitic acids.

    PubMed

    Seyedi, Samira; Koocheki, Arash; Mohebbi, Mohebbat; Zahedi, Younes

    2015-01-01

    Stearic and palmitic fatty acids (10%, 20% and 30%, W/W gum) were used to improve the barrier properties of Lepidium perfoliatum seed gum (LPSG) film. The impact of the incorporation of fatty acids into the film matrix was studied by investigating the physical, mechanical, and barrier properties of the films. Addition of stearic and palmitic fatty acids to LPSG films reduced their water vapor permeability (WVP), moisture content, water solubility and water adsorption. Increasing fatty acid concentration from 10% to 30%, reduced the elongation at break (EB). Lower values of tensile strength (TS) and elastic modulus (EM) were obtained in the presence of higher fatty acids concentrations. Incorporation of fatty acids led to production of opaque films and the opacity increased as function of fatty acids concentration. Results showed that moisture content, water solubility and WVP decreased as the chain length of fatty acid increased. Therefore, LPSG-fatty acids composite film could be used for packaging in which a low affinity toward water is needed.

  9. In situ formation and gelation mechanism of thermoresponsive stereocomplexed hydrogels upon mixing diblock and triblock poly(lactic acid)/poly(ethylene glycol) copolymers.

    PubMed

    Mao, Hailiang; Pan, Pengju; Shan, Guorong; Bao, Yongzhong

    2015-05-28

    A novel in situ formed gel system with potential biodegradability and biocompatibility is developed by mixing the diblock and triblock poly(lactic acid)/poly(ethylene glycol) (PLA/PEG) copolymers with opposite configurations of PLA blocks. In situ gelation of such system is extremely fast, which happens within 10 s after mixing. In situ gelation, gel-to-sol transition, crystalline structure, microstructures, and mechanical properties of PLA-PEG/PLA-PEG-PLA enantiomerically mixed gels are significantly influenced by the mixing ratio, degree of polymerization for PEG block in triblock (DPPEG,tri) and diblock copolymers (DPPEG,di). It is found that in situ gelation of PLA-PEG/PLA-PEG-PLA enantiomeric mixture just happen at relatively smaller PLA-PEG/PLA-PEG-PLA mass ratio and larger DPPEG,tri. Hydrodynamic diameters of PLA-PEG and PLA-PEG-PLA copolymers in dilute solution increase remarkably upon mixing, indicating the formation of bridging networks. Stereocomplexed crystallites are formed for the PLA hydrophobic domains in PLA-PEG/PLA-PEG-PLA enantiomeric mixtures. As indicated by synchrotron-radiation SAXS analysis, the enantiomeric mixture changes from a compactly to loosely aggregated structure and the intermicellar distance enhances with increasing DPPEG,tri, DPPEG,di, or PLA-PEG-PLA fraction. Gelation mechanism of PLA-PEG/PLA-PEG-PLA enantiomeric mixture is proposed, in which part of PLA-PEG-PLA chains act as the connecting bridges between star and flower-like micelles and the stereocomplexed crystallites in micelle cores act as physically cross-linked points.

  10. Electrophoretic deposition of hyaluronic acid and composite films for biomedical applications

    NASA Astrophysics Data System (ADS)

    Ma, R.; Li, Y.; Zhitomirsky, I.

    2010-06-01

    Hyaluronic acid (HYH) is a natural biopolymer, which has tremendous potential for various biomedical applications. Electrophoretic deposition (EPD) methods have been developed for the fabrication of HYH films and composites. New methods for the immobilization of drugs and proteins have been utilized for the fabrication of organic composites. Electrophoretic deposition enabled the fabrication of organic-inorganic composites containing bioceramics and bioglass in the HYH matrix. It was shown that the deposition yield, microstructure, and composition of the films can be controlled. Potential applications of EPD for the surface modification of biomedical implants and fabrication of biosensors are highlighted.

  11. Silicon dioxide thin film mediated single cell nucleic acid isolation.

    PubMed

    Bogdanov, Evgeny; Dominova, Irina; Shusharina, Natalia; Botman, Stepan; Kasymov, Vitaliy; Patrushev, Maksim

    2013-01-01

    A limited amount of DNA extracted from single cells, and the development of single cell diagnostics make it necessary to create a new highly effective method for the single cells nucleic acids isolation. In this paper, we propose the DNA isolation method from biomaterials with limited DNA quantity in sample, and from samples with degradable DNA based on the use of solid-phase adsorbent silicon dioxide nanofilm deposited on the inner surface of PCR tube.

  12. Silicon Dioxide Thin Film Mediated Single Cell Nucleic Acid Isolation

    PubMed Central

    Bogdanov, Evgeny; Dominova, Irina; Shusharina, Natalia; Botman, Stepan; Kasymov, Vitaliy; Patrushev, Maksim

    2013-01-01

    A limited amount of DNA extracted from single cells, and the development of single cell diagnostics make it necessary to create a new highly effective method for the single cells nucleic acids isolation. In this paper, we propose the DNA isolation method from biomaterials with limited DNA quantity in sample, and from samples with degradable DNA based on the use of solid-phase adsorbent silicon dioxide nanofilm deposited on the inner surface of PCR tube. PMID:23874571

  13. Rheological and thermal properties of polylactide/silicate nanocomposites films.

    PubMed

    Ahmed, Jasim; Varshney, Sunil K; Auras, Rafeal

    2010-03-01

    Polylactide (DL)/polyethylene glycol/silicate nanocomposite blended biodegradable films have been prepared by solvent casting method. Rheological and thermal properties were investigated for both neat amorphous polylactide (PLA-DL form) and blend of montmorillonite (clay) and poly (ethylene glycol) (PEG). Melt rheology of the PLA individually and blends (PLA/clay; PLA/PEG; PLA/PEG/clay) were performed by small amplitude oscillation shear (SAOS) measurement. Individually, PLA showed an improvement in the viscoelastic properties in the temperature range from 180 to 190 degrees C. Incorporation of nanoclay (3% to 9% wt) was attributed by significant improvements in the elastic modulus (G') of PLA/clay blend due to intercalation at higher temperature. Both dynamic modulii of PLA/PEG blend were significantly reduced with addition of 10% PEG. Rheometric measurement could not be conducted while PLA/PEG blends containing 25% PEG. A blend of PLA/PEG/clay (68/23/9) showed liquid-like properties with excellent flexibility. Thermal analysis of different clay loading films indicated that the glass transition temperatures (T(g)) remained unaffected irrespective of clay concentration due to immobilization of polymer chain in the clay nanocomposite. PEG incorporation reduced the T(g) of the blend (PLA/PEG and PLA/PEG/clay) significantly. Both rheological and thermal analysis data supported plasticization and flexibility of the blended films. It is also interesting to study competition between PLA and PEG for the intercalation into the interlayer spacing of the clay. This study indicates that PLA/montmorillonite blend could serve as effective nano-composite for packaging and other applications.

  14. Analysis of tellurium thin films electrodeposition from acidic citric bath

    NASA Astrophysics Data System (ADS)

    Kowalik, Remigiusz; Kutyła, Dawid; Mech, Krzysztof; Żabiński, Piotr

    2016-12-01

    This work presents the description of the electrochemical process of formation thin tellurium layers from citrate acidic solution. The suggested methodology consists in the preparation of stable acidic baths with high content of tellurium, and with the addition of citrate acid. In order to analyse the mechanism of the process of tellurium deposition, the electroanalytical tests were conducted. The tests of cyclic voltammetry and hydrodynamic ones were performed with the use of polycrystalline gold disk electrode. The range of potentials in which deposition of tellurium in direct four-electron process is possible was determined as well as the reduction of deposited Te° to Te2- and its re-deposition as a result of the comproportionation reaction. On the basis of the obtained results, the deposition of tellurium was conducted by the potentiostatic method. The influence of a deposition potential and a concentration of TeO2 in the solution on the rate of tellurium coatings deposition was examined. The presence of tellurium was confirmed by X-ray spectrofluorometry and electron probe microanalysis. In order to determine the phase composition and the morphology, the obtained coatings were analysed with the use of x-ray diffraction and scanning electron microscopy.

  15. Kinetic model and thermodynamic study of Acid Red 1 entrapment at electropolymerised polypyrrole films.

    PubMed

    Haque, Md Mominul; Wong, Danny K Y

    2015-11-01

    This work is focussed on the determination of a kinetic model and the thermodynamic study of the electrochemical entrapment of the model azo dye, Acid Red 1, at conducting polypyrrole films, which is proposed as a potential green technology for treatment of azo dyes in industrial effluents. The entrapment kinetic data were found to follow a pseudosecond order model involving an intra-particle diffusion. However, the equilibrium data obtained for Acid Red 1 entrapment at polypyrrole did not obey any common surface adsorption models such as the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherms. Accordingly, the entrapment process may lead to an enhanced quantity of dye embedded in a polypyrrole film, making it a more effective and efficient technology than those involving only adsorption. Similarly, dye leakage from polypyrrole film surface to a sample matrix will be easily prevented. For this treatment process, a negative ΔG° range between -1.46±0.78 and -2.94±0.24 kJ mol(-1) at the corresponding temperature range of 298-318 K, and a ΔH° of 20.5±2.5 kJ mol(-1) indicate a spontaneous and endothermic entrapment process. Also, a positive ΔS° (73.6±8.2 J mol(-1) K(-1)) reveals increased randomness of the interface and an affinity of Acid Red 1 towards polypyrrole films. A low activation energy (7.67±0.80 kJ mol(-1)) confirms a physical process for Acid Red 1 entrapment at polypyrrole films.

  16. Surface characterization and cell response of a PLA/CaP glass biodegradable composite material.

    PubMed

    Navarro, M; Engel, E; Planell, J A; Amaral, I; Barbosa, M; Ginebra, M P

    2008-05-01

    Bioabsorbable materials are of great interest for bone regeneration applications, since they are able to degrade gradually as new tissue is formed. In this work, a fully biodegradable composite material containing polylactic acid (PLA) and calcium phosphate (CaP) soluble glass particles has been characterized in terms of surface properties and cell response. Cell cultures were performed in direct contact with the materials and also with their extracts, and were evaluated using the MTT assay, alkaline phosphatase activity, and osteocalcin measurements. The CaP glass and PLA were used as reference materials. No significant differences were observed in cell proliferation with the extracts containing the degradation by-products of the three materials studied. A relation between the materials wettability and the material-cell interactions at the initial stages of contact was observed. The most hydrophilic material (CaP glass) presented the highest cell adhesion values as well as an earlier differentiation, followed by the PLA/glass material. The incorporation of glass particles into the PLA matrix increased surface roughness. SEM images showed that the heterogeneity of the composite material induced morphological changes in the cells cytoskeleton.

  17. Comportement en fatigue et influence de la temperature sur les proprietes en traction du PLA

    NASA Astrophysics Data System (ADS)

    Menard, Claire

    Current environmental issues reduce the use of materials obtained from fossil resources. The usual plastics therefore tend to be replaced by more green polymers such as polylactic acid (PLA), a bio-based and biodegradable polymer. Knowledge on the properties of this material is essential, especially in terms of fatigue strength and influence of temperature on tensile stiffness and strength. In this study, the PLA samples are submitted to monotonic tensile tests, according to ASTM D638-10, at various temperatures between room temperature (23°C) and the glass transition temperature of the material (55-60°C). The results show a decrease of 30% of the modulus of elasticity and 60% of the tensile strength between these two temperatures. This decrease is mainly due to a significant drop in the mechanical properties beyond 50°C. In addition, tensile fatigue tests were conducted at loads rate between 40 and 80% of tensile strength, at room temperature in order to plot the Wohler curve of PLA. The ruptured specimens were finally observed with a scanning electron microscope (SEM) to analyze the failure mechanisms in fatigue of PLA.

  18. Electrospun fibers of PLA/P3HT blends for device and sensor applications

    NASA Astrophysics Data System (ADS)

    Serrano, William; Pinto, Nicholas

    2013-03-01

    The thermoplastic aliphatic polyester, poly (lactic acid) (PLA) is a biodegradable polymer that is sometimes used in implant screws for bone repair. Our focus was to fabricate fibers of this polymer and its blends with p-doped poly (3-hexylthiophene)-(P3HT) in order to extend its use to devices and/or sensors. PLA/P3HT fibers were prepared in air at room temperature using the electrospinning technique that is cheap, fast and reliable. Scanning Electron Microscope images of the fibers reveal that the presence of P3HT does not affect the fabrication of PLA fibers at low or high polymer concentrations in chloroform, retaining the same morphological structure of pure PLA fibers. The fiber diameters were in the range 1-10 microns. A slight increase in fiber formation results with the addition of P3HT, most likely due to a reduction of the solution surface tension. Results of the electrical characterization of this material will be presented. DoD and NSF

  19. Correlation between crystallization behaviour and interfacial interactions in plasticized PLA/POSS nanocomposites

    NASA Astrophysics Data System (ADS)

    Kodal, Mehmet; Şirin, Hümeyra; Özkoç, Güralp

    2016-03-01

    In this study, the correlation between crystallization behavior and surface chemistry of polyhedral oligomeric silsesquioxanes (POSS) for plasticized poly(lactic acid) (PLA)/POSS nanocomposites was investigated. Four different kinds of POSS particles having different chemical structures were used. Poly(ethylene glycol) (PEG, 8000 g/mol) was utilized as the plasticiser. The nanocomposites were melt-compounded in an Xplore Instruments 15 cc twin screw microcompounder at 180°C barrel temperature and 100 rpm screw speed. Non-isothermal crystallization behaviour of PLA/PEG/POSS nanocomposites were evaluated from common kinetic models such as Avrami and Avrami-Ozawa and Kissinger by using the thermal data obtained from differantial scanning calorimetry (DSC). A polarized optical microscope (POM) equipped with a hot-stage was used to examine the morphology during the crystal growth. In order to investigate the interfacial interactions between POSS particles and plasticized PLA, thermodynamic work of adhesion approach was adopted using the experimentally determined surface energies. A strong correlation was obtained between interfacial chemistry and the nucleation rate in plasticized PLA/POSS nanocomposites. It was found that the polar interactions were the dominating factor which determines the nucleation activity of the POSS particles.

  20. Bp-13 PLA2: Purification and Neuromuscular Activity of a New Asp49 Toxin Isolated from Bothrops pauloensis Snake Venom

    PubMed Central

    Sucasaca-Monzón, Georgina; Randazzo-Moura, Priscila; Rocha, Thalita; Vilca-Quispe, Augusto; Ponce-Soto, Luis Alberto; Marangoni, Sérgio; da Cruz-Höfling, Maria Alice; Rodrigues-Simioni, Léa

    2015-01-01

    A new PLA2 (Bp-13) was purified from Bothrops pauloensis snake venom after a single chromatographic step of RP-HPLC on μ-Bondapak C-18. Amino acid analysis showed a high content of hydrophobic and basic amino acids and 14 half-cysteine residues. The N-terminal sequence showed a high degree of homology with basic Asp49 PLA2 myotoxins from other Bothrops venoms. Bp-13 showed allosteric enzymatic behavior and maximal activity at pH 8.1, 36°–45°C. Full Bp-13 PLA2 activity required Ca2+; its PLA2 activity was inhibited by Mg2+, Mn2+, Sr2+, and Cd2+ in the presence and absence of 1 mM Ca2+. In the mouse phrenic nerve-diaphragm (PND) preparation, the time for 50% paralysis was concentration-dependent (P < 0.05). Both the replacement of Ca2+ by Sr2+ and temperature lowering (24°C) inhibited the Bp-13 PLA2-induced twitch-tension blockade. Bp-13 PLA2 inhibited the contractile response to direct electrical stimulation in curarized mouse PND preparation corroborating its contracture effect. In biventer cervicis preparations, Bp-13 induced irreversible twitch-tension blockade and the KCl evoked contracture was partially, but significantly, inhibited (P > 0.05). The main effect of this new Asp49 PLA2 of Bothrops pauloensis venom is on muscle fiber sarcolemma, with avian preparation being less responsive than rodent preparation. The study enhances biochemical and pharmacological characterization of B. pauloensis venom. PMID:25789175

  1. Chitosan/PLA nanoparticles as a novel carrier for the delivery of anthraquinone: synthesis, characterization and in vitro cytotoxicity evaluation.

    PubMed

    Jeevitha, D; Amarnath, Kanchana

    2013-01-01

    Designing novel materials for biomedical applications generally require the use of biodegradable materials. This study aims to engineer a biodegradable [chitosan (CS) and poly (lactic acid) (PLA)] as AQ carrier with nanometer dimensions and to evaluate the anticancer potency of the prepared CS/PLA-AQ NPs in human carcinoma (HepG2) cells. CS-PLA complex, which are well dispersed and stable in aqueous solution, was prepared by the precipitation of lactic acid in chitosan solution by dropping method and characterized by SEM, TEM, DLS and FTIR. The results thus displayed that the prepared nanoparticles carried a positive charge and showed the size in the range from 100 to 200 nm. The in vitro (AQ) release study showed that these nanoparticles provided a continuous release of the entrapped AQ for 10 days, and the release behavior was influenced by the pH value of the medium thereby making feasible to develop CS-PLA for enhanced and sustained release of AQ. MTT assay revealed higher cytotoxic efficacy of CS/PLA-AQ NPs than Free AQ in HepG2 cells. Further, the mitochondrial membrane damage indicated by loss of mitochondrial membrane potential and necrotic cell death could be attributed to the increased reactive oxygen species production. Our results also suggest that upon CS/PLA-AQ NPs exposure the cell viability decreased due to apoptosis, as demonstrated by the formation of apoptotic bodies, sub-G1 hypodiploid cells, and DNA fragmentation. Henceforth, CS/PLA-AQ NPs demonstrated a strong antitumor activity in vitro by reducing cell viability, inducing cell necrosis, decreasing the negative surface charge and mitochondrial membrane potential, and fragmenting DNA.

  2. Evaporation of water and uptake of HCl and HBr through hexanol films at the surface of supercooled sulfuric acid.

    PubMed

    Glass, Samuel V; Park, Seong-Chan; Nathanson, Gilbert M

    2006-06-22

    Vacuum evaporation and molecular beam scattering experiments have been used to monitor the loss of water and dissolution of HCl and HBr in deuterated sulfuric acid at 213 K containing 0 to 100 mM hexanol. The addition of 1-hexanol to the acid creates a surface film of hexyl species. This film becomes more compact with decreasing acidity, ranging from approximately 62% to approximately 68% of maximum packing on 68 to 56 wt % D(2)SO(4), respectively. D(2)O evaporation from 68 wt % acid remains unaltered by the hexyl film, where it is most porous, but is impeded by approximately 20% from 56 and 60 wt % acid. H --> D exchange experiments further indicate that the hexyl film on 68 wt % acid enhances conversion of HCl and HBr into DCl and DBr, which is interpreted as an increase in HCl and HBr entry into the bulk acid. For this permeable hexyl film, the hydroxyl groups of surface hexanol molecules may assist uptake by providing extra sites for HCl and HBr hydrogen bonding and dissociation. In contrast, HCl --> DCl exchange in 60 wt % D(2)SO(4) at first rises with hexyl surface coverage but then drops back to the bare acid value as the hexyl species pack more tightly. HCl entry is actually diminished by the hexyl film on 56 wt % acid, where the film is most compact. These experiments reveal a transition from a porous hexanol film on 68 wt % sulfuric acid that enhances HCl and HBr uptake to one on 56 wt % acid that slightly impedes HCl and D(2)O transport.

  3. Self-doping effect in poly(o-methoxyaniline)/poly(3-thiopheneacetic acid) layer-by-layer films.

    PubMed

    Trivinho-Strixino, Francisco; Pereira, Ernesto C; Mello, Sarita V; Oliveira, Osvaldo N

    2004-04-27

    Nanostructured films from two conducting polymers, poly(o-methoxyaniline) (POMA) and poly(3-thiopheneacetic acid) (PTAA), were fabricated with the layer-by-layer (LBL) technique. The electrochemical response of the LBL films differs from that of a POMA cast film, even in a potential range where PTAA is inactive. This is attributed to differences in the diffusion-controlled charge and mass transport, where distinct ionic species participate in the LBL films, as demonstrated by quartz crystal microbalance measurements. The results show that the transport properties of conducting polymers can be changed by alternation with layers of appropriate materials in LBL films.

  4. Controlled release of ethacrynic acid from poly(lactide-co-glycolide) films for glaucoma treatment.

    PubMed

    Wang, Yong; Challa, Pratap; Epstein, David L; Yuan, Fan

    2004-08-01

    Ethacrynic acid (ECA) is a potential glaucoma drug that can reduce intraocular pressure. However, conventional methods of ECA administration may cause toxicity to normal eye tissues and are inconvenient to patients. Therefore, we developed and characterized an ECA loaded poly(lactide-co-glycolide) (PLGA) copolymer film, and quantified the therapeutic efficacy of the film implanted in the rabbit eye. In the aqueous medium, the release of ECA from the PLGA50:50 film was time dependent and more than 90% of ECA was released within a week. This release profile was consistent with the kinetics of water uptake and microstructural changes of PLGA50:50 films as revealed by an electron microscopy examination. ECA release and PLGA degradation caused a gradual pH decrease in the release medium. The total pH decrease was 0.4 unit in 3 days. We also observed that the initial rate of ECA release was positively correlated with the weight ratio of ECA versus PLGA and inversely correlated with the molar ratio of lactide versus glycolide in PLGA films. At the end of a 3-day incubation, the cumulative release of ECA from PLGA50:50, PLGA85:15 and PLGA100:00 films were 78.8%, 9.35% and 3.60%, respectively. When the PLGA50:50 film loaded with ECA was implanted into the sclera of rabbit eyes, the intraocular pressure was significantly reduced and the reduction was maintained for at least 10 days. These data indicate that PLGA films have a potential to be used as a controlled ECA release device for glaucoma treatment.

  5. Hyaluronan-Itaconic Acid-Glutaraldehyde Films for Biomedical Applications: Preliminary Studies.

    PubMed

    Calles, Javier Adrián; Ressia, Jorge Aníbal; Llabot, Juan Manuel; Vallés, Enrique Marcelo; Palma, Santiago Daniel

    2016-01-01

    New hyaluronic acid-itaconic acid films were synthesized as potential materials with biomedical applications. In this work, we explored the homogeneous cross-linking reactions of hyaluronic acid using glutaraldehyde in the presence of itaconic acid and triacetin as plasticizers. Biomechanical properties were assessed in terms of stability by measuring swelling in aqueous environments, investigating wettability using contact angle tests, and evaluating bioadhesive performance. The ductility of the materials was evaluated through stress-strain measurements and the morphology was explored by scanning electron microscopy. The results show that the incorporation of itaconic acid improved most of the desirable properties, increasing adhesiveness and reducing wettability and swelling. The use of triacetin enhanced the strength, bioadhesiveness, and ductility of the material.

  6. Optical and thermal properties of azo derivatives of salicylic acid thin films

    NASA Astrophysics Data System (ADS)

    Ghoneim, M. M.; El-Ghamaz, N. A.; El-Sonbati, A. Z.; Diab, M. A.; El-Bindary, A. A.; Serag, L. S.

    2015-02-01

    N-acryloyl-4-aminosalicylic acid (4-AMSA), monomer (HL) and 5-(4‧-alkyl phenylazo)-N-acryloyl-4-aminosalicylic acid (HLn) are synthesized and characterized with various physico-chemical techniques. Thin films of 5-(4‧-alkyl phenylazo)-N-acryloyl-4-aminosalicylic acid (HLn) are prepared by spin coating technique. The X-ray diffraction (XRD) patterns of 4-aminosalicylic acid (4-ASA) and its derivatives are investigated in powder and thin film forms. Thermal properties of the compounds are investigated by thermogravemetric analysis (TGA). The optical energy gap and the type of optical transition are investigated in the wavelength range (200-2500 nm) for 4-ASA, HL and HLn. The values of fundamental energy gap (Eg) are in the range 3.60-3.69 eV for all compounds and the type of optical transition is found to be indirect allowed. The onset energy gap Eg∗ appeared only for azodye compounds is found to be in the range 0.95-1.55 eV depending on the substituent function groups. The refractive index, n, shows a normal dispersion in the wavelength range 650-2500 nm, while shows anomalous dispersion in the wavelength rang 200-650 nm. The dispersion parameters ε∞, εL, Ed, Eo and N /m∗ are calculated. The photoluminescence phenomena (PL) appear for thin films of 4-ASA and its derivatives show three main emission transitions.

  7. Optical and thermal properties of azo derivatives of salicylic acid thin films.

    PubMed

    Ghoneim, M M; El-Ghamaz, N A; El-Sonbati, A Z; Diab, M A; El-Bindary, A A; Serag, L S

    2015-02-25

    N-acryloyl-4-aminosalicylic acid (4-AMSA), monomer (HL) and 5-(4'-alkyl phenylazo)-N-acryloyl-4-aminosalicylic acid (HLn) are synthesized and characterized with various physico-chemical techniques. Thin films of 5-(4'-alkyl phenylazo)-N-acryloyl-4-aminosalicylic acid (HLn) are prepared by spin coating technique. The X-ray diffraction (XRD) patterns of 4-aminosalicylic acid (4-ASA) and its derivatives are investigated in powder and thin film forms. Thermal properties of the compounds are investigated by thermogravemetric analysis (TGA). The optical energy gap and the type of optical transition are investigated in the wavelength range (200-2500 nm) for 4-ASA, HL and HLn. The values of fundamental energy gap (Eg) are in the range 3.60-3.69 eV for all compounds and the type of optical transition is found to be indirect allowed. The onset energy gap Eg(∗) appeared only for azodye compounds is found to be in the range 0.95-1.55 eV depending on the substituent function groups. The refractive index, n, shows a normal dispersion in the wavelength range 650-2500 nm, while shows anomalous dispersion in the wavelength rang 200-650 nm. The dispersion parameters ε∞, εL, Ed, Eo and N/m(∗) are calculated. The photoluminescence phenomena (PL) appear for thin films of 4-ASA and its derivatives show three main emission transitions.

  8. Biodegradable polyester films from renewable aleuritic acid: surface modifications induced by melt-polycondensation in air

    NASA Astrophysics Data System (ADS)

    Jesús Benítez, José; Alejandro Heredia-Guerrero, José; Inmaculada de Vargas-Parody, María; Cruz-Carrillo, Miguel Antonio; Morales-Flórez, Victor; de la Rosa-Fox, Nicolás; Heredia, Antonio

    2016-05-01

    Good water barrier properties and biocompatibility of long-chain biopolyesters like cutin and suberin have inspired the design of synthetic mimetic materials. Most of these biopolymers are made from esterified mid-chain functionalized ω-long chain hydroxyacids. Aleuritic (9,10,16-trihydroxypalmitic) acid is such a polyhydroxylated fatty acid and is also the major constituent of natural lac resin, a relatively abundant and renewable resource. Insoluble and thermostable films have been prepared from aleuritic acid by melt-condensation polymerization in air without catalysts, an easy and attractive procedure for large scale production. Intended to be used as a protective coating, the barrier's performance is expected to be conditioned by physical and chemical modifications induced by oxygen on the air-exposed side. Hence, the chemical composition, texture, mechanical behavior, hydrophobicity, chemical resistance and biodegradation of the film surface have been studied by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), atomic force microscopy (AFM), nanoindentation and water contact angle (WCA). It has been demonstrated that the occurrence of side oxidation reactions conditions the surface physical and chemical properties of these polyhydroxyester films. Additionally, the addition of palmitic acid to reduce the presence of hydrophilic free hydroxyl groups was found to have a strong influence on these parameters.

  9. Biocatalyzed approach for the surface functionalization of poly(L-lactic acid) films using hydrolytic enzymes.

    PubMed

    Pellis, Alessandro; Acero, Enrique Herrero; Weber, Hansjoerg; Obersriebnig, Michael; Breinbauer, Rolf; Srebotnik, Ewald; Guebitz, Georg M

    2015-09-01

    Poly(lactic acid) as a biodegradable thermoplastic polyester has received increasing attention. This renewable polyester has found applications in a wide range of products such as food packaging, textiles and biomedical devices. Its major drawbacks are poor toughness, slow degradation rate and lack of reactive side-chain groups. An enzymatic process for the grafting of carboxylic acids onto the surface of poly(L-lactic acid) (PLLA) films was developed using Candida antarctica lipase B as a catalyst. Enzymatic hydrolysis of the PLLA film using Humicola insolens cutinase in order to increase the number of hydroxyl and carboxylic groups on the outer polymer chains for grafting was also assessed and showed a change of water contact angle from 74.6 to 33.1° while the roughness and waviness were an order of magnitude higher in comparison to the blank. Surface functionalization was demonstrated using two different techniques, (14) C-radiochemical analysis and X-ray photoelectron spectroscopy (XPS) using (14) C-butyric acid sodium salt and 4,4,4-trifluorobutyric acid as model molecules, respectively. XPS analysis showed that 4,4,4-trifluorobutyric acid was enzymatically coupled based on an increase of the fluor content from 0.19 to 0.40%. The presented (14) C-radiochemical analyses are consistent with the XPS data indicating the potential of enzymatic functionalization in different reaction conditions.

  10. Cellular behavior of neointima-like cells onto vitamin E-enriched poly(D,L)lactic acid.

    PubMed

    Renò, Filippo; Traina, Vincenzina; Cannas, Mario

    2007-09-01

    In-stent restenosis is a process that occurs in 10-50% of cases currently treated with stent and it is caused by an abnormal smooth muscle cell (SMC) proliferation and migration in the vascular lumen. One of the most promising strategy to reduce restenosis is stent coating with biodegradable polymers to deliver in situ anti-proliferative drugs. Poly(D,L)lactic acid (P(D,L)LA), one of the most interesting candidate for stent coating, has been observed to induce inflammation and neointimal proliferation. In our laboratory, we developed P(D,L)LA enriched with Vitamin E (Vit.E), an anti-oxidative and anti-inflammatory agent that reduces also SMC proliferation. In order to evaluate the in vitro cellular behaviour of neointima cells onto Vitamin E-enriched P(D,L)LA, cell adhesion and proliferation along with the expression of two SMC migration markers (MMP-9 and hyaluronic acid receptor CD44) were measured in rat vascular SMC A10 cells seeded onto control P(D,L)LA (PLA) and P(D,L)LA films containing 10-30% (w/w) Vit.E (PLA10-30). Cell adhesion, proliferation and MMP-9 production were unaffected by the Vit.E presence in the PLA films after 24 h, while proliferation was slowed or blocked after 48 and 72 h onto PLA10, 20 and 30. MMP-9 production was almost blocked and CD44 density decreased significantly after 72 h for cells grew onto PLA30 compare to cells seeded onto PLA. These data indicate that Vit.E-enriched P(D,L)LA could be an interesting polymer for stent coating.

  11. Novel silk fibroin films prepared by formic acid/hydroxyapatite dissolution method.

    PubMed

    Ming, Jinfa; Liu, Zhi; Bie, Shiyu; Zhang, Feng; Zuo, Baoqi

    2014-04-01

    Bombyx mori silk fibroin from the silkworm was firstly found to be soluble in formic acid/hydroxyapatite system. The rheological behavior of silk fibroin solution was significantly influenced by HAp contents in dissolved solution. At the same time, silk fibroin nanofibers were observed in dissolved solution with 103.6±20.4nm in diameter. Moreover, the structure behavior of SF films prepared by formic acid/hydroxyapatite dissolution method was examined. The secondary structure of silk fibroin films was attributed to silk II structure (β-sheet), indicating that the hydroxyapatite contents in dissolved solution were not significantly affected by the structure of silk fibroin. The X-ray diffraction results exhibited obviously hydroxyapatite crystalline nature existing in silk fibroin films; however, when the hydroxyapatite content was 5.0wt.% in dissolved solution, some hydroxyapatite crystals were converted to calcium hydrogen phosphate dehydrate in silk fibroin dissolution process. This result was also confirmed by Fourier transform infrared analysis and DSC measurement. In addition, silk fibroin films prepared by this dissolution method had higher breaking strength and extension at break. Based on these analyses, an understanding of novel SF dissolution method may provide an additional tool for designing and synthesizing advanced materials with more complex structures, which should be helpful in different fields, including biomaterial applications.

  12. Starch-based Antimicrobial Films Incorporated with Lauric Acid and Chitosan

    NASA Astrophysics Data System (ADS)

    Salleh, E.; Muhamad, I. I.

    2010-03-01

    Antimicrobial (AM) packaging is one of the most promising active packaging systems. Starch-based film is considered an economical material for antimicrobial packaging. This study aimed at the development of food packaging based on wheat starch incorporated with lauric acid and chitosan as antimicrobial agents. The purpose is to restrain or inhibit the growth of spoilage and/or pathogenic microorganisms that are contaminating foods. The antimicrobial effect was tested on B. substilis and E. coli. Inhibition of bacterial growth was examined using two methods, i.e. zone of inhibition test on solid media and liquid culture test (optical density measurements). The control and AM films (incorporated with chitosan and lauric acid) were produced by casting method. From the observations, AM films exhibited inhibitory zones. Interestingly, a wide clear zone on solid media was observed for B. substilis growth inhibition whereas inhibition for E. coli was not as effective as B. substilis. From the liquid culture test, the AM films clearly demonstrated a better inhibition against B. substilis than E. coli.

  13. Investigation of Carboxylic Acid-Neodymium Conversion Films on Magnesium Alloy

    NASA Astrophysics Data System (ADS)

    Cui, Xiufang; Liu, Zhe; Lin, Lili; Jin, Guo; Wang, Haidou; Xu, Binshi

    2015-01-01

    The new carboxylic acid-neodymium anhydrous conversion films were successfully prepared and applied on the AZ91D magnesium alloy surface by taking absolute ethyl alcohol as solvent and four kinds of soluble carboxylic acid as activators. The corrosion resistance of the coating was measured by potentiodynamic polarization test in 3.5 wt.% NaCl solution in pH 7.0. The morphology, structure, and constituents of the coating were observed by scanning electron microscope, energy dispersivespectrum, x-ray photoelectron spectrum, and Fourier infrared spectrometer. Results show that corrosion resistance properties of samples coated with four different anhydrous conversion films were improved obviously. The corrosion potential increased, corrosion current density decreased, and polarization resistance increased. Among these four kinds of conversion films the one added with phytic exhibits the best corrosion resistant property. The mechanism of anhydrous-neodymium conversion film formation is also analyzed in this paper. It reveals that the gadolinium conversion coating is mainly composed of stable Nd2O3, MgO, Mg(OH)2, and carboxylate of Nd. And that the sample surface is rich in organic functional groups.

  14. Characterization of thin-film deposition in a pulsed acrylic acid polymerizing discharge

    SciTech Connect

    Voronin, Sergey A.; Bradley, James W.; Fotea, Catalin; Zelzer, Mischa; Alexander, Morgan R.

    2007-07-15

    In this study, thin-film deposition in a pulsed rf polymerizing discharge (13.56 MHz) struck in acrylic acid has been investigated by mass spectrometry, x-ray photoelectron spectroscopy, and quartz crystal microbalance techniques. The experiment was conducted at a fixed acrylic acid pressure of 1.3 Pa and 'on' pulse duration of 0.1 ms, whereas the 'off' time was varied between 0 and 20 ms. The rf input power in the 'on' time and gas flow rate were varied between 10 and 50 W and 1.5 and 4.8 sccm (sccm denotes cubic centimeter per minute at STP), respectively. These changes of the discharge conditions resulted in large-scale progressive variations in film and gas-phase plasma composition. In particular, the -COOH functionality of the monomer was increasingly retained in the plasma-generated thin films as the duty cycle was lowered (i.e., with lowered time-averaged powers). The monomer retention reached its maximum value of 66% for 'off' times exceeding 5 ms, when the discharge was operating in the power-deficient regime. The results show that the film deposition rate is a strong function of the monomer flow rate, whereas -COOH retention is correlated to the amount of unfragmented monomer in the plasma, controlled by the applied power.

  15. Mice deficient in Group VIB phospholipase A2 (iPLA2γ) exhibit relative resistance to obesity and metabolic abnormalities induced by a Western diet

    PubMed Central

    Song, Haowei; Wohltmann, Mary; Bao, Shunzhong; Ladenson, Jack H.; Semenkovich, Clay F.

    2010-01-01

    Phospholipases A2 (PLA2) play important roles in metabolic processes, and the Group VI PLA2 family is comprised of intracellular enzymes that do not require Ca2+ for catalysis. Mice deficient in Group VIA PLA2 (iPLA2β) develop more severe glucose intolerance than wild-type (WT) mice in response to dietary stress. Group VIB PLA2 (iPLA2γ) is a related enzyme distributed in membranous organelles, including mitochondria, and iPLA2γ knockout (KO) mice exhibit altered mitochondrial morphology and function. We have compared metabolic responses of iPLA2γ-KO and WT mice fed a Western diet (WD) with a high fat content. We find that KO mice are resistant to WD-induced increases in body weight and adiposity and in blood levels of cholesterol, glucose, and insulin, even though WT and KO mice exhibit similar food consumption and dietary fat digestion and absorption. KO mice are also relatively resistant to WD-induced insulin resistance, glucose intolerance, and altered patterns of fat vs. carbohydrate fuel utilization. KO skeletal muscle exhibits impaired mitochondrial β-oxidation of fatty acids, as reflected by accumulation of larger amounts of long-chain acylcarnitine (LCAC) species in KO muscle and liver compared with WT in response to WD feeding. This is associated with increased urinary excretion of LCAC and much reduced deposition of triacylglycerols in liver by WD-fed KO compared with WT mice. The iPLA2γ-deficient genotype thus results in a phenotype characterized by impaired mitochondrial oxidation of fatty acids and relative resistance to the metabolic abnormalities induced by WD. PMID:20179248

  16. iPLA2β deficiency attenuates obesity and hepatic steatosis in ob/ob mice through hepatic fatty-acyl phospholipid remodeling.

    PubMed

    Deng, Xiuling; Wang, Jiliang; Jiao, Li; Utaipan, Tanyarath; Tuma-Kellner, Sabine; Schmitz, Gerd; Liebisch, Gerhard; Stremmel, Wolfgang; Chamulitrat, Walee

    2016-05-01

    PLA2G6 or GVIA calcium-independent PLA2 (iPLA2β) is identified as one of the NAFLD modifier genes in humans, and thought to be a target for NAFLD therapy. iPLA2β is known to play a house-keeping role in phospholipid metabolism and remodeling. However, its role in NAFLD pathogenesis has not been supported by results obtained from high-fat feeding of iPLA2β-null (PKO) mice. Unlike livers of human NAFLD and genetically obese rodents, fatty liver induced by high-fat diet is not associated with depletion of hepatic phospholipids. We therefore tested whether iPLA2β could regulate obesity and hepatic steatosis in leptin-deficient mice by cross-breeding PKO with ob/ob mice to generate ob/ob-PKO mice. Here we observed an improvement in ob/ob-PKO mice with significant reduction in serum enzymes, lipids, glucose, insulin as well as improved glucose tolerance, and reduction in islet hyperplasia. The improvement in hepatic steatosis measured by liver triglycerides, fatty acids and cholesterol esters was associated with decreased expression of PPARγ and de novo lipogenesis genes, and the reversal of β-oxidation gene expression. Notably, ob/ob livers contained depleted levels of lysophospholipids and phospholipids, and iPLA2β deficiency in ob/ob-PKO livers lowers the former, but replenished the latter particularly phosphatidylethanolamine (PE) and phosphatidylcholine (PC) that contained arachidonic (AA) and docosahexaenoic (DHA) acids. Compared with WT livers, PKO livers also contained increased PE and PC containing AA and DHA. Thus, iPLA2β deficiency protected against obesity and ob/ob fatty liver which was associated with hepatic fatty-acyl phospholipid remodeling. Our results support the deleterious role of iPLA2β in severe obesity associated NAFLD.

  17. Retinal pigment epithelium cell culture on thin biodegradable poly(DL-lactic-co-glycolic acid) films.

    PubMed

    Lu, L; Garcia, C A; Mikos, A G

    1998-01-01

    Thin films of 50:50 and 75:25 poly(DL-lactic-co-glycolic acid) (PLGA) were manufactured with a controlled thickness of less than 10 microm. The effect of PLGA copolymer ratio on in vitro cell attachment, proliferation, morphology, and tight junction formation was evaluated using a human D407 retinal pigment epithelium (RPE) cell line. Almost complete cell attachment was achieved on both PLGA films after 8 h of cell seeding, which was comparable to that on tissue culture polystyrene (TCPS) controls. The initial cell seeding density affected attachment, and the optimal value for 50:50 PLGA was 25000 cells cm(-2). After 7 days of in vitro culture, cell density on 50:50 and 75:25 PLGA films increased 45 and 40 folds, respectively, and a 34-fold increase was observed on TCPS. The RPE cells cultured on PLGA films at confluence had a characteristic cobblestone morphology. Confluent RPE cells also developed normal tight junctions in vitro which were concentrated mainly at the apical surfaces of cell-cell junctions. These results demonstrated that thin biodegradable PLGA films can provide suitable substrates for human RPE cell culture, and may serve as temporary carriers for subretinal implantation of organized sheets of RPE.

  18. Influence of different factors on the destruction of films based on polylactic acid and oxidized polyethylene

    NASA Astrophysics Data System (ADS)

    Podzorova, M. V.; Tertyshnaya, Yu. V.; Pantyukhov, P. V.; Shibryaeva, L. S.; Popov, A. A.; Nikolaeva, S.

    2016-11-01

    Influence of different environmental factors on the degradation of film samples based on polylactic acid and low density polyethylene with the addition of oxidized polyethylene was studied in this work. Different methods were used to find the relationship between degradation and ultraviolet, moisture, oxygen. It was found that the addition of oxidized polyethylene, used as a model of recycled polyethylene, promotes the degradation of blends.

  19. Development of flexible antimicrobial packaging materials against Campylobacter jejuni by incorporation of gallic acid into zein-based films.

    PubMed

    Alkan, Derya; Aydemir, Levent Y; Arcan, Iskender; Yavuzdurmaz, Hatice; Atabay, Halil I; Ceylan, Cagatay; Yemenicioğlu, Ahmet

    2011-10-26

    In this study, antimicrobial films were developed against Campylobacter jejuni by incorporation of gallic acid (GA) into zein-based films. The zein and zein-wax composite films containing GA between 2.5 and 10 mg/cm(2) were effective on different C. jejuni strains in a concentration-dependent manner. Zein and zein-wax composite films showed different release profiles in distilled water but quite similar release profiles at solid agar medium. Depending on incorporated GA concentration, 60-80% of GA released from the films, while the remaining GA was bound or trapped by film matrix. The GA at 2.5 and 5 mg/cm(2) caused a considerable increase in elongation (57-280%) of all zein films and eliminated their classical flexibility problems. The zein-wax composite films were less flexible than zein films, but the films showed similar tensile strengths and Young's modulus. Scanning electron microscopy indicated different morphologies of zein and zein-wax composite films. This study clearly showed the good potential of zein and GA to develop flexible antimicrobial films against C. jejuni.

  20. Fundamental study on improvement of piezoelectricity of poly(ι-lactic acid) and its application to film actuators.

    PubMed

    Tajitsu, Yoshiro

    2013-08-01

    We designed a new film actuator, whose driving force is generated by a surface wave, which induces rotational motion. Its performance is similar to that of a rotation motor even though the new film actuator has no complex mechanical parts. To realize the film actuator, we used a poly(l-lactic acid) (PLLA) film with improved piezoelectricity. First, we theoretically investigated the necessary conditions for a surface wave to be generated on the end face of a PLLA film by the fusion of its shear piezoelectricity and resonance, and then experimentally realized this. Using the actuator made using the PLLA film, we demonstrated that the clockwise and counterclockwise rotation of an object placed on the end face of the PLLA film actuator could be freely controlled by changing the frequency of the ac voltage applied to the actuator.

  1. Hydrolytic and oxidate stability of L-(+) -ascorbic acid supported in pectin films: Influence of the macromolecular structure and calcium presence

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The hydrolytic and oxidative stability of L-(+)-ascorbic acid (AA) into plasticized pectin films were separately studied in view of preserving vitamin C activity and/or to achieve localized antioxidant activity at pharmaceutical and food interfaces. Films were made with each one of the enzymatically...

  2. Biocompatibility and characterization of polylactic acid/styrene-ethylene-butylene-styrene composites.

    PubMed

    Tsou, Chi-Hui; Kao, Bo-Jyue; Yang, Ming-Chien; Suen, Maw-Cherng; Lee, Yi-Hsuan; Chen, Jui-Chin; Yao, Wei-Hua; Lin, Shang-Ming; Tsou, Chih-Yuan; Huang, Shu-Hsien; De Guzman, Manuel; Hung, Wei-Song

    2015-01-01

    Polylactic acid (PLA)/styrene-ethylene-butylene-styrene (SEBS) composites were prepared by melt blending. Differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WXRD) were used to characterize PLA and PLA/SEBS composites in terms of their melting behavior and crystallization. Curves from thermal gravimetric analysis (TGA) illustrated that thermostability increased with SEBS content. Further morphological analysis of PLA/SEBS composites revealed that SEBS molecules were not miscible with PLA molecules in PLA/SEBS composites. The tensile testing for PLA and PLA/SEBS composites showed that the elongation at the break was enhanced, but tensile strength decreased with increasing SEBS content. L929 fibroblast cells were chosen to assess the cytocompatibility; the cell growth of PLA was found to decrease with increasing SEBS content. This study proposes possible reasons for these properties of PLA/SEBS composites.

  3. Probing titanate nanowire surface acidity through methylene blue adsorption in colloidal suspension and on thin films.

    PubMed

    Horváth, Endre; Szilágyi, István; Forró, László; Magrez, Arnaud

    2014-02-15

    The interaction of the cationic dye methylene blue (MB) with titanate nanowires (TiONWs) was investigated in different pH environments using visible spectroscopy and electrophoresis on thin films as well as in aqueous suspension. The surface charge of the TiONWs depends on the pH and ionic strength leading to positive charge under acidic and negative under alkaline conditions. The TiONWs have the same adsorption capacity on films and in suspensions at neutral pH while under alkaline conditions they are able to adsorb significantly more MB in suspension due to their higher surface area. Detailed adsorption studies in water revealed that dye cations form monomers, dimers and larger aggregates of H-type (face-to-face) on the TiONW films. The results indicate that below pH = 4.0 the TiONWs' external surface consists of Brøntsted acid sites capable of protonating MB. It was suggested that reversible indicator role of MB molecule dimers probes the TiONW surface acidity (Brøntsted sites).

  4. Performance of alginate films for retention of L-(+)-ascorbic acid.

    PubMed

    De'Nobili, M D; Curto, L M; Delfino, J M; Soria, M; Fissore, E N; Rojas, A M

    2013-06-25

    In view of acting as controlled delivery systems for nutritional supplementation, therapy or antioxidant activity at interfaces, alginate films of different copolymer composition and glycerol plasticizer levels were developed in the presence of Ca(2+) for achieving higher stability of L-(+)-ascorbic acid (AA). The ability of the alginate network to preserve AA from hydrolysis, tested by storage under vacuum at 25 °C, only decreased with the relative humidity (RH) increase when alginates were mainly constituted by guluronic-guluronic acid blocks (GG), whereas also decreased with the glycerol level increase when mannuronic-mannuronic acid (MM) and/or alternating guluronic-mannuronic (GM+MG) flexible blocks were present in higher proportions. This result could be probably related to the lower capability of the latter alginate block compositions to immobilize water in the network as they are not able to constitute Ca(2+) mediated junction zones where water molecules are highly retained. Films also studied under air storage showed that even at less favorable conditions of RH and glycerol levels, both GG and GM+MG enriched alginate networks in general preserved AA from oxidation. It also demonstrated that hydrolysis is the principal way by which AA is lost when supported in films.

  5. Characterization of bioactive RGD peptide immobilized onto poly(acrylic acid) thin films by plasma polymerization

    NASA Astrophysics Data System (ADS)

    Seo, Hyun Suk; Ko, Yeong Mu; Shim, Jae Won; Lim, Yun Kyong; Kook, Joong-Ki; Cho, Dong-Lyun; Kim, Byung Hoon

    2010-11-01

    Plasma surface modification can be used to improve the surface properties of commercial pure Ti by creating functional groups to produce bioactive materials with different surface topography. In this study, a titanium surface was modified with acrylic acid (AA) using a plasma treatment and immobilized with bioactive arginine-glycine-aspartic acid (RGD) peptide, which may accelerate the tissue integration of bone implants. Both terminals containing the -NH2 of RGD peptide sequence and -COOH of poly(acrylic acid) (PAA) thin film were combined with a covalent bond in the presence of 1-ethyl-3-3-dimethylaminopropyl carbodiimide (EDC). The chemical structure and morphology of AA film and RGD immobilized surface were investigated by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR), atomic force microscopy (AFM), and scanning electron microscopy (SEM). All chemical analysis showed full coverage of the Ti substrate with the PAA thin film containing COOH groups and the RGD peptide. The MC3T3-E1 cells were cultured on each specimen, and the cell alkaline phosphatase (ALP) activity were examined. The surface-immobilized RGD peptide has a significantly increased the ALP activity of MC3T3-E1 cells. These results suggest that the RGD peptide immobilization on the titanium surface has an effect on osteoblastic differentiation of MC3T3-E1 cells and potential use in osteo-conductive bone implants.

  6. Taste Sensing Based on Frequency Characteristics of Quartz Resonator with Oleic Acid Film Electrodeposition

    NASA Astrophysics Data System (ADS)

    Mukai, Keiichi; Misawa, Kenji; Kitama, Masataka; Yamashita, Masaji; Arisawa, Junij

    In this paper, we studied a possibility of a taste sensing using a quartz crystal microbalance (hereafter cited as QCM) sensor. We modified oleic acid film to Au electrode of the quartz resonator by an electrodeposition method. The electrodeposition film was used as the adsorber for taste substances. We consider that oscillation frequency decreases with the mass changes due to adsorption. Frequency characteristics differed in each basic taste solution. Their characteristics were based on chemical nature of taste substances. Ions or organic molecules were attached to electrodeposition film by electrostatic interaction or hydrophobic interaction respectively. Moreover, we studied the taste evaluation of sweetness solutions and sourness solutions. As a result, in case of sweetness solutions, the frequency changes correlated with Brix (%) (r = -0.98). In case of sourness solutions, especially, the frequency changes correlated in pH (r = 0.89) of organic acids. Differences of the frequency changes depended on the amount of undissociated molecule in the acid solutions. Additionally, taste evaluation by the QCM sensor related to gustatory sense of human. Therefore, we suggested the validity of the QCM sensor for evaluation of the taste solutions.

  7. Ruthenium oxide ion selective thin-film electrodes for engine oil acidity monitoring

    NASA Astrophysics Data System (ADS)

    Maurya, D. K.; Sardarinejad, A.; Alameh, K.

    2015-06-01

    We demonstrate the concept of a low-cost, rugged, miniaturized ion selective electrode (ISE) comprising a thin film RuO2 on platinum sensing electrode deposited using RF magnetron sputtered in conjunction with an integrated Ag/AgCl and Ag reference electrodes for engine oil acidity monitoring. Model oil samples are produced by adding nitric acid into fresh fully synthetic engine oil and used for sensor evaluation. Experimental results show a linear potential-versus-acid-concentration response for nitric acid concentration between 0 (fresh oil) to 400 ppm, which demonstrate the accuracy of the RuO2 sensor in real-time operation, making it attractive for use in cars and industrial engines.

  8. Simulation of mechanical behavior and optimization of simulated injection molding process for PLA based antibacterial composite and nanocomposite bone screws using central composite design.

    PubMed

    Heidari, Behzad Shiroud; Oliaei, Erfan; Shayesteh, Hadi; Davachi, Seyed Mohammad; Hejazi, Iman; Seyfi, Javad; Bahrami, Mozhgan; Rashedi, Hamid

    2017-01-01

    In this study, injection molding of three poly lactic acid (PLA) based bone screws was simulated and optimized through minimizing the shrinkage and warpage of the bone screws. The optimization was carried out by investigating the process factors such as coolant temperature, mold temperature, melt temperature, packing time, injection time, and packing pressure. A response surface methodology (RSM), based on the central composite design (CCD), was used to determine the effects of the process factors on the PLA based bone screws. Upon applying the method of maximizing the desirability function, optimization of the factors gave the lowest warpage and shrinkage for nanocomposite PLA bone screw (PLA9). Moreover, PLA9 has the greatest desirability among the selected materials for bone screw injection molding. Meanwhile, a finite element analysis (FE analysis) was also performed to determine the force values and concentration points which cause yielding of the screws under certain conditions. The Von-Mises stress distribution showed that PLA9 screw is more resistant against the highest loads as compared to the other ones. Finally, according to the results of injection molding simulations, the design of experiments (DOE) and structural analysis, PLA9 screw is recommended as the best candidate for the production of biomedical materials among all the three types of screws.

  9. Molecular modeling of the inhibition of enzyme PLA2 from snake venom by dipyrone and 1-phenyl-3-methyl-5-pyrazolone

    NASA Astrophysics Data System (ADS)

    Silva, S. L. Da; Comar, M., Jr.; Oliveira, K. M. T.; Chaar, J. S.; Bezerra, E. R. M.; Calgarotto, A. K.; Baldasso, P. A.; Veber, C. L.; Villar, J. A. F. P.; Oliveira, A. R. M.; Marangoni, S.

    Phospholipases A2 (PLA2) are enzymes that trigger the degradation cascade of the arachidonic acid, leading to the formation of pro-inflammatory eicosanoids. The selective inhibition of PLA2s is crucial in the search for a more efficient anti-inflammatory drug with fewer side effects than the drugs currently used. Hence, we studied the influences caused by two pyrazolonic inhibitors: dipyrone (DIP) and 1-phenyl-3-methyl-5-pyrazolone (PMP) on the kinetic behavior of PLA2 from Crotalus adamanteus venom. Molecular modeling results, by DFT and MM approaches, showed that DIP is strongly associated to the active site of PLA2 through three hydrogen bonds, whereas PMP is associated to the enzyme just through hydrophobic interactions. In addition, only PMP presents an intramolecular hydrogen bond that make difficult the formation of more efficient interactions with PLA2. These results help in the understanding of the experimental observations. Experimentally, the results showed that PLA2 from C. adamanteus present a typical Michaelian behavior. In addition, the calculated kinetic parameters showed that, in the presence of DIP or PMP, the maximum enzymatic velocity (VMAX) value was kept constant, whereas the Michaelis constant (KM) values increased and the inhibition constant (KI) decreased, indicating competitive inhibition. These results show that the phenyl-pyrazolonic structures might help in the development and design of new drugs able to selectively inhibit PLA2.

  10. Electrodeposited non-stoichiometric tungstic acid for electrochromic applications: film growth modes, crystal structure, redox behavior and stability

    NASA Astrophysics Data System (ADS)

    Pugolovkin, Leonid V.; Cherstiouk, Olga V.; Plyasova, Lyudmila M.; Molina, Irina Yu.; Kardash, Tatyana Yu.; Stonkus, Olga A.; Yatsenko, Dmitriy A.; Kaichev, Vasily V.; Tsirlina, Galina A.

    2016-12-01

    Bath composition for cathodic electrodeposition of non-stoichiometric hydrated tungstic acid with high electrochromic efficiency is optimized with account for selective electroreduction of certain isopolytungstates. XRD data for thin electrodeposited films and chemically synthesized bulk tungstic acid dihydrate are compared in the context of reversible oxidation and reduction in hydrogen atmosphere, in presence of Pt catalyst. XPS and TEM techniques are attracted to understand the nature of reversible and less reversible transformations of films in the course of their storage and operation.

  11. Films.

    ERIC Educational Resources Information Center

    Philadelphia Board of Education, PA. Div. of Instructional Materials.

    The Affective Curriculum Research Project produced five films and two records during a series of experimental summer programs. The films and records form part of a curriculum designed to teach to the concerns of students. The films were an effort to describe the Philadelphia Cooperative Schools Program, to explain its importance, and to…

  12. Identification and characterization of novel poly(DL-lactic acid) depolymerases from metagenome.

    PubMed

    Mayumi, Daisuke; Akutsu-Shigeno, Yukie; Uchiyama, Hiroo; Nomura, Nobuhiko; Nakajima-Kambe, Toshiaki

    2008-07-01

    Many poly(lactic acid) (PLA)-degrading microorganisms have been isolated from the natural environment by culture-based methods, but there is no study about unculturable PLA-degrading microorganisms. In this study, we constructed a metagenomic library consisting of the DNA extracted from PLA disks buried in compost. We identified three PLA-degrading genes encoding lipase or hydrolase. The purified enzymes degraded not only PLA, but also various aliphatic polyesters, tributyrin, and p-nitrophenyl esters. From their substrate specificities, the PLA depolymerases were classified into an esterase rather than a lipase. Among the PLA depolymerases, PlaM4 exhibited thermophilic properties; that is, it showed the highest activity at 70 degrees C and was stable even after incubation for 1 h at 50 degrees C. PlaM4 had absorption and degradation activities for solid PLA at 60 degrees C, which indicates that the enzyme can effectively degrade PLA in a high-temperature environment. On the other hand, the enzyme classification based on amino acid sequences showed that the other PLA depolymerases, PlaM7 and PlaM9, were not classified into known lipases or esterases. This is the first report on the identification and characterization of PLA depolymerase from a metagenome.

  13. Thin-film sulfuric acid anodizing as a replacement for chromic acid anodizing

    NASA Technical Reports Server (NTRS)

    Kallenborn, K. J.; Emmons, J. R.

    1995-01-01

    Chromic acid has long been used to produce a thin, corrosion resistant (Type I) coating on aluminum. Following anodizing, the hardware was sealed using a sodium dichromate solution. Sealing closes up pores inherent in the anodized coating, thus improving corrosion resistance. The thinness of the brittle coating is desirable from a fatigue standpoint, and chromium was absorbed by the coating during the sealing process, further improving corrosion resistance. Unfortunately, both chromic acid and sodium dichromate contain carcinogenic hexavalent chromium. Sulfuric acid is being considered as a replacement for chromic acid. Sulfuric acid of 10-20 percent concentration has traditionally been used to produce relatively thick (Types II and III) or abrasion resistant (Type III) coatings. A more dilute, that is five weight percent, sulfuric acid anodizing process, which produces a thinner coating than Type II or III, with nickel acetate as the sealant has been developed. The process was evaluated in regard to corrosion resistance, throwing power, fatigue life, and processing variable sensitivity, and shows promise as a replacement for the chromic acid process.

  14. Activation of mitochondrial calcium-independent phospholipase A2γ (iPLA2γ) by divalent cations mediating arachidonate release and production of downstream eicosanoids.

    PubMed

    Moon, Sung Ho; Jenkins, Christopher M; Liu, Xinping; Guan, Shaoping; Mancuso, David J; Gross, Richard W

    2012-04-27

    Calcium-independent phospholipase A(2)γ (iPLA(2)γ) (PNPLA8) is the predominant phospholipase activity in mammalian mitochondria. However, the chemical mechanisms that regulate its activity are unknown. Here, we utilize iPLA(2)γ gain of function and loss of function genetic models to demonstrate the robust activation of iPLA(2)γ in murine myocardial mitochondria by Ca(2+) or Mg(2+) ions. Calcium ion stimulated the production of 2-arachidonoyl-lysophosphatidylcholine (2-AA-LPC) from 1-palmitoyl-2-[(14)C]arachidonoyl-sn-glycero-3-phosphocholine during incubations with wild-type heart mitochondrial homogenates. Furthermore, incubation of mitochondrial homogenates from transgenic myocardium expressing iPLA(2)γ resulted in 13- and 25-fold increases in the initial rate of radiolabeled 2-AA-LPC and arachidonic acid (AA) production, respectively, in the presence of calcium ion. Mass spectrometric analysis of the products of calcium-activated hydrolysis of endogenous mitochondrial phospholipids in transgenic iPLA(2)γ mitochondria revealed the robust production of AA, 2-AA-LPC, and 2-docosahexaenoyl-LPC that was over 10-fold greater than wild-type mitochondria. The mechanism-based inhibitor (R)-(E)-6-(bromomethylene)-3-(1-naphthalenyl)-2H-tetrahydropyran-2-one (BEL) (iPLA(2)γ selective), but not its enantiomer, (S)-BEL (iPLA(2)β selective) or pyrrolidine (cytosolic PLA(2)α selective), markedly attenuated Ca(2+)-dependent fatty acid release and polyunsaturated LPC production. Moreover, Ca(2+)-induced iPLA(2)γ activation was accompanied by the production of downstream eicosanoid metabolites that were nearly completely ablated by (R)-BEL or by genetic ablation of iPLA(2)γ. Intriguingly, Ca(2+)-induced iPLA(2)γ activation was completely inhibited by long-chain acyl-CoA (IC(50) ∼20 μm) as well as by a nonhydrolyzable acyl-CoA thioether analog. Collectively, these results demonstrate that mitochondrial iPLA(2)γ is activated by divalent cations and inhibited by acyl

  15. Hydrophobic-modified nano-cellulose fiber/PLA biodegradable composites for lowering water vapor transmission rate (WVTR) of paper.

    PubMed

    Song, Zhaoping; Xiao, Huining; Zhao, Yi

    2014-10-13

    New biodegradable nanocomposites have been successfully prepared by incorporating modified nano-cellulose fibers (NCF) in a biodegradable polylactic acid (PLA) matrix in this work. The hydrophobic-modified NCF was obtained by grafting hydrophobic monomers on NCF to improve the compatibility between NCF and PLA during blending. The resulting NCF/PLA composites were then applied on paper surface via a cast-coating process in an attempt to reduce the water vapor transmission rate (WVTR) of paper. The WVTR tests, conducted under various testing conditions and with different coating weights, demonstrated that the modified NCF/PLA composites coating played a critical role in lowering WVTR of paper. The lowest WVTR value was 34 g/m(2)/d, which was obtained with an addition of 1% of modified NCF to PLA and the composites coating weight at 40 g/m(2) and substantially lower than the control value at 1315 g/m(2)/d. The paper coated with the modified biodegradable composite is promising as green-based packaging materials.

  16. GS/DBM/PLA porous composite biomaterial for the treatment of infective femoral condyle defect in rats

    PubMed Central

    LIU, XIAOMING; YANG, LIN; LI, JING; ZHANG, YUMING; XU, WEIJUN; REN, YAN; LIU, BIWANG; YANG, BIAO; LI, BAOXING

    2016-01-01

    A bone defect resulting from open bone trauma may easily become infected; however, the administration of efficacious systemic antibiotics cannot be performed at safe levels. Previous studies have investigated anti-infective biomaterials that incorporate into bone and facilitate the direct application of high-concentration local antibiotics. In the present study, the effect of a novel porous composite with gentamicin sulfate (GS) in treating infected femoral condyle defects was investigated using a rat model. A novel porous composite biomaterial was prepared based on a supercritical carbon dioxide fluid technique that combined GS, demineralized bone matrix (DBM) and polylactic acid (PLA). A rat femoral condyle fracture model of infection was established. The GS/DBM/PLA composite biomaterial was implanted and its physicochemical characteristics, biocompatibility and ability to facilitate repair of infected bone defect were assessed. The GS/DBM/PLA composite biomaterial maintained the antibiotic activity of GS, with good anti-compression strength, porosity and biocompatibility. The results of the animal experiments indicated that the GS/DBM/PLA composite biomaterial exerted marked anti-infective effects and facilitated bone defect repair, while simultaneously controlling infection. Porous GS/DBM/PLA is therefore a promising composite biomaterial for use in bone tissue engineering. PMID:27284292

  17. Simultaneous voltammetric determination of ascorbic acid, dopamine and uric acid using polybromothymol blue film-modified glassy carbon electrode.

    PubMed

    Xu, Xiongwei; Lin, Qihuang; Liu, Ailin; Chen, Wei; Weng, Xiuhua; Wang, Changlian; Lin, Xinhua

    2010-06-01

    A sensitive and selective electrochemical method for simultaneous determination of ascorbic acid (AA), dopamine (DA), and uric acid (UA) using an electropolymerized bromothymol blue (BTB)-modified glassy carbon electrode (GCE) was developed. The electrochemically synthesized film was investigated using electrochemical impedance spectroscopy and voltammetric methods. The electrochemical behavior of the polymer-modified electrode depends on film thickness, i.e., the electropolymyerization time. The poly-BTB-modified GCE shows excellent electrocatalytic activity toward the oxidation of AA, DA, and UA in phosphate buffer solution (pH 5.0). The voltametric peak separations of AA/DA, DA/UA, and AA/UA on this modified electrode are 118 mV, 298 mV, and 455 mV, respectively. Therefore the voltammetric responses of these three compounds can be resolved well on the polymer-modified electrode, and simultaneous determination of these three compounds can be achieved. In addition, this modified electrode can be successfully applied to determine AA and DA in injection and UA in urine samples without interference.

  18. Reaction of isoprene on thin sulfuric acid films: kinetics, uptake, and product analysis.

    PubMed

    Connelly, Brandon M; Tolbert, Margaret A

    2010-06-15

    A high vacuum Knudsen flow reactor was used to determine the reactive uptake coefficient, gamma, of isoprene on sulfuric acid films as a function of sulfuric acid weight percent, temperature, and relative humidity. No discernible dependence was observed for gamma over the range of temperatures (220 - 265 K) and pressures (10(-7) Torr -10(-4) Torr) studied. However, the uptake coefficient increased with increased sulfuric acid concentration between the range of 78 wt % (gamma(i) approximately 10(-4)) and 93 wt % (gamma(i) approximately 10(-3)). In addition to the Knudsen Cell, a bulk study was conducted between 60 and 85 wt % H(2)SO(4) to quantify uptake at lower acid concentrations and to determine reaction products. After exposing sulfuric acid to gaseous isoprene the condensed phase products were extracted and analyzed using gas chromatography/mass spectrometry (GC/MS). Isoprene was observed to polymerize in the sulfuric acid and form yellow/red colored monoterpenes and cyclic sesquiterpenes. Finally, addition of water to the 85 wt % sulfuric acid/isoprene product mixture released these terpenes from the condensed phase into the gas phase. Together these experiments imply that direct isoprene uptake will not produce significant SOA; however, terpene production from the small uptake may be relevant for ultrafine particles and could affect growth and nucleation.

  19. Ferulic acid-coupled chitosan: thermal stability and utilization as an antioxidant for biodegradable active packaging film.

    PubMed

    Woranuch, Sarekha; Yoksan, Rangrong; Akashi, Mitsuru

    2015-01-22

    The aim of the present research was to study the thermal stability of ferulic acid after coupling onto chitosan, and the possibility of using ferulic acid-coupled chitosan (FA-CTS) as an antioxidant for biodegradable active packaging film. FA-CTS was incorporated into biodegradable film via a two-step process, i.e. compounding extrusion at temperatures up to 150°C followed by blown film extrusion at temperatures up to 175°C. Although incorporation of FA-CTS with a content of 0.02-0.16% (w/w) caused decreased water vapor barrier property and reduced extensibility, the biodegradable films possessed improved oxygen barrier property and antioxidant activity. Radical scavenging activity and reducing power of film containing FA-CTS were higher than those of film containing naked ferulic acid, by about 254% and 94%, respectively. Tensile strength and rigidity of the films were not significantly affected by the addition of FA-CTS with a content of 0.02-0.08% (w/w). The above results suggested that FA-CTS could potentially be used as an antioxidant for active packaging film.

  20. 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.

  1. Comparative NH 3-sensing characteristic studies of PANI/TiO II nanocomposite thin films doped with different acids

    NASA Astrophysics Data System (ADS)

    Tai, Huiling; Jiang, Yadong; Xie, Guangzhong; Yu, Junsheng; Ying, Zhihua; Chen, Xuan

    2008-02-01

    Polyaniline/titanium dioxide (PANI/TiO II) nanocomposite thin films were synthesized by in-situ self-assembly method, which were doped with p-toluene sulphonic acid (p-TSA) and hydrochloric acid (HCl), respectively. The thin films were characterized by using UV-Vis absorption spectroscopy and scanning electron microscope (SEM), and the NH 3 gas sensitive properties of the thin films were investigated at room temperature. The results showed that the PANI/TiO II thin film doped with HCl was superior to that doped with p-TSA in terms of response-recovery characteristics. The surface morphology characterization of the thin films were performed to explain the different gas-sensing properties.

  2. UCN enhances TGF-beta-mediated mitoinhibition of VSMCs via counteracting TGF-beta-induced cPLA2 expression and activation.

    PubMed

    Zhu, Chao; Cao, Changchun; Wang, Xiaofei; Yuan, Jie; Jin, Lai; Li, Shengnan

    2016-11-01

    Urocortins (UCNs) and transforming growth factor-beta (TGF-beta) have been demonstrated to participate in various cardiovascular diseases, many of which involve vascular smooth muscle cells (VSMCs) proliferation. Cytosolic phospholipase A2 (cPLA2)-mediated arachidonic acid (AA) release is an important cause of VSMCs proliferation. The work was to investigate the regulation of VSMCs proliferation by UCN/TGF-beta and whether cPLA2 was a link between their signaling pathways. VSMCs proliferation was measured by colorimetric assay and immunofluorescence microscopy. Using cell flow cytometry, the changes in the cell cycle phases were investigated. Lentiviral Vector Particle was performed to overexpress cPLA2 gene. Both UCN and TGF-beta inhibited VSMCs proliferation and an additive effect was observed when the cells were treated with UCN plus TGF-beta. TGF-beta increased the percentage of cells in G1-phase while UCN increased the cell percentage in G2-phase with a concomitant decrease in S-phase. Furthermore, cPLA2 expression was increased by TGF-beta but decreased by UCN and UCN attenuated TGF-beta-induced cPLA2 expression. In primary VSMCs, TGF-beta induced cPLA2 phosphorylation, and this effect was also attenuated by UCN. Similar to UCN, the cPLA2 inhibitor, pyrrophenone (PYR), also played a role in enhancing TGF-beta-mediated mitoinhibition. Inversely, overexpression of cPLA2 eliminated the effect of UCN on the mitoinhibition. The pretreatment with UCN counteracted TGF-beta-mediated cPLA2 expression and activation, thereby contributing to TGF-beta-mediated mitoinhibition of VSMCs.

  3. Overcoming the Fundamental Challenges in Improving the Impact Strength and Crystallinity of PLA Biocomposites: Influence of Nucleating Agent and Mold Temperature.

    PubMed

    Nagarajan, Vidhya; Zhang, Kunyu; Misra, Manjusri; Mohanty, Amar K

    2015-06-03

    Poly(lactic acid) (PLA), one of the widely studied renewable resource based biopolymers, has yet to gain a strong commercial standpoint because of certain property limitations. This work is a successful attempt in achieving PLA biocomposites that showed concurrent improvements in impact strength and heat deflection temperature (HDT). Biocomposites were fabricated from a super toughened ternary blend of PLA, poly(ether-b-amide) elastomeric copolymer and ethylene-methyl acrylate-glycidyl methacrylate and miscanthus fibers. The effects of varying the processing parameters and addition of various nucleating agents were investigated. Crystallinity was controlled by optimizing the mold temperature and cycle time of the injection process. With the addition of 1 wt % aromatic sulfonate derivative (Lak-301) as a nucleating agent at a mold temperature of 110 °C, PLA biocomposites exhibited dramatic reduction in crystallization half time to 1.3 min with crystallinity content of 42%. Mechanical and thermal properties assessment for these biocomposites revealed a 4-fold increase in impact strength compared to neat PLA. The HDT of PLA biocomposites increased to 85 °C from 55 °C compared to neat PLA. Crystallization behavior was studied in detail using differential scanning calorimetry and was supported with observations from wide-angle X-ray diffraction profiles and polarized optical microscopy. The presence of a nucleating agent did not alter the crystal structure of PLA; however, a significant difference in spherulite size, crystallization rate and content was observed. Fracture surface morphology and distribution of nucleating agent in the PLA biocomposites were investigated through scanning electron microscopy.

  4. Accelerated Amidization of Branched Poly(ethylenimine)/Poly(acrylic acid) Multilayer Films by Microwave Heating.

    PubMed

    Lin, Kehua; Gu, Yuanqing; Zhang, Huan; Qiang, Zhe; Vogt, Bryan D; Zacharia, Nicole S

    2016-09-13

    Chemical cross-linking of layer-by-layer assembled films promotes mechanical stability and robustness in a wide variety of environments, which can be a challenge for polyelectrolyte multilayers in saline environments or for multilayers made from weak polyelectrolytes in environments with extreme pHs. Heating branched poly(ethylenimine)/poly(acrylic acid) (BPEI/PAA) multilayers at sufficiently high temperatures drives amidization and dehydration to covalently cross-link the film, but this reaction is rather slow, typically requiring heating for hours for appreciable cross-linking to occur. Here, a more than one order of magnitude increase in the amidization kinetics is realized through microwave heating of BPEI/PAA multilayers on indium tin oxide (ITO)/glass substrates. The cross-linking reaction is tracked using infrared spectroscopic ellipsometry to monitor the development of the cross-linking products. For thick films (∼1500 nm), gradients in cross-link density can be readily identified by infrared ellipsometry. Such gradients in cross-link density are driven by the temperature gradient developed by the localized heating of ITO by microwaves. This significant acceleration of reactions using microwaves to generate a well-defined cross-link network as well as being a simple method for developing graded materials should open new applications for these polymer films and coatings.

  5. Multilayer scaffold of electrospun PLA-PCL-collagen nanofibers as a dural substitute.

    PubMed

    Wang, Yu-fei; Guo, Hong-feng; Ying, Da-jun

    2013-11-01

    Dural closure after the neurosurgery can prevent postoperative complications. Although many types of dural substitute have been developed, most of them lack functional and structural characteristics compared with the natural dura mater. In this study, we used electrospinning method to fabricate a multilayer scaffold to promote dural repair. The inner layer of the scaffold that faces the brain tissue is composed of poly-lactic acid (PLA) to reduce tissue adhesion. The middle layer of the scaffold is composed of poly-ɛ-caprolactone and PLA, which provides a watertight seal. The outer layer of the scaffold contains a large amount of collagen to promote cell attachment and proliferation. The results from in vitro study and an animal model have shown that this multilayer fibrous scaffold has sufficient mechanic strength and biochemical properties to enhance dural repair. Therefore, fabrication of scaffold with multiple functional and structural layers may provide a novel approach for tissue engineering.

  6. PEDOT-Au nanocomposite films for electrochemical sensing of dopamine and uric acid.

    PubMed

    Mathiyarasu, J; Senthilkumar, S; Phani, K L N; Yegnaraman, V

    2007-06-01

    In this work, conducting polymer impregnated gold nanoparticles are synthesized through a sequence of chemical and electrochemical routes. The nanocomposite film is characterized using UV-vis, FTIR spectroscopy, and SEM techniques to study the formation of oxidized PEDOT and Au0. The advantages of these films are demonstrated for sensing biologically important compounds such as dopamine and uric acid in presence of excess ascorbic acid, one of the major interferants in the detection of DA and UA (mimicking the physiological conditions), with superior selectivity and sensitivity when compared to the polymer film alone. Simultaneous determination is realized at 115 mV and 246 mV for DA and UA, respectively. The PEDOT matrix is recognized to be responsible for the peak separation (selectivity) while also favouring catalytic oxidation of the above compounds and the nanometer-sized gold particles allow nanomolar sensing of DA and UA (sensitivity). Thus, it is possible to detect nanomolar levels of DA and UA in presence of excess of AA. The combined effect of Au nanoparticles and the PEDOT matrix is rationalized that the Aunano surrounded by a "hydrophobic sheath (PEDOT)" tending to reside within these hydrophobic regions of PEDOT, thus favouring the selectivity and sensitivity of the DA/UA detection. This new generation of nanocomposites is expected to enhance the value of electroanalytical techniques, as it is possible to tune their properties suiting the analytical needs.

  7. Identification and characterization of phospholipase A/sub 2/ (PLA/sub 2/) in bovine pulmonary endothelial cells (BPEC)

    SciTech Connect

    Martin, T.W.; Wysolmerski, R.B.; Lagunoff, D.

    1986-03-01

    Phosphatidylcholine labeled in the sn-2 position with /sup 3/H-oleic acid was used to measure PLA/sub 2/ in cell sonicates (CS) prepared from confluent cultures of BPEC. Substrate at 10-200 ..mu..M was incubated with 5-30 ..mu..g of CS protein in HEPES buffer at 37/sup 0/C. A plot of /sup 3/H-oleic acid release vs time was linear and proportional to the amount of CS protein. Lineweaver-Burk plots of the data were linear with V/sub max/ = 22.2 nmole/mg protein/hr and K/sub d/ = 121 ..mu..M. Under these conditions, phospholipase C activity was 20-fold lower, and phospholipase A/sub 1/ activity was not detectable. PLA/sub 2/ activity was pH-dependent with optima at 4.5 and 7.5. Ca/sup + +/ was not required for activity, and addition of up to 10 mM Ca/sup + +/ to CS in EDTA increased activity by only 10-20%. After centrifugation of CS at 100,000 g for 90 min, 62% of the PLA/sub 2/ activity was recovered in the particular fraction. Triton X-100 (0.006-0.4%) inhibited PLA/sub 2/ up to 90%, whereas 2 mM deoxycholate produced nearly 3-fold activation. Of several agents tested, bromophenacylbromide (BPB) was the most effective inhibitor. Treatment of CS with BPB at 37/sup 0/C for 30 min produced up to 9% inhibition (K/sub i/ = 5 ..mu..M). Phenylmethanesulfonyl fluoride at 200 ..mu..m produced 41% inhibition. Quinacrine at 1 mM inhibited PLA/sub 2/ by 18%. These data define characteristics of BPEC PLA/sub 2/ that should prove useful in studies of the role of this enzyme in specific cellular functions.

  8. Single phase dynamic CMOS PLA using charge sharing technique

    NASA Astrophysics Data System (ADS)

    Dhong, Y. B.; Tsang, C. P.

    A single phase dynamic CMOS NOR-NOR programmable logic array (PLA) using triggered decoders and charge sharing techniques for high speed and low power is presented. By using the triggered decoder technique, the ground switches are eliminated, thereby, making this new design much faster and lower power dissipation than conventional PLA's. By using the charge-sharing technique in a dynamic CMOS NOR structure, a cascading AND gate can be implemented. The proposed PLA's are presented with a delay-time of 15.95 and 18.05 nsec, respectively, which compare with a conventional single phase PLA with 35.5 nsec delay-time. For a typical example of PLA like the Signetics 82S100 with 16 inputs, 48 input minterms (m) and 8 output minterms (n), the 2-SOP PLA using the triggered 2-bit decoder is 2.23 times faster and has 2.1 times less power dissipation than the conventional PLA. These results are simulated using maximum drain current of 600 micro-A, gate length of 2.0 micron, V sub DD of 5 V, the capacitance of an input miniterm of 1600 fF, and the capacitance of an output minterm of 1500 fF.

  9. Single phase dynamic CMOS PLA using charge sharing technique

    NASA Technical Reports Server (NTRS)

    Dhong, Y. B.; Tsang, C. P.

    1991-01-01

    A single phase dynamic CMOS NOR-NOR programmable logic array (PLA) using triggered decoders and charge sharing techniques for high speed and low power is presented. By using the triggered decoder technique, the ground switches are eliminated, thereby, making this new design much faster and lower power dissipation than conventional PLA's. By using the charge-sharing technique in a dynamic CMOS NOR structure, a cascading AND gate can be implemented. The proposed PLA's are presented with a delay-time of 15.95 and 18.05 nsec, respectively, which compare with a conventional single phase PLA with 35.5 nsec delay-time. For a typical example of PLA like the Signetics 82S100 with 16 inputs, 48 input minterms (m) and 8 output minterms (n), the 2-SOP PLA using the triggered 2-bit decoder is 2.23 times faster and has 2.1 times less power dissipation than the conventional PLA. These results are simulated using maximum drain current of 600 micro-A, gate length of 2.0 micron, V sub DD of 5 V, the capacitance of an input miniterm of 1600 fF, and the capacitance of an output minterm of 1500 fF.

  10. The electroplated Pd-Co alloy film on 316 L stainless steel and the corrosion resistance in boiling acetic acid and formic acid mixture with stirring

    NASA Astrophysics Data System (ADS)

    Li, Sirui; Zuo, Yu; Tang, Yuming; Zhao, Xuhui

    2014-12-01

    Pd-Co alloy films were deposited on 316 L stainless steel by electroplating. Scanning electronic microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, weight loss test and polarization test were used to determine the properties of the Pd-Co alloy films. The Pd-Co films show fine grain size, low porosity and obviously high micro-hardness. The Co content in the film can be controlled in a large range from 21.9 at.% to 57.42 at.%. Pd is rich on the Pd-Co film surface, which is benefit to increase the corrosion resistance. In boiling 90% acetic acid plus 10% formic acid mixture with 0.005 M Br- under stirring, the Pd-Co plated stainless steel samples exhibit evidently better corrosion resistance in contrast to Pd plated samples. The good corrosion resistance of the Pd-Co alloy film is explained by the better compactness, the lower porosity, and the obviously higher micro-hardness of the alloy films, which increases the resistance to erosion and retards the development of micro-pores in the film.

  11. Biodegradation of high molecular weight polylactic acid

    NASA Astrophysics Data System (ADS)

    Stloukal, Petr; Koutny, Marek; Sedlarik, Vladimir; Kucharczyk, Pavel

    2012-07-01

    Polylactid acid seems to be an appropriate replacement of conventional non-biodegradable synthetic polymer primarily due to comparable mechanical, thermal and processing properties in its high molecular weight form. Biodegradation of high molecular PLA was studied in compost for various forms differing in their specific surface area. The material proved its good biodegradability under composting conditions and all investigated forms showed to be acceptable for industrial composting. Despite expectations, no significant differences in resulting mineralizations were observed for fiber, film and powder sample forms with different specific surface areas. The clearly faster biodegradation was detected only for the thin coating on porous material with high specific surface area.

  12. Radiation-sensitive indicator based on radiation-chemical formation of acids in polyvinyl butyral films containing chloral hydrate

    NASA Astrophysics Data System (ADS)

    Abdel-Fattah, Atef A.; El-Kelany, M.

    1998-03-01

    Radiation-sensitive indicators based on dyed polyvinyl butyral (PVB) containing acid-sensitive dye (bromophenol blue, BPB) and chloral hydrate (CCl 3CH(OH) 2, 2,2,2-trichloroethane-1, 1-diol) have been developed. These plastic film dosimeters undergo colour change from blue (the alkaline form of BPB) to yellow (the acidic form of BPB), indicating acid formation. The concentration of radiation-formed acids in the films containing different concentrations of chloral hydrate was calculated at different doses. The kinetics of the acid-formation reaction is discussed, indicating a half-order reaction with respect to chloral hydrate concentration. These films can be used as dosimeters for food irradiation applications where the maxima of the useful dose ranges are between 1 and 4 kGy depending on chloral hydrate concentration in the film. The response of these films depends on temperature during irradiation; therefore a correction should be applied. These films have the advantage of negligible humidity effects on response in the intermediate range of relative humidity from 10 to 70% as well as good post-irradiation stability when stored in the dark at room temperature.

  13. Possible involvement of aiPLA2 in the phosphatidylserine-containing liposomes induced production of PGE2 and PGD2 in microglia.

    PubMed

    Takayama, Fumiko; Wu, Zhou; Ma, Hong Mei; Okada, Ryo; Hayashi, Yoshinori; Nakanishi, Hiroshi

    2013-09-15

    Liposomes containing phosphatidylserine (PSL) produce PGE2 after being phagocytosed by microglia, but the precise underlying mechanism behind it still remains unclear. Here, we showed that liposomes consisting of phosphatidylserine and lysophosphatidylcholine, a lipolysis product of phosphatidylcholine by PLA2, were phagocytosed by microglia, but failed to induce secretion of PGE2. Furthermore, PSL-induced PGE2 secretion was significantly inhibited by MJ33, an aiPLA2 inhibitor, but not by AACOCF3, a cPLA2 inhibitor. PSL also produced PGD2 and 15d-PGJ2 in microglia. We thus hypothesize that free arachidonic acid is supplied through aiPLA2-mediated lipolysis of phagocytosed phosphatidylcholine, leading to the production of PGH2 and its downstream metabolites.

  14. PEG-b-PLA micelles and PLGA-b-PEG-b-PLGA sol-gels for drug delivery.

    PubMed

    Cho, Hyunah; Gao, Jieming; Kwon, Glen S

    2016-10-28

    Poly(ethylene glycol)-block-poly(D,L-lactic acid) (PEG-b-PLA) micelles and poly(D,L-lactic-co-glycolic acid)-block-polyethylene glycol)-block-poly(D,L-lactic-co-glycolic acid) (PLGA-b-PEG-b-PLGA) sol-gels have been extensively researched for systemic and localized drug delivery applications, respectively, and they have both progressed into humans for paclitaxel, an important yet poorly water-soluble chemotherapeutic agent. In this review article, preclinical and clinical research on PEG-b-PLA micelles and PLGA-b-PEG-b-PLGA sol-gels that has focused on paclitaxel will be updated, and recent research on other poorly water-soluble anticancer agents and delivery of drug combinations (i.e. multi-drug delivery) that seeks synergistic anticancer efficacy will be summarized. PEG-b-PLA micelles are a first-generation platform for the systemic multi-delivery of poorly water soluble anticancer agents. PLGA-b-PEG-b-PLGA sol-gels are a first-generation platform for the localized multi-drug delivery of water-soluble and/or poorly water-soluble anticancer agents. In summary, PEG-b-PLA micelles and PLGA-b-PEG-b-PLGA sol-gels may safely enable pre-clinical evaluation and clinical translation of poorly water-soluble anticancer agents, especially for promising, rapidly emerging anticancer combinations.

  15. Design of PEG-grafted-PLA nanoparticles as oral permeability enhancer for P-gp substrate drug model Famotidine.

    PubMed

    Mokhtar, Mohamed; Gosselin, Patrick M; Lacasse, François; Hildgen, Patrice

    2017-02-02

    Bioavailability of oral drugs can be limited by an intestinal excretion process mediated by P-glycoprotein (P-gp). Polyethylene glycol (PEG) is a known P-gp inhibitor. Dispersion of Famotidine (a P-gp substrate) within PEGylated nanoparticles (NPs) was used to improve its oral bioavailability. In this work, we evaluated the potential impact of NPs prepared from a grafted copolymer of polylactic acid and PEG on P-gp function by studying in vitro permeability of Famotidine across Caco-2 cells. Copolymers of PEG grafted on polylactic acid a (PLA) backbone (PLA-g-PEG) were synthesized with 1 mol% and 5 mol% PEG vs. lactic acid monomer using PEG 750 and 2000 Da. The polymers were used to prepare Famotidine-loaded NPs and tested in vitro on Caco-2 cells. Significant decrease in basolateral-to-apical transport of Famotidine was observed when Famotidine was encapsulated in NPs prepared from PLA-g-PEG5%. NPs prepared from PLA-g-PEG5% are promising to improve oral bioavailability of P-gp substrates.

  16. Preparation and characterization of collagen/PLA, chitosan/PLA, and collagen/chitosan/PLA hybrid scaffolds for cartilage tissue engineering.

    PubMed

    Haaparanta, Anne-Marie; Järvinen, Elina; Cengiz, Ibrahim Fatih; Ellä, Ville; Kokkonen, Harri T; Kiviranta, Ilkka; Kellomäki, Minna

    2014-04-01

    In this study, three-dimensional (3D) porous scaffolds were developed for the repair of articular cartilage defects. Novel collagen/polylactide (PLA), chitosan/PLA, and collagen/chitosan/PLA hybrid scaffolds were fabricated by combining freeze-dried natural components and synthetic PLA mesh, where the 3D PLA mesh gives mechanical strength, and the natural polymers, collagen and/or chitosan, mimic the natural cartilage tissue environment of chondrocytes. In total, eight scaffold types were studied: four hybrid structures containing collagen and/or chitosan with PLA, and four parallel plain scaffolds with only collagen and/or chitosan. The potential of these types of scaffolds for cartilage tissue engineering applications were determined by the analysis of the microstructure, water uptake, mechanical strength, and the viability and attachment of adult bovine chondrocytes to the scaffolds. The manufacturing method used was found to be applicable for the manufacturing of hybrid scaffolds with highly porous 3D structures. All the hybrid scaffolds showed a highly porous structure with open pores throughout the scaffold. Collagen was found to bind water inside the structure in all collagen-containing scaffolds better than the chitosan-containing scaffolds, and the plain collagen scaffolds had the highest water absorption. The stiffness of the scaffold was improved by the hybrid structure compared to plain scaffolds. The cell viability and attachment was good in all scaffolds, however, the collagen hybrid scaffolds showed the best penetration of cells into the scaffold. Our results show that from the studied scaffolds the collagen/PLA hybrids are the most promising scaffolds from this group for cartilage tissue engineering.

  17. Managing Conflict: Examining Recent PLA Writings on Escalation Control

    DTIC Science & Technology

    2016-02-01

    PLA texts write about the need to “turn crisis into opportunity,” i.e., to seek advantage while resolving a crisis.  Some PLA writings advocate...using kinetic strikes as a form of pre-war deterrence.  Some PLA texts argue that it may be necessary to conduct pre-emptive strikes early in a...advocates going on the offensive early in a war, has serious escalatory implications.  Several texts argue that in a state of pre-war “armed

  18. An amperometric biosensor for uric acid determination prepared from uricase immobilized in polypyrrole film.

    PubMed

    Cete, Servet; Yaşar, Ahmet; Arslan, Fatma

    2006-01-01

    In order to prepare a biosensor for the determination of uric acid, electropolymerization of pyrrole on Pt surface was carried out with an electrochemical cell containing pyrrole, ferrocene (as a electron mediator) and tetrabutylammonium tetrafluoroborat in acetonitrile by cyclic voltammetry between 0.0 and 1.0 V (vs. Ag/AgCl) at a scan rate of 50 mV/s upon Pt electrode. Uricase was immobilized by a glutaraldehyde/gelatine croslinking procedure on to polypyrrole film after the electropolymerization processes. The response of the biosensor against uric acid was measured after 330 seconds following the application of a constant potential of +0.7 V (vs. Ag/AgCl). The resulting biosensor exhibits excellent electrocatalysis for the uric acid. The amperometric determination is based on the electrochemical detection of H2O2, which is generated in enzymatic reaction of uric acid. The sensor responds to uric acid with a detection limit of 5.0 x 10(-7) M. The sensor remains relatively stable for 5 weeks. Interference effect were investigated on the amperometric response of the biosensor. Determination of uric acid was carried out in the biological fluids by biosensor.

  19. Surface Partitioning and Stability of Mixed Films of Fluorinated Alcohols and Acids at the Air- Water Interface

    NASA Astrophysics Data System (ADS)

    Rontu, N. A.; Vaida, V.

    2007-05-01

    The production of fluorinated compounds over the past 50 years has had numerous industrial applications. For example, perfluorinated carboxylic acids are used in the synthesis of polymers and fire retardants, perfluoroalkyl sulfonates act as surface protectors, and fluorotelomer alcohols are incorporated into products such as paints, coatings, polymers, and adhesives. Fluorotelomer alcohols (FTOHs) are linear polyfluorinated alcohols with the formula CF3(CF2)nCH2CH2OH (n=1,3,5,...). They have been suggested as possible precursors for perfluorinated carboxylic acids and detected in the troposphere over several North American sites. Perfluorocarboxylic acids have even been detected in the arctic food chain, human blood, tissues of animals and environmental waters. We report the surface activity of fluorotelomer alcohols and perfluorinated carboxylic acids at the air-water interface by using a Langmuir trough. Isotherms of the pure compounds along with mixed films with other organic carboxylic acids were collected. The main objective of these experiments was to understand their heterogeneous chemistry by characterizing the pure and mixed films, which serves as a representative model for organic films on atmospheric surfaces such as those found on oceans and aqueous aerosols. Film properties and behavior, notably stabilization, evaporation from the subphase, and miscibility in the single-component mixtures as well as in the mixed films will be discussed. An important consequence of FTOHs and perfluorocarboxylic acids being found to partition to the air-water interface is the possibility of their transport and widespread distribution and deposition using atmospheric aerosols.

  20. Aldol Condensation Products and Polyacetals in Organic Films Formed from Reactions of Propanal in Sulfuric Acid at Upper Troposphere/Lower Stratosphere (UT/LS) Aerosol Acidities

    NASA Astrophysics Data System (ADS)

    Bui, J. V. H.; Perez-Montano, S.; Li, E. S. W.; Nelson, T. E.; Ha, K. T.; Leong, L.; Iraci, L. T.; Van Wyngarden, A. L.

    2015-12-01

    Aerosols in the upper troposphere and lower stratosphere (UT/LS) consist mostly of concentrated sulfuric acid (40-80 wt. %) which is highly reflective towards UV and visible radiation. However, airborne measurements have shown that these particles may also contain a significant amount of organic material. Experiments combining organics (propanal, glyoxal and/or methylglyoxal) with sulfuric acid at concentrations typical of UT/LS aerosols produced highly colored surface films (and solutions) that have the potential to impact chemical, optical and/or cloud-forming properties of aerosols. In order to assess the potential for such films to impact aerosol chemistry or climate properties, experiments were performed to identify the chemical processes responsible for film formation. Surface films were analyzed via Attenuated Total Reflectance-FTIR and Nuclear Magnetic Resonance spectroscopies and are shown to consist primarily of aldol condensation products and cyclic and linear polyacetals, the latter of which are likely responsible for separation from the aqueous phase.

  1. Modification of fish skin collagen film and absorption property of tannic acid.

    PubMed

    Liu, Haiying; Zhao, Lu; Guo, Shidong; Xia, Yu; Zhou, Peng

    2014-06-01

    Fish collagen is a biomacromolecule material and is usually used as a clarifying agent. However, fish collagen is not recyclable, and sedimentation usually occurs in the clarification process using fish collagen so that the filtration process is inevitable. This work aimed to provide a recyclable modified fish skin collagen film (MFCF) for adsorption of tannic acids. The collagen from channel catfish skin was extracted and used for preparation of the fish skin collagen film (FCF) and MFCF. The result indicated that the mechanical properties of MFCF were improved by addition of 2 ml/L glycerol, 6 ml/L polyvinyl alcohol (PVA) and 2 ml/L glutaraldehyde in 15 g/L collagen solution. As the most important property of adsorption material, the hydroscopicity of MFCF was only 54%, significantly lower than that of FCF (295%). Therefore, MFCF would not collapse in water. The infrared and thermal properties of MFCF were also investigated in this work. Results indicated that, in comparison to FCF, the physical and chemical properties of MFCF had been improved significantly. MFCF had higher shrink temperature (79.3 °C) and it did not collapse in distilled water at normal temperature. Furthermore, absorption and desorption properties of tannic acid were studied. MFCF showed good capability of absorption and desorption of tannic acid, which leaded to the suggestion that MFCF could have potential applications in adsorption material.

  2. Electrochemical treatment of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) in groundwater impacted by aqueous film forming foams (AFFFs).

    PubMed

    Schaefer, Charles E; Andaya, Christina; Urtiaga, Ana; McKenzie, Erica R; Higgins, Christopher P

    2015-09-15

    Laboratory experiments were performed to evaluate the use of electrochemical treatment for the decomposition of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS), as well as other perfluoroalkyl acids (PFAAs), in aqueous film forming foam (AFFF)-impacted groundwater collected from a former firefighter training area and PFAA-spiked synthetic groundwater. Using a commercially-produced Ti/RuO2 anode in a divided electrochemical cell, PFOA and PFOS decomposition was evaluated as a function of current density (0-20 mA/cm(2)). Decomposition of both PFOA and PFOS increased with increasing current density, although the decomposition of PFOS did not increase as the current density was increased above 2.5 mA/cm(2). At a current density of 10 mA/cm(2), the first-order rate constants, normalized for current density and treatment volume, for electrochemical treatment of both PFOA and PFOS were 46 × 10(-5) and 70 × 10(-5) [(min(-1)) (mA/cm(2))(-1) (L)], respectively. Defluorination was confirmed for both PFOA and PFOS, with 58% and 98% recovery as fluoride, respectively (based upon the mass of PFOA and PFOS degraded). Treatment of other PFAAs present in the groundwater also was observed, with shorter chain PFAAs generally being more recalcitrant. Results highlight the potential for electrochemical treatment of PFAAs, particularly PFOA and PFOS, in AFFF-impacted groundwater.

  3. Effects of dry method esterification of starch on the degradation characteristics of starch/polylactic acid composites.

    PubMed

    Zuo, Ying Feng; Gu, Jiyou; Qiao, Zhibang; Tan, Haiyan; Cao, Jun; Zhang, Yanhua

    2015-01-01

    Maleic anhydride esterified corn starch was prepared by dry method. Esterified starch/polylactic acid (PLA) biodegradable composite was produced via melt extrusion method with blending maleic anhydride esterified corn starch and PLA. The influence of the dry method esterification of starch on the degradation characteristics of starch/PLA composites was investigated by the natural aging degradation which was soil burial method. Test results of mass loss rate showed that the first 30 days of degradation was mainly starch degradation, and the degradation rate of esterified starch/PLA (ES/PLA) was slower than that of native starch/PLA (NS/PLA). Therefore, the damage degree of ES/PLA on the surface and inside was smaller than that of NS/PLA, and the infrared absorption peak intensities of C-O, C=O and C-H were stronger than that of NS/PLA. With the increasing time of soil burial degradation, the damage degree of NS/PLA and ES/PLA on the exterior and interior were gradually increased, whereas the infrared absorption peak intensities of C-O, C=O and C-H were gradually decreased. The XRD diffraction peak intensity of PLA in composites showed an increased trend at first which was then followed by a decreased one along with the increasing time of soil burial degradation, indicating that the degradation of amorphous regions of PLA was earlier than its crystalline regions. When the soil burial time was the same, the diffraction peak intensity of PLA in ES/PLA was stronger than that of NS/PLA. If the degradation time was the same, T0, Ti and residual rate of thermal decomposition of NS/PLA were larger than those of ES/PLA. The tensile strength and bending strength of composites were decreased gradually with soil burial time increasing. Both the tensile strength and bending strength of ES/PLA were stronger than those of NS/PLA.

  4. Three-dimensional patterns from the thin-film drying of amino acid solutions

    PubMed Central

    Zhang, Xuehua; Crivoi, Alexandru; Duan, Fei

    2015-01-01

    Experimental atomic force microscopy (AFM) images show the dried-in patterns from amino acid solutions which can be in the form of dots or networks. The three-dimensional lattice-gas Kinetic Monte Carlo (KMC) model is applied to simulate the formation of dot-like and network-like particle structures from the evaporating thin films of solutions. A sigmoidal jump in the chemical potential value is implemented to obtain dual-scale structures with the grain size distribution peaking at two distinctive values. The simulated and experimental results are qualitatively comparable. PMID:26039636

  5. Coping with the Dragon: Essays on PLA Transformation and the U.S. Military

    DTIC Science & Technology

    2007-12-01

    Command Automation System,’” Liberation Army Daily, 25 May 1999. 53 Yu Yongjun , “Jiefangjun Bao Urges PLA to Implement Orders ‘Creatively,’ Avoid...criteria discussed above. 57 Yu Yongjun . PLA Reform • 55 Old PLA Proposed New PLA Jointness and

  6. Films

    NASA Astrophysics Data System (ADS)

    Li, Ming; Zhang, Yang; Shao, Yayun; Zeng, Min; Zhang, Zhang; Gao, Xingsen; Lu, Xubing; Liu, J.-M.; Ishiwara, Hiroshi

    2014-09-01

    In this paper, we investigated the microstructure and electrical properties of Bi2SiO5 (BSO) doped SrBi2Ta2O9 (SBT) films deposited by chemical solution deposition. X-ray diffraction observation indicated that the crystalline structures of all the BSO-doped SBT films are nearly the same as those of a pure SBT film. Through BSO doping, the 2Pr and 2Ec values of SBT films were changed from 15.3 μC/cm2 and 138 kV/cm of pure SBT to 1.45 μC/cm2 and 74 kV/cm of 10 wt.% BSO-doped SBT. The dielectric constant at 1 MHz for SBT varied from 199 of pure SBT to 96 of 10 wt.% BSO-doped SBT. The doped SBT films exhibited higher leakage current than that of non-doped SBT films. Nevertheless, all the doped SBT films still had small dielectric loss and low leakage current. Our present work will provide useful insights into the BSO doping effects to the SBT films, and it will be helpful for the material design in the future nonvolatile ferroelectric memories.

  7. Polymeric prodrug-functionalized polypropylene films for sustained release of salicylic acid.

    PubMed

    Magaña, Hector; Palomino, Kenia; Cornejo-Bravo, Jose M; Díaz-Gómez, Luis; Concheiro, Angel; Zavala-Lagunes, Edgar; Alvarez-Lorenzo, Carmen; Bucio, Emilio

    2016-09-10

    Medical devices decorated with salicylic acid-based polymer chains (polymeric prodrug) that slowly release this anti-inflammatory and anti-biofilm drug at the implantation site were designed. A "grafting from" method was implemented to directly grow chains of a polymerizable derivative of salicylic acid (2-methacryloyloxy-benzoic acid, 2MBA) onto polypropylene (PP). PP was modified both at bulk and on the surface with poly(2MBA) by means of an oxidative pre-irradiation method ((60)Co source), in order to obtain a grafted polymer in which salicylic acid units were linked by means of labile ester bonds. The grafting percent depended on absorbed dose, reaction time, temperature and monomer concentration. The functionalized films were analyzed regarding structure (FTIR-ATR, SEM-EDX, fluorescence microscopy), temperature stability (TGA), interaction with aqueous medium (water contact angle and swelling), pH-responsive release and cytocompatibility (fibroblasts). In the obtained poly(2MBA)-grafted biomaterial, poly(2MBA) behaved as a polymeric prodrug that regulates salicylic acid release once in contact with aqueous medium, showing pH-dependent release rate.

  8. Synthesis of PP-g-MA as compatibilizer for PP/PLA biocomposites: Thermal, mechanical and biodegradability properties

    NASA Astrophysics Data System (ADS)

    Ghozali, Muhammad; Rohmah, Elfi Nur

    2017-01-01

    A synthesis of polypropylene-graft-maleic anhydride (PP-g-MA) with benzoyl peroxide (BPO) as an initiator has been conducted in a stainless-steel reactor at 120°C for 1 hours. The composition of maleic anhydride (MA) was varied between 10-40 phr, whereas BPO was between 0.5-2.0 phr. The grafting degree (GD) was determined by calculating the MA monomer grafted into polypropylene (PP). Fourier Transform Infrared (FTIR) analysis was performed to study the functional group in the copolymer PP-g-MA. The result shows that the highest GD of 11.85% was obtained when the use of MA and BPO are 40 phr and 1 phr, respectively. PP/PLA biocomposites have been manufactured by adding polypropylene (PP), polylactic acid (PLA) and PP-g-MA as compatibilizer into rheomix at a temperature of 200-210°C with a stirring speed of 25 rpm for 7-10 minutes. PP/PLA biocomposites were varied at a ratio of 0/100, 20/80, 40/60, 60/40, 80/20 and 100/0. Fourier Transform Infrared (FTIR), Ultimate Testing Machine (UTM), Thermogravimetric Analysis (TGA) and biodegradation analysis were performed to determine the functional groups, thermal stability, tensile strength and the biodegradability level of PP/PLA biocomposites, respectively. Thermal and mechanical analysis results indicate that the addition of PLA into PP/PLA biocomposites can reduce the thermal stability and mechanical properties, however the biodegradability is increased.

  9. Biological and biochemical characterization of two new PLA2 isoforms Cdc-9 and Cdc-10 from Crotalus durissus cumanensis snake venom.

    PubMed

    Romero-Vargas, Frey Francisco; Ponce-Soto, Luis Alberto; Martins-de-Souza, Daniel; Marangoni, Sergio

    2010-01-01

    This work reports the purification, biological characterization and amino acid sequence of two new basic PLA(2) isoforms, Cdc-9 and Cdc-10, purified from the Crotalus durissus cumanensis venom by one step analytical chromatography reverse phase HPLC. The molecular masses of the PLA(2) were 14,175+/-2.7 Da for Cdc-9 and 14,228+/-3.5 Da for Cdc-10 both deduced by primary structure and confirmed by MALDI-TOF. The isoforms presented an amino acid sequence of 122 amino acid residues, being Cdc-9: SLVQFNKMIK FETRKSGLPF YAAYGCYCGW GGQRPKDATD RCCFVHDCCY GKVAKCNTKW DIYSYSLKSG YITCGKGTWC KEQICECDRV AAECLRRSLS TYKNEYMFYP DSRCREPPEY TC with pI value of 8.25 and Cdc-10: SLLQFNKMIK FETRKSGVPF YAAYGCYCGW GGRRPKDPTD RCCFVHDCCY GKLTKCNTKW DIYSYSLKSG YITCGKGTWC KEQICECDRV AAECLRRSLN TYKNEYMFYP DSRCRGPPEY TC with a pI value of 8.46, showing highly conserved Ca(2+)-binding and catalytic sites. The PLA(2) activity decreased when the isoforms Cdc-9 and Cdc-10 were incubated with 4-bromophenacyl bromide (p-BPB), anhydrous acetic acid and p-nitrobenzene sulfonyl fluoride (NBSF) when compared with the activity of both native isoforms. In mice, the PLA(2) isoforms Cdc-9 and Cdc-10 induced myonecrosis and edema. Myotoxic and edema activities were reduced after treatment of the isoforms with p-BPB; acetylation of the lysine residues and the treatment of PLA(2) with NBSF have also induced edema reduction. However, p-BPB strongly diminishes the local and systemic myotoxic effects.

  10. 3D-Printed ABS and PLA Scaffolds for Cartilage and Nucleus Pulposus Tissue Regeneration.

    PubMed

    Rosenzweig, Derek H; Carelli, Eric; Steffen, Thomas; Jarzem, Peter; Haglund, Lisbet

    2015-07-03

    Painful degeneration of soft tissues accounts for high socioeconomic costs. Tissue engineering aims to provide biomimetics recapitulating native tissues. Biocompatible thermoplastics for 3D printing can generate high-resolution structures resembling tissue extracellular matrix. Large-pore 3D-printed acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) scaffolds were compared for cell ingrowth, viability, and tissue generation. Primary articular chondrocytes and nucleus pulposus (NP) cells were cultured on ABS and PLA scaffolds for three weeks. Both cell types proliferated well, showed high viability, and produced ample amounts of proteoglycan and collagen type II on both scaffolds. NP generated more matrix than chondrocytes; however, no difference was observed between scaffold types. Mechanical testing revealed sustained scaffold stability. This study demonstrates that chondrocytes and NP cells can proliferate on both ABS and PLA scaffolds printed with a simplistic, inexpensive desktop 3D printer. Moreover, NP cells produced more proteoglycan than chondrocytes, irrespective of thermoplastic type, indicating that cells maintain individual phenotype over the three-week culture period. Future scaffold designs covering larger pore sizes and better mimicking native tissue structure combined with more flexible or resorbable materials may provide implantable constructs with the proper structure, function, and cellularity necessary for potential cartilage and disc tissue repair in vivo.

  11. 3D-Printed ABS and PLA Scaffolds for Cartilage and Nucleus Pulposus Tissue Regeneration

    PubMed Central

    Rosenzweig, Derek H.; Carelli, Eric; Steffen, Thomas; Jarzem, Peter; Haglund, Lisbet

    2015-01-01

    Painful degeneration of soft tissues accounts for high socioeconomic costs. Tissue engineering aims to provide biomimetics recapitulating native tissues. Biocompatible thermoplastics for 3D printing can generate high-resolution structures resembling tissue extracellular matrix. Large-pore 3D-printed acrylonitrile butadiene styrene (ABS) and polylactic acid (PLA) scaffolds were compared for cell ingrowth, viability, and tissue generation. Primary articular chondrocytes and nucleus pulposus (NP) cells were cultured on ABS and PLA scaffolds for three weeks. Both cell types proliferated well, showed high viability, and produced ample amounts of proteoglycan and collagen type II on both scaffolds. NP generated more matrix than chondrocytes; however, no difference was observed between scaffold types. Mechanical testing revealed sustained scaffold stability. This study demonstrates that chondrocytes and NP cells can proliferate on both ABS and PLA scaffolds printed with a simplistic, inexpensive desktop 3D printer. Moreover, NP cells produced more proteoglycan than chondrocytes, irrespective of thermoplastic type, indicating that cells maintain individual phenotype over the three-week culture period. Future scaffold designs covering larger pore sizes and better mimicking native tissue structure combined with more flexible or resorbable materials may provide implantable constructs with the proper structure, function, and cellularity necessary for potential cartilage and disc tissue repair in vivo. PMID:26151846

  12. Mesenchymal stem cells growth and proliferation enhancement using PLA vs PCL based nanofibrous scaffolds.

    PubMed

    Marei, Narguess H; El-Sherbiny, Ibrahim M; Lotfy, Ahmed; El-Badawy, Ahmed; El-Badri, Nagwa

    2016-12-01

    Electrospinning of polymers is the most commonly used technique for nanofiber fabrication. polylactic acid (PLA) and polycaprolactone (PCL) have been shown to be ideal for nanofiber preparation in various biomedical applications, due to characteristics such as biodegradablity and their ability to promote the cell growth, similar to native tissues. The aim of this study was to develop biocompatible and biodegradable PLA and PCL-based nanofibrous scaffolds for enhancing stem cell growth and proliferation. The scaffolds were prepared by electrospinning, and their physicochemical properties were studied using Fourier Transform Infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and X-ray diffraction (XRD). The surface morphology of the developed scaffolds was determined using scanning electron microscopy (SEM). Mesenchymal stem cells (MSCs), derived from both adipose tissue and bone marrow, were seeded onto the prepared nanofibrous scaffolds. The effect of scaffold type, and structural characteristics on survival and proliferation of MSCs were evaluated. Our results show that after full physicochemical characterization of PCL and PLA nanofibrous scaffolds both were safe and non-toxic to the evaluated cells and both scaffolds supported cell attachment and proliferation of bone marrow and adipose tissue-derived MSCs.

  13. Axially aligned 3D nanofibrous grafts of PLA-PCL for small diameter cardiovascular applications.

    PubMed

    Sankaran, Krishna Kumar; Krishnan, Uma Maheswari; Sethuraman, Swaminathan

    2014-01-01

    Axially aligned nanofibrous matrices were evaluated as small diameter cardiovascular grafts. Grafts were prepared using the poly(L-lactic acid) (PLA) and poly(ε-caprolactone) (PCL) physical blends in the ratios of 75:25 and 25:75 with the dimension of (40 × 0.2 × 4) millimeter by electrospinning using dynamic collector (1500 RPM). Hydrophobicity and tensile stress were significantly higher in PLA-PCL (75:25), whereas tensile strain and fiber density were significantly higher in PLA-PCL (25:75). Properties such as anastomatic strength porosity, average pore size, degradation with retained fiber orientation, and thromboresistivity were comparable between blends. Human umbilical vascular endothelial cells (HUVEC) adhesion on the scaffolds was observed within 24 h. Cell viability and proliferation were rationally influenced by the aligned nanofibers. Gene expression reveals the grafts thromboresistivity, elasticity, and aided neovascularization. Thus, these scaffolds could be an ideal candidate for small diameter blood vessel engineering.

  14. Study of the electrospun PLA/silk fibroin-gelatin composite nanofibrous scaffold for tissue engineering.

    PubMed

    Gui-Bo, Yin; You-Zhu, Zhang; Shu-Dong, Wang; De-Bing, Shi; Zhi-Hui, Dong; Wei-Guo, Fu

    2010-04-01

    In this article, a nanofibrous composite scaffold of poly L-lactic acid(PLA)/silk fibroin(SF)-gelatin was fabricated by multilayer electrospinning. To investigate the feasibility of PLA/SF-gelatin use as scaffolds, the porosity and mechanical properties were examined; in particular, the biocompatibilities were evaluated in vivo and in vitro by the means of cell adhesion and cytotoxicity testing, short-term subcutaneous implantation testing, and acute hemolysis testing according to the requirements of ISO 10993. The results showed the scaffold achieved the desirable levels of pliability (elastic up to 7.3% strain) and the appropriate breaking strength (2.22 MPa). The porosity of the SF-gelatin layer was 87% and the pore diameter was 142 nm. After 12 days of cultivation, SEM observation demonstrated the scaffold was nontoxic, biocompatible, and capable of supporting 3T3 mouse fibroblasts attachment, spreading, and growth. The hemolysis test proved the scaffolds with hemolytic rates from 3.1 to 4.5%. The subcutaneous implantation test indicated minor inflammatory reactions surrounding the scaffolds and biodegradation were initially observed in about 3 months. The desired porous structure, strong and pliable properties, combined with the ability of PLA/SF-gelatin scaffold to support cell growth in vitro, especially excellent biocompatibility in vivo, suggested potential application for tissue engineering scaffolds.

  15. Anodic luminescence, structural, photoluminescent, and photocatalytic properties of anodic oxide films grown on niobium in phosphoric acid

    NASA Astrophysics Data System (ADS)

    Stojadinović, Stevan; Tadić, Nenad; Radić, Nenad; Stefanov, Plamen; Grbić, Boško; Vasilić, Rastko

    2015-11-01

    This article reports on properties of oxide films obtained by anodization of niobium in phosphoric acid before and after the dielectric breakdown. Weak anodic luminescence of barrier oxide films formed during the anodization of niobium is correlated to the existence of morphological defects in the oxide layer. Small sized sparks generated by dielectric breakdown of formed oxide film cause rapid increase of luminescence intensity. The luminescence spectrum of obtained films on niobium under spark discharging is composed of continuum radiation and spectral lines caused by electronic spark discharging transitions in oxygen and hydrogen atoms. Oxide films formed before the breakdown are amorphous, while after the breakdown oxide films are partly crystalline and mainly composed of Nb2O5 hexagonal phase. The photocatalytic activity of obtained oxide films after the breakdown was investigated by monitoring the degradation of methyl orange. Increase of the photocatalytic activity with time is related to an increase of oxygen vacancy defects in oxide films formed during the process. Also, higher concentration of oxygen vacancy defects in oxide films results in higher photoluminescence intensity.

  16. Natamycin based sol-gel antimicrobial coatings on polylactic acid films for food packaging.

    PubMed

    Lantano, Claudia; Alfieri, Ilaria; Cavazza, Antonella; Corradini, Claudio; Lorenzi, Andrea; Zucchetto, Nicola; Montenero, Angelo

    2014-12-15

    In this work a comprehensive study on a new active packaging obtained by a hybrid organic-inorganic coating with antimicrobial properties was carried out. The packaging system based on polylactic acid was realised by sol-gel processing, employing tetraethoxysilane as a precursor of the inorganic phase and polyvinyl alcohol as the organic component, and incorporating natamycin as the active agent. Films with different organic-inorganic ratios (in a range between 1:19 and 1:4) were prepared, and the amount of antimycotic entrapped was found to be modulated by the sol composition, and was between 0.18 and 0.25mg/dm(2). FTIR microspectroscopic measurements were used to characterise the prepared coatings. The antifungal properties of the films were investigated against mould growth on the surface of commercial semi-soft cheese. The release of natamycin from the films to ethanol 50% (v/v) was studied by means of HPLC UV-DAD. The maximal level released was about 0.105 mg/dm(2), which is far below the value allowed by legislation.

  17. The procoagulant properties of hyaluronic acid-collagen (I)/chitosan complex film.

    PubMed

    Hu, Yi; Wu, Yangzhe; Cai, Jiye; Ma, Shuyuan; Wang, Xiaoping

    2009-01-01

    Biomaterial-induced human platelet activation remains one of the most crucial factors to determine the procoagulant properties of the biomaterial. In this experiment, a new type of biomacromolecule complex film (hyaluronic acid-collagen (I)/chitosan, HCC) was prepared using the electrostatic self-assembly method. Then the procoagulant properties of this complex film were characterized. Based on the nano-resolution of atomic force microscopy, the platelet-derived microparticles (PMPs) that present the activation of platelets were clearly visualized on the membrane surface of platelets for the first time, and the measurement indicated that the size of PMPs is around 50-110 nm. Furthermore, the results of AFM measurement were confirmed by flow cytometry analysis. The expression of CD62P (P-selectin) dramatically increased after the platelet-rich plasma interacted with the biomaterial solution. From the results, we could draw the conclusion that this biomacromolecule complex film has promising procoagulant properties, and has the potential to be practically used as procoagulant material.

  18. Data of thermal degradation and dynamic mechanical properties of starch–glycerol based films with citric acid as crosslinking agent

    PubMed Central

    González Seligra, Paula; Medina Jaramillo, Carolina; Famá, Lucía; Goyanes, Silvia

    2016-01-01

    Interest in biodegradable edible films as packaging or coating has increased because their beneficial effects on foods. In particular, food products are highly dependents on thermal stability, integrity and transition process temperatures of the packaging. The present work describes a complete data of the thermal degradation and dynamic mechanical properties of starch–glycerol based films with citric acid (CA) as crosslinking agent described in the article titled: “Biodegradable and non-retrogradable eco-films based on starch–glycerol with citric acid as crosslinking agent” González Seligra et al. (2016) [1]. Data describes thermogravimetric and dynamical mechanical experiences and provides the figures of weight loss and loss tangent of the films as a function of the temperature. PMID:27158645

  19. Data of thermal degradation and dynamic mechanical properties of starch-glycerol based films with citric acid as crosslinking agent.

    PubMed

    González Seligra, Paula; Medina Jaramillo, Carolina; Famá, Lucía; Goyanes, Silvia

    2016-06-01

    Interest in biodegradable edible films as packaging or coating has increased because their beneficial effects on foods. In particular, food products are highly dependents on thermal stability, integrity and transition process temperatures of the packaging. The present work describes a complete data of the thermal degradation and dynamic mechanical properties of starch-glycerol based films with citric acid (CA) as crosslinking agent described in the article titled: "Biodegradable and non-retrogradable eco-films based on starch-glycerol with citric acid as crosslinking agent" González Seligra et al. (2016) [1]. Data describes thermogravimetric and dynamical mechanical experiences and provides the figures of weight loss and loss tangent of the films as a function of the temperature.

  20. Blending Novatein¯ thermoplastic protein with PLA for carbon dioxide assisted batch foaming

    NASA Astrophysics Data System (ADS)

    Walallavita, Anuradha; Verbeek, Casparus J. R.; Lay, Mark

    2016-03-01

    The convenience of polymeric foams has led to their widespread utilisation in everyday life. However, disposal of synthetic petroleum-derived foams has had a detrimental effect on the environment which needs to be addressed. This study uses a clean and sustainable approach to investigate the foaming capability of a blend of two biodegradable polymers, polylactic acid (PLA) and Novatein® Thermoplastic Protein (NTP). PLA, derived from corn starch, can successfully be foamed using a batch technique developed by the Biopolymer Network Ltd. NTP is a patented formulation of bloodmeal and chemical additives which can be extruded and injection moulded similar to other thermoplastics. However, foaming NTP is a new area of study and its interaction with blowing agents in the batch process is entirely unknown. Subcritical and supercritical carbon dioxide have been examined individually in two uniquely designed pressure vessels to foam various compositions of NTP-PLA blends. Foamed material were characterised in terms of expansion ratio, cell size, and cellular morphology in order to study how the composition of NTP-PLA affects foaming with carbon dioxide. It was found that blends with 5 wt. % NTP foamed using subcritical CO2 expanded up to 11 times due to heterogeneous nucleation. Morphology analysis using scanning electron microscopy showed that foams blown with supercritical CO2 had a finer cell structure with consistent cell size, whereas, foams blown with subcritical CO2 ranged in cell size and showed cell wall rupture. Ultimately, this research would contribute to the production of a biodegradable foam material to be used in packaging applications, thereby adding to the application potential of NTP.

  1. Participation of PLA2 and PLC in DhL-induced activation of Rhinella arenarum oocytes.

    PubMed

    Zapata-Martínez, J; Medina, M F; Gramajo-Bühler, M C; Sánchez-Toranzo, G

    2016-08-01

    Rhinella arenarum oocytes can be artificially activated, a process known as parthenogenesis, by a sesquiterpenic lactone of the guaianolide group, dehydroleucodine (DhL). Transient increases in the concentration of cytosolic Ca2+ are essential to trigger egg activation events. In this sense, the 1-4-5 inositol triphosphate receptors (IP3R) seem to be involved in the Ca2+ transient release induced by DhL in this species. We analyzed the involvement of phosphoinositide metabolism, especially the participation of phospholipase A2 (PLA2) and phospholipase C (PLC) in DhL-induced activation. Different doses of quinacrine, aristolochic acid (ATA) (PLA2 inhibitors) or neomycin, an antibiotic that binds to PIP2, thus preventing its hydrolysis, were used in mature Rhinella arenarum oocytes. In order to assay the participation of PI-PLC and PC- PLC we used U73122, a competitive inhibitor of PI-PLC dependent events and D609, an inhibitor of PC-PLC. We found that PLA2 inhibits quinacrine more effectively than ATA. This difference could be explained by the fact that quinacrine is not a specific inhibitor for PLA2 while ATA is specific for this enzyme. With respect to the participation of PLC, a higher decrease in oocyte activation was detected when cells were exposed to neomycin. Inhibition of PC-PLC with D609 and IP-PLC with U73122 indicated that the last PLC has a significant participation in the effect of DhL-induced activation. Results would indicate that DhL induces activation of in vitro matured oocytes of Rhinella arenarum by activation of IP-PLC, which in turn may induce IP3 formation which produces Ca2+ release.

  2. Electrospun PLA: PCL composites embedded with unmodified and 3-aminopropyltriethoxysilane (ASP) modified halloysite nanotubes (HNT)

    NASA Astrophysics Data System (ADS)

    Haroosh, Hazim J.; Dong, Yu; Chaudhary, Deeptangshu S.; Ingram, Gordon D.; Yusa, Shin-ichi

    2013-02-01

    Electrospinning is a simple and versatile fiber synthesis technique in which a high-voltage electric field is applied to a stream of polymer melt or polymer solution, resulting in the formation of continuous micro/nanofibers. Halloysite nanotubes (HNT) have been found to achieve improved structural and mechanical properties when embedded into various polymer matrices. This research work focuses on blending poly( ɛ-caprolactone) (PCL) (9 and 15 wt%/v) and poly(lactic acid) (PLA) (fixed at 8 wt%/v) solutions with HNT at two different concentrations 1 and 2 wt%/v. Both unmodified HNT and HNT modified with 3-aminopropyltriethoxysilane (ASP) were utilized in this study. Fiber properties have been shown to be strongly related to the solution viscosity and electrical conductivity. The addition of HNT increased the solution viscosity, thus resulting in the production of uniform fibers. For both PCL concentrations, the average fiber diameter increased with the increasing of HNT concentration. The average fiber diameters with HNT-ASP were reduced considerably in comparison to those with unmodified HNT when using 15 wt%/v PCL. Slightly better dispersion was obtained for PLA: PCL composites embedded with HNT-ASP compared to unmodified HNT. Furthermore, the addition of HNT-ASP to the polymeric blends resulted in a moderate decrease in the degree of crystallinity, as well as slight reductions of glass transition temperature of PCL, the crystallization temperature and melting temperature of PLA within composite materials. The infrared spectra of composites confirmed the successful embedding of HNT-ASP into PLA: PCL nanofibers relative to unmodified HNT due to the premodification using ASP to reduce the agglomeration behavior. This study provides a new material system that could be potentially used in drug delivery, and may facilitate good control of the drug release process.

  3. Prognostic value of PLA2R autoimmunity detected by measurement of anti-PLA2R antibodies combined with detection of PLA2R antigen in membranous nephropathy: A single-centre study over 14 years

    PubMed Central

    Mihout, Fabrice; Cachanado, Marine; Brocheriou, Isabelle

    2017-01-01

    Introduction Clinical course of membranous nephropathy (MN) is difficult to predict. Measurement of circulating anti-PLA2R autoantibodies (PLA2R-Ab) and detection in immune deposits of PLA2R antigen (PLA2R-Ag) are major advances in disease understanding. We evaluated the clinical significance of these biomarkers. Methods In this 14-year retrospective study, we collected data from 108 MN patients and assessed the relationship between clinical course, PLA2R-Ab and PLA2R-Ag. We also assessed THSD7A status. Results Eighty-five patients suffered from primary MN (PMN) and 23 patients from a secondary form. The median follow-up was 30.4 months [interquartile range, 17.7;56.7]. Among the 77 patients with PMN and available serum and/or biopsy, 69 (89.6%) had PLA2R-related disease as shown by anti-PLA2R-Ab and/or PLA2R-Ag, while 8 patients (8/77, 10.4%) were negative for both. There was no significant difference between these two groups in age at diagnosis and outcome assessed by proteinuria, serum albumin level and eGFR. Two of the 8 negative patients were positive for THSD7A. In patients with PLA2R related PMN, younger age, lower proteinuria, higher eGFR, and lower PLA2R-Ab level at baseline and after 6 months were associated with remission of proteinuria. Initial PLA2R-Ab titer ≤ 97.6 RU/mL and complete depletion of PLA2R-Ab within 6-months were significantly associated with spontaneous remission at the end of follow-up. In rituximab treated patients, lower PLA2R-Ab titer at initiation of treatment, and absence of PLA2R-Ab and higher serum albumin level at 3 months were significantly associated with remission. Noticeably, 81.8% of the patients who achieved remission completely cleared PLA2R-Ab. Depletion of PLA2R-Ab and increase of serum albumin level preceded the decrease of proteinuria. Conclusion Assessment of PLA2R autoimmunity is essential for patient management. Combination of PLA2R-Ab and PLA2R-Ag increases diagnosis sensitivity. PLA2R-Ab titer is a biomarker of

  4. Adsorption and photocatalytic and photosensitised bleaching of acid orange 7 on multilayer mesoporous films of TiO2.

    PubMed

    Mills, Andrew; O'Rourke, Christopher; Kalousek, Vit; Rathousky, Jiri

    2012-04-15

    A series of mesoporous films of titania of different thicknesses are prepared and their surface areas and porosities determined by physical adsorption using Kr as the adsorbate. The amounts of acid orange 7 (AO7) adsorbed by these films are found to be proportional to their measured surface areas and so the possibility of using this as a method of determining the surface area of thin titania films is discussed. The initial rates of UV-driven photocatalytic- and visible-driven photosensitised-bleaching of AO7 in solution, upon UVA and visible light irradiation, respectively, are also directly dependent upon the measured surface areas of the titania films. The quantum efficiencies for the UV photocatalytic- and visible photosensitised-bleaching of AO7 by the thickest of the AO7 films were estimated to be 0.08 and 0.01%, respectively.

  5. Controllably local gene delivery mediated by polyelectrolyte multilayer films assembled from gene-loaded nanopolymersomes and hyaluronic acid

    PubMed Central

    Teng, Wei; Wang, Qinmei; Chen, Ying; Huang, Hongzhang

    2014-01-01

    To explore a spatiotemporally controllable gene delivery system with high efficiency and safety, polyelectrolyte multilayer (PEM) films were constructed on titanium or quartz substrates via layer-by-layer self-assembly technique by using plasmid deoxyribonucleic acid-loaded lipopolysaccharide–amine nanopolymersomes (pNPs) as polycations and hyaluronic acid (HA) as polyanions. pNPs were chosen because they have high transfection efficiency (>95%) in mesenchymal stem cells (MSCs) and induce significant angiogenesis in zebrafish in conventional bolus transfection. The assembly process of PEM films was confirmed by analyses of quartz crystal microbalance with dissipation, X-ray photoelectron spectroscopy, infrared, contact angle, and zeta potential along with atomic force microscopy observation. Quartz crystal microbalance with dissipation analysis reveals that this film grows in an exponential mode, pNPs are the main contributor to the film mass, and the film mass can be modulated in a relatively wide range (1.0–29 μg/cm2) by adjusting the deposition layer number. Atomic force microscopy observation shows that the assembly leads to the formation of a patterned film with three-dimensional tree-like nanostructure, where the branches are composed of beaded chains (pNP beads are strung on HA molecular chains), and the incorporated pNPs keep structure intact. In vitro release experiment shows that plasmid deoxyribonucleic acid can be gradually released from films over 14 days, and the released plasmid deoxyribonucleic acid exists in a complex form. In vitro cell experiments demonstrate that PEM films can enhance the adhesion and proliferation of MSCs and efficiently transfect MSCs in situ in vitro for at least 4 days. Our results suggest that a (pNPs/HA)n system can mediate efficient transfection in stem cells in a spatially and temporally controllable pattern, highlighting its huge potential in local gene therapy. PMID:25378927

  6. Potential of a PLA-PEO-PLA-based scaffold for skin tissue engineering: in vitro evaluation.

    PubMed

    Garric, Xavier; Guillaume, Olivier; Dabboue, Hinda; Vert, Michel; Molès, Jean-Pierre

    2012-01-01

    This study aimed to investigate the in vitro behaviour of porous degradable scaffolds of the PLA-PEO-PLA-type designed prior to in vivo evaluation for skin tissue engineering. Two tri-block co-polymers were synthesized from PEO and DL-lactide and their degradation was studied under conditions that mimic a cutaneous wound environment. 3-D porous scaffolds with interconnected pores were fabricated using the salt leaching method and characterized by ESEM and Hg porosimetry. The degrading action of gamma sterilization was studied on the co-polymers. The less degraded one was selected to make porous scaffolds on which human dermal fibroblasts and human epidermal keratinocytes were cultured. The capacity of such scaffolds to act as a dermal equivalent was also considered. Colonization by human dermal fibroblasts was shown after hematoxylin staining and the production of major proteins normally found in the extracellular matrix was assessed by Western blotting of protein extracts. Finally, a skin substitute was generated by seeding human keratinocytes on the dermal equivalent and a new epidermis was characterized by using immuno-histological staining. Results show that gamma sterilization and that degradation under conditions that mimic skin wound healing were acceptable. The fact that fibroblasts produce extracellular matrix and that keratinocytes generated an epidermal barrier argues in favour of the interest of this type of porous scaffold for skin reconstruction.

  7. Controlled release of tyrosol and ferulic acid encapsulated in chitosan-gelatin films after electron beam irradiation

    NASA Astrophysics Data System (ADS)

    Benbettaïeb, Nasreddine; Assifaoui, Ali; Karbowiak, Thomas; Debeaufort, Frédéric; Chambin, Odile

    2016-01-01

    This work deals with the study of the release kinetics of antioxidants (ferulic acid and tyrosol) incorporated into chitosan-gelatin edible films after irradiation processes. The aim was to determine the influence of electron beam irradiation (at 60 kGy) on the retention of antioxidants in the film, their release in water (pH=7) at 25 °C, in relation with the barrier and mechanical properties of biopolymer films. The film preparation process coupled to the irradiation induced a loss of about 20% of tyrosol but did not affect the ferulic acid content. However, 27% of the ferulic acid remained entrapped in the biopolymer network during the release experiments whereas all tyrosol was released. Irradiation induced a reduction of the release rate for both compounds, revealing that cross-linking occurred during irradiation. This was confirmed by the mechanical properties enhancement which tensile strength value significantly increased and by the reduction of permeabilities. Although molecular weights, molar volume and molecular radius of the two compounds are very similar, the effective diffusivity of tyrosol was 40 times greater than that of ferulic acid. The much lower effective diffusion coefficient of ferulic acid as determined from the release kinetics was explained by the interactions settled between ferulic acid molecules and the gelatin-chitosan matrix. As expected, the electron beam irradiation allowed modulating the retention and then the release of antioxidants encapsulated.

  8. Development of biodegradable metaloxide/polymer nanocomposite films based on poly-ε-caprolactone and terephthalic acid.

    PubMed

    Varaprasad, Kokkarachedu; Pariguana, Manuel; Raghavendra, Gownolla Malegowd; Jayaramudu, Tippabattini; Sadiku, Emmanuel Rotimi

    2017-01-01

    The present investigation describes the development of metal-oxide polymer nanocomposite films from biodegradable poly-ε-caprolactone, disposed poly(ethylene terephthalate) oil bottles monomer and zinc oxide-copper oxide nanoparticles. The terephthalic acid and zinc oxide-copper oxide nanoparticles were synthesized by using a temperature-dependent precipitation technique and double precipitation method, respectively. The terephthalic acid synthesized was confirmed by FTIR analysis and furthermore, it was characterized by thermal analysis. The as-prepared CuO-ZnO nanoparticles structure was confirmed by XRD analysis and its morphology was analyzed by SEM/EDS and TEM. Furthermore, the metal-oxide polymer nanocomposite films have excellent mechanical properties, with tensile strength and modulus better than pure films. The metal-oxide polymer nanocomposite films that were successfully developed show a relatively brighter colour when compared to CuO film. These new metal-oxide polymer nanocomposite films can replace many non-degradable plastics. The new metal-oxide polymer nanocomposite films developed are envisaged to be suitable for use in industrial and domestic packaging applications.

  9. Effect of β-glucan-fatty acid esters on microstructure and physical properties of wheat straw arabinoxylan films.

    PubMed

    Ali, Usman; Bijalwan, Vandana; Basu, Santanu; Kesarwani, Atul Kumar; Mazumder, Koushik

    2017-04-01

    Arabinoxylans (AX) was isolated from wheat straw, whereas β-glucan (BG) was extracted from oat flour. The compositional analysis indicated wheat straw AX contained arabinose and xylose as major constituent sugars whereas higher β-glucan content (77%) was found in the extracted material from oat flour. The BG was conjugated with lauric (LA), myristic (MA), palmitic (PA), stearic (SA) and oleic (OA) acid to prepare corresponding β-glucan-fatty acid esters (BGFAs) with nearly similar degree of substitution. The effect of BGFAs to AX films on the water barrier, optical and mechanical properties were investigated. The addition of LABG and MABG to AX formed laminar structures in the composite films which limited water vapor permeability, giving rise to more opacity. Films prepared by blending AX with SABG and OABG were less effective as water vapor barrier due to their non-layer film microstructures; however they were less opaque. The laminar structures also imparted less mechanical strength and flexibility in the composite films. Furthermore, thermogravimetric analysis (TGA) revealed that all AX-BGFAs composite films were thermally more stable than pure AX and AX-BG films.

  10. Fabrication and characterization of Sb-doped Sn02 thin films derived from methacrylic acid modified tin(IV)alkoxides

    NASA Astrophysics Data System (ADS)

    Kololuoma, Terho K.; Tolonen, Ari; Johansson, Leena-Sisko; Campbell, Joseph M.; Karkkainen, Ari H. O.; Hiltunen, Marianne; Haatainen, Tomi; Rantala, Juha T.

    2002-10-01

    We report on the fabrication of transparent, conductive and directly photopatternable, pure and Sb-doped tin dioxide thin films. Precursors used were antimony(III)isopropoxide and a photo-reactive tin alkoxide synthesized from tin(IV)isopropoxide and methacrylic acid. The synthesis of methacrylic acid modified tin alkoxide was monitored in-situ using IR- and ESI-TOF mass spectroscopic techniques. Sb-doped organo-tin films were deposited via single layer spin coating. After deposition the films were patterned via photopolymerization, using a mercury I-line UV-lamp. All investigated materials could be patterned with 3 μm features. After development in isopropanol, the films were annealed in air, in order to obtain crystalline and conductive films. The electrical conductivities of the annealed thin films with, and without, UV-irradiation were determined using a linear four-point method. The direct photopatterning process was found to increase the film conductivity for all the Sb-doping levels tested. The mechanisms for the increased conductivity were characterized using AFM, XPS and XRD techniques.

  11. Uptake measurements of acetic acid on ice and nitric acid-doped thin ice films over upper troposphere/lower stratosphere temperatures.

    PubMed

    Romanias, Manolis N; Zogka, Antonia G; Papadimitriou, Vassileios C; Papagiannakopoulos, Panos

    2012-03-08

    The adsorption of gaseous acetic acid (CH(3)C(O)OH) on thin ice films and on ice doped with nitric acid (1.96 and 7.69 wt %) was investigated over upper troposphere and lower stratosphere (UT/LS) temperatures (198-208 K), and at low gas concentrations. Experiments were performed in a Knudsen flow reactor coupled to a quadrupole mass spectrometer. The initial uptake coefficients, γ(0), on thin ice films or HNO(3)-doped ice films were measured at low surface coverage. In all cases, γ(0) showed an inverse temperature dependence, and for pure thin ice films, it was given by the expression γ(0)(T) = (4.73 ± 1.13) × 10(-17) exp[(6496 ± 1798)/T]; the quoted errors are the 2σ precision of the linear fit, and the estimated systematic uncertainties are included in the pre-exponential factor. The inverse temperature dependence suggests that the adsorption process occurs via the formation of an intermediate precursor state. Uptakes were well represented by the Langmuir adsorption model, and the saturation surface coverage, N(max), on pure thin ice films was (2.11 ± 0.16) × 10(14) molecules cm(-2), independent of temperature in the range 198-206 K. Light nitration (1.96 and 7.69 wt %) of ice films resulted in more efficient CH(3)C(O)OH uptakes and larger N(max) values that may be attributed to in-bulk diffusion or change in nature of the gas-ice surface interaction. Finally, it was estimated that the rate of adsorption of acetic acid on high-density cirrus clouds in the UT/LS is fast, and this is reflected in the short atmospheric lifetimes (2-8 min) of acetic acid; however, the extent of this uptake is minor resulting in at most a 5% removal of acetic acid in UT/LS cirrus clouds.

  12. Humidity-dependent compression-induced glass transition of the air-water interfacial Langmuir films of poly(D,L-lactic acid-ran-glycolic acid) (PLGA).

    PubMed

    Kim, Hyun Chang; Lee, Hoyoung; Jung, Hyunjung; Choi, Yun Hwa; Meron, Mati; Lin, Binhua; Bang, Joona; Won, You-Yeon

    2015-07-28

    Constant rate compression isotherms of the air-water interfacial Langmuir films of poly(D,L-lactic acid-ran-glycolic acid) (PLGA) show a distinct feature of an exponential increase in surface pressure in the high surface polymer concentration regime. We have previously demonstrated that this abrupt increase in surface pressure is linked to the glass transition of the polymer film, but the detailed mechanism of this process is not fully understood. In order to obtain a molecular-level understanding of this behavior, we performed extensive characterizations of the surface mechanical, structural and rheological properties of Langmuir PLGA films at the air-water interface, using combined experimental techniques including the Langmuir film balance, X-ray reflectivity and double-wall-ring interfacial rheometry methods. We observed that the mechanical and structural responses of the Langmuir PLGA films are significantly dependent on the rate of film compression; the glass transition was induced in the PLGA film only at fast compression rates. Surprisingly, we found that this deformation rate dependence is also dependent on the humidity of the environment. With water acting as a plasticizer for the PLGA material, the diffusion of water molecules through the PLGA film seems to be the key factor in the determination of the glass transformation properties and thus the mechanical response of the PLGA film against lateral compression. Based on our combined results, we hypothesize the following mechanism for the compression-induced glass transformation of the Langmuir PLGA film; (1) initially, a humidified/non-glassy PLGA film is formed in the full surface-coverage region (where the surface pressure shows a plateau) during compression; (2) further compression leads to the collapse of the PLGA chains and the formation of new surfaces on the air side of the film, and this newly formed top layer of the PLGA film is transiently glassy in character because the water evaporation rate

  13. Methanogenesis from volatile fatty acids in downflow stationary fixed-film reactor.

    PubMed

    Bhadra, A; Scharer, J M; Moo-Young, M

    1987-08-05

    Methanogenesis was studied in downflow stationary fixed-film bioreactors. The support materials in this study included ceramic Raschig rings, hardwood chips, and sized charcoal. The performances of these support materials have been compared using both synthetic acid mixture and acid products obtained from paper mill sludge. Woodchips appeared to be the most promising support material: The maximum methane productivity of 3.56 L/L day at a nominal retention time of 0.78 day was obtained using initial total acid concentrations of 9.125 g/L. Higher productivity was achieved at the cost of efficiency of the process in terms of conversion of acids. From nitrogen balances, it was deduced that ammonia supplemented methane generation by supplying hydrogen for there duction of carbon dioxide.An ionic balance was developed to ascertain the relationship between the composition and the pH of the liquid and the mole fraction of carbon dioxide in the gas phase. From these ionic balance equations, it was possible to predict the gas phase composition at various retention times. The maximum error between the computed and the experimental values was less than 13%.

  14. Influence of Glacial Acetic Acid and Nitric Acid as a Chelating Agent in Sol-gel Process to the Nanostructured Titanium Dioxide Thin Films

    NASA Astrophysics Data System (ADS)

    Ahmad, M. K.; Rusop, M.

    2009-06-01

    The comparison between different chelating agents in sol-gel process for deposition of nanostructured Titanium Dioxide (TiO2) thin film has been studied. Glacial Acetic Acid (GA) and Nitric Acid (NA) were used in 0.2 M of concentration. The effects to the structural, electrical and optical properties have been studied. The effects of these properties were characterized using X-Ray Diffractometer (XRD), 2-point probe I-V measurement and UV-Vis-NIR Spectrophotometer. For electrical properties, it showed that nanostructured TiO2 thin film that using GA (TF-GA) as chelating agent gives better low sheet resistance compare to nanostructured TiO2 thin film using NA (TF-NA). From XRD results, it indicates that no significantly different between both TiO2 thin film. Both of thin films have crystalline anatase phase at 2θ degree 25.8° which corresponded to (101) orientation. For optical properties, sol-gel using GA has slightly higher in transmittance spectra properties but both of films fully absorbed UV light at 300 nm of wavelength. As for optical band gap, both sol-gels using GA and NA has similar optical band gap which is 3.27 eV.

  15. Evaluation of self-assembled HCPT-loaded PEG- b-PLA nanoparticles by comparing with HCPT-loaded PLA nanoparticles

    NASA Astrophysics Data System (ADS)

    Yang, Xiangrui; Wu, Shichao; Wang, Yange; Li, Yang; Chang, Di; Luo, Yin; Ye, Shefang; Hou, Zhenqing

    2014-12-01

    We present a dialysis technique to prepare the 10-hydroxycamptothecin (HCPT)-loaded nanoparticles (NPs) using methoxypolyethylene glycol-poly( d, l-lactide) (PEG- b-PLA) and PLA, respectively. Both HCPT-loaded PEG- b-PLA NPs and HCPT-loaded PLA NPs were characterized by differential scanning calorimetry (DSC), dynamic light scattering (DLS), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). The results showed that the HCPT-loaded PEG- b-PLA NPs and HCPT-loaded PLA NPs presented a hydrodynamic particle size of 120.1 and 226.8 nm, with a polydispersity index of 0.057 and 0.207, a zeta potential of -31.2 and -45.7 mV, drug encapsulation efficiency of 44.52% and 44.94%, and drug-loaded content of 7.42% and 7.49%, respectively. The HCPT-loaded PEG- b-PLA NPs presented faster drug release rate compared to the HCPT-loaded PLA NPs. The HCPT-loaded PEG- b-PLA NPs presented higher cytotoxicity than the HCPT-loaded PLA NPs. These results suggested that the HCPT-loaded PEG- b-PLA NPs presented better characteristics for drug delivery compared to HCPT-loaded PLA NPs.

  16. Effectiveness of a polyamide film releasing lactic acid on the growth of E. coli O157:H7, Enterobacteriaceae and Total Aerobic Count on vacuum-packed beef.

    PubMed

    Smulders, F J M; Paulsen, P; Vali, S; Wanda, S

    2013-10-01

    The suitability of a polyamide 6 monolayer film containing lactic acid for use as an antimicrobial package for fresh beef cuts was studied. The release of lactic acid in an aqueous environment was immediate (within 1h) and was from approx. 55 μg lactic acid/cm(2) film at 0-8°C to approx. 67 μg lactic acid/cm(2) film at 12-20°C. Beef was contaminated with an Escherichia coli O157:H7 isolate with known minimum inhibitory concentration against lactic acid (0.09% v/v), then wrapped with the lactic-acid polyamide film and vacuum packaged. During storage at 12°C, the numbers of E. coli were 1 log unit lower than that of a control (untreated polyamide film) and decreased by an additional 1 log during storage for 14 days.

  17. Poly(Lactic Acid) Hemodialysis Membranes with Poly(Lactic Acid)-block-Poly(2-Hydroxyethyl Methacrylate) Copolymer As Additive: Preparation, Characterization, and Performance.

    PubMed

    Zhu, Lijing; Liu, Fu; Yu, Xuemin; Xue, Lixin

    2015-08-19

    Poly(lactic acid) (PLA) hemodialysis membranes with enhanced antifouling capability and hemocompatibility were developed using poly(lactic acid)-block-poly(2-hydroxyethyl methacrylate) (PLA-PHEMA) copolymers as the blending additive. PLA-PHEMA block copolymers were synthesized via reversible addition-fragmentation (RAFT) polymerization from aminolyzed PLA. Gel permeation chromatography (GPC) and (1)H-nuclear magnetic resonance ((1)H NMR) were applied to characterize the synthesized products. By blending PLA with the amphiphilic block copolymer, PLA/PLA-PHEMA membranes were prepared by nonsolvent induced phase separation (NIPS) method. Their chemistry and structure were characterized with X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and atomic force microscopy (AFM). The results revealed that PLA/PLA-PHEMA membranes with high PLA-PHEMA contents exhibited enhanced hydrophilicity, water permeability, antifouling and hemocompatibility. Especially, when the PLA-PHEMA concentration was 15 wt %, the water flux of the modified membrane was about 236 L m(-2) h(-1). Its urea and creatinine clearance was more than 0.70 mL/min, lysozyme clearance was about 0.50 mL/min, BSA clearance was as less as 0.31 mL/min. All the results suggest that PLA-PHEMA copolymers had served as effective agents for optimizing the property of PLA-based membrane for hemodialysis applications.

  18. An optical sensor based on H-acid/layered double hydroxide composite film for the selective detection of mercury ion.

    PubMed

    Sun, Zhiyong; Jin, Lan; Zhang, Shitong; Shi, Wenying; Pu, Min; Wei, Min; Evans, David G; Duan, Xue

    2011-09-19

    A novel optical chemosensor was fabricated based on 1-amino-8-naphthol-3,6-disulfonic acid sodium (H-acid) intercalated layered double hydroxide (LDH) film via the electrophoretic deposition (EPD) method. The film of H-acid/LDH with the thickness of 1 μm possesses a well c-orientation of the LDH microcrystals confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The fluorescence detection for Hg(II) in aqueous solution was performed by using the H-acid/LDH film sensor at pH 7.0, with a linear response range in 1.0 × 10(-7) to 1.0 × 10(-5) mol L(-1) and a detection limit of 6.3 × 10(-8) mol L(-1). Furthermore, it exhibits excellent selectivity for Hg(II) over a large number of competitive cations including alkali, alkaline earth, heavy metal and transitional metals. The specific fluorescence response of the optical sensor is attributed to the coordination between Hg(II) and sulfonic group in the H-acid immobilized in the LDH matrix, which was verified by NMR spectroscopy and UV-vis spectra. In addition, density functional theory (DFT) calculation further confirms that the coordination occurs between one Hg(2+) and two O atoms in the sulfonic group, which is responsible for the significant fluorescence quenching of the H-acid/LDH film. The results indicate that the H-acid/LDH composite film can be potentially used as a chemosensor for the detection of Hg(2+) in the environmental and biomedical field.

  19. Anti-Phospholipase A2 Receptor (PLA2R) Antibody and Glomerular PLA2R Expression in Japanese Patients with Membranous Nephropathy

    PubMed Central

    Tachibana, Shohei; Iseri, Ken; Saito, Tomohiro; Yamamoto, Yasutaka; Suzuki, Taihei; Wada, Yukihiro; Matsumoto, Kei; Shibata, Takanori

    2016-01-01

    The phospholipase A2 receptor (PLA2R) is the major target antigen (Ag) in idiopathic membranous nephropathy (IMN). Recently, several types of immunoassay systems for anti-PLA2R antibody (Ab) have been developed. However, the correlation of serum anti-PLA2R Abs and glomerular expression of PLA2R Ag, and their association with clinicopathological characteristics have yet to be proven in Japanese patients. We examined serum anti-PLA2R Abs by both ELISA and cell-based indirect immunofluorescence assay (CIIFA), and glomerular PLA2R expression by immunofluorescence (IF) in 59 biopsy-proven MN patients including IMN (n = 38) and secondary MN (SMN) (n = 21). In this study, anti-PLA2R Abs were present in 50% of IMN patients, but was absent in SMN patients. The concordance rate between ELISA and CIIFA was 100%. Serum IgG levels were significantly lower in anti-PLA2R Ab-positive patients. Serum albumin levels correlated inversely with serum anti-PLA2R Ab titers. The prevalence and intensity of glomerular staining for IgG4 by IF were significantly higher in anti-PLA2R Ab-positive patients than in -negative patients. Glomerular PLA2 Ag expression evaluated by IF was positive in 52.6% of IMN patients, but was absent in SMN patients. The concordance rate between the prevalence of glomerular PLA2R Ag expression and anti-PLA2R Ab was 84.2%. The prevalence of anti-PLA2R Abs measured by ELISA/CIIFA was equivalent to previous Japanese studies evaluated using Western blotting. These analyses showed an excellent specificity for the diagnosis of IMN, and anti-PLA2R positivity was associated with some clinicopathological features, especially glomerular IgG4-dominant deposition. PMID:27355365

  20. An investigation of crystallization and rheological behaviors of PLA/HDPE/Nano-CaCO3 composites by experimental design

    NASA Astrophysics Data System (ADS)

    de Oliveira, Amanda G.; Teixeira, Viviane G.; da Silva, Ana Lúcia N.; de Sousa, Ana Maria F.

    2015-05-01

    Nowadays, the development of products from renewable raw material has been an important subject of interest for a great number of researchers. Poly(lactic acid) is versatile polymer, synthesized from renewable resources, biodegradable and biocompatible and that has been considered as stronger candidate to replace fossil-based polymers in many application. However, the PLA still has some shortcomings to be solved, such as low thermal resistance, rate crystallization, impact resistance and gas barrier properties. Thus, adding nanofiller can be an interesting method to extend and to improve the PLA properties. The aim of this work is to evaluate the rheological and thermal properties of composites based on PLA/nano-CaCO3/HDPE by using a design of experiments (DOE)-2n Factorial, with three center points. Three factors were studied: HDPE/nano-CaCO3 masterbatch content, temperature and mixer speed. All PLA/Nano-CaCO3/HDPE experiments were characterized by differential scanning calorimetry (DSC), torque rheometry and melt flow index analysis (MFI). It was noticed that torque rheometry was affected by the addition of the HDPE/nano-CaCO3 masterbatch content and it was also observed a synergism among the factors. The nanofiller content, added in the masterbatch, also affected the flow behavior of composites produced.

  1. Antibacterial activity of phenyllactic acid against Listeria monocytogenes and Escherichia coli by dual mechanisms.

    PubMed

    Ning, Yawei; Yan, Aihong; Yang, Kun; Wang, Zhixin; Li, Xingfeng; Jia, Yingmin

    2017-08-01

    Phenyllactic acid (PLA), a phenolic acid phytochemical, is considered to be a promising candidate for use as a chemical preservative due to its broad antimicrobial activity. The antibacterial target of PLA has rarely been reported, thus investigations were performed to elucidate the antibacterial mechanism of PLA against Listeria monocytogenes and Escherichia coli. Flow cytometry analysis stained with propidium iodide (PI) demonstrated that PLA could damage the membrane integrity of L. monocytogenes, while it could not disrupt that of E. coli. The uptake of 1-N-phenylnaphthylamine (NPN) indicated that PLA interrupted the outer membrane permeability of E. coli. Scanning electron microscopy (SEM) observation visualized the damage caused by PLA as morphological changes in L. monocytogenes and E. coli. Fluorescence assays demonstrated that PLA could interact with bacterial genomic DNA in the manner of intercalation. This finding suggested dual antibacterial targets of PLA, namely membrane and genomic DNA.

  2. Poly(lactic acid)-Mass production, processing, industrial applications, and end of life.

    PubMed

    Castro-Aguirre, E; Iñiguez-Franco, F; Samsudin, H; Fang, X; Auras, R

    2016-12-15

    Global awareness of material sustainability has increased the demand for bio-based polymers like poly(lactic acid) (PLA), which are seen as a desirable alternative to fossil-based polymers because they have less environmental impact. PLA is an aliphatic polyester, primarily produced by industrial polycondensation of lactic acid and/or ring-opening polymerization of lactide. Melt processing is the main technique used for mass production of PLA products for the medical, textile, plasticulture, and packaging industries. To fulfill additional desirable product properties and extend product use, PLA has been blended with other resins or compounded with different fillers such as fibers, and micro- and nanoparticles. This paper presents a review of the current status of PLA mass production, processing techniques and current applications, and also covers the methods to tailor PLA properties, the main PLA degradation reactions, PLA products' end-of-life scenarios and the environmental footprint of this unique polymer.

  3. Ozone oxidation of oleic acid surface films decreases aerosol cloud condensation nuclei activity

    NASA Astrophysics Data System (ADS)

    Schwier, A. N.; Sareen, N.; Lathem, T. L.; Nenes, A.; McNeill, V. F.

    2011-08-01

    Heterogeneous oxidation of aerosols composed of pure oleic acid (C18H34O2, an unsaturated fatty acid commonly found in continental and marine aerosol) by gas-phase O3 is known to increase aerosol hygroscopicity and activity as cloud condensation nuclei (CCN). Whether this trend is preserved when the oleic acid is internally mixed with other electrolytes is unknown and addressed in this study. We quantify the CCN activity of sodium salt aerosols (NaCl and Na2SO4) internally mixed with sodium oleate (SO) and oleic acid (OA). We find that particles containing roughly one monolayer of SO/OA show similar CCN activity to pure salt particles, whereas a tenfold increase in organic concentration slightly depresses CCN activity. O3 oxidation of these multicomponent aerosols has little effect on the critical diameter for CCN activation for unacidified particles at all conditions studied, and the activation kinetics of the CCN are similar in each case to those of pure salts. SO-containing particles which are acidified to atmospherically relevant pH before analysis in order to form oleic acid, however, show depressed CCN activity upon oxidation. This effect is more pronounced at higher organic concentrations. The behavior after oxidation is consistent with the disappearance of the organic surface film, supported by Köhler Theory Analysis (KTA). The κ-Köhler calculations show a small decrease in hygroscopicity after oxidation. The important implication of this finding is that oxidative aging may not always enhance the hygroscopicity of internally mixed inorganic-organic aerosols.

  4. Acidity-Controlled Conducting Polymer Films for Organic Thermoelectric Devices with Horizontal and Vertical Architectures

    PubMed Central

    Lee, Woongki; Song, Myeonghun; Park, Soohyung; Nam, Sungho; Seo, Jooyeok; Kim, Hwajeong; Kim, Youngkyoo

    2016-01-01

    Organic thermoelectric devices (OTEDs) are recognized one of the next generation energy conversion platforms because of their huge potentials for securing electricity continuously from even tiny heat sources in our daily life. The advantage of OTEDs can be attributable to the design freedom in device shapes and the low-cost fabrication by employing solution coating processes at low temperatures. As one of the major OTE materials to date, poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) has been used, but no study has been yet carried out on its acidity control even though the acidic components in OTEDs can seriously affect the device performance upon operation. Here we demonstrate that the addition of aniline (a weak base) can control the acidity of PEDOT:PSS and enhance the performance of OTEDs. In particular, the vertical OTEDs with aniline-doped PEDOT:PSS films (active area = 1.0 cm2) could continuously generate electricity (0.06 nW) even at low temperatures (<38 °C) when they were mounted on a desk lamp (power = 24 W). PMID:27667013

  5. Acidity-Controlled Conducting Polymer Films for Organic Thermoelectric Devices with Horizontal and Vertical Architectures

    NASA Astrophysics Data System (ADS)

    Lee, Woongki; Song, Myeonghun; Park, Soohyung; Nam, Sungho; Seo, Jooyeok; Kim, Hwajeong; Kim, Youngkyoo

    2016-09-01

    Organic thermoelectric devices (OTEDs) are recognized one of the next generation energy conversion platforms because of their huge potentials for securing electricity continuously from even tiny heat sources in our daily life. The advantage of OTEDs can be attributable to the design freedom in device shapes and the low-cost fabrication by employing solution coating processes at low temperatures. As one of the major OTE materials to date, poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) has been used, but no study has been yet carried out on its acidity control even though the acidic components in OTEDs can seriously affect the device performance upon operation. Here we demonstrate that the addition of aniline (a weak base) can control the acidity of PEDOT:PSS and enhance the performance of OTEDs. In particular, the vertical OTEDs with aniline-doped PEDOT:PSS films (active area = 1.0 cm2) could continuously generate electricity (0.06 nW) even at low temperatures (<38 °C) when they were mounted on a desk lamp (power = 24 W).

  6. Enrichment and Viability Inhibition of Circulating Tumor Cells on a Dual Acid-Responsive Composite Nanofiber Film.

    PubMed

    Wang, Wenqian; Cheng, Yaya; Li, Yansheng; Zhou, Hao; Xu, Li-Ping; Wen, Yongqiang; Zhao, Liang; Zhang, Xueji

    2017-04-06

    The formation and metastatic colonization of circulating tumor cells (CTCs) are responsible for the vast majority of cancer-related deaths. Over the last decade, drug-delivery systems (DDSs) have rapidly developed with the emergence of nanotechnology; however, most reported tumor-targeting DDSs are able to deliver drugs only to solid tumor cells and not CTCs. Herein, a novel DDS comprising a composite nanofiber film was constructed to inhibit the viability of CTCs. In this system, gold nanoparticles (Au NPs) were functionalized with doxorubicin (DOX) through an acid-responsive cleavable linker to obtain Au-DOX NPs. Then, the Au-DOX NPs were mixed in a solution of an acid-responsive polymer {i.e., poly[2-(dimethylamino)ethyl methacrylate]} to synthesize the nanofiber film through electrospinning technology. After that, the nanofiber film was modified with a specific antibody (i.e., anti-EpCAM) to enrich the concentration of CTCs on the film. Finally, the Au-DOX NPs were released from the nanofiber film, and they consequently inhibited the viability of CTCs by delivering DOX to the enriched CTCs. This composite nanofiber film was able to decrease the viability of CTCs significantly in the suspended and fluid states, and it is expected to limit the migration and proliferation of tumor cells.

  7. Strategies to optimize biosensors based on impedance spectroscopy to detect phytic acid using layer-by-layer films.

    PubMed

    Moraes, Marli L; Maki, Rafael M; Paulovich, Fernando V; Rodrigues Filho, Ubirajara P; de Oliveira, Maria Cristina F; Riul, Antonio; de Souza, Nara C; Ferreira, Marystela; Gomes, Henrique L; Oliveira, Osvaldo N

    2010-04-15

    Impedance spectroscopy has been proven a powerful tool for reaching high sensitivity in sensor arrays made with nanostructured films in the so-called electronic tongue systems, whose distinguishing ability may be enhanced with sensing units capable of molecular recognition. In this study we show that for optimized sensors and biosensors the dielectric relaxation processes involved in impedance measurements should also be considered, in addition to an adequate choice of sensing materials. We used sensing units made from layer-by-layer (LbL) films with alternating layers of the polyeletrolytes, poly(allylamine) hydrochloride (PAH) and poly(vinyl sulfonate) (PVS), or LbL films of PAH alternated with layers of the enzyme phytase, all adsorbed on gold interdigitate electrodes. Surprisingly, the detection of phytic acid was as effective in the PVS/PAH sensing system as with the PAH/phytase system, in spite of the specific interactions of the latter. This was attributed to the dependence of the relaxation processes on nonspecific interactions such as electrostatic cross-linking and possibly on the distinct film architecture as the phytase layers were found to grow as columns on the LbL film, in contrast to the molecularly thin PAH/PVS films. Using projection techniques, we were able to detect phytic acid at the micromolar level with either of the sensing units in a data analysis procedure that allows for further optimization.

  8. Pinolenic Acid in Structured Triacylglycerols Exhibits Superior Intestinal Lymphatic Absorption As Compared to Pinolenic Acid in Natural Pine Nut Oil.

    PubMed

    Chung, Min-Yu; Woo, Hyunjoon; Kim, Juyeon; Kong, Daecheol; Choi, Hee-Don; Choi, In-Wook; Kim, In-Hwan; Noh, Sang K; Kim, Byung Hee

    2017-03-01

    The positional distribution pattern of fatty acids (FAs) in the triacylglycerols (TAGs) affects intestinal absorption of these FAs. The aim of this study was to compare lymphatic absorption of pinolenic acid (PLA) present in structured pinolenic TAG (SPT) where PLA was evenly distributed on the glycerol backbone, with absorption of pine nut oil (PNO) where PLA was predominantly positioned at the sn-3 position. SPT was prepared via the nonspecific lipase-catalyzed esterification of glycerol with free FA obtained from PNO. Lymphatic absorption of PLA from PNO and from SPT was compared in a rat model of lymphatic cannulation. Significantly (P < 0.05) greater amounts of PLA were detected in lymph collected for 8 h from an emulsion containing SPT (28.5 ± 0.7% dose) than from an emulsion containing PNO (26.2 ± 0.6% dose), thereby indicating that PLA present in SPT has a greater capacity for lymphatic absorption than PLA from PNO.

  9. Transfer molding processes for nanoscale patterning of poly-L-lactic acid (PLLA) films

    NASA Astrophysics Data System (ADS)

    Dhakal, Rabin; Peer, Akshit; Biswas, Rana; Kim, Jaeyoun

    2016-03-01

    Nanoscale patterned structures composed of biomaterials exhibit great potential for the fabrication of functional biostructures. In this paper, we report cost-effective, rapid, and highly reproducible soft lithographic transfer-molding techniques for creating periodic micro- and nano-scale textures on poly (L-lactic acid) (PLLA) surface. These artificial textures can increase the overall surface area and change the release dynamics of the therapeutic agents coated on it. Specifically, we use the double replication technique in which the master pattern is first transferred to the PDMS mold and the pattern on PDMS is then transferred to the PLLA films through drop-casting as well as nano-imprinting. The ensuing comparison studies reveal that the drop-cast PLLA allows pattern transfer at higher levels of fidelity, enabling the realization of nano-hole and nano-cone arrays with pitch down to ~700 nm. The nano-patterned PLLA film was then coated with rapamycin to make it drug-eluting.

  10. Holographic gratings recorded in poly(lactic acid)/azo-dye films

    NASA Astrophysics Data System (ADS)

    Cambiasso, Javier; Goyanes, Silvia; Ledesma, Silvia

    2015-09-01

    Diffraction gratings were recorded in biodegradable polymer films of poly(lactic acid) doped with the photoisomerisable azo-dye (Disperse Orange 3). It is shown that the diffraction efficiency of the recorded grating can be improved by 220% via an all-optical treatment. This all-optical treatment consists of a pre-irradiation of the sample with the writing laser beam at high power during a short period of time, preventing damage of the material, followed by a much longer inscription at relatively low power. Furthermore, it is shown that the addition of a small amount of 0.05 wt% of multi-walled carbon nanotubes to the photoresponsive polymer increases the maximum diffraction efficiency as well as the remanent efficiency by 20%. Finally, this last photoresponsive nano-composite is also sensitive to the pre-irradiation treatment.

  11. Enhanced optoelectronic quality of perovskite thin films with hypophosphorous acid for planar heterojunction solar cells

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Pathak, Sandeep; Sakai, Nobuya; Stergiopoulos, Thomas; Nayak, Pabitra K.; Noel, Nakita K.; Haghighirad, Amir A.; Burlakov, Victor M.; Dequilettes, Dane W.; Sadhanala, Aditya; Li, Wenzhe; Wang, Liduo; Ginger, David S.; Friend, Richard H.; Snaith, Henry J.

    2015-11-01

    Solution-processed metal halide perovskite semiconductors, such as CH3NH3PbI3, have exhibited remarkable performance in solar cells, despite having non-negligible density of defect states. A likely candidate is halide vacancies within the perovskite crystals, or the presence of metallic lead, both generated due to the imbalanced I/Pb stoichiometry which could evolve during crystallization. Herein, we show that the addition of hypophosphorous acid (HPA) in the precursor solution can significantly improve the film quality, both electronically and topologically, and enhance the photoluminescence intensity, which leads to more efficient and reproducible photovoltaic devices. We demonstrate that the HPA can reduce the oxidized I2 back into I-, and our results indicate that this facilitates an improved stoichiometry in the perovskite crystal and a reduced density of metallic lead.

  12. Grafting of acrylic acid onto polypropylene films irradiated with argon ions

    NASA Astrophysics Data System (ADS)

    Massa, G.; Mazzei, R.; García Bermúdez, G.; Filevich, A.; Smolko, E.

    2005-07-01

    Polypropylene (PP) foils were irradiated with 100 keV energy Argon ions at different fluences ranging from 1012 up to 2 × 1015 cm-2 and then grafted with acrylic acid (AA). The grafting yield was measured by weight difference and the structural changes on the films were analysed using Fourier transform infrared spectroscopy (FTIR). Different parameters that determined the grafting process such us fluence, grafting time and monomer concentration were analysed. The grafting reached an optimum value at 79% in aqueous solution at 30 min grafting time. The grafting yield as a function of the ion fluence plot, presented a maximum value, as previously found in a study of heavy beam on polymers.

  13. Enhanced optoelectronic quality of perovskite thin films with hypophosphorous acid for planar heterojunction solar cells.

    PubMed

    Zhang, Wei; Pathak, Sandeep; Sakai, Nobuya; Stergiopoulos, Thomas; Nayak, Pabitra K; Noel, Nakita K; Haghighirad, Amir A; Burlakov, Victor M; deQuilettes, Dane W; Sadhanala, Aditya; Li, Wenzhe; Wang, Liduo; Ginger, David S; Friend, Richard H; Snaith, Henry J

    2015-11-30

    Solution-processed metal halide perovskite semiconductors, such as CH3NH3PbI3, have exhibited remarkable performance in solar cells, despite having non-negligible density of defect states. A likely candidate is halide vacancies within the perovskite crystals, or the presence of metallic lead, both generated due to the imbalanced I/Pb stoichiometry which could evolve during crystallization. Herein, we show that the addition of hypophosphorous acid (HPA) in the precursor solution can significantly improve the film quality, both electronically and topologically, and enhance the photoluminescence intensity, which leads to more efficient and reproducible photovoltaic devices. We demonstrate that the HPA can reduce the oxidized I2 back into I(-), and our results indicate that this facilitates an improved stoichiometry in the perovskite crystal and a reduced density of metallic lead.

  14. Enhanced optoelectronic quality of perovskite thin films with hypophosphorous acid for planar heterojunction solar cells

    DOE PAGES

    Zhang, Wei; Pathak, Sandeep; Sakai, Nobuya; ...

    2015-11-30

    Solution-processed metal halide perovskite semiconductors, such as CH3NH3PbI3, have exhibited remarkable performance in solar cells, despite having non-negligible density of defect states. A likely candidate is halide vacancies within the perovskite crystals, or the presence of metallic lead, both generated due to the imbalanced I/Pb stoichiometry which could evolve during crystallization. Herein, we show that the addition of hypophosphorous acid (HPA) in the precursor solution can significantly improve the film quality, both electronically and topologically, and enhance the photoluminescence intensity, which leads to more efficient and reproducible photovoltaic devices. We demonstrate that the HPA can reduce the oxidized I2 backmore » into I-, and our results indicate that this facilitates an improved stoichiometry in the perovskite crystal and a reduced density of metallic lead.« less

  15. Enhanced optoelectronic quality of perovskite thin films with hypophosphorous acid for planar heterojunction solar cells

    PubMed Central

    Zhang, Wei; Pathak, Sandeep; Sakai, Nobuya; Stergiopoulos, Thomas; Nayak, Pabitra K.; Noel, Nakita K.; Haghighirad, Amir A.; Burlakov, Victor M.; deQuilettes, Dane W.; Sadhanala, Aditya; Li, Wenzhe; Wang, Liduo; Ginger, David S.; Friend, Richard H.; Snaith, Henry J.

    2015-01-01

    Solution-processed metal halide perovskite semiconductors, such as CH3NH3PbI3, have exhibited remarkable performance in solar cells, despite having non-negligible density of defect states. A likely candidate is halide vacancies within the perovskite crystals, or the presence of metallic lead, both generated due to the imbalanced I/Pb stoichiometry which could evolve during crystallization. Herein, we show that the addition of hypophosphorous acid (HPA) in the precursor solution can significantly improve the film quality, both electronically and topologically, and enhance the photoluminescence intensity, which leads to more efficient and reproducible photovoltaic devices. We demonstrate that the HPA can reduce the oxidized I2 back into I−, and our results indicate that this facilitates an improved stoichiometry in the perovskite crystal and a reduced density of metallic lead. PMID:26615763

  16. Enhanced optoelectronic quality of perovskite thin films with hypophosphorous acid for planar heterojunction solar cells

    SciTech Connect

    Zhang, Wei; Pathak, Sandeep; Sakai, Nobuya; Stergiopoulos, Thomas; Nayak, Pabitra K.; Noel, Nakita K.; Haghighirad, Amir A.; Burlakov, Victor M.; deQuilettes, Dane W.; Sadhanala, Aditya; Li, Wenzhe; Wang, Liduo; Ginger, David S.; Friend, Richard H.; Snaith, Henry J.

    2015-11-30

    Solution-processed metal halide perovskite semiconductors, such as CH3NH3PbI3, have exhibited remarkable performance in solar cells, despite having non-negligible density of defect states. A likely candidate is halide vacancies within the perovskite crystals, or the presence of metallic lead, both generated due to the imbalanced I/Pb stoichiometry which could evolve during crystallization. Herein, we show that the addition of hypophosphorous acid (HPA) in the precursor solution can significantly improve the film quality, both electronically and topologically, and enhance the photoluminescence intensity, which leads to more efficient and reproducible photovoltaic devices. We demonstrate that the HPA can reduce the oxidized I2 back into I-, and our results indicate that this facilitates an improved stoichiometry in the perovskite crystal and a reduced density of metallic lead.

  17. Electrocatalytic oxidation and voltammetric determination of ciprofloxacin employing poly(alizarin red)/graphene composite film in the presence of ascorbic acid, uric acid and dopamine.

    PubMed

    Zhang, Xin; Wei, Youli; Ding, Yaping

    2014-07-04

    A glassy carbon electrode modified with poly(alizarin red)/electrodeposited graphene (PAR/EGR) composite film was prepared and applied to detect ciprofloxacin (CPFX) in the presence of ascorbic, uric acid and dopamine. The morphology and interface property of PAR/EGR films were examined by scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The electrocatalytic oxidation of CPFX on AR/EGR was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The linearity ranged from 4 × 10(-8) to 1.2 × 10(-4) M with a detection limit (S/N=3) of 0.01 μM. The modified electrode could be applied to the individual determination of CPFX as well as the simultaneous determination of CPFX, ascorbic acid, uric acid and dopamine. This method proved to be a simple, selective and rapid way to determine CPFX in pharmaceutical preparation and biological media.

  18. A new anti-adhesion film synthesized from polygalacturonic acid with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide crosslinker.

    PubMed

    Lee, Ming-Wei; Hung, Chia-Lu; Cheng, Jian-Chuan; Wang, Yng-Jiin

    2005-06-01

    The most commonly used anti-adhesion device for separation and isolation of wounded tissues after surgery is the polymeric film. In this study, a new anti-adhesion membrane based on polygalacturonic acid (PGA) has been synthesized, and its biocompatibility and anti-adhesion capabilities evaluated. The PGA film was reacted with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) to obtain a cross-linked PGA film with an 86% gel content and a 47% water content when immersed in aqueous solution. This PGA-EDC film did not show any evidence of cytotoxic effects since it did not induce any significant increase in cytoplasmic LDH release from the L929 cells in contact with it. When implanted into rats, the PGA-EDC film exhibited a most promising anti-adhesion potential with only 1 out of 21 rats operated not forming any tissue adhesion. This anti-adhesion potency is significantly higher than that found for Seprafilm and untreated rats where 11 out of 21 and 18 out of 21 operated rats, respectively, formed tissue adhesions. The implanted PGA-EDC film did not elicit any acute inflammatory reaction based on the results of histological examination and peritoneal fluid leukocytes analysis. The newly developed PGA-EDC film thus has a great potential for future use in clinical applications.

  19. Enhancement of Colorimetric Response of Enzymatic Reactions by Thermally Evaporated Plasmonic Thin Films: Application to Glial Fibrillary Acidic Protein.

    PubMed

    Abel, Biebele; Kabir, Tabassum S; Odukoya, Babatunde; Mohammed, Muzaffer; Aslan, Kadir

    2015-02-07

    We report the enhancement of the colorimetric response of horseradish peroxidase (HRP) and alkaline phosphatase (AP) in bioassays by thermally evaporated silver, gold, copper and nickel thin films. In this regard, a model bioassay based on biotin-avidin interactions was employed. Biotin groups and enzymes were introduced to all surfaces using a biotinylated linker molecule and avidin, respectively. The colorimetric response of HRP in the model bioassay carried out on the plasmonic thin films were up to 4.4-fold larger as compared to control samples (i.e., no plasmonic thin films), where the largest enhancement of colorimetric response was observed on silver thin films. The colorimetric response of AP on plasmonic thin films was found to be similar to those observed on control samples, which was attributed to the loss of enzymes from the surface during the bioassay steps. The extent of enzymes immobilized on to plasmonic thin films was found to affect the colorimetric response of the model bioassay. These findings allowed us to demonstrate the use of silver thin films for the detection of glial fibrillary acidic protein (GFAP), where the colorimetric response of the standard bioassays for GFAP was enhanced up to 67% as compared to bioassays on glass slides.

  20. Enhancement of Colorimetric Response of Enzymatic Reactions by Thermally Evaporated Plasmonic Thin Films: Application to Glial Fibrillary Acidic Protein

    PubMed Central

    Abel, Biebele; Kabir, Tabassum S.; Odukoya, Babatunde; Mohammed, Muzaffer; Aslan, Kadir

    2015-01-01

    We report the enhancement of the colorimetric response of horseradish peroxidase (HRP) and alkaline phosphatase (AP) in bioassays by thermally evaporated silver, gold, copper and nickel thin films. In this regard, a model bioassay based on biotin-avidin interactions was employed. Biotin groups and enzymes were introduced to all surfaces using a biotinylated linker molecule and avidin, respectively. The colorimetric response of HRP in the model bioassay carried out on the plasmonic thin films were up to 4.4-fold larger as compared to control samples (i.e., no plasmonic thin films), where the largest enhancement of colorimetric response was observed on silver thin films. The colorimetric response of AP on plasmonic thin films was found to be similar to those observed on control samples, which was attributed to the loss of enzymes from the surface during the bioassay steps. The extent of enzymes immobilized on to plasmonic thin films was found to affect the colorimetric response of the model bioassay. These findings allowed us to demonstrate the use of silver thin films for the detection of glial fibrillary acidic protein (GFAP), where the colorimetric response of the standard bioassays for GFAP was enhanced up to 67% as compared to bioassays on glass slides. PMID:25663850

  1. Polymer blend of PLA/PHBV based bionanocomposites reinforced with nanocrystalline cellulose for potential application as packaging material.

    PubMed

    Dasan, Y K; Bhat, A H; Ahmad, Faiz

    2017-02-10

    The current research discusses the development of poly (lactic acid) (PLA) and poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) reinforced nanocrystalline cellulose bionanocomposites. The nanocrystalline cellulose was derived from waste oil palm empty fruit bunch fiber by acid hydrolysis process. The resulting nanocrystalline cellulose suspension was then surface functionalized by TEMPO-mediated oxidation and solvent exchange process. Furthermore, the PLA/PHBV/nanocrystalline cellulose bionanocomposites were produced by solvent casting method. The effect of the addition of nanocrystalline cellulose on structural, morphology, mechanical and barrier properties of bionanocomposites was investigated. The results revealed that the developed bionanocomposites showed improved mechanical properties and decrease in oxygen permeability rate. Therefore, the developed bio-based composite incorporated with an optimal composition of nanocrystalline cellulose exhibits properties as compared to the polymer blend.

  2. Surfactant control of gas uptake: effect of butanol films on HCl and HBr entry into supercooled sulfuric acid.

    PubMed

    Lawrence, Jennifer R; Glass, Samuel V; Park, Seong-Chan; Nathanson, Gilbert M

    2005-08-25

    The entry of HCl into 60-68 wt % D(2)SO(4) and HBr into 68 wt % acid containing 0-0.18 M 1-butanol was monitored by measuring the fractions of impinging HCl and HBr molecules that desorb as DCl and DBr after undergoing H --> D exchange within the deuterated acid. The addition of 0.18 M butanol to the acid creates butyl films that reach approximately 80% surface coverage at 213 K. Surprisingly, this butyl film does not impede exchange but instead enhances it: the HCl --> DCl exchange fractions increase from 0.52 to 0.74 for 60 wt % D(2)SO(4) and from 0.14 to 0.27 for 68 wt % D(2)SO(4). HBr --> DBr exchange increases even more sharply, rising from 0.22 to 0.65 for 68 wt % D(2)SO(4). We demonstrate that this enhanced exchange corresponds to enhanced uptake into the butyl-coated acid for HBr and infer this equivalence for HCl. In contrast, the entry probability of the basic molecule CF(3)CH(2)OH exceeds 0.85 at all acid concentrations and is only slightly diminished by the butyl film. The OD groups of surface butanol molecules may assist entry by providing extra interfacial protonation sites for HCl and HBr dissociation. The experiments suggest that short-chain surfactants in sulfuric acid aerosols do not hinder heterogeneous reactions of HCl or HBr with other solute species.

  3. PLA/chitosan/keratin composites for biomedical applications.

    PubMed

    Tanase, Constantin Edi; Spiridon, Iuliana

    2014-07-01

    Novel composites based on PLA, chitosan and keratin was obtained via blend preparation. The goal of this contribution was to evaluate mechanical and in vitro behavior of the composites. The results point out composites with improved Young modulus and decreased tensile strength, significant increase in hardness (compared to PLA) and a good uptake of the surface properties. Biological assessments using human osteosarcoma cell line on these composites indicate a good viability/proliferation outcome. Hence preliminary results regarding mechanical behavior and in vitro osteoblast response suggest that these composites might have prospective application in medical field.

  4. Preparation of hierarchical structured nano-sized/porous poly(lactic acid) composite fibrous membranes for air filtration

    NASA Astrophysics Data System (ADS)

    Wang, Zhe; Pan, Zhijuan

    2015-11-01

    Hierarchical structured nano-sized/porous poly(lactic acid) (PLA-N/PLA-P) composite fibrous membranes with excellent air filtration performance were prepared via an electrospinning technique. Firstly, PLA-P fibers with different morphology were fabricated by varying the relative humidity, and the nanopores on fiber surface played a key role in improving the specific surface area and filtration performance of the resultant membranes. Secondly, hierarchical structure of PLA-N/PLA-P interlaced structured membranes and PLA-N/PLA-P double-layer structured membranes with different mass ratios for further enhanced air filtration performance were also successfully prepared by combining PLA-N fibers with PLA-P fibers. Filtration tests by measuring the penetration of sodium chloride (NaCl) aerosol particles with a 260 nm mass median diameter revealed that a moderate mass ratio of PLA-P fibers and PLA-N fibers contributed to improving the filtration performance of the hierarchical structured PLA-N/PLA-P composite membrane, and the double-layer structured PLA-N/PLA-P membrane possessed a higher filtration efficiency and quality factor than that of an interlaced structured PLA-N/PLA-P membrane with the same mass ratio. The as-prepared PLA-N/PLA-P double-layer structured membrane with a mass ratio of 1/5 showed a high filtration efficiency (99.999%) and a relatively low pressure drop (93.3 Pa) at the face velocity of 5.3 cm/s.

  5. Electropolymerized molecularly imprinted polymer films of a bis-terthiophene dendron: folic acid quartz crystal microbalance sensing.

    PubMed

    Apodaca, Dahlia C; Pernites, Roderick B; Ponnapati, Ramakrishna R; Del Mundo, Florian R; Advincula, Rigoberto C

    2011-02-01

    A folic acid sensor was prepared via an electropolymerized molecularly imprinted polymer (E-MIP) film of a bis-terthiophene dendron on a quartz crystal microbalance (QCM). The cyclic voltammetry (CV) electrodeposition of the imprinted polymer film was monitored by electrochemical QCM or E-QCM, enabling in situ monitoring and characterization of E-MIP film formation and the viscoelastic behavior of the film. A key component of the E-MIP process is the use of a bifunctional monomer design to precomplex with the template and function as a cross-linker. The complex was electropolymerized and cross-linked by CV to form a polythiophene matrix. Stable cavities were formed that specifically fit the size and shape of the folic acid template. The same substrate surface was used for folic acid sensing. The predicted geometry of the 1:2 folic acid/terthiophene complex was obtained through semiempirical AM1 quantum calculations. The analytical performance, expressed through the figures of merit, of the sensor in aqueous solutions of the analyte was investigated. A relatively good linearity, R(2) = 0.985, was obtained within the concentration range 0-100 μM folic acid. The detection limit was found to be equal to 15.4 μM (6.8 μg). The relative cross selectivity of the folic acid imprinted polymer against the three molecules follows this trend: pteroic acid (= 50%) > caffeine (= 41%) > theophylline (= 6%). The potential and limitations of the E-MIP method were also discussed.

  6. Extended chain conformational preference of solid films of poly(2,6-benzoxazole) processed from Lewis acid coordination complexes

    SciTech Connect

    Chen, X.L.; Jenekhe, S.A.

    1996-12-31

    Polybenzoxazoles such as poly(2,6-benzoxazole)(2,6-PBO), poly(2,6-benzothiazole)(2,6-PBT) and poly(2,5(6)-benzimidazole) are semi-flexible, high temperature, and high modulus polymers which have been of wide interest as the matrix components of molecular composites. These polymers and their rigid-rod relatives polybenzobisazoles(PBZT, PBO, etc) also exhibit interesting electroactive and photoactive properties. As previously shown for rigid-rod polybenzobisazoles, we have found that the semi-flexible polybenzoazoles are soluble in Lewis acid (e.g. GaCl{sub 3}, AlCl{sub 3})/nitromethane solvent systems from which films and fibers could be processed. Remarkably, 2,6-PBO films prepared by complexation mediated processing from Lewis acid/nitromethane solutions of the polymer exhibit the extended chain (trans) conformation as evidenced by optical absorption and photoluminescence spectroscopies. In contrast, 2,6-PBO films prepared from formic acid/methanesulfonic acid(FA/MSA) solvent am predominantly of cis-conformation. The origin of this extended chain conformation preference of 2,6-PBO films prepared from Lewis acid/nitromethane solutions lies in the stereochemical control exerted by Lewis(MX{sub 3}) coordination to the imine nitrogens of 2,6-PBO resulting in an all-trans conformation after film processing and decomplexation. Since the trans- and cis-(2,6-PBO) have dramatically different solid state properties such as optical absorption and luminescence, our results demonstrate how a high degree of control of solid state structure and properties can be achieved by novel polymer processing.

  7. Reduced graphene oxide/molecular imprinted polymer-organic thin film transistor for amino acid detection

    NASA Astrophysics Data System (ADS)

    Halim, Nurul Farhanah AB.; Musa, Nur Hazwani; Zakaria, Zulkhairi; Von Schleusingen, Mubaraq; Ahmad, Mohd Noor; Derman, Nazree; Shakaff, Ali Yeon Md.

    2017-03-01

    This works reports the electrical performance of reduced graphene oxide (RGO)/Molecular imprinted polymer (MIP)- organic thin film transistor (OTFT) for amino-acid detection, serine. These biomimetic sensors consider MIP as man-tailored biomimetic recognition sites that play an important role in signal transduction. MIP provides recognition sites compatible with serine molecules was developed by dispersing serine with methylacrylate acid (MAA) as functional monomer and Ethylene glycol dimethylacrylate (EGDMA) as cross-linker. The imprinted polymeric were mixed with reduced graphene oxide to produced sensing layer for the sensor. RGO-MIP layer was introduced between source and drain of OTFT via spin coating as a detecting layer for serine molecules. RGO was introduced into MIP, to allow a highly conductive sensing material thus enhanced selectivity and sensitivity of the sensor. By analyzing the electrical performance of the sensors, the performances of OTFT sensor enhanced with RGO/MIP interlayer and OTFT sensor with MIP interlayer when exposed to serine analyte were obtained. The results showed that there were remarkable shifts of drain current (ID) obtained from OTFT sensor with RGO/MIP interlayer after exposed to serine analyte. Moreover, the sensitivity of OTFT sensor with RGO/MIP interlayer was nearly higher than the OTFT sensor with MIP interlayer. Hence, it proved that RGO successfully enhanced the sensing performance of OTFT sensor.

  8. sPLA2 -IIA Overexpression in Mice Epidermis Depletes Hair Follicle Stem Cells and Induces Differentiation Mediated Through Enhanced JNK/c-Jun Activation.

    PubMed

    Sarate, Rahul M; Chovatiya, Gopal L; Ravi, Vagisha; Khade, Bharat; Gupta, Sanjay; Waghmare, Sanjeev K

    2016-09-01

    Secretory phospholipase A2 Group-IIA (sPLA2 -IIA) catalyzes the hydrolysis of the sn-2 position of glycerophospholipids to yield fatty acids and lysophospholipids. sPLA2 -IIA is deregulated in various cancers; however, its role in hair follicle stem cell (HFSC) regulation is obscure. Here we report a transgenic mice overexpressing sPLA2 -IIA (K14-sPLA2 -IIA) showed depletion of HFSC pool. This was accompanied with increased differentiation, loss of ortho-parakeratotic organization and enlargement of sebaceous gland, infundibulum and junctional zone. The colony forming efficiency of keratinocytes was significantly reduced. Microarray profiling of HFSCs revealed enhanced level of epithelial mitogens and transcription factors, c-Jun and FosB that may be involved in proliferation and differentiation. Moreover, K14-sPLA2 -IIA keratinocytes showed enhanced activation of EGFR and JNK1/2 that led to c-Jun activation, which co-related with enhanced differentiation. Further, depletion of stem cells in bulge is associated with high levels of chromatin silencing mark, H3K27me3 and low levels of an activator mark, H3K9ac suggestive of alteration in gene expression contributing toward stem cells differentiation. Our results, first time uncovered that overexpression of sPLA2 -IIA lead to depletion of HFSCs and differentiation associated with altered histone modification. Thus involvement of sPLA2 -IIA in stem cells regulation and disease pathogenesis suggest its prospective clinical implications. Stem Cells 2016;34:2407-2417.

  9. Transparent indium oxide films doped with high Lewis acid strength Ge dopant for phosphorescent organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Kang, Sin-Bi; Lim, Jong-Wook; Lee, Sunghun; Kim, Jang-Joo; Kim, Han-Ki

    2012-08-01

    We report on Ge-doped In2O3(IGO) films prepared by co-sputtering GeO2 and In2O3 targets for anode of phosphorescent organic light-emitting diodes (POLEDs). Under optimized annealing conditions, the IGO film exhibited a low sheet resistance of 14.0 Ω/square, a high optical transmittance of 86.9% and a work function of 5.2 eV, comparable to conventional Sn-doped In2O3 (ITO) films. Due to the higher Lewis acid strength of the Ge4+ ion (3.06) than that of Sn3+(1.62), the IGO film showed higher transparency in the near infrared and higher carrier mobility of 39.16 cm2 V-1 s-1 than the ITO films. In addition, the strongly preferred (2 2 2) orientation of the IGO grains, caused by Zone II grain growth during rapid thermal annealing, increased the carrier mobility and improved the surface morphology of the IGO film. POLEDs fabricated on IGO anodes showed identical current density-voltage-luminance curves and efficiencies to POLEDs with ITO electrodes due to the low sheet resistance and high transmittance of the IGO anode.

  10. Nanoassembled thin film gas sensors. III. Sensitive detection of amine odors using TiO2/poly(acrylic acid) ultrathin film quartz crystal microbalance sensors.

    PubMed

    Lee, Seung-Woo; Takahara, Naoki; Korposh, Sergiy; Yang, Do-Hyeon; Toko, Kiyoshi; Kunitake, Toyoki

    2010-03-15

    Quartz crystal microbalance (QCM) gas sensors based on the alternate adsorption of TiO(2) and polyacrilic acid (PAA) were developed for the sensitive detection of amine odors. Individual TiO(2) gel layers could be regularly assembled with a thickness of approximately 0.3 nm by the gas-phase surface sol-gel process (GSSG). The thickness of the poly(acrylic acid) (PAA) layer is dependent on its molecular weight, showing different thicknesses of approximately 0.4 nm for PAA(25) (Mw 250,000) and 0.6-0.8 nm for PAA(400) (Mw 4,000,000). The QCM sensors showed a linear response to ammonia in the concentration range 0.3-15 ppm, depending on the deposition cycle of the alternate TiO(2)/PAA layer. The ammonia binding is based on the acid-base interaction to the free carboxylic acid groups of PAA and the limit of detection (LOD) of the 20-cycle TiO(2)/PAA(400) film was estimated to be 0.1 ppm when exposed to ammonia. The sensor response was very fast and stable in a wide relative humidity (rH) range of 30-70%, showing almost the same frequency changes at a given concentration of ammonia. Sensitivity to n-butylamine and ammonia was higher than to pyridine, which is owing to the difference of molecular weight and basicity of the amine analytes. The alternate TiO(2)/PAA(400) films have a highly effective ability to capture amine odors, and the ambient ammonia concentration of 15 ppm could be condensed up to approximately 20,000 ppm inside the films.

  11. Nature-Inspired One-Step Green Procedure for Enhancing the Antibacterial and Antioxidant Behavior of a Chitin Film: Controlled Interfacial Assembly of Tannic Acid onto a Chitin Film.

    PubMed

    Wang, Yuntao; Li, Jing; Li, Bin

    2016-07-20

    The final goal of this study was to develop antimicrobial food-contact materials based on a natural phenolic compound (tannic acid) and chitin, which is the second most abundant polysaccharide on earth, using an interfacial assembly approach. Chitin film has poor antibacterial and antioxidant ability, which limits its application in industrial fields such as active packaging. Therefore, in this study, a novel one-step green procedure was applied to introduce antibacterial and antioxidant properties into a chitin film simultaneously by incorporation of tannic acid into the chitin film through interfacial assembly. The antibacterial and antioxidant behavior of chitin film has been greatly enhanced. Hydrogen bonds and hydrophobic interaction were found to be the main driving forces for interfacial assembly. Therefore, controlled interfacial assembly of tannic acid onto a chitin film demonstrated a good way to develop functional materials that can be potentially applied in industry.

  12. PLA2-responsive and SPIO-loaded phospholipid micelles

    PubMed Central

    Gao, Qiang; Yan, Lesan; Chiorazzo, Michael; Delikatny, E. James; Tsourkas, Andrew; Cheng, Zhiliang

    2015-01-01

    A PLA2-responsive and superparamagnetic iron oxide (SPIO) nanoparticle-loaded phospholipid micelle was developed. The release of phospholipid-conjugated dye from these micelles was triggered due to phospholipid degradation by phospholipase A2. High relaxivity of the encapsulated SPIO could enable non-invasive magnetic resonance imaging. PMID:26139589

  13. Novel scaffold design with multi-grooved PLA fibers.

    PubMed

    Chung, Sangwon; Gamcsik, Mike P; King, Martin W

    2011-08-01

    A novel prototype nonwoven textile structure containing polylactide (PLA) multigrooved fibers has been proposed as a possible scaffold material for superior cell attachment and proliferation. Grooved cross-sectional fibers with larger surface area were obtained by a bi-component spinning system and the complete removal of the sacrificial component was confirmed by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and x-ray photon spectroscopy (XPS) analysis. These PLA nonwoven scaffolds containing the grooved fibers exhibited enhanced wettability, greater flexibility and tensile properties, and a larger surface area compared to a traditional PLA nonwoven fabric containing round fibers. To evaluate cellular attachment on the two types of PLA nonwoven scaffolds, NIH 3T3 fibroblasts were cultured for up to 12 days. It was evident that the initial cellular attachment was superior on the scaffold with grooved fibers, which was confirmed by MTT viability assay (p < 0.01) and SEM analysis. In the future, by modulating the size of the grooves on the fibers, such a scaffold material with a large surface area could serve as an alternative matrix for culturing different types of cells.

  14. All Work and No PLA Makes Jack a Dull Boy

    ERIC Educational Resources Information Center

    Popova-Gonci, Viktoria

    2009-01-01

    In this article, the author presents an assortment of approaches--building blocks--commonly used in Prior Learning Assessment (PLA) practices (this list is certainly not comprehensive): (1) course matching (comparing course requirements to a student's prior learning experiences); (2) student's ability to articulate learning gained from…

  15. Structural mechanisms as revealed by real time mechano optical behavior of polylactic acid films in uni and biaxial deformation and heat setting processes

    NASA Astrophysics Data System (ADS)

    Ou, Xuesong

    In this study, structural development during PLA film processing was investigated with a new instrumented biaxial stretcher capable of real time monitoring of true stress, true strain and in-plane as well as out-of-plane birefringence under fast deformation rates. The effects of stretching rate and mode on mechano-optical behaviors and correspondent morphology development were investigated. At low deformation levels, a linear regime I associated with orientation of amorphous chains was observed in all modes of deformation. Following regime I, a steeper regime II associated with stress induced crystallization was observed during uniaxial constrained width (UCW) stretching under low rates before birefringence begins to level off in regime III due to finite extensibility of chains. During UCW stretching under high rate, regime I transformed directly into regime III, and this is associated with the formation of a very stable nematic mesophase. Direct transformation from regime I to regime III is observed during simultaneous biaxial (SIM) stretching under all rates. The kinetics of structural changes during heat setting from a pre-oriented state was investigated by rapid tracking of in and out-of-plane birefringence of pre-oriented films with a new instrumented annealing chamber capable of fast sample insertion and removal. Development of birefringence, which reflects overall chain orientation, and associated structural evolution during constrained annealing of extended PLA films were clarified. Structural evolution is determined by the competition between chain relaxation and registration of segments into well oriented nuclei that grow during annealing, leading to formation of a long range network of chains that arrests the chains in their oriented state. At low deformation the temporal evolution of birefringence first involves relaxation followed by a rapid increase associated with crystallization. The initial relaxation disappears with increase in deformation in the

  16. Preparation, cell compatibility and degradability of collagen-modified poly(lactic acid).

    PubMed

    Cui, Miaomiao; Liu, Leili; Guo, Ning; Su, Ruixia; Ma, Feng

    2015-01-05

    Poly(lactic acid) (PLA) was modified using collagen through a grafting method to improve its biocompatibility and degradability. The carboxylic group at the open end of PLA was transferred into the reactive acylchlorided group by a reaction with phosphorus pentachloride. Then, collagen-modified PLA (collagen-PLA) was prepared by the reaction between the reactive acylchlorided group and amino/hydroxyl groups on collagen. Subsequently, the structure of collagen-PLA was confirmed by Fourier transform infrared spectroscopy, fluorescein isothiocyanate-labeled fluorescence spectroscopy, X-ray photoelectron spectroscopy, and DSC analyses. Finally, some properties of collagen-PLA, such as hydrophilicity, cell compatibility and degradability were characterized. Results showed that collagen had been grafted onto the PLA with 5% graft ratio. Water contact angle and water absorption behavior tests indicated that the hydrophilicity of collagen-PLA was significantly higher than that of PLA. The cell compatibility of collagen-PLA with mouse embryonic fibroblasts (3T3) was also significantly better than PLA in terms of cell morphology and cell proliferation, and the degradability of PLA was also improved after introducing collagen. Results suggested that collagen-PLA was a promising candidate for biomedical applications.

  17. In vitro antimicrobial activity of solution blow spun poly(lactic acid)/ polyvinylpyrrolidone nanofibers loaded with Copaiba (Copaifera sp.) oil

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In this study poly(lactic acid)(PLA) and polyvinylpyrrolidone (PVP) micro and nanofibers mats loaded with copaiba (Copaifera sp.) oil were produced by solution blow spinning (SBS). The copaiba (Copaifera sp.) oil was characterized by gas chromatography (GC). Neat PLA and four PLA/ PVP blends contain...

  18. Bioprocessing of glycerol into glyceric Acid for use in bioplastic monomer.

    PubMed

    Fukuoka, Tokuma; Habe, Hiroshi; Kitamoto, Dai; Sakaki, Keiji

    2011-01-01

    Utilization of excess glycerol supplies derived from the burgeoning biodiesel industry has recently become very important. Glyceric acid (GA) is one of the most promising glycerol derivatives, and it is abundantly obtained from glycerol by a bioprocess using acetic acid bacteria. In this study, a novel branched-type poly(lactic acid) (PLA) was synthesized by polycondensation of lactide in the presence of GA. The resulting branched PLA had lower crystallinity and glass transition temperatures than the conventional linear PLA, and the peak associated with the melting point of the branched PLA disappeared. Moreover, in a blend of the branched polymer, the crystallization of the linear PLA occurred at a lower temperature. Thus, the branched PLA containing GA synthesized in this study could potentially be used as a novel bio-based modifier for PLA.

  19. Complex chemical composition of colored surface films formed from reactions of propanal in sulfuric acid at upper troposphere/lower stratosphere aerosol acidities

    NASA Astrophysics Data System (ADS)

    Van Wyngarden, A. L.; Pérez-Montaño, S.; Bui, J. V. H.; Li, E. S. W.; Nelson, T. E.; Ha, K. T.; Leong, L.; Iraci, L. T.

    2015-04-01

    Particles in the upper troposphere and lower stratosphere (UT/LS) consist mostly of concentrated sulfuric acid (40-80 wt%) in water. However, airborne measurements have shown that these particles also contain a significant fraction of organic compounds of unknown chemical composition. Acid-catalyzed reactions of carbonyl species are believed to be responsible for significant transfer of gas phase organic species into tropospheric aerosols and are potentially more important at the high acidities characteristic of UT/LS particles. In this study, experiments combining sulfuric acid (H2SO4) with propanal and with mixtures of propanal with glyoxal and/or methylglyoxal at acidities typical of UT/LS aerosols produced highly colored surface films (and solutions) that may have implications for aerosol properties. In order to identify the chemical processes responsible for the formation of the surface films, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) and 1H nuclear magnetic resonance (NMR) spectroscopies were used to analyze the chemical composition of the films. Films formed from propanal were a complex mixture of aldol condensation products, acetals and propanal itself. The major aldol condensation products were the dimer (2-methyl-2-pentenal) and 1,3,5-trimethylbenzene that was formed by cyclization of the linear aldol condensation trimer. Additionally, the strong visible absorption of the films indicates that higher-order aldol condensation products must also be present as minor species. The major acetal species were 2,4,6-triethyl-1,3,5-trioxane and longer-chain linear polyacetals which are likely to separate from the aqueous phase. Films formed on mixtures of propanal with glyoxal and/or methylglyoxal also showed evidence of products of cross-reactions. Since cross-reactions would be more likely than self-reactions under atmospheric conditions, similar reactions of aldehydes like propanal with common aerosol organic species like glyoxal and

  20. Complex chemical composition of colored surface films formed from reactions of propanal in sulfuric acid at upper troposphere/lower stratosphere aerosol acidities

    NASA Astrophysics Data System (ADS)

    Van Wyngarden, A. L.; Pérez-Montaño, S.; Bui, J. V. H.; Li, E. S. W.; Nelson, T. E.; Ha, K. T.; Leong, L.; Iraci, L. T.

    2014-11-01

    Particles in the upper troposphere and lower stratosphere (UT/LS) consist mostly of concentrated sulfuric acid (40-80 wt %) in water. However, airborne measurements have shown that these particles also contain a significant fraction of organic compounds of unknown chemical composition. Acid-catalyzed reactions of carbonyl species are believed to be responsible for significant transfer of gas phase organic species into tropospheric aerosols and are potentially more important at the high acidities characteristic of UT/LS particles. In this study, experiments combining sulfuric acid (H2SO4) with propanal and with mixtures of propanal with glyoxal and/or methylglyoxal at acidities typical of UT/LS aerosols produced highly colored surface films (and solutions) that may have implications for aerosol properties. In order to identify the chemical processes responsible for the formation of the surface films, Attenuated Total Reflectance-Fourier Transform Infrared and 1H Nuclear Magnetic Resonance spectroscopies were used to analyze the chemical composition of the films. Films formed from propanal were a complex mixture of aldol condensation products, acetals and propanal itself. The major aldol condensation products were the dimer (2-methyl-2-pentenal) and 1,3,5-trimethylbenzene, which was formed by cyclization of the linear aldol condensation trimer. Additionally, the strong visible absorption of the films indicates that higher order aldol condensation products must also be present as minor species. The major acetal species were 2,4,6-triethyl-1,3,5-trioxane and longer-chain linear polyacetals which are likely to separate from the aqueous phase. Films formed on mixtures of propanal with glyoxal and/or methylglyoxal also showed evidence for products of cross-reactions. Since cross-reactions would be more likely than self-reactions under atmospheric conditions, similar reactions of aldehydes like propanal with common aerosol organic species like glyoxal and methylglyoxal

  1. Complex chemical composition of colored surface films formed from reactions of propanal in sulfuric acid at upper troposphere/lower stratosphere aerosol acidities

    PubMed Central

    Van Wyngarden, A. L.; Pérez-Montaño, S.; Bui, J. V. H.; Li, E. S. W.; Nelson, T. E.; Ha, K. T.; Leong, L.; Iraci, L. T.

    2016-01-01

    Particles in the upper troposphere and lower stratosphere (UT/LS) consist mostly of concentrated sulfuric acid (40–80 wt %) in water. However, airborne measurements have shown that these particles also contain a significant fraction of organic compounds of unknown chemical composition. Acid-catalyzed reactions of carbonyl species are believed to be responsible for significant transfer of gas phase organic species into tropospheric aerosols and are potentially more important at the high acidities characteristic of UT/LS particles. In this study, experiments combining sulfuric acid (H2SO4) with propanal and with mixtures of propanal with glyoxal and/or methylglyoxal at acidities typical of UT/LS aerosols produced highly colored surface films (and solutions) that may have implications for aerosol properties. In order to identify the chemical processes responsible for the formation of the surface films, attenuated total reflectance–Fourier transform infrared (ATR-FTIR) and 1H nuclear magnetic resonance (NMR) spectroscopies were used to analyze the chemical composition of the films. Films formed from propanal were a complex mixture of aldol condensation products, acetals and propanal itself. The major aldol condensation products were the dimer (2-methyl-2-pentenal) and 1,3,5-trimethylbenzene that was formed by cyclization of the linear aldol condensation trimer. Additionally, the strong visible absorption of the films indicates that higher-order aldol condensation products must also be present as minor species. The major acetal species were 2,4,6-triethyl-1,3,5-trioxane and longer-chain linear polyacetals which are likely to separate from the aqueous phase. Films formed on mixtures of propanal with glyoxal and/or methylglyoxal also showed evidence of products of cross-reactions. Since cross-reactions would be more likely than self-reactions under atmospheric conditions, similar reactions of aldehydes like propanal with common aerosol organic species like glyoxal and

  2. Complex chemical composition of colored surface films formed from reactions of propanal in sulfuric acid at upper troposphere/lower stratosphere aerosol acidities.

    PubMed

    Van Wyngarden, A L; Pérez-Montaño, S; Bui, J V H; Li, E S W; Nelson, T E; Ha, K T; Leong, L; Iraci, L T

    Particles in the upper troposphere and lower stratosphere (UT/LS) consist mostly of concentrated sulfuric acid (40-80 wt %) in water. However, airborne measurements have shown that these particles also contain a significant fraction of organic compounds of unknown chemical composition. Acid-catalyzed reactions of carbonyl species are believed to be responsible for significant transfer of gas phase organic species into tropospheric aerosols and are potentially more important at the high acidities characteristic of UT/LS particles. In this study, experiments combining sulfuric acid (H2SO4) with propanal and with mixtures of propanal with glyoxal and/or methylglyoxal at acidities typical of UT/LS aerosols produced highly colored surface films (and solutions) that may have implications for aerosol properties. In order to identify the chemical processes responsible for the formation of the surface films, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) and (1)H nuclear magnetic resonance (NMR) spectroscopies were used to analyze the chemical composition of the films. Films formed from propanal were a complex mixture of aldol condensation products, acetals and propanal itself. The major aldol condensation products were the dimer (2-methyl-2-pentenal) and 1,3,5-trimethylbenzene that was formed by cyclization of the linear aldol condensation trimer. Additionally, the strong visible absorption of the films indicates that higher-order aldol condensation products must also be present as minor species. The major acetal species were 2,4,6-triethyl-1,3,5-trioxane and longer-chain linear polyacetals which are likely to separate from the aqueous phase. Films formed on mixtures of propanal with glyoxal and/or methylglyoxal also showed evidence of products of cross-reactions. Since cross-reactions would be more likely than self-reactions under atmospheric conditions, similar reactions of aldehydes like propanal with common aerosol organic species like glyoxal and

  3. Low-temperature preparation of highly conductive thin films from acrylic acid-stabilized silver nanoparticles prepared through ligand exchange.

    PubMed

    Vo, Duc Quy; Shin, Eun Woo; Kim, Jae-Seong; Kim, Sunwook

    2010-11-16

    The preparation of AcA-stabilized Ag nanoparticles and its application to make highly conductive thin films are reported. The AcA-stabilized Ag nanoparticles were prepared through a ligand exchange of original oleylamine (OLA)-coated Ag nanoparticles with acrylic acid (AcA), which acted as both an antisolvent and a modifying ligand during the ligand exchange process. Efficiencies of the ligand exchange as well as the properties of Ag nanoparticles were analyzed using various techniques including TEM, FT-IR, XPS, TGA, and UV-vis methods. The thin films were fabricated by annealing spin-coated AcA-stabilized Ag nanoparticles. Further, the effects of annealing temperature, time, and film thickness on both the film morphology and electrical conductivity have been investigated. In this work, due to the low boiling temperature of stabilizer (AcA) and adjustment of annealing conditions, high electrical conductivity was obtained for the Ag thin films. For example, when annealing at 175 °C for 30 min, a 70 nm thick film showed a maximum electrical conductivity of 1.12 × 10(5) S cm(-1). A conductive layer on a flexible polymer substrate (e.g., PET) sheet has been successfully prepared by annealing a spin-coated film at 140 °C for 30 min. The combined advantages of long-term stability of the AcA-stabilized Ag nanoparticles, low annealing temperature, and high conductivity of the prepared thin films make this relatively simple method attractive for applications in flexible electronics.

  4. Stability of polydopamine and poly(DOPA) melanin-like films on the surface of polymer membranes under strongly acidic and alkaline conditions.

    PubMed

    Wei, Houliang; Ren, Jun; Han, Bo; Xu, Li; Han, Lulu; Jia, Lingyun

    2013-10-01

    This study investigated the stability of polydopamine and poly(3,4-dihydroxyphenylalanine) (poly(DOPA)) melanin-like films on the surface of polymer substrates. Three polymer membranes, polypropylene (PP), poly(vinylidenefluoride) (PVDF) and nylon, were modified with polydopamine or poly(DOPA), and then immersed in 0.1M HCl or NaOH, followed by UV-vis spectrometry analysis to detect the presence of film detachment. The results showed that the outer parts of both polydopamine and poly(DOPA) films were detached, probably due to electrostatic repulsion between the polymers within the film, when the modified membranes were washed in HCl or NaOH solution. These two films were more stable in strongly acidic solution, but the stability of poly(DOPA) film was better than that of polydopamine film. Compared to the films on the surface of PVDF or nylon membrane, films on PP surface showed the lowest stability, possibly because of the hydrophobic property of PP. The process of film detachment was analyzed by GPC, which showed that unreacted dopamine or DOPA monomers were still present in the freshly formed films. The unreacted monomers, as well as polydopamine or poly(DOPA) that were incorporated in the film via noncovalent interactions, became detached when the film was exposed to strongly acidic or alkaline solution. Oxidation of freshly formed films could significantly enhance their stability. The results therefore provide us with a better understanding of the stability of melanin-like films, and allow us to develop an effective strategy for constructing stable films.

  5. China’s Military Modernization; An Analysis of the PLA Improved Logistic Capability

    DTIC Science & Technology

    2013-02-14

    involvement in any crisis, be it humanitarian , domestic or foreign, allows PLA logisticians to build knowledge, especially in time distance factors ...training support (military exercises, non-military exercises, and humanitarian operations). Although these categories are somewhat board, analysis of... humanitarian operations) is critical for the PLA to learn and develop the requirements for sustainment (logistics) of combat operations. The PLA has not been

  6. Voltammetric determination of ferulic acid by didodecyldimethylammonium bromide/nafion composite film-modified carbon paste electrode.

    PubMed

    Luo, Liqiang; Wang, Xia; Li, Qiuxia; Ding, Yaping; Jia, Jianbo; Deng, Dongmei

    2010-01-01

    A simple and rapid method for the determination of ferulic acid in pharmaceutical formulations by didodecyldimethylammonium bromide (DDAB)/Nafion composite film-modified carbon paste electrode is presented. The electrochemical behavior of ferulic acid at the proposed electrode was investigated by cyclic voltammetry and a well-defined oxidation peak was observed at +0.44 V versus saturated calomel electrode in 0.1 M acetate buffer (pH 5.5) solutions. Some experimental parameters affecting the electrochemical response of the modified electrode were optimized. Under optimal conditions, the oxidation peak currents of ferulic acid increase linearly with the concentration of ferulic acid in the range from 2.0 x 10(-6) to 1.2 x 10(-4) M with a detection limit of 3.9 x 10(-7) M (S/N = 3). The proposed method was successfully applied to the determination of ferulic acid in pharmaceutical tablets.

  7. Novel silver-based nanoclay as an antimicrobial in polylactic acid food packaging coatings.

    PubMed

    Busolo, Maria A; Fernandez, Patricia; Ocio, Maria J; Lagaron, Jose M

    2010-11-01

    This paper presents a comprehensive performance study of polylactic acid (PLA) biocomposites, obtained by solvent casting, containing a novel silver-based antimicrobial layered silicate additive for use in active food packaging applications. The silver-based nanoclay showed strong antimicrobial activity against Gram-negative Salmonella spp. Despite the fact that no exfoliation of the silver-based nanoclay in PLA was observed, as suggested by transmission electron microscopy (TEM) and wide angle X-ray scattering (WAXS) experiments, the additive dispersed nicely throughout the PLA matrix to a nanoscale, yielding nanobiocomposites. The films were highly transparent with enhanced water barrier and strong biocidal properties. Silver migration from the films to a slightly acidified water medium, considered an aggressive food simulant, was measured by stripping voltammetry. Silver migration accelerated after 6 days of exposure. Nevertheless, the study suggests that migration levels of silver, within the specific migration levels referenced by the European Food Safety Agency (EFSA), exhibit antimicrobial activity, supporting the potential application of this biocidal additive in active food-packaging applications to improve food quality and safety.

  8. Free radical grafting of gallic acid (GA) on cellulose nanocrystals (CNCS) and evaluation of antioxidant reinforced gellan gum films

    NASA Astrophysics Data System (ADS)

    Criado, P.; Fraschini, C.; Salmieri, S.; Becher, D.; Safrany, A.; Lacroix, M.

    2016-01-01

    Antiradical properties were introduced on cellulose nanocrystals (CNCs) by redox pair (RP) initiator and γ-radiation treatments. Different procedures were tested on CNC, first a 2 h reaction of hydrogen peroxide (H2O2)/ascorbic acid (AA) was performed on CNC solution. γ-Radiation treatment at 20 kGy dose was then applied and immediately after GA was reacted during 24 h with the pretreated CNCs, giving CNC-H2O2-AA-γ-GA. The formation of new carboxylic acids and carbonyl groups were characterized by FT-IR at 1650 and 1730 cm-1 respectively. Carboxylic acid functionalities were also analyzed by conductometric titration where an increase from 49 to 134 mmol COOH kg-1 was found from native to irradiated CNCs. A similar increase in the carboxylic acid content (132 mmol kg-1) was observed for CNC-H2O2-AA-γ-GA, showing the highest radical scavenging properties (8 mM Trolox eq/mg CNC). Thermogravimetric analysis confirmed the structural changes onto CNC. Film packaging containing 20% of CNC-H2O2-AA-γ-GA was then added to a gellan-based film packaging. A significant improvement (p<0.05) of the tensile strength (TS), the tensile modulus (TM) and the elongation at break (EB) and water vapor permeability reduction was observed when CNC-H2O2-AA-γ-GA was added to the film packaging formulation.

  9. Aging properties of films of plasticized vital wheat gluten cast from acidic and basic solutions.

    PubMed

    Olabarrieta, Idoia; Cho, Sung-Woo; Gällstedt, Mikael; Sarasua, Jose-Ramon; Johansson, Eva; Hedenqvist, Mikael S

    2006-05-01

    In order to understand the mechanisms behind the undesired aging of films based on vital wheat gluten plasticized with glycerol, films cast from water/ethanol solutions were investigated. The effect of pH was studied by casting from solutions at pH 4 and pH 11. The films were aged for 120 days at 50% relative humidity and 23 degrees C, and the tensile properties and oxygen and water vapor permeabilities were measured as a function of aging time. The changes in the protein structure were determined by infrared spectroscopy and size-exclusion and reverse-phase high-performance liquid chromatography, and the film structure was revealed by optical and scanning electron microscopy. The pH 11 film was mechanically more stable with time than the pH 4 film, the latter being initially very ductile but turning brittle toward the end of the aging period. The protein solubility and infrared spectroscopy measurements indicated that the protein structure of the pH 4 film was initially significantly less polymerized/aggregated than that of the pH 11 film. The polymerization of the pH 4 film increased during storage but it did not reach the degree of aggregation of the pH 11 film. Reverse-phase chromatography indicated that the pH 11 films were to some extent deamidated and that this increased with aging. At the same time a large fraction of the aged pH 11 film was unaffected by reducing agents, suggesting that a time-induced isopeptide cross-linking had occurred. This isopeptide formation did not, however, change the overall degree of aggregation and consequently the mechanical properties of the film. During aging, the pH 4 films lost more mass than the pH 11 films mainly due to migration of glycerol but also due to some loss of volatile mass. Scanning electron and optical microscopy showed that the pH 11 film was more uniform in thickness and that the film structure was more homogeneous than that of the pH 4 film. The oxygen permeability was also lower for the pH 11 film. The

  10. Cytosolic phospholipase A2 is coupled to hormonally regulated release of arachidonic acid.

    PubMed Central

    Lin, L L; Lin, A Y; Knopf, J L

    1992-01-01

    Cytosolic phospholipase A2 (cPLA2) binds to natural membrane vesicles in a Ca(2+)-dependent fashion, resulting in the selective release of arachidonic acid, thus implicating cPLA2 in the hormonally regulated production of eicosanoids. Here we report that the treatment of Chinese hamster ovary (CHO) cells overexpressing cPLA2 with ATP or thrombin resulted in an increased release of arachidonic acid as compared with parental CHO cells, demonstrating the hormonal coupling of cPLA2. In contrast, CHO cells overexpressing a secreted form of mammalian PLA2 (sPLA2-II) failed to show any increased hormonal responsiveness. Interestingly, we have noted that the activation of cPLA2 with a wide variety of agents stimulates the phosphorylation of cPLA2 on serine residues. Pretreatment of cells with staurosporin blocked the ATP-mediated phosphorylation of cPLA2 and strongly inhibited the activation of the enzyme. Increased cPLA2 activity was also observed in lysates prepared from ATP-treated cells and was sensitive to phosphatase treatment. These results suggest that in addition to Ca2+, the phosphorylation of cPLA2 plays an important role in the agonist-induced activation of cPLA2. Images PMID:1631101

  11. Properties of PLA/PCL particles as vehicles for oral delivery of the androgen hormone 17α-methyltestosterone.

    PubMed

    Sacchetin, Priscila Soares Costa; Setti, Rafaela Ferreira; Vieira e Rosa, Paulo de Tarso; Moraes, Ângela Maria

    2016-01-01

    The aim of this study was to produce PLA (poly(lactic acid)) and PCL (polycaprolactone) oral carriers through the precipitation of the polymer solutions using supercritical CO2 as an antisolvent for the controlled release of the hydrophobic model drug 17α-methyltestosterone (MT). Such drug is a steroidal hormone used orally to develop and sustain primary and secondary male sex characteristics, e.g. for female Nile tilapia sex reversal in aquaculture. The influence of hormone, PLA and PCL concentrations on particle formation was analyzed, showing that high PCL concentrations produced particles with rougher surfaces and greater mean diameters. The incorporation efficiency of MT ranged from 20 to 51%, and its addition resulted in increases in particle mean diameter from 23 to 54 μm. Aggregation was observed for particles incorporating or not MT and high concentrations of MT led to the formation of more amorphous structures, changing the thermal behavior of the particles. The exposure of the PLA/PCL particles to pH conditions simulating gastrointestinal fish conditions showed that hormone release fraction at acidic pH ranged from 8 to 63% (over 2h), while in the basic pH the proportion released varied from 23 to 60% (over 10h), reaching levels adequate for the desired in vivo activity.

  12. Enhanced selectivity of boron doped diamond electrodes for the detection of dopamine and ascorbic acid by increasing the film thickness

    NASA Astrophysics Data System (ADS)

    Qi, Yao; Long, Hangyu; Ma, Li; Wei, Quiping; Li, Site; Yu, Zhiming; Hu, Jingyuan; Liu, Peizhi; Wang, Yijia; Meng, Lingcong

    2016-12-01

    In this paper, boron doped diamond (BDD) with different thickness were prepared by hot filament chemical vapor deposition. The performance of BDD electrodes for detecting dopamine (DA) and ascorbic acid (AA) were investigated. Scanning electron microscopy and Raman spectra reveal the grain size increases and the film quality improves with the increase of film thickness. Electrochemical test show that the transfer coefficient in [Fe3 (CN) 6]3-/4- redox system increases with the increase of the film thickness. The results of selectivity and sensitivity for DA mixed with AA detection show that 8h-BDD and 12h-BDD electrodes possess well selective separated oxidation peaks of DA and AA, and the 12h-BDD electrode exhibits optimal sensitivity until the DA concentration drops to 1 μ M.

  13. The influence of nanotexturing of poly(lactic-co-glycolic acid) films upon human ovarian cancer cell attachment

    NASA Astrophysics Data System (ADS)

    Yaşayan, Gökçen; Xue, Xuan; Collier, Pamela; Clarke, Philip; Alexander, Morgan R.; Marlow, Maria

    2016-06-01

    In this study, we have produced nanotextured poly(lactic-co-glycolic acid) (PLGA) films by using polystyrene (PS) particles as a template to make a polydimethylsiloxane mould against which PLGA is solvent cast. Biocompatible, biodegradable and nanotextured PLGA films were prepared with PS particles of diameter of 57, 99, 210, and 280 nm that produced domes of the same dimension in the PLGA surface. The effect of the particulate monolayer templating method was investigated to enable preparation of the films with uniformly ordered surface nanodomes. Cell attachment of a human ovarian cancer cell line (OVCAR3) alone and co-cultured with mesenchymal stem cells (MSCs) was evaluated on flat and topographically nano-patterned surfaces. Cell numbers were observed to increase on the nanotextured surfaces compared to non-textured surfaces both with OVCAR3 cultures and OVCAR3-MSC co-cultures at 24 and 48 h time points.

  14. Study of field-induced chain conformation transformation in poly(L-lactic acid) based piezoelectric film by infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Du, Xinyu; Zhao, Chunlin; Zhang, Jinxi; Ren, Kailiang

    2016-10-01

    In this investigation, the chain conformation transformation of the piezoelectric polymer of a poly(L-Lactic Acid) (PLLA) film was analyzed under an electric field for the first time using infrared spectroscopy. It is revealed that the piezoelectric shear mode coefficient d14 (˜10 pC/N) of a stretched α form PLLA film mainly comes from the rotation of C  O dipoles inside the polymer main chain. The reorientation of the dipoles causes the deformation of the crystal structure, which corresponds to a shear mode strain macroscopically in the PLLA film along a 45° direction to the polymer length. The back-bone of the molecular chain keeps its own conformation of a 103 helix under an external field up to 100 MV/m.

  15. Stereocomplexes of enantiomeric lactic acid and sebacic acid ester-anhydride triblock copolymers.

    PubMed

    Slivniak, Raia; Domb, Abraham J

    2002-01-01

    A systematic study on the synthesis, characterization, degradation, and drug release of d-, l-, and dl-poly(lactic acid) (PLA)-terminated poly(sebacic acid) (PSA) and their stereocomplexes is reported. PLA-terminated sebacic acid polymers were synthesized by melt condensation of the acetate anhydride derivatives of PLA oligomers and sebacic anhydride oligomers to yield ABA triblock copolymers of molecular weights between 3000 and 9000 that melt at temperatures between 35 and 80 degrees C. Pairs of the corresponding enantiomeric ABA copolymers composed of l-PLA-PSA-l-PLA and d-PLA-PSA-d-PLA were solvent mixed to form stereocomplexes. The formed stereocomplexes exhibited higher crystalline melting temperature than the enantiomeric polymers, which indicate stereocomplex formulation. The PLA terminals had a significant effect on the polymer degradation and drug release rate. PSA with up to 20% w/w of PLA terminals degraded and released the incorporated drug for more than 3 weeks as compared with 10 days for PSA homopolymer.

  16. Evidence for Proteolytic Processing and Stimulated Organelle Redistribution of iPLA

    PubMed Central

    Song, Haowei; Bao, Shunzhong; Lei, Xiaoyong; Jin, Chun; Zhang, Sheng; Turk, John; Ramanadham, Sasanka

    2010-01-01

    Over the past decade, important roles for the 84–88 kDa Group VIA Ca2+-independent phospholipase A2 (iPLA2β) in various organs have been described. We demonstrated that iPLA2β participates in insulin secretion, insulinoma cells and native pancreatic islets express full-length and truncated isoforms of iPLA2β, and certain stimuli promote perinuclear localization of iPLA2β. To gain a better understanding of its mobilization, iPLA2β was expressed in INS-1 cells as a fusion protein with EGFP, enabling detection of subcellular localization of iPLA2β by monitoring EGFP fluorescence. Cells stably-transfected with fusion protein expressed nearly 5-fold higher catalytic iPLA2β activity than control cells transfected with EGFP cDNA alone, indicating that co-expression of EGFP does not interfere with manifestation of iPLA2β activity. Dual fluorescence monitoring of EGFP and organelle Trackers combined with immunoblotting analyses revealed expression of truncated iPLA2β isoforms in separate subcellular organelles. Exposure to secretagogues and induction of ER stress are known to activate iPLA2β in β-cells and we find here that these stimuli promote differential localization of iPLA2β in subcellular organelles. Further, mass spectrometric analyses identified iPLA2β variants from which N-terminal residues were removed. Collectively, these findings provide evidence for endogenous proteolytic processing of iPLA2β and redistribution of iPLA2β variants in subcellular compartments. It might be proposed that in vivo processing of iPLA2β facilitates its participation in multiple biological processes. PMID:20132906

  17. 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.

  18. Corrosion behavior and characteristics of the product film of API X100 steel in acidic simulated soil solution

    NASA Astrophysics Data System (ADS)

    Du, Cui-wei; Zhao, Tian-liang; Liu, Zhi-yong; Li, Xiao-gang; Zhang, Da-wei

    2016-02-01

    The short-term corrosion behavior of API X100 steel in an acidic simulated soil was investigated by electrochemical measurements and soaking experiments, followed by corrosion morphology observations and X-ray photoelectron spectroscopy analyses. The results show that X100 steel exhibits an obvious pitting susceptibility in an acidic soil environment. Pits nucleate after approximately 10 h of immersion. Along with the nucleation and growth of the pits, the charge-transfer resistance and open-circuit potential first increase sharply, then decrease slowly, and eventually reach a steady state. The maxima of the charge-transfer resistance and open-circuit potential are attained at approximately 10 h. The evolution of the electrochemical process is confirmed by the analysis of the product film. The product film exhibits a porous and loose structure and could not protect the substrate well. The product film is primarily composed of ferrous carbonate and ferrous hydroxide (Fe(OH)2). The concentration of Fe(OH)2 in the product film increases from the inside to the outside layer.

  19. [Prognostic implications of GP3a glucoprotein gene PLA1/PLA2 allele in prostatic cancer: pilot results of the study].

    PubMed

    Loran, O B; Itkes, A V; Seregin, A A; Miandina, G I

    2005-01-01

    We studied the role of integrins, primarily, the role of allele distribution of GP3a gene in development of prostatic cancer (PC) and assessment of its prognostic significance. From November 2003 to May 2004 we examined 32 patients with PC: 11 patients with local PC T1-2N0M0; 14 patients with locally advanced cancer T3N0M0 and 7 patients with invasive and/or metastatic cancer T3-4N10-1 or T3-4N0-1M1. The blood from all the patients we studied with PCR for alleles of GP3a gene, PSA. Seventeen patients were found to have alleles PLA1A1, 14(44%)--alleles PLA1A2, 1(3%)--alleles PLA2A2. Alleles PLA1A2 occurred significantly more often than in the population (p < 0.005). The group analysis has found that 8 patients with local PC had alleles PLA1A1, 3 patients--alleles PLA1A2 (27%). We discovered alleles PLA2A2, PLA1A1 and PLA1A2 in 1(7%), 5(36%) and 8(57%) patients with locally advanced PC, respectively. Among patients with metastatic and/or invasive prostatic cancer, there were 4 (57%) and 3 (43%) cases of alleles PLA1A1 and PLA1A2, respectively. Our study demonstrated influence of carriage of PLA2 allele on occurrence of PC risk (5-fold higher) and its invasive forms (10-fold higher and more). Probability to develop local invasion among patients with prostatic cancer--carriers allele PLA1A2 is 6 times higher than among carriers of alleles PLA1A1. A PC course in carriers of alleles PLA1A2 may be characterized by faster development of local invasion and metastasizing vs carriers of alleles PLA1A1. These findings can be used in design of nomograms for prognostication of invasion of clinically small tumors in verification of significance on greater number of the patients.

  20. Controlling E. coli adhesion on high-k dielectric bioceramics films using poly(amino acid) multilayers.

    PubMed

    Lawrence, Neil J; Wells-Kingsbury, Jamie M; Ihrig, Marcella M; Fangman, Teresa E; Namavar, Fereydoon; Cheung, Chin Li

    2012-03-06

    The influence of high-k dielectric bioceramics with poly(amino acid) multilayer coatings on the adhesion behavior of Escherichia coli (E. coli) was studied by evaluating the density of bacteria coverage on the surfaces of these materials. A biofilm forming K-12 strain (PHL628), a wild-type strain (JM109), and an engineered strain (XL1-Blue) of E. coli were examined for their adherence to zirconium oxide (ZrO(2)) and tantalum oxide (Ta(2)O(5)) surfaces functionalized with single and multiple layers of poly(amino acid) polyelectrolytes made by the layer-by-layer (LBL) deposition. Two poly(amino acids), poly(l-arginine) (PARG) and poly(l-aspartic acid) (PASP), were chosen for the functionalization schemes. All three strains were found to grow and preferentially adhere to bare bioceramic film surfaces over bare glass slides. The bioceramic and glass surfaces functionalized with positively charged poly(amino acid) top layers were observed to enhance the adhesion of these bacteria by up to 4-fold in terms of bacteria surface coverage. Minimal bacteria coverage was detected on surfaces functionalized with negatively charged poly(amino acid) top layers. The effect of different poly(amino acid) coatings to promote or minimize bacterial adhesion was observed to be drastically enhanced with the bioceramic substrates than with glass. Such observed enhancements were postulated to be attributed to the formation of higher density of poly(amino acids) coatings enabled by the high dielectric strength (k) of these bioceramics. The multilayer poly(amino acid) functionalization scheme was successfully applied to utilize this finding for micropatterning E. coli on bioceramic thin films.

  1. Titania nanotubes from weak organic acid electrolyte: fabrication, characterization and oxide film properties.

    PubMed

    Munirathinam, Balakrishnan; Neelakantan, Lakshman

    2015-04-01

    In this study, TiO2 nanotubes were fabricated using anodic oxidation in fluoride containing weak organic acid for different durations (0.5h, 1h, 2h and 3h). Scanning electron microscope (SEM) micrographs reveal that the morphology of titanium oxide varies with anodization time. Raman spectroscopy and X-ray diffraction (XRD) results indicate that the as-formed oxide nanotubes were amorphous in nature, yet transform into crystalline phases (anatase and rutile) upon annealing at 600°C. Wettability measurements show that both as-formed and annealed nanotubes exhibited hydrophilic behavior. The electrochemical behavior was ascertained by DC polarization and AC electrochemical impedance spectroscopy (EIS) measurements in 0.9% NaCl solution. The results suggest that the annealed nanotubes showed higher impedance (10(5)-10(6)Ωcm(2)) and lower passive current density (10(-7)Acm(-2)) than the as-formed nanotubes. In addition, we investigated the influence of post heat treatment on the semiconducting properties of the oxides by capacitance measurements. In vitro bioactivity test in simulated body fluid (SBF) showed that precipitation of Ca/P is easier in crystallized nanotubes than the amorphous structure. Our study uses a simple strategy to prepare nano-structured titania films and hints the feasibility of tailoring the oxide properties by thermal treatment, producing surfaces with better bioactivity.

  2. Novel ammonia sensor based on polyaniline/polylactic acid composite films

    NASA Astrophysics Data System (ADS)

    Sotirov, S.; Bodurov, I.; Marudova, M.

    2017-01-01

    We propose a new type of ammonia sensor based on composite film between polyaniline (emeraldine base) dissolved in dimethylformamide, and poly(DL-lactic) acid dissolved in chloroform. The two solutions were mixed in weight ratio of the components 1:1 and cast on Al2O3 substrate, on which silver electrodes were deposited previously. The active layer structure and morphology were examined by atomic force microscopy. The sensor resistance at constant humidity and different ammonia concentrations was measured. It was found that an increase in the ammonia concentration leads to resistance increase. This result is explained in the terms of ionic interactions between the polyaniline and the ammonia, which change the permittivity of the sensor active media. A response between 2% and 590% was shown depending on the ammonia concentration. The sensor is reversible and possesses response time of typically 100 s. Based on the changes of the sensor resistance, ammonia concentration from 10 ppm to 1000 ppm could be detected.

  3. Kinetic evaluation and process performance of a fixed film bioreactor removing phthalic acid and dimethyl phthalate.

    PubMed

    Pirsaheb, Meghdad; Mesdaghinia, Ali-Reza; Shahtaheri, Seyed Jamaleddin; Zinatizadeh, Ali Akbar

    2009-08-15

    Phthalate esters are toxic organic contaminants which can enter into the environment through various industrial processes. In this study, a 6-liter fixed film bioreactor was used to examine biodegradation of phthalic acid (PA) and dimethyl phthalate (DMP) in synthetic wastewater. Effect on the process of two operating factors, namely hydraulic retention time (HRT) (at four levels ranging between 6 and 48 h) and initial phthalate concentrations (at six levels ranging from 10mg to 500 mg/l), was investigated. The process was stable at all operating conditions, except for the condition with influent PA and DMP of 500 mg/l and HRT of 6h. More than 95% removal efficiency was achieved for the conditions with HRT longer than 10h. Remarkable amount of DMP (398 mg/kg of sludge) was adsorbed on the biomass due to its higher hydrophobicity compared to PA (171 mg/kg). The kinetic parameters (mu(m,)K(s), Y and K(d)) were determined and compared for both substrates, PA and DMP.

  4. Langmuir-Blodgett films of random copolymers of fluoroalkyl(meth)acrylate and methacrylic acid: Fabrication and X-ray diffraction study

    SciTech Connect

    Safronov, V.; Feigin, L.A.; Budovskaya, L.D.; Ivanova, V.N.

    1994-12-31

    Langmuir-Blodgett films of amphiphilic fluorinated copolymers were fabricated and studied by X-ray diffraction. Although these films show poor interlayer periodicity, they possess a uniform thickness even in the case of very thin films of one bilayer (22 {angstrom}). This feature was used to obtain complex LB structures (superlattices) with alteration of copolymer and fatty acid bilayers. X-ray diffraction data proved the regular periodical organization of these structures and allowed to calculate electron density distribution across the superlattices.

  5. Acid-Base Properties Of Glass Substrate And SiO2 - Bi2O3 Thin-Film Systems Obtained On It

    NASA Astrophysics Data System (ADS)

    Mal'chik, A. G.; Litovkin, S. V.; Filonov, A. V.; Ulyanova, O. V.; Gromov, V. E.

    2017-01-01

    The article describes an experimental research as a result of which SiO2 - Bi2O3 films have been synthesized of film-forming solutions based on tetraethoxysilane and bismuth nitrate (III). Acid-base properties of a glass substrate and SiO2 - Bi2O3 films obtained on it have been studied. The dependency of physical and chemical properties of SiO2 - Bi2O3 composites on their percentage composition have been revealed.

  6. Effect of surface modified hydroxyapatite on the tensile property improvement of HA/PLA composite

    NASA Astrophysics Data System (ADS)

    Li, J.; Lu, X. L.; Zheng, Y. F.

    2008-11-01

    In this study, we modified the surface of hydroxyapatite (HA) particle by ring-opening polymerization of lactide (LA). The modified HA particles were characterized by IR and TGA. It was shown that LA could be graft-polymerized onto the surface of HA. A series of composites based on modified HA/PLA were further prepared and characterized. It indicated that the modified HA particles were well dispersed in PLA matrix than unmodified HA particles and the adhesion between HA particle and PLA matrix was improved. The modified HA/PLA composites showed good mechanical properties than that of unmodified HA/PLA.

  7. A nitrilo-tri-acetic-acid/acetic acid route for the deposition of epitaxial cerium oxide films as high temperature superconductor buffer layers

    SciTech Connect

    Thuy, T.T.; Lommens, P.; Narayanan, V.; Van de Velde, N.; De Buysser, K.; Herman, G.G.; Cloet, V.; Van Driessche, I.

    2010-09-15

    A water based cerium oxide precursor solution using nitrilo-tri-acetic-acid (NTA) and acetic acid as complexing agents is described in detail. This precursor solution is used for the deposition of epitaxial CeO{sub 2} layers on Ni-5at%W substrates by dip-coating. The influence of the complexation behavior on the formation of transparent, homogeneous solutions and gels has been studied. It is found that ethylenediamine plays an important role in the gelification. The growth conditions for cerium oxide films were Ar-5% gas processing atmosphere, a solution concentration level of 0.25 M, a dwell time of 60 min at 900 {sup o}C and 5-30 min at 1050 {sup o}C. X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscopy (AFM), pole figures and spectroscopic ellipsometry were used to characterize the CeO{sub 2} films with different thicknesses. Attenuated total reflection-Fourier transform infrared (ATR-FTIR) was used to determine the carbon residue level in the surface of the cerium oxide film, which was found to be lower than 0.01%. Textured films with a thickness of 50 nm were obtained. - Graphical abstract: Study of the complexation and hydrolysis behavior of Ce{sup 4+} ions in the presence of nitrilo-tri-acetic acid and the subsequent development of an aqueous chemical solution deposition route suited for the processing of textured CeO{sub 2} buffer layers on Ni-W tapes.

  8. Acid yellow 9 as a dispersing agent for carbon nanotubes: preparation of redox polymer-carbon nanotube composite film and its sensing application towards ascorbic acid and dopamine.

    PubMed

    Kumar, S Ashok; Wang, Sea-Fue; Yang, Thomas C-K; Yeh, Chun-Ting

    2010-08-15

    In this study, we show that acid yellow 9 (4-amino-1-1'-azobenzene-3,4'-disulfonicacid, AY) is a good stabilizing agent for multi-walled carbon nanotubes (MWCNTs). MWCNTs dispersed in AY solution was remained stable about three months and even remained stable after centrifugation at 10,000 rpm for 30 min. Using MWCNTs/AY dispersion, thin-films were prepared on indium tin oxide coated glass electrode and glassy carbon electrodes. Further, dried films of MWCNTs/AY were subjected to electropolymerization in 0.1M H(2)SO(4) solution. Adsorbed AY molecules on MWCNTs get polymerized and they yield a polymer-MWCNTs nanocomposite film on electrode surface which is found to be electrochemically active in wide pH range (1-11). Characterization studies were performed using cyclic voltammetry and SEM. These studies are supported that hybrid material PAY/MWCNTs was obtained. Moreover, newly synthesized PAY-MWCNTs composite film showed excellent electrocatalytic activity towards oxidation of dopamine (DA) and ascorbic acid (AA) with high sensitivity in physiological pH. Linear sweep voltammetry was employed to the determination of DA in the presence of AA in the range of 2x10(-7) to 1.4x10(-6) M. Amperometry was employed to determination of AA at 0.0 V in the range from 1x10(-6) to 5.6x10(-5) M, and DA, uric acid are not interfered on the steady-state current of AA. In addition, real samples such as dopamine injection and AA spiked into human urine were analyzed using PAY/MWCNTs composite modified electrode and satisfactory results were obtained.

  9. Novel procedure to enhance PLA surface properties by chitosan irreversible immobilization

    NASA Astrophysics Data System (ADS)

    Stoleru, Elena; Dumitriu, Raluca Petronela; Munteanu, Bogdanel Silvestru; Zaharescu, Traian; Tănase, Elisabeta Elena; Mitelut, Amalia; Ailiesei, Gabriela-Liliana; Vasile, Cornelia

    2016-03-01

    A novel two step procedure was applied for poly(lactic acid) (PLA) functionalization consisting in the exposure to cold radiofrequency plasma in nitrogen atmosphere or to gamma irradiation followed by "grafting to" of a chitosan layer using carbodiimide chemistry. The adhesion and stability of the deposited surface layer was assured by plasma/gamma irradiation treatment while the chitosan layer offers antifungal/antibacterial/antioxidant activities. Chitosan with different viscosities/deacetylation degree was deposited by electrospinning or immersion methods. Correlations between rheological behavior of chitosan solutions and chitosan layer deposition conditions are made. The PLA surface properties were investigated by water contact angle measurements, ATR-FTIR spectroscopy, AFM, chemiluminiscence, etc. It has been established that the surface roughness increases direct proportional with cold plasma duration and gamma irradiation dose and further increases by chitosan coating which at its turn depends on chitosan characteristics (viscosity and deacetylation degree) and method of deposition. Nano-fibers with relatively homogeneous and reproducible features are obtained by electrospinning of highly viscous chitosan while with the other two types of chitosan both microparticles and nano-fibers are formed. The chitosan coating obtained by immersion is more homogenous and compact and has a better antibacterial activity than the electrospun layer as fiber meshes.

  10. Flexural Properties of PLA Components Under Various Test Condition Manufactured by 3D Printer

    NASA Astrophysics Data System (ADS)

    Jaya Christiyan, K. G.; Chandrasekhar, U.; Venkateswarlu, K.

    2016-10-01

    Rapid Prototyping (RP) technologies have emerged as a fabrication method to obtain engineering components in the resent past. Desktop 3D printing, also referred as an additive layer manufacturing technology is a powerful method of RP technique that can fabricate 3 dimensional engineering components. In this method, 3D digital data is converted into real product. In the present investigation, Polylactic Acid (PLA) was considered as a starting material. Flexural strength of PLA material was evaluated using 3-point bend test, as per ASTM D790 standard. Specimens with flat (0°) and vertical (90°) orientation were considered. Moreover, layer thicknesses of 0.2, 0.25, and 0.3 mm were considered. To fabricate these specimens, printing speed of 38 and 52 mm/s was maintained. Nozzle diameter of 0.4 mm with 40 % of infill density were used. Based on the experimental results, it was observed that 0° orientation, 38 mm/s printing speed, and 0.2 mm layer thickness resulted maximum flexural strength, as compared to all other specimens. The improved flexural strength was due to the lower layer thickness (0.2 mm) specimens, as compared with other specimens made of 0.25 and 0.30 mm layer thicknesses. It was concluded that flexural strength properties were greatly influenced by lower the layer thickness, printing speed, and orientation.

  11. Magnetic nanoparticles-loaded PLA/PEG microspheres as drug carriers.

    PubMed

    Frounchi, Masoud; Shamshiri, Soodeh

    2015-05-01

    Surface-modified magnetite (Fe3 O4 ) nanoparticles with an average size of 22 nm were prepared. The nanoparticles had a saturation magnetization of 50.7 emu g(-1) . Then magnetite and drug-loaded microspheres of poly (lactic acid)/poly (ethylene glycol) were prepared at various compositions. The microspheres were spherical in shape and had smooth surface. The diameter size of the microspheres ranged between about 0.2 and 4 μm. Doxorubicin hydrochloride for cancer treatment was the drug that loaded into the microspheres. The prepared microspheres were characterized by FTIR, XRD, VSM, SEM and drug-release measurements. It was found that the drug cumulative release percentage was proportional to (time) (n) where 0.61 < n < 0.75 depending on PEG and Fe3 O4 contents. The drug release was controlled through a combination of diffusion and PLA hydrolysis and obeyed a non-fickian mechanism. The drug release was facilitated by presence of poly (ethylene glycol) as PLA plasticizer and was higher under applied external magnetic field. The obtained magnetic microspheres could be used as drug carriers for targeted drug delivery purposes.

  12. Evaluation of PHBHHx and PHBV/PLA fibers used as medical sutures.

    PubMed

    He, Yu; Hu, Zhiwei; Ren, Mengda; Ding, Changkun; Chen, Peng; Gu, Qun; Wu, Qiong

    2014-02-01

    Two types of fibers were prepared by using bio-based materials: a mono-filament made from poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) and a multi-filament made from poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and polylactic acid (PLA) blend. The two fibers were evaluated for mechanical properties, biocompatibility and degradability for the potential application as medical sutures. The PHBHHx fiber showed remarkable biocompatibility by H.E. Stainning, with very little impact to the surrounding tissues. The degradation of the fiber was observed by SEM after implantation for 36 weeks, and the major degradation product was detected after 96 weeks. Consistently, the PHBHHx fiber maintained more than half of the mechanical properties after 96 weeks. The other fiber was prepared by twisting PHBV/PLA blend strands to a bunch, and showed high biocompatibility and relatively high degradability. The bunched structure loosed after 36 weeks of implantation. These low-cost and easily prepared fibers have great potential in medical applications, since they could avoid the formation of fibrous capsule, reduce the size of scar, and degrade into non-toxic and even beneficial products.

  13. 3D printed PLA-based scaffolds: a versatile tool in regenerative medicine.

    PubMed

    Serra, Tiziano; Mateos-Timoneda, Miguel A; Planell, Josep A; Navarro, Melba

    2013-10-01

    Rapid prototyping (RP), also known as additive manufacturing (AM), has been well received and adopted in the biomedical field. The capacity of this family of techniques to fabricate customized 3D structures with complex geometries and excellent reproducibility has revolutionized implantology and regenerative medicine. In particular, nozzle-based systems allow the fabrication of high-resolution polylactic acid (PLA) structures that are of interest in regenerative medicine. These 3D structures find interesting applications in the regenerative medicine field where promising applications including biodegradable templates for tissue regeneration purposes, 3D in vitro platforms for studying cell response to different scaffolds conditions and for drug screening are considered among others. Scaffolds functionality depends not only on the fabrication technique, but also on the material used to build the 3D structure, the geometry and inner architecture of the structure, and the final surface properties. All being crucial parameters affecting scaffolds success. This Commentary emphasizes the importance of these parameters in scaffolds' fabrication and also draws the attention toward the versatility of these PLA scaffolds as a potential tool in regenerative medicine and other medical fields.

  14. Polylactic acid composites incorporating casein functionalized cellulose nanowhiskers

    PubMed Central

    2013-01-01

    Background Polylactic acid (PLA) is considered to be a sustainable alternative to petroleum-based polymers for many applications. Using cellulose fiber to reinforce PLA is of great interest recently due to its complete biodegradability and potential improvement of the mechanical performance. However, the dispersion of hydrophilic cellulose fibers in the hydrophobic polymer matrix is usually poor without using hazardous surfactants. The goal of this study was to develop homogenously dispersed cellulose nanowhisker (CNW) reinforced PLA composites using whole milk casein protein, which is an environmentally compatible dispersant. Results In this study, whole milk casein was chosen as a dispersant in the PLA-CNW system because of its potential to interact with the PLA matrix and cellulose. The affinity of casein to PLA was studied by surface plasmon resonance (SPR) imaging. CNWs were functionalized with casein and used as reinforcements to make PLA composites. Fluorescent staining of CNWs in the PLA matrix was implemented as a novel and simple way to analyze the dispersion of the reinforcements. The dispersion of CNWs in PLA was improved when casein was present. The mechanical properties of the composites were studied experimentally. Compared to pure PLA, the PLA composites had higher Young’s modulus. Casein (CS) functionalized CNW reinforced PLA (PLA-CS-CNW) at 2 wt% filler content maintained higher strain at break compared to normal CNW reinforced PLA (PLA-CNW). The Young’s modulus of PLA-CS-CNW composites was also higher than that of PLA-CNW composites at higher filler content. However, all composites exhibited lower strain at break and tensile strength at high filler content. Conclusions The presence of whole milk casein improved the dispersion of CNWs in the PLA matrix. The improved dispersion of CNWs provided higher modulus of the PLA composites at higher reinforcement loading and maintained the strain and stress at break of the composites at relatively low

  15. Investigation of the Effect of Mixing Methods and Chemical Treatments on the Conductivity of the CNT/PLA Based Composites

    NASA Astrophysics Data System (ADS)

    Talwar, Brijpal Singh

    The growing popularity of Poly lactic acid (PLA) is mainly due to its biocompatibility, good mechanical properties, and its synthesis from renewable resources. PLA can be compounded with electrically conductive fillers (e.g., carbon nanotubes (CNTs)) to form conductive polymer composites (CPCs). These fillers provide conductive functionality to the composite material by forming percolation paths. Featuring very low weight densities, CPCs have the potential to replace metals in the electronic industry, if they exhibit similar electrical conductivities to that of the metals. The current challenges being faced during the mixing of CNTs in the polymer matrix are: formation of aggregates due to strong van der Waals forces and breakage of CNTs during dispersion. In this study, we compare: (1) two fabrication methods to create CPCs (i.e., solution mixing by sonication and melt extrusion) (2) effect of various CNT functionalization techniques (i.e., acid and plasma treatments) on the conductivity of CPCs and (3) effect of using binding molecules like para-phenylenediamine, that act as bridges in between the CNTs in the CPCs and its effect on the conductivity of CPCs. Such conductive composite materials find widespread technological applications which either require, or could benefit from, the ability to pattern micro-sized features in two-dimensional (2D) and three-dimensional (3D) architectures. Direct-write fabrication technique is used to realise these printed patterns, using the CPC solution as ink. First, the composites comprising of 30% PLA by weight in Dichloromethane (DCM) and CNTs in different concentrations (up to 5wt. %) are fabricated using a two-step sonication method (i.e., dissolving PLA in DCM and then dispersing the CNTs in this polymer solution). Second, CPCs are fabricated using a twin screw micro extruder operating at 180°C. To verify the effects of functionalization of the CNTs on the conductivity of composites, the CNTs are functionalized by three

  16. The effects of solvent polarity and pKa on the absorption of solvents into poly(glutaric acid-glycerol) films

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In this study, solvent absorption into the matrices of poly(glutaric acid-glycerol) films has been evaluated. It was determined that the combined effects of polarity and the size and shape of the solvent molecule, rather than pKa, have the most significant influence on absorption into the films. P...

  17. Preparation and properties of films cast from mixtures of poly(vinyl alcohol) and submicron particles prepared from amylose-palmitic acid inclusion complexes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The use of starch in polymer composites for film production has been studied extensively for increasing biodegradability, improving film properties and reducing cost. Starch nanoparticles have received much attention, primarily those obtained by acid hydrolysis of starch granules. In this study, nan...

  18. Efficacy of two acidic sanitizers for microbial reduction on metal cans and low-density polyethylene film surfaces.

    PubMed

    Lee, J; Gupta, M J; Lopes, J; Pascall, M A

    2007-10-01

    This study investigated 2 sanitizer formulations and compared them with hydrogen peroxide (H(2)O(2)). Formulation number 1 contained citric acid and sodium dodecylbenzene sulfonate (SDBS). Formulation number 2 contained SDBS, citric, lactic, phosphoric acids, and benzoic acid. Low concentration levels of the sanitizers (1.0% for formulation 1 and 0.5% for formulation 2) were compared with 35% H(2)O(2) for their efficacies on Escherichia coli, Listeria innocua, and Saccharomyces cerevisiae inoculated onto low-density polyethylene (LDPE) films and metal cans at room temperature (23 +/- 1 degrees C) and 40 degrees C. The results showed that both formulations 1 and 2 required >120 s to sanitize both materials from microbial populations at room temperature, while <15 s was needed for the H(2)O(2). Except for formulation 1 on the E. coli inoculated LDPE film surface, the sanitizers completely eliminated the bacterial populations on both materials in 60 s at 40 degrees C. In general, the formulations were more effective for reduction of the microbial numbers on the can material when compared with the LDPE film. The E. coli showed greater tolerance for the sanitizers when exposed to the process conditions in this study. All sanitizers completely eliminated the test organisms in

  19. Preservation of homochirality of aspartic acid films irradiated with 8.5 eV vacuum ultraviolet light

    NASA Astrophysics Data System (ADS)

    Izumi, Yudai; Matsui, Takahiro; Koketsu, Toshiyuki; Nakagawa, Kazumichi

    2008-10-01

    Enantiomeric excess was reported for amino acids detected from some meteorites. These results imply that these amino acids might escape from racemization processes in space. Here, in an attempt to examine whether non-polarized vacuum ultraviolet (VUV) light was one of racemization factors, we irradiated solid films of homochiral L- or D-aspartic acid ( L- or D-Asp) with a 146 nm excimer lamp in vacuum at 290 K. After irradiation for L-Asp films, L-alanine ( L-Ala) and β-Ala were observed, but D-Asp or D-Ala was not observed. On the contrast, for irradiation to D-Asp films, D-Ala and β-Ala were observed, but L-Asp or L-Ala was not observed. Therefore, we concluded that the chirality was preserved through the photolysis of Asp to Ala. It is of interest to carry out the similar experiments using high-energy particles and/or γ-ray irradiation.

  20. Membranous nephropathy PLA2R+ associated with Chagas disease

    PubMed Central

    Silva, Vanessa dos Santos; Viero, Rosa Marlene

    2015-01-01

    Chagas disease (CD) — a tropical parasitic disease caused by the protozoan Trypanosoma cruzi — is a major health problem in Latin America. The immune response against the parasite is responsible for chronic CD lesions. Currently, there are no reports of an association between CD and membranous nephropathy (MN). The detection of the phospholipase A2 receptor (PLA2R) as a target antigen in idiopathic MN can improve the differential diagnosis of primary and secondary forms of MN. The authors report the case of a male patient with positive serology for CD who presented sudden death and underwent autopsy. Histological sections of the heart showed multifocal inflammatory infiltrate composed mainly of mononuclear cells, leading to myocardiocytes necrosis and interstitial fibrosis. The kidneys showed a MN with positive expression for PLA2R. As far as we know, this is the first report of a case of primary MN in a patient with CD, with severe chronic cardiomyopathy and heart failure. PMID:26558244

  1. PLA2G16 promotes osteosarcoma metastasis and drug resistance via the MAPK pathway.

    PubMed

    Li, Lin; Liang, Shoulei; Wasylishen, Amanda R; Zhang, Yanqin; Yang, Xueli; Zhou, Bingzheng; Shan, Luling; Han, Xiuxin; Mu, Tianyang; Wang, Guowen; Xiong, Shunbin

    2016-04-05

    The prognosis of metastatic osteosarcoma is dismal and a better understanding of the mechanisms underlying disease progression is essential to improve treatment options and patient outcomes. We previously demonstrated Pla2g16 overexpression in mouse osteosarcoma contributes to metastasis phenotypes and increased expression of PLA2G16 is associated with metastasis and poor prognosis in human tumors. To further examine the mechanisms through which PLA2G16 contributes to human osteosarcoma metastasis and explore the potential of PLA2G16 as a therapeutic target in osteosarcoma, we generated a panel of human osteosarcoma cell lines expressing different levels of PLA2G16. The functional analyses of these cell lines demonstrated high levels of PLA2G16 expression increased osteosarcoma cell migration, invasion, clonogenic survival, and anchorage-independent colony formation. Importantly, this activity was dependent on the phospholipase activity of PLA2G16. Additionally, PLA2G16 overexpression decreased the sensitivity of cells to a panel of chemotherapeutic agents. Analysis of downstream pathways revealed the pro-metastasis functions of PLA2G16 were mediated through the MAPK pathway, as knockdown of PLA2G16 decreased ERK1/2 phosphorylation and pharmacological inhibition of MEK significantly repressed PLA2G16 mediated cell migration and clonogenic survival. Furthermore, PLA2G16 overexpression promoted xenograft tumor growth in vivo, and these tumors exhibit increased ERK1/2 phosphorylation. Lastly, the expression of PLA2G16 is strongly correlated with the increased ERK1/2 phosphorylation in human osteosarcoma samples, and the combined lesions are associated with reduced overall and metastasis-free survival. Collectively, these results demonstrate increased PLA2G16 expression activates the MAPK pathway to enhance osteosarcoma metastasis and may be a novel therapeutic target for these cancers.

  2. Water vapour permeability of poly(lactic acid): Crystallinity and the tortuous path model

    NASA Astrophysics Data System (ADS)

    Duan, Z.; Thomas, N. L.

    2014-02-01

    The water vapour transmission rates (WVTR) through samples of polylactic acid of different crystallinities have been measured. Three different grades of commercial poly(lactic acid) (PLA) were used with different ratios of L-lactide and D-lactide to give a range of crystallinities from 0% to 50%. Sheets of PLA were prepared by melt compounding followed by compression moulding and annealing at different temperatures and for different times to give the range of crystallinities required. Crystallinity was measured by differential scanning calorimetry and the morphology of the samples was observed under crossed polars in a transmitted light microscope. Water vapour transmission rates through the films were measured at 38 °C and at a relative humidity of 90%. It was found that the measured values of WVTR decreased linearly with increasing crystallinity of the PLA from 0% to 50%. The results are discussed in terms of the effect of crystallinity on solubility and shown to fit the "Tortuous Path Model." The model was also successfully used to explain published data on water permeability of polyethylene terephthalate.

  3. Beyond the Strait: PLA Missions Other Than Taiwan

    DTIC Science & Technology

    2009-04-01

    this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington...PLA Missions Other Than Taiwan, does not suggest that the Taiwan issue has been resolved as a potential flashpoint or is no longer at the center of...However, the accelerated increase in China’s defense spending since 1996 as shown in Figure 1 suggests something else in addition to Taiwan is

  4. Synthesis and study of sericin-g-PLA

    NASA Astrophysics Data System (ADS)

    Saetae, S.; Magaraphan, R.

    2015-05-01

    In this paper we present an experiment for bulk synthesis of the sericin-g-PLA by using Sn(Oct)2 as catalyst and study the effect of Thai silk cocoon species (Dok Bua, Luang Pirote, Nang Noi and Nang Lai) on properties of the sericin-g-PLA. We investigated the chemical structure of the grafted copolymers by using FTIR and GPC. Moreover, the grafting percentage was determined by soxhlet extaction. The IR spectra of extracted sample showed peaks at 1188 and 1215 cm-1 that assigned to the symmetric C-O-C stretching modes of the ester group. The methyl rocking stretching and C-CH3 vibration of polylactide appeared at 1130 and 1045 cm-1, respectively. The peak positioned 3440 cm-1 belonged to the hydroxyl group and the amino group of sericin which became less after polymerized with lactide. These evidences suggested that the lactide was reacted with sericin. Also, the molecular weight of the grafted copolymers were in range from 5.2 to 6.1 kg/mole. And Nang Lai-g-PLA showed the highest grafting percentage of the grafted copolymers.

  5. Chitosan-whey protein isolate composite films for encapsulation and stabilization of fish oil containing ultra pure omega-3 fatty acids.

    PubMed

    Duan, Jingyun; Jiang, Yan; Zhao, Yanyun

    2011-01-01

    Chitosan (1.5%, w/v)-whey protein isolate (WPI, 5% w/v) composite films were developed for encapsulating and stabilizing fish oil (FO) containing 93.7% eicosapentaenoic acid (EPA). Chitosan-WPI film-forming solutions (FFS) were incorporated with 1.5% or 2% FO (w/v), 2% (w/v) glycerol, Tween 80 (3 times weight of FO), and 0.5% (w/v) oregano or rosemary essential oil (EO), and cast for films at room conditions. Dried films were stored at 2 °C for 30 d for evaluating encapsulation efficiency (EE), lipid stability, and film functionality. Total oil contents in films from FFS incorporating 1.5% or 2% FO were 28.1% to 32.5% and 33.4% to 37.3%, respectively, and free oil contents were 13.5% to 14.7% and 15.5% to 16.3%, respectively. EE, moisture content, and water activity of the films were 47.8% to 66%, 18.7% to 24.9%, and 0.42% to 0.50%, respectively, without significant difference among differently formulated films. Increasing FO concentration from 1.5% to 2% in FFS decreased tensile strength of the films from 0.57-0.73 to 0.34-0.44 MPa, but not the film elongation. Addition of oregano EO in FFS retarded lipid oxidation of the fish oil encapsulated in the films, in which a 43% to 53% reduction in thiobarbituric acid-reactive substances value and 39% to 51% reduction in peroxide value were achieved. Chitosan-WPI composite films with incorporation of oregano essential oil could be applied as a simple and economic means for encapsulating and stabilizing fish oil for fortifying omega-3 fatty acids in various applications.

  6. Enhanced bone formation in large segmental radial defects by combining adipose-derived stem cells expressing bone morphogenetic protein 2 with nHA/RHLC/PLA scaffold.

    PubMed

    Hao, Wei; Dong, Jinlei; Jiang, Ming; Wu, Junwei; Cui, Fuzhai; Zhou, Dongsheng

    2010-12-01

    In this study, rabbit adipose-derived stem cells (rASCs) were isolated, cultured in vitro, and transfected with recombinant adenovirus vector containing human bone morphogenetic protein 2 (Ad-hBMP2). These cells were combined with a nano-hydroxyapatite/recombinant human-like collagen/poly(lactic acid) scaffold (nHA/RHLC/PLA) to fabricate a new biocomposite (hBMP2/rASCs-nHA/RHLC/PLA, group 1) and cultured in osteogenic medium. Non-transfected rASCs mixed with nHA/RHLC/PLA (rASCs-nHA/RHLC/PLA, group 2) and nHA/RHLC/PLA scaffold alone (group 3) served as controls. Scanning electron microscope (SEM) demonstrated integration of rASCs with the nHA/RHLC/PLA scaffold. Quantitative real-time RT-PCR analyses of collagen I, osteonectin, and osteopontin cDNA expression indicated that the osteogenic potency of rASCs was enhanced by transfection with Ad-hBMP2. After in vitro culture for seven days, three groups were implanted into 15-mm length critical-sized segmental radial defects in rabbits. After 12 weeks, radiographic and histological analyses were performed. In group 1, the medullary cavity was recanalised, bone was rebuilt and moulding was finished, the bone contour had begun to remodel and scaffold was degraded completely. In contrast, bone defects were not repaired in groups 2 or 3. Furthermore, the scaffold degradation rate in group 1 was significantly higher than in groups 2 or 3. In summary, after transduction with Ad-hBMP2, the osteogenesis of rASCs was enhanced; a new biocomposite created with these cells induced repair of a critical bone defect in vivo in a relatively short time.

  7. A combined study based on experimental analyses and theoretical calculations on properties of poly (lactic acid) under annealing treatment

    NASA Astrophysics Data System (ADS)

    Loued, W.; Wéry, J.; Dorlando, A.; Alimi, K.

    2015-02-01

    In this paper, the significance of annealing, in two different atmospheres (air and vacuum), on the surface characteristics of poly (lactic acid) (PLA) films was investigated. X-ray diffraction (XRD) measurements correlated to atomic force microscopy (AFM) observations of the cast PLA films show that thermal treatment under air atmosphere is responsible for a significant increase of crystallinity with the increase of temperature. However, band gap energy of the title compound is slightly affected by annealing at different temperatures. As for the untreated PLA, the molecular geometry was optimized using density functional theory (DFT/B3LYP) method with 6-31g (d) basis set in ground state. From the optimized geometry, HOMO and LUMO energies and quantum chemical parameters were performed at B3LYP/6-31g (d). The theoretical results, applied to simulated optical spectra of the compound, were compared to the observed ones. On the basis of theoretical vibrational analyses, the thermodynamic properties were calculated at different temperatures, revealing the correlation between internal energy (U), enthalpy (H), entropy (S), Free energy (G) and temperatures.

  8. Neuroprotective Effect of Transplanted Neural Precursors Embedded on PLA/CS Scaffold in an Animal Model of Multiple Sclerosis.

    PubMed

    Hoveizi, Elham; Tavakol, Shima; Ebrahimi-Barough, Somayeh

    2015-01-01

    Multiple sclerosis (MS) is an immune-mediated demyelinating disease of the central nervous system (CNS). Cell transplantation may be an attractive therapeutic approach for MS which may promote remyelination and suppress the inflammatory process. Neural precursor cells are promising in transplantation strategies to treat an injury to the CNS, because of their ability to differentiate into neural cells. Here, we investigated the use of polylactic acid/chitosan (PLA/CS) scaffold as 3D system which increases neural cell differentiation. Nerve growth factor (NGF), basic fibroblast growth factor (bFGF), and conditioned media were employed to induce PC12 cells into neural-like cells (NLCs) on nanofibrous PLA/CS scaffold. Enhanced numbers of neural structures and staining of nestin, microtubule-associated protein (Map2), and class III β-tubulin (β3-tub) were observed with PC12-cell-seeded nanofibrous scaffolds when compared with control medium. The results revealed that PC12 cells attach, grow, and undergo differentiation on the nanofibrous PLA/CS scaffold. Additionally, our study illustrates that transplanted PC12-derived NLCs into the brain lateral ventricles of mice induced with experimental autoimmune encephalomyelitis (EAE), the animal model of MS, significantly reduced the clinical signs of EAE. Histological examination showed attenuation of the inflammatory process in transplanted animals, which was correlated with the reduction of both axonal damage and demyelination.

  9. Modification of poly(L-lactic acid) electrospun fibers and films with poly(propylene imine) dendrimer

    NASA Astrophysics Data System (ADS)

    Khaliliazar, Sh.; Akbari, S.; Kish, M. H.

    2016-02-01

    Poly(L-lactic acid) (PLLA) electrospun fibers and films were modified with the second generation of poly(propylene imine) dendrimer (PPI-G2) by three different approaches, namely, sodium hydroxide hydrolysis, plasma treatment and direct application of PPI-G2. For the first and the second approaches, PLLA was modified by sodium hydroxide hydrolysis or plasma treatment to produce carboxylic acid groups. Then, the carboxylic acid groups were activated by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDAC) and N,N‧-dicyclohexyl carbodiimide (DCC) as a hetero bi-functional cross-linker. The cross-linkers promoted the grafting of carboxylic acid groups on the modified PLLA with NH2 groups of PPI-G2. In the third approach, the PPI-G2 dendrimer was directly used as an aminolysis agent for the functionalization of PLLA in a one step process. FTIR analysis confirmed the presence of sbnd NH2 groups of PPI-G2 on the modified PLLA samples, resulting from each one of the three modification methods. Studies by SEM shows bead free electrospun fibers. Also, FE-SEM shows nano-cracks on the surface of films after modification. Contact angle, drug release tests, antibacterial effects and the dying results confirmed that these functionalization methods increased hydrophilicity and reactive side-chains of PLLA in the wet chemical process resulted in providing host-guest properties on the PLLA surface for adsorbing various kinds of guest molecules.

  10. A study of the formation and self-lubrication mechanisms of boric acid films on boric oxide coatings

    SciTech Connect

    Erdemir, A.; Fenske, G.R.; Erck, R.A.

    1990-01-01

    An investigation was made of the formation and self-lubrication mechanisms of boric acid films on boric oxide coatings prepared by vacuum evaporation. Measured friction coefficients of a steel ball sliding on a boric-oxide-coated-steel disk and a sapphire ball sliding on a boric-oxide-coated-alumina disk were 0.025 to 0.05 at steady state, depending on load and substrate material. This low friction was correlated with the formation of a lubricious boric acid film on boric oxide coatings exposed to open air. For the mechanism of self-lubrication, the layered-triclinic-crystal structure of boric acid was proposed. The atoms