Continuous uniform nanofibers of PVA, PVAc, and a blend of these polymers loaded with CipHCl were successfully electrospun. Addition of the drug reduced the size and narrowed the distribution of electrospun nanofiber diam- eters, which could be attributed to the decrease in solu- tion viscosity. The amount of drug loaded in nanofibers affected the release behavior and the initial drug release from PVA and PVAc nanofibers. Regardless of the initial rapid release, rate of drug release from PVAc electrospun nanofibrous mats was very slow: about 50% of the drug was released during 80 days in a linear fashion, whereas the PVA nanofiber mats released the drug within 3 days. Using the blend nanofiber mats of PVA:PVAc (50:50) greatly affected drug release behavior; it reduced the amount of the drug released at earlier stages, and sustained the drug release profile for longer times compared with PVA nanofiber mats. However, blending PVAc with PVA solution made blend nanofiber mats more flexible and more comfortable for use as a wound dressing because of a very significant increase in the degree of swelling comparison with PVAc. Increasing the thickness of the blend nanofiber mats controlled both the initial release and the rate of drug release, and increased the degree of swelling, making the mats suitable for healing deep wounds. All formulations showed Fickian drug release kinetics.
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Electrospinning was performed by the laboratory spinning unit (ANSTCO-N/VI, Tehran, Iran), which was designed in terms of a vertical working principle. Each solution of CS-PEO containing 0, 2.5, and 5 % of green tea (GT) methanolic extract was placed in a 10 mL syringe and sent to the drum collector (covered with aluminum foil) through a nozzle. The power supply (AC) was set for a positive voltage of 21 kV. The flow rate of the solution was also determined by setting up the syringe pump at 1 mL/h. The rotational speed of the drum collector was 2500 rpm and its distance was set to 10 cm (optimum distance based on preliminary tests) away from the nozzle. Finally, neural conduction channels were provided by folding the CS- PEO-GT nanofibrous mats.
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AgNPs in the PVA nanofibers can also be easily obtained either by the single electrospinning process or when left under mild conditions, but bearing with distinct sizes and size distributions. The as-prepared PVA-Ag electrospun nanofi- brous mats were observed under TEM (shown in top row of Figure 3A), and interestingly the approximately spherical AgNPs are formed in aligned arrays along the orientation of the fibers. The high voltage (15 kV) applied to the PVA-Ag solution during the electrospinning process is believed to contribute to this unique linear arrangement as well as elec- tron transfer of oxido-reduction reaction between the R-OH and Ag + to produce final AgNPs. When a high voltage was
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healing. Antibiotic based dressings not only localize the drug at the wound site but also help in reducing systemic toxicity, especially in cases of foot ulcers due to diabetes. Ahmed A. Elzatahry et al. reported nanofibers with carbenes (N-heterocyclic), with a small amount of gold acetate or chloride effectively as bis (imino) acenaphthene (BIAN). The dressing materials were tinctured with polyvinyl alcohol (PVA) against microbes. The study was conducted over different strains of bacteria and fungi. The complex of gold chloride were more effective among gram positive strains than fungi. This proved the nanofibrous composite was effective against microbes and as an aid in wound dressings . Metal nanoparticles embedded in in-situ polymeric gelling systems is gaining rapid acceptance.
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In the present endeavor, the electrospinning technique was used to produce nanoscale fibers of nylon-6. The core objective of this study was to fabricate nanofibers of high molecular weight of nylon-6 for understanding entanglement of linear polymer chains and its effect on morphology and jet stability of electrospun fibers. To substantiate our study it was necessary to probe low and medium molecular weight nylon-6 and compare with the high molecular weight nylon-6. Variation in surface tension was insignificant with an increase in molecular weight and concentration of polymer. Molecular weight and concentration are prime factors affecting the morphology of the nanofibers. At same concentration level, low molecular weight nylon-6 formed small droplets, while medium molecular weight fibers just started to form nanofibers but high molecular weight nylon-6 formed mats of nanofibers. An increase in relaxation time (as molecular weight increases) suppresses the jet instability due to increased chain entanglements, forming unbeaded and continuous fibers.
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Composites loaded with electrically conductive fillers have been proposed for applications such as flexible, porous, and lightweight strain sensors in filter media . To meet the require- ments of this application, a material useful as a strain sensor should possess many properties at the same time, e.g. sufficient mechanical properties, electrical conductivity as a result of a percolation process , and high porosity. As a previous study reported, electrospun porous nanofibrous mats with the addition of conductive fillers are a great candidate to satisfy those requirements . Conductive fillers which have been reported include metal powder , car- bon fillers like carbon fiber , carbon black , and multi-wall carbon nanotubes (MWNTs) . Among those, MWNT recently attracts much attention due to its unique combination of desirable mechanical properties, low density, semi-conductive or conductive properties, high aspect-ratio, and nano-scale size.
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To simulate the degradation process, the hydrolysis in vitro under physiological conditions at pH 7.4 using PBS [18, 19] have been studied. The visual changes of the webs, after 6 days, two weeks and four weeks of incubation in PBS during in vitro degradation, are shown in Fig. 5. As it is clear, the physical integrity of the nanofibrous web was depressed after 2 weeks and the integrity was completely destroyed after 4 weeks post-examination. In this regard Ajalloueian et al.  investigated the in vitro degradation of nanofibrous mats (PLGA/chitosan) in comparison with PLGA nanofibers and they observed a higher mass loss for the polyblend nanofibrous mat (PLGA/chitosan) in all time points in comparison with PLGA. It was concluded that the result I due to hydrophilic properties of chitosan in the blend form.
In order to extend the stability of the electrospun mats in physiological conditions, all electrospun CO–CS mats were cross-linked with the EDC carbodiimide in the presence of NHS at two concentrations, ie, 200 and 600 mM with the ratio-EDC/NHS = 2:1 W/W. The reaction mechanism is pre- sented in Figure 1. Cross-linking of CO–CS mats was carried out by soaking the scaffolds in 200 and 600 mM of EDC/NHS solutions in an acetone/water mixture (V ethanol /V H2O = 90/10) and incubated through shaking for 4 h, respectively. Later, cross-linked mats were rinsed in deionized water to remove the residual cross-linking solution and put in an oven at 30 ° C for 24 h. The surface characteristics of modified fibers were studied by scanning electron microscopy (SEM, Hitachi S-3000N) to analyze the changes in the surface morphology. Attenuated total reflectance-Fourier transform infrared spec- troscopy (ATR-FTIR) studies were carried out for mats of electrospun before and after cross-linking using ATR-FTIR (Spectrum Two, Perkin Elmer Inc., Waltham, MA, USA). The tensile strength (stress–strain analysis) of CO–CS nanofibrous mats (thickness = 0.04 mm, width = 14 mm) was measured using a universal testing machine (Dak System Inc. U.T.M. 7200, India) under an extension rate of 1 mm/min and 100 N load cell. All data are given as mean and SEM unless noted. One-way analysis of variance with post hoc Tukey mean comparison tests and unpaired Student’s t-tests were conducted at a significant level of P,0.05. A minimum of three replicate samples were used for all experiments.
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Electrospun chitosan nanofibrous mats were fabricated as previously described (Norowski et al., in review). Briefly, a 5.50 wt% chitosan solution in 70(v/v)% trifluoroacetic acid and 30(v/v)% methylene chloride was mixed with genipin for 30 minutes prior to the start of electrospin- ning. The genipin concentrations investigated were 0, 5, or 10 mM. The solution was electrospun at 25 kV and the fibers were collected on a non-stick aluminum foil target (Reynolds wrap ® ) rotated at 8.4 RPM by an AC motor to
Abstract: Bentonite absorbs water to a greater extent than any other ordinary plastic clay and as a consequence it swells depending on the change in its moisture content. This paper aims to give an overview of the swelling characteristic of bentonites with particular observations from that of prehydrated clay mats. How the swelling characteristics vary with the type of clay, water, and the encompassing boundary materials is presented. Accordingly, it examines the swelling response of the clay mat and the pressure exerted when the swelling is both fully and partially restrained. The development of a new apparatus to measure pressures exerted by the clay as a result of the swelling process is also described. A theoretical study is made to postulate how these pressures can be evaluated for field situations. Though bentonites are known to have very high swelling pressures, how this is negated by the compressibility of the composite behaviour with the necessary backfill is demonstrated. Tests show significant differences in swelling behaviour and pressure development when the GCL is in deionized water and sea water environments. Free swell characteristics were similarly affected.. Unique variation of pressure exerted due to swelling in partially restrained conditions was established with experimental observations made during the study.
Abstract To suppress the activity of house dust mites in tatami mats, where they tend to breed, a tatami mat con- sisting of hinoki (Chamaecyparis obtusa) wood-wool was prepared. The suppressive effect of hinoki wood-wool on house dust mites (Dermatophagoides pteronyssinus) was then measured. To investigate the effective period of the wood-wool on the mites, 5-day exposure tests were con- ducted every few weeks for a total of 52 weeks. In the tests of the first and sixth weeks, the activity of the mites was strongly suppressed, and no walking or moving mite was found after 5 days of exposure. The suppressive effect on mites was maintained for 52 weeks. It was concluded that using hinoki wood-wool to produce tatami mats is an effec- tive method of suppressing the activity of mites for about 1 year.
responsibilities and could devote more time to making mats. From the accounts of Siwon and Kobec, it seemed as if making mats for the family, including or maybe particularly for grandchildren, was a special, happy responsibility of the older women. Siwon ‟ s mother had made trademarked mats for all her grandchildren; Kobec avidly described a twin mat which she was looking forward to making for her son ‟ s children. Everyone in Malesiga is a maker. In Malesiga women ‟ s mats and baskets, as well as men ‟ s carving, are the main sources of income. According to Siwon, this economic activity underpins the continuation of Tami communities. The teaching of these activities to the next generation is perceived as critical to the survival of the village. In mat making, girls as young as six (for example, Malum ‟ s niece Albina) are very capable with regard to collecting, carrying, drying and scraping the leaves in preparation for sewing the mats. These young girls, although they are learning some tasks, spend most of their time in playing. Sewing of the leaves to make mats seems to be restricted to girls in their late teens and married women. Older informants said that they learned to make mats around the time of onset of menses. Mondo of Bukaua, who was born in approximately 1948, said that once the girls in her village had had their first menses they then had to settle down to learning w omen‟ s work. Research from the 1960s through the 1980s has shown that menarche in rural Papua New Guinean women occurs between the ages of 15 to 20. This late onset of menarche is attributed to low intakes of protein (Gillett, 1990). It can be assumed that most of the respondents over 65 in the study had their menarche at approximately this age, especially when the additional effects of war deprivation are taken into account.
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Among various drug, gallic acid (3,4,5-trihydroxybe- nzoic acid) is a natural phenolic compounds mostly fo- und in gallnuts, sumac, witch hazel, grapes, oak bark, and green tea. It has several biological activities includ- ing antioxidant, antityrosinase, antimicrobial, anti-infla- mmatory and anticancer activities [16-18]. Due to its promising antioxidant activity, gallic acid is added in various skincare products in the form of natural herbal extracts. Gallic acid is also used as a standard substance in many antioxidant assays. Gallic acid has been shown to possess scavenging activities against several radicals, for example: superoxide anion, hydroxyl radicals, singlet oxygen or peroxyl radicals, and to protect cells from damage induced by UV-B or ionizing irradiation . Additionally, gallic acid showed an antibacterial property against Escherichia coli, Staphylococcus aureus, Pseu- domonas aeruginosa and especially Klebsiella pneumo- niae . From above mentioned this substance has many biological activities that has been potentially de- veloped as active compound for skin or transdermal de- livery system. However, the main limitation of gallic acid is its poor water solubility (11.5 mg/mL) [21,22]. In order to overcome this problem, electrospun fiber mats was use as a drug delivery carrier of gallic acid due to their high surface area should improve the solubility or releasing of gallic acid.
Bacterial cellulose (BC) can be used in wide area of applied scientific, especially for tissue regene- ration and regenerative medicine, lately, bacterial cellulose mats are used in the treatment of skin conditions such as burns and ulcers, because of the morphology of fibrous biopolymers serving as a support for cell proliferation, its pores allow gas exchange between the organism and the envi- ronment. Moreover, the nanostructure and morphological similarities with collagen make BC at- tractive for cell immobilization, cell support and Natural Extracellular Matrix (ECM) Scaffolds. In this scope, Natural ECM is the ideal biological scaffold since it contains all the components of the tissue. The development of mimicking biomaterials and hybrid biomaterial can further advance directed cellular differentiation without specific induction. The extracellular matrix (ECM) con- tains several signals that are received by cell surface receptors and contribute to cell adhesion and cell fate which control cellular activities such as proliferation, migration and differentiation. As such, regenerative medicine studies often rely on mimicking the natural ECM to promote the for- mation of new tissue by host cells, and characterization of natural ECM components is vital for the development of new biomimetic approaches. In this work, the bacterial cellulose fermentation process is modified by the addition of vegetal stem cell to the culture medium and natural mate- rials before the bacteria are inoculated. In vivo behavior using natural ECM for regenerative medi- cine is presented.
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An alternative development concept is to aim to use envi- ronmentally friendly products. One aspect of being environ- mentally friendly is effective utilization of unused resources. Using agricultural wastes, forest product wastes, textile wastes, and so on, as the raw materials of thermal insulation products is favorable for working towards a sustainable society based on resource recycling. For instance, Binici et al.  investigated the k-value of fiber mats made of sunflower stalks, Zhou et al.  reported a k-value for binderless cotton stalk fiberboards, and Yamauchi et al.  published a k-value for thick insulation panels made from sugi (Cryptomeria japonica D. Don) bark and used as a floor heating base material. The k-values of these insulation materials range from 0.050 to 0.073 W/(mK) because their density is more than 150 kg/m 3 . Although these k-values are greater than (i.e., inferior to) that of the glass wool commonly used in buildings, the materials are nevertheless fully usable, as long as a Parts of this report were presented at the 62nd Annual Meeting of the
For electrospinning the fish scale collagen peptide/COS nanofibrous membranes, FSCP with an average manufac- turer’s specified MW of 800 Da were used (Hubei Reco Bio-Tech Co Ltd, Wuhan, China), and chitosan, with a manufacturer’s specified MW of 8 kDa and deacetyla- tion degree of 90%, was purchased from Shanghai Lanji Technology Development Co, Ltd (Shanghai, China). PVA was purchased from Sinopharm Chemical Reagent Co, Ltd (Shanghai, China). The cells used in this study were human skin fibroblasts (HSF) (Anhui Medical University, Hefei, China). Fetal bovine serum (FBS), dimethyl sulfox- ide (DMSO), and Dulbecco’s modified Eagle’s medium (DMEM) were purchased from Sigma-Aldrich Chemical Co (St Louis, MO). All other chemicals were analytical grade.
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Aligned fibers can, for example, be obtained by the use of rapidly rotating cylindrical collectors, which either serves as counter electrode or are combined with an electrode [21-23]. Combination of synthetic polymers and a bioceramic can take advantages of the mechanical properties, degradation stability and cell affinities of the individual components. Thus, incorporation of nanohydroxyapatite (nHA), into a nanofibrous matrix not only mimics the natural bone structure but also can enhance the mechanical properties and biological response of the scaffolds . The objective of this study was to prepare and characterize aligned and random nanofibrous scaffolds of nHA, poly (ε-caprolactone) (PCL) and Poly (vinyl alcohol) (PVA) witch can be used in bone tissue engineering.
alcohol oxidation . As shown in Table 2, the yolk-shell structure of our catalyst was more active than other catalyst, indicating a promising application for methanol oxidation. The activity and selectivity of nano-catalyst can be manipulated by tailoring chemical and physical properties like size, shape, composition and morphology. Besides, the large space between fibers can significantly increase the accessibility of the active sites of the nanofibrous Dy 2 Ce 2 O 7 . That is why, the nanofibrous
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In spite of the fact that cementitious and concrete materials are mainly used on a large scale and in huge quantities for roads, dams, bridges and building constructions, the mechanical behavior of these materials depends to a great extend on structural elements and phenomena which are effective on a micro and nanoscale. Although this is well known by researchers, material producers and engineers for many years, the aspect of nanoscience and nanotechnology has hardly found any special attention, so far. New efforts and possibilities of material engineering on nanoscale in other fields may well lead to a new leap forward to improve mechanical and physical properties as well as durability of this important group of composite construction materials. This paper intends to stimulate the application and development of nanoscientific and nanotechnological concepts of nanofiber materials and their applications in concrete. Due to the wide range of possibilities, however, it does not claim to present a complete overview of the whole field. This would clearly go beyond the scope of this paper. It rather gives a short outline on the related cementitious and concrete material problems and research topics where nanoscience and nanotechnology could produce a major contribution to improve the nanofibrous materials where research needs to be done. Capability to accurately predict failure in joints offers significant potential for developing higher performance structural designs that are safer at the same time since these nanotubes can be used to accurately assess the behavior of joints, members and structures. Nanofibrous cement based materials can monitor regions of partial damages, localized changes in strains, stresses and temperatures of any joints and members.
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Degradation is the process through which useful physico- chemical properties of the polymers are lost. This can include loss of polymer mass through mechanisms such as solvation and depolymerization. Degradation behavior of PVA and PVA/chitosan nanofibrous scaffolds using the PBS immer- sion method is shown in Figure 8. It was clearly observed that the degradation rate of PVA/chitosan scaffolds was much slower than PVA samples. This could be due to higher density of chemical cross-linking between GA and amine groups of chitosan and leads to slower depolymerization. 52,53
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