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ABSTRACT: Poly(vinyl pyrrolidone) was used successfully to control the size and distribution of silver nanoparticles generated on inorganic
silica nanofibers. The inorganic nanofibers were electrospun using sol-gel chemistry of silicates, and the diameter of the
prepared nanofibers was unaffected by adding up to 7% of poly(vinyl pyrrolidone). The silver ions, in the form of silver nitrate,
were introduced into the silica nanofibers and reduced to metallic silver by ultraviolet irradiation with a subsequent thermal
treatment. The size of the generated silver particles was decreased dramatically by adding poly(vinyl pyrrolidone). The size
of the silver nanoparticles was 73 nm when no poly(vinyl pyrrolidone) was added but 23 nm with the addition of only 1% of
poly(vinyl pyrrolidone). The extent of reduction could be checked by determining the concentration of silver ions leached
into water from the silica nanofibers. After thermal treatment of the silica nanofibers, more than 99% of the silver remained
in the nanofibers, indicating almost complete reduction of the silver ions to silver metal.
Keywordselectrospinning–silica nanofibers–silver nanoparticle–poly(vinyl pyrrolidone)
Macromolecular Research 05/2012; 16(7):626-630. · 1.15 Impact Factor
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ABSTRACT: Sodium cellulose carbonate (CC-Na) dissolved in 8.5 wt% NaOH/ZnO (100/2–3, w/w) aqueous solution was spun into some acidic
coagulant systems. Diameter of regenerated cellulose fibers obtained was in the range of 15–50µm. Serrated or circular cross sectional views were obtained by controlling salt concentration or acidity in the acid/salt/water
coagulant systems. Velocity ratio of take-up to spinning was controlled up to 4/1 with increasing spinning velocity from 5
to 40 m/min. Skin structure of was developed at lower acidity or higher concentration of coagulants. Fineness, tenacity and
elongation of the regenerated cellulose fibers were in the range of 1.5–27 denier, 1.2–2.2 g/d, and 8–11.3%, respectively.
All of CC-Na and cellulose fibers spun from CC-Na exhibited cellulose II crystalline structure. Crystallinity index was increased
with increasing take-up speed.
Fibers and Polymers 04/2012; 6(2):95-102. · 0.84 Impact Factor
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ABSTRACT: Silk fibroin (SF) was dissolved in calcium chloride/ethanol/water mixture (1/2/8 in mole ratio) at 70°C for 4 h. The dissolved
silk fibroin was regenerated by casting the dialyzed solution into the films. The films were treated with 50% aqueous solution
of methanol for different times, and their antithrombogenicity was evaluated byin vitro andin vivo tests.In vivo blood tests were made by a method of peripheral vein indwelling suture. It was found that the silk fibroin had a good anti-thrombogenicity
and an absorbability even though the polymer showed foreign body reaction. Finally, the blood compatibilty of silk fibroin
films which were subjected to structural change by the methanol treatment, was examined in connection with their interfacial
surface energy, and a correlation between these properties was found to be present.
Fibers and Polymers 04/2012; 2(2):58-63. · 0.84 Impact Factor
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BIODEVICES 2011 - Proceedings of the International Conference on Biomedical Electronics and Devices, Rome, Italy, 26-29 January, 2011; 01/2011
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ABSTRACT: We have synthesized APBT and APTBT containing benzothiadiazole units by Suzuki cross-coupling reaction with good yield. The polymers showed blue emission colors in aqueous solutions, while long wavelength shift was observed in the solid state due to facilitated exciton migration. APBT and APTBT are water-soluble and highly-fluorescent conjugated polymers with negatively charged sulfonate side chains and thus they can be electrostatically assembled with oppositely charged polyelectrolyte such as cationic polymer, poly(dimethyldiallylammonium chloride) (PDAC) via layer-by-layer (LbL) deposition technique on a glass slide. According to the increased the number of bilayer, we found that the assembled film exhibited larger enhancement of the long wavelength emission relative to the blue emission, due to the increased excition migration.
Journal of Nanoscience and Nanotechnology 10/2010; 10(10):6977-80. · 1.56 Impact Factor
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ABSTRACT: Poly(L-lactic acid) (PLLA) microfibrous scaffolds with three-dimensional (3D) structures were fabricated using an electrospinning technique with a subsequent mechanical expansion process. To achieve a 3D fibrous structure, the fusion at the contact points of the as-spun PLLA microfibers was avoided using an appropriate binary solvent system of methylene chloride and acetone. The solvent composition was optimized based on the solvent power, volatility, and viscosity (methylene chloride:acetone = 9:1 volume ratio). The final 3D structure of the electrospun scaffolds was obtained after mechanical expansion of the electrospun microfibrous mats. The pore sizes of the scaffolds were controlled by varying the degree of expansion of the nonbonded microfibrous mats, and they were in the range of several microns up to 400 μm. The 3D scaffolds were examined for their morphological properties and their potential use for the proliferation of osteoblasts. Generally recognized electrospun 2D nanofibrous membranes were also tested in order to compare the cell behaviors using different scaffold geometries. The 3D scaffolds demonstrated a high level of osteoblast proliferation (1.8-fold higher than nanofibrous membranes in a week). The osteoblasts actively penetrated the inside of the 3D scaffold and showed a spatial cell distribution, as confirmed by SEM and H&E staining, while a monolayer formed in the case of the 2D nanofibrous membranes with limited cell infiltration. In vivo results further showed that 3D electrospun microfibrous matrices were a favorable substrate for cell infiltration and bone formation after 2 and 4 weeks, using a rabbit calvarial defect model. In this study, the 3D microfibrous PLLA scaffolds fabricated using electrospinning techniques might be an innovative addition to tissue engineering applications.
Journal of Biomedical Materials Research Part B Applied Biomaterials 10/2010; 95(1):150-60. · 2.15 Impact Factor
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ABSTRACT: A heat-treated PVA nanofibrous matrix containing silver (Ag) was prepared by electrospinning an aqueous 10 wt% PVA solution and followed by heat treatment at 150 degrees C for 10 min. The average diameter of the as-spun and heat-treated PVA nanofibers was 330 nm. The heat-treated PVA nanofibrous matrix containing Ag was irradiated with UV light to transform the Ag ions in the nanofibrous matrix into Ag nanoparticles. The in vitro cytotoxicity of the Ag ions and/or nanoparticles on normal human epidermal keratinocytes (NHEK) and fibroblasts (NHEF) cultures was examined. The PVA nanofibrous matrix containing Ag showed slightly higher level of attachment and spreading in the early stage culture (1 h) than the PVA nanofibers without Ag (control). However, compared with the PVA nanofibers without Ag, the heat-treated and UV-irradiated PVA nanofibers, containing mainly Ag ions and nanoparticles, respectively, showed reduced cell attachment and spreading. This shows that both Ag ions and Ag nanoparticles are cytotoxic to NHEK and NHEF. There was no significant difference in cytotoxicity to NHEK and NHEF between Ag ions and Ag nanoparticles. NHEF appeared to be more sensitive to Ag ions or particles than NHEK. In addition, the residual nitrate ions (NO3(-)) in the PVA nanofibers had an adverse effect on the culture of both cells.
Colloids and surfaces. B, Biointerfaces 07/2010; 78(2):334-42. · 2.60 Impact Factor
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ABSTRACT: Considerable effort has been directed towards regenerating defective tissues using tissue-engineering methods. Recently, peptides have been recognized as a valuable scientific tool in the field of tissue-engineering. The PPFLMLLKGSTR motif of the human laminin-5 alpha3 chain has been previously reported to promote keratinocyte survival; however, the in vivo effects of the PPFLMLLKGSTR motif have not yet been studied. These studies raised the hypothesis that a laminin-5-derived peptide can promote wound healing by accelerating re-epithelialization in vivo. To examine this hypothesis, we applied chitin microfibrous matrices coated with the PPFLMLLKGSTR motif in both rat and rabbit full-thickness cutaneous wound models. Compared with vehicle-treated and peptide-treated cutaneous wounds, the application significantly promoted early-stage wound healing by accelerating re-epithelialization, notably reduced inflammatory cell infiltration, and prominently enhanced fibroblast proliferation. These findings support our hypothesis that the PPFLMLLKGSTR motif acts as a very effective wound healing accelerator by enhancing re-epithelialization.
Biomaterials 03/2010; 31(17):4725-30. · 7.40 Impact Factor
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ABSTRACT: Recent studies have shown that polymeric scaffolds as a synthetic extracellular matrix (ECM) are essential for regenerating tissues or organs in tissue engineering approaches. Controlling the surface functionality of polymer scaffolds is critical in regulation of cellular responses to the scaffolds during tissue formation. However, the stress response of cells to polymer scaffolds with different surface characteristics is not yet clear. We investigated the expression of heat shock protein (HSP) and Bcl-2 in fibroblasts cultured on electrospun nanofiber matrices with different surface characteristics. The hydrophilicity and chemical composition of electrospun poly(lactic-co-glycolic acid) (PLGA) nanofibers was regulated by plasma treatment in the presence of ammonia gas. We found that expression levels of HSP and Bcl-2 in fibroblasts were strongly dependent on the surface hydrophilicity and concentration of nitrogen-containing functional groups on the nanofiber matrices. The controlled hydrophilicity and surface chemical composition of nanofiber matrices enhanced adhesion and spreading of cells on the matrices, resulting in reduction of cellular stress. This approach to controlling the surface properties and regulating expression of a stress gene could be useful in the design of synthetic ECMs for many tissue engineering applications.
Colloids and surfaces. B, Biointerfaces 01/2010; 77(1):90-5. · 2.60 Impact Factor
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ABSTRACT: A PVA nanofibrous matrix was prepared by electrospinning an aqueous 10 wt % PVA solution. The mean diameter of the PVA nanofibers electrospun from the PVA aqueous solution was 240 nm. The water resistance of the as-spun PVA nanofibrous matrix was improved by physically crosslinking the PVA nanofibers by heat treatment at 150 degrees C for 10 min, which were found to be the optimal heat treatment conditions determined from chemical and morphological considerations. In addition, the heat-treated PVA (H-PVA) nanofibrous matrix was coated with a chitosan solution to construct biomimetic nanofibrous wound dressings. The chitosan-coated PVA (C-PVA) nanofibrous matrix showed less hydrophilic and better tensile properties than the H-PVA nanofibrous matrix. The effect of the chitosan coating on open wound healing in a mouse was examined. The C-PVA and H-PVA nanofibrous matrices showed faster wound healing than the control. The histological examination and mechanical stability revealed the C-PVA nanofibrous matrix to be more effective as a wound-healing accelerator in the early stages of wound healing than the H-PVA nanofibrous matrix.
Journal of Biomedical Materials Research Part B Applied Biomaterials 12/2009; 92(2):568-76. · 2.15 Impact Factor
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ABSTRACT: Laminin-5 and alpha3beta1 integrin promote keratinocyte survival; however, the downstream signaling pathways for laminin-5/alpha3beta1 integrin-mediated cell survival had not been fully established. We report the unexpected finding of multiple interactions between 14-3-3 isoforms and proapoptotic proteins in the survival signaling pathway. Ln5-P4 motif within human laminin-5 alpha3 chain promotes cell survival and anti-apoptosis by inactivating Bad and YAP. This effect is achieved through the formation of 14-3-3zeta/p-Bad and 14-3-3sigma/p-YAP complexes, which is initiated by alpha3beta1 integrin and FAK/PI3K/Akt signaling. These complexes result in cytoplasmic sequestration of Bad and YAP and their subsequent inactivation. An increase in Akt1 activity in cells induces 14-3-3zeta and sigma, p-Bad, and p-YAP, promoting cell survival, whereas decreasing Akt activity suppresses the same proteins and inhibits cell survival. Suppression of 14-3-3zeta with RNA-interference inhibits cell viability and promotes apoptosis. These results reveal a new mechanism of cell survival whereby the formation of 14-3-3zeta/p-Bad and 14-3-3sigma/p-YAP complexes is initiated by laminin-5 stimulation via the alpha3beta1 integrin and FAK/PI3K/Akt signaling pathways, thereby resulting in cell survival and anti-apoptosis.
Experimental Cell Research 09/2009; 315(18):3187-200. · 3.58 Impact Factor
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ABSTRACT: Electrospinning techniques enable the production of continuous fibers with dimensions on the scale of nanometers from a wide range of natural and synthetic polymers. The number of recent studies regarding electrospun polysaccharides and their derivatives, which are potentially useful for regenerative medicine, is increasing dramatically. However, difficulties regarding the processibility of the polysaccharides (e.g., poor solubility and high surface tension) have limited their application. In this review, we summarize the characteristics of various polysaccharides such as alginate, cellulose, chitin, chitosan, hyaluronic acid, starch, dextran, and heparin, which are either currently being used or have potential to be used for electrospinning. The recent progress of nanofiber matrices electrospun from polysaccharides and their biomedical applications in tissue engineering, wound dressings, drug delivery, and enzyme immobilization are discussed.
Advanced drug delivery reviews 08/2009; 61(12):1020-32. · 11.96 Impact Factor
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ABSTRACT: Silk fibroin (SF) nanofibers were prepared by electrospinning and treated with plasma in the presence of oxygen or methane gas to modify their surface characteristics. The surface characteristics of the SF nanofibers after plasma treatment were examined using contact angle measurements and XPS analysis. The hydrophilicity of the electrospun SF nanofibers decreased slightly by the CH(4) plasma treatment. On the other hand, the hydrophilicity of the SF nanofibers increased greatly by an O(2) plasma treatment. The O(2)-treated SF nanofibers showed higher cellular activities for both normal human epidermal keratinocytes (NHEK) and fibroblasts (NHEF) than the untreated ones.
International journal of biological macromolecules 01/2009; 44(3):222-8. · 2.37 Impact Factor
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ABSTRACT: Although the knot security of suture materials has been widely investigated, there are few reports on the effects of knot tying conditions. With respect to foreign body reaction, it is preferable to use the minimum possible amount of suture materials and to use an appropriate material to ensure knot security. In this study, the different effects of knot tying conditions, such as knot type, tying force, and tying speed, were investigated. Knot tying was performed by a tensile tester for reproducible testing with the least amount of hand tying variation. The square knot (1 = 1 = 1) was shown to be the most appropriate knot type to evaluate monofilament sutures with a tensile tester. Increasing the tying speed and tying force enhanced knot security. The mechanical tying method was found to be a useful alternative to hand tying and provided reproducible test results. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Journal of Applied Polymer Science 07/2008; 109(2):918 - 922. · 1.29 Impact Factor
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ABSTRACT: To fabricate a biomimetic nanostructured bicomponent scaffolds, two types of chitin/silk fibroin (SF) nanofibrous scaffolds (blend scaffolds and hybrid scaffolds) were prepared by electrospinning or simultaneous electrospinning of chitin/SF solutions. The chitin/SF bicomponent scaffolds were after-treated with water vapor, and their nanofibrous structures were almost maintained. From the cytocompatibility and cell behavior on the chitin/SF blend or hybrid nanofibrous scaffolds, the hybrid matrix with 25% chitin and 75% SF as well as the chitin/SF blend nanofibers could be a potential candidate for tissue engineering scaffolds.
International Journal of Biological Macromolecules 06/2008; 42(4):324-34. · 2.45 Impact Factor
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ABSTRACT: Electrospinning of collagen (COL)/silk fibroin (SF) blend solutions in 1,1,1,3,3,3-hexafluoro-2-propanol was investigated for fabrication of a biocompatible and biomimetic nanostructured scaffold for tissue engineering. The morphology of the electrospun COL/SF blend nanofibers was observed by scanning electron microscopy. The average diameters of COL/SF blend fibers ranged from 320 to 360 nm, irrespective of SF content in the blends. Both COL and SF components in the as-spun COL/SF blend matrices were stabilized by glutaraldehyde and water vapor, respectively, under the saturated glutaraldehyde aqueous solution at 25 degrees C. The glutaraldehyde vapor chemically stabilized the COL component via cross-linking, whereas the water vapor physically stabilized the SF component via crystallization to the beta-sheet structure. These structural changes of after-treated COL/SF blend matrices were examined using ATR-IR and CP/MAS (13)C NMR spectroscopy. To assay the cytocompatibility and cellular behavior of the COL/SF blend nanofibrous scaffolds, cell attachment and the spreading of normal human epidermal keratinocytes (NHEK) and fibroblasts (NHEF) seeded on the scaffolds were studied. In addition, both morphological changes and cellular responses of COL/SF blend nanofibrous matrices were also compared with COL/SF hybrid nanofibrous matrices. Generally similar levels of cell attachment and spreading of NHEF were shown in the COL/SF blend nanofibrous matrix compared with those of the pure COL and pure SF matrices; the cellular responses of NHEK were, however, markedly decreased in the COL/SF blend nanofibrous matrix as compared to the pure matrices. In contrast, cell attachment and spreading of NHEK on the COL/SF hybrid nanofibrous matrix were significantly higher than that of the COL/SF blend nanofibrous matrix. Our results indicate that a COL/SF hybrid nanofibrous matrix may be a better candidate than a COL/SF blend nanofibrous matrix for biomedical applications such as wound dressing and scaffolds for tissue engineering.
Biomacromolecules 05/2008; 9(4):1106-16. · 5.48 Impact Factor
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ABSTRACT: A poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) fibrous surface with various bead-on-string structures was fabricated by electrospinning. PHBV was electrospun at various concentrations and then CF4 plasma treatment was employed to further improve the hydrophobicity of the PHBV fiber surfaces. The surface morphology of the electrospun PHBV mats was observed by scanning electron microscopy (SEM). The surface properties were characterized by water contact angle (WCA) measurements and X-ray photoelectron spectroscopy (XPS). The surface morphology of the electrospun PHBV fibrous mats with the bead-son-string structure varied with the solution concentration. The WCA of all of the electrospun PHBV mats was higher than that of the PHBV film. In particular, a very rough fiber surface including porous beads was observed when PHBV was electrospun from the solution with a concentration of 26 wt%. Also, its WCA further increased from 141 degrees to 158 degrees after CF(4) plasma treatment for 150 s. PHBV can be rendered superhydrophobic by controlling the surface morphology and surface energy, which can be achieved by adjusting the electrospinning and plasma treatment conditions.
Journal of Colloid and Interface Science 05/2008; 320(1):91-5. · 3.07 Impact Factor
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ABSTRACT: Compared with braided multifilament sutures, absorbable monofilaments are attractive suture materials as they exhibit less tissue drag and cause less tearing because of their smooth surfaces. However, monofilament sutures are less flexible and more difficult to tie a knot than multifilament ones, and their knots are more likely to loosen due to inferior knot security. Although various approaches have been reported to improve the flexibility of monofilament sutures, they still have limitations regarding poor knot security. To address this problem, we developed a novel technique to fabricate monofilament sutures by a conjugate spinning method, resulting in the formation of a sea/islands type of bicomponent monofilament suture. These sea/islands type bicomponent monofilament sutures, which can place many fine strands of a polymeric fiber within a matrix of another polymer, exhibited excellent knot security, flexibility, and low strain energy, compared with commercially available monofilament sutures.
Journal of Biomedical Materials Research Part B Applied Biomaterials 12/2007; 83(2):499-504. · 2.15 Impact Factor
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ABSTRACT: PLGA nanofibers were prepared by an electrospinning method (mean diameter, 340 nm) and treated with plasma in the presence of either oxygen or ammonia gas to modify the surface of the nanofibers. The surface hydrophilicity of electrospun PLGA nanofibers was greatly increased by plasma treatment, which was confirmed by contact angle measurement. XPS analysis demonstrates that the number of polar groups on the surface of PLGA nanofibers after plasma treatment was increased, and this was considered to contribute to the enhanced surface hydrophilicity of the nanofibers. This approach to controlling the surface properties and structures of nanofibers could be useful in the design and tailoring of novel synthetic extracellular matrices for tissue engineering applications.
Macromolecular Symposia 03/2007; 249-250(1):103 - 108.
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ABSTRACT: YBa2Cu3O7−δ superconducting nanofibres were successfully fabricated via the electrospinning method in combination with the sol–gel process. The solution was prepared by the sol–gel process with a homogeneous aqueous PVA solution containing Y, Ba, and Cu acetates. The viscosity of the precursor sol for electrospinning was controlled by the evaporation of solvent and a condensation reaction. The electrospun nanofibres were pyrolysed to remove PVA or volatile components, and then sintered to generate a superconducting phase. The critical transition temperature (Tc) of superconducting YBa2Cu3O7−δ nanofibres was measured by DC susceptibility tests. By optimizing the electrospinning process and following heat treatments, superconducting YBa2Cu3O7−δ nanofibres with a Tc = 92.2 K could be produced.
Superconductor Science and Technology 10/2006; 19(12):1264. · 2.66 Impact Factor
