Preparation and antibacterial activity of electrospun chitosan/poly(ethylene oxide) membranes containing silver nanoparticles

Fairly uniform chitosan (CS)/poly(ethylene oxide) (PEO) ultrafine fibers containing silver nanoparticles (AgNPs) were successfully prepared by electrospinning of CS/PEO solutions containing Ag/CS colloids by means of in situ chemical reduction of Ag ions. The presence of AgNPs in the electrospun ultrafine fibers was confirmed by X-ray diffraction patterns. The AgNPs were evenly distributed in CS/PEO ultrafine fibers with the size less than 5 nm observed under a transmission electron microscope. X-ray photoelectron spectroscopy suggested that the existence of Ag―O bond in the composite ultrafine fibers led to the tight combination between Ag and CS. Evaluation of antimicrobial activities of the electrospun Ag/CS/PEO fibrous membranes against Escherichia coli showed that the AgNPs in the ultrafine fibers significantly enhanced the inactivation of bacteria.     

Thermomechanical and structural characterization of polybutadiene/poly(ethylene oxide)/CNT stretchable electrospun fibrous membranes

It is difficult to produce rubbery polymer nanofibers, that is, polybutadiene, by the method of electrospinning, since during electrospinning rubbery polymer fibers join and entangles due to their low T_g. For this reason, it is not easy to achieve the fiber form out of these polymers. Homogeneously electrospun carbon nanotubes (CNT)‐filled polybutadiene (PBu) and poly(ethylene oxide) (PEO) composite elastomeric fibers exhibit distinctive physical features such as uniform fiber diameter and distribution with significant improvements in thermomechanical properties. Controlled hydrophilicity/hydrophobicity with the components allows to generate homogenous, thermally stable and stretchable bio‐composite scaffold, and fibrous antibacterial membrane scaffolds out of PBu/PEO/CNT composite. We have combined the exciting properties of PEO with high pore density with the rubber elasticity of PBu via dissolving them in a dichloromethane/ethyl acetate organic solvent, and subsequently producing electrospun woven fibers with different PBu/PEO ratios. Frequency‐dependent thermomechanical characterization via dynamic mechanical analysis reveals pronounced changes in the onset and extent of melting, as well as the storage and loss modulus values at the onset of melting, in particular when small amounts (1.25% by wt%) of CNTs are present. The characteristic bands were detected for the PBu/PEO and PBu/PEO/CNT samples by means of Raman and Fourier‐transform infrared spectroscopy. CNT addition increases the hydrophobicity via the increase in roughness as attained by atomic force microscopy.     

Zein supports scaffolding capacity toward mammalian cells and bactericidal and antiadhesive properties on poly(ε-caprolactone)/zein electrospun fibers

Studies investigate the electrospinnability of poly(ε-caprolactone)/protein blends to produce fibers for tissue engineering applications. However, no reports show that zein can improve the scaffolding capacity toward stem cells and promote antiadhesive and bactericidal properties to the poly(ε-caprolactone)/zein fibers. We create fibers with average diameters ranging from 200 to 400 nm from the electrospinning of poly(ε-caprolactone)/protein mixtures. Poly(ε-caprolactone)/zein blends are electrospinnable at zein concentration between 20 and 40 wt% in a 70/30 formic acid/acetic acid mixture. Water contact angle measurements indicate that zein increases fiber hydrophilicity. The water contact angle decreases from 118° (pure poly(ε-caprolactone) fiber) to 73° for the scaffold containing 40 wt% zein. The zein (40 wt%) significantly increases Young's modulus from 260 MPa (pure poly(ε-caprolactone) fibers) to 980 MPa (poly(ε-caprolactone)/zein fibers) with no substantial influence on elongation at break (ε ≥ 125%) and tensile strength (≥0.040 MPa). The electrospun scaffolds containing zein also promote cell adhesion, proliferation, and spreading of adipose-derived human mesenchymal stem cells for at least 7 days of culture. The zein on poly(ε-caprolactone)/zein fibers can prevent the attachment and proliferation of Escherichia coli and Staphylococcus aureus. We propose these materials for wound healing and skin repair.     

Electrospinning of ultra-thin polymer fibers

The electrospinning technique was used to spin ultra-thin fibers from several polymer/solvent systems. The diameter of the electrospun fibers ranged from 16 nm to 2 μm. The morphology of these fibers was investigated with an atomic force microscope (AFM) and an optical microscope. Polyethylene oxide) (PEO) dissolved in water or chloroform was studied in greater detail. PEO fibers spun from aqueous solution show a “beads on a string” morphology. An AFM study showed that the surface of these fibers is highly ordered. The “beads on a string” morphology can be avoided if PEO is spun from solution in chloroform; the resulting fibers show a lamellar morphology. Polyvinylalcohol (PVA) dissolved in water and cellulose acetate dissolved in acetone were additional polymer/solvent systems which were investigated. Furthermore, the electrospinning process was studied: different experimental lay-outs were tested, electrostatic fields were simulated, and voltage - current characteristics of the electrospinning process were recorded.     

Mimetics of Eggshell Membrane Protein Fibers by Electrospinning

Summary: Mimetics of eggshell membrane protein fibers have been obtained with an electrospinning technique based on soluble eggshell membrane protein (SEP) prepared previously. Poly(ethylene oxide), a biocompatible and water soluble polymer, is used to improve the processability of SEP. Blends of SEP/PEO aqueous solutions were electrospun. The diameters of the fibers are 0.3–20 μm depending on the concentration of the solution and the proportion of SEP/PEO. Two “cross‐linking” methods are investigated in order to improve the anti‐water property of the fibers.

Scanning electron micrograph of electrospun fibers.     

Morphology,Crystallization Behavior and Tensile Properties of β-Nucleated Isotactic Polypropylene Fibrous Membranes Prepared by Melt Electrospinning

β-nucleated isotactic polypropylene(iPP) fibers with diameters less than 5 μm were prepared through melt electrospinning. The effects of electrospinning process and rare earth β-nucleating agent(WBG) on the crystal structure of iPP fibers were investigated. The results indicate that the addition of WBG can improve the fluidity of iPP melt remarkably and help the formation of fine fibers with thinner diameter, while the electrostatic force applied on the iPP melt is not favorable for the formation of β-crystal in iPP fibers. In addition, the morphology and crystalline structure of WBG/iPP electrospun fibers depended on the content of WBG. Both the crystallinity and the percentage of β-crystal form of WBG/iPP electrospun fibers increase with the rise of the content of nucleating agent, which endows the prepared electrospun fibers excellent mechanical properties. The β-nucleated iPP electrospun fibrous membranes prepared in this study can be used for protective clothing material, filtration media, reinforcement for composites and tissue engineering scaffolds.     

Electrospinning of poly(vinyl pyrrolidone)-iodine complex and poly(ethylene oxide)/poly(vinyl pyrrolidone)-iodine complex - a prospective route to antimicrobial wound dressing materials

New nanofibers containing poly(vinyl pyrrolidone)-iodine complex (PVP-iodine) were obtained by electrospinning in order to prepare materials suitable for wound dressings. Different approaches were used: a one-step method based on electrospinning of PVP-iodine or poly(ethylene oxide)/PVP-iodine solutions and a three-step method based on electrospinning of PVP or poly(ethylene oxide)/PVP mixed solutions followed by photo-mediated crosslinking of the obtained nanofibers and subsequent complexation with iodine. The average diameters of the fibers were in the range 150-470 nm depending on the composition and on the applied field strength (AFS) and increased with increasing the amount of PEO in the spinning solutions. Higher AFS resulted in greater fiber diameter and in size distribution broadening. Photo-mediated crosslinking in the presence of 4,4′-diazidostilbene-2,2′-disulfonic acid disodium salt successfully stabilized the electrospun PVP and PEO/PVP nanofibers against water and water vapor.     

Electrospinning of nylon-6,66,1010 terpolymer

Ultrafine nylon fibers were prepared by electrospinning of nylon-6,66,1010 terpolymer solution in 2,2,2-trifluoroethanol (TFE). The morphology, crystallinity and mechanical properties of the electrospun nylon-6,66,1010 fibers were investigated by scanning electron microscope (SEM), differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXD) and tensile test. The effects of electrospun process parameters such as solution concentration, voltage and tip-to-collector distance on the morphology and the average size of the electrospun fibers were also studied. The results show that the spinnable concentration of nylon-6,66,1010/TFE solution is in the range of 6-14 wt%, and higher solution concentration favors the formation of uniform fibers without beads. The diameters of the electrospun fibers increase with increasing the solution concentration and decrease slightly with increasing the voltage and needle tip-to-collector distance. But no obvious morphology changes were found with the increase of the voltage and collection distance. DSC and WAXD results suggest that the electrospun nylon-6,66,1010 membranes have lower crystallinity than those of the corresponding casting films. The electrospun nylon-6,66,1010 membrane obtained from the 14 wt% concentration exhibits the largest tensile strength and elongation at break.     

Emulsion electrospinning: composite fibers from drop breakup during electrospinning

We evaluate the feasibility of electrospinning oil‐in‐water type emulsions. The emulsions had an aqueous solution of polyethylene oxide (PEO) as the continuous phase, and either mineral oil or a polystyrene (PS) in toluene solution as the drop phase. The Taylor cones and electrified liquid jets were stable even when the emulsion drops were as large as a few‐ten microns in diameter. The resulting electrospun PEO fibers incorporated the dispersed phase of the emulsion in the form of drops (in case of mineral oil), or in the form of solid particles (in case of PS). Mineral oil drops appear to be completely encapsulated in the PEO fibers, whereas the PS particles are either incompletely encapsulated, or covered by only a very thin layer of PEO. Calculations show that in both cases, the initially large emulsion drops are broken during the electrospinning process. Copyright © 2007 John Wiley & Sons, Ltd.     

Effects of poly(ethylene oxide) and pH on the electrospinning of whey protein isolate

Poly(ethylene oxide) (PEO) is known for facilitating the electrospinning of biopolymer solutions, which are otherwise not electrospinnable. The objective of this study was to improve the understanding of the positive effects of PEO on the electrospinning of whey protein isolate (WPI) solutions under different pH conditions. Alterations in protein secondary structure and polymer solution properties (viscosity, conductivity, and dynamic surface tension), as induced by pH changes, significantly affected the electrospinning behavior of WPI/PEO (10% w/w: 0.4% w/w PEO) solutions. Acidic solutions resulted in smooth fibers (707 ± 105 nm) while neutral solutions produced spheres (2.0 ± 1.0 μm) linked with ultrafine fibers (138 ± 32 nm). In comparison, alkaline solutions produced fibers (191 ± 36 nm) that were embedded with spindle‐like beads (1.0 ± 0.5 μm). ¹³C NMR and FTIR spectroscopies showed that the increase in random coil and α‐helix secondary structures in WPI were the main contributors to the formation of bead‐less electrospun fibers. The electrospinning‐enabling properties of PEO on aqueous WPI solutions were attributed to physical chain entanglement between the two polymers, rather than specific polymer–polymer interactions. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Centrifugally spun poly(ethylene oxide) fibers rival the properties of electrospun fibers

Centrifugal force spinning (CFS), also known as centrifugal spinning, forcespinning, or rotary jet spinning, provides considerably higher production rates than electrospinning (ES), but the more widespread use of CFS as an alternative depends on the ability to produce fibers with robust thermal and mechanical properties. Here, we report the CFS of poly(ethylene oxide) (PEO) fibers made using a spinning dope formulated with acetonitrile (AcN) as the volatile solvent, and we describe the thermal and mechanical properties of the centrifugally-spun fibers. Even though the formation, diameter, and morphology of electrospun and centrifugally-spun PEO fibers are relatively well-studied, the article presents three crucial contributions: the pioneering use of PEO solutions in AcN as spinning dope, characterization of crystallinity and mechanical properties of the centrifugally-spun PEO fibers, and a comparison with the corresponding properties of electrospun fibers. We find that fiber formation occurrs for the chosen CFS conditions if polymer concentration exceeds the entanglement concentration, determined from the measured specific viscosity. Most significantly, the centrifugally spun PEO fibers display crystallinity, modulus, elongation-at-break, and fiber diameter that rival the properties of electrospun PEO fibers reported in the literature.     

Electrospun poly(3‐hexylthiophene)/poly(ethylene oxide)/graphene oxide composite nanofibers: effects of graphene oxide reduction

In this article, we report on the production by electrospinning of P3HT/PEO, P3HT/PEO/GO, and P3HT/PEO/rGO nanofibers in which the filler is homogeneously dispersed and parallel oriented along the fibers axis. The effect of nanofillers' presence inside nanofibers and GO reduction was studied, in order to reveal the influence of the new hierarchical structure on the electrical conductivity and mechanical properties. An in‐depth characterization of the purity and regioregularity of the starting P3HT as well as the morphology and chemical structure of GO and rGO was carried out. The morphology of the electrospun nanofibers was examined by both scanning and transmission electron microscopy. The fibrous nanocomposites are also characterized by differential scanning calorimetry to investigate their chemical structure and polymer chains arrangements. Finally, the electrical conductivity of the electrospun fibers and the elastic modulus of the single fibers are evaluated using a four‐point probe method and atomic force microscopy nanoindentation, respectively. The electrospun materials crystallinity as well as the elastic modulus increase with the addition of the nanofillers while the electrical conductivity is positively influenced by the GO reduction. Copyright © 2016 John Wiley & Sons, Ltd.     

Electrospinning and cutting of ultrafine bioerodible poly(lactide‐co‐ethylene oxide) tri‐ and multiblock copolymer fibers for inhalation applications

Triblock copolymers made up of poly(ethylene oxide) (PEO) and polylactide (PLA) were synthesized and converted to fibers by the electrospinning process. A two‐step in situ‐synthesis in bulk was applied to extend PLA‐PEO‐PLA triblock copolymers with relatively short block length and low molecular weight in order to obtain electrospinnable materials. DL‐lactide was polymerized to the hydroxyl chain ends of PEO via the stannous octoate route. Hexamethylene diisocyanate (HDI) was added as chain extender in the second step, leading to poly(ether‐ester‐urethane) multiblock copolymers. The materials were electrospun from solutions in chloroform. Different concentrations and voltages were analyzed. The ether and ester blocks were varied in their block length and their effects on the fiber morphology was studied. Variations in the electrical conductivity of the chloroform solutions were investigated by adding triethyl benzyl ammonium chloride (TEBAC) in different amounts. Finally, with high quality electrospun PLA‐PEO‐PEO triblock copolymer fibers mechanical cutting was possible. Copyright © 2009 John Wiley & Sons, Ltd.     

Novel antibacterial fibers of quaternized chitosan and poly(vinyl pyrrolidone) prepared by electrospinning

The preparation of continuous defect-free fibers from quaternized chitosan derivative (QCh) has been achieved by electrospinning of mixed aqueous solutions of QCh with poly(vinyl pyrrolidone) (PVP). The average fiber diameter significantly decreases from 2800 to 1500 nm on increasing the polyelectrolyte content. In order to impart to QCh/PVP electrospun fibers stability to water and water vapor, the fibers have been crosslinked by incorporation of photo-crosslinking additives into QCh/PVP spinning solutions and subsequent UV irradiation of the electrospun fibers. Photo-crosslinked QCh-containing electrospun mats show high antibacterial activity against the Gram-positive bacteria Staphylococcus aureus and Gram-negative bacteria Escherichia coli.     

Chitosan/PEO nanofibers electrospun on metallized track-etched membranes: fabrication and characterization

The development of next-generation adsorption, separation, and filtration materials is growing with an increased research focus on polymer composites. In this study, a novel blend of chitosan (CS) and polyethylene oxide (PEO) nanofiber mats was electrospun on titanium (Ti)-coated polyethylene terephthalate (PET) track-etched membranes (TMs) with after-treatment by glutaraldehyde in the vapor phase for enhancing the nanofiber stability by crosslinking. The prepared composite, titanium-coated track-etched nanofiber membrane (TTM-CPnf) was characterized by Fourier transform infra-red (FTIR), water contact angle, and scanning electron microscopy (SEM) analyses. Smooth and uniform CS nanofibers with an average fiber diameter of 156.55 nm were produced from a 70/30 CS/PEO blend solution prepared from 92 wt. % acetic acid and electrospun at 15 cm needle to collector distance with 0.5 mL/h flow rate and an applied voltage of 30 kV on the TTM-CPnf. Short (15 min) and long (72 h)-term solubility tests showed that after 3 h, crosslinked nanofibers were stable in acidic (pH = 3), basic (pH = 13), and neutral (pH = 7) solutions. The crosslinked TTM-CPnf material was biocompatible based on the low mortality of freshwater crustaceans Daphnia magna. The composite membranes comprised of electrospun nanofiber and TMs proved to be biocompatible and may thus be suitable for diverse applications such as dual adsorption–filtration systems in water treatment.     

Lignin bio-oil-based electrospun nanofibers with high substitution ratio property for potential carbon nanofibers applications

We reported a new approach for development of lignin bio-oil-based electrospun nanofibers (LENFs) that had high substitution ratio (up to 80 wt%) and good morphology. This approach was particularly unique and translatable as it used small molecule lignin bio-oil with high reactivity and low heterogeneity obtained via lignin depolymerization reaction to produce well-oriented LENFs. Firstly, effects of various blends solutions ratios and electrospinning parameters on the characteristics of the obtained LENFs were analyzed. The results showed that the optimal parameters that resulted in the best electrospun nanofibers were as follows: blend solution ratio, the 20 wt% blend solution containing 80 wt% straw lignin bio-oil (SLB) and 20 wt% polyacrylonitrile (PAN), flow rate, 1 mL/h, voltage, 20 kV, rotational speed, 500 r/min and the distance between needle and collection screen, 20 cm. Secondly, used the best LENFs, we also applied to prepare lignin bio-oil-based carbon nanofibers (LCNFs) and estimated its properties by scanning electron microscope (SEM), X-ray diffraction (XRD) patterns, Raman spectroscopy and tension testing. Our results demonstrated that compared with pure PAN carbon nanofibers (PCNFs), the as-prepared LCNFs had similar smooth surfaces, similar crystallinity and similar mechanical properties. This work can promote the utilization of lignin depolymerization main-products to produce lignin-based materials, while also help to reduce use of high-cost PAN.     

Electrospinning of cyclodextrin functionalized polyethylene oxide (PEO) nanofibers

By means of the electrospinning technique we have successfully synthesized cyclodextrin (CD) functionalized polyethylene oxide (PEO) nanofibers (PEO/CD) with the ultimate goal to develop functional nanowebs. Three different types of CDs; α-CD, β-CD and γ-CD are incorporated individually in electrospun PEO nanofibers. The aqueous solutions containing different amount of PEO (3%, 3.5% and 4% (w/v), with respect to solvent) and CDs (25% and 50% (w/w), with respect to PEO) are electrospun and bead-free nanofibers are obtained. The presence of the CDs in the PEO solutions is found to facilitate the electrospinning of bead-free nanofibers from the lower polymer concentrations and this behavior is attributed to the high conductivity and viscosity of the PEO/CD solutions. The presence of CDs in the electrospun PEO nanofibers is confirmed by Fourier transform infrared (FTIR) spectroscopy studies. The 2-D X-ray diffraction (XRD) spectra of PEO/CD nanowebs did not show any significant diffraction peaks for CDs indicating that the CD molecules are distributed within the polymer matrix without any phase separated crystalline aggregates.     

聚乙二醇-b-聚乳酸的合成及其电纺形成超细纤维研究

为了提高聚乳酸的亲水性,以辛酸亚锡为催化剂、聚乙二醇单甲醚(mPEG)为大分子引发剂进行丙交酯(LLA)开环聚合,合成聚乙二醇-b-聚乳酸两嵌段共聚物(PELA).以红外光谱1、H核磁共振谱、接触角测试、差热扫描量热分析等方法对PELA的结构及性能进行表征.结果表明,通过调控mPEG与LLA的投料比可以控制PELA的相对分子质量,而随着mPEG组分含量或链长增加,共聚物亲水性增强,但其Tg、Tcc、Tm有所降低.由普通电纺制备PELA超细纤维,并分别由乳液电纺和同轴电纺得到以水溶性聚氧化乙烯(PEO)为芯、PELA为壳的芯/壳结构复合超细纤维(E-PEO/PELA和C-PEO/PELA).扫描电镜和透射电镜结果表明,PELA、E-PEO/PELA和C-PEO/PELA超细纤维形貌良好.随着PELA中mPEG含量的增加,电纺PELA纤维膜的吸水率增强,而由乳液电纺和同轴电纺制备的PEO/PELA芯/壳结构超细纤维膜,亲水性均好于PELA超细纤维膜.     

Enhanced orientation of PEO polymer chains induced by nanoclays in electrospun PEO/clay composite nanofibers

Polymer fibers composed of poly(ethylene oxide) (PEO) and nanoclay were fabricated by electrospinning. The morphology of the composite nanofibers was characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM), which showed aligned nanoclays in the fibers. Polarized Fourier transform infrared (FT-IR) spectroscopy revealed that the PEO chains in the composite fibers exhibit a higher degree of orientation than that in PEO nanofibers containing no nanoclay. It is believed that spatial confinement is present in the electrospun nanofibers, which results in the enforcement of the mutual restriction. The anisotropic hierarchical nanostructure may have potential applications in optics, mechanical materials, and biomedical materials for cell culture.     

聚偏氟乙烯电纺膜及其电化学性能的研究

用电纺的方法制备了聚偏氟乙烯纳米纤维膜,它们具有多微孔结构,能够作为锂电池聚合物电解质.电纺中聚合物溶液的浓度对制备的电纺膜的结构形态有很大的影响,低浓度(10 wt%)时得到珠丝结构的膜,浓度15 wt%时则为纤维结构,而高浓度(18 wt%)时,电纺膜为交联的网状结构.用电纺法制备的聚偏氟乙烯纳米纤维微孔膜具有较高的孔隙率,而且它们与锂金属电极具有良好的界面稳定性;在25℃时吸液率最高可达340%,以这种膜制备的聚合物电解质室温电导率可达到1.57×10-3S.cm-1;由该电解质组装的扣式电池以0.5 mA.cm-2恒流充放电,25℃时50次循环后几乎无容量损失,具有良好的循环性能;即使60℃时,电池仍能保持良好的工作稳定性.