Electrospinning Of Poly Research Articles

Boosted electrochemical properties of polyimide-based carbon nanofibers containing micro/mesopore for high-performance supercapacitors by thermal rearrangement

In this work, the hydroxyl-containing polyimide(HPI) nanofibers were fabricated by the electrospinning of poly(amic acid)(PAA) derived from pyromellitic anhydride(PMDA) and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane(6FAP), followed by thermal imidization. After further thermal rearrangement from HPI to polybenzoxazole(PBO) and pyrolysis, the HPI-based carbon nanofibers(HPICNFs) were obtained with abundant nitrogen and oxygen doping content. The effects of PAA concentration, thermally rearranged time and carbonizing temperature on the electrochemical performance of HPICNFs were evaluated. When the PAA concentration was 20%, the thermal rearrangement time was 2 h and the carbonization temperature was 800 °C, the specific surface area and pore volume of the HPICNFs reached 1107.6 m2 g−1 and 0.6204 cm3 g−1. Due to the abundant micro- and mesoporous structures, the HPICNFs exhibited a high specific capacitance of 263.9 F g−1 and excellent capacity retention rate about 75% from 0.5 to 10 A g−1. After 10,000 charging and discharging cycles, the capacitance retention of the symmetrical coin cell was maintained at about 99.82%, indicating superior long-term charging-discharging cycle stability. Additionally, a light-emitting diode was successfully lighted up by the three coin cells. Thus, this work provides a facile way to prepare the HPICNFs by thermal rearrangement and carbonization, which are expected to be used as high-performance electrode materials for supercapacitors.

Bicomponent PLA Nanofiber Nonwovens as Highly Efficient Filtration Media for Particulate Pollutants and Pathogens.

Herein, a novel form of bicomponent nanofiber membrane containing stereo-complex polylactic acid (SC-PLA) was successfully produced by the side-by-side electrospinning of Poly (L-lactic acid) (PLLA) and Poly (D-lactic acid) (PDLA). We demonstrate that through these environmentally sustainable materials, highly efficient nanofiber assemblies for filtration can be constructed at very low basis weight. The physical and morphological structure, crystalline structure, hydrophobicity, porous structure, and filtration performance of the fibrous membranes were thoroughly characterized. It was shown that the fabricated polylactic acid (PLA) side-by-side fiber membrane had the advantages of excellent hydrophobicity, small average pore size, high porosity, high filtration efficiency, low pressure drop as well as superior air permeability. At the very low basis weight of 1.1 g/m2, the filtration efficiency and pressure drop of the prepared side-by-side membrane reached 96.2% and 30 Pa, respectively. Overall, this biomass-based, biodegradable filtration material has the potential to replace the fossil fuel-based polypropylene commercial meltblown materials for the design and development in filtration, separation, biomedical, personal protection and other fields.

Pepsin immobilization by electrospinning of poly(vinyl alcohol) nanofibers

AbstractThe enzyme pepsin (E.C. 3.4.23.1, strength ≥400 μ/mg) was immobilized in poly(vinyl alcohol) (PVA) nanofibers for the first time by the electrospinning technique. The morphology of the nanofibers analyzed by SEM showed a diameter in the nanometric range of 70–165 nm. The presence of pepsin in the nanofibrous matrix was proved by infrared spectroscopy (FTIR). The immobilization process was carried out through crosslinking by exposure to glutaraldehyde (GA) vapor. The thermal analysis by differential scanning calorimetry (DSC) showed the effect of crosslinking time and enzyme concentration on the glass transition temperature (Tg) and heat of fusion (Hf) of the nanofibrous matrix. The optimum catalytic performance of the immobilized pepsin was reached at pH 3, 1 h of crosslinking and 25% of enzyme concentration. The enzymatic activity of immobilized pepsin reached 96% of the crude enzyme. The immobilization process allowed 4 cycles of reuse and up to 10 days of storage for the crosslinked samples. PVA nanofibers was successfully used as vehicle for the encapsulation and immobilization of the pepsin enzyme.

The performance of heparin modified poly(ε-caprolactone) small diameter tissue engineering vascular graft in canine-A long-term pilot experiment in vivo.

Long-term in vivo observation in large animal model is critical for evaluating the potential of small diameter tissue engineering vascular graft (SDTEVG) in clinical application, but is rarely reported. In this study, a SDTEVG is fabricated by the electrospinning of poly(ε-caprolactone) and subsequent heparin modification. SDTEVG is implanted into canine's abdominal aorta for 511 days in order to investigate its clinical feasibility. An active and robust remodeling process was characterized by a confluent endothelium, macrophage infiltrate, extracellular matrix deposition and remodeling on the explanted graft. The immunohistochemical and immunofluorescence analysis further exhibit the regeneration of endothelium and smooth muscle layer on tunica intima and tunica media, respectively. Thus, long-term follow-up reveals viable neovessel formation beyond graft degradation. Furthermore, the von Kossa staining exhibits no occurrence of calcification. However, although no TEVG failure or rupture happens during the follow-up, the aneurysm is found by both Doppler ultrasonic and gross observation. Consequently, as-prepared TEVG shows promising potential in vascular tissue engineering if it can be appropriately strengthened to prevent the occurrence of aneurysm.

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.

Effect of coating on the mechanical properties of electrospun poly(3-hydroxybutyrate) materials with targeted fibers alignment

Understanding the mechanical behavior of electrospun materials and how to control it is important and valuable in terms of their future applications. That is why, in this study, materials with controlled fibers alignment and desired mechanical properties were fabricated by electrospinning of poly(3-hydroxybutyrate) (PHB) onto three types of rotating collectors – drum (smooth), blade and grid (patterned). In addition, by controlling the collector rotation speed and by coating of the PHB mats with chitosan or cellulose acetate, purposely tailored fibers alignment and targeted design of the materials were achieved. Further, the detailed surface morphology, thermal behavior and crystallinity of the PHB materials were characterized by SEM, DSC and XRD. It was demonstrated that patterned collectors had a significant impact on fibers alignment only at lower rotation speed, whereas with the increase in the collector speed the fibers alignment increased in the direction of collector rotation. The materials strength was evaluated by tensile tests and indicated that PHB materials fabricated at lower collector rotation speed exhibited isotropic mechanical properties, whereas those at higher collector rotation speed – anisotropic. In addition, coating of PHB materials with chitosan or cellulose acetate enhanced their mechanical properties. Hence, this study demonstrates the possibilities for fabrication of electrospun materials with desired fibers alignment and thus, with targeted mechanical properties.

Electrospinning of Poly(1,4‐Cyclohexanedimethylene Acetylene Dicarboxylate): Study on the Morphology, Wettability, Thermal and Biodegradation Behaviors

AbstractThis study is conducted to evaluate the biodegradation and thermal features of poly(1,4‐cyclohexanedimethylene acetylene dicarboxylate) (PCA) based films and fibers. The PCA is characterized by Fourier transform infrared (FT‐IR) and proton nuclear magnetic resonance (1H‐NMR) spectroscopies and gel permeation chromatography (GPC). The beadless fibers of PCA are achieved by electrospinning from its solution under ambient conditions for the first time. The effects of applied voltage and tip‐to‐collector distance (TCD) on the various properties such as morphology, wettability, thermal, and biodegradability behaviors of fibers are investigated by comparing the non‐electrospun PCA. Morphologies and average frequency distributions of the electrospun samples are elucidated by scanning electron microscopy (SEM). Wettability properties of the studied samples are determined by water contact angle (WCA) measurements, whereas thermo‐stabilities and glass transition temperatures (Tg) are established by thermogravimetric and differential scanning calorimetry analyses (TGA and DSC), respectively. Biodegradation studies indicate that 28% of electrospun PCA achieved at 8 mL h−1 flow rate, 20 cm TCD and 25 kV applied voltage can be enzymatically degraded within 15 days. It is thus estimated that PCA with good electrospun and biodegradation abilities will favorable candidates for bio‐polyester applications.

Electrospun pH responsive poly (acrylic acid-co- acrylamide) hydrogel nanofibrous mats for drug delivery

In the present study hydrogel nanofibrous mats are prepared through electrospinning of poly (acrylamide-co-acrylic acid) dope solution having polyethylene glycol as cross-linker. The electrospun mats are heat treated at 150 °C to induce esterification crosslinking reaction. The mats are characterized for their structural, morphological and thermal behaviour. The average diameter of hydrogel nanofibers is found to be 275 ± 94.5 nm. The swelling behaviour of nanofibrous mats is evaluated in the phosphate buffer solutions of different pHs in the range of 2 to 8.5 and is found to be highest at neutral pH. The nanofibrous mats are loaded with amoxicillin drug for antimicrobial activity and drug release behaviour. The drug loaded mats form a clear inhibition zone with both Gram-positive bacteria S. aureus and Gram-negative bacteria E. coli in disc diffusion test. Drug is released at all the pHs (2 to 8.5) and maximum release is observed at neutral pH. The kinetics of drug release follows Fickian diffusion (n < 0.5) at tested pH.

Electrospun Poly(ε-caprolactone)/Gelatin Nanofibrous Mat Containing Selenium as a Potential Wound Dressing Material: In Vitro and In Vivo Study

In the current study, selenium particles were loaded into poly(e-caprolactone)/gelatin nanofibrous matrices in order to fabricate a potential wound dressing. The mats were produced by electrospinning of poly(e-caprolactone)/Gelatin (1:1 (w/w)) solution supplemented with 1 and 10 % (w/v) of selenium particles. Prepared wound dressings were investigated regarding their morphology, mechanical properties, surface wettability, water-uptake capacity, water vapor permeability, porosity, blood compatibility, microbial penetration test and cellular response. Dressings containing 1 % and 10 % selenium and selenium free mats were chosen to treat the full-thickness excisional wounds in Wistar rats. The study revealed that after 14 days, the wound closure of the mat containing 1 % selenium was about 95.5±6.38 % while wound closure of the negative control group was about 48.83±4.03 %. Our results showed the capability of nanofibrous containing selenium for successful wound treatment.

Asymmetric Wettable Composite Wound Dressing Prepared by Electrospinning with Bioinspired Micropatterning Enhances Diabetic Wound Healing.

Wound dressings with asymmetric wettability surfaces can effectively prevent bacterial colonization and tissue dehydration and have shown great potential for diabetic wound healing applications. However, the construction of a highly hydrophobic outer surface with high biocompatibility and permeability is still the major challenge in the preparation of asymmetric wettable dressings. Inspired by the superhydrophobic surface structures existing in nature, an asymmetric wettable composite wound dressing with a highly hydrophobic outer layer was successfully prepared for diabetic wound healing in this study. The hydrophobic outer layer was fabricated by the electrospinning of poly(ε-caprolactone) (PCL) on a micron-pore-size nylon mesh template, and the hydrophilic inner layer was obtained by the electrospinning of pioglitazone-incorporated gelatin (Gel-pio). The hydrophobic outer layer of the dressing with a hierarchical micro-nanostructure exhibits excellent ability to waterproof and prevent bacterial adhesion, whereas the hydrophilic inner layer can promote cell proliferation, migration, and angiogenesis by its nanofiber structure and biocompatible gelatin composition. The presented dressing has good mechanical properties, permeability, and high biocompatibility. More importantly, the results of full-thickness skin wound model evaluation on db/db mice (type 2 diabetes) and STZ rats (type 1 diabetes) indicate that the developed dressing can promote wound healing by stimulating cell proliferation, angiogenesis, collagen deposition, and re-epithelialization. The findings of this study suggest that the bioinspired asymmetric wettable composite wound dressing can be used as a promising candidate for diabetic wound healing.

A comprehensive study on electrospinning of poly (vinyl alcohol): effects of the TCD, applied voltage, flow rate, and solution concentration

In the present work, the electrospun fibers of poly (vinyl alcohol) (PVA) are fabricated from its solution in water under ambient conditions, and the effect of altered working parameters used such as tip‐to‐collector distance (TCD), applied voltage, flow rate and solution concentration on the average diameter and frequency distribution of them is deeply discussed. The mean electrospun PVA fiber diameters and its distributions are estimated by combination of Scanning electron microscope (SEM) and ImageJ analyzer program which is extensively utilized in respective sciences. The achieved results from the experiments indicate that higher both TCD and applied voltage used decrease the average electrospun PVA fiber diameter. Conversely, when the flow rate or solution concentration is increased, diameters of achieved fibers are soared. It is anticipated that this comprehensive study will be beneficial to academia and industry worked on potential PVA fiber applications.

Effect of Mixed Solvents on the Structure and Properties of PLLA/PDLA Electrospun Fibers

The electrospinning of poly(L-lactic acid)/poly(D-lactic acid) (PLLA/PDLA) microfiber membranes were carried out with dichloromethane (DCM), DCM/ethanol, DCM/acetone, DCM/hexane as the spinning solvent. Scanning electron microscope observation showed that the electrospun fiber obtained using DCM/ethanol (L/D-DE) mixed solvent was homogeneous without visible bead, which was better than any others. Moreover, plenty of pores could be found on the surface of the fibers obtained using the mixed solvents. The porous structure of fibers was significantly influenced by the ethanol (non-solvent) content. When the DCM/ethanol was 50:10 (v/v), the fibers were uniform and had isolated pores. XRD and DSC results indicated that the exclusive stereocomplex poly(lactide acid) (sc-PLA) crystallites without any homocrystallites poly(lactide acid) (hc-PLA) did form in all types of fibers. The crystallinity of sc-PLA in the L/D-DE fiber was higher than other samples due to the slowest evaporation rate. TGA test further indicated that the thermal stabilities of PLLA/PDLA electrospun fibers were slightly better than the PLLA. Furthermore, L/D-DE had the excellent mechanical properties and underwent the course of ductile fracture. Possible mechanisms accounting for the morphologies and tensile properties were also proposed in this study.

Kefiran/poly(vinyl alcohol)/poly(vinyl pyrrolidone) composite nanofibers: fabrication, characterization and consideration of effective parameters in electrospinning

The kefiran/polyvinyl alcohol and polyvinyl pyrrolidone nanofibers were effectively fabricated for the first time using electrospinning of poly(vinyl alcohol), poly(vinyl pyrrolidone) and kefiran blend solution. The effect of solution parameters, such as kefiran concentration and poly(vinyl alcohol)/poly(vinyl pyrrolidone) mixing ratio, were considered. The parameters’ effects, such as voltage, nozzle-to-collector distance and feeding rate on nanofibers morphology, were also checked by the scanning electron microscopy images. After changing the parameters on different steps, designed by the chemo metrics software, the finest nanofibers were produced in the following conditions: 2% kefiran concentration, 30/70 kefiran/polymer mixing ratio, 12 kV voltage, 200 mm needle-to-collector distance and 0.5 (mL/h) polymer injection rate. The nanofibers produced in these conditions were uniform without knots or adhesion in the lowest diameter of 156 nm. Kefiran concentration and kefiran/polymer mixing ratio were found as the most effective parameter in the morphology and diameter size of the nanofibers. The attenuated total reflectance (ATR-Ft-IR), atomic force spectroscopy, differential scanning calorimeters and thermal gravimetric analysis were used to investigate molecular structures, three-dimensional morphology and heating properties of the nanofibers, respectively.

Improvement of Oxygen‐Depolarized Cathodes in Highly Alkaline Media by Electrospinning of Poly(vinylidene fluoride) Barrier Layers

AbstractOxygen‐depolarized cathodes (ODC) were developed for chlor‐alkali electrolysis to replace the hydrogen evolution reaction (HER) by the oxygen reduction reaction (ORR) providing electrical energy savings up to 30 % under industrially relevant conditions. These electrodes consist of micro sized silver grains and polytetrafluoroethylene, forming a homogeneous electrode structure. In this work, we report on the modification of ODCs by implementing an electrospun layer of hydrophobic poly(vinylidene fluoride) (PVDF) into the ODC structure, leading to a significantly enhanced ORR performance. The modified electrodes are physically characterized by liquid flow porometry, contact angle measurements and scanning electron microscopy. Electrochemical characterization is performed by linear sweep voltammetry and chronopotentiometry. The overpotential for ORR at application near conditions could be reduced by up to 75 mV at 4 kA m−2 and 135 mV at a higher current density of 9.5 kA m−2. Consequently, we propose that modifying ODCs by electrospinning is an effective and cost‐efficient way to further reduce the energy demand of the ORR in highly alkaline media.

Electrospinning of Poly(vinyl alcohol)-Graphene oxide aligned fibers

Abstract Electrospinning is a well know technology for the production of nano and micro fibers. Graphene has been used in different fields due to its unique stability. Reduced graphene oxide (rGO) is prepared from the reduction of graphene oxide. In this work, we electrospun of Polyvinyl Alcohol (PVA) solutions with rGO to combine the different physical properties of the materials, on a rotating collector to verify the influence of the solutions and rotation on the morphology of the fibers. The optimization of the process highlighted the influence of the flow rate and tip-collector distance in relation to the rotation speed used.

Biological evaluation of the effects of Hyaluronic acid on Poly (3-hydroxybutyrate) based Electrospun Nanocomposite scaffolds for cartilage tissue engineering application

ABSTRACTThis study aimed to develop a nanocomposite scaffold using electrospinning of Poly (3-hydroxybutyrate) (PHB), Chitosan (Cs), Multi Wall Carbon Nanotubes (MWNTs), and different concentrations of Hyaluronic Acid (HA). The results showed that an increasing in HA concentration from 0 to 15%wt significantly increased the nanofibers diameter and hydrophilicity and insignificantly decreased the porosity and tensile strength of the nanocomposite scaffolds. The bioactivity and biodegradation assessment showed that PHB-Cs-MWNTs-HA 15% scaffold has proper bioactivity and biodegradability. These findings indicated that the incorporation of HA increased the hydrophilicity, and subsequently enhanced the biodegradation and the bioactivity of the nanocomposite scaffolds. In vitro cell culture studies showed that chondrocytes were able to attach onto the surface of electrospun scaffolds. These results clearly implied that the fabricated nanofibers can be effectively used as the cartilage tissue engineering and HA has positive effects on the biological properties of the nanocomposite scaffolds.

Rheological Aspects and Extension‐Induced Phase Separation in Electrospinning of Poly(N‐isopropyl acrylamide) Solutions in Dimethylformamide

AbstractSolutions of poly(N‐isopropyl acrylamide) in dimethylformamide are used to study the relation between the rheological properties and electrospinning behavior. Light scattering of electrospinning jet is conducted to obtain the jet diameter at the straight jet end, from which the average extension rate of the jet is derived based on a simple approach. The extension rate is found to be higher than the terminal relaxation rate of polymer chains determined from the dynamic rheological properties. Based on this finding, the original single‐phase polymer solutions may undergo extensional flow‐induced phase separation in the straight jet section during electrospinning. String‐like structures in the liquid jet as well as in the solid fiber are observed by OM, SEM, TEM, and AFM to validate the hypothesis. The inhomogeneity in the jet, due to the presence of dissipative string structures, may serve as the potential precursor to produce lateral perturbations of jet motion to initiate the macroscopic bending instability at the straight jet end for the jet whipping. Moreover, the formation of the beaded fiber, that is, beads‐on‐a‐string structures, is likely relevant with the dissipative structures developed in the jet, besides the Rayleigh instability of the jet arising from surface tension.

Mechanical behaviour of MWCNTs reinforced electrospun nanofibres

The nanoscale dimension of electrospun polymeric nanofibres produced by electrospinning are highly captivating, yet facing limitation of resisting external forces due to the weak tensile properties. Carbon nanotubes providing tremendous toughness due to extraordinary strong sp2 bonding network of carbon atoms in honeycomb lattice structure, augmented the physical resistant strength and is easily recover to its original state after load is removed. This study reports the performance of multi-walled carbon nanotubes (MWCNTs) as filler in the electrospinning of poly (L-lactide)-co-ε-caprolactone) (PLCL) composite nanofibres. Voltage of 10 kV is applied to the spinning solution mixture of 11 wt% (w/v) PLCL and MWCNTs, yielded nanofibres having diameters less than 400 nm. Results obtained showed the formation of composite nanofibres with tailored tensile behavior by modifying the content of MWCNTs. The addition of MWCNTs improved the tensile properties of resultant composite nanofibres, signified by tensile strength of 5.82 to 15.95 MPa, which were obtained using 0.1 to 1.0 wt% of MWCNTs. The structural integrity of nanofibres mats were retained in phosphate buffer saline (PBS) medium. Scanning Electron Microscopy (SEM) micrographs revealed the minimal of fiber deformation over 30 days of incubation and are closely identical to the initial diameter of as-spun fiber.

Electrospinning of poly(β-hydroxybutyrate) scaffolds: morphology and aging

Fibrous polymeric scaffolds that comprise capabilities of biomimicry to the native tissue architecture and achieve functional tissue-engineered products with minimal surgical implantation. This research focused on the production of fibrous scaffolds of biodegradable microbial poly(β-hydroxybutyrate) (PHB) by electrospinning. Processing conditions were found to influence the morphology of the scaffolds, which, in turn, controlled the wettability and aging behavior, quite important for medical applications. Commercial and biosynthesized PHB from a mutant Azotobacter vinelandii OP strain were investigated. The morphology and wettability of the fibrous scaffolds were characterized using optical, atomic and scanning electron microscopy. Tuning the voltage and the solution concentration (at constant flow rate) produced either a filamentous morphology or aggregates of filaments. The wettability correlated with the degree of porosity, and predominantly a hydrophobic behavior was attained in an otherwise hydrophilic material. Aging, monitored at room temperature up to 11 months by degree of crystallinity, α, showed that scaffolds with filamentous morphology exhibited an increase in crystallinity, leading to brittleness. However, scaffolds with aggregated filaments were quite stable as the degree of crystallinity remained constant over the 11-month period. Applications are envisioned for PHB biomimetic scaffolds in cell growth and bone tissue regeneration.

Electrospinning of highly porous yet mechanically functional microfibrillar scaffolds at the human scale for ligament and tendon tissue engineering

Electrospun fibers offer tremendous potential for tendon and ligament tissue engineering, yet developing porous scaffolds mimicking the size, stiffness and strength of human tissues remains a challenge. Previous studies have rolled, braided, or stacked electrospun sheets to produce three-dimensional (3D) scaffolds with tailored sizes and mechanical properties. A common limitation with such approaches is the development of low porosity scaffolds that impede cellular infiltration into the body of the implant, thereby limiting their regenerative potential. Here, we demonstrate how varying the rotational speed of the collecting mandrel during the electrospinning of poly(ε-caprolactone) (PCL) can be used to limit inter-fiber fusion (or fiber welding). Increasing the fraction of unfused fibers reduced the flexural rigidity of the electrospun sheets, which in turn allowed us to bundle the fibers into 3D scaffolds with similar dimensions to the human anterior cruciate ligament (ACL). These unfused fibers allowed for higher levels of porosity (up to 95%) that facilitated the rapid migration of mesenchymal stem cells (MSCs) into the body of the scaffolds. Mechanical testing demonstrated that the fiber-bundles possessed a Young’s modulus approaching that of the native human ACL. The scaffolds were also capable of supporting the differentiation of MSCs towards either the fibrocartilage or ligament/tendon lineage. This novel electrospinning strategy could be used to produce mechanically functional, yet porous, scaffolds for a wide range of biomedical applications.