Coaxial Electrospun Fibers Research Articles

Highly stretchable coaxial P3HT electrospun fibers with enhanced reversibility

Highly stretchable and reversible electrospun fibers with a fracture strain of approximately 1000% were developed. The doped fibers maintain electrical conductivity up to 400% strain.

In-situ generation of metal nanoparticle decorated N-doped carbon secondary reticular structure on coaxial electrospinning fibers for oxygen electrocatalysis

Combining metal-organic frameworks with electrospinning technology, this work employs coaxial electrospun fibers decorated with ZIF-67 as precursors. The Fe3+/Co2+/Ni2+ ions in the electrospun fibers are converted into FeCoNi alloy nanoparticles which catalyze the pyrolysis of ZIF-67 on the fiber surface to generate reticulated carbon microfibers. This produces an efficacious bifunctional oxygen electrocatalyst. This new N-doped carbon hierarchical network (NCHNs) catalyst with a distinct secondary reticulated carbon structure possesses larger surface area and pore volume. Besides, the decoration of FeCoNi nanoparticles on the NCHNs provides effective active sites. With rapid mass and electron transfer between the hollow fibers, the synergistic effect between the FeCoNi nanoparticles and the layered carbon network can contribute to the high activity and kinetics of oxygen electrochemistry. At 10 mA cm−2, the FeCoNi/NCHNs exhibit an ORR half-wave potential of 0.885 V and an OER potential of 1.610 V, which exceeds that of the existing Pt/C and RuO2 catalysts. Furthermore, the FeCoNi/NCHNs-based rechargeable Zn-Air battery has an excellent power density (160.5 mV cm−2), high open-circuit voltage (1.48 V), large specific capacity (792 mAh g−1) and excellent cycling stability (>200 h). This work provides a convenient method for designing high performance and low cost catalysts.

Co-axial fibrous scaffolds integrating with carbon fiber promote cardiac tissue regeneration post myocardial infarction

Myocardium is an excitable tissue with electrical conductivity and mechanical strength. In this work, carbon fibers (CFs) and co-axial fibrous mesh were integrated which combined the high modulus and excellent electrical conductivity of CFs and the fibrous and porous structures of the electrospun fibers. The scaffold was fabricated by simply integrating coaxial electrospun fibers and carbon fibers through a freeze-drying procedure. It was shown that the integration of carbon fibers have the conductivity and Young's modulus of the fibrous mesh increased significantly, meanwhile, upregulated the expression of CX43, α-actinin, RhoA of the neonatal rat primary cardiomyocytes and primary human umbilical vein endothelial cells (HUVECs), and promoted the secretion of VEGF of HUVECs. Moreover, the cardiomyocytes grown on the scaffolds increased the ability of HUVECs migration. When implanted to the injury area post myocardial infraction, the scaffolds were able to effectively enhance the tissue regeneration and new vessel formation, which rescued the heart dysfunction induced by the myocardial infraction, evidenced by the results of echocardiography and histochemical analysis. In conclusion, the composite scaffolds could promote the myocardium regeneration and function's recovery by enhancing cardiomyocytes maturation and angiogenesis and establishing the crosstalk between the cardiomyocytes and the vascular endothelial cells.

Drug-loaded PCL electrospun nanofibers as anti-pancreatic cancer drug delivery systems

Cancer is one of the main causes of death worldwide, being pancreatic cancer the second deadliest cancer in Western countries. Surgery, chemotherapy and radiotherapy form the basis of pancreatic cancer’s current treatment. However, these techniques have several disadvantages, such as surgery complications, chemotherapy systemic side effects and cancer recurrence. Drug delivery systems can reduce side effects, increasing the effectivity of the treatment by a controlled release at the targeted tumor cells. In this context, coaxial electrospun fibers can increase the control on the release profile of the drug. The aim of this study was to encapsulate and release different anticancer drugs (5-Fluorouracil and Methotrexate) from a polymeric fiber mat. Different flows and ratios were used to test their effect on fiber morphology, FTIR spectrum, drug encapsulation and release. Good integration of the anticancer drugs was observed and the use of a desiccator for 24 h showed to be a key step to remove solvent remanence. Moreover, the results of this study demonstrated that the polymeric solution could be used to encapsulate and release different drugs to treat cancers. This makes coaxial electrospinning a promising alternative to deliver complex chemotherapies that involve more than one drug, such as FOLFIRINOX, used in pancreatic cancer treatment.

Promotion of skin regeneration through co-axial electrospun fibers loaded with basic fibroblast growth factor

Promotion of skin regeneration through co-axial electrospun fibers loaded with basic fibroblast growth factor

Core‐Shell Nanofibers of Polyvinyl Alcohol/Polylactic Acid Containing TiO2 Nanotubes for Natural Sunlight Driven Photocatalysis

AbstractHighly stable and efficient coaxial electrospun fibers of polyvinyl alcohol (PVA) and polylactic acid (PLA) nanocomposite filled with titanium dioxide (TiO2) nanotubes areaccomplished for natural sunlight‐driven photocatalytic dye degradation. The coaxial electrospinning process generates well‐defined concentric cylinder‐like morphology, with the polymeric core and sheath phases, with TiO2 present only in the outer phases. The nanofibers are characterized for their coaxial morphology and the distribution of TiO2 in the sample is monitored through EDAX studies. Coaxial electrospinning process influences the polymeric structural and functional performances, regulates the crystallization kinetics, and ensures the entanglement of TiO2 nanopowders without allowing them to leach out. Photodecomposition of Rhodamine B and methylene blue dye are observed by the UV–visible studies and ≈80% and ≈85% degradation is achieved respectively after 8 h. A higher efficiency of degradation is achieved for the TiO2 nanocomposites, due to the photocatalytic activity of the TiO2 semiconductors, and also because of its presence in the sheath phase. The efficiency of dye degradation is correlated with the mechanical and dynamic mechanical properties of the fibers and with the typical fiber morphology and spinning mechanism. While the dye molecules get trapped in the porous sites of composite fibers, the TiO2 radicals initiates the photocatalysis process. The current technology is promising in manipulating flexible, durable, and environmentally friendly polymer nanocomposite fibers for industrial wastewater purification.

Coaxial fibers of poly(styrene-co-maleic anhydride)@poly(vinyl alcohol) for wound dressing applications: Dual and sustained delivery of bioactive agents promoting fibroblast proliferation with reduced cell adherence

The prevalence of chronic and acute wounds, as well as the complexity of their treatment represent a great challenge for health systems around the world. In this context, the development of bioactive wound dressings that release active agents to prevent infections and promote wound healing, appears as the most promising solution. In this work, we develop an antibacterial and biocompatible wound dressing material made from coaxial electrospun fibers of poly(styrene-co-maleic anhydride) and poly(vinyl alcohol) (PSMA@PVA). The coaxial configuration of the fibers consists of a shell of poly (styrene-co-maleic anhydride) containing a variable concentration of silver nanoparticles (AgNPs) 0.1–0.6 wt% as antibacterial agent, and a core of PVA containing 1 wt% allantoin as healing agent. The fibers present diameters between 0.72 and 1.7 µm. The release of Ag+ in a physiological medium was studied for 72 h, observing a burst release during the first 14 h and then a sustained and controlled release during the remaining 58 h. Allantoin release curves showed significant release only after 14 h. The meshes showed an antibacterial activity against Pseudomonas aeruginosa and Bacillus subtilis that correlates with the amount of AgNPs incorporated and the release rate of Ag+. Indeed, meshes containing 0.3 and 0.6 wt% of AgNPs showed a 99.99% inhibition against both bacteria. The adherence and cell viability of the meshes were evaluated in mouse embryonic fibroblasts NIH/3T3, observing a significant increase in cell viability after 72 h of incubation accompanied by a reduced adhesion of fibroblasts that decreased in the presence of the active agents. These results show that the material prepared here is capable of significantly promoting fibroblast cell proliferation but without strong adherence, which makes it an ideal material for wound dressings with non-adherent characteristics and with potential for wound healing.

Preparation of pH-sensitive polylactic acid-naringin coaxial electrospun fiber membranes for maintaining and monitoring salmon freshness

Seafood spoilage can be prevented by inhibiting the quorum sensing (QS) system between bacteria. However, membrane materials combining freshness indicators with QS inhibition features have rarely been reported. Therefore, in this study, pH-sensitive polylactic acid-naringin coaxial electrospun fibers capable of maintaining and monitoring freshness were prepared and investigated. Surface analysis revealed that the fiber membranes exhibited a smooth surface and an average diameter of 243 nm. FTIR spectroscopy analysis revealed characteristic absorption peaks at 3265 and 1124 cm−1, confirming the successful loading of naringin and bromocresol purple. Release behavior analysis verified the uninterrupted release of naringin within 192 h, which enabled the fibers to achieve a protease inhibitory activity rate of 35.94%. Furthermore, the coaxial fibers successfully inhibited the expression of rhlI, rhlR, aprA, and fliA in Pseudomonas fluorescens. The real-world applicability of the coaxial fibers was evaluated by the salmon spoilage assay, where a 4-d extension to the shelf life of the coated fillets was attained. Additionally, the color of the coaxial fibers changed with the deterioration of salmon quality and the ΔE value increased from 4.75 to 26.51. These results verify that the prepared fibers can effectively monitor the freshness of seafood products and improve their storage conditions.

Study on Preparation and Properties of Coaxial Electrospun PLGA/Gelatin Fibers

The coaxial electrospun fibers with large specific surface area, high porosity and core-shell structure have been great applied in biomedical field, especially as drug delivery carriers. In this paper, PLGA(polylactic acid/glycolic acid copolymer) was used as the core and the mixture of PLGA and gelatin was used as the shell. PLGA/gelatin fiber was prepared by coaxial electrospinning technology. The effects of different parameters on the surface morphology and the diameter of fibers were investigated.

Fabrication of Electrospun Levodopa-Carbidopa Fixed-Dose Combinations

We report in this work coaxial electrospun fibers with potential applications in the treatment of Parkinson’s disease. The fibers comprise a fixed dose combination (FDC) containing the active ingredients levodopa and carbidopa, loaded in a fast dissolving polyvinylpyrrolidone (PVP) shell and an insoluble but swellable Eudragit® RLPO core. Under appropriate processing conditions we are able to prepare fibers with distinct core/shell architectures and diameters of approximately 400 nm. X-ray diffraction and differential scanning calorimetry analyses revealed that the drugs are dispersed on the molecular level within the polymer carriers, and IR spectroscopy indicated the presence of intermolecular interactions. At pH 1, the composite fibers yields extended release over more than 8 h, with an initial loading dose being freed from the PVP shell and then a sustained release phase following from the insoluble core. This is markedly extended over the release period of the commercial FDC product, and thus the fibers generated here have the potential to be used to reduce the required dosing frequency.Graphic

Preparation of Coaxial Polylactic Acid-Propyl Gallate Electrospun Fibers and the Effect of Their Coating on Salmon Slices during Chilled Storage.

Pseudomonas fluorescens bacteria can grow well in cold-storage conditions and cause food spoilage. Quorum sensing (QS) is a biological pathway existing in a large number of microorganisms, through which bacteria regulate several of their physiological activities. A number of substances have been identified as quorum sensing inhibitors (QSIs); they can interfere with the QS system and control bacterial spoilage characteristics and production of virulence factors. In our previous study, propyl gallate at sub-minimum inhibitory concentration levels showed a potent anti-QS activity. Thus, in this study, coaxial polylactic acid-propyl gallate electrospun fibers were fabricated and their physicochemical properties were characterized. Salmon slices were coated with these electrospun fibers and the effect of this coating on the salmon slices during chilled storage was evaluated. The results showed that the electrospun fibers had a small diameter and smooth surface with no beads or other defects. The thermal stability, tensile strength, and other properties of the fibers were suitable for refrigerated storage conditions. Without inhibiting the bacterial growth in the salmon slices, the QSI-containing electrospun fibers exerted a significant inhibitory effect on the production of total volatile base nitrogen and trimethylamine. Furthermore, the deterioration of muscle tissue in the salmon slices was significantly delayed during cold storage. Quantitative analysis indicated that the electrospun fibers had a significant inhibitory effect on the bacterial spoilage ability. The results suggested that the electrospun fibers loaded with QSIs might be an effective strategy to control food spoilage and enhance the quality of aquatic food products.

Controlled dual drug release by coaxial electrospun fibers – Impact of the core fluid on drug encapsulation and release

Controlled release of hydrophilic drugs from carriers is still faced with problems due to the poor compatibility of such substances with slowly degradable polymers leading to challenges regarding fabrication as well as undesired burst release of the encapsulated drugs. In this context, coaxial electrospinning being capable of simultaneously using two different solvent systems provides a promising strategy. However, the coaxial electrospinning process is extremely complex and numerous parameters might impact the incorporation as well as release kinetics of the drugs. To address this gap, we fabricated coaxial fibers for controlled co-delivery of two different drugs: bovine serum albumin as a model protein and acyclovir as a small molecule. Controlled release of both embedded drugs was achieved, and drug release profiles could be modulated through modifying spinning techniques as well as compositions and process parameters of the core fluid. Especially, the interactions of the co-incorporated drugs were found to be of key significance for affecting drug distribution within the fibers, and thus ultimately impacting drug release kinetics. Based on our findings, key factors for influencing drug encapsulation and release kinetics from coaxial fibers could be identified, providing a valuable guidance for rational development of coaxial fiber-based drug carriers.

Cefazolin-loaded polycaprolactone fibers produced via different electrospinning methods: Characterization, drug release and antibacterial effect

Antibiotic containing polycaprolactone (PCL) fibers were produced by using three electrospinning methods: blend, emulsion and co-axial electrospinning (labeled as S1, S2 and S3, respectively). The profiles of drug release from three different systems were studied and antimicrobial properties of produced materials were evaluated. Morphology of the produced fibers was characterized and revealed that cefazolin-loaded PCL fibers had smaller diameter compared to neat PCL fibers, while the chemical interaction between the antibiotic and PCL showed that cefazolin neither had reacted with PCL phase, nor had degraded during the electrospinning process. The crystallinity and thermal characterization of fabricated fibers showed that the addition of cefazolin decreased the crystallinity of PCL. The results of the drug release behavior of the blend and co-axial electrospun fibers was on a higher level (~68% and ~43%, respectively) compared to the emulsion electrospun fibers (~5%), after a period of 30 days. The obtained data had the best fitting with the first order model and the Higuchi model, while the Korsmeyer-Peppas model showed a Pseudo-Fickian diffusion of the drug. Antibacterial evaluations showed that cefazolin-loaded PCL fibers had better effects on Staphylococcus aureus compared to Escherichia coli during the treatment period and that the effect of the emulsion fibers was notably weaker than the other two studied systems. The aim of the study was to test different systems for control drug release of different dynamics, which will be applied for prevent bacterial accumulation when indwelling urinary catheters, applied for different periods of time.

Influence of controlled release of resveratrol from electrospun fibers in combination with siRNA on leukemia cells

In this study, we evaluated the possibility of i) local release of resveratrol from poly(ε-caprolactone) (PCL) and gelatin (GT) electrospun fibers and ii) combining (i) with siRNA designed to downregulate BCR-ABL pathway on K562 cancer cells. Initially, K562 cell culture experiments were performed using various bolus doses of resveratrol in combination with siRNA for 3 days using a factorial design of experiments approach. Resveratrol content was analyzed using HPLC and cell viability was assessed using Annexin V (Non-viable), and Propidium Iodide (PI) (Necrotic) based flow cytometry. Coaxial electrospun fibers with resveratrol were made using 1:1 PCL-GT blends in different configurations: single fibers and coaxial fibers with same polymer blends, or with PCL inner core. Loading efficiency and release profile over five days were analyzed. Based on release profile, K562 cell viability with fibers was analyzed over eight days. Dose dependent cell death was observed with bolus resveratrol and siRNA in the culture. However, resveratrol content depleted significantly when added directly to solution. The combination therapy was additive in solution. SEM analysis showed no phase separation of components and resveratrol loading efficiency varied from 77% to 88% in different configurations; 95% of resveratrol was released by day five. Permeability of resveratrol showed no significant dependency on fiber configuration. After 8 days, non-viable cell percentages with controlled release were similar to that at three-day bolus dose of resveratrol. However, siRNA interacted with the fibers, resulting in reduced effect on cells. Loading resveratrol into electrospun fibers provides a localized delivery at therapeutic level, and increased resveratrol's apoptotic effect. Using single fibers is sufficient for controlled release.

Effect of interface and confinement size on the crystallization behavior of PLLA confined in coaxial electrospun fibers

ABSTRACTPoly(l‐lactide)/polyacrylonitrile (PLLA/PAN) core‐sheath composite fibers were fabricated by coaxial electrospinning. The crystallization behavior of PLLA within the coaxial electrospun fibers was studied by differential scanning calorimetry (DSC). The PLLA/PAN coaxial electrospun fiber with a PLLA diameter of ∼32 nm (C1) exhibits a crystallization temperature (Tc) of 22.5 °C higher but a cold‐crystallization temperature (Tcc) of 10 °C lower than bulk PLLA. The crystallinity of C1 fiber is also higher than bulk PLLA. In both isothermal melt‐ and cold‐crystallization, PLLA in C1 fiber crystallizes faster than the bulk PLLA, as revealed by the smaller half crystallization times (t1/2). The enhanced crystallizability of PLLA in the C1 fiber may be attributed to the increased nuclei number and crystal growth rate induced by the PAN surface, i.e., surface‐induction effect. However, PLLA also suffers a nano‐confinement effect exerted by PAN sheath in the coaxial electrospun fiber, which can suppress PLLA crystallization. When the diameter of PLLA is too small (< 32 nm), the nano‐confinement effect may prevail over the surface‐induction effect, leading to a slower crystallization rate and smaller crystallinity. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45980.

Coaxial hybrid perovskite fibers: Synthesis and encapsulation in situ via electrospinning

In this study, a new method for producing fibers with hybrid organic–inorganic perovskite (HOIP) cores and hydrophobic polystyrene shells via coaxial electrospinning is introduced. The presence of the HOIP, CH3NH3PbI3, was verified through the use of ultraviolet to visible spectroscopy and x-ray diffractography to confirm successful synthesis in situ. Morphologies of the coaxial fibers were investigated using scanning electron microscopy to confirm the core/shell geometry and assess the fiber diameter. Finally, the interaction of liquid water and the fiber mats was studied to assess improvements to moisture resistance garnered from encapsulation in coaxial electrospun fibers.

Effect of annealing‐induced interfacial demixing on crystallization of PEO confined in coaxial electrospun nanofibers

ABSTRACTGlassy polymer nanofibers with spatially confined poly(ethylene oxide) (PEO) were fabricated by coaxial electrospinning of PEO with polyacrylonitrile (PAN) or polystyrene. The effect of melt‐annealing on the crystallization behavior of the confined PEOs was studied using differential scanning calorimetry. It is found that the crystallization behavior of the confined PEOs varies with annealing temperature (Ta), annealing time (ta), and molecular weight of PEO. Notably, it is observed that the crystallization temperature (Tc) and melting temperature (Tm) of PEO increase with prolongation of ta, for PEO600K/PAN and PEO2K/PAN coaxial electrospun fibers. This phenomenon can be interpreted by the annealing‐induced demixing at the core‐sheath interface. After the coaxial electrospinning, the core and sheath of the PEO/PAN coaxial fibers are partially compatible due to the miscible solvents used for the core and sheath polymers. Upon annealing, demixing occurs at the core‐sheath interface, leading to improved crystallizability of PEO. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45760.

Evaluation of the potential of kartogenin encapsulated poly(L-lactic acid-co-caprolactone)/collagen nanofibers for tracheal cartilage regeneration.

Tracheal stenosis is one of major challenging issues in clinical medicine because of the poor intrinsic ability of tracheal cartilage for repair. Tissue engineering provides an alternative method for the treatment of tracheal defects by generating replacement tracheal structures. In this study, we fabricated coaxial electrospun fibers using poly(L-lactic acid-co-caprolactone) and collagen solution as shell fluid and kartogenin solution as core fluid. Scanning electron microscope and transmission electron microscope images demonstrated that nanofibers had uniform and smooth structure. The kartogenin released from the scaffolds in a sustained and stable manner for about 2 months. The bioactivity of released kartogenin was evaluated by its effect on maintain the synthesis of type II collagen and glycosaminoglycans by chondrocytes. The proliferation and morphology analyses of mesenchymal stems cells derived from bone marrow of rabbits indicated the good biocompatibility of the fabricated nanofibrous scaffold. Meanwhile, the chondrogenic differentiation of bone marrow mesenchymal stem cells cultured on core-shell nanofibrous scaffold was evaluated by real-time polymerase chain reaction. The results suggested that the core-shell nanofibrous scaffold with kartogenin could promote the chondrogenic differentiation ability of bone marrow mesenchymal stem cells. Overall, the core-shell nanofibrous scaffold could be an effective delivery system for kartogenin and served as a promising tissue engineered scaffold for tracheal cartilage regeneration.

Ultrafine Carbon Fibers with Hollow-Porous Multilayered Structure for Supercapacitors

Electrospun fibers of mixed polyacrylonitrile/polyvinyl pyrrolidine (PAN/PVP) sheath and silicone oil core were obtained by coaxial electrospinning. PVP and silicone oil were then removed from the coaxial electrospun fibers via phase separation and carbonization processes, respectively, to make the hollow-porous multilayered ultrafine carbon fibers. The relationship between the morphology and electrochemical performance of ultrafine carbon fibers was investigated. Results show that the supercapacitor based on electrode of hollow-porous multilayered ultrafine carbon fibers exhibits high conductivity, fast ion diffusion, high specific capacitance (231.6 F·g−1), high charging/discharging efficiency (99.7%), and low internal resistance (0.2Ω) using tetraethylammonium tetrafluoroborate in acetonitrile as electrolyte. Additionally, this work also demonstrates a great potential in the preparation of carbon nano-materials with graphene-like multilayer structure.

Inside Cover Image, Volume 8, Issue 5

image The inside cover image, by Evan K. Wujcik et al., is based on the Overview Coaxial electrospun fibers: applications in drug delivery and tissue engineering, DOI: 10.1002/wnan.1391.