Core-shell Fibers Research Articles

Sodium alginate/polycaprolactone co-axial wet-spun microfibers modified with N-carboxymethyl chitosan and the peptide AAPV for Staphylococcus aureus and human neutrophil elastase inhibition in potential chronic wound scenarios

In chronic wound (CW) scenarios, Staphylococcus aureus-induced infections are very prevalent. This leads to abnormal inflammatory processes, in which proteolytic enzymes, such as human neutrophil elastase (HNE), become highly expressed. Alanine-Alanine-Proline-Valine (AAPV) is an antimicrobial tetrapeptide capable of suppressing the HNE activity, restoring its expression to standard rates. Here, we proposed the incorporation of the peptide AAPV within an innovative co-axial drug delivery system, in which the peptide liberation was controlled by N-carboxymethyl chitosan (NCMC) solubilization, a pH-sensitive antimicrobial polymer effective against Staphylococcus aureus. The microfibers' core was composed of polycaprolactone (PCL), a mechanically resilient polymer, and AAPV, while the shell was made of the highly hydrated and absorbent sodium alginate (SA) and NCMC, responsive to neutral-basic pH (characteristic of CW). NCMC was loaded at twice its minimum bactericidal concentration (6.144 mg/mL) against S. aureus, while AAPV was loaded at its maximum inhibitory concentration against HNE (50 μg/mL), and the production of fibers with a core-shell structure, in which all components could be detected (directly or indirectly), was confirmed. Core-shell fibers were characterized as flexible and mechanically resilient, and structurally stable after 28-days of immersion in physiological-like environments. Time-kill kinetics evaluations revealed the effective action of NCMC against S. aureus, while elastase inhibitory activity examinations proved the ability of AAPV to reduce HNE levels. Cell biology testing confirmed the safety of the engineered fiber system for human tissue contact, with fibroblast-like cells and human keratinocytes maintaining their morphology while in contact with the produced fibers. Data confirmed the engineered drug delivery platform as potentially effective for applications in CW care.

Core-shell-typed selective-area ion doping wollastonite bioceramic fibers enhancing bone regeneration and repair in situ

Silicate-based bioceramics are being received great attention because of its potential osteostimulative properties in facilitating bone regeneration. Meanwhile, foreign ion doping in bioceramics is a versatile strategy for regulating the biological performances. Herein we developed the new core-shell-typed wollastonite bioceramic fibers (Zn8@Mg10) with 8% Zn and 10% Mg selective-area doping. It was found that the fibrous diameter of Zn-doped core layer could be finely tuned by the extrusion force through the coaxially aligned bi-nozzle system and thus the ultralong bioceramic fibers with different core-shell thickness ratios (2:4, 3:3; 4:2) could be fabricated after sintering treatment. The Zn8@Mg10 fibers exhibited tailorable Zn and Mg ion release and more controllable bio-dissolution in vitro in comparison with the mechanically mixed Zn8/Mg10 fibers. The osteogenic efficacy of core-shell fibers was validated in femoral bony defect in rabbits. The fibers with equal core/shell thickness (3:3) showed more appreciable osteogenic capability after 8 weeks and the new bone tissue could grow into the entire defected region, while the Zn8/Mg10 group only presented new bone at the boundary. Histological examination also indicated more appreciable bone formation in the core-shell fiber groups, whereas less new bone ingrowth was observed in the Zn8/Mg10 group. These findings indicate that bone repair can be enhanced by component distribution design to control bioactive ion release and osteostimulation in vivo. It is demonstrated that selective-area ions doping bioceramics can be translated to a core-shell-structuring strategy through layer thickness adjustment and fiber fabrication with strong clinical translation.

From amyloid fibrils to microfiber condensates: Tuning microfluidic coextrusion of food-grade β-lactoglobulin-pectin core-shell fibers by changes of protein structure

Protein-based microfibers have potential applications in bioengineering and food but preserving and utilizing the unique nanomechanical properties of their protein building blocks at the micrometer scale remains a challenge. This study investigates the bottom-up fabrication of core-shell fibers by coaxial microfluidic spinning of pectin and β-lactoglobulin in different conformational states (monomeric, amyloid fibrils, shortened amyloid fibrils in their isotropic/nematic phases), gelled in CaCl2 solution. Fiber diameters ranged between 478 and 855 μm (wet state) and 107–135 μm (dry state). They showed clear core-shell cross-sections, except pectin-β-lactoglobulin monomer fibers where the compact protein is presumably understood to diffuse through the pectin matrix. The molecular orientation of the fiber building blocks was expressed as order parameters representing the alignment of pectin chains and amyloid fibrils parallel to the fiber axis calculated from synchrotron wide-angle X-ray scattering (WAXS) with a spatial resolution of 20 μm. Introduction of amyloid fibrils as the protein core increased the Young's modulus from 3.3 to 6.4 GPa and tensile strength from 117 to 182 MPa compared to pure pectin fibers. Increasing the protein core flow rate from 1 to 2 mL/h, however, caused helical bending of the core jet, a decrease in order, and ultimately worsened mechanical performance. Overall, full length amyloid fibrils proved to be more beneficial to the mechanical properties than shortened amyloid fibrils. By providing insight into the relationship between protein conformation, spinning flow rate, and resulting mechanical properties of core-shell microfibers, these results may contribute to the field of novel fibrous protein-based materials.

Piezoelectric Effect Polyvinylidene Fluoride (PVDF): From Energy Harvester to Smart Skin and Electronic Textiles

AbstractWith the great demand for flexible self‐powered sensors and nanogenerators, polyvinylidene fluoride (PVDF) is widely investigated for outstanding piezoelectric and dielectric constant. In the pursuit for increasing β content, electrospinning is exhibited to be an effective method without external high voltage pooling or mechanical stretching and thus is considered a cost‐effective and simple method, because the molecular dipoles in the PVDF can be aligned during the process of electrospinning with high voltage field and stretching. The methods for improving piezoelectric characteristics are briefly introduced in this review, electrospinning fibers including uniaxial fibers, highly aligned fibers, core–shell fibers and Janus fibers are revealed, and research on theoretical modeling is carried out for efficiency in the design of piezoelectric nanogenerator. Last, studies on prospective applications based on electrospun PVDF and its copolymer PVDF‐TrFE, from sensors to smart skin, from energy harvesters to electronic textiles, are being conducted.

Single-Walled Carbon Nanotube/Copper Core-Shell Fibers with a High Specific Electrical Conductivity.

Carbon nanotube (CNT)/Cu core-shell fibers are a promising material for lightweight conductors due to their higher conductivity than pure CNT fibers and lower density than traditional Cu wires. However, the electrical properties of the hybrid fiber have been unsatisfactory, mainly because of the weak CNT-Cu interfacial interaction. Here we report the fabrication of a single-walled CNT (SWCNT)/Cu core-shell fiber that outperforms commercial Cu wires in terms of specific electrical conductivity and current carrying capacity. A dense and uniform Cu shell was coated on the surface of wet-spun SWCNT fibers using a combination of magnetron sputtering and electrochemical deposition. Our SWCNT/Cu core-shell fibers had an ultrahigh specific electrical conductivity of (1.01 ± 0.04) × 104 S m2 kg-1, 56% higher than Cu. Experimental and simulation results show that oxygen-containing functional groups on the surface of a wet-spun SWCNT fiber interact with the sputtered Cu atoms to produce strong bonding. Our hybrid fiber preserved its integrity and conductivity well after more than 5000 bending cycles. Furthermore, the current carrying capacity of the coaxial fiber reached 3.14 × 105 A cm-2, three times that of commercial Cu wires.

Highly conductive, hydrophobic, and acid/alkali-resistant MXene@PVDF hollow core-shell fibers for efficient electromagnetic interference shielding and Joule heating

To endow transition metal carbide (MXene) fibers with satisfactory chemical resistances, high electrical conductivity and enhanced ductility, multifunctional hollow core-shell fibers with ductile polyvinylidene fluoride (PVDF) shell and compactly ordered MXene hollow core are fabricated with a coaxial wet-spinning assembly strategy. The partial hydroxylation of the PVDF occurred during the coagulation in the presence of ammonium hydroxide enhances the interfacial interaction of the PVDF layer with the MXene layer. The hollow core consisting of compact and ordered MXene layer provides the fibers with a high electrical conductivity of 3.08 × 105 S m−1, while the PVDF shell endows the fibers with enhanced ductility and excellent resistances to acid, alkali, and seawater. The hollow core-shell structure makes the fiber lightweight, and facilitates multiple scattering of electromagnetic waves, resulting in increased electromagnetic wave absorption and attenuation. The ductile and conductive textile made of the hollow core-shell fibers with a 6 μm-thick MXene layer exhibits a high electromagnetic interference shielding effectiveness of ∼60 dB. Moreover, the resultant fibers exhibit exceptional Joule heating performances for human thermal management. The high conductivity, enhanced ductility, strong chemical resistances, and satisfactory Joule heating properties make the hollow core-shell fibers promising for electromagnetic interference shielding and wearable heating applications.

Natural and biocompatible dressing unit based on tea carbon dots modified core-shell electrospun fiber for diabetic wound disinfection and healing

Wound infection and healing in patients with diabetes is one of the complex problems in trauma treatment. Therefore, designing and preparing an advanced dressing membrane for treating the wounds of such patients is essential. In this study, a zein film with biological tea carbon dots (TCDs) and calcium peroxide (CaO2) as the main components for promoting diabetic wound healing was prepared by an electrospinning technique, which combines the advantages of natural degradability and biosafety. CaO2 is a biocompatible material with a microsphere structure that reacts with water to release hydrogen peroxide and calcium ions. TCDs with a small diameter were doped in the membrane to mitigate its properties while improving the antibacterial and healing effects of the membrane. TCDs/CaO2 was mixed with ethyl cellulose-modified zein (ZE) to prepare the dressing membrane. The antibacterial properties, biocompatibility and wound-healing properties of the composite membrane were investigated by antibacterial experiment, cell experiment and a full-thickness skin defect. TCDs/CaO2 @ZE exhibited significant anti-inflammatory and wound healing-promoting properties in diabetic rats, without any cytotoxicity. This study is meaningful in developing a natural and biocompatible dressing membrane for diabetic wound healing, which shows a promising application in wound disinfection and recovery in patients with chronic diseases.

Artificial Tendrils Mimicking Plant Movements by Mismatching Modulus and Strain in Core and Shell.

Motile organs have evolved in climbing plants enabling them to find a support and, after secure attachment, to reach for sunlight without investing in a self-supporting stem. Searching movements, the twining of stems, and the coiling of tendrils are involved in successful plant attachment. Such coiling movements have great potential in robotic applications, especially if they are reversible. Here, the underlying mechanism of tendril movement based on contractile fibers is reported, as illustrated by a function-morphological analysis of tendrils in several liana species and the encoding of such a principle in a core-shell multimaterial fiber (MMF) system. MMFs are composed of a shape-memory core fiber (SMCF) and an elastic shell. The shape-memory effect of the core fibers enables the implementation of strain mismatch in the MMF by physical means and provides thermally controlled reversible motion. The produced MMFs show coiling and/or uncoiling behavior, with a high reversible actuation magnitude of ≈400%, which is almost 20 times higher compared with similar stimuli for sensitive soft actuators. The movements in these MMFs rely on the crystallization/melting behavior of oriented macromolecules of SMCF.

Sewable high-performance poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/layered double hydroxide core-shell fiber electrodes for flexible supercapacitors

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)-based fibers are one of the most competitive fiber-type electrodes but still suffer from low electrochemical surface areas (ECSAs) and oversensitivity to humidity for fiber supercapacitor applications. Herein, through rational design, a sewable core-shell fiber electrode of PEDOT:PSS/waterborne polyurethane (WPU) fiber wrapped with nickel/cobalt-layered double hydroxides (NiCo-LDH) has been synthesized via wet-spinning and solution reaction. The fiber core acts as a conductive channel for charge carrier transport. The NiCo-LDH shell possesses unique hybrid architectures of honeycomb-like nanosheet array and hollow nanocages, which provide numerous electrochemical active sites. Simultaneously, the water barrier effect of the NiCo-LDH shell and the interaction between Co2+/Ni2+ and PSS reduce fiber water uptake, thus endowing the fiber with a better geometric stability with low swelling ratio. The as-prepared PEDOT:PSS/LDH fiber has a large ECSA (4060 cm2 g−1) and ultrahigh conductivities no matter in dry (1237.3 S cm−1) or wet (1018.7 S cm−1) state. It also exhibits a high capacitance (188.5 F g−1 at 1 A g−1) and long lifespan (capacitance retention of 94% after 10,000 cycles). The fiber-based supercapacitor shows superb flexibility with stable capacitive behavior under deformation. These characteristics manifest the potential of PEDOT:PSS/LDH fibers for stable high-performance energy storage to support wearable electronics.

Preparation and Evaluation of Core–Shell Nanofibers Electrospun from PEU and PCL Blends via a Single-Nozzle Spinneret

The core–shell structured nanofibers are routinely fabricated by coaxial solution and single-nozzle emulsion electrospinning of two polymers. Herein, the core–shell structured polymeric nanofibers were electrospun from mixed solutions of poly(ether urethane) (PEU) with poly(ε-caprolactone) (PCL) or other biodegradable aliphatic polyesters via a single-nozzle spinneret. For comparison, the mixed solutions electrospinning of poly(carbonate urethane) (PCU) with these polyesters including PCL was also conducted. The morphologies and hierarchical structures of the as-spun nanofibers were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), in vitro lipase degradation, differential scanning calorimeter (DSC), and Fourier-transform infrared (FTIR) analyses. It was shown that the blends of PEU with PCL or other biodegradable aliphatic polyesters were solely electrospun into the core–shell structured nanofibers with PEU as a shell and PCL or other biodegradable aliphatic polyesters as a core. The thickness of core/shell layers from 833/606 to 193.3/54.2 μm was adjustable by varying the feeding mass ratio from 1:3 to 3:1 of PEU to PCL or other biodegradable aliphatic polyesters. In DSC analysis, the Tonset of PEU@PCL core–shell fiber was 1.31 °C higher than that of the PCL fiber, while Tm was approximate. Furthermore, changing the electrospinning solvents of PEU with PCL or other biodegradable aliphatic polyesters retained the formation of core–shell nanofibers. In contrast, the blends of PCU with these polyesters tended to form co-continuous structured nanofibers. The effects of the physicochemical properties of mixed solutions on the charged liquid droplets, whipped jets, and morphology of the electrospun nanofibers were also inspected. The creation of core–shell nanofibers from the blends of PEU with PCL or other biodegradable aliphatic polyesters was most likely due to the interaction between the inherent thermodynamic phase separation of the polymers and their external stretching kinetic phase separation during electrospinning.

Hydrogel-Inducing Graphene-Oxide-Derived Core-Shell Fiber Composite for Antibacterial Wound Dressing.

The study reveals the polymer-crosslinker interactions and functionality of hydrophilic nanofibers for antibacterial wound coatings. Coaxial electrospinning leverages a drug encapsulation protocol for a core-shell fiber composite with a core derived from polyvinyl alcohol and polyethylene glycol with amorphous silica (PVA-PEG-SiO2), and a shell originating from polyvinyl alcohol and graphene oxide (PVA-GO). Crosslinking with GO and SiO2 initiates the hydrogel transition for the fiber composite upon contact with moisture, which aims to optimize the drug release. The effect of hydrogel-inducing additives on the drug kinetics is evaluated in the case of chlorhexidine digluconate (CHX) encapsulation in the core of core-shell fiber composite PVA-PEG-SiO2-1x-CHX@PVA-GO. The release rate is assessed with the zero, first-order, Higuchi, and Korsmeyer-Peppas kinetic models, where the inclusion of crosslinking silica provides a longer degradation and release rate. CHX medicated core-shell composite provides sustainable antibacterial activity against Staphylococcus aureus.

Coaxial electrospun core-shell lithium-ion battery separator with flame retardant and thermal shutdown functions

The preparation of flame-retardant encapsulated electrospun core-shell fibrous membrane (ECSFM) is the key to ensure both high performance and safety of battery separator. However, there are lacks of simulation analysis on the thermal deformation behaviour of core-shell fibers, and stable, controllable, and batch preparation method of ECSFM, which makes it difficult to efficiently prepare ECSFM with higher safety. Here, the thermal deformation process of core-shell fiber was simulated to analyze the core and shell ratio with the best flame retardancy and thermal shutdown performance. The results showed that a high ratio of shell layer would make it difficult for the flame retardant in core layer to spill out in time, causing insufficient flame retardancy, while the low ratio would lead to the insufficient thermal shutdown performance of the ECSFM. The ECSFM was prepared by coaxial electrospinning with the optimal proportion of shell and core layer, in which the shell layer was polyvinylidene fluoride (PVDF) and the core layer was triphenyl phosphate (TPP), and the optimized one (TPP@PVDF) had shutdown temperature (177 °C), a membrane rupture temperature (227 °C), and a short self-extinguishing time (1.82 s), while the unoptimized one could not thermal shutdown and had longer self-extinguishing time (2.13 s). Moreover, the batch preparation of TPP@PVDF was realized by sheath focusing multi-nozzle coaxial electrospinning, the output increased by 20.33 times compared with single coaxial electrospinning, and the comprehensive performance was better than commercial battery separator. This work provides a convenient method for the rapid fabrication of safe and high-performance battery separators.

Effect of Ce3+ on the morphology, composition, and thermal properties of single and core-shell polyethylene oxide electrospun fibers

Cerium polymeric composites have novel applications in fuel cells, optical devices, gas sensors, catalysis, ultraviolet absorbers, hydrogen storage materials, and biomedicines. This study reports the fabrication of low-cost electrospun single and core-shell polyethylene oxide (PEO) doped with Cerium fibers fabricated in two moisture ambients. Scanning electron microscopy and atomic force microscopy revealed that obtaining the thinnest average fiber diameter requires 47-52 %RH and 2 % Cerium dopant. Using a PEO capping (shell fiber) allows the increment of Cerium in the inner matrix (core-fiber) to produce non-beading continuous fibers with 3.5% of the dopant. The undoped single or core-shell fibers presented a 52.7 to 54.2 % crystallinity, indecently of relative humidity used during the fabrication process. In contrast, the use of Cerium dopant up to 2% induces an increase in their crystallinity due to the formation of Ce-O species, enhancing their thermal properties, regardless of the moisture during manufacturing as was found with Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis.

Covalent-architected molybdenum disulfide arrays on Ti3C2T MXene fiber towards robust capacitive energy storage

• Use microfluidic and micro-reaction strategy to fabricate MoS 2 -Ti 3 C 2 T x fibers. • The vertically-aligned MoS 2 can provide abundant diffusion paths for ion storage. • The covalent engineering can facilitate rapidly interfacial electron conduction. • The MoS 2 -Ti 3 C 2 T x fiber has high energy density and superior durability. • The as-prepared F-SC can realize stable energy supply for wearable electronics. Ti 3 C 2 T x MXene fiber has shown extraordinary potential for supercapacitor electrode in wearable electronics and textile energy storage, but realizing high energy density and practical-powered applications remains a great challenge. Here, we report a covalent-architected molybdenum disulfide-Ti 3 C 2 T x (MoS 2 -Ti 3 C 2 T x ) core-shell fiber for high-performance supercapacitor. Benefiting from the microfluidic and micro-reaction strategies, the ordered MoS 2 arrays are strongly bridged on Ti 3 C 2 T x fiber via Ti-O-Mo bond, resulting in large exposed surface, enhanced porosity and excellent interfacial conduction for charges high diffusion and faradaic transfer. The MoS 2 -Ti 3 C 2 T x fiber exhibits ultra-large capacitance of 2028 F cm −3 and admirable reversibility in 1 M H 2 SO 4 aqueous electrolyte. Meanwhile, MoS 2 -Ti 3 C 2 T x fiber-based solid-state supercapacitor presents high energy density of 23.86 mWh cm −3 , capacitance of 1073.6 F cm −3 and superior cycling ability of 92.13% retention after 20000 cycles, which can realize stable energy supply for wearable watch, LEDs, electric fans, toy ship and self-powered devices. Our work may provide an insightful guidance for the advanced design of structural fiber towards robust new energy and next-generation wearable industry.

Core-shell oxygen-releasing fibers for annulus fibrosus repair in the intervertebral disc of rats.

The repair of annulus fibrosus (AF) defect after discectomy in the intervertebral disc (IVD) has presented a challenge over the past decade. Hostile microenvironments in the IVD, including, compression and hypoxia, are critical issues that require special attention. Till date, little information is available on potential strategies to cope with the hypoxia dilemma in AF defect sites. In this study, perfluorotributylamine (PFTBA) core-shell fibers were fabricated by coaxial electrospinning to construct oxygen-releasing scaffold for promoting endogenous repair in the AF after discectomy. We demonstrated that PFTBA fibers (10% chitosan, chitosan: PCL, 1:6) could release oxygen for up to 144​h. The oxygen released from PFTBA fibers was found to protect annulus fibrosus stem cells (AFSCs) from hypoxia-induced apoptosis. In addition, the PFTBA fibers were able to promote proliferation, migration and extracellular matrix (ECM) production in AFSCs under hypoxia, highlighting their therapeutic potential in AF defect repair. Subsequent in vivo studies demonstrated that oxygen-supplying fibers were capable of ameliorating disc degeneration after discectomy, which was evidenced by improved disc height and morphological integrity in rats with the oxygen-releasing scaffolds. Further transcriptome analysis indicated that differential expression genes (DEGs) were enriched in "oxygen transport" and "angiogenesis", which likely contributed to their beneficial effect on endogenous AF regeneration. In summary, the oxygen-releasing scaffold provides novel insights into the oxygen regulation by bioactive materials and raises the therapeutic possibility of oxygen supply strategies for defect repair in AF, as well as other aerobic tissues.

Effect of nanofiller concentration on its dispersion in a system of liquid crystalline SB(3R)-11 and single walled carbon nanotubes

We report on the concentration dependence of the dispersion of single walled carbon nanotubes, SWCNTs, in a nanocomposite with a recently synthesized ferroelectric and optically active thermotropic liquid crystal ((R,E)-4-(4-((3,7-dimethyloctyl) oxy) styryl) phenyl 4-(undecyloxy)benzoate. Excellent dispersion of the SWCNTs in the concentration range from 0.01 up to 10 wt % was proven by means of differential scanning calorimetry, polarized optical microscopy, and Raman spectroscopy. It is believed to be facilitated by the formation of core-shell fibres, consisting of liquid crystal decorated SWCNTs, yet in the solution state. The fibres are maintained after the solvent evaporation and so the aggregation at elevated temperatures is prevented. The preservation of the liquid crystalline behaviour in all investigated cases can be considered as an additional benefit.

Ultralow platinum loading for redox-flow battery by electrospinning the electrocatalyst and the ionomer in core-shell fibers

Hydrogen Bromine Redox Flow Batteries (HBRFB) are promising candidates for large scale energy storage, having an excellent balance of system, inexpensive and abundant electrolytes, high power density and near zero kinetic limitations. However, they suffer from corrosion of the hydrogen electrode due to bromine species crossover, which requires a high loading of precious group metal (PGM) electrocatalyst. Herein, a standard catalyst has been used in an electrospun (ES) fiber mat electrode, allowing for a significant (six-fold) reduction in platinum loading from 0.3 mgPt/cm2 down to 0.05 mgPt/cm2. At this very low loading, the electrospun electrode attained an impressive specific power of 11.5 W/mgPt, and exhibited excellent durability, with constant power output for 140 charge/discharge cycles. The excellent performance of the electrospun hydrogen electrode is attribute to its unique core-shell nanofiber structure, which improves the stability of the catalyst by preventing bromide species from reaching the catalyst surface.

Bioactive Insulin-Loaded Electrospun Wound Dressings for Localized Drug Delivery and Stimulation of Protein Expression Associated with Wound Healing.

Effective therapy of wounds is difficult, especially for chronic, non-healing wounds, and novel therapeutics are urgently needed. This challenge can be addressed with bioactive wound dressings providing a microenvironment and facilitating cell proliferation and migration, ideally incorporating actives, which initiate and/or progress effective healing upon release. In this context, electrospun scaffolds loaded with growth factors emerged as promising wound dressings due to their biocompatibility, similarity to the extracellular matrix, and potential for controlled drug release. In this study, electrospun core-shell fibers were designed composed of a combination of polycaprolactone and polyethylene oxide. Insulin, a proteohormone with growth factor characteristics, was successfully incorporated into the core and was released in a controlled manner. The fibers exhibited favorable mechanical properties and a surface guiding cell migration for wound closure in combination with a high uptake capacity for wound exudate. Biocompatibility and significant wound healing effects were shown in interaction studies with human skin cells. As a new approach, analysis of the wound proteome in treated ex vivo human skin wounds clearly demonstrated a remarkable increase in wound healing biomarkers. Based on these findings, insulin-loaded electrospun wound dressings bear a high potential as effective wound healing therapeutics overcoming current challenges in the clinics.

Experimental Investigation and Characterization of Abaca Fiber Lumens as Potential Carriers in Self-Healing Applications

ABSTRACT This paper presents a novel plant-derived core-shell fiber carrier that can be used in self-healing applications. The study used abaca fiber lumens as a self-healing carrier for the first time. The fibers were characterized under SEM at different positions to know the lumen structure and achieved a 39.19% lumens fraction and 16.13 µm lumen diameter. Healing resins were embedded in the lumens using modified VARTM. The core was confirmed using FESEM-EDX. Thermal degradation was determined via TGA under a nitrogen atmosphere. The mechanical and self-healing properties, as well as a single-fiber tensile test, were conducted with a cell load of 5 kgf. The healing resin (VE-CN)-embedded fibers showed a strength improvement of 14.78% compared with the strength of pure abaca fibers. The improved strength is attributed to the reorientation of the crystalline cellulose in the tensile direction. Additionally, some of the tensile-fractured fibrils self-healed after 24 h and showed a restored strength of 100.71 MPa. The restored strength explains that the fiber lumens are the potential to carry a healing resin and release upon the damage.

Liquid Oil Trapped inside PVA Electrospun Microcapsules.

Electrospinning makes it possible to obtain solid fibers, in addition to core-shell fibers, using coextrusion. However, an exhaustive control of parameters allows the core-shell fibers from emulsion electrospinning to be obtained. The solvent in the outer surface tends to evaporate and the polymer density increases, moving the emulsion drops towards the center, which in turn promotes coalescence, thus creating the core. The aim of this work was to avoid coalescence and obtain a net of nanofibers entrapping oil microcapsules. We obtained an emulsion oil in water (O/W), with polyvinyl alcohol (W) and two essential oils (O), sage and thyme. An electrospinning process was used to place the microcapsules of oil inside a net of nanofibers. The electrospun veil was characterized by organoleptic testing, SEM microscopy, FTIR spectroscopy, DSC thermal analysis, and pressure tests. Organoleptic testing, FTIR spectroscopy, and DSC thermal analysis demonstrated the presence of the oil, which was retained in the spheres observed by SEM microscopy, while pressure tests revealed that the oil remained in a liquid state. Furthermore, we demonstrated a strong relationship between the emulsion size and the final microcapsules created, which are slightly larger due to the shell formation. The size of the emulsion determines whether the spheres will be independent or embedded in the nanofibers. Furthermore, the nanofiber diameter was considerably reduced compared to the nanofibers without the oil.