Xin Ding

Emulsion electrospun vascular endothelial growth factor encapsulated poly(l-lactic acid-co-ε-caprolactone) nanofibers for sustained release in cardiac tissue engineering

Emulsion electrospinning is a novel approach to fabricate core–shell nanofibers, and it is associated with several advantages such as the alleviation of initial burst release of drugs and it protects the bioactivity of incorporated drugs or proteins. Aiming to develop a sustained release scaffold which could be a promising substrate for cardiovascular tissue regeneration, we encapsulated vascular endothelial growth factor (VEGF) with either of the protective agents, dextran or bovine serum albumin (BSA) into the core of poly(l-lactic acid-co-ε-caprolactone) (PLCL) nanofibers by emulsion electrospinning. The morphologies and fiber diameters of the emulsion electrospun scaffolds were determined by scanning electron microscope, and the core–shell structure was evaluated by laser scanning confocal microscope. Uniform nanofibers of PLCL, PLCL–VEGF–BSA, and PLCL–VEGF–DEX with fiber diameters in the range of 572xa0±xa092, 460xa0±xa063, and 412xa0±xa061xa0nm, respectively were obtained by emulsion spinning. The release profile of VEGF in phosphate-buffered saline for up to 672xa0h (28xa0days) was evaluated, and the scaffold functionality was established by performing cell proliferations using human bone marrow derived mesenchymal stem cells. Results of our study demonstrated that the emulsion electrospun VEGF containing core–shell structured PLCL nanofibers offered controlled release of VEGF through the emulsion electrospun core–shell structured nanofibers and could be potential substrates for cardiac tissue regeneration.

Drug-loaded emulsion electrospun nanofibers: characterization, drug release and in vitro biocompatibility

Emulsion electrospinning is a flexible and promising technique for encapsulating various drugs into nanofibers. In this work, nanofibrous scaffolds were produced by emulsion electrospinning of either metformin hydrochloride (MH) or metoprolol tartrate (MPT) with poly(e-caprolactone) (PCL) or poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) (PHBV). The influence of preparation processes and emulsion compositions (polymer/drug/surfactant Span 80) towards the drug release behaviour of the scaffolds, together with their morphology, surface and thermal properties were evaluated. In vitro release studies indicated that the emulsion electrospun nanofibers significantly alleviated the burst release and produced a sustained release of drugs compared to the blended electrospun nanofibers. Between the two polymers studied, PCL demonstrated a better drug delivery carrier compared to PHBV, and MPT incorporated nanofibers showed less burst release than the others. The emulsion electrospun nanofibers were evaluated for their cytotoxicity using human mesenchymal stem cells and the cytotoxicity results showed that the emulsion electrospun MPT/PCL scaffold favoured cell growth compared to other tested scaffolds. Our study shows that emulsion electrospinning could be a better technique than normal blend electrospinning, especially in modulating the drug release properties by regulating the oil phase and water phase of the emulsions to obtain the desired drug release for the drug delivery systems. And PCL may be a better drug delivery carrier than PHBV.

Fabrication of Nerve Growth Factor Encapsulated Aligned Poly(ε-Caprolactone) Nanofibers and Their Assessment as a Potential Neural Tissue Engineering Scaffold

Peripheral nerve injury is a serious clinical problem to be solved. There has been no breakthrough so far and neural tissue engineering offers a promising approach to promote the regeneration of peripheral neural injuries. In this study, emulsion electrospinning technique was introduced as a flexible and promising technique for the fabrication of random (R) and aligned (A) Poly(ε-caprolactone) (PCL)-Nerve Growth Factor (NGF)&Bovine Serum Albumin (BSA) nanofibrous scaffolds [(R/A)-PCL-NGF&BSA], where NGF and BSA were encapsulated in the core while PCL form the shell. Random and aligned pure PCL, PCL-BSA, and PCL-NGF nanofibers were also produced for comparison. The scaffolds were characterized by Field Emission Scanning Electron Microscopy (FESEM) and water contact angle test. Release study showed that, with the addition of stabilizer BSA, a sustained release of NGF from emulsion electrospun PCL nanofibers was observed over 28 days. [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt; MTS] assay revealed that (R/A)-PCL-NGF and (R/A)-PCL-NGF&BSA scaffolds favored cell growth and showed no cytotoxicity to PC12 cells. Laser scanning confocal microscope images exhibited that the A-PCL-NGF&BSA scaffold increased the length of neurites and directed neurites extension along the fiber axis, indicating that the A-PCL-NGF&BSA scaffold has a potential for guiding nerve tissue growth and promoting nerve regeneration.

Biocompatibility evaluation of emulsion electrospun nanofibers using osteoblasts for bone tissue engineering.

Emulsion electrospinning is an advanced technique to fabricate core-shell structured nanofibrous scaffolds, with great potential for drug encapsulation. Incorporation of dual factors hydroxyapatite (HA) and laminin, respectively, within the shell and core of nanofibers through emulsion electrospinning might be of advantageous in supporting the adhesion, proliferation, and maturation of cells instead of single factor-encapsulated nanofibers. We fabricated poly(L-lactic acid-co-ϵ-caprolactone) (PLCL)/hydroxyapaptite (PLCL/HA), PLCL/laminin (PLCL/Lam), and PLCL/hydroxyapatite/laminin (PLCL/HA/Lam) scaffolds with fiber diameter of 388u2009±u200935, 388u2009±u200981, and 379u2009±u200957u2009nm, respectively, by emulsion electrospinning. The elastic modulus of the prepared scaffolds ranged from 22.7–37.0u2009MPa. The osteoblast proliferation on PLCL/HA/Lam scaffolds, determined on day 21, was found 10.4% and 12.0% higher than the cell proliferation on PLCL/Lam or PLCL/HA scaffold, respectively. Cell maturation determined on day 14, by alkaline phosphatase (ALP) activity, was significantly higher on PLCL/HA/Lam scaffolds than the ALP activity on PLCL/HA and PLCL/Lam scaffolds (pu2009⩽u20090.05). Results of the energy dispersive X-ray studies carried out on day 28 also showed higher calcium deposition by cells seeded on PLCL/HA/Lam scaffolds. Osteoblasts were found to adhere, proliferate, and mature actively on PLCL/HA/Lam nanofibers with enhanced cell proliferation, ALP activity, bone protein expression, and mineral deposition. Based on the results, we can conclude that laminin and HA individually played roles in osteoblast proliferation and maturation, and the synergistic function of both factors within the novel emulsion electrospun PLCL/HA/Lam nanofibers enhanced the functionality of osteoblasts, confirming their potential application in bone tissue regeneration.

Emulsion electrospun nanofibers as substrates for cardiomyogenic differentiation of mesenchymal stem cells

The potential of cardiomyogenic differentiation of human mesenchymal stem cells (hMSCs) on emulsion electrospun scaffold containing poly(l-lactic acid)-co-poly-(ε-caprolactone), gelatin and vascular endothelial growth factor (PLCL/GV) was investigated in this study. The characterizations of the scaffold were carried out using scanning electron microscope (SEM), transmission electron microscope, water contact angle and porometer. The proliferation of hMSCs showed that 73.4xa0% higher cell proliferation on PLCL/GV scaffolds than that on PLCL scaffold after 20xa0days of cell culture. Results of 5-chloromethylfluorescein diacetate staining and SEM morphology analysis indicated that hMSCs differentiated on PLCL/GV scaffolds showed irregular morphology of cardiomyocyte phenotype compared to the typical long and thin hMSC phenotype. Immunostaining results showed the expression of alpha actinin and myosin heavy chain. Our studies identified emulsion electrospinning as a method for fabrication of core–shell fibers suitable for the differentiation of stem cells to cardiac cells, with potential application in cardiac regeneration.

Emulsion electrospinning of polycaprolactone: influence of surfactant type towards the scaffold properties

Producing uniform nanofibers in high quality by electrospinning remains a huge challenge, especially using low concentrated polymer solutions. However, emulsion electrospinning assists to produce nanofibers from less concentrated polymer solutions compared to the traditional electrospinning process. The influence of individual surfactants towards the morphology of the emulsion electrospun poly (ɛ-caprolactone)/bovine serum albumin (PCL/BSA) nanofibers were investigated by using (i) non-ionic surfactant sorbitane monooleate (Span80); (ii) anionic sodium dodecyl sulfate (SDS); and (iii) cationic benzyltriethylammonium chloride, and poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) triblock copolymer Pluronic F108 of different concentrations. The morphology, along with the chemical and mechanical properties of the fibers, was evaluated by field emission scanning electron microscopy, attenuated total reflectance Fourier transform infrared spectroscopy, differential scanning calorimetry, water contact angle, and tensile tester. With the addition of surfactants, the electrospinnability of dilute PCL solution was enhanced, with either branched or uniform fibers were obtained. Electrospinning of an emulsion containing 0.4% (w/v) SDS produced the smallest and the most uniform nanofibers (167 ± 39 nm), which was attributed to the high conductivity of the solution. Analysis revealed that the emulsion electrospun nanofibers containing different surfactants and surfactant concentrations differ in fiber morphology and mechanical properties. Results suggest that surfactants have the ability to modulate the fiber morphology via electrostatic and hydrogen bonding, depending on their chemical structure.

A triboelectric textile templated by a three-dimensionally penetrated fabric

Commercially available 3D spacer fabrics with a three-dimensionally penetrated structure are directly coated with PDMS to fabricate triboelectric textiles without a multilayer structure and metal materials. The resulting triboelectric textile with a size of 5 × 5 cm2 and a thickness of 8 mm generates an open-circuit voltage up to −500 V and a short-circuit current amplitude of 20 μA, corresponding to a peak power density of 153.8 mW m−2 at a load resistance of 1 GΩ. In addition, the performance of the triboelectric textile depends on its thickness, area, the frequency and force of pressing and remains stable after pressing and releasing for over 3000 cycles. Besides, in order to prove that the triboelectric textile is a reliable power source, a LCD and 49 LEDs lit up by a TET without any energy storage unit or rectification circuit have been exhibited apparently. The ingenious structure and simple fabrication are unique advantages of the triboelectric textile, which make it possible to realize practical applications and industrialization.

Flexible supercapacitor with a record high areal specific capacitance based on a tuned porous fabric

To meet the rapidly growing demand for wearable electronics, much research has been devoted to developing flexible supercapacitors. Now, we are awash with abundant examples, but there remain challenges associated with obtaining a high loading of active material for high areal specific capacitance. Herein, a tuned porous fabric has been designed as the substrate to incorporate active materials with a high loading capability. A conducting polymer of polypyrrole with a high mass loading of 12.3 mg cm−2 was developed, and a record high areal specific capacitance of 4117 mF cm−2 has been achieved in the resulting supercapacitor. The supercapacitor is also flexible, and it maintains a high electrochemical performance under bending and twisting for 500 cycles.

Enhanced capacities of carbon nanosheets derived from functionalized bacterial cellulose as anodes for sodium ion batteries

We studied carbon nanosheets prepared from bacterial cellulose (BC) and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) oxidized-BC through carbonization at temperatures ranging from 900 to 1100 °C. Based on experimental results, we propose a comprehensive perspective of Na storage for BC based anode material. The pyrolysis TEMPO-oxidized BC delivers the highest capacity at annealing temperature of 1000 °C under different current densities, and displays excellent rate capability and cyclability. The superior electrochemical performance is attributed to the increasing interlayer distance, rich porous structure and oxygen-containing functional groups. The experimental studies reveal that the introduction of carboxyl is an effective strategy to enhance the specific capacity and cycling stability for Na-ion storage.

Highly conductive graphene-bonded polyimide yarns for flexible electronics

Recently there has been a strong interest in flexible and conductive fibers to meet the demands of wearable electronics. However, how to combine high conductivity, good durability and low cost in one fiber is still a big challenge. Here, we fabricate graphene-bonded polyimide yarns through a large-scale dip-reduction process with an initial alkali treatment. The role of interfacial bonding on conductivity and durability is investigated. Resultantly, conductive yarns of 1.02 × 103 S m−1 are obtained and possess outstanding stability after bending up to 100 times, water wash, and even Scotch tape test. Furthermore, the graphene-bonded polyimide yarns can serve as an effective flexible conductor wire. Supercapacitors made from two conductive yarns show a high specific capacitance of 22.89 F cm−3. These highly conductive yarns are demonstrated to have a great potential in flexible electronics.