Spontaneous core-sheath formation in electrospun nanofibers

Chondrogenic preconditioning of mesenchymal stem/stromal cells within a magnetic scaffold for osteochondral repair

Stem cell therapy using mesenchymal stromal/stem cells (MSCs) represents a novel approach to treating severe diseases, including osteoarthritis (OA). However, the therapeutic benefit of MSCs is highly dependent on their differentiation state, which can be regulated by many factors. Herein, three-dimensional (3D) magnetic scaffolds were successfully fabricated by incorporating magnetic nanoparticles (MNPs) into electrospun gelatin nanofibers. When positioned near a rotating magnet (f= 0.5 Hz), the magnetic scaffolds with the embedded MSCs were driven upward/downward in the culture container to induce mechanical stimulation to MSCs due to spatial confinement and fluid flow. The extracellular matrix-mimicking scaffold and the alternating magnetic field significantly enhanced chondrogenesis instead of osteogenesis. Furthermore, the fibre topography could be tuned with different compositions of the coating layer on MNPs, and the topography had a significant impact on MSC differentiation. Selective up-regulation of chondrogenesis-related genes (COL2A1andACAN) was found for the magnetic scaffolds with citric acid-coated MNPs (CAG). In contrast, osteogenesis-related genes (RUNX2andSPARC) were selectively and significantly up-regulated for the magnetic scaffolds with polyvinylpyrrolidone-coated MNPs (PVPG). Prior to implantation in vivo, chondrogenic preconditioning of MSCs within the CAG scaffolds under a dynamic magnetic field resulted in superior osteochondral repair. Hence, the magnetic scaffolds together with an in-house rotating magnet device could be a novel platform to initiate multiple stimuli on stem cell differentiation for effective repair of osteochondral defects.

Progress of superconducting nanofibers via electrospinning

Superconducting nanofibers have attracted much attention in basic researches and practical applications due to their unique physical properties such as broad phase transition temperature, excellent heat conductivity, and high critical current density, etc. Electrospinning, as a common method to prepare nanofibers, also has many applications for the preparation of superconducting nanofibers. However, a few of the new methods to fabricate superconducting nanofibers via electrospinning still need further investigations. This review firstly introduces several potential electrospinning methods to obtain superconducting nanofibers, then proceeds to summarize the recent progress in the field of electrospun superconducting materials. The preparation process, difficulties and problems, physical properties of the superconducting nanofibers or nanonetworks (such as superconducting transition temperature, critical current density, critical magnetic field strength, fiber morphology, and structure, etc), theoretical analysis of the properties, and the techniques to improve the performance are also reviewed. In addition, some suggestions and prospects for the development and applications of electrospun superconducting materials in the future are discussed.

Study on hydrophilicity and degradability of chitosan/polylactide-co-polycaprolactone nanofibre blend electrospun membrane

Electrospinning is an interesting technique to produce polymer membranes made of entangled nanofibres. The technique is raising interest in pharmaceutical and biomedical areas. Either electrospun membranes are studied for tissue regeneration purposes, or incorporation of nanoparticles in electrospun membranes can be an opportunity to control the delivery of drug or to obtain dual drug delivery system. In this work suspensions of hydrochloride chitosan salt in copolymer polylactide-co-polycaprolactone (PLA-PCL) solution were electrospun in order to assess an advanced study for developing polymer nanofibre blend membrane loaded with chitosan polymer. The aim of the work was to investigate the properties and stability of chitosan/PLA-PCL electrospun membranes considering their application for tissue regeneration and drug delivery. The electrospun membranes were characterized for their physico-chemical (FT-IR) morphology (SEM) and in vitro biological properties (cytocompatibility and cells engraftment). Results show that homogeneous electrospun PLA-PCL/chitosan blend nanofibres in the range size 800 nm were obtained. Chitosan was loaded inside the nanofibres up to 27.2% (w/w) without modifying nanofibre shape, and only 6% of the loaded chitosan resulted to be on the nanofibre surface. The presence of chitosan in the nanofibres has shown to accelerate the electrospun membranes degradation in vitro.

Nanofibers of resorcinol-formaldehyde for effective adsorption of As (III) ions from mimicked effluents

In the present study, the core-shell structured RF/PVA nanofibers have been developed and used for the adsorption of As³⁺ ions from the mimicked liquid effluents. Efficient-facile fabrication of the structured nanofibers (300-417 nm diameter) was accomplished using facile electrospinning technique. Chi parameter (χ = 25.56) and free energy of mixing (E_mix = 17.19 kcal/mol) calculated via molecular dynamics simulations depicted compatibility of the polymeric system resulting supermolecular core-shell nanofibers, whose adsorption results were also supported by the FE-SEM, FT-IR, and UV-VIS spectroscopy analysis. The adsorption analysis was performed using both linear and non-linear regression methods, for kinetic models and adsorption isotherms. The developed nanofibers demonstrated an adsorption capacity of 11.09 mg/g at a pH of 7, and an adsorption efficiency of 97.46% on protracted exposure, which is even adaptable at high temperatures with 93.1% reclamation. FE-SEM analysis and FT-IR spectra confirm the adsorption of As (III) ions on RF/PVA nanofibers and the presence of embedded hydrophilic oxygen sites for metal ion adsorption. The developed RF/PVA nanofibers demonstrate scalability in fabrication, low-cost, recycling, and less solid waste generation, depicting the large-scale applicability in removing arsenic ions from effluent waste. Graphical Abstract ᅟ.

Conductive PVDF-HFP nanofibers with embedded TTF-TCNQ charge transfer complex

Tetrathiafulvalene-tetracyanoquinodimethane charge-transfer complex (TTF-TCNQ CTC) represents a promising organic conductive system. However, application of this donor-acceptor pair is highly limited, because of its ultrafast crystallization kinetics and very low solubility. In this work, conductive organic nanofibers were generated via a coelectrospinning process of poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) with embedded TTF and TCNQ in the shell and core solutions, respectively. Upon supply of the polymer solutions, a core-shell droplet was formed at the exit of the spinneret. The electron donor TTF and the electron acceptor TCNQ migrated toward each other, within the compound droplet, to produce conductive CTC crystals. In the presence of a sufficiently strong electric field, jetting set in at the droplet tip, which yielded solidified PVDF-HFP nanofibers embedded with aligned CTC. Fiber diameters ranged between 100 and 500 nm. X-ray analysis showed strong equatorial reflections (110,200) of oriented copolymer PVDF-HFP crystals (β-phase) with copolymer chains oriented along the fiber axis, and of CTC (001), indicating that the CTC molecular planes were aligned parallel to the nanofiber axis. In addition, reflections of unreacted TCNQ (120,220) and TTF (110) crystals were observed. The electrospun nanofibers were collected to form a fiber mat, which was evaluated as a working electrode in a three-electrode cell system, exhibiting differential conductance of 5.23 μmho.

Carbon microfibers with hierarchical porous structure from electrospun fiber-like natural biopolymer

Electrospinning offers a powerful route for building one-dimensional (1D) micro/nanostructures, but a common requirement for toxic or corrosive organic solvents during the preparation of precursor solution has limited their large scale synthesis and broad applications. Here we report a facile and low-cost way to prepare 1D porous carbon microfibers by using an electrospun fiber-like natural product, i.e., silk cocoon, as precursor. We surprisingly found that by utilizing a simple carbonization treatment, the cocoon microfiber can be directly transformed into 1D carbon microfiber of ca. 6 μm diameter with a unique three-dimensional porous network structure composed of interconnected carbon nanoparticles of 10~40 nm diameter. We further showed that the as-prepared carbon product presents superior electrochemical performance as binder-free electrodes of supercapacitors and good adsorption property toward organic vapor.