Electrospun nanofibers of ZnO‐TiO2 hybrid: characterization and potential as an extracellular scaffold for supporting myoblasts

One‐dimensional nanofibers have attracted tremendous attention because of their potential applications. Electrospinning technology enables industrial production of these nanofibers. This study aims to fabricate one‐dimensional ZnO doped TiO₂ by electrospinning and to characterize these hybrid nanofibers. The nanocomposite was prepared using colloidal gel composed of zinc nitrate, titanium isopropoxide and polyvinyl acetate. X‐ray diffraction, energy dispersive x‐ray analysis and transmission electron microscopy analysis confirmed the purity and crystalline nature of this material, whereas the diameter of these nanofibres estimated from scanning electron microscope (SEM), field emission SEM and transmission electron microscopy are between 200 and 300 nm. Cell counting with Kit‐8 assay at regular time intervals and phase‐contrast microscopy data revealed that C2C12 cells proliferated well on ZnO/TiO₂ nanofibers between 1 and 10 µg/ml, and cellular attachments are visible by SEM. The nanostructured ZnO/TiO₂ hybrid nanofibers show higher cell adhesion, proliferation and spreading behavior compared with the titanium substrate and control. Our study suggests that ZnO/TiO₂ nanofibers could potentially be used in tissue engineering applications. The scalability, low cost, reproducibility and high‐throughput capability of this technology is potentially beneficial to examine and optimizing a wide array of cell‐nanofiber systems prior to in vivo experiments. Copyright © 2013 John Wiley & Sons, Ltd.     

Micro‐Nanostructures of Cellulose‐Collagen for Critical Sized Bone Defect Healing

Bone tissue engineering strategies utilize biodegradable polymeric matrices alone or in combination with cells and factors to provide mechanical support to bone, while promoting cell proliferation, differentiation, and tissue ingrowth. The performance of mechanically competent, micro‐nanostructured polymeric matrices, in combination with bone marrow stromal cells (BMSCs), is evaluated in a critical sized bone defect. Cellulose acetate (CA) is used to fabricate a porous microstructured matrix. Type I collagen is then allowed to self‐assemble on these microstructures to create a natural polymer‐based, micro‐nanostructured matrix (CAc). Poly (lactic‐co‐glycolic acid) matrices with identical microstructures serve as controls. Significantly higher number of implanted host cells are distributed in the natural polymer based micro‐nanostructures with greater bone density and more uniform cell distribution. Additionally, a twofold increase in collagen content is observed with natural polymer based scaffolds. This study establishes the benefits of natural polymer derived micro‐nanostructures in combination with donor derived BMSCs to repair and regenerate critical sized bone defects. Natural polymer based materials with mechanically competent micro‐nanostructures may serve as an alternative material platform for bone regeneration.     

Electrospun Heparin‐Loaded Core–Shell Nanofiber Sutures for Achilles Tendon Regeneration In Vivo

Achilles tendon reconstruction surgery is the primary clinical method for repairing acute Achilles tendon ruptures. However, the efficacy of the postoperative healing process and the recovery of physiological function are inadequate. This study examines the healing mechanism of ruptured rat Achilles tendons seamed with heparin‐loaded core–shell fiber sutures fabricated via near‐field electrospinning. High‐heparin‐concentration sutures (PPH3.0) perform better than the low‐heparin‐concentration sutures and commercial sutures (CSs). The PPH3.0 suture recruits fewer inflammatory cells and shows good histocompatibility in peritoneal implantation experiments. Staining of the Achilles tendon rupture repair zone demonstrates that a high heparin concentration in sutures reduces immune‐inflammatory responses. Immunohistochemical analysis reveals that the transforming growth factor‐β staining scores of the PPH3.0 sutures are not significantly different from those of the corresponding control group but are significantly different from those of the CSs and non‐heparin‐loaded‐suture groups. According to vascular endothelial growth factor (VEGF) analysis, the concentration of VEGF in the group treated with the PPH3.0 suture increases by 37.5% compared with that in its control group. No significant difference in tension strength is observed between the PPH3.0 group and healthy Achilles tendons. These findings illustrate that this novel method effectively treats Achilles tendon rupture and promotes healing and regeneration.     

Electrospun V2O5 Nanostructures with Controllable Morphology as High‐Performance Cathode Materials for Lithium‐Ion Batteries

Porous V₂O₅ nanotubes, hierarchical V₂O₅ nanofibers, and single‐crystalline V₂O₅ nanobelts were controllably synthesized by using a simple electrospinning technique and subsequent annealing. The mechanism for the formation of these controllable structures was investigated. When tested as the cathode materials in lithium‐ion batteries (LIBs), the as‐formed V₂O₅ nanostructures exhibited a highly reversible capacity, excellent cycling performance, and good rate capacity. In particular, the porous V₂O₅ nanotubes provided short distances for Li⁺‐ion diffusion and large electrode–electrolyte contact areas for high Li⁺‐ion flux across the interface; Moreover, these nanotubes delivered a high power density of 40.2 kW kg^?1 whilst the energy density remained as high as 201 W h kg^?1, which, as one of the highest values measured on V₂O₅‐based cathode materials, could bridge the performance gap between batteries and supercapacitors. Moreover, to the best of our knowledge, this is the first preparation of single‐crystalline V₂O₅ nanobelts by using electrospinning techniques. Interestingly, the beneficial crystal orientation provided improved cycling stability for lithium intercalation. These results demonstrate that further improvement or optimization of electrochemical performance in transition‐metal‐oxide‐based electrode materials could be realized by the design of 1D nanostructures with unique morphologies.     

Nanofiber‐Based Multi‐Tubular Conduits with a Honeycomb Structure for Potential Application in Peripheral Nerve Repair

Peripheral nerve injury is a large‐scale problem and it is a great challenge to repair the long lesion in a thick nerve. The design of a multi‐tubular conduit with a honeycomb structure by mimicking the anatomy of a peripheral nerve for the potential repair of large defects in thick nerves has been reported. A bilayer mat of electrospun nanofibers is rolled up to form a single tube, with the inner and outer layers comprised aligned and random nanofibers, respectively. Seven such tubes are then assembled into a hexagonal array and encased within the lumen of a larger tube to form the multi‐tubular conduit. By introducing an adhesive to the regions between the tubes, the conduit is robust enough for handling during surgery. The seeded bone marrow stem cells (BMSCs) are able to proliferate in all the tubes with even circumferential and longitudinal distributions. Under chemical induction, the BMSCs are transdifferentiated into Schwann‐like cells in all the tubes. While the cellular version holds great promise for peripheral nerve repair, the multi‐tubular conduit can also be used to investigate the fundamental aspects involved in the development of peripheral nervous system and migration of cells.     

Hyperbranched polymers as scaffolds for multifunctional reversible addition–fragmentation chain‐transfer agents: A route to polystyrene‐core‐polyesters and polystyrene‐block‐poly(butyl acrylate)‐core‐polyesters

Polydisperse hyperbranched polyesters were modified for use as novel multifunctional reversible addition–fragmentation chain‐transfer (RAFT) agents. The polyester‐core‐based RAFT agents were subsequently employed to synthesize star polymers of n‐butyl acrylate and styrene with low polydispersity (polydispersity index < 1.3) in a living free‐radical process. Although the polyester‐core‐based RAFT agent mediated polymerization of n‐butyl acrylate displayed a linear evolution of the number‐average molecular weight (M_n) up to high monomer conversions (>70%) and molecular weights [M_n > 140,000 g mol^?1, linear poly(methyl methacrylate) equivalents)], the corresponding styrene‐based system reached a maximum molecular weight at low conversions (≈30%, M_n = 45,500 g mol^?1, linear polystyrene equivalents). The resulting star polymers were subsequently used as platforms for the preparation of star block copolymers of styrene and n‐butyl acrylate with a polyester core with low polydispersities (polydispersity index < 1.25). The generated polystyrene‐based star polymers were successfully cast into highly regular honeycomb‐structured microarrays. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3847–3861, 2003     

Thermo‐responsive glycopolymer chains grafted onto honeycomb structured porous films via RAFT polymerization as a thermo‐dependent switcher for lectin Concanavalin a conjugation

Stable and surface‐modified films with regular porous arrays were created by crosslinking honeycomb structured porous films prepared via breath figures from poly(styrene‐co‐maleic anhydride). The formation of open or closed pores of the films was controlled by the addition of a polyion complex. Subsequent crosslinking of the films with 1,8‐diaminooctane led to films, which maintain their structure in solvents. In addition, excess amino functionality after crosslinking allowed the attachment of RAFT agent, 3‐benzylsulfanyl thiocarbonyl sulfanylpropionic acid, for the controlled surface polymerization of N‐isopropyl acrylamide (NIPAAm) and N‐acryloyl glucosamine (AGA). The attachment of thermo‐responsive glycopolymers onto the honeycomb structured porous films was confirmed using contact angle measurements and confocal fluorescence microscopy. Cleavage of surface anchored polymers via aminolysis revealed that the molecular weights of the surface grafted chains are significantly larger than the molecular weight of the chains generated in solution. The honeycomb structured porous films with their grafted PNIPAAm‐ran‐PAGA polymer chains showed selective recognition of Concanavalin A (ConA). Below the lower critical solution temperature (LCST) of the surface, the conjugation is switched off, while above the LCST the surface grafted glucose moieties bind strongly to ConA. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3440–3455, 2010     

The use of poly(L-lactide-co-caprolactone) as a scaffold for adipose stem cells in bone tissue engineering: application in a spinal fusion model

Since the early 1990s, tissue engineering has been heralded as a strategy that may solve problems associated with bone grafting procedures. The original concept of growing bone in the laboratory, however, has proven illusive due to biological, logistic, and regulatory problems. Fat-derived stem cells and synthetic polymers open new, more practicable routes for bone tissue engineering. In this paper, we highlight the potential of poly(L-lactide-co-caprolactone) (PLCL) to serve as a radiolucent scaffold in bone tissue engineering. It appears that PLCL quickly and preferentially binds adipose stem cells (ASCs), which proliferate rapidly and eventually differentiate into the osteogenic phenotype. An in vivo spinal fusion study in a goat model provides a preclinical proof-of-concept for a one-step surgical procedure with ASCs in bone tissue engineering.