Impact of Solvent on Electrospinning of Zein and Analysis of Resulting Fibers

Zein fibers have been produced by electrospinning from acetic acid, aqueous methanol, ethanol and isopropyl alcohol. Alcohol solutions produced fibers that were predominantly ribbons. Fibers spun from acetic acid solution have a round morphology with a narrower distribution of diameters when spun under suitable conditions. The IR spectra of electrospun fibers display increased absorbance at 1 650 cm^?1 relative to starting material, indicative of increased α‐helical structure. Raman spectra of fibers spun from acetic acid solution had spectral differences, having increased absorbance at 680, 750 and 860 cm^?1, versus fibers spun from alcoholic solvents suggesting different tertiary structure within the fiber, which may result from different structures in solution. Polarized Raman spectroscopy taken parallel and perpendicular to the fiber axis displayed no differences, suggesting similar secondary and tertiary structures in these directions. All of the fibers had some degree of birefringence demonstrating the presence of orientation. The smaller fibers were highly birefringent throughout the fiber, while the larger fibers had orientation at the surface only. Quality fibers could not be produced from N,N‐dimethylformamide, acetone/water, acetic acid/water, 8 M urea/water or 10% NaOH/water zein solutions.

     

Online UV Curing of Electrospun Polysulfone Fibers Containing an Acrylate as Cross‐Linker

In this work, a sustainable, in situ UV‐induced reactive electrospinning technique is demonstrated to produce solvent stable electrospun membranes in a single operation. This approach is based on the addition of an acrylated cross‐linker into the polysulfone‐based dope solution and on the online irradiation of the solution while it is electrospun, thus allowing reaction during formation of the fibers. The electrospinning parameters and UV curing conditions are thoroughly optimized. Mats are also prepared via an offline approach in which UV curing is performed on the previously electrospun mats and compared with the membranes fabricated via the online curing method. As opposed to pristine polysulfone fibers, the electrospun mats containing acrylate are stable in a variety of solvents, such as tetrahydrofurane (THF), acetone, ethyl acetate, dimethylsulfoxide (DMSO), and toluene. The online irradiated mats of desired thickness are produced in a single step operation and the sustainability of the process is achieved through the optimization of electrospinning and solution parameters.

     

Nanofibrous scaffold from electrospinning biodegradable waterborne polyurethane/poly(vinyl alcohol) for tissue engineering application

A series of nanofibrous scaffolds, free of organic solvents, are prepared by electrospinning biodegradable waterborne polyurethane (BWPU) emulsion blending with aqueous poly(vinyl alcohol)(PVA). Tuning the proration of BWPU to PVA, various nanofibers with diameter from 370 to 964 nm are obtained. Strong intermolecular interaction existing between them benefits to the electrospun of BWPU emulsion, which is demonstrated by dynamic thermomechanical analysis and Fourier transform infrared spectroscopy. The nontoxic nanofibrous scaffolds with porous structure, which is similar to the natural extracellular matrix, favor to the attachment and proliferation of the L929 fibroblasts. Thus, the scaffolds are promising to be used as biomaterials for many natural tissues repair.     

三种形貌静电纺丝膜片的制备及其与牙周膜细胞的相容性

目的探讨三种形貌静电纺丝膜片的制备方法,并比较其对牙周膜细胞（periodontal ligament cells,PDLCs）的细胞相容性。方法通过控制纺丝溶液成分、空气湿度、流速,制成3种静电纺丝膜片,利用扫描电镜观察其形貌;将PDLCs与三种膜片共培养,DAPI染色观察PDLCs的形貌、分布;MTT法检测PDCFs的增殖;活-死细胞染色法比较PDLCs的活力。结果研究显示,制得纤维状,液滴状,圆盘状三种形貌的膜片;在共培养第7、11天,PDLCs在圆盘状膜片上的细胞增殖和活性明显优于另两种膜片（P〈0.01）。结论通过调控静电纺丝的溶液成分、空气湿度、温度及流速,可以改变纺丝膜片的微观结构和形貌,从而影响材料的细胞相容性。圆盘状膜片具有更好的细胞相容性。     

Assessment of Electrospun Pellethane-Based Scaffolds for Vascular Tissue Engineering

We examined the physicochemical properties and the biocompatibility and hemocompatibility of electrospun 3D matrices produced using polyurethane Pellethane 2363-80A (Pel-80A) blends Pel-80A with gelatin or/and bivalirudin. Two layers of vascular grafts of 1.8 mm in diameter were manufactured and studied for hemocompatibility ex vivo and functioning in the infrarenal position of Wistar rat abdominal aorta in vivo (n = 18). Expanded polytetrafluoroethylene (ePTFE) vascular grafts of similar diameter were implanted as a control (n = 18). Scaffolds produced from Pel-80A with Gel showed high stiffness with a long proportional limit and limited influence of wetting on mechanical characteristics. The electrospun matrices with gelatin have moderate capacity to support cell adhesion and proliferation (~30–47%), whereas vascular grafts with bivalirudin in the inner layer have good hemocompatibility ex vivo. The introduction of bivalirudin into grafts inhibited platelet adhesion and does not lead to a change hemolysis and D-dimers concentration. Study in vivo indicates the advantages of Pel-80A grafts over ePTFE in terms of graft occlusion, calcification level, and blood velocity after 6 months of implantation. The thickness of neointima in Pel-80A–based grafts stabilizes after three months (41.84 ± 20.21 µm) and does not increase until six months, demonstrating potential for long-term functioning without stenosis and as a suitable candidate for subsequent preclinical studies in large animals.     

The Thickness Effect of PSF Nanofibrous Mat on Fracture Toughness of Carbon/Epoxy Laminates

The geometrical features of nanofibers, such as nanomat thickness and the diameter of nanofibers, have a significant influence on the toughening behavior of composite laminates. In this study, carbon/epoxy laminates were interleaved with polysulfone (PSF) nanofibrous mats and the effect of the PSF nanomat thickness on the fracture toughness was considered for the first time. For this goal, the nanofibers were first produced by the electrospinning method. Then, double cantilever beam (DCB) specimens were manufactured, and mode-I fracture tests were conducted. The results showed that enhancing the mat thickness could increase the fracture toughness considerably (to about 87% with the maximum thickness). The toughening mechanism was also considered by presenting a schematic picture. Micrographs were taken using a scanning electron microscope (SEM).     

Biomimetic method for combining the nucleus pulposus and annulus fibrosus for intervertebral disc tissue engineering

Tissue engineering strategies for the intervertebral disc (IVD) have traditionally focused either on the annulus fibrosus (AF) or the nucleus pulposus (NP) in isolation, or have simply compared AF cells and NP cells in identical culture conditions. Recently, others in the field have become aware of the advantage of combining the AF and NP into a more comprehensive strategy to address IVD tissue engineering, and have introduced biomimetic approaches to either AF or NP tissue engineering. Here, we introduced a new method for developing a biomimetic, cell-seeded IVD by electrospinning circumferentially-orientated polycaprolactone fibres (AF analogue), seeding them with cells (porcine chondrocytes) and then gelling a cell-agarose solution in the centre (NP analogue). Scanning electron microscopy images demonstrated a high degree of fibre alignment and, along with fluorescent actin staining, confirmed a preferred orientation of cells in the direction of the fibres. Viability assays and histology collectively demonstrated that cells were viable and well-distributed around the interface between the NP and AF regions. In addition, mechanical testing confirmed that the composite IVD scaffolds had higher moduli than the agarose hydrogels alone. As we enter the new decade and the fields of AF and NP tissue engineering begin to merge into a new interfacial and functional IVD tissue-engineering field, approaches such as the method presented here will serve as the foundation for continuously advancing technology that we ultimately endeavour to bring to the clinic for the treatment of patients severely afflicted by degenerative disc disease.     

Hybrid PGS–PCL microfibrous scaffolds with improved mechanical and biological properties

Poly(glycerol sebacate) (PGS) is a biodegradable elastomer that has generated great interest as a scaffold material due to its desirable mechanical properties. However, the use of PGS in tissue engineering is limited by difficulties in casting micro‐ and nanofibrous structures, due to high temperatures and vacuum required for its curing and limited solubility of the cured polymer. In this paper, we developed microfibrous scaffolds made from blends of PGS and poly(ε‐caprolactone) (PCL) using a standard electrospinning set‐up. At a given PGS:PCL ratio, higher voltage resulted in significantly smaller fibre diameters (reduced from ～4 µm to 2.8 µm; p < 0.05). Further increase in voltage resulted in the fusion of fibres. Similarly, higher PGS concentrations in the polymer blend resulted in significantly increased fibre diameter (p < 0.01). We further compared the mechanical properties of electrospun PGS:PCL scaffolds with those made from PCL. Scaffolds with higher PGS concentrations showed higher elastic modulus (EM), ultimate tensile strength (UTS) and ultimate elongation (UE) (p < 0.01) without the need for thermal curing or photocrosslinking. Biological evaluation of these scaffolds showed significantly improved HUVEC attachment and proliferation compared to PCL‐only scaffolds (p < 0.05). Thus, we have demonstrated that simple blends of PGS prepolymer with PCL can be used to fabricate microfibrous scaffolds with mechanical properties in the range of a human aortic valve leaflet. Copyright © 2010 John Wiley & Sons, Ltd.