Tri-layered Electrospinning to Mimic Native Arterial Architecture using Polycaprolactone,Elastin, and Collagen: A Preliminary Study

Throughout native artery, collagen and elastin play an important role, providing a mechanical backbone, preventing vessel rupture, and promoting recovery under pulsatile deformations. The goal of this study was to mimic the structure of native artery by fabricating a multi-layered electrospun conduit composed of poly(caprolactone) (PCL) with the addition of elastin and collagen with blends of 45-45-10, 55-35-10, and 65-25-10 PCL-ELAS-COL to demonstrate mechanical properties indicative of native arterial tissue, while remaining conducive to tissue regeneration. Whole grafts and individual layers were analyzed using uniaxial tensile testing, dynamic compliance, suture retention, and burst strength. Compliance results revealed that changes to the middle/medial layer changed overall graft behavior with whole graft compliance values ranging from 0.8 - 2.8 % / 100 mmHg, while uniaxial results demonstrated an average modulus range of 2.0 - 11.8 MPa. Both modulus and compliance data displayed values within the range of native artery. Mathematical modeling was implemented to show how changes in layer stiffness affect the overall circumferential wall stress, and as a design aid to achieve the best mechanical combination of materials. Overall, the results indicated that a graft can be designed to mimic a tri-layered structure by altering layer properties.     

Electrospun cellulose acetate nanofibers: The present status and gamut of biotechnological applications

Cellulose acetate (CA) has been a material of choice for spectrum of utilities across different domains ranging from high absorbing diapers to membrane filters. Electrospinning has conferred a whole new perspective to polymeric materials including CA in the context of multifarious applications across myriad of niches. In the present review, we try to bring out the recent trend (focused over last five years' progress) of research on electrospun CA fibers of nanoscale regime in the context of developmental strategies of their blends and nanocomposites for advanced applications. In the realm of biotechnology, electrospun CA fibers have found applications in biomolecule immobilization, tissue engineering, bio-sensing, nutraceutical delivery, bioseparation, crop protection, bioremediation and in the development of anti-counterfeiting and pH sensitive material, photocatalytic self-cleaning textile, temperature-adaptable fabric, and antimicrobial mats, amongst others. The present review discusses these diverse applications of electrospun CA nanofibers.     

Adapting the Electrospinning Process to Provide Three Unique Environments for a Tri-layered In Vitro Model of the Airway Wall

Electrospinning is a highly adaptable method producing porous 3D fibrous scaffolds that can be exploited in in vitro cell culture. Alterations to intrinsic parameters within the process allow a high degree of control over scaffold characteristics including fiber diameter, alignment and porosity. By developing scaffolds with similar dimensions and topographies to organ- or tissue-specific extracellular matrices (ECM), micro-environments representative to those that cells are exposed to in situ can be created. The airway bronchiole wall, comprised of three main micro-environments, was selected as a model tissue. Using decellularized airway ECM as a guide, we electrospun the non-degradable polymer, polyethylene terephthalate (PET), by three different protocols to produce three individual electrospun scaffolds optimized for epithelial, fibroblast or smooth muscle cell-culture. Using a commercially available bioreactor system, we stably co-cultured the three cell-types to provide an in vitro model of the airway wall over an extended time period.This model highlights the potential for such methods being employed in in vitro diagnostic studies investigating important inter-cellular cross-talk mechanisms or assessing novel pharmaceutical targets, by providing a relevant platform to allow the culture of fully differentiated adult cells within 3D, tissue-specific environments.     

静电纺丝的主要参数对ＰＬＧＡ纤维支架形貌和纤维直径的影响

目的以聚乳酸-羟基乙酸共聚物(PLGA)为材料,采用静电纺丝方法制备纤维支架,考察制备参数对纤维支架结构及纤维直径的影响规律。方法以四氢呋喃(THF)和N,N-二甲基甲酰胺(DMF)的混合液为溶剂,调节PLGA溶液浓度、流量及电场强度分别制备了具有不同表面形貌的纤维支架。通过扫描电镜(SEM)观察了纺丝溶液的浓度、流量及电场强度对纤维形貌和直径的影响。同时在制备的PLGA纤维支架上接种了人的真皮成纤维细胞,并对细胞在PLGA支架上的黏附和增殖情况进行了研究,从而来评价支架材料的细胞相容性。结论结果表明,随着纺丝溶液浓度的增加,纤维直径逐渐增大,纤维直径的分布也随之增大。随着流量的增加,纤维直径略有增大。随着电场强度的增大,纤维直径没有明显的变化。但是电压和浓度的增大有助于减少珠丝的产生。体外细胞培养实验证明,制备的PLGA纤维支架能支持细胞正常的黏附和增殖活动。     

Control of cell migration in two and three dimensions using substrate morphology

We have shown that en masse cell migration of fibroblasts on the planar surface results in a radial outward trajectory, and a spatially dependent velocity distribution that decreases exponentially in time towards the single cell value. If the cells are plated on the surface of aligned electropsun fibers above 1 μm in diameter, they become polarized along the fiber, expressing integrin receptors which follow closely the contours of the fibers. The velocity of the cells on the fibrous scaffold is lower than that on the planar surface, and does not depend on the degree of orientation. Cells on fiber smaller than 1 μm migrate more slowly than on the planar surface, since they appear to have a large concentration of receptors. True three-dimensional migration can be observed when plating the droplet on a scaffold comprises of at least three layers. The cells still continue to migrate on the fibers surfaces, as they diffuse into the lower layers of the fibrous scaffold.     

乳液法静电纺丝PLGA组织工程缓释纤维的研究

目的：研究Dextran对蛋白药物的释放影响。方法：将模型蛋白BSA溶解于多糖溶液中,通过W/O乳液法静电纺丝制备缓释纤维。采用MicroBCA法测定该纤维体外释放行为,采用SEC-HPLC检测制备前后蛋白的聚集程度,并与不含多糖的BSA纤维做对照。结果：添加Dextran以后蛋白的包封率由52.68%提高到63.92%,第一天突释不大于药物载量的15%,对蛋白单体的保持达到85%以上。结论：Dextran可以改善一般组织工程纤维中蛋白药物的释放,提高蛋白药物在制剂、贮存、释放过程中的稳定性,增加纤维的载药量。     

Electrospun polyvinyl alcohol/bovine serum albumin biocomposite membranes for horseradish peroxidase immobilization

Electrospinning, a simple and versatile method to fabricate nanofibrous supports, has attracted attention in the field of enzyme immobilization. Biocomposite nanofibers were fabricated from mixed PVA/BSA solution and the effects of glutaraldehyde treatment, initial BSA concentration and PVA concentration on protein loading were investigated. Glutaraldehyde cross-linking significantly decreased protein release from nanofibers and BSA loading reached as high as 27.3% (w/w). In comparison with the HRP immobilized into the nascent nanofibrous membrane, a significant increase was observed in the activity retention of the enzyme immobilized into the PVA/BSA biocomposite nanofibers. The immobilized HRP was able to tolerate much higher concentrations of hydrogen peroxide than the free enzyme and thus the immobilized enzyme did not demonstrate substrate inhibition. The immobilized HRP retained ⿼50% of the free enzyme activity at 6.4 mM hydrogen peroxide and no significant variation was observed in the KM value of the enzyme for hydrogen peroxide after immobilization. In addition, reusability tests showed that the residual activity of the immobilized HRP were 73% after 11 reuse cycles. Together, these results demonstrate efficient immobilization of HRP into electrospun PVA/BSA biocomposite nanofibers and provide a promising immobilization strategy for biotechnological applications.     

Postproduction Processing of Electrospun Fibres for Tissue Engineering

Electrospinning is a commonly used and versatile method to produce scaffolds (often biodegradable) for 3D tissue engineering.^{1, 2, 3} Many tissues in vivo undergo biaxial distension to varying extents such as skin, bladder, pelvic floor and even the hard palate as children grow. In producing scaffolds for these purposes there is a need to develop scaffolds of appropriate biomechanical properties (whether achieved without or with cells) and which are sterile for clinical use. The focus of this paper is not how to establish basic electrospinning parameters (as there is extensive literature on electrospinning) but on how to modify spun scaffolds post production to make them fit for tissue engineering purposes - here thickness, mechanical properties and sterilisation (required for clinical use) are considered and we also describe how cells can be cultured on scaffolds and subjected to biaxial strain to condition them for specific applications.Electrospinning tends to produce thin sheets; as the electrospinning collector becomes coated with insulating fibres it becomes a poor conductor such that fibres no longer deposit on it. Hence we describe approaches to produce thicker structures by heat or vapour annealing increasing the strength of scaffolds but not necessarily the elasticity. Sequential spinning of scaffolds of different polymers to achieve complex scaffolds is also described. Sterilisation methodologies can adversely affect strength and elasticity of scaffolds. We compare three methods for their effects on the biomechanical properties on electrospun scaffolds of poly lactic-co-glycolic acid (PLGA).Imaging of cells on scaffolds and assessment of production of extracellular matrix (ECM) proteins by cells on scaffolds is described. Culturing cells on scaffolds in vitro can improve scaffold strength and elasticity but the tissue engineering literature shows that cells often fail to produce appropriate ECM when cultured under static conditions. There are few commercial systems available that allow one to culture cells on scaffolds under dynamic conditioning regimes - one example is the Bose Electroforce 3100 which can be used to exert a conditioning programme on cells in scaffolds held using mechanical grips within a media filled chamber.⁴ An approach to a budget cell culture bioreactor for controlled distortion in 2 dimensions is described. We show that cells can be induced to produce elastin under these conditions. Finally assessment of the biomechanical properties of processed scaffolds cultured with or without cells is described.     

Novel hybrid scaffolds for the cultivation of osteoblast cells

In this study, natural biodegradable polysaccharide, chitosan, and synthetic biodegradable polymer, poly(?-caprolactone) (PCL) were used to prepare 3D, hybrid polymeric tissue scaffolds (PCL/chitosan blend and PCL/chitosan/PCL layer by layer scaffolds) by using the electrospinning technique. The hybrid scaffolds were developed through HA addition to accelerate osteoblast cell growth. Characteristic examinations of the scaffolds were performed by micrometer, SEM, contact angle measurement system, ATR-FTIR, tensile machine and swelling experiments. The thickness of all electrospun scaffolds was determined in the range of 0.010 ± 0.001-0.012 ± 0.002 mm. In order to optimize electrospinning processes, suitable bead-free and uniform scaffolds were selected by using SEM images. Blending of PCL with chitosan resulted in better hydrophilicity for the PCL/chitosan scaffolds. The characteristic peaks of PCL and chitosan in the blend and layer by layer nanofibers were observed. The PCL/chitosan/PCL layer by layer structure had higher elastic modulus and tensile strength values than both individual PCL and chitosan structures. The layer by layer scaffolds exhibited the PBS absorption values of 184.2; 197.2% which were higher than those of PCL scaffolds but lower than those of PCL/chitosan blend scaffolds. SaOs-2 osteosarcoma cell culture studies showed that the highest ALP activities belonged to novel PCL/chitosan/PCL layer by layer scaffolds meaning better cell differentiation on the surfaces.     

Investigation of cellular morphology and proliferation on patterned electrospun PLA-gelatin mats

Journal of Biological Physics - The morphology and proliferation of eukaryotic cells depend on their microenvironment. When electrospun mats are used as tissue engineering scaffolds, the local...