静电纺丝在组织工程的应用:距离临床转化还有多远?

背景:静电纺丝是一种制备组织工程支架材料极有前途的技术手段。目的:综述目前静电纺丝技术在组织工程中的应用进展及其在应用中存在的主要问题。方法:应用计算机检索Medline数据库、中国知网数据库2000至2013年文章,检索关键词为"静电纺丝,组织工程;Electrospinning,tissue engineering"。结果与结论:静电纺丝技术制备的纳米纤维无纺布材料,其结构类似于细胞外基质,具有高的比表面积,可控机械性能良好,便于加工,已被广泛应用到组织工程中生物降解材料和高分子聚合物的合成领域。静电纺丝在组织工程中的应用进展快速,尤其所选用的电纺材料或者与不同技术结合的电纺。静电纺丝能将材料的性能与组织的不同形态结构相结合,一系列新的聚合物被成功引入到组织工程支架中作为细胞再生和增殖的基质,然而重要的问题是,如何控制支架与生物系统的相互作用即实现细胞的浸润性生长,如何控制孔隙大小,机械性能,毒性等,在该技术应用到真正实用的生物医学中之前仍然需要进一步研究,尤其是体内研究。     

软组织和硬组织再生过程中的电纺纳米纤维支架

背景：目前，静电纺丝纳米纤维是天然细胞外基质的仿生材料，其包含互连孔隙的三维网络，已成功用作各种组织再生的支架，但目前仍面临着如何将生物材料扩展成三维结构以再现组织微环境的生理、化学以及机械性能的挑战。目的：总结归纳静电纺丝的工艺、原理，探讨由此生产的静电纺丝纳米纤维在皮肤、血管、神经、骨骼、软骨和肌腱/韧带等组织再生中的应用。方法：以“静电纺丝、电纺纳米纤维、电纺纳米纤维支架、组织再生”为中文检索词，“Electrospinning,electrospun nanofibers,electrospun nanofiber scaffolds,tissue regeneration”为英文检索词，检索Google学术、PubMed和中国知网数据库，最终纳入88篇文献进行综述分析。结果与结论：(1)静电纺丝纳米纤维是天然纤维状细胞外基质的仿生材料，并包含互连孔隙的三维网络，在各种组织再生的支架领域中应用较多。(2)多篇文献阐述了电纺纳米支架应用于皮肤、血管、神经、骨骼、软骨和肌腱/韧带组织再生的巨大潜力，为其最终应用于临床疾病治疗，或转化为实际产品进入市场提供了坚实的理论基础。(3)但目...     

静电纺三维结构组织工程支架:应用中的问题与发展前景

背景:静电纺技术制备的生物支架能够模拟细胞外基质的纳米纤维结构,因此在再生医学和组织工程领域受到了普遍关注。目的:回顾近年来在增加静电纺纳米纤维支架孔隙率,增大孔隙直径,促进细胞渗透的相关技术,以期发现最具有实用性和经济性的支架制作工艺。方法:由第一作者检索CNKI全文数据库、万方数据库及Pub Med数据库2004年1月至2014年10月的相关文献,检索关键词为"细胞渗透,静电纺,三维支架;cell infiltration,3D scaffold,electrospinning"。结果与结论:静电纺技术是目前制备纳米纤维支架的最有效方法,使用静电纺支架作为组织工程支架的基础研究逐年增加。然而,纳米纤维支架内部的纳米级孔隙使细胞只能局限于支架表面生长,因此近年来的研究热点已从制备二维支架向具有疏松多孔结构,能够促进细胞渗透生长的三维支架转换。从简单的调整电纺速率,改变电纺原料简易方法到需要各种复杂设备的方法已被应用于该领域的研究,但现有研究方法仍不成熟稳定,并且多数只应用于体外细胞植入或小动物皮下植入后观察研究,尚未将以上各类方法应用于具体器官的组织工程修复,仍需要进一步的长期比较性研究以证实各类方法的可行性。     

纤维基组织工程支架结构对细胞行为的影响

有效引导细胞的生长对于组织工程的发展至关重要,而目前研究表明细胞与支架的相互作用受到材料表面结构的影响,这为设计细胞诱导生长的新型支架提供理论依据。通过静电纺丝技术制备的纤维基支架可以模拟天然细胞外基质的纤维网络结构,对于细胞的生长和组织修复有促进作用,因此成为组织工程支架设计的研究热点。从纤维直径、空间排列、孔径等方面综述支架结构对细胞增殖、迁移、分化等行为的影响,并进一步讨论利用静电纺和静电纺复合技术制备不同纤维结构的常用方法,并展望纤维基支架的未来发展方向。     

静电纺纳米纤维基组织工程大孔支架的研究进展

静电纺丝作为一种纳米纤维支架的仿生构建方法,已在组织工程和再生医学领域中得到越来越多的应用和关注。但是,静电纺支架的主要问题是密集排列的纳米纤维之间的空隙很小,阻碍细胞的长入和三维(3 D)组织的形成。为了解决这一问题,近年来已发展了许多用于扩大静电纺纳米纤维支架孔尺寸的制备方法。首先概述组织工程支架中大孔对细胞行为的影响,然后对静电纺纳米纤维3 D大孔支架的制备方法和技术研究进展进行综述,讨论这些3 D大孔支架促进细胞长入的效果,最后对静电纺3 D大孔支架在组织工程中应用的主要挑战和前景,提出了看法。     

电纺纳米羟基磷灰石/聚酯酰胺复合支架材料的制备及其细胞相容性

背景：采用静电纺丝技术将功能性无机纳米微粒复合高分子超细纤维,形成类细胞外基质结构和功能的复合支架材料是骨组织工程支架领域一个新的研究方向。 目的：通过静电纺丝法构建纳米羟基磷灰石/脂肪族聚酯酰胺复合纤维支架材料,并初步考察其细胞相容性。 方法：以静电纺丝法制备纳米羟基磷灰石/脂肪族聚酯酰胺超细纤维支架材料,通过扫描电镜、原子能谱等表面形貌的物相分析,进行细胞在复合材料上的形态学观察。 结果与结论：通过静电纺丝法成功制备出纳米羟基磷灰石/脂肪族聚酯酰胺超细纤维复合材料,成骨细胞直接培养于材料上呈现良好生长行为,初步证实了复合支架材料的细胞相容性。说明静电纺丝技术在构建类骨细胞外基质结构和功能的仿生复合材料方面具有独特优势,电纺超细纤维复合材料有望成为新型的骨组织工程支架。     

脱细胞基质复合支架在组织再生中的应用

背景：目前的脱细胞方法不可避免地会对脱细胞基质支架造成损伤,为更好地发挥其作为组织工程支架的优势,对脱细胞基质支架进行修饰以改善性能显得尤为重要。目的：综述脱细胞基质复合支架在组织再生中的应用进展。方法：以“decellularized extracellular matrix,tissue engineering,crosslinking,Electrospun nanofibers,3D bioprinting technology,tissue regeneration;脱细胞基质,组织工程,交联,静电纺丝纳米纤维,三维生物打印技术,组织再生”等作为关键词,在PubMed数据库、万方数据库、中国知网数据库进行检索,文献的语种限定为中文和英文,检索时限为2009-2022年。共检索到文献142余篇,最终纳入79篇进行综述。结果与结论：采用化学、物理及生物方法对组织或器官去除细胞的过程,会对脱细胞基质支架的超微结构造成损伤,导致支架的机械性能差与不可控的降解等。通过交联、静电纺丝技术、三维生物打印技术、纳米颗粒、甲氧基聚乙二醇及生长因子修饰构建复合支架,可优化脱细胞基质支架的性能,其...     

新型组织工程血管材料：静电纺复合纳米纤维小口径管状支架

背景：小口径人工血管对生物相容性和抗凝血的要求远远高于普通大口径人工血管,因此血管移植体内原位诱导组织再生成为了新的研究方向。 目的：总结近几年静电纺复合纳米纤维小口径管状支架的主要研究进展,并讨论其在体内原位诱导血管再生方面的重要应用。 方法：由第一作者检索中国期刊网CNKI全文数据库、万方数据库及ISI Web of Knowledge外文数据库,有关复合纳米纤维小口径管状支架的制备方法、血管支架仿生天然细胞外基质微环境的表面修饰以及种植体植入后生物相容性和安全性评价等方面的文献。 结果与结论：静电纺复合纳米纤维制备小口径管状支架,即将天然材料和合成材料共纺在一起,这样既能克服天然生物高分子材料力学性能的不足,又能避免合成材料在生物相容性和安全性的缺陷,成为制备小口径血管组织工程支架的必然趋势。同时制备多层血管,进行功能化修饰,模拟天然细胞外基质的结构和功能,将成为用于心血管组织修复及再生小口径血管组织工程研究的新方向。在获得上述新进展的同时,经动物实验检验的静电纺血管支架以聚合物为主。尽管这类支架采用了各种手段避免血栓、炎症等不良反应,其生物相容性仍旧无法与天然材料相比。由此可见,在天然材料与合成材料之间找到一个最佳比例,使复合材料的力学性能和血管相容性达到一个平衡,将会显著提高静电纺复合纳米纤维支架在小口径血管组织再生中的应用。     

纳米PLLA有序膜制备及其对内皮生长晕细胞的促进作用

通过观察内皮生长晕细胞（EOCs）在纳米PLLA有序膜表面黏附、增殖的情况,为优化组织工程材料提供一种新途径。通过静电纺丝技术制备的纳米PLLA纤维支架,进行低温等离子体技术改性及I型胶原表面涂覆,与EOCs复合培养。采用细胞生长曲线和光镜、荧光显微镜及扫描电镜观察支架材料对种子细胞黏附、增殖、形态特征等方面的影响。结果显示：制得的纳米PLLA纤维孔径为300~400 nm,孔隙率〉90%;有序膜和超级有序膜组吸光度A值与无序膜、单纯细胞组有显著性差异（P〈0.05）;细胞在支架膜上生长良好,纳米无序膜细胞生长较散在、杂乱;有良好空间定向效果的有序纤维及超级有序纤维支架有利于细胞沿纤维定向附着、伸展、增殖,分泌胞外基质,而超级有序膜更有利于保持其结构。内皮生长晕细胞是理想的血管组织工程种子细胞来源;纳米PLLA有序及超级有序膜支架能促进种子细胞在材料表面的黏附、增殖,并能较好地保持细胞的形态,是一种理想的血管组织工程支架材料。     

静电纺聚合物纳米纤维在骨组织工程研究中的进展

组织工程骨在骨缺损、骨不连及骨折延期愈合等骨骼疾病的治疗中有重要应用前景,、组织工程支架是组织工程研究的核心内容之一,静电纺丝制备的纳米纤维以其优异的性能,近年来已开始成为骨组织支架材料的重要研究对象。综述了静电纺聚合物纳米材料包括天然高分子聚合物、人工合成聚合物及复合聚合物纺丝纤维在骨组织工程研究中的进展,提出复合聚合物电纺纤维及其改性是今后骨组织工程支架材料研究的重要方向之一;并探讨了其研究中存在的问题与应用前景。     

The use of thermal treatments to enhance the mechanical properties of electrospun poly(epsilon-caprolactone) scaffolds

Nonwoven nanofiber scaffolds fabricated by electrospinning technology have been widely used for tissue engineering applications. Although electrospun nanofiber scaffolds fulfill many requirements for tissue engineering applications, they sometimes lack the necessary biomechanical properties. To attempt to improve the biomechanical properties of electrospun poly(epsilon-caprolactone) (PCL) scaffolds, fibers were bonded by thermal treatment. The thermal fiber bonding was performed in Pluronic F127 solution at a range of temperatures from 54 degrees C to 60 degrees C. Thermally bonded electrospun PCL scaffolds were characterized by analyzing the changes in morphology, fiber diameter, pore area, tensile properties, suture retention strength, burst pressure strength, and compliance. The biomechanical properties of the thermally bonded electrospun PCL scaffolds were significantly increased without any gross observable and ultrastructural changes when compared to untreated PCL scaffolds. This study suggests that the introduction of thermal fiber bonding to electrospun PCL scaffolds improved the biomechanical properties of these scaffolds, making them more suitable for tissue engineering applications.     

Increasing the pore size of electrospun scaffolds

Electrospinning has gained much attention in the past decade as an effective means of generating nano- to micro-scale polymer fibers that resemble native extracellular matrix. High porosity, pore interconnectivity, and large surface area to volume ratio of electrospun scaffolds make them highly conducive to cellular adhesion and growth. However, inherently small pores of electrospun scaffolds do not promote adequate cellular infiltration and tissue ingrowth. Cellular infiltration into the scaffold is essential for a range of tissue engineering applications and is particularly important in skin and musculoskeletal engineering. Pore size, porosity, and pore interconnectivity dictate the extent of cellular infiltration and tissue ingrowth into the scaffold; influence a range of cellular processes; and are crucial for diffusion of nutrients, metabolites, and waste products. A number of electrospinning techniques and postelectrospinning modifications have, therefore, been developed in order to increase the pore size of electrospun scaffolds. Diverse techniques ranging from simple variations in the electrospinning parameters to complex methodologies requiring highly specialized equipment have been explored and are described in this article.     

Mechanical properties of electrospun fibrinogen structures

Fibrin and fibrinogen have a well-established track record in tissue engineering due to their innate ability to induce improved cellular interaction and subsequent scaffold remodeling compared to synthetic scaffolds. Use of fibrinogen as a primary scaffold component, however, has been limited by traditional processing techniques that render scaffolds with insufficient mechanical properties. The goal of this study was to demonstrate, based on mechanical properties, that electrospun fibrinogen overcomes these limitations and can be successful as a tissue engineering scaffold or wound dressing. Electrospun fibrinogen scaffolds were characterized for fiber diameter and pore area and subsequently tested for uniaxial mechanical properties while dry and hydrated. In addition, uniaxial mechanical testing was conducted on scaffolds treated to regulate scaffold degradation in serum-containing media by supplementing the media with aprotinin or cross-linking the scaffolds with glutaraldehyde vapor. A linear relationship between electrospinning solution concentration and measured fiber diameter was seen; fiber diameters ranged from 120 to 610 nm over electrospinning concentrations of 80 to 140 mg/ml fibrinogen, respectively. Pore areas ranged from 1.3 microm(2) to 13 microm(2) over the same fibrinogen concentrations. Aprotinin in the culture media inhibited scaffold degradation in a predictable fashion, but glutaraldehyde vapor fixation produced less reliable results as evidenced by mechanical property testing. In conclusion, the mechanical characteristics of electrospun fibrinogen strongly support its potential use as a tissue engineering scaffold or wound dressing.     

Controlling the porosity of fibrous scaffolds by modulating the fiber diameter and packing density

Porosity has been shown to be a key determinant of the success of tissue engineered scaffolds. A high degree of porosity and an appropriate pore size are necessary to provide adequate space for cell spreading and migration as well as to allow for proper exchange of nutrients and waste between the scaffold and the surrounding environment. Electrospun scaffolds offer an attractive approach for mimicking the natural extracellular matrix (ECM) for tissue engineering applications. The efficacy of electrospinning is likely to depend on the interaction between cells and the geometric features and physicochemical composition of the scaffold. A major problem in electrospinning is the tendency of fibers to accumulate densely, resulting in poor porosity and small pore size. The porosity and pore sizes in the electrospun scaffolds are mainly dependent on the fiber diameter and their packing density. Here we report a method of modulating porosity in three dimensional (3D) scaffolds by simultaneously tuning the fiber diameter and the fiber packing density. Nonwoven poly(ε-caprolactone) mats were formed by electrospinning under various conditions to generate sparse or highly dense micro- and nanofibrous scaffolds and characterized for their physicochemical and biological properties. We found that microfibers with low packing density resulted in improved cell viability, proliferation and infiltration compared to tightly packed scaffolds.     

Bicomponent electrospinning to fabricate three-dimensional hydrogel-hybrid nanofibrous scaffolds with spatial fiber tortuosity

Electrospun fibrous mats have emerged as powerful tissue engineering scaffolds capable of providing highly effective and versatile physical guidance, mimicking the extracellular environment. However, electrospinning typically produces a sheet-like structure, which is a major limitation associated with current electrospinning technologies. To address this challenge, highly porous, volumetric hydrogel-hybrid fibrous scaffolds were fabricated by one Taylor cone-based side-by-side dual electrospinning of poly (ε-caprolactone) (PCL) and poly (vinyl pyrrolidone) (PVP), which possess distinct properties (i.e., hydrophobic and hydrogel properties, respectively). Immersion of the resulting scaffolds in water induced spatial tortuosity of the hydrogel PVP fibers while maintaining their aligned fibrous structures in parallel with the PCL fibers. The resulting conformational changes in the entire bicomponent fibers upon immersion in water led to volumetric expansion of the fibrous scaffolds. The spatial fiber tortuosity significantly increased the pore volumes of electrospun fibrous mats and dramatically promoted cellular infiltration into the scaffold interior both in vitro and in vivo. Harmonizing the flexible PCL fibers with the soft PVP-hydrogel layers produced highly ductile fibrous structures that could mechanically resist cellular contractile forces upon in vivo implantation. This facile dual electrospinning followed by the spatial fiber tortuosity for fabricating three-dimensional hydrogel-hybrid fibrous scaffolds will extend the use of electrospun fibers toward various tissue engineering applications.     

Fabrication of large pores in electrospun nanofibrous scaffolds for cellular infiltration: a review

In the past decade, considerable effort has been made to construct biomimetic scaffolds from electrospun nanofibers for engineering different tissues. However, one of the major concerns with electrospun nanofibrous scaffolds is that the densely arranged architecture of fibers and small pores or voids between fibers hinder efficient cellular infiltration or prevent three dimensional (3D) cellular integration with host tissue in vivo after implantation. To overcome this problem, many concepts or strategies applicable during the electrospinning or post-electrospinning procedures have been proposed to enlarge pore size of electrospun scaffolds. This article addresses the issues of pore geometry and cellular infiltration of electrospun scaffolds, and first reviews the fabrication solutions/approaches applied to achieve larger micropores in electrospun mats. The evidence and potential for fostering cellular infiltration using these improved porous scaffolds are then discussed. Finally, it is hoped that this will enable us to better exploit viable technologies or develop new ones for constructing ideal nanofibrous architecture for fulfilling specific tissue engineering needs.     

Electrospinning: applications in drug delivery and tissue engineering

Despite its long history and some preliminary work in tissue engineering nearly 30 years ago, electrospinning has not gained widespread interest as a potential polymer processing technique for applications in tissue engineering and drug delivery until the last 5-10 years. This renewed interest can be attributed to electrospinning's relative ease of use, adaptability, and the ability to fabricate fibers with diameters on the nanometer size scale. Furthermore, the electrospinning process affords the opportunity to engineer scaffolds with micro to nanoscale topography and high porosity similar to the natural extracellular matrix (ECM). The inherently high surface to volume ratio of electrospun scaffolds can enhance cell attachment, drug loading, and mass transfer properties. Various materials can be electrospun including: biodegradable, non-degradable, and natural materials. Electrospun fibers can be oriented or arranged randomly, giving control over both the bulk mechanical properties and the biological response to the scaffold. Drugs ranging from antibiotics and anticancer agents to proteins, DNA, and RNA can be incorporated into electrospun scaffolds. Suspensions containing living cells have even been electrospun successfully. The applications of electrospinning in tissue engineering and drug delivery are nearly limitless. This review summarizes the most recent and state of the art work in electrospinning and its uses in tissue engineering and drug delivery.     

Preparation and characterization of electrospun PLGA/gelatin nanofibers as a drug delivery system by emulsion electrospinning

Novel biocompatible poly(lactide-co-glycolide) (PLGA) nanofiber mats with favorable biocompatibility and good mechanical strength were prepared, which could serve as an innovative type of tissue engineering scaffold or an ideal controllable drug delivery system. Both hydrophobic and hydrophilic drugs, Cefradine and 5-fluorouracil were successfully loaded into PLGA nanofiber mats by emulsion electrospinning. The natural bioactive protein gelatin (GE) was incorporated into the nanofiber mats to improve the surface properties of the materials for cell adhesion. Nanofibrous scaffolds were characterized by scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, contact angle and tensile measurements. Emulsion electrospun fibers with GE had perfect hydrophilic and good mechanical property. The in vitro release test showed thedrugs released from emulsion electrospun fibers, which achieved lower burst release. The cells cytotoxicity experiment indicated that emulsion electrospun fibers were less toxic and tended to promote fibroblasts cells attachment and proliferation, which implied that the electrospun fibers had promising potential application in tissue engineering or drug delivery.