组织工程多孔支架材料制备技术的研究进展

组织工程多孔支架材料作为组织工程学的三大要素之一,除本身的性质外,支架材料的形状、孔径大小和孔隙率都直接影响着种子细胞的黏附、增殖和分化,因此如何制备具有高孔隙率、孔径大小合适且内部联通的多孔支架材料.为种子细胞的生长提供良好的微环境是非常重要的.回顾了近年来发展的组织工程多孔支架材料制备技术:纤维粘接法、乳液冷冻干燥法、溶液浇注,沥滤法、气体发泡法、热致相分离法及静电纺丝法.并重点介绍了目前国内外研究较多的快速成形技术;总结分析认为各种基本制备技术的联合应用和具备结构高度可控性、个体化制备特点的快速成形技术将是今后组织工程多孔支架材料制备技术的发展方向.     

组织工程用高度多孔生物可降解支架的制备

多孔性生物可降解支架材料的选择和制备是组织工程技术成功运用的关键。除了考虑材料的化学性能 ,材料的物理性能如孔隙率、孔的尺寸以及用于细胞粘附的表面积等也极其重要。本文综述了制备多孔性生物可降解支架的几种不同方法 :纤维粘接、溶液浇铸 /粒子沥滤、熔融成型、气体发泡、相分离 /乳化、热致凝胶化与其它方法结合制备纳米级纤维细胞外基质和聚合物微球聚集法 ;并从孔隙率、孔的尺寸以及对促进细胞和组织生长等方面对上述方法进行了比较     

聚乙烯醇及其复合材料在组织工程支架中的应用

背景：聚乙烯醇是具有良好生物相容性和生物降解特性的聚合物,因其水溶性、成膜性、乳化性、胶黏性,而且无味无毒,被广泛用于临床领域。目的：综述聚乙烯醇及其复合材料在骨、软骨、皮肤、血管等组织工程支架中的应用。方法：由第一作者检索2000年1月至2011年12月中国知网数据库、1980年1月至2012年12月Pubmed数据库及 Elsevier数据库中,有关聚乙烯醇及其复合材料在骨、软骨、皮肤、血管等组织工程支架中应用的文章,中文关键词为 “聚乙烯醇,复合材料,组织工程支架”,英文关键词为 “Poly (vinyl alcohol),composite material, tissue engineering scaffold”。结果与结论：虽然聚乙烯醇及其复合材料还存在强度不够高、植入后有并发症等缺点,但这类材料具有良好的生物相容性和生物可降解特性,在组织工程中的应用从实验室到临床前研究都有很大的进展。对于其修复的长期效果还需要进一步深入研究。通过对材料表面进行修饰,改善细胞与支架材料的相互作用;通过模拟细胞生长微环境,制备仿生材料,提高材料的亲水性、对细胞的黏附性,促进细胞的分化增殖;构建具有可控三维多孔结构的支架,并赋予其控制释放细胞生长因子等功能,更好地仿生天然细胞外基质的结构和功能;制备出降解速度与机械强度能够完全适应组织再生需要的支架,研制复合、仿生材料是今后支架材料研究的主要方向。     

Optimization and evaluation of silk fibroin-chitosan freeze-dried porous scaffolds for cartilage tissue engineering application

Silk fibroin/chitosan blend has been reported to be an attractive biomaterial that provides a 3D porous structure with controllable pore size and mechanical property suitable for tissue engineering applications. However, there is no systematic study for optimizing the ratio of silk fibroin (SF) and chitosan (CS) which seems to influence the scaffold property to a great extent. The present research, therefore, investigates the effect of blend ratio of SF and CS on scaffold property and establishes the optimum value of blend ratio. Among the various blends, the scaffolds with blend ratio of SF/CS (80:20) were found to be superior. The scaffold possesses pore size in the range 71–210 μm and porosity of 82.2 ± 1.3%. The compressive strength of the scaffold was measured as 190 ± 0.2 kPa. The cell supportive property of the scaffold in terms of cell attachment, cell viability, and proliferation was confirmed by cell culture study using mesenchymal stem cells derived from umbilical cord blood. Furthermore, the assessment of glycosaminoglycan secretion on the scaffolds indicates its potentiality toward cartilage tissue regeneration.     

牙髓牙本质组织工程生物支架材料的研究进展

背景：组织工程方法中选择合适的支架是关键性的步骤。 目的：回顾分析牙髓牙本质组织工程中支架材料的应用研究。 方法：由第一作者检索1993至2012年 PubMed数据及万方数据库有关牙髓牙本质组织工程中支架材料应用研究等方面的文献。 结果与结论：在牙髓牙本质组织工程中有包括天然生物、人工合成材料和复合材料在内的大量生物材料可供选择,每一种材料都有各自的生物学特点。其中胶原、聚酯、羟基磷灰石等是研究较多的支架材料。自组装多肽水凝胶是由氨基酸制成的新型支架材料,满足理想牙髓牙本质组织工程支架材料的大部分要求,是一种前景广阔的牙髓牙本质组织工程支架材料。     

Biodegradable porous scaffolds for tissue engineering

 Three-dimensional scaffolds play an important role in tissue engineering as an adhesive substrate for implanted cells and a physical support to guide the formation of new organs. The scaffolds should facilitate cell adhesion, promote cell growth, allow the retention of differentiated cell functions, and be biocompatible, biodegradable, highly porous with a large surface-to-volume ratio, mechanically strong, and malleable. A number of biodegradable three-dimensional scaffolds have been developed for tissue engineering. This paper reviews some of the recent events in the development of these scaffolds. Received: March 6, 2002     

Electrospun scaffolds for tissue engineering of vascular grafts

There is a growing demand for off-the-shelf tissue engineered vascular grafts (TEVGs) for the replacement or bypass of damaged arteries in various cardiovascular diseases. Scaffolds from the decellularized tissue skeletons to biopolymers and biodegradable synthetic polymers have been used for fabricating TEVGs. However, several issues have not yet been resolved, which include the inability to mimic the mechanical properties of native tissues, and the ability for long-term patency and growth required for in vivo function. Electrospinning is a popular technique for the production of scaffolds that has the potential to address these issues. However, its application to human TEVGs has not yet been achieved. This review provides an overview of tubular scaffolds that have been prepared by electrospinning with potential for TEVG applications.     

Solvent-free polymer/bioceramic scaffolds for bone tissue engineering: fabrication,analysis, and cell growth

This study examines the potential use of porous polycaprolactone (PCL) and polycaprolocatone/hydroxyapatite (PCL/HA) scaffolds fabricated through melt molding and porogen leaching for bone tissue engineering. While eliminating organic solvents is desirable, the process steps proposed in this study for uniformly dispersing HA particles (~5?μm in size) within the scaffold can also contribute to homogeneous properties for these porous composites. Poly(ethylene oxide) (PEO) was chosen as a porogen due to its similar density and melting point as PCL. Pore size of the scaffold was controlled by limiting the size of PCL and PEO particles used in fabrication. The percent of HA in the fabricated scaffolds was quantified by thermogravimetric analysis (TGA). Mechanical testing was used to compare the modulus of the scaffolds to that of bone, and the pore size distribution was examined with microcomputed tomography (μCT). Scanning electron microscopy (SEM) was used to examine the effect on scaffold morphology caused by the addition of HA particles. Both μCT and SEM results showed that HA could be incorporated into PCL scaffolds without negatively affecting scaffold morphology or pore formation. Energy-dispersive X-ray spectroscopy (EDS) and elemental mapping demonstrated a uniform distribution of HA within PCL/HA scaffolds. Murine calvaria-derived MC3T3-E1 cells were used to determine whether cells could attach on scaffolds and grow for up to 21 days. SEM images revealed an increase in cell attachment with the incorporation of HA into the scaffolds. Similarly, DNA content analysis showed a higher cell adhesion to PCL/HA scaffolds.     

纳米纤维支架的制备及其在组织工程皮肤中的应用

本文通过综述现阶段纳米纤维支架的制备方法、可用材料及制备后的生物功能修饰等方面的研究进展,为设计真正意义的组织工程皮肤纳米纤维支架提供理论帮助。多聚物纳米纤维支架能够提供三维空间结构,并且能够调节细胞行为,具有传递生物分子的潜能,因此它们在组织工程应用中具有广泛的前景。现在能应用多种方法及材料制备纳米纤维结构,但是通过现有的方法和材料还不能将纳米纤维的所有优点完全体现出来,并构建成功一个真正意义上的纳米纤维三维支架结构。所以对纳米纤维支架制备技术的不断改进和对应用的材料体系的深入了解,将对未来临床成功地应用聚合纳米纤维组织工程支架奠定坚实基础。     

Versatile fabrication of vascularizable scaffolds for large tissue engineering in bioreactor

Despite significant progresses were achieved in tissue engineering over the last 20 years, a number of unsolved problems still remain. One of the most relevant issues is the lack of a proper vascularization that is limiting the size of the engineered tissues to smaller than clinically relevant dimensions. Sacrificial molding holds great promise to engineered construct with perfusable vascular architectures, but there is still the need to develop more versatile approaches able to be independent of the nature and dimensions of the construct. In this work we developed a versatile sacrificial molding technique for fabricating bulk, cell-laden and porous scaffolds with embedded vascular fluidic networks. These branched fluidic architectures are created by highly resistant thermoplastic sacrificial templates, made of poly(vinyl alcohol), representing a remarkable progress in manufacturability and scalability. The obtained architecture, when perfused in bioreactor, has shown to prevent the formation of a necrotic core in thick cell-laden constructs and enabled the rapid fabrication of hierarchically branched endothelium. In conclusion we demonstrate a novel strategy towards the engineering of vascularized thick tissues through the integration of the PVA-based microfabrication sacrificial approach and perfusion bioreactors. This approach may be able to scale current engineered tissues to clinically relevant dimensions, opening the way to their widespread clinical applications.     

胶原-壳聚糖复合材料作为组织工程支架的研究

目的 本研究考察壳聚糖对于胶原膜理化性质的影响,选择合适比例的胶原-壳聚糖复合膜作为骨髓间充质干细胞（BMSCs）载体.方法 胶原溶涨液中添加一定比例的壳聚糖,交联并冷冻干燥制备多孔组织工程支架,研究壳聚糖对胶原膜形态学、孔隙率、机械强度、降解特性等理化性质的影响,并初步探讨了胶原-壳聚糖材料作为组织工程三维支架材料与BMSCs的相容性.结果 制备的胶原-壳聚糖支架孔径分布均匀;相对于单纯胶原海绵支架,胶原-壳聚糖复合材料支架降低体外降解速度,提高支架材料的力学性能,稳定支架的结构.BMSCs种植于胶原-壳聚糖（mCol∶mCS=9∶1）支架14 d时,SEM观察到细胞通过微绒毛与支架纤维复合,细胞相容性好.结论 胶原-壳聚糖复合支架有良好的细胞相容性,作为BMSCs诱导体外支架材料具有好的研究前景.     

Development and evaluation of cross-linked collagen-hydroxyapatite scaffolds for tissue engineering

This study examines the tissue engineering potential of type I collagen cross-linked in the presence of hydroxyapatite (HAp). Scaffolds were prepared by controlled freezing followed by lyophilization of composite mixtures of collagen and HAp in acetic acid, followed by cross-linking with 0.3% glutaraldehyde. Scaffolds of three ratios were prepared, corresponding to collagen/HAp ratios of 1:2, 1:4, and 1:6. The scaffolds were evaluated for their microstructure, chemical and physical properties, swelling behavior, mechanical strength, biodegradability hemocompatability, cytocompatibility, and histopathology following subcutaneous implantation in Sprague Dawley rats. The collagen/HAp matrices showed a smaller pore size of 10–40?μm compared to 50–100?μm for pure collagen scaffolds. Pure collagen showed a mechanical strength of 0.25?MPa, and the value almost doubled for cross-linked composites with collagen/HAp ratio 1:6. The improvement in mechanical strength corresponded to a decrease in swelling and enzymatic degradation (measured by resistance to collagenases). FTIR spectra results in conjunction with scanning electron micrographs showed that cross-linking in the presence of HAp did not significantly alter the structure of collagen. MTT assay and calcein AM staining revealed prominent and healthy growth of mesenchymal stem cells in both the pure collagen as well as collagen:HAp composites of ratio 1:2. In vivo implantation in Sprague Dawley rats showed an initial acute inflammatory response during days 3 and 7, followed by a chronic, macrophage-mediated inflammatory response on days 14 and 28. Overall, a cross-linked collagen/HAp composite scaffold of ratio 1:2 was identified as having potential for further development in tissue engineering.     

神经组织工程支架材料的研究进展

神经组织工程运用于中枢神经损伤与疾病治疗,用以恢复病变或损伤的中枢神经系统的解剖结构与功能,神经支架材料发挥支撑与营养作用。对神经组织工程中支架材料的研究现状进行综述,并提出面临的问题及今后的研究方向。     

快速成型方法制备组织工程支架的研究与应用

背景：快速成型是基于材料堆积法,结合计算机、数控、激光和材料技术于一体的高新制造技术。 目的：综述快速成型技术在组织工程支架制备中的应用。 方法：由第一作者检索万方数据库、中国知网数据库和Elsevier Science Direct Online有关支架材料的生物力学性能、支架材料发展前景及快速成型技术在支架材料制备领域中应用研究等方面的文献。 结果与结论：快速成型技术应用于组织工程支架的制备已经越来越成熟,快速成型技术不但克服了传统制造方法中存在的支架复杂外形制造困难和内部微结构无法控制的缺陷,而且还可以通过有限元分析预先对支架的结构进行优化,以实现改善支架机械强度等某些特殊的要求。但是,由于组织器官的特殊性和排外性及细胞的黏附条件,不但要从结构上改善支架,而且需要快速成型技术与具有组织相容性及可降解的材料相结合,使支架植入生物体后,细胞能更好地增殖和分化,促进组织再生,修复缺损组织。     

Bone tissue engineering with porous hydroxyapatite ceramics

The main principle of bone tissue engineering strategy is to use an osteoconductive porous scaffold in combination with osteoinductive molecules or osteogenic cells. The requirements for a scaffold in bone regeneration are: (1) biocompatibility, (2) osteoconductivity, (3) interconnected porous structure, (4) appropriate mechanical strength, and (5) biodegradability. We recently developed a fully interconnected porous hydroxyapatite (IP-CHA) by adopting the “form-gel” technique. IP-CHA has a three-dimensional structure with spherical pores of uniform size that are interconnected by window-like holes; the material also demonstrated adequate compression strength. In animal experiments, IP-CHA showed superior osteoconduction, with the majority of pores filled with newly formed bone. The interconnected porous structure facilitates bone tissue engineering by allowing the introduction of bone cells, osteotropic agents, or vasculature into the pores. In this article, we review the accumulated data on bone tissue engineering using the novel scaffold, focusing especially on new techniques in combination with bone morphogenetic protein (BMP) or mesenchymal stem cells.     

提高骨组织工程支架材料生物相容性的关键影响因素

骨组织工程领域除了对支架材料本身的构成和性能加以研究之外，其研究范围还包括：对支架材料的孔径、孔隙率及三维相通性的研究；种子细胞的筛选、生物活性因子的参与以及生物复合材料的构建等相关因素的研究，这些因素对支架材料的生物相容性以及体内的骨传导性和骨诱导性都至关重要。从这些方面人手，有可能使骨组织工程支架材料的发展取得长足的进步。     

Preparation of a pure autologous biodegradable fibrin matrix for tissue engineering

Parallel to the growing role of tissue engineering, the need for cell embedding materials, which allow cells to stabilise in a three-dimensional distribution, has increased. Although several substances have been tested, fibrin is thus far the only one that permits the clinical application of cultured tissue. To date, can cause severe immunological side effects. The objective of this study was to explore the practicability of obtaining autologous thrombin from a single patient in an adequate concentration and amount. Fibrinogen was cryoprecipitated from 200 ml of freshly-frozen plasma. Thrombin was isolated from the supernatant through ionexchange chromatography. The thrombin was first bound to Sephadex A-50 and then eluated using 2ml of a salt buffer (2.0M NaCl in 0.015M trisodiumcitrate, pH 7.0). The activity of the thrombin (51 NIH ml⁻¹ to 414 NIH ml⁻¹) reached levels comparable to those in commercially available fibrin glues (4–500 NIH ml⁻¹). The study has shown that it is possible to obtain a sufficient amount of autologous thrombin from a single donor to create a fibrin matrix of high efficiency without the risk of immunological and infectious side effects.     

Design of scaffolds for blood vessel tissue engineering using a multi-layering electrospinning technique

Aiming to develop a scaffold architecture mimicking morphological and mechanically that of a blood vessel, a sequential multi-layering electrospinning (ME) was performed on a rotating mandrel-type collector. A bi-layered tubular scaffold composed of a stiff and oriented PLA outside fibrous layer and a pliable and randomly oriented PCL fibrous inner layer (PLA/PCL) was fabricated. Control over the level of fibre orientation of the different layers was achieved through the rotation speed of the collector. The structural and mechanical properties of the scaffolds were examined using scanning electron microscopy (SEM) and tensile testing. To assess their capability to support cell attachment, proliferation and migration, 3T3 mouse fibroblasts and later human venous myofibroblasts (HVS) were cultured, expanded and seeded on the scaffolds. In both cases, the cell-polymer constructs were cultured under static conditions for up to 4 weeks. Environmental-scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), histological examination and biochemical assays for cell proliferation (DNA) and extracellular matrix production (collagen and glycosaminoglycans) were performed. The findings suggest the feasibility of ME to design scaffolds with a hierarchical organization through a layer-by-layer process and control over fibre orientation. The resulting scaffolds achieved the desirable levels of pliability (elastic up to 10% strain) and proved to be capable to promote cell growth and proliferation. The electrospun PLA/PCL bi-layered tube presents appropriate characteristics to be considered a candidate scaffold for blood vessel tissue engineering.     

聚乙烯醇-壳聚糖-胶原组织工程支架的研究

目的 以聚乙烯醇（PVA）、壳聚糖（Cs）和胶原（Col）为主要原料制备PVA-Cs—Col复合支架,并研究其作为组织工程支架材料的可行性。方法 把聚乙烯醇、壳聚糖和胶原按一定配比复合,测定复合材料的含水率、膨胀率和力学性能,扫描电镜观察材料横截面的组织形态。结果 不同分子量PVA与不同质量的cs和Col复合,得到的复合支架材料湿态抗张强度为5．70MPa,含水率在60．15％-72．50％,膨胀率在185．33％～317．57％。不同配比的复合支架具有不同的内部组织形态结构。结论 PVA—Cs—Col复合支架材料具有较高的含水率和适宜的膨胀率,内部孔洞丰富,Cs：PVA：Col的质量比为30：15：0．20时,复合支架综合性能较佳,适合用于组织工程支架材料。