人工软骨支架材料、结构设计与制备技术研究进展

骨软骨是一种半透明状组织,主要功能是传递、吸收应力和减少摩擦。由于结构和功能复杂性,软骨一旦受损很难修复和再生,软骨缺损治疗仍是一大临床难题。随着再生医学蓬勃发展,组织工程人工软骨技术有望在软骨修复和治疗领域发挥重要作用。首先介绍了天然关节软骨不同分层的解剖结构和功能特征,然后重点从人工软骨支架构建材料、结构设计和制备技术等方面系统地综述了人工软骨组织工程技术的最新进展,最后讨论了人工软骨支架当前面临主要问题和未来发展方向,以期为相关研究提供参考。     

可降解水凝胶作为关节软骨修复材料的研究进展

可降解水凝胶因其良好的生物相容性和生物降解性被广泛用于关节软骨的修复和再生。本文以可降解水凝胶在软骨组织工程中的三类应用策略为主线,概述了用于原位成型可注射水凝胶的蛋白多糖类材料及纳米复合类材料;系统总结了传统工艺制造组织工程支架的优缺点及多种工艺结合的制备方法;重点归纳了近年来3D打印组织工程支架从纯软骨到骨/软骨一体化、从单层到多层的研究进展;最后分析了可降解水凝胶作为关节软骨支架材料在微观定向结构和生物活性功能化方面的局限性,并作出展望：未来开展多材料、多尺度、多诱导的高仿生梯度支架是关节软骨组织工程的一个重要研究方向。     

电纺纳米纤维构建组织工程支架研究新进展

电纺是制备纳米纤维的有效方法.纤维直径通常介于数十纳米至数微米之间,与细胞外基质中胶原等纤维支架的尺寸相近.采用天然高分子或合成高分子电纺纤维构建组织工程支架,可以仿生细胞外基质的结构乃至生物学功能,利于细胞的黏附、分化和增殖,引导组织的再生与修复,成为组织工程支架的研究热点.大量研究报道显示,电纺纳米纤维支架可以提供理想的细胞黏附、增殖和分化微环境.简要介绍了静电纺丝技术以及电纺纳米纤维的特点,重点总结了近几年来电纺纳米纤维在构建皮肤、血管、神经、骨与软骨等组织工程支架的研究进展,并展望了纳米纤维支架的应用前景.     

骨膜组织工程的研究进展

一直以来,由创伤、肿瘤切除和先天畸形引起的临界性骨缺损的临床治疗都存在极大的挑战,包括自体骨移植在内的传统骨缺损治疗方法,由于供体不足和免疫排斥反应等问题,已经不足以满足临床需求。而组织工程的发展改变了骨修复的传统治疗模式,基于人工和天然生物材料的各种组织工程复合支架被用于修复受损骨。与此同时,也有越来越多的学者认识到骨膜在骨缺损修复中的重要作用,尤其是组织工程支架的整合性和血管化。除了自体或异体骨膜移植,研究者将组织工程的理念融入到骨膜修复中,从结构和功能上模拟天然骨膜。从组织工程骨膜的不同设计理念出发,简单回顾了4类组织工程骨膜的研究进展,包括结构仿生型、微观结构仿生型、血管化型和外力刺激型,这些将为骨组织工程构建和骨膜深入研究提供理论基础并开启新的思路和方法。     

新型骨-软骨一体化修复支架材料的制备

利用可降解聚合物微球的相互粘结制备了一种新型的组织工程支架材料, 可用于软骨和软骨下骨损伤的修复。采用光学显微镜、 扫描电镜对支架的表面形貌、 内部结构进行了表征, 同时研究了支架材料的力学性能, 此外还研究了微球的粒径对支架材料孔隙率的影响。结果显示, 该材料在结构上分为乳酸-羟基乙酸共聚物(PLGA)层和PLGA/生物活性玻璃(BG)层; 材料的孔隙三维连通、 分布均匀; 采用粒径为150~200μm微球所制备的支架孔隙率为(53.37±4.39)%, 在10%的应变下材料压缩强度便已达到了0.9MPa, 显示了较强的力学性能; 随着微球粒径的变小, 材料孔隙率逐渐增大。这种微球支架在骨-软骨组织缺损修复方面有着很大的研究价值和应用价值。      

组织工程三维多孔骨支架内部微流体流场研究

组织工程支架作为培养组织的载体,能为组织提供各种微环境,是决定组织培养能否成功的关键。针对骨组织工程体外培养对支架内部微流体流场的要求,设计了包括仿生结构和螺旋结构的4种骨组织工程三维多孔支架。基于Navier-Stokes方程建立了骨支架内部流场的数学模型,利用ANSYS Fluent对骨组织工程支架内部营养液和骨细胞流动状态进行了数值模拟,分别得到了4种骨组织工程支架流场的压力分布云图、速度分布云图和剪应力变化曲线。研究结果表明,仿生结构骨支架主管道与哈佛管、浮克曼管的流速相差很大,而螺旋结构支架流体速度分布均匀;分析了壁面流体剪应力分布情况,仿生结构骨支架壁面流体剪应力偏大,且分布不均匀,而螺旋结构支架剪应力偏小,但分布均匀;通过调整边界条件与优化内部结构,流体压力、流速更均匀,流体剪应力达到0.2～0.3 Pa之间,满足人体组织生长的需要。这对骨组织工程支架的设计与应用提供一定的指导作用。     

聚氨酯软骨-骨双层复合材料的构建及性能研究

关节软骨损伤是临床上的常见病,由于其组织再生能力差,可能导致骨性关节炎的发生,因此,研究开发骨-软骨移植替代材料非常重要。目的就是设计一体化软骨-骨双层复合材料,以解决软骨与骨的整合问题。该双层复合体上层软骨材料为聚氨酯,软骨下骨为羟基磷灰石/聚氨酯复合支架材料,两层结构中引用了同一种材料——聚氨酯,将双层结构有机黏合在一起,使黏合更牢固。下层多孔HA/PU复合支架材料的孔与孔之间相互贯通,孔隙率约为83%,孔径范围分布在200～600μm。体外细胞相容性实验表明,该一体化双层复合材料为细胞的黏附、增殖以及生存活力的维持提供了有利环境。上述结果表明该双层复合材料有望用于软骨组织工程修复。     

仿生功能化骨修复材料研究

由肿瘤、炎症及各类创伤而导致的骨组织坏死、病变、缺失及骨折是临床多发病症,自体骨移植虽然是临床治疗的“金标准”,但由于供体受限而很难满足需求。通过对天然骨本身的成分、结构特性及矿化过程的模仿,应用先进材料制备技术,特别是纳米技术,对材料的组成、结构进行设计与凋控,获得仿生型骨修复材料或者对传统材料进行仿生功能化修饰,以满足临床对痫损或缺失的骨组织进行有效修复和功能重建具有重要意义。阐述了仿生功能化骨修复材料的相关研究,主要包括类骨钙磷纳米矿物的合成,有机分子摸板对纳米矿物尺寸和形貌的调控,以及仿生多孔结构支架的构建等。     

上海硅酸盐所在多功能介孔生物活性玻璃用于骨、软骨及牙周组织工程研究中取得系列重要创新进展

正骨、软骨及牙周缺损修复是目前临床上面临的最具有挑战性的问题之一,虽然组织工程方法为解决这类问题提供了新方法,但是传统的组织工程支架材料因结构与功能单一,在组织工程应用中仍然存在诸多问题。中国科学院上海硅酸盐研究所常江研究员与吴成铁研究员带领的研究小组在过去3年中,通过与昆士兰科技大学和浙江大学合作,在多功能介孔     

壳聚糖类复合材料应用于骨修复的研究进展

壳聚糖是天然多糖类高分子化合物甲壳素的脱乙酰产物,具有良好的生物相容性、可降解性和生物活性,可作为骨修复材料,并可应用于骨组织工程材料中的三维生长支架,作为种子细胞或活性生长因子的生物载体材料.综述了壳聚糖类复合材料在骨填充修复材料、骨组织工程和软骨组织工程方面应用的状况及前景.     

Three-dimensional printing of multilayered tissue engineering scaffolds

The field of tissue engineering has produced new therapies for the repair of damaged tissues and organs, utilizing biomimetic scaffolds that mirror the mechanical and biological properties of host tissue. The emergence of three-dimensional printing (3DP) technologies has enabled the fabrication of highly complex scaffolds that offer a more accurate replication of native tissue properties and architecture than previously possible. Of strong interest to tissue engineers is the construction of multilayered scaffolds that target distinct regions of complex tissues. Musculoskeletal and dental tissues in particular, such as the osteochondral unit and periodontal complex, are composed of multiple interfacing tissue types, and thus benefit from the usage of multilayered scaffold fabrication. Traditional 3DP technologies such as extrusion printing and selective laser sintering have been used for the construction of scaffolds with gradient architectures and mixed material compositions. Additionally, emerging bioprinting strategies have been used for the direct printing and spatial patterning of cells and chemical factors, capturing the complex organization found in the body. To better replicate the varied and gradated properties of larger tissues, researchers have created scaffolds composed of multiple materials spanning natural polymers, synthetic polymers, and ceramics. By utilizing high-precision 3DP techniques and judicious material selection, scaffolds can thus be designed to address the regeneration of previously challenging musculoskeletal, dental, and other heterogeneous target tissues. These multilayered 3DP strategies show great promise in the future of tissue engineering.     

Preparation of a biphasic scaffold for osteochondral tissue engineering

Tissue engineering has been developed as a prospective approach for the repair of articular cartilage defects. Engineered osteochondral implants can facilitate the fixation and integration with host tissue, and therefore promote the regeneration of osteochondral defects. A biphasic scaffold with a stratified two-layer structure for osteochondral tissue engineering was developed from biodegradable synthetic and naturally derived polymers. The upper layer of the scaffold for cartilage engineering was collagen sponge; the lower layer for bone engineering was a composite sponge of poly(DL-lactic-co-glycolic acid) (PLGA) and naturally derived collagen. The PLGA–collagen composite sponge layer had a composite structure with collagen microsponge formed in the pores of a skeleton PLGA sponge. The collagen sponge in the two respective layers was connected. Observation of the collagen/PLGA–collagen biphasic scaffold by scanning electron microscopy (SEM) demonstrated the connected stratified structure. The biphasic scaffold was used for culture of canine bone-marrow-derived mesenchymal stem cells. The cell/scaffold construct was implanted in an osteochondral defect in the knee of a one-year old beagle. Osteochondral tissue was regenerated four months after implantation. Cartilage- and bone-like tissues were formed in the respective layers. The collagen/PLGA–collagen biphasic scaffold will be useful for osteochondral tissue engineering.     

Bioactive glass scaffolds for bone tissue engineering: state of the art and future perspectives

The repair and regeneration of large bone defects resulting from disease or trauma remains a significant clinical challenge. Bioactive glass has appealing characteristics as a scaffold material for bone tissue engineering, but the application of glass scaffolds for the repair of load-bearing bone defects is often limited by their low mechanical strength and fracture toughness. This paper provides an overview of recent developments in the fabrication and mechanical properties of bioactive glass scaffolds. The review reveals the fact that mechanical strength is not a real limiting factor in the use of bioactive glass scaffolds for bone repair, an observation not often recognized by most researchers and clinicians. Scaffolds with compressive strengths comparable to those of trabecular and cortical bones have been produced by a variety of methods. The current limitations of bioactive glass scaffolds include their low fracture toughness (low resistance to fracture) and limited mechanical reliability, which have so far received little attention. Future research directions should include the development of strong and tough bioactive glass scaffolds, and their evaluation in unloaded and load-bearing bone defects in animal models.     

Personalised bone tissue engineering scaffold with controlled architecture using fractal tool paths in layered manufacturing

The scaffolds for bone tissue engineering should consider the functional requirements such as the external shape of the replacement, porosity for vessel and nutrient conduit, and stiffness in order to avoid stress shielding and to stimulate growth of the new tissue. Layered manufacturing (LM) has shown great promise in fabricating such porous bone scaffold. The present work proposes a biomimetic design and LM of patient- and site-specific controlled porosity scaffolds for optimised mechanical properties for repair and regeneration of bone. Correlation models between porosity and modulus for bone, and known biomaterials processable by LM are used to estimate the site-specific porosity requirements in the scaffold model. A novel method for generating a tool path using space-filling fractal curves eliminates representation difficulties associated with LM of porous objects. A representative study of a hydroxyapatite scaffold for a cortical bone defect site in human femur is presented to illustrate the methodology.     

Fabrication and cell affinity of biomimetic structured PLGA/articular cartilage ECM composite scaffold

An ideal scaffold for cartilage tissue engineering should be biomimetic in not only mechanical property and biochemical composition, but also the morphological structure. In this research, we fabricated a composite scaffold with oriented structure to mimic cartilage physiological morphology, where natural nanofibrous articular cartilage extracellular matrix (ACECM) was used to mimic the biochemical composition, and synthetic PLGA was used to enhance the mechanical strength of ACECM. The composite scaffold has well oriented structure and more than 89% of porosity as well as about 107 μm of average pore diameter. The composite scaffold was compared with ACECM and PLGA scaffolds. Cell proliferation test showed that the number of MSCs in ACECM and composite scaffolds was noticeably bigger than that in PLGA scaffold, which was coincident with results of SEM observation and cell viability staining. The water absorption of ACECM and composite scaffolds were 22.1 and 10.2 times respectively, which was much higher than that of PLGA scaffolds (3.8 times). The compressive modulus of composite scaffold in hydrous status was 1.03 MPa, which was near 10 times higher than that of hydrous ACECM scaffold. The aforementioned results suggested that the composite scaffold has the potential for application in cartilage tissue engineering.     

3D bioprinting of multicellular scaffolds for osteochondral regeneration

Regeneration of osteochondral tissue is of great potentialities in repairing severe osteochondral defects. However, anisotropic physiological characteristics and tissue linage difference make the regeneration of osteochondral tissue remain a huge challenge. Herein, a multicellular system based on a bilayered co-culture scaffold mimicking osteochondral tissues was successfully developed for an alternative of osteochondral regeneration via a 3D bioprinting strategy. The dual function of integrally repairing both cartilage and bone could be achieved by designing multiple-cells distribution and a cell-induced bioink containing bioceramic particles. As an important bioactive agent, the Li-Mg-Si bioceramics-containing bioink exhibited the function of simultaneously stimulating multiple cells for differentiation towards specific directions. The 3D bioprinted co-culture scaffolds showed the capacity for osteochondral tissue regeneration by inducing osteogenic and chondrogenic differentiation in vitro and accelerating the repair of severe osteochondral defects in vivo. This study offers a potential strategy for complex tissue reconstruction through bioprinting multiple tissue cells in combination of bioceramics-stimulating bioinks.     

Preparation and characterization of collagen/PLA,chitosan/PLA,and collagen/chitosan/PLA hybrid scaffolds for cartilage tissue engineering

In this study, three-dimensional (3D) porous scaffolds were developed for the repair of articular cartilage defects. Novel collagen/polylactide (PLA), chitosan/PLA, and collagen/chitosan/PLA hybrid scaffolds were fabricated by combining freeze-dried natural components and synthetic PLA mesh, where the 3D PLA mesh gives mechanical strength, and the natural polymers, collagen and/or chitosan, mimic the natural cartilage tissue environment of chondrocytes. In total, eight scaffold types were studied: four hybrid structures containing collagen and/or chitosan with PLA, and four parallel plain scaffolds with only collagen and/or chitosan. The potential of these types of scaffolds for cartilage tissue engineering applications were determined by the analysis of the microstructure, water uptake, mechanical strength, and the viability and attachment of adult bovine chondrocytes to the scaffolds. The manufacturing method used was found to be applicable for the manufacturing of hybrid scaffolds with highly porous 3D structures. All the hybrid scaffolds showed a highly porous structure with open pores throughout the scaffold. Collagen was found to bind water inside the structure in all collagen-containing scaffolds better than the chitosan-containing scaffolds, and the plain collagen scaffolds had the highest water absorption. The stiffness of the scaffold was improved by the hybrid structure compared to plain scaffolds. The cell viability and attachment was good in all scaffolds, however, the collagen hybrid scaffolds showed the best penetration of cells into the scaffold. Our results show that from the studied scaffolds the collagen/PLA hybrids are the most promising scaffolds from this group for cartilage tissue engineering.     

Electrospinning of PLGA/gelatin randomly-oriented and aligned nanofibers as potential scaffold in tissue engineering

Electrospinning technique can be used to produce the three-dimensional nanofibrous scaffold similar to natural extracellular matrix, which satisfies particular requirements of tissue engineering scaffold. Randomly-oriented and aligned poly(lactic-co-glycolic acid) (PLGA) and PLGA/gelatin biocomposite scaffolds were successfully produced by electrospinning in the present study. The resulting nanofibrous scaffolds exhibited smooth surface and high porous structure. Blending PLGA with gelatin enhanced the hydrophilicity but decreased the average fiber diameter and the mechanical properties of the scaffolds under the same electrospinning condition. The cell culture results showed that the elongation of the osteoblast on the aligned nanofibrous scaffold was parallel to the fiber arrangement and the cell number was similar to that of randomly-oriented scaffold, indicating that the aligned nanofibrous scaffold provide a beneficial approach for the bone regeneration.     

Human-like collagen/nano-hydroxyapatite scaffolds for the culture of chondrocytes

Three dimensional (3D) biodegradable porous scaffolds play a key role in cartilage tissue repair. Freeze-drying and cross-linking techniques were used to fabricate a 3D composite scaffold that combined the excellent biological characteristics of human-like collagen (HLC) and the outstanding mechanical properties of nano-hydroxyapatite (nHA). The scaffolds were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and compression tests, using Relive® Artificial Bone (RAB) scaffolds as a control. HLC/nHA scaffolds displayed homogeneous interconnected macroporous structure and could withstand a compression stress of 2.67 ± 0.37 MPa, which was higher than that of the control group. Rabbit chondrocytes were seeded on the composite porous scaffolds and cultured for 21 days. Cell/scaffold constructs were examined using SEM, histological procedures, and biochemical assays for cell proliferation and the production of glycosaminoglycans (GAGs). The results indicated that HLC/nHA porous scaffolds were capable of encouraging cell adhesion, homogeneous distribution and abundant GAG synthesis, and maintaining natural chondrocyte morphology compared to RAB scaffolds. In conclusion, the presented data warrants the further exploration of HLC/nHA scaffolds as a potential biomimetic platform for chondrocytes in cartilage tissue engineering.