组织工程三维多孔支架材料制备技术的研究现状

组织工程支架材料是组织工程成败之关键因素,制备一种既具有良好生物相容性和生物降解性,又具有,特定形状和三维连通多孔结构的支架材料是组织工程的一个重要方面.主要综述了组织工程多孔支架材料制备技术的研究现状,分析和总结了各制备技术的优缺点,并对其发展趋势进行了展望.     

静电纺丝制备组织工程支架的研究进展

静电纺丝作为一种制备纳米纤维的技术,具有效率高、成本低、易实现等优点,已经成为制备组织工程支架的主要方法之一。简要介绍了组织工程及静电纺丝的原理;综述了几种单组分高分子组织工程支架的研究进展,并总结了静电纺丝制备多组分支架的方法;最后,提出了目前采用静电纺丝法制备组织工程支架存在的主要问题,并展望了未来的研究方向。     

激光微细加工技术在医疗器材领域的应用

激光微细加工技术具有超快、超精密等特性，在医疗器材领域的应用中有着传统加工技术无可比拟的独特优势，尤其是对生物材料表面加工改性，提高材料生物相容性方面有着不可替代的作用。本文综述了近年来激光微加工技术在医疗器材制造加工领域的最新应用，着重介绍了血管支架和骨支架的结构与表面制造，生物材料表面改性与抗菌性处理等。最后对目前激光微加工技术存在的局限性做了讨论，对未来激光微加工技术在医疗器材领域的应用发展做了展望。     

连续箱梁现浇支架设计与施工控制

进入到新世纪以后,随着我国国民经济的快速发展,我国的桥梁、隧道、公路、铁路工程项目都得到了快速发展,这些行业的竞争也是日趋激烈。面对着日益严酷的竞争,设计单位在进行结构设计时,大多数都采用连续箱梁现浇支架设计,这种结构设计的方式具有以下优点:适用性强、功能多、承载能力强、效率高、加工容易、拆卸方便以及受力均匀等特点,因此在我国上个世纪90年代的工程项目中,连续箱梁现浇支架设计就已经得到了较为广泛的应用。本文便对连续箱梁现浇支架设计、连续箱梁支架预压及预拱度设置以及连续箱梁现浇支架的拆除三个方面的内容进行了详细的分析和探讨,从而详细的论述了连续箱梁现浇支架设计过程中的几个施工技术问题。     

桥梁工程现浇盖梁支架施工工艺

伴随着我国社会经济的飞速发展,桥梁施工单位也在历史的推动下不断发展进步、改革创新。对于桥梁工程飞速发展的当今社会,桥梁建设的工程技术问题越来越重要。只有不断的加强桥梁工程的建设,保障桥路方面的通畅,才能够使我国经济的发展不受限制的飞速前进。在桥路技术工程之中,现浇盖支架技术已经被广泛的运用于桥路建设的实践当中去了。本文对于在桥梁建设方面的现浇盖支架技术进行分析探讨,以便就该项技术的施工工艺做简单的介绍,为我国的桥梁工程现浇盖梁支架的发展提供相应的技术借鉴。     

高分子微球在三维细胞培养领域的应用进展

三维细胞培养能够模拟细胞在体内的形态和功能，因此成为新兴的细胞培养技术。在不同的三维细胞培养方法中，微球支架为模拟微环境下的三维空间细胞黏附、增殖和细胞相互作用提供了一种有价值的工具。其中，基于可降解高分子的微球支架因优异的生物相容性和生物降解性得到了广泛的研究。综述了基于可降解高分子微球支架的最新进展，包括天然高分子和合成高分子以及在三维细胞培养方面的应用，探讨了高分子微球支架的应用局限性和潜在的解决方法，并指明了其未来发展方向。     

冻干支架孔隙形态的影响因素

随着组织工程学的发展，真空冻干燥技术（冻干技术）在构筑三维可生物降解聚合物支架中得到了新的应用，并体现出操作简便、支架形态可控、清洁安全等特点。通过样品预冻过程数值分析，结合国外冷冻干燥构筑多孔聚合物支架的实验研究，分析影响冻干支架孔隙形态的主要因素，讨论真空冷冻干燥支架孔隙形态的控制途径。     

可注射型天然高分子软骨组织支架材料

作为理想的组织工程支架材料，可注射水凝胶材料受到医学和材料学领域科学家的广泛关注，而天然高分子材料由于具有良好的生物相容性和安全性，在这一领域备受青昧。综述了胶原、纤维蛋白和海藻酸盐在用于可注射型软骨组织支架材料方面的特征和研究现状，展望了这一领域的发展。     

新型钛合金血管内支架研究

钛合金血管内支架由钛合金管经激光雕刻而成，此类支架血管壁之间是面接触，能够提供较高的径向支撑强度．对新型钛合金血管内支架的加工、表面处理、性能测试、生物学评价等4个方面做了系统研究．激光雕刻后的钛合金血管支架通过机械、电化学等方法进行表面处理后，经测试，得出：钛合金血管内支架柔韧性好、支撑力强，回缩率低，整体性能达标，且具有优良的生物相容性，再狭窄率低，符合现有国际支架的标准。     

浅析液压支架的发展趋势

液压支架作为综合机械化采煤作业中非常重要的一项设备,在采煤作业中具有非常重要的作用。近年来在科学技术的快速发展下,我国液压支架取得了较快的发展,许多方面已达到国际领先水平,有效的推动矿产行业的快速发展。本文从液压支架的发展入手,分析了国内液压支架与国外技术的差距,并进一步对液压支架的发展前景进行了具体的阐述。     

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.     

聚乳酸组织工程支架表面涂覆钙磷盐的工艺研究

提出了以聚乳酸／钙磷盐／胶原的骨组织工程支架快速成形制造的材料系统，对比了两种在聚乳酸(PLA)表面涂覆钙磷盐的工艺．一种是将聚乳酸组织工程支架浸泡在模拟体液中采用平衡反应法沉积钙磷盐；另一种是在聚乳酸薄膜上采用非平衡反应法沉积钙磷盐；系统地研究了沉积时间和沉积量、钙磷摩尔比和相结构演变的关系；通过控制反应时间和调整反应物配比获得磷酸四钙(TetCP)-PLA和无定形磷酸钙(ACP)—PLA等材料组合；并对所获得的复合材料进行生物相容性试验．对比试验证明细胞在材料表面生长良好，采用两种方法涂覆钙磷盐均改进了聚乳酸的生物相容性．     

A comparison study of different physical treatments on cartilage matrix derived porous scaffolds for tissue engineering applications

Native cartilage matrix derived (CMD) scaffolds from various animal and human sources have drawn attention in cartilage tissue engineering due to the demonstrable presence of bioactive components. Different chemical and physical treatments have been employed to enhance the micro-architecture of CMD scaffolds. In this study we have assessed the typical effects of physical cross-linking methods, namely ultraviolet (UV) light, dehydrothermal (DHT) treatment, and combinations of them on bovine articular CMD porous scaffolds with three different matrix concentrations (5%, 15% and 30%) to assess the relative strengths of each treatment. Our findings suggest that UV and UV–DHT treatments on 15% CMD scaffolds can yield architecturally optimal scaffolds for cartilage tissue engineering.     

Image processing and fractal box counting: user-assisted method for multi-scale porous scaffold characterization

Image analysis has gained new effort in the scientific community due to the chance of investigating morphological properties of three dimensional structures starting from their bi-dimensional gray-scale representation. Such ability makes it particularly interesting for tissue engineering (TE) purposes. Indeed, the capability of obtaining and interpreting images of tissue scaffolds, extracting morphological and structural information, is essential to the characterization and design of engineered porous systems. In this work, the traditional image analysis approach has been coupled with a probabilistic based percolation method to outline a general procedure for analysing tissue scaffold SEM micrographs. To this aim a case study constituted by PCL multi-scaled porous scaffolds was adopted. Moreover, the resulting data were compared with the outputs of conventionally used techniques, such as mercury intrusion porosimetry. Results indicate that image processing methods well fit the porosity features of PCL scaffolds, overcoming the limits of the more invasive porosimetry techniques. Also the cut off resolution of such IP methods was discussed. Moreover, the fractal dimension of percolating clusters, within the pore populations, was addressed as a good indication of the interconnection degree of PCL bi-modal scaffolds. Such findings represent (i) the bases for a novel approach complementary to the conventional experimental procedure used for the morphological analysis of TE scaffolds, in particular offering a valid method for the analysis of soft materials (i.e., gels); also (ii) providing a new perspective for further studies integrating to the structural and morphological data, fluid-dynamics and transport properties modelling.     

Polyelectrolyte-complex nanostructured fibrous scaffolds for tissue engineering

In the current work, polyelectrolyte complex (PEC) fibrous scaffolds for tissue engineering have been synthesized and a mechanism of their formation has been investigated. The scaffolds are synthesized using polygalacturonic acid and chitosan using the freeze drying methodology. Highly interconnected pores of sizes in the range of 5–20 µm are observed in the scaffolds. The thickness of the fibers was found to be in the range of 1–2 µm. Individual fibers have a nanogranular structure as observed using AFM imaging. In these scaffolds, PEC nanoparticles assemble together at the interface of ice crystals during freeze drying process. Further investigation shows that the freezing temperature and concentration have a remarkable effect on structure of scaffolds. Biocompatibility studies show that scaffold containing chitosan, polygalacturonic acid and hydroxyapatite promotes cell adhesion and proliferation. On the other hand, cells on scaffolds fabricated without hydroxyapatite nanoparticles showed poor adhesion.     

Inverse Opal Scaffolds and Their Biomedical Applications

Three‐dimensional porous scaffolds play a pivotal role in tissue engineering and regenerative medicine by functioning as biomimetic substrates to manipulate cellular behaviors. While many techniques have been developed to fabricate porous scaffolds, most of them rely on stochastic processes that typically result in scaffolds with pores uncontrolled in terms of size, structure, and interconnectivity, greatly limiting their use in tissue regeneration. Inverse opal scaffolds, in contrast, possess uniform pores inheriting from the template comprised of a closely packed lattice of monodispersed microspheres. The key parameters of such scaffolds, including architecture, pore structure, porosity, and interconnectivity, can all be made uniform across the same sample and among different samples. In conjunction with a tight control over pore sizes, inverse opal scaffolds have found widespread use in biomedical applications. In this review, we provide a detailed discussion on this new class of advanced materials. After a brief introduction to their history and fabrication, we highlight the unique advantages of inverse opal scaffolds over their non‐uniform counterparts. We then showcase their broad applications in tissue engineering and regenerative medicine, followed by a summary and perspective on future directions.     

A novel porous scaffold fabrication technique for epithelial and endothelial tissue engineering

Porous scaffolds have the ability to minimize transport barriers for both two- (2D) and three-dimensional tissue engineering. However, current porous scaffolds may be non-ideal for 2D tissues such as epithelium due to inherent fabrication-based characteristics. While 2D tissues require porosity to support molecular transport, pores must be small enough to prevent cell migration into the scaffold in order to avoid non-epithelial tissue architecture and compromised function. Though electrospun meshes are the most popular porous scaffolds used today, their heterogeneous pore size and intense topography may be poorly-suited for epithelium. Porous scaffolds produced using other methods have similar unavoidable limitations, frequently involving insufficient pore resolution and control, which make them incompatible with 2D tissues. In addition, many of these techniques require an entirely new round of process development in order to change material or pore size. Herein we describe “pore casting,” a fabrication method that produces flat scaffolds with deterministic pore shape, size, and location that can be easily altered to accommodate new materials or pore dimensions. As proof-of-concept, pore-cast poly(ε-caprolactone) (PCL) scaffolds were fabricated and compared to electrospun PCL in vitro using canine kidney epithelium, human colon epithelium, and human umbilical vein endothelium. All cell types demonstrated improved morphology and function on pore-cast scaffolds, likely due to reduced topography and universally small pore size. These results suggest that pore casting is an attractive option for creating 2D tissue engineering scaffolds, especially when the application may benefit from well-controlled pore size or architecture.     

A comparative study of the chondrogenic potential between synthetic and natural scaffolds in an in vivo bioreactor

Abstract

The clinical demand for cartilage tissue engineering is potentially large for reconstruction defects resulting from congenital deformities or degenerative disease due to limited donor sites for autologous tissue and donor site morbidities. Cartilage tissue engineering has been successfully applied to the medical field: a scaffold pre-cultured with chondrocytes was used prior to implantation in an animal model. We have developed a surgical approach in which tissues are engineered by implantation with a vascular pedicle as an in vivo bioreactor in bone and adipose tissue engineering. Collagen type II, chitosan, poly(lactic-co-glycolic acid) (PLGA) and polycaprolactone (PCL) were four commonly applied scaffolds in cartilage tissue engineering. To expand the application of the same animal model in cartilage tissue engineering, these four scaffolds were selected and compared for their ability to generate cartilage with chondrocytes in the same model with an in vivo bioreactor. Gene expression and immunohistochemistry staining methods were used to evaluate the chondrogenesis and osteogenesis of specimens. The result showed that the PLGA and PCL scaffolds exhibited better chondrogenesis than chitosan and type II collagen in the in vivo bioreactor. Among these four scaffolds, the PCL scaffold presented the most significant result of chondrogenesis embedded around the vascular pedicle in the long-term culture incubation phase.     

Biomedical applications of magneto-responsive scaffolds

Stimuli-responsive biomaterials, capable of responding on-demand to changes in their local environment, have become a subject of interest in the field of regenerative medicine. Magneto-responsive biomaterials, which can be manipulated spatiotemporally via an external magnetic field, have emerged as promising candidates as active scaffolds for advanced drug delivery and tissue regeneration applications. These specialized biomaterials can be synthesized by physically and/or chemically incorporating magnetic nanoparticles into the biomaterial structure. However, despite their promising impact on the future of regenerative medicine, magneto-responsive biomaterials still have several limitations that need to be overcome before they can be implemented clinically in a reliable manner, as predicting their behavior and biocompatibility remains an ongoing challenge. This review article will focus on discussing the current fabrication methods used to synthesize magneto-responsive materials, efforts to predict and characterize magneto-responsive biomaterial behavior, and the application of magneto-responsive biomaterials as controlled drug delivery systems, tissue engineering scaffolds, and artificial muscles.     

Prototypes for Bone Implant Scaffolds Designed via Topology Optimization and Manufactured by Solid Freeform Fabrication

The linking of computational design with precision solid freeform fabrication has tremendous potential for producing tissue scaffolds with tailored properties. We consider a new approach to optimizing the architecture of scaffolds based on jointly maximizing scaffold stiffness and diffusive transport in the interconnected pores. The stiffness of the scaffolds is matched to that of bone by choosing a suitable scaffold porosity. Moreover, the templates can be scaled to achieve target pore sizes whilst preserving their elastic and diffusive properties. The resultant structures have two major design benefits. First, the scaffolds do not have directions of low stiffness. In contrast, the Young's modulus of conventional layered‐grid designs can be 86% less under diagonally‐aligned loads than under axis‐aligned loads. Second, the mass of the scaffold is used efficiently throughout the structure rather than being clumped in non load‐bearing regions. We fabricate prototypes of the implants using selective laser melting and test their elastic properties. Excellent agreement between theory and experiment provides important confirmation of the viability of this route to scaffold design and fabrication.