Trabecular scaffolds created using micro CT guided fused deposition modeling

Free form fabrication and high resolution imaging techniques enable the creation of biomimetic tissue engineering scaffolds. A 3D CAD model of canine trabecular bone was produced via micro CT and exported to a fused deposition modeler, to produce polybutylene terephthalate (PBT) trabeculated scaffolds and four other scaffold groups of varying pore structures. The five scaffold groups were divided into subgroups (n = 6) and compression tested at two load rates (49 N/s and 294 N/s). Two groups were soaked in a 25 °C saline solution for 7 days before compression testing. Micro CT was used to compare porosity, connectivity density, and trabecular separation of each scaffold type to a canine trabecular bone sample. At 49 N/s the dry trabecular scaffolds had a compressive stiffness of 4.94 ± 1.19 MPa, similar to the simple linear small pore scaffolds and significantly more stiff (p < 0.05) than either of the complex interconnected pore scaffolds. At 294 N/s, the compressive stiffness values for all five groups roughly doubled. Soaking in saline had an insignificant effect on stiffness. The trabecular scaffolds matched bone samples in porosity; however, achieving physiologic connectivity density and trabecular separation will require further refining of scaffold processing.     

浆料粘度对纳米羟基磷灰石/聚酰胺66复合支架孔结构与力学性能的影响

浆料粘度是热诱导相分离法制备支架材料的关键因素,采用不同粘度的纳米羟基磷灰石/聚酰胺66(n-HA/PA66)复合浆料制备了相应的n-HA/PA66多孔支架,并对不同粘度浆料制备支架材料的泡孔结构和力学性能等进行了对比研究。结果表明,浆料粘度对n-HA/PA66复合多孔支架的孔径、孔径分布、孔隙率、开孔率、力学强度等性能有显著的影响。随着浆料粘度的增大,制备支架的孔径、孔隙率、开孔率逐渐减小,而力学强度却逐渐增大。当浆料粘度为330Pa.s时,制备出的n-HA/PA66复合多孔支架综合性能最好,其孔径主要分布在200～500μm,平均孔径(324±67.1)μm,孔隙率为(75±1.6)%,开孔率为(59±2.5)%,抗压强度为(2.12±0.90)MPa,能够较好地满足骨组织工程支架材料对孔径、孔隙率和力学性能的要求。     

Preparation of porous scaffold from hydroxyapatite powders

Hydroxyapatite (HA) powder was prepared by wet chemical method. The hydroxyapatite phase was stable up to 1250 °C without decomposition to beta-tricalcium phosphate. Interconnected porous hydroxyapatite scaffold resembling trabecular bone structure was developed from polymeric replica sponge method. The prepared scaffold has 60 vol.% porosity having a major fraction of ~ 50–125 μm pore diameter. The pore content, pore morphology, pore interconnectivity of scaffold and their compressive strength were dependent on the solid loading and binder content. In-vitro bioactivity and bioresorbability confirmed the feasibility of the developed scaffolds.     

Fabrication and characterization of poly-d-l-lactide/nano-hydroxyapatite composite scaffolds with poly (ethylene glycol) coating and dexamethasone releasing

The control of pore size and structure, drug release capacity, and biodegradation of scaffolds is of importance for bone tissue engineering. In this study, a technique combining polymer coagulation, cold compression molding, salt particulate leaching and drug coating method was developed to fabricate poly (ethylene glycol)/dexamethasone coated porous poly-d-l-lactide/nano-hydroxyapatite (PDLLA/nano-HAp) scaffolds. These scaffolds possess homogenous pore networks with high porosity (66-82%) and controllable pore size (200-300 μm). The compressive moduli and strength of the scaffolds after incorporation of nano-HAp were improved by 50% and 20%, respectively. The surface hydrophilicity of the scaffold was significantly improved by poly (ethylene glycol)/dexamethasone coating and nano-HAp addition, leading to a higher initial drug loading amount. The results showed that the drug release behavior of the scaffolds after 35-day immersion in water could be adjusted by varying the porosity level and by incorporation of 20 wt.% of nano-HAp.     

新型可降解钙磷骨水泥多孔支架研究

采用一种特殊的方法制备了孔径、孔隙率和孔形状可控的多孔羟基磷灰石骨水泥支架. 材料的抗压强度可达4MPa, 孔隙率可达70%, 孔与孔之间互相贯通, 大孔壁富含微孔. 细胞在材料表面黏附铺展且增殖良好, 体外模拟实验显示材料的降解速度随孔隙率的增加和Ca/P比的降低而加快, 多孔支架有优良的生物降解性和生物相容性. 该材料可用于修复骨组织缺损和作为支架材料用于组织工程.     

介孔生物活性玻璃/脱钙骨复合支架的制备及性能研究

将介孔生物活性玻璃(MBG)与脱钙骨(DB)复合, 利用浸渍法制备出MBG/DB复合支架材料. 采用红外光谱(FTIR), 扫描电镜(SEM), X射线衍射(XRD), 电子万能材料试验机等方法对牛松质骨(CB)、DB、MBG/DB复合支架进行表征. 结果表明, CB经浸酸处理后制备的DB, 孔径大小在200~600μm范围内, 孔隙率约为71%, 抗压性能比CB明显降低(1.10±0.31)MPa, 而采用浸渍法制备的复合支架, 孔隙率降为40%左右, 而压缩强度明显提高(8.49± 2.14)MPa. 体外生物活性测试表明: 复合支架具有良好的生物活性.     

In Vitro Characterizations of PLLA/β-TCP Porous Matrix Materials and RMSC-PLLA-β-TCP Composite Scaffolds

To develop a novel degradable poly (L-lactic acid)/β-tricalcium phosphate (PLLA/β-TCP) bioactive materials for bone tissueengineering, β-TCP powder was produced by a new wet process. Porous scaffolds were prepared by three steps, i.e. solventcasting, compression molding and leaching stage. Factors influencing the compressive strength and the degradation behaviorof the porous scaffold, e.g. weight fraction of pore forming agent-sodium chloride (NaCl), weight ratio of PLLA: β-TCP,the particle size of β-TCP and the porosity, were discussed in details. Rat marrow stromal cells (RMSC) were incorporatedinto the composite by tissue engineering approach. Biological and osteogenesis potential of the composite scaffold weredetermined with MTT assay, alkaline phosphatase (ALP) activity and bone osteocalcin (OCN) content evaluation. Resultsshow that PLLA/β-TCP bioactive porous scaffold has good mechanical and pore structure with adjustable compressive strengthneeded for surgery. RMSCs seeding on porous PLLA/     

复合明胶涂层对钙磷陶瓷多孔支架的增强作用

采用有机泡沫浸渍工艺制备了高孔隙率的钙磷多孔陶瓷支架, 将多孔陶瓷样品浸于明胶溶液中渗涂得到陶瓷/明胶复合支架; 采用复合明胶涂层的方法对钙磷多孔陶瓷支架进行增强处理, 在不破坏多孔支架孔隙特征的情况下, 成功地在样品的孔壁上复合了明胶涂层。复合明胶涂层提高了样品的压缩强度和压缩模量, 与未涂覆样品相比, 涂敷样品受压时的应变特性发生了明显变化。尤其是渗涂5%明胶溶液的多孔样品, 在保持高孔隙率(82.8%)的条件下其压缩强度和压缩模量分别由原来的1.04MPa 和 0.105GPa增加到5.17MPa和0.325GPa。研究结果表明, 孔壁上复合明胶涂层可以有效地增强多孔陶瓷支架。      

用于软骨和软骨下骨修复的纳米羟基磷灰石/聚乙烯醇/聚酰胺66功能梯度材料的制备和表征

利用反复冷冻-解冻法和相分离法,制备出用于软骨和软骨下骨修复的纳米羟基磷灰石(nHA)/聚乙烯醇(PVA)/聚酰胺(PA66)功能梯度材料。研究表面层PVA的力学性能和摩擦学性能,及软骨下骨nHA/PA66(m(HA)∶m(PA66)=1∶1)支架的力学性能及生物学性能。结果表明PVA拉伸强度为1.938MPa,平均摩擦系数在生理盐水及代血浆润滑条件下分别为0.076和0.085;nHA/PA66复合多孔支架孔隙率为80.93%,孔径为50～500μm,压缩强度和压缩模量分别为0.88和15.21MPa,且具有良好的生物相容性。     

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.     

Fabrication and characterization of chitosan microspheres agglomerated scaffolds for bone tissue engineering

In the presented paper authors describe a method for bone scaffolds fabrication. The technique is based on the agglomeration of chitosan microspheres. The fabrication process is complex and consists of a few steps: chitosan spheres extrusion, scaffold formation by compression followed by the spheres agglomeration and bonding with cross-linking agent (STPP, sodium tripolyphosphate). The described method allows manufacturing of porous materials with controllable shape, pore size distribution and their interconnectivity. In this technique 3D scaffold porosity can be regulated by altering spheres diameter. Authors studied influence of cross-linker concentrations and time of cross-linking process on the scaffold morphology, mechanical properties, enzymatic degradation rate (in the presence of lysozyme) and human osteoblasts response. Surface morphology and topography were evaluated by SEM. Porosity and pore interconnectivity were observed via μCT scanning. Mechanical tests showed that chitosan scaffolds perform compression characteristic (Young Modulus) similar to natural bone. Cytotoxicity established by XTT assay confirmed that most of the developed composite materials do not show toxic properties. Osteoblast adhesion and morphology were analyzed by SEM and optical microscopy.     

具有良好贯通性的颗粒造孔支架的制备及表征

支架孔隙贯通性的研究一直是多孔生物陶瓷的研究重点之一.采用石蜡球作为造孔剂, 在常规的颗粒造孔法制备多孔陶瓷支架的基础上,通过二甲苯处理以便在石蜡球间形成桥联结构, 以扩大颗粒间的接触面积,从而提高多孔陶瓷支架的孔隙贯通性. 借助扫描电镜(SEM)观察陶瓷支架的多孔结构,评价二甲苯处理石蜡球对陶瓷支架孔隙贯通性的改善效果; 采用密度法测定了陶瓷支架的孔隙率并计算其收缩率,并用成骨细胞评价陶瓷支架的细胞相容性. 结果表明,通过二甲苯的处理, 不仅改善了陶瓷支架孔隙的贯通性,而且提高了其孔隙率, 但孔隙率对陶瓷支架的收缩率无明显影响.细胞培养实验显示成骨细胞可进入多孔陶瓷支架内部, 并在材料表面正常生长,贯通性好的多孔陶瓷支架可为成骨细胞生长提供更充分的空间.     

磷灰石-硅灰石/β-磷酸三钙复合多孔支架材料的制备和表征

以磷灰石-硅灰石玻璃陶瓷(AW)粉和β-磷酸三钙(β-TCP)粉为原料. 以硬脂酸为致孔剂. 经模压成型、1170℃烧结制备磷灰石-硅灰石/β-磷酸三钙复合多孔支架材料(AW/βTCP). 采用X射线衍射(XRD)、扫描电镜(SEM)、能谱(EDS)、诱导耦合等离子体原子发射光谱(ICP-AES)等方法分析支架的晶相组成、显微结构、物理性能、生物活性和降解性. 将大鼠骨髓间充质干细胞(rMSCs)与支架体外复合培养评价支架的生物相容性. 结果表明: 所制备的AW/β-TCP支架材料的抗压强度达14.3MPa. 孔隙率达66.9%. 孔径为100～700μm. 具有良好的生物相容性、生物活性和降解性. 可作为骨组织工程支架的候选材料.     

Tissue differentiation in an in vivo bioreactor: in silico investigations of scaffold stiffness

Scaffold design remains a main challenge in tissue engineering due to the large number of requirements that need to be met in order to create functional tissues in vivo. Computer simulations of tissue differentiation within scaffolds could serve as a powerful tool in elucidating the design requirements for scaffolds in tissue engineering. In this study, a lattice-based model of a 3D porous scaffold construct derived from micro CT and a mechano-biological simulation of a bone chamber experiment were combined to investigate the effect of scaffold stiffness on tissue differentiation inside the chamber. The results indicate that higher scaffold stiffness, holding pore structure constant, enhances bone formation. This study demonstrates that a lattice approach is very suitable for modelling scaffolds in mechano-biological simulations, since it can accurately represent the micro-porous geometries of scaffolds in a 3D environment and reduce computational costs at the same time.     

基于选择性激光烧结聚己内酯/蛋壳多孔支架的制备和表征

以聚己内酯(PCL)和鸡蛋壳粉末(ES)为原材料,采用选择性激光烧结技术制备纯PCL支架和PCL/ES混合材料支架。通过显微镜观察了支架形貌,测定了各组支架的孔隙率和压缩强度。结果表明ES的加入能使支架的压缩强度有所提高,但同时孔隙率稍有降低,填充速度为1380~1880 mm/min时PCL/ES支架能取得较高的孔隙率(80%)和压缩强度(8.28 MPa),达到松质骨的要求(孔隙率≥70%,压缩强度≥8.2 MPa);差示扫描量热分析和热重分析结果表明ES的加入改善了复合支架的结晶性能和热稳定性;对粉末和支架的X射线衍射和衰减全反射傅里叶变换红外光谱检测证实了ES的成分和选择性激光烧结工艺没有破坏原材料的分子官能团;用MTT比色法测定了支架毒性试验,结果表明PCL/ES复合支架无明显毒性且具有良好的生物相容性。因此,选择性激光烧结制备的PCL/ES支架具有很好的外形可塑性和空隙结构,其良好的力学性能和生物相容性使其有望在骨组织工程支架中得到应用。     

具有复杂形状的聚ε-己内酯多孔支架的模压制备方法

通过聚ε-己内酯(PCL)支架的制备，尝试了一种制备具有复杂形状的组织工程三雏多孔支架的新方法一改进的模压／粒子浸出法，并对所得外耳状多孔支架的形态、孔结构和孔隙率进行了表征。模压针对聚ε-己内酯熔体和大量盐粒的混合物进行。该方法所得支架孔隙率高达90％以上。可望用于各种不同复杂形状的三雏多孔支架的制备。     

Porous CaP/silk composite scaffolds to repair femur defects in an osteoporotic model

The most common complication for patients with postmenopausal osteoporosis is bone-related defects and fractures. While routine medication has a high probability of undesirable side effects, new approaches have aimed to develop regeneration procedures that stimulate new bone formation while reversing bone loss. Recently, we have synthesized a new hybrid CaP/silk scaffold with a CaP-phase distribution and pore architecture better suited to facilitate cell differentiation and bone formation. The aim of the present study was to compare the involved remodeling process and therapeutic effect of porous CaP/silk composite scaffolds upon local implantation into osteoporotic defects. Wistar rats were used to induce postmenopausal osteoporotic model by bilateral ovariectomy. The pure silk and hybrid CaP/silk scaffolds were implanted into critical sized defects created in distal femoral epiphysis. After 14 and 28 days, the in vivo osteogenetic efficiency was evaluated by μCT analysis, hematoxylin and eosin staining, Safranin O staining, tartrate-resistant acid phosphatase staining, and immunohistochemical assessment. Animals with or without critical-sized defects were used as drill or blank controls, respectively. The osteoporotic defect model was well established with significantly decreased μCT parameters of BV/TV, Tb.N and increased Tb.Sp, porosity, combined with changes in histological observations. During the healing process, the critical-sized drill control defects failed to regenerate appreciable bone tissue, while more significantly increased bone formation and mineralization with dynamic scaffold degradation and decreased osteoclastic bone resorption could be detected within defects with hybrid CaP/silk scaffolds compared to pure silk scaffolds.     

聚乳酸-羟基乙酸共聚物/磷酸钙骨水泥多孔复合支架的制备

利用定向冰晶-冷冻干燥法制备了具有定向孔隙结构的磷酸钙骨水泥支架材料, 将两种具有不同降解速率的聚乳酸-羟基乙酸共聚物(PLGA) 与磷酸钙骨水泥多孔支架进行多次浸润复合, 以改善支架的力学性能。结果表明: PLGA 与支架材料复合可大大提高复合支架材料的抗压强度, 经过PLGA 二次复合后, 复合支架抗压强度可达6. 37 MPa ±0. 54 MPa 。经过PLGA 复合的支架材料保持了复合前的孔隙结构, 在孔的轴向方向上具有定向排列的开口孔隙, 这些开口孔隙的存在有利于植入初期新生组织的长入。覆盖在骨水泥基体表面的PLGA 膜可以增强基体的强度并弥补基体表面的缺陷, 充填在孔隙内部的PLGA 泡沫体可以很好地承受外加载荷, 使复合支架材料具有较好的强度和韧性。      

基于Micro-CT不同多孔结构陶瓷支架的建模及其贯通性与液流分布分析

贯通性是骨组织工程支架的重要参数, 决定包含蛋白和细胞的体液渗入和组织生长。本研究采用Micro-CT技术对三种不同工艺(球粒堆积、蜡球造孔、纤维堆积)构建的羟基磷灰石多孔支架进行断层扫描, 并从三方面研究支架的贯通性: (1)通过影像重建定量分析支架孔隙的三维贯通结构; (2)统计分析比较三种支架在贯流方向上的孔隙率变化; (3)有限元模拟支架的内部液流分布情况。结果表明, 球粒堆积支架与蜡球造孔支架孔隙率分布较均匀, 而纤维堆积支架孔隙分布较杂乱。液流模拟(流速分布)发现, 球粒堆积支架与蜡球造孔支架中液体流动均匀, 但是蜡球造孔支架孔壁近表面区域存在大量“漩涡流”, 不利于支架内细胞与液流之间的物质交换, 该结果有可能解释球粒堆积支架体内成骨性优于蜡球造孔支架的动物体内实验结果。     

Processing and degradation behavior of porous magnesium scaffold for biomedical applications

Porous magnesium has the potential to be used as degradable bone scaffolds. In this study, porous magnesium scaffolds were fabricated through powder metallurgy route utilizing spherical naphthalene particle as porogen. Porogen was removed at 120?°C for 24?h followed by sintering at 550?°C for 2?h in argon atmosphere. Micro-computed tomography (micro CT) results indicated that scaffolds have interconnected porous structure with an equivalent pore diameter of nearly 60?µm. Compressive strength of the scaffolds was found in the range of 24?±?4.54?MPa to 184?±?9.9?MPa and decreased with increasing porogen content. In vitro degradation study in phosphate buffered saline (PBS) showed that scaffold degradation behavior was governed by its porosity content. Our results indicate that modulating the porogen content we can tailor the mechanical and degradation behavior of the Mg scaffolds to the application need.