纳米复合支架结构与生物学性能

通过复合成型致孔一体技术制备纳米羟基磷灰石/聚酰胺66 (n-HA/PA66) 硬组织修复支架,采用SEM、XRD、IR和燃烧实验等测试手段对复合支架进行表征。结果表明:n-HA粒子以纳米尺度均匀分布于复合支架材料中;复合材料的两相界面为氢键键合和配位键合;支架的孔隙相互贯通,不仅有平均孔径约450 μ m的大孔,大孔壁上还富含0.5~50 μ m的微孔。动物实验证实,该纳米复合支架具有高的生物活性和好的组织相容性,能与硬组织形成骨性结合,其孔隙范围有利于骨组织、血管、骨细胞的长入,可作为硬组织修复的良好载体。      

纳米磷灰石晶体/聚酰胺复合骨组织工程支架材料的研究

采用常压共溶、共沉淀和水热处理的方法制备了纳米磷灰石晶体／聚酰胺复合骨组织工程支架材料。纳米磷灰石在复合材料中含量高达60wt％(重量比),纳米磷灰石和聚酰胺之间有化学键结合,材料的力学性能接近自然骨水平。复合材料可加工成块状多孔体,材料的孔隙率为55％-70％,平均孔径为300μm,多孔支架不仅有大孔,而且大孔壁上含有丰富微孔,是一种非常有发展前景的组织工程材料。     

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.     

多孔 n2 HA/ PA26复合材料的制备及性能

采用注塑方法制备了多孔纳米磷灰石/聚酰胺26 (n2 HA/ PA26) 复合材料 , 采用 SEM、XRD、IR、 力学性能测试考察了多孔材料的性能。结果发现 : 多孔纳米磷灰石/聚酰胺26复合材料的孔隙分布均匀 , 贯通性良好 , 孔的尺寸约为 100～700μm , 平均孔径约 300～500μm , 大孔壁上有丰富的微孔 ; 所得多孔复合材料的孔隙率可控 , 总孔隙率最高可达 881 6 %; 多孔材料的总孔隙率降低 , 则开孔率随之降低 ; 多孔纳米磷灰石/聚酰胺26 复合材料的抗压强度为 1. 1～15. 6 MPa , 压缩模量为 0. 4～1. 4 GPa ; 在总孔隙率相近的条件下 , 多孔材料的抗压强度随 n2 HA质量分数增加而升高; 发泡剂和发泡过程对组成纳米磷灰石/聚酰胺26复合材料的两组元材料的性质和结构无影响。这种多孔材料可望作为人体非承重部位的植入骨修复体和组织工程支架使用。     

纳米羟基磷灰石/聚酰胺多孔支架材料的制备及性能研究

使用多种致孔剂采用粒子沥滤法制备了纳米羟基磷灰石／聚酰胺多孔支架材料，用IR、XRD、SEM等手段对多孔复合材料的组成结构及形貌进行了表征，并检测了其物理性能指标。结果表明，复合材料中两相分散均匀，且发生了界面结合；材料的孔隙率与致孔剂的含量成正比，支架中大孔与微孔并存且相互贯通；以NaCl作致孔剂且孔隙率达到80％左右时的支架材料可以同时满足组织工程对孔隙率和力学强度的双重要求。     

羟基磷灰石/胶原蛋白/壳聚糖多孔支架的制备及性能研究

通过共滴定法合成工艺制备出羟基磷灰石/胶原蛋白粉体,以制备的羟基磷灰石/胶原蛋白粉体为原料,选用冷冻干燥成型技术,制备羟基磷灰石/胶原蛋白/壳聚糖复合多孔支架材料.研究结果表明:通过X射线衍射分析和透射电镜分析,羟基磷灰石/胶原蛋白纳米粉体中羟基磷灰石晶粒是针状的弱结晶的晶体,与天然骨中的纳米羟基磷灰石晶粒相近;羟基磷灰石/胶原蛋白/壳聚糖复合多孔支架的抗压强度、孔隙率、平均孔径可达到骨组织工程支架材料的要求,是由有机-无机三相复合、具有三维多孔结构、又有良好机械性能的具有发展潜力的骨支架材料.     

纳米非计量磷灰石/聚合物复合支架的制备和性能研究

采用快速成形法制备了孔径和孔隙率可控、大孔互相贯通的纳米缺钙羟基磷灰石(cd-HA)与聚己内酯(PCL)复合材料多孔支架,并对复合支架的微结构进行了表征.通过细胞培养和体内动物实验研究了该支架的生物学性能.结果表明:复合材料的亲水性和细胞粘附率随磷灰石含量增加而提高;成骨细胞在复合支架上的增殖明显高于纯PCL;μ-CT和组织学分析结果显示,新骨在支架的表面形成并长入其中.相互贯通的多孔支架促进了细胞的增殖和新骨长入支架内部.cd-HA/PCL复合材料支架具有很好的生物相容性,在组织工程领域中有潜在的应用前景.     

纳米羟基磷灰石／丝素蛋白多孔支架材料的制备和表征

采用硝酸钙-丝素蛋白溶液与磷酸钠反应仿生合成纳米羟基磷灰石/丝素蛋白(n-HA/SF)复合材料,并以NaHCO3和NaCl为致孔剂制备了多孔复合支架材料,采用TEM、IR、SEM和EDX对其进行了表征.结果表明,复合材料中HA的粒径在20～50nm之间,是一种CO2-3部分替代型弱结晶类骨针晶,在形貌和尺寸等方面类似于人体骨磷灰石晶体;HA和SF两相间存在强烈的键合作用,复合支架材料呈高度多孔结构,孔壁上富含微孔,孔隙间贯通性高.EDX分析结果表明,HA在有机基体中分布均匀,钙磷元素比为1.66,当复合材料和致孔剂的比例为1:0.5时,其抗压强度可达20.23MPa.     

仿生矿化法制备可降解羟基磷灰石/氧化细菌纤维素复合材料

细菌纤维素是具有天然纳米网状结构的支架材料,对其进行氧化改性后可获得可调控的降解性能。通过仿生矿化氧化改性的细菌纤维素支架,制备了可降解羟基磷灰石/氧化细菌纤维素复合骨组织工程支架材料。观察并分析了仿生矿化过程氧化细菌纤维素的降解和羟基磷灰石的形成,并通过SEM、EDS、XRD对羟基磷灰石在可降解氧化细菌纤维素支架上沉积进行了表征,矿化7天的羟基磷灰石/氧化细菌纤维素复合材料表面和内部均有磷灰石形成,测得磷灰石的钙磷比为1.75,主要为羟基磷灰石,伴有少量碳羟磷灰石。结果表明,使用仿生矿化法成功获得了一种新型可降解羟基磷灰石/氧化纤维素复合材料支架。     

不同热处理温度下纳米羟基磷灰石/聚酰胺66多孔支架制备及力学性能研究

热处理温度是热致相分离法制备多孔支架材料的关键因素。在不同热处理温度下(60℃、75℃和90℃)制备了纳米羟基磷灰石/聚酰胺66(n-HA/PA66)复合多孔支架材料。对比研究了不同热处理温度下制备的多孔支架孔隙结构、孔隙率及力学性能。结果表明:处理温度对多孔支架的孔隙结构,孔隙率,力学性能有显著的影响,随着温度的升高,多孔支架的孔隙率、平均孔径升高,贯通性改善,但弹性模量和屈服极限降低。多孔支架的热处理温度为75℃时,其孔径、孔隙率和力学性能与天然松质骨相当,是较为理想的骨组织工程支架材料。     

A 3D biodegradable protein based matrix for cartilage tissue engineering and stem cell differentiation to cartilage

A protein based 3D porous scaffold is fabricated by blending gelatin and albumin. The biomimetic biodegradable gelatin, promoted good cell adhesion and its hydrophilic nature enabled absorption of culture media. Albumin is proposed to serve as a nontoxic foaming agent and also helped to attain a hydrophobic-hydrophilic balance. The hydrophobic-hydrophilic balance and appropriate crosslinking of the scaffold avoided extensive swelling, as well as retained the stability of scaffold in culture medium for long period. The scaffold is found to be highly porous with open interconnected pores. The adequate swelling and mechanical property of the scaffold helped to withstand the loads imparted by the cells during in vitro culture. The scaffold served as a nontoxic material to monolayer of fibroblast cells and is found to be cell compatible. The suitability of scaffold for chondrocyte culture and stem cell differentiation to chondrocytes is further explored in this work. The scaffold provided appropriate environment for chondrocyte culture, resulting in deposition of cartilage specific matrix molecules that completely masked the pores of the porous scaffold. The scaffold promoted the proliferation and differentiation of mesenchymal stem cells to chondrocytes in presence of growth factors. The transforming growth factor, TGFbeta3 promoted better chondrogenic differentiation than its isoform TGFbeta1 in this scaffold.     

Electrochemistry assisted reacting deposition of hydroxyapatite in porous chitosan scaffolds

Electrochemistry assisted reacting deposition method was employed to prepare porous chitosan/hydroxyapatite (CS/HA) composite scaffold with a new design device using ion exchange membranes to separate calcium salt and phosphate solutions. The results determined from XRD and SEM indicates hydroxyapatite can be electrochemically deposited in the chitosan scaffold using the device. After electrochemistry assisted reacting deposition, the surface of the chitosan scaffold was coated with low crystalline HA, particularly at the frame edge of the scaffold. The pores in the scaffold still kept interconnected well and the deposited hydroxyapatite has a cluster microsphere shape whose size is about 3-5 μm.     

Osteogenic effect of hyaluronic acid sodium salt in the pores of a hydroxyapatite scaffold

According to previous reports, a large volume of bone marrow cells (1 × 10⁷ cells/ml) is required for bone regeneration in the pores of a scaffold in vivo. We theorized that immersion of a porous hydroxyapatite (HA) scaffold in hyaluronic acid solution would facilitate bone formation in the scaffold at 1 × 10⁶ cells/ml density of bone marrow cells. The cells were respectively seeded into pores of the cylindrical HA scaffolds with a hollow center after immersion in hyaluronic acid solution or in culture medium. The scaffolds were implanted in the dorsal subcutis of rats for 4 weeks. Thereafter, serially sectioned paraffin specimens were made and observed histologically. Bone formation was observed in many pores of HA scaffold by immersion in hyaluronic acid solution. However, there were no or less pores with new bone formation in the scaffold by immersion in culture medium. The cells were cultured with and without hyaluronic acid in vitro. There was no significant difference in bone formation in vitro with and without hyaluronic acid. The results of this study suggest that hyaluronic acid binds to the cells on the wall of three-dimensional structure and effectively promotes new bone formation.     

Morphology-controllable modeling approach for a porous scaffold structure in tissue engineering

Heterogeneous structures represent an important new frontier for twenty-first-century engineering. In this paper, based on the shape function in the finite element method, a morphology-controllable modelling approach for constructing tissue engineering (TE) bone scaffold with various irregular pores is presented. The modelling approach consists of both irregular element modelling and the whole bone scaffold modelling. Accepting the elements’ information after all-hex mesh generation as inputs, the basic pore-making element can be mapped into various irregular elements based on the shape function. In the bone scaffold modelling, the Boolean difference between the contour model of the solid entity and the pore model which can be constructed by the Boolean operation union would generate a porous bone scaffold model. Compared to the stochastic geometry method and the discrete element packing method, the bone scaffold model obtained in this paper has a continuous, smooth contour and various irregular pores. Moreover, a decrease in computational complexity is achieved in this paper.     

Genipin-crosslinked gelatin scaffolds for articular cartilage tissue engineering with a novel crosslinking method

A novel crosslinking method with directly crosslinking the gelatin gel, being cut to a disc of chosen size beforehand, for the fabrication of porous gelatin scaffold was proposed. This novel method of gel-crosslinking was compared with the traditional methods of mixing-crosslinking and scaffold-crosslinking. The structure of the scaffold fabricated by the gel-crosslinking method shows uniformly distributed and interconnected pores which can be much smaller than those made by the other two methods. All three methods have the last step as freeze-drying; nevertheless, freeze-drying once more will increase the uniformity of the structure and the interconnecting pores. Crosslinking of gelatin was carried out at room temperature with glutaraldehyde (GTA) or genipin (GP). In vitro cell culture of Wistar rat's joint chondrocytes demonstrates that the GTA-crosslinked scaffold is much worse than the GP-crosslinked one; a tissue containing collagen and glycosaminoglycan was produced in the GP-crosslinked scaffold in just 9 days after cell seeding, and a tissue with a cell distribution resembling that of the native cartilage was developed after 30 day cell culture. It was concluded that the novel method is feasible for application in articular cartilage tissue engineering.     

Microspheres leaching for scaffold porosity control

Scaffold morphology plays a key role in the development of tissue engineering constructs. The control of pore size, shape and interconnection is needed to achieve adequate nutrient transport and cell ingrowth. Several techniques are available for scaffold manufacturing, but none allows easy control of morphology and is, at the same time, applicable to a wide variety of materials. To investigate the possibility of processing a wide range polymers by solvent casting/particulate leaching with accurate control of scaffold morphology, three different porogens (gelatin microspheres, paraffin microspheres and sodium chloride crystals) were used to fabricate scaffolds from commonly employed biodegradable polymers. The outcome of processing was evaluated in terms of scaffold morphology and structure/properties relationships. Highly porous scaffolds were obtained with all porogens and well defined spherical pores resulted from microspheres leaching. Furthermore, scaffolds with spherical pores showed better mechanical performance and lower flow resistance. Cytocompatibility tests performed showed no evidence of processing residuals released from the scaffolds. Solvent casting/microspheres leaching, particularly gelatin microspheres leaching, can be used to process a large number of polymers and enables to tailor scaffold pore size, shape and interconnection, thus providing a powerful tool for material selection and optimization of scaffold morphology.     

造孔剂和发泡剂结合法制备氟化羟基磷灰石多孔支架研究

本研究采用添加造孔剂和发泡剂相结合法制备多孔氟化羟基磷灰石, 合成具有大孔与小孔套连、3D方向上分布的多孔支架。通过化学沉淀法制备了氟化羟基磷灰石(FHA)粉体, 以碳酸氢铵为发泡剂、PMMA为造孔剂, 通过烘干和烧结工艺制备孔洞均匀且相互贯通、坯体致密的多孔支架。经X射线衍射分析, 支架的相组成是FHA和β-TCP。SEM观察结果显示支架孔洞形貌规整、大孔尺寸100~400 µm, 小孔尺寸10~50 µm。以HA和β-TCP为原料对造孔方法的普适性进行验证, 并对支架孔的形成及其影响因素进行了分析。     

Indirect fabrication of gelatin scaffolds using rapid prototyping technology

Scaffold-based tissue engineering strategies often face the problem of tissues forming only within the periphery layers of the scaffold due to mass transfer issues. In the present study, we attempt to overcome this limitation by incorporating a three-dimensional (3D) interconnected network of channels within the scaffold as part of the fabrication process so as to enhance nutrient delivery and cell migration. A scaffold material with the ability to foam was also used in conjunction with this process in order to produce highly interconnected pores within the scaffold. This article describes the developmental process of an indirect fabrication approach which involves the application of rapid prototyping (RP) technology as well as the use of a foaming scaffold material to produce highly and uniformly porous scaffolds with complex channel architectures. Finally, cytotoxicity assessment confirmed that the multiple steps involved in the fabrication process did not induce toxicity within the scaffold.     

Fibrous hydrogel scaffolds with cells embedded in the fibers as a potential tissue scaffold for skin repair

A novel approach was undertaken to create a potential skin wound dressing. L929 fibroblast cells and alginate solution were simultaneously dispensed into a calcium chloride solution using a three-dimensional plotting system to manufacture a fibrous alginate scaffold with interconnected pores. These cells were then embedded in the alginate hydrogel fibers of the scaffold. A conventional scaffold with cells directly seeded on the fiber surface was used as a control. The encapsulated fibroblasts made using the co-dispensing method distributed homogeneously within the scaffold and showed the delayed formation of large cell aggregates compared to the control. The cells embedded in the hydrogel fibers also deposited more type I collagen in the extracellular matrix and expressed higher levels of fgf11 and fn1 than the control, indicating increased cellular proliferation and attachment. The results indicate that the novel co-dispensing alginate scaffold may promote skin regeneration better than the conventional directly-seeded scaffold.     

Construct of asymmetrical scaffold and primary cells for tissue engineered esophagus

Porous polymeric scaffolds have been widely employed as analogues of native extracellular matrix to create a living construct that would mimic the complexities of human tissue function in the field of tissue engineering. An asymmetrical porous 3-D substitute to be used as a scaffold for tissue engineered esophagus was fabricated using thermally induced phase separation (TIPS) method. The scaffold in which there are pores with 1–10 µm diameter on one side and ≥ 50–100 µm size on the other side and in the bulk was designed to mimic the mucosa constitute that is the most important functional layer of a normal esophagus. The cell and scaffold construct was evaluated using Hematoxylin and Eosin (H&E) staining as well as fluorescein diacetate (FDA) viable cell staining. It was found for the scaffold to be able to support the growth of primary esophageal epithelial cells on the side with micropores and fibroblasts in the scaffold bulk with large pores and good connectivity. A confluent layer of epithelial cells was observed throughout the surface with micropores, with multilayer of cells found at some locations. Clusters of fibroblasts were found on the other side as well as within the bulk of the scaffold.