Bone tissue engineering in a rotating bioreactor using a microcarrier matrix system

A novel approach was utilized to grow in vitro mineralized bone tissue using lighter-than-water, polymeric scaffolds in a high aspect ratio rotating bioreactor. We have adapted polymer microencapsulation methods for the formation of hollow, lighter-than-water microcarriers of degradable poly(lactic-co-glycolic acid). Scaffolds were fabricated by sintering together lighter-than-water microcarriers from 500 to 860 microm in diameter to create a fully interconnected, three-dimensional network with an average pore size of 187 microm and aggregate density of 0.65 g/mL. Motion in the rotating bioreactor was characterized by numerical simulation and by direct measurement using an in situ particle tracking system. Scaffold constructs established a near circular trajectory in the fluid medium with a terminal velocity of 98 mm/s while avoiding collision with the bioreactor wall. Preliminary cell culture studies on these scaffolds show that osteoblast-like cells readily attached to microcarrier scaffolds using controlled seeding conditions with an average cell density of 6.5 x 10(4) cells/cm(2). The maximum shear stress imparted to attached cells was estimated to be 3.9 dynes/cm(2). In addition, cells cultured in vitro on these lighter-than-water scaffolds retained their osteoblastic phenotype and showed significant increases in alkaline phosphatase expression and alizarin red staining by day 7 as compared with statically cultured controls.     

Fabrication and characterization of novel nano- and micro-HA/PCL composite scaffolds using a modified rapid prototyping process

Novel three-dimensional scaffolds consisting of nano- and microsized hydroxyapatite (HA)/poly(epsilon-caprolactone) (PCL) composite were fabricated using a modified rapid-prototyping (RP) technique for bone tissue engineering applications. The size of the nano-HA ranged from 20 to 90 nm, whereas that of the micro-HA ranged from 20 to 80 microm. The scaffold macropores were well interconnected, with a porosity of 72-73% and a pore size of 500 microm. The compressive modulus of the nano-HA/PCL and micro-HA/PCL scaffolds was 3.187 +/- 0.06 and 1.345 +/- 0.05 MPa, respectively. The higher modulus of the nano-HA/PCL composite (n-HPC) was to be likely caused by a dispersion strengthening effect. The attachment and proliferation of MG-63 cells on n-HPC were better than that on the micro-HA/PCL composite (m-HPC) scaffold. The n-HPC was more hydrophilic than the m-HPC because of the greater surface area of HA exposed to the scaffold surface. This may give rise to better cell attachment and proliferation. Bioactive n-HA/PCL composite scaffold prepared using a modified RP technique has a potential application in bone tissue engineering.     

A comparative study of shear stresses in collagen-glycosaminoglycan and calcium phosphate scaffolds in bone tissue-engineering bioreactors

The increasing demand for bone grafts, combined with their limited availability and potential risks, has led to much new research in bone tissue engineering. Current strategies of bone tissue engineering commonly use cell-seeded scaffolds and flow perfusion bioreactors to stimulate the cells to produce bone tissue suitable for implantation into the patient's body. The aim of this study was to quantify and compare the wall shear stresses in two bone tissue engineering scaffold types (collagen-glycosaminoglycan (CG) and calcium phosphate) exposed to fluid flow in a perfusion bioreactor. Based on micro-computed tomography images, three-dimensional numerical computational fluid dynamics (CFD) models of the two scaffold types were developed to calculate the wall shear stresses within the scaffolds. For a given flow rate (normalized according to the cross-sectional area of the scaffolds), shear stress was 2.8 times as high in the CG as in the calcium-phosphate scaffold. This is due to the differences in scaffold geometry, particularly the pore size (CG pore size approximately 96 microm, calcium phosphate pore size approximately 350 microm). The numerically obtained results were compared with those from an analytical method that researchers use widely experimentalists to determine perfusion flow rates in bioreactors. Our CFD simulations revealed that the cells in both scaffold types were exposed to a wide range of wall shear stresses throughout the scaffolds and that the analytical method predicted shear stresses 12% to 21% greater than those predicted using the CFD method. This study demonstrated that the wall shear stresses in calcium phosphate scaffolds (745.2 mPa) are approximately 40 times as high as in CG scaffolds (19.4 mPa) when flow rates are applied that have been experimentally used to stimulate the release of prostaglandin E(2). These findings indicate the importance of using accurate computational models to estimate shear stress and determine experimental conditions in perfusion bioreactors for tissue engineering.     

Design, fabrication, and characterization of a composite scaffold for bone tissue engineering

Poly(lactide-co-glycolide) (PLGA) scaffolds have been successfully used in bone tissue engineering, with or without hydroxyapatite (HA) and with a macroporosity given either by simple PLGA sphere packaging and/or by leaching out NaCl. The objective of this work was the optimization of the design parameters for bone tissue engineering scaffolds made by sintering microspheres of PLGA, HA nanocrystals for matrix reinforcement and osteoconduction, and salt crystals for macroporosity and control of matrix pore size. Microsphere fabrication by a single-emulsion and solvent evaporation technique was first optimized to obtain a high yield of PLGA microspheres with a diameter between 80 and 300 microm. The influence of the sintering process and matrix composition on the scaffold structure was then evaluated morphologically and mechanically. Three scaffold types were tested for biocompatibility by culturing with human fibroblasts for up to 14 days. The most important parameters to obtain microspheres with the selected diameter range were the viscosity ratio of the dispersed phase to the continuous phase and the relative volume fraction of the 2 phases. The Young's modulus and the ultimate strength of the sintered matrices ranged between 168-265 MPa and 6-17 MPa, respectively, within the range for trabecular bone. Biocompatibility was demonstrated by fibroblast adhesion, proliferation, and spreading throughout the matrix. This work builds upon previous work of the PLGA/HA sintering technique to give design criteria for fabricating a bone tissue engineered matrix with optimized morphological, functional, and biological properties to fit the requirements of bone replacements.     

Effects of common sterilization methods on the structure and properties of poly(D,L lactic-co-glycolic acid) scaffolds

While methods for the production of scaffolds with the appropriate mechanical properties and architecture for tissue engineering are attracting much attention, the effects of subsequent sterilization processes on the scaffold properties have often been overlooked. This study sought to determine the effects of sterilization with ethanol, peracetic acid, ultraviolet irradiation, and antibiotic solution on the structure of 50:50 (mol:mol) 65:35, and 85:15 poly(D,L-lactic-co-glycolic acid [PLGA]) flat-sheet and hollow-fiber scaffolds. All methods resulted in scaffold sterilization, but scanning electron microscopy revealed deformations to the scaffold surface for all treatments. The extent of surface damage increased with treatment duration. This was further investigated by measurement of pore sizes, water flux, breaking strain, and Young's modulus. External pore size and water flux was found to be increased by all treatments in the following order: ethanol (largest), antibiotics, ultraviolet light, and peracetic acid. Pore sizes were 0.25 to 0.17 microm and water flux ranged from 0.01 kg x m(-2) x s(-1) to 3.34 kg x m(-2) x s(-1). For all samples, the Young's modulus was 1.0 to 31.1 MPa and breaking strain was 1.2 to 2.4 MPa. The results of this study suggest that antibiotic treatment shows the most potential to sterilize PLGA hollow fibers for tissue engineering.     

Accurately shaped tooth bud cell-derived mineralized tissue formation on silk scaffolds

Based on the successful use of silk scaffolds in bone tissue engineering, we examined their utility for mineralized dental tissue engineering. Four types of hexafluoroisopropanol (HFIP) silk scaffolds-(250 and 550 microm diameter pores, with or without arginine-glycine-aspartic acid (RGD) peptide) were seeded with cultured 4-day postnatal rat tooth bud cells and grown in the rat omentum for 20 weeks. Analyses of harvested implants revealed the formation of bioengineered mineralized tissue that was most robust in 550 microm pore RGD-containing scaffolds and least robust in 250 microm pore sized scaffolds without RGD. The size and shape of the silk scaffold pores appeared to guide mineralized tissue formation, as revealed using polarized light imaging of collagen fiber alignment along the scaffold surfaces. This study is the first to characterize bioengineered tissues generated from tooth bud cells seeded onto silk scaffolds and indicates that silk scaffolds may be useful in forming mineralized osteodentin of specified sizes and shapes.     

Mechanical properties of electrospun fibrinogen structures

Fibrin and fibrinogen have a well-established track record in tissue engineering due to their innate ability to induce improved cellular interaction and subsequent scaffold remodeling compared to synthetic scaffolds. Use of fibrinogen as a primary scaffold component, however, has been limited by traditional processing techniques that render scaffolds with insufficient mechanical properties. The goal of this study was to demonstrate, based on mechanical properties, that electrospun fibrinogen overcomes these limitations and can be successful as a tissue engineering scaffold or wound dressing. Electrospun fibrinogen scaffolds were characterized for fiber diameter and pore area and subsequently tested for uniaxial mechanical properties while dry and hydrated. In addition, uniaxial mechanical testing was conducted on scaffolds treated to regulate scaffold degradation in serum-containing media by supplementing the media with aprotinin or cross-linking the scaffolds with glutaraldehyde vapor. A linear relationship between electrospinning solution concentration and measured fiber diameter was seen; fiber diameters ranged from 120 to 610 nm over electrospinning concentrations of 80 to 140 mg/ml fibrinogen, respectively. Pore areas ranged from 1.3 microm(2) to 13 microm(2) over the same fibrinogen concentrations. Aprotinin in the culture media inhibited scaffold degradation in a predictable fashion, but glutaraldehyde vapor fixation produced less reliable results as evidenced by mechanical property testing. In conclusion, the mechanical characteristics of electrospun fibrinogen strongly support its potential use as a tissue engineering scaffold or wound dressing.     

Cartilage tissue engineering on the surface of a novel gelatin-calcium-phosphate biphasic scaffold in a double-chamber bioreactor

Tissue engineering is a new approach to articular cartilage repair; however, the integration of the engineered cartilage into the host subchondral bone is a major problem in osteochondral injury. The aim of the present work, therefore, was to make a tissue-engineered osteochondral construct from a novel biphasic scaffold in a newly designed double-chamber bioreactor. This bioreactor was designed to coculture chondrocytes and osteoblasts simultaneously. The aim of this study was to prove that engineered cartilage could be formed with the use of this biphasic scaffold. The scaffold was constructed from gelatin and a calcium-phosphate block made from calcined bovine bone. The cartilage part of the scaffold had a uniform pore size of about 180 microm and approximate porosity of 75%, with the trabecular pattern preserved in the bony part of the scaffold. The biphasic scaffolds were seeded with porcine chondrocytes and cultured in a double-chamber bioreactor for 2 or 4 weeks. The chondrocytes were homogeneously distributed in the gelatin part of the scaffold, and secretion of the extracellular matrix was demonstrated histologically. The chondrocytes retained their phenotype after 4 weeks of culture, as proven immunohistochemically. After 4 weeks of culture, hyaline-like cartilage with lacuna formation could be clearly seen in the gelatin scaffold on the surface of the calcium phosphate. The results show that this biphasic scaffold can support cartilage formation on a calcium-phosphate surface in a double-chamber bioreactor, and it seems reasonable to suggest that there is potential for further application in osteochondral tissue engineering.     

In vitro assessment of cell penetration into porous hydroxyapatite scaffolds with a central aligned channel

There is a clinical need for synthetic scaffolds that promote bone regeneration. A common problem encountered when using scaffolds in tissue engineering is the rapid formation of tissue on the outer edge of the scaffold whilst the tissue in the centre becomes necrotic. To address this, the scaffold design should improve nutrient and cell transfer to the scaffold centre. In this study, hydroxyapatite scaffolds with random, open porosity (average pore size of 282+/-11microm, average interconnecting window size of 72+/-4microm) were manufactured using a modified slip-casting methodology with a single aligned channel inserted into the centre. By varying the aligned channel diameter, a series of scaffolds with channel diameters ranging from 170 to 421microm were produced. These scaffolds were seeded with human osteosarcoma (HOS TE85) cells and cultured for 8 days. Analysis of cell penetration into the aligned channels revealed that cell coverage increased with increasing channel diameter; from 22+/-3% in the 170microm diameter channel to 38+/-6% coverage in the 421microm channel. Cell penetration into the middle section of the 421microm diameter channel (average cell area coverage 121x10(3)+/-32x10(3)microm(2)) was significantly greater than that observed within the 170microm channel (average cell area coverage 26x10(3)+/-6x10(3)microm(2)). In addition, the data presented demonstrates that the minimum channel (or pore) diameter required for cell penetration into such scaffolds is approximately 80microm. These results will direct the development of scaffolds with aligned macroarchitecture for tissue engineering bone.     

Optimising bioactive glass scaffolds for bone tissue engineering

A 3D scaffold has been developed that has the potential to fulfil the criteria for an ideal scaffold for bone tissue engineering. Sol-gel derived bioactive glasses of the 70S30C (70 mol% SiO2, 30 mol% CaO) composition have been foamed to produce 3D bioactive scaffolds with hierarchical interconnected pore morphologies similar to trabecular bone. The scaffolds consist of a hierarchical pore network with macropores in excess of 500 microm connected by pore windows with diameters in excess of 100 microm, which is thought to be the minimum pore diameter required for tissue ingrowth and vasularisation in the human body. The scaffolds also have textural porosity in the mesopore range (10-20 nm). The scaffolds were sintered at 600, 700, 800 and 1000 degrees C. As sintering temperature was increased to 800 degrees C the compressive strength increased from 0.34 to 2.26 MPa due to a thickening of the pore walls and a reduction in the textural porosity. The compressive strength is in the range of that of trabecular bone (2-12 MPa). Importantly, the modal interconnected pore diameter (98 microm) was still suitable for tissue engineering applications and bioactivity is maintained. Bioactive glass foam scaffolds sintered at 800 degrees C for 2 h fulfill the criteria for an ideal scaffold for tissue engineering applications.     

Poly(propylene fumarate) reinforced dicalcium phosphate dihydrate cement composites for bone tissue engineering

Calcium phosphate cements have many desirable properties for bone tissue engineering, including osteoconductivity, resorbability, and amenability to rapid prototyping-based methods for scaffold fabrication. In this study, we show that dicalcium phosphate dihydrate (DCPD) cements, which are highly resorbable but also inherently weak and brittle, can be reinforced with poly(propylene fumarate) (PPF) to produce strong composites with mechanical properties suitable for bone tissue engineering. Characterization of DCPD-PPF composites revealed significant improvements in mechanical properties for cements with a 1.0 powder to liquid ratio. Compared with nonreinforced controls, flexural strength improved from 1.80 ± 0.19 MPa to 16.14 ± 1.70 MPa, flexural modulus increased from 1073.01 ± 158.40 MPa to 1303.91 ± 110.41 MPa, maximum displacement during testing increased from 0.11 ± 0.04 mm to 0.51 ± 0.09 mm, and work of fracture improved from 2.74 ± 0.78 J/m(2) to 249.21 ± 81.64 J/m(2) . To demonstrate the utility of our approach for scaffold fabrication, 3D macroporous scaffolds were prepared with rapid prototyping technology. Compressive testing revealed that PPF reinforcement increased scaffold strength from 0.31 ± 0.06 MPa to 7.48 ± 0.77 MPa. Finally, 3D PPF-DCPD scaffolds were implanted into calvarial defects in rabbits for 6 weeks. Although the addition of mesenchymal stem cells to the scaffolds did not significantly improve the extent of regeneration, numerous bone nodules with active osteoblasts were observed within the scaffold pores, especially in the peripheral regions. Overall, the results of this study suggest that PPF-DCPD composites may be promising scaffold materials for bone tissue engineering.     

Synthetic scaffold morphology controls human dermal connective tissue formation

Engineering tissues in bioreactors is often hampered by disproportionate tissue formation at the surface of scaffolds. This hinders nutrient flow and retards cell proliferation and tissue formation inside the scaffold. The objective of this study was to optimize scaffold morphology to prevent this from happening and to determine the optimal scaffold geometric values for connective tissue engineering. After comparing lyophilized crosslinked collagen, compression molded/salt leached PEGT/PBT copolymer and collagen-PEGT/PBT hybrid scaffolds, the PEGT/PBT scaffold was selected for optimization. Geometric parameters were determined using SEM, microcomputed tomography, and flow permeability measurements. Fibroblast were seeded and cultured under dynamic flow conditions for 2 weeks. Cell numbers were determined using CyQuant DNA assay, and tissue distribution was visualized in H&E- and Sirius Red-stained sections. Scaffolds 0.5 and 1.5 mm thick showed bridged connected tissue from top-to-bottom, whereas 4-mm-thick scaffolds only revealed tissue ingrowth until a maximum depth of 0.6-0.8 mm. Rapid prototyped scaffold were used to assess the maximal void space (pore size) that still could be filled with tissue. Tissue bridging between fibers was only found at fiber distances < or =401 +/- 60 microm, whereas filling of void spaces in 3D-deposited scaffolds only occurred at distances < or =273 +/- 55 microm. PEGT/PBT scaffolds having similar optimal porosities, but different average interconnected pore sizes of 142 +/- 50, 160 +/- 56 to 191 +/- 69 microm showed comparable seeding efficiencies at day 1, but after 2 weeks the total cell numbers were significantly higher in the scaffolds with intermediate and high interconnectivity. However, only scaffolds with an intermediate interconnectivity revealed homogenous tissue formation throughout the scaffold with complete filling of all pores. In conclusion, significant amount of connective tissue was formed within 14 days using a dynamic culture process that filled all void spaces of a PEGT/PBT scaffolds with the following geometric parameters: thickness 1.5-1.6 mm, pore size range 90-360 microm, and average interconnecting pore size of 160 +/- 56 microm.     

Comparative effects of scaffold pore size, pore volume, and total void volume on cranial bone healing patterns using microsphere-based scaffolds

Bony craniofacial deficits resulting from injury, disease, or birth defects remain a considerable clinical challenge. In this study, microsphere-based scaffold fabrication methods were use to study the respective effects of scaffold pore size, open pore volume, and total void volume fraction on osseous tissue infiltration and bone regeneration in a critical size rat cranial defect. To compare the healing effects of these parameters, three different scaffolds types were fabricated: solid 100 microm spheres, solid 500 microm spheres, and hollow 500 microm spheres. These constructs were implanted into surgically created rat calvarial defects. By 90-days post op, results of micro computed tomography (CT) analysis showed that all scaffolds generated similar amounts of new bone which was significantly greater than untreated controls. Interestingly, the spatial distribution of new bone within the defect area varied by scaffold group. MicroCT and histological analysis demonstrated healing restricted to the dural side in the hollow 500 microm group, whereas the solid 500 microm group demonstrated healing along the dural side and within the center of the defect. Solid 100 microm groups demonstrated healing along the dural layer, periosteal layer, and within the center of the defect. These results suggest that pore size and closed void volume may both play important roles in scaffold degradation patterns and associated bone healing.     

Crosslinked poly(epsilon-caprolactone/D,L-lactide)/bioactive glass composite scaffolds for bone tissue engineering

A series of elastic polymer and composite scaffolds for bone tissue engineering applications were designed. Two crosslinked copolymer matrices with 90/10 and 30/70 mol % of epsilon-caprolactone (CL) and D,L-lactide (DLLA) were prepared with porosities from 45 to 85 vol % and their mechanical and degradation properties were tested. Corresponding composite scaffolds with 20-50 wt % of particulate bioactive glass (BAG) were also characterized. Compressive modulus of polymer scaffolds ranged from 190+/-10 to 900+/-90 kPa. Lactide rich scaffolds absorbed up to 290 wt % of water in 4 weeks and mainly lost their mechanical properties. Caprolactone rich scaffolds absorbed no more than 110 wt % of water in 12 weeks and kept their mechanical integrity. Polymer and composite scaffolds prepared with P(CL/DLLA 90/10) matrix and 60 vol % porosity were further analyzed in simulated body fluid and in osteoblast culture. Cell growth was compromised inside the 2 mm thick three-dimensional scaffold specimens as a static culture model was used. However, composite scaffolds with BAG showed increased osteoblast adhesion and mineralization when compared to neat polymer scaffolds.     

The bone formation in vitro and mandibular defect repair using PLGA porous scaffolds

Highly porous scaffolds of poly(lactide-co-glycolide) (PLGA) were prepared by solution-casting/salt-leaching method. The in vitro degradation behavior of PLGA scaffold was investigated by measuring the change of normalized weight, water absorption, pH, and molecular weight during degradation period. Mesenchymal stem cells (MSCs) were seeded and cultured in three-dimensional PLGA scaffolds to fabricate in vitro tissue engineering bone, which was investigated by cell morphology, cell number and deposition of mineralized matrix. The proliferation of seeded MSCs and their differentiated function were demonstrated by experimental results. To compare the reconstructive functions of different groups, mandibular defect repair of rabbit was made with PLGA/MSCs tissue engineering bone, control PLGA scaffold, and blank group without scaffold. Histopathologic methods were used to estimate the reconstructive functions. The result suggests that it is feasible to regenerate bone tissue in vitro using PLGA foams with pore size ranging from 100-250 microm as scaffolding for the transplantation of MSCs, and the PLGA/MSCs tissue engineering bone can greatly promote cell growth and have better healing functions for mandibular defect repair. The defect can be completely recuperated after 3 months with PLGA/MSCs tissue engineering bone, and the contrastive experiments show that the defects could not be repaired with blank PLGA scaffold. PLGA/MSCs tissue engineering bone has great potential as appropriate replacement for successful repair of bone defect.     

新型组织工程椎间盘纤维环支架的制备与性能检测

背景：以组织工程技术修复退变椎间盘,目前的研究多集中在如何修复摘除的髓核组织,然而髓核组织工程方法无法完整重建椎间盘的结构和功能,所以相应的纤维环组织工程被认为是组织工程椎间盘治疗策略的主要限制因素之一。 目的：制备天然猪脱细胞脱钙骨基质明胶,并验证其作为组织工程椎间盘纤维支架的可行性。 方法：取猪股骨近端松质骨,用环钻钻取直径10 mm、内径5 mm、厚3 mm的中空环状骨,高压水枪冲洗,进行脱脂、脱钙、脱细胞等相关处理,制成环状的支架材料。对材料进行大体、组织学、光镜、扫描电镜观察,并对支架的吸水率、孔隙率、生物力学参数等进行检测。分离培养犬骨髓间充质干细胞,采用MTT法分析支架浸提液毒性。 结果与结论：支架为乳白色,中空环状,质地柔软的多孔结构。苏木精-伊红染色示组织无细胞结构残留。光镜及扫描电镜示支架孔隙均匀,孔隙相通,平均孔径为(401.4±13.1) μm,孔隙率为(62.12±1.52)%,吸水率为(409.77±11.34)%。生物力学结果示支架的弹性模量为(47.75±6.32) kPa。MTT法显示不同浓度支架浸提液与对照 DMEM 培养液吸光度值比较,差异无显著性意义(P > 0.05),支架无细胞毒性。提示猪脱细胞脱钙骨基质明胶去细胞彻底,具有良好的孔径、孔隙率及生物力学强度,并且无毒,具备良好的生物相容性,可作为组织工程椎间盘纤维环支架材料。     

Computational study of culture conditions and nutrient supply in a hollow membrane sheet bioreactor for large-scale bone tissue engineering

Successful bone tissue culture in a large implant is still a challenge. We have previously developed a porous hollow membrane sheet (HMSh) for tissue engineering applications (Afra Hadjizadeh and Davod Mohebbi-Kalhori, J Biomed. Mater. Res. Part A [2]). This study aims to investigate culture conditions and nutrient supply in a bioreactor made of HMSh. For this purpose, hydrodynamic and mass transport behavior in the newly proposed hollow membrane sheet bioreactor including a lumen region and porous membrane (scaffold) for supporting and feeding cells with a grooved section for accommodating gel-cell matrix was numerically studied. A finite element method was used for solving the governing equations in both homogenous and porous media. Furthermore, the cell resistance and waste production have been included in a 3D mathematical model. The influences of different bioreactor design parameters and the scaffold properties which determine the HMSh bioreactor performance and various operating conditions were discussed in detail. The obtained results illustrated that the novel scaffold can be employed in the large-scale applications in bone tissue engineering.     

Flow Perfusion Culture of Marrow Stromal Cells Seeded on Porous Biphasic Calcium Phosphate Ceramics

Calcium phosphate ceramics have been widely used for filling bone defects to aid in the regeneration of new bone tissue. Addition of osteogenic cells to porous ceramic scaffolds may accelerate the bone repair process. This study demonstrates the feasibility of culturing marrow stromal cells (MSCs) on porous biphasic calcium phosphate ceramic scaffolds in a flow perfusion bioreactor. The flow of medium through the scaffold porosity benefits cell differentiation by enhancing nutrient transport to the scaffold interior and by providing mechanical stimulation to cells in the form of fluid shear. Primary rat MSCs were seeded onto porous ceramic (60% hydroxyapatite, 40% β-tricalcium phosphate) scaffolds, cultured for up to 16 days in static or flow perfusion conditions, and assessed for osteoblastic differentiation. Cells were distributed throughout the entire scaffold by 16 days of flow perfusion culture whereas they were located only along the scaffold perimeter in static culture. At all culture times, flow perfused constructs demonstrated greater osteoblastic differentiation than statically cultured constructs as evidenced by alkaline phosphatase activity, osteopontin secretion into the culture medium, and histological evaluation. These results demonstrate the feasibility and benefit of culturing cell/ceramic constructs in a flow perfusion bioreactor for bone tissue engineering applications.     

制备软骨组织工程支架的方法

背景：软骨组织工程支架作为软骨细胞外基质的替代物,其外形和孔结构对实现其作用和功能具有非常重要的意义。 目的：回顾目前若干种常用软骨组织工程中三维多孔支架的制备方法。 方法：由第一作者检索2000至2013年PubMed数据库,ELSEVIER SCIENCEDIRECT、万方数据库、中国知网数据库。英文检索词为“Cartilage tissue engineering;scaffolds;fabrication”,中文检索词为“软骨组织工程;制备方法;支架材料;多孔支架”。 结果与结论：制备软骨组织工程支架的方法有相分离/冷冻干燥法、水凝胶技术、快速成型技术、静电纺丝法、溶剂浇铸/粒子沥滤法及气体发泡法等。目前研究发现,支架中孔径的大小对组织的重建有着直接的影响,孔径为100-250 μm的孔有益于骨及软骨组织的再生。通过溶液浇铸/粒子沥滤法、气体发泡法所制备的支架孔径大小在这一范围内,因此比较适合用于骨、软骨组织工程支架的构建。研究人员通常将多种方法结合起来,以期能制备出生物和力学性能方面更加仿生的组织工程多孔支架。中国组织工程研究杂志出版内容重点：生物材料;骨生物材料; 口腔生物材料; 纳米材料; 缓释材料; 材料相容性;组织工程全文链接：