A novel bioactive porous CaSiO3 scaffold for bone tissue engineering

The aim of this study was to fabricate bioactive porous CaSiO3 scaffolds and examine their effects on proliferation and differentiation of osteoblast-like cells. In this study, porous CaSiO3 scaffolds were obtained by sintering a ceramic slip-coated polymer foam at 1350 degrees C. X-ray diffraction (XRD) of the scaffolds indicated that the products were essentially pure alpha-CaSiO3. The obtained scaffolds had a well-interconnected porous structure with pore sizes ranging from several micrometers to more than 100 microm and porosities of 88.5 +/- 2.8%. The in vitro bioactivity of the scaffolds was investigated by soaking them in simulated body fluid (SBF) for 7 days and then characterizing them by scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) analysis. The results indicated that hydroxyapatite (HAp) was formed on the surface of the scaffolds. In addition, the scaffolds were incubated in Ringer's solution at 37 degrees C to study the in vitro degradation by measurement of weight loss after incubation, which showed that the CaSiO3 scaffolds were degradable. The cellular responses to the scaffolds were assessed in terms of cell proliferation and differentiation. Osteoblast-like cells were seeded into the CaSiO3 scaffolds. SEM observations showed that there was significant cell adhesion, as the cells spread and grew in the scaffolds. In addition, the proliferation rate and alkaline phosphatase (ALP) activity of the cells in the scaffolds were improved as compared to the controls. These studies demonstrate initial in vitro cell compatibility and their potential application to bone tissue engineering.     

In vivo evaluation of a porous hydroxyapatite/poly-DL-lactide composite for bone tissue engineering

As reported previously, a porous composite of uncalcined hydroxyapatite (u-HA) and poly-DL-lactide (PDLLA) showed excellent osteoconductivity and biodegradability as a bone substitute in rabbit model. In this study, to investigate the usefulness of this composite as a scaffold loaded with cells, we estimated whether this material showed osteogenesis on implantation to extraosseous site. On loading with syngeneic bone marrow cells and implantation into rat dorsal subcutaneous tissue, osteogenesis with enchondral ossification was seen both on and in the material at 3 weeks after implantation. The osteogenesis in the u-HA/PDLLA had progressed, and newly formed bone tissue was found in the material by 6 weeks. To investigate the osteoinductive properties of the material, we implanted this porous composite material into extraosseous canine dorsal muscle. At 8 weeks, osteogenesis was seen in the pores of the material. Newly formed bone could be observed adjacent to the material. In addition, cuboidal osteoblasts adjacent to the newly formed bone were evident. Neither cartilage nor chondrocytes were found. These results might indicate that the material induced osteogenesis by intramembranous ossification. Conversely, similar porous PDLLA did not induce osteogenesis during the observation period. Therefore, porous HA/PDLLA, which has osteoconductive and osteoinductive properties, might be a useful material for use as a bone substitute and cellular scaffold.     

In vivo bone tissue engineering using mesenchymal stem cells on a novel electrospun nanofibrous scaffold

The objective of this study was to assess bone formation from mesenchymal stem cells (MSCs) on a novel nanofibrous scaffold in a rat model. A highly porous, degradable poly(epsilon-caprolactone) (PCL) scaffold with an extracellular matrix-like topography was produced by electrostatic fiber spinning. MSCs derived from the bone marrow of neonatal rats were cultured, expanded, and seeded on the scaffolds. The cell-polymer constructs were cultured with osteogenic supplements in a rotating bioreactor for 4 weeks, and subsequently implanted in the omenta of rats for 4 weeks. The constructs were explanted and characterized by histology, immunohistochemistry, and scanning electron microscopy. The constructs maintained the size and shape of the original scaffolds. Morphologically, the constructs were rigid and had a bone-like appearance. Cells and extracellular matrix (ECM) formation were observed throughout the constructs. In addition, mineralization and type I collagen were also detected. This study establishes the ability to develop bone grafts on electrospun nanofibrous scaffolds in a well-vascularized site using MSCs.     

In vivo evaluation of a multiphased scaffold designed for orthopaedic interface tissue engineering and soft tissue-to-bone integration

Achieving functional graft integration with subchondral bone poses a significant challenge for orthopaedic soft tissue repair and reconstruction. Soft tissues such as the anterior cruciate ligament (ACL) integrate with bone through a fibrocartilage interface, which minimizes stress concentrations and mediates load transfer between soft and hard tissues. We propose that biological fixation can be achieved by regenerating this fibrocartilage interface on biological or synthetic ACL grafts. This study focuses on the in vivo evaluation of a stratified scaffold predesigned to mimic the multitissue transition found at the ACL-to-bone interface. Specifically, the scaffold consists of three distinct yet continuous phases: Phase A for ligament formation, Phase B for the interface, and Phase C for the bone region. Interface-relevant cell types, specifically fibroblasts, chondrocytes, and osteoblasts, will be tri-cultured on this scaffold, and the formation of cell type- and phase-specific matrix heterogeneity as well as fibrocartilage formation will be evaluated over 8 weeks in a subcutaneous athymic rat model. Acellular scaffolds as well as scaffolds co-cultured with fibroblasts and osteoblasts will serve as controls. It was found that the triphasic scaffold supported multilineage cellular interactions as well as tissue infiltration and abundant matrix production in vivo. In addition, controlled phase-specific matrix heterogeneity was induced on the scaffold, with distinct mineral and fibrocartilage-like tissue regions formed in the tri-cultured group. Cell seeding had a positive effect on both host infiltration and matrix elaboration, which also translated into increased mechanical properties in the seeded groups compared to the acellular controls. In summary, the biomimetic and multiphasic design coupled with spatial control of cell distribution enables multitissue regeneration on the stratified scaffold, and demonstrates the potential for regenerating the interface between soft tissue grafts and bone.     

In vitro and in vivo evaluation of a novel nanosize hydroxyapatite particles/poly(ester-urethane) composite scaffold for bone tissue engineering

Scaffolds for bone tissue engineering should provide an osteoconductive surface to promote the ingrowth of new bone after implantation into bone defects. This may be achieved by hydroxyapatite loading of distinct scaffold biomaterials. Herein, we analyzed the in vitro and in vivo properties of a novel nanosize hydroxyapatite particles/poly(ester-urethane) (nHA/PU) composite scaffold which was prepared by a salt leaching–phase inverse process. Microtomography, scanning electron microscopy and X-ray spectroscopy analyses demonstrated the capability of the material processing to create a three-dimensional porous PU scaffold with nHA on the surface. Compared to nHA-free PU scaffolds (control), this modified scaffold type induced a significant increase in in vitro adsorption of model proteins. In vivo analysis of the inflammatory and angiogenic host tissue response to implanted nHA/PU scaffolds in the dorsal skinfold chamber model indicated that the incorporation of nHA particles into the scaffold material did not affect biocompatibility and vascularization when compared to control scaffolds. Thus, nHA/PU composite scaffolds represent a promising new type of scaffold for bone tissue engineering, combining the flexible material properties of PU with the advantage of an osteoconductive surface.     

In vitro evaluation of novel bioactive composites based on Bioglass-filled polylactide foams for bone tissue engineering scaffolds

Highly porous poly(DL-lactic acid) (PDLLA) foams and Bioglass-filled PDLLA composite foams were characterized and evaluated in vitro as bone tissue engineering scaffolds. The hypothesis was that the combination of PDLLA with Bioglass in a porous structure would result in a bioresorbable and bioactive composite, capable of supporting osteoblast adhesion, spreading and viability. Composite and unfilled foams were incubated in simulated body fluid (SBF) at 37 degrees C to study the in vitro degradation of the polymer and to detect hydroxyapatite (HA) formation, which is a measure of the materials' in vitro bioactivity. HA was detected on all the composite samples after incubation in SBF for just 3 days. After 28 days immersion the foams filled with 40 wt % Bioglass developed a continuous layer of HA. The formation of HA for the 5 wt % Bioglass-filled foams was localized to the Bioglass particles. Cell culture studies using a commercially available (ECACC) human osteosarcoma cell line (MG-63) were conducted to assess the biocompatibility of the foams and cell attachment to the porous substrates. The osteoblast cell infiltration study showed that the cells were able to migrate through the porous network and colonize the deeper regions within the foam, indicating that the composition of the foams and the pore structures are able to support osteoblast attachment, spreading, and viability. Rapid formation of HA on the composites and the attachment of MG-63 cells within the porous network of the composite foams confirms the high in vitro bioactivity and biocompatibility of these materials and their potential to be used as scaffolds in bone tissue engineering and repair.     

A collagen-phosphophoryn sponge as a scaffold for bone tissue engineering

Non-collagenous phosphoproteins that interact with a type-I collagen are thought to nucleate bone mineral into collagen networks of mineralized tissues. Previously, phosphophoryn cross-linked to type-I collagen was reported to be an effective nucleator of appatite. However, free phosphophoryn molecules inhibit the formation of apatite in vitro. On the basis of the above study, we expected a collagen-phosphophoryn sponge to be a good scaffold for bone-tissue engineering and examined the formation of bone in orthotopically transplanted composites of the sponge and bone marrow osteoblasts in vivo in Fischer rats. Osteoblastic primary cells were obtained from the bone shaft of femorae of Fisher rats, according to the method of Maniatopoulous et al. A suspension of marrow cells was distributed through a flask with standard culture medium and incubated at 37 degrees C. When cultures were nearly confluent after 10 days, they were concentrated by centrifugation to 10(6) cells/ml and subcultured onto the synthesized collagen-phosphophoryn sponge and a collagen sponge (control). After 14 days, the composites of collagen-phosphophoryn and osteoblastic cells as well as control composites were transplanted into bone-defect sites of Fisher rats (holes 2 mm in diameter) and then the wounds were sutured. The composites were harvested at 1-8 weeks after implantation, and stained with hematoxylin and eosin. It was found that more bone was formed in the composites of collagen-phosphophoryn sponge and osteoblasts than control composites from 1 week to 8 weeks, suggesting that the collagen-phosphophoryn sponge is a good candidate as a scaffold for bone-tissue engineering.     

In vitro evaluation of poly[bis(ethyl alanato)phosphazene] as a scaffold for bone tissue engineering

Polyphosphazenes with amino acid ester as side groups are biocompatible polymers that could provide valid scaffolds for cell growth. In the present study we investigate the adhesion and growth of osteoblasts obtained from rat bone marrow on matrices composed of thin fibers of poly[bis(ethyl alanato)phosphazene] (PAlaP), poly(d,l-lactic acid) (PDLLA), or PAlaP/PDLLA blend. Our data show that scaffolds of PAlaP or PAlaP/PDLLA blend enhanced the cell adhesion and growth in comparison with that observed in cultures seeded on polystyrene tissue culture plates. Although collagenase-digestible protein synthesis remained unchanged, all scaffolds induced a decrease in alkaline phosphatase activity, suggesting that osteoblasts are in the proliferation phase. Both PAlaP and PAlaP blended with PDLLA may represent a new and interesting substrate for bone tissue engineering.     

Submicron bioactive glass tubes for bone tissue engineering

Herein we describe a method to fabricate submicron bioactive glass tubes using sol-gel and coaxial electrospinning techniques for applications in bone tissue engineering. Heavy mineral oil and gel solution were delivered by two independent syringe pumps during the coaxial electrospinning process. Subsequently, submicron bioactive glass tubes were obtained by removal of poly(vinyl pyrrolidone) and heavy mineral oil via calcination at 600 °C for 5 h. Tubular structure was confirmed by scanning electron microscopy and transmission electron microscopy imaging. We examined the bioactivity of submicron bioactive glass tubes and fibers and evaluated their biocompatibility, using electrospun poly(ε-caprolactone) fibers--a bioinactive material--for comparison. The bioactivity of the glass tubes was examined in a simulated body fluid and they demonstrated the formation of hydroxyapatite-like minerals on both the outer and inner surfaces. In contrast, mineralization only occurred on their surface for bioactive glass solid fibers. Energy-dispersive X-ray data suggested that the bioactive glass tubes had a faster induction of mineral formation than the solid fibers. We demonstrate that the proliferation rate of mouse preosteoblastic MC3T3-E1 cells on bioactive glass tubes was comparable to that on solid fibers. We also show that bioactive glass tubes can be loaded with a model protein drug, bovine serum albumin, and that these structures exhibit delayed release properties. The bioactivity of released lysozyme can be as high as 90.9%. Taken together, these data suggest that submicron bioactive glass tubes could hold great potential for use in bone tissue engineering as well as topical drug or gene delivery.     

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.     

骨组织工程支架材料的研究现状与应用前景

背景：目前组织工程骨修复骨缺损在临床应用中较为关键的问题是建立血管网,为新骨的形成提供氧气及营养物质,并为机体提供代谢途径。 目的：综述近年组织工程骨支架材料的特点,并着重介绍复合支架材料的研究现状。 方法：以“骨组织工程,血管化,支架材料,复合支架材料”为中文检索词,以“bone tissue engineering, vascularization,scaffold,composite scaffold”英文检索词,应用计算机在中国期刊全文数据库和PubMed数据库检索2001年1月至2014年1月的相关文章,将所有文章进行初步筛选后,对保留的文章进一步详细分析、归纳并总结。 结果与结论：按照组织工程骨支架材料的来源不同,可将其分为人工合成材料、天然衍生材料和复合支架材料,单一支架材料难以作为最理想的材料修复骨缺损,复合支架材料能在不同程度上弥补单一支架材料的缺陷,因此近年来组织工程支架材料的发展由单一材料发展为复合材料,并呈现人工合成材料与天然材料有机结合的趋势。但复合支架材料在临床应用中仍然有许多尚待解决的问题,主要有控制复合材料比例,使材料降解速率与组织细胞的生长速率相适应,保持复合材料的多孔隙和高机械强度。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：     

Characterization of a bovine collagen-hydroxyapatite composite scaffold for bone tissue engineering

Different biomaterials have been used as scaffolds for bone tissue engineering. Here we characterize a biomaterial composed of sintered (1100 degrees C) and powdered hydroxyapatite (HA) and type I collagen (Coll), both of bovine origin, designed for osteoconductive and osteoinductive scaffolds. Coll/HA proportions were 1/2.6 and 1/1 (wet weight), and particles sizes varied from 200 to 400 microm. Vv (volume density) and Sv (surface to volume density) for the HA particles in the composite ranged from 0.48 +/- 0.06 to 0.55 +/- 0.02 and 5.090 +/- 0.545 to 6.366 +/- 0.289 microm(-1), respectively. Due to the relatively small changes in Vv and Sv, a macroporosity could be characterized for the biocomposite. X-ray diffraction and infrared spectroscopy showed that the sintered bone was composed essentially of HA with minimum additional groups such as surface calcium hydroxide, surface and crystal water, free carbon dioxide and possibly brushite. Mass spectrometry detected carbonates at A and B sites of HA, and weakly bound to the structure. Human osteoblasts adhered and spread on both the HA particle surface and the collagen fibers, which seemed to guide cells between adjacent particles. The biocomposite studied has several characteristics considered as ideal for its use as a scaffold for osteoconduction and osteoinduction.     

Generation of bioactive nano-composite scaffold of nanobioglass/silk fibroin/carboxymethyl cellulose for bone tissue engineering

Abstract

The development of bone tissue construct through tissue engineering approach offers a great promise in meeting the increasing demand for repair and regeneration of damaged and/or diseased bone tissue. For the generation of bone tissue engineered construct, polymer-ceramic composite matrices with nanostructure architecture and mesenchymal stem cells (hMSCs) of human origin are of prime requirement. Keeping these in view, in the present work a novel electrospun nanofibrous silk fibroin (SF)/carboxymethyl cellulose (CMC)/nano-bioglass (nBG) composite scaffold that mimics native bone extracellular matrix with appropriate composition was designed and fabricated by free liquid surface electrospinning technique. The scaffold possesses desired morphological, structural, biodegradability, bioactivity, surface roughness and mechanical properties thereby exhibited an excellent platform to support the growth of cells. The in-vitro culture of hMSCs over the developed scaffold has shown adhesion, proliferation and viability of cells, thus facilitated cell-scaffold construct generation and further extracellular bone matrix formation through osteogenic differentiation as evident from alkaline phosphatase activity, biomineralization, immunostaining and Runx2/osteocalcin expression assessment. Thus, the developed hMSCs seeded scaffold construct might be suitable for bone tissue engineering applications.     

A biodegradable polyurethane-ascorbic acid scaffold for bone tissue engineering

A novel, nontoxic, biodegradable, sponge-like polyurethane scaffold was synthesized from lysine-di-isocyanate (LDI) and glycerol. Ascorbic acid (AA) was copolymerized with LDI-glycerol. Our hypothesis was that the AA-containing polymer foam would enhance the biological activity of the osteoblastic precursor cell (OPCs). The LDI-glycerol-AA matrix degraded in aqueous solution to the nontoxic products of lysine, glycerol, and AA. The degradation products did not significantly affect the solution pH. The physical properties of the polymer network supported the cell growth in vitro. Mouse OPCs attached to the polymer matrix and remained viable. OPCs produced multilayered confluent cultures, a characteristic typical of bone cells. Furthermore, AA release stimulated cell proliferation, type I collagen, and alkaline phosphatase synthesis. Cells grown on the LDI-glycerol-AA matrix also showed an enhancement of mRNA expression for pro-alpha1 (I) collagen and transforming growth factor-alpha1 after 1 week. Data were tested for significance with an analysis of variance model and multiple comparison test (Fisher's Protected Least Significant Difference) at p < or = 0.05. The observations suggest that AA-containing polyurethane may be useful in bone tissue engineering applications.     

Alkali-free bioactive glasses for bone tissue engineering: a preliminary investigation

An alkali-free series of bioactive glasses has been designed and developed in the glass system CaO-MgO-SiO₂-P₂O₅-CaF₂ along the diopside (CaMgSi₂O₆)-fluorapatite (Ca₅(PO₄)₃F)-tricalcium phosphate (3CaO·P₂O₅) join. The silicate network in all the investigated glasses is predominantly coordinated in Q² (Si) units, while phosphorus tends to remain in an orthophosphate (Q⁰) environment. The in vitro bioactivity analysis of glasses has been made by immersion of glass powders in simulated body fluid (SBF) while chemical degradation has been studied in Tris-HCl in accordance with ISO-10993-14. Some of the investigated glasses exhibit hydroxyapatite formation on their surface within 1-12 h of their immersion in SBF solution. The sintering and crystallization kinetics of glasses has been investigated by differential thermal analysis and hot-stage microscopy, respectively while the crystalline phase evolution in resultant glass-ceramics has been studied in the temperature range of 800-900 °C using powder X-ray diffraction and scanning electron microscopy. The alkaline phosphatase activity and osteogenic differentiation for glasses have been studied in vitro on sintered glass powder compacts using rat bone marrow mesenchymal stem cells. The as-designed glasses are ideal candidates for their potential applications in bone tissue engineering in the form of bioactive glasses as well as glass/glass-ceramic scaffolds.     

Electrospun nanofibrous 3D scaffold for bone tissue engineering

Tissue engineering aims at developing functional substitutes for damaged tissues by mimicking natural tissues. In particular, tissue engineering for bone regeneration enables healing of some bone diseases. Thus, several methods have been developed in order to produce implantable biomaterial structures that imitate the constitution of bone. Electrospinning is one of these methods. This technique produces nonwoven scaffolds made of nanofibers which size and organization match those of the extracellular matrix. Until now, seldom electrospun scaffolds were produced with thickness exceeding one millimeter. This article introduces a new kind of electrospun membrane called 3D scaffold of thickness easily exceeding one centimeter. The manufacturing involves a solution of poly(ε-caprolactone) in DMF/DCM system. The aim is to establish parameters for electrospinning in order to characterize these 3D scaffolds and, establish whether such scaffolds are potentially interesting for bone regeneration.     

Three-dimensional biocompatible ascorbic acid-containing scaffold for bone tissue engineering

A biodegradable, biocompatible, ascorbic acid-containing three-dimensional polyurethane matrix was developed for bone tissue-engineering scaffolds. This matrix was synthesized with lysine-di-isocyanate (LDI), ascorbic acid (AA), glycerol, and polyethylene glycol (PEG). LDI-glycerol-PEG-AA prepolymer when reacted with water foamed with the liberation of CO(2) to provide a pliable, spongy urethane polymer with pore diameters of 100 to 500 microm. The LDI-glycerol-PEG-AA matrix degraded in aqueous solution and yielded lysine, glycerol, PEG, and ascorbic acid as breakdown products. The degradation products did not significantly affect the solution pH. The LDI-glycerol-PEG-AA matrix can be fabricated into diverse scaffold dimensions and the physicochemical properties of the polymer network supported in vitro cell growth. Green fluorescent protein-transgenic mouse bone marrow cells (GFP-MBMCs) attached to the polymer matrix and remained viable, and the cells became confluent cultures. Furthermore, ascorbic acid released from LDI-glycerol-PEG-AA matrix stimulated cell proliferation, type I collagen, and alkaline phosphatase synthesis in vitro. Cells grown on LDI-glycerol-PEG-AA matrix did not differ phenotypically from cells grown on tissue culture polystyrene plates as assessed by cell growth, expression of mRNA for collagen type I, and transforming growth factor beta(1). These observations suggest that AA-containing polyurethane may be useful in bone tissue-engineering applications.     

新型脱细胞骨基质材料的制备及理化评估

背景：传统的结构性天然骨脱细胞的方法存在许多不足之处。 目的：用新的理化方法对结构性骨块进行脱细胞处理制作新型骨支架材料的可行性,并检测其理化性能。 方法：以股骨头负重区结构性骨块为原料,高压水枪冲洗,继而利用Triton-100、脱氧胆酸钠等进行脱细胞等理化处理,制备新型脱细胞骨基质材料,并对支架进行大体、组织学、扫描电镜、Micro-CT观察、生物力学等相关检测。 结果与结论：新型脱细胞骨基质材料保留了骨的细胞外基质成分,脱细胞彻底,扫描电镜及Micro-CT观察显示支架具备三维多孔网状结构系统,具有天然骨的孔径和孔隙率;生物力学测试脱细胞组支架的弹性模量为(552.56±58.92) MPa,强度为(11.34±3.49) MPa,与新鲜骨的弹性模量及强度比较,差异无显著性意义(P > 0.05),可作为骨组织工程支架的良好载体。     

Paper-based bioactive scaffolds for stem cell-mediated bone tissue engineering

Bioactive, functional scaffolds are required to improve the regenerative potential of stem cells for tissue reconstruction and functional recovery of damaged tissues. Here, we report a paper-based bioactive scaffold platform for stem cell culture and transplantation for bone reconstruction. The paper scaffolds are surface-engineered by an initiated chemical vapor deposition process for serial coating of a water-repellent and cell-adhesive polymer film, which ensures the long-term stability in cell culture medium and induces efficient cell attachment. The prepared paper scaffolds are compatible with general stem cell culture and manipulation techniques. An optimal paper type is found to provide structural, physical, and mechanical cues to enhance the osteogenic differentiation of human adipose-derived stem cells (hADSCs). A bioactive paper scaffold significantly enhances in vivo bone regeneration of hADSCs in a critical-sized calvarial bone defect. Stacking the paper scaffolds with osteogenically differentiated hADSCs and human endothelial cells resulted in vascularized bone formation in vivo. Our study suggests that paper possesses great potential as a bioactive, functional, and cost-effective scaffold platform for stem cell-mediated bone tissue engineering. To the best of our knowledge, this is the first study reporting the feasibility of a paper material for stem cell application to repair tissue defects.     

Preparation and characterization of a multilayer biomimetic scaffold for bone tissue engineering

In scaffold based bone tissue engineering, both the pore size and the mechanical properties of the scaffold are of great importance. However, an increase in pore size is generally accompanied by a decrease in mechanical properties. In order to achieve both suitable mechanical properties and porosity, a multilayer scaffold is designed to mimic the structure of cancellous bone and cortical bone. A porous nano-hydroxyapatite-chitosan composite scaffold with a multilayer structure is fabricated and encased in a smooth compact chitosan membrane layer to prevent fibrous tissue ingrowth. The exterior tube is shown to have a small pore size (15-40 microm in diameter) for the enhancement of mechanical properties, while the core of the multilayer scaffold has a large pore size (predominantly 70-150 microm in diameter) for nutrition supply and bone formation. Compared with the uniform porous scaffold, the multilayer scaffold with the same size shows an enhanced mechanical strength and larger pore size in the center. More cells are shown to grow into the center of the multilayer scaffold in vitro than into the uniform porous scaffold under the same seeding condition. Finally, the scaffolds are implanted into a rabbit fibula defect to evaluate the osteoconductivity of the scaffold and the efficacy of the scaffold as a barrier to fibrous tissue ingrowth. At 12 weeks post operation, affluent blood vessels and bone formation are found in the center of the scaffold and little fibrous tissue is noted in the defect site.