氧化石墨烯-海藻酸钠-壳聚糖复合支架的制备及表征

通过冷冻干燥技术, 将不同量的氧化石墨烯与海藻酸钠和壳聚糖复合, 构建复合支架材料. 研究了不同的氧化石墨烯含量(质量分数0, 0.3%, 0.5%, 0.7%, 1%)对支架材料微观结构、 孔隙率、 溶胀比、 体外降解性能、 机械性能及生物相容性的影响, 以确定复合支架中最佳氧化石墨烯含量. 研究结果表明, 复合材料呈固态海绵状结构, 具有一定的形态可塑性; 扫描电子显微镜观察发现, 各组支架均为三维网状结构, 随着氧化石墨烯含量的增加, 孔隙尺寸逐渐降低, 孔壁厚度增加, 孔隙尺寸在140~240 μm之间; 随氧化石墨烯含量的增加, 复合支架溶胀比和体外降解速率逐渐降低, 而机械强度明显增强; 体外细胞毒性显示, 当氧化石墨烯质量分数为0.3%时, 细胞存活率最高, 而当氧化石墨烯含量增高时, 细胞活性会被明显抑制, 造成细胞死亡. 因此, 氧化石墨烯在复合支架中最佳含量为0.3%.     

海藻酸钠和壳聚糖静电复合弹性支架的制备和表征

通过静电作用和相分离技术制备海藻酸钠/壳聚糖静电复合弹性支架,研究了冷冻温度和固含量对支架材料孔径的影响及组分比对材料力学性能、亲水性、降解性能和生物相容性的影响.固含量为2%(质量分数)及冷冻温度为-24℃时,支架孔径为110~170μm,并且亲水性良好,平衡溶胀度大于1400%.改变固含量和组分比可调控材料的力学性能;循环力学测试表明,湿态支架具有良好的弹性和一定的耐疲劳性;降解速率可由组分比调控;兔脂肪干细胞(rASCs)在支架上的培养结果表明,羧基和氨基摩尔比为2∶1和1∶1时细胞以聚集体存在;羧基和氨基摩尔比为1∶2时细胞黏附于支架上,实现细胞黏附/聚集体的调控.     

海藻酸壳聚糖可塑性支架材料的制备及表征

利用海藻酸钠和壳聚糖2种原料, 采用阴阳离子静电复合原理, 通过滴注法层层自组装成可搭载药物的缓释微球, 再按一定比例与海藻酸钠-壳聚糖溶液混合制成缓释微球型支架材料, 将缓释微球结构嵌入疏松多孔海绵状结构中. 研究了缓释微球的组分比对缓释微球型支架材料的孔隙率、 收缩率、 亲水性及降解性能的影响; 扫描电子显微镜照片显示, 微球结构相对完整, 多孔海绵状结构孔径为140~200 μm; 支架浸出液细胞毒性检测实验组对照组未见差异. 缓释微球体积所占比例即组分比为10%的缓释微球型支架材料孔隙率最高为68.2%~70.8%, 亲水性最好, 收缩率最低为4.4%~5.2%; 支架降解速率随缓释微球组分比升高而减慢, 组分比为20%的缓释微球型支架材料综合性能更优; 缓释微球型支架材料冻干成型前为液态, 具有良好可塑性. 缓释微球型支架材料为缓释系统与多孔支架材料有机结合提供了新思路.     

纳米羟基磷灰石/丝素蛋白复合支架材料的降解特性及生物相容性研究

应用共混法制备了纳米羟基磷灰石/丝素蛋白复合支架材料, 通过体外降解和细胞培养实验研究了复合支架材料的降解特性和生物相容性. 体外降解实验结果显示, 复合支架材料具有稳定的降解能力; 在降解过程中, 羟基磷灰石由于与降解液发生钙、磷等离子的交换, 使其结晶得到了进一步生长和完善. 利用细胞计数法、四甲基偶氮唑盐(MTT)比色法和碱性磷酸酶(ALP)活性测定等分析了复合支架材料的生物相容性, 结果表明, MG63细胞在复合支架材料上具有良好的粘附、增殖能力, 并可引起早期的骨分化. 因此, 纳米羟基磷灰石/丝素蛋白复合支架作为骨组织工程的支架材料具有良好的应用前景.     

HA/GCPU复合多孔支架的可控制备及细胞相容性

以脂肪族异佛尔酮二异氰酸酯(IPDI)作为硬段、蓖麻油甘油酯(GCO)作为软段,通过原位聚合法制备了羟基磷灰石/蓖麻油甘油酯基聚氨酯(HA/GCPU)复合多孔支架.利用红外光谱和扫描电子显微镜对复合支架进行表征,并测试其力学性能及孔隙率.研究结果表明,HA/GCPU复合多孔支架的孔隙率和抗压强度依赖羟基磷灰石的含量,并具有明显的可控性.HA质量分数分别为0,20%和40%时,HA/GCPU复合多孔支架孔隙率分别为(61±3)%,(68±2)%和(57±3)%,抗压强度分别为(605±61),(2125±58)和(4588±260)k Pa,可见HA质量分数为20%时,HA/GCPU复合多孔支架具有与松质骨较为匹配的孔隙率和抗压强度.将MG63细胞与多孔支架共培养,通过倒置显微镜和扫描电子显微镜观察,用噻唑蓝(MTT)法表征HA/GCPU复合多孔支架的细胞相容性,结果表明,HA/GCPU复合多孔支架表面细胞黏附,生长良好,无细胞毒性,在骨组织工程领域具有一定的应用前景.     

聚乳酸-聚己内酯复合纳米纤维支架的制备和表征

在二氧六环/乙醇溶剂体系中,采用凝胶抽提相分离法制备了聚乳酸-聚己内酯(PLLA-PCL)复合纳米纤维支架,研究了凝胶温度、聚合物比例、聚合物浓度、致孔剂及二氧六环/乙醇(溶剂/非溶剂)比例对复合纳米纤维支架结构与性能的影响.结果表明,当凝胶温度处于-20~-10℃,PCL含量为30%~50%,非溶剂含量不超过15%,致孔剂与溶质质量比不超过20∶1时,均能得到具有类似于天然细胞外基质的纳米纤维(50~500 nm)结构的PLLA-PCL复合纤维支架.随着PCL含量的增加,复合纤维支架的弹性模量减小;PCL含量为30%时,复合支架的相容性和结晶性最好.该复合纤维支架具有良好的生物活性和一定的降解性能.     

高性能锂-硫电池用复合正极的构造与粘结剂

采用球磨混合及热处理方法制备了含有多壁碳纳米管(MCNTs)的硫基复合正极材料,利用X射线衍射(XRD)和扫描电子显微镜(SEM)测定材料的结构和形貌,较系统地研究了MCNTs含量和粘结剂种类对硫基复合正极容量、循环稳定性和自放电行为等的影响.结果表明:MCNTs的合适含量为5%-8%(w,质量分数),以水性粘结剂环糊精制备的硫基复合正极电化学性能最佳.锂-硫电池在常温和半充电状态下放置30天几乎没有自放电;当电流倍率为0.1C时,β-环糊精为粘结剂的正极初始充电容量为687.7mAh.g-1,100次循环以后可逆容量为623.8mAh.g-1,容量保持率达90.7%.     

基于多巴胺的黏合水凝胶的制备及表征

以1-(3-二甲氨基丙基)-3-乙基碳二亚胺/N-羟基琥珀酰亚胺(EDC/NHS)为催化剂, 将多巴胺通过酰胺化反应连接到氧化海藻酸钠上, 制得含邻苯二酚结构的氧化海藻酸钠(COA), 将COA与胶原(COL)复合, 制得具有黏合性能的COA-COL水凝胶, 通过紫外-可见光谱(UV-Vis)、 傅里叶变换红外光谱(FTIR)和核磁共振波谱(¹H NMR)方法表征了COA的结构, 用扫描电子显微镜、 体外膨胀降解、 万能电子拉力机和噻唑蓝(MTT)法分别表征了COA-COL水凝胶的形貌结构、 平衡溶胀率、 降解率、 黏合强度和细胞毒性. 研究结果表明, 多巴胺已引入到氧化海藻酸钠上, 取代度分别为12.5%, 18%和22%; COA-COL水凝胶的内部形成了典型的海绵体多孔网状结构, 平衡溶胀率随着多巴胺取代度的提高先减小后增大, 降解率随着取代度的提高依次减小, COA-COL水凝胶的黏合强度从未经多巴胺改性时的(20.43±4.21) kPa提高到多巴胺取代度为22%时的(29.91±6.10) kPa, 而且具有良好的生物相容性.     

低热-高压法制备PLGA多孔支架及其体外降解研究

采用低热-高压法制备了聚(dl-丙交酯／乙交酯)75／25(PLGA75／25)组织工程多孔支架。该方法避免了使用有机溶剂，支架的孔隙率在90％以上，孔径大小分布均匀。多孔支架经过酒精处理后，支架表面产生许多微小的凹陷；用藻酸钙改性处理后，支架形态保持良好。两种处理都使支架的压缩强度有所增大，亲水性增强。虽然孔隙率高的支架降解速率稍慢，但其体外降解规律基本一致：特性粘数争力学强度衰减快，而质量损失较慢，降解6周后，支架的质量损失仅为3％左右；体外降解3周后，支架的形态保持良好，可望在细胞移植争组织修复的早期发挥支撑作用。     

原位沉淀法制备CS/nHA多孔复合支架及其性能

通过原位沉淀法和冷冻相分离技术得到含有钙磷前驱体(CaP)的初始多孔支架, 利用多孔支架表面原位生成的壳聚糖(CS)膜减缓NaOH溶液中OH^-离子的渗透速率, 以达到纳米羟基磷灰石(nHA)缓慢形成的目的, 从而制得nHA 分布均匀的CS/nHA多孔复合支架. 利用扫描电镜(SEM)和万能试验机研究复合支架的结构和性能, 发现nHA为针状结构, 长度为80200 nm, 宽度为2050 nm. 随着nHA含量的增加, 复合支架的孔隙率下降, 由(93.8±3.3)%降至(87.7±3.8)%, 压缩强度则逐渐提高, 由(0.5±0.09) MPa增加至(1.5±0.06) MPa. 当复合支架中nHA质量分数为25%时, 未发现nHA团聚现象, nHA均匀地分布于CS基体中. 通过红外光谱(FTIR)、 X射线衍射(XRD)及X射线光电子能谱(XPS)等分析推断, nHA与CS之间可能存在配位和氢键作用. 细胞实验结果表明, CS/nHA多孔复合支架具有良好的生物相容性, 细胞在支架内部贴壁黏附生长. CS/nHA多孔复合支架有望在骨组织工程领域具有良好的应用前景.     

Porous composite scaffolds of hydroxyapatite/silk fibroin via two‐step method

A two‐step method was used to fabricate the hydroxyapatite (HAP)/silk fibroin (SF) scaffolds, i.e. the nano‐sized HAP/SF composite powders were prepared by co‐precipitation, which were then blended with SF solution to fabricate the HAP/SF composite scaffolds. The obtained scaffolds showed a 3D porous structure. The porosity was higher than 90% with the average macropore size of 214.2 µm. Moreover, the nano‐sized HAP/SF composite powders were uniformly dispersed in the silk fibroin matrix, which provided the scaffolds enhanced compressive properties. The cell culture assay showed that the scaffolds fabricated by the two‐step method could improve the cell proliferation and osteogenic differentiation when compared with those prepared by the conventional one‐step blending method. The results suggested that the two‐step method could promote the uniform dispersion of HAP in the SF matrix and efficient combination between the HAP and the matrix, which may provide a potential application in the composite scaffold preparation for tissue engineering. Copyright © 2009 John Wiley & Sons, Ltd.     

Improving mechanical and biological properties of macroporous HA scaffolds through composite coatings

Interconnected porous hydroxyapatite (HA) scaffolds are widely used for bone repair and replacement, owing to their ability to support the adhesion, transfer, proliferation and differentiation of cells. In the present study, the polymer impregnation approach was adopted to produce porous HA scaffolds with three-dimensional (3D) porous structures. These scaffolds have an advantage of highly interconnected porosity (≈85%) but a drawback of poor mechanical strength. Therefore, the as-prepared HA scaffolds were lined with composite polymer coatings in order to improve the mechanical properties and retain its good bioactivity and biocompatibility at the same time. The composite coatings were based on poly(d,l-lactide) (PDLLA) polymer solutions, and contained single component or combination of HA, calcium sulfate (CS) and chondroitin sulfate (ChS) powders. The effects of composite coatings on scaffold porosity, microstructure, mechanical property, in vitro mineralizing behavior, and cell attachment of the resultant scaffolds were investigated. The results showed that the scaffolds with composite coatings resulted in significant improvement in both mechanical and biological properties while retaining the 3D interconnected porous structure. The in vitro mineralizing behaviors were mainly related to the compositions of CS and ChS powders in the composite coatings. Excellent cell attachments were observed on the pure HA scaffold as well as the three types of composite scaffolds. These composite scaffolds with improved mechanical properties and bioactivities are promising bone substitutes in tissue engineering fields.     

Fabrication and Evaluation of Alginate/Bacterial Cellulose Nanocrystals–Chitosan–Gelatin Composite Scaffolds

It is common knowledge that pure alginate hydrogel is more likely to have weak mechanical strength, a lack of cell recognition sites, extensive swelling and uncontrolled degradation, and thus be unable to satisfy the demands of the ideal scaffold. To address these problems, we attempted to fabricate alginate/bacterial cellulose nanocrystals-chitosan-gelatin (Alg/BCNs-CS-GT) composite scaffolds using the combined method involving the incorporation of BCNs in the alginate matrix, internal gelation through the hydroxyapatite-d-glucono-δ-lactone (HAP-GDL) complex, and layer-by-layer (LBL) electrostatic assembly of polyelectrolytes. Meanwhile, the effect of various contents of BCNs on the scaffold morphology, porosity, mechanical properties, and swelling and degradation behavior was investigated. The experimental results showed that the fabricated Alg/BCNs-CS-GT composite scaffolds exhibited regular 3D morphologies and well-developed pore structures. With the increase in BCNs content, the pore size of Alg/BCNs-CS-GT composite scaffolds was gradually reduced from 200 μm to 70 μm. Furthermore, BCNs were fully embedded in the alginate matrix through the intermolecular hydrogen bond with alginate. Moreover, the addition of BCNs could effectively control the swelling and biodegradation of the Alg/BCNs-CS-GT composite scaffolds. Furthermore, the in vitro cytotoxicity studies indicated that the porous fiber network of BCNs could fully mimic the extracellular matrix structure, which promoted the adhesion and spreading of MG63 cells and MC3T3-E1 cells on the Alg/BCNs-CS-GT composite scaffolds. In addition, these cells could grow in the 3D-porous structure of composite scaffolds, which exhibited good proliferative viability. Based on the effect of BCNs on the cytocompatibility of composite scaffolds, the optimum BCNs content for the Alg/BCNs-CS-GT composite scaffolds was 0.2% (w/v). On the basis of good merits, such as regular 3D morphology, well-developed pore structure, controlled swelling and biodegradation behavior, and good cytocompatibility, the Alg/BCNs-CS-GT composite scaffolds may exhibit great potential as the ideal scaffold in the bone tissue engineering field.     

Incorporation of nanohydroxyapatite and vitamin D3 into electrospun PCL/Gelatin scaffolds: The influence on the physical and chemical properties and cell behavior for bone tissue engineering

Scaffold, an essential element of tissue engineering, should provide proper physical and chemical properties and evolve suitable cell behavior for tissue regeneration. Polycaprolactone/Gelatin (PCL/Gel)‐based nanocomposite scaffolds containing hydroxyapatite nanoparticles (nHA) and vitamin D3 (Vit D3) were fabricated using the electrospinning method. Structural and mechanical properties of the scaffold were determined by scanning electron microscopy (SEM) and tensile measurement. In this study, smooth and bead‐free morphology with a uniform fiber diameter and optimal porosity level with appropriate pore size was observed for PCL/Gel/nHA nanocomposite scaffold. The results indicated that adding nHA to PCL/Gel caused an increase of the mechanical properties of scaffold. In addition, chemical interactions between PCL, gelatin, and nHA molecules were shown with XRD and FT‐IR in the composite scaffolds. MG‐63 cell line has been cultured on the fabricated composite scaffolds; the results of viability and adhesion of cells on the scaffolds have been confirmed using MTT and SEM analysis methods. Here in this study, the culture of the osteoblast cells on the scaffolds showed that the addition of Vit D3 to PCL/Gel/nHA scaffold caused further attachment and proliferation of the cells. Moreover, DAPI staining results showed that the presence and viability of the cells were greater in PCL/Gel/nHA/Vit D3 scaffold than in PCL/Gel/nHA and PCL/Gel scaffolds. The results also approved increasing cell proliferation and alkaline phosphatase (ALP) activity for MG‐63 cells cultured on PCL/Gel/nHA/Vit D3 scaffold. The results indicated superior properties of hydroxyapatite nanoparticles and vitamin D3 incorporated in PCL/Gel scaffold for use in bone tissue engineering.     

Biocompatibility In-vitro of Gel/HA Composite Scaffolds Containing Nano-Bioactive Glass for Tissue Engineering

Designing and fabricating nanocomposite scaffolds for bone regeneration from different biodegradable polymers and bioactive materials are an essential step to engineer tissues. In this study, the composite scaffold of gelatin/hyaluronic acid (Gel/HA) containing nano-bioactive glass (NBG) was prepared by using freeze-drying method. The biocompatibilities in-vitro of the Gel-HA/NBG composite scaffolds, including MTT assay, ALP activity, von Kossa staining and tetracycline staining, were investigated. The SEM observations revealed that the prepared scaffolds were porous with three-dimensional (3D) and interconnected microstructure, agglomerated NBG particles were uniformly dispersed in the matrix. MTT results indicated that the tested materials didn't show any cytotoxicity. The presence of NBG in the composite scaffold further enhanced the ALP activity in comparison with the pure Gel/HA scaffold. The von Kossa staining and tetracycline staining results also indicated that the NBG may improve the cell response. Therefore, the results indicated the nanocomposite scaffold made from Gel, HA and NBG particles could be considered as a potential bone tissue engineering implant.     

A comparative study of the in vitro degradation of poly(l-lactic acid)/β-tricalcium phosphate scaffold in static and dynamic simulated body fluid

Porous poly(l-lactic acid)/β-tricalcium phosphate (PLLA/β-TCP) composite is a new promising scaffold for bone tissue engineering. Porous scaffolds fabricated by liquid anti-solvent precipitation principle were subjected to degradation in dynamic simulated body fluid (DSBF) and in static simulated body fluid (SSBF) at 37 °C for 24 weeks, respectively. Results indicated that a large number of apatite layer were formed on the scaffolds. The results further indicated that SBF flow decreased the degradation rate of molecular weight and compressive strength significantly. The porosity and mass changes were related to the apatite formation and SBF flow. All the results might be owed to the mutual effects of the flow of SBF and the addition of β-TCP. The degradation rate of scaffolds could be adjusted by the additional fraction of β-TCP to meet the requirements of application in vivo.     

Microstructure and mechanical properties of bacterial cellulose/chitosan porous scaffold

A family of polysaccharide based scaffold materials, bacterial cellulose/chitosan (BC/CTS) porous scaffolds with various weight ratios (from 20/80 to 60/40 w/w%) were prepared by freezing (−30 and −80 °C) and lyophilization of a mixture of microfibrillated BC suspension and chitosan solution. The microfibrillated BC (MFC) was subjected to 2,2,6,6-tetramethylpyperidine-1-oxyl radical (TEMPO)-mediated oxidation to introduce surface carboxyl groups before mixing. The integration of MFC within chitosan matrix was performed by 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC)-mediated cross-linking. The covalent amide bond formation was determined by ATR-FTIR. Because of this covalent coupling, the scaffolds retain their original shapes during autoclave sterilization. The composite scaffolds are three-dimensional open pore microstructure with pore size ranging from 120 to 280 μm. The freezing temperature and mean pore size take less effect on scaffold mechanical properties. The compressive modulus and strength increased with increase in MFC content. The results show that the scaffolds of higher MFC content contribute to overall better mechanical properties.     

Physicochemical characterisation of degrading polycaprolactone scaffolds

A degradation study investigating the hydrolysis of different scaffolds of polycaprolactone suspended in phosphate buffer solution at 37 °C was performed over a three month period. Structures included electrospun fibres, held as 2D mats and 3D bundles, and solvent cast films. These structures and their surrounding solutions were physiochemically characterised using a range of techniques. Changes in scaffold physicochemical properties were observed over the course of the study, including significant loss in molecular mass, increases in thermal properties and crystallinity, and increases in tensile properties. The presence of degradation products, such as capronic acid containing compounds was also identified in the surrounding solution. 3D electrospun bundles - as a consequence of being the least crystalline scaffold and hence most susceptible to hydrolysis - demonstrated greatest reduction in molecular mass over the three months, followed by 2D electrospun mats, and the lowest mass loss was observed for solvent cast films.