生物活性玻璃与壳聚糖复合的骨修复材料

背景：生物活性玻璃是一种多相复合材料,具有良好的生物活性、骨传导性及生物相容性,但作为骨修复材料仍然存在不能完全降解、机械强度较低等不足。 目的：设计生物活性玻璃/壳聚糖复合材料骨组织工程支架,并检测其理化性能。 方法：将2.0%壳聚糖盐酸溶液与β-甘油磷酸钠以7∶1的体积比混合制备壳聚糖溶液。称取0.5,1.0,1.5 g生物活性玻璃分别加入上述壳聚糖溶液中,使得壳聚糖与生物活性玻璃的质量比为2∶1,1∶1及1∶1.5。将复合材料浸泡于模拟生理体液中7 d进行体外矿化。 结果与结论：扫描电镜见复合支架具有相互贯通的多孔结构,孔隙率最高可达89%,孔径大小合适,为100-  300 µm,生物活性玻璃以针状形式分散在壳聚糖支架之间,均匀排列,被壳聚糖支架充分包裹结合紧密。随生物活性玻璃含量的增加,复合材料的孔隙率逐渐下降,断裂强度逐渐升高,他们之间呈正相关性。X射线衍射图及傅里叶变换红外光谱证实复合支架中的单一材料未发生性质改变,示差扫描量热法分析显示正常体温情况下材料无质量丢失。矿化3 d后材料表面形成的羟基磷灰石逐渐长大为绒毛状,数量也明显增多;矿化7 d后绒毛状的羟基磷灰石长成为针状,数量进一步增多,且众多的矿化物结成球状。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：     

不同接种方式对组织工程牙龈种子细胞黏附效果的影响

背景：如何在体外将支架材料和种子细胞高效地复合以构建组织工程牙周组织是目前牙周病治疗及牙周缺损修复研究的重要方向。 目的：比较传统沉淀接种法和胶原包裹接种法的细胞黏附状况,优化细胞接种方式。 方法：将一定浓度的犬牙龈成纤维细胞,分别采用传统沉淀接种法和胶原包裹接种法接种到聚乳酸-壳聚糖-明胶梯度孔径和均匀孔径支架上,通过细胞计数测定支架上贴附的细胞数量,计算其接种率,并进行对比分析。 结果与结论：采用胶原凝胶包裹接种法将细胞接种至均匀孔径支架和梯度孔径支架上,其接种率均明显高于传统的沉淀接种法(P < 0.01)。用胶原凝胶包裹种子细胞行细胞接种可以有效提高种子细胞的接种率,增加支架上的细胞初始浓度,可以选用胶原凝胶包裹细胞接种方式用于牙龈工程组织构建。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：     

羟基丁酸-羟基辛酸聚合物/胶原软骨组织工程支架的细胞亲和性

背景：已有很多实验证明,单独高分子材料或生物性材料制备的组织工程支架无法满足组织工程研究。 目的：评价羟基丁酸-羟基辛酸聚合物/胶原组织工程支架的生物学特性及细胞亲和性。 方法：以羟基丁酸-羟基辛酸聚合物作为主体材料,按质量分数复合不同比例(2%,4%,6%,8%,10%)的胶原,采用溶剂浇铸-颗粒沥滤法制备组织工程支架。通过扫描电镜观察材料内部结构及孔径大小,液体位移法测定材料孔隙率。将羟基丁酸-羟基辛酸聚合物/胶原支架、羟基丁酸-羟基辛酸聚合物支架分别与兔软骨细胞复合培养,MTT法测定细胞的生长曲线,扫描电镜观察细胞在材料上的生长黏附情况。 结果与结论：羟基丁酸-羟基辛酸聚合物/胶原复合软骨组织工程支架孔径大小200 μm左右,孔隙率为(85±2)%,细胞亲水性随加入胶原比例的增加而升高。与羟基丁酸-羟基辛酸聚合物支架比较,不同比例的羟基丁酸-羟基辛酸聚合物/胶原支架可明显促进软骨细胞的黏附、增殖。证实羟基丁酸-羟基辛酸聚合物/胶原复合支架具备更好的细胞亲和性。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：     

滑膜间充质干细胞与软骨细胞三维条件下混合培养向软骨细胞的分化

背景：软骨细胞通过自分泌及旁分泌的作用可以为滑膜间充质干细胞向软骨细胞分化提供所需的生长因子及微环境,三维条件下更有利于细胞的黏附增殖与分化。目的：观察滑膜间充质干细胞与软骨细胞混合培养于壳聚糖/Ⅰ型胶原复合支架材料中向成软骨细胞分化的能力。方法：取SD大鼠滑膜组织及软骨组织,用酶消化法获得滑膜间充质干细胞及软骨细胞分别进行培养。取第3代滑膜间充质干细胞及第2代软骨细胞,将二者以1∶2的比例混合培养负载于壳聚糖/Ⅰ型胶原复合支架材料21 d,进行激光共聚焦扫描及免疫组织化学检测。结果与结论：培养72 h后,扫描电镜观察细胞黏附于支架材料表面,并可见细胞分泌大量基质成分。培养     21 d后,激光共聚焦扫描可见细胞在支架表面分布均匀,逐层扫描后细胞逐渐减少。免疫组织化学检测可见基质能被Ⅱ型胶原染色,细胞染色呈现棕黄色。结果表明壳聚糖/Ⅰ型胶原复合支架材料提供三维生长空间,利用软骨细胞分泌生长因子及细胞间的相互作用可以诱导滑膜间充质干细胞向软骨细胞分化。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：     

3D打印成型纳米羟基磷灰石/壳聚糖/聚己内酯三元复合支架材料的构建及表征

文题释义： 组织工程骨：将体外培养的功能相关的种子细胞种植于天然的或人工合成的支架材料内,加入生长因子体外培养一段时间,将他们移植到体内,促进组织修复和骨再生的人工骨。组织工程骨形成的3要素为：支架材料、成骨细胞、生长因子。 生物陶瓷：生物表面活性陶瓷通常含有羟基,还可做成多孔性,生物组织可长入并同其表面发生牢固的键合;生物吸收性陶瓷的特点是能部分吸收或者全部吸收,在生物体内能诱发新生骨的生长。生物活性陶瓷具有骨传导性,它作为一个支架,成骨在其表面进行;还可作为多种物质的外壳或填充骨缺损。生物陶瓷有羟基磷灰石陶瓷、磷酸三钙陶瓷等。  背景：目前常用的骨缺损修复支架材料种类较多,但单一类型材料难以满足骨组织工程支架材料的要求,通过合适的方法将几种单一材料组合形成复合型材料,综合考虑各种材料优缺点,是近年来学者们的研究重点。 目的：构建纳米羟基磷灰石/壳聚糖/聚己内酯三元复合支架材料,并作表征分析研究。 方法：采用3D打印成型技术制备纳米羟基磷灰石/壳聚糖/聚己内酯多孔三元复合支架材料,从X射线衍射分析、吸水率、抗压强度、体外降解性能、孔径分析、扫描电镜分析等多个维度对支架材料进行表征研究。 结果与结论：①X射线衍射分析显示,纳米羟基磷灰石/壳聚糖/聚己内酯多孔三元复合支架的晶型峰图与羟基磷灰石粉末衍射标准卡片类似,表明该三元复合支架是通过物理作用相互结合的,不影响羟基磷灰石的生物学功能;②三元复合支架的吸水率为18.28%,亲水性好,支架可承受的最大压力为1 415 N,其体外降解速率与成骨速率相当;③显微镜下可见三元复合支架的内孔为方形,孔径250 µm,孔径大小均匀、分布有致;④扫描电镜下三元复合支架可见,壳聚糖和聚己内酯组成的纤维排列整齐有序,成网格状, 羟基磷灰石呈颗粒状在纤维表面均匀分布,三元复合材料呈现均匀、疏松的微孔结构;⑤结果表明,通过3D打印成型技术可成功制备纳米羟基磷灰石/壳聚糖/聚己内酯三元复合支架材料,其具有适度的抗压强度、一定的孔隙率、适宜的降解速度和吸水率,能为修复骨缺损的奠定基础。 ORCID: 0000-0002-6321-9160(余和东) 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       

聚乳酸/壳聚糖纳米纤维/纳米羟基磷灰石支架与兔软骨细胞的相容性

背景：传统的支架材料存在疏水性强,材料表面缺乏细胞表面受体特异结合的生物活性分子,材料的酸性降解产物易引发无菌性炎性反应等不足。根据仿生原理及软骨真实结构和构成来选择和制备组织工程软骨支架能够获得理想效果。 目的：制备聚乳酸/壳聚糖纳米纤维/纳米羟基磷灰石支架,评价其与兔膝关节软骨细胞的生物相容性,探讨其应用于关节软骨组织工程的可行性。 方法：采用二次相分离技术制备聚乳酸/壳聚糖纳米纤维/纳米羟基磷灰石复合支架,将第3代新西兰兔软骨细胞接种至复合支架材料上复合培养,倒置相差显微镜下观察细胞生长情况。细胞-支架复合物在24孔板中培养5 d以后,将其植入裸鼠皮下8周。 结果与结论：聚乳酸/壳聚糖纳米纤维/纳米羟基磷灰石支架材料经化学合成后,具有合适的三维多孔结构,孔隙率为90%,孔径300~450 μm;植入裸鼠皮下8周后Ⅱ型胶原免疫组织化学染色和甲苯胺蓝染色显示细胞-支架复合物中的软骨细胞可以像天然软骨一样分泌黏多糖和Ⅱ型胶原。提示生物材料聚乳酸/壳聚糖纳米纤维/纳米羟基磷灰石对于兔软骨细胞有良好的生物相容性,可作为生物组织工程支架。     

海藻酸钠/壳聚糖复合凝胶的制备与细胞毒性评价

背景：海藻酸钠和壳聚糖分别是聚阳离子和聚阴离子的天然高分子材料,二者可以互为交联剂形成复合凝胶,避免使用普通交联剂产生的细胞毒性。 目的：制备海藻酸钠壳聚糖复合凝胶并评价其体外细胞毒性。 方法：以0.25 mol/L乙酸溶解壳聚糖,制成质量浓度30 g/L溶液,再以0.1 mol/L的NaOH中和酸性得到壳聚糖絮状沉淀,将壳聚糖絮状沉淀与质量浓度3%海藻酸钠等比例混合,高频振动混匀,使二者形成复合凝胶。使用傅里叶变换红外光谱、扫描电镜分析观察凝胶成分和交联纤维网络结构。分别以海藻酸钠壳聚糖复合凝胶24,72 h浸提液、聚乙烯24,72 h浸提液及苯酚溶液培养L-929细胞,体外检测其细胞毒性。 结果与结论：傅里叶变换红外光谱检测到海藻酸钠壳聚糖复合凝胶特征性峰值改变,扫描电镜显示其内部形成丰富间隙的空间网络结构。浸提液法检测海藻酸钠壳聚糖复合凝胶的细胞毒性为合格,表明海藻酸钠/壳聚糖复合凝胶具有成为组织工程支架材料的良好条件。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：     

大鼠成骨细胞与壳聚糖/羟基磷灰石复合支架降解产物的生物相容性

背景：人们对壳聚糖/羟基磷灰石复合多孔生物支架在体内的降解过程并非十分清楚,而且有关其降解产物对成骨细胞的影响研究也较少。 目的：分析大鼠成骨细胞与壳聚糖/羟基磷灰石复合多孔生物支架降解产物的生物相容性。 方法：将培养的第2代大鼠成骨细胞分别在壳聚糖/羟基磷灰石复合支架降解产物浸提液和含体积分数10%胎牛血清的DMEM培养液中培养,培养第2,4,6,8,10天分别对两组细胞做MTT细胞计数,采用联合会推荐法测定细胞碱性磷酸酶活性,采用BCA蛋白定量法测定总蛋白。 结果与结论：在壳聚糖/羟基磷灰石复合多孔生物支架降解产物浸提液中培养的大鼠成骨细胞增殖速度、细胞碱性磷酸酶活性、细胞总蛋白合成及碱性磷酸酶与总蛋白的比值明显高于在体积分数为10%胎牛血清DMEM培养液中培养的细胞(P < 0.05)。表明壳聚糖/羟基磷灰石复合多孔生物支架的降解产物不仅可促进大鼠成骨细胞的黏附、生长和增殖,还可增强其骨化功能,具有较好的生物相容性。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：     

复合胰岛素样生长因子1壳聚糖胶原支架与人牙周膜细胞的增殖

背景：胰岛素样生长因子1具有促进成纤维细胞有丝分裂的作用,同时具有促进牙周细胞生长、分化及合成细胞外基质的作用。 目的：观察负载胰岛素样生长因子1的壳聚糖胶原支架对于人牙周膜细胞增殖的作用。 方法：将人牙周膜细胞分别接种于负载胰岛素样生长因子1的壳聚糖胶原支架与普通胶原支架上,于接种的1 h、24 h及1周检测重组人转化生长因子β1的释放,于第1,7,28天检测两组细胞的黏附和增殖情况。 结果与结论：负载胰岛素样生长因子1的壳聚糖胶原支架组第1,24小时和第1周的重组人转化生长因子β1释放率明显低于普通胶原支架组(P < 0.01)。两组接种第1天的细胞黏附和增殖检测比较差异无显著性意义  (P > 0.05),负载胰岛素样生长因子1的壳聚糖胶原支架组接种第7,28天的细胞黏附和增殖情况优于普通胶原支架组(P < 0.01)。表明负载胰岛素样生长因子1的壳聚糖胶原支架可显著促进人牙周膜细胞的增殖。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：     

仿生支架材料骨形态发生蛋白7多肽/壳聚糖/纳米羟基磷灰石/胶原的制备及其细胞相容性

背景：目前骨组织工程常用的支架材料主要有无机材料、有机高分子材料及天然衍生材料等,上述材料各有优缺点,为了充分发挥各类材料的优势,弥补其不足,目前多采用联合材料制备复合支架。 目的：制备新型仿生支架材料骨形态发生蛋白7多肽/壳聚糖/纳米羟基磷灰石/胶原,并观察其对骨髓间充质干细胞增殖、黏附及分化的影响。 方法：制备壳聚糖/纳米羟基磷灰石/胶原复合支架材料,扫描电镜观察支架材料表面微观形貌;采用真空吸附法将骨形态发生蛋白7多肽与支架材料复合,高效液相色谱仪检测骨形态发生蛋白7多肽在体外的释放规律;将骨髓间充质干细胞接种到复合骨形态发生蛋白7多肽的仿生支架材料上,以未复合多肽的支架材料作为对照,检测支架材料表面细胞增殖、黏附率、生长形态及碱性磷酸酶活性。 结果与结论：壳聚糖/纳米羟基磷灰石/胶原支架材料呈多孔状,孔径10~100 µm;骨形态发生蛋白7多肽可以从支架材料中缓慢释出;在复合多肽的仿生支架材料表面,骨髓间充质干细胞的黏附及向成骨细胞方向分化能力均明显强于对照组(P < 0.05),而增殖能力与对照组差异无显著性意义(P > 0.05)。说明新型仿生支架材料骨形态发生蛋白7多肽/壳聚糖/纳米羟基磷灰石/胶原是一种理想的骨组织工程支架材料,具有良好的细胞相容性。     

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.     

Fabrication, characterization, and in vitro degradation of composite scaffolds based on PHBV and bioactive glass

Composite scaffolds of polyhydroxybutyrate-polyhydroxyvalerate (PHBV) with sol-gel-derived bioactive glass (BG, 58S) are fabricated by compression molding, thermal processing, and salt particulate leaching method. Structure and mechanical properties of the scaffolds are determined. The bioactivity of the composites is evaluated by soaking the scaffolds in a simulated body fluid (SBF), and the formation of the apatite layer on the scaffolds is determined by scanning electron microscopy (SEM) and energy-dispersive spectrometry (EDS). The results show that the PHBV/BG composites are bioactive as they induce the formation of apatite on the composite scaffolds after soaking in SBF for 3 days. In addition, the measurements of the water contact angles suggest that incorporation of BG into PHBV can improve the hydrophilicity of the composites and the enhancement is dependent on the BG content. Furthermore, the degradation assessment of the scaffolds is performed in phosphate-buffered saline (PBS) solution at 37 C. Weight loss and water absorption of the scaffolds, pH of the incubation media, and molecular weight measurements of the PHBV in the scaffolds are used to monitor the degradation of the scaffolds during a nine-week incubation in PBS. It has been found that the incorporation of bioactive glass into the PHBV delayed the degradation of PHBV in the composite scaffolds for the period investigated. The present results show not only a useful method to prepare composite scaffolds with improved properties but also a way of adjusting the in vitro degradation behavior of composite scaffolds by tailoring the content of bioactive glass.     

Degradation, Bioactivity, and Osteogenic Potential of Composites Made of PLGA and Two Different Sol�CGel Bioactive Glasses

We have developed poly(L: -lactide-co-glycolide) (PLGA) based composites using sol-gel derived bioactive glasses (S-BG), previously described by our group, as composite components. Two different composite types were manufactured that contained either S2-high content silica S-BG, or A2-high content lime S-BG. The composites were evaluated in the form of sheets and 3D scaffolds. Sheets containing 12, 21, and 33?vol.% of each bioactive glass were characterized for mechanical properties, wettability, hydrolytic degradation, and surface bioactivity. Sheets containing A2 S-BG rapidly formed a hydroxyapatite surface layer after incubation in simulated body fluid. The incorporation of either S-BG increased the tensile strength and Young's modulus of the composites and tailored their degradation rates compared to starting compounds. Sheets and 3D scaffolds were evaluated for their ability to support growth of human bone marrow cells (BMC) and MG-63 cells, respectively. Cells were grown in non-differentiating, osteogenic or osteoclast-inducing conditions. Osteogenesis was induced with either recombinant human BMP-2 or dexamethasone, and osteoclast formation with M-CSF. BMC viability was lower at higher S-BG content, though specific ALP/cell was significantly higher on PLGA/A2-33 composites. Composites containing S2 S-BG enhanced calcification of extracellular matrix by BMC, whereas incorporation of A2 S-BG in the composites promoted osteoclast formation from BMC. MG-63 osteoblast-like cells seeded in porous scaffolds containing S2 maintained viability and secreted collagen and calcium throughout the scaffolds. Overall, the presented data show functional versatility of the composites studied and indicate their potential to design a wide variety of implant materials differing in physico-chemical properties and biological applications. We propose these sol-gel derived bioactive glass-PLGA composites may prove excellent potential orthopedic and dental biomaterials supporting bone formation and remodeling.     

京尼平交联3D打印胶原/壳聚糖支架的表征北大核心

背景:胶原/壳聚糖支架需交联才能达到相应力学性能,有研究表示调节交联剂浓度可以在一定范围内调控支架的理化性能。目的:探究京尼平浓度对胶原/壳聚糖支架理化性能的影响,制备理化性能可调节的组织工程支架。方法:将胶原和壳聚糖粉末分别溶于弱酸后混合均匀,作为打印墨水,利用生物3D打印机低温打印胶原支架与胶原/壳聚糖支架,经冻干、中和处理后分别以1,3,5 mmol/L的京尼平进行交联。检测各组支架的表观结构稳定性、抗拉能力、溶胀性能、降解性能与生物相容性。结果与结论:①将支架在PBS中浸泡3 d后,对比未交联的冻干支架,交联后胶原支架表面维持规则的孔结构,但是支架出现明显变形;交联后胶原/壳聚糖支架表面结构规则,仅1 mmol/L京尼平交联的胶原/壳聚糖支架存在轻微变形。②随着京尼平浓度的增加,各组支架的力学性能增加,并且对应交联浓度下的胶原/壳聚糖支架力学性能好于胶原支架。③随着京尼平浓度的增加,胶原支架的溶胀率下降,胶原/壳聚糖支架的溶胀率无明显变化。④浸泡于胶原酶溶液中后,不同浓度京尼平交联的胶原支架在1 h内被完全降解,胶原/壳聚糖支架的降解速率随京尼平浓度的增加而降低,均呈现先快速后平缓的趋势。⑤将骨髓间充质干细胞接种于各组交联支架3 d后,1,3 mmol/L京尼平交联的胶原/壳聚糖支架(或胶原支架)上的细胞数量明显多于5 mmol/L京尼平交联的胶原/壳聚糖支架(P<0.05)。⑥结果表明,京尼平可在一定范围调节胶原/壳聚糖支架理化性能,其中3 mmol/L京尼平交联的胶原/壳聚糖支架具有较好的力学性能、抗酶解能力与生物相容性。     

Chitosan/bioactive glass nanoparticle composite membranes for periodontal regeneration

Barrier membranes are used in periodontal applications with the aim of supporting periodontal regeneration by physically blocking migration of epithelial cells. The present work proposes a combination of chitosan (CHT) with bioactive glass nanoparticles (BG-NPs) in order to produce a novel guided tissue and bone regeneration membrane, fabricated by solvent casting. The CHT/BG-NP nanocomposite membranes are characterized in terms of water uptake, in mechanical tests, under simulated physiological conditions and in in vitro bioactivity tests. The addition of BG-NPs to CHT membranes decreased the mechanical potential of these membranes, but on the other hand the bioactivity improved. The membranes containing the BG-NPs induced the precipitation of bone-like apatite in simulated body fluid (SBF). Biological tests were carried out using human periodontal ligament cells and human bone marrow stromal cells. CHT/BG-NP composite membranes promoted cell metabolic activity and mineralization. The results indicate that the CHT/BG-NP composite membrane could potentially be used as a temporary guided tissue regeneration membrane in periodontal regeneration, with the possibility to induce bone regeneration.     

Direct ink writing of highly porous and strong glass scaffolds for load-bearing bone defects repair and regeneration

The quest for synthetic materials to repair load-bearing bone lost because of trauma, cancer, or congenital bone defects requires the development of porous, high-performance scaffolds with exceptional mechanical strength. However, the low mechanical strength of porous bioactive ceramic and glass scaffolds, compared with that of human cortical bone, has limited their use for these applications. In the present work bioactive 6P53B glass scaffolds with superior mechanical strength were fabricated using a direct ink writing technique. The rheological properties of Pluronic® F-127 (referred to hereafter simply as F-127) hydrogel-based inks were optimized for the printing of features as fine as 30 μm and of three-dimensional scaffolds. The mechanical strength and in vitro degradation of the scaffolds were assessed in a simulated body fluid (SBF). The sintered glass scaffolds showed a compressive strength (136 ± 22 MPa) comparable with that of human cortical bone (100–150 MPa), while the porosity (60%) was in the range of that of trabecular bone (50–90%). The strength is ∼100-times that of polymer scaffolds and 4–5-times that of ceramic and glass scaffolds with comparable porosities. Despite the strength decrease resulting from weight loss during immersion in SBF, the value (77 MPa) is still far above that of trabecular bone after 3 weeks. The ability to create both porous and strong structures opens a new avenue for fabricating scaffolds for load-bearing bone defect repair and regeneration.     

Synthesis and characterization of macroporous chitosan/calcium phosphate composite scaffolds for tissue engineering

Chitosan scaffolds reinforced by beta-tricalcium phosphate (beta-TCP) and calcium phosphate invert glass were fabricated with a low-cost, bioclean freeze-drying technique via thermally induced phase separation. The microstructure, mechanical performance, biodegradation, and bioactivity of the scaffolds were studied. The composite scaffolds were macroporous, and the pore structures of the scaffolds with beta-TCP and the glass appeared very different. Both the compressive modulus and yield strength of the scaffolds were greatly improved, and reinforced microstructures were achieved. The bioactivity tests showed a continuous decrease in both Ca and P concentrations of a simulated body fluid (SBF) after the scaffolds with beta-TCP were immersed in the SBF for more than 20 h, which suggests that an apatite layer might be formed on the scaffolds. However, the same was not observed for the pure chitosan scaffolds or the scaffolds incorporated with the glass. This was further confirmed by micrographs from scanning electron microscopy. This study suggests that the desirable pore structure, biodegradation rate, and bioactivity of the composite scaffolds might be achieved through controlling the ratio of chitosan and calcium phosphates or beta-TCP and the glass.     

Evaluation of 3-D bioactive glass scaffolds dissolution in a perfusion flow system with X-ray microtomography

Bioactive glass has high potential for bone regeneration due to its ability to bond to bone and stimulate osteogenesis whilst dissolving in the body. Although three-dimensional (3-D) bioactive glass scaffolds with favorable pore networks can be made from the sol-gel process, compositional and structural evolutions in their porous structures during degradation in vivo, or in vitro, have not been quantified. In this study, bioactive glass scaffolds were put in a simulated body fluid flow environment through a perfusion bioreactor. X-ray microtomography (μCT) was used to non-destructively image the scaffolds at different degradation stages. A new 3-D image processing methodology was developed to quantify the scaffold's pore size, interconnect size and connectivity from μCT images. The accurate measurement of individual interconnect size was made possible by a principal component analysis-based algorithm. During 28 days of dissolution, the modal interconnect size in the scaffold was reduced from 254 to 206 μm due to the deposition of mineral phases. However, the pore size remained unchanged, with a mode of 682 μm. The data presented are important for making bioactive glass scaffolds into clinical products. The technique described for imaging and quantifying scaffold pore structures as a function of degradation time is applicable to most scaffold systems.     

Development of biodegradable polyurethane and bioactive glass nanoparticles scaffolds for bone tissue engineering applications

The development of polymer/bioactive glass has been recognized as a strategy to improve the mechanical behavior of bioactive glass-based materials. Several studies have reported systems based on bioactive glass/biopolymer composites. In this study, we developed a composite system based on bioactive glass nanoparticles (BGNP), obtained by a modified St?ber method. We also developed a new chemical route to obtain aqueous dispersive biodegradable polyurethane. The production of polyurethane/BGNP scaffolds intending to combine biocompatibility, mechanical, and physical properties in a material designed for tissue engineering applications. The composites obtained were characterized by structural, biological, and mechanical tests. The films presented 350% of deformation and the foams presented pore structure and mechanical properties adequate to support cell growth and proliferation. The materials presented good cell viability and hydroxyapatite layer formation upon immersion in simulated body fluid.