RhBMP-2-loaded calcium silicate/calcium phosphate cement scaffold with hierarchically porous structure for enhanced bone tissue regeneration

Calcium phosphate cement scaffold (CPC) has been widely used as bone graft substitutes, but undesirable osteoinductivity and slow degradability greatly hamper their clinic application. To address these problems, a recombinant human bone morphogenetic protein-2 (rhBMP-2)-loaded calcium silicate/calcium phosphate cement scaffold (CSPC) with hierarchical pores was developed in this study. The CSPC scaffold with both interconnected macropores on the order of 200–500 μm and micropores of 2–5 μm was synthesized from CPC and calcium silicate (CS) by a NaCl particulate-leaching method. In vitro cell culture with C2C12 model cells, in vivo ectopic bone formation and rabbit femur cavity defect repair were performed to evaluate the osteogeneic capacity of the CSPC/rhBMP-2 scaffold. CPC, CSPC and CPC/rhBMP-2 scaffolds were parallelly investigated for comparison. The results demonstrated that the hierarchical macro/microporous structure, whether in presence of CS or rhBMP-2, highly favored the adhesion of C2C12 cells and bone in-growth into the CPC-based scaffolds. But, in comparison to the CPC-based scaffolds with CS or rhBMP-2 alone, the CSPC/rhBMP-2 scaffold strongly promoted osteogenic differentiation in vitro and osteogenetic efficacy in vivo. Further studies demonstrated that Si ions derived from CSPC contributed mainly to maintain the conformation of rhBMP-2 and thus stimulate the synergistic action of CS and rhBMP-2 in osteogenic differentiation and osteoinductivity. Additionally, the incorporation of CS was also beneficial for the dissolution of the scaffold. Those results suggest that the CSPC has superior properties for incorporation of rhBMP-2 and our developed CSPC/rhBMP-2 scaffold have great potential for future use in bone tissue regeneration.     

可注射壳聚糖/纳米羟基磷灰石/胶原复合材料的生物相容性实验研究

目的　评价可注射壳聚糖/纳米羟基磷灰石/胶原复合材料的组织相容性,以及探讨材料负载骨髓基质干细胞进行骨修复的可行性。 方法　壳聚糖/纳米羟基磷灰石/胶原材料与BrdU标记的rBMSc混合,注射入大鼠皮下,于皮下植入后24 h,14 d和28 d分别断颈处死大鼠,进行大体观察、HE、MASSON染色、免疫组化染色。 结果　壳聚糖/纳米羟基磷灰石/胶原材料在室温呈液态,经1 ml注射器26号针头注射入大鼠皮下后,材料在体内可以迅速原位成形成凝胶状态,并在原位保持形状,BrdU标记的rBMSc弥散于材料中,28 d的免疫组化结果显示细胞存活良好。 结论　壳聚糖/纳米羟基磷灰石/胶原复合材料具有良好的组织相容性,是一种良好的负载干细胞的骨组织工程支架。     

Effects of the controlled-released TGF-beta 1 from chitosan microspheres on chondrocytes cultured in a collagen/chitosan/glycosaminoglycan scaffold

The objectives of this study were (1) to develop a three-dimensional collagen/chitosan/glycosaminoglycan (GAG) scaffold in combination with transforming growth factor-beta1 (TGF-beta 1)-loaded chitosan microspheres, and (2) to evaluate the effect of released TGF-beta 1 on the chondrogenic potential of rabbit chondrocytes in such scaffolds. TGF-beta 1 was loaded into chitosan microspheres using an emulsion-crosslinking method. The controlled release of TGF-beta 1, as measured by enzyme-linked immunosorbent assay (ELISA), was monitored for 7 days. The porous scaffolds containing collagen and chitosan were fabricated by using a freeze drying technique and crosslinked using 1-ethyl-3-(3-dimethyl aminopropyl)carbodiimide (EDC) in the presence of chondroitin sulfate (CS), as a GAG component. The TGF-beta 1 microspheres were encapsulated into the scaffold at a concentration of 10 ng TGF-beta 1/scaffold and then chondrocytes were seeded in the scaffold and incubated in vitro for 3 weeks. Both proliferation rate and glycosaminoglycan (GAG) production were significantly higher in the TGF-beta 1 microsphere-incorporated scaffolds than in the control scaffolds without microspheres. Extracellular matrix staining by Safranin O and immunohistochemistry for type II collagen were elevated in the scaffold with TGF-beta 1 microspheres. These results suggest that TGF-beta 1 microspheres when incorporated into a scaffold have the potential to enhance cartilage formation.     

I型胶原-壳聚糖复合材料的生物相容性研究*

目的评价I型胶原-壳聚糖复合材料作为组织工程支架材料的生物相容性。方法体外培养兔骨髓间充质干细胞﹙BMSCs﹚,采用四甲基偶氮唑盐﹙MTT﹚比色法检测不同分组的BMSCs生长情况,酶标仪测吸光度值﹙OD﹚,计算细胞相对增值率﹙RGR%﹚;利用材料浸提液与兔新鲜血混合观察红细胞溶解情况,评价材料细胞生物相容性。结果空白组﹙A组﹚,50%浓度组﹙B组﹚和100%浓度组﹙C组﹚BMSCs均生长良好,并于1、3、5天逐渐增殖,阳性对照组﹙D组﹚细胞于第1天开始变圆、皱缩,3天和5天均皱缩死亡。A、B、C三组细胞在第1、3、5天各组吸光度值无显著差异﹙P>0.05﹚,但均与D组有明显统计学差异﹙P<0.05﹚。材料相对溶血率为4.1%。结论 I型胶原-壳聚糖复合材料无明显细胞毒性,有良好的生物相容性。     

A human-like collagen/chitosan electrospun nanofibrous scaffold from aqueous solution: electrospun mechanism and biocompatibility

Novel human-like collagen (HLC)/chitosan blended with poly(ethylene oxide) (PEO) nanofibrous meshes of different ratios were fabricated by electrospinning from aqueous solutions. Through studying the effects of the three composition on the solution rheological properties and the morphology of electrospun meshes, the mechanism of electrospinning was explored at the molecular level, and the ratio of PEO/(HLC & chitosan) (w/w) should be controlled below 1/4 as a plasticizer and HLC/chitosan maintained 4/3 w/w. Obtained meshes were treated by 0.2% glutaraldehyde solution (95% ethanol) for crosslinking and 0.2 M glycine solution for blocking unreacted aldehyde groups and became insoluble with fiber diameters of 151 ± 33 to 278 ± 46 nm, PEO was leached out after crosslinking and rinsing. HLC/chitosan scaffolds (4/3, w/w) could mimic native ECM in both chemical component and structure and support cellular in-growth in vivo while exhibited proper degradation rate in vivo. Bone marrow stromal cells adopted a flattened shape with filopodia- and lamellipodia-like extensions in the scaffolds and grew as a confluent layer after 7 days of culture in vitro. This study indicated the feasibility of electrospun nanofabrious HLC/chitosan scaffold from aqueous solution for tissue engineering application.     

3D打印胶原/壳聚糖支架改善大鼠脊髓损伤后神经功能恢复

文题释义：壳聚糖：为一种天然多糖,是虾蟹等低等动物外壳的重要成分,具有一定的机械强度,并且具有良好的生物相容性和抗菌性,在生物工程领域具有较好的应用前景。 3D生物打印：是组织工程中最重要的技术之一。目前常用的三维生物打印方法包括喷墨打印、挤压生物打印和激光生物打印,选择好合适的材料后,在计算机指导下根据所选择的生物材料和细胞类型逐层准确地打印出所设计的结构。 背景：3D打印技术可以根据需求制备出满足脊髓植入形状、大小和表面形态要求的生物支架。 目的：观察3D打印胶原/壳聚糖支架对脊髓损伤大鼠神经功能恢复的影响。 方法：将胶原和壳聚糖按2∶1的质量比混合,采用冷冻干燥法制备普通胶原/壳聚糖支架,采用3D打印机制备3D打印胶原/壳聚糖支架,分别测量两种支架的孔隙率和弹性模量,电镜观察支架形态。将神经干细胞分别与3D打印胶原/壳聚糖支架、普通胶原/壳聚糖支架共培养,进行扫描电镜观察与CCK-8检测。将40只雌性SD大鼠(由中国人民解放军医学科学院军事科学院提供)随机分成4组：假手术组、脊髓损伤组、普通胶    原/壳聚糖支架组和3D打印胶原/壳聚糖支架组,后3组制作脊髓全横断损伤模型,普通胶原/壳聚糖支架组和3D打印胶原/壳聚糖支架组损伤处填充对应的支架材料,术后相应时间点进行后肢功能BBB评分、斜坡实验、神经电生理检测与磁共振平扫。实验方案经天津市神经创伤重点实验室伦理委员会批准。 结果与结论：①扫描电镜显示,3D打印胶原/壳聚糖支架具有互连的多孔结构,普通胶原/壳聚糖支架内部结构紊乱;②神经干细胞在3D打印胶原/壳聚糖支架表面生长良好,完全伸展,且3D打印胶原/壳聚糖支架表面神经干细胞的活性显著高于普通胶原/壳聚糖支架组(P < 0.05);③3D打印胶原/壳聚糖支架的孔隙率与弹性模量均高于普通胶原/壳聚糖支架组(P < 0.05);④3D打印胶原/壳聚糖支架组术后3-8周的BBB评分高于脊髓损伤组、普通胶原/壳聚糖支架组(P < 0.05),术后4,6,8周的斜坡实验角度大于脊髓损伤组、普通胶原/壳聚糖支架组(P < 0.05);⑤3D打印胶原/壳聚糖支架组术后8周的运动诱发电位振幅、体感诱发电位振幅大于脊髓损伤组与普通胶原/壳聚糖支架组(P < 0.05),运动诱发电位潜伏期、体感诱发电位潜伏期短于脊髓损伤组与普通胶原/壳聚糖支架组(P < 0.05);⑥磁共振平扫显示与脊髓损伤组及普通胶原/壳聚糖支架组比较,3D打印胶原/壳聚糖支架组损伤处具有较好的连续性与较多的神经纤维束通过;⑦结果表明,3D打印胶原/壳聚糖支架可促进脊髓损伤大鼠神经功能的修复。 ORCID: 0000-0001-5771-8222(史新宇) 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     

实时超声在介导评估可注射CS/nHAC骨支架材料中的应用

目的　探讨实时超声在介导可注射骨材料的注入过程和评估其原位成骨情况中的应用价值。  方法　将可注射性壳聚糖/纳米羟基磷灰石/胶原（CS/nHAC）支架材料注入大鼠皮下组织,分别于注射后1、14、28 d进行超声成像检查,定量测定支架的灰度值,半定量监测支架的体积及内部血供情况。 结果　在实时超声的监测下,支架材料准确注入骨缺损部位,并且在通过超声对材料的体内评估中发现,与壳聚糖/胶原（CS）支架相比,CS/nHAC支架表现出较大的硬度,较稳定的体内降解率及较好的血供。  结论　实时超声可直观、安全、准确地介导骨支架材料的注入过程,并能无创地评估可注射性骨支架材料在体内的固化过程、降解过程和血供情况,在评估可注射性骨材料方面有较好的应用前景。     

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：     

Developing an alginate/chitosan hybrid fiber scaffold for annulus fibrosus cells

A fibrous scaffold made of alginate or alginate/chitosan was fabricated for annulus fibrosus (AF) cell culture using a wet-spinning and lyophilization technique. The scaffolds were evaluated using several in vitro tests. Scanning electron microscopy showed the scaffold fibers generally aligned in one direction with individual fiber diameters varying between 40-100 microm. The alginate/chitosan hybrid scaffold exhibited a slower degradation rate, while both scaffold types did not display any cyto-toxicity to 3T3 fibroblasts and could maintain canine AF cell growth. The AF cells retained their spherical shape within the fibrous scaffold at the beginning of the culture period and formed into cell clusters at later times. Specific extracellular matrix molecules, including collagen I, collagen II, and aggrecan, could be detected in the AF cell clusters. These results demonstrate the feasibility of using this hybrid alginate/chitosan scaffold for AF cell culture, and the potential application for intervertebral disc tissue engineering.     

透明质酸改性壳聚糖-胶原-羟基磷灰石复合支架力学特性及成骨细胞的增殖

背景：组织工程中,种子细胞需依赖于细胞外基质的存在才能发挥功能。因此支架材料的选择具有重大意义。 目的：制备一种新型改性壳聚糖-胶原-羟基磷灰石复合支架,优化易于细胞黏附的组织工程支架材料工艺。 方法：壳聚糖与透明质酸进行交联,红外和差示扫描量热图谱检测其结构;改性壳聚糖与胶原按1∶2,1∶1和2∶1制备3种改性壳聚糖-胶原-羟基磷灰石复合支架,将复合支架与成骨细胞MC3T3-E1联合培养,CCK-8法检测增殖,绘制生长曲线。 结果与结论：透明质酸和壳聚糖以酰胺键形成交联的新化合物,孔径在50~250 μm之间,孔隙率随着胶原水平、弹性模量的增加而增加,而密度则减少;增加胶原的含量在细胞联合培养初期有利于细胞对支架的黏附和增殖,但从第10天开始,3种样品中细胞数量相差不大,均出现平台期;苏木精-伊红染色发现成骨细胞在培养初期沿着支架材料内部空隙贴壁生长,随着培养天数的增加,贴壁细胞呈集落样生长,可明显看到细胞间连接。说明透明质酸改性壳聚糖/胶原/纳米羟基磷灰石复合材料可以作为骨支架材料供成骨细胞黏附、增殖,其中胶原与壳聚糖的体积比为1∶1为较优配比。     

壳聚糖/纳米羟基磷灰石分层复合支架的生物相容性研究

制备壳聚糖/纳米羟基磷灰石(CS/nHA)分层复合支架,对其进行细胞毒性评价.分离培养大鼠软骨细胞接种于支架,相差显微镜和扫描电镜观察细胞的黏附及生长情况.动物皮下埋植试验观察其组织相容性.实验结果证实壳聚糖/纳米羟基磷灰石分层复合支架具有良好的生物相容性,有望成为较好的骨软骨组织工程支架.     

Gradient collagen/nanohydroxyapatite composite scaffold: development and characterization

This paper reports an in situ diffusion method for the fabrication of compositionally graded collagen/nanohydroxyapatite (HA) composite scaffold. The method is diffusion based and causes the precipitation of nano-HA crystallites in situ. A collagen matrix acts as a template through which calcium ions (Ca(2+)) and phosphate ions (PO4(3-)) diffuse and precipitate a non-stoichiometric HA. It was observed that needle-like prismatic nano-HA crystallites (about 2 x 2 x 20 nm) precipitated in the interior of the collagen template onto the collagen fibrils. Chemical and microstructural analysis revealed a gradient of the Ca to P ratio across the width of the scaffold template, resulting in the formation of a Ca-rich side and a Ca-depleted side of scaffold. The Ca-rich side featured low porosity and agglomerates of the nano-HA crystallites, while the Ca-depleted side featured higher porosity and nano-HA crystallites integrated with collagen fibrils to form a porous network structure.     

磷酸钙活性人工骨与自体骨颗粒环抱式植骨治疗四肢骨不连#br#

目的　探讨固化型磷酸钙活性人工骨(CPC/rhBMP-2)与自体骨颗粒环抱式植骨治疗四肢非感染性萎缩型骨不连的临床疗效。 方法　对2013年9月至2017年9月年间治疗的16例四肢非感染性萎缩型骨不连患者进行回顾性分析,其中男12例,女4例;年龄（37.06±16.31）岁（16~67岁）。骨不连部位：下肢11例（胫骨6例、股骨3例、跟骨1例、腓骨1例）,上肢5例（桡骨3例、锁骨1例、手舟骨1例）,所有患者均行断端新鲜化,骨缺损中央植入自体骨颗粒,外周植入CPC/rhBMP-2形成环抱式植骨。术后复查X线片观察骨折愈合情况,记录并发症发生情况,随访患者直到骨折愈合。采用上肢功能障碍评定量表（DASH）、下肢功能量表(LEFS)和SF-12生活质量量表对治疗前、后进行疗效评定。 结果　本组16例均获随访,随访时间（16.93±4.06）月（12~26月）。X片显示全部病例均获得骨性愈合,愈合时间（5.43±2.25）月（3~10月）;术后DASH、LEFS和SF-12评分与术前比较均有统计学差异(P<0.05)。 结论　固化型磷酸钙活性人工骨(CPC/rhBMP-2)和自体骨颗粒环抱式植骨治疗四肢萎缩型骨不连的愈合率及安全性高,疗效可靠。     

Hierarchically biomimetic bone scaffold materials: nano-HA/collagen/PLA composite

A bone scaffold material (nano-HA/ collagen/PLA composite) was developed by biomimetic synthesis. It shows some features of natural bone both in main composition and hierarchical microstructure. Nano-hydroxyapatite and collagen assembled into mineralized fibril. The three-dimensional porous scaffold materials mimic the microstructure of cancellous bone. Cell culture and animal model tests showed that the composite material is bioactive. The osteoblasts were separated from the neonatal rat calvaria. Osteoblasts adhered, spread, and proliferated throughout the pores of the scaffold material within a week. A 15-mm segmental defect model in the radius of the rabbit was used to evaluate the bone-remodeling ability of the composite. Combined with 0.5 mg rhBMP-2, the material block was implanted into the defect. The segmental defect was integrated 12 weeks after surgery, and the implanted composite was partially substituted by new bone tissue. This scaffold composite has promise for the clinical repair of large bony defects according to the principles of bone tissue engineering.     

胶原-纳米羟基磷灰石复合支架的细胞相容性

背景：观察成骨细胞在生物材料上的形态、增殖和分化等项目,可评估生物支架材料的生物相容性。 目的：观察复合支架材料纳米羟基磷灰石/胶原对成骨细胞增殖、分化的影响。 方法：取新生24 h内Wistar大鼠的颅盖骨,采用改良胶原酶消化法进行成骨细胞原代培养,取第3代细胞与纳米羟基磷灰石/胶原支架或普通羟基磷灰石材料体外复合培养。培养3,6,9 d后,观察材料周边的细胞形态及支架材料对细胞分化、增殖的影响。 结果与结论：纳米羟基磷灰石/胶原材料较普通的羟基磷灰石材料更有利于成骨细胞的黏附、生长、分化、增殖,证实其生物相容性更好,有望成为一种新型的骨组织工程支架材料。     

纳米羟基磷灰石/壳聚糖/半水硫酸钙为可注射骨组织工程支架材料的可行性

背景：前期实验采用仿生学原理制备了可注射性纳米羟基磷灰石/壳聚糖/半水硫酸钙复合材料,但其与骨髓间充质干细胞的生物相容性还不十分清楚。目的：探讨纳米羟基磷灰石/壳聚糖/半水硫酸钙作为注射型骨组织工程支架材料的可行性。方法：将第3代兔骨髓间充质干细胞与可注射纳米羟基磷灰石/壳聚糖/半水硫酸钙支架复合培养,作为实验组;以单纯接种培养的骨髓间充质干细胞为对照组,倒置显微镜下观察细胞生长情况,MTT法检测细胞增殖,扫描电镜观察细胞在材料表面生长与增殖。将纳米羟基磷灰石/壳聚糖/半水硫酸钙支架埋植在家兔背部肌袋内,埋植后2,4,6,8周进行病理学观察。结果与结论：实验组细胞生长、增殖良好,与对照组无明显差异。支架埋植后2周,材料周围有中等量中性粒细胞、淋巴细胞和巨细胞浸润,可见小血管与纤维母细胞增生,材料已被炎性细胞分割、围绕散碎;埋植后4周,可见少量淋巴细胞、纤维母细胞聚集,炎症反应进一步消退,肌纤维排列、形态正常;埋植后6周,材料周围炎症反应轻微,组织水肿不明显;埋植后8周,炎症反应基本消退,材料基本降解完成,肌纤维形态基本正常。表明纳米羟基磷灰石/壳聚糖/半水硫酸钙复合物具有良好的细胞相容性和生物降解性,可作为注射型支架材料。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：     

Apatite-coated collagen scaffold for bone morphogenetic protein-2 delivery

Bone morphogenetic proteins (BMPs) are the most potent osteoinductive growth factors. BMP-2 is clinically used for spine fusion and bone fracture healing. Commercially available BMP-2 uses a type I collagen scaffold as a carrier, but it only releases BMP-2 for a short period of time, which may release the bone formation efficacy. In the present study, we hypothesize that apatite coating of a collagen scaffold increases the release period as well as the osteogenic efficacy of BMP-2. Apatite coating was achieved by incubating collagen scaffolds in simulated body fluids (SBFs). Apatite coating on collagen scaffolds was confirmed by X-ray diffraction, electron spectroscopy for chemical analysis, attenuated total reflectance-Fourier transform infrared spectroscopy, and scanning electron microscopy. The rate and period of BMP-2 release from apatite-coated collagen scaffolds varied depending on the concentration of SBFs used. The 5× and 10× SBF apatite-coated collagen scaffolds released 91.8%±11.5% and 82.2%±13.1% of their loaded BMP-2 over 13 days in vitro, respectively, whereas noncoated collagen scaffold released 98.3%±2.2% over the initial one day. BMP-2 released from apatite-coated collagen scaffold significantly increased the alkaline phosphatase activity of cultured osteoblasts, compared with BMP-2 released from noncoated collagen scaffold. Computed tomography and histomorphometry showed that BMP-2 delivery using apatite-coated collagen scaffolds resulted in 2.5-fold higher bone formation volume and 4.0-fold higher bone formation area than BMP-2 delivery using noncoated collagen scaffolds. This study shows that simple apatite coating of a collagen scaffold results in a BMP-2 carrier that renders long-term release of BMP-2 and dramatically enhances osteogenic efficacy.     

Crosslinked collagen/chitosan matrix for artificial livers

Matrices composed of collagen and chitosan may create an appropriate environment for the regeneration of livers. In this study, we have prepared, characterized and evaluated a new collagen/chitosan matrix (CCM). The CCM was made by using crosslinking agent 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) in N-hydroxysuccinimide (NHS) and a 2-morpholinoethane sulfonic acid (MES) buffer system. The chemical characteristics were evaluated by Fourier-transformed infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The mechanical strength was measured by tensile tests. The platelet deposition and hepatocyte culture experiments show that CCM has excellent blood and cell compatibility. The results suggest that the CCM is a promising candidate matrix for implantable bioartificial livers.     

Preparation of alginate/galactosylated chitosan scaffold for hepatocyte attachment

Galactose-carrying lactobionic acid was covalently coupled with chitosan for determining hepatocyte specificity. Galactosylated chitosan (GC) was reacted with Ca-alginate (ALG) gel through the electrostatic interaction of carboxylic groups of alginate with amine groups of GC. Highly porous, three-dimensional sponge composed of ALG and GC was prepared to provide specific hepatocyte recognition signals and enhance the mechanical property of the ALG sponge. Observation of the sponge through scanning electron microscopy revealed that sponge was a highly porous microstructure with interconnected pores. Porosity and pore size of the sponge were greatly dependent on the content and molecular weight of GC, and freezing temperature. The mechanical property of the ALG/GC sponge was enhanced with an increase of the GC content. Spheroid formation and viability of hepatocytes of the ALG/GC sponge were higher than those of the ALG one.     

Collagen-coated polylactide microcarriers/chitosan hydrogel composite: injectable scaffold for cartilage regeneration

A novel structure of injectable scaffold is designed and fabricated by combining collagen-coated polylactide (PLA) microcarriers and crosslinkable chitosan hydrogel. The collagen-coated PLA microcarriers were firstly mixed with the hydrogel precursor, a thickening agent of konjac glucomannan (KGM), and redox initiators of ammonium persulfate and tetramethylethylenediamine (TMEDA). The mixture was then injected into a mold and incubated at 37 degrees C to obtain the composite scaffold. The hydrogel can deliver the collagen-coated PLA microcarriers to the desired site and, after gelation, will prevent them from uncontrolled movement. On the other hand, the collagen-coated PLA microcarriers can substantially enhance the mechanical properties of the composite system. It was found that the microcarriers suspended stably in 0.6% KGM/1% chitosan derivative (CML) solution at 37 degrees C at least for 15 min. The dynamic elastic modulus (G') of the composite scaffold increased along with the increase of the microcarrier content. G' of the composite scaffold with 10% microcarriers was measured as 0.87-2.15 MPa at a frequency range of 0.1-100 rad/s, which was 120-90 times higher than that of its hydrogel system alone (12.1-24.4 kPa). In vitro culture of chondrocytes/composite scaffold showed that the cell metabolic activity increased rapidly before day 9, then leveled off. Cells in the hydrogel could attach and grow on the surface of the collagen-coated PLA microcarriers to form confluent cell layers after days 9-12. These features make the composite scaffold to be injectable and applicable in either tissue engineering, or regenerative medicine, and in particular, in orthopaedics.