去甲二氢愈创木酸交联猪去细胞脊髓支架及其相关特性研究

目的 :观察去甲二氢愈创木酸(nordihydroguaiaretic acid,NDGA)交联猪去细胞脊髓支架的结构及性能。方法:取成年猪胸段脊髓,采用2次冻融化学萃取法对脊髓行去细胞处理,再用2.5g/L NDGA溶液进行交联处理。在体视显微镜及扫描电镜下分别观察猪去细胞脊髓支架及NDGA交联猪去细胞脊髓支架的结构。采用Instrong生物力学测试仪检测正常猪脊髓(正常组)、猪去细胞脊髓支架(未交联支架组)及NDGA交联猪去细胞脊髓支架(交联支架组)的极限抗拉强度和弹性模量。取第4代SD大鼠星形胶质细胞分别与未交联支架和NDGA交联支架联合培养,采用CCK8法检测细胞生长率,评价支架的细胞毒性。将未交联支架和交联支架分别包埋至SD大鼠背部皮下,在1、2、4周取出检测其包埋后的降解率,并取包埋4周的组织行HE染色,评价支架的生物相容性。结果:正常组脊髓组织为圆柱状,呈乳白色,横切面可见灰质与白质分界明显;未交联支架基本保持原组织外形,呈白色半透明状,白质与灰质无明显分界;交联支架质地稍变硬,呈棕黄色。扫描电镜显示未交联支架与交联支架内的基质纤维保存完好,相互交织成网状三维结构,内部孔洞连通。未交联支架的抗拉强度及弹性模量较正常组显著性下降(P0.05);交联支架抗拉强度和弹性模量较未交联支架显著性增强,两组比较有统计学差异(P0.05),但仍低于正常组(P0.05)。星形胶质细胞在交联支架及未交联支架中均生长良好,共培养时间越久,OD值越大,两组相同时间点OD值比较无统计学差异(P0.05)。相同时间点交联组在体内降解率明显低于未交联组(P0.05)。包埋4周后未交联组支架HE染色可见炎症细胞及成纤维细胞浸润,并且有肉芽组织聚集在内部孔隙中;交联组支架炎症细胞明显减少,且可见新生血管状结构。结论:NDGA交联猪去细胞脊髓支架与未交联猪去细胞脊髓支架比较三维结构未见明显改变,但生物力学性能和体内抗降解能力显著性增强,生物相容性提高,且无明显细胞毒性,可作脊髓损伤修复的支架材料。     

Quantitative solubilization and analysis of insoluble paired helical filaments from alzheimer disease

In this study, we evaluate the ability of several solvents to solubilize insoluble paired helical filaments (PHF) of Alzheimer disease. Specifically, we use protein extraction and reduction in the volume of insoluble material as quantitative assays to establish solvents of PHF. Using sequential categories of protein solvent to analyze insoluble PHF, only alkali or exhaustive proteolysis are effective in completely solubilizing PHF, while a variety of denaturants are ineffective. Alkali does not affect the phosphorylation state of PHF and complete dephosphorylation of PHF with hydrofluoric acid does not affect PHF solubility. These findings suggest that the ‘hyperphos-sphorylation’ of PHF proteins is not responsible for PHF insolubility. However the in vitro glycation of τ generates PHF that are insoluble in SDS and soluble in alkali. These findings suggest that protein crosslinks, including advanced glycation endproduct-derived crosslinks which were recently described in Alzheimer disease, play a major role in effecting PHF insolubility in vivo.     

3种不同后路内固定方式及其横连治疗胸腰段骨折的力学性能比较

目的比较3种不同后路内固定方式及其有无横连杆治疗胸腰段骨折的生物力学性能差异,寻找最优化的后路内固定方式。方法在已验证的正常T12~L2有限元模型基础上,模拟L1椎体爆裂性骨折。将T12椎体上半皮质骨切除并赋予内部松质骨损伤材料属性,分别建立无、有横连杆经伤椎单侧螺钉(模型A1、A2)、常规短节段(模型B1、B2)和经伤椎双侧螺钉(模型C1、C2)6种内固定模型。分别比较6组模型在各种生理应力下的活动范围(range of the motion,ROM)以及螺钉和棒的最大Von Mises应力情况。结果在屈伸和侧屈应力下,经伤椎单侧和双侧螺钉内固定模型组ROM均明显小于常规短节段内固定组;而经伤椎单侧和双侧螺钉内固定组,在屈伸应力下两者ROM无显著差异,在侧屈应力下经伤椎双侧螺钉模型的稳定性优于经伤椎单侧螺钉固定。应力主要集中在上位螺钉钉尾和上位螺钉与伤椎螺钉之间的棒体,经伤椎双侧内固定组上位螺钉最大应力明显低于经伤椎单侧和常规短节段内固定组螺钉最大应力。横连可增加各内固定组在扭转应力下的稳定性,也可降低上位螺钉和棒在扭转应力下的最大应力,而屈伸和侧屈应力下螺钉和棒的最大应力未见明显差异。结论经伤椎置钉后路内固定可获得较好的生物力学稳定性,且添加横连不仅能改善构型扭转刚度,而且能降低螺钉和棒的最大扭转应力,是治疗胸腰椎不稳定骨折良好选择。     

枝化状聚乙二醇交联改善猪去细胞主动脉瓣的力学性能比较

目的 采用不同相对分子质量枝化状聚乙二醇(PEG)交联巯基化的猪去细胞瓣,观察其对去细胞瓣膜力学性能的影响.方法 将25例猪去细胞主动脉瓣随机分为5组:PEG3400组、PEG8000组、PEG12000组、PEG20000组和对照组,常温反应时间4 h.测定残余巯基计算交联效率;静态拉伸实验测定力学性能.结果 4 h交联率依次为92.40%、89.88%、87.87%和87.46%,相对分子质量越小,交联效率越高,PEG3400组与其他各组比较,差异有统计学意义(P＜0.05);力学测试显示,相对分子质量越大,力学强度越高,呈一定的正相关,PEG12000和PEG20000组抗拉强度分别为(3.22±0.41)MPa和(3.19±0.15)MPa,与对照组比较,差异有统计学意义(P＜0.05).结论 相对分子质量12000 Da和20000 Da枝化状聚乙二醇交联可有效改善猪去细胞瓣的力学性能,有望用于构建新型复合的组织工程瓣膜支架材料的研究应用.

Abstract：

Objective Branched polyethylene glycols (PEG) with different molecular weight were cross-linked to the porcine decellularized aortic valve (DAV) and the effects of PEG cross-linking on the mechanical properties were investigated. Methods A total of 25 porcine DAVs were randomly assigned into 5 groups: PEG3400, PEG8000, PEG12000, PEG20000 and control. The reactive time was 4 h at room temperature. The efficiency of crosslinking was calculated by measuring the residual thiol group. The mechanical properties were obtained by static tensile test. Results The efficiency of crosslinking was 92. 40% , 89. 88% , 87. 87% and 87. 46% in PEG3400, PEG8000, PEG12000, PEG20000 groups, respectively. As compared with other groups, the PEG3400 group had significantly greater increase in the crosslinking degree (P ＜ 0. 05). Tensile test showed the tensile strength of PEG12000 and PEG20000 groups was (3. 22 ±0.41) and (3. 19 ±0. 15) MPa, respectively, and significantly different from that in control group (P ＜ 0. 05). The tensile strength and young' s modulus had a positive correlation with the molecular weight of PEG. Conclusion Branched PEG with the molecular weight of 12 000 Da and 20 000 Dacan effectively crosslink to the porcine decellularized aortic valves and improve their mechanical behaviors, and has the potential to be used as the material of fabricating new hybrid scaffold of tissue engineering heart valves.     

Structure and biochemistry of collagen

The structure and immunochemistry of the interstitial collagens (types I, II, and III), and the structure of basement membrane collagen (type IV) and filamentous collagen (type VI) are described, together with the implications of the different types of collagen.     

聚乙二醇改性去细胞猪主动脉瓣膜构建复合支架及其体外细胞毒性试验

目的 对去细胞猪主动脉瓣膜进行聚乙二醇(PEG)化改性,并评价改性后复合支架的细胞毒性.方法 合成功能基团为丙烯酰基的枝化状聚乙二醇衍生物,在去细胞猪主动脉瓣膜引入巯基,通过迈克尔加成反应完成PEG对去细胞猪主动脉瓣膜的交联,并作PEG改性前后瓣膜的生物力学测定.制作去细胞瓣膜的浸提液,浸提液分为单纯去细胞瓣膜组、PEG改性去细胞瓣膜组和阴性对照组(培养液),采用CCK-8法检测复合支架的浸提液对人脐静脉内皮细胞增殖率的影响,评价其细胞毒性.结果 PEG改性去细胞瓣膜反应条件温和,改性效果确切.复合瓣膜支架的抗拉强度明显高于去细胞瓣膜[(7.53±0.29)MPa比(5.65±0.24)MPa,P＜0.05],但与天然瓣膜[(7.68±0.20)MPa]差异无统计学意义(P＞0.05).复合支架和去细胞瓣膜毒性评级均0级,与阴性对照组差异无统计学意义(P＞0.05).人脐静脉内皮细胞经各浸提液的培养液培养后形态良好,增殖旺盛.结论 PEG改性能明显改善去细胞猪主动脉瓣膜的力学性能,且改性后的复合支架无细胞毒性,为进一步研究提供依据.     

The effect of elastomer chain flexibility on protein adsorption

Cells are known to respond differently when grown on materials of varying stiffness. However, the mechanism by which a cell senses substrate stiffness is unknown. Lower crosslink density elastomers formed from acrylated star-poly(d,l lactide-co-?-caprolactone) have previously been shown to support higher smooth muscle cell proliferation in in vitro culture. This difference in growth was hypothesized to be due to differences in protein adsorption that resulted from differences in polymer chain mobility at the surface. Therefore, layer mass and viscoelastic properties were measured for HSA, IgG, fibronectin, vitronectin, and serum supplemented media adsorbed to elastomers of two crosslink densities. Significantly more fibronectin adsorbed to the lower crosslink density surface while significantly more IgG adsorbed to the higher crosslink density surface. Furthermore, differences in fibronectin and IgG layer shear moduli were observed, suggesting that there was a difference in the conformation of the adsorbed protein. ATR-FTIR analysis showed that the lower crosslink density elastomer absorbed more surface water. The increased amount of water may cause greater entropic gains upon protein adsorption to the lower crosslink density surface, which increases total protein adsorption from serum and may cause differences in protein conformation and thus cell behavior.     

新型聚合物／液晶复合膜的研究 Ⅱ．二氧化碳气体的分离性能

以顺丁橡胶（ｃｉｓ－ＰＢ）为高分子基质材料，与具有反应性基团的低分子液晶化合物溶液共混后成膜，后经Ｓ２Ｃｌ２气相硫化制得交联型聚合物／液晶复合膜．研究了测试温度、压力、交联时间以及成膜条件对膜的气体分离性能的影响。结果发现，制得的复合膜在５０℃以下有很好的富二氧化碳性能．在此实验条件下，Ｎ２、Ｏ２的透过系数很小，而ＣＯ２的透过系数为２．０－４．０×１０－８ｃｍ３（ＳＴＰ）ｃｍ／ｃｍ２·ｓ·ｃｍＨｇ。     

不同交联改性牛心包材料的细胞毒性研究

本研究采用培养的人胚肺纤维细胞分析比较戊二醛、环氧１铬交联处理后４％甲醛保存的牛心包材料的细胞毒性。在浸泡前与浸泡１０、２０、３０天的周期中，不同交联处理的牛心包材料与浸出液的细胞增殖抑制指数显示：９１）三种交联剂处理的心包材料均有明显的细胞毒性。（２）随浸泡时期的延长，心包材料与浸出液的细胞毒性逐渐降低。（３）铬交联处理的牛心包材料与浸出液的细胞毒性显著高于其他交联材料。     

Water sorption and dynamic mechanical properties of dentin adhesives with a urethane-based multifunctional methacrylate monomer

ObjectivesOur previous study showed the synthesis and characterization of a novel urethane-linked trimethacrylate monomer for use as a co-monomer in dentin adhesives. The objective of this work was to further investigate the performance of dentin adhesives containing a new monomer, with particular emphasis on the water sorption and viscoelastic behavior of the crosslinked networks.Materials and methodsDentin adhesives contained 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy) phenyl]-propane (BisGMA), 2-hydroxyethyl methacrylate (HEMA), and a new multifunctional methacrylate with urethane-linked groups-1,1,1-tri-[4-(methacryloxyethylaminocarbonyloxy)-phenyl]ethane (MPE) and were photo-polymerized in the presence or absence of water. Adhesives were characterized with regard to degree of conversion (DC), viscosity, water sorption/solubility, and dynamic mechanical analysis (DMA) and compared with BisGMA/HEMA controls.ResultsThe experimental adhesives exhibited DC and solubility comparable to that of the control, regardless of the presence or absence of water. All the experimental adhesives tested showed less water sorption, lower tan δ peak heights, and higher rubbery modulus than the control.SignificanceDentin adhesives containing a new multifunctional methacrylate showed better dynamic thermomechanical properties and water sorption relative to controls, without compromising DC and solubility. Thus, MPE, when included as a component of methacrylate dentin adhesives, may provide enhanced durability in the moist environment of the mouth.