拉伸法测Mersilk缝合线的力学性能

为了获得非吸收性Mersilk缝合线的力学性能,用JCD3型读数显微镜代替JC10型读数显微镜改进了FD-YC-II型杨氏模量测定仪,利用拉伸法测量1-0型Mersilk缝合线在加载、卸载时的轴向伸长量,得到了拉伸Mersilk缝合线的应力-应变曲线与滞后回线,测得Mersilk缝合线直径为（0.372±0.003） mm、拉伸强度为（320.87±4.64） MPa、断裂伸长率为（11.91±0.11）%、杨氏模量为（65.91±0.88） MPa,并测定了应力-应变滞后回线。实验结果表明,用FD-YC-II型杨氏模量测定仪测定手术缝合线力学性能的实验方法简单、结果可靠,可以为医学临床应用提供数据参考,也可用于医学物理实验教学。     

羧甲基壳聚糖-羧甲基纤维素防粘连膜的制备及其理化特性

背景:壳聚糖能有效预防粘连,可制成不同的剂型,如凝胶、溶液、海绵状以及薄膜等,但其缺点是溶液、凝胶易流动,不易在局部形成较高浓度,而单纯应用壳聚糖制成海绵状及薄膜机械强度及韧性不够。目的:以羧甲基壳聚糖、羧甲基纤维素为主要成分,制备具有优良物理、生物性能,预防粘连的生物膜。方法:将羧甲基壳聚糖和羧甲基纤维素按一定比例混合,加入戊二醛、硫酸铝铵进行双交联,甘油增塑。根据膜的色泽、拉伸强度、吸水率、溶胀比等指标通过正交试验筛选处方构成,优化膜的制备工艺,初步确定膜的制备工艺流程。通过扫描电镜、红外光谱等对制备样本的理化特性进行检测,并将膜植入SD大鼠体内观察膜的降解情况。结果与结论:得到优化后膜的处方构成为:羧甲基壳聚糖/羧甲基纤维素为1:1;硫酸铝铵浓度为0.15%;甘油含量为0.8%;戊二醛含量为0.003%。在以上工艺条件下制得的膜呈半透明状,微黄,上表面略粗躁,下表面光滑;膜的平均厚度为0.09mm;吸水率为964%;溶胀比为3.25;干态下膜的最大拉伸强度为20MPa,湿态下膜的最大拉伸强度为5MPa;接触角平均为35°。羧甲基壳聚糖和羧甲基纤维素间形成了较强的分子间作用力。膜表面结构呈相互交错的纤维状,表面有不规则的孔状结构。膜植入鼠体内后10d左右水化成凝胶,1个月后体内完全降解吸收。提示羧甲基壳聚糖-羧甲基纤维素膜是一种生物相容性良好、可降解吸收、具有一定手术缝合强度的生物膜。     

Ⅱ型胶原-丝素蛋白-透明质酸复合支架的制备及力学性能检测北大核心

背景:Ⅱ型胶原、丝素蛋白和透明质酸3种天然生物可降解材料能够为细胞提供理想的微环境,已成为理想的软骨修复支架材料。目的:将Ⅱ型胶原、丝素蛋白和透明质酸3种材料制备成软骨组织工程支架,评价其理化性质及生物力学性能。方法:采用低温3D打印技术制备Ⅱ型胶原-丝素蛋白-透明质酸复合支架,检测其微观结构、孔隙率与吸水膨胀率。采用不同的应变率对该复合支架进行压缩实验,考察支架的率相关性能;在该复合支架表面施加恒定的应力水平或恒定的应变,保持3600 s,观察其蠕变应变变化及应力松弛行为。结果与结论:①Ⅱ型胶原-丝素蛋白-透明质酸复合支架呈三维多孔结构,孔径大小一致,相通性好,孔隙率为(85.1±1.6)%,吸水膨胀率为(1071.7±131.6)%;②在不同的应变率作用下,软骨支架的压缩应力-应变曲线不重合,说明软骨支架的压缩力学性能具有率相关性;随着应变率的增加,复合支架的杨氏模量增加;③当应力水平恒定时,复合支架的蠕变应变呈现先快速增加后缓慢增加的趋势,当应力水平增加时蠕变应变也增加;④当压缩应变恒定时,支架的应力随着松弛时间先快速降低后缓慢降低,随着压缩应变的增大,不同时刻的应力都增大;⑤力学性能实验表明,制备的Ⅱ型胶原-丝素蛋白-透明质酸软骨支架力学性能特征与宿主软骨组织相似,都是非线性黏弹性材料。     

壳聚糖管状支架的制备及生物降解性

背景:作者课题组在进行肺组织瓣修补食管缺损实验中,发现硅胶支架和金属支架都不理想,都存在排斥反应和远期并发症,为寻找一种理想的生物型可自行降解支架,将壳聚糖制成管型支架,观察其在生物体内的相容性和降解性,为食管重建提供一种可降解支架。目的:探讨壳聚糖管状支架的制备方法及其生物特性。方法:利用乙酸溶液制备60g/L的壳聚糖乙酸水溶胶,采用成膜方法制管后用NaOH脱下壳聚糖导管,取内径5mm管,切成段,长度2mm,消毒,并将壳聚糖管植入大鼠组织内,分别于不同时间段大体及光镜下观察其生物相容性及体内降解性。结果与结论:壳聚糖导管光滑,韧性好,吸收水分变软,组织生物相容性好,随时间可被组织吸收降解。该方法提供了制备壳聚糖导管的一种新方法,并证实了其组织相容性和生物可降解性。     

编织型丝素纤维人工韧带及其体外降解性能研究

该研究制备了一种丝素纤维人工韧带,分别在PBS和蛋白酶XIV溶液中进行体外降解试验。并对其表面形态、质量损失、降解液pH及力学性能等进行了观察和测试。结果表明,PBS溶液中降解70天后,丝素纤维人工韧带表面形貌和质量损失率没有发生明显变化,力学性能基本保持不变,溶液pH稳定呈中性。而酶降解70天的丝素纤维人工韧带表面发现多根纤维断裂,质量损失率高达18.4%,丝素纤维人工韧带材料直径下降达21.8%,最大断裂强力损失了近50%。降解后溶液的pH值呈弱酸性,且溶液中存在肉眼可见的絮状物。蛋白酶XIV对天然蛋白丝素纤维人工韧带材料具有明显的降解作用。该研究可为体外评价可降解人工韧带降解速率、建立体内外降解性能之间的关系提供参考。     

液氮保存3个月至8年人类同种主动脉瓣叶和主动脉壁的生物力学特性对比研究

目的 :研究液氮保存时间对人类同种主动脉瓣叶和主动脉管壁的生物力学特性的影响 ,从力学性能角度探讨同种瓣的有效使用期限 ,指导临床应用。方法 :将同种主动脉瓣叶和管壁随机分为 10组 ,Ⅰ组为新鲜组 ,Ⅱ组为新鲜冷冻组 ,Ⅲ～Ⅹ组分别为液氮保存 3个月、6个月、1年、1.5年、2年、3年、4年和 8年组。每组 6个瓣叶和管壁。测量瓣叶及管壁的厚度、宽度 ,分别进行应力应变试验和破坏试验 ,比较各组瓣叶和管壁的厚度、截面积、应力应变曲线参数、破坏应力有无差异。结果 :各组瓣叶和管壁的平均厚度、截面积、破坏应力和同一应力下的伸长比之间无明显差异。Ⅱ～Ⅷ组的应力应变曲线有集中趋势 ,而Ⅸ、Ⅹ组的应力应变曲线呈离散趋势。主动脉壁的横向破坏应力明显强于纵向破坏应力 (P <0 .0 5 )。结论 :程控降温、液氮保存法对同种瓣生物力学性能无明显影响。液氮保存 3年以内的主动脉瓣叶和主动脉壁的生物力学特性更趋于稳定 ,个体之间差异明显减小 ,可用于手术 ;液氮保存 4年以上的同种瓣个体间差异明显增加 ,不宜应用于临床。术中应用同种主动脉壁加宽右室流出道时应注意其生物力学各向异性的特点。     

壳聚糖/磷酸三钙复合组织工程支架材料的制备及其性能*

背景：通过适当的工艺混合、加工来制备复合支架材料,可以弥补单一材料的不足,最大限度地满足组织工程的需要。 目的：制备壳聚糖/磷酸三钙复合支架,探讨其作为牙髓组织工程支架材料的可行性。 方法：壳聚糖粉末溶于微量冰醋酸溶液中,搅拌均匀,静置脱泡,预冷冻,交联,再次冷冻制成海绵状多孔壳聚糖/磷酸三钙支架。 结果与结论：冻干法制备的壳聚糖/磷酸三钙多孔支架平均孔隙率达85.78%,最高孔隙率达90%以上,孔径在100~300 μm,复合后的支架材料具有良好的韧性,当轴向压缩变形量超过5 mm时,材料仍然没有发生破坏。材料浸提液与牙髓细胞复合培养后,细胞毒性均为0级,由此可见壳聚糖/磷酸三钙复合材料具有良好的生物相容性、细胞亲和性和一定的力学性能,满足生物材料基本要求。     

兔跟腱被动牵拉后的病理学及力学特性

用特殊设计的仪器分组牵拉兔跟腱后分别对跟腱进行组织学、组织化学及生物力学试验,发现随牵拉次数的增加,跟腱的病理变化逐渐加重,跟腱的最大断裂负荷和最大断裂应力逐渐增加。最大断裂形变率在牵拉两周时稍有上升,四周则有所下降。各组跟腱在高形变率时,其最大断裂载荷、应力、能量数值较高,反之在低形变率时其最大断裂载荷、应力、能量数值较低。从应力—应变曲线发现,牵拉四周组其杨氏模量最大,两周组和未牵拉组次之。而“坡脚区”未牵拉组最长,牵拉两周组和四周组逐渐缩短。根据病理学和生物力学的实验结果,对运动训练与跟腱损伤和跟腱生物力学特性之间的关系进行了讨论。     

左旋聚乳酸的改性实验

背景：目前临床上大量使用的金属支架永久存留于人体,对人体存在潜在的风险。 目的：观察改性对左旋聚乳酸的作用以及改性材料用于可降解支架制备的可行性。 方法：以左旋聚乳酸/聚己内酯为95∶5的比例,用溶液法制备左旋聚乳酸、聚乳酸/聚己内酯共聚材料(PLCL-J 9505)和聚乳酸/聚己内酯共混材料(PLCL-H 9505)薄膜。 结果与结论：力学性能测试结果显示,3个月左旋聚乳酸材料的脆性明显升高,材料变得容易断裂,成为制备支架的一大缺陷;PLCL-J材料力学性能损失过快,第3周屈服完全消失,第4周拉伸强度开始急剧下降,到第10周已经完全丧失力学性能;PLCL-H材料不仅初始时断裂伸长率高,而且在降解过程中能始终保持较高的弹性。特性黏数测试和表面形态观测结果显示PLCL-J材料的降解速率过快,不适合在支架上应用,而左旋聚乳酸和PLCL-H基本是匀速的水解,且PLCL-H相对于左旋聚乳酸降解速率有一定程度的增加。提示左旋聚乳酸与聚己内酯共混改性比例为95∶5时不仅能保证材料具备支架所需的力学强度,还能显著提高材料的断裂伸长,达到了增塑目的的同时,也加快降解速率,有望成为制备可降解支架的新型材料。     

胶原/生物活性玻璃/壳聚糖增强型复合支架

背景：生物活性玻璃/胶原复合材料具有优良的成骨活性和的生物学性能,然而其在人体环境中易降解而导致支架溃散、力学性能下降。 目的：构建具有良好力学性能、抗降解性能和骨修复特性的胶原/生物活性玻璃/壳聚糖增强型复合支架。 方法：以壳聚糖作为分散剂,将生物活性玻璃粉体预先在壳聚糖溶液中均匀分散,然后与胶原溶液混合,结合冷冻干燥法制备多孔胶原/生物活性玻璃/壳聚糖增强型复合骨修复支架。采用傅里叶变换红外光谱仪、场发射扫描电子显微镜、X射线衍射仪、动态生物力学试验机等对复合支架的结构和性能进行表征。 结果与结论：由于壳聚糖和生物活性玻璃粉体在微酸性环境下的电荷吸引,使在壳聚糖中预分散的生物活性玻璃颗粒在复合支架中分散更均匀;壳聚糖的引入大量增加了机体中的羟基和氨基,使分子间的相互作用增强,显著提高了材料的抗压模量和强度;壳聚糖和胶原在分子尺度的混合,使胶原分子被壳聚糖包裹,降低了胶原酶对胶原分子的酶切能力,显著提高了复合支架的抗胶原酶解性;壳聚糖分子使生物活性玻璃颗粒更均匀的包裹在大分子基相中,减少了生物活性玻璃颗粒的团聚和暴露,导致复合支架在模拟体液中的矿化活性略微降低。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：     

Performance modification of chitosan membranes induced by gamma irradiation

Trauma of the nervous system often results in permanent functional loss because the spontaneous regeneration of nerves is very difficult. Thus, various methods have been developed to facilitate the restoration of damaged nerve. The biodegradable nerve conduit is one of the most promising methods for nerve regeneration. Chitosan, a natural polysaccharide that has excellent biocompatibility and biodegradability, can be used as conduit material. But, nerves regenerated by nerve conduits made from chitosan have some problems, for example, with their mechanical properties. This article shows that the mechanical properties of chitosan film were markedly improved by selected doses of gamma radiation and cell culturing experiments on the surface of the irradiated chitosan film indicated that the film still has excellent biocompatibility.     

Improving the mechanical properties of chitosan-based heart valve scaffolds using chitosan fibers

Chitosan is being widely studied for tissue engineering applications due to its biocompatibility and biodegradability. However, its use in load-bearing applications is limited due to low mechanical properties. In this study, we investigated the effectiveness of a chitosan fiber reinforcement approach to enhancing the mechanical properties of chitosan scaffolds. Chitosan fibers were fabricated using a solution extrusion and neutralization method and incorporated into porous chitosan scaffolds. The effects of fiber/scaffold mass ratio, fiber mechanical properties and fiber length on scaffold mechanical properties were studied. The results showed that incorporating fibers improved scaffold strength and stiffness in proportion to the fiber/scaffold mass ratio. A fiber-reinforced, heart valve scaffold achieved leaflet tensile strength values of 220±17 kPa, comparable to the radial values of human pulmonary valve leaflets. Additionally, the effects of 2 mm fibers were found to be up to threefold greater than 10 mm fibers at identical mass ratios. Heparin crosslinking of fibers produced a reduction in fiber strength, and thus failed to produce additional improvements to fiber-reinforced scaffold properties. Despite this reduction in fiber strength, heparin-modified fibers still improved the mechanical properties of reinforced scaffolds, but to a lesser extent than unmodified fibers. The results demonstrate that chitosan fiber reinforcement can be used to achieve porous chitosan scaffold strength approaching that of tissue, and that fiber length and mechanical properties are important parameters in defining the degree of mechanical improvement.     

壳聚糖材料在脊髓损伤后神经再生的研究与作用

背景：组织工程支架材料壳聚糖能复合多种种子细胞和神经因子,维持受损组织正常的解剖结构,防止胶质瘢痕挤压,对脊髓损伤后神经再生具有重要的意义。 目的：介绍壳聚糖材料在修复脊髓损伤后神经再生领域的研究现状。 方法：由第一作者检索1990至2012年 PubMed数据库、CNKI数据库及万方数据库有关壳聚糖材料特性、壳聚糖导管移植治疗脊髓损伤的相关文献。 结果与结论：壳聚糖具有良好的物理、化学性能,并且具有良好的生物相容性、生物降解性,免疫抗原性小和无毒性等特殊生物医学特性,与嗅鞘细胞、骨髓间充质干细胞及神经干细胞具有良好的亲和性。壳聚糖材料制备的神经导管、支架能在脊髓损伤后桥接神经断端,维持神经再生的正常解剖结构,提供种子细胞及细胞因子载体,为损伤后神经再生提供良好的微环境,但目前对于壳聚糖导管的研究仍不够全面,仍有很多问题待解决。     

组织诱导性神经导管的制备及性能评价

本研究的目的是构建一种新型的组织诱导性神经导管并评价其生物学性能。壳聚糖包被中药川芎嗪制备微球,利用体外缓释方法检测壳聚糖/川芎嗪微球的缓释效果;壳聚糖/川芎嗪微球与胶原蛋白复合构建组织诱导性神经导管,2%京尼平交联导管;万能材料试验机评价交联前后神经导管的力学特征;体外降解试验分析交联前后神经导管的降解性能;应用织物手感评价仪检测神经导管的柔韧性;扫描电镜(SEM)观察神经导管交联前后空间结构及微球的分布;光学显微镜(LMS)和免疫荧光方法观察并评价壳聚糖微球/胶原蛋白神经导管与大鼠间充质干细胞(MSCs)共培养对MSCs向神经细胞定向分化的影响;SEM和细胞免疫荧光方法分别评价神经导管与MSCs的复合情况及对细胞定向分化的影响。结果显示:壳聚糖微球具有良好的缓释效果;交联前后神经导管的最大载荷和断裂载荷分别为(0.23±0.09)N、(0.76±0.15)N和(0.20±0.12)N、(0.69±0.17)N,两者相比具有统计学意义(P<0.05);体外降解实验表明,交联前后导管的平均失重率分别为(58.62±7.59)mg和(9.23±2.47)mg,两者相比具有统计学意义(P<0.01);干湿态神经导管的平均线性度分别为(0.597±0.012)LC和(0.333±0.015)LC,两者相比差异具有统计学意义(P<0.01),湿态神经导管的柔韧性较干态好;交联后神经导管中胶原蛋白排列紧密,微球均匀分布于胶原支架材料;神经导管与MSCs共培养后,微球缓释的川芎嗪能促进MSCs表达神经细胞相关标志分子NSE和MAP2;神经导管与MSCs复合培养,通过缓释的川芎嗪促进MSCs增殖和NSE的表达。构建的组织工程化神经导管具有良好的组织相容性和组织诱导性功能。     

Porous chitosan tubular scaffolds with knitted outer wall and controllable inner structure for nerve tissue engineering

In this study, a novel method was developed to create porous tubular scaffolds with desirable mechanical properties and controllable inner structure from chitosan, for nerve tissue engineering. Chitosan fiber-based yarns were first used to create porous hollow tubes, which served as the outer wall of the scaffolds, through an industrial knitting process. Then, an innovative molding technique was developed and used to produce inner matrices with multiple axially oriented macrochannels and radially interconnected micropores. Acupuncture needles were used as mandrels during molding to improve the safety and controllability of the process. In vitro characterization demonstrated that the scaffolds possessed suitable mechanical strength, porosity, swelling, and biodegradability for applications in nerve tissue engineering. In vitro cell culture experiments showed that differentiated Neuro-2a cells grew along the oriented macrochannels and the interconnected micropores were beneficial for nutrient diffusion and cell ingrowth to the scaffold's interior. Collectively, the well-defined architectural features in addition to the desirable mechanical and biological properties of the scaffolds make them promising for nerve tissue engineering.     

Preparation and characterization of keratin-chitosan composite film.

Keratin-chitosan composite film was prepared by casting the mixed solution of both biopolymers in 75% acetic acid. Although keratin film without any additive is very fragile, 10-30 wt% of chitosan addition gave strong and flexible film (ultimate strength: 27-34 MPa, ultimate elongation: 4-9%). Glycerol (20 wt%) also afforded flexibility to keratin film (ultimate strength: 1 MPa, ultimate elongation: 28%). Further addition of chitosan to glycerol-containing keratin film increased the ultimate strength to 9-14 MPa but gave little effect on ultimate elongation. These data suggest that mechanical properties of keratin film are adjustable by appropriately adding chitosan and glycerol. Waterproof characteristics such as swelling behavior and mechanical properties after swelling were much ameliorated for the composite film compared with keratin and chitosan films, respectively. Furthermore, keratin-chitosan composite film as well as chitosan film decreased bacteria number when the bacteria suspension was treated with a film owing to the irreversible adsorption of bacteria onto the film. The composite film as well as keratin and chitosan films supported fibroblast attachment and proliferation, demonstrating to be a good substrate for mammalian cell culture.     

In vivo mechanical properties of thoracic aortic aneurysmal wall estimated from in vitro biaxial tensile test

To investigate the mechanism of aneurysm rupture, it is necessary to examine the mechanical properties of aneurysm tissues in vivo. A new approach to evaluate in vivo mechanical properties of aortic aneurysmal tissues has been proposed in this study. The shape of the aneurysm was modeled as a sphere, and equi-biaxial stress in the in vivo state was estimated from the diameter and the wall thickness of each aneurysm and mean blood pressure of each patient. The mechanical properties of the aneurysm at the in vivo stress were estimated from its in vitro biaxial tensile properties. There were no significant correlations among maximum diameter D, wall thickness t, and mean infinitesimal strain in the in vivo state epsilon(m). This indicates the wall deformation during aneurysm development was not elastic but plastic. The mean incremental elastic modulus H(m), an index of tissue stiffness, had a significant positive correlation with elastic modulus anisotropy index K(H). This indicates the aneurysmal wall got more anisotropic in vivo as it becomes stiffer.     

壳聚糖的生物相容性*

背景：壳聚糖是惟一一种被广泛应用于生物医学工程领域的碱性、带有正电荷的天然多糖,其生物相容性是决定这些应用价值的关键。 目的：综述了壳聚糖的生物相容性,包括组织相容性、血液相容性和力学相容性。 方法：由第一作者检索1990/2011 PubMed数据库、中国知网数据库及万方数据库有关壳聚糖及其衍生物在生物医学上的应用和生物相容性等方面的文献。 结果与结论：壳聚糖作为可生物降解高分子材料具有良好的组织相容性及与人体组织相匹配所需要的力学相容性,被逐渐应用于人工皮肤、手术缝合线、眼科修复、人工骨骼、牙齿修复、肿瘤治疗等方面。但壳聚糖的促凝血作用使其血液相容性很差,目前很多研究关注于寻找解决这一问题的方法,改善其血液相容性,扩展其在生物医学工程上的应用领域,使其更加安全有效地与人体心血管系统直接接触。 关键词：壳聚糖;组织相容性;血液相容性;力学相容性;生物材料 doi:10.3969/j.issn.1673-8225.2012.12.034     

Effects of the degree of deacetylation on the physicochemical properties and Schwann cell affinity of chitosan films

Chitosan is a potential material for the preparation of nerve repair conduits. In order to find a better chitosan for the application in peripheral nerve regeneration, the effects of the degree of deacetylation (DD) on the physicochemical properties and Schwann cell affinity of chitosan films have been evaluated. Six kinds of chitosan samples with similar molecular weight, but various DD in a range from 70.1 to 95.6% were prepared from one stock chitosan material and fabricated into films. X-ray diffraction analysis showed that there were more crystalline regions in the higher DD chitosan films. Swelling and mechanical property measurements revealed that the swelling index of chitosan films decreased and their elastic modulus and tensile strength increased with the increase in DD. The adsorption amount of fibronectin and laminin on chitosan films was measured by means of enzyme-linked immunosorbent assay (ELISA). Culture of adult rat Schwann cells on the films showed that the chitosan films with higher DD provided better substrata for Schwann cell spreading and proliferation. In conclusion, DD of chitosan plays an important role in their physicochemical properties and affinity with Schwann cells. The results suggest that chitosan with a DD higher than 90% is considered as a promising material for application in peripheral nerve regeneration.