海藻酸纤维的研究发展及生物医学应用

背景：海藻酸纤维是一种多形式且多功能性物质,目前已被逐步应用于生物医学及临床.目的：全面评述海藻酸纤维的结构与功能,同时介绍海藻酸与壳聚糖、海藻酸与明胶共混纤维的特性及在医学上研究的应用情况.方法：由第一作者检索1990至2012年 PubMed 数据库及万方数据库有关海藻酸纤维制作过程、海藻酸纤维结构及性能、海藻酸纤维在生物医学的应用情况及其相关共混纤维的特性与应用等方面的文献.结果与结论：海藻酸盐已被广泛应用于农业化工、生物防治、组织工程、缓释药物系统、创伤修复、净化环境等方面.通过共混改性得到的各种新型混合纤维,不但改善了海藻酸纤维应用上的不足,同时也赋予其更多的性能,成为了当今和未来生物材料的研究热点.目前生物医学材料正向着环保、高功能、智能化等方向发展,自然界储存量丰富、成本价格低廉、具有良好生物相容性及降解性的海藻纤维、壳聚糖纤维和明胶纤维及以它们为基质通过共混和/或改性等方法制造出来的功能性纤维潜力巨大,在生物医学及仿生医学领域有待进一步开发.     

两种聚（左旋乳酸-己内酯）静电纺纳米纤维膜的性能比较

背景:聚左旋乳酸和聚己内酯各自都有其优点与缺点,而共聚或共混后性能可以得到有效的改善,但因为两者添加比例的不同会对性能有一定的影响,在不吲的纺丝溶液浓度下纺出的纤维性能亦会有所差异.目的:通过对两种原料聚(左旋乳酸-己内酯)(75/25;50/50)在不同纺丝液浓度下制得的纳米纤维膜各种性能的比较,选出最佳的原料和相应的纺丝液浓度.设计、时间及地点:对比观察实验,于2007-09/2008-11在东华大学生物材料与组织工程实验室完成.材料:将聚聚(左旋乳酸-己内酯)材料在乳酸/己内酯为75/25和50/50两种比例下,在质量分数为4%,6%,8%和10%纺丝液浓度下通过静电纺丝制备纳米纤维膜.方法:扫描电镜样品经表面喷金后在10 kV加速电压下观察纤维膜的彤貌.在万能材料测试机测试其断裂强度和断裂伸长率.采用MTT法测试猪髋动脉内皮细胞在纳米纤维膜上的黏附与增殖情况.主要观察指标:静电纺纳米纤维膜的纤维形态、力学性能及生物相容性.结果:通过扫描电镜观察发现由质量分数为6%聚(左旋乳酸-己内酯)(50/50)制备的纤维膜具有更好的纤维形态,且直径分布均匀;拉伸力学测试显示由聚(左旋乳酸-己内酯)(50/50)制备的纤维膜比聚(左旋乳酸-己内酯)(75/25)具有更高的断裂伸长率,但断裂应力较低;细胞生物相容性实验表明猪髋动脉内皮细胞在质鼍分数为6%和8%聚(左旋乳酸-己内酯)(50/50)的纳米纤维膜上更能有效的黏附与增殖.结论:纺丝液质量分数为6%的聚(左旋乳酸-己内酯)(50/50)制得的纳米纤维膜各项性能较优.     

电纺丝技术制备组织工程食管仿生支架

背景：前期实验中曾发现纤维的取向可以引导平滑肌细胞的取向生长,因此,设想通过制备取向排列的电纺丝纤维支架,以引导食管平滑肌细胞的有序生长,从而有利于维持肌细胞的形貌及生物功能。目的：以可降解聚己内酯、明胶、丝素蛋白为基材,采用自制的电纺丝系统制备无规和有序的纳米级多孔纤维。方法：将聚己内酯与丝素蛋白以4：1质量比混合,通过调整溶液浓度、电压、喷射速度等参数,采用自制的电纺丝系统制备聚己内酯,丝素蛋白电纺丝纤维。将聚己内酯与明胶分别以2：1、1：1、1：2质量比混合,在金属平板接收器下,通过调整溶液浓度、电压、喷射速度等参数,采用自制的电纺丝系统制备聚己内酯,明胶无规电纺丝纤维;同时改用滚轴接收装置,通过调整滚轴转数、电压、喷射速度等参数,制备聚己内酯/明胶有序电纺丝纤维。结果与结论：在溶液质量浓度为0．08g／mL、纺丝液流速1．6mL／h和电压22．5kV的条件下,制得了均匀、无串珠、纤维直径为（535．9±126．7）nm的聚己内酯,丝素蛋白多孔纳米纤维膜。在溶液质量浓度为O．10g／mL、纺丝液流速0．8mUh和电压22．5kV的条件下,制得了无明显串珠、纤维直径为（257．9±117．8）nm的聚己内酯,明胶多孔纳米纤维膜;并且在1：2质量比时更易成纤维,纤维尺寸更均匀。在滚轴转速3000r/min。溶液流速O．8mUh。电压15kV的条件下,制得的聚己内酯,明胶有序电纺丝纤维排序更理想,纤维也更均匀。於学婵．     

聚酯酰胺静电纺纳米纤维膜的制备及其生物相容性

采用静电纺技术制备聚酯酰胺纳米纤维膜,用扫描电镜观察纳米纤维的表面形貌,发现随着纺丝液质量浓度的增加,纤维的直径由10%时的180 nm递增到20%时的350 nm;用红外光谱表征聚酯酰胺的化学结构,结果表明化学结构在纺丝前后没有发生明显变化;X射线衍射法测试表明聚酯酰胺在经过溶剂处理和纺丝后,结晶度下降;差示扫描量热法表征了热力学特性,发现聚酯酰胺经过溶剂处理和纺丝后,结晶度下降;力学性能测试表明平均厚度为(0.50±0.05)mm的聚酯酰胺纳米纤维膜的平均断裂强度和平均断裂伸长率分别达到(1.00±0.18)MPa和(18.20±2.86)%;MTT结果表明内皮细胞在聚酯酰胺纳米纤维膜上增殖活跃,内皮细胞在纤维表面黏附并显示出良好的生长形态.     

再生丝素纤维的力学性能及其生物可降解特征

背景:再生丝素纤维溶解过程中丝素蛋白的分子量不可避免地会产生一定的降解,致使再生丝素纤维至今未进入实用阶段。目的:获得生物可降解的再生丝素纤维。设计:单一样本实验。单位:苏州大学材料工程学院丝绸工程江苏省重点实验室。材料:下脚蚕丝由苏州丝绸进出口公司提供。方法:2003-01/2004-12在苏州大学材料工程学院丝绸工程江苏省重点实验室完成。通过控制废弃天然丝素纤维在中性盐溶解时分子量的变化、湿法纺丝工艺条件和牵伸倍率方法纺制具有一定力学性能和生物可降解的再生丝素纤维。具体步骤:①制备丝素。②制备纺丝液。③再生丝素纤维湿法纺丝。④采用十二烷基硫酸钠-聚丙稀酰胺凝胶电泳法测定溴化锂溶解后丝素溶液的分子量。⑤测定丝素纤维的结晶度和取向度。⑥测定再生丝素纤维的力学性能。⑦测定丝素纤维的体外酶降解率。主要观察指标:①经溴化锂溶解的丝素蛋白的相对分子质量。②X射线衍射结果。③再生丝素纤维的体外酶降解率。结果:①经溴化锂溶解后,丝素蛋白纺丝液的分子量主要分布在10万以下。②在再生丝素纤维湿法纺丝的凝固、牵伸过程中,丝素的构象从无规卷曲转变为分子链中β-折叠和无规卷曲/α-螺旋构象共存。③用放线菌酶对六氟异丙醇法纺制的再生丝素纤维的体外酶降解实验表明,再生丝素纤维其30d的降解率为37.16%,天然丝素纤维的30d的降解率为10.70%。结论:通过控制再生丝素纺丝液分子量、湿法纺丝工艺条件和牵伸倍率方法,可纺制具有一定力学性能和生物可降解的再生丝素纤维。     

用于医疗护理的形状可调节舒适性纤维的制备及性能研究

本研究采用具有形状记忆的 SMPU M5560和普通 PAN 两种切片原料,按照不同比例配制一系列纺丝液,采用湿法纺丝方法,制备出兼具形状记忆与一定强度的智能纤维。混合后的纤维强度比纯 SMPU 纤维的强度明显增加,利用 TG 和 DSC 对纤维进行测试,得到的纤维能够保持一定的耐热性及形状记忆功能。这种混合纤维在医疗服装的开发上具有一定的应用价值。     

再生丝素纤维的力学性能及其生物可降解特征

背景：再生丝素纤维溶解过程中丝素蛋白的分子量不可避免地会产生一定的降解，致使再生丝素纤维至今未进入实用阶段。目的：获得生物可降解的再生丝素纤维。设计：单一样本实验。单位：苏州大学材料工程学院丝绸工程江苏省重点实验室。材料：下脚蚕丝由苏州丝绸进出口公司提供。方法：2003-01／2004-12在苏州大学材料工程学院丝绸工程江苏省重点实验室完成。通过控制废弃天然丝素纤维在中性盐溶解时分子量的变化、湿法纺丝工艺条件和牵伸倍率方法纺制具有一定力学性能和生物可降解的再生丝素纤维。具体步骤：①制备丝素。②制备纺丝液。③再生丝素纤维湿法纺丝。④采用十二烷基硫酸钠-聚丙稀酰胺凝胶电泳法测定溴化锂溶解后丝素溶液的分子量。⑤测定丝素纤维的结晶度和取向度。⑥测定再生丝素纤维的力学性能。⑦测定丝素纤维的体外酶降解率。主要观察指标：①经溴化锂溶解的丝素蛋白的相对分子质量：②X射线衍射结果。③再生丝素纤维的体外酶降解率。结果：①经溴化锂溶解后，丝素蛋白纺丝液的分子量主要分布在10万以下：②在再生丝素纤维湿法纺丝的凝固、牵伸过程中，丝素的构象从无规卷曲转变为分子链中β-折叠和无规卷曲α-螺旋构象共存。③用放线菌酶对六氟异丙醇法纺制的再生丝素纤维的体外酶降解实验表明，再生丝素纤维其30d的降解率为37．16％，天然丝素纤维的30d的降解率为10.70％。结论：通过控制再生丝素纺丝液分子量、湿法纺丝工艺条件和牵伸倍率方法，可纺制具有一定力学性能和生物可降解的再生丝素纤维。     

海藻酸盐基生物医用材料

目的:海藻酸盐基生物医用材料是一种多形式且多功能性物质,为推动该物质的广泛且有效地临床应用,以综述的方式全面评述其结构与功能、制备与应用。资料来源:采用计算机检索Medline 2004-01/2006-12关于海藻酸盐的文章。检索词“alginate,microcapsule”并限定文章的语言种类为English。同时利用计算机检索中国期刊全文数据库2000-01/2006-12的相关文章,检索词为“海藻酸,微囊”,限定文章语言种类为中文。资料选择:对资料进行初审核,纳入标准:①关于海藻酸盐基生物医用材料的结构和功能。②对其生物相容性的研究等。排除标准:重复性研究。资料提炼:共收集到符合上述要求的文献76篇,排除重复性研究21篇。55篇符合纳入标准:其中25篇关于海藻酸基生物医用材料的结构和功能,30篇关于生物相容性研究。资料综合:从海藻酸盐基生物医用材料的结构与功能、产品标准、微囊、栓塞剂及其生物相容性等5个方面综合述评。①海藻酸不同的组成成分及其不同的结构和构象表现出凝胶化性能、金属离子螯合性能、生物学性能。②海藻酸微囊的制备目前常用的是与人工合成的阳离子聚合物--聚赖氨酸藉单凝聚法或/和复凝聚法。近年来尝试采用壳聚糖代替或修饰制备海藻酸微囊,其制备方法温和、简单、成囊速度快,其微囊球性度和光洁度好,药物稳定性好且利用度高。现已将海藻酸盐微囊化应用于细胞、疫苗、蛋白质及药物中。③海藻酸盐栓塞剂由于其生物相容性好,靶向栓塞定位好,栓塞球大小易控而且质量稳定等优点,现已应用于原发性肝癌和子宫肿瘤的治疗中。④海藻酸囊化材料不仅要与囊化供体组织细胞相容,而且还与宿主环境中的组织及免疫系统相容。结论:海藻酸盐独特的性能赋予其能安全地用于人体,而且在用于药物缓释和再生医学方面还有很大的发展空间。     

利用DMF溶解顺铂制备的DDP/PLA膜对口腔癌CAL-27细胞增殖抑制作用研究

目的以N,N-二甲基甲酰胺(DMF)为顺铂的溶剂,利用静电纺丝法制备载顺铂(DDP)聚乳酸(PLA)纳米纤维膜,并与H2O/CHCl3作为溶剂制备的DDP/PLA膜相比较,探讨其对口腔癌CAL-27细胞增殖抑制作用。方法将不同浓度DDP、PLA分别溶于DMF、CHCl3中配置混合溶液,利用静电纺丝技术将其制备成不同质量分数的聚乳酸静电纺丝膜(PLA膜)和不同载药量的载顺铂聚乳酸静电纺丝膜(DDP/PLA膜);通过扫描电镜(SEM)观察表观形态;紫外分光光度分析法测定PLA膜的降解速率;MTT比色法进行生物相容性测试;体外实验观察不同载药量DDP/PLA膜对CAL-27细胞的作用。结果 SEM显示静电纺丝纳米纤维微观形貌变化表现随着PLA浓度由5%增加到9%纤维趋向均匀平滑,纳米纤维平均直径由(182±66)nm增加到(1624±370)nm,载DDP后纤维直径平均维持在(2187±568)nm;体外释放测试显示24h时累计释放量在35%左右,后期释放平缓,持续释放到18天左右;PLA膜具有很好的生物相容性;随着载药量增加DDP/PLA膜对CAL-27细胞增殖抑制作用增强,具有浓度依赖性;DDP投入量相同的情况下,使用DMF的DDP/PLA膜对CAL-27细胞增殖抑制作用更强。结论利用DMF溶解DDP可显著提高DDP/PLA膜的载药量,增强对CAL-27细胞增殖抑制作用,具有更高的药物利用率和包封效果,使得等量的药物发挥更强的作用。     

新型海藻酸盐水凝胶真皮支架材料的制备及其表征

背景:海藻酸钠水凝胶具有与真皮基质成分蛋白多糖类似的结构,是较为理想的成纤维细胞培养材料,但以往制备海藻酸钠水凝胶大部分都是以CaCl2为交联剂,这一体系存在严重不足。目的:利用碳化二亚胺作为催化剂、乙二胺作为交联剂制备新型海藻酸盐水凝胶支架材料,并对其性能进行表征,探讨其作为组织工程支架材料的可行性。设计、时间及地点:形态学描述及自身对照实验,于2005-10/2006-10在中山大学附属第一医院骨科实验室完成。材料:自制乙二胺溶液,碳化二亚胺和海藻酸钠购自Sigma公司。方法:利用碳化二亚胺作为催化剂、乙二胺作为交联剂,采用共价交联及冻干法制备新型海藻酸盐水凝胶支架,对照为用传统交联剂CaCl2制备的样品。主要观察指标:观察海藻酸钠的理想反应浓度;用扫描电镜观察藻酸盐组织工程支架的微观结构,排液法测定其孔隙率及含水量;并观察其体外降解规律。结果:成功制备了海藻酸盐水凝胶真皮支架,该支架材料的海藻酸钠理想反应浓度为2%,其含水量为(95.32±1.24)%,孔隙率为(85.55±0.98)%,均高于对照材料;2周后海藻酸盐水凝胶的体外降解率为(12.26±2.25)%。结论:新型海藻酸盐组织工程真皮支架克服了传统以钙离子作为交联剂的诸多缺点,其吸水性、孔隙率、降解性能满足真皮支架材料的物理性能所需,能够做为成纤维细胞的三维培养系统。     

海藻纤维膜片促进大鼠损伤坐骨神经的再生

背景：课题组和青岛大学高分子材料研究所合作研制的海藻纤维生物膜,具有优良的生物相容性,常被用作制备各种复合材料。目的：观察海藻纤维膜片包绕覆盖神经断端吻合口对大鼠坐骨神经损伤后再生的影响。方法：切断36只雄性Wistar大鼠右侧坐骨神经,随机分组：对照组行神经外膜端端吻合;实验组行神经外膜端端缝合,将海藻纤维膜片包绕并覆盖神经吻合口远近端各约0.5 cm,形成封闭再生室。术后观察海藻纤维膜片降解吸收规律及缝合处粘连情况,组织学切片行苏木精-伊红染色、锇酸染色、白细胞介素2及白细胞介素4免疫组织化学染色。结果与结论：术后4-6周,实验组海藻纤维膜片逐渐被降解吸收,与周围组织粘连较少,炎性细胞浸润程度较轻,纤维组织增生较少。两组术后1,7,14 d的白细胞介素2及白细胞介素4含量比较差异无显著性意义。实验组术后6周再生神经纤维分布规则且大小较为均一,其神经纤维数量、轴突大小及髓鞘厚度等指标均显著优于对照组（P 〈0.05）。表明海藻纤维膜片具有良好的生物降解性和组织相容性,其包绕覆盖坐骨神经形成的神经再生密闭室可促进大鼠损伤坐骨神经再生。     

藻酸盐对家兔肺组织的免疫损伤作用

目的：建立藻酸盐免疫性肺炎动物模型，研究藻酸盐对肺组织的致病作用；以探讨细菌生物被膜对呼吸系统的致病机制。方法：本实验用乙醇沉淀法提取细菌藻酸盐；A组用生理盐水作对照，B组、C组分别用海藻藻酸盐、细菌藻酸盐免疫家兔。比较三组家兔的体温、血象及血循环免疫复合物(CIC)水平；比较支气管肺泡灌洗液(BALF)细菌计数；观察肺组织的病理改变。结果：两种藻酸盐免疫组家兔的血CIC水平皆较处理前及生理盐水对照组显著增高，BALF培养无细菌生长。经两种藻酸盐免疫后皆出现细支气管旁淋巴细胞浸润、淋巴小结形成及细支气管管腔狭窄等病理改变。结论：海藻藻酸盐和细菌藻酸盐都能导致家兔肺组织非感染性免疫损伤，其主要病理改变为细支气管旁淋巴细胞浸润及淋巴小结形成；这种免疫损伤是呼吸道生物被膜病的致病机制之一。     

Improvement of islet function and survival by integration of perfluorodecalin into microcapsules in vivo and in vitro

Hypoxic injury of islets is a major obstacle for encapsulated islet transplantation into the peritoneal cavity. To improve oxygen delivery to encapsulated islets, we integrated 20% of the oxygen carrier material, perfluorodecalin (PFD), in alginate capsules mixed with islets (PFD‐alginate). Integration of PFD clearly improved islet viability and decreased reactive oxygen species production compared to islets encapsulated with alginate only (alginate) and naked islets exposed to hypoxia in vitro. In PFD‐alginate capsules, HIF‐1α expression was minimal, and insulin expression was well maintained. Furthermore, the best islet function represented by glucose‐stimulated insulin secretion was observed for the PFD‐alginate capsules in hypoxic condition. For the in vivo study, the same number of naked islets and encapsulated islets (alginate and PFD‐alginate) was transplanted into streptozotocin‐induced diabetic mice. Nonfasting blood glucose levels and the area under the curve for glucose based on intraperitoneal glucose tolerance tests in the PFD‐alginate group were lower than in the alginate group. The harvested islets stained positive for insulin in all groups, but the ratio of dead cell area was 4 times higher in the alginate group than in the PFD‐alginate group. In conclusion, integration of PFD in alginate microcapsules improved islet function and survival by minimizing the hypoxic damage of islets after intraperitoneal transplantation.     

Preparation and characterization of an electrospun colon-specific delivery system for salmon calcitonin

A novel electrospun colon-specific delivery system for salmon calcitonin (SCT) was developed to improve its stability and bioavailability. Firstly, the pectin-coated SCT liposomes were prepared by film dispersion method and then a liposomes/sodium alginate/polyvinyl alcohol fiber mat was fabricated by electrospining. Scanning electron microscopy analysis indicated that the obtained nanofibers were uniform and smooth with an average diameter of about 350 nm. The release of SCT in different simulated digestive fluids was studied and corresponding release kinetics models were built. It was found that the fiber mat containing pectin-coated SCT liposomes had better stability and colon-specific properties compared with that containing uncoated SCT liposomes and the release of SCT in the colon followed the case II transport mechanism. In addition, there is no significant change in the bioactivity of released SCT measured by ELISA. This study shows that the electrospun colon-specific fiber mat is a potential delivery system for bioactive peptides.

The electrospun colon-specific fiber mat is a promising delivery system for SCT.     

Antifibrotic effect of rapamycin containing polyethylene glycol‐coated alginate microcapsule in islet xenotransplantation

Islet microencapsulation is an attractive strategy for the minimization or avoidance of life‐long immunosuppression after transplantation. However, the clinical implementation of this technique is currently limited by incomplete biocompatibility. Thus, the aim of the present study was to demonstrate the improved biocompatibility of rapamycin‐containing polyethylene glycol (Rapa–PEG)‐coating on alginate microcapsules containing xenogeneic islets. The Rapa–PEG‐coating on the alginate layer was observed using scanning electron microscopy (SEM) and the molecular cut‐off weight of the microcapsules was approximately 70 kDa. The viabilities of the alginate‐encapsulated and Rapa–PEG‐coated alginate‐encapsulated islets were lower than the viability of the naked islets just after encapsulation, but these the differences diminished over time in culture dishes. Rapa–PEG‐coating on the alginate capsules effectively decreased the proliferation of macrophage cells compared to the non‐coating and alginate coating of xenogeneic pancreas tissues. Glucose‐stimulated insulin secretion did not significantly differ among the groups prior to transplantation. The random blood glucose levels of diabetic mice significantly improved following the transplantation of alginate‐encapsulated and Rapa–PEG‐coated alginate‐encapsulated islets, but there were no significant differences between these two groups. However, there was a significant decrease in the number of microcapsules with fibrotic cell infiltration in the Rapa–PEG‐coated alginate microcapsule group compared to the alginate microcapsule group. In conclusion, Rapa–PEG‐coating might be an effective technique with which to improve the biocompatibility of microcapsules containing xenogeneic islets. Copyright © 2015 John Wiley & Sons, Ltd.     

氧化海藻酸钠应用于体外循环管路

背景：目前体外循环肝素涂层管路应用较广,但是价格昂贵,限制了其广泛应用。目的：将多醛基海藻酸钠涂层到医用聚氯乙烯体外循环管路,筛选出最佳涂层条件和所制备管路的稳定性及抗凝性能。方法：利用高碘酸钠氧化海藻酸钠,制备高碘酸钠和海藻酸钠摩尔比分别为1∶8、1∶10和1∶12的多醛基氧化海藻酸钠,采用化学结合的方法将不同氧化度海藻酸钠固定到医用聚氯乙烯体外循环管路表面,筛选出最佳氧化度。以硫酸浓度、聚乙烯亚胺浓度、氧化海藻酸钠浓度、氧化海藻酸钠pH值和温度为因素,采用正交实验筛选最佳涂层条件,评价所制备管路氧化海藻酸钠固定的稳定性及抗凝血性能,并与空白对照组和肝素涂层组进行比较和分析。结果与结论：氧化海藻酸钠最佳氧化度为高碘酸钠和海藻酸钠摩尔比为1∶10。筛选出的最佳涂层条件为50%浓硫酸、0.05%聚乙烯亚胺、反应溶液pH值为3.5、反应温度为40℃和氧化海藻酸钠质量浓度为2g/L。氧化海藻酸钠涂层管路组脱落率与肝素涂层组有相似的结果,抗凝血性能稍劣于肝素涂层组（P〈0.05）,但显著优于空白对照组。表明氧化海藻酸钠涂层体外循环管路具有良好的抗凝血性能和较好的稳定性。     

海藻酸盐与异种骨构建组织工程载体的适宜浓度

背景:研究认为,载体的结构在很大程度上影响着载体的功能。目的:探讨不同浓度的海藻酸盐凝胶与去抗原异种骨构建组织工程载体的生物学性能。设计:观察性实验。单位:解放军第四军医大学西京医院全军创伤骨科研究所。材料:海藻酸盐,氯化钙,骨髓基质细胞,异种骨。方法:取小牛松质骨,制成骨粒,脱脂、脱蛋白,真空冻干;选择孔隙直径在300～500μm左右的骨粒,环氧乙烷消毒。将提纯后的海藻酸钠以DMEM培养液为溶剂,配制成0.5%,2%,8%和16%的海藻酸钠DMEM溶液;将诱导后的骨髓基质细胞以1×1012L-1浓度等体积与海藻酸钠DMEM溶液充分混合,在0.5MPa的负压状态下复合,使细胞悬液充分占据松质骨的空隙,以50g/L的葡萄酸钙浸渍30s,以使海藻酸钠获得交联。置于CO2培养箱中,培养4d。观察异种骨孔隙中凝胶复合情况及其中细胞生长情况。观察不同藻酸密度复合松质骨粒中细胞生长情况。主要观察指标:观察海藻酸盐凝胶与去抗原异种骨复合情况,复合后的载体中细胞生长状态和基质分泌情况。结果:海藻酸盐的浓度为0.25%,1%时,凝胶在异种骨中均匀复合,浓度为4%和8%时藻酸仅复合在松质骨表面。体外培养4d后,0.25%海藻酸盐复合异种骨的表面大部分凝胶脱落,1%的海藻酸盐均匀复合在异种骨的骨孔中,细胞形态饱满,基质分泌;4%的海藻酸盐中,细胞生长受到限制;8%的凝胶的质地不均匀,无法见到细胞结构。结论:1%的海藻酸盐适宜与异种骨复合构建骨组织工程载体。     

Bioadhesive interaction and hypoglycemic effect of insulin-loaded lectin-microparticle conjugates in oral insulin delivery system.

Biodegradable microparticles were prepared with alginate by the piezoelectric ejection process, and lectin (wheat germ agglutinin, WGA) was conjugated to alginate microparticles to take advantage of the protective effects of alginate microparticles and the mucoadhesive properties of WGA for improved oral delivery of insulin. Their specific interaction with model mucin was determined by pig mucin (PM) immobilized surface plasmon resonance (SPR) biosensor and in vitro adsorption studies. The hypoglycemic effects of alginate and WGA-conjugated alginate microparticles were examined after oral administration in streptozotocin-induced diabetic rats. The alginate microparticles were fabricated by ejecting alginate/insulin solution into 0.1 M CaCl2 solution through a nozzle actuated by the piezoelectric transducer. The WGA was conjugated to alginate microparticles by activating hydroxyl groups with carbonyldiimidazole (CDI). The affinity constant (K(A)) of alginate-WGA microparticles from the SPR data (K(A)=5.455 g(-1) L) was about nine times greater than alginate microparticles (K(A)=0.628 g(-1) L). In vitro experiments in the mucin solution showed that the conjugated WGA enhanced the interaction about three times. In vivo studies with diabetic rats showed that the blood glucose level of SPF rats was lowest when alginate-WGA microparticles were orally administered. Larger K(A) of alginate-WGA microparticles resulted in larger glucose change (%) from base level. Still, it is not clear whether the transport of insulin through the intestinal mucous membrane was influenced by the increase of residence time at intestinal membrane through the specific adsorption of WGA-conjugated microparticles. However, it is concluded that alginate-WGA microparticles enhance the intestinal absorption of insulin sufficient to drop the glucose level of blood.     

Permeability characteristics of calcium alginate films

The permeability of acetaminophen in hydrated calcium alginate films was measured in side-byside glass diffusion cells. The films were prepared by ionically crosslinking dry sodium alginate films by immersion in aqueous solutions of calcium acetate (0.1 to 1.0 M) for 1 to 15 minutes. Permeability of acetaminophen in hydrated calcium alginate films varied approximately 14.6-fold, depending upon calcium acetate concentration and immersion duration used in the cross-linking process. Permeability of acetaminophen in calcium alginate films prepared by immersion of dry sodium alginate in aqueous solutions of calcium acetate for 3 to 8 minutes reached a limiting value at all calcium acetate concentrations. However, the magnitude of the limiting value was dependent upon the concentration of calcium acetate used in the crosslinking procedure. The highest limiting permeability was observed in films prepared using the lowest concentration of calcium acetate, whereas the lowest limiting permeability was observed in films prepared using the highest concentration of calcium acetate. When calcium alginate films were prepared by immersion in calcium acetate solutions of greater concentration than 0.5 M and immersion times less than 10 minutes, permeability coefficients were higher for the higher calcium acetate concentrations. Only when immersion times were greater than 10 minutes did permeability decrease as calcium acetate concentration increased. It is suggested that this is a result of the rapid crosslinking of sodium alginate at the surface, which in turn slows the diffusion of calcium ions into the film. Because of the relatively short immersion time, a high degree of crosslinking is not attained and this results in a calcium alginate film that is more permeable.