聚乳酸在生物医药领域的改性研究进展

聚乳酸类材料是一种用途广泛的生物降解高分子材料,已经成为生物医用材料中最受重视的材料之一。但由于聚乳酸本身的缺陷,限制了其在生物医学工程中的应用。对聚乳酸的改性工作就一直备受关注。本文综述了近几年聚乳酸生物降解材料的物理改性和化学改性研究进展,经改性后聚乳酸的力学性能、降解性能、亲水性能和生物活性得到有效改善,从而更好地满足了生物医用需要。     

生物可降解材料聚乳酸结晶行为研究进展

聚乳酸是一种具有良好生物相容性、可生物降解的热塑性脂肪族聚脂,是一种环境友好材料。聚乳酸的结晶性能对其力学性能和降解速率有着重要的影响,因而其结晶行为也逐渐成为人们研究的热点。本文针对聚乳酸的结晶行为综述了聚乳酸及其共混、共聚体系的最新研究进展。     

增容剂对聚对二氧环己酮/聚乳酸复合材料体外降解的影响

以聚对二氧环己酮与聚乳酸的无规共聚物作为增容剂,在聚对二氧环己酮/聚乳酸复合物中添加不同比例的增溶剂后,在37℃的缓冲溶液(pH 7.44)中,进行为期八周的体外降解实验,定期观察其吸水率与质量损失,pH值以及机械性能的改化,结果发现增容剂的添加,加快了聚对二氧环己酮/聚乳酸复合物的降解速度。     

生物降解材料聚乳酸合成史略

1　聚乳酸研究的兴起世界塑料产量已经超过 1亿吨 ,其广泛应用使废弃物迅速增加 ,估计世界年废塑料量可达 2 0 0 0万吨 ,已引起严重的环境污染问题。减少废塑料污染的重要方法之一是使用在自然界无论生物体内外都可以自然降解、不会造成环境污染的生物降解材料[1] 。图 1　聚乳酸合成、降解循环示意图Fig .1　ThecirculationsketchofPLA’ssynthesesanddegradation在生物降解材料中 ,聚乳酸 (PLA)具有其特殊性 ,这不仅是因为聚乳酸具有很好的生物降解性能 ,具有良好的生物相容性和生物可吸收性 ,而且是因为聚乳酸是一种生物原料制品。乳…     

生物医用PLA改性研究进展北大核心CSCD

聚乳酸(polylactic acid)材料是一种用途广泛的可生物降解高分子材料,已经成为生物医用材料中最受重视的材料之一。但是聚乳酸也存在许多缺陷,限制了其在医药领域的广泛应用。本文综述了聚乳酸疏水性强、细胞亲和性差、力学性能不足,降解产物造成局部酸性积累而导致机体发生无菌性炎症反应,缺乏修复、降解、吸收速度与细胞的增殖、组织修复速度匹配的系列产品,成本高,均聚物成孔性能差等缺陷,总结了近些年国内外针对以上各个缺陷做出的改进方案,并对聚乳酸医用改性的研究发展方向进行了展望。     

聚乳酸眼科植入材料的制备及其降解性能

聚乳酸眼科植入材料的制备及其降解性能卓仁禧＊尹超吴颖楠祝磊曾水清（武汉大学化学系武汉４３００７２）（同济医科大学附属协和医院武汉）关键词聚乳酸，制备，生物可降解性，眼科植入材料１９９６－０８－１８收稿，１９９７－０１－１７修回国家自然科学基金资助项目...     

聚乳酸接枝葡聚糖共聚物的合成及其体外降解行为的研究

研究了聚乳酸接枝葡聚糖梳型共聚物的合成 ,以及共聚物的结构特征、亲水性能及降解行为的表征 .结果表明由于亲水性葡萄糖单元组分的引入以及共聚物的梳型结构特征 ,聚乳酸接枝葡聚糖共聚物的亲水性明显优于相应的线型聚乳酸 ,而且降解速度也明显加快 .由于这类梳型结构的聚多糖 聚酯共聚物综合了聚多糖细胞亲和性好和聚酯生物降解速率可调节性的特点 ,因此有望成为一类优良的细胞支架材料 .     

植物纤维增强聚乳酸可降解复合材料的研究

聚乳酸因具有优良的生物相容性、易降解、强度高,可塑性强,易加工成型等优点,近年来倍受高分子材料行业的青睐。但是由于存在脆性高、热性能较差、降解速度不易控制等缺陷,限制了使用效果,因此需进行改性研究。植物纤维质轻、价廉、比强度高并可降解,近年来作为增强材料发展迅速,用来增强聚乳酸,不但可以提高材料的性能,而且赋予复合材料...     

可生物降解的聚乳酸弹性体的性能研究

对制备的聚乳酸（聚醚）酯型聚氨酯弹性体进行了动态力学、力学性能和降解性能的测试．结果表明，弹性体的强度和弹性都较好，它们受交联度、ＰＥＧ含量和ＰＥＧ分子量的影响．该弹性体的降解速度较快．降解过程中存在自催化效应，而且是从表面开始由表及里逐渐降解的．但材料降解过程中也会出现内部降解较快的现象．动物实验表明，该弹性体是一种能满足尿道支撑管要求的有实际应用价值的材料．     

聚乳酸-木粉-甲基丙烯酸缩水甘油酯接枝乙烯辛烯共聚物复合材料的制备及性能

选用甲基丙烯酸缩水甘油酯接枝乙烯辛烯共聚物(POE-GMA)和聚乳酸、木粉在Haake转矩流变仪中熔融共混.通过拉伸、冲击、差示扫描量热、扫描电镜等测试方法对共混复合材料的性能进行了研究.结果表明:聚乳酸木塑复合材料的拉伸强度和弯曲性能随POE-GMA添加量的增加而减小；POE-GMA的加入使聚乳酸木塑复合材料的结晶温度下降,结晶度升高；当m(PLA)∶m(WF)∶m(POE-GMA)=80∶20∶20时,复合材料的表面自由能最低,接触角最大,吸水性最低；随着木粉含量的增加,复合材料的起始热降解温度降低,POE-GMA的含量增加对聚乳酸木塑复合材料的起始热降解温度影响不大.     

一种提高色谱指纹谱保留时间重现性的新方法

通过色谱热力学分析发现，在相同的分析条件下，即使采用不同的液相色谱系统或不同的色谱柱，组分的保留时间存在简单的线性关系，应用该线性关系可提高不同反相C18柱间保留时间重现性，经过实际样品在不同操作条件下的验证，表明该方法是正确而可行的。     

部分水解聚丙烯酰胺浓度对结构形貌的影响

本文用原子力显微镜(AFM)研究了不同浓度的部分水解聚丙烯酰胺(HPAM)溶液在云母片上成膜后的结构形貌。浓度不同,AFM下观察到的结构形貌差别很大。50ppm和1000ppm的HPAM在云母片上成膜后不能形成规则的排列,而100ppm的HPAM在云母片上成膜后形成规则的排列,但不同位置处的排列不同,500ppm的HPAM在云母片上成膜后可形成树枝生长的分形结构。     

Investigation on the relationship of proline with wheat anti-drought under soil water deficits

Proline (content) is closely with plant anti-drought, especially under soil water deficits. Many reports from crops and other plants have proved this. Wheat is the second important crop on the globe, whose research in this aspect of importance for food quality, safety, and yield in field. The related difference in physiological indicators and proline content for different soil water treatments among wheat with different genotypes is not clear, which has limited deep study of wheat anti-drought molecular biology and related anti-drought biotechnological breeding. Our current study was focused on the physiological relationship of proline and different genotype wheat anti-drought under soil water deficits. Main results showed that different wheat genotype had different soil water stress threshold. Pro content had closed relationship with soil water stress threshold and wheat anti-drought. Developmental course also impacted Pro content for different wheat genotypes.     

Sequence Hiberarchy Evolution Measurement Method and its Application

A novel method based on discrete wavelet transform （DWT） and cross-covariance for revealing the evolution of species at different spatial resolutions is presented. The trypsin proteins of different species are chosen as an example to describe the evolution relationship according to the evolution vectors by using this method. The results indicated that this method is a promising approach to reveal species evolution at different spatial resolutions.     

Self-organization in the flow of complex fluids (colloid and polymer systems). Part 2: Theoretical models

Flow induced transitions in complex fluids are usually accompanied by changes in the internal media structure and the flow symmetry. In this review paper, we discuss the theoretical models and approaches that have been used for the analysis of different types of flow instabilities and flow patterns. The main attention is focused on the basic fluid models which reveal vortex and banding flow structures at high shear rates. The Oldroyd-B fluid is one of such models. The Reynolds and the Weissenberg (or Deborah) numbers are the parameters governing its flow behavior. For this model, the secondary flow patterns arising in viscometric flows of different geometries at the bifurcation point are described. Complex fluids which are able to exist in multiple states can form coexisting bands of different structures with different rheological properties and flowing with different shear rates at the same shear stress. Shear banding is typical for fluids demonstrating non-monotonous flow curves described by such models as the diffusive Johnson-Segalman fluid model, for example. Recent progress in exploring this phenomenon is discussed.     

Janus‐Partikel

Anisotropic particles are a materials class, which allows to induce multifunctional properties in a particular solid. This approach presents the possibility that different functions are packed in one particle, for example different surface polarities or optical and magnetic properties. The extraordinary structure of this particle consisting of two different compartments is expressed by the name Janus‐Particles. The chemical challenge is the synthetic approach to such particle structures. The reaction rooms on the length scale of the particle have to be differentiated in such a way that an anisotropy of growth and functionalization processes is generated. In this regard reactions at interphases play a major role. Meanwhile many different Janus‐material combinations are established and the first systems are transferred to technological processes.     

介电弹性体致动器的结构设计及应用

介电弹性体作为一种新型的电活性高分子聚合物,当受到电场的激励时会产生变形,撤销电场后能够恢复原状,具有将电能直接转换为机械能的特点。通过将其设计成具有不同结构的致动器,能够提高变形能力,并且满足不同的应用需求。本文介绍了介电弹性体致动器的致动机理,阐明了它们是能够以直线方式产生运动的线性致动器,在此基础上可设计出不同结构的致动器,主要归纳了各种介电弹性体致动器,从它们的性能特征、加工技术和潜在应用等方面进行了讨论。     

Facile synthesis and functionalization of fluoranthenes via intramolecular [4 + 2] annulations between thiophenes and alkynes

Fluoranthenes have attracted tremendous attention due to their unique optoelectronic properties and extensive applications. Although several synthetic methodologies have been developed for the preparation of fluoranthene derivatives, it is still unfavorable to functionalize the fluoranthene framework at different positions due to the relatively low selectivity and reactivity. Herein, a catalyst-free intramolecular [4 + 2] annulation between thiophenes and alkynes is developed towards the synthesis of fluoranthenes. Altogether 20 examples have been demonstrated using this method. Various functional groups can be precisely introduced into the fluoranthene skeleton at different positions by simply tuning the substituents on the thiophenes and alkynes. The conjugation of the fluoranthene can be facilely extended through different directions. Furthermore, the feasibility of this [4 + 2] annulation reaction is also investigated by density functional theory calculations. Therefore, this protocol provides not only a synthetic methodology towards fluoranthenes with substituents functionalized at different positions, but also an effective pathway to construct large polycyclic aromatic hydrocarbons containing fluoranthene moieties.     

惰性载气对TPR动力学的影响

对于一些气-固相反应,同样条件下的动力学行为随惰性载气不同有所差异^[1,2]。为从实验上进一步揭示这一问题,并从理论上给出圆满的解释,我们对程序升温还原(TPR)^[8]过程进行了系统的考察,同时研究了不同惰性载气条件下铜氧化物还原反应的动力学问题,结合有关反应机理和统计热力学的概念,讨论惰性载气对气-固相还原反应动力学的影响。     

Identification of herb Acanthopanax senticosus (Rupr. Et Maxim.) harms by capillary electrophoresis with electrochemical detection.

In this paper, a rapid, high efficient, sensitive and inexpensive approach based on a combination of simple ultrasonic extract and capillary electrophoresis (CE) separation with electrochemical detection (ED), is described to identify herbs by comparing their CE-ED profiles (namely, CE-ED electropherograms). The proposed method takes advantage of ultra-small sample volume, low consumption of organic solvent, simple sample pretreatment and easy cleanup procedure. It was applied to analyze the CE-ED profiles of stems of herb Acanthopanax senticosus (Rupr. Et Maxim.) Harms from different sources and different parts (roots, rhizomes, stems and leaves) of this herb. By comparing peak number, peak height and peak height ratio, we found that the CE-ED profiles showed big differences for the herbs from the different sources and the different parts of this herb. In addition, the distribution of bioactive compounds (isofraxidin, rutin and chlorogenic acid) in the different parts of this herb and their content variations affected by the source were studied with the CE-ED method. Based on their own unique CE-ED profiles, these herbs from the different sources and the different parts of this herb could be easily distinguished. Therefore, the proposed approach could be used as a rapid, high efficient and sensitive method for the identification of herbal medicines.