Prevention of postoperative tendon adhesion by biodegradable electrospun membrane of poly(lactide-co-glycolide)

An electrospun poly(lactide-co-glycolide)(PLGA) membrane was prepared and used to perform the anti-adhesion of Achilles tendon. Throughout the experiments, the membrane showed an appropriate degradation rate, and the p H values of degradation media were maintained at around 7.4. Simultaneously, the excellent biocompatibility of the membrane in vitro and in vivo was confirmed by live/dead and histopathological analyses. Meanwhile, the membrane can reduce tendon adhesion significantly and promote functional recovery effectively. The encouraging results were further demonstrated by hematoxylin and eosin(HE), and Masson's trichrome stainings, and type I collagen immunohistochemical analysis. It was concluded that the model treated with the electrospun PLGA membrane was significantly better with respect to the adhesion prevention and tissue repair than that without treatment. Considering the results of degradation and adhesion prevention efficacy, the electrospun PLGA membrane would be a great candidate for the prevention of postoperative tendon adhesion.     

Biodegradable thermogel as culture matrix of bone marrow mesenchymal stem cells for potential cartilage tissue engineering

Poly（lactide-co-glycolide）-poly（ethylene glycol）-poly（lactide-co-glycolide）（PLGA-PEG-PLGA） triblock copolymer was synthesized through the ring-opening polymerization of LA and GA with PEG as macroinitiator and stannous octoate as catalyst. The amphiphilic copolymer self-assembled into micelles in aqueous solutions, and formed hydrogels as the increase of temperature at relatively high concentrations（〉 15 wt%）. The favorable degradability of the hydrogel was confirmed by in vitro and in vivo degradation experiments. The good cellular and tissular compatibilities of the thermogel were demonstrated. The excellent adhesion and proliferation of bone marrow mesenchymal stem cells endowed PLGA-PEGPLGA thermogelling hydrogel with fascinating prospect for cartilage tissue engineering.     

四臂聚乙二醇-聚丙交酯立体复合胶束及其药物传输性能

以异辛酸亚锡为催化剂,通过四臂聚乙二醇(4-armed PEG)引发右旋丙交酯(DLA)或左旋丙交酯(LLA)开环聚合合成四臂PEG-PLA对映体共聚物.通过纳米沉淀的方法制备了四臂PEG-b-PDLA胶束(PDM)、四臂PEG-b-PLLA胶束(PLM)和四臂PEG-b-PDLA/四臂PEG-b-PLLA立体复合胶束(SCM),并对其形貌、粒径、稳定性和立体复合机理等进行系统表征.以阿霉素(DOX)为模型抗肿瘤药物载入胶束中,与PDM和PLM相比,SCM具有更优异的药物负载能力.与DOX相比,载药四臂PEG-PLA胶束,尤其是负载DOX的SCM,表现出更优异的肿瘤细胞增殖抑制效果,作用更持久,并且对正常细胞的毒性较小,从而揭示了其作为潜在抗肿瘤药物载体的良好前景.     

Poly(<Emphasis Type="Italic">β</Emphasis>-cyclodextrin)-mediated polylactide-cholesterol stereocomplex micelles for controlled drug delivery

A series of host-guest interaction-adjusted polylactide stereocomplex micelles was prepared via the self-assembly of 4-armed poly(ethylene glycol)-block-poly(L-lactide/D-lactide)-cholesterol (4-armed PEG-b-PLLA/PDLA-CHOL) and poly(β-cyclodextrin) (PCD) with the molar ratios of CHOL/β-CD at 1:0.5, 1:1, and 1:2 in an aqueous environment. The hydrodynamic diameters of the micelles ranged from 84.1 nm to 107 nm depending on the molar ratio of CHOL/β-CD. It was shown that the micelle with the largest proportion of PCD possessed excellent abilities in drug release, cell internalization as well as proliferation inhibitory effect toward human A549 lung cancer cells. The results demonstrated that the stereocomplex and host-guest interactions-mediated PLA micelles exhibited great potential in sustained drug delivery.     

糖聚肽高分子的合成、自组装及生物医学应用

糖聚肽高分子是一类由聚肽(也称聚氨基酸)和糖类化合物(包括单糖、寡糖和多糖)构成的生物可降解高分子.糖聚肽高分子具有与天然糖蛋白分子类似的化学组成,能够在一定程度上模拟天然糖蛋白的结构和性能,近年来引起了学术界的广泛研究兴趣.本文总结了糖聚肽高分子的合成方法及其在水溶液中的自组装行为,并着重评述了糖聚肽高分子在生物分子识别、靶向基因/药物传输和组织工程支架等生物医学领域中的应用.     

功能性聚氨基酸纳米凝胶

聚合物纳米凝胶具有稳定的三维结构、高载药效率、刺激响应性等特性,在药物递送、基因治疗和生物成像等多个生物医学领域应用前景可期。聚氨基酸纳米凝胶由于其优异的生物相容性、性能易于调节、降解产物安全无毒等特性,在生物医学领域获得了广泛的关注。特别地,具有内源性刺激(例如:还原性、活性氧、pH和酶)或外源性刺激(例如:光和温度)响应能力的功能性聚氨基酸纳米凝胶可通过适度的转变达到药物递送可控的目的。本文系统地介绍了不同功能性聚氨基酸纳米凝胶的制备、应用和面临的挑战。     

一种考虑速度随机慢化概率动态演化的交通流元胞自动机模型

在NS模型的基础上,利用司机的记忆效应和当前交通环境动态地调整随机慢化概率,从而得到一个改进的交通流元胞自动机模型.数值实验表明,该模型可以很好地刻画司机记忆效应对交通流的影响,记忆效应的引入可以提高平均速度和流量. 关键词： 交通流 元胞自动机模型 记忆效应 随机慢化概率     

考虑停靠站影响的公交运输系统模型

受停靠站影响,公共交通系统运行过程中容易产生集簇现象.本文细致地考虑了公交停靠站长度和停靠站在线路上的分布情况,构建了一个新的公交运输系统元胞自动机模型.数值模拟结果表明,在引入停靠站长度和停靠站分布两种因素后,模型在微观层面上更清晰地刻画了车辆在公交线路上的时空分布,再现了公交运行中的集簇现象,定量地评价了停靠站分布对车辆平均速度的影响.本研究对进一步认识集簇现象的形成机理和优化停靠站设计具有指导意义.     

Dynamic properties of chasers in a moving queue based on a delayed chasing model

A delayed chasing model is proposed to simulate the chase behavior in the queue, where each member regards the closest one ahead as the target, and the leader is attracted to a target point with slight fluctuation. When the initial distances between neighbors possess an identical low value, the fluctuating target of the leader can cause an amplified disturbance in the queue. After a long period of time, the queue recovers the stable state from the disturbance, forming a straightline-like pattern again, but distances between neighbors grow. Whether the queue can keep stable or not depends on initial distance, desired velocity, and relaxation time. Furthermore, we carry out convergence analysis to explain the divergence transformation behavior and confirm the convergence conditions, which is in approximate agreement with simulations.     

肿瘤酸度响应性聚(L-赖氨酸)-阿霉素键合药的制备与表征

用丁二酸酐(SA)和顺式乌头酸酐(CA)分别对阿霉素(DOX)进行修饰, 得到非酸响应的SA-DOX(SAD)和酸响应的CA-DOX(CAD). 通过SAD或CAD、端羧基化的聚乙二醇单甲醚(mPEG-COOH)与聚(L-赖氨酸)(PLL)的缩合反应, 制得非酸响应的PLL-g-mPEG/SAD和酸响应的PLL-g-mPEG/CAD键合药. 通过核磁共振氢谱和红外光谱表征键合药的化学结构, 并通过紫外-可见分光光度计测定药物键合量. 动态激光光散射研究结果表明, 两亲性的PLL-DOX键合药可以在pH=7.4的磷酸缓冲溶液中自组装形成稳定的纳米微粒. 体外释放实验及噻唑蓝检测结果表明, PLL-g-mPEG/SAD在实验pH范围和时间段内只释放出少量DOX, 不具有酸响应特性, 且对HeLa细胞增殖抑制作用较小. 而PLL-g-mPEG/CAD在生理条件(pH=7.4)下相对稳定, 在弱酸性条件(pH=5.3, 6.8)下, CAD中酸响应的酰胺键能快速水解并释放出DOX, 表现出较强的HeLa细胞增殖抑制效果.