壳聚糖接枝聚乳酸共聚物性能及其体外释药行为研究

采用原位聚合法合成了含聚乳酸链段的壳聚糖接枝共聚物.通过X射线衍射(XRD)和热重(TG)分析研究共聚物的结晶性能和热失重行为.结果表明,共聚物的结晶度和热分解温度降低,壳聚糖的高结晶性能得到改善.接触角测试表明,相对于聚乳酸,共聚物材料具有较好的亲水性.通过溶剂挥发法制备了5-氟尿嘧啶/共聚物载药微球,并用紫外分光光...     

聚乳酸类药物控释载体材料研究进展

生物降解性载体材料已越来越多地应用到药物控释体系中,聚乳酸因其原料易得、容易加工、生物相容性好、具有可生物降解性等优点,已经成为当今药剂载体材料中的一大研究热点。本文从控释机理、给药系统的制备以及影响控释因素三方面入手,论述了聚乳酸类药物控释载体材料的最新研究进展。     

干扰素壳聚糖/海藻酸钠微囊控释制剂载体的初步研究

目的研究蛋白质类药物口服控释给药的可行性。方法壳聚糖与海藻酸钠通过聚电解质络合反应制备成壳聚糖/海藻酸钠微囊,以干扰素为模型药物,研究不同pH条件下,药物的控制释放情况。结果微囊的粒径为1 mm左右,其干扰素的包封率达90.0%以上,微囊在模拟胃液(pH1.0)中,3h药物释放不到5%;在模拟肠液(pH7.4)中,3h药物释放近100%。结论壳聚糖/海藻酸钠微囊有可能成为蛋白质类药物口服控释制剂的载体。     

药物与聚乳酸包埋物缓释性能的研究

采用包埋法制备了聚乳酸与药物的混合物,测定了聚乳酸相对分子质量大小、聚乳酸与药物的配比、聚乳酸与不同药物形成的包埋物及光照对药物释放量的影响,研究了包埋物在不同环境下的释放能力。     

壳聚糖氧化降解性能的研究

对壳聚糖在2％乙酸溶液中的氧化降解行为进行了探讨,着重考察了温度、时间和用量比R(H2O2与糖单元的物质量比)对相对分子质量的影响。同时对氧化降解的动力学规律作了初步研究,结果表明,氧化降解分为两个阶段,在后阶段的降解行为符合无规降解规律。     

壳聚糖在药物控释载体方面的应用研究

壳聚糖是一种具有很好的生物相容性和生物降解性的新型医用高分子材料,其在医药及制剂方面有着广泛的应用.本文就近年来壳聚糖在药物控释载体方面的应用研究作了一个概述,以进一步加深人们对这一方面研究状况的了解.     

酶酸连续降解壳聚糖制备低分子量水溶性壳聚糖的研究

采用酶酸连续降解壳聚糖制备低分子量水溶性壳聚糖。首先确定了单因素降解壳聚糖的最佳技术参数：木瓜蛋白酶降解壳聚糖时最优条件为45℃、2h;醋酸降解壳聚糖时最优条件为30℃、4h;盐酸降解壳聚糖最优条件为90℃、8h;然后根据单因素降解壳聚糖最优条件确定了酶酸连续降解壳聚糖新工艺,并优化反应时间为7h。在相同条件下,酶酸连用方法最终降解产物的粘度低于单因素降解产物的粘度,产物表面性状有很大不同,分子量由降解前的33523．14下降到3134．11。     

β-环糊精琥珀酸钠/壳聚糖离子复合膜的制备及其药物控释研究

采用酯化反应,以琥珀酸酐(SUC)为酰化剂,合成了琥珀酰β 环糊精酯(β CD SUC),进一步与NaOH反应生成β 环糊精琥珀酸钠(β CD SUS),并以此为离子交联剂与阳离子聚合物壳聚糖(CTS)复合,制备了含β 环糊精结构单元的壳聚糖复合膜(β CD SUS/CTS)。滴定实验表明了离子间存在着静电相互作用,并决定了膜在水溶液中具有pH敏感性。选用喜树碱(CPT)为模型药物,通过研究环糊精与CPT以及环糊精与CTS间的相互作用,探讨了其药物控制释放机理。     

壳聚糖改性蒙脱石作为药物控释载体的研究

采用壳聚糖(CS)对钠基蒙脱石(MMT)进行改性制备有机蒙脱石(CS-MMT),对改性后的蒙脱石进行红外光谱(FT-IR)和X射线衍射(XRD)等分析表征.以5-氟尿嘧啶(5-FU)为药物模型制备出壳聚糖改性蒙脱石载药复合物(5-FU/CS-MMT),并以钠基蒙脱石载药复合物(5-FU/MMT)作为对照,探究载药复合物在模拟人工胃液、人工小肠液和人工结肠液中的药物释放情况.结果 表明,当CS的用量是MMT的1.0倍阳离子交换容量时,形成的有机蒙脱石的层间距增大,且对5-FU的载药量达到393 mg/g,而同等情况下,MMT的载药量为239 mg/g.体外释放试验的结果表明,5-FU/CS-MMT中5-FU的体外释放能力主要受释放介质pH值的影响,当pH值为7.4时,5-FU的累积释放率最大,在pH值为1.5时的结果最小.     

低相对分子质量氨基甲酸酯丙烯酸酯的合成与研究

选用6种不同结构的小分子二元羟基化合物、异佛尔酮二异氰酸酯和丙烯酸羟乙酯或季戊四醇三丙烯酸酯为原料,合成了12种不同结构的低相对分子质量氨基甲酸酯丙烯酸酯(UA)与2种已商业化应用的不添加二元羟基化合物的无间隔结构UA对比样品。采用红外光谱进行结构表征,通过实时红外光谱研究了各样品的光聚合动力学,并进行了体积收缩率、力学性能与常规表面性能测试,研究了链长和链段结构类型对UA综合性能的影响。结果表明:带有小分子二元羟基化合物结构的低相对分子质量UA样品具有柔韧性好、硬度高、刚性高、体积收缩率低、双键转化率高等优点,并且样品对PET膜和ABS基材有较高的附着力。     

熔融缩聚法合成高分子量聚L-乳酸

以L-乳酸为原料,采用分步除水、丙交酯回流、优选催化剂等工艺,通过熔融缩聚法制备了高分子量聚L-乳酸(PLLA),研究了脱水产物、反应装置、催化剂、聚合工艺等对产物分子量、产率及色泽的影响,并对产物分子结构进行了表征。在加装丙交酯回流装置后,以Sn(Ot)2/SnC l2.2H2O/TSA为催化剂,在170℃,反应12h所得PLLA黏均分子量(Mη)可达10.6万,产率为76%。     

一种新型成核剂对聚乳酸等温结晶行为的影响(英文)

The effect of a novel active nucleating agent(TBC8-eb) on the isothermal crystallization of poly(L-lactic acid) (PLLA) was studied by differential scanning calorimetry(DSC) and Fourier transform infrared spectroscopy(FTIR) . The analysis on kinetics demonstrates that TBC8-eb can not only accelerate the crystallization rate but also transform most of the original spherulite crystals of PLLA into sheaf-like crystals. Furthermore,the free energy of folding(σe) of PLLA and PLLA with TBC8-eb is 0.15 and 0.06 J·m-2,respectively,which suggests that the addition of TBC8-eb favors the regular folding of molecule chains in the crystallization of PLLA,improv-ing its crystallization rate. The FTIR results show that TBC8-eb can accelerate the conformational ordering of PLLA in the isothermal crystallization. The conformational ordering of PLLA nucleated with TBC8-eb begins with the interchain interaction of CH3,and then a short helix emerges where a couple of CH3 groups interact.     

Influence of Poly(L-lactic acid) Molecular Weight on the Encapsulation Efficiency of Urea in Microcapsule Using a Simple Solvent Evaporation Technique

Poly(L-lactic acid) microencapsulated urea was prepared in water-in-oil-in-water (W₁/O/W₂) system by the solvent evaporation technique. The influence of poly(L-lactic acid) molecular weight on the percent loading, encapsulation efficiency, and the microcapsule morphology was studied using poly(L-lactic acid) having different number average molecular weights (M_n). Using the higher M_n, the smoother shell with complete encapsulation microcapsules was formed. Moreover, the percent loading and encapsulation efficiency of urea also increased with the poly(L-lactic acid) molecular weight. At 80,000 g/mol of poly(L-lactic acid), the obtained microcapsule gave the highest both percent loading (32%) and encapsulation efficiency (56%). The urea control release study of the prepared microcapsules was implemented by in vitro testing. The encapsulated urea was gradually released from the microcapsules, approximately 53, 29, and 22% of poly(L-lactic acid) at 3,000, 30,000, and 80,000 g/mol, respectively, for a month. These results presented the possibility of the prepared poly(L-lactic acid) microcapsules-encapsulated urea for urea control release that could be utilized in agricultural applications.     

In vitro degradation of poly(L-lactic acid) fibers produced by melt spinning

In vitro degradation of poly(L -lactic acid) fibers was investigated for a period of 16 weeks in Ringer solution at 37°C. Two sets of fibers, with similar initial mechanical properties, molar mass, and crystallinity content, but markedly different in diameter (72 and 120 μm) were studied. Viscometric molar mass decreased during the immersion time at a faster rate for the thinner fibers compared to the thicker ones. As a consequence, the fiber mechanical properties changed; the elastic modulus was only slightly affected by the molar mass decrease whereas ultimate mechanical properties (stress and strain at break) showed a strong decrease. A quantitative correlation between tensile strength and viscometric-average molar mass was attempted. A possible explanation of the faster degradation rate of the thinner fibers was proposed on the basis of the higher surface/volume ratio and water uptake. Dynamic mechanical properties were also measured as a function of immersion time. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 213–223, 1997     

熔融共聚法用外消旋乳酸直接合成聚乙醇酸-乳酸及其表征

以乙醇酸(GA)、廉价的外消旋乳酸(D,L-LA)为原料,以氯化亚锡(质量分数0.5％)为催化剂,在165℃、70 Pa下熔融聚合10 h,通过熔融共聚法直接合成了不同配比的系列生物降解材料聚乙醇酸-乳酸(PGLA),用凝胶渗透色谱、傅里叶变换红外光谱、核磁共振氢谱、差示扫描量热分析、X射线衍射等系统地对其进行了表征。当n(GA):n(D,L-LA)=1:1,直接熔融聚合法获得的D,L-PGLA 50／50的重均相对分子质量为24 300,比相同条件下合成的L-PGLA 50／50的18 000要高。     

Experimental investigation on the properties of poly (L-lactic acid) vascular stent after accelerated in vitro degradation

Poly (L-lactic acid) (PLLA) vascular stents are promising to be used to treat vascular stenosis. However, the degradation of these implanted stents has a great influence on the mechanical properties. In this work, we studied the factors that can influence the mechanical properties by accelerating the degradation of PLLA stents with crimping and expansion in phosphate buffer solution (PBS) at 70°C. The typical influence factors such as the real-time weight-average molecular weight (M_w), crystallinity, surface morphologies, and mass loss of these samples were analyzed in detail. Results showed that radial strength of the stents increased from 877 to 1204 mmHg after accelerated degradation for 2 days and then decreased to almost 0 mmHg after 10 days. Meanwhile, radial stiffness showed an upward trend which is caused by the decrease in M_w, increase in crystallinity and local damage during the crimping and expansion process. Moreover, negligible mass loss of stents was observed in this period and the bulk degradation behavior predominated in the whole process.     

异佛尔酮二异氰酸酯溶液扩链合成聚乳酸类药物缓释剂

以外消旋乳酸(D,L-LA)直接熔融聚合得到的低相对分子质量聚外消旋乳酸(PDLLA)为原料,通过二异氰酸酯扩链合成了聚乳酸类药物缓释材料。当采用异佛尔酮二异氰酸酯(IPD I)为扩链剂,反应在四氢呋喃溶液中进行时,扩链反应工艺条件为:扩链剂用量n(NCO)∶n(OH)=2∶1时,66℃下回流反应2 h,相对分子质量增加近2.92倍。与2,4-甲苯二异氰酸酯(TD I)扩链法相比,IPD I溶液扩链法不仅提高产物相对分子质量的效果非常接近,具有反应温和、条件易调控等优点,而且使所得聚乳酸类药物缓释材料具有较高的生理安全性。     

聚乳酸纤维的静电纺丝及其形态结构研究

采用二氯甲烷为溶剂,以滚筒为收集装置,利用静电纺丝法制备了聚乳酸纳米纤维。分析了溶液体系和滚筒转速对纤维形态结构的影响。结果表明:在质量分数相同的条件下,采用相对分子质量较大的聚乳酸切片所纺纤维直径细而均匀;质量分数增加时,电纺丝产品由一些高分子微/纳米液滴渐变为成形较好、珠状较少的平滑纤维,其平均纤维直径先增加后减小;控制收集滚筒的转速在一定范围内,可以获得排列取向较好的纤维。