【作者】 陈维；

【导师】 钟志远；

【作者基本信息】 苏州大学 ， 应用化学， 2010， 硕士

【摘要】 生物可降解脂肪族聚碳酸酯是生物医用材料的一个重要组成部分。它是一类表面溶蚀材料,可经水解、酶解或细菌降解为中性的二元醇(酚)和二氧化碳。生物可降解聚碳酸酯具有良好的生物相容性和物理机械性能,而且种类繁多,通过改变主链化学结构和引入侧链功能基团可以使高分子材料具有广泛的物理,化学和生物学性质,以满足不同需要。论文第一章对生物可降解脂肪族聚碳酸酯的种类、结构、合成方法及应用作了简要概述。论文第二章讲述了基于酸敏感聚碳酸酯的两亲性聚合物自组装形成具有pH响应性的生物可降解胶束。通过两步合成法成功制备得到两种新型的环状脂肪族碳酸酯单体,即2,4,6-三甲氧基苯甲缩醛季戊四醇碳酸酯(TMBPEC, 2a)和对甲氧基苯甲缩醛季戊四醇碳酸酯(MBPEC, 2b)。以甲氧基PEG为引发剂,双(双三甲基硅基)胺锌为催化剂,在CH2Cl2中50℃下通过开环聚合2a和2b,分别合成得到分子量分布较窄(PDI:1.03-1.04)的共聚物PEG-PTMBPEC(3a)和PEG-PMBPEC(3b)。DLS和TEM测试表明该两亲性共聚物自组装形成150 nm左右的胶束。胶束3a疏水链段侧链缩醛的水解速率显示出优异的pH响应性,胶束在pH7.4下比较稳定,但在pH4.0和5.0条件下,水解半衰期分别为1小时和6.5小时。胶束3a能以较高的包封率装载紫杉醇(65 %)和多柔比星(60 %)抗癌药物(载药量分别为:13.0和11.7 wt%),并在体外释放实验中呈现出明显的pH响应性。论文第三章讲述了基于酸敏感的两亲性共聚物PEG-PTMBPEC自组装形成具有pH响应性的生物可降解囊泡作为亲水和疏水抗癌药物载体,并比较了囊泡和胶束的药物包裹和释放行为。DLS和TEM测试结果表明聚合物PEG1.9k-PTMBPEC6.0k形成的囊泡平均粒径为100-200 nm。PEG1.9k-PTMBPEC6.0k囊泡和PEG5k-PTMBPEC5.8k胶束缩醛的水解速率接近,都呈现出明显的pH响应性。聚合物囊泡能同时包封疏水药物紫杉醇和亲水药物多柔比星盐酸盐(包封率分别为:61.4-65.2%和30.0-37.7%),而聚合物胶束只能单独装载疏水药物。在体外释放实验中,囊泡对亲水和疏水药物的释放显示出优异的pH响应性。在相同条件下,囊泡释放疏水药物紫杉醇的速率明显快于胶束。论文第四章讲述了基于(甲基)丙烯酸酯环状碳酸酯单体,结合开环聚合和Michael加成反应,合成了不同性能的功能性生物可降解材料。通过四步合成法成功制备得到(甲基)丙烯酸酯环状碳酸酯单体,总产率约为40%。(甲基)丙烯酸酯环状碳酸酯单体和己内酯或丙交酯的开环共聚以异丙醇为引发剂、辛酸亚锡为催化剂、在甲苯110℃下进行。结果表明合成的共聚物的分子量和功能基团的含量都可方便得到控制。聚合物侧链丙烯酸酯双键和巯基类分子(如:巯基乙醇、巯基丙酸、半胱胺、半胱氨酸和RGDC多肽等)可在温和反应条件下通过Michael加成进行修饰改性。其中,巯基乙醇、半胱胺和半胱氨酸的功能化程度接近100%。初步细胞实验发现用RGD修饰改性的聚合物膜表面具有较好的细胞粘附性。更多还原

【Abstract】 Biodegradable aliphatic polycarbonates are one of the most important biomedical materials. Aliphatic polycarbonates are usually degraded via surface erosion mechanism to neutral diols and carbon dioxide. Biodegradable polycarbonates have good biocompatibility and physico-mechanical properties. The physical, chemical and biological properties of polycarbonates may further be tuned by changing their main chain strutures and incorporating functional pendent groups. The first chapter of this thesis gives a general introduction to biodegradable aliphatic polycarbonates including their structures, syntheses and applications.The second chapter describes rapidly pH-responsive biodegradable micelles based on block copolymers of a novel acid-labile polycarbonate hydrophobe and poly(ethylene glycol) (PEG). Two new cyclic aliphatic carbonate monomers, mono-2,4,6-trimethoxybenzylidene-pentaerythritol carbonate (TMBPEC, 2a) and mono-4-methoxybenzylidene-pentaerythritol carbonate (MBPEC, 2b) were designed and successfully synthesized via a two-step procedure. The ring-opening polymerization of 2a or 2b in the presence of methoxy PEG in dichloromethane at 50°C using zinc bis[bis(trimethylsilyl)amide] as a catalyst yielded the corresponding block copolymers PEG-PTMBPEC (3a) or PEG-PMBPEC (3b) with low polydispersities (PDI 1.03-1.04). These block copolymers readily formed micelles in water with sizes of about 150 nm as determined by dynamic light scattering (DLS). The hydrolysis of the acetals of the polycarbonate showed that the acetals of micelles 3a while stable at pH7.4 are prone to rapid hydrolysis at mildly acidic pH of 4.0 and 5.0, with a half life of 1 and 6.5 hrs, respectively. Both paclitaxel and doxorubicin could be efficiently encapsulated into micelles 3a achieving high drug loading content (13.0 wt.% and 11.7 wt.%, respectively). The in vitro release studies showed clearly a pH dependent release behavior.The third chapter reports pH-sensitive degradable polymersomes based on PEG-PTMBPEC copolymer for triggered released of hydrophilic and hydrophobic anti-cancer drugs. DLS showed that polymersomes of PEG1.9k-PTMBPEC6k had average sizes of 100~200 nm. The acetals of polymersomes, similar to those of PEG5k-PTMBPEC5.8k micelles, though stable at pH7.4 were prone to fast hydrolysis at mildly acidic pH of 4.0 and 5.0, with half lives of 0.5 and 3 d, respectively. Drug encapsulation studies revealed that polymersomes were able to simultaneously load paclitaxel (61.4-65.2%) and doxorubicin hydrochloride (30.0-37.7%), whereas micelles loaded PTX only. The in vitro release studies demonstrated that release of PTX and DOX HCl from polymersomes was highly pH-dependent. Furthermore, much higher release rates were observed for PTX release from the polymersomes compared to that from the micelles under otherwise the same conditions.The fourth chapter describes versatile synthesis of functional biodegradable polymers from novel cyclic carbonate monomers, acryloyl carbonate (AC) and methacryloyl carbonate (MAC), by combining ring-opening polymerization (ROP) and Michael addition chemistry. AC and MAC monomers were synthesized in four straightforward steps with good overall yields (ca. 40%). AC and MAC were able to copolymerize withε-caprolactone (ε-CL) and D,L-lactide (LA) in toluene at 110°C using stannous octoate as a catalyst, yielding biodegradable copolymers with controlled acryloyl functional groups and molecular weights. The acryloyl groups were amenable to the Michael addition conjugate reaction with varying thiol-containing molecules such as 2-mercaptoethanol, 3-mercaptopropanoic acid, cysteamine, cysteine, and arginine-glycine-aspartic acid-cysteine (RGDC) peptide under mild conditions. Notably, 100% functionalization was achieved with 2-mercaptoethanol, cysteamine and cysteine. Initial cell culture studies demonstrated enhanced cell adhesion and growth on films containing functional RGDC peptides as compared to those of the parent copolymer as well as tissue culture plastic.更多还原