β-环糊精聚合物的合成、自组装及作为药物/基因载体的应用研究

【作者】 熊青青；

【导师】 张其清；

【作者基本信息】 北京协和医学院 ， 生物医学工程， 2014， 博士

【摘要】 环糊精(CD)具有独特的圆筒状疏水性内腔和亲水性外沿结构,其空腔对多种疏水性分子具有良好的包合性能。在药学领域,CD可通过主-客体相互作用包载多种疏水性药物,并提高药物的溶解性、稳定性及生物利用度等。环糊精聚合物(CDP)是在聚合物链上引入多个CD单元形成的聚合物,由于CDP链上相邻的CD单元之间存在协同作用,其可以包合更多不能被单一CD分子包合的客体分子。近年来在纳米自组装、药物及基因载体等领域受到了越来越多的关注。本论文以β-CD为基础,采用原子转移自由基聚合法(ATRP)合成了多种结构规整、组成明确的β-CDP,包括星型、线型及线-梳型结构等。详细研究了其与多种客体分子通过主-客体相互作用驱动形成的自组装体的性质,并评价了其作为药物/基因载体材料的应用前景。主要研究工作如下：1.采用“臂-引发”(arm-first)的方法,以溴代聚乙二醇(PEG-Br)为大分子引发剂,使用ATRP法同时引发甲基丙烯酸酯多取代β-环糊精单体(GECD)及甲基丙烯酸二甲基氨基乙酯(DMAEMA)的聚合得到核交联的星型聚合物PEG-(PCD-co-PDMAEMA)。之后,研究了其通过主-客体相互作用与疏水性小分子芘及疏水性聚合物聚乳酸(PLA)之间的自组装性质。结果显示：此星型聚合物可与这两种客体分子自组装形成纳米粒子；改变溶液pH值,客体分子类型及比例,纳米粒子的形态发生规律性的变化,即疏水部分比例增加可观察到纳米粒子由球形向棒状或囊泡结构转变。2.以阿霉素(DOX)为药物模型,通过主-客体相互作用将其包载于上述制备的星型聚合物中得到载药纳米粒子(DOX-NPs),详细研究了DOX-NPs的粒径、载药量、稳定性、体外药物释放行为及其在HeLa、HepG2和L929细胞中的摄取及毒性情况。结果表明：DOX可以包载于星型聚合物中形成稳定的纳米粒子,载药量在1.6-30.0%范围内,粒径为86-333nm；载药纳米粒子的药物体外释放具有pH值响应性；细胞摄取依赖于细胞类型、载体浓度和摄取时间；载体中的药物在细胞核和细胞浆中均有分布；DOX-NPs对肿瘤细胞HeLa和HepG2的体外细胞毒性高于非肿瘤细胞L929。动物实验结果进一步表明,与游离药物相比,DOX-NPs对接种HeLa细胞的BALB/c雌性裸鼠具有更高的体内抑瘤效果。以上结果表明,该星型聚合物有望作为药物载体应用于癌症治疗。3.通过对以往环糊精单体制备方法进行改进,在温和的反应条件下,使用简单易行的方法合成了一种新的甲基丙烯酸酯单取代β-环糊精单体GACD,并以PEG-Br为引发剂,引发了GACD的ATRP聚合,得到了侧链悬垂β-CD单元的二嵌段共聚物PEG-b-PCD。然后,以其作为“主体”聚合物研究了其与多种客体分子(罗丹明B、金刚烷聚合物、端基为金刚烷的均聚物ADA-PDMAEMA、PL A)之间的组装性质。结果显示：此共聚物可以与上述客体分子通过主-客体相互作用形成自组装体；改变客体分子类型、主/客体分子比例,自组装体呈现出不同的尺寸和形态。4.将PEG-b-PCD与2-溴异丁基酰溴反应制得ATRP引发剂PEG-b-P(CD-Br),采用ATRP法引发DMAEMA的聚合得到了组成明确的线-梳型阳离子聚合物刷PEG-b-P(CD-g-PDMAEMA)。此聚合物刷梳型嵌段的侧链可被认为由星型聚合物构成,星型聚合物的核为β-CD,臂为阳离子聚合物PDMAEMA。之后,详细研究了其作为基因载体的应用。结果表明：该聚合物刷具有高密度的PDMAEMA链,可以有效复合质粒DNA(pDNA)形成100-200nm的球形纳米粒子；与单一的星型聚合物相比,聚合物刷具有更高的转染效率；与聚乙烯亚胺(PEI25k)相比,聚合物刷具有相当或更高的转染效率,且表现出较低的细胞毒性。综上所述,本研究制备得到的一系列组成明确的β-CD聚合物,可以通过主-客体相互作用与多种客体分子进行自组装,得到具有不同结构和功能的纳米组装体,在药物和基因传递系统中具有良好的应用前景。事实上,本研究所用策略具有一定的通用性,改变环糊精种类、单体种类、客体分子种类及环境刺激等条件,可以制备得到更多具有不同形态及功能的材料,在药物/基因传递系统、生物传感器、自修复材料、催化、电化学、表面抗污染材料等多种领域均具有良好的应用前景。更多还原

【Abstract】 Cyclodextrin (CD) is characteristic of a hydrophilic exterior surface and hydrophobic interior cavity, which can accommodate a wide range of guest molecules. In pharmaceutical field, CD has been widely utilized to complex with the hydrophobic drugs via host-guest interactions to improve their solubility, stability and bioavailability. CD-based polymer (CDP), the polymer composed of multiple CD rings threaded or tethered on a polymer chain, are able to bind guest molecules that are too large to be accommodated in a single CD cavity, due to the cooperation of adjacent CD moieties on a polymer chain. Thus, CDP has inspired much interest in the fields of nanostructure fabrication, pharmaceutics and biomedicine.In this thesis, well-defined β-CDPs with various structures including star shape, linear shape and coil-comb shape are prepared by atom transfer radical polymerization (ATRP). The properties of self-assemblies formed by the CDPs in the presence of various guest molecules are studied in detail. Moreover, the potential application of CDPs in drug and gene delivery system is evaluated as well. The main contents of this work are as follows:1. Cyclodextrin-based star polymer is synthesized using the "arm-first" method by ATRP. Copolymerization of a mixture of mono-and multi-methacrylate substituted (3-cyclodextrin (GECD) and2-(dimethylamino) ethyl methacrylate (DMAEMA) initiated by poly(ethylene glycol) macroinitiator produces a core cross-linked star polymer PEG-P(CD-co-PDMAEMA). The star polymer can self-assemble into nanostructures via host-guest interactions between the cyclodextrin polymers and hydrophobic guest molecules. The morphologies of these nanostructures showed regular transitions by altering the type of guest molecules, the ratio of star polymer to guest, and the pH of the solution.2. Doxorubicin (DOX), as the model drug, can be loaded into the star polymer to form nanoparticles (DOX-NPs) via host-guest interactions. The size, drug loading content, stability and drug release kinetics of DOX-NPs are investigated in detail and the cellular uptake and cytotoxicity are evaluated in HeLa, HepG2and L929cells as well. The cellular uptake of DOX-NPs is in a concentration-, time-and cell type-dependent manner. DOX is distributed both in the cytoplasm and nucleus for DOX-NPs, while it is mainly located in the cell nucleus for the free drug. Moreover, a significantly higher level of cytotoxicity is achieved with DOX-NPs towards HeLa and HepG2cancer cells than that towards L929non-cancer cells. The in vivo anti-tumor experiment is conducted on BALB/c mice bearing cervical tumor, which shows that DOX-NPs suppress the growth of tumor significantly. These findings suggest that the cyclodextrin-based pH-responsive star polymer shows potential in developing novel drug delivery system for cancer therapy.3. A new mono-methacrylate substituted β-cyclodextrin (GACD) is prepared in a mild condition. Thus, well-defined hydrophilic diblock copolymer poly(ethylene glycol)-b-poly(cyclodextrin)(PEG-b-PCD) with high CD density can be easily synthesized via ATRP of GACD from poly(ethylene glycol) macro initiator. The block copolymer is able to include a variety of guest molecules and self-assemble into advanced nanostructures due to the synergistic effect of CD moieties. By altering the type of guest molecules and the ratio of PEG-b-PCD to guest, the self-assembled nanostructures show different size and morphology.4. The CD moieties on diblock copolymer PEG-b-PCD are then reacted with2-bromoisobutyryl bromide to obtain macroinitiator PEG-b-P(CD-Br). Well-defined coil-comb polycationic brushes PEG-b-P(CD-g-PDMAEMA) are synthesized via ATRP of DMAEMA and used as gene carriers. The side chains of the comb block are composed of star polymers with β-CD as the core and PDMAEMA as the arm. With such super-high grafting density of PDMAEMA, the brushes effectively condense pDNA into spherical nanoparticles of100-200nm in size and exhibit significantly higher transfection capability compared to the single star polymer. In some cases, they also show comparable or higher transfection efficiency and lower cytotoxicity than PEI25K. The results indicate these brushes have good promise for the potential gene therapy.In summary, a series of well-defined β-CDPs are synthesized via ATRP in this thesis. Advanced nanostructures can be formed by the inclusion interactions between these CDPs and various guest molecules. And these nanostructures show good promise for the potential drug and gene therapy. Actually, this strategy provides a facile method to prepare well-defined CDPs with various structures and a versatile method for the design of nanostructures based on CDPs. These CDPs and the self-assembled nanostructures may find attractive applications in the fields of drug and gene delivery, self-healing materials, catalysts and coatings, etc.更多还原