【作者】 程义云；

【导师】 施蕴渝； 徐铜文；

【作者基本信息】 中国科学技术大学 ， 结构生物学， 2008， 博士

【摘要】 树枝形分子是一类具有树的拓扑结构的人工合成大分子。这类分子具有大量的表面官能团,相对疏水的内部空腔,独特的球形几何外观,可控的尺寸和分子量,以及卓越的单分散性。由于这些结构特点,这种纳米尺寸的明星高分子材料在主客体化学,电化学,光化学,纳米化学,污染治理,单分子膜,传感器,环氧树脂固化,催化剂,药物运输,基因转染,肿瘤诊断等领域取得了重要的应用。近来,树枝形分子在药物运输系统中的应用研究吸引了越来越多的研究者的关注,目前这个方向已经发展成为纳米医药,药物运输系统以及制药科学中的一个研究热点。本论文旨在设计,开发一类基于树枝形分子的新型药物运输系统并将该运输系统应用于预临床研究。研究了树枝形分子对多个家族的药物的溶解度,扩散释放,药理活性,药物动力学影响;提出了一套树枝形分子与药物分子相互作用的基本理论;对这类给药系统的潜在给药方式进行了初步的探讨;并建立了一套基于树枝形分子的肿瘤靶向诊断与治疗的载体平台。论文共包括7章,第1章首先对树枝形分子的发展史,结构,合成方法,物理,化学性质,及其在多个领域的应用研究作了一个全面的概述,同时介绍了药物运输系统以及纳米医药的概念,并阐述了建立一套基于树枝形分子的药物运输系统的重要性。第2章介绍了聚酰胺胺类树枝形分子对药物溶解度,体外释放,药理活性的影响。包括非甾体抗炎药,磺胺类及喹诺酮类抗菌药,甲氨蝶呤,6—巯基嘌呤,喜树碱等抗癌药,以及抗癫痫药物在内的多种药物因为溶解度差,体内半衰期短,严重的肠胃道毒性等特点而限制了其在临床上的应用。树枝形分子与这些药物形成的水溶性复合物能够很大程度上克服这些缺点,极大地改善药物溶解度,降低药物的体外以及体内释放速率,对药物的活性影响较小,甚至能够提高药物的生理活性。这对开发这些药物的静脉注射,静脉滴注,滴眼液等剂型提供了理论基础。第3章用多维核磁共振技术研究了聚酰胺胺类树枝形分子与药物分子的相互作用,并结合溶解度实验结果得出了几个重要的普适性规律。研究结果表明树枝形分子与药物分子之间的相互作用包括三种相互作用方式:树枝形分子表面的阳离子电荷与药物分子的局部负电荷之间的静电相互作用,树枝形分子的内部空腔与疏水的药物分子间的疏水相互作用,以及树枝形分子内部的酰胺基团,三级胺基团与药物分子的氢键供体或受体之间的氢键相互作用。这些相互作用模型之中,发生在树枝形分子表面的静电相互作用比发生在分子内部的疏水作用以及氢键作用的总和对药物分子溶解度增加的贡献更大。同时发现高代数的树枝形分子比低代数的分子更加容易发生内部包裹,而低代数的树枝形分子比高代数的分子更加容易发生静电吸附。第4章研究了聚酰胺胺类树枝形分子与表面活性剂的相互作用,提出了一种全新的组装模型。利用多维核磁共振技术给出了表面活性剂进入树枝形分子内部空腔的有力证据,从而纠正了传统模型中表面活性剂分子只在树枝形分子表面组装的结论。并初步探索了树枝形分子—表面活性剂—药物分子组成的三元体系在药物运输系统中的应用。树枝形分子与表面活性剂形成的聚集体能够进一步提高树枝状分子的载药效率,降低树枝形分子的成本,实现可控的药物释放。结合树枝形分子自身的结构特点,可以预测这种药物新剂型在经皮给药,鼻腔黏膜给药等途径中具有重要的应用前景。第5章研究了树枝形分子药物的潜在给药途径。以非甾体抗炎药为例,比较了树枝形分子与非甾体抗炎药的复合物在口服给药以及经皮给药中的体外释放行为,体内药理行为以及药物动力学行为差异。结果表明树枝形分子药物更适合经皮给药,可以在口服给药的基础上进一步提高药物的生物利用度,延长药物的有效作用时间,并在给药途径上增加病人的耐受度。结合文献报道的结果进一步探讨了树枝形分子药物在多种给药方式中的适用性。第6章合成了基于聚酰胺胺类树枝形分子和生物素的肿瘤靶向诊断及治疗的高分子载体平台,并通过流式细胞仪和激光共聚焦显微镜等技术探讨了这类纳米平台在细胞水平的靶向能力及靶向机理。结果发现这类基于树枝形分子与生物素的高分子载体具有很好的靶向能力,这种靶向作用具有剂量依赖性,孵育时间依赖性,能量依赖性,高度的选择性,而且能够被生物素特异性抑制。这类高分子载体具有卓越的生物兼容性,能够作为一个有潜力的纳米载体平台应用于临床诊断与治疗中。本章最后部分比较了各种配基介导的靶向系统的优缺点,提出了一种能够兼顾靶向效率与成本,合成周期等问题的最佳配置方案。第7章对全文进行了总结,并展望了树枝形分子药物运输系统在临床诊断治疗中的应用。尽管基于树枝形分子的药物运输系统还处于婴儿期,它已经向我们展示了一系列的优点。这种新型纳米医药载体有望在生物医学,纳米制药,临床诊断治疗等多领域发挥越来越大的作用。它可以与药物及多种生物活性的客体分子以共价或者非共价的方式相互作用,从而为这些分子提供一个多功能的纳米载体平台。它作为药剂中的添加成分可以提高药物的溶解度,稳定性,生物利用度,细胞射入能力,以及靶向能力。同时它所带来的各种给药途径能够增加病人的耐受程度,并且降低细胞的抗药性。当前该领域的科学家们正针对这些纳米分子的安全性进行预临床的评估,相信不久的将来,树枝形分子的药物运输系统将会真正地造福人类。更多还原

【Abstract】 Dendrimers are a class of artificial macromolecules that have a topological structure like a tree. They are hyperbranched, monodisperse, three-dimensional molecules with well-defined shapes, molecular weights, sizes, branched layers, hydrophobic pockets, and surface functionalities. Due to these structural properties, dendrimers have been widely applied in many fields, such as supramolecular chemistry or host-guest chemistry, electrochemistry, photochemistry, nanoparticle synthesis, pollution management, dye decolorization, preparation of monomolecular membranes, curing of epoxy resins, catalysis, drug delivery, gene transfection, and cancer diagnosis. Recently, the applications of dendrimers in drug delivery systems have received a great deal of attention in the field of nanomedicine, drug delivery systems, and pharmaceutical sciences.The research in this dissertation focuses on the design and development of dendrimer-based drug delivery systems, and their applications in pre-clinical trails. The effect of dendrimers on the solubility, dissolution, release, pharmacodynamic and pharmacokinetic behaviors of non-covalently attached drugs is investigated. General rules on dendrimer and drug interactions are proposed. Potential administration routes of these dendrimer-based drug formulations are discussed. Also, a nano-platform based on dendrimers and biotin molecules is established for cancer targeting therapy and diagnosis.The dissertation comprises seven chapters. Chapter 1 begins with a summary on dendrimer history, structure, synthesis, physico-chemical properties, and applications in different fields. The definition of drug delivery systems and nanomedicine is introduced. On the basis of the summary, the importance of the development of dendrimer-based drug delivery systems is given.Chapter 2 systematically introduces the effect of poly（amidoamine） （PAMAM） dendrimers on the solubility, in vitro release rate, pharmacodynamic behaviors of drugs. Several classes of drugs including non-steroidal anti-inflammatory drugs, sulfonamide antimicrobials, quinolone antimicrobials, anti-cancer drugs, and anti-epileptic drugs are limited in clinical trials due to their extremely low solubility in water, short half-life time in blood, and serious gastrointestinal side effects when administrated in oral route. The water-soluble dendrimer-drug complexes can overcome these disadvantages by significantly enhancing the solubility of drugs, decreasing in vitro and in vivo release rate of the drugs from dendrimer matrixes, and increasing their bio-activity. These data provide a platform for the development of drug formulations in intravenous injection and ocular administration route.In Chapter 3, multi-dimensional nuclear magnetic response （NMR） techniques were employed to investigate the interactions between PAMAM dendrimers and drugs. In combination with solubility results, several rules are deduced. The results suggest that there are three types of interactions between dendrimers and drugs in the complexes: electrostatic interactions between cationic dendrimers and negatively charged drugs, hydrophobic interactions between relative non-polar cavities of dendrimer and hydrophobic drugs, and hydrogen-bond interactions between the cavities and drug molecules. Among these interaction mechanisms, the electrostatic interaction contributes more to the solubility enhancement of the drugs than hydrophobic interaction and hydrogen-bond interaction. Besides, higher generation dendrimers are more capable of encapsulating drugs than lower generation ones, while lower generation ones are much easier for the electrostatic attachment of drugs than higher generation ones.The interactions between PAMAM dendrimers and surfactants are investigated in Chapter 4. A new interaction model is proposed. Evidence from the multi-dimensional NMR studies suggests that the surfactant penetrate into the interior cavities of dendrimers. The dendrimer-surfactant-drug ternary systems are evaluated in drug delivery systems. The results show that dendrimer-surfactant aggregates enhance the drug loading efficiency of dendrimers, decrease the high cost of dendrimers, and release the drugs from the aggregate in a controllable manner. The new drug formulations based on dendrimer-surfactant aggregates is promising in transdermal and nasal administration routes in clinical trails.Chapter 5 deals with the potential administration routes of the dendrimer-based drug formulations. Take non-steroidal anti-inflammatory drugs for example, the in vitro release, pharmacodynamic and pharmacokinetic behaviors of the dendrimer-drug complexes are compared when administrated in oral route and transdermal route, respectively. The results show that the dendrimer-drug complexes are more suitable in transdermal route than in oral route, and can further increase the bioavailability of the drugs, prolong the effective time of drugs in blood, and enhance the patient compliance. Furthermore, the potential of dendrimers to be administrated in different routes with particular reference to oral, intravenous, transdermal, ocular, and nasal delivery systems are discussed.In Chapter 6, polymeric nano-platforms based on PAMAM dendrimers and biotin molecules are synthesized for cancer targeting therapy and diagnosis. As revealed by flow cytometry and confocal microscopy, the dendrimer-biotin conjugate exhibits much higher cellular uptake into Hela cells than the conjugate without biotin. The uptake is dose-dependent, incubation time-dependent, energy-dependent, and can be effectively blocked by biotin molecules. The results indicate that the biocompatible nano-platform is promising in cancer therapy and diagnosis. In addition, the advantages and disadvantages of several targeting ligand mediated targeting delivery systems are discussed, and an optimized biotechnology is proposed to enhance the targeting efficiency of small molecules such as folic acid and biotin, and to shorten the synthesis period of dendrimer-antibody conjugates.Chapter 7 summarizes the full dissertation and gives perspectives of dendrimers in biomedical fields. Although dendrimer-mediated drug delivery is in its infancy, it offers a number of attractive features. These nanomaterials are expected to play a key role in the fields of biomedicine, nanomedicine, and clinical therapy and diagnosis in the 21^st century. They provide uniform platforms for bioactive molecule attachment and have the ability to encapsulate or bind drugs through several mechanisms. They are useful additives in drug formulations for increasing the solubility, stability, bioavailability, cellular uptake, targeting ability and patient compliance of the administrated drugs, and for decreasing the drug resistance and irritation. Scientists in this field are now in the process of conducting preclinical tests to evaluate the safety of dendrimers in animals and human. We will really benefit from the dendrimer-based drug delivery systems in a near future.更多还原