【作者】 郭新东；

【导师】 钱宇；

【作者基本信息】 华南理工大学 ， 化学工程， 2010， 博士

【摘要】 利用化学产品工程的理论和方法,依据目标药物性质和最终的性能要求,设计了新型的纳米胶束药物传输系统,多尺度探讨了体系的微观、介观结构与性能之间的关系。纳米胶束药物传输系统属于复杂的多相多组分体系,其性能不仅与载体材料、药物等组分的性质有关,还由体系微/介观结构、药物与载体相容性等决定。因此,研究系统微/介观结构与性能的关系对药物传输系统的设计与开发具有重要的意义。针对疏水性化学药物的性质,以及细胞内外pH值的差异,以疏水性药物阿霉素(doxorubicin, DOX)为模型药物,设计并合成了胆固醇-组氨酸-精氨酸三嵌段多肽共聚物作为药物的载体材料。该共聚物在溶液中通过自扩散形成纳米胶束,其中,胆固醇构成胶束的内核,用来装载疏水性DOX;组氨酸作为pH敏感层,在pH 7.4(人体正常血液环境)下表现为疏水性,也可用来包载药物,同时使胶束结构紧密,控制药物的释放,而在pH 5.0(细胞内涵体pH值环境)下表现为亲水性,使胶束由紧密结构向松散结构转变,为DOX的释放提供了扩散通道,加速DOX的释放;精氨酸基团具有细胞穿透功能,分布于胶束的外表面,增强胶束穿过细胞膜进入细胞的能力,进而提高药物的利用率。利用介观模拟方法研究了载体材料多肽分子与药物之间的相互作用、药物在胶束中的分布状况以及pH值对胶束结构的影响等。制备了载阿霉素胶束,并对其结构和性能进行了表征,包括载药胶束的结构形态、粒径分布、zeta电位、pH敏感性、释药性能以及毒性评价等。运用数学模型,对阿霉素的释放曲线进行了理论分析,探讨了影响药物释放的主要因素。基因作为一类特殊的药物,与传统药物相比,具有作用特异、靶向性好、敏感、毒副作用低等诸多优点,近年来在肿瘤治疗上也取得了长足的进展。本研究将胆固醇-组氨酸-精氨酸三嵌段多肽共聚物胶束也用于基因的传输。其中,组氨酸具有内涵体释放DNA的功能;通过控制pH值,使精氨酸带正电荷,与DNA通过静电结合形成稳定的复合物,另外,精氨酸还具有细胞穿透功能,可有效提高基因表达效率。另外,本研究设计并合成了具有alpha螺旋结构的多肽作为基因的载体材料。具有alpha螺旋结构的多肽可有效穿透细胞膜而不引起细胞毒性,进而增加基因表达效率。设计的alpha螺旋结构的多肽主链由CKHLAKALAKALAC构成,其中半胱氨酸(C)可通过二硫键相互交联,形成具有alpha螺旋状的主链结构,支链由组氨酸(H)、赖氨酸(K)、天冬氨酸(N)和RGD靶向基团构成,其中H用于内涵体释放DNA,K用于提供正电荷与DNA结合,N的作用是为靶向基团提供作用空间。本文对以上两种多肽聚合物及其载基因复合体的结构和性能进行了研究,包括复合体结构形态、粒径分布、与基因结合强度、多肽二级结构等,并在HepG2、HEK293和4T1三种细胞系中评价了多肽对基因的表达效率和毒性。本文还运用介观模拟的方法详细探讨了药物传输系统的结构-性能关系,直观描述实验难以观察到的现象,以协助药物传输系统的设计与开发,有效缩短开发周期。以疏水性药物紫杉醇为模型药物,研究了聚乙二醇-聚乳酸( poly(ethylene oxide)-b-poly(lactide), PEO-b-PLA)载药体系的介观相行为和载药颗粒微观结构-性能的关系。根据组分配比对载药微颗粒形貌的影响,绘制了PEO-b-PLA载阿霉素体系的相图,研究了聚合物旋光性和分子量对载药微颗粒微结构的影响,并根据载药颗粒微观结构预测其释放行为。以疏水性药物硝苯地平为模型药物,PLA为载体,聚乙烯醇(poly vinyl alcohol, PVA)为稳定剂,研究了药物、PLA和PVA含量对载药微颗粒形貌的影响,获得形成球形载药颗粒的参考配方,并提出载药颗粒形成的机理模型。本研究将实验分析、计算机模拟和理论分析相结合,深入探讨了药物传输系统中微/介观结构与宏观性能之间的关系,为药物传输系统的产品设计与开发提供了新的设计思路和方法。更多还原

【Abstract】 Based on the theories and methods of chemical product engineering, novel drug/gene delivery systems were designed and developed, which can meet the requirement of desired drug/gene. The releationship between micro-/meso-structure and performance of drug carriers was also investigated using multi-scale methods. Due to the complexity of drug delivery system (DDS), the desired performance of DDS is decided not only by the formulation of systems, but the most important by the micro-structure and compatibility of carriers and drugs, which is remarkably influenced by the molecular structure of carrier and the formulation of systems. Thus, the relationship between structure and performance is significant to chemical product design and development in DDS.Doxorubicin (DOX) was selected as the model drug. Based on the character of DOX and the pH difference between inside and outside of celles, cholesterol conjugated His10Arg10 (HR20) and His10Arg5 (HR15) were designed and synthesized as the drug carriers. These amphiphilic peptides are able to self-assemble into cationic micelles in aqueous solution. Cholesterol, an essential constituent in mammalian cell membranes, is selected as the hydrophobic core for carrying drugs. The pH-sensitive histidine residues distribute in the middle layer of micelles. This layer is hydrophobic at the physiological environment (pH 7.4) to prevent the release of DOX. However, it converses to hydrophilic ones by protonation of imidazole groups once internalized and transferred to a lysosome (pH 5.0), leadiing to the faster release of DOX. The cell-penetrating arginine residues were selected as the outer layer, which can improve the bioavailability of DOX. The interaction between peptides and DOX, effect of pH on the micelle structure, etc, were investigated using mesoscale simulation. DOX-loaded micelles were prepared and characterized by experimental techniques, such as particle size, zeta potential, SEM, AFM, drug release profiles, cytotoxicity, etc. In addition, the mechanism of drug release was also investigated using mathematics modelling.The development of gene delivery system is an important theme due to its safety and the cost of manufacture. In this work, the micelles self-assembled from HR15-Chol and HR20-Chol were also used for gene delivery. Cholesterol was used for improving the stability of core/shell structure, histidine was employed for endolysosomal release of genes, and cell penetrating arginine is for DNA binding. In addition, peptides with alpha-helical structure were designed and synthesized for gene delivery. The backbone of alpha-helical peptides was CKHLAKALAKALAC, in which, the two cysteine residues could be self-crosslinked to di, tri- and tetra-peptides. The branch was composed of histidine, lysine, asparagines, and RGD group. The lysine residues were used for DNA binding, histidine residues were employed for endolysosomal release of genes, asparagines residues could provide the spacer for RGD targeting group. The peptides/DNA complexes were prepared and characterized by a variety of experimental techniques, such as particle size, zeta potential, SEM, DNA binding, gene expression efficiency, cytotoxicity, etc.The relationship between structure and performance was investigated using mesoscale simulation method. Paclitaxel (PTX) was selected as a model drug. The phase behavior of PTX-loaded poly(ethylene oxide)-b-poly(L-lactide) (PEO-b-PLA) in mixed solvent (water and N,N-dimethylformamide (DMF)) was studied. And a phase diagram of PTX-loaded PEO-b-PLA in the sovent was mapped. The effect of chirality and molecular weight of PLA segments on the micro-structure of PTX loaded nanoparticles were also studied. Another hydrophobic drug, nifedipine, was also selected as a model drug. The effect of composition on the formation of PLA microsphers was studied, based on which a phase diagram for the formation of spherical microparticles was mapped. Finally, the mechanism of spherical microparticles was proposed, which can guide the developing of DDS.In this work, experimental research, computer simulation, and theoretical analysis were employed to investigate the relationship between structure and performance with several case studies, which provided a novel technique and method for designing chemical products in drug/gene delivery systems.更多还原