Dendritic Block Copolymer Micelles as New Targeted Drug Delivery Systems

有效递送癌症化疗药物的障碍是将毒性药物转运到特定的肿瘤细胞，确保癌细胞对药物的高摄取，同时避免非癌细胞。实现这种方法的一种方法是使用添加到纳米级药物外部的配体基团 承运人;然而，关于使这些配体相互作用最大化以实现功效的数量级改善和副作用的减少，还没有太多的了解。 这项工作的主要目标是合成新的两亲性线性树枝状嵌段共聚物，自组装在溶液状态下产生稳定的胶束与高度支化，致密的树枝状基团的外壳。由于树枝状外块的独特性质，这些胶束将充当具有高度可调的配体3D呈现的容器，使得能够产生具有均质或非均质表面的递送纳米颗粒，所述均质或非均质表面能够实现配体的簇呈现。细胞与配体相互作用的生物学研究表明，不仅化合价，但空间因素，如分支模式和本地集群的群体是重要的影响结合和下游信号传导过程。靶向的这一重要方面可能对从脂质体到无机纳米颗粒的所有类型的纳米颗粒递送系统具有潜在的重大影响。如果这种能力可以转移到药物递送载体，它可能会极大地影响靶向递送的功效和特异性。与所提出的系统的初步研究结果表明，配体聚类可以导致显着更高的胶束细胞摄取相比，均匀分布的配体。 第一个具体目标是合成优化的线性树枝状二嵌段共聚物系列中产生的哈蒙德组，由生物相容性的线性多肽疏水性嵌段和亲水性聚酯树枝状基元，靶向配体将通过PEG连接体共轭。研究了线性骨架修饰、直接药物偶联和疏水核内的光交联基团，以提高药物的载药量和缓释效果。将进行胶束稳定性和药物释放研究，以确定每个系统在生理和内体条件下的释放特征。这些研究的结果将用于指导进一步的共聚物的合成，并最终选择最有前途的共聚物体系进行进一步的研究。这项工作的第二个具体目的是通过使用混合胶束簇来检查化合价和配体簇的作用，以显著增强体外递送细胞毒性药物的功效，特别强调使用噬菌体展示方法发现的肽序列LyP-1，其对包括乳腺癌的肿瘤细胞和肿瘤淋巴细胞亚群上的p32表面受体表现出高度特异性识别。该系统将具有特殊的治疗和临床相关性，并将用于解决效价影响的普遍性 以及通过将该概念扩展到不同的受体类型而在配体呈递中聚类。本目标的结果将与最近获得的叶酸靶向胶束的结果进行比较，以确定聚类的显着性差异。在第三个具体目标中，将使用体内动物模型评估来自该分析的最佳胶束-药物纳米颗粒制剂。这些研究将集中在叶酸和LyP-1作为具有潜在临床意义的特异性肿瘤配体，重点是药代动力学、生物分布和代谢。 时间、器官特异性、药物载体的积累、肿瘤内摄取和肿瘤抑制以及细胞毒性的函数。

A barrier to the effective delivery of cancer chemotherapy drugs is the transport of the toxic drug to specific tumor cells, ensuring high uptake of drug by cancer cells while avoiding noncancerous ones. One means of accomplishing this method is the use of ligand groups added to the exterior of a nano-scale drug carrier; however, much is not understood about maximizing these ligand interactions to achieve orders of magnitude improvements in efficacy and reduced side effects. The primary objective of this work is the synthesis of new amphiphilic linear-dendritic block copolymers that self-assemble in the solution state to generate stable micelles with highly branched, dense dendritic groups in the exterior shell. Due to the unique nature of the dendritic outer block, these micelles will act as vessels with a highly tunable 3D presentation of ligand, enabling the creation of delivery nanoparticles with homo- or heterogeneous surfaces that enable cluster presentation of ligand. Biological studies of cellular interactions with ligands indicate that not only the valency but spatial factors such as branching mode and the localized clustering of groups are important in influencing binding and downstream signaling processes. This important aspect of targeting may have potentially significant impact on all kinds of nanoparticle delivery systems, from liposomes to inorganic nanoparticles. If this capability can be transferred to drug delivery vehicles, it may greatly impact efficacy and specificity of targeted delivery. Preliminary findings with the proposed systems suggest that ligand clustering can lead to significantly higher micelle cellular uptake compared to homogeneous distribution of ligand. The first specific aim is the synthetic optimization of a linear-dendritic diblock copolymer series generated in the Hammond group, consisting of a biocompatible linear polypeptide hydrophobic block and a hydrophilic polyester dendron to which targeting ligands will be conjugated via PEG linkers. Linear backbone modification, direct drug conjugation and photocrosslinkable groups within the hydrophobic core will be investigated to enhance drug loading and sustained release of drug. Micelle stability and drug release studies will be performed to determine release characteristics of each system under physiological and endosomal conditions. Results of these studies will be used to guide further synthesis of the copolymer and to ultimately select the most promising copolymer systems for further study. The second specific aim of this work is to examine the role of valency and ligand clustering through the use of mixed micelle clusters to significantly enhance efficacy in the delivery of cytotoxic drugs in vitro, with specific emphasis on peptide sequence, LyP-1, discovered using phage display methods, which exhibits a highly specific recognition to p32 surface receptors on a subset of tumor cells and tumor lymphatic cells including breast carcinomas. This system will be of particular therapeutic and clinical relevance, and will be used to address the universality of impact of valency and clustering in ligand presentation by extending the concept to different receptor types. Results of this Aim will be compared with recently obtained results from folate targeted micelles to determine differences in the significance of clustering. In the third specific aim, the best micellar-drug nanoparticle formulations from this analysis will be evaluated using an in vivo animal model. These studies will focus on both folate and LyP-1 as specific tumor ligands with potential clinical interest, with a focus on pharmacokinetics, biodistribution as a function of time, organ specificity, accumulation of drug carriers, intratumor uptake, and tumor inhibition as well as cytotoxicity.