ROS响应树枝状大分子的高效制备及其构建基因-药物纳米复合载体的抗肿瘤性能研究

Cancer is one of the deadly diseases of the world. Safe and well effective methods for treating cancer have great significance for the health condition of residents. Dendrimers are structurally uniform and capable of efficiently as carriers; however, the difficulties in fabrication and biodegradation restrict their wide application. For delivery systems, carriers with 100 nm will be accumulated in the tumor more efficiently via the enhanced permeability and retention (EPR) effect, but they are too large to diffuse into tumor tissues composed of tightly packed cells in a dense extracellular matrix. In view of the above problems, based on our research about intelligent stimulus responsive gene carriers, this proposal provides a new idea to construct a kind of “cluster bomb” nanoassembly by loaded ROS-responsive dendrimer/DNA complexes and the angiotensin inhibitor losartan with pH-sensitive liposome for tumor therapy. We demonstrate a highly efficient approach to synthesis of reactive oxygen species (ROS)-responsive dendrimer with thioacetal group by selective double addition of the thiol to alkyne as a gene carrier. The pH-sensitive “cluster bomb” nanoassembly would be accumulated in the tumor by EPR effect and subsequent decomposed to release losartan and dendrimer/DNA complexes, which act as “bomblets”. Losartan will increase vascular perfusion and lower the tumor interstitial pressure by decreasing the collagen level of tumor. This regulation will improve the penetration of the “bomblets” into the tumor tissue. The ROS-responsive feature of the dendrimer will boost specific and efficient disassembly of the dendrimer/DNA complexes in ROS-rich cancer cells for effective gene delivery. This project will broaden the application of dendrimers in the biomedical materials field, and the combination strategy of gene therapy and antihypertensive drugs might be a promising tactic for better treatment of solid tumors.

加快研究肿瘤诊疗新方法对于提高居民健康水平迫在眉睫。针对传统树枝状大分子制备繁琐、难以降解等缺点，以及载体在肿瘤部位滞留与穿透能力对粒径要求的矛盾关系，本项目拟使用pH敏感脂质体包裹活性氧（ROS）响应降解树枝状大分子基因载体和降压药氯沙坦，制备一种定点投放、内部渗透、快速释放的“集束炸弹”式纳米复合载体用来进行肿瘤治疗。利用炔-巯基高效加成反应制备以硫代缩醛结构为支化点的树枝状大分子作为基因载体，硫代缩醛结构将赋予基因载体在ROS高表达肿瘤细胞中快速降解的性能。“集束炸弹”式纳米复合载体通过EPR效应富集于肿瘤部位后，在微酸环境中响应投放“小炸弹”-基因载体和氯沙坦；氯沙坦可降低I型胶原的合成来降低肿瘤间质压，有利于“小炸弹”深入肿瘤内部发挥治疗作用。此项目的实施将推动树枝状大分子在生物医用材料领域的应用，并为降压药物协同进行肿瘤治疗提供具有重要科学意义的理论应用模型。

为了提高化疗效果，降低化疗过程中伴随的严重的毒副作用，本项目构建了一系列高效低毒的药物/基因载体，并探索了载体与药物分子之间的作用机制以及协同药物在化疗过程中所发挥出的协同效应。通过实验与计算机模拟相结合的方法，详细研究并阐述了PAMAM树枝状大分子作为载体与3种常用化疗药物分子（阿霉素、紫杉醇、喜树碱）之间的作用力与空间构型。将树枝状大分子与海藻酸相结合，制得高效低毒的基因载体，探究了树枝状大分子作为阳离子电解质进行基因传递的性能。通过以缩硫酮键连接的HCPT为前药，制备了系列ROS响应的多药共递送载体，实现HCPT与地塞米松的同时递送，阐明了地塞米松作为协同药物在肿瘤化疗中促进疗效、降低副作用的机制。通过本项目的研究，开发了新型的药物/基因载体，明确了非共价键结合下载体与药物分子之间的作用关系以及化疗协同药物的作用机制，为将来药物/基因载体的设计与制备打下了基础。