用于癌症化疗的可注射酸敏感前药纳米体系及其温敏超分子水凝胶系统

Improving the drug concentration in tumor, facilitating the drug penetration, prolonging the drug exposure, reducing the drug-associated adverse effects as well as overcoming the multi-drug resistance are crucial approaches to achieve the successful cancer chemotherapy. The locoregional chemotherapy of nanoparticulate drug delivery systems is one of the most efficient routes to perform these roles. In this project, an unprecedented temperature-induced supramolecular hydrogel was developed, which was self-assembled by acid-responsive prodrug nanoparticles as driven by the hydrogen-bond and the hydrophobic interaction of nanoparticles under the stimuli of body temperature. The aggregation of high concentrated prodrug nanoparticles in aqueous solution retained sufficient drugs in tumor and greatly extended the drug effect time. The sustained dissociation of prodrug nanoparticles confirmed the spatial diffusion and penetration of drug depending on the EPR effect of tumor vessels, the active blood circulation in tumor and the diffusion of nanoparticles themselves. Furthermore, the prodrug nanoparticles could be uptaken by cells in the form of membrane-mediated endocytosis, bypassing the cell membrane-associated resistance mechanism, and then drugs would be rapidly released in lysosome triggered by the acid environment (pH 4-5) and diffused into nucleus to eliminate the cancer cells. The synthesis of prodrug amphiphiles, construction of prodrug nanoparticles and supramolecular hydrogel and the corresponding antitumor activity would be investigated. Additionally, the diffusion and permeation of nanoparticles in tumor and the combat of drug resistance were also evaluated. If satisfactory achievements were obtained in this project, the novel chemotherapy formulation developed would be promising in clinic.

提高肿瘤内的药物浓度、促进药物在肿瘤内的充分渗透、延长药物暴露时间、降低药物毒副作用以及克服癌细胞耐药性等都是癌症化疗成功的关键因素。高剂量纳米药物的局部化疗是实现这些目标的一种有效手段。本项目拟利用两亲性前药纳米粒自身的温敏特性，在氢键以及疏水相互作用的驱动下，高剂量酸敏感前药纳米粒自组装成温敏超分子水凝胶系统。在体内，水凝胶系统将前药纳米粒固定在肿瘤组织，提高局部药物浓度并延长与癌细胞作用时间。纳米粒长期缓慢、持续的解体，在肿瘤内依靠EPR效应，血液运输和渗透扩散，以内吞的形式进入癌细胞并在细胞内快速释放出药物分子，克服癌细胞细胞膜介导的耐药机制，最终取得化疗的成功。本项目将系统研究聚合物的合成、前药纳米体系的构建、温敏超分子水凝胶系统的组装及两种体系的体内外抗癌性能、纳米体系和药物在瘤内的扩散与渗透、抵抗耐药性效果。一旦取得突破性成果，则有助于开发具有良好临床应用前景的癌症化疗制剂。

国家癌症中心发表研究数据表明2015年中国癌症死亡人数大约为2814,000，新增癌症发病人数4292,000。化疗是临床治疗癌症的主要方式之一，目前小分子药物全身化疗的方式存在多次给药、药物循环时间短、肿瘤组织靶向效率低、细胞包吞量少、毒副作用大等缺陷，导致癌症化疗效果不是很理想。纳米药物可以解决小分子药物细胞包吞与组织渗透较差的问题，但是自身也存在药物负载量低、循环时间短等缺点。本项目首先针对纳米药物的缺点，开发了两种前药纳米药物。以靶向肿瘤血管内皮细胞表面过度表达的神经毡蛋白-1的RGDK修饰的阿霉素与聚乙二醇嵌段高分子（RGDK-PEG-CAD）纳米药物为例，此纳米药物的药物负载量达14.6%，RGDK的修饰赋予其肿瘤组织靶向能力和良好的组织渗透效果，用来连接聚乙二醇与阿霉素的顺式乌头酰基使得纳米药物具有酸敏感释放的特性。与小分子阿霉素和未修饰靶向基团的纳米药物相比，该纳米药物能够将更多的药物递送至肿瘤组织，同时延长其滞留时间。在后续的工作中，我们将负载阿霉素的纳米药物通过温敏自组装的方式，形成了可注射的水凝胶剂型，用于肿瘤的局部化疗研究。在体内，水凝胶系统将纳米药物固定在肿瘤组织，纳米药物的持续解离，在肿瘤内依靠EPR效应，血液运输和渗透扩散，以内吞的形式进入癌细胞并在细胞内快速释放出药物分子，提高药物在肿瘤组织的滞留作用时间与浓度，持续的杀伤肿瘤细胞。小鼠肿瘤模型研究结果表明，该水凝胶系统可以延长药物在肿瘤内的存留时间达21天以上，能够有效的抑制肿瘤生长，同时降低药物的毒副作用。然后，我们将阿霉素与紫杉醇共负载到温敏可注射水凝胶中，实现了两种不同治疗机制药物的协同负载与独立释放。体内动物实验结果表明，两种药物联合化疗的方式与单一药物高剂量治疗相比具有更好的肿瘤生长抑制效果，小鼠存活时间长达29天以上，在治疗周期内未见动物死亡。这些研究可以为癌症化疗提供潜在的临床转化前景的纳米药物与水凝胶制剂。