肿瘤微环境H2O2触发的信号循环放大程序化控释纳米体系用于肿瘤协同治疗的研究

The smart nano-drug delivery systems have gained considerable attentions in recent years, using tumor specific microenvironment as the stimulus based on the differences between tumor and normal tissue. However, the differences are often not significant enough for accurately controlled drug release. The strategies of how to use the trace differences between tumor and normal tissue as stimuli and further amplify this trace signal, are the key to improve therapeutic efficacy, while reduce other side effects. This project aims to design a “Smart nano-drug delivery system with the ability of in situ circularly amplification of H2O2 that initiated by the trace amount of H2O2 in tumor microenvironment” for the programmable controlled drug release to achieve synergistic therapy of cancer. This programmable controlled release nano-system can significantly enhance the specificity and controllability of drug release in the tumor site, and can effectively integrate the “H2O2 toxicity therapy”, “starvation” therapy, hypoxia-activated “chemotherapy” and “enhancing chemotherapy response” together to increase tumor therapeutic efficacy. The stimuli amplification, controlled drug release, synergistic therapy and corresponding mechanisms of the nano-system will be studied both in vitro and in vivo, and the biocompatibility also will be systematically investigated. Therefore, this project can provide significant new insights for cancer treatment.

利用肿瘤组织与正常组织之间的差异，以肿瘤特定微环境为信号源的智能纳米递药系统是近年研究热点。然而肿瘤组织与正常组织之间的差异往往不够显著，使得控释行为难以精确进行；如何利用肿瘤组织与正常组织之间的细微差异作为引发，进一步放大它们之间的差异，是进一步提高疗效、降低毒副作用的关键。本项目拟构建“以肿瘤微环境H2O2为触发信号，且兼具肿瘤内H2O2信号循环放大功能和H2O2信号刺激响应释放功能的程序化纳米控释体系”，实现具有协同治疗功能的多种肿瘤药物的程序化靶向释放。该程序化控释体系，能显著增加肿瘤部位药物释放的特异性与可控性，并能有效的协同H2O2毒性治疗、“饥饿”治疗、缺氧活化的“化疗”及“化疗增敏”于一体，以增加肿瘤疗效。通过体外、细胞、动物等不同层面，研究该纳米体系的信号放大功能、控制释放功能、协同治疗作用及相应机制，并系统探讨其生物相容性。因此，本项目的顺利开展可为肿瘤治疗提供新思路。

针对目前肿瘤微环境响应的纳米药物控释系统中存在的刺激源信号不强， 药物在肿瘤和正常组织中的释放差异不显著，治疗药物之间难以有效协同等问题，本项目构建了一类“以肿瘤微环境 H2O2为触发信号，且兼具肿瘤内 H2O2信号循环放大功能和 H2O2信号刺激响应释放功能的程序化纳米控释体系”，实现缺氧活化药物（AQ4N）和缺氧改善药物（ACF）的程序化协同治疗。开展的主要工作如下：（1）设计合成了一种过氧草酸酯（PO）桥接的聚乙二醇（PEG）和聚己内酯（PCL）三嵌段ABA型嵌段共聚物，利用自组装形成智能化纳米囊泡（PAG）并负载葡萄糖氧化酶（GOD）和AQ4N。PAG可以有效地避免GOD和AQ4N在循环过程中泄露，当其在肿瘤部位富集后，肿瘤细胞内高水平的H2O2可以促使囊泡表面部分PO键的氧化断裂，增加膜的渗透性，葡萄糖分子得以跨膜进入囊泡内部，被 GOD氧化分解并生成大量的H2O2，这一过程不仅会消耗肿瘤细胞内的葡萄糖，也会造成细胞的氧化损伤，促使囊泡完全降解，释放负载的药物AQ4N。此外，葡萄糖的氧化也会消耗胞内的氧分子，加剧乏氧微环境，促使释放的AQ4N转化为胞毒性的AQ4，发挥化疗作用。（2）在前述工作基础上，进一步将PAG与DSPE-PEG-N3共杂化组装，并利用点击反应在其表面修饰具有肝癌靶向功能的适配体（TLS11a），实现两种功能互补药物拉帕醌和替拉扎明在肝癌部位的靶向共输送。由于肿瘤细胞内NQO1酶表达较高，可以诱导拉帕醌生成ROS造成细胞凋亡，同时由于耗氧使氧含量下降，级联引起下游药物替拉扎明在缺氧的环境中转化成毒性代谢产物进一步放大对肿瘤细胞的损伤。综上所述，本项目利用ROS信号放大和级联程序化控释体系，能显著增加肿瘤部位药物释放的特异性与可控性，并能有效的协同 H2O2毒性治疗、“饥饿”治疗、缺氧活化的“化疗”及“化疗增敏”于一体，以增加肿瘤疗效。