自满足式肿瘤过氧化氢响应性嵌段聚合物多功能纳米载体的构筑及应用

As compared with normal tissues, tumor tissue microenvironment shows distinct features which offer possibility for endogenous stimuli-responsiveness of the responsive polymers in the extracellular environment. However, the differences between normal tissues and tumor tissues are very subtle hampering the in vivo applications of stimuli-responsive polymers as drug nanocarriers. Herein, we propose the strategy of specific upregulation of tumor tissue signals to amplify the signal differences between normal tissues and tumor tissue via multifunctional polymeric nanoparticles. Vitamin c (Vc) moiety-containing molecule, L-ascorbyl palmitate (PA), is proposed to incorporate into nanocarriers to specifically upregulate hydrogen peroxide (H2O2) concentration for simultaneous H2O2-responsiveness in tumor tissues. Two designs will be performed. First, amphiphilic block copolymers, PEG-b-PBEMA (PEG is polyethylene glycol, PBEMA is obtained from polymerization of arylboronic ester-modified 2-hydroxyethyl methacrylate at its hydroxyl) will be prepared and used to encapsulate PA, which can upregulate H2O2 concentration of tumor tissue and subsequent H2O2-triggered release of quinone methide that has been confirmed to decrease antioxidant capability of tumor cells, achieving synergistically amplified oxidation therapy of cancers. Second, arylboronic ester-caged cell penetrating molecules will be used to modify PEG-b-PLA block copolymers. After self-assembly into polymeric micelles, paclitaxel and PA will be simultaneously encapsulated. As H2O2 concentration increases in tumor tissue, the cell-penetrating molecules can be efficiently activated for efficient cellular internalization of nanocarriers. Combined oxidation-chemotherapy of cancers can be achieved. This project will validate a novel strategy to exert stimuli-responsiveness in extracellular environment of the tumor tissues for the applications of stimuli-responsive polymeric nanocarriers.

肿瘤组织细胞外微环境相对于正常组织存在信号特异性明显，响应性高分子可在组织层面响应等诸多优势，但信号差异微小，为响应性高分子应用带来困难。本项目拟通过在过氧化氢(H2O2)响应性高分子纳米载体中，引入可选择性调高肿瘤H2O2浓度的含维生素C(Vc)基团分子，实现高效肿瘤组织H2O2响应性。拟以两种设计验证该设想：一、制备含聚乙二醇(PEG)和芳基硼酸酯修饰的两亲性嵌段共聚物胶束，并负载抗坏血酸棕榈酸酯(PA)，调高肿瘤组织H2O2浓度的同时，H2O2响应性释放4-亚甲基环己-2,5-二烯酮减弱癌细胞抗氧化能力，实现肿瘤协同放大氧化疗法；二、以芳基硼酸酯保护的细胞穿膜分子修饰PEG-b-PLA(PLA为聚丙交酯)，用于同时负载紫杉醇和PA。调高肿瘤组织H2O2浓度的同时激活细胞穿膜分子，实现高效细胞内吞及联合肿瘤氧化-化疗。该项目的实施有望为环境响应性高分子载体的体内应用提供新的响应性策略。

嵌段聚合物前药是将抗肿瘤药物通过化学键接枝到嵌段聚合物上，其优点是在递送过程中结构稳定，不易出现泄漏的现象，大大降低药物毒副作用，提高递送效率。但是稳定的结构也导致其在目标位置药物释放困难。肿瘤组织细胞外微环境相对于正常组织存在显著的微环境差异，可以作为响应性聚合物前药释放药物的刺激因素，但这种差异通常难以达到高效切断化学键释放药物的程度，为响应性药物释放带来困难。在该项目的支持下，针对该问题，我们取得了系列成果：（1）提出并构建了兼具调高肿瘤氧化环境并氧化响应性释放药物的多功能高分子前药纳米载体，分别研究了载体负载抗坏血酸棕榈酸酯、拉帕醌、或者葡萄糖氧化酶。所发展的体系显著提高了肿瘤H2O2浓度，高浓度的H2O2一方面可以促进氧化响应性药物释放，同时也增加了癌细胞对药物的敏感性，最终提升治疗效果。（2）在嵌段聚合物前药纳米载体中引入响应性基元，通过肿瘤组织微环境响应性表面电荷转变，例如咪唑基团的引入，可以实现肿瘤微酸性响应表面电荷由电中性转变为正电荷，从而大幅度增加细胞内吞效率，利用用胞内环境促进高效的响应性药物释放。该体系具有高效克服一系列体内生理环境障碍的多功能性，相对于目前在临床实验阶段的一些嵌段聚合物前药来说，在提高药物递送效率和治疗效果方面，性能提升显著。（3）发展了一类新型的聚合物放疗增敏剂，通过将甲硝唑接枝到聚乙二醇-嵌段-聚谷氨酸侧链，调节接枝效果和自组装形态，提升了肿瘤富集和渗透效率。相对于目前临床使用的小分子放疗增敏剂（例如甘胺双唑钠），显著提高了肿瘤放疗增敏效果。在本项目的支持下发表影响因子>6 的SCI 论文19篇，共发表SCI 论文23 篇，中文综述一篇，授权发明专利4 项。培养毕业博士生7 人，硕士生2 人。在国内外相关会议中，做邀请报告10余次。