逐级pH响应PEG可脱落肿瘤靶向纳米给药系统的构建及作用机制研究

With development of material sciences, the problems of traditional chemotherapeutic formulations such as the poor water solubility and poor selectivity for tumor cells have been partly solved by the emrgence of nanoscale drug delivery systems (NDDS). Polycation nanoparticles are easily taken up by negatively charged tumor cells, however, the positive charge on the surface also leads the carrier to be rapidly cleared during the circulation by the reticuloendthelial system. In addition, the efficacy of the drug is also limited by the defects such as low drug loading and poor stability in the body to some extent. In view of the above problems, this topic design a stepwise pH-sensitive targeted nanoparticles with sheddable PEGylated profile, it does not affect the uptake of cells while increasing drug loading, stability, and circulation time in the body. Further studies will focus on: ①developing PAE modified with small molecule cholesterol as the hydrophobic core, and FA-PEG-DA containing β-carboxylic amide group as hydrophilic shell; ②constructing nanoparticles loaded with paclitaxel, and to carry out its physical and chemical properties; ③evaluating the antitumor activities both in vitro and in vivo, and antitumor mechanisms of the nanoparticles. This study provides theoretical basis and practical experience for the targeted delivery of antitumor drugs.

基于高分子材料的纳米药物传递系统可有效解决传统化疗药物溶解性低、毒副作用大等缺点，已成为一种颇具潜力的化疗药物传递工具。聚阳离子纳米粒易于被带有负电荷的肿瘤细胞摄取，但表面的正电荷同时也会使得载体在体内循环过程中被快速清除；此外，载药量低、体内稳定性差等问题也一定程度上影响了药物的疗效。针对以上问题，本课题拟构建一种具有逐级pH响应、PEG化外壳可“脱落”的靶向纳米粒，在提高载药量、稳定性和体内循环时间的同时不影响细胞的摄取。主要研究内容：合成小分子胆固醇修饰的PAE疏水内核与β-羧酸酰胺化的FA-PEG-DA亲水外壳；制备载多烯紫杉醇的靶向纳米粒并对其理化性质进行考察；进行体内外抗肿瘤活性评价，解析纳米粒的抗肿瘤作用机制。本课题为抗肿瘤药物的靶向递送提供理论与实验依据。

构建既能在体循环过程中稳定存在，又能高效渗透肿瘤组织，进而蓄积在肿瘤细胞的靶向递药系统是肿瘤治疗的关键所在。本项目通过静电相互作用将叶酸修饰肿瘤酸度敏感的β-羧酰胺功能化 PEG 层引入pH敏感的聚阳离子载药内核表面，成功制备了一种具有逐级pH响应PEG“可脱落”多功能纳米粒（FPDPCNPs），用于抗肿瘤药物多烯紫杉醇（DTX）的靶向递送。经过筛选与优化，获得了粒径均一（182.38±1.57 nm）、表面荷负电（-13.65±0.86 mV）的载药多功能纳米粒（FPDPCNPs/DTX）。该纳米粒具有明显的pH敏感释药行为，在生理环境下（pH 7.4）释药缓慢，在微酸性环境下（pH 5.5）释药速度明显加快。采用共聚焦显微镜和流式细胞仪观察纳米粒在肿瘤细胞内的吸收情况，结果显示FPDPCNPs能够增加MCF-7细胞对DTX的摄取，主要通过内吞途径进入细胞。细胞毒性及细胞凋亡结果均显示FPDPCNPs能够显著增强DTX对肿瘤细胞的杀伤能力。采用4T1乳腺癌荷瘤小鼠对纳米粒的抗肿瘤活性进行评价，结果显示FPDPCNPs/DTX能有效抑制肿瘤细胞的生长，延长荷瘤小鼠的生存期。同时，活体成像结果显示，FPDPCNPs高效富集于肿瘤区域，具有很好的体内肿瘤靶向性。本项目的成功实施，为抗肿瘤药物的靶向递送研究了奠定理论和实践基础。