主链含铂光敏聚阳离子复合基因纳米颗粒的联合治疗研究

Polymeric nano-carrier mediated co-delivery of drugs and genes for cancer therapy is limited by low drug loading capacity and uncontrolled release fashion, difficulty for genes’ endosomal escape and unpacking. There is correspondingly a clear incentive to develop new polymeric co-delivery systems for simultaneous high loading capacity and controlled release of both drugs and genes. Anti-cancer prodrugs, photo-activated platinum(IV) complexes, are creatively used as photosensitizers and hydrophobic monomers to prepare photo-sensitive (from UV to NIR light) platinum-backboned polycation for gene delivery. After complexing with gene, the formed nanoparticles are polymeric combination therapy systems. When the nanoparticles were internalized by cancer cells and irradiated with feasible light, photo-activated platinum(IV) complexes would release oxidizing azidyl radicals to assist gene escape from endosomes/lysosomes by membranes disruption, and simultaneously photo-reduction to release active platinum(II) anti-cancer drugs after light-induced fast degradation of the polycation backbones to improve gene unpacking. Then the synergistic effect of platinum drug and gene could be fully realized, resulting in enhanced anticancer efficacy and even cisplatin resistance reversal. Taking advantages of simultaneous high loading capacity and controlled release of both drug and gene, and tunable sensitive wavelengths of the polymeric co-delivery systems, the light-controlled combination therapy efficacy and synergy mechanisms are in-depth studied, providing theoretical guidance and experimental basis for the design of other high-level polymeric nano-carrier mediated co-delivery systems of drugs and genes for cancer therapy.

高分子化疗和基因药物纳米共输送体系用于癌症治疗受到化疗药物担载量低、释放不可控，基因药物内涵体逃逸与卸载困难等问题限制，开发新型高分子纳米共输送体系同时实现两类药物的高效担载和可控释放具有非常重要的意义。本项目创新性地将抗癌“前药”，四价光敏铂化合物，作为光敏剂和疏水组分引入高分子主链，制备了一类从紫外光到近红外光敏感的主链含铂聚阳离子；静电复合基因药物后形成的纳米颗粒即可实现联合治疗。该纳米颗粒内吞入癌细胞后，光照下四价光敏铂化合物会释放叠氮自由基破坏内涵体膜实现载体内涵体逃逸；同时还会光还原成二价铂药，诱导载体主链结构迅速崩解，实现光控铂药释放和基因卸载；充分发挥两类药物间协同增效作用，逆转肿瘤耐药性。利用该体系中两类药物同时高效担载和光控释放以及光控波长可调的优势，深入研究其联合治疗效果与协同作用机理，为更高水平的高分子化疗和基因药物纳米共输送体系设计提供理论指导和试验依据。

金属铂类化合物是目前应用最广泛的一类化疗药物，相对于经典的二价铂药，四价铂前药具有毒性较低的优势，且可以在外界光照条件下或肿瘤细胞内较高还原环境下被还原成相应的二价铂药。针对目前存在的高分子纳米载体共输送化疗和基因药物担载量较低、内涵体逃逸与卸载困难等问题，本项目主要开展一系列主链含铂光敏聚阳离子复合基因纳米颗粒的联合治疗研究，具体包括以下内容：.开发了一个光可激活的Pt(IV)前药骨架阳离子聚合物(PtCP)纳米颗粒共递送si(c-fos)和Pt (IV)前药物来协同治疗耐药卵巢癌。c-fos基因在基于铂药的化疗中涉及DNA合成和修复, 常过表达于铂类化疗失败患者的卵巢癌细胞和肿瘤组织中，将铂药与c-fos沉默的基因治疗结合可以有效逆转卵巢癌的耐药性。通过静电相互作用，PtCP组装纳米颗粒(NPPtCP)可以有效地复合si(c-fos)，形成复合纳米颗粒(NPPtCP/si(c-fos))。将能够靶向CD44受体的负电荷聚合物（PEG接枝的透明质酸(HA-PEG, HP)）进一步包覆在NPPtCP/si(c-fos)，得到具有高稳定性和靶向肿瘤的纳米粒CNPPtCP/si(c-fos)。CNPPtCP/si(c-fos)具有极高的载药量和光控药物释放行为，肿瘤部位蓄积较多，可诱导溶酶体逃逸和si(c-fos)的卸载，有效抑制DNA修复相关基因(c-fos)的表达，从而有效逆转卵巢癌的耐药性，增强光照条件下卵巢癌细胞(A2780DDP)及其皮下异种移植裸鼠模型的抗肿瘤疗效。.进一步我们以上转换纳米粒（UCNP）和光敏铂聚前药（PtP）为基础制备了一个多功能纳米共递送系统（UCNP@Pt@siRNA），可以同时实现三模式成像及NIR光激活Pt(IV) 前药和siRNA释放。将光敏感Pt(IV) 前药聚合物PPt接枝到UCNP的表面，随后通过静电相互作用复合siRNA得到UCNP@Pt@siRNA。该UCNP@Pt@siRNA在体内具有良好的上转换荧光成像（UCL）、核磁共振成像（MRI）及CT成像能力。在980 nm NIR光激发下，可以发射出紫外到可见光，激活表面PPt，释放出高毒性的Pt(II)。同时，由于表面聚合物结构的改变，促进了siRNA释放。基于以上优秀的性能，可以实现多模式介导下光控按需释放化疗药物与基因药物，为癌症联合治疗策略提供了一种更便捷路径。