靶向相变型载药PLGA纳米粒超声分子显像及定向药物递送研究

Ultrasound molecular imaging and targeted therapy have been hindered by microbubbles for their congenital defects. Firstly, microbubbles can't pass through the endothelial gap of tumor vessels on account of their large size, which restrict thier targeting efficiency. Secondly, the stability of microbubbles is poor and the circulation time is short in vivo. Lastly, microbubbles suffer from poor drug/gene loading efficirncy for targeted therapy in coupled with focused Ultrasound triggered.The development of appropriate probes is urgent to the technologies of ultraound molecular imaging and targed therapy. In this project, we will develop a folate receptor targeted, 10-HCPT loaded and perfluorocarbon encapsuled nanoparticles that can generate phase transition with the application of low focus ultrasound and so as to be applied to ultrasound molecular imaging and targeted chemisry therapy. The targeted iamging and therapy effect will be studied in vivo and in vitro xenotransplanted tumor models. We aim to resolve the essential problems in ultrasound molecular imaging and therapy technology and provide a new means and method for tumor diagnosis and treatment.

超声微泡因以下严重缺陷是超声分子成像及靶向治疗发展的瓶颈：①微泡粒径较大，通常达微米级，较难通过血管内皮细胞间隙，从而影响其靶向性；②结构的稳定性差，体内循环时间短；③携带药物或基因的装载率较低。本课题基于前期的研究基础，通过成熟的双乳化法，采用高分子PLGA为膜材料，连接肿瘤表面分子量小且成熟的靶点叶酸配体、包裹可相变的液态氟碳及单次治疗剂量低的抗肿瘤药物10-羟基喜树碱，研制一种靶向肿瘤细胞、可液气相转化的载药纳米粒，并联合低强度聚焦超声及诊断超声在多种肿瘤模型上研究其靶向显像、定向释药及分析其治疗效果，以解决目前超声分子显像与治疗中的核心问题。

靶向微泡携带药物或基因联合超声靶向破坏微泡（Ultrasound targeted microbubble destruction,UTMD）技术，可显著提高靶器官的药物/基因浓度。由于微泡自身不可避免的缺陷，限制了其进一步的应用。缺氧是肿瘤常见的一种状态，是影响肿瘤治疗效果的因素之一，也是肿瘤转移、进展、耐药、残留的重要原因。针对以上问题，本课题选用cRGD肽作为微球的靶点，以聚乳酸-羟基乙酸共聚物（PLGA）作为壳膜材料，包裹可携带氧气的全氟溴辛烷(PFOB)及较小剂量及可达到治疗目的的化疗药物10-HCPT，在低强度聚焦超声的激发下实现可控释药。.本课题采用双乳化法制备非靶向纳米微球，以碳二亚胺法链接cRGD制备成靶向的cRGD-PLGA@10-HCPT-PFOB纳米微球。其平均粒径（322.03±5.34）nm，平均表面电位（-1.55±0.10）mV；扫描电镜示靶向纳米粒呈球形；透射电镜示其为核壳结构；10-HCPT包封率和载药量分别为（81.34±2.28）%和（13.24±1.24）%。共聚焦显微镜观察及流式细胞仪显示其对卵巢癌SKOV3细胞有良好的靶向性。充入氧气后的靶向纳米微球有明显缓释显像，且能实现B超/CT的双模态显像。体内治疗实验显示尽管不能完全消灭肿瘤，但在抑瘤率及肿瘤生长曲线相比对照组有明显的统计学差异，为肿瘤的早期检测、多模态显像、靶向治疗开辟了新的思路，具有良好的应用前景。