基于iRGD靶向载药脂质体-微泡复合体的超声成像引导给药治疗肿瘤的研究

It often limits the effect and applicability of many chemotherapeutic drugs due to the following some reasons: 1) drugs are not to be observed in patients' body in a real-time manner;2)they are difficult to be released by a controllable way; and 3) they are not to be able or just partly to infiltrate tumors. Microbubbles are ideal ultrasound molecular probes and ultrasound-activated drug carriers due to their characteristics of ultrasound imaging, drug carriers and ultrasound-activated drug release. iRGD is a peptide which can target and bind integrin receptors such as αvβ3 and Neuropilin-l. More importantly, iRGD can enhance drug delivery inside tumor via a coadministration and conjugated injection. Therefore, taking these advantages of microbubbles and iRGD peptides, we propose a novel agent and method in order to achieve the aim of ultrasound-guided drug delivery for treating early-stage tumor. In this project, drug (paclitaxol) will be encapsulated into iRGD-targeted liposomes and further conjugated onto the surface of microbubbles via biotin-avidin linkage to get iRGD-targeted drug-loaded liposome-microbubble complexes, which can actively target tumor vascular endothelial cells through the interaction between iRGD and αvβ3/Neuropilin-l. The drug accumulation at the tumor site can be observed by ultrasound molecular imaging in a real-time manner and the drug release can be achieved by ultrasound-targeted microbubble destruction technology. The released drugs can further infiltrate the tumors with the help of iRGD peptides, and thus improves the effect of drugs. Our previous study demonstrated that liposome-microbubble complex may increase drug-loaded amount of microbubbles and enhance the efficacy of paclitaxol. This project will further combine ultrasound molecular imaging and ultrasound-assisted drug delivery to achieve ultrasound-guided drug delivery for treatment of early-stage tumors and to enhance the effect of drugs.

化疗药物难于实时追踪、可控释放及渗透到肿瘤内部在一定程度上限制了药物的疗效和应用价值。微泡具有造影、载药以及超声释药等特性，是一种理想的可用于超声成像引导给药治疗的声敏药物载体。iRGD具有靶向肿瘤血管内皮细胞整合素受体和加速药物肿瘤内递送等功能。本项目提出一种基于iRGD和载药微泡来实现超声成像引导给药治疗肿瘤的超声可视化药物及其方法，拟通过构建iRGD靶向载紫杉醇的脂质体-微泡复合物，利用iRGD的靶向作用将载药脂质体-微泡复合物靶向肿瘤新生血管，通过超声成像实时观察其在肿瘤组织的聚集，再通过超声爆破载药微泡复合物释放药物，释放的药物在iRGD的协助下加速渗透到肿瘤内部从而提高药物的疗效。我们前期的研究证实载紫杉醇脂质体-微泡复合物联合超声能够提高药物的抗肿瘤效果。本项目的研究将进一步把超声分子成像与超声给药治疗结合起来，有望实现肿瘤早期的超声成像引导的可视化给药治疗并增强药物的疗效。

构建载药量高、靶向性好、声学性能优良的靶向载药微泡是实现超声分子影像引导的药物递送增强药物疗效的关键，本课题利用iRGD具有靶向肿瘤血管内皮细胞整合素受体和促进药物肿瘤渗透的功能，首先通过化学方法合成iRGD修饰的DSPE-PEG2000-iRGD脂肽，进而制备iRGD靶向载药脂质体，通过HPLC测定其对紫杉醇的包封率为83.22%，利用生物素-亲和素桥接系统构建获得iRGD靶向载紫杉醇的脂质体-微泡复合物，借助细胞靶向性实验确认了该靶向微泡复合物具有良好的血管内皮细胞靶向性和结合特异性，利用体外仿体、体内动物进一步证实该靶向复合物具有良好的超声成像性能，实现了肿瘤的超声分子成像检测，注射该靶向复合物的肿瘤超声信号强度比对照提高了8倍；优化得到超声促发载药脂质体-微泡复合物释放药物的条件参数，使得超声促发药物释放量达到84.77%，有效提高了肿瘤细胞对药物的摄取效率和浓度；通过体内动物实验表明iRGD 靶向载药脂质体-微泡复合物联合超声可有效增强药物的抗肿瘤效果。综合上述结果，本研究基本实现了超声分子影像引导的给药治疗并显著增强了药物的疗效，为探讨肿瘤超声成像引导的可视化给药治疗奠定了坚实的基础。