我们已证实超声辐照可增加双配体载药纳米粒对乳腺癌耐药细胞MCF-7/Tax的敏感性，但体内应用需针对肿瘤环境进行改进。多药耐药是化疗失败的重要原因，乏氧微环境是肿瘤产生多药耐药和恶性进展的促成因素，通过氧供改善乏氧微环境可能改善治疗的反应性，进而对抗多药耐药。全氟碳化合物（Perfluorocarbon，PFC）在血液中弥散性差、对氧气溶解能力高，是较好的氧气载体。将氧气和气态PFC混合构建载氧微泡，在超声显像同时超声辐照爆破微泡，将氧气递送到肿瘤组织，是改善化疗抵抗的策略，但微泡到达肿瘤时氧含量难以维持较高水平。利用液态PFC携氧能力强，稳定性好，释氧充分且液气相变后显像好的特点，我们制备载氧相变纳米滴-携iRGD肽载药肝素纳米粒复合物，通过超声干预促进复合物相变及释氧、释药，研究氧气释放对肿瘤化疗及耐药性能的改善作用及机制，构建一种兼具高效药物运载及分子显像潜能的新型载药系统

It has been demonstrated in our previous experiments that ultrasound can increase the sensitivity of dual-ligand drug-loaded nanoparticles on MCF-7/Tax multidrug resistant breast cancer cells, but it needs to be improved according to the characteristic of tumor microenvironment for better application in vivo. Multidrug resistance (MDR) is an important reason for the failure of chemotherapy. Since hypoxic microenvironment in tumor contributes to MDR and malignant tumor progressing, it may improve the reaction to chemotherapy by increasing oxygen in tumor tissue thereby overcoming MDR. Perfluorocarbon (PFC) is a good oxygen carrier with a poor dispersion in blood and high solubility to oxygen. Oxygen combined with PFC to prepare oxygen-loaded microbubbles can deliver oxygen to tumor tissue and image at the same time assisted by ultrasound. It is an effective strategy to reduce chemotherapy resistance in tumor, however, the oxygen carried in microbubbles is limited and not enough to facilitate tumor therapy. Previous research have shown that liquid PFC not only exerts a high oxygen carrying capability and good stability, but also releases oxygen well and displays a good ultrasound imaging after liquid-gas phase transition. Here, we will prepare a complex composed of oxygen-loaded phase-change nanodroplets and iRGD-drug-loaded heparin nanoparticles through avidin-biotin linkage. The phase change of the complex and its release of oxygen and free drug assisted by ultrasound will be investigated. Importantly, we try to explore the mechanism of complex in improving tumor chemotherapy and overcoming multidrug resistance attributed to high level of oxygen delivery, constructing a novel drug delivering system with high chemotherapeutic drug carrying capability and good potential for ultrasound molecular imaging.