Application of Magnetic Stealth Liposomes in External Magnetic Field for Gene Therapy -Research for the Clinical Application of New Drug Delivery System-

我们研制了磁性ADR脂质体，在磁力作用下可以有效地输送到实体瘤中，表明静脉注射磁性ADR脂质体可以有效地将ADR输送到植入磁铁的骨肉瘤中。为了研究DDS的临床应用，我们研究了隐形脂质体(磁性ADR聚乙二醇脂质体)的效率和通过可控的磁系统而不是通过在实体瘤中植入磁铁来提高肿瘤外磁场的效率。此外，我们还研制了磁性阳离子脂质体作为基因治疗的载体，并检测了体外靶向基因表达的效率，给药后1小时，磁性ADR脂质体的血药浓度有所下降，但磁性ADR聚乙二醇脂质体的血药浓度相对保持不变。这一结果表明，血液循环中的滞留将得到改善。瘤外磁场对肿瘤的靶向效率低于瘤内磁场。我们研制了由DC-CHOL和DOPE(摩尔比为3：2)组成的磁性阳离子脂质体，并制备了DNA/脂质体复合体。我们以LacZ为报告基因。在磁场力作用下，将这些复合体导入骨肉瘤细胞。LacZ表达的Lebel值与无磁场组相比，前者在3h内较高，但在6h后两者的Lebel值基本相同，提示修饰聚乙二醇制得的隐形脂质体具有逃避肝脏Kupffer细胞摄取的作用，可减少化疗的副作用。对于这种治疗方法的临床应用，我们认为必须考察可控磁铁系统的最佳条件。由于靶细胞周围DNA/脂质体复合体浓度较高，故认为磁性阳离子脂质体可以提高基因的转染率。

We developed magnetic ADR liposomes which could be effectively delivered to solid tumors under magnetic force and indicated that intravenously administered magnetic ADR liposomes could be used to effectively deliver ADR to osteosarcoma implanted with a magnet. For clinical application of this DDS, we investigated the efficiency of stealth liposomes (magnetic ADR PEG-liposome) and that of magnetic field of extratumor by the controllable magnetic system not by the implantation of a magnet in a solid tumor. Furthermore we also developed magnetic cationic liposomes as a vector for gene therapy, and examined the efficiency of targeting of gene expression in vitro.The concentration of ADR in blood after administration of magnetic ADR liposomes became decreased one hour later, but that of magnetic ADR PEG-liposomes was maintained comparatively. This result demonstrated the retainment in blood circulation would be improved. The magnetic field of extratumor caused the less efficiency of targeting to tumor than that of intratumor. We developed the magnetic cationic liposomes composed of DC-chol and DOPE (3 : 2 by molar ratio) and prepared DNA/liposome complex. We used plasmid LacZ as a reporter gene. These complexes were transfected to osteosarcoma cells under magnetic force. Compared the lebel of LacZ expression with that of under no magnetic force, the former was higher within 3 hours after transfection but the both lebels of 6 hours later were almost equal.Our results suggested that the stealth liposomes by modificated of PEG resulted in the evasion from uptake by Kupffer cells of the liver and this system would reduce side effects of chemotherapy. For the clinical use of this treatment, we thought to have to examine the optimal condition of controllable magnet system. It was considered gene transfection became more efficient by magnetic cationic liposomes according to the high concentration of DNA/liposome complex around the targeted cells.