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，该脂质体可以在磁力作用下有效地递送到实体瘤中，并表明静脉给药的磁性ADR脂质体可以有效地递送到植入磁铁的骨肉瘤中。为了临床应用，我们研究了隐身脂质体（磁性ADR - peg -脂质体）的效率和可控制的磁性系统对瘤外磁场的影响，而不是在实体瘤中植入磁铁。此外，我们还开发了磁性阳离子脂质体作为基因治疗的载体，并在体外检测了靶向基因表达的效率。ADR磁性脂质体给药1 h后血液中ADR浓度下降，而ADR peg磁性脂质体给药1 h后血液中ADR浓度相对保持不变。这一结果表明，血液循环潴留将得到改善。肿瘤外磁场对肿瘤的靶向效率低于肿瘤内磁场。我们开发了由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/脂质体复合物。我们使用质粒LacZ作为报告基因。这些复合物在磁力作用下转染到骨肉瘤细胞中。转染后3 h内LacZ的表达水平与未转染时比较，前者较高，但6 h后两者的表达水平基本相等。我们的研究结果表明，聚乙二醇修饰的隐形脂质体可以逃避肝脏库普弗细胞的摄取，该系统可以减少化疗的副作用。对于这种治疗的临床应用，我们认为有必要研究可控磁系统的最佳条件。由于靶细胞周围有高浓度的DNA/脂质体复合物，因此认为磁性阳离子脂质体的基因转染效率更高。

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.