血小板靶向载药系统的研制及其抗白血病效应的研究

More attention has been focused on the targetd therapy of cancer including leukemia in resent years. Transferrin receptors (TfR) were found to be highly expressed on the surface of tumor cell in many studies. Our experimental group cooperation with the University of California, Berkeley propose a new targeted drug delivery system: 1.Transferrin (Tf) will be linked to the platelet surface to direct to the leukemia cells; 2.Kabiramide C (KabC) inhibits the regulation function of actin filament dynamic, then inhibits the activation of platelets to extend its lifetime to 9 days in blood circulation; 3. A fluorescence form of KabC (TMR-KabC) allows us to visualize the drug-loaded platelet in cell culture and after injection into mice; 4. A signle platelet will contain about 60 million molecules of drug, excessively higher than that with any nanoparticles. In this study we present a newtype active targeted delivery system of TMR-KabC-platelet-Tf to deliver a variety of different antitumor drugs to target leukemia cells. The targeted anti-tumor ability against types of leukemia cells and animals will be observed. Biocompatibility, pharmacokinetic and side effects will also be studied at the same time. TMR-KabC-platelet-Tf will be an effective approach to the clinic targeted therapy of leukemia.

肿瘤(包括白血病)靶向治疗是目前研究的热点，近年国内外研究发现肿瘤细胞膜表面转铁蛋白受体（TfR）高表达。本实验组与美国加州大学伯克利分校生物工程系合作提出一个新型靶向载药系统：1.血小板的膜表面修饰转铁蛋白（Tf）形成主动靶向性载体；2.环内酯C（KabC）可有效抑制细胞肌动蛋白纤维动力调节功能，处理血小板可以抑制其活化，使血循环中的载药血小板寿命延长至正常生理9天左右；3.将荧光标记物TMR联接KabC后处理血小板，便于我们观察载药血小板处理细胞及动物模型小鼠后的情况；4.血小板可包含6千万的药物分子，远远高于任何纳米颗粒。因此，本研究拟构建一种对白血病细胞具有主动靶向性能的新型药物传递体系TMR-KabC-血小板-Tf，应用此载体携载不同的抗肿瘤药物，观察其对白血病细胞和动物的靶向治疗作用，同时对其生物相容性、药代动力学和毒副作用进行深入的研究，为临床肿瘤的靶向治疗提供新的有力手段.

提高药物对肿瘤组织的靶向性，减少其在非靶向部位的聚集是提高抗肿瘤药物疗效及安全性的关键。目前研究人员越发聚焦于生物体来源的细胞、分子等作为载体构建纳米药物传输系统。我们的研究利用血小板对肿瘤细胞的天然的亲和粘附力，外加转铁蛋白（transferrin, Tf）的修饰，从而能够在被动和主动的双重动力下转运药物靶向肿瘤细胞。通过细胞实验，动物实验研究其治疗肿瘤（白血病、多发性骨髓瘤）的疗效及体内靶向分布性。本课题利用KabC有效地抑制血小板胞浆内肌动蛋白的聚合反应，成功制备KabC-血小板-Tf及KabC-纳米血小板-Tf靶向载体。激光共聚焦显微镜动态观察结果表明，KabC-血小板-Cy5 Tf 能够特异性粘附在表面高表达转铁蛋白受体的肿瘤细胞 RPMI8226和K562细胞表面。动物活体成像结果表明，KabC-血小板-Cy7 Tf 在荷异种种植瘤的小鼠体内的半衰期可达144 h，能够特异性聚集在体内种植瘤部位，并且能够显像早期颅内 RPMI8226细胞种植瘤。通过温和超声破碎制备的KabC-纳米血小板的平均直径约70~250 nm，膜结构完整。进一步的动物实验结果表明 KabC-纳米血小板-Cy7 Tf 能够靶向显像小鼠体内 RPMI8226 细胞种植瘤，并且对小鼠皮下 RPMI8226 细胞种植瘤具有较好的肿瘤抑制作用。