188Re标记免疫靶向磁性纳米微粒及其生物学分布

目的研究^188Re标记具有HER-2／neu癌基因靶向特异性的Herceptin免疫磁性纳米微粒及其在小鼠体内的生物学分布。方法利用戊二醛作为交联剂，将人源性单克隆抗体Herceptin与化学修饰的磁性纳米微粒进行连接，构建免疫磁性纳米微粒。采用直接标记法将^188Re标记到免疫磁性纳米微粒上。采用羰基铼标记法，以fac-[^188Re（CO）3（H2O）3]^＋作为放射性标记前体，对表面固载组氨酸的磁性纳米微粒进行标记。分别测定所制备^188Re标记物的标记率和体外稳定性及免疫磁性纳米微粒的单克隆抗体免疫活性，并观察^188Re标记的磁性纳米微粒及免疫磁性纳米微粒的小鼠体内生物分布。结果经扫描电镜证实免疫磁性纳米微粒的单个粒径大小平均为60nm，而表面固载组氨酸的磁性纳米微粒的粒径平均为30nm。^188Re对Herceptin、免疫磁性纳米微粒及固载组氨酸的磁性纳米微粒的标记率均〉90％，在小牛血清中具有良好的体外稳定性，并且磁性纳米微粒上连接的单克隆抗体仍保持较高的免疫活性。小鼠体内分布实验显示^188Re标记的磁性纳米微粒及免疫磁性纳米微粒在血液中有较高的放射性分布且血循环时间较长，同时两者在肝内均有较多的摄取。结论^188Re标记的磁性纳米微粒及免疫磁性纳米微粒在体外及动物体内较稳定，无明显的^188Re脱落。可用于下一步荷瘤裸鼠体内的研究。

188Re labeling and biodistribution of magnetic nanoparticles for the tumor targeting

Objective To prepare ~(188)Re labeled monoclonal antibody(Herceptin)-coated magnetic uanoparticles for tumor targeting and to study its biodistribution in mice.Methods Herceptin and histidine were covalently linked to the amine group upon silica-coated magnetic nanoparticles modified by N-[3-(tri- methyoxysilyl)propyl]-ethylenediamine using glutaraldebyde method.The Heceptin-coated magnetic nano- particles and Herceptin were radiolabeled with ~(188)Re by a direct labelling method,whereas the histidine-coa- ted magnetic nanoparticles was radiolabeled with ~(188)Re using fac-[~(188)Re(CO)_3(H_2O)_3]~+as a precursor. The labelling efficiency and immunoreactivity as well as labelling stability were determined.Also,the bio- distribution of ~(188)Re-magnetic and ~(188)Re-Herceptin-magnetic nanoparticles were observed in mice.Results Herceptin-coated magnetic nanoparticles was characterized by transmission electron microscope(TEM)with diameter about 60 nm,while histidine-coated magnetic nanoparticles about 30 nm.The labeling efficiency for ~(188)Re-Herceptin,~(188)Re-magnetic nanoparticles and ~(188)Re-Herceptin-magnetic nanoparticles were all> 90% and had a better stability in vitro.The immunoreaetivity of Herceptiu linked to magnetic nanoparticles was still high.The biodistribution in mice was shown that ~(188)Re-magnetic nanoparticles and ~(188)Re-Herceptin- magnetic nanoparticles had higher radioactivity levels in blood.Magnetic nanoparticles with diameter of 30 or 60 nm had a long half-life in blood stream and were accumulated in liver.Conclusion The efficiency and stability of labelling Herceptin-coated magnetic nanoparticles and labeling magnetic nanoparticles with ~(188)Re are suitable for in vivo study in tumor-bearing nude mice models.