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目的 :研究克服99mTc标记抗癌胚抗原 (carcinoembryonicantigen ,CEA)单抗体内生物半衰期长、血液廓清速度慢、晚时相放射性信号弱等缺点的方法 ,用直接标记法进行了99mTc标记抗CEA抗体C5 0片断Fab’的研究。方法 :经胃蛋白酶切得的C5 0片断F(ab’) 2 用适量的 2 巯基乙醇还原 ,SephadexG5 0柱分离获得纯度大于 90 %的Fab’片断。取 0 .6～ 1.0mg纯化的片段Fab’(体积 <1.0ml) ,加入 0 .4～ 0 .8mg葡庚糖酸钠及新鲜配制的SnCl2溶液 5～ 10 μg ,然后加入新鲜淋洗的Na99mTcO4 淋洗液 ,反应 10～ 15min。用高压液相色谱监测放化纯度和抗体纯度。荷CL 187(结肠癌 )裸鼠静脉注射99mTc Fab’ ,观察标记抗体片段在不同时相的体内分布。结果 :标记率大于 90 %。荷瘤裸鼠体内分布结果显示 :在注射99mTc Fab’ 4h后瘤 /血、瘤 /肝、瘤 /肺放射性摄取比分别为 1.93、2 .35和 3 .13 ,2 4h后则分别为 4.91、2 .6 2和 5 .2 6 ,肿瘤的ID(% ) / g(每克组织的摄取率 )为 2 .73。虽然注射99mTc标记的全抗C5 0后 2 4h ,肿瘤的ID(% ) /g高达 12 .5 ,但瘤 /血比值仅为 1.5 1。结论 :采用99mTc直接法标记Fab’是成功的 ,肿瘤与非肿瘤 (T/NT)的比值除肾外在早期 4h时均大于 2 .0 ,明显高于全抗的T/NT比值 ,有利于在注射后短时
OBJECTIVE: To overcome the shortcomings of the long biological half-life, low blood clearance rate, and weak late radioactive signal of 99mTc-labeled anti-carcinoembryonic antigen (CEA) single antibody, 99mTc-labeled anti-CEA antibody C5 was directly labeled. Study of 0-fragment Fab’. METHODS : The p50 digested by pepsin F(ab’) 2 was reduced with an appropriate amount of 2-mercaptoethanol, and Sephadex G50 column was used to obtain the Fab’ fragment with a purity greater than 90%. Take 0.6-1.0 mg of purified Fab’ fragment (<1.0 ml volume), add 0.4-0.8 mg of glucoheptonic acid sodium and freshly prepared SnCl2 solution 5-10 μg, then add freshly washed Na99mTcO4. Eluent, reaction 10 ~ 15min. Radiochemical purity and antibody purity were monitored by high pressure liquid chromatography. The CL 187 (colon cancer) nude mice were injected with 99mTc Fab’ intravenously to observe the in vivo distribution of the labeled antibody fragments at different phases. Result : The mark rate is greater than 90%. The distribution of tumor-bearing nude mice showed that the radioactivity uptake ratios of tumor/blood, tumor/liver, and tumor/lung after 99mTc Fab’ injection for 4 h were 1.93, 2.35, and 3.13, respectively, and 4.91 after 24 h. For 2.62 and 5.26, the tumor ID (%)/g (uptake rate per gram tissue) was 2.73. Although the tumor ID (%)/g was as high as 12.5 after injection of 99mTc-labeled anti-C5O for 24 h, the tumor-to-blood ratio was only 1.5 1 . Conclusions: The direct 99mTc labeling of Fab’ was successful. The ratio of tumor to non-tumor (T/NT) was greater than 2.0 in the early 4 h in the kidney, which was significantly higher than the T/NT ratio of the whole antibody. Shortly after injection