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目的 探索抗体生物素化的条件、MR预定位增强方法和增强特点 ,以达到提高MR免疫成像敏感性的目的。方法 (1)将抗癌胚抗原 (CEA)单克隆抗体CL-3 和生物素酯 (NHS LS biotin) ,按 1/ 30～ 5 0摩尔比 ,在碱性条件下活化。 (2 )GdCl3 和二乙三胺五乙酸 生物胞素 (diethylenetriaminepentaaceticacid biocyin ,DTPA B)反应后 ,用G 10凝胶层析法去除游离的Gd3 + 离子。 (3)将动物分为3组 :预定位组 ,抗体对照组和Gd DTPA组。进行平扫 ,注射Gd对比剂增强后 2 0min、2h、8h及 2 4h ,共 5次扫描 ,测定各时间点肿瘤信号强度。结果 (1)CL-3 单克隆抗体在生物素化后 ,每个抗体可结合 11～ 2 3个生物素分子 ,抗体活性高达 94 9%。 (2 )预定位法对肿瘤有特异性增强作用 ,在注射钆二乙三胺五乙酸生物素 (gadolinium diethylenetriaminepentaaceticacid biotin ,Gd DTPA Bt) 2 0min ,肿瘤信号强度明显升高 ,以后呈缓慢下降趋势 ,在 2 4h后仍可见到有差别。 (3)预定位法有信号放大作用 ,强化率为抗体直接标记法的 2 4倍。结论 预定位法对荷人大肠癌裸鼠肿瘤有特异性增强作用和信号放大作用 ,优于传统的抗体直接标记法。
Objective To explore the conditions of biotinylation of antibodies, MR pretargeting enhancement methods and enhanced features to achieve the purpose of improving the sensitivity of MR imaging. Methods (1) The anti-carcinoembryonic antigen (CEA) monoclonal antibody CL-3 and NHS LS biotin were activated at alkaline conditions at a molar ratio of 1/30 to 50. (2) GdCl3 and diethylenetriaminepentaacetic acid biocyin (DTPA B) were reacted and free Gd3 + ions were removed by G 10 gel chromatography. (3) Animals were divided into 3 groups: pre-positioning group, antibody control group and Gd DTPA group. The plain scan was performed. After injection of Gd contrast agent was enhanced for 20 min, 2 h, 8 h, and 24 h, a total of 5 scans were performed, and the signal intensity at each time point was measured. Results (1) After the biotinylation of CL-3 monoclonal antibody, each antibody could bind 11 to 23 biotin molecules, and the antibody activity was as high as 94%. (2) The prepositioning method had a specific enhancement effect on tumors. After injection of gadolinium diethylenetriaminepentaacetic acid biotin (Gd DTPA Bt) for 20 min, the signal intensity of the tumor increased significantly and then decreased slowly. Differences can still be seen after 24 hours. (3) The pre-positioning method has a signal amplification effect and the enhancement rate is 2 4 times that of the direct antibody labeling method. Conclusion The prepositioning method has specific enhancement and signal amplification effects on human colorectal cancer tumors in nude mice, which is superior to traditional direct antibody labeling methods.