99Tcm-MAG3-RRL肿瘤靶向肽的标记和性质鉴定

将具有肿瘤靶向性的精氨酸-精氨酸-亮氨酸（RRL）多肽与双功能螯合剂MAG₃相连，摸索其螯合⁹⁹Tc^m的适宜标记条件并评价探针的体外稳定性。标记利用SnCl₂还原法进行⁹⁹Tc^m标记，对影响标记的主要变量因素分别进行探究以获得适宜标记条件，采用纸层析法测定标记率和放射化学纯度。实验所得MAG₃-RRL纯度为98.94%，适宜标记条件下，标记率为93.67%±1.10%，纯化后放射化学纯度为94.32%±0.19%（n=3）。⁹⁹Tc^m-MAG₃-RRL在生理盐水和50%牛血清白蛋白（BSA）中放置，6 h内放射化学纯度均大于90%（n=3），在半胱氨酸溶液中的最高置换率为0.57%±0.21%，生理盐水对照为0.41%±0.04%（n=3，P＞0.05）。⁹⁹Tc^m-MAG₃-RRL的脂水分配系数为lg P=-0.15±0.01（n=3）。结果表明：MAG3可成功连接RRL多肽，并能进一步提高标记率；探针制备方法简单快速，体外稳定性好，为进一步的生物学实验提供了良好的基础。

Labeling and Characterization of 99 Tcm-MAG3-RRL Tumor Targeting Peptide

Arginine-arginine-leucine(RRL) a tumor targeting peptide is designed to link the bifunctional chelator mercaptoacetyltriglycine(MAG₃), aiming to explore the labeling conditions of ⁹⁹Tc^m and to evaluate the stability of this probe in vitro. Then ⁹⁹Tc^m was labeled through the SnCl₂ reduction method, and the main factors affecting the labeling were investigated respectively to obtain the suitable labeling conditions. The paper chromatography was used to determine the labeling rate and radiochemical purity. As a result, the purity of MAG₃-RRL is 98.94%. Under the suitable labeling conditions, the labeling rate is 93.67%±1.10%, and the radiochemical purity is 94.32%±0.19%(n=3). When⁹⁹Tc^m-MAG₃-RRL is placed in normal saline at room temperature and 50% BSA at 37 ℃, the radiochemical purity of⁹⁹Tc^m-MAG₃-RRL is more than 90% (n=3) within 6 hours. The highest replacement rate of⁹⁹Tc^m-MAG₃-RRL is 0.57%±0.21% in cysteine solution, and 0.41%±0.04% in normal saline control(n=3, P>0.05). The distribution coefficient lg P of⁹⁹Tc^m-MAG₃-RRL is -0.15±0.01(n=3). In conclusion, the results show that MAG3 can successfully be connected to RRL polypeptide and further improve the labeling rate, and the preparation method of⁹⁹Tc^m-MAG₃-RRL is simple and fast.⁹⁹Tc^m-MAG₃-RRL probe has good stability in vitro, which provides a good basis for further biological experiments.