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目的:制备一种针对整合素αM(CD11b)受体的预定位分子探针n 68Ga-1，4，7-三氮杂环壬烷-1，4，7-三乙酸-甘氨酸-精氨酸-谷氨酸-精氨酸-谷氨酸-十一聚乙二醇-1，2，4，5-四嗪/CD11b抗体片段-反式-环辛烯[n 68Ga-NOTA-Polypeptide-PEGn 11-Tz/anti-CD11b-F(ab′)n 2-TCO]，并通过microPET显像探讨其作为CD11b受体靶向分子探针的可行性。n 方法:采用免疫荧光法检测小鼠巨噬细胞RAW264.7膜表面CD11b受体的表达情况。将CD11b抗体与TCO连接，并通过酶切法得到anti-CD11b-F(ab′)n 2-TCO。对配体NOTA-Polypeptide-PEGn 11-Tz进行n 68Ga标记，检测标记率以及放化纯。进行预定位细胞结合实验，建立CT26结肠癌荷瘤裸鼠模型，进行预定位生物分布以及microPET显像实验。用免疫组织化学检查验证肿瘤微环境中CD11bn +细胞的浸润情况。用单因素方差分析比较组间差异。n 结果:免疫荧光检测结果显示RAW264.7细胞膜表面高度表达CD11b受体。十二烷基硫酸钠聚丙烯酰胺凝胶电泳(SDS-PAGE)验证成功合成anti-CD11b-F(ab′)n 2-TCO。放射性配体n 68Ga-NOTA-Polypeptide-PEGn 11-Tz标记率约为94.6%，比活度为7.0~7.4 MBq/μg，放化纯大于95%。预定位细胞结合实验证实该分子探针与CD11b受体有较好的靶向性。生物分布及显像结果示，在预定位4、12以及24 h时间间隔下，模型鼠肾放射性摄取较高，表明分子探针通过肾代谢；肿瘤/肌肉比值为9.23±1.45、12.53±1.36和10.74±1.11(n F＝848.8，n P<0.05)；在预定位12 h注射放射性配体后1 h显像，肿瘤与非靶器官对比度最佳：肿瘤标准摄取值(SUV)为0.67±0.12，肌肉SUV为0.09±0.04。免疫组织化学结果示，CT26结肠癌微环境中浸润了大量CD11bn +细胞。n 结论:成功合成预定位分子探针n 68Ga-NOTA-Polypeptide-PEGn 11-Tz/anti-CD11b-F(ab′)n 2-TCO，该标记物对CD11b阳性结肠癌具有较强的靶向能力，有望用于靶向CD11b受体的体内示踪。n “,”Objective:To prepare a n 68Ga labeled probe targeting integrin alpha M(CD11b) receptor, namely n 68Ga-1, 4, 7-triazacyclononane-1, 4, 7-triacetic acid-Glycine-Arginine-Glutamate-Arginine-Glutamate-polyethylene glycoln 11-1, 2, 4, 5-terazine/CD11b antibody-F(ab′)n 2-trans-cyclooctene (n 68Ga-NOTA-Polypeptide-PEGn 11-Tz/anti-CD11b-F(ab′)n 2-TCO), and to explore its feasibility as a molecular probe for CD11b receptor through microPET imaging.n Methods:Immunofluorescence was used to detect the expression of CD11b on the surface of RAW264.7 cell. CD11b specific monoclonal antibody (M1/70) was conjugated with TCO, and anti-CD11b-F(ab′)n 2-TCO fragment was obtained. The ligand NOTA-Polypeptide-PEGn 11-Tz was labeled with n 68Ga, and its specific activity and radiochemical purity were detected. Pre-targeted cell binding experiment was conducted to evaluate the binding ability of molecular probe. CT26 colon cancer bearing mouse models were established, and then pre-targeted biodistribution and imaging experiments were performed. Immunohistochemical experiment was used to verify the expression of CD11b receptor in tumor. The one-way analysis of variance was used to compare the data.n Results:The results of immunofluorescence demonstrated CD11b receptor was highly expressed on the surface of RAW264.7 cell. Anti-CD11b-F(ab′)n 2-TCO fragment was verified by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). n 68Ga-NOTA-Polypeptide-PEGn 11-Tz was successfully synthesized, with the labeling efficiency of 94.6%. The specific activity was 7.0-7.4 MBq/μg, and the radiochemical purity was higher than 95%. Pre-targeted cell binding experiment confirmed that the molecular probe bound to the CD11b receptor. The biodistribution and imaging experiments showed that the kidney radioactivity uptake was high at pre-targeted 4, 12 and 24 h intervals, which proved that probe was excreted through the urinary system. In addition, molecular probe had higher radioactive uptake at the tumor site, with the tumor/muscle ratios of 9.23±1.45, 12.53±1.36 and 10.74±1.11 (n F=848.8, n P<0.05). When the radioligand was injected 1 h after the pre-positioned 12 h interval, the images contrast was the best, with the standardized uptake value (SUV) in tumor and muscle of 0.67±0.12, 0.09±0.04, respectively. Immunohistochemistry verified the highly expression of CD11b receptor in tumor.n Conclusions:The pre-targeted molecular probe n 68Ga-NOTA-Polypeptide-PEGn 11-Tz/anti-CD11b-F(ab′)n 2-TCO is successfully synthesized. The molecular probe has targeting ability for CD11bn + colon cancer, and is expected to be used as a tracer targeting CD11b receptor n in vivo.n