【摘要】 目的：采用定点标记技术构建靶向紧密连接蛋白18.2（Claudin 18.2,CLDN18.2）的正电子发射体层成像（positron emission tomography,PET）探针⁶⁸Ga-THP-ACN376，并评估其体内外生物学性能。方法：以THP-Mal作为螯合剂，与靶向CLDN18.2的纳米抗体ACN376进行定点偶联，合成前体化合物THP-ACN376，对偶联后的前体进行⁶⁸Ga放射性标记。通过放射性薄层色谱法（radio thin layer chromatography,Radio-TLC）测定探针的标记率、放射化学纯度及体外稳定性，并进行探针在BALB/c裸小鼠的micro-PET/计算机体层成像（computed tomography,CT）显像实验，评估其体内药代动力学特性与靶向能力。结果：⁶⁸Ga-THP-ACN376显示出高标记率（>99%）、高放射化学纯度（>99%）以及较高的比活度16 GBq/μmol，并且在生理盐水、5%人血清白蛋白（human serum albumin,HSA）和磷酸盐缓冲溶液（phosphate buffered saline,PBS）中保持稳定。Micro-PET/CT结果表明探针⁶⁸Ga-THP-ACN376在小鼠体内代谢符合纳米抗体的代谢规律，且在胃部的摄取在0.5 h至2 h逐步提高，2 h胃部最大标准摄取值(maximum standard uptake value,SUV_max)为1.35±0.07。结论：本研究以定点标记的方法成功构建了靶向CLDN18.2探针⁶⁸Ga-THP-ACN376，标记率高，具有显著的稳定性及靶向性，是一种有潜力的PET探针，可用于CLDN18.2蛋白表达水平的检测。更多还原

【Abstract】 Objective: To construct a Claudin 18.2（CLDN18.2）-targeted positron emission tomography（PET） probe, ⁶⁸GaTHP-ACN376, using a site-specific labeling technique, and to evaluate its in vitro and in vivo biological performance. Methods: The chelator THP-Mal was site-specifically conjugated to the CLDN18.2-targeting nanobody ACN376 to synthesize the precursor compound THP-ACN376, which was subsequently radiolabeled with ⁶⁸Ga. The labeling efficiency, radiochemical purity, and in vitro stability of the probe were determined by radio thin layer chromatography（Radio-TLC）. Micro-PET/computed tomography（CT） imaging was performed in BALB/c nude mice to assess its in vivo pharmacokinetic properties and targeting capability. Results: ⁶⁸Ga-THP-ACN376 exhibited high labeling efficiency（>99%）, high radiochemical purity（>99%）, and a high specific activity of 16 GBq/μmol. It remained stable in saline, 5% human serum albumin（HSA）, and phosphate buffered saline（PBS）. Micro-PET/CT results demonstrated that the metabolism of the probe in mice followed the typical profile of nanobodies, with tracer uptake in the stomach gradually increasing from 0.5 to 2 h. The maximum standardized uptake value SUV_max in the stomach at 2 h was 1.35±0.07. Conclusion: This study successfully constructed a CLDN18.2-targeted PET probe, ⁶⁸Ga-THP-ACN376, using a site-specific labeling method. The probe demonstrates high labeling efficiency, remarkable stability, and significant targeting ability, showing great potential for detecting CLDN18.2 protein expression levels.更多还原