Department of Nuclear Medicine, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
J Nucl Med. 2010 Mar;51(3):454-61. doi: 10.2967/jnumed.109.066902. Epub 2010 Feb 11.
Several methods have been developed to label peptides with (18)F. However, in general these are laborious and require a multistep synthesis. We present a facile method based on the chelation of (18)F-aluminum fluoride (Al(18)F) by 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA). The method is characterized by the labeling of NOTA-octreotide (NOTA-d-Phe-cyclo[Cys-Phe-d-Trp-Lys-Thr-Cys]-Throl (MH(+) 1305) [IMP466]) with (18)F.
Octreotide was conjugated with the NOTA chelate and labeled with (18)F in a 2-step, 1-pot method. The labeling procedure was optimized with regard to the labeling buffer, peptide, and aluminum concentration. Radiochemical yield, specific activity, in vitro stability, and receptor affinity were determined. Biodistribution of (18)F-IMP466 was studied in AR42J tumor-bearing mice and compared with that of (68)Ga-labeled IMP466. In addition, small-animal PET/CT images were acquired.
IMP466 was labeled with Al(18)F in a single step with 50% yield. The labeled product was purified by high-performance liquid chromatography to remove unbound Al(18)F and unlabeled peptide. The radiolabeling, including purification, was performed in 45 min. The specific activity was 45,000 GBq/mmol, and the peptide was stable in serum for 4 h at 37 degrees C. Labeling was performed at pH 4.1 in sodium citrate, sodium acetate, 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid, and 2-(N-morpholino)ethanesulfonic acid buffer and was optimal in sodium acetate buffer. The apparent 50% inhibitory concentration of the (19)F-labeled IMP466 determined on AR42J cells was 3.6 nM. Biodistribution studies at 2 h after injection showed a high tumor uptake of (18)F-IMP466 (28.3 +/- 5.2 percentage injected dose per gram [%ID/g]; tumor-to-blood ratio, 300 +/- 90), which could be blocked by an excess of unlabeled peptide (8.6 +/- 0.7 %ID/g), indicating that the accumulation in the tumor was receptor-mediated. Biodistribution of (68)Ga-IMP466 was similar to that of (18)F-IMP466. (18)F-IMP466 was stable in vivo, because bone uptake was only 0.4 +/- 0.2 %ID/g, whereas free Al(18)F accumulated rapidly in the bone (36.9 +/- 5.0 %ID/g at 2 h after injection). Small-animal PET/CT scans showed excellent tumor delineation and high preferential accumulation in the tumor.
NOTA-octreotide could be labeled rapidly and efficiently with (18)F using a 2-step, 1-pot method. The compound was stable in vivo and showed rapid accretion in somatostatin receptor subtype 2-expressing AR42J tumors in nude mice. This method can be used to label other NOTA-conjugated compounds with (18)F.
介绍一种基于（18）F-铝氟化物（Al（18）F）与 1,4,7-三氮杂环壬烷-1,4,7-三乙酸（NOTA）螯合的简便多肽标记方法。方法：采用两步一锅法，将奥曲肽与 NOTA 螯合，用（18）F 标记。优化了标记缓冲液、肽和铝浓度。测定放射性化学产率、比活度、体外稳定性和受体亲和力。在 AR42J 荷瘤小鼠中研究了（18）F-IMP466 的生物分布，并与（68）Ga 标记的 IMP466 进行了比较。此外，还进行了小动物 PET/CT 扫描。
IMP466 以 50%的产率一步标记为 Al（18）F。标记产物通过高效液相色谱法进行纯化，以去除未结合的 Al（18）F 和未标记的肽。放射性标记，包括纯化，在 45 分钟内完成。比活度为 45000GBq/mmol，肽在 37°C 血清中 4 小时稳定。在柠檬酸钠、醋酸钠、4-（2-羟乙基）-1-哌嗪乙磺酸和 2-（吗啉代）乙磺酸缓冲液中，在 pH4.1 下进行标记，在醋酸钠缓冲液中最佳。在 AR42J 细胞上测定的（19）F 标记 IMP466 的 50%抑制浓度为 3.6nM。注射后 2 小时的生物分布研究表明，（18）F-IMP466 在肿瘤中的摄取率很高（28.3±5.2%注入剂量/克[ID/g]；肿瘤与血液比，300±90），可被过量未标记的肽阻断（8.6±0.7%ID/g），表明肿瘤的积累是受体介导的。（68）Ga-IMP466 的生物分布与（18）F-IMP466 相似。（18）F-IMP466 在体内稳定，因为骨摄取仅为 0.4±0.2%ID/g，而游离 Al（18）F 在注射后 2 小时内迅速在骨骼中积累（36.9±5.0%ID/g）。小动物 PET/CT 扫描显示肿瘤轮廓清晰，肿瘤优先积聚。
采用两步一锅法，NOTA-奥曲肽可快速、高效地用（18）F 标记。该化合物在体内稳定，在裸鼠中表达生长抑素受体亚型 2 的 AR42J 肿瘤中迅速积聚。该方法可用于用（18）F 标记其他 NOTA 缀合化合物。
