This study aims at analyzing complexation properties of two new short somatostatin analogues, their synthesis, radiolabeling with 44Sc, 207Bi, and 152Eu and stability in vitro. Short tetrapeptide Phe-d-Trp-Lys-Thr and pentapeptide Thz-Phe-d-Trp-Lys-Thr were first conjugated with the DOTA macrocyclic chelator. These conjugates were radiolabeled with 44Sc, 207Bi, and 152Eu and characterized by thin-layer chromatography (TLC) and HPLC. The radiochemical purity was measured using digital autoradiography and gamma spectrometry. Optimum conditions of DOTA-conjugate labeling were found: 0.1mM, pH 8.0 to 8.4 at 90°C for DOTA-tetrapeptide complexes with 207Bi and 152Eu; 0.05mM, pH 4.0 to 5.0 at 90°C for 44Sc-DOTA-tetrapeptide; 0.2mM, pH 4.0 to 5.0 at 90°C for 44Sc-DOTA-pentapeptide. Complexes of DOTA-pentapeptide with 207Bi and 152Eu of radiochemical purity more than 95% were probably unstable at temperature higher than 37°C and were obtained at 37°C, pH 8.0 to 8.4 within 4 days. Mass spectra of the Eu-DOTA-pentapeptide revealed the presence of small fragments of the pentapeptide conjugate in the complex solution. in vitro stability studies were performed in saline in the presence of serum proteins and biologically relevant metal cations. All complexes demonstrated no cation release in vitro within 1 to 4 hours.
本研究旨在分析两种新型短体
生长抑素类似物的复合特性、合成、44Sc、207Bi 和 152Eu 放射性标记以及体外稳定性。首先将短四肽 Phe-d-Trp-Lys-Thr 和五肽 Thz-Phe-d-Trp-Lys-Thr 与 DOTA 大环
螯合剂共轭。用 44Sc、207Bi 和 152Eu 对这些共轭物进行放射性标记,并用薄层色谱法(TLC)和高效
液相色谱法(HPLC)对其进行表征。放射
化学纯度是通过数字自动射线照相术和伽马能谱仪测定的。结果发现 DOTA-共轭物标记的最佳条件为:0.1mM,pH 8.0 至 8.4,90°C,DOTA-四肽与 207Bi 和 152Eu 的复合物;0.05mM,pH 4.0 至 5.0,90°C,44Sc-DOTA-四肽;0.2mM,pH 4.0 至 5.0,90°C,44Sc-DOTA-五肽。放射
化学纯度超过 95% 的 DOTA-五肽与 207Bi 和 152Eu 的复合物在高于 37°C 的温度下可能不稳定,在 37°C、pH 值为 8.0 至 8.4 的条件下,4 天内即可获得。Eu-DOTA 五肽的质谱显示,复合物溶液中存在五肽共轭物的小片段。体外稳定性研究是在有血清蛋白和
生物相关
金属阳离子存在的生理盐
水中进行的。所有复合物在体外 1 到 4 小时内都没有阳离子释放。