The Influence of the Combination of Carboxylate and Phosphinate Pendant Arms in 1,4,7-Triazacyclononane-Based Chelators on Their 68Ga Labelling Properties
作者:Gábor Máté、Jakub Šimeček、Miroslav Pniok、István Kertész、Johannes Notni、Hans-Jürgen Wester、László Galuska、Petr Hermann
DOI:10.3390/molecules200713112
日期:——
In order to compare the coordination properties of 1,4,7-triazacyclononane (tacn) derivatives bearing varying numbers of phosphinic/carboxylic acid pendant groups towards 68Ga, 1,4,7-triazacyclononane-7-acetic-1,4-bis(methylenephosphinic) acid (NOPA) and 1,4,7- triazacyclononane-4,7-diacetic-1-[methylene(2-carboxyethyl)phosphinic] acid (NO2AP) were synthesized using Mannich reactions with trivalent or pentavalent forms of H-phosphinic acids as phosphorus components. Stepwise protonation constants logK1–3 12.06, 3.90 and 1.95, and stability constants with GaIII and CuII, logKGaL 24.01 and logKCuL 16.66, were potentiometrically determined for NOPA. Both ligands were labelled with 68Ga and compared with NOTA (tacn-N,N′,N″-triacetic acid) and NOPO, a TRAP-type [tacn-N,N′,N″- tris(methylenephosphinic acid)] chelator. At pH 3, NOPO and NOPA showed higher labelling efficiency (binding with lower ligand excess) at both room temperature and 95 °C, compared to NO2AP and NOTA. Labelling efficiency at pH = 0–3 correlated with a number of phosphinic acid pendants: NOPO >> NOPA > NO2AP >> NOTA; however, it was more apparent at 95 °C than at room temperature. By contrast, NOTA was found to be labelled more efficiently at pH > 4 compared to the ligands with phosphinic acids. Overall, replacement of a single phosphinate donor with a carboxylate does not challenge 68Ga labelling of TRAP-type chelators. However, the presence of carboxylates facilitates labelling at neutral or weakly acidic pH.
为了比较带有不同数量的膦酸/羧酸悬垂基团的 1,4,7-三氮杂环壬烷(tacn)衍生物对 68Ga 的配位性质,研究人员利用曼尼希反应合成了 1,4,7-三氮杂环壬烷-7-乙酸-1,4-双(亚甲基膦酸)(NOPA)和 1、1,4,7- 三氮杂环壬烷-4,7-二乙酸-1-[亚甲基(2-羧乙基)膦酸](NO2AP)是以三价或五价形式的 H-膦酸作为磷组分,通过曼尼希反应合成的。经电位测定,NOPA 的阶跃质子化常数 logK1-3 为 12.06、3.90 和 1.95,与 GaIII 和 CuII 的稳定性常数 logKGaL 为 24.01,logKCuL 为 16.66。用 68Ga 标记了这两种配体,并将其与 NOTA(tacn-N,N′,N″-三乙酸)和 NOPO(一种 TRAP 型[tacn-N,N′,N″-三(亚甲基膦酸)]螯合剂)进行了比较。在 pH 值为 3 时,与 NO2AP 和 NOTA 相比,NOPO 和 NOPA 在室温和 95 ℃ 下的标记效率更高(以较低的配体过量结合)。pH = 0-3 时的标记效率与膦酸悬臂的数量有关:NOPO >> NOPA >> NO2AP >> NOTA;不过,在 95 °C 时比室温时更明显。相比之下,与含膦酸的配体相比,NOTA 在 pH > 4 时的标记效率更高。总的来说,用羧酸盐取代单一的膦酸盐供体不会对 TRAP 型螯合剂的 68Ga 标记造成挑战。不过,羧酸盐的存在有利于在中性或弱酸性 pH 下进行标记。