A High-Denticity Chelator Based on Desferrioxamine for Enhanced Coordination of Zirconium-89
作者:Elaheh Khozeimeh Sarbisheh、Akam K. Salih、Shvan J. Raheem、Jason S. Lewis、Eric W. Price
DOI:10.1021/acs.inorgchem.0c01629
日期:2020.8.17
Herein we report a new high-denticity chelator based on the iron siderophore desferrioxamine (DFO). Our new chelator—DFO2—is acyclic and was designed and synthesized with the purpose of improving the coordination chemistry and radiolabeling performance with radioactive zirconium-89. The radionuclide zirconium-89 ([89Zr]Zr4+) has found wide use for positron emission tomography (PET) imaging when it is coupled with proteins, antibodies, and nanoparticles. DFO2 has a potential coordination number of 12, which uniquely positions this chelator for binding large, high-valent, and oxophilic metal ions. Following synthesis of the DFO2 chelator and the [natZr]Zr-(DFO2) complex we performed density functional theory calculations to study its coordination sphere, followed by zirconium-89 radiolabeling experiments for comparisons with the “gold standard” chelator DFO. DFO (CN 6) can coordinate with zirconium in a hexadentate fashion, leaving two open coordination sites where water is thought to coordinate (total CN 8). DFO2 (potential CN 12, dodecadentate) can saturate the coordination sphere of zirconium with four hydroxamate groups (CN 8), with no room left for water to directly coordinate, and only binds a single atom of zirconium per chelate. Following quantitative radiolabeling with zirconium-89, the preformed [89Zr]Zr-(DFO) and [89Zr]Zr-(DFO2) radiometal–chelate complexes were subjected to a battery of in vitro stability challenges, including human blood serum, apo-transferrin, serum albumin, iron, hydroxyapatite, and EDTA. One objective of these stability challenges was to determine if the increased denticity of DFO2 over that of DFO imparted improved complex stability, and another was to determine which of these assays is most relevant to perform with future chelators. In all of the assays DFO2 showed superior stability with zirconium-89, except for the iron challenge, where both DFO2 and DFO were identical. Substantial differences in stability were observed for human blood serum using a precipitation method of analysis, apo-transferrin, hydroxyapatite, and EDTA challenges. These results suggest that DFO2 is a promising next-generation scaffold for zirconium-89 chelators and holds promise for radiochemistry with even larger radionuclides, which we anticipate will expand the utility of DFO2 into theranostic applications.
在此,我们报告了一种基于铁苷酸去铁胺(DFO)的新型高致性螯合剂。我们的新型螯合剂--DFO2--是无环的,其设计和合成的目的是为了改善与放射性锆-89 的配位化学和放射性标记性能。放射性核素锆-89([89Zr]Zr4+)与蛋白质、抗体和纳米粒子偶联后,被广泛用于正电子发射断层扫描(PET)成像。DFO2 的潜在配位数为 12,这是这种螯合剂结合大分子、高价和亲氧化金属离子的独特之处。在合成了 DFO2 螯合剂和 [natZr]Zr-(DFO2) 复合物后,我们进行了密度泛函理论计算以研究其配位圈,随后进行了锆-89 放射性标记实验,以便与 "金标准 "螯合剂 DFO 进行比较。DFO(CN 6)可以六价方式与锆配位,留下两个开放的配位位点,水被认为可以在其中配位(总计 CN 8)。而 DFO2(潜在的 CN 12,十二配位)可以使锆的配位圈中的四个羟基氨基达到饱和(CN 8),不给水留下直接配位的空间,并且每个螯合物只能结合一个锆原子。用锆-89 进行定量放射性标记后,预制的 [89Zr]Zr-(DFO) 和 [89Zr]Zr-(DFO2) 辐射金属螯合物接受了一系列体外稳定性测试,包括人血清、载脂蛋白、血清白蛋白、铁、羟基磷灰石和 EDTA。这些稳定性测试的目的之一是确定 DFO2 的齿性是否比 DFO 的齿性更强,从而提高了复合物的稳定性,另一个目的是确定在这些测试中,哪一种与未来的螯合剂最相关。在所有试验中,DFO2 与锆-89 的稳定性都更胜一筹,只有铁挑战除外,在铁挑战中,DFO2 和 DFO 的稳定性完全相同。使用沉淀分析法对人血清、载脂蛋白转铁蛋白、羟基磷灰石和乙二胺四乙酸(EDTA)进行挑战时,观察到两者的稳定性存在很大差异。这些结果表明,DFO2 是锆-89 螯合剂很有前途的下一代支架,并有望用于更大放射性核素的放射化学。