Synthesis, characterisation and evaluation of a novel copper-64 complex with selective uptake in EMT-6 cells under hypoxic conditions
作者:James C. Knight、Melinda Wuest、Fawaz A. Saad、Monica Wang、David W. Chapman、Hans-Soenke Jans、Suzanne E. Lapi、Benson M. Kariuki、Angelo J. Amoroso、Frank Wuest
DOI:10.1039/c3dt50960e
日期:——
The radiometal 64Cu is now widely used in the development of diagnostic imaging agents for positron emission tomography (PET). The present study has led to the development and evaluation of a novel chelating agent for 64Cu: the new monothiourea tripodal ligand 1-benzoyl-3-6-[(bis-pyridin-2-ylmethyl-amino)-methyl]-pyridin-2-yl}-thiourea (MTUBo). X-ray crystallographic analysis has shown this ligand forms a mononuclear complex with copper(II) and co-ordinates via a trigonal bipyramidal N4S array of donor atoms. Promisingly, cell uptake studies revealed that 64Cu-MTUBo selectively accumulates in EMT-6 cells incubated under hypoxic conditions which may result from its relatively high CuII/I redox potential. Small-animal PET imaging and ex vivo biodistribution studies in EMT-6 tumor bearing BALB/c mice revealed significant tumor uptake after 1 h p.i., yielding tumor-to-muscle (T/M) and tumor-to-blood (T/B) ratios of 8.1 and 1.1, respectively. However, injection of 64Cu-acetate resulted in similar uptake indicating that the observed uptake was most likely non-specific. Despite showing high in vitro stability, it is likely that in vivo the complex undergoes transchelation to proteins within the blood in a relatively short timeframe. For comparison, the hypoxia imaging agent 64Cu-ATSM was also evaluated in the same murine tumor model and showed about 60% higher tumor uptake than 64Cu-MTUBo.
放射性金属 64Cu 目前被广泛用于正电子发射断层扫描(PET)诊断成像剂的开发。本研究开发并评估了一种新型 64Cu 螯合剂:新型单硫脲三元配体 1-苯甲酰基-3-6-[(双吡啶-2-基甲基氨基)-甲基]-吡啶-2-基}-硫脲(MTUBo)。X 射线晶体学分析表明,这种配体与铜(II)形成单核配合物,并通过供体原子的三叉双锥 N4S 阵列配位。令人欣慰的是,细胞吸收研究表明,64Cu-MTUBo 可选择性地在缺氧条件下培养的 EMT-6 细胞中积累,这可能是由于它具有相对较高的 CuII/I 氧化还原电位。在携带 EMT-6 肿瘤的 BALB/c 小鼠体内进行的小动物 PET 成像和体内外生物分布研究显示,肿瘤在注射 1 小时后显著吸收,肿瘤与肌肉(T/M)和肿瘤与血液(T/B)的比率分别为 8.1 和 1.1。然而,注射醋酸 64Cu 会产生类似的摄取,这表明所观察到的摄取很可能是非特异性的。尽管该复合物在体外显示出很高的稳定性,但在体内,它很可能在相对较短的时间内与血液中的蛋白质发生转切作用。作为比较,缺氧成像剂 64Cu-ATSM 也在相同的小鼠肿瘤模型中进行了评估,其肿瘤摄取量比 64Cu-MTUBo 高出约 60%。