Synthesis and evaluation of two uncharged<sup>99m</sup>Tc-labeled derivatives of thioflavin-T as potential tracer agents for fibrillar brain amyloid
作者:K. Serdons、D. Vanderghinste、M. Van Eeckhoudt、J. Cleynhens、T. de Groot、G. Bormans、A. Verbruggen
DOI:10.1002/jlcr.1592
日期:2009.5.30
Thioflavin-T is a fluorescent dye for in vitro detection of fibrillar amyloid β, a protein found in the brain of patients suffering from Alzheimer's disease. We synthesized and biologically evaluated two uncharged 99mTc-labeled derivatives of thioflavin-T. The precursors for labeling were synthesized by coupling an S,S′-bis-triphenylmethyl-N-tert-butoxycarbonyl bis-amino-bis-thiol tetradentate ligand via a propoxy spacer to 2-(4′-aminophenyl)-1,3-benzothiazole at the 6-position or the 2′-position. Deprotection and labeling with 99mTc were done via a one-pot procedure (15% yield) after which the labeled compound was isolated by high performance liquid chromatography (LC). LC in combination with mass spectrometry (MS) was used for identity confirmation of the labeled compounds. Results of electrophoresis and log P determination supported the assumption that the radiolabeled compounds could cross the blood–brain barrier by passive diffusion. However, in normal mice both compounds showed a low brain uptake 2 min post injection. They were mainly excreted through the hepatobiliary system, with some accumulation in the stomach. Sixty minutes after intravenous injection, 37% of the 99mTc-activity in the blood corresponded to the original compound. In view of the low brain uptake, it is concluded that the studied 99mTc-labeled derivatives of thioflavin-T are not suitable as tracer agents for in vivo visualization of amyloid in brain. Copyright © 2009 John Wiley & Sons, Ltd.
硫黄素-T 是一种荧光染料,可用于体外检测阿尔茨海默病患者大脑中的纤维状淀粉样蛋白 β。我们合成了两种不带电荷的 99mTc 标记的硫黄素-T 衍生物,并对其进行了生物学评估。用于标记的前体是通过丙氧基间隔物将 S,S′-双-三苯甲基-N-叔丁氧羰基双-氨基-双-硫醇四价配体与 2-(4′-氨基苯基)-1,3-苯并噻唑的 6 位或 2′位偶联而合成的。99m锝的去保护和标记是通过一锅法完成的(收率为 15%),然后用高效液相色谱法(LC)分离出标记化合物。液相色谱法与质谱法相结合,用于确认标记化合物的身份。电泳和对数 P 测定的结果支持了放射性标记化合物可通过被动扩散穿过血脑屏障的假设。然而,在正常小鼠体内,两种化合物在注射后 2 分钟的脑吸收率都很低。它们主要通过肝胆系统排出体外,在胃中也有一些蓄积。静脉注射 60 分钟后,血液中 37% 的 99mTc 活性与原始化合物一致。鉴于大脑摄取量较低,结论是所研究的 99mTc 标记的硫黄素-T 衍生物不适合作为体内观察大脑淀粉样蛋白的示踪剂。版权所有 © 2009 约翰威利父子有限公司。