METHODS: To improve and automate the radiolabeling of [(18)F]FPBM, 1, an intermediate, [(18)F]3-fluoropropyltosylate, [(18)F]4, was prepared first, and then it was reacted with the phenol precursor (4-(2-aminophenylthio)-3-((dimethylamino)methyl)phenol, 3) to afford [(18)F]FPBM, 1. To optimize the labeling, this O-alkylation reaction was evaluated under different temperatures, using different bases and varying amounts of precursor 3. The desired product was obtained after a solid phase extraction (SPE) purification.
RESULTS: This two-step radiolabeling reaction successfully produced the desired [(18)F]FPBM, 1, with an excellent radiochemical purity (>95%, n = 8). Radiochemical yields were between 31% and 39% (decay corrected, total time of labeling: 70 min, n = 8). The SPE purification cannot completely remove pseudo-carriers in the final dose of [(18)F]FPBM, 1. The concentrations of major pseudo-carriers were measured by UV-HPLC (476-676, 68-95 and 50-71 μg for precursor 3, O-hydroxypropyl and O-allyloxy derivatives, 5 and 6, respectively). To investigate the potential inhibition of SERT binding of these pseudo-carriers, we performed in vitro competition experiments evaluated by autoradiography. Known amounts of \'standard\' FPBM, 1, of the pseudo-carriers, 5 and 6, were added to the HPLC-purified [(18)F]1 dose. The inhibition of \'standard\' FPBM, 1, binding to the SERT binding sites, using monkey brain sections, were measured (EC50=13, 46, 7.1 and 8.3 nM, respectively for 1, precursor 3, O-hydroxypropyl and O-allyloxy derivative of 3).
CONCLUSIONS: An improved radiolabeling method by a SPE purification for preparation of [(18)F]FPBM, 1, was developed. The results suggest that it is feasible to use this labeling method to prepare [(18)F]FPBM, 1, without affecting in vivo SERT binding.
方法:为了改进和自动化[(18)F]FPBM的放射性标记,1、中间、[(18)F]3-氟丙基甲苯磺酸酯,[(18)F]4,首先准备好了,然后与苯酚前体(4-(2-氨基苯硫基)-3-((二甲基氨基)甲基)苯酚反应,3)提供[(18)F]FPBM,1.要优化标签,该O-烷基化反应在不同温度下进行评价,使用不同的碱和不同量的前体3.在固相萃取(SPE)纯化后获得所需产物。
结果:这种两步放射性标记反应成功地产生了所需的[(18)F]FPBM,1,具有优异的放射化学纯度(>95%,n=8)。放射化学产率在31%和39%之间(衰变校正,标签的总时间:70分钟,n=8)。SPE纯化不能完全去除[(18)F]FPBM最终剂量中的假载体,1.通过UV-HPLC测量主要假载体的浓度(前体3,O-羟丙基和O-烯丙氧基衍生物的476-676、68-95和50-71μg,分别为5和6)。为了研究这些假载体的SERT结合的潜在抑制作用,我们进行了体外竞争实验,通过放射自显影评估。已知数量的\'标准\'FPBM,1,在伪载波中,将5和6加入到HPLC纯化的[(18)F]1剂量中。“标准”FPBM的抑制,1,与SERT结合位点结合,用猴子的大脑切片,测量(EC50=13、46、7.1和8.3nM,分别为1,前体3,O-羟丙基和O-烯丙氧基衍生物3)。
结论:通过SPE纯化制备[(18)F]FPBM的改进的放射性标记方法,1、开发。结果表明,使用该标记方法制备[(18)F]FPBM是可行的,1,不影响体内SERT结合。