AUTHOR=Jiang Xiao , Li Yingchun , Wang Xiaoxiong , Shen Taipeng , Li Xiuli , Yao Yutang , Zhang Ge , Kou Ying , Shen Jiaqi , Luo Zhifu , Cheng Zhuzhong 

TITLE=Quick Automatic Synthesis of Solvent-Free 16α-[18F] Fluoroestradiol: Comparison of Kryptofix 222 and Tetrabutylammonium Bicarbonate

JOURNAL=Frontiers in Oncology

VOLUME=10

YEAR=2020

URL=https://www.frontiersin.org/journals/oncology/articles/10.3389/fonc.2020.577979

DOI=10.3389/fonc.2020.577979

ISSN=2234-943X

ABSTRACT=<p>Estrogen receptor (ER) expression level of human breast cancer often reflects the stage of disease and is usually monitored by immunohistochemical staining <italic>in vitro</italic>. The preferable non-invasive and real-time diagnosis <italic>in vivo</italic> is more accessible by PET scan using 16α-[<sup>18</sup>F]FES. The objective of this study was to develop a quick automatic method for synthesis of solvent-free 16α-[<sup>18</sup>F]FES using a CFN-MPS-200 synthesis system and compare the catalytic efficiency of two phase transfer catalysts, Kryptofix 222/K<sub>2</sub>CO<sub>3</sub> (K222/K<sub>2</sub>CO<sub>3</sub>) and tetrabutylammonium hydrogen carbonate (TBA·HCO<sub>3</sub>). In this method, phase transfer catalysts K222/K<sub>2</sub>CO<sub>3</sub> and TBA·HCO<sub>3</sub> were used, respectively. The intermediate products were both hydrolyzed with hydrochloric acid and neutralized with sodium bicarbonate. The crude product was purified with semi-preparative HPLC, and the solvent was removed by rotary evaporation. The effects of radiofluorination temperature and time on the synthesis were also investigated. Radiochemical purity of solvent-free product was above 99% and the decay-corrected radiochemical yield of 16α-[<sup>18</sup>F]FES was obtained in 48.7 ± 0.95% (catalyzed by K222/K<sub>2</sub>CO<sub>3</sub>, <italic>n</italic> = 4) and 46.7 ± 0.77% (catalyzed by TBA·HCO<sub>3</sub>, <italic>n</italic> = 4, respectively). The solvent-free 16α-[<sup>18</sup>F]FES was studied in clinically diagnosed breast cancer patients, and FES-PET results were compared with pathology diagnosis results to validate the diagnosis value of 16α-[<sup>18</sup>F]FES. The new method was more reliable, efficient, and time-saving. There was no significant difference in catalytic activity between K222/K<sub>2</sub>CO<sub>3</sub> and TBA·HCO<sub>3</sub>.</p>