Abstract
632
Objectives: Astatine-211 (211At) is a promising α-emitting radionuclide for therapy of cancer cells. This nuclide can be produced in the 209Bi(α, 2n)211At reaction using an accelerator and can be separated from the Bi target through a dry distillation method. Dry distilled At is then trapped on a cooled surface and dissolved in various solutions such as HNO3, methanol and chloroform. However, these solutions are toxic to living body, and it is desirable to dissolve dry distilled 211At with non-toxic solutions for following preclinical studies. In this study, dissolution efficiency of dry distilled 211At with some non-toxic aqueous solutions was investigated. Chemical components of At dissolved in these aqueous solutions were checked by a thin layer chromatography (TLC).
Methods: The 211At was produced in the 209Bi(α, 2n)211At reaction using AVF cyclotron at Research Center for Nuclear Physics, Osaka University. The produced 211At was separated using the dry distillation apparatus shown in Fig. 1. The irradiated Bi target was heated up to 850°C, and evaporated 211At was transported to Teflon trap tube, which is cooled by ice water, with mixed He and O2 gas flow. The trapped 211At was then dissolved in 100-200 μL of pure water, saline or sodium ascorbate solution. As comparison with these non-toxic aqueous solutions, methanol, acetonitrile and chloroform were also used for dissolution of 211At. The dissolution efficiency of 211At was calculated from the measurement of 211At solution and Teflon trap tube with a Ge detector. TLC analysis of 211At solution was conducted with silica gel plate.
Results: The dissolution efficiencies of dry distilled 211At with pure water, saline and sodium ascorbate solution were approximately 85%. On the other hand, methanol, acetonitrile and chloroform dissolved dry distilled 211At more than 95%. Although organic solutions are better solvents for efficient dissolution of 211At, these non-toxic aqueous solutions also can sufficiently dissolve dry distilled 211At. The TLC analysis for these aqueous solutions of 211At showed that oxidized At, astatine chloride and astatide ion may exist in pure water, saline and sodium ascorbate solution, respectively.
Conclusions: The dissolution efficiencies of dry distilled 211At with non-toxic aqueous solutions are sufficiently high, and use of these aqueous solutions is advantageous for preclinical studies with 211At. Fig. 1. Schematic diagram of the dry distillation apparatus for At-211.
