Accelerator Production of the Medical Isotope At-211 and Monoclonal Antibody Labeling

At-211, with a half-life of 7.2 h, is an excellent radionuclide being investigated for use in targeted alpha therapy as the result of very high linear energy transfer. However, the production of At-211 is limited by At-210, because At-210 decays to produce long half-life (138.4 d) extremely toxic daughter 210Po. The production of At-211 via Bi-209(a,2n) nuclear reaction and At-210 via 209Bi(a,3n) nuclear reaction, as the energy of incident a-particle increases, the ratio of N(At-210)/N(At-211) increases. In this research, the a-particle is provided by the Chinese Accelerator Driven Sub-critical System (ADS) Front-end Demo Linac at Institute of Modern Physics, Chinese Academy of Sciences. The technical process of At-211 produced was studied systematically, including accelerator irradiation, separation by dry distillation method, quality analysis, and monoclonal antibody labeling. The bismuth targets were irradiated with a-particle by 28.18, 28.34, 28.48 28.92 MeV, and the target chamber adopts an inclined target with water cooling to improve the cooling effect. The dry distillation separation was carried out at a high temperature of 850., oxygen as the carrier gas, chloroform and ethanol as eluent, and the chloroform solution containing At-211 was blow dry with nitrogen. The results showed that the total recovery of dry distillation separation of 211At reached 78.53%. After separation, the quality analysis of At-211 was performed using a high-purity Ge-detector, alpha energy spectrometer, and mass spectrometer. The obtained solid At-211 had high specific activity, radionuclide purity and chemical purity, where the content of impurity elements Bi, Cu, Zn, and Al was less than 100 ng/GBq, and the ratio of N(At-210)/N(At-211) was less than 10(-5) when the incident particle energy is below 28.2 MeV. Finally, the labeling of 211At-nimotuzumab was realized through N-succinimidyl-3-(trimethylstannyl)benzoate, and the labeling rate was 94.86%. Based on this research, a set of simple and efficient separation methods was established, which laid a good foundation for the subsequent production and application of At-211 in China.