AT-211-LABELING OF POLYMER PARTICLES FOR RADIOTHERAPY - SYNTHESIS, PURIFICATION AND STABILITY

Cyclotron-produced At-211 was distilled from a Bi metal target and cou pled to N-succinimidyl-3-(trimethylstannyl)benzoate. The resulting N-s uccinimidyl-3-(At-211)astatobenzoate was thereafter coupled to aminate d monosized polymer particles with a diameter of 1.8 mum. The total ti me elapsed from the end of the cyclotron irradiation until the final p roduct was prepared was about 2.5 hours. From 23 to 51 % of the target activity at the end of bombardment was measured in the final conjugat e. Solid-liquid extraction purification of the astatinated intermediat e, using Sep-pak columns (Waters), gave more reproducible yields in th e final conjugation step. The At-211-labelled particles were incubated with fetal calf serum, human serum and human full blood at room tempe rature. The At-211 activity on the particles was measured before and a fter three times washing at 4, 24 and 48 hours. The stability was not significantly different from 100 % for all media and for all time poin ts. This indicates that At-211-labelled particles can be stable under in vivo conditions, and may thereby be a promising agent for intracavi tary radiotherapy on free-floating cancer cells or surface fixed cells .