Rapid biochemical synthesis of (11)C-labeled single chain variable fragment antibody for immuno-PET by cell-free protein synthesis.

Immuno-PET is a promising approach for improved cancer diagnosis, by taking advantage of the high specificity of antibodies. Here, we present a novel cell-free protein synthesis method for preparing a positron emitter labeled-antibody. Functional anti-human EGFRvIII single chain Fv, MR1-1, was successfully labeled with carbon-11 (half-life=20.4 min) in 5 min (36% yield) by the direct incorporation of the clinical PET tracer, l-[(11)C]methionine. The product [(11)C]MR1-1 was easily and rapidly isolated with high radiochemical purity (>95%) from the reaction solution, by affinity purification. This method would be widely applicable to the preparation of radiolabeled antibodies for PET imaging.