The radiolabeling of proteins by the [18F]AlF method

A new ([18F]AlF)2+-binding ligand that contains 1,4,7-triazacyclononane-1,4-diacetate (NODA) attached to a methyl phenylacetic acid group (MPA) was conjugated to N-(2-aminoethyl)maleimide (EM) to form NODA-MPAEM. The NODA-MPAEM was labeled with ([18F]AlF)2+ at 105 °C in 49–82% yield and conjugated at room temperature to an antibody Fab' fragment in 69–80% yield (total time ∼50 min) and with retention of immunoreactivity. These data indicate that the rapid and simple [18F]AlF-labeling method can be easily adapted for preparing heat-sensitive compounds with 18F quickly and in high yields.

► The F-18 labeling of the NODA-maleimide was one-step, fast and obtained in high yield (49–82%).
► The [18F]AlF-NODA-maleimide was conjugated rapidly to a Fab′–SH in high yield (69–80%) at 21 °C.
► The [18F]AlF-NODA-MPAEM-antibody Fab′ was stable in vitro and in vivo.