Labeling of human C-peptide by conjugation with N-succinimidyl-4-[18F]fluorobenzoate

We have labeled proinsulin connecting peptide (C-peptide) with fluorine-18 (t(1/2) = 109.7min) in order to perform in vivo biodistribution and pharmacokinetic studies with position emission tomography (PET). This study reports the optimization of the conjugation labeling in the N-terminal with N-succinimidyl-4-[F-18]fluorobenzoate ([F-18]SFB). In preparative runs N-4-[F-18]fluorobenzoyl-C-peptide ([F-18]FB-C-peptide) was produced in 8-12% decay-corrected yields, counted from resolubilized [F-18]F-, in less than 5h. The specific radioactivity of [F-18]FB-C-peptide, determined using ELISA for one of the preparations, was around 70 GBq/mu mol at end of synthesis.