Fast indirect fluorine-18 labeling of protein/peptide using the useful 6-fluoronicotinic acid-2,3,5,6-tetrafluorophenyl prosthetic group: A method comparable to direct fluorination.

Abstract

Fluorine-18 labeling of biomolecules is mostly performed by an indirect labeling method using a prosthetic group. Fluorine-18 labeled 6-fluoronicotinic acid-2,3,5,6-tetrafluorophenyl ester is a useful prosthetic group to radiolabel a protein. Recently, we reported an improved preparation of this prosthetic group. To test the conjugation efficiency of the labeled ester prepared by this method, we have performed conjugation reactions with a peptide, a protein, and a small molecule. Prostate-specific membrane antigen targeting small molecule [18 F]DCFPyL, αvβ3 integrin receptors targeting peptide [18 F]c(RGDfK) and [18 F]albumin were prepared in good radiochemical yields. The conjugation reactions were completed at 40°C to 50°C in 10minutes. The overall radiochemical yield was 25% to 43% in 30 to 45minutes.