One-step 18F-labeling of peptides for positron emission tomography imaging using the SiFA methodology

Here we present a procedure to label peptides with the positron-emitting radioisotope fluorine-18 (F-18) using the silicon-fluoride acceptor (SiFA) labeling methodology. Positron emission tomography (PET) has gained high importance in noninvasive imaging of various diseases over the past decades, and thus new specific imaging probes for PET imaging, especially those labeled with F-18, because of the advantageous properties of this nuclide, are highly sought after. N-terminally SiFA-modified peptides can be labeled with F-18(-) in one step at room temperature (20-25 degrees C) or below without forming side products, thereby producing satisfactory radiochemical yields of 46 +/- 1.5% (n = 10). The degree of chemoselectivity of the F-18-introduction, which is based on simple isotopic exchange, allows for a facile cartridge-based purification fully devoid of HPLC implementation, thereby yielding peptides with specific activities between 44.4 and 62.9 GBq mu mol(-1) (1,200-1,700 Ci mmol(-1)) within 25 min.