Recent trends in the nucleophilic [¹⁸F]-radiolabeling method with no-carrier-added [¹⁸F]fluoride

Noninvasive imaging in living subjects with positron emission tomography (PET) provides early detection of diseases in humans. For this application, it is necessary to prepare specific molecular imaging probes labeled with positron-emitting radioisotopes such as fluorine-18 for obtaining high-quality PET imaging. In this review, we describe recent trends in the F-18 radiolabeling method for the introduction of no-carrier-added fluorine-18, which was obtained from an ¹⁸O(p,n)¹⁸F reaction, into a specific molecular site, which in turn is intended to serve as an imaging agent for PET study. These labeling protocols are based on ionic liquid media ¹⁸F radiofluorination in the presence of some water, enzymatic ¹⁸F fluorination using fluorinase in water solution, non-polar protic alcohol media ¹⁸F radiofluorination and its mechanism, and nucleophilic ¹⁸F fluorination of an aromatic iodonium salt precursor.