'Click' chemistry contribution for labeling nucleosides and oligonucleotides with carbon-11 and fluorine-18 as potential radiotracers for Positron Emission Tomography (PET) imaging

Positron Emission Tomography (PET) is a powerful molecular-imaging technique for physiological and biological investigations in various areas, such as oncology, cardiology, and neurosciences, as well as for drug development. Due to the increasing need of this technique for in vivo applications, there is always a demand for the development of new tracers and radiolabeling strategies. Furthermore, because of their excellent targeting capacities and easy synthesis along with a high level of diversity, oligonucleotides are already extensively used in vitro as ligands for nucleic acids (antisense oligonucleotides), proteins, and small related molecules (aptamer oligonucleotides). The use of aptamers for in vivo imaging appears especially promising, because of the wide range of possibilities available to introduce variations in their structure through defined chemical modifications. However, only few examples of oligonucleotide labeling for PET have been reported. In this context, we have developed two methodological ways to introduce the radioisotope (¹¹C, ¹⁸F), by 'click' chemistry, at the last radiosynthesis step in order to label nucleoside and oligonucleotide as potential radiotracers for PET. (author)