Labelling via [Al18F]2+ Using Precomplexed Al-NODA Moieties

Over the past 20 years, Ga-68-labelled radiopharmaceuticals have become an important part in clinical routine. However, the worldwide supply with Ge-68/Ga-68 generators is limited as well as the number of patient doses per batch of Ga-68 radiopharmaceutical. In the recent years, a new technique appeared, making use of the ease of aqueous labelling via chelators as with Ga-68 but using F-18 instead. This technique takes advantage of the strong coordinative bond between aluminium and fluoride, realized in the aqueous cation [(AlF)-F-18](2+). Most applications to date make use of one-pot syntheses with free Al(III) ions in the system. In contrast, we investigated the labelling approach split into two steps: generating the Al-bearing precursor in pure form and using this Al compound as a precursor in the labelling step with aqueous [F-18]fluoride. Hence, no free Al3+ ions are present in the labelling step. We investigated the impact of parameters: temperature, pH, addition of organic solvent, and reaction time using the model chelator NH2-MPAA-NODA. With optimized parameters we could stably achieve a 80% radiochemical yield exerting a 30-min reaction time at 100 degrees C. This technique has the potential to become an important approach in radiopharmaceutical syntheses.