Multiparametric labeling optimization and synthesis of ⁶⁸Ga-labeled compounds applying a continuous-flow microfluidic methodology

The synthesis and functional evaluation of a wide variety of radiolabeled chelator-biomolecule conjugates with high specific activity and radiochemical purity are crucial to development of personalized nuclear medicine. An excellent platform technology for achieving this objective involves use of generator-produced positron emission tomography (PET)-radionuclide ⁶⁸Ga. Currently, applied manual methodology for optimization and development for new labeling techniques offers only slow screening with relatively high precursor consumption. A capillary-based microfluidic synthesis module with online high-performance liquid chromatography (HPLC) was constructed for the optimization of reaction parameters of ⁶⁸Ga-PET tracers. This approach enables performance of ⁶⁸Ga-labeling reactions in 10 μL volumes, followed by sample analysis. The high-throughput capacity of the system allows very rapid optimization. The optimal pH and ligand concentration from the experiments were utilized directly to the production of ⁶⁸Ga-NODAGA-(RGD)₂ and ⁶⁸Ga-NOPO-RGD. Applying optimal parameters to production of these aforementioned radiopharmaceuticals allowed their synthesis with high radiochemical purity (over 95%) and with surprisingly negligible retention of residual activity in the system.