Radiosynthesis of Novel⁶⁸Ga-labeled α-Cyclodextrin for PET Imaging

Background: Cyclodextrins (CDs) are cyclic oligosaccharides composed of glucose units linked by α-1, 4 glycosidic bond. Recently, CDs have been promising for the application of medical imaging, especially nuclear medicine imaging. Herein, we aim to simply radiosynthesis⁶⁸Ga-alpha-cyclodextrin (⁶⁸Ga-αCD) by directly radiolabeling Ga-68 to αCD. Method: Ga-68 was eluted from the⁶⁸Ge/⁶⁸Ga generator. αCD solution was prepared and added to the reaction vial. The vial was heated at 100 °C for 20 min. After that, the reaction was allowed to cool down at room temperature. Radioactivity was measured using instant thin layer chromatography (iTLC) and the obtained iTLC paper was scanned by a TLC scanner. The radiochemical purity (RCP) was calculated. The pH of the resulting solution was measured using a pH meter and its mass to charge ratio was measured using mass spectrometry (MS). The radiosynthesis process was then optimized to increase the RCP of⁶⁸Ga-αCD. Result: Initially, RCP of the⁶⁸Ga-αCD was very low (0.236 ± 0.02%, n=3). Upon the optimization using sodium ascorbate as radiostabilizer together with 1 mg/ml αCD solution and purified by C-18 cartridge, the RCP is increased. Ultimately, we have successfully achieved an RCP of 18.4 ± 1.1%. Conclusion: In this study, we successfully radiosynthesized⁶⁸Ga-αCD by directly radiolabeling Ga-68 with αCD. Although our findings reveal significant possibilities, further investigation of biodistribution studies using PET imaging is required to thoroughly understand the potential of these novel radiopharmaceuticals.