Simplified NaCl based 68Ga concentration and labeling procedure for rapid synthesis of 68Ga radiopharmaceuticals in high radiochemical purity

A simple sodium chloride (NaCl) based 68Ga eluate concentration and labeling method that enables rapid, high-efficiency labeling of DOTA conjugated peptides in high radiochemical purity is described. The method utilizes relatively few reagents and comprises minimal procedural steps. It is particularly well-suited for routine automated synthesis of clinical radiopharmaceuticals. For the 68Ga generator eluate concentration step, commercially available cation-exchange cartridges and 68Ga generators were used. The 68Ga generator eluate was collected by use of a strong cation exchange cartridge. 98% of the total activity of 68Ga was then eluted from the cation exchange cartridge with 0.5 mL of 5 M NaCl solution containing a small amount of 5.5 M HCl. After buffering with ammonium acetate, the eluate was used directly for radiolabeling of DOTATOC and DOTATATE. The 68Ga-labeled peptides were obtained in higher radiochemical purity compared to other commonly used procedures, with radiochemical yields greater than 80%. The presence of 68Ge could not be detected in the final product. The new method obviates the need for organic solvents, which eliminates the required quality control of the final product by gas chromatography, thereby reducing postsynthesis analytical effort significantly. The 68Ga-labeled products were used directly, with no subsequent purification steps, such as solid-phase extraction. The NaCl method was further evaluated using an automated fluid handling system and it routinely facilitates radiochemical yields in excess of 65% in less than 15 min, with radiochemical purity consistently greater than 99% for the preparation of 68Ga-DOTATOC.

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