Abstract
This study aimed to develop an efficient concentration methodology to enhance the specific activity of (68)Ga. By systematically optimizing chelation parameters, we established the relationships between the molar amounts of single-stranded DNA (A20) and varying (68)Ga specific activities, thereby maximizing the radiochemical yield in DNA radiolabeling systems. Method: The (68)Ga eluate was subjected to ionic enrichment and initially purified using cation-exchange chromatography, followed by concentration through an organic/aqueous phase protocol employing acetone/NaCl eluents. Systematic chelation experiments were performed by reacting gradient concentrations of A20 (1 or 3 nmol) with radiometal solutions at defined specific activities (1, 5, and 10 mCi/mL). The resulting reaction mixtures were subsequently purified using PD-10 columns. Dynamic PET/CT imaging of the purified (68)Ga-labeled A20 ((68)Ga-A20) was performed over a 60 min interval to assess its biodistribution and metabolic kinetics in murine models. Results: Extraction of (68)Ga using water resulted in the introduction of sodium ions, which could interfere with subsequent labeling reactions. In contrast, acetone-based extraction effectively prevented contamination from exogenous ions. Optimization of the extraction protocol led to a 5-fold increase in the radioactivity concentration of (68)Ga. Labeling studies demonstrated an efficiency of 75.03% when 3 nmol (100 μM) of A20 was used, and the (68)Ga radioactivity concentration was maintained at 1 mCi/mL. Dynamic PET/CT imaging revealed that (68)Ga-A20 was predominantly eliminated via the renal pathway in healthy mice. Following curve-fitting analysis, the calculated half-lives were 6.61 ± 0.26 min in blood, 13.53 ± 1.04 min in kidney, and 7.61 ± 0.27 min in liver. Conclusion: This study demonstrated that the radioactivity concentration of (68)Ga can be effectively enhanced by processing the (68)Ga solution through cation-exchange chromatography followed by acetone extraction, representing a critical advancement in improving radiolabeling efficiency. Additionally, the results indicated that (68)Ga-A20 was primarily eliminated via the renal pathway in healthy mice.