Effect of Antioxidants on the Preparation of $^{99m}Tc-MDP$

$^{99m}Tc-MDP$ 제조시 산화방지제 첨가영향

To improve the quality of $^{99m}Tc-methylenediphonate$ $(^{99m}Tc-MDP)$ for skeletal imaging, different composed $^{99m}Tc-MDP$ complexes were prepared with addition of antioxidants such as ascorbic acid, getisic acid, and p-aminobenzoic acid. To characterize the different $^{99m}Tc-MDP$ preparations, some physical and biochemical properties of $^{99m}Tc-MDP$ such as thermal stability, lipophilicity and bindability to serum protein were studied and organ distribution pattern of these complexes also compared. The thermal stabilities of $^{99m}Tc-MDP$ contained antioxidants were dependant mainly on pH, temperature, and elapsed time after the preparation. $^{99m}Tc-MDP$ complex contained gentisic acid as antioxidant was extremely unstable at alkaline condition. The most stable $^{99m}Tc-MDP$ was found in the presence of p-aminobenzoic acid. $^{99m}Tc-MDP$ complexes with antioxidants were very lipophilic but lipophilicity differences in antioxidants were not observed. The bindability of $^{99m}Tc-MDP$ to serum protein was not affect at pH $5.0\sim9.0$ by the different antioxidants. However, protein binding percentage of $^{99m}Tc-MDP$ with ascorbic acid was relatively low (22.7%) at pH 9.0. In biodistribution studies in mice, bone to muscle ratios of $^{99m}Tc-MDP$ preparations containing ascorbic acid, gentisic acid, and p-aminobenzoic acid were 15.3, 24.5, and 30.1, respectively. Im to our results, p-aminobenzoic acid is fond to be the most promising antioxidant.