Radiocomplexation, Biological Evaluation, and Characterization of [^99mTc]-5-[(3-Carboxy-4-hydroxyphenyl)diazenyl]-2-hydroxybenz oic Acid as a Novel Agent for Imaging of Ulcerative Colitis in Mice

A procedure was developed for preparing [Tc-99m]-tricarbonyl-5-[(3-carboxy-4-hydroxyphenyl)diazenyl]-2-hydroxybenzoic acid complex ([Tc-99m]-tricarbonyl-Olsalazine), for ulcerative colitis (UC) imaging. High yield and 98.5% radiochemical purity of [Tc-99m]-tricarbonyl-Olsalazine were reached under optimized conditions. Thin layer chromatography (TLC) was used for the purification of the labeled compound. Reversed-phase high-performance liquid chromatography (RP-HPLC) was also used. A biodistribution study performed with a microbial mouse model of UC showed that the colon localization of [Tc-99m]-tricarbonyl-Olsalazine was the highest (77 & PLUSMN; 1.7% ID/g) at 120 min post injection. The agent was still present in the ulcerated colon for up to 24 h post injection (75% ID/g). Such level was not reached in previous studies. Thus, [Tc-99m]-tricarbonyl-Olsalazine can be used as a radiotracer for UC imaging in mice.