Technetium-99m labeling and evaluation of olsalazine: a novel agent for ulcerative colitis imaging

Ulcerative colitis is a chronic disease having a regressive nature. Commonly used diagnostic methods have the disadvantage to be invasive, time-consuming, and expensive. Therefore, a new sensitive method for the detection and monitoring of disease activity is urgently needed in clinical practice. In the current investigation, radio complexation of olsalazine with technetium-99m, its characterization, and optimization of the labeling conditions were explored. Optimum radiochemical yield of Tc-99m-olsalazine (97.6%+/- 1.8%) was obtained via direct complexation with technetium-99m (similar to 200MBq) in the presence of stannous chloride dihydrate (100 mu g) as reducing agent at pH6. It was observed that the complex showed significant in vitro stability in serum at 37 degrees C for more than 11h. The computer-generated optimized geometries of the Tc-99m-olsalazine were reported, and biodistribution studies were carried out using chemically and microbiologically mice-induced ulcerative colitis models. The tracer showed a good localization in both models and was excreted mainly via liver and to some extent via kidney. Imaging can be performed at 1-2h post-injection; at that time, the background activity has cleared, and the activity is concentrated in the target site. All the gathered biological data supported the usefulness of Tc-99m-olsalazine as a potential imaging agent for ulcerative colitis.