Labeling, quality control and biological evaluation of 99mTc-vibramycin for infection sites imaging

The use of radiolabeled antibiotics as diagnostic agents is an emerging area of medical research. Vibramycin is a semisynthetic antibiotic of the tetracycline family prescribed to treat a variety of infections. We present in this study a new technetium-99m labeled vibramycin radiopharmaceutical using SnCl2.2H2O as a reducing agent. The stability of 99mTc-vibramycin was evaluated in human serum at 37 0C. Biodistribution studies of 99mTc-vibramycin were performed on a model of bacterially infected Sprague-Dawley rats. In vitro studies were performed to determine the binding interaction of the labeled antibiotic with bacteria and its stability. Scintigraphic study was done with a γ-camera 1 h, 4 h and 24 h after radiotracer injection in rats having infectious intramuscular lesions. It was confirmed through this study that 99mTc-vibramycin possesses high radiolabeling yield (95%) as determined by instant thin-layer chromatography. The binding assay shows good binding with S. aureus. Scintigraphy in rabbits showed uptake of 99mTc-vibramycin in the infectious lesions 1 h, 4 h and 24 h after injection. Biodistribution studies of 99mTc-vibramycin revealed that the radiopharmaceutical accumulated significantly at the infection sites and showed the renal route of excretion. Target-tonon target ratios for 99mTc-vibramycin for the infectious lesion and the control muscle were found to be significantly different. The study demonstrated that 99mTc-vibramycin shows preferential binding to living bacteria. The biological activity (in vitro) of 99mTc-vibramycin was studied using the optimized parameters and the 99mTc-vibramycin was found to be a good infection imaging agent.