Freeze-Dried Cold Kit for Preparation of Tc-99m-Ciprofloxacin As an Infection Imaging Agent

Introduction: Radiolabeled antibiotics are being used for the specific diagnosis of infection by exploiting their specific binding properties to the bacterial components, thereby making it possible to differentiate infection from sterile lesions. The aim of this work was to prepare and evaluate a freeze-dried kit of ciprofloxacin designed for the labeling with Tc-99m. Methods: Factors like amount of reducing agent and optimum pH were investigated to make the ciprofloxacin kit. The kit was reconstituted with Tc-99m at room temperature and the radiochemical purity was evaluated by ITLC method. Stability and protein binding in human serum followed by in vitro binding to bacteria were assessed. Biodistribution of labeled kit in staphylococcus aureus infected rats muscles were studied using ex vivo counting and scintigraphy. Results: Labeling yield of > 90% was obtained corresponding to a specific activity of 178 GBq/mmol. The stability of radiolabeled kit in human serum was 84.2% after 1 hour post incubation. In-vitro studies showed 75 % of radioactivity was bound to bacteria. After injection into mice clearance from the circulation occurred mainly by biliary-renal clearance and site of infection was rapidly detected within 30 min. Target to non-target muscle ratio was 3.23 +/- 0.05 % at 30 min post injection. Conclusion: 99mTc-ciprofloxacin showed favorable radiochemical and biological characteristics which permitted detection of the infection with optimal visualization.