Synthesis and biological characterization of 99mTc-labeled ciprofloxacin

Investigations aimed at the creation of a standard kit for the synthesis of 99mTc-labeled ciprofloxacin (fluoroquinolone antibiotic) have been carried out. For isotope labeling, eluate from a technetium-99m generator was added to dry sterile mixtures of ciprofloxacin hydrochloride (CFH) with a reducing agent (tin chloride, SnCl2) in various ratios. The mixtures were incubated for 20 min at room temperature. The influence of components of the reaction mixture on the amount of radiochemical impurity in the resulting radiopharmaceuticals was estimated using TLC. Three 99mTc-containing complexes and a colloid related to the hydrolysis of tin compounds were formed. The tin content in each complex has been determined by introducing a 117mSn isotope label. Ways to decrease colloid formation by changing the pH of the medium and by reducing the SnCl2 concentration in the kit have been investigated. The kit composition has been optimized. It is established that radiopharmaceuticals containing less than 0.175 mg SnCl2 per 5 mg CFH can be used without additional filtration. Tests on experimental animals (rabbits) with model inflammation in soft tissues showed the functional suitability of 99mTc-labeled ciprofloxacin for diagnosis of infectious-inflammatory processes.