99mTc labeled levofloxacin as an infection imaging agent: a novel method for labeling levofloxacin using cysteine•HCl as co-ligand and in vivo study

Levofloxacin was labeled with Tc-99m using cysteine center dot HCl as co-ligand and SnCl2 center dot 2H(2)O as reducing agent. The influence of various parameters such as amount of cysteine center dot HCl, reducing agent, pH value, and reaction time on labeling process was studied. After optimizing the conditions the labeling was performed at pH 5 using 1 mg of levofloxacin, 500 mu g of cysteine center dot HCl, 50 mu g of SnCl2 center dot 2H(2)O, and 15 min reaction time. The radiochemical purity was determined with the help of instant thin layer chromatography (ITLC) and reverse phase high performance liquid chromatography (RP-HPLC) which was more than 95% and was stable for up to 6 h. Biodistribution of Tc-99m-levofloxacin (Tc-99m-lefx) was studied in infection induced rat models using live Staphylococcus aureus and heat killed S. aureus (sterile inflammation model). In the case of the live S. aureus induced abscess model, the accumulation of Tc-99m-lefx at target was 3.96, which was higher than that of Tc-99m-ciprofloxacin (Tc-99m-cifx), taken as the control.