$^{99m}Tc$ labeled levofloxacin as an infection imaging agent: a novel method for labeling levofloxacin using cysteine·HCl as co-ligand and in vivo study

Abstract

Levofloxacin was labeled with $^{99m}Tc$ using cysteine·HCl as co-ligand and $SnCl_2.2H_2O$ as reducing agent. The influence of various parameters such as amount of cysteine·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 μg of cysteine· HCl, 50 μg of $SnCl_2.2H_2O$, 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 $^{99m}Tc$-levofloxacin ( $^{99m}Tc$-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 $^{99m}Tc$-lefx at target was 3.96, which was higher than that of $^{99m}Tc$-ciprofloxacin ( $^{99m}Tc$-cifx), taken as the control.