Optimization condition in labeling of Ofloxacin with 99mTc and its biological evaluation in Staphylococcus aureus and Escherichia coli for infection imaging

The use of radiopharmaceuticals is a powerful tool in the management of patients with infectious or inflammatory diseases in nuclear medicine. In this study ofloxacin as a second-generation fluoroquinolone is used to design a desired infection imaging agent after labeling with 99mTc via direct labeling. Ofloxacin was radiolabeled with 99mTc using different concentrations of ligand, stannous chloride, sodium pertechnetate and at different pH. Then labeling yield, stability in saline and serum, lipophilicity, binding with Staphylococcus aureus and Escherichia coli and biodistribution in infected mice for labeled compound were studied. The final complex was characterized by TLC and HPLC and radiochemical purity of >90% was obtained when 1.5 mg ofloxacin in presence of 75 µg SnCl2 was labeled with 370 MBq sodium pertechnetate. The complex showed specific binding to Staphylococcus aureus and Escherichia coli. Biodistribution results showed that radioligand had high affinity in the infected site in mice. The uptake for Staphylococcus aureus induced infections (T/NT = 2.33 ± 0.17 at 1 h post injection) was higher than that was for Escherichia coli (T/NT = 1.96 ± 0.13 at 1 h post injection). This complex may lead to further development of a radiotracer for imaging of infections induced by gram-positive or gram-negative bacteria.