Study on the preparation and biological evaluation of 99mTc–gatifloxacin and 99mTc–cefepime complexes

The aim of this work is the development of new radiopharmaceuticals for imaging infection and inflammation in human. Gatifloxacin (fluoroquinolone derivative) and cefepime (cephalosporine derivative) are antibiotics used to treat bacterial infections were investigated to label with one of the most important radioactive isotopes (technetium-99m). The reaction parameters that affect the labeling yield such as substrate concentration, stannous chloride dihydrate concentration, pH of the reaction mixture, and reaction time were studied to optimize the labeling conditions. Maximum radiochemical yield of 99mTc–gatifloxacin (90  ± 1.8%) complex was obtained by using 50 μg SnCl2·2H2O and 2.5 mg gatifloxacin at pH 10 while 99mTc–cefepime was prepared at pH 8 with a maximum radiochemical yield of 98  ± 1.4% by adding 99mTc to 5 mg cefepime in the presence of 50 μg SnCl2·2H2O. Biological distribution of 99mTc–gatifloxacin and 99mTc–cefepime was carried out in experimentally induced infection rats, in the left thigh, using Escherichia coli. Both thighs of the rats were dissected and counted and the ratio of bacterial infected thigh/contralateral thigh was then evaluated. T/NT for both 99mTc–gatifloxacin and 99mTc–cefepime was found to be 4.5  ± 0.3 and 8.4  ± 0.1, respectively, which was higher than that of the commercially available 99mTc–ciprofloxacin. The abscess to normal muscle ratio indicated that 99mTc–cefepime could be used for infection imaging. Besides, in vitro studies showed that 99mTc–cefepime can differentiate between bacterial infection and sterile inflammation.