Optimized chromatographic separation and biological evaluation of 99mTc-clarithromycin for infective inflammation diagnosis

Abstract

Clarithromycin antibiotic was labeled with technetium-99m by adding ^99mTc to clarithromycin in the presence of SnCl₂·2H₂O. The radiochemical yield of ^99mTc-clarithromycin was determined by chromatographic methods. Gel chromatographic method was investigated for separation of the reaction mixture using different eluents including NaCl and phosphate, citrate, and carbonate buffer solutions. Also, free ^99mTcO₄^- and ^99mTc-clarithromycin were efficiently separated by reversed-phase HPLC on RP18 column. The maximum radiochemical yield reached 98 ± 0.2%. ^99mTc-clarithromycin is stable for 6 h. Biological distribution of ^99mTc-clarithromycin was studied for mice with the infection in the left thigh induced using Staphylococcus aureus. The target-to-nontarget (T/NT) ratio for ^99mTc-clarithromycin was found to be 7.33 ± 0.13 at 2 h after intravenous injection, with the subsequent gradual decline. This value is higher than that of commercially available ^99mTc-ciprofloxacin. The abscess to normal muscle ratio shows that ^99mTc-clarithromycin can be successfully used for infection imaging, allowing differentiation between bacterial infection and sterile inflammation.