99m Tc-labeled teicoplanin and its biological evaluation in experimental animals for detection of bacterial infection

Labeling of teicoplanin with 99m Tc using SnCl2·2H2O as reducing agent was performed. The dependence of the 99m Tc-teicoplanin yield on the concentrations of teicoplanin and reducing agent, pH of the reaction mixture, reaction time, and reaction temperature was studied. Under optimum conditions (2 mg of teicoplanin, 5 μg of SnCl2·2H2O, pH 9, 30 min, 25°C), the labeling yield of 99m Tc-teicoplanin of 87.7 ± 1.3% was achieved. 99m Tc-teicoplanin is stable for 4 h after labeling; then its relative content decreased gradually to reach 81.7 ± 1.1% in 8 h. Biodistribution studies in mice with infection induced in the left thigh by Staphylococcus aureus were carried out. The bacterial infected thigh/contralateral thigh uptake ratio (T/NT) was evaluated. The time for the maximum accumulation of 99mTc-teicoplanin in the infection site was 2 h after administration of the labeled compound. The abscess-to-muscle ratio for 99m Tc-teicoplanin was 4.33 ± 0.3, while that for commercially available 99m Tc-ciprofloxacin was 3.8 ± 0.5 under similar conditions. Thus, 99m Tc-teicoplanin can be used for infection imaging.