Radiolabeling, quality control, and biological characterization of ¹⁷⁷ Lu-labeled kanamycin

Kanamycin is an antibiotic, isolated from Streptomyces kanamyceticus, which is used to treat serious bacterial infections. The fact that the present radioligand ^99m Tc-kanamycin used for diagnosis is short-lived, raised a need to label and study kanamycin with one of the most important beta (β) radiation emitting isotope ¹⁷⁷ Lu. Labeling yield of ¹⁷⁷ Lu-kanamycin was confirmed by different chromatography techniques such as paper chromatography, TLC, HPLC. Several experiments were performed to optimize labeling with changing reaction conditions such as pH, temperature, amount of ligand, and reaction time. In vitro stability analysis was performed incubation with human serum. Electrophoresis analysis was also conducted to determine the charge on ¹⁷⁷ Lu-kanamycin. The biodistribution and scintigraphy were performed in normal mice and rabbit, respectively, at different time intervals of postinjection. ¹⁷⁷ Lu-kanamycin was prepared with very high yield (~100%), with excellent stability in vivo and in vitro (>99% 6 hr postprep.), at pH 7. Maximum labeling was achieved at less reaction time (15 min), with maximum conjugation of the ligand (12.5 mg) with ¹⁷⁷ Lu. Electrophoresis analysis showed net neutral charge. The radioligand showed rapid clearance from body in biodistribution and scintigraphy studies. The preparation ¹⁷⁷ Lu-kanamycin could be used as a radio-pharmaceutical for infection imaging purpose, especially when transporting the radioligand to long-range distances.