Synthesis and biological evaluation of 99mTc-tricarbonyl complexes of C-3 carboxy derivatives of fluoroquinolones in infection and tumor animal models

Fluoroquinolones (FQ) are clinically used antibacterial agents. Antibacterial fluoroquinolone derivatives have been shown to exhibit cytotoxic properties in tumor cells. In this work, C3-carboxy fluoroquinolones derivatives were radiolabeled with the diagnostic radionuclide technetium-99 m and were evaluated as infection-and tumor-targeted agents. First, ciprofloxacin and enrofloxacin were converted to 3-hydrazides and then to the respective pyridine hydrazones (L1 and L2). Secondly, 3-carboxamide of enrofloxacin was converted to dipicolylamine (L3), and picolylaminoacetate (L4) tridentate chelators. The respective rhenium-tricarbonyl complexes of L1-L4 were synthesized and characterized by spectroscopic methods and were used as non-radioactive standards to characterize the analogous 99mTc-radiotracers. The 99mTc-tricarbonyl complexes were synthesized and their lipophilicity and stability were evaluated in vitro. The most stable tracers 99mTcL3, 99mTcL4, were incubated with E. coli cells and CT-26 murine colon adenocarcinoma cells to assess their cellular uptake. Also, the 99mTc-tracers were injected in mice, infected with E. coli, as well as in mice, bearing CT-26 tumors.