[^99m Tc-HYNIC/EDDA]-MccJ25 antimicrobial peptide analog as a potential radiotracer for detection of infection

Bacterial infections are a serious risk to human health, and therefore techniques for early detection of infectious foci need to be further developed to begin treatment quickly and achieve better results. Antimicrobial peptides labeled with gamma-emission radio nuclides are important diagnostic radiotracers in nuclear medicine. This study was conducted to evaluate the potential of a ^99m Tc-labeled MicrocinJ25 (MccJ25) antimicrobial peptide analog for early detection of infection. For this purpose, a HYNIC conjugated cyclic peptide derivative based on the primary structure of MccJ25 peptide was prepared and labeled by ^99m Tc with tricine and EDDA as coligands. The [^99m Tc-HYNIC/EDDA]-MccJ25 peptide analog showed high radiochemical purity (˃90% (n = 5)) which was stable up to 24 hr after labeling. The radiotracer showed specific uptake to the Escherichia coli (E. coli) bacterial (40.45 ± 5.21%) at 1 hr incubation. High kidneys uptake of radioactivity (4.71 ± 0.84% and 3.76 ± 0.45% ID/g at 1 and 4 hr after injection respectively) demonstrates that most of the whole body clearance was proceeded via the urinary system. Significant radioactivity uptake (1.71 ± 0.34%ID/g) was observed in thigh muscle of mouse with E. coli induced infection at 1 hr after injection. In the blocking test, due to the significant decrease of radioactivity uptake in the infection site (0.62 ± 0.21%ID/g after 1 hr), the specificity of infection uptake was reviled. Despite the high activity of the bladder due to urinary excretion, the infected area was somewhat visible. Hence, the results indicate the potential of this new radiotracer to be used as a diagnostic agent in E. coli infections.