In vitro and in vivo assessment of 99mTc-UBI specificity for bacteria

Nucl Med Biol. 2003 Aug;30(6):597-603. doi: 10.1016/s0969-8051(03)00054-4.


Technetium-99m labeled ubiquicidin peptide 29-41 ((99m)Tc-UBI) is a cationic human antimicrobial peptide fragment that has been shown to bind bacteria in vitro and accumulates at sites of infection in experimental animals. To help determine if (99m)Tc-UBI is bound to the bacterial cell envelope by a simple nonspecific electrostatic interaction, a comparative study of the in vitro binding of (99m)Tc-UBI and two different (99m)Tc labeled cationic peptides ((99m)Tc-Tat-1-Scr and (99m)Tc-Tat-2-Scr) to bacteria and to two tumor cell line (LS174T and ACHN) was performed. The in vivo specificity of (99m)Tc-UBI for infection in mice was also evaluated using dual labels in the same animal and comparing the target/non-target ratio for (67)Ga-citrate and (99m)Tc-UBI at sites of induced infection and sterile inflammation. Under conditions of this study, the in vitro binding of (99m)Tc-UBI, (99m)Tc-Tat-1-Scr and (99m)Tc-Tat-2-Scr to S. aureus was 35, 78 and 87% respectively. While the binding of (99m)Tc-Tat-1-Scr and (99m)Tc-Tat-2-Scr was 37 and 33% to colon tumor cells (LS174T) and 39 and 41% to renal tumor cells (ACHN) respectively, the binding of (99m)Tc-UBI to both cell types was much lower at less than 4%. In vivo studies revealed that there is a significant difference (p < 0.05) in the radioactive accumulation of (99m)Tc-UBI between the sites of infection and inflammation compared to (67)Ga-citrate. Thus, (99m)Tc-UBI showed an average infection/inflammation ratio of 2.08 +/- 0.49 compared to 1.14 +/- 0.45 for (67)Ga-citrate. In conclusion, the in vitro and in vivo results provide evidence that a specific mechanism is responsible of the (99m)Tc-UBI bacterial intracellular accumulation.

Publication types

  • Comparative Study
  • Evaluation Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Validation Study

MeSH terms

  • Animals
  • Carcinoma, Renal Cell / diagnostic imaging*
  • Carcinoma, Renal Cell / metabolism*
  • Cell Line, Tumor
  • Citrates / pharmacokinetics
  • Colonic Neoplasms / diagnostic imaging*
  • Colonic Neoplasms / metabolism*
  • Gallium / pharmacokinetics
  • Humans
  • Kidney Neoplasms / diagnostic imaging
  • Kidney Neoplasms / metabolism
  • Mice
  • Organotechnetium Compounds / pharmacokinetics*
  • Peptide Fragments / pharmacokinetics*
  • Radionuclide Imaging
  • Radiopharmaceuticals / pharmacokinetics
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Staphylococcal Infections / diagnostic imaging*
  • Staphylococcal Infections / metabolism*
  • Staphylococcus aureus / isolation & purification
  • Staphylococcus aureus / metabolism*


  • Citrates
  • Organotechnetium Compounds
  • Peptide Fragments
  • Radiopharmaceuticals
  • technetium 99m ubiquicidin(29-41)
  • Gallium
  • gallium citrate