Radiosynthesis and Bioevaluation of 99m Tc-Labeled Isocyanide Ubiquicidin 29-41 Derivatives as Potential Agents for Bacterial Infection Imaging.

To develop a novel 99m Tc-labeled ubiquicidin 29-41 derivative for bacterial infection single-photon emission computed tomography (SPECT) imaging with improved target-to-nontarget ratio and lower nontarget organ uptake, a series of isocyanide ubiquicidin 29-41 derivatives (CNnUBI 29-41, n = 5-9) with different carbon linkers were designed, synthesized and radiolabeled with the [ 99m Tc]Tc(I) + core, [ 99m Tc][Tc(I)(CO) 3 (H 2 O) 3 ] + core and [ 99m Tc][Tc(V)N] 2+ core. All the complexes are hydrophilic, maintain good stability and specifically bind Staphylococcus aureus in vitro. The biodistribution in mice with bacterial infection and sterile inflammation demonstrated that [ 99m Tc]Tc-CN5UBI 29-41 was able to distinguish bacterial infection from sterile inflammation, which had an improved abscess uptake and a greater target-to-nontarget ratio. SPECT imaging study of [ 99m Tc]Tc-CN5UBI 29-41 in bacterial infection mice showed that there was a clear accumulation in the infection site, suggesting that this radiotracer could be a potential radiotracer for bacterial infection imaging.