An Upgraded Solid-Phase Assembly of Chelators (DOTA and NOTA) Enabled Bacterial Uptake Studies of Radiolabeled Peptide

Among popular radio metal chelators, DOTA and NOTA have been remarkably considered in radionuclide therapy and imaging studies due to several advantages in pharmacology. Here, we developed a practical and general method for assembling DOTA and NOTA in the solid phase peptide (pseudo-dilute conditions) using a wide range of solvents with easily accessible and economical feedstocks, which mitigated unprecedented challenges associated with previously reported methods. This upgraded approach enabled an efficient installation of these two chelators on various bioactive peptide sequences. Finally, we assessed the antimicrobial activity of the DOTA- and NOTA-attached Combi peptides to B. subtilis, which was intact. The authenticity of the assembled DOTA framework was assessed by labeling ¹⁷⁷Lu and in vitro bacterial uptake in E. coli and S. aureus. ¹⁷⁷Lu-labeled DOTA-Combi peptide exhibited promising uptake for developing a bacterial infection imaging agent while negligible hemolysis activity even at >200 μM. This contribution will be valued for developing peptide radiopharmaceuticals with operational simplicity and economic approaches.