Synthesis and antimicrobial evaluation of two peptide LyeTx I derivatives modified with the chelating agent HYNIC for radiolabeling with technetium-99m

• Published in: Journal of Venomous Animals and Toxins including Tropical Diseases
• Main Authors: Leonardo Lima Fuscaldi, Daniel Moreira dos Santos, Natália Gabriela Silva Pinheiro, Raquel Silva Araújo, André Luís Branco de Barros, Jarbas Magalhães Resende, Simone Odília Antunes Fernandes, Maria Elena de Lima, Valbert Nascimento Cardoso
• Format: Article in Journal/Newspaper
• Language: English
• Published: SciELO 2016
• Subjects: Septic and aseptic inflammation; Differential diagnosis; Antimicrobial peptides LyeTx I derivatives; MALDI-ToF-MS RP-HPLC; Technetium-99m; HYNIC EDDA Tricine; Arctic medicine. Tropical medicine; RC955-962; Toxicology. Poisons; RA1190-1270; Zoology; QL1-991; Arctic
• Online Access: https://doi.org/10.1186/s40409-016-0070-y; https://doaj.org/article/d242fb137093419d9e77c23140871a9d

Abstract Background Current diagnostic methods and imaging techniques are not able to differentiate septic and aseptic inflammation. Thus, reliable methods are sought to provide this distinction and scintigraphic imaging is an interesting option, since it is based on physiological changes. In this context, radiolabeled antimicrobial peptides have been investigated as they accumulate in infectious sites instead of aseptic inflammation. The peptide LyeTx I, from the venom of Lycosa erythrognatha, has potent antimicrobial activity. Therefore, this study aimed to synthesize LyeTx I derivatives with the chelating compound HYNIC, to evaluate their antimicrobial activity and to radiolabel them with 99mTc. Methods Two LyeTx I derivatives, HYNIC-LyeTx I (N-terminal modification) and LyeTx I-K-HYNIC (C-terminal modification), were synthesized by Fmoc strategy and purified by RP-HPLC. The purified products were assessed by RP-HPLC and MALDI-ToF-MS analysis. Microbiological assays were performed against S. aureus (ATCC® 6538) and E. coli (ATCC® 10536) in liquid medium to calculate the MIC. The radiolabeling procedure of LyeTx I-K-HYNIC with 99mTc was performed in the presence of co-ligands (tricine and EDDA) and reducing agent (SnCl2. 2H2O), and standardized taking into account the amount of peptide, reducing agent, pH and heating. Radiochemical purity analysis was performed by thin-layer chromatography on silica gel strips and the radiolabeled compound was assessed by RP-HPLC and radioactivity measurement of the collected fractions. Data were analyzed by ANOVA, followed by Tukey test (p-values < 0.05). Results Both LyeTx I derivatives were suitably synthesized and purified, as shown by RP-HPLC and MALDI-ToF-MS analysis. The microbiological test showed that HYNIC-LyeTx I (N-terminal modification) did not inhibit bacterial growth, whereas LyeTx I-K-HYNIC (C-terminal modification) showed a MIC of 5.05 μmol.L−1 (S. aureus) and 10.10 μmol.L−1 (E. coli). Thus, only the latter was radiolabeled with 99mTc. The radiochemical ...