Effects of Conjugation of Ferrocene and Gallic Acid On desCys¹¹/Lys¹²/Lys¹³-(p-BthTX-I)2K Peptide: Structure, Permeabilization and Antibacterial Activity

Background: Antimicrobial resistance is an emerging global health challenge that has led researchers to study alternatives to conventional antibiotics. A promising alternative is antimicrobial peptides (AMPs), produced as the first line of defense by almost all living organisms. To improve its biological activity, the conjugation of AMPs is a promising approach. Objective: In this study, we evaluated the N-terminal conjugation of p-Bt (a peptide derived from Bothrops Jararacuçu`s venom) with ferrocene (Fc) and gallic acid (GA). Acetylated and linear versions of p-Bt were also synthesized to evaluate the importance of N-terminal charge and dimeric structure. Methods: The compounds were obtained using solid-phase peptide synthesis. Circular dichroism, vesicle permeabilization, antimicrobial activity, and cytotoxicity studies were conducted. Results: No increase in antibacterial activity against Escherichia coli was observed by adding either Fc or GA to p-Bt. However, Fc-p-Bt and GA-p-Bt exhibited improved activity against Staphylococcus aureus. No cytotoxicity upon fibroblast was observed for GA-p-Bt. On the other hand, conjugation with Fc increased cytotoxicity. This toxicity may be related to the membrane permeabilization capacity of this bioconjugate, which showed the highest carboxyfluorescein leakage in vesicle permeabilization experiments. Conclusion: Considering these observations, our findings highlight the importance of adding bioactive organic compounds in the N-terminal position as a tool to modulate the activity of AMPs.