Effect of Terminal Modifications on the Antimicrobial Activity of the Designed G3 Peptide

Traditional antibiotics are increasingly limited by resistance, creating an urgent need for alternatives. Antimicrobial peptides (AMPs) are promising candidates due to their unique mechanisms and low resistance induction, but their clinical use is hindered by toxicity and limited activity. To address this, a series of cationic amphiphilic peptides were rationally designed based on the AMP G3 by varying amino acid type, number, and position, with particular focus on terminal modifications. The designed peptides showed strong antibacterial activity against <i>Escherichia coli</i> and reduced cytotoxicity compared with G3. Among them, CKKII14 and CKKII15, both with higher hydrophobicity, displayed potent short-term bactericidal activity, eliminating 99% of bacteria within 2 h, albeit with increased hemolysis relative to that of G3. Mechanistic studies indicated that CKKII14 exerted its activity mainly by disrupting the bacterial membranes. In vivo studies using an <i>Staphylococcus aureus</i>-infected mouse wound model confirmed the therapeutic efficacy of CKKII14, which accelerated wound closure and tissue regeneration. Immunohistochemical analysis further revealed that CKKII14 promoted angiogenesis by upregulating vascular endothelial growth factor and CD31 expression during early healing. Overall, this work clarifies the structure-function relationship of AMPs, highlighting the critical role of terminal modifications in balancing antibacterial potency and cytotoxicity. These findings provide valuable insights for the rational design of novel AMPs with enhanced efficacy and improved safety profiles, advancing their potential for clinical translation.