Background: Peptidomimetics are promising new antibiotics that are often refractory to the development of bacterial resistance. These antimicrobial peptide mimics (AMPMs) include short peptide mimics and N-substituted glycine peptoids, which are structurally different.[1-3] These structural disparities may influence their modes of action.
Methods: Three assays were employed to investigate the impact of these AMPMs on Pseudomonas aeruginosa. Sodium deoxycholate was used to assess the effects of the AMPMs on the outer membrane. The Limulus ameboid Lysate (LAL) assay examined peptoids' interaction with lipopolysaccharides (LPS) in the outer membrane. The DiSC3-5 assay evaluated the effect on inner membrane potential through fluorescence intensity changes. Intracellular leakage, indicating further inner membrane disruption, was confirmed by assessing ATP release. Morphological changes were captured via scanning electron microscopy. [4, 5]
Results: The peptide mimic 1083 and peptoid TM18 were able to disrupt the outer membrane of P. aeruginosa, resulting in disruption of 55% and 60%, respectively. TM18 exhibited a slightly higher LPS neutralization activity compared to 1083. Both peptidomimetics induced inner membrane disruption within 5 minutes, correlating with reductions in bacterial viability. Within 10 minutes, these peptoids facilitated the release of substantial amounts of cellular ATP, reaching 70% and 79%, respectively. Electron microscopy images depicted swollen membranes, providing visual confirmation of the disruptive effects exerted by these peptoids.
Conclusion: The two types of AMPMs demonstrated similar membrane disruption and release of intracellular contents. These findings emphasise their promising role in combating bacterial infections and supporting further exploration for therapeutic applications.