Characterization of cell selectivity, physiological stability and endotoxin neutralization capabilities of α-helix-based peptide amphiphiles

While naturally occurring antimicrobial peptides (AMPs) have been of increasing interest as alternative antibiotics due to their broad-spectrum antimicrobial activity and reduced possibility for the development of bacterial drug-resistance, some concerns such as potential cytotoxicity, poor antimicrobial activity and weak physiological stability may ultimately weaken their development as antimicrobial agents. To generate AMPs with enhanced therapeutic potential, we designed α-helical hybrid peptides based on PRW4, Fowlicidin-2, Protegrin-3 and Tritrpticin sequences to gain insights into their selectivities, physiological stabilities and endotoxin neutralization capabilities. The designed hybrid peptides PR-FO, PR-PG and PR-TR exhibited high cell selectivity towards bacterial cells over human red blood cells (hRBCs). Their activities were maintained in the presence of physiological concentrations of salts or serum, indicating a high stability in vitro. The results from fluorescence spectroscopy, flow cytometry, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that these designed peptides killed microbial cells by increasing membrane permeability and damaging membrane envelope integrity. Moreover, the hybrid peptides effectively neutralized endotoxins while causing minimal cytotoxicities. Collectively, our results suggest that these hybrid peptides, in particular PR-FO, have tremendous potential for use as novel antimicrobial and antisepsis agents.