Broad-spectrum hybrid antimicrobial peptides derived from PMAP-23 with potential LPS binding ability.

Antimicrobial peptides, as an integral part of the innate immune system, kill bacteria through a special mechanism of action, making them less susceptible to drug resistance. However, Lipopolysaccharide (LPS) as the permeation barrier on the bacterial membrane, inhibits the antibacterial activity of antimicrobial peptides and triggers the inflammatory response. GWKRKRFG is an LPS binding sequence with a ß-boomerang motif that can be linked to antimicrobial peptides to enhance their LPS affinity and reduce the possibility of LPS-induced inflammatory responses. In this study, a series of hybrid peptides were designed by conjugating the reported LPS binding sequence to the C-/N-terminal sequences of the natural porcine antimicrobial peptide PMAP-23 to increase the LPS affinity of peptides. Among all the designed hybrid peptides, 4R-PP-G8 showed the best antibacterial activity, nonhemolytic activity, and excellent cell selectivity. The presence of LPS not only induced the secondary structure transformation of 4R-PP-G8 from a random structure to an α-helical structure but also reduced the antibacterial activity of 4R-PP-G8 in a dose-dependent manner, indicating the excellent binding ability of 4R-PP-G8 to LPS. The LPS/LTA binding assay further verified the interaction between the peptide and LPS. The membrane permeability test verified that 4R-PP-G8 possessed a strong capability to penetrate the bacterial membrane after interacting with LPS. More direct membrane disruption was observed under FE-SEM and TEM. In conclusion, we provided a simple and efficient method to improve the LPS binding ability of antimicrobial peptides and enhance their antimicrobial activity, resulting in the peptide 4R-PP-G8 with clinical application potential.

Fabrication of Supramolecular Antibacterial Nanofibers with Membrane-Disruptive Mechanism.

By studying the principles of self-assembly and combining the structural parameters required for the asymmetric distribution of antimicrobial peptides (AMPs), we newly designed and screened the high-activity and low-toxicity AMP F2I-LL. This peptide can form a supramolecular hydrogel with a nanofiber microstructure in a simulated physiological environment (phosphate buffered saline), which exhibits broad-spectrum antibacterial activity. Compared with monomeric peptides, the introduction of a self-assembly strategy not only improved the bactericidal titer but also enhanced the serum stability of AMPs. Mechanistic studies showed that the positive charge enriched on the surface of the nanofiber was conducive to its rapid binding to the negatively charged part of the outer membrane of bacteria and further entered the inner membrane, increasing its permeability and ultimately leading to cell membrane rupture and death. This work provides insights into the design of nanopeptides with broad-spectrum antibacterial activity and provides new results for the development of biomedicine.