Membrane Selectivity of Star-Shaped Peptides: A Comparative Molecular Dynamics Study across Different Bacterial and Mammalian Bilayers

Star-shaped peptides a.k.a. structurally nanoengineered antimicrobial peptide polymers (SNAPPs) are emerging as promising selective agents against bacterial membranes. In this study, we used all-atom molecular dynamics simulation techniques to investigate the interaction of a promising cationic SNAPP architecture (Alt-SNAPP with 8 arms made of alternating lysine and valine residues) with modeled Gram-negative, Gram-positive, mammalian, and red blood cell membranes. Alt-SNAPP exhibited rapid and stable binding to bacterial membranes, driven by electrostatic interactions with anionic lipids such as phosphatidylglycerol (PG) and cardiolipin (CL), and supported by membrane fluidity. In contrast, mammalian and red blood cell membranes, enriched in zwitterionic lipids and cholesterol, resisted peptide association entirely. Analyses of center-of-mass distance, partial density, hydrogen bonding, and interaction energy confirmed that SNAPP remains fully excluded from host-like membranes while forming stable, multivalent interactions with bacterial bilayers. These findings provide mechanistic insight into SNAPP's membrane selectivity and offer a molecular framework for designing next-generation antimicrobial polymers with minimal off-target toxicity.