Molecular Architecture And Charging Effects Enhance The In Vitro And In Vivo Performance Of Multi-Arm Antimicrobial Agents Based On Star-Shaped Poly(L-Lysine)

Molecular architecture is a largely neglected and unexplored factor that could impart a significant difference to the antimicrobial activity of antimicrobial peptides. In this article, the advantages (i.e., improved charging effect and enhanced proteolytic stability) of star-shaped poly(L-lysine)s (PLLs) over their linear analogs are extensively explored by the methods of computational simulation and experiments. A series of PEI-g-PLL with a hyperbranched polyethylenimine (PEI) core and PLL peripheral chains are designed as a class of versatile molecular scaffold for the development of star-shaped antimicrobial peptides. Computational simulations and zeta-potential measurements reveal that the change in PLL conformation from linear to star-shaped significantly increases the cationic charge density, allowing enhanced binding affinity toward the bacterial membrane. The minimum inhibitory concentration and killing kinetics measurements demonstrate that PEI-g-PLLs exhibit higher antimicrobial activity and bactericidal efficiency in vitro than the linear PLL counterparts. The absence of hydrophobic segments in PEI-g-PLLs weakens the nonspecific interactions with eukaryotic cells and offers remarkable selectivity, as evidenced by their negligible hemolytic activity. Furthermore, PEI-g-PLLs demonstrate enhanced proteolytic stability and unprecedented antimicrobial activity in vivo. PEI-g-PLLs, with their high antimicrobial activity, enormous selectivity, and remarkable proteolytic stability, represent a new series of potent antimicrobial peptides to treat drug-resistant infections.