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.