Engineering the interface: pH-dependent self-assembly of lysine-tyrosine synthetic copolypeptides for anti-biofilm implant coatings.

Abstract

Developing resilient antimicrobial coatings for medical implants requires a sophisticated balance between direct bactericidal activity and resistance to bacterial adhesion. While poly(L-lysine) provides effective membrane disruption, its performance is often compromised by the accumulation of cellular debris, which facilitates secondary biofilm formation. In this study, we engineered a block copolypeptide, pK30Y10, designed to bridge this functional gap by combining 30 cationic lysine residues with 10 aromatic tyrosine units. By utilizing ring-opening polymerization of N-carboxyanhydrides, we synthesized a scalable, structurally defined material that leverages tyrosine's unique phenolic properties specifically π-π stacking and hydrogen bonding to drive surface-anchored self-assembly. We systematically investigated the material's transition from molecular chains to complex assemblies across a pH range of 2.0 to 10.0, identifying a critical link between solution-phase conformation and interfacial performance. Physicochemical characterization confirmed that pH-induced ionization states dictate the peptide's secondary structure and aggregation behavior. Crucially, these distinct structural phases resulted in strain-specific antimicrobial outcomes: while pK30Y10 coatings effectively disrupted both pathogens, the optimal assembly state for biomass reduction differed between Staphylococcus aureus and Pseudomonas aeruginosa. This suggests that the biological efficacy is not merely a product of chemical composition, but a direct consequence of how the block architecture organizes at the interface under varying environmental conditions.