Roles of Self-Assembly and Secondary Structures in Antimicrobial Peptide Coatings

Antimicrobial peptide (AMP) coatings are promising alternatives to conventional antibiotics for the prevention of medical device- and implant-associated infections. Compared to covalent immobilization methods, coatings relying on physical interactions are more versatile but usually less stable. Previous work has developed stable noncovalent coatings on titanium and hydroxyapatite with a model AMP, GL13K, leveraging the strong hydrogen bonding between β-sheet-formed self-assemblies and polar substrates. In this work, a different GL13K self-assembly process was triggered with the formation of α-helices in ethanol/water cosolvent. We compared three different coatings on titanium to investigate the roles of self-assembly and secondary structures, including free GL13K in unordered structures, self-assembled GL13K with the formation of α-helices, and self-assembled GL13K with the formation of β-sheets. X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and water contact angle results confirmed the successful coatings of all three physiosorbed GL13K conditions. Self-assembled GL13K, either in α-helices or β-sheets, formed more effective antimicrobial coatings in killing Gram-positive Staphylococcus aureus than free GL13K. These findings could help design more stable and effective antimicrobial coatings using self-assembled AMPs.