14-helical beta-peptides with antifungal activity against Candida albicans planktonic cells and biofilms

We designed 14-helical beta-peptides (beta-amino acid oligomers) that mimic the amphiphilic, helical, and cationic properties of many natural antimicrobial peptides and evaluated their activity against Candida albicans planktonic cells and biofilms. beta-Peptides offer several advantages over antimicrobial peptides composed of alpha-amino acids, including conformational stability and resistance to proteases.;Our beta-peptides inhibited the growth of planktonic C. albicans cells with minimum inhibitory concentrations (MICs) as low as 8 microg/mL, and properly designed beta-peptides exhibited low levels of hemolysis at their MICs. The role of beta-peptide sequence and structural properties in eliciting antifungal activity was assessed. Global amphiphilicity was necessary for antifungal activity, and net charge, length, and 14-helical conformation also affected activity. beta-Peptide enantiomers had indistinguishable activity. These results are consistent with a mechanism of action that involves cell membrane disruption without a distinct chiral target.;We developed a scheme to fluorescently label a beta-peptide while retaining the activity of the unlabeled beta-peptide. The labeled beta-peptide penetrated the cell membrane and accumulated in the cytoplasm of C. albicans cells. The labeled beta-peptide was detected only in metabolically inactive cells, suggesting that beta-peptide entry is correlated with cell death.;beta-Peptides that were lethal to planktonic cells also had activity against C. albicans biofilms. Concentrations of 1--16 times the planktonic MICs were needed to achieve 80% reduction in metabolic activity of the biofilms, and, at concentrations of 128--256 microg/mL, no biofilm metabolic activity was detected. The fluorescently labeled beta-peptide penetrated yeast and hyphal cells throughout the depth of biofilms. At concentrations near their MICs, beta-peptides completely prevented planktonic C. albicans cells from forming biofilms, indicating that beta-peptides may be useful in functionalizing surfaces to prevent fungal colonization and biofilm formation. Surfaces were functionalized by non-covalently incorporating the fluorescently labeled beta-peptide into polyelectrolyte multilayered film coatings. The beta-peptide maintained antifungal activity after incorporation and was toxic to C. albicans cells on the surface.;Our work provides the foundation for more in-depth explorations of the interactions of beta-peptides with C. albicans planktonic cells and biofilms and reveals the potential for using beta-peptides to create antifungal surfaces that resist biofilm formation.