Liposome formulation of a myristoylated antimicrobial peptide derived from Chionodracine: preparation, physico-chemical characterization and biological activity

Second-generation antimicrobial lipopeptides are considered very promising tools to combat the spread of systemic fungal infections caused by fungi multidrug resistance and biofilm-associated infections. The present work reports a study on the lipopeptide Myr-B, derived from myristoylation of the natural antimicrobial peptide Chionodracine. The aim was to exploit its therapeutic potential by developing a suitable procedure for its encapsulation in liposomes, with a view to overcoming its in vivo instability and tendency to aggregation. A systematic investigation allowed to select two optimal liposome formulations, based on dimyristoylphosphatidylcholine, having chains of the same length of the lipopetide, and cholesterol and/or cholesterylhemisuccinate. Thin-film hydration and lipid-cake preparation methods were explored, and chemical-physical characterization was integrated with molecular dynamics simulations. The lipid-cake method proved to be the optimal approach, yielding monodisperse, stable liposomes with high encapsulation efficiency. Encapsulation in both liposome formulations markedly enhanced antifungal activity, lowering minimum inhibitory concentrations more than ten-fold against Candida albicans and approximately four-fold against Candida tropicalis compared to free Myr-B. LIVE/DEAD imaging also confirmed a strong reduction in biofilm formation. Liposomes displayed minimal haemolysis, low cytotoxicity toward human fibroblasts, and good in vivo tolerability in Galleria mellonella. Notably, specific interactions between cholesteryl-hemisuccinate and the peptide involved a peculiar liposome structure and a slower release from the liposome. Overall, both Myr-B–loaded liposomes produced by the lipid cake protocol significantly potentiates MYR-B efficacy while maintaining a favourable safety profile. These formulations are not universally applicable to all lipopeptides; however, the underlying criteria presented in this work are.