Nanostructure and Collagen-Stimulating Activity of Cationic Pentapeptide Lipopeptides

The self-assembly in aqueous solutions, cytocompatibility, and collagen production of lipopeptide C₁₆-KTTKS and a variant with arginine substitution for lysine, C₁₆-RTTRS, are investigated. C₁₆-KTTKS is known commercially as Matrixyl and is used in cosmetic formulations as it can stimulate collagen production. The self-assembly and conformations and collagen-stimulating effects of the two lipopeptides in two salt forms, trifluoroacetate (TFA) and acetate, are compared. Lipopeptide C₁₆-KTTKS self-assembles into nanotapes based on a multi-bilayer stacking across a pH range pH 4-7 and micelles at pH 2, with little influence of the counterion. In contrast, C₁₆-RTTRS forms a substantial population of spherical micelles for the acetate salt for pH 2-7, but mainly nanotapes for the TFA salt for pH 4-7. Conditions for hydrogel formation by C₁₆-KTTKS were identified. Both lipopeptides show good cytocompatibility to fibroblasts at sufficiently low concentration. The two lipopeptides also stimulate collagen production in Human Dermal Fibroblasts (HDFa) at low concentration (0.0062 wt%). No significant effect of the counterion was noted on cell viability or collagen production. Our results suggest that the peptide sequence influences the pH-dependent self-assembly properties and that this can be modulated for certain lipopeptides by the nature of the counterions.