Interactions and release of two palmitoyl peptides from phytantriol cubosomes.

Phytantriol cubosomes loaded with two palmitoyl peptides (Palpepcubes), namely GHKcube and GQPRcube, were prepared using an ultrasonication protocol. The Palpepcubes dimensions were characterized by dynamic light scattering (DLS) and cryo-transmission electron microscopy (cryo-TEM). Small-angle X-ray scattering (SAXS) analyses revealed that the bicontinuous cubic structure remained even at palmitoyl peptide contents as high as 5wt.%, with an increase in the cell parameter from approximately 6.5 to 7.2nm. Isothermal titration calorimetry (ITC) was used to elucidate the interactions between the blank cubosomes and the palmitoyl peptides, revealing an exothermic process of interaction. Moreover, the in vitro release of the palmitoyl peptides from the Palpepcubes was studied using a dialysis method coupled with liquid chromatography-mass spectrometry (LC/MS) technique, in which a sustained release of up to a few days was observed. Finally, the stability of the aqueous solutions of the palmitoyl peptides and the Palpepcubes kept at room temperature and at low temperature (4°C) was studied by LC/MS method, indicating that incorporation into cubosomes increases the peptide stability significantly.