The study shows that copper linked to the small skin‑friendly peptide GHK (and also GSH) can pass through a model of the outer skin layer. In simple lab tests, these copper‑peptide complexes moved through a membrane that mimics the skin’s barrier, meaning they could deliver copper directly into the skin when used in creams or serums.

This study concerning the permeability through skin barriers of copper complexes with peptides is an important part of the research on their biological activity. The transport of copper complexes through the skin is essential in treatment of dermatological dysfunctions connected to the deficiency of these elements in the skin. During the last several years, a special interest in transepidermal copper delivery has been observed. This is the reason why copper compounds have been used as active compounds in care cosmetics. Yet, the transport process of copper complexes with tripeptides, glycyl-histidyl-lysine GHK, or gamma-glutamyl-cysteinyl-glycine GSH through the stratum corneum has received very little attention in the literature so far. The penetration ability of GHK-Cu and GSH-Cu through the stratum corneum and the influence of the complexes with tripeptide on the copper ion transport process is the key factor in their cosmetic and pharmaceutical activity. The in vitro penetration process was studied in the model system, a Franz diffusion cell with a liposome membrane, where liquid crystalline systems of physicochemical properties similar to the ones of the intercellular cement of stratum corneum were used as a standard model of a skin barrier. The results obtained demonstrated that copper complexes permeate through the membranes modeling the horny lipid layer and showed the influence of peptides on the dynamics of copper ion diffusion.