Topically applied GHK as an anti-wrinkle peptide: Advantages, problems and prospective.

Introduction: Peptides are promising and attractive anti-wrinkle active ingredients, amongst which glycyl-histidyl-lysine peptide (GHK) is one of the most broadly promoted peptide for topical application. This simple sequence of amino acid residues not only has the capability of tissue regeneration and the enhancement of collagen and glycosaminoglycans synthesis but also is able to increase nerve outgrowth and angiogenesis. Consequently, GHK has several properties, from wound healing to prevention/reduction wrinkles. GHK-Cu and Pal-GHK are metal complex and palmitoylated derivatives of GHK, respectively. Although GHK-Cu and Pal-GHK are widely used in anti-wrinkle products available on the cosmetic market, the published information on their skin permeability, effectiveness, physicochemical properties and so on is insufficient. Methods: This review aims to highlight whether GHK is sufficiently effective on wrinkle prevention/reduction. Apart from the effectiveness, another question that is tried to be answered is whether skin permeability of GHK allows it to act as an anti-wrinkle peptide at its site of action? Skin permeation enhancement methods employed so far are also reviewed. Results: Based on cellular studies, undoubtedly, GHK can be considered as an anti-wrinkle ingredient. Although GHK-Cu and Pal-GHK have been of interest as effective peptides to be incorporated in the anti-wrinkle products, there is a surprising absence of clinical studies using them. Metal complexation and chemical modification with a hydrophobic moiety increase permeability of this peptide. Besides, cell penetrating peptides seem promising to increase skin permeation of GHK and its derivatives. Skin pretreatment with microneedles also has the potential to be further studied for permeation enhancement of such peptides. As peptide ingredients, their formulation may encounter some challenges, mainly due to their hydrophilic (high aqueous solubility and low partition coefficient) and unstable nature. Conclusion: Although GHK-Cu and Pal-GHK are effective and relatively skin permeable, their permeability could be successfully increased using permeation enhancement methodologies.