Caprooyl tetrapeptide-3 is a synthetic chain of four amino acids with a caproyl fatty acid attached. It was developed to act on a specific structure most peptides ignore: the dermal-epidermal junction.
What the junction is and why it matters
The epidermis and dermis are not simply stacked. They interlock along a wavy boundary, with finger-like projections of dermis reaching up into the epidermis. Anchoring fibrils, made largely of collagen VII, hold the two layers together across this boundary.
With age, that boundary flattens. The projections shorten, the interlocking reduces, and the surface area of contact between the layers decreases. This contributes to skin laxity, to reduced mechanical resilience, and to less efficient exchange between the two layers.
Most anti-ageing ingredients target collagen I in the dermis. Very few address this junction specifically, which is what makes this peptide unusual.
The proposed mechanism
Caprooyl tetrapeptide-3 is studied for its effect on the components of anchoring fibrils, principally collagen VII and laminin-5. The proposal is that supporting these structures helps maintain the interlocking of the two layers.
Why the fatty acid is attached
The caproyl group is a six-carbon fatty acid chain. Attaching it makes the peptide more lipophilic, improving compatibility with the lipid-rich stratum corneum.
This is a standard approach to the delivery problem all peptides face, and it does not solve it entirely. A more lipophilic peptide penetrates the outer barrier more readily, but reaching the dermal-epidermal junction requires travelling through the full thickness of the epidermis.
The evidence
Research comes largely from the ingredient manufacturer, which is the norm for cosmetic peptides and worth stating. Independent replication is limited.
The underlying biology of the dermal-epidermal junction is well established. Whether a topically applied peptide meaningfully affects it is the less settled part.
