Peptides

Peptides are short chains of amino acids, typically ranging from 2 to 50 amino acids in length, linked by peptide bonds. In skincare, they function as bioactive signaling molecules that communicate with cells to trigger specific biological responses. The science of topical peptides began in the 1980s when researchers discovered that small fragments of structural proteins like collagen — known as matrikines — could signal fibroblasts to produce new collagen. This was a paradigm shift: rather than trying to deliver whole collagen molecules (which are far too large to penetrate skin), scientists realized they could use tiny peptide fragments to instruct the skin to build its own collagen.

Peptides used in skincare fall into several functional categories. Signal peptides, such as palmitoyl tripeptide-1 (a fragment of type I collagen) and palmitoyl pentapeptide-4 (Matrixyl), work by mimicking extracellular matrix degradation products, tricking fibroblasts into "thinking" collagen has been broken down and stimulating new synthesis. Carrier peptides, most notably GHK-Cu (glycyl-L-histidyl-L-lysine copper complex), transport essential trace elements like copper to cells, where copper serves as a cofactor for lysyl oxidase, superoxide dismutase, and other enzymes critical for collagen cross-linking and antioxidant defense. Enzyme-inhibiting peptides, such as soy-derived peptides and silk fibroin peptides, interfere with enzymes like matrix metalloproteinases (MMPs) that break down collagen and elastin.

A fourth category, neurotransmitter-affecting peptides (sometimes called neuropeptides), includes ingredients like acetyl hexapeptide-3 (Argireline) and pentapeptide-18 (Leuphasyl). These peptides modulate neurotransmitter release at the neuromuscular junction, inhibiting the SNARE complex that drives acetylcholine vesicle fusion with the presynaptic membrane. The result is a mild, temporary reduction in the intensity of muscle contractions responsible for expression lines. While often marketed as "topical Botox," their effect is far more subtle than botulinum toxin injection and requires consistent daily application to maintain results.

Copper peptides (GHK-Cu) deserve special attention due to their unusually broad range of biological activities. The GHK tripeptide naturally occurs in human plasma, saliva, and urine, and its concentration declines significantly with age. When complexed with copper (II), GHK-Cu has been shown to stimulate collagen I, collagen III, and elastin synthesis, promote glycosaminoglycan production, activate tissue remodeling through controlled MMP activity, enhance angiogenesis, and exhibit anti-inflammatory and antioxidant effects. It also upregulates genes involved in stem cell function and DNA repair, making it one of the most biologically active peptides studied in dermatology.