Peptides are a new class of compounds, that came to be used in cosmetology fairly recently.
Peptides are technically protein molecules consisting of several amino acids.
If a molecule contains more than 50 amino acids, it is generally called protein. Less than 50 amino acids in a molecule makes it a peptide. Sometimes they are also called oligopeptides (Latin “oligo” meaning “little”), to stress once more that there are only a few amino acids in the compound. Cosmetology mostly employs tiny peptides with less than 10 amino acids.
Peptides are small in size but they still need help to penetrate into skin.
That help is usually provided by fatty acids attached to a peptide chain. This lipid tail allows peptides to squeeze through the skin’s keratinous layer and impact its deep layers.
Most peptides are very fragile molecules.
Peptides are sensitive to pH levels. They become inactive in the presence of acids and retinoid and are destroyed by free radicals and the enzymes of deep skin layers. Peptide-based solutions can only be combined with compatible skincare and makeup products.
New peptides emerge practically every week.
Today the list of peptides that can be used in cosmetics includes hundreds of denominations. These compounds are often referred to as “the cosmetics of the future” because they are not allergenic, rarely have side effects, are well tolerated by practically anybody and with correct application are very effective and quick to improve the skin’s condition. It is however very important to remember that peptides, unlike some traditional cosmetic ingredients, can be easily damaged or destroyed. If a peptide solution turns out ineffective, it is very often because of its wrong application or even the mistakes made by production engineers when creating the formula. Theoretically, one can create millions of different combinations on the basis of a dozen amino acids. It gets rather complicated though, because sequence matters — the same acids combined in different order can have a very different effect. Change the position of only two amino acids, and you end up turning a fat splitting peptide into a rejuvenating one!
Stimulating and Barrier Peptides
Stimulating peptides can strengthen the ability of the skin cells to synthesise the substances it needs. It is well known that the skin gradually loses this ability with age and the syntheses of collagen, elastin and hyaluronic acid become less active, making the skin thinner and less resilient, bringing about and deepening the wrinkles.
Matrikines, or signallers, are very active in young skin. When the skin lacks structural substances and the deficit is not compensated by the skin's own resources, matrikines join the skin cells receptors and transfer to them the signal to increase the activity. With age the skin’s own matrikines’ activity declines, and their signals to the cells become fewer and less effective. But biologically active matrikine peptides penetrating into the skin can render a pronounced stimulating effect and revive the skin cells. Another variation of the effect is the activation of protein affecting the dermal growth factor that boosts the syntheses of structural substances.
Skin ageing is not just accompanied by the decrease of collagen fibres. In young skin collagen fibres are arranged in particular order into groups called fibrillae. The correct assembly of collagen is regulated by peptides — proteoglycans, and their number naturally decreases with age. But if a cosmetic solution with peptide assemblers is applied to the skin, it can, at least partly, restore the process of collagen assembly and increase the skin’s resilience and thickness. The isolated use of remodelling peptides is sensible when the skin is just starting to show first signs of ageing and there is still enough collagen in the skin. If age related changes have already occurred, it is better to use the assemblers together with signal peptides.
In the process of ageing, connection between derma and epidermis, the deep and the surface skin layers, weakens. This junction is formed by particular proteins — VII type collagen and syndecan — and their production decreases with age as well. This is what makes mature skin look languid and papery. But now we have peptides that stimulate the syntheses of collagen and syndecan, restoring and thickening the junction, at the same time re-establishing the epidermis foundation—basal membrane. Unlike most vegetable and chemically synthesised ingredients, peptides re-launch the physiological processes in the skin restoring their natural rates characteristic for young and healthy skin, rather than interfere with the already ongoing processes in the skin. Peptides of this kind are used to treat skin injuries, as well as to care for thinning and sensitive skin. Peptides that stabilise the skin, increasing its own protective potential in various ways, can be separated into an independent group. Some of them are antioxidants, replacing the antioxidant peptide systems that the skin loses with age. Others are anti-glycation peptides tearing up the sugar ties that bond collagen fibres together and turn them into useless tangles unable to stretch and contract. Some peptides specialise in fighting the stress caused by the active forms of oxygen that ultraviolet radiation generates in the skin. Some peptides contain copper, a mineral essential for the healing process and for the functioning of the enzymes, participating in the development of the skin’s structure.
Stabilising peptides are useful in the after sun solutions and anti-stress cosmetics for big city dwellers. They can also reduce the skin damage caused by tobacco smoking.
Peptides with Direct Effect
Not all peptides affect the skin generally improving its protective functions or its elasticity and resilience. Biotechnologists have created plenty of peptide molecules, that can directly affect certain skin structures and cells, providing various effects — from skin brightening to reducing its sensitivity to the cold.
Myorelaxant peptides able to reduce the mobility of mimic muscles were one of the first to appear. They are often referred to as peptides with botox effect, even though the mechanics of their action are not always similar to that of botulinum toxin. Notably, many myorelaxant peptides demonstrate a high level of activity and in laboratory conditions can practically paralyse the muscles. But to achieve that in real life one would need to create a special set of conditions, which is only possible for some peptides. The most effective solutions that actually reduce the mobility of the forehead muscles and help get rid of wrinkles in the upper and middle thirds of the face, usually include several peptides in rather high concentrations. In most cases while using these solutions one must avoid retinoid and acid containing cosmetics, because these ingredients can destroy the peptides. The way acids and retinoids affect the skin conflicts with peptides action—the latter need to establish connections with certain cells and compounds, while acids and retinoids cause inflammatory reaction in the skin and activate the blood circulation interfering with the connection between a peptide and its object.
The best known myorelaxant is a peptide called Argireline. Similarly to botox, it competes with one of the proteins taking part in the creation of the protein complex that is necessary to release acetylcholine into synaptic chain making a muscle contract. Argireline replaces one of those proteins, the complex stops functioning and the muscle contraction stops. For a complete (and prolonged!) relaxation effect, the solution should be applied onto the skin for at least 30–35 days. Argireline remains popular for over 10 years now, even though new peptides have emerged.
There are myorelaxants with different mechanics of action. Leuphasyl, for instance, reduces the sensitivity of the nerve cells to stimuli, suppressing the in-flow of calcium through the membrane — it actually imitates the effect of one of the “happy hormones,” enkephalin. Syn-Ake, more commonly known as the venom of Indian temple viper (it replicates the molecular structure of the snake venom toxin) blocks the receptors of muscular cells which “open doors” for the in-flow of natrium ions. In the absence of natrium there is no muscle contraction. Vialox and Inyline act similarly.
Myorelaxants can only reduce mimic wrinkles, they don’t affect the wrinkles that appeared with age. Cosmetics with myorelaxants can be used at a young age too, and some of them support and prolong the effect of botulinum toxin. When the wrinkles are not too deep, a myorelaxant solution can substitute the injection method. It is very important to remember that myorelaxants must not ever be applied in the eye area. The reduced mobility of the eyelid muscle can lead to the development of ptosis—the eyelid paralysis. Myorelaxants are often combined with signal and remodelling peptides to achieve dual effect: muscle relaxation and filling in the wrinkles.
Pigmenting peptides imitate melanin-concentrating hormone (MCH), which, being in its turn of peptide nature, is necessary to launch the process of melanin synthesis in the skin. This hormone connects with the receptors of melanocytes, the cells synthesising pigment melanin, and activates the process of melanin production. Most plant components block the enzymes taking part in the synthesis, particularly tyrosinase. Biotechnologists have created several peptides imitating MCH, that can stimulate the process of pigmentation without causing inflammation and skin redness. These peptides, Melitane and Melatime, are used to prepare the skin for suntan. Naturally, there is a peptide for skin brightening (Melanostatine)—it blocks the cells’ receptors and stops the synthesis of the pigment.
Examples: Acetyl Hexapeptide-1 (Melitane).
The action of opioid peptides is not unlike that of opium. They are sometimes called “happy skin peptides”. Opioid peptides benumb the skin receptors’ sensitivity to pain, temperature change and chemical impact making the skin much less sensitive and preventing allergic reactions. This is how Calmosensine and Skinasensil work.
Immune peptides participate in the works of the skin’s immune system. Ageing comes with increased release of the substances activating inflammations and boosting the syntheses of collagen, elastin and hyaluronic acid destroying ferments. A peptide called Rigin was developed to fight this, it is used in the ageing skin care products. Another immune peptide, Bodyfensine, helps synthesise protective proteins increasing the skin’s resistance to infectious diseases.