Hyaluronic acid is an unbranched polymer naturally produced by our body and widely spread in connective, epithelial and nervous tissue.
Its presence guarantees, at the skin level, elasticity, softness, brightness and hydration to face and body skin, and protects it from damage caused by UV rays, external factors such as smog and physical stress.
The hyaluronic acid present in the tissues is continuously metabolized and eliminated, therefore it’s very important that the body continues to synthesize it again to replace the metabolized one. During the physiological aging process, or in the presence of particular pathological conditions, the hyaluronic acid production tends to decrease, thus favoring the related phenomena appearance, for example, the joint problems onset, as happens with the osteoarthritis process.
From a chemical point of view, hyaluronic acid is identified as a glycosaminoglycan, that is a long linear polymer chain formed by the repetition of disaccharide units, composed in turn by the molecules alternation of glucuronic acid and N-acetylglucosamine, joined together by glycosidic and hydrogen bonds.
This structure makes hyaluronic acid capable of retaining large amounts of water and providing hydration to the human body connective tissues.
Depending on the type of treatment and the composition of the acid, two categories can be distinguished: linear hyaluronic acid and cross-linked hyaluronic acid.
The cross-link is a process that allows linear hyaluronic acid molecules to be linked together, to obtain new structures consisting of several hyaluronic acid filaments with a higher molecular weight.
With the cross-link technique, molecular weights of 6 MDalton (average hyaluronic acid molecular weight of a healthy joint) can be reached up to real gels, in which the individual molecules have lost their individuality.
Difference between cross linked hyaluronic acid and linear hyaluronic acid
Linear hyaluronic acid was the first to be used and marketed and is made up of unchanged hyaluronic acid linear chains. These molecules, once extracted from cockscombs or bacterial cultures, are found as they are in the finished product. Linear hyaluronic acid can be classified as having high molecular weight and low molecular weight.
Cross-linked Hyaluronic Acids, on the other hand, are more recent and are characterized by the creation, in the production phase, of cross-links between several molecules of linear Hyaluronic Acid. These cross-links are transversal bridges that join together multiple chains with the aim of creating hyaluronic acid macromolecules with greater size, higher molecular weight, and, consequently, greater density and permanence.
Cosmetics and cross linked hyaluronic acid
Hyaluronic acid is known for its moisturizing, repairing and regenerative properties. The benefits on the skin following the hyaluronic acid products vary according to the molecular weight and the percentage of hyaluronic acid use within the cosmetic preparation. The molecular structure of hyaluronic acid allows it to bind and retain water molecules, thus helping to maintain skin elasticity and the water balance state of epidermis.
Learn more about the properties and benefits of hyaluronic acid.