Biologically sourced substances continue to gain popularity as ingredients in skin and hair care products. This trend is in response to consumer and government demands for more natural and sustainable products, and is strongly driven by advances in fundamental understanding of biomaterials. One such material is hyaluronic acid, a biopolymer highly valued in cosmetics for its hydrating and nourishing properties. Its value as a beneficial topical skin cream agent is fairly well accepted, but does it improve the performance of hair care products? What results can the consumer expect from shampoos, conditioners, or styling products that contain hyaluronic acid, and are there any potential drawbacks for curly haired users? The answers can be found in the relatively simple structure, yet surprisingly complex physical and biochemistry of the molecule.
What is Hyaluronic Acid?
Its name is relatively simple and deceptive, conjuring images of various small molecule acids, such as ascorbic, acetic and citric acid. However, hyaluronic acid is a surprisingly complex biopolymer. HA is a polysaccharide categorized as a glycosaminoglycan (GAG”>, and is a very high molecular weight (107 Da”> , non-sulfated, anionic (negatively-charged”> polymer. Its physical structure is linear and is comprised of alternating units of D-glucoronic acid and D-N-acetyl glucosamine. This polymer is found in virtually all vertebrate tissues, and is particularly active in the extracellular matrix (ECM”> in connective tissue.
The ECM fills the space between cells and is a complex array of proteins and polysaccharides that self-assemble to form a network that provides support, structure, and mechanical integrity to the tissue. Depending upon the function of the tissue, the type and structure of polymeric and small molecule components varies, which facilitates the development of the specific mechanical properties necessary for the particular tissue type (i.e. bone versus skin, etc.”>.
As a component of the ECM, hyaluronic acid performs many functions, including acting as a tissue scaffold to which sulfated proteoglycans can attach, creating a complex three-dimensional hydroscopic network that forms a viscous gel. Its highly hydrophilic structure causes it to attract and bind water to itself, which enables it to hydrate and provide turgor (rigidity”> to tissue. This enables the matrix to resist compression, which allows it to provide cushion to joints, organs, and the dermal layer. It is also thought to provide hydrated pathways that promote and regulate cellular movement and migration. Additionally, hyaluronic acid interacts with cell membranes receptors (specifically CD44″> to trigger intercellular signaling pathways that direct and control cellular processes involved in growth, healing, and also some pathological processes such as inflammation and tumor development and growth. Hyaluronic acid also aids in protection of tissue and processes by scavenging free radicals and is thus an effective antioxidant.