As a polysaccharide substance, Hyaluronic acid（HA） has a strong moisturizing effect. It is natural and non-toxic. It is widely used in the cosmetics industry. With the in-depth understanding and extensive development of Hyaluronic acid , HA is continuously used in new field. The following is the application of HA in cosmetics.
What is Hyaluronic acid?
Hyaluronic acid (HA), also known as hyaluronic acid, is a disaccharide derivative connected by N-acetyl-D-glucosamine and β- 1,3-glycosidic bonds, and multiple repeating units connected to form a polysaccharide. The length and molecular weight of HA molecular chains are different. The number of disaccharides is generally 300-11000 pairs, and the range of molecular weight is 0.2 ×106 – 7.0 ×106.
Hyaluronic acid (HA) is white powder, without a fixed shape, odorless, and easily soluble in water, Ether and other organic solvents. The aqueous solution is acidic and has a negative charge, which moves to the positive electrode during electrophoresis. When the concentration is very high, the molecules will form cross-links due to hydrogen bonds, which exist in a network form with high viscoelasticity and osmotic pressure.
In the early 19th century, Mayer, a professor of ophthalmology at Columbia University in the United States, restricted the use of animal tissue as a raw material to isolate Hyaluronic acid (HA) from bovine vitreous.
As the most widely distributed acid mucopolysaccharide in the human body, it mainly exists in connective tissue. The matrix is one of the components of the skin and has a good moisturizing effect. Therefore, it is widely used in cosmetics and is called natural moisturizing factor (NMF). HA binds to the CD44 receptor of the cell to differentiate the cell. When epidermal cells are mutagenized with squamous cell carcinoma, the differentiation of epidermal cells is stopped.
HA is a signal substance that can reflect cell physiology. It binds to receptors on the surface of epidermal cells to produce a stimulating effect and can slow down the differentiation to apoptosis. HA can scavenge the active oxygen free radicals generated by ultraviolet radiation in the epidermal cells to prevent skin damage. It is called an efficient free radical “scavenger”. Oxygen free radicals will oxidize lipids, and HA and free radicals react first to decompose and then settle.
At present, the production of Hyaluronic acid (HA) is extracted from animal tissues and converted to production by microbial fermentation, which increases the yield and reduces the cost.
Distribution of Hyaluronic Acid at Different Ages
In the 3-month-old fetus, Hyaluronic Acid (HA) is concentrated in the epidermis. As the gestational age increases, it gradually transfers from the epidermis to the dermis.
This is an important point where scientists study the distribution of Hyaluronic acid and scarless healing. Most fetal tissues contain very rich Hyaluronic acid, which forms a gel, which can provide the required space and plasticity, and provide space for rapid proliferation and migration of embryonic cells.
The human body has the highest HA content during the embryonic period, and gradually decreases after birth. If the HA content of the 20-year-old is positioned at 100%, the 30, 50, and 60-year-olds will drop to 65%, 45%, and 25% respectively. When the HA is lower than a certain level, the skin’s moisture content will decrease, the stratum corneum will be metabolized slowly, and aging. This phenomenon generally appears after the age of 25.
This is also the main reason for the gap between the skin of middle-aged and children.
Skin Penetration and Absorption of Exogenous Hyaluronic Acid
Apply the same concentration of Hyaluronic acid (HA) with different molecular weights to intact pig skin and pig skin with stratum corneum peeled off.
In normal skin, Hyaluronic acid with a molecular weight of 5kDa is located in the stratum corneum and epidermis, with a scattered distribution; Hyaluronic acid with a higher molecular weight is limited to the stratum corneum. In pig skin with peeled stratum corneum, the content of 5kDa and 1MDa in the epidermis is more than that of different molecular weights of 5kDa.
Skin aging is related to the loss of skin moisture. Low-molecular-weight HA and high-molecular-weight HA have a more significant effect difference in enhancing the moisturizing effect and elasticity of the skin.
Scientists have tested HA of 50 kDa, 300 kDa, 800 kDa and 1500 kDa and found that low-molecular-weight Hyaluronic acid may affect the expression of many genes in the epidermis due to its stronger penetration ability, including aging skin and light damage. The skin reduces the related genes that promote the differentiation of keratinocytes and are closely connected with cells.
Compared with high molecular weight HA, low molecular weight HA has better moisturizing and skin elasticity effects. High-molecular-weight HA and low-molecular-weight HA have different efficacies. High-molecular-weight HA is used synergistically in cosmetics, and the effect will be better.
Application of Hyaluronic acid (HA) in cosmetics
The main function of HA in cosmetics is to moisturize. The advantage is that the moisture retention is less affected by the surrounding environment and the moisturizing time is long.
Compared with glycerin, HA has the highest moisture absorption under lower humidity, but has the lowest moisture absorption under higher humidity. This property can adapt to the skin’s moisturizing effect in different seasons and different environmental humidity.
HA is used as a moisturizer. The agent is rarely used alone, and is often used in conjunction with other moisturizers.
Without adding other emulsifiers, adding HA and phospholipids in the oil phase and the water phase can form a stable emulsion. The characteristic of this emulsifier composed of HA and phospholipid is that it contains both emulsification and moisturizing functions. It is incomparable with other emulsifiers.
A safe and effective emulsifier like HA can be used in preparation of various cosmetics.
HA (molecular weight 3000 kDa) solution has very high viscosity. Similarly, polyoxyethylene (molecular weight 100-5000 kDa) is one of the commonly used thickeners in cosmetics. When the two are mixed, the viscosity is greater than the sum of their respective viscosities, so HA- polyoxyethylene solution is a good thickening agent and at the same time it has a good moisturizing function.
It can be used in creams, emulsions, gels and other cosmetics, especially suitable for making various translucent viscoelastic gels, such as shaving gel, eye gel, sunscreen gel, etc.
HA has the characteristics of molecular encapsulation for substances. It can be used in fragrance products and used as a fixative and a combination of fragrances to reduce the volatilization rate of fragrances and make fragrances more durable. It is suitable for perfumes and other various cosmetic products. HA also has two advantages:
– Reduce the bad irritation of fragrance to sensitive skin;
– Prevent the reaction between certain flavors and skin secretions, prevent the formation of odors, and can be applied to creams, lotions, gels, etc.
HA will form a thin film on the skin surface, which is conducive to the absorption of active substances by the stratum corneum of the skin.
HA can directly penetrate into the dermis layer and promote skin tissue metabolism. The nutrient components can be used to transfer to improve the physiological characteristics of the skin to achieve an effective supply of nutrients and produce nourishing skin functions, such as the application in facial mask and facial cleanser.
Antibacterial and Anti-inflammatory Effect
When animals contain a small amount of hyaluronic acid, it can inhibit bacteria and reduce inflammation. Hyaluronic acid has the characteristics of film-forming, it is easy to form a hydration film to isolate bacteria and have an anti-inflammatory effect.
In addition, protein and HA are combined in the skin matrix to form a protein complex. This substance has a normal metabolism and water-holding function in cell tissues, prevents harmful substances from invading cells, plays a role in preventing and treating various infections, and has certain protection to the skin. It is also widely used in cosmetology and clinical medicine.
Hyaluronic acid can repair cell damage. HA increases in the wound. In different stages of wound healing, Hyaluronic acid and fibrin play a structural and regulatory role together. HA and fibrin matrix promote or induce cell migration and regulate the functions of many cells involved in the inflammatory process.
Excellent moisturizing effect, keeping skin moisture relatively stable, maintaining appropriate intracellular and intracellular moisture content, ensuring the relative balance and free movement of various nutrients (including inorganic salts), and providing wound healing.
Studies have shown that when the skin has ulcers and mild burns, applying related products containing HA can relieve pain, accelerate wound healing, and reduce the occurrence of scars.
UV radiation can cause lipid peroxidation, destroy cell membranes, and cause pigmentation. It can also limit the access of lipid peroxidation enzymes to the cell membrane, thereby reducing the entry and exit of free radicals outside the cell.
Skin care products containing Hyaluronic acid can make cells differentiate. Combining Hyaluronic acid in sunscreen has synergistic benefits.
Hyaluronic acid is a polysaccharide with good film-forming properties. Skin care products that use it on the skin can be observed to have a good lubricating effect.
When using HA, a hydration film is formed on the surface of the skin to make the skin feel smooth. This effect is incomparable with other skin care products.
HA is a glycosaminoglycan. It has no species specificity and it is one of the human body components. It will not cause immune response.
Injections containing it have good lipid compatibility, high safety, and generally do not cause allergy reaction, making HA a filling material. The Hyaluronic acid is refracted to the required part and filled from the inside to give the skin its original luster.
Hair Growth Function
In addition to inhibiting the production of testosterone, the mechanism of action of other drugs is not clear. Finasteride, which inhibits testosterone, is not suitable for male patients.
Scholars found that after several weeks of subcutaneous injection of low molecular weight HA in mice, hair growth was significantly induced. The effective rate of subcutaneous injection of low molecular weight HA is 100%.
It is preliminarily speculated that subcutaneous injection of low-molecular-weight HA can induce the initial stage of hair production, which may be due to the ability of HA to bind to receptors in injured tissues that affect hair growth.
What is Sodium Hyaluronate and how is it related to Hyaluronic Acid?
Sodium Hyaluronate (SH) is the sodium salt of Hyaluronic Acid (HA). It is white fibrous and has good hydrating and moisturizing properties. It is easily soluble in water but not soluble in organic solvents such as Ether. The SH aqueous solution is a fluid and has good rheology.
According to research, the human body contains more than 70% water. It is very important to maintain a large amount of water in the body. As we age, the SH content in the skin decreases, which leads to a decrease in moisture in the skin, rough skin, loss of elasticity, and wrinkles. Exogenous SH can effectively supplement the endogenous SH of the skin. This can prevent skin aging and play a role in beauty.
At present, SH is widely used in moisturizing products such as skin creams, skin creams, etc. In addition, SH has also begun to be used in the medical beauty industry. A variety of beauty and health products have emerged. For example, as an injection, it can effectively eliminate forehead lines, smile lines, and wrinkles around the eyes and nose. It can also increase the bridge of the nose and make the lips are full and beautiful. It can also make the person younger and more beautiful. However, injections containing SH have low sensitization and are easy to promote.
The amount added in cosmetics
At present, the purity of HA products is generally around 38%-42%. The addition amount of HA in cosmetics is 0.05%-0.1% (W/V). If the addition amount is too low, it will not exert the moisturizing effect of HA. While too high will make people feel sticky and tight. Due to the macromolecular properties of HA, it is normal to dissolve slowly. According to different products, there are several ways to use it:
– Add HA and other components into the water phase and stir to dissolve;
– After adding HA to the water phase to dissolve, add other ingredients;
– First, dissolve HA into 0.5% -1% solution with water, and then add the solution to the formula quantitatively according to the added amount.
Precautions for the application in cosmetics
– HA is a highly nutritious polysaccharide substance. It is very easy to be infected with bacteria. You should pay attention to the sanitation of the container and the sanitation of the environment when using it. After the HA is dissolved into a liquid, try to use it all at once. You must add the preservative in it, if there is any surplus, and refrigerate and seal it. The storage time should not be too long. If you don’t want to use chemical preservatives, you can try pure natural plant extract preservatives. Although their efficacy is not as good as chemical preservatives, they are purely natural.
– HA is easily damaged by ultraviolet rays, easily decomposed at high temperature, and easy to absorb moisture. Therefore, the product should be protected from light, stored at low temperature, and placed in a dry place. Adding HA to the product should be carried out in the later stage of processing, and the temperature should not exceed 60℃.
– Use soft water or deionized water as much as possible when dissolving HA with water. The quality of the water directly affects the transparency of its aqueous solution. To speed up the dissolution rate in water, it can be dispersed in propylene glycol or glycerin first, and then dissolved in water.
– When HA is used in emulsified products, non-ionic or anionic emulsifiers should be used, and cationic emulsifiers should be avoided. Otherwise the structure of HA will be destroyed and turbid precipitation will occur.
As an excellent cosmetic additive, Hyaluronic acid powder is used more and more widely. However, before use, especially when used as an injection, you still need to consult a doctor and choose a regular medical institution.