February 2021 • Vol. 27 • Issue 2
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Survey of Applications of Alginates for Cosmetic and Dermatological Uses …by Paul Thau
arly in my career, I had a challenging project to develop a face mask formulation based upon potassium alginate, calcium sulfate, and a sequestering agent that would have superior setting properties than a commercial product (Dory Face Mask). As a result, I became intrigued about the range of commercial applications for naturally sourced alginate products.
History of Discovery
In 1883, E.C.C. Sanford became interested in seaweed as a source of useful byproducts. He extracted an acidic substance with unusual gelling properties that he named “alginic acid” after the Latin word alga, meaning seaweed. Although its usage at first was slow, it eventually expanded into many industries, including dentistry, cosmetics, and foods.1 Sodium alginate is characterized as a hydrophilic colloidal polysaccharide alginate that has similar properties to pectin and other vegetable gums. However, alginate soluble salts have physically and chemically distinct properties from other colloids. For example, the reactivity of alginate salts with metal ions is a unique property.
Applications for Alginates • • • • • • • •
Gelling agent Emulsion stabilizer Film former Moisturizing ingredient Spherical encapsulation To form irreversible hydrocolloid gels Dermatological film dressings Styptic agent
Figure 1: Molecular structure of sodium alginate.
Cosmetic Masks Based on Alginates
The chemistry and composition of cosmetic face masks are similar to dental impression formulas. However, cosmetic formulations contain inert, cosmetic grade, powder fillers, such as kaolin, magnesium stearate, etc. Alginate impression compositions can be designed so that they are fixed by a chemical reaction that cross-links the carbohydrate polymer.2 The working time is provided by competing chemical reactions that delay the cross-linking step. When the powder composition is mixed with water, the alginate powder dissolves, as does calcium sulfate and sodium phosphate (sequestering agent). Initially, the calcium ions react with the phosphate ions and precipitate out of solution. The calcium ions do not react with the dissolved alginate until all the phosphate ions have reacted. After the retarder (the phosphate ions) has reacted, the setting reaction becomes the dominant reaction. Cosmetic face mask formulations are usually designed to prevent setting for at least five minutes. Typically, these products fill all the skin pores and wrinkles, plus provide good cleansing and hydration to skin. (continued on Page 6)
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...see pages 4-5 for more information.
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