Applications of CDs with Empty Cavities

Some guest molecules with bad odors can be stored in the cavities of CDs and form non-volatile inclusion complexes ^{[1, 2]}. Therefore, CDs with empty cavities can be used as deodorant formulations and added to perfumes and other personal care products to eliminate bad odors from the human body and the environment. For example, powdered CD derivatives with molecular particle sizes less than 12 mm are often used in products such as baby diapers, sanitary napkins, and towels to eliminate undesired odors.

CD itself has the ability to absorb oil compounds. It can inhibit the exudation of polyunsaturated fatty acids from the skin and prevent its oxidation and deterioration, as well as inhibit the formation of free radicals, which is beneficial to reducing skin infection and inflammation. This allows it to be added to skin care products. On the other hand, when CDs with cavities are added as additives to cosmetics or skin care products, they can further encapsulate the free anti-acne active ingredients in the products and better exert their anti-acne effects. Therefore, CDs with cavities are also often used as anti-acne formulas to treat skin acne.
For example, azelaic acid is highly valued in skin care and is often used to clear up acne and prevent its recurrence. After CD with empty cavities are added to products containing free azelaic acid, azelaic acid can be encapsulated in the cavity to form a water-soluble azelaic acid-CD-inclusion complex, which not only effectively avoids the irritating effect of free azelaic acid on the skin but also enhances its anti-acne effects.

Cosmetic or personal care products are often formulated with oil-soluble and water-soluble ingredients. In order to form a uniform system, surfactants are often added for emulsification. Most surfactants are organic solvents, which may be harmful to the skin. Safe and water-soluble CDs can replace surfactants for emulsification, thus improving the safety of products.
Researchers found that when CD molecules with empty cavities were added to an emulsion containing two phases of liquid paraffin and water, a stable three-phase inclusion complex was formed without deterioration. Consequently, CDs with empty cavities can be used as safe emulsified formulas for cosmetics and personal care products ^[3].