Silicone oil is a liquid organic polymer with good thermal stability and flowable form, often used as an industrial lubricant. Silicone oil in skin care products has anti-aging and moisturizing effects and can be used in therapeutic products and skin protection preparations to fight skin diseases such as atopic dermatitis (AD) or irritant contact dermatitis (ICD). The protective film formed by silicone oil is not greasy, does not inhibit the natural breathing of the skin, and protects against mechanical factors and water evaporation. In addition, this group of compounds can make the skin soft and smooth, thereby improving the performance of cosmetics.

Most importantly, they are safe, non-comedogenic, hypoallergenic and water-resistant. It also protects the skin from environmental toxins and other factors that cause aging. Thiolated silicone oil has been used as a new ingredient in protective creams to prevent skin diseases. It is synthesized by forming amide bonds between the primary amino groups of poly[dimethylsiloxane-co-(3-aminopropyl)-methylsiloxane] and the carboxyl groups of thiol ligands (3-mercaptopropionic acid (MPA), thioglycolic acid (TGA), 2-mercaptonicotinic acid (MNA)) using carbodiimide as coupling agent. Among other techniques, thiomers are obtained by forming amide bonds between the primary amine groups of silicone oil and the carboxyl groups of MNA dimers. In the reaction with the dimer, fully S-protected silicone oils are obtained, which are used as second-generation mucoadhesives.

The adhesion of thiopolymers to mucous membranes, the presence of free thiol groups in human skin, and the various uses of silicones in skin applications were the starting points for the study of silicone-MPA and silicone-TGA. The ideal agent for protecting the skin from allergens, irritants and contact dermatitis must have higher bioadhesion, longer residence time on the skin surface after topical application, resistance to washing, low water vapor permeability and the ability to reduce transepidermal water loss (TEWL). When silicone sulfopolymers are used instead of methyl silicones in barrier cream formulations, better properties such as occlusive power, spreadability and adhesion can be achieved.

References:

[1] AGNIESZKA KULAWIK-PIóRO. Thiolated Silicone Oils as New Components of Protective Creams in the Prevention of Skin Diseases.[C]//14 16. 2021. DOI:10.3390/ma14164723.

[2] A. O’LENICK; K. O. Silicone Polymers in Skin Care[J]. Mrs Bulletin, 2007, 32 1: 801-806. DOI:10.1557/mrs2007.167.