Beauty

Collagen is the substance that makes our skin elastic. Mature and UV-damaged skin loses some of its collagen, becoming flabby and less elastic. Such skin is deprived of its natural fats, vitamins and even minerals, as a result it becomes dry and ugly. Creams and lotions that can replace the lost elements will help in such a situation, and liposomes have found their application in this area.

A typical moisturizer contains the following ingredients: water (referred to as «aqua» on the label), humectants, occlusive agents, liposomes, antioxidants, and preservatives. The skin always needs water to maintain its structure and appearance, a humectant is a substance that helps tissues absorb water. The most commonly used humectant today is glycerol, while sorbitol is a more modern humectant. Occlusive substances act as a barrier to water loss, the most effective of which are considered to be lanolin, obtained from sheep’s wool, and petroleum jelly, which is one of the products of petroleum distillation.

Liposomes are a universal carrier of cream components to the deep layers of the skin. They are the smallest spheres in which the active ingredients are enclosed. In this form, active substances: anesthetics, vitamins, hormones, steroids — can penetrate the skin to such a depth that they themselves are not able to diffuse. The shell of a liposome consists of phospholipids — chemical structures that form the cytoplasmic membranes of all cells in our body. Each phospholipid is a glycerol residue with two fatty acid chains and one phosphate group attached to it.

The phosphate group has a free negatively charged oxygen atom. Due to the interaction of this atom with the positively charged nitrogen atom of the holino group, the latter can bind to the phospholipid molecule. The charged atoms allow the phospholipids to interact with each other to form two-layer membrane structures in which the charges are outside and the fatty acids are inside the film, resulting in a waterproof membrane about four nanometers thick. The most common phospholipid is lecithin, it is produced in large quantities in plants and animals, it is extracted from egg white or soybeans. This substance is widely used in the food industry.

Liposomes are nanometer droplets, typically 100 nanometers in diameter (which is one ten-millionth of a meter, so they are invisible to the naked eye), each capable of containing billions of active agent molecules. They penetrate into the deeper layers of the skin, where they slowly release the active agent through their membrane. Liposomes are an ideal vehicle for substances that do not penetrate the skin well.

The ability of liposomes to carry various molecules and ions was first described in the early 1960s by Alec Bangum, who worked at the Institute of Animal Physiology, located near Cambridge. Then liposomes began to be used as a model system for studying the cell membrane. They turned out to be amazingly stable structures, ideal carriers for various chemical molecules. Phospholipids can form spheres ranging in diameter from 20 nanometers to 100 microns, the two figures differing by a factor of five thousand. The smallest liposomes are sometimes called nanosomes.

Liposomes are obtained by evaporation of a lipid solution in chloroform or methanol until a film forms on the surface of the mixture. The film is transferred to water and shaken, while it breaks up into small pieces, which are twisted into spheres containing molecules to be transported inside. Spheres can be reduced in size using ultrasound or high pressure forcing through micropores.

The cosmetic industry uses special lipids, which, unlike natural phospholipids, do not carry an electrical charge. These so-called non-polar lipids are dissolved in ethanol and homogenized, after which the resulting liposomes are passed through the pores to obtain spheres with a diameter of about 200 nanometers, this size is considered ideal for penetration of the liposome into the skin.

Even pure water, delivered by liposomes to the inner layers of the skin, has a positive effect on it due to hydration and elasticity. If the antioxidant vitamins A, C and E are enclosed in a liposome, even better, since these substances help resist the action of free radicals, which are so detrimental to cells. Of the three vitamins named, vitamin A (another name is retinol) has received special attention as an anti-wrinkle agent, it really allows the skin to look younger and reduces wrinkles, makes age spots invisible and smooths out the roughness of the skin surface.

In the past, vitamin A-related substances, such as tretinoin, were used with varying degrees of success in the treatment of acne, today they are mainly used to delay skin aging. The commercial name for tretinoin in the UK is Retinova, and in the United States, where it was approved by the Food and Drug Administration as an anti-wrinkle agent in the mid-1990s, it is sold under the brand name Retin-A. Tretinoin began to be used in the 1970s to treat acne, but those who used it began to notice that it also reduced wrinkles. The drug is sold without a prescription, after two months of its use, age spots and wrinkles begin to decrease, and after six months they become significantly smaller. Tretionine works by stimulating collagen synthesis and delaying its breakdown, a similar effect that can last for several years.

Liposomes initially caught the attention of cosmetic chemists at L’Oreal and Christian Dior, and in 1987 a new liposome-based anti-aging formula went on the market. This tool belonged to exclusive goods and cost a lot of money, but soon a similar product from the competitor company Nivea appeared in supermarkets, which was much cheaper.

Source: based on materials from John Emsley’s book «On the benefits and harms of the products we love to buy»

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