May. 02, 2020

What are liposomes in skincare?

It is known that the properties of a cosmetic product are not only due to the active substances, but also to the efficiency of these substances to penetrate the skin. The delivery of active substances directly into the skin is one of the biggest challenges in skin care. This challenge has led to the development of liposomes in cosmetics.

Your skin barrier

The skin, the body's largest and most important protective organ, covers the entire external surface of the body and serves as a physical barrier to the environment. It has many functions, including protection against ultraviolet (UV) light, temperature regulation, trauma, pathogens, microorganisms and toxins, among others. The skin also plays a role in immunological surveillance, sensory perception, control of refractory water loss, and homeostasis in general.

Not surprisingly, the skin has a complex architecture that can vary depending on where the body is located. Human skin consists of three layers, from the surface: the epidermis , dermis , and subcutaneous tissue , all with their specific cells and respective functions. Skin appendages - such as follicles and sebaceous and sweat glands - also play different roles in overall function.

Epidermis
They form a protective barrier against environmental influences. The outer layer of the epidermis - the horny layer - consists of dead cells or horny cells embedded in the epidermal lipids and covered by the hydrolipidic layer, which contains the acid mantle.

The epidermal lipids and corneocytes are often modeled as a stone wall. The horny cells are considered the bricks and the layers of lipids between the cells are considered the mortar. The lipid "mortar" is the main barrier to the water passing through the stratum corneum. The permeability of the lipid-soluble molecules is modeled by making their way around the horny cell stones by spreading the lipid mortar.

Dermis & subcutaneous tissue
The other two layers of the skin - the dermis and subcutaneous tissue - also contribute to the skin's protective barrier.

The complex story behind liposomes

Liposomes are spherical vesicles consisting of one or more phospholipid bilayers enclosing an internal aqueous volume. These vesicles are formed when amphiphilic lipids encounter an aqueous environment. Both hydrophilic and lipophilic substances can be transported in liposomes. The structure of the phospholipids is as follows: at one end of the molecule are the (yellow) hydrophilic (= strong affinity for water) heads and at the other end are the (black) hydrophobic (= low affinity for water) chains. The molecules are automatically aggregated and aligned in a two-part form.

Therapeutic applications of liposomes

The great popularity of liposomes is partly due to the ability to transport both water and lipid-soluble components, the flexibility of the system and the wide variety of possible applications. Liposomes can be used as a drug or as a protein delivery system . In immunology, liposomes are excellent carriers for protein antigens, as they can contain large amounts of antigen, possibly in combination with adjuvants. Liposome structures are also very useful in antimicrobial, antifungal and antiviral therapy.

Possible benefits of using liposomes:

The ability of ultra-thin liposomes to nucleate active molecules and carry them through the outer impermeable barrier layer to the epidermis. This results in the improved efficacy and tolerability of these products.
Protecting and supplying otherwise unstable ingredients.
Liposomes can not only be used to deliver active ingredients in cosmetics, but also as a medicine these structures can be very useful.
Offer a time-release mechanism.

Liposomes are non-toxic, biodegradable and easy to prepare on a large scale.

The use of these structures in cosmetics

Liposomes are, by definition, small vesicles made of the same material as a cell membrane. In cosmetic formulations they are used as a 'vector' or delivery system for active ingredients to transport them to the deeper layers of the epidermis.

There is debate around whether intact liposomes penetrate the viable epidermis or not, but they have been shown to be able to disrupt the complex structure of the upper intercellular lipid layer. The result is an improvement in the penetration of molecules via the 'polar lipid' pathways. In this way, liposomes deliver nutrients directly to aging cells and are said to improve skin hydration and texture.

In recent years, smaller ultra-deformable liposomes have been used so that they can penetrate deeper into the skin and release the active ingredients for a longer period of time.

How do you know if a product contains liposomes?

There is no easy way to find out unless it is specifically stated on the packaging . Companies are not required to refer to liposomes in the ingredient list, but they must list the components from which the product is made. So if you don't find the word "liposome" on the package, look for ingredients like phospholipids , phosphatidylethanolamine , phosphatidylinositol , and lecithin . Then there is a good chance that it is a liposomal formulation.

My doctoral research

After my studies as a bio-engineer, I started a PhD at the Department of Dermatology at Ghent University. During my PhD research I designed, developed and characterized liposomes for gene transfer to human skin. The primary goal of this thesis was to find a cationic, non-viral lipid-based carrier system suitable for sufficient ubiquitous siRNA delivery and to evaluate this new therapeutic approach in a hyperpigmentation model to determine its clinical feasibility. My observations and insights were the basis of what Nomige is today.

Read Barbara Geusens' doctoral research