May. 02, 2020

What are liposomes in skin care?

It is known that properties of a cosmetic not only result from the active substances, but also from the efficiency of these substances to penetrate into the skin. The delivery of active ingredients 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 largest and primary protective organ in the body, covers the body's entire external surface and serves as a physical barrier against the environment. It has many functions including protection against ultraviolet (UV) light, temperature regulation, trauma, pathogens, microorganisms, and toxins, among others. Also, the skin plays a role in immunologic surveillance, sensory perception, control of insensible fluid loss, and homeostasis in general.

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

Epidermis
They form a protective barrier against environmental influences. The external layer of the epidermis – the stratum corneum or horn layer - is made up of dead cells or corneocytes embedded in epidermal lipids and is covered by the hydrolipid film, which includes the acid mantle.

The epidermal lipids and corneocytes are often modeled as a brick wall. The corneocytes are considered to be the bricks, and the layers of lipids found between the cells are considered to be the mortar. The lipid "mortar" is the main barrier to water passing out through the stratum corneum. The permeabilityof lipid soluble molecules is modeled by considering them to find their way around the corneocyte bricks by diffusing through the lipid mortar.

Dermis & subcutis
The other two layers of the skin - the dermis and the subcutis - also contribute to skin’s protective barrier.

The complex story behind liposomes

Liposomes are sphere-shaped vesicles consisting of one or more phospholipid bilayers that enclose an internal aqueous volume. These vesicles are formed when amphiphilic lipids confront with aqueous milieu. Both hydrophilic and lipophilic substances can be transported in liposomes. The structure of phospholipids is as follows: on the one end of the molecule are the (yellow) hydrophilic (=strong affinity for water) heads and on the other end (black) hydrophobic (= low affinity for water) chains. The molecules aggregate and align automatically in a bilayer form.

Therapeutic applications of liposomes

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

Possible advantages when using liposomes:

The ability of ultradeformable liposomes to encapsulate active molecules and carry them through the outer impenetrable barrier layer, into the epidermis. This results in the enhanced efficacy and tolerability of these products.
Protecting and delivering otherwise unstable ingredients.
Liposomes cannot 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 are readily prepared on a large scale.

The use of these structures in cosmetics

Liposomes are, by definition, a tiny bubble, made out of the same material as a cell membrane. In cosmetic formulations they are used as a delivery system, carrying active ingredients present in cosmetic products, to the deeper layers of the epidermis.

It is disputable whether intact liposomes penetrate into the viable epidermis or not but they have demonstrated to be able to disorder the complex structure of the upper intercellular lipid sheets. The result is an enhancement of penetration of chemicals via the ‘polar and lipid' routes. In this way liposomes deliver nutrients directly to aging cells and would improve skin hydration and texture, reduce fine lines and diminish wrinkles.

Recent years, they use smaller ultradeformable liposomes, so they can enter deeper into the skin and deliver the active ingredients for a longer period.

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 obliged to refer to liposomes in the ingredient list, but instead they should disclose the components of which the product is made. So if you don’t find the word ‘liposome’ on the packaging, search for ingredients such as phospholipids, phosphatidylethanolamine, phosphatidylinositol and lecithin. Then there will be a high chance that it is a liposomal formulation.

My PhD 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 of liposomes for gene delivery into human skin. The primary aim of this thesis was to find a cationic, non-viral lipid based carrier system suitable for sufficient cutaneous siRNA delivery and to evaluate this novel therapeutic approach in a hyperpigmentation model to determine its clinical feasibility. My observations and learnings were the basis of what Nomige is today.