Biphasic serum and biomimicry: what are the advantages of a treatment inspired by the skin?

Mixed-phase serums stand out for their simple yet ingenious design, in which two distinct phases—a watery phase and an oily phase—coexist, unlike most serums, which are either water-based or oil-based. Before each application, these two phases must be shaken to briefly mix, forming a light, unstable emulsion. This duality follows a scientific logic of providing the skin with both hydration and nourishment simultaneously. The aqueous phase, often composed of water, plant extracts, or hydrosoluble actives such as hyaluronic acid or glycerin, supplies the water needed to the upper layers of the epidermis. Conversely, the oily phase contains lipids, such as plant oils, esters, or squalane, whose role is to reinforce the skin’s lipid barrier and limit water loss.

Unlike traditional aqueous serums, which are often lightweight but minimally occlusive, biphasic formulas allow for prolonged hydration thanks to the presence of film-forming agents that slow the evaporation of water from the stratum corneum. This occlusive effect, however, is not sufficient to fully protect the skin from dehydration, and the application of a biphasic serum should be followed by the use of a moisturizing cream. Biphasic serums also differ from pure oil-based serums, whose texture is sometimes considered too rich by the combination or oily skin. Biphasic serums thus mimic the behavior of the natural hydrolipidic film: a thin, semi-permeable layer composed of water and lipids.

Biphasic serums already anticipate the concept of biomimicry.

This approach was recently confirmed by a clinical study on a biphasic serum containing 17.5% vegetable oils, 61% water, 2% panthenol, 2.7% glycerin, and hyaluronic acid. The trial, conducted on 8 volunteers over 14 days, aimed to measure changes in stratum corneum hydration and transepidermal water loss. Measurements were performed using a corneometer and a tewameter. The results, presented in the table below, showed a significant and rapid improvement in skin barrier function in the group using the biphasic serum, while no significant change was observed in the control group.

These results confirm the efficacy of a biphasic serum containing humectants and lipids to improve skin hydration and strengthen its barrier function.

Biomimicry involves drawing inspiration from living organisms to replicate their mechanisms and structures. In cosmetics, a biomimetic formulation seeks to support the skin by respecting its lipid, aqueous, and protein composition. It reproduces the skin’s natural logic by often drawing on two elements:

• The hydrolipidic film : This mixture of water, sebum, sweat, free fatty acids, and trace elements forms a thin layer on the skin’s surface. It serves as the first barrier that limits water loss while protecting the skin from external aggressors (pollution, UV radiation, temperature fluctuations…)

• The internal lipid barrier : Composed of intercellular lipids (ceramides, fatty acids, cholesterol…), it ensures cohesion among the corneocytes of the stratum corneum. Closely interlocked, these cells are less likely to let water escape or allow pathogens to enter.

These two structures work together to maintain hydration and protect the skin from external stressors. A biomimetic formula thus seeks to mimic both the composition and organization of these natural components in order to integrate seamlessly into the skin’s processes. It contains biomimetic actives, such as the squalane, phospholipids, ceramides and also NMF-like (Natural Moisturizing Factors), which have a chemical structure very similar to that of molecules naturally present in the skin. This molecular similarity enhances their biological affinity and tolerance and allows for reinforcing the skin’s barrier function.

To more concretely understand how a biomimetic formula works, a recent clinical study analyzed the effects of a biomimetic serum combining natural moisturizing factors and skin barrier lipids on 44 volunteers with dry skin. The tested formulation specifically contained NMF components (10% urea, amino acids, lactate, and PCA) and a biomimetic lipid combination (ceramide NP, cholesterol, and sunflower oil enriched with linoleic acid). It was compared to its vehicle, i.e., the same cream without the NMF components and the biomimetic lipid combination. The results, deemed significant by the researchers, are presented in the table below.

The application of the biomimetic formula therefore resulted in increased stratum corneum hydration within 24 hours, accompanied by a reduction in transepidermal water loss, indicating a strengthened barrier function.

In parallel, the researchers asked 22 volunteers to apply the biomimetic serum daily. After 14 days, they conducted an analysis of the epidermal transcriptome, which revealed a significant overexpression of 15 genes involved in different skin functions.

• Cohesion of the stratum corneum (FLG, FLG2, IVL, LOR, TGM1, CASP14, CDSN) : These genes encode essential structural proteins for stratum corneum formation. Filaggrin (FLG, FLG2) and involucrin (IVL) contribute to keratin aggregation and corneocyte integrity. Loricrin (LOR) and transglutaminase 1 (TGM1) ensure the cross-linking of cornified envelope proteins, while caspase 14 (CASP14) aids in the production of natural moisturizing factors (NMF). Together, they maintain a cohesive and resilient skin barrier.

• Cellular permeability and cohesion (OCLN, CLDN1) : The genes OCLN and CLDN1 code respectively for occludin and claudin-1, two key proteins of the tight junctions linking keratinocytes. These structures control the passage of molecules between cells, regulate skin permeability, and maintain barrier integrity. Their proper function prevents water loss and the entry of irritant or pathogenic substances.

• Corneocyte renewal (KLK5, KLK7) : Kallikreins 5 and 7 are proteolytic enzymes involved in the controlled desquamation of corneocytes. They degrade adhesion proteins between dead cells, enabling their gradual elimination. Proper desquamation is essential to prevent thickening of the stratum corneum, which impairs the skin barrier.

• Hydration and water transport (AQP3, AQP9) : Aquaporins 3 and 9 are membrane channels that facilitate the passage of water and glycerol between epidermal cells. AQP3 is particularly abundant in the basal layers and plays a key role in skin suppleness and plasticity. Their activation promotes optimal hydration and supports barrier function by maintaining the skin’s water balance.

• Epidermal lipid metabolism (ELOVL4, SMPD1, HMGCR) : These genes are involved in the synthesis and processing of the lipids that make up the intercellular cement. ELOVL4 elongates fatty acid chains, SMPD1 participates in sphingolipid metabolism, and HMGCR regulates cholesterol production. These lipids form an impermeable matrix that prevents water loss and protects the skin from external aggressions.

Other clinical studies have sought to determine whether biomimetic formulations could outperform traditional occlusive-based creams, especially in mature skin, where the hydrolipidic film and intercellular lipid cohesion are often compromised with age. One study evaluated the efficacy of a biomimetic cream containing 2.5% lipids (ceramides, cholesterol, and long-chain fatty acids) incorporated into a standardized emulsified base with glycerin, compared with a conventional emulsion on the skin of 20 individuals over 60 years old. These participants applied one formulation or the other for two weeks.

The results show that, on the hands, application of the biomimetic cream induced a significant increase in hydration that was maintained after the study, unlike the control cream. A similar observation can be made on the legs. It can be assumed that the biomimetic treatment promoted prolonged hydration by stimulating the maturation of epidermal lamellar bodies, those small structures located within the cells of the stratum corneum that release lipids essential to skin cohesion. This process supports the restoration of the lipid cement and limits water loss. In contrast, the traditional cream, although effective in the short term, did not support the physiological mechanisms involved in skin barrier regeneration.

Combining biomimicry with a biphasic formula essentially involves directly drawing inspiration from the workings of the hydrolipidic film, which is composed of an aqueous phase and a lipid phase. By replicating this structure, a biphasic serum can more accurately restore the balance between water delivery and lipid reinforcement, two essential factors for maintaining the skin’s barrier integrity.

Biomimetic supplementation consists of selecting molecules similar to those naturally found in the epidermis: essential fatty acids, ceramides, cholesterol, and natural moisturizing factors. This structural affinity promotes their integration into the skin’s superficial layers and minimizes the risk of irritation. That’s why biomimetic formulations often exhibit a better skin tolerability, particularly on sensitive skin.

However, it is important to emphasize that the chemical structures of the molecules used in cosmetics are not always perfectly identical to those naturally present in the skin, even though they are similar. This difference can influence their biological behavior, and further research is still required to confirm their ability to reproduce exactly the same functions. Moreover, the stratum corneum, the outermost layer of the skin, serves as a physical and selective barrier: not all biomimetic molecules are absorbed or utilized in the same way. Parameters such as molecular size, lipophilicity, and formulation are critical to their penetration and efficacy.

Thus, even though biomimicry enhances skin compatibility and the likelihood of integration, the effectiveness of these molecules depends on both their chemical structure and their ability to penetrate the skin.

Formulated with a complex mimicking natural skin factors (NGF), squalane and hyaluronic acid, our bi-phase repair serum repairs the skin barrier of sensitive, atopic and rosacea-prone skin to soothe redness and discomfort. Developed in collaboration with a dermatologist, this 99% natural origin treatment has a two-phase formula that is directly inspired by the composition of the skin, in order to ensure optimal effectiveness while offering excellent skin tolerance. Application after application, it reconstructs the hydrolipidic film and relieves the most sensitive skin.

• SLOBODANKA T. & al. An in vivo comparative study on ageing skin: A biomimetic versus a traditional approach to skin moisturisation. University of Applied Sciences (2015).

• KUREK-GORECKA A. & al. Assessment of the moisturizing potential of a two-phase topical care product containing vegetable oils, glycerin, panthenol, and sodium hyaluronate – A preliminary studies. Acta Poloniae Pharmaceutica (2022).

• GRÖNNIGERA E. & al. A biomimetic combination of actives enhances skin hydration and barrier function via modulation of gene expression: Results of two double-blind, vehicle-controlled clinical studies. Skin Pharmacology and Physiology (2022).