Better bioavailability with SmartLipids

SmartLipids, submicron lipid particles, ensure that active ingredients in formulations last longer and work more effectively.

Consumers are demanding more and more from topical applications. The products are expected to deliver quick results – whether in anti-ageing, skin lightening or skin refining – without compromising on skin compatibility and sensory attributes.

While the choice of potent actives on the cosmetics market seems to be endless, there are often challenges to the formulator when using these ingredients. In many cases, active ingredients cannot be simply mixed into a cosmetic formulation and be expected to have the same activity in vivo as they have in vitro. The substance must penetrate the skin efficiently in a meaningful and effective concentration; it has to be bioavailable. In many cases, this is difficult due to the active’s poor solubility or sensitivity to chemical degradation. Active ingredients often need a delivery system to enhance their penetration or control their release into the skin. 

Introduction to lipid based delivery systems

In a conventional emulsion such as a cream, chemically unstable lipophilic active ingredients are prone to degradation because they are able to move around between the oil and water phases through diffusion. 

SLN (solid lipid nanoparticles) are carrier systems based on solid lipids. They resemble a classic emulsion, in which the liquid oil droplets of the dispersed phase are replaced by solid lipids (with a melting point higher than skin temperature and a particle size below 1 micron) that remain solid after application to the skin. 

NLC (nanostructured lipid carriers) are the second generation of this type of carrier.[1] In contrast to SLN, they typically consist of a mixture of one liquid and one solid lipid, in which the active ingredient is embedded and protected. Nevertheless, the loading capacity can be limiting and they have a tendency to form (partially) ordered structures over time, which may cause the active ingredient to be released too early.

SmartLipids (submicron lipid particles), obtained by a patented technology, are the latest version of SLN and NLC.[2] They consist of many more different solid and liquid lipids which are screened, selected and adjusted according to the particular active ingredient to be encapsulated. Because of the more complex lipid structure, the lipids arrange themselves chaotically which leads to a higher loading capacity and a lower tendency to form ordered structures, thus resulting in better stabilisation of the sensitive ingredients. 

A closer look into a SmartLipid

Figure 1 (page 28) shows the general structure of a SmartLipid. Different lipids, consisting of solid (green) and liquid lipids (blue), form a chaotically structured matrix. Active ingredients that are lipid-soluble can be embedded in the resulting gaps, and are effectively prevented from escaping into the surrounding water phase. Sensitive ingredients are firmly enclosed and therefore physically protected against oxygen, light, and other external influences that could lead to their degradation. The size of the SmartLipids particles is between 0.1–1.0 µm, which makes them submicrometer particles. Their presence and stability can easily be proved by X-ray analysis[3] and DSC (differential scanning calorimetry).[4]

SmartLipids are typically available as a stabilised suspension in water, which means that they can easily be dosed and added to any o/w-emulsion or water-based formulation.

What happens when SmartLipids are applied to the skin? They form an invisible, uniform layer – similar to a second skin. Due to their small size (0.1-1.0 µm), their lipidic nature and their solid state even at skin temperature, SmartLipids adhere especially well to the skin, extending the release of the active substance, enhancing penetration through their occlusive effect, and helping to restore an imbalanced or damaged skin barrier by reducing TEWL (transepidermal water loss).[4,5] Figure 2 illustrates the mode of action on the skin. 

Whereas the encapsulated active is firmly enclosed while the SmartLipids are suspended in water or in a formulation, the situation on the skin is different: the active ingredient is now able to diffuse into the skin with the aid of the concentration gradient as a driving force. On reaching the relevant skin layers, the active can deploy its full biological effect and is metabolised at the same time. This in turn removes the active ingredient from the skin, maintaining the concentration gradient. In this way, each SmartLipids particle gradually “empties” its active depot.

SmartLipids and active ingredients

Anti-ageing: Coenzyme Q10 is a well-known molecule naturally occurring in the skin, but its level decreases with age. By encapsulation with SmartLipids technology, Q10 is stabilised against degradation and exhibits improved bioavailability and penetration for effective anti-ageing results.

Retinol is one of the most researched and effective anti-ageing actives, as it promotes the normalisation of the cell renewal process, reduces wrinkles, and improves the elasticity of the skin. However, its instability against oxygen, light, heavy metals and acidic conditions makes working with this active a real challenge. Furthermore, retinol can cause strong irritation and reddening of the skin. When retinol is encapsulated in SmartLipids it is effectively protected against degradation; its penetration into the skin is enhanced while ensuring extended gradual release which reduce possible irritations and side effects. The carrier itself can strengthen the skin barrier by forming an invisible film on the skin.

Whitening: Glabridin is a powerful lightening agent obtained from the liquorice root. Its poor solubility, resulting in poor bioavailability, and its tremendous price make SmartLipids the ideal technology for meeting these challenges. Tapestrip experiments show better and deeper penetration of glabridin from SmartLipids than from a pure glabridin powder (95% purity) suspension in water. Furthermore, in vivo experiments demonstrate impressive results for lightening dark spots after 12 weeks of use (fig. 3).

Lemongrass oil is a natural essential oil with mild whitening properties. Incorporation into SmartLipids enhances this effect by increasing bioavailability and supporting the skin barrier (fig 4).

Ceramides are naturally occurring components of the skin’s own barrier. Together with sterols and a multitude of different fatty acids, they are an indispensable part of the stratum corneum, protecting the skin against attacks from outside while keeping moisture inside. An encapsulated SmartLipids version of these valuable natural components of the skin can therefore assist normalisation of a damaged skin barrier and strengthen the skin’s ability to reduce TEWL by forming a “second skin”. It may be especially helpful in cases of dry skin, skin with a weakened barrier or skin with a tendency towards atopic dermatitis and psoriasis.

Outlook into the future

The multiplicity of the lipids that can be chosen to encapsulate cosmetic actives permits tailor-made concepts. Even poorly soluble or highly sensitive ingredients can be encapsulated using SmartLipids technology to improve their stability, bioavailability, performance or handling.