FORMULATING FOR MILDNESS 55
Distribution of caffeine in skin compartments after 24h BiophilicTM
H Control * p,0.05 (vs. contol)
14 12 10 8 6 4 2 0
* * x2.3 * 6 * * 4 2 0
Stratum corneum
Epidermis (E)
Dermis (D)
Receptor fluid (RF)
Total
bioavailable (E+D+RF)
Caffeine: Low molecular weight & high absorption capacity
effective delivery of actives. Being highly compatible with the skin, lamellar emulsions act as a ‘second skin’ to protect skin functions and restore damaged skin.3 Such emulsions merge with the skin for an ultra-cocooning sensation. Lamellar emulsifiers are fantastic tools to create a beautiful texture without too much work. The promotion of lamellar structures by the biomimetic emulsifier was studied for different formulations of various concentrations by freeze fracture transmission electron microscopy (TEM) and polarised microscopy. A small volume of each sample was applied between two copper plates, then flash frozen in liquid nitrogen. The ‘sandwich’ was moved into the freeze fracture device at -160°C with a vacuum of 10-7
- 10-8 bars. Once the fracture
had occurred, the sample surface was shadowed at an angle of 45° with a platinium–carbon alloy, then pure carbon was also projected at an angle of 90° to improve its mechanical resistance. The obtained replica was cleaned with Hellmanex solution and rinsed with water. Finally, the replica was trapped using a 400 mesh copper grid and introduced into a Technai G2 (200 kV) transmission electron microscope. Images were captured with an ssCDD Eagle (FEI) camera. Birefringence investigation was performed using a polarised light microscope equipped with a Nikon DS-Fi1 digital camera. In Figure 1 (left panel), the TEM photograph reveals densely packed layers where transversal fractures occurred (red arrows) attesting the formation of lamellar structures. No birefringence was noticed in optical microscopy (not shown). The saturated state of hydrogenated phospholipids and the strong packed organisation of the components of the biomimetic emulsifier create a rigid lamellar structure inducing a gel-like behaviour and bringing consistency to formulas.
April 2018
Stratum corneum
Epidermis (E)
Dermis (D)
Receptor fluid (RF)
Total
bioavailable (E+D+RF)
Hexapeptide: High molecular weight & moderate absorption capacity Diffusion of caffeine in human skin during 24h BiophilicTM 10 x2.3 more effective 8 6 4 2 0 0 2 4 6 Figure 2: Biophilic H as a delivery system.
Formulation characteristics Table 1 resumes the formulation characteristics of the biomimetic emulsifier. As an emulsifier, the biomimetic emulsifier is performant and versatile. By itself, it can emulsify up to 30% oil. It is compatible with all kinds of oils, pigments, as well as chemical and physical UV filters, bringing shine and consistency to formulations. It can also be added at lower concentrations in formulations, as a co-emulsifier or skin- feel enhancer, offering formulators the flexibility to create a variety of luxurious textures from fluid to buttery.
Delivery system
The biomimetic emulsifier is more than just an emulsifier. It can also deliver active ingredients to the skin. To be efficient, active ingredients must reach their target which often is located within the epidermis or even deeper in the skin. The stratum corneum being a strong barrier that cannot be easily crossed, most actives need a little help to reach their destination. Several types of permeation enhancers are available for this purpose, unfortunately
most of them will delipidated the stratum corneum in the process, compromising the skin barrier and inducing skin irritation. Phospholipid-based emulsifiers offer a gentler alternative. Their remarkable ability to mimic the stratum corneum lipid organisation by forming lamellar structures in emulsions makes them ideal vehicles to facilitate skin penetration of active molecules without affecting skin integrity. The performance of the biomimetic emulsifier (5%) as a delivery system was documented using caffeine (1.5%) and hexapeptide (300 ppm) as actives. Four formulas were prepared, with caffeine (molecule A) or hexapeptide (molecule B), with or without the biomimetic emulsifier. Formulas were applied at a dose of 10 mg/cm² on the surface of skin explants and incubated for 24h. In the case of caffeine (molecule A), receptor fluid samples were collected at T2h, T4h, T8h, T12h, T18h, and T24h during incubation and skin compartments were collected at the end of the incubation period (T24h). For hexapeptide (molecule B), samples of the receptor fluid and skin compartments were
PERSONAL CARE EUROPE
8 10 12 14 16 18 20 22 24 Time (h)
x1.9 faster H Control * 8 * x8.5
Distribution of hexapeptide in skin compartments after 24h BiophilicTM
H Control 10 * p,0.05 (vs. contol)
% absorbed molecules (compared to the intitial dose)
% absorbed molecules (compared to the intitial dose)
% absorbed molecules (compared to the intitial dose)
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