ANTI-AGEING Cristalhyal® e-Perfection 0 Mattifying Skin smoothing Fine lines 0 Long lasting hydration 50 100 0 50 100 Clay 50 Detoxification & antipollution 100 100 50
HMW HA alone
0
Cristalhyal® e-Perfection
45
Figure 1: Cristalhyal e-Perfection mode of action
hyaluronate form. To demonstrate this, the Zeta potential of Cristalhyal alone (a HMW HA) and the bentonite clay HA active ingredient were measured and compared. Results demonstrate that the bentonite clay
HA active ingredient presents a zeta potential profile which is significantly different from HA alone, even more negative, specifically at ‘high’ pH (>7). This behaviour improves the affinity of HA molecules for the skin depth, and can thus explain a better penetration. Indeed, it is well documented that there is a natural pH gradient in the skin,3
with
an increase of pH when going deeper into the epidermis (up to 7.5). This leads to an electrostatic attraction (Coulomb’s law) of the negative HA molecules present in the clay complex, ultimately resulting into an enhanced skin penetration, through intercellular diffusion.
Deeper skin penetration Regarding skin penetration, skin explants from a Caucasian, 47 year-old donor were topically treated with Cristalhyal at 1% (a HMW HA) or the bentonite clay HA active ingredient at 10% (equivalent to HA content of 1%). Raman spectroscopy analysis was then performed after eight hours, to assess products penetration profiles. Results demonstrate that the standard
high molecular weight hyaluronic acid shows no skin penetration, and remains at the surface of the skin. The bentonite clay HA active ingredient enables the HMW HA penetration into the skin, with an average signal up to 60-75μm in the skin. In the meantime, it can be observed that the clay does not penetrate the skin, as all of its signal remains at the surface.
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Figure 2: Skin depth penetration profile
Long-lasting hydration Human skin explants from a 22 year-old donor were topically treated either with Cristalhyal at 0.1%, the bentonite clay HA active ingredient at 1% (equivalent to a HA content of 0.1%), clay at 1% or left untreated, and incubated for eight and 24 hours. Force measurements were then performed
using the Atomic Force Microscopy (AFM) coupled to an epifluorescence microscope (for a precise positioning of the AFM probe), and elastic modulus (Ea, related to the suppleness of the stratum corneum) was then quantified thanks to BioMeca Analysis software. This value of elastic modulus is inversely
correlated to the hydration level, as a better hydration will result in a more supple, less stiff, stratum corneum. Results demonstrate that after eight hours, both HA alone and the bentonite clay HA active ingredient result in a significant increase of the stratum corneum suppleness, respectively by +47% and +98%. Clay alone has no significant hydration benefit.
After 24 hours, both clay and HMW HA are back to a basal level (or even a bit lower for clay alone), with no positive impact on the hydration level. Only the bentonite clay HA active ingredient is able to provide a prolonged and long-lasting hydration, by +108% versus untreated conditions. Regarding the smoothing of the skin’s surface,
compared to untreated conditions, no significant change can be observed on the explants treated with clay only. The skin is not smoothed, and corneocytes can still be visualised very easily. The use of HMW HA alone enables a slight smoothing of the skin, but corneocytes can still be observed clearly.
The use of the bentonite clay HA active
ingredient results in a significant smoothing of the skin, as the corneocytes cannot be distinguished easily anymore.
Anti-adhesion and detoxification benefits Human skin explants from a 57 year-old donor were topically treated with the bentonite clay HA active ingredient at 1% or left untreated. Skin explants were photographed, then 3mg of carbon particles were applied to mimic an exposure to pollution. The skin explants were again photographed, then the particles were rinsed and a D-squame® sample was taken on each zone in order to quantify the remaining particles at the surface of the skin explants. Results demonstrate that the quantity of
particles found after carbon application was significantly lower in presence of the bentonite clay HA active ingredient, down to -50%, demonstrating an anti-adhesion benefit of the active. After rinsing, the quantity of carbon
particles was significantly reduced in comparison to untreated condition, down to -29%, showing that the skin was detoxified in presence of the bentonite clay HA active ingredient.
Sensoriality booster with a satin touch By combining high molecular weight hyaluronic acid and clay, two ingredients recognised for their sensorial benefits, the bentonite clay HA active ingredient enables to improve significantly the sensoriality and texture of finished products. These benefits were evaluated thanks to a sensorial panel, composed of 50 persons, specifically trained for sensorial evaluation. The bentonite clay HA active ingredient was
spontaneously associated predominantly to a feeling of softness, with a very pleasant touch
July 2022 PERSONAL CARE
EPIDERMIS Clay signal HA signal
Skin depth (µm)
Skin depth (µm)
Low to high concentration
Low to high concentration
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