78 SKIN CARE
Skin surface SC
~20µm deep
Total depth in skin 60µm
3.5 a.u
Area ratio CD/CH
0 a.u Figure 4: Confocal Raman image analysis: SDS-applied skin.
the cells intact, classified a surfactant as a non-irritant. A mean tissue viability less than 50%, indicating that a surfactant destroyed more than 50% of the skin cells, classified a surfactant as an irritant.
Polyglyceryl-10 caprylate/caprate mild surfactant and PEG-80 sorbitan laurate scored close to the saline negative control of 100%, and thus qualified as non-irritants. Decyl glucoside, by contrast, had a mean tissue viability of just 17%, classifying it as an irritant.
Polyglyceryl-10 caprylate/caprate mild surfactant has an excellent skin irritation profile, equal to PEG 80 sorbitan laurate, and generates foam as well as decyl glucoside. PEG-80 sorbitan laurate also has an excellent irritation profile but does not foam well, as highlighted in the previous study.
The EpiOcular™ Irritation test (Table 2) evaluates possible eye irritation of the various surfactants. PEG-80 sorbitan laurate, with a mean tissue viability of 256 – determined by the MatTek specific gravity method — was classified as a minimal irritant. Polyglyceryl-10 caprylate/caprate mild surfactant, with a mean tissue viability of about 33, is classified as a mild irritant. Polyglyceryl-10 caprylate/caprate mild surfactant outperformed decyl glucoside and cocamidopropyl betaine.
Figure 5: Confocal Raman image analysis: skin applied with Polyaldo 10-1- CC mild surfactant + SDS.
Skin penetration test Traditional surfactants have the potential to penetrate the stratum corneum, which resides about 20 um below the skin surface. A key property for a cleanser is to stay closer to the skin surface and avoid penetrating the stratum corneum, where it can cause potential damage and disruptions to the moisture balance of the skin. The goal of the skin penetration study is to evaluate Polyglyceryl-10
caprylate/caprate mild surfactant for the ability to mitigate the penetration of surfactants into the stratum corneum, thus reducing the negative effects caused by some surfactants. The surfactant skin penetration test used surgical human abdominal skin (ex vivo) as the medium. In addition to evaluating the Polyglyceryl-10 caprylate/caprate mild surfactant, Lonza evaluated sodium dodecyl sulfate (SDS), recognised as a positive skin irritant. Samples of Polyglyceryl-10
caprylate/caprate + SDS surfactants, and SDS alone were each applied to the ex vivo skin medium and measured via a WITec Alpha 300R Plus Confocal Raman Microscope. Scientists measured the penetration of SDS into the stratum corneum - the outer layer of the skin, 20 microns beneath the skin surface - and the presence of water in the stratum corneum. The images were processed with WITec
Area ratio
Skin surface SC
~20µm deep
CD/CH 3.5 a.u
Skin surface SC
~20µm deep Project Plus software.
Skin applied with SDS alone had significant SDS penetration into the stratum corneum (Fig 4). High surfactant penetration can compromise the surface of the skin and cause disruptions to the stratum corneum. Figure 5 shows skin applied with a surfactant combination of Polyglyceryl-10 caprylate/caprate mild surfactant and SDS. Surfactant presence is limited to the skin surface, mitigating the penetration of SDS into the stratum corneum.
The Polyglyceryl-10 caprylate/caprate mild surfactant thus protects the surface of the skin and the stratum corneum from potential damage caused by some harsh surfactants. Traditional surfactants have the potential not only to damage the stratum corneum, but disrupt the delicate balance of water and potentially create issues with how the skin functions. The effects of surfactant penetration can be shown by measuring the amount of moisture in and below the stratum corneum. Figure 6 shows the presence of water in
untreated healthy skin, the control for the water content analysis. Red, yellow and orange indicate higher concentrations of water in the skin. Purple indicates low water content, and the dotted line represents the skin surface. In general, there is less water content nearer to the surface because more
Total depth in skin 60µm
0 a.u
Figure 6: Confocal Raman image analysis of water content: Untreated, control skin.
PERSONAL CARE ASIA PACIFIC
Total depth in skin 60µm
Figure 7: Confocal Raman image analysis of water content: SDS-applied skin.
November 2017
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