Immediate and long-lasting skin tightening

Obtaining a tensor effect during the development of active ingredients requires the creation of a three-dimensional molecular network. This can be developed at two levels. On one hand, on the cutaneous surface by creating a reticulated molecular network able to adsorb, to spread out and to form a continuous and elastic film on the skin. On the other hand, in depth, by favoring not only the organisation of the threedimensional dermal network but also the maintenance of mechanical forces in tissues.

To respond to the first aim, we have set up an innovative technology of polymerisation able to amplify the lifting potential properties of natural proteins. This technology allows, starting from monomeric natural proteins pre-selected according to their molecular weight after enzymatic hydrolysis, to create a threedimensional network of high molar mass.

Polymerisation is based on three essential factors: the reticulating agent depending on the chemical nature of monomers, the size and structure of monomers, dependent on the degree of enzymatic hydrolysis and the degree of polymerisation, responsible for the intensity of cross-linking that depends on the rate of reticulating agent used. The optimisation and the standardisation of these three parameters make it possible to standardise the configuration and the effectiveness of the biological polymer. First active set up according to this process is a biopolymer of sweet almond proteins of high molecular weight (>500,000 Da) perfectly adapted to the improvement of the cutaneous surface properties. The reticulation increases considerably the tensor effect of monomeric sweet almond proteins while preserving their strong solubility in aqueous mediums and thus their ease of formulation. Otherwise a tightening active can also act on the deep cutaneous tissue as an internal tensor thanks to a biological lifting effect. By preserving the skin mechanical resistance but also by stimulating the metabolic and contractile properties of the fibroblasts, the biological homeostasis as well as the three-dimensional fibrillar organisation of the dermal network are maintained. Such are the action mechanisms of a rye extract, rich in arabinoxylans purified from the rye seeds. This rye extract boosts the activities of both mechanical receptors and stress fibers of fibroblasts that act synergistically to regulate the tautness of the three-dimensional fibrillar network of the dermis. By this means, the rye extract having self-lifting properties is able to tighten the skin and to provide a biological and long-lasting tensor effect. The cosmetic benefits of the two active ingredients were studied using the same in vivo tools and methods: cutometry to evaluate tensor effect and profilometry to determine smoothing and anti-wrinkle properties. Moreover, the biopolymer properties were studied two hours after one single application in order to highlight its immediate and mechanical effects whereas the rye extract properties were analysed after 56 days of twice-daily treatment to highlight its biological and long-term effects.

Results

Biopolymer for an immediate and mechanical tightening effect
Immediate tensor properties
The assessment of the immediate tensor effect of the sweet almond biopolymer formulated at 4% in an emulsified gel was realised, vs. placebo, on 12 healthy female volunteers. The study was carried out by cutometry (Courage & Khazaka, Germany). The parameters, Uf characteristic of the immediate extensibility and Ue, characteristic of the total elongation, were measured two hours after a single application of the biopolymer on the face. In comparison with the placebo, the sweet almond biopolymer significantly increases –Uf (+7.1% ; P=0.0120) and –Ue (+12.1% ; P=0.0100) parameters characteristics of the skin tension (Fig. 1).

Immediate lifting properties
The immediate lifting properties of the sweet almond biopolymer formulated at 4% in an emulsified gel was determined vs. placebo using profilometry equipped with an image analysis. Silicone polymer replicas were taken before and after 2h of a single application of the products on the forearms and crow’s feet to evaluate respectively the smoothing and anti-wrinkle properties of the biopolymer.

a) Immediate smoothing properties
The study was conducted on 13 healthy female volunteers (mean age 29 ± 1 years). The replicas were analysed using QUANTILINE® 99 software (Monaderm, Monaco). Provided was the roughness parameter Ra. In the conditions of this study, two hours after a single application and in comparison with the placebo, the biopolymer reduced the skin roughness by 4.6% (P=0.0690) at the level of forearms. The study of the distribution of the results shows that 69% of the volunteers presented a smoothing of the skin microrelief.

b) Immediate anti-wrinkle properties
The study was conducted on 17 healthy female volunteers (mean age 53 ± 2 years). The replicas were analysed using QUANTIRIDE® 99 software (Monaderm, Monaco) and provided were the following parameters: total wrinkled surface and total length of wrinkles. In the conditions of this study, two hours after a single application on the crow’s feet and in comparison with the placebo, the biopolymer significantly reduced: • The total wrinkled surface by 14.8% (P=0.0350) • The total length of wrinkles by 14.4% (P=0.0479). This immediate anti-wrinkle effect was observed in 76% of the volunteers. These results are illustrated with an example of replicas taken before and after treatment of the crow’s feet of a volunteer with the biopolymer (Fig. 2).

Consumer test
The sensations observed when using the tightening biopolymer vs. placebo twice daily for one month were determined using self-evaluation questionnaires. Recruited were 120 women to form two groups: one applied the tightening biopolymer formulated at 4% in an emulsified gel, the other used the placebo. After four weeks of twice daily applications, the questionnaires were returned. The analysis of the answers of the consumer test highlighted a rate of comments highly favourable for the tightening active ingredient compared to the placebo. The tensor and lifting effect were more often recognised, and this to a significant degree, by the users of the tensor active ingredient (Fig. 3). They also perceived an improvement in term of disappearance of wrinkles, firmness, suppleness and tone of their skin compared to the users of the placebo treatment.

Rye extract for a long-term and biological tightening effect
Long-term tensor properties The study was conducted on 20 healthy female volunteers (mean age 56 ± 8 years). Measurements on the face were made with a SEM 575 Cutometer® (Courage & Khazaka, Germany), before and after 56 days of twice daily treatment with the rye extract formulated at 4% in an emulsion vs. placebo. Skin tension was evaluated with the parameters -Uf and -Ue. In the conditions of this study, after 56 days of twice daily applications and in comparison with the placebo, the rye extract significantly improved parameters -Uf (16%, P = 0.0136) and -Ue (19%, P = 0.0173), representative of skin tension (Fig. 4). This effect was observed in 78% of the volunteers.

Long-term lifting properties
The study was conducted on 20 healthy female volunteers (mean age 56 ± 8 years). Silicone polymer replicas were made of the crow’s feet and the nasolabial fold before and after 56 days of twice daily treatment with the rye extract formulated at 4% in an emulsion vs. placebo.

a) Long-term smoothing properties
The smoothing effect at the crow’s feet was analysed by observing replicas with a profilometer equipped with an image analyser (QUANTILINES, Monaderm, Monaco). Two parameters characteristic of skin surface microrelief were studied: the index of mean roughness (Ra) and that of maximal roughness (Rz). In the conditions of this study, after 56 days of twice daily applications and in comparison with the placebo, the rye extract smoothed skin microrelief by significantly reducing parameters Ra (-7.8%, P = 0.0071) and Rz (-5.0%, P = 0.0247). The smoothing effect was observed in 72% of volunteers.

b) Long-term anti-wrinkle properties
The anti-wrinkle effect was analysed by observing the replicas with a profilometer equipped with an image analyser (QUANTIRIDES 99®, Monaderm, Monaco). Three parameters were studied: the number, the total surface and the total length of wrinkles.

After 56 days of twice daily applications and in comparison with the placebo, the rye extract formulated at 4% in an emulsion provided a significant anti-wrinkle effect (P < 0.05) at both the crow’s feet and the nasolabial fold (Fig. 5), respectively: a 13% and 23% decrease in the number of wrinkles, a 15% and 26% reduction of the total surface of wrinkles, and a 16% and 27% reduction of their length. Figure 6 shows an example of replicas of the crow’s feet (a) and photographs of the nasolabial fold (b) taken before and after treatment with the rye extract. The study of distribution of the results showed that 67% and 78% of the volunteers presented a decrease in the total wrinkled surface at the crow’s feet and nasolabial fold, respectively.

Conclusion
The current trend to include in the anti-age creams tensor active ingredients that lift the skin, thanks to an immediate mechanical action on the cutaneous surface, takes into account the needs of consumers in search of immediate perceptible and visible effects. However, the use of a natural and biological tensor effect in order to remodel and to tauten again the dermal tissue seems to be today primordial to fight against the slackening of the skin for a longer term.

Silab thus proposes an innovative and complete approach of tightening ingredients with two active ingredients having complementary action mechanisms. On one hand, a sweet almond biopolymer providing mechanical and short-term effects by creating a cohesive and viscoelastic film on the skin surface; and on the other hand, a rye extract acting as an internal tensor in the deep cutaneous layer thanks to biological and long-lasting effects.

Tested directly in vivo on volunteers versus placebo, the biopolymer shows immediate – tightening, smoothing and anti-wrinkle – properties that are perceived by the users whereas the rye extract gives elasticity to the skin but also improves its microrelief after 56 days of twice-daily treatment.

It seems to be interesting to determine the synergic activity between the sweet almond biopolymer and the rye extract by evaluating the cosmetic benefits of a formula containing these two active ingredients in terms of surface and biomechanical properties of the skin.

Abstract
In order to propose an innovative and complete approach for tightening ingredients, Silab puts forward two active ingredients having complementary action mechanisms to obtain a global lifting effect at the level of skin surface as well as in dermal tissue. These two active ingredients are able to create a three-dimensional network on the skin surface for the sweet almond biopolymer and in the deep cutaneous tissue for the rye extract. The sweet almond biopolymer thus brings a mechanical and short-term effect whereas the rye extract acts as an internal tensor thanks to a biological and long-lasting effect. The cosmetic benefits of the two active ingredients were studied using the same in vivo methods two hours after one single application for studying the biopolymer properties and after 56 days of twice-daily treatment for analysing rye extract properties in order to highlight respectively their immediate and long-lasting effects.