A new generation of tensor actives: polymerization is a new technology that can amplify the potential lifting and viscoelastic properties of vegetal proteins.

AFTER AGE 50, OR THEREABOUTS, women experience a slackening of the skin and a loss of elasticity and tone. Cutaneous aging results primarily in the appearance of more or less marked wrinkles, which are accentuated on the photo-exposed body areas such as the face, the neck or hands. In order to "erase" the effects of age, consumers are eager to test an entire range of anti-wrinkle substances, or take more drastic measures such as undergoing plastic surgery.

The anti-aging segment within the skin care market is very promising for the cosmetics industry. Even so, cosmetic chemists must take into account the consumer's needs and provide them with a visible and immediate anti-aging effect. The current trend thus consists of including in the anti-wrinkle creams, tensor active ingredients likely to smooth the skin, to reorganize it and fight against the harmful relaxation and effects of gravity.

The tensor active ingredients have as a principal property the capacity to be adsorbed and to be spread out on the surface of the skin to form an elastic, cohesive and continuous film supporting the smoothing of the skin (Figure 1).

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Until now, the strategy of development of a tensor active ingredient focused on preserving the tertiary structure of proteins. The preservation of the globular structure of proteins allows the formation of a film on the surface of the skin thanks to its adsorption properties and spreads out as opposed to peptides that adsorb but are unable to spread out.

Proteins of high molecular weight are neither very soluble or stable in emulsion and lead to an anarchic arrangement of aggregates unlikely to form a continuous proteic film that exerts smoothing properties. This article details an innovative and patented polymerization technology that improves the skin tightening properties of high molecular weight proteins.

Starting with monomeric natural proteins pre-selected according to their molecular weight, polymerization allows cosmetic chemists to create a three-dimensional network of high molar mass that is able to induce a molecular architecture perfectly adapted to the improvement of the biomechanical properties of the skin (Figure 2). The polymerized proteins have better stability in terms of pH and conductivity, as well as better solubility in all types of formulation.

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The Benefits of Polymerization

Polymerization guarantees a good reproducibility of the process. A study was conducted on the tensor effect as a function of the degree of hydrolysis (characterized by enzyme levels) (Figure 3) and of the degree of polymerization (affected by the quantity of polymerizing agent) (Figure 4). It can be concluded that polymerization is based on two essential factors:

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* The size and structure of monomers, dependent on the degree of enzymatic hydrolysis and

* The degree of polymerization, responsible for the intensity of cross-linking.

The configuration and efficacy of these biological polymers are rendered normal by the optimization and standardization of these two parameters.

The optimization and the standardization of these two parameters make it possible to standardize the configuration and the effectiveness of these biological polymers.

Adaptable Process

Polymerization can be thought of as a new technology that can amplify the potential lifting and viscoelastic properties of new native proteins. In order to validate this concept, we tested our technology on various types of proteins, including :

* Lupin proteins,

* Almond proteins and

* Prune pit proteins.

The results obtained prove that our cross-linking process increases the tensor effect of monomeric proteins of varied plant origins.

Polymerization supports the improvement of the tensor potential of protein. The monomeric proteins present a slight tensor effect. The reticulation allows the chemist to increase considerably the tensor effect of monomeric proteins while preserving their strong solubility in aqueous mediums.

Mechanism of Action

Increasing the quantity of hydrophobic groups on protein chains, supports the hydrophobic interactions and increases the affinity and adsorption of polymer on skin lipids.

Thus, a Cutometer study conducted on the forearms of 20 volunteers showed that the polymer, tested at 4% in an emulsified gel, lost its tensor properties if skin lipids were first removed with acetone (Figure 5).

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To highlight the tensor aspect of an active ingredient such as that obtained by polymerization, it is important to study at the same time the physical properties via objective methods and the sensorial properties via subjective methods.

An objective study of this type of active ingredient relies on three criteria:

* To measure the tensor effect to evaluate the biomechanical properties;

* To observe the immediate anti-wrinkle effect and

* To feel the tensor effect using a consuming test.

To study the physicochemical properties of the product we called upon two methods of cutaneous biometrology:

* cutometry and

* profilometry.

The choice of the cutometer to measure the properties of skin extensibility allows to evaluate the cutaneous resistance to a deformation after the application of a tensor active ingredient and the formation of a film at the skin surface by this tensor. The deformation in this case is induced by the probe of the measuring tools.

Profilometry itself allows one to study the relief of the cutaneous surface and to visualize the immediate anti-wrinkle effect caused by polymer.

The description of sensorial qualities of the active ingredient rely on consumer tests which allow to better apprehend the feelings perceived by the users.

The assessment of the immediate tensor effect was realized, vs. placebo, with the tensor polymer formulated at 4% in four types of formulations (gel, emulsified gel, emulsion 1 containing 30% of oily phase and emulsion 2 containing 53% of oily phase).

Under the conditions of this study, two hours after a single application and in comparison with the placebo, one can highlight an improvement of the parameters characteristic of the skin tension, Uf and Ue, whatever the studied formula. The polymer presents an immediate tensor effect in various formulations and can still be expressed when it is formulated in an emulsion containing 53% of oily phase (Figure 6).

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The study of the immediate anti-wrinkle properties was carried out by profilometry after two hours of treatment with the polymer formulated at 4% in emulsified gel (Figure 7).

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The study of the distribution of the results showed that 76% of the volunteers presented an immediate anti-wrinkle effect (Figure 7). This effect could be quantified: the polymer significantly reduced the total wrinkled surface (-14.8%) and the total length of wrinkles (-14.4%).

The sensations observed when using the tightening polymer vs. placebo twice daily for one month were determined using self-evaluation questionnaires. One hundred twenty women were recruited to form two groups, one applying the tightening polymer formulated in an emulsified gel, the other using the placebo. After four weeks of twice daily applications, the questionnaires were returned. The questionnaires contained so-called closed questions and also free comments.

Consumers very much preferred the the tightening active ingredient compared to the placebo. The tensor and lifting effect was more often recognized and, to a significant degree, by the users of the tensor active ingredient. Moreover, the consumer test allowed us to conclude that the product out-performed the placebo by a very large margin in several key areas including: radiant complexion (+53.3%), firmness (+53.3%) and skin vitality (+51.7%) (Figure 8).

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As a new technology, the polymerization enables chemists to develop new tightening active ingredients from vegetal sources, having high water soluble molecular weight and being stable in formulation. After adsorption on the cutaneous lipids, our polymer immediately presents a visible effect by forming an immediate elastic film that is able to spread out on the skin surface and to smooth the microrelief.

The evaluation of a tensor active ingredient can be done according to three approaches:

* By measuring the biomechanical properties of the skin;

* By observing the immediate anti-wrinkle effect and

* By perceiving the feeling of the tensor effect

The first two methods enable chemists to get objective information concerning the performance of the tensor by studying the physicochemical characteristics of this type of active ingredient. It allows them to highlight the concrete and visual efficacy of a tensor and to respond to consumer expectations for an immediate and visible effect.

Thanks to the consumer test, we could establish a correlation between the answers of users and the results of the physicochemical studies and we could show that we fulfill another consumer expectations: perception of the performance of the active ingredient.

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