WO2015181209A1

WO2015181209A1 - Cosmetic process for attenuating wrinkles

Info

Publication number: WO2015181209A1
Application number: PCT/EP2015/061659
Authority: WO
Inventors: Xavier Schultze; Bertrand Lion; Andrew Greaves
Original assignee: LOreal SA
Current assignee: LOreal SA
Priority date: 2014-05-28
Filing date: 2015-05-27
Publication date: 2015-12-03
Anticipated expiration: 2016-11-28
Also published as: FR3021537A1; FR3021537B1

Abstract

The invention relates to a cosmetic process for caring for the skin, in particular wrinkled skin, comprising the application to the skin of a composition comprising a hyaluronic acid polymer grafted with (meth)acrylate groups with a degree of grafting ranging from 20% to 80%. The invention also relates to the use of said grafted hyaluronic acid polymer as a skin tensioning agent.

Description

Cosmetic process for attenuating wrinkles

The present invention relates to a skincare process, in particular a cosmetic skincare process, intended to attenuate wrinkles, comprising the application to the skin of a composition comprising a grafted hyaluronic acid polymer, and to the use of this polymer as a skin tensioning agent.

During the ageing process, various signs appear on the skin, which are very characteristic of this ageing, resulting in particular in a modification of skin structure and functions. The main clinical signs of skin ageing are in particular the appearance of fine lines and deep wrinkles, which increase with age.

It is known practice to treat these signs of ageing using cosmetic or dermatological compositions containing active agents capable of combating ageing, such as a-hydroxy acids, β-hydroxyacids and retinoids. These active agents act on wrinkles by eliminating dead skin cells and by accelerating the cell renewal process. However, these active agents have the drawback of only being effective for the treatment of wrinkles after a certain application time. However, it is increasingly sought to obtain a quick or immediate effect of the active agents used, rapidly resulting in smoothing out of wrinkles and fine lines and in the disappearance of the signs of fatigue.

Hyaluronic acid is known for its skin tensioning properties.

The inventors have discovered that a hyaluronic acid polymer grafted with (meth)acrylate groups has an improved tensioning effect on the skin and thus makes it possible to attenuate wrinkles on the skin, notably quickly or immediately after application on the skin.

Polymers of hyaluronic acid grafted with (meth)acrylate groups are described in document WO 2007/106738 and the publications J. Burdick et al "Controlled degradation and mechanical behavior photopolymerized hyaluronic acid networks", Biomacromolecules, 2005, 6, pages 386-391 ; Mark Grinstaff "Photocrosslinkable polysaccharides for in situ hydrogel formation", Journal of biomedical materials research, 2001 , volume 55, Issue 2, pages 1 15-121. They have been used to form hydrogels after crosslinking.

More specifically, a subject of the present invention is a process, in particular a cosmetic process, for caring for the skin, more particularly facial skin, in particular wrinkled skin, comprising the topical application to the skin of a composition, in particular a cosmetic composition, comprising a hyaluronic acid polymer grafted with (meth)acrylate groups with a degree of grafting ranging from 20% to 80%. The process according to the invention is in particular intended for smoothing out human facial and/or body skin and/or for decreasing or effacing the signs of skin ageing, in particular for reducing or effacing wrinkles and/or fine lines on the skin.

A subject of the invention is also the use, in particular cosmetic use, as a skin, in particular wrinkled skin, tensioning agent, of a grafted hyaluronic acid polymer as previously defined. A subject of the invention is also the use, in particular cosmetic use, of a grafted hyaluronic acid polymer as previously defined as a skin anti-wrinkle agent.

A subject of the invention is also a composition comprising, in a physiologically acceptable medium, a grafted hyaluronic acid polymer as previously defined, said polymer being non-crosslinked, and at least one cosmetic additive chosen from emulsifiers, fillers, sequestering agents, fragrances, thickeners, colorants, oils, waxes and film-forming polymers.

The term "tensioning agent" is intended to mean compounds capable of having a noticeable tensioning effect, i.e. of smoothing out the skin and immediately reducing, or even causing to disappear, the wrinkles and fine lines.

The tensioning effect may be characterized by means of an in vitro retraction test as described in Example 3.

Hyaluronic acid is a linear glycosaminoglycan composed of repeating D-glucuronic acid and N-acetyl-D-glucosamine units linked together via alternating beta-1 ,4 and beta-1 ,3 glycosidic linkages. Preferably, the grafted hyaluronic acid polymer has a weight-average molecular weight ranging from 5000 to 1 000 000 daltons, more preferentially ranging from

10 000 to 500 000 daltons, and even more preferentially ranging from 15 000 to 350 000 daltons.

The molecular weight can be determined in particular by liquid chromatography, the eluent being 0.1 M sodium chloride and 330 mg/l of sodium azide in water, with dextran as standard, and Wyatt Optilab T-Rex refractometer and Wyatt Dawn-Heleos

11 light scattering detectors.

Advantageously, the grafted hyaluronic acid polymer has a degree of grafting with (meth)acrylate groups ranging from 20% to 80%, preferably ranging from 40% to 70%, and preferentially ranging from 45% to 65%. The degree of grafting corresponds to the mole percentage of hydroxyl groups of the hyaluronic acid which are grafted with a (meth)acrylate group. By way of example, a degree of grafting of 50% corresponds to 2 acrylate groups grafted onto the 4 hydroxyls of the repeating unit of the hyaluronic acid.

The grafting of hyaluronic acid with (meth)acrylate groups results from the presence of a (meth)acrylate ester group formed with the free hydroxyls of hyaluronic acid.

Preferably, the hyaluronic acid is grafted with acrylate groups (of formula -CO-CH=CH₂). The hyaluronic acid grafted with (meth)acrylate groups can be obtained by reaction of the hyaluronic acid with (meth)acrylic anhydride. The reaction is advantageously carried out in a basic aqueous medium, in particular in the presence of an organic or inorganic base such as, for example, sodium hydroxide. Preferably, the reaction is carried out at a temperature ranging from 5 to 10°C, in particular for a period of time ran ing from 24 hours to 48 hours.

Various degrees of grafting with the (meth)acrylate groups can be obtained by varying the amount of (meth)acrylic anhydride used proportionally to the amount of hyaluronic acid. According to one embodiment of the invention, the grafted hyaluronic acid used in the process according to the invention is non-crosslinked.

The grafted hyaluronic acid polymer as previously defined may be present in the composition used according to the invention in a content ranging from 0.1 % to 10% by weight, relative to the total weight of the composition, preferably ranging from 0.5% to 10% by weight of active material, preferentially ranging from 1 % to 8% by weight, and more preferentially ranging from 1 % to 6% by weight.

The composition used according to the invention is generally suitable for topical application to the skin and thus generally comprises a physiologically acceptable medium, i.e. a medium that is compatible with the skin and/or skin appendages. It is preferably a cosmetically acceptable medium, i.e. a medium which has a pleasant colour, odour and feel and which does not cause any unacceptable discomfort (stinging, tautness or redness) liable to discourage the consumer from using this composition. The composition according to the invention may be in any galenic form conventionally used for a topical application and especially in the form of dispersions of aqueous gel or lotion type, emulsions of liquid or semi-liquid consistency of the milk type, obtained by dispersing a fatty phase in an aqueous phase (O W) or vice versa (W/O), or suspensions or emulsions of soft, semi-solid or solid consistency of the cream or gel type, or alternatively multiple emulsions (W/O/W or O/W/O), microemulsions, vesicular dispersions of ionic and/or nonionic type, or wax/aqueous phase dispersions. These compositions are prepared according to the usual methods.

According to one preferred embodiment of the invention, the composition is in the form of an O/W emulsion or an aqueous gel.

Advantageously, the composition used according to the invention comprises water, in particular in a content which can range from 10% to 99% by weight and preferably ranging from 50% to 99% by weight, relative to the total weight of the composition.

The composition used according to the invention may also contain one or more attachments commonly used in the cosmetics field, such as emulsifiers, fillers, preservatives, sequestering agents, fragrances, thickeners, colorants, oils, waxes or film-forming polymers.

Needless to say, those skilled in the art will take care to select this or these optional additional compound(s), and/or the amount thereof, such that the anti-wrinkle properties of the composition according to the invention are not, or are not substantially, adversely affected by the envisaged addition.

The application of the composition according to the invention is carried out according to the usual techniques, for example by application (in particular of creams, gels, sera or lotions) to the skin intended to be treated, in particular facial and/or neck skin, especially the skin of the area around the eyes. In the context of this process, the composition may, for example, be a care composition or a makeup composition, in particular a foundation composition. The invention will now be described with reference to the examples that follow, which are given as non-limiting illustrations.

Example 1 : Hyaluronic acid 60% functionalized with acrylic anhydride

In a thermostated reactor, 5 g of hyaluronic acid (Hyacare® 50 from Evonik) were dissolved in 100 ml of water and the mixture was maintained at a temperature of 7°C, then 14.8 g of acrylic anhydride were added dropwise over the course of approximately 2 min. The pH was adjusted to 7.7 by slowly adding (over the course of approximately one hour) sodium hydroxide at 30% in water (7 M). The mixture was left to react for 24 hours.

The mixture obtained was purified by dialysis (polymer in 150 ml of water, 3.3% by weight) on a Spectra/Por® 15 kDa membrane for 5 days in 5 litres of water (water changed 4 times, i.e. 20 litres in total), then the purified fraction was lyophilized by freezing using a mixture of dry ice and acetone at -80°C and by placing the frozen mixture in a lyophilization apparatus for 4 days.

2.5 g of a white solid were obtained.

Analyses:

¹H NMR D₂0: 2.45 (7.36/3) OH units functionalized for 4 OH units available.

The hyaluronic acid obtained is 60%-functionalized with acrylate groups.

Example 2: Hyaluronic acid 50% functionalized with acrylic anhydride

The polymer was prepared according to the procedure described in Example 1 , using 5 g of hyaluronic acid (Hyacare® 50 from Evonik) and 7.9 g of acrylic anhydride.

After purification, 2.5 g of a white solid were obtained.

Analyses:

¹H NMR D₂0: 1.96 OH units functionalized for 4 OH units available.

The hyaluronic acid obtained is 50%-functionalized with acrylate groups.

Example 3 (not in the invention): Hyaluronic acid 18% functionalized with acrylic anhydride

The polymer was prepared according to the procedure described in Example 1 , using 5 g of hyaluronic acid (Hyacare® 50 from Evonik) and 3.15 g of acrylic anhydride.

After purification, 3.2 g of a white solid were obtained. Analyses:

¹H NMR D₂0: 0.74 OH unit functionalized for 4 OH units.

The hyaluronic acid obtained is 18%-functionalized with acrylate groups. Example 4 (not in the invention): Hyaluronic acid 12% functionalized with acrylic anhydride

The polymer was prepared according to the procedure described in Example 1 , using 5 g of hyaluronic acid (Hyacare® 50 from Evonik) and 1.58 g of acrylic anhydride. After purification, 3.3 g of a white solid were obtained. Analyses:

¹H NM D₂0: 0.50 OH unit functionalized for 4 OH units.

The hyaluronic acid obtained is 12%-functionalized with acrylate groups.

Example 5:

Demonstration of the tensioning effect of the polymers used according to the invention

The tensioning effect of the polymers of Examples 1 to 4 was evaluated by means of an in vitro retraction test.

This test consists in comparing, in vitro, the tensioning capacity of the polymer to be evaluated, relative to a reference tensioning polymer: Hybridur^® 875 polymer dispersion from Air Products (aqueous dispersion at 40% by weight of particles of an interpenetrated network of polyurethane and acrylic polymers). The polymer to be evaluated is deposited on a nitrile rubber strip cut from a glove sold under the reference Safeskin Nitrile Criticial No. 038846 by the company Dominique Dutscher SA, having a surface area of 3.5 cm², stretched taut beforehand on a support. An aqueous solution containing the polymer to be evaluated is therefore deposited on the elastomer strip, by depositing 1.8 mg (of solids) of polymer.

26 μΙ of an aqueous solution containing 7% AM of Hybridur^® 875 polymer are thus deposited on a nitrile rubber strip so as to thus obtain a reference tensioning strip, and 52 μΙ of an aqueous solution containing 3.5% AM of acrylate-functionalized hyaluronic acid to be evaluated are deposited on another strip.

After drying for 24 hours at ambient temperature (25°C), the curving (retraction) of the strip treated with the hyaluronic acid polymer is observed in comparison with that obtained for the control (Hybridur^® 875).

Likewise, non-modified hyaluronic acid (Hyacare® 50 from Evonik) was evaluated.

The following results were obtained:

Polymer tested Tensioning effect

Hybridure 875 reference correct

Example 1 Same as reference

Example 2 Same as reference

Example 3 Less than the reference

Example 4 Less than the reference Polymer tested Tensioning effect

Hyaluronic acid Less than the reference

The results obtained show that the hyaluronic acid polymers of Examples 1 and 2 have a tensioning effect, whereas the polymers of Examples 3 and 4 do not have a tensioning effect.

Furthermore, the polymers of Examples 1 and 2 have a tensioning effect greater than that of the non-modified hyaluronic acid.

Example 6:

An anti-wrinkle gel having the following composition was prepared:

- polymer of Example 1 1 g

- hydroxyethylcellulose (NATROSOL® 250 HHR CS from Ashland) 0.5 g - Preservatives qs

- Water qs 100 g

A similar composition was also prepared using the polymer of Example 2. The compositions obtained, when they are applied to the face, make it possible to effectively smooth out wrinkles.

Claims

1. Cosmetic process for caring for the skin, more particularly facial skin, in particular wrinkled skin, comprising the topical application to the skin of a cosmetic composition comprising a hyaluronic acid polymer grafted with (meth)acrylate groups with a degree of grafting ranging from 20% to 80%.

2. Process according to the preceding claim, characterized in that the grafted hyaluronic acid polymer has a degree of grafting ranging from 40% to 70%.

3. Process according to Claim 1 or 2, characterized in that the hyaluronic acid polymer is grafted with acrylate groups.

4. Process according to any one of the preceding claims, characterized in that the grafted hyaluronic acid polymer has a weight-average molecular weight ranging from

5000 to 1 000 000 daltons, preferably ranging from 10 000 to 500 000 daltons, preferentially ranging from 15 000 to 350 000 daltons.

5. Process according to any one of the preceding claims, characterized in that the hyaluronic acid polymer is present in the composition in a content ranging from 0.1 % to

10% by weight, relative to the total weight of the composition, preferably from 0.5% to 10% by weight of active material, preferentially ranging from 1 % to 8% by weight, and more preferentially ranging from 1 % to 6% by weight.

6. Process according to any one of the preceding claims, characterized in that the composition is in the form of an O/W emulsion or an aqueous gel.

7. Process according to any one of the preceding claims, characterized in that it is intended for attenuating wrinkles.

8. Cosmetic use, as a skin tensioning agent, in particular a wrinkled-skin tensioning agent, of a grafted hyaluronic acid polymer as defined in any one of Claims 1 to 4.

9. Cosmetic use of a grafted hyaluronic acid polymer as defined in any one of Claims 1 to 4 as a skin anti-wrinkle agent.

10. Composition comprising, in a physiologically acceptable medium, a grafted hyaluronic acid polymer as defined in any one of Claims 1 to 4 and which is non- crosslinked, and at least one cosmetic additive chosen from emulsifiers, fillers, sequestering agents, fragrances, thickeners, colorants, oils, waxes and film-forming polymers.