Pseudo stratum corneum for evaluating skin permeability and method for evaluating cosmetic permeability

Abstract

To provide a clear determination of the permeability of cosmetics to the horny layer by simple and quantitative comparison using a pseudo-horny layer, thereby providing consumers with accurate judgment of the permeation superiority or inferiority of various cosmetics to the horny layer.SOLUTION: A soft solid mixture comprising keratin is provided as a main component and 10 to 50% by mass of lipid as an additive component as a pseudo-horny layer material. A dye, which is insoluble in the pseudo-horny layer material and soluble in the cosmetic to be evaluated, is used as a pseudo-horny layer for the permeability evaluation test of a cosmetic composed of a single-layer molded article held in a dispersed state in the pseudo-horny layer material. The permeability of a cosmetic can be evaluated by bringing the cosmetic into contact with the surface of the pseudo-horny layer and visually determining the depth of penetration of the cosmetic from the surface by the color reaction of the dye that progresses over time.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a pseudo stratum corneum for evaluating the permeability of a cosmetic material, which is used to evaluate the permeability of a cosmetic material from the skin surface into the stratum corneum, and a method for evaluating the permeability of a cosmetic material using the pseudo stratum corneum. [Background technology]

[0002] Human skin has an epidermis that protects the internal environment from the outside world, and its outermost layer is the stratum corneum, which is approximately 0.02 mm thick.

[0003] The stratum corneum, also known as the stratum corneum, is structured with keratinocytes piled up like bricks, with intercellular substances embedded between them like mortar. The intercellular substances are formed of lipid molecular aggregates whose main components are ceramide, fatty acid, and cholesterol.

[0004] Such a stratum corneum prevents water from leaking out of the skin and maintains an appropriate amount of moisture, thereby giving the skin flexibility and also protecting it from the invasion of foreign substances and irritation from outside the body.

[0005] Cosmetics that maintain the above-mentioned functions of the stratum corneum in good condition include facial cleansers, lotions, beauty essences, milky lotions, creams, and other cosmetics that are also called basic cosmetics.

[0006] In such cosmetics, the functions of specific ingredients, which are blended according to the purpose, are efficiently exerted by allowing the ingredients to penetrate into the stratum corneum, and therefore it is necessary to evaluate the permeability of the ingredients into the stratum corneum.

[0007] For example, a method is known in which a cosmetic is applied to a keratin film made from a solution of hair keratin protein using a finger, and the distortion and physical changes in shear force caused by the penetration of the cosmetic are measured over time, or the change over time in the contact angle of a droplet of the cosmetic applied to the skin is measured (Patent Document 1).

[0008] Furthermore, a method is known in which, using mammalian skin stratum corneum or cultured skin stratum corneum, the permeability of skin whitening agents, skin roughness prevention agents, etc. is examined by X-ray diffraction measurement of the stratum corneum, i.e., by evaluating the area of ​​the diffraction peak in a specific region in the X-ray diffraction profile, to examine whether or not the test substance has permeated into the stratum corneum (Patent Document 2).

[0009] Furthermore, a method for evaluating the permeability of cosmetics into the stratum corneum is known in which the stratum corneum is peeled off from the surface of the skin with adhesive tape using a tape stripping method, and observed under a microscope. The intensity of staining with fluorescein, rose bengal, or the like of the stratum corneum (specimen) taken before and after treating the skin to be observed with the cosmetic is compared by measuring the fluorescence brightness (Patent Document 3). [Prior art documents] [Patent documents]

[0010] [Patent Document 1] JP 2017-72397 A [Patent Document 2] JP 2015-40702 A [Patent Document 3] JP 2014-139540 A Summary of the Invention [Problem to be solved by the invention]

[0011] However, the evaluation method described in Patent Document 1, which involves measuring the distortion and shear force of a keratin film and the change over time in the contact angle of a droplet of a cosmetic material, does not allow evaluation of penetration in the depth direction.

[0012] Furthermore, the X-ray diffraction measurement using cultured skin stratum corneum, etc., described in Patent Document 2, estimates the permeability of a cosmetic from the stratum corneum after penetration, and therefore, although it is possible to qualitatively determine whether or not a cosmetic has permeability, it is difficult to quantitatively compare differences in the degree of permeability, and X-ray diffraction measurement is not an evaluation method that can be easily performed.

[0013] Furthermore, the evaluation method described in Patent Document 3 makes it possible to determine the degree of rough skin by observing the surface of the stratum corneum sheet under a microscope, but it is difficult to grasp the differences in the grade of penetration ability of the same type of cosmetic into the stratum corneum, and it is not a method that allows cosmetic users to easily understand differences in the penetration ability of the same type of cosmetic.

[0014] Therefore, the object of the present invention is to solve the problems in the prior art described above, and to enable the permeability of cosmetics into the stratum corneum to be clearly distinguished through a simple and quantitative comparison using a pseudo stratum corneum, and to enable consumers and the like to visually understand the relative merits of the permeability of various cosmetics into the stratum corneum, thereby enabling them to more accurately and easily distinguish between cosmetics with different permeability. [Means for solving the problem]

[0015] In order to solve the above problems, in this invention, a pseudo-stratum corneum material is a soft solid mixture containing keratin as the main component and 10 to 50 mass % lipids as an additional component, and a dye that is insoluble in this pseudo-stratum corneum material but soluble in the cosmetic material to be evaluated is dispersed in the pseudo-stratum corneum material to form a single-layer molded body to be used in cosmetic permeability evaluation tests.

[0016] The pseudo-stratum corneum of the present invention constructed as described above has a predetermined dye that is insoluble in the pseudo-stratum corneum material and soluble in the cosmetic material to be evaluated, and is dispersed in the pseudo-stratum corneum material. When a cosmetic material is brought into contact with the surface of a single-layered molded product made of such a pseudo-stratum corneum material, the dye that has penetrated into the single-layered molded product from the surface dissolves in the cosmetic material and develops color, thereby staining the pseudo-stratum corneum material.

[0017] Therefore, by simply observing a single-layer molded body made of a pseudo-stratum corneum material from the thickness direction of the layer visually or via images, it is possible to directly and quantitatively grasp the depth to which the cosmetic material penetrates into the stratum corneum, as well as the penetration power of the cosmetic material, taking into account factors such as the penetration depth over time.

[0018] Since it is preferable for the pseudo stratum corneum material to be composed of components that have as similar a permeability as possible to the actual stratum corneum in order to accurately grasp the penetration power of a cosmetic agent, it is preferable that the above lipids are one or more lipids selected from squalene, ceramide, fatty acids and cholesterol.

[0019] For the same reason as above, and in order to correspond to the softness of the stratum corneum on the actual skin surface, it is preferable that the lipid contains 10% by mass or more of lipid components that are liquid at room temperature. More preferably, the lipid components that are liquid at room temperature are W Preferably, the lipid component is keratin or oleic acid, or a combination of both, and the blending mass ratio of the keratin to the lipid is 6:4 to 8:2.

[0020] Furthermore, the dye can be any dye that dissolves in the cosmetic to be evaluated depending on its polarity. In other words, if the dye dispersed in the pseudo stratum corneum dissolves and develops color depending on the polarity of the cosmetic to the depth to which the cosmetic has penetrated, the penetration power of the cosmetic into the stratum corneum (depth of penetration) can be visually grasped from the colored dye by simply observing the pseudo stratum corneum visually or with an image. The dye that exhibits such an effect may be either a water-soluble dye or an oil-soluble dye, and may be, for example, a water-soluble dye that is soluble in a cosmetic preparation containing 15 to 95% by mass of water.

[0021] In particular, when the dye is a water-soluble acid dye, it dissolves in water and the acid dye is ionically bonded to the amino group of keratin to dye.Therefore, the dye remains at the colored position, so that the difference in the penetration speed of the cosmetic into the stratum corneum and the difference in the depth that can be penetrated can be accurately grasped.As such a water-soluble acid dye, azulene sulfonate or water-soluble food coloring can be used to obtain favorable results.

[0022] In this manner, the above-described pseudo stratum corneum can be used to contact a cosmetic material on its surface, and the depth to which the cosmetic material has penetrated from the surface can be visually determined by the color reaction of the dye that progresses over time, thereby evaluating the penetration of the cosmetic material. Effect of the Invention

[0023] In this invention, as described above, the pseudo-stratum corneum material is a soft solid mixture containing keratin as the main component and a predetermined amount of lipids as an added component, and a single-layer molded body in which a dye that is insoluble in this pseudo-stratum corneum material but soluble in the cosmetic to be evaluated is held in a dispersed state is used as the pseudo-stratum corneum, and this is used to perform a cosmetic permeability evaluation test.The cosmetic is brought into contact with the surface of the pseudo-stratum corneum, and the depth of penetration of the cosmetic from the surface can be visually determined by the color reaction of the dye that progresses over time, thereby evaluating the permeability of the cosmetic.

[0024] This makes it possible to easily and clearly distinguish the permeability of cosmetics into the stratum corneum using a pseudo-stratum corneum, and also makes it possible to visually understand the relative merits of the permeability of various cosmetics into the stratum corneum, thereby offering the advantage that consumers can more accurately distinguish between cosmetics with different permeability. [Brief description of the drawings]

[0025] [Figure 1] Photographs showing the results of visual evaluation tests of the examples [Diagram 2] A diagram showing the relationship between test time (min) and penetration depth (mm) showing the results of visual evaluation tests in the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] The pseudo-stratum corneum in an embodiment of the present invention uses a single-layer molded body that uses a pseudo-stratum corneum material made of a soft solid mixture containing keratin as the main component and 10 to 50 mass% lipids as an additional component, and that contains in a dispersed state a dye that is insoluble in the pseudo-stratum corneum material but soluble in the cosmetic material to be evaluated.

[0027] The keratin used in the above embodiment may be a commercially available product called keratose or keratose powder, which is prepared by sufficiently oxidizing a low molecular weight powdery substance obtained by hydrolysis of a raw material of biological origin such as wool. Keratose powder is commercially available as a material for cosmetics and a moisture absorption and release regulator, etc., as a substance that exhibits moisturizing properties, water absorption, water permeability, and oil absorption properties.

[0028] The lipids used in the present invention are selectively employed to mimic intercellular lipids in the stratum corneum, and it is preferable to employ, for example, one or more lipids selected from squalene, ceramide, fatty acids and cholesterol.

[0029] Squalene is a component that accounts for approximately 13% of human sebum. W As for the oil, one extracted from shark liver oil can be used.

[0030] Ceramide is a component of cell membranes and an intercellular lipid of the human stratum corneum, and is a compound formed by an amide bond between sphingosine and a fatty acid. Well-known human ceramides produced using yeast or the like, natural ceramides, ceramides extracted from plants such as rice bran oil, and synthetic ceramides can be used.

[0031] The fatty acid is preferably a fatty acid having a molecular weight similar to that of free fatty acids released into the blood when body fat is decomposed by lipase, and examples of the fatty acids that can be used include long-chain fatty acids present in adipose tissue, such as behenic acid, palmitic acid, and stearic acid.

[0032] Cholesterol is purified from natural products and is a solid, such as a white or pale yellow powder, at room temperature; an industrial material that is also used in cosmetics, pharmaceuticals, liquid crystals, etc., can be used.

[0033] Such lipids include not only solid lipids with melting points higher than room temperature, such as ceramide, cholesterol, and behenic acid (free fatty acid), but also lipids that are WIn order to form a single-layer molded article into which the cosmetic preparation can be easily absorbed, it is preferable to use a composition containing 25% by mass or more of a lipid component that is liquid at room temperature, such as propylene or oleic acid.

[0034] In addition, the amount of lipid to keratin (mass ratio) is preferably 6:4 to 8:2 in order to make the pseudo stratum corneum homogeneous and to ensure sufficient permeability of the cosmetic. If the amount of lipid to keratin is less than the above-mentioned range, voids are likely to occur in the pseudo stratum corneum before the cosmetic is permeated, which is undesirable as the density within the layer becomes non-uniform, and the permeability becomes too high, which is undesirable as the hydrophobicity is not the same as that of the skin. For these reasons, the amount of lipid to keratin (mass ratio) is more preferably 6:4 to 7:3.

[0035] The dye used in this invention is selectively one that is insoluble in the constituent components of the pseudo stratum corneum material described above and soluble in the cosmetic material to be evaluated; if the cosmetic material is an aqueous cosmetic material, a water-soluble dye that can dissolve in it is used; and if the cosmetic material is an oil-based cosmetic material, an oil-soluble dye that can dissolve in it is used. The water-based cosmetic preparations used in this invention for permeability evaluation are those whose continuous phase is composed mainly of water or a water-soluble component, including O / W type emulsion cosmetic preparations.Similarly, the oil-based cosmetic preparations used in this invention for permeability evaluation are those whose continuous phase is composed mainly of oil or an oil-soluble component, including W / O type emulsion cosmetic preparations.

[0036] In addition, among the above-mentioned water-soluble dyes, it is preferable to use water-soluble acid dyes. Such water-soluble acid dyes dissolve in the water in the cosmetic, and at the same time, the acid dyes are ionically bonded to the amino groups of the keratin that constitutes the pseudo stratum corneum, and are dyed. Since the dye that has been colored in this way remains at its position, the penetration position of the cosmetic in the pseudo stratum corneum is fixed over time, so that even if the pseudo stratum corneum is not left stationary and moves or tilts, the dye remains at a specific position, and the permeability of the cosmetic into the stratum corneum can be more reliably understood. For the same reason, when an oil-soluble dye is used, it is preferable to use an oil-soluble acid dye.

[0037] Specific examples of the water-soluble acid dye include azulene sulfonate and water-soluble food dyes. The water-soluble dye is a dye that has a hydrophilic group, such as sodium sulfonate, and is easily soluble in water. For example, sodium azulene sulfonate, New Coccine (commonly known as Food Red No. 102), etc. can be used.

[0038] In addition, examples of oil-soluble dyes include the above-mentioned water-soluble dyes that have been insolubilized in water by converting them into salts of calcium, barium, etc. In addition, water-soluble dyes can also be insolubilized in water by treating them with calcium sulfate, zirconium sulfate, or the like.

[0039] It is preferable to add sodium chloride in addition to the above-mentioned constituent materials of the pseudo stratum corneum, because this allows for a more accurate evaluation of the permeability of a cosmetic preparation into skin that physiologically contains sodium chloride.

[0040] In addition, by adding sodium chloride to the constituent materials of the pseudo stratum corneum, it becomes possible to evaluate the properties of cosmetics that react to salt on the skin. The mixing ratio of sodium chloride is preferably keratin:lipid:sodium chloride in a mass ratio of 6.0-6.75:3.25-4.0:0-0.5 in order to reproduce the skin in an actual sweating state.

[0041] To prepare the above-mentioned constituent raw material of the pseudo stratum corneum, the blending ratio (mass ratio) of lipid to keratin is 6:4 to 8:2. That is, the constituent raw material (100 mass%) containing keratin as the main component, 20 to 40 mass% lipid as an added component, a specified dye and other added components (surfactants, etc.) as required is mixed to form a paste, and it is preferable to knead so that the specified dye is uniformly dispersed.

[0042] The obtained paste-like mixture is placed in a transparent cylindrical container such as a test tube or cell, and a pseudo-stratum corneum is formed as a single-layer molded body of appropriate thickness so that the difference in the permeability of various cosmetic materials can be visually confirmed. For example, it is preferable to fill the closed end of the container so as to form a uniform single-layer molded product of about 1 to 1000 mm, and to mold the surface of the pseudo-stratum corneum facing the opening of the container to be approximately flat, like the surface of skin.

[0043] In this invention, the type of cosmetic is not particularly limited, but it is preferable that the cosmetic contains 15 to 95% by mass of water, for example, lotions and gels that contain 30 to 95% by mass of water per 100% by mass, and liquid, cream, and semi-solid cosmetic products made of an emulsion composition that contain about 15 to 95% by mass of water are preferable as the test subject. In addition, even if the cosmetic is made of a powder or compressed powder, a cosmetic product to which an appropriate amount of water has been added can be used as the test subject, assuming a state in which the cosmetic contains 15% or more by mass of water on the skin.

[0044] The cosmetics to be tested can be any of those containing ingredients that are typically found in skin lotions and other basic cosmetics, without any particular limitations. For example, glycerin, NMF components, hyaluronic acid, etc. may also be included.

[0045] The cosmetic material of the above embodiment is poured or layered into the cylindrical container so as to cover the entire surface of the pseudo stratum corneum, and if necessary, is brought into contact with the skin with a pressure similar to that applied when in use.

[0046] The time that has elapsed since the contact is then recorded, and the depth to which the cosmetic has penetrated from the surface is evaluated by the color reaction of the dye, and if necessary, the penetration of the cosmetic can be evaluated by recording it using photographs (still images) or videos (video images). EXAMPLES

[0047] Keratin as protein, sucrose as lipid WAzulene and sodium chloride as salt were mixed in a mass ratio of 10:5.2:0.8, and 0.4 mass% of sodium azulene sulfonate, a water-soluble acid dye capable of dyeing keratin protein blue, was added to 100 mass% of this mixture. The mixture was mixed using a three-roller mill until it became a paste-like material so that the plastic components were uniformly dispersed, preparing a grayish-white pseudo-stratum corneum material.

[0048] The pseudo stratum corneum material obtained as described above was filled into multiple spectrophotometer cells, which are transparent containers of uniform volume, without leaving any voids inside to form a single-layer molded body. This was used as a pseudo stratum corneum for cosmetic permeability evaluation tests, and the number of samples (9 pieces) required for the following tests was prepared.

[0049] Using the obtained simulated stratum corneum of the example, a permeability evaluation test for cosmetics A, B and a control (purified water) was carried out as follows. Cosmetics A and B are lotions (skin lotions) of different grades as products, and contain mainly moisturizing ingredients and purified water, but the amounts of polyols contained therein are slightly different.

[0050] As samples, cosmetic A, cosmetic B, and a control (purified water) were dropped in equal amounts (0.4 ml) into the cell filled with the simulated stratum corneum of the example so that the simulated stratum corneum was fully immersed, and the cell was left to stand.

[0051] The depth (mm) from the surface of the pseudo-stratum corneum where the sample had come into contact with the sample and had turned blue over time from the surface to the deeper parts was visually evaluated from the front of each pseudo-stratum corneum immediately after dropping the sample, and 5 minutes, 30 minutes, 45 minutes, 60 minutes, and 120 minutes later. Digital images taken from the same positions were analyzed to accurately determine the penetration depth, and the results are shown in Table 1 and Figures 1 and 2.

[0052] In Figure 1, in order to clearly show the penetration depth of the cosmetic material into the simulated stratum corneum in the figure (photo), a dotted line is drawn at the boundary between the dye or water permeated and non-permeated areas. For each sample, the above test was performed three times for each measurement and evaluation, and the average penetration depth is plotted in Figure 2, with a line connecting the maximum and minimum values ​​also added to the figure.

[0053] [Table 1]

[0054] As is clear from the results in Table 1 and Figures 1 and 2, Cosmetic Preparations A and B had higher permeability into the simulated stratum corneum of the Examples than purified water as a control, and the difference in permeability of Cosmetic Preparation A compared to Cosmetic Preparation B could be easily and clearly visually determined simply by visual inspection of the photograph in Figure 1. This could also be determined more accurately from the results of image analysis shown in Figure 2 and Table 1. From these results, it was confirmed that consumers can more accurately and easily distinguish between cosmetics A and B, which have different permeability, by using the pseudo stratum corneum of the examples.

Claims

1. The pseudo stratum corneum for cosmetic permeability evaluation tests is a single-layer molded body in which a soft solid mixture containing keratin as the main component and 10 to 50 mass % of one or more lipids selected from squalene, ceramide, fatty acid and cholesterol as an added component is used as a pseudo stratum corneum material, and a dye that is insoluble in the pseudo stratum corneum material but soluble in the cosmetic material to be evaluated is dispersed in the pseudo stratum corneum material.

2. The pseudo stratum corneum for use in a cosmetic permeability evaluation test according to claim 1 , wherein the lipid contains 10% by mass or more of a lipid component that is liquid at room temperature.

3. 3. The pseudo stratum corneum for use in a cosmetic permeability evaluation test according to claim 2, wherein the lipid component which is liquid at room temperature is a lipid component containing squalene, oleic acid, or a combination of both.

4. The pseudo stratum corneum for use in a cosmetic permeability evaluation test according to any one of claims 1 to 3, wherein a blending ratio by mass of said keratin and said lipid is 6:4 to 8:

2.

5. The pseudo stratum corneum for use in a cosmetic permeability evaluation test according to any one of claims 1 to 4, wherein the dye is a water-soluble dye that is soluble in a cosmetic containing 15 to 95% by mass of water.

6. The pseudo stratum corneum for use in a cosmetic permeability evaluation test according to claim 5 , wherein the water-soluble dye is a water-soluble acid dye.

7. The pseudo stratum corneum for use in a cosmetic permeability evaluation test according to claim 6, wherein the water-soluble acid dye is an azulene sulfonate or a water-soluble food dye.

8. A method for evaluating the permeability of a cosmetic, comprising contacting a cosmetic with the surface of the pseudo stratum corneum according to any one of claims 1 to 7 and evaluating the depth of penetration of the cosmetic from the surface by a color reaction of a dye.

9. 9. The method for evaluating the permeability of a cosmetic according to claim 8, wherein the cosmetic contains 15 to 95% by mass of water.

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