RU2819154C2 - Method for selecting skin barrier system acceptable for infants and young children - Google Patents

Abstract

FIELD: cosmetic industry.

SUBSTANCE: group of inventions relates to the development of skin barrier systems, particularly for infants or young children. Disclosed is a method for assessing the ability of a protective system to protect infant skin from external irritants, involving: a) topical application of said protective system on adult skin; b) local application of an external irritant on said protective system treated skin of an adult; c) monitoring the production of inflammatory molecules in said protective system-treated skin of an adult; d) using a computational model of skin inflammation of an adult for visualizing the effect of an external stimulus by optimizing inflammation parameters so that the adult skin inflammation profiles model corresponds to the experimental data; e) transfer of optimized inflammation parameters into a computational model of infant skin and f) determining the effect of the stimulus in the computational model of the infant's skin. Also disclosed is a system representing a cream or a moisturizer selected by evaluation in accordance with the method.

EFFECT: group of inventions provides selection of a skin barrier system acceptable for infants and young children.

5 cl, 14 dwg

Description

Technical field

The present invention relates to the development of skin barrier systems, particularly for infants or young children, wherein the level of skin protection is assessed by analyzing test results on adult skin. The invention allows the level of protection of the skin barrier system to be assessed based on objective data, without resorting to testing on young children or infants.

Prerequisites for creating the invention

Skin cleansers contain surfactants that can cause disruption of the skin's barrier against external aggressors, resulting in skin irritation. Assessing the gentleness of a cleanser on the skin is typically done by clinical evaluation and measurement of changes in transepidermal water loss (TEWL) as measured by the Exaggerated Allergy Patch Test or Exaggerated Wash Test protocols. These methods are partially subjective and often produce varying results.

The gentleness of skin care products (particularly cleansing products that contain potentially irritating surfactant systems) is typically assessed in vivo in adults using normal use tests, exaggerated (repeated) use tests, or patch allergy tests. Even for children's products, evaluation is first carried out in adults, and after positive results are obtained, normal use tests are sometimes carried out in infants. The mildness of the action is assessed as the absence of irritation (usually skin erythema (redness)). Effects on the skin barrier are typically assessed instrumentally by measuring transepidermal water loss (TEWL). The effects of products on the skin barrier can also be studied ex vivo using Franz cells and measuring skin resistance.

However, previous methods suffer from a number of disadvantages and difficulties. For example, normal application tests typically require a large application area to distinguish between different levels of mildness, which can be costly and time consuming. In patch allergy tests, surfactants may behave differently under patch closure conditions compared to normal application conditions. Hand immersion test results may be affected by weather conditions. In fold wash tests, the area of skin tested may not be representative of other areas of the body.

Each of the above items is additionally assessed subjectively (clinical observation), which may introduce variability in the assessment results. Finally, most of these tests are either designed to be performed on adult skin without the required correlation with infant skin, or such studies are performed on infants/young children, and clinical studies on infants raise ethical and technical issues. As noted, the correctness of the direct transfer of data obtained for adults to the case of infant skin has already been questioned. For example, infant skin is not typically treated with Franz cells, and the transfer of such findings to infant skin is questionable. These methods are always used with a safety factor (typically 10 times) that reflects the uncertainty of such tests.

It would be worth developing a method by which the effect of a surfactant system on the skin barrier of an infant and/or young child could be assessed by objectively assessing the concentration profile of some marker (such as caffeine) that penetrates the skin of adult patients. The present invention focuses on assessing exposure by performing biomarker tests on adult skin, using a computational model to assess exposure on infant/young child skin, and developing a surfactant system based on the results of the tests and assays performed.

Humectants are mixtures of chemical agents specifically formulated to soften the outer layers of skin or hair. Compositions for personal hygiene having moisturizing properties are known. Consumers expect such compositions to satisfy a number of requirements. In addition to the skin/hair care effects that determine their intended use, various parameters such as dermatological compatibility, appearance, organoleptic sensation, shelf stability and ease of use are considered important. Another beneficial effect of many moisturizers is the protection of the skin from environmental influences and agents.

Description of graphic materials

In FIG. 1A and 1B depict the observation of absorption of exogenously applied water by Raman confocal microspectroscopy 10 seconds after application of water to the skin of the lower anterior arm.

In FIG. Figure 2 shows a comparison of experiment (adult), model (adult) and prediction (child).

In FIG. Figure 3 shows a comparison of experiment, model, and prediction for the effects of water and SLS on adult and infant skin .

In FIG. Figure 4 shows a comparison of several surfactant formulations.

In FIG. Figure 5 shows the in silico modeling of experimental data in an adult human epidermis model.

In FIG. Figure 6 shows predicted permeability curves for caffeine after surfactant treatment.

In FIG. 7 shows the predicted absorbed amount in stratum corneum of the epidermis in a child, area under the curve in the depth range 0-10 µm (mmol caffeine/g keratin)

In FIG. Figure 8 shows experimental data for adult skin.

In FIG. 9 shows a simulation of the skin of an adult.

In FIG. Figure 10 shows the predicted results for the baby's skin.

In FIG. 11 shows experimental data for adult skin.

In FIG. 12 shows a simulation of the skin of an adult.

In FIG. Figure 13 shows the predicted results for an infant's skin.

Detailed description

The present invention relates to a method for assessing the gentleness of a skin care product on the skin of an infant and, in particular, the effect of topical application of a substance and/or composition on the skin barrier of infants and preparing and/or using a surfactant system based on such assessment. As used herein, the term “infant skin” refers to the skin of newborn human infants, but also refers to and includes the skin of children under 12 months of age. The term "young child" or "young children" refers to infants, but also includes children aged 12 to 36 months.

The purpose of the present invention is to be able to evaluate the safety, gentleness, etc. of a product on the skin of infants and/or young children by safely evaluating the product on the skin of an adult. The method includes applying a substance to the skin of an adult, collecting data on marker penetration on the treated adult skin, transferring information into a computational model of adult skin, extracting penetration parameters from this model, transferring parameters to a computational model of infant skin, and visualizing marker penetration into the skin model. infant with conclusions about the effects of a topical product on the infant's skin. Ultimately, the method includes obtaining a surfactant system as a result of such evaluation and/or applying a surfactant system based on the results of such evaluation and the resulting system.

US Patent Application Published No. 20150285787 filed by Laboratoires Expanscience describes a method for identifying at least one biological marker for a child's skin, which comprises: a) measuring the expression level of the putative biological marker in at least one sample (A) of skin cells, wherein said sample is from a donor less than 16 years of age, b) measuring the expression level of said putative biological marker in at least one control sample (B) of skin cells, c) calculating the ratio of the expression level in step a) to the expression level in step b) and d) determining whether the suspected marker is a biological marker of the child's skin.

WO2015150426 and WO2017103195 issued by Laboratoires Expanscience describe methods for evaluating in vivo formulations that comprise a) contacting an active agent or formulation with a reconstituted skin model, said model being derived from a child's skin sample; b) bringing the reconstructed skin model from step a) into contact with urine; and c) measuring the expression level of at least one of the established biological markers in the skin model after stage b).

US Patent Application Published No. 20180185255 filed by Procter & Gamble describes a method for screening cleansers for gentleness, comprising: a) measuring the level of one or more ceramides on an area of skin before applying the cleanser; b) applying the cleanser to the skin area for at least 7 days; c) measuring the level of one or more ceramides after applying the product to the skin area for at least 7 days; wherein the cleanser is mild if the level of one or more ceramides is at least 10% compared to the untreated control.

U.S. Patent No. 10,036,741 to Procter & Gamble describes a method for assessing the effects of perturbagen on skin homeostasis and formulating a perturbagen-containing skin care composition, comprising causing a computer processor to query the architecture of stored perturbagen-related skin samples with a gene expression signature for the disease. skin, the query comprising comparing the gene expression signature for unhealthy skin for each stored skin sample and assigning a connectivity index to each sample.

EP 1248830A1 issued by Procter & Gamble describes the use of a controlled application test on the forearm to evaluate the mildness of a surfactant.

In Saadatmand et al., Skin hydration analysis by experiment and computer simulations and its implications for diapered skin, Skin Res. Technol., 2017: 1-14 describes a model of reversible hydration of the stratum corneum of the epidermis, which models the loss of water through evaporation and the thickness of the stratum corneum of the epidermis depending on possible exposure scenarios, such as time-dependent relative humidity, air temperature, skin temperature and wind speed .

In Maxwell et al., Application of a systems biology approach for skin allergy risk assessment, Proc. ^6th World Congress on Alternatives & Animal Use in Life Sciences, pp. 381-388 (2007) describes an in silico model for inducing skin sensitization to characterize and quantify the contribution of each pathway to the overall biological process.

In Strube et al., The flex wash test: a method for evaluating the mildness of personal washing products, J. Soc. Cosmet. Chem., 40:297-306 (1989) describes the use of elbow rinse for sixty seconds three times daily to evaluate the irritant potential of rinse products.

In Keswick et al., Comparison of exaggerated and normal use techniques for accessing the mildness of personal cleansers, J. Soc. Cosmet. Chem., 43:187-193 (1992) describes a comparison of the forearm test and the elbow wash test with home use to determine how well the tests simulate home use.

Frosch et al., Journal of the American Academy of Dermatology, Volume 1, Issue 1, 35-41 (1979) describes a chamber test to evaluate the irritant effects of soaps, which involves exposure for five working days of the week to 8% solutions with recording data about peeling and redness.

Many in vivo tests are not suitable for experimental use on infant skin. The references listed above do not describe or suggest the assessment of adult skin and the use of computational models to establish a correlation with how a certain ingredient may affect infant skin. Thus, the invention does not require an in vivo test on infant skin.

Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one skilled in the art to which the invention relates. In addition, all publications, patent applications, patents and other literature referenced herein are incorporated herein in their entirety by reference. All percentages herein are percentages by weight unless otherwise noted. In addition, all ranges specified herein are intended to include any combination of values between and inclusive of the two endpoints.

In the present invention, the method can be used to distinguish between different cleanser formulations according to their effects on the resistance of the skin barrier to external penetrations. The present invention provides a composition analysis method that can objectively assess the effect of topical cleansers on the skin barrier's resistance to penetration by aggressive external agents, and which can be used to evaluate the gentleness of the cleanser. The results of this analysis can be used to provide or obtain an acceptable formulation that is considered to be gentle on the skin of an infant and/or adolescent.

The present invention is directed to a predictive method for assessing the mildness of a topical substance on the skin of a patient, preferably a young child. It also relates to a predictive method for assessing the penetration of a compound (marker) through the skin of infants. The present invention also provides a predictive method for assessing the effect of a topical agent on the penetration of a compound (marker) through the skin of an infant. In addition, the present invention may provide a method for measuring and/or predicting the barrier enhancing effect of a topical application substance(s).

In one aspect, the present invention may include a certain number of method steps. It may include phase 1 (in vivo) and phase 2 (in silico), with an optional phase 3 (intelligent process), and ultimately the process culminates in the preparation of a suitable surfactant system that is assayed to pass the tests mentioned above, or the process ends with the application of a surfactant system to the skin of an infant and/or young child.

Phase I, in vivo

A. Application of a topical substance to the skin of an adult, for example, by direct application or application to a patch or other delivery system.

B. Topically applying a marker to the skin of an adult and collecting data on the penetration of said marker on the treated adult skin. This step involves applying the marker and subsequently monitoring its concentration profile in the skin, for example using confocal Raman microspectroscopy (CRM).

Phase II, in silico

C. Transferring information (penetration data) into a computational model of adult skin and extracting penetration parameters from this model.

This step can also be described as the application of a computational model of adult human skin to visualize marker penetration by optimizing penetration parameters (e.g., local surface concentration and permeability coefficients) such that the model penetration profiles match the experimental data.

D. Transfer of the obtained penetration parameters (after appropriate transformations) into a computational model of the baby’s skin and visualization of the penetration of the marker into the baby’s skin model.

Optional Phase III, Intelligent Process

E. Formulation of conclusions about the mildness of the action (effect) of a product for topical application to the skin of an infant based on the amount of marker that penetrated the model of the infant's skin.

Once the above process steps have been completed and the conclusions have been formulated in Step E, the surfactant system can be prepared, applied or distributed to users.

Substance for topical application

The invention includes one or more topical agents for evaluation, wherein the topical agent is being considered for use in the final surfactant system. A topical agent is any type of substance applied to the skin that affects the permeability of the stratum corneum of the epidermis. The topical agent modifies the penetration of the marker through the skin. The impact of a topical agent can be assessed by measuring marker penetration. Typically, in the tests described above, a patch is soaked in a topical agent, which is then kept in contact with the skin for 30 minutes, after which a marker is applied. The patch test may include one or more topical agents.

Within the scope of the present invention, different types of topical agents may be evaluated, for example, the topical agent may be an aggressive agent(s) that may reduce skin barrier properties and increase marker penetration. In this case, the present invention may allow the creation of a classification of substance(s) by gentleness and help to select a milder version when developing a new skin care product composition, without conducting in vivo or in vitro testing. In other aspects, the topical agent may include barrier agent(s) that are configured to help protect and enhance skin barrier properties, thereby reducing penetration of the marker through the skin. As noted above, the present invention can assist in selecting the most effective solution without the need for in vitro or in vivo tests on the infant's skin.

Marker

In the present invention, one or more markers or biomarkers are used in the evaluation method. Any type of marker is acceptable as long as there is a way to track the marker and generate its concentration profile (eg permeation data). In the example using confocal Raman microspectroscopy, the marker must have a traceable signal in the Raman spectrum. In another example, it is possible to trace a fluorescent marker using confocal fluorescence microscopy. The permeation kinetics of the marker should preferably be such that the equilibrium state of its concentration profile is reached within a reasonable time (eg, up to one hour).

The marker may be hydrophilic, lipophilic, or amphoteric, which will determine the type of protective effect that the evaluator will examine. For example, one acceptable marker is caffeine. In the case of caffeine, the analysis examines the protective properties against hydrophilic substances.

The marker of the present invention may include any molecule that is toxicologically and dermatologically safe, has reasonable permeation kinetics, and can be monitored using confocal analysis techniques.

- Safety. Some markers used in the past are unacceptable for toxicological reasons (the use of dansyl chloride (suggested in Paye et al. " Dansyl chloride labeling of stratum corneum: its rapid extraction from skin can predict skin irritation due to surfactants and cleansing products " Contact Dermatitis 30(2) , 91-96, 1994) was discontinued due to the risk of sensitization and skin damage from skin contact).

- Kinetics of penetration. A molecule that penetrates the skin, for example, does so quickly enough, but not too quickly. For example, a molecule having a permeability coefficient similar to caffeine can be used: kp=1.16 x 10 ^-4 cm/h, as reported in Dias M et al. " Topical delivery of caffeine from some commercial formulations" Int J Pharm 1999182(1):41-7.

- Confocal analysis techniques are non-invasive and provide data on the depth of penetration of markers. In contrast, for example, scraping with adhesive tape is invasive and destroys the barrier; this is not allowed in the present invention.

Penetration data

The present invention involves analyzing penetration data. The permeation data represents a concentration profile; this means the concentration of the marker depending on the depth in the skin. The present invention may use any desired assay method suitable for measuring the marker concentration profile as a function of depth in the skin, and more specifically in the epidermis and, in particular, in the stratum corneum of the epidermis. Any desired method may be used, but non-invasive methods are preferred. Confocal techniques are preferred because they are noninvasive and provide sufficient resolution, such as 3 to 5 μm resolution perpendicular to the skin surface at depths of up to 200 μm. One such method involves confocal Raman microspectroscopy, but other methods, including confocal fluorescence microscopy, are also possible.

Computational model of adult/infant skin

In the present invention, computational models are used to evaluate the components of the surfactant system under test. Any model that can construct a marker concentration profile in the skin can be used. The user can select any type of computational model of skin penetration, which, based on specified penetration parameters, can build a marker concentration profile in the skin. Using both an adult skin model and a skin model simultaneously requires the models to take into account the structure of skin architecture and the differences that exist between the two skin types.

For example, one can use the physiological model published in Sutterlin et al., “A 3D self-organizing multicellular epidermis model of barrier formation and hydration with realistic cell morphology based on EPISIM,” Scientific Reports, volume 7, article 43472, 2017; with modifications to integrate the diffusion of substances (eg marker) through the skin layers. In Sutterlin et al. describes a cellular behavioral model (CBM) encompassing regulatory feedback loops between the epidermal barrier, water loss to the environment, and calcium flow within the tissue. The EPISIM platform consists of two ready-to-use software tools: (i) EPISIM Modellar (graphical modeling system) and (ii) EPISIM Simulator (agent-based modeling environment). Each EPISIM-based model is made of at least a cellular behavioral model and a biomechanical model (CBM and BM). BM covers all spatial and biophysical properties of the cell. CBMs represent decisions made by cells. In accordance with the invention, a two-dimensional or three-dimensional version of the model can be used (a version of the two-dimensional model, but without the stratum corneum component of the epidermis, is described in: Suetterlin et al. “Modeling multi-cellular behavior in epidermal tissue homeostasis via finite state machines in multi-agent systems” , Bioinformatics, 25(16), 2057-2063, 2009.

In one method, the process is initiated by the user, allowing the simulation to reach an equilibrium state corresponding to epidermal homeostasis. Subsequently, at a given point in time corresponding to topical application of the marker, the evaluator enters a user-specified variable corresponding to the concentration of the marker on the skin surface (C _surface ). The value of this parameter is determined from the experimentally obtained concentration profile, and it corresponds to the concentration of the marker at depth 0 (skin surface). A cellular variable is introduced into the model, which determines the concentration of the marker in the cell (C _cell ). At each time point, this parameter is adjusted based on Fick's law of diffusion as the marker is allowed to diffuse from each cell to its immediate neighbors. To apply Fick's law, the parameter of the permeability coefficient (P) is introduced into the model. This permeability coefficient parameter essentially corresponds to the diffusion coefficient, the diffusion resistance due to the partition coefficient, and the diffusion resistance due to the length of the path that a substance must travel to move from one cell to another. The permeability coefficient differs for the stratum corneum of the epidermis ( _PRS ) and the living epidermis ( _PLE ). If the substance reaches the lower part of the epidermis, it is allowed to diffuse into the dermal compartment, which is modeled as a “sink” for penetration.

These modifications are introduced into both the adult skin model and the infant skin model.

An infant skin model is created by modifying the parameters of an adult skin model to reflect the higher rate of turnover (proliferation and desquamation) of infant skin.

Penetration parameters

Penetration parameters characterize the kinetics of penetration, i.e., how easy it is for a substance to pass through the surface and penetrate deep into the skin. This role can be played, for example, by the distribution coefficient, diffusion coefficient and/or permeability coefficient.

Softness index

The concentration profile of the marker in a model of adult human skin at steady state is compared with the experimental concentration profile. If the profiles do not agree, the penetration parameters (C _surface , P _PC and P _ZhE ) are adjusted and the simulation is repeated. Subsequently, once the two profiles are matched, the parameters are used to calculate the appropriate parameters for marker penetration into the infant skin models. Due to the higher hydrophilicity of children's skin, the C _surface parameter is higher (usually twice as high as for adult skin*), and other penetration parameters remain the same in both models.

*See, for example, Nikolovski et al., Barrier function and water-holding and transport properties of infant stratum comeum are different from adult and continue to develop through the first year of life, Journal of Investigative Dermatology (2008), Vol. 128, which used tools such as transepidermal water loss (TEWL), skin capacitance, absorption-desorption, and confocal Raman spectroscopy to show that the water-holding and water-transport properties of the stratum corneum in the infant differ from those in the adult. Specifically, the work referenced describes the observation of absorption of exogenously applied water using confocal Raman microspectroscopy 10 seconds after application of water to the skin of the lower anterior arm. In FIG. 5a (and reproduced in Fig. 1A) shows that the stratum corneum of the epidermis in infants less than 12 months of age accounts for a significant portion of water absorption. In FIG. 5b (and reproduced in FIG. 1B) shows that, in contrast, there is no significant water absorption in adult skin after water is applied to the skin. The penetration of caffeine, which is highly hydrophilic, is expected to be similar to that of water.

Subsequently, marker penetration is allowed to reach an equilibrium state in the infant skin model (about 1000 stages, where each stage corresponds to 30 min of physiological time). The profile of the average concentration of the marker in the equilibrium state is calculated (dependence of the average concentration on depth). For a concentration profile, the area under the curve (AUC, integral) is calculated down to a given depth (for example, up to 20 μm).

A mildness index scale can then be determined from the AUC values corresponding to the different product treatments. This creates a conventional scale used to classify the mildness of topical substances.

The mildness index value allows the evaluator to compare the mildness of a topical test substance with the mildness of two reference substances: water (mild) and sodium lauryl sulfate (SLS) 0.1% (harsh). With water and SLS 0.1% as two reference points, it is possible to construct a scale to measure the mildness of other topical agents.

It should be noted that this mildness indicator is optional and the mildnesses can be omitted and the relative mildnesses of different topical agents directly compared directly to each other based on the combination of their predicted penetration curves (eg, calculated AUC values).

Examples

1- Comparison of experiment (adult), model (adult) and prediction (child). See FIG. 2.

Goals

Demonstrate the predicted effects on infant skin of two extreme strength topical solutions, one aggressive (containing 0.1% SLS) and one mild (water).

Demonstrate that the adult model fits the experimental data.

Demonstrate that topical agents do not have the same effect on adult skin as on infant skin, and infant skin is more permeable to the marker.

Comparison of experiment, model and prediction for the effects of water and SLS on adult and infant skin. See FIG. 3.

In FIG. Figure 3 above shows the penetration depth (in µm) of caffeine (marker), expressed in mmol per gram of keratin, obtained in an in vivo experiment on adult skin (lines + and ○) and in a predictive model in silico (lines ∆, ×, ◊ and □).

In FIG. Figure 3 depicts the effect on caffeine penetration of 2 topical solutions: water and 0.1% SLS. The data calculated in the model for an adult are represented by lines ∆ and ◊; for water and SLS respectively. The predicted data for the infant are represented by the × and □ lines for water and SLS, respectively.

In vivo experimental data collected on adult skin is subsequently transferred to a computational model of adult skin to simulate the depth of penetration of caffeine into adult skin. The prediction of caffeine penetration into an infant's skin by the model of the present invention is represented by a line with oblique crosses (×) for the case where the skin is treated with a water patch before applying caffeine, and a line with squares (□) for the case when the skin is treated with a patch before caffeine is applied. with 0.1% SLS.

The area under the curve in the skin depth range from 0 to 20 µm indicates the level of mildness of the topical substance. The smaller it is, the softer the effect of the substance on the skin. The area under the curve is a key parameter that allows comparisons between different treatments.

2- Comparison of several surfactants. See FIG. 4.

Target

To create a predictive classification of surfactants based on their gentleness on infant skin.

Stage 2.1. Experimental data, penetration of caffeine into adult skin, in vivo

The studied compositions are shown in Fig. 4.

The experimental protocol is as described in Stamatas et al., Development of a non-invasive optical method for assessment of skin barrier to external penetration, Biomedical Optics and 3D Imaging OSA (2012) for material and method. The work of Stamatas et al. describes the use of a characteristic Raman spectrum of caffeine to monitor the penetration of caffeine through adult human skin to demonstrate the effects of (1) sodium lauryl sulfate and (2) a barrier cream on the protective function of the stratum corneum of the epidermis.

Stage 2.2. Simulation of experimental data in an in silico model of the adult human epidermis. See FIG. 5.

The experimental data on caffeine penetration obtained in step 2.1 are transferred to a computational model of adult skin. Skin penetration simulations are performed for each topical agent; one simulation per substance may be sufficient. Caffeine penetration parameters (local surface concentration and permeability coefficients) are extracted.

Stage 2.3. Predicted permeation curves for caffeine after surfactant treatment. See FIG. 6.

The caffeine penetration parameters obtained from the adult skin model in step 2.2 are transferred to the computational model of infant skin. For each topical agent, a simulation of penetration into the infant's skin is performed. The predicted caffeine penetration results are extracted and plotted as shown in Graph 4 above.

Stage 2.4. Predicted absorbed amount in the stratum corneum of the epidermis in a child, area under the curve in the depth range 0-10 μm (mmol caffeine/g keratin). See FIG. 7.

The prediction curves for each topical agent presented in FIG. 6 of step 2.3, integrated to obtain for each topical agent the predicted absorbed amount of caffeine in the stratum corneum epidermis in an infant. These values are reflected in Fig. 7.

In other words, this predictive scheme shows how much caffeine will penetrate the first 10 microns (not mm) of the stratum corneum of the epidermis. The greater the amount of caffeine present, the more aggressive the substance is for topical application.

results

It was unexpectedly found that this scheme predicts that a topical agent will not always have the mildness index value on infant skin reflected in the experimental values obtained on adult skin:

Formulation 3 will have a milder effect than composition 5.

Formulation 4 will have a milder effect than composition 2.

As a result of this experiment, a composition comprising the composition of Formulations 3 and/or 4 can be prepared and applied to the skin of an infant and/or the skin of a young child as preferable to the composition of Formulations 5 and 2, respectively.

In a further embodiment, the invention relates to the development of protective systems, in particular for infants or young children, wherein the level of protective effect is assessed by analyzing test results on adult skin.

The invention makes it possible to evaluate the level of protection of the protective system based on objective data, without resorting to testing on young children or infants.

Way

Stages I and II described above remain unchanged. Generate predictive data on the penetration of the marker into the infant's skin.

Stage III is different in that that the data now relate to the use of low permeability and diffusion of the marker through the skin to predict the protective effect that a topical agent applied in Stage I A would have on the skin of an infant or young child.

This methodology can be used to evaluate leave-on products (e.g. creams/moisturizers)

Experiments

Example 3

Material and method

Adult skin data were obtained from healthy volunteers with normal skin who agreed not to apply any other skin care products to the forearms for at least 24 hours before the study and during the study.

Tools used.

In vivo confocal Raman microspectrometer (Skin Composition Analyzer Model 3510, River Diagnostics, Rotterdam, The Netherlands)

Caffeine patch: 180 mg caffeine in 10 ml demineralized water, 1.8%.

Example 4. Modeling protective cream

Experimental data were obtained on 5 female volunteers aged from 20 to 35 years.

Test substances for topical application.

Protective cream: Desitin® Creamy (diaper rash cream)

List of items according to the International Nomenclature of Cosmetic Ingredients (USA): zinc oxide 10%, inactive ingredients (aloe vera leaf juice), cyclomethicone, dimethicone, fragrance, methylparaben, microcrystalline wax, mineral oil, propylparaben, purified water, sodium borate, sorbitan sesquioleate, vitamin E, white petroleum jelly, white wax.

Protocol

1 - Acclimatize for 5 minutes in a temperature and humidity controlled room

2 - Application of topical substance to the forearm

3 - Acclimatize for 30 minutes in a temperature and humidity controlled room

4 - Apply a caffeine patch to the forearm (in the same place) for 30 minutes

5 - Measurement in the characteristic region of the Raman spectrum

results

1- Experimental data on adult skin. See FIG. 8.

Data from Desitin cream-treated skin (squares) are compared with data from untreated skin (i.e., skin that was not treated with topical agent in step 2 of the protocol) (circles).

Penetration data is extracted from the experimental results and transferred to a computational model of adult skin.

2- Construction of a model of adult human skin. See FIG. 9.

The next stage is to determine the skin permeability parameters on a computational model of adult skin so that it can accurately simulate the experimental data presented above.

These parameters are calculated from the slope of the caffeine penetration profile.

The results obtained from an adult human skin model are shown below.

Protective cream-treated skin (squares) is compared with untreated skin (circles).

Penetration parameters are extracted from a computational model of adult human skin.

3- Predicted results for baby's skin. See FIG. 10.

The final step involves transferring the caffeine penetration parameters with appropriate transformations into a computational model of the infant's skin to simulate the predicted penetration of caffeine into the infant's skin.

Predicted results for caffeine penetration on barrier cream-treated skin (squares) and untreated skin (circles) are shown below

Finally, from the ratio shown below, which includes the area under the curve (AUC) for untreated skin and the AUC for barrier cream-treated skin, the predicted percent protection for the barrier cream can be calculated:

% protection = 100 × (AUC (untreated) - AUC (treated)) / AUC (untreated) = 89.18%

Examples 5 Humidifier simulation

Experimental data were obtained on 6 volunteers aged from 18 to 40 years.

Test substances for topical application.

- Humectant A: emulsion containing: glycerin (12%), petrolatum (4%), distearyldimonium chloride, water

- Humectant B: structured emulsion containing: petrolatum (40%), glycerin (12%), distearyldimonium chloride, water

Protocol

1- Acclimatize for 5 minutes in a temperature/humidity controlled room

2- Apply a topical substance to the forearm for 30 minutes

3- Apply a caffeine patch to the forearm (in the same place) for 30 minutes

4- Measurement in a characteristic region of the spectrum

results

1- Experimental data on adult skin

Data from moisturizer A-treated skin (squares) are compared with data from moisturizer B-treated skin (triangles) and untreated skin (ie, skin not treated with topical agent in step 2 of the protocol) (circles).

Penetration data is extracted from the experimental results and transferred to a computational model of adult skin.

2- Construction of a model of adult human skin. See FIG. 12.

The next stage is to determine the skin permeability parameters on a computational model of adult skin so that it can accurately simulate the experimental data presented above.

These parameters are calculated from the slope of the caffeine penetration profile.

The results obtained from an adult human skin model are shown below.

Moisturizer A-treated skin (squares) is compared with moisturizer B-treated skin (triangles) and untreated skin (circles).

Penetration parameters are extracted from a computational model of adult human skin.

3- Predicted results for baby's skin

The final step involves transferring the caffeine penetration parameters with appropriate transformations into a computational model of the infant's skin to simulate the predicted penetration of caffeine into the infant's skin.

Predicted results for caffeine penetration on moisturizer A-treated skin (squares), moisturizer B-treated skin (triangles), and untreated skin (circles) are depicted in FIG. 13.

Finally, from the ratio shown below, which includes the area under the curve (AUC) for untreated skin and the AUC for moisturizer-treated skin, the predicted percent protection for the moisturizer can be calculated.

For humidifier A

% Protection: Not applicable.

For humidifier A, the area under the curve was greater than the area under the curve for the untreated standard. Modeling predicts no protective effect for infant skin.

For humidifier B

% protection = 100 × (AUC (untreated) - AUC (treated)) / AUC (untreated) = 17.72%.

Model of acute skin inflammation

The substance penetration model was used to obtain a reliable model of acute skin inflammation.

The model can be used to assess the skin's response to local external stimuli. A necessary behavior of the model is that application and penetration of the irritant into the skin can cause the production of inflammatory molecules. Then, if the keratinocytes are no longer in contact with the stimulus, the system will return to homeostasis.

Inflammatory molecules are produced and degraded by keratinocytes. The inflammatory response begins when the irritant crosses the barrier formed by the SC. Then, when the apparent concentration of the irritant in the cell reaches a certain value, called the irritant threshold, the keratinocytes begin to produce inflammatory molecules [IM] according to the following equation:

where pIM and dIM represent the rate of production and degradation of inflammatory molecules in keratinocytes.

When the apparent concentration of the substance is below the irritant threshold, inflammatory molecules are no longer produced (pIM=0), but continue to be degraded. At each stage, cells diffuse their inflammatory molecules to neighboring cells according to the following equation:

where the subscript n refers to neighboring cells and DIM represents the diffusion coefficient of inflammatory molecules.

Finally, inflammatory cells are lost from the dermis at a basal level according to

where Pdermis;IM [IM] corresponds to the permeability of the dermis to the stimulus.

Data from the literature were used to evaluate the different parts of the model according to the criteria below.

the irritant was applied topically;

the study was conducted in vivo on humans;

inflammation was measured quantitatively (size of erythema or redness, blood flow, etc.);

several concentrations of the stimulus were tested;

the irritant does not affect the normal function of the skin barrier (only a slight change in transepidermal water loss, TEWL, is observed).

Andersen et al. studied skin irritation using reflectance spectroscopy [14]. They examined the skin response of eight volunteers to four compounds: sodium lauryl sulfate (SLS), hydrochloric acid (HCl), nonanoic acid (NON) and imipramine (IMI). They measured oxygenated and deoxygenated hemoglobin using reflectance spectroscopy, blood flow using laser Doppler flow cytometry, and TEWL using an evaporator. For each compound, four concentrations were tested using patches over 24 hours. The inventors focused on two compounds that increased the smallest TEWL: imipramine and nonanoic acid. Oxygenated hemoglobin was an effective indicator of inflammation and showed dose-dependent curves. The data for these molecules did not support our model.

The inventors decided to explore more lipophilic compounds since both nonanoic acid and imipramine are lipophilic. They had data on the penetration of pure oils into SC from a study published in 2008 [18]. Concentrations of paraffin and petroleum jelly at several depths in the SC were measured using Raman spectroscopy. In the literature, the inventors found Kp values for paraffin and petroleum jelly [19]:

Kp(paraffin)=13:3 (cm=h)

Kp(vaseline)=2:02 103 (cm=h)

For both of these compounds, the inventors were able to obtain effective approximations to clinical data using model calculations.

The inflammation demonstrated by the model is dose dependent. In addition, the inventors demonstrated that depending on the values of parameters derived from the physical properties of the molecules (PSC (permeability of the stratum corneum) and PVE (permeability of the viable epidermis), the model exhibits inflammation with different intensities. Finally, the inventors demonstrated that the model inflammation is fully functional in both adult and child skin models, and has even gained insight into the role that skin structure may play in the dynamics of inflammation.

It should be understood that while various aspects of the present specification have been illustrated and described by way of examples, the invention claimed herein is not limited thereto, but may be practiced in various other manners within the scope of the claims included herein and/or any related application herein. for a patent.

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Claims (11)

1. A method for assessing the ability of the protective system to protect the baby’s skin from external irritants, including: a) local application of said protective system to the skin of an adult; b) local application of an external irritant to said adult skin treated with a protective system; c) monitoring the production of inflammatory molecules in said protective system-treated adult skin; d) applying a computational model of adult skin inflammation to visualize the effect of an external stimulus by optimizing inflammation parameters so that the model of adult skin inflammation profiles matches the experimental data; e) transfer of optimized inflammation parameters to a computational model of infant skin; And f) determining the effect of the stimulus in a computational model of the infant's skin. 2. The method according to claim 1, in which the irritant is selected from paraffin and petroleum jelly. 3. The method according to claim 1, in which EPISIM is used as a computational model of penetration into the skin of an adult. 4. The method according to claim 1, in which an agent-based model is used as a computational model of adult skin inflammation. 5. A protective system, which is a cream or moisturizer, selected by evaluation in accordance with the method according to claim 1.