A method for selecting a skin barrier system suitable for infants and toddlers

Abstract

The present invention discloses a method for selecting a skin barrier system suitable for infants and toddlers.

Description

Technical Field

[0001] The present invention relates to the development of a skin barrier system, specifically for the development of a skin barrier system for infants or toddlers, and at the same time evaluates the level of skin protection by analyzing adult skin tests. The present invention allows the evaluation of the protection level of a skin barrier system with objective data, without the need to test infants or toddlers. Background Art

[0002] Skin cleansers contain surfactants that can damage the integrity of the skin's resistance to the penetration of external invaders, resulting in skin irritation. The evaluation of the mildness of a cleanser on the skin is usually carried out by clinically evaluating and measuring changes in transepidermal water loss (TEWL) according to exaggerated patch test or exaggerated washing test protocols. These methods are partially subjective and usually have variable results.

[0003] The mildness of skin care products is usually evaluated in adults using normal use tests, exaggerated (repeated) use tests, or patch tests (especially for cleansing products containing potentially irritating surfactant systems). Even for infant products, they are first evaluated in adults, and once passed the evaluation, sometimes normal use tests are carried out in infants. Mildness is evaluated as non-irritating (usually skin erythema (redness)). The effect on skin barrier is usually evaluated instrumentally by measuring transepidermal water loss (TEWL). The Franz cell can also be used and skin impedance measured to study the effect of products on skin barrier in vitro.

[0004] However, the previous methods have many drawbacks and problems. For example, normal use tests usually require a large panel size to distinguish different levels of mildness, which can be costly and time-consuming. In patch tests, surfactants can respond differently under occluded conditions compared to normal use conditions. The results of the arm immersion test can depend on the climate. In the flexure washing test, the skin sites tested may not be representative of other areas of the body.

[0005] In addition, each of the above items is subjectively evaluated (clinical observation), which can result in variations. Finally, most of these tests are either for adult skin and have nothing to do with infant skin, or these studies are carried out on infants / toddlers, but clinical studies on infants raise ethical and technical issues. As pointed out, the validity of directly transferring data collected from adults to the infant skin situation is questioned. For example, infant skin is usually not used in Franz cells, and the transfer of this data to infant skin is problematic. The use of these methods always involves a safety factor margin (usually 10-fold) that reflects uncertainty.

[0006] It would be useful to develop a method for evaluating the impact of surfactant systems on the skin barrier of infants and / or toddlers by objectively assessing the concentration distribution of markers (such as caffeine) that penetrate the skin of adult subjects. The present invention attempts to evaluate the impact by using biomarker testing on adult skin, using a computational model to evaluate the impact on infant / toddler skin, and developing surfactant systems as a result of these tests and analyses.

[0007] Humectants are mixtures of chemical reagents specifically designed to make the outer layer of skin or hair softer. Personal care compositions with humectant properties are known. Consumers expect such compositions to meet a range of requirements. In addition to determining the skin / hair care effects of the intended application, values are set for various parameters such as dermatological compatibility, appearance, sensory impression, storage stability, and ease of use. Another beneficial effect provided by many humectants is to protect the skin from exposure to the external environment and reagents. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1A and Figure 1B Shows the absorption of exogenously applied water observed via Raman confocal microspectroscopy 10 seconds after applying water to the skin of the lower abdominal arm.

[0009] Figure 2 Shows a comparison between experiment (adult), model (adult), and prediction (infant).

[0010] Figure 3 Shows Comparison between experiments, models and predictions of water and SLS on adult and infant skin

[0011] Figure 4 Shows a comparison between several surfactant formulations.

[0012] Figure 5 Shows modeling experimental data in a computer-simulated adult epidermis model.

[0013] Figure 6 Shows the predicted caffeine penetration curve after surfactant treatment.

[0014] Figure 7 Shows the predicted absorption in the infant stratum corneum, the area under the curve (mmol caffeine / g keratin) for a depth of 0 μm - 10 μm.

[0015] Figure 8 Shows experimental data on adult skin.

[0016] Figure 9 Shows the modeling of adult skin.

[0017] Figure 10 Shows the predicted results for infant skin.

[0018] Figure 11 Shows experimental data on adult skin.

[0019] Figure 12 Shows the modeling of adult skin.

[0020] Figure 13 Shows the prediction results for infant skin. Detailed implementation

[0021] The present invention relates to a method for evaluating the mildness of skin care products on infant skin, and specifically evaluating the effect of topical application of substances and / or formulations on the skin barrier of infants, and preparing and / or using a surfactant system based on this evaluation. As used herein, the term "infant skin" refers to the skin of human neonates, but also refers to and includes the skin of children up to 12 months old. The term "toddler" refers to infants from 12 to 36 months old, but also includes children.

[0022] The object of the present invention is to be able to evaluate the safety, mildness, etc. of products on infant and / or toddler skin by safely evaluating the products on adult skin. The method involves applying a substance on adult skin, collecting the penetration data of a marker on the treated adult skin, transmitting this information to a computational model of adult skin, extracting the penetration parameters from this model, transmitting the parameters to a computational model of infant skin, and visualizing the penetration of the marker in the infant skin model and drawing conclusions about the effect of the topical product on infant skin. Finally, the method then includes preparing a surfactant system as a result of this evaluation, and / or using the surfactant system based on this assessment and the final preparation of the system.

[0023] The US published patent application 20150285787 granted to Laboratoires Expanscience discloses a method for identifying at least one biomarker of children's skin, the method comprising: a) measuring the expression level of a candidate biomarker in at least one skin cell sample (A), said sample being obtained from a donor under 16 years old; b) measuring the expression level of said candidate biomarker in at least one control sample (B) of skin cells; c) calculating the ratio between the expression level of step a) and the expression level of step b); and d) determining whether the candidate marker is a biomarker of children's skin.

[0024] WO2015150426 and WO2017103195, granted to Laboratoires Expanscience, disclose methods for evaluating in vivo formulations, which include: a) contacting an active agent or formulation with a reconstructed skin model obtained from a skin sample of a child; b) contacting the reconstructed skin model after step a) with urine; and c) measuring the expression level of at least one biomarker in the list of specified biomarkers in the skin model after step b).

[0025] U.S. Published Patent Application 20180185255, granted to Procter & Gamble, discloses a method for screening mild detergents, which includes: a) measuring the level of one or more ceramides on a skin area before applying the detergent; b) applying the detergent to the skin area for at least 7 days; c) measuring the level of one or more ceramides at least 7 days after applying the product on the skin area; wherein if the level of the one or more ceramides is at least 10% relative to an untreated control, the detergent is mild.

[0026] U.S. Patent 10,036,741, granted to Procter & Gamble, discloses a method for evaluating the effect of an antigen on skin homeostasis and formulating a skin care composition containing the antigen, which includes querying a data architecture of skin cases stored in a computer processor associated with antigens having an unhealthy skin gene expression profile, wherein the query includes comparing the unhealthy skin gene expression profile with each stored skin case and assigning a relevance score to each case.

[0027] EP 1248830A1, granted to Procter & Gamble, discloses the use of a controlled forearm application test to evaluate surfactant mildness.

[0028] "Skin hydration analysis by experiment and computer simulations and its implications for diapered skin" by Saadatmand et al. (Skin Res. Technol., 2017: 1 - 14) discloses a stratum corneum reversible hydration model that simulates evaporative water loss and stratum corneum thickness varying with exposure scenarios such as time - dependent relative humidity, air temperature, skin temperature, and wind speed).

[0029] "Application of a systems biology approach for skinallergy risk assessment" by Maxwell et al. (Proc. 6 th World Congress on Alternatives & Animal Use in Life Sciences, pp. 381 - 388, 2007) discloses a computer simulation model of skin sensitization induction to characterize and quantify the contribution of each pathway to the overall biological process.

[0030] "The flex wash test: a method for evaluating the mildness of personal washing products" by Strube et al. (J. Soc. Cosmet. Chem., 40:297 - 306 (1989)) discloses the use of a sixty - second wash (three times daily) with a flex arm to evaluate the potential irritation of washing products.

[0031] "Comparison of exaggerated and normal use techniques for accessing the mildness of personal cleansers" by Keswick et al. (J. Soc. Cosmet. Chem., 43:187 - 193 (1992)) discloses a comparison of forearm tests and flex wash tests with home use to determine the extent to which the tests approximate casual use.

[0032] "Journal of the American Academy of Dermatology" by Frosch et al. (Vol. 1, No. 1, pp. 35 - 41, 1979) discloses a chamber test for evaluating the irritation of soaps, which requires exposure to an 8% solution for five working days and shows scaling and redness.

[0033] For experimental use on infant skin, many in - vivo tests are unacceptable. The cited references do not disclose or propose evaluating adult skin and using a computational model to relate how ingredients will affect infant skin. Thus, the present invention does not require in - vivo testing on infant skin.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Additionally, all publications, patent applications, patents, and other references mentioned herein are incorporated herein by reference in their entirety. Unless otherwise specified, all percentages used herein are by weight. Further, all ranges shown herein are intended to include any combination of values between the two endpoints (including the endpoints).

[0035] In the present invention, the method can be used to distinguish different detergent formulations based on the effect of the skin barrier against external penetration by different detergent formulations. The present invention provides a method for analyzing formulations that objectively evaluates the effect of a topical detergent on the skin barrier against the penetration of external invaders and can be used to evaluate the mildness of detergents. One can utilize the results of this analysis and provide or prepare a suitable formulation that is considered mild for the skin of infants and / or toddlers.

[0036] The present invention relates to a predictive method for evaluating the mildness of a topical substance on the skin of a subject (preferably a toddler). The present invention also relates to a predictive method for evaluating the penetration of a compound (marker) through the skin of an infant. The present invention also relates to a predictive method for evaluating the effect of a topically administered substance on the penetration of a compound (marker) through the skin of an infant. Additionally, the present invention can provide a method for measuring and / or predicting the barrier enhancement effect of a topical substance.

[0037] In one aspect, the present invention can include a plurality of method steps. It can include Phase 1 (in vivo) and Phase 2 (computer simulation), and optionally Phase 3 (intellectual process), and finally the method ends with the preparation of a suitable surfactant system that can pass the above tests through analysis, or the method ends with the application of the surfactant system to the skin of an infant and / or toddler.

[0038] Phase I, in vivo

[0039] A. Apply the topical substance to the skin of an adult, such as by direct application or application on a patch or other delivery system.

[0040] B. Apply the marker topically to the skin of an adult and collect the penetration data of the marker on the adult skin treated with the substance. This step includes applying the marker and then collecting its concentration profile through the skin, for example, using confocal Raman microspectroscopy (CRM).

[0041] Phase II, computer simulation

[0042] C. Transfer this information (penetration data) to a computational model of adult skin and extract the penetration parameters from the model.

[0043] This step can also be described as using a computational adult skin penetration model to visualize the penetration of a marker by optimizing penetration parameters (e.g., local surface concentration and permeability coefficient) such that the modeled penetration profile matches the experimental data.

[0044] D. Transfer the penetration parameters (after appropriate transformation) to a computational model of infant skin and visualize the penetration of the marker in the infant skin model.

[0045] (Optional), Phase III, intellectual process

[0046] E. Draw conclusions about the mildness (effect) of the topical product on infant skin based on the amount of marker that has penetrated the infant skin model.

[0047] Once the above method steps have been completed and conclusions have been drawn in step E, the user can prepare, apply, or dispense the surfactant system.

[0048] Topical substance

[0049] The present invention includes one or more topical substances to be evaluated, where the topical substances are intended for use in a final surfactant system. A topical substance is any type of substance that has an effect on the permeability of the stratum corneum when applied to the skin. The topical substance will alter the penetration of the marker through the skin. By measuring the marker penetration, the effect of the topical substance can be evaluated. Typically, for the tests outlined above, the topical substance is impregnated on a patch that remains in contact with the skin for 30 minutes before the marker is applied. The patch can include one or more topical substances for the application of the test.

[0050] Different types of topical substances can be evaluated within the scope of the present invention. For example, the topical substance can be an irritating substance that reduces the skin barrier and increases the penetration of the marker. In this case, the present invention can allow for the creation of a mildness classification of substances and help select a milder solution when designing new skin product compositions without the need for in vivo or in vitro testing. In other aspects, the topical substance can include a barrier substance that is designed to help protect the skin and increase its barrier, thus reducing the penetration of the marker through the skin. As described above, the present invention can help select the most effective solution without having to perform in vitro or in vivo testing on infant skin.

[0051] Marker

[0052] The present invention uses one or more markers or biomarkers in the evaluation method. Any type of marker is suitable as long as there is a method for tracking the marker and generating a concentration profile (e.g., permeation data). In an example using confocal Raman microspectroscopy, the marker should have a traceable signal in the Raman spectrum. For another example, confocal fluorescence microscopy can be used to track fluorescent markers. Desirably, the permeation kinetics of the marker should be such that a steady state of the concentration profile is reached within a reasonable time (e.g., within one hour at most).

[0053] The marker can be hydrophilic, lipophilic, or amphoteric, which will define which type of barrier effect the evaluator is examining. For example, a suitable marker is caffeine. In the case of caffeine, the analysis examines the barrier to hydrophilic substances.

[0054] The marker according to the present invention can include any molecule that is safe in terms of toxicology and dermatology, has reasonable permeation kinetics, and can be tracked by confocal analysis.

[0055] - Safety; some markers used in the past were unacceptable due to toxicity reasons (dansyl chloride (proposed in "Dansyl chloride labelling of stratum corneum: its rapid extraction from skin can predict skin irritation due to surfactants and cleansing products" by Paye et al., Contact Dermatitis 30(2), 91 - 96, 1994), and production has been discontinued due to the risk of sensitization and skin corrosion upon contact with the skin).

[0056] - Permeation kinetics; the molecule permeating the skin is, for example, fast enough but not too fast. For example, a molecule with a permeability coefficient close to that of caffeine can be employed: kp = 1.16×10 -4 cm / h, as reported in "Topical delivery of caffeine from some commercial formulations" by Dias M et al. (Int J Pharm 1999 182(1): 41 - 7).

[0057] - Confocal analysis is non - invasive and provides data on the depth of penetration of the marker. In contrast, for example, tape stripping is invasive and destroys the barrier; this is unacceptable in the present invention.

[0058] Permeation data

[0059] The present invention analyzes permeation data. The permeation data is a concentration profile; this means that the concentration of the marker is a function of the depth through the skin. The present invention can use any desired analytical method suitable for measuring the variation of the concentration profile of the marker with depth in the skin, more precisely in the epidermis, and in particular in the stratum corneum. Any desired method can be used, and non-invasive methods are preferred. Confocal techniques are preferred because they are non-invasive and provide reasonable resolution, for example, a resolution of 3 μm to 5 μm in the direction perpendicular to the skin surface and a depth of up to 200 μm. One such method includes confocal Raman microspectroscopy, but other methods can also be used, including confocal fluorescence microscopy.

[0060] Computational model of adult / infant skin

[0061] The present invention uses a computational model to evaluate the components of the surfactant system being tested. Any model that can generate a concentration profile of the marker permeating through the skin can be employed. The user can select any type of computational skin permeation model that can generate a concentration profile of the marker permeating through the skin given the permeation parameters. The use of both adult skin and skin models requires the model to take into account the structure of the skin architecture and the differences that exist between the two.

[0062] For example, a physiological model published in “A 3D self-organizing multicellular epidermis model of barrier formation and hydration with realistic cell morphology based on EPISIM,” by Sutterlin et al. (Scientific Reports, Volume 7, Article 43472, 2017) can be used; and modified to integrate substances (e.g., markers) diffusing through the skin layers. Sutterlin et al. disclosed a cell behavior model (CBM) that encompasses epidermal barrier, water loss in the environment, and regulatory feedback loops between water flow 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 (reagent-based simulation environment). Each EPISIM-based model is composed of at least a cell behavior model and a biomechanical model (CBM and BM). The BM encompasses all spatial and biophysical cell properties. The CBM is a model of cell determination. The 2D or 3D form of the model can be used according to the present invention (the form of the 2D model (but without the stratum corneum component) is described in: “Modeling multi-cellular behavior in epidermal tissue homeostasis via finite state machines in multi-agent systems” by Suetterlin et al. (Bioinformatics, 25(16), 2057-2063, 2009)).

[0063] In one method, the process begins with the user allowing the simulation to reach a steady state corresponding to epidermal homeostasis. Then, at a given time point corresponding to the local application of the marker, the evaluator introduces a user-defined variable corresponding to the skin surface concentration (C 表面 ) of the marker. The value of this parameter is defined by the concentration profile obtained through experiments and corresponds to the marker concentration at depth 0 (skin surface). A cell variable is introduced into the model that defines the concentration (C 细胞 ) of the marker in the cell. This parameter is modified based on Fick's law of diffusion at each step, as the marker is allowed to diffuse from each cell to its neighboring cells. To apply Fick's law, a permeability coefficient parameter (P) is introduced into the model. This permeability coefficient parameter inherently takes into account the diffusion coefficient, the diffusion resistance due to the partition coefficient, and the diffusion resistance due to the path distance that the substance must cross from one cell to the next. For the living epidermis (PVE ) has different permeability coefficients compared to the stratum corneum (P SC ). If the substance reaches the bottommost part of the epidermis, it is allowed to diffuse into the epidermal compartment modeled as a permeation "sink".

[0064] These modifications apply to both the adult skin and infant skin models.

[0065] The infant skin model is created by modifying the parameters of the adult model to reflect the higher turnover rate (proliferation and desquamation) in infant skin.

[0066] Permeation parameter

[0067] The permeation parameters characterize the permeation kinetics, the ease with which a substance crosses the surface and penetrates into the skin. It can be, for example, the partition coefficient, the diffusion coefficient, and / or the permeability coefficient.

[0068] Gentleness index

[0069] In the steady state, the concentration profile of the marker in the adult skin model is compared with the experimental concentration profile. If the profiles do not match, the permeation parameters (C 表面 , P SC and P ve ) are adjusted and the simulation is repeated. Once the two profiles match, the parameters are used to calculate the corresponding parameters for marker permeation in the infant skin model. Since infant skin has a higher hydrophilicity, the C 表面 parameter is higher (usually twice that of adult skin*), while the other permeation parameters remain the same between the two models.

[0070] * See, for example, Nikolovski et al., "Barrier function and water-holding and transport properties of infant stratum corneum are different from adult and continue to develop through the first year of life" (Journal of Investigative Dermatology, Vol. 128, 2008), which uses tools such as transepidermal water loss (TEWL), skin capacitance, adsorption-desorption, and Raman confocal spectroscopy to confirm that the water storage and water transport properties of the infant stratum corneum are different from those of adults. Specifically, this reference discloses the observation of the absorption of exogenously applied water via Raman confocal microscopy 10 seconds after application of water to the skin of the lower abdominal arm. Among them Figure 5 a (and inFigure 1A ) showed that a significant amount of water absorption was found in the stratum corneum of infants younger than 12 months of age. Figure 5 b(and Figure 1B ) show that, in contrast, no significant water absorption was found in adult skin after application of water. It is expected that the penetration of highly hydrophilic caffeine will behave similarly to water penetration.

[0071] The marker is then allowed to penetrate to reach a steady state in the infant skin model (approximately 1000 steps, each corresponding to 30 minutes of physiological time). At steady state, the average concentration profile of the marker is calculated (average concentration as a function of depth). The area under the curve (AUC, integral) is calculated for the concentration profile down to a defined depth (such as 20 μm).

[0072] The Mildness Index scale can be defined by the AUC values corresponding to different product treatments. This is an agreed scale for classifying the mildness of topical substances.

[0073] This mildness index value allows the evaluator to compare the mildness of the tested topical substance relative to two reference substances: water (mild) and sodium lauryl sulfate (SLS) 0.1% (irritant). Using water and SLS 0.1% as two reference points, it is possible to establish a scale to measure the mildness of other topical substances.

[0074] It should be noted that this mildness index is optional and one can ignore the mildness index and compare the relative mildness of different topical substances to each other directly based on the integration of their predicted penetration curves (ie, calculated AUC values).

[0075] Example

[0076] 1 - Comparison between experiment (adult), model (adult) and prediction (infant).

[0077] See Figure 2 .

[0078] Target:

[0079] • To demonstrate the predicted effects on infant skin of two extreme topical solutions: a harsh solution (containing 0.1% SLS) and a mild solution (water).

[0080] · Show that the adult model is consistent with experimental data.

[0081] Shows that topical substances have different effects on adult and infant skin, with the markers penetrating infant skin more easily.

[0082] Comparison between experiments, models, and predictions of water and SLS on adult and infant skin. See Figure 3 .

[0083] superiorFigure 3 The penetration depth (in μm) of caffeine (the marker), expressed in mmol / g keratin, obtained from in vivo experiments (lines + and ○) on adult skin or from a computer-simulated prediction model (lines Δ, ×, ◇, and □), is shown.

[0084] The effects of two topical solutions on caffeine penetration are shown in Figure 3 : water and 0.1% SLS. Model-calculated data for adults are represented by lines Δ and ◇; for water and SLS, respectively. Predicted data for infants are represented by lines × and □, for water and SLS, respectively.

[0085] In vivo experimental data on adult skin were collected and then transferred to an adult skin model to simulate the penetration depth of caffeine in adult skin. The predictions of caffeine penetration in infant skin made by the model of the present invention are represented by a diagonal line (×) when the skin is treated with a water patch before caffeine application and by a square line (□) when the skin is treated with a 0.1% SLS patch before caffeine application.

[0086] The area under the curve for a skin depth of 0 μm to 20 μm gives an indication of the mildness level of a topical substance. The smaller the area, the milder the substance is on the skin. The area under the curve is a key parameter for comparing different treatments.

[0087] Comparison between several surfactant formulations. See Figure 4 .

[0088] Objective:

[0089] · Create a predictive surfactant formulation classification based on the mildness of surfactant formulations on infant skin.

[0090] Step 2.1: Experimental data, caffeine permeation in adult skin, in vivo

[0091] The tested formulations are shown in Figure 4 .

[0092] The experimental protocol is as disclosed in the materials and methods of the article by 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)). Stamatas et al. disclosed using the characteristic Raman spectrum of caffeine to track the penetration of caffeine through adult skin to demonstrate the effects of (1) sodium lauryl sulfate and (2) barrier creams on the barrier function of the stratum corneum.

[0093] Step 2.2: Modeling experimental data in the computer-simulated adult epidermal model. See Figure 5 .

[0094] The experimental caffeine permeation data collected at step 2.1 were transferred to a computational model of adult human skin. Skin permeation simulations were performed for each topical substance; a single simulation per substance was sufficient. Caffeine permeation parameters (local surface concentration and permeability coefficient) were extracted.

[0095] Step 2.3: Predicted caffeine permeation curve after surfactant treatment. See Figure 6 .

[0096] The caffeine permeation parameters obtained from the adult skin model in step 2.2 were transferred to the computational model of infant skin. Infant skin permeation simulations were performed for each topical substance. The predicted caffeine permeation results were extracted and displayed on Figure 4 middle.

[0097] Step 2.4: Predicted absorption in infant stratum corneum, area under the curve at a depth of 0 μm - 10 μm (mmol coffee due to / g keratin). See Figure 7 .

[0098] For step 2.3 Figure 6 The predicted curves for each topical agent shown in were integrated to obtain the predicted amount of caffeine absorbed into the infant stratum corneum for each topical agent. These values are shown in Figure 7 middle.

[0099] In other words, the prediction graph shows how much caffeine will penetrate within the first 10 μm (not mm) of the SC. The more caffeine that penetrates, the more aggressive the topical substance.

[0100] Results

[0101] Surprisingly, one would predict from this graph that topical agents would not have mildness index values on baby skin that would always be reflected by experimental values obtained on adult skin:

[0102] Formula 3 will be milder than Formula 5.

[0103] Formula 4 will be milder than Formula 2.

[0104] As a result of this experiment, compositions comprising the formulations of Formula 3 and / or Formula 4 can be prepared and applied to infants' skin and / or toddlers' skin, respectively, and are more preferred than Formulas 5 and 2.

[0105] In a next embodiment, the present invention relates to the development of a barrier system, in particular for infants or young children, while simultaneously evaluating the level of barrier effectiveness by analyzing adult skin tests.

[0106] The present invention allows objective data to be used to assess the level of protection provided by a barrier system without the need for testing on young children or infants.

[0107] Methods

[0108] Steps I and II disclosed above remain the same. Predictive data on the percutaneous penetration of the marker in infant skin is generated.

[0109] Step III is different in that the data relates to the low penetration and diffusion of the marker through the skin to predict the barrier effect of the topical substance administered in Step IA on the skin of infants or young children.

[0110] This method can be used to evaluate wash-free products (such as creams / moisturizers).

[0111] Experiment

[0112] Example 3

[0113] Materials and methods

[0114] Adult skin data of healthy volunteers with normal skin is collected. These healthy volunteers agreed not to use any other skin care treatments on their forearms for at least 24 hours before the study and during the study.

[0115] Instruments used:

[0116] In vivo confocal micro Raman spectrometer (Skin Care Composition Analyzer Model 3510, River Diagnostics, Rotterdam, The Netherlands)

[0117] Caffeine patch: 10 mL deionized aqueous solution of 180 mg caffeine, 1.8%

[0118] Example 4 Barrier cream simulation

[0119] Experimental data of 5 female volunteers aged between 20 and 35 years old is collected.

[0120] Topical substances tested:

[0121] Barrier cream: Cream (diaper rash cream)

[0122] US INCI list: 10% zinc oxide, inactive ingredients (aloe leaf juice), cyclomethicone, dimethicone, fragrance, methylparaben, microcrystalline wax, mineral oil, propylparaben, purified water, sodium borate, sorbitan sesquioleate, vitamin E, white petrolatum, white wax.

[0123] Protocol

[0124] 1 - Acclimatize for 5 minutes in a room with controlled temperature and humidity

[0125] 2 - Apply a topical substance on the forearm

[0126] 3 - Acclimatize for 30 minutes in a room with controlled temperature and humidity

[0127] 4 - Apply a caffeine patch on the forearm (same location) and keep it for 30 minutes

[0128] 5 - Conduct measurements in the Raman fingerprint region

[0129] Results

[0130] 1 - Experimental data on adult skin. See Figure 8 。

[0131] Compare the data obtained from the Desitin - treated skin (squares) with the data from the untreated reference skin (circles), i.e., the skin on which no topical substance was applied in step 2 of the protocol

[0132] Extract the permeation data from the experimental results and transfer it to a computational model of adult skin

[0133] Modeling the skin of adults. See Figure 9 。

[0134] The next step is to define the skin permeation parameters on the computational model of adult skin such that it can accurately simulate the experimental data provided above

[0135] These parameters are calculated from the slope of the caffeine permeation profile

[0136] The results of the adult model are shown below

[0137] Compare the skin treated with the barrier cream (squares) with the reference untreated skin (circles)

[0138] Extract the permeation parameters from the computational adult model

[0139] 3 - Prediction results on the skin of infants. See Figure 10 。

[0140] The last step involves transferring the caffeine permeation parameters to the computational model of infant skin using an appropriate transformation to simulate the predicted caffeine permeation in infant skin

[0141] The predicted results of caffeine permeation on the skin treated with the barrier cream (squares) and the reference untreated skin (circles) are shown below

[0142] Finally, from the ratio of the area under the curve (AUC) of the curve related to the untreated skin shown below to the AUC of the skin treated with the barrier cream, we can calculate the predicted protection percentage of the barrier cream

[0143] Percent protection = 100×(AUC(untreated) - AUC(product)) / AUC(untreated) = 89.18%

[0144] Example 5 Moisturizer simulation

[0145] Experimental data were collected from 6 volunteers aged between 18 and 40 years old.

[0146] Topical substances tested:

[0147] - Humectant A: An emulsion containing glycerol (12%), petrolatum (4%), distearyldimethylammonium chloride, and water

[0148] - Humectant B: A structured emulsion containing petrolatum (40%), glycerol (12%), distearyldimethylammonium chloride, and water

[0149] Protocol

[0150] 1 - Acclimatize for 5 minutes in a temperature / humidity controlled room

[0151] 2 - Apply the topical substance on the forearm and keep it for 30 minutes

[0152] 3 - Apply a caffeine patch on the forearm (same location) and keep it for 30 minutes

[0153] 4 - Make measurements in the fingerprint area

[0154] Results

[0155] 1 - Experimental data on adult skin

[0156] Data obtained from skin treated with Humectant A (squares) were compared with data obtained from skin treated with Humectant B (triangles) and reference untreated skin (circles) (i.e., no topical substance was applied in step 2 of the protocol).

[0157] Extract the permeation data from the experimental results and transfer it to a computational model of adult skin.

[0158] Modeling the skin of adults. See Figure 12 。

[0159] The next step is to define skin permeation parameters on the computational model of adult skin such that it can accurately simulate the experimental data provided above.

[0160] These parameters are calculated from the slope of the caffeine permeation profile.

[0161] The results of the adult model are shown below.

[0162] The skin treated with humectant A (squares) was compared with the skin treated with humectant B (triangles) and with reference untreated skin (circles).

[0163] Permeation parameters were extracted from the computational adult model.

[0164] 3 - Predicted results on infant skin

[0165] The final step consisted of transferring the caffeine permeation parameters to the infant skin computational model using an appropriate transformation to simulate predicted caffeine permeation in infant skin.

[0166] The predicted results of caffeine permeation on the skin treated with humectant A (squares), the skin treated with humectant B (triangles), and the reference untreated skin (circles) are as Figure 13 shown.

[0167] Finally, from the ratio of the area under the curve (AUC) for untreated skin shown below to the AUC for humectant-treated skin, we can calculate the predicted protection percentage of the humectant:

[0168] For moisturizer A

[0169] Protection %: Not applicable

[0170] The area under the curve of humectant A was better than that of the untreated reference. The simulation predicted no protective effect on infant skin.

[0171] For moisturizer B

[0172] Protection % = 100 × (AUC(untreated) - AUC(product)) / AUC(untreated) = 17.72%.

[0173] Skin acute inflammation model

[0174] A substance permeation model was used to implement a reliable model of skin acute inflammation.

[0175] The model can be used to evaluate the skin's response to topically applied external irritants. The desired model behavior is that the application and permeation of the irritant in the skin will induce the production of inflammatory molecules. Then, when the keratinocytes are no longer in contact with the stimulant, the system will return to a steady state.

[0176] Inflammatory molecules are only produced and degraded by keratinocytes. When the irritant crosses the barrier formed by the SC, the inflammatory response begins. Then, when the apparent concentration of the irritant in the cells reaches a certain value called the stimulation threshold, the keratinocytes begin to produce inflammatory molecules [IM] according to the following equation:

[0177]

[0178] where pIM and dIM are the production and degradation rates of inflammatory molecules in keratinocytes.

[0179] When the apparent concentration of the substance is below the stimulation threshold, no more inflammatory molecules are produced (pIM = 0), but degradation continues. At each step, the cell diffuses its inflammatory molecules to adjacent cells according to the following equation:

[0180]

[0181] where the subscript n refers to the adjacent cell, and DIM is the diffusion coefficient of the inflammatory molecule.

[0182] Finally, the inflammatory cells disappear from the dermis at the basal level as follows:

[0183]

[0184] where Pdermis;IM[IM] corresponds to the dermal permeability of the stimulant.

[0185] Data in the literature were used to evaluate different parts of the model according to the following criteria.

[0186] The stimulant was applied topically;

[0187] The study was performed in humans in vivo;

[0188] Inflammation was measured quantitatively (erythema size or redness, blood flow,...);

[0189] Several concentrations of the stimulant were tested;

[0190] The stimulant did not interfere with normal skin barrier function (only small changes in transepidermal water loss, TEWL, were observed).

[0191] Andersen et al. studied skin irritation using reflectance spectroscopy

[14] . They studied the skin responses of eight volunteers to four compounds: sodium lauryl sulfate (SLS), hydrochloric acid (HCl), nonanoic acid (NON), and imipramine (IMI). The levels of oxygenated and deoxygenated hemoglobin were measured with a reflectance spectrometer, blood flow was measured with a laser Doppler flowmeter, and TEWL was measured using an evaporimeter. For each compound, four concentrations were tested using patches over a 24-hour period. Two compounds that increased TEWL the least were focused on: imipramine and nonanoic acid. Oxygenated hemoglobin appeared to be a good indicator of inflammation and a dose–response curve was generated. The data for these molecules did not validate our model.

[0192] We decided to study more lipophilic compounds because both nonanoic acid and imipramine are lipophilic. Have collated data on pure oil penetration in the SC from a study published in 2008

[18] . Measure the concentrations of paraffin and petrolatum at several depths in the SC by Raman spectroscopy. Found the Kp values for paraffin and petrolatum in the literature

[19] :

[0193] Kp(paraffin) = 13:3 (cm = h)

[0194] Kp(petrolatum) = 2:02 103 (cm = h)

[0195] For these compounds, it was possible to obtain a good fit of the clinical data by simulation using our model.

[0196] The inflammation generated by the model is dose-dependent. In addition, we demonstrated that depending on the parameter values derived from the molecular physical properties (PSC (stratum corneum permeability) and PVE (viable epidermis permeability)), the model generates inflammation of different intensities. Finally, we showed that the inflammation model is fully functional in both adult and infant skin model settings and even gained insights into the role the skin structure can play in the inflammation dynamics.

[0197] It should be understood that while various aspects of the present disclosure have been shown and described by way of example, the invention as claimed herein is not limited thereto, but may be otherwise differently implemented according to the scope of the claims set forth in this patent application and / or any derivative patent application.

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[0207]

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[0208]

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[0209]

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[0215]

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[0216]

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Claims

1. A method for evaluating the ability of a skin barrier system to protect infant skin from external irritants, the method comprising: a) topically applying the barrier system to adult skin; b) topically applying an external irritant to the adult skin treated with the barrier system; c) applying confocal analysis to measure the penetration of the irritant into the adult skin treated with the barrier system to determine the production of inflammatory molecules in the adult skin treated with the barrier system; d) using a computational model of adult skin inflammation to visualize the effect of the external irritant by optimizing inflammatory parameters such that the model of the adult skin inflammation distribution matches the experimental data; e) transferring the optimized inflammatory parameters to a computational model of infant skin; and f) determining the effect of the irritant in the computational model of the infant skin, wherein the irritant is selected from paraffin and petrolatum, wherein step c) includes tracking the concentration distribution of the irritant through the skin, wherein the concentration distribution is measured using confocal Raman microspectroscopy or confocal fluorescence microscopy, Among them, the penetration parameter is selected from: skin surface concentration C 表面 , stratum corneum permeability coefficient P SC and active epidermal permeability coefficient P VE ;as well as Among them, in step e), transfer the parameter so that the skin surface concentration C in the computational model of the infant skin 表面 is higher than that in the computational model of adult skin penetration, and make the stratum corneum permeability coefficient P SC and the permeability coefficient P of the viable epidermis VE the same.

2. The method according to claim 1, wherein EPISIM is used as the computational model of adult skin inflammation.

3. The method according to claim 1, wherein the computational model of adult skin inflammation is a reagent-based model.

4. The method according to claim 1, wherein the skin surface concentration C in the computational model of the infant skin 表面 parameter is twice the skin surface concentration C 表面 parameter in the computational model of adult skin permeation.

5. A barrier system selected by the method according to claim 1.

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