WO2019219393A1

WO2019219393A1 - Evaluating the efficacy of leave-on cosmetic compositions to protect from pollutants

Info

Publication number: WO2019219393A1
Application number: PCT/EP2019/061200
Authority: WO
Inventors: Guoqiang Chen; Yi Fang; Nan Huang; Chengdong JI; Sheng MENG; Shangchun YI; Caigen Yuan
Original assignee: Unilever N.V.; Unilever Plc; Conopco, Inc., D/B/A Unilever
Priority date: 2018-05-17
Filing date: 2019-05-02
Publication date: 2019-11-21

Abstract

Disclosed is an in vitro method to determine efficacy of a cosmetic composition or an active ingredient comprised therein to inhibit an atmospheric pollutant from contacting skin, comprising the steps of: (i) filling a sample holder of known dimensions with a known amount of said composition to form a layer of defined thickness therein; (ii) depositing, on said layer, a known amount of a model fine particulate matter which resembles a particulate atmospheric pollutant and is responsive to a spectroscopic or microscopic chemical imaging technique; (iii) performing said chemical imaging; (iv) for a defined period, recording and analyzing the interaction of said model fine particulate matter with and within said layer by the imaging technique, where interaction indicates the penetration speed of said model fine particulate matter in the layer; and, (v) ascertaining said efficacy from the information of step (iv) wherein the slope of a plot of data obtained from said imaging technique against time in the range of 1 to 100 minutes is indicative of short-term efficacy of said composition and the nature of the plot beyond 100 minutes is indicative of long- term efficacy and wherein long-term inhibition factor of said composition is calculated as follows: Long term inhibition factor = Formula (1) where, x is the distance between the bottom of the chamber and the assumed centre of the Gaussian distribution of the model fine particulate model in the layer, σ is the width of the Gaussian distribution and μ is the mean of the Gaussian distribution, where it is assumed that distribution of the model fine particulate matter in said layer follows Gaussian distribution.

Description

EVALUATING THE EFFICACY OF LEAVE-ON COSMETIC COMPOSITIONS TO

PROTECT FROM POLLUTANTS

Field of the invention

The present invention relates to a method of evaluating efficacy of cosmetic compositions. More particularly, the invention relates to a method for evaluating efficacy of leave-on cosmetic compositions to prevent or inhibit particulate pollutants from contacting skin.

Background of the invention

The World Health Organization (WHO) reports that outdoor air pollution originates from natural and anthropogenic sources. While natural sources contribute substantially to local air pollution in arid regions more prone to forest fires and dust storms, the contribution from human activities far exceeds natural sources.

Such human activities include fuel combustion, heat and power generation and industrial facilities (e.g. manufacturing factories, mines, and oil refineries). WHO classifies pollutants into particulate matter, black carbon, ground-level ozone and oxides of carbon, nitrogen and sulphur.

Particulate matter (PM) are inhalable particles composed of sulphate, nitrates, ammonia, sodium chloride, black carbon, mineral dust and water. Particles with a diameter of less than 10 microns (PM10), including fine particles less than 2.5 microns (PM2.5) pose the greatest risks to health, as they can enter the lungs and the bloodstream. Carbon black (soot) and dust (mineral oxides, such as iron oxides and the like) comprise much of the particulate matter in these size ranges.

WHO defines air pollution as contamination of indoor or outdoor environments by any chemical, physical, or biological agent that modifies the natural characteristics of the atmosphere. The U.S. Environmental Protection Agency (EPA) and the WHO have summarized the global extent of common atmospheric pollutants. In addition, there are innumerable reports and scientific publications pertaining to adverse effects of pollution on human skin. These adverse effects include premature ageing, development of fine lines and wrinkles, pigmented spots, hyperpigmentation, rash and inflammation.

Some cosmetic compositions claim to prevent, inhibit or restrict the particulate pollutants from contacting human skin by forming a protective layer, i.e., they partly or fully block environmental pollutants like particles, oxide/superoxides and gases from contacting human skin. Formulation scientists often find it necessary to be able to substantiate such claims with evidence. Therefore, several manufacturers and researchers have published their own methods of testing/analysing or verifying the efficacy of such compositions. A purpose of such methods is to ascertain the efficacy of a candidate cosmetic composition. At times the purpose also is to compare the efficacy of one or more compositions or active ingredients, e.g. polymers, and rank them accordingly. Some of these tests are conducted on human volunteers. Some others have been conducted on suitable skin-equivalents such as plastic membranes, living-skin equivalents, Vitro- Skin®, in vitro skin models, ex vivo skin and the like. While human skin-equivalents is one components of such test methods, selection of an appropriate pollutant is equally important. However, it is not always possible to perform tests with real-life pollutants therefore model pollutants are often used.

DE4340827 C1 (Aerochemica, 1995) discloses a method and device for in-vitro determination of efficacy against chemical substances and substance mixtures. The barrier effect of a cosmetic is determined in a well-defined amount and thickness on a predetermined surface of a skin simulating membrane, like cellulose nitrate, nylon or PTFE. The concerned composition is applied to this membrane. Subsequently, the membrane is sandwiched on a specific dry indicator paper laid and stretched while maintaining flat contact with the membrane. Then, a measured drop of the defined pollutant is applied over the layer of the cosmetic. Depending on the effectiveness of the preparation, the pollutant may permeate rapidly and trigger a color change in the indicator paper. This change is monitored by irradiating white light via fibers onto the indicator paper by means of a statistically split optical fiber bundle. The remaining, about 50% receiver fibers absorb the scattered light and lead it to a detector. Here there is signal filtering and amplification followed by recording. For example, a photodiode receives the light from the fiber optic cable, an amplifier amplified linearly or logarithmically (depending on the color change of the indicator paper) and gives the signal through the output to a recorder.

The method disclosed in DE4340827 relies on the use of color-changing indicators therefore using this method it is possible to find out when the colour changes which tells the point in time at which the membrane is no longer able to provide barrier effect.

Zhai et al have disclosed an invivo method in Contact Dermatitis, 1996, 35, 92-96, to measure the effectiveness of skin protective creams against two dye indicator solutions: methylene blue in water and oil red in ethanol, representative of model hydrophilic and lipophilic compounds. Three commercial compositions were assayed by measuring the dye in cyanoacrylate strips of protected skin samples after various application times. The flexural surfaces of the forearms of 6 normal volunteers (3 female and 3 male, mean age 26.8 years) were treated.

Solutions of 5% methylene blue in water and 5% oil red in ethanol are prepared, and applied to untreated skin and protective-cream pre-treated skin with the aid of aluminium occlusive chambers, at zero time and 4 hours, respectively. At the end of the application time, the creams are removed. Consecutive skin surface biopsies (SSB) from I to 4 strips were taken. The amount of stain in each strip was determined by colorimetry (Chroma Meter CR 300), and the cumulative amount of stain from 1 to 4 strips in each

measurement was calculated. The cumulative amount represents the amount of permeation of each solution at each time point, and the efficacy of skin barrier cream. A somewhat similar method of Marks et.al, is disclosed in British Journal of Dermatology (1989) 120, 655-6.

Nizard et.al have disclosed a method in H&PC Today, 10 (1 ) January/February 2015.

In this method, a skin explant is exposed under a patch to 32 pollutants (27 heavy metals and 5 hydrocarbons) as an ex-vivo model for pollution damage. The author’s formula is claimed to protect against pollution damage (skin morphology integrity scoring) and lipids peroxidation (by Malondialdehyde measurement). As their formula is applied on explants before the patch with pollutants, the formula creates a physical barrier.

Dow Corning has disclosed a test method to quantify the extent of protection conferred by its product, Splash Shield®, against particulate adhesion. A thin film of the test material is formed on collagen followed by surface analysis and exposure to carbon black repeat analysis.

Further, Dow Corning has disclosed yet another test method in which a test material is coated on a synthetic substrate through which ozone can diffuse. At the other end is a receptacle containing solution of a dye which changes colour upon contact with ozone. Intensity of the colour is inversely proportional to the protection offered by the test material. BASF has disclosed an ex-vivo model to determine the efficacy of its product named Purisoft® against cigarette smoke. The method relies on organotypic cultures of human skin on which the concerned products are applied followed by exposure to smoke. This is followed by biopsies and confocal microscopy to determine the extent of protection offered by the compound of interest.

Lipotec has disclosed a somewhat similar method for a similar purpose about their product Pollushield®.

In Contact Dermatitis, 1996, 35, 219 - 225, Olivarius et.al. have disclosed a method which relies on the colour of crystal violet which binds firmly to keratin (stratum corneum) when painted on the skin. When the skin is pretreated with a water-repellant cream, the penetration of aqueous solution of crystal violet is impaired, leading to lesser binding and paler colour. The relative efficacy of different creams is evaluated visually by comparing intensities quantified by measurement of skin reflectance. Low reflectance indicates a high binding. The protection offered by the cream is calculated as the additional colour resistance induced by the cream (x-y), divided by the maximal additional colour resistance obtainable (100-y). WO9721097 A1 (LVMH Rech) discloses novel polymeric agents for mimicking the skin barrier or the mucosal barrier to evaluate the behaviour of cosmetic or pharmaceutical products for topical use. The new polymeric agents are particularly applicable to carry out the following operations, predictive measurement of the penetration of

pharmacologically active molecules or likely to exhibit toxicity at the cutaneous level. The family of polymers, all of which are crosslinked acrylic or methacrylic polymers, may be used as agents intended to mimic the effect of the cutaneous barrier or mucosal barrier to evaluate the behavior of the products or compositions for cosmetic or pharmaceutical use, in particular dermatological, for topical use.

Despite availability of the methods disclosed hereinabove, there is need for a robust method which makes it possible to determine as accurately as possible, the dynamics of penetration of a model pollutant from the atmosphere over a period to determine the short-term efficacy and the long term efficacy of cosmetic compositions that claim to prevent, or at least delay the contact of particulate atmospheric pollutants with human skin by forming to the extent possible, a barrier between the skin and the pollutant.

The present invention addresses the needs by overcoming at least one drawback, disadvantage or limitation of the state of the art.

Summary of the invention

In accordance with a first aspect is disclosed an in vitro method to determine efficacy of a cosmetic composition or an active ingredient comprised therein to inhibit an atmospheric pollutant from contacting skin, comprising the steps of:

(i) filling a sample holder of known dimensions with a known amount of said

composition to form a layer of defined thickness therein;

(ii) depositing, on said layer, a known amount of a model fine particulate matter which resembles a particulate atmospheric pollutant and is responsive to a spectroscopic or microscopic chemical imaging technique;

(iii) performing said chemical imaging;

(iv) for a defined period, recording and analyzing the interaction of said model fine particulate matter with and within said layer by the imaging technique, where interaction indicates the penetration speed of said model fine particulate matter in the layer; and,

(v) ascertaining said efficacy from the information of step (iv)

wherein the slope of a plot of data obtained from said imaging technique against time in the range of 1 to 100 minutes is indicative of short-term efficacy of said composition and the nature of the plot beyond 100 minutes is indicative of long- term efficacy and wherein long-term inhibition factor of said composition is calculated as follows:

Long term inhibition factor

where, x is the distance between the bottom of the chamber and the assumed centre of the Gaussian distribution of the model fine particulate model in the layer, o is the width of the Gaussian distribution and m is the mean of the Gaussian distribution, where it is assumed that distribution of the model fine particulate matter in said layer follows Gaussian distribution.

In accordance with a second aspect is disclosed an apparatus to determine efficacy of a cosmetic composition or an active ingredient comprised therein to inhibit an atmospheric pollutant from contacting skin, comprising:

(i) a sample holder of known dimensions to accommodate a known amount of said composition to form a layer of defined thickness therein;

(ii) means for depositing, on said layer, a known amount of a model fine particulate matter which resembles a particulate atmospheric pollutant and is responsive to a spectroscopic or microscopic chemical imaging technique;

(iii) means for performing said spectroscopic or microscopic chemical imaging technique for a defined period;

(iv) means for recording and analyzing the interaction of said model fine particulate matter with and within said layer by the imaging technique for a defined period, where interaction indicates the penetration speed of said model fine particulate matter in the layer. In accordance with a third aspect is disclosed a process of demonstrating efficacy of a cosmetic composition or an active ingredient comprised therein to inhibit an atmospheric pollutant from contacting skin, comprising the steps of:

(i) filling a sample holder of known dimensions with a known amount of said

composition to form a layer of defined thickness therein;

(iii) for a defined period performing said chemical imaging;

(iv) throughout said defined period, recording and analyzing the interaction of said model fine particulate matter with and within said layer by the imaging technique, where interaction indicates the penetration speed of said model fine particulate matter in the layer; and,

(v) ascertaining and thereby demonstrating said efficacy from the information of step (iv)

wherein the slope of a plot of data obtained from said imaging technique against time in the range of 1 to 100 minutes is indicative of short-term efficacy of said composition and the nature of the plot beyond 100 minutes is indicative of long-term efficacy and wherein long-term inhibition factor of said composition is calculated as follows:

Long term inhibition factor

Detailed description of the invention

As used herein the term“comprising” encompasses the terms“consisting essentially of and“consisting of”. Where the term“comprising” is used, the listed steps or options need not be exhaustive. Unless otherwise specified, numerical ranges expressed in the format "from x to y" are understood to include x and y. In specifying any range of values or amounts, any particular upper value or amount can be associated with any particular lower value or amount. Except in the examples and comparative

experiments, or where otherwise explicitly indicated, all numbers are to be understood as modified by the word“about”. All percentages and ratios contained herein are calculated by weight unless otherwise indicated. As used herein, the indefinite article “a” or“an” and its corresponding definite article“the” means at least one, or one or more, unless specified otherwise. The various features of the present invention referred to in individual sections above apply, as appropriate, to other sections mutatis mutandis. Consequently, features specified in one section may be combined with features specified in other sections as appropriate. Any section headings are added for convenience only, and are not intended to limit the disclosure in any way. The examples are intended to illustrate the invention and are not intended to limit the invention to those examples per se. The term cosmetic composition means any cosmetic composition. More particularly the cosmetic composition is a leave-on cosmetic.“Leave-on" as used herein means compositions that are applied to the skin and are not intended to be washed or rinsed off for some time, as contrasted with cleansing or wash-off or rinse-off compositions. Preferably the leave-on cosmetic composition is a serum, hand creams, face creams, body lotions, make up compositions such as foundations, lipsticks, hair styling gels, hair styling creams and deodorants and antiperspirants such as roll on or sticks. The compositions may accordingly be in a variety of formats as described hereinbefore. The term in vitro means that the method in accordance with the invention is not carried out on human volunteers, for example, on forearms of human volunteers.

The term active ingredient means any ingredient, including film forming polymers included in the cosmetic composition to inhibit or prevent the contact of particulate pollutants with human skin. Non-limiting examples thereof include silicone polymers and extracts of natural products such as extract of roots or leaves of any plant. Human skin acts like a natural shield which protects our body from external influences. However, at times, and under certain conditions, the skin may no longer perform this function fully and efficiently. There is plethora of evidence to substantiate that atmospheric pollutants affect the normal functioning of human skin. Particulate pollutants tend to top the list at least in some countries or some regions of the world.

Formulation scientists have explored and continue to explore newer and more effective cosmetic compositions to protect the skin from particulate pollutants, including the compositions or active agents which can resist, restrict or prevent the contact of such pollutants with skin. However, as discussed at length under the section of background and prior art, there is need for a more robust and reliable method for demonstrating the efficacy of such compositions. The present invention addresses such as need, at least in part. The term particulate pollutant, also called particulate matter or PM, means a mixture of solids and liquid droplets floating in the air. Some particles are released directly from a specific source, while others form in complicated chemical reactions in the atmosphere. Suitable examples include dust, dirt, soot, or smoke. Particulate pollutants are described in terms of particle size: P M2.5 and PM10 having an aerodynamic diameter less than 2.5 pm and 10 pm, respectively. It is preferred that in the method in accordance with the invention, the model fine particulate matter resembles PM_2.5 or PM₁₀ at least in size.

The method in accordance with the invention is carried out on in a sample holder. To perform said method, the sample holder is filled with a known amount of the composition to form a layer of defined thickness therein. Preferably the amount is equivalent to the amount applied under in use conditions. Usually cosmetic compositions comprise water, other volatile solvents or oils. Water and other volatile solvents evaporate upon application of the composition to the skin. On the other hand, where the compositions comprise oils, the oils tend to be absorbed by the skin. Eventually the composition dries up and leaves behind a film or layer on the skin, which, depending on the amount applied or the recommended amount for application, could range from a few microns to few thousand microns. Therefore, preferably the known amount of the composition is that amount which is sufficient to form, upon drying for 12 hours, a layer of 100 to 300 pm in the sample holder. Further preferably the known amount of said composition is from 10 to 100 pl_. It is preferred that the material of construction of said sample holder is non-interfering with the chemical imaging technique. This might become necessary to ensure that the data and thereby the inference drawn from it, is not erroneous. Preferably the length of the sample holder is 200 to 500 pm. further preferably the sample-holder is a cuvette or a microplate having plurality of sample wells arranged in a matrix where each well serves as a sample holder. It is preferred that the material of construction of the sample holder is a polymer, more preferably polystyrene.

Alternatively, the material of construction is a human skin-equivalent, i.e. a material that resembles the skin of human beings. Preferably the human skin-equivalent is artificial skin, or a living skin equivalent. Further preferably it is a regenerated tissue. Currently, several HSEs are commercially available for such applications. Examples include Apligraf^®, Epicel^®, Dermagraft^®, Alloderm^®, Transcyte^®, Orcel^®, Integra^® DRT, Epistem^® and StrataGraft^®. These HSEs can be divided into three major categories: epidermal, dermal, and full-thickness models. A particularly preferred human skin-equivalent is Vitro-Skin®. It is a type of polymeric artificial skin. Other equivalents include cellulose nitrate, nylon or PTFE membrane.

Chemical imaging refers to an analytical method to create a visual image of components distribution from simultaneous measurement of spectra and spatial, time information. Imaging instrumentation has three components: a radiation source to illuminate the sample, a spectrally selective element, and usually a detector array (the camera) to collect the images. The data format is called a hypercube. The data set may be visualized as a data cube, a three-dimensional block of data spanning two spatial dimensions (x and y), with a series of wavelengths (l) making up the third (spectral) axis. The hypercube can be visually and mathematically treated as a series of spectrally resolved images (each image plane corresponding to the image at one wavelength) or a series of spatially resolved spectra. In one aspect the chemical imaging technique is spectroscopic chemical imaging technique. Preferably such a technique is IR, Raman or XRF and said model fine particulate matter is correspondingly responsive to the technique. Alternatively, the chemical imaging technique is microscopic chemical imaging technique. Preferably such a technique is fluorescence microscopy, MS Imaging, light microscopy or SEM and said model fine particulate matter is correspondingly responsive to the technique. It is preferred that the model fine particulate matter comprises a synthetic polymeric material, a natural polymeric material, a water- insoluble salt, a mineral, a metal, an alloy, glass or a mixture thereof. Further preferably the synthetic polymeric material is a polyamide, polyacetate, polyester, polyacrylate, polystyrene, polyethylene, polypropylene, rayon, polyvinyl chloride or a mixture thereof. Further preferably the natural polymeric material is cellulose, regenerated cellulose, starch, microcrystalline cellulose or a mixture thereof. It is particularly preferred that the model fine particulate matter is in the form of beads comprising polystyrene and a fluorescent material, said microscopic imaging technique is fluorescence microscopy. In such a case it is preferred that the diameter of said model fine particulate matter is 200 to 800 nm. This enable easy experimentation. Further preferably the fluorescent material absorbs and emits radiation of wavelength 400 to 800 nm, more preferably 400 to 600 nm. In such a case it is preferred that the intensity of fluorescence of emitted radiation is measured in-line with the excitation radiation. It is particularly preferred that the defined period is from 1 to 150 minutes. In such a case, the slope of a plot of data obtained from said chemical image analysis against time in the range of 1 to 100 minutes is indicative of short-term efficacy and the nature of the plot beyond 100 minutes is indicative of long-term efficacy. It is necessary to be able to determine as accurately as possible, the dynamics of penetration (speed) of a model pollutant from the atmosphere over a period so that is thereby possible to determine the short-term efficacy and the long-term efficacy of cosmetic compositions that claim to prevent, or at least delay the contact of particulate atmospheric pollutants with human skin by forming to the extent possible, a barrier between the skin and the pollutant. Usually, after elapse of time upon application of a leave-on cosmetic composition to the skin, the composition forms a layer on the skin, which performs the intended function. When such a cosmetic is intended to act as a barrier against environmental pollutants such as PM_2.5, in the initial stage the layer effectively prevents or resists the contact of the pollutant with the skin. However, over a period, the pollutant may enter the bulk of the layer and then try to migrate or move towards the skin. The layer will resist this migration, to the extent it can, depending on the nature of the composition and the efficacy of active ingredient therein, if any, such as film forming polymers. Eventually the pollutant may even pass through the layer and establish contact with the skin.

To be able to get the data pertaining to long and short-term efficacy, said data is preferably collected at intervals of every 3 to 10 minutes starting from T=0. In such a case, the slope of the linear fit of the data between T=0 to T=100, more preferably T=0 to T=75 minutes indicates the penetration speed of said model fine particulate matter in the layer. The reciprocal of this slope (1/slope) indicates the short-term inhibition factor of said composition Using this information, it becomes possible to easily and correctly distinguish between an efficacious composition from a non-efficacious composition or even a less efficacious composition from a more efficacious or potent composition.

Further in the method according to the invention, the long-term inhibition factor of the composition is calculated as:

Long term inhibition factor

In accordance with the present invention, it is particularly preferred that the model fine particulate matter is in the form of beads comprising polystyrene and a fluorescent material, said microscopic imaging technique is fluorescence microscopy and said human skin-equivalent is artificial skin. A particularly preferred material is Fluorescent Probes, which are Polystyrene-based particles (1 pm diameter) with fluorescent tagging Ex. Polysciences Inc.

To ensure that there is negligible interference during the measurement/analysis, it is preferred that the material of construction of said sample holder is unresponsive to the chemical image analysis. Preferably the length of said sample holder is 200 to 500 pm. Further preferably sample-holder is a cuvette or a microplate having plurality of sample wells arranged in a matrix where each well serves as a sample holder.

Plate readers, also known as microplate readers or microplate photometers, are instruments which are used to detect biological, chemical or physical events of samples in microtiter plates. They are widely used in research, drug discovery, bioassay validation, quality control and manufacturing processes in the pharmaceutical and biotechnological industry and academic organizations. Sample reactions can be assayed in 6 to 1536 well format microtiter plates. The most common microplate format used in academic research laboratories or clinical diagnostic laboratories is 96-well (8 by 12 matrix) with a typical reaction volume between 100 and 200 pL per well. Higher density microplates (384- or 1536-well microplates) are typically used for screening applications, when throughput (number of samples per day processed) and assay cost per sample become critical parameters, with a typical assay volume between 5 and 50 pL per well. Common detection modes for microplate assays are

absorbance, fluorescence intensity, luminescence, time-resolved fluorescence, and fluorescence polarization.

Fluorescence detection technique has been used widely along with microplate readers. In this type of instrumentation, a first optical system (excitation system) illuminates the sample using a specific wavelength (selected by an optical filter, or a monochromator). As a result of the illumination, the sample emits light (it fluoresces) and a second optical system (emission system) collects the emitted light, separates it from the excitation light (using a filter or monochromator system), and measures the signal using a light detector such as a photomultiplier tube (PMT). It is preferred that the known amount of the composition is that amount which is sufficient to form, upon drying for 12 hours, a layer of 100 to 300 pm in the sample holder. The known amount of the composition, preferably, is from 10 to 100 pL.

To simulate actual real-life situation to the extent possible, the amount of the model particulate matter should be enough to simulate such conditions. Therefore, it is preferred that 1 to 10 pL of said model fine particulate matter is deposited on the layer. The demonstration may be useful for any consumer promotion event, or a consumer demonstration such as in a mall or supermarket or a consumer fair. The demonstration may also be useful for claim support and advertising.

The Composition

The compositions can be applied directly to the skin. Alternatively, they can be delivered by various transdermal delivery systems, such as transdermal patches as known in the art. For example, for topical administration, the active ingredient can be formulated in a solution, gel, lotion, ointment, cream, suspension, paste, liniment, powder, tincture, aerosol, patch, or the like in a cosmetically acceptable form by methods known in the art. The composition can be any of a variety of forms common in the cosmetic arts for topical application to humans.

The compositions may be made into a wide variety of product types that include but are not limited to solutions, suspensions, lotions, creams, gels, toners, sticks, sprays, ointments, pastes, foams, powders, mousses, strips, patches, electrically-powered patches, hydrogels, film-forming products, facial and skin masks, make-up such as foundations and the like. These product types may contain several types of

cosmetically-acceptable carriers including, but not limited to solutions, suspensions, emulsions such as microemulsions and nanoemulsions, gels, solids and liposomes.

The compositions can be formulated as solutions which include an aqueous or organic solvent, e.g., 50 to 90 wt% of a cosmetically acceptable aqueous or organic solvent. Examples of suitable organic solvents include: propylene glycol, polyethylene glycol (200-600), polypropylene glycol (425-2025), glycerol, 1 ,2,4-butanetriol and sorbitol esters. A lotion can be made from such a solution. Lotions typically contain from about 1% to about 20 wt% emollient(s) and from 50 to 90 wt% owater.

Another type of product that may be formulated from a solution is a cream. A cream typically contains 5 to 50 wt% emollient(s) and 45 to 85 wt% water.

The compositions described herein can also be formulated as emulsions. If the carrier is an emulsion, then 1 to 10 wt% of the carrier contains an emulsifier(s). Emulsifiers may be nonionic, anionic or cationic.

Lotions and creams can be formulated as emulsions. Typically, such lotions contain 0.5 to 5 wt% emulsifier(s), while such creams typically contain 1 % to 20 wt% emulsifier(s).

Single emulsion skin care preparations, such as lotions and creams, of the oil-in-water type and water-in-oil type are well-known in the art and are useful in compositions and methods described herein. Multiphase emulsion compositions, such as the water-in-oil- in-water type or the oil-in-water-in-oil type, are also useful in the compositions and methods describe herein. In general, such single or multiphase emulsions contain water, emollients, and emulsifiers as essential ingredients.

The compositions described herein can also be formulated as a gel (e.g., an aqueous, alcohol, alcohol/water, or oil gel using a suitable gelling agent(s)). Suitable gelling agents for aqueous and/or alcoholic gels include, but are not limited to, natural gums, acrylic acid and acrylate polymers and copolymers, and cellulose derivatives (e.g., hydroxymethyl cellulose and hydroxypropyl cellulose). Suitable gelling agents for oils (such as mineral oil) include, but are not limited to, hydrogenated

butylene/ethylene/styrene copolymer and hydrogenated ethylene/propylene/styrene copolymer. Such gels typically contain 0.1 to 5 wt% gelling agents.

Cosmetic compositions described herein may typically comprise a derivative of any compound or composition described herein and optionally, a polar solvent. Solvents suitable for use in the formulations described herein include any polar solvent capable of dissolving the derivative. Suitable polar solvents may include: water; alcohols (such as ethanol, propyl alcohol, isopropyl alcohol, hexanol, and benzyl alcohol); polyols (such as propylene glycol, polypropylene glycol, butylene glycol, hexylene glycol, maltitol, sorbitol, and glycerine); and panthenol dissolved in glycerine, flavor oils and mixtures thereof. Mixtures of these solvents can also be used. Exemplary polar solvents may be polyhydric alcohols and water. Examples of solvents may include glycerine, panthenol in glycerine, glycols such as propylene glycol and butylene glycol, polyethylene glycols, water and mixtures thereof. Additional polar solvents for use may be alcohols, glycerine, panthenol, propylene glycol, butylene glycol, hexylene glycol and mixtures thereof.

An emollient may also be added. The emollient component can comprise fats, oils, fatty alcohols, fatty acids and esters which aid application and adhesion, yield gloss and provide occlusive moisturization. Suitable emollients for use may be isostearic acid derivatives, isopropyl palmitate, lanolin oil, diisopropyl dimerate, maleated soybean oil, octyl palmitate, isopropyl isostearate, cetyl lactate, cetyl ricinoleate, tocopheryl acetate, acetylated lanolin alcohol, cetyl acetate, phenyl trimethicone, glyceryl oleate, tocopheryl linoleate, wheat germ glycerides, arachidyl propionate, myristyl lactate, decyl oleate, propylene glycol ricinoleate, isopropyl linoleate, pentaerythrityl tetrastearate, neopentylglycol dicaprylate/dicaprate, hydrogenated coco-glycerides, isononyl isononanoate, isotridecyl isononanoate, myristyl myristate, triisocetyl citrate, cetyl alcohol, octyl dodecanol, oleyl alcohol, panthenol, lanolin alcohol, linoleic acid, linolenic acid, sucrose esters of fatty acids, octyl hydroxystearate and mixtures thereof. Examples of other suitable emollients can be found in the Cosmetic Bench Reference, (1996), or in the International Cosmetic Ingredient Dictionary and Handbook, eds. Wenninger and McEwen, pp. 1656-61 , 1626, and 1654-55 (The Cosmetic, Toiletry, and Fragrance Assoc., Washington, D.C., 7.sup.th Edition, 1997) (hereinafter "ICI

Handbook").

Other suitable solid/liquid agents may include vitamins and their derivatives.

Compositions of the present invention may include vitamins as the desired active. Illustrative vitamins are Vitamin A (retinol) as well as retinol esters like retinol palmitate and retinol propionate, Vitamin B2, Vitamin B3 (niacinamide), Vitamin B6, Vitamin C, Vitamin D, Vitamin E, Folic Acid and Biotin. Derivatives of the vitamins may also be employed. For instance, Vitamin C derivatives include ascorbyl tetraisopalmitate, magnesium ascorbyl phosphate and ascorbyl glycoside. Derivatives of Vitamin E include tocopheryl acetate, tocotrienol, tocopheryl palmitate and tocopheryl linoleate. DL-panthenol and derivatives may also be employed. Total amount of vitamins when present in the compositions may range from 0.001 to 10%. Sunscreen agents may also be included in compositions of the present invention as solid/liquid agents. Particularly preferred are such materials as phenylbenzimidazole sulfonic acid (Ensulizole), ethylhexyl salicylate (octyl salicylate), ethylhexyl p- methoxycinnamate, available as Parsol MCX.RTM., Avobenzene, available as Parsol 1789®. and benzophenone-3, also known as Oxybenzone®. Octocrylene is also suitable for use. Amounts of the sunscreen agents when present may generally range from 0.1 to 30 wt%.

Suitable oils include esters, triglycerides, hydrocarbons and silicones. These can be a single material or a mixture of one or more materials. They may normally comprise 0.5 to 90 wt%.

Examples of surface active agents which may be used in the compositions described herein include sodium alkyl sulfates, e.g., sodium lauryl sulfate and sodium myristyl sulfate, sodium N-acyl sarcosinates, e.g., sodium N-lauroyl sarcosinate and sodium N- myristoyl sarcosinate, sodium dodecylbenzenesulfonate, sodium hydrogenated coconut fatty acid monoglyceride sulfate, sodium lauryl sulfoacetate and N-acyl glutamates, e.g., N-palmitoyl glutamate, N-methylacyltaurin sodium salt, N- methylacylalanine sodium salt, sodium alpha-olefin sulfonate and sodium

dioctylsulfosuccinate; N-alkylaminoglycerols, e.g., N-lauryl-diamino-ethylglycerol and N-myristyldiaminoethylglycerol, N-alkyl-N-carboxymethylammonium betaine and sodium 2-alkyl-1-hydroxyethylimidazoline betaine; polyoxyethylenealkyl ether, polyoxyethylenealkylaryl ether, polyoxyethylenelanolin alcohol, polyoxyethyleneglyceryl monoaliphatic acid ester, polyoxyethylenesorbitol aliphatic acid ester, polyoxyethylene aliphatic acid ester, higher aliphatic acid glycerol ester, sorbitan aliphatic acid ester, Pluronic type surface active agent, and polyoxyethylenesorbitan aliphatic acid esters such as polyoxyethylenesorbitan monooleate and polyoxyethylenesorbitan

monolaurate. Emulsifier-type surfactants known to those of skill in the art can be used in the compositions described herein.

The surfactants can be used at levels from 4 to 90% depending on the type of the composition. In addition, these compositions may include therapeutic agents, carriers, adjuvants, and the like. Some particular additional agents may include retinoids; antioxidants; hydroxy acids; fatty acids, acceptable non-toxic metal salts of naturally occurring amino acids or of hydroxyalkyl acids; botanical extracts, salicylic acid, keratolytic agents, complexing agents, colorants and fragrance ingredients.

The invention will now be described in detail with the following non-limiting examples. Examples Example 1 :

The method of the invention was carried out on two cosmetic creams, each comprising the same film forming polymer. One of the creams had 3 wt% polymer while the other had 7 wt% polymer. For negative control, a third composition, devoid of the polymer, was also prepared but which was identical to the other two in all other respects.

The formulations of the compositions tested were as follows:

Table 1

Fluoresbrite® YG carboxylate microspheres (2.5% aqueous suspension), from

Polysciences, were used as model PM 2.5, which are carboxy-modified monodispersed polystyrene particles with nominal diameters of 0.5 pm. Their maximum excitation and emission spectrums peak at 441 nm and 486 nm respectively.

The measurement chambers were adapted from Corning Costar® 48 well clear TC- Treated Multiple Well Plates (product #3548). The plates were made by polystyrene material with flat bottom, the growth area for each well is 0.95 cm². During the sample preparation step, 80 pL of sample skin product cream was injected by multi-channel pipette into each well, centrifugation (3000 RPM, 5 minutes) on the horizontal plane is applied to the plate smooth the cream surface level and get rid of the air inside the cream. The cream samples were placed in fume hood for eight hours at room temperature until the thickness of the layer of the cream was about 100 pm after this drying process. Before measurement, one droplet of model pollutant suspension (3 pL) was added via pipette on top of the layer at time T=0.

Excitation and emission radiations were set at 441 nm and 486 nm for the highest detection sensitivity, the measurement lasted for about 3 hours. The sample cream products in all 24 wells could be measured simultaneously, and the total fluorescence of each well was recorded as a function of time for every five minutes.

As the model pollutant penetrates through sample cream layer, the total fluorescence intensity increases as a function of time. A linear fit is used to describe the increase of the time-dependent fluorescence intensity. The slope from linear fit was used to indicate the penetration speed of the model pollutant through the layer. The efficacy of the cosmetic composition to inhibit the atmospheric pollutant (in this experiment, the model) from contacting skin is directly proportional to the slope.

The observations are tabulated in Table 2 below.

Table 2

The data in Table 1 makes it clear that the composition comprising 7 wt% MQ is the most efficacious of all. While this inference is not surprising or unexpected in itself, the method in accordance with the invention is a robust method to arrive at such an inference, especially to distinguish between the efficacy of two or more closely related compositions which claim to provide one and the same benefit.

Long term efficacy

During the experiments, it is observed that beyond a particular time, the intensity of fluorescence reaches a plateau, i.e., there is little change in the values. At this stage the intensity is the highest. This time is considered to represent the steady state at which movement of the model particulate pollutant in the layer of the cosmetic composition has considerably slowed, down therefore the intensity of fluorescence remains virtually constant.

At such a stage if it is assumed that the distribution of the model particulate pollutant in the layer of the cosmetic composition follows Gaussian distribution, it is possible to determine the total intensity fluorescence at this steady state by the following equation:

Long term inhibition factor = )

The penetration speed of the model particulate pollutants in the film can then be defined as 1-/₀ p(x) dx

where L = thickness of the layer of the cosmetic composition.

The data shown in Table 2 was subject to further analysis and calculations after which the short-term inhibition factor of each composition and the penetration speed of the model pollutant in the layer of the composition was determined. This information is tabulated in Table 3.

Table 3

Note: The R² for the linear fit was about 0.99 for each of the three slopes The slope is inversely proportional to the efficacy of the composition

The data in Table 3 clearly indicates not only that Formulation 2 is far more efficacious than Formulation 1 but also the extent by which it is efficacious, thereby informing formulation scientists about how such products could be formulated efficiently to thereby get the desired extent of protection against pollutants, especially particulate pollutants. The long-term inhibition factor (for readings from 120 to 220 minutes) was determined as the penetration speed and long-term inhibition factor (1 - penetration speed). It was assumed that the population of the model pollutant inside the creams follows a normal (Gaussian) distribution. This data is tabulated in Table 4.

Table 4

The data in Table 4 again clearly reiterates the observations and inference that is drawn from the data contained in Table 3.

The illustrated examples clearly indicate that the method in accordance with the invention is a robust and reliable tool for measuring and comparing the efficacy of cosmetic cleansing compositions to remove particulate pollutants adhering to the skin. The method could be used to measure and demonstrate cleansing efficacy of cosmetic cleansing compositions against atmospheric pollutants, especially particulate pollutants such as PM2.5 and PM10. The testing could be monadic, alternatively paired-testing or further alternatively discrete-choice testing. Outcome of the method could potentially be useful for relative ranking of various cleansing compositions belonging to the same category of products, such as a soap-based cleanser v/s a non-soap surfactant-based cleanser, or even, where necessary, between two or more products belonging to different categories of products for example, a shampoo against a soap bar. The method could also be useful to determine the efficacy of one or more active ingredients such as surfactants and polymers by suitably formulating the candidate compositions to be tested. Further, the method of the invention could also be used as a demonstration tool for consumer promotion or activation of new or existing cosmetic cleansing compositions. Outcome of the method could also be used for claim-support.

Claims

1. An in vitro method to determine efficacy of a cosmetic composition or an active

ingredient comprised therein to inhibit an atmospheric pollutant from contacting skin, comprising the steps of:

(i) filling a sample holder of known dimensions with a known amount of said composition to form a layer of defined thickness therein;

(iii) performing said chemical imaging;

(iv) for a defined period, recording and analyzing the interaction of said

model fine particulate matter with and within said layer by the imaging technique where interaction indicates the penetration speed of said model fine particulate matter in the layer; and,

(v) ascertaining said efficacy from the information of step (iv)

Long term inhibition factor

2. A method as claimed in claim 1 wherein said model fine particulate matter

resembles PM2.5 or PM10 at least in size.

3. A method as claimed in claim 1 or 2 wherein said spectroscopic chemical imaging technique is IR, Raman or XRF and said model fine particulate matter is correspondingly responsive to said technique.

4. A method as claimed in claim 1 or 2 wherein said microscopic chemical imaging technique is fluorescence microscopy, MS Imaging, SEM or light microscopy and said model fine particulate matter is correspondingly responsive to said technique.

5. A method as claimed in any of claims 1 to 4 wherein said defined period is from 1 to 150 minutes.

6. A method as claimed in claim 5 wherein said data is collected at intervals of every 3 to 10 minutes starting from T=0.

7. A method as claimed in claim 5 or 7 wherein slope of the linear fit of the data between T=0 to T=75 minutes indicates the penetration speed of said model fine particulate matter in said layer.

8. A method as claimed in any of claims 1 to 7 wherein said model fine particulate matter comprises a synthetic polymeric material, a natural polymeric material, a water- insoluble salt, a mineral, a metal, an alloy, glass or a mixture thereof.

9. A method as claimed in claim 8 wherein said model fine particulate matter is in the form of beads comprising polystyrene and a fluorescent material, said microscopic imaging technique is fluorescence microscopy.

10. A method as claimed in any of claims 1 to 9 wherein said sample-holder is a cuvette or a microplate having plurality of sample wells arranged in a matrix where each well serves as a sample holder.

11. A composition as claimed in any of claims 1 to 10 wherein said known amount of said composition is that amount which is sufficient to form, upon drying for 12 hours, a layer of 100 to 300 pm in the sample holder.

12. An apparatus to determine efficacy of a cosmetic composition or an active

ingredient comprised therein to inhibit an atmospheric pollutant from contacting skin, comprising:

(iii) means for performing said spectroscopic or microscopic chemical

imaging technique for a defined period;

(iv) means for recording and analyzing the interaction of said model fine particulate matter with and within said layer by the imaging technique for a defined period, where interaction indicates the penetration speed of said model fine particulate matter in the layer.