Effects of solar radiations on stratum corneum hydration: Part I, protective role of skin surface lipids.

This study used Raman spectroscopy to develop a new approach to evaluate the effects of solar radiation on the stratum corneum (SC). The method measures the SC's hydration and dehydration kinetics by calculating the vOH/vCH ratio to monitor the relative water content during the drying process. The study also investigated the role of skin surface lipids (SSLs) in protecting the SC from solar radiation. The SSLs film is a complex mixture of free fatty acids, triglycerides, wax esters, squalene, free and esterified cholesterols, that play a crucial role in the skin's barrier function. The results showed that solar radiation alters the water content and balance within the SC, and SSLs provide protection by acting as an optical filter by absorbing some of the energy of the solar light. This is confirmed by high temperature gas chromatography coupled to mass spectrometry analyses by revealing a decrease in specific lipids after irradiating the SSLs .

Characterization of triglycerides photooxidation under solar radiations: A stepwise Raman study.

Triglycerides (TGs) are one of the main components of the glycerolipid family. Their main task in cells is to store excess fatty acids. TG energy storage is mainly concentrated in adipocytes. TGs and free fatty acids constitute the majority (57.5%) of the skin surface lipids (SSLs). TGs are essential for the formation of the skin water barrier. This work is the second part of a global study that aims to evaluate the effect of solar radiations on SSLs using vibrational spectroscopy. In the first part of this work, a stepwise characterization of free fatty acids was performed, and different spectral descriptors were used to follow the different structural modifications during the photo-oxidation process, that is hydrogen abstraction, formation of hydroperoxides and peroxyl radicals as primary oxidation products and the formation of aldehydes, ketones, alcohol as secondary products. In this second part, the photo-oxidation of TGs was evaluated using Raman spectroscopy. A decrease in the CH2/CH3 stretching bands ratio that confirmed the hydrogen abstraction, an increase in the 1165/1740 cm-1 ((δ(OH) and υ(C-O))/ν(C=O) (ester)) ratio indicated the formation of secondary oxidation products such as hydroperoxides. And finally, an increase in the 1725/1740 cm-1 (υ(C=O) (ald.)/υ(C=O) (ester)) ratio and the trans ν(C=C)/cis ν(C=C) ratio highlighted the formation of aldehydes, alcohols, ketone, trans secondary products and others.

Studying the effects of suberythemal UV doses on the human stratum corneum by in vivo confocal Raman spectroscopy

Background: The stratum corneum (SC) plays an important role in skin barrier function. It acts as a protective barrier against water loss, eliminates foreign substances and micro-organisms and acts against harmful effects of UVR. Objectives: Our aim was to study the impact of suberythemal doses of UVA and UVB exposure on the molecular structure, organization and barrier function of the SC by following different Raman descriptors. Materials & Methods: Twenty female volunteers, aged 20-30 years, with healthy skin were enrolled. Doses of 95 mJ/cm² UVA and 15 mJ/cm² UVB were applied to volunteers' forearms. In vivo Raman measurements were performed at irradiated and control regions. Results: The impact of UVA and UVB irradiation was observed following several Raman descriptors, i.e. the ratio of vasymCH2/vsymCH2 (2885 cm-1/2850 cm-1) corresponding to the organizational order of the lipid bilayer. Water content and mobility descriptors were obtained by calculating vOH/vCH ratio. Finally, protein secondary structure was evaluated based on the 1670 cm-1/1650 cm-1 ratio related to ß sheets and α helices, respectively. Conclusion: UVA induced a loosening of the lateral packing of lipids immediately after irradiation. In contrast, delayed impact caused a tightening of the lipid barrier, an increase in water content -mainly in the unbound water fraction and a higher relative amount of ß sheets in SC proteins. Overall, these observations may explain the thickening of the SC observed in previous studies. A UVB dose of 15 mJ/cm² was apparently below the threshold necessary to induce significant changes despite the trends observed in this study.

Stratum corneum ceramide profiles in vitro, ex vivo, and in vivo: characterization of the α-hydroxy double esterified ceramides.

The presence of a new ceramide subclass, the 1-O-acyl omega-linoleoyloxy ceramides [1-O-E (EO) Cer], has been previously highlighted in reconstructed human epidermis (RHE). These ceramides are double esterified on two positions. The first is the 1-O position of the sphingoid base moiety with a long to very long chain of acyl residues (1-O-E), and the second is the position of the ω-hydroxyl group of the fatty acid moiety with linoleic acid (EO). Considering its chemical structure and hydrophobicity, this subclass can contribute to the skin barrier. Thus, it is important to determine whether this subclass is also present in native human stratum corneum (SC). This work compares ceramide structures of this novel subclass between RHE (in vitro) and two sources of human SC (in vivo and ex vivo) using normal-phase high-performance liquid chromatography coupled to high-resolution mass spectrometry (NP-HPLC/HR-MSn). The results confirm the presence of this double esterified ceramide subclass [1-O-E (EO) Cer] in human SC. The molecular profile obtained from the RHE was very close to that found in the human SC (in vivo and ex vivo). In addition, thanks to the targeted MS2/MS3 analysis, a new ceramide subclass was discovered and characterized in the three studied samples. We propose to name it [A-1-O-E (EO) Cer] because in these ceramides species, the fatty acid-esterified with the sphingoid base on the 1-O position-is hydroxylated on the α position. These results highlight the potential of both the analytical method and the characterization approach employed in this study.

EBT3 Gafchromic® film as a new substrate for in vitro evaluation of sun protection factor.

There exist different methods for the determination of sun protection factor (SPF) values for sunscreens. We aimed to develop a new in vitro method using EBT3 Gafchromic® film as a substrate. The colour of EBT3 Gafchromic® film changes when exposed to UV light. Films were covered by sunscreen preparations of different SPF values ranging from 0 to 50. Uncovered and covered films were exposed to different solar light energies and their colour change was compared. Absorbance spectra of films was measured at 633 nm using a UV-VIS spectrophotometer apparatus. The colour of the film darkens when ultraviolet energy increases, which means that absorbance increases with exposure time. However, when films are covered by sunscreens, the colour change is less visible and the absorbance significantly decreases with increasing SPF value. There is a linear correlation between the absorbance of EBT3 Gafchromic® film and SPF value of sunscreens covering the film. Statistical analysis demonstrated that the SPF value of a sunscreen can be predicted using EBT3 Gafchromic® film as a substrate. This is the first report of an in vitro method based on colour change of a substrate which takes into consideration exposure time, and relates more closely to conditions of real-life. Based on these parameters, this is a reliable in vitro method for SPF testing.

Raman confocal microscopy and biophysics multiparametric characterization of the skin barrier evolution with age.

Skin aging is a multifactorial phenomenon that involves alterations at the molecular, cellular and tissue levels. Our aim was to carry out a multiparametric biophysical and Raman characterization of skin barrier between individuals of different age groups (<24 and >70 years old). Our results showed a significant decrease of lipids to proteins ratio overall the thickness of the stratum corneum and higher lateral packing in the outer part of the SC for elderly. This can explain the decrease in trans epidermal water loss measured values rather than only SC thickening. Both age groups showed similar water content at SC surface while elderly presented higher water content in deep SC and viable epidermis. Mechanical measurements showed a decrease in the elasticity and an increase in the fatigability with age and were correlated with partially bound water. Highest correlation and anti-correlation values were observed for the deepest part of the SC and the viable epidermis.

Assessment of the skin barrier function in the reconstructed human epidermis using a multimodal approach at molecular, tissue and functional levels.

Reconstructed human epidermis models are used as epidermis alternatives in skin research studies. It is necessary to provide molecular and functional characterization in order to assess these models. Our aim is to establish a link between the barrier function and the structure and composition of the stratum corneum using several complementary techniques. The following three studies were performed on reconstructed human epidermis during the keratinocyte differentiation process: (i) caffeine percutaneous penetration kinetics, (ii) epidermis thickness measurement, stratum corneum formation and lipid organization by Raman microspectroscopy and (iii) lipid composition evolution by liquid chromatography coupled to high-resolution mass spectrometry. The results demonstrated that the caffeine penetration decreased along the differentiation process. Raman in-depth images demonstrated an increase in stratum corneum and RHE thickness accompanied by the evolution of lipid organization. Lipid analysis showed an increase of the ceramide amount and an inverse relationship between ceramide and its precursor levels during the differentiation process. Different behaviors between several ceramide subclasses are highlighted and they relied on the corresponding differentiation stages. The generation of the most important ceramides for the barrier function is closely followed. A period shift between lipid generation and their organization was found. Our analytical data allowed identifying the following 3 groups of maturation days: before day 15, between days 15 and 19, and after day 19. The chemical and physiological states of the barrier function for each group are described thanks to a multimodal approach.

Biomolecular modifications during keratinocyte differentiation: Raman spectroscopy and chromatographic techniques.

From the basal layer until the stratum corneum, lipid and protein biomarkers associated with morphological changes denote keratinocyte differentiation and characterize each epidermis layer. Herein, we followed keratinocyte differentiation in the early stages using HaCaT cells over a period of two weeks by two complementary analytical techniques: Raman microspectroscopy and high-performance liquid chromatography coupled with high resolution mass spectrometry. A high concentration of calcium in the medium induced HaCaT cell differentiation in vitro. The results from both techniques underlined the keratinocyte passage from the granular layer (day 9) to the stratum corneum layer (day 13). After 13 days of differentiation, we observed a strong increase in the lipid content, decrease in proteins, decrease in DNA, and a decrease in glucosylceramides/ceramides and sphingomyelins/ceramides ratios.

Comprehensive characterization of the structure and properties of human stratum corneum relating to barrier function and skin hydration: modulation by a moisturizer formulation.

The stratum corneum (SC) is key in the maintenance of the biomechanical barrier and hydration of skin. Our previous investigations showed beneficial effects of a combination of emollients on water capture and retention and protein and lipid organization, all of which are linked to dryness and dry skin damage. Here, we show how a formulation containing an emollient combination ("Trio") and its basal formulation (placebo) impacted the descriptors of SC hydration in SC layers. Only the Trio formulation-not its placebo formulation-modified SC biomechanical drying stress behaviour and imparted a high capacity to protect it from dehydration. This was in accordance with findings at the molecular level using Raman analyses and at the structural level using cryo-scanning electron microscopy (SEM). After topical application, only the Trio formulation profoundly increased lateral packing of lipids and their compactness. Cryo-SEM showed that, unlike the placebo formulation, the Trio formulation prevented the water loss when applied before the dehydration process. In conclusion, these studies demonstrate that stresses in the SC due to dehydration can be alleviated using a formulation containing emollients that interact with the SC lipid components.

The stratum corneum water content and natural moisturization factor composition evolve with age and depend on body site.

BACKGROUND: The study objective was to examine if age and chronic environmental exposure affect the water content and the composition of the natural moisturizing factors (NMFs) of the stratum corneum (SC). METHODS: Forty healthy Caucasian women 18-70 years of age were recruited. Measurements were done on the cheek and on two skin sites on the arm (one relatively protected and one exposed to environmental factors). SC water content and NMF composition were measured by Raman confocal microspectroscopy. RESULTS: The SC water content was gradually reduced with age, reaching statistically significant levels only on the exposed arm site. The SC water content remained higher on the face than on the two arm sites throughout the ages tested. The age-dependent concentration changes of various amino acids were species-specific, potentially indicating different protein sources. Interestingly, on the arm sites, the sum of decreasing amino acid concentrations is compensated by the sum of those increasing, resulting in constant total amino acid content. However, on the face, the total amino acid content statistically increased with age potentially relating to the declining cell turnover rates. The lactate content was higher on the face for all ages and statistically decreased on both arm sites. CONCLUSION: Both chronological aging and chronic exposure to environmental factors mildly affect SC hydration, while they have variable effects in the concentrations of NMF components. The dynamics of NMF composition may at least partially explain the age-related changes in SC hydration.

Skin surface lipid composition in women: increased 2,3-oxidosqualene correlates with older age.

The importance of the hydrolipidic film of skin has been well documented, however, few data are available in cases of very old age. Our aim was to characterize the difference in skin surface lipid (SSL) composition between individuals of different age groups. Data were collected from the forehead of 22 young volunteers (18-24 years old) and 18 senior volunteers (70-75 years old). The amount of sebum was obtained by sebumetry. To acquire relevant information about the molecular composition of high complex mixtures, SSLs were analysed in a single run to ensure that the lipid structures remain intact, using high-temperature gas chromatography coupled with mass spectrometry. The major features associated with aged skin were documented. In aged skin, a lower sebum content was observed, together with modification of the relative SSL composition involving a significant reduction in the intensity of many components of the hydrolipidic film. In contrast, the intensity of 2,3-oxidosqualene was shown to increase with an inverse relationship between triglycerides and their hydrolytic products. These adaptations could be related to modifications of enzymatic activity.

Nanoscale investigation of human skin and study of skin penetration of Janus nanoparticles.

Janus nanoparticles (JNP) are innovative nanocarriers with an interesting pharmaceutical and cosmetic potential. They are characterized by the presence of a lipid compartment associated with an aqueous compartment delimited by a phospholipid bilayer containing phospholipids and non-ionic surfactants. The hydrodynamic diameter of JNP varies between 150 and 300 nm. The purpose of this study was to answer the following questions: after cutaneous application, are JNP penetrating? If so, how deep? And in which state, intact or degraded? It was essential to understand these phenomena in order to control the rate and kinetics of diffusion of active ingredients, which can be encapsulated in this vehicle for pharmaceutical or cosmetic purposes. An innovative technique called AFM-IR, was used to elucidate the behavior of JNP after cutaneous application. This instrument, coupling atomic force microscopy and IR spectroscopy, allowing to perform chemical analysis at the nanometer scale thanks to local absorption measurements. The identification of organic molecules at the nanoscale is possible without any labelling. Before cutaneous application of JNP, the nano-structure of untreated human skin was investigated with AFM-IR. Then, in vitro human skin penetration of JNP was studied using Franz cells, and AFM-IR allowed us to perform ultra-local information investigations.

Comprehensive characterization and simultaneous analysis of overall lipids in reconstructed human epidermis using NPLC/HR-MSn: 1-O-E (EO) Cer, a new ceramide subclass.

Stratum corneum lipids are responsible for the skin's barrier function. They are the final product of epidermis lipid biosynthesis. During this process, lipids evolve from simple to complex structures in three main levels respectively (stratum basal level, stratum granulosum level, and stratum corneum level). Our aim was to simultaneously analyze and characterize the structure of total epidermis lipids. A powerful analytical method (normal-phase liquid chromatography coupled with high-resolution mass spectrometry (NPLC/HR-MSn)) was developed in order to separate, in a single run, lipid classes with a wide polarity range. Chromatographic conditions were particularly designed to analyze lipids of intermediate polarity such as ceramides. Rich information was obtained about the molecular structure of keratinocyte differentiation biomarkers such as ceramides, glucosylceramides, and sphingomyelins and the microstructures of reconstructed human epidermis lipids using HR-MSn. A new subclass of ceramides, 1-O-Acyl Omega-linoleoyloxy ceramides [1-O-E (EO) Cer] has been highlighted. This class is double esterified on the 1-O-position of sphingoid base with long to very long chain acyl residues (1-O-E) and on the position of ω-hydroxyl group of fatty acid with the linolenic acid (EO). Considering its chemical structure and hydrophobicity, this subclass can contribute to the skin barrier. In addition, we detected a new epidermis sphingomyelins. Our lipidomic approach offers a direct access to epidermis biomarkers.

Skin lightening effect of natural extracts coming from Senegal botanical biodiversity.

BACKGROUND: Skin depigmentation is increasingly oriented toward plant extracts because of harmfulness of depigmenting active ingredients used in cosmetics and dermatology. Reconstructed human pigmented epidermis (RHPE) is the closest in vitro model to human skin and offers the possibility to test the global depigmenting effect of a plant extract. These co-cultures of keratinocytes and melanocytes are the most advanced and newest models for testing depigmentation, and until now very few studies have been done with these cultures. We investigated the cytotoxicity and the inhibitory effect on tyrosinase and melanogenesis of four extracts from Combretum micranthum (G. Don) leaves, Anacardium occidentale (L.) fruits, Moringa oleifera (Lam.) seeds, and Adansonia digitata (L.) seeds. METHODS: The vegetal extracts were obtained by ultrasound-assisted extraction and the vegetal oils by maceration. Anti-tyrosinase properties of two aqueous extracts were evaluated. Then, the cytotoxicity and depigmenting effects of these plant extracts were tested in vitro with RHPE model delivered by SkinEthic® . RESULTS: Antityrosinase activities were found to be 84.58% and 31.02% for C. micranthum and A. occidentale, respectively. All extracts, except A. occidentale, showed to be nontoxic. C. micranthum, M. oleifera, A. digitata, and mixture of M. oleifera and A. digitata extracts have shown, for the first time, an in vitro depigmenting activity equivalent or even more important than kojic acid. CONCLUSIONS: These natural extracts coming from Senegal botanical biodiversity could be used in cosmetic and dermatology as alternative agents to achieve skin depigmentation. Further study should be focused on the mechanism of action of these plant extracts.

ATR-FTIR Characterization of Janus Nanoparticles-Part II: Follow-Up Skin Application.

Attenuated total reflection by Fourier transform infrared (ATR-FTIR) was used to implement reliable infrared descriptors over time of Janus nanoparticles (JNP), to follow their behavior before and after cutaneous application. In the last study, ATR-FTIR spectroscopic analysis allowed us to identify the evolution of intensity ratio of ν(C=O) at 1739 cm-1 and δ(H-O-H) at 1639 cm-1 as a spectroscopic descriptor, for JNP before cutaneous application (on the CaF2 window). This descriptor can be used to follow the physical stability (presence) of nanoparticles over time. The purpose of this study was to understand the behavior of JNP on the surface of the human skin. Therefore, a comparative study with the untreated skin and the skin after cutaneous application of lipophilic phase (Labrafil) of JNP was conducted using Franz cells. The suitability of the ATR-FTIR descriptor of JNP was evaluated, and a research of other descriptors was performed to understand the interaction that may exist between nanoparticles and the skin.

Phytochemical screening and antityrosinase activity of carvacrol, thymoquinone, and four essential oils of Lebanese plants.

OBJECTIVE: In our study, we aim to explore the ability of four essential oils (EO) of Lebanese plants to inhibit the tyrosinase activity and to correlate their efficiency level to their phytochemical compositions. METHODS: The EO have been extracted by hydrodistillation using a Clevenger apparatus and have been studied by GC-MS analysis. Active compounds of Origanum species were identified and antityrosinase activities of EO and active molecules (carvacrol and thymoquinone) have been tested in tubo. RESULTS: Antityrosinase activities were obtained as follows: EO of Origanum syriacum (80.41% ± 2.00%), EO of Origanum ehrenbergii (45.33% ± 2.20%), EO of Salvia fruticosa (14.62% ± 2.30%), EO of Calamintha origanifolia (16.51% ± 5.80%), Carvacrol (56.55% ± 3.10%), and Thymoquinone (19.49% ± 1.50%). CONCLUSION: Origanum essential oils resulted in the highest antityrosinase activity due to their high content in carvacrol. However, when present together with carvacrol, thymoquinone decreases the efficiency of carvacrol, which is the case of O. ehrenbergii essential oil. Thus, for improved antityrosinase activity, O. syriacum and O. ehrenbergii should be harvested during flowering stage where carvacrol is present at its highest dosage and thymoquinone at its lowest.

Origanum essential oils reduce the level of melanin in B16-F1 melanocytes.

BACKGROUND: Hyperpigmentation disorders are considered signs of skin aging and are aesthetically unpleasant. Most active ingredients used against hyperpigmentation disorders predominantly target tyrosinase activity. OBJECTIVES: To study the effect of two Origanum essential oils on the melanogenic activity of B16-F1 murine melanocytes. The main component of these oils, carvacrol, was also investigated and a model for anti-melanogenic activity is proposed. MATERIALS AND METHODS: B16-F1 melanocytes were exposed to different concentrations of essential oils and carvacrol. The level of tyrosinase and melanin was determined using spectrophotometric measurements. RESULTS: Essential oils of Origanum syriacum and Origanum ehrenbergii led to a significant 14% and 17% reduction in melanin level at 40 µg mL-1, respectively. However, neither demonstrated a significant effect on the level of intracellular tyrosinase. The same effects were found for carvacrol which led to a 30% reduction in melanin at 45 µg mL-1. CONCLUSION: Our results indicate that the oils studied are anti-melanogenic. We propose a mechanism, similar to that for hydroquinone, whereby carvacrol functions as a competitive inhibitor of tyrosinase, thus inhibiting oxidation of tyrosine and causing a deregulation of melanogenesis.

Clustering-based preprocessing method for lipidomic data analysis: application for the evolution of newborn skin surface lipids from birth until 6 months.

After life in utero and birth, the skin is submitted to an important process of adaptation to a relatively dry gaseous environment. Skin surface lipids (SSLs) contribute actively to the protection of the skin barrier. Within this context, our objective was to study the evolution of each lipid compound during the postnatal period. SSLs were collected from six newborns a few days after birth until the age of 6 months. Seventy samples were analyzed using high-temperature gas chromatography coupled to mass spectrometry (HT-GC/MS). The use of separative techniques coupled to mass spectrometry for the analysis of samples containing complex mixtures of lipids generates a large volume of data which renders the results interpretation very difficult. In this study, we propose a new approach to handle the raw data, a clustering-based preprocessing method (CB-PPM), in order to achieve (1) volume reduction of data provided by each chromatogram without loss of information, (2) alignment of time retention shift between different runs, (3) clustering of mass spectra of the same molecule in one qualitative group, (4) and integration of all data into a single matrix to be explored by chemometric tools. This approach allowed us to gather data variations in 256 qualitative groups and therefore enabled us to highlight the variation of compounds including those of low intensity. Moreover, the representation of all data gathered in one matrix rendered reading of the results rapid and efficient. Thus, using this approach, we have demonstrated an increase of cholesterol esterification with epidermal fatty acids (C20 to C25) with age. This epidermis participation in SSL production at a molecular level in the first period of life has not been previously shown. These data can be very interesting for the development and improvement of products destined for the protection of infant skin. Graphical abstract ᅟ.

Retinoblastoma membrane models and their interactions with porphyrin photosensitisers: An infrared microspectroscopy study.

Fourier Transform Infrared (FTIR) microspectroscopy was used to highlight the interactions between two photosensitisers (PS) of different geometries, TPPmOH4 and a glycoconjugated analogous, TPPDegMan, and lipid bilayers modelling retinoblastoma cell membranes. Retinoblastoma is a rare disease occurring in young infants, for whom conservative treatments may present harmful side-effects. Photodynamic therapy (PDT) is expected to induce less side-effects, as the photosensitiser is only activated when the tumour is illuminated. Since efficiency of the treatment relies on photosensitiser penetration in cancer cells, bilayers with three lipid compositions - pure SOPC, SOPC/SOPE/SOPS/Chol (56:23:11:10) and SOPC/SOPE/SOPS/Chol/CL (42:32:9:8:6) - were used as plasma and mitochondria model membranes. FTIR spectra showed that the interaction of the PSs with the lipid bilayers impacted the lipid organization of the latter, causing significant spectral variations. Both studied photosensitisers inserted at the level of lipid hydrophobic chains, increasing chain fluidity and disorder. This was confirmed by surface pressure measurements. Photosensitisers - TPPmOH4 more than TPPDegMan - also interacted with the polar region of the bilayer, forming hydrogen bonds with phosphate groups that induced major shifts of phosphate absorption bands. This difference in PS interaction with moieties in the polar region was more pronounced with the models with complex lipid composition.

Measurement of the biomechanical function and structure of ex vivo drying skin using raman spectral analysis and its modulation with emollient mixtures.

An important aspect of the biomechanical behaviour of the stratum corneum (SC) is the drying stresses that develop with water loss. These stresses act as a driving force for damage in the form of chapping and cracking. Betasitosterol is a plant sterol with a structure similar to cholesterol, a key component in the intercellular lipids of the outermost layer of human skin, the SC. Cholesterol plays an important role in stabilizing the SC lipid structure, and altered levels of cholesterol have been linked with SC barrier abnormalities. Betasitosterol is currently applied topically to skin for treatment of wounds and burns. However, it is unknown what effect betasitosterol has on the biomechanical barrier function of skin. Here, by analysing the drying stress profile of SC generated during a kinetics of dehydration, we show that betasitosterol, in combination with two emollient molecules, isocetyl stearoyl stearate (ISS) and glyceryl tri-2-ethylhexanoate (GTEH), causes a significant modulation of the drying stress behaviour of the SC by reducing both the maximal peak stress height and average plateau of the drying stress profile. Raman spectra analyses demonstrate that the combination of betasitosterol with the two emollients, ISS and GTEH, allows a high water retention capacity within the SC, while the lipid conformational order by increasing the amount of trans conformers. Our study highlights the advantage of combining a biomechanical approach together with Raman spectroscopy in engineering a suitable combination of molecules for alleviating dryness and dry skin damage.