In vivo confirmation of hydration-induced changes in human-skin thickness, roughness and interaction with the environment (original) (raw)
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Novel confocal Raman microscopy method to investigate hydration mechanisms in human skin
Skin Research and Technology, 2019
Background: Skin hydration is essential for maintaining stratum corneum (SC) flexibility and facilitating maturation events. Moisturizers contain multiple ingredients to maintain and improve skin hydration although a complete understanding of hydration mechanisms is lacking. The ability to differentiate the source of the hydration (water from the environment or deeper skin regions) upon application of product will aid in designing more efficacious formulations. Materials and Methods: Novel confocal Raman microscopy (CRM) experiments allow us to investigate mechanisms and levels of hydration in the SC. Using deuterium oxide (D 2 O) as a probe permits the differentiation of endogenous water (H 2 O) from exogenous D 2 O. Following topical application of D 2 O, we first compare in vivo skin depth profiles with those obtained using ex vivo skin. Additional ex vivo experiments are conducted to quantify the kinetics of D 2 O diffusion in the epidermis by introducing D 2 O under the dermis. Results: Relative D 2 O depth profiles from in vivo and ex vivo measurements compare well considering procedural and instrumental differences. Additional in vivo experiments where D 2 O was applied following topical glycerin application increased the longevity of D 2 O in the SC. Reproducible rates of D 2 O diffusion as a function of depth have been established for experiments where D 2 O is introduced under ex vivo skin. Conclusion: Unique information regarding hydration mechanisms are obtained from CRM experiments using D 2 O as a probe. The source and relative rates of hydration can be delineated using ex vivo skin with D 2 O underneath. One can envision comparing these depth-dependent rates in the presence and absence of topically applied hydrating agents to obtain mechanistic information.
Biomedical Optics Express
Confocal Raman microscopy has a number of advantages in investigating the human stratum corneum (SC) in vivo and ex vivo. The penetration profiles of xenobiotics in the SC, as well as depth profiles of the physiological parameters of the SC, such as the concentration of water depending on the strength of hydrogen bonds, total water concentration, the hydrogen bonding state of water molecules, concentration of intercellular lipids, the lamellar and lateral packing order of intercellular lipids, the concentration of natural moisturizing factor molecules, carotenoids, and the secondary and tertiary structure properties of keratin are well investigated. To consider the depth-dependent Raman signal attenuation, in most cases a normalization procedure is needed, which uses the main SC's protein keratin-related Raman peaks, based on the assumption that keratin is homogeneously distributed in the SC. We found that this assumption is not accurate for the bottom part of the SC, where the water concentration is considerably increased, thus, reducing the presence of keratin. Our results demonstrate that the bottom part of the SC depth profile should be multiplied by 0.94 in average in order to match this non-homogeneity, which result in a decrease of the uncorrected values in these depths. The correctly normalized depth profiles of the concentration of lipids, water, natural moisturizing factor and carotenoids are presented in this work. The obtained results should be taken into consideration in future skin research using confocal Raman microscopy.
Combined In Vivo Confocal Raman Spectroscopy and Confocal Microscopy of Human Skin
Biophysical Journal, 2003
In vivo confocal Raman spectroscopy is a noninvasive optical method to obtain detailed information about the molecular composition of the skin with high spatial resolution. In vivo confocal scanning laser microscopy is an imaging modality that provides optical sections of the skin without physically dissecting the tissue. A combination of both techniques in a single instrument is described. This combination allows the skin morphology to be visualized and (subsurface) structures in the skin to be targeted for Raman measurements. Novel results are presented that show detailed in vivo concentration profiles of water and of natural moisturizing factor for the stratum corneum that are directly related to the skin architecture by in vivo crosssectional images of the skin. Targeting of skin structures is demonstrated by recording in vivo Raman spectra of sweat ducts and sebaceous glands in situ. In vivo measurements on dermal capillaries yielded high-quality Raman spectra of blood in a completely noninvasive manner. From the results of this exploratory study we conclude that the technique presented has great potential for fundamental skin research, pharmacology (percutaneous transport), clinical dermatology, and cosmetic research, as well as for noninvasive analysis of blood analytes, including glucose.
Skin Pharmacology and Physiology
Confocal Raman microspectroscopy is widely used in dermatology and cosmetology for analysis of the concentration of skin components (lipids, natural moisturizing factor molecules, water) and the penetration depth of cosmetic/medical formulations in the human stratum corneum (SC) in vivo. In recent years, it was shown that confocal Raman microspectroscopy can also be used for non-invasive in vivo depth-dependent determination of the physiological parameters of the SC, such as lamellar and lateral organization of intercellular lipids, folding properties of keratin, water mobility and hydrogen bonding states. The results showed that the strongest skin barrier function, which is primarily manifested by the orthorhombic organization of intercellular lipids, is provided at ≈20–40% SC depth, which is related to the maximal bonding state of water with surrounding components in the SC. The secondary and tertiary structures of keratin determine water binding in the SC, which is depth-dependen...
In vitro and in vivo Raman spectroscopy of human skin
Biospectroscopy, 1998
Noninvasive techniques that provide detailed information about molecular composition, structure, and interactions are crucial to further our understanding of the relation between skin disease and biochemical changes in the skin, as well as for the development of penetration enhancers for transdermal drug administration. In this study we present in vitro and in vivo Raman spectra of human skin. Using a Raman microspectrometer, in vitro spectra were obtained of thin cross sections of human skin. They provided insight into the molecular composition of different skin layers. Evidence was found for the existence of a large variation in lipid content of the stratum corneum. A simple experimental setup for in vivo confocal Raman microspectroscopy of the skin was developed. In vivo Raman spectra of the stratum corneum were obtained at different positions of the arm and hand of three volunteers. They provided evidence for differences in the concentration of natural moisturizing factor at the...
Fourier transform Raman spectroscopy a novel application for examining human stratum corneum
International Journal of Pharmaceutics, 1992
Fourier transform Raman spectroscopy has been used for the first time to characterise human stratum corneum. Raman and infrared spectra were compared and differences, for example due to water effects or response linearity, were noted. The technique should prove valuable in fundamental and practical studies with human and animal skin.
Transactions of the Materials Research Society of Japan
We compared experimental results of confocal Raman microscope and Time Domain Reflectometry (TDR) measurements using a coaxial electrode with a flat-end termination for water content distribution in the depth direction of the human skin. The TDR method suggests an average value of water contents in depth direction from the skin surface to a certain depth. On the other hand, the confocal Raman microscope offers a value of the water content at each depth of the skin. The difference between water contents thus obtained by the both methods was well described by the quadratic expression of the depth from the skin surface. The water content in the skin detected by the electric field from the coaxial electrode on the skin surface used in TDR method decays in proportion to the square of the depth from the contact surface. It is expected that TDR measurements with the flat-end electrode thus characterized in the present study make it possible to offer newer simple experimental techniques to evaluate human skin. Key word: Time Domain Reflectometry, Confocal Raman Spectroscopy, human skin, water content
European Journal of Pharmaceutical Sciences, 2013
The stratum corneum is a strong barrier that must be overcome to achieve successful transdermal delivery of a pharmaceutical agent. Many strategies have been developed to enhance the permeation through this barrier. Traditionally, drug penetration through the stratum corneum is evaluated by employing tape-stripping protocols and measuring the content of the analyte. Although effective, this method cannot provide a detailed information regarding the penetration pathways. To address this issue various microscopic techniques have been employed. Raman microscopy offers the advantage of label free imaging and provides spectral information regarding the chemical integrity of the drug as well as the tissue. In this paper we present a relatively simple method to obtain XZ-Raman profiles of human stratum corneum using confocal Raman microscopy on intact full thickness skin biopsies. The spectral datasets were analysed using a spectral unmixing algorithm. The spectral information obtained, highlights the different components of the tissue and the presence of drug. We present Raman images of untreated skin and diffusion patterns for deuterated water and beta-carotene after Franz-cell diffusion experiment.
Applications of Raman spectroscopy to skin research
Skin Research and Technology, 1997
Backgroundlaims: Raman spectroscopy has been used for a range of biomedical applications: the study of normal and diseased tissues, and the interaction of chemical agents with tissues, implants and even single cells. The object here was to review the extent to which the Raman spectroscopic technique has been applied to skin research, considering the implications of different instrumentation, comparing animal and human skin, healthy and diseased skin and in vivo and in vitro sampling.