Potential of short-wave infrared spectroscopy for quantitative depth profiling of stratum corneum lipids and water in dermatology

Abstract

Abstract:We demonstrate the feasibility of short wave infrared (SWIR) spectroscopy combined with tape stripping for depth profiling of lipids and water in the stratum corneum of human skin. The proposed spectroscopic technique relies on differential detection at three wavelengths of 1720, 1750, and 1770 nm, with varying ratio of the lipid-to-water absorption coefficient and an 'isosbestic point'. Comparison of the data acquired using SWIR spectroscopy with that obtained by a gold standard for non-invasive quantitative molecularspecific skin measurements, namely confocal Raman spectroscopy (CRS), revealed specificity of the proposed modality for water and lipid quantification. At the same time, we provide evidence showing aberrant sensitivity of Corneometer hydration read-outs to the presence of skin surface lipids, and a lack of sensitivity of the Sebumeter when attempting to measure the lipids of the cornified lipid envelope and intracellular lipid layers. We conclude that a spectroscopic SWIR-based spectroscopic method combined with tape stripping has the potential for depth profiling of the stratum corneum water and lipids, due to superior measurement sensitivity and specificity compared to the Corneometer and Sebumeter. References and links1. D. J. Tobin, "Introduction to skin aging," J. Tissue Viability 26(1), 37-46 (2017). 2. P. C. Arck, A. Slominski, T. C. Theoharides, E. M. Peters, and R. Paus, "Neuroimmunology of stress: skin takes center stage," J. Invest. Dermatol. 126(8), 1697-1704 (2006). 3. K. R. Feingold and P. M. Elias, "Role of lipids in the formation and maintenance of the cutaneous permeability barrier," Biochim. Biophys. Acta 1841(3), 280-294 (2014). 4. D. J. Tobin, "Biochemistry of human skin--our brain on the outside," Chem. Soc. Rev. 35(1), 52-67 (2006). 5. M. Akiyama, "Corneocyte lipid envelope (CLE), the key structure for skin barrier function and ichthyosis pathogenesis," J. Dermatol. Sci. 88(1), 3-9 (2017). 6. K. C. Madison, "Barrier function of the skin: "la raison d'être" of the epidermis," J. Invest. Dermatol. 121(2), 231-241 (2003). 7. D. J. Tobin, "Introduction to skin aging," J. Tissue Viability 26(1), 37-46 (2017 75-83 (2015). 13. R. J. Richters, N. E. Uzunbajakava, D. Falcone, J. C. Hendriks, E. J. Jaspers, P. C. van de Kerkhof, and P. E. van Erp, "Clinical, biophysical and immunohistochemical analysis of skin reactions to acute skin barrier disruptiona comparative trial between participants with sensitive skin and those with nonsensitive skin," Br. J. Dermatol. 174(5), 1126-1133 (2016). 14. M. Akiyama, "Corneocyte lipid envelope (CLE), the key structure for skin barrier function and ichthyosis pathogenesis," J. Dermatol. Sci. 88(1), 3-9 (2017). 15. M. Sullivan, N.B. Silverberg, "Current and emerging concepts in atopic dermatitis pathogenesis," Clin, Dermatol.35 (

Short‐wave infrared light imaging measures tissue moisture and distinguishes superficial from deep burns

“…Thus, measuring the reflectance of light in the SWIR range was proposed for interrogation of moisture and microscopic structural changes . We further surmise that the SWIR light reflectance sensitivity to tissue factors and moisture could also make it an important marker of skin tissue viability in burns, as suggested by the correlation between water loss and epidermal barrier dysfunction . Previous literature, especially in dermatologic journals, has characterized the composition of healthy cutaneous tissues.…”

“…While non‐spectral modalities have also been proposed, variability in skin conditions and imaging methods hamper comparisons of water absorbance of SWIR light between different studies . Furthermore, the need for a consistent electrical contact with the skin surface as well as an exquisite sensitivity to ambient temperature render electrical measurements for the assessment of trans‐epidermal water loss, such as capacitance, as sub‐optimal when compared to our imaging results …”

“…Previous literature, especially in dermatologic journals, has characterized the composition of healthy cutaneous tissues. Namely, strong water signals have been characterized within the stratum corneum and viable epidermis . Furthermore, studies investigating compositional changes after mechanical damage to the cutaneous layer have demonstrated increases in transepidermal water loss, that is, decrease in moisture content .…”

“…The moisture imaging data shown in Figure is consistent with the ability of 1,940 nm reflectance to detect moisture levels in vivo amounts of <30 μL, but the relation of 1,940‐nm light reflectance to burn depth has not been fully established as our imaging analysis in the agar slabs of >1 mm in thickness (Figure ) and burns with damaged collagen at depth between about 0.5 and 1 mm (Figure ) show similar levels of absorbance or reflectance of 1,940‐nm light. Further investigation is required to clarify the effect of water content at different skin depths on the SWIR light reflectance …”

“…12 We further surmise that the SWIR light reflectance sensitivity to tissue factors and moisture could also make it an important marker of skin tissue viability in burns, as suggested by the correlation between water loss and epidermal barrier dysfunction. [13][14][15] Previous literature, especially in dermatologic journals, has characterized the composition of healthy cutaneous tissues. Namely, strong water signals have been characterized within the stratum corneum and viable epidermis.…”