Comparison of stratum corneum thickness between two proposed methods of calculation using Raman spectroscopic depth profiling of skin water content.

BACKGROUND/PURPOSE: The stratum corneum (SC) is the most important layer for the barrier function of skin, so investigation of the SC is very important in cosmetic and medical research. Here, we calculated the SC thickness using the depth profile of the skin's water concentration based on previously described methods, and then compared the results. METHODS: Seven Korean women in their 30s participated in this study. Raman spectroscopy was used to measure the in vivo depth profile of skin water concentration. A total of 21 areas were measured at forearm. Microsoft Excel 2007 was used to calculate SC thickness based on the slope and intersection methods. RESULTS: The slope method and the intersection method gave a forearm SC thickness calculated at 21.3 ± 2.6 µm and 17.6 ± 2.8 µm, respectively. There was a significant difference between the two calculation methods but the two methods showed strong correlation of SC thickness results (r = .899). CONCLUSION: Although there was a difference in calculated SC thickness of about 20% between the two methods, these results reveal that the two SC thickness calculation methods using Raman spectroscopy were suitable for measuring SC thickness, a finding consistent with other published results.

Comparison of the stratum corneum thickness measured in vivo with confocal Raman spectroscopy and confocal reflectance microscopy.

BACKGROUND: Thickness measurement of the outermost layer of the skin, the stratum corneum (SC), is essential for in-vivo measurement of the cutaneous bioavailability of topically applied drugs and cosmetics. Our aim was to compare SC thickness calculated from confocal Raman spectroscopy (CRS) data with results of SC thickness based on confocal laser scanning microscopy (CLSM) measurements and with literature data, to validate CRS data with CLSM data and vice versa. METHODS: SC thickness was measured with two non-invasive devices, confocal Raman spectroscopy and confocal laser scanning microscopy, on four different areas of the body: volar forearm, leg, face and palm in 18 healthy adult subjects. RESULTS: Comparable results of SC thickness were obtained with both methods, structure analysis of CLSM images, and computation of Fick's first law on water gradients measured with CRS: 20 µm and 19 µm (volar forearm), 21 µm and 22 µm (lower leg), and 13 µm with both methods (cheek), respectively. DISCUSSION: For the first time it was possible to accurately determine the thickness of SC with CRS and CLSM and to validate both systems against each other and with results of literature data. CONCLUSION: Both methods, CRS and CLSM, were found to be suitable to measure SC thickness correctly. Therefore, when using CRS, for example to obtain detailed information about the molecular composition of the skin, it is additionally possible to accurately measure SC thickness with the same device to have an orientation in which skin layer molecules are found.