In vivo determination of dermal water content in chronological skin aging by confocal Raman spectroscopy

The study involves 73 female participants including 40 healthy young (19–37 years), 17 non-diabetic elderly (50–80 years) and 16 diabetic elderly (54–91 years). The main purpose of this study is to evaluate the water content of human dermis by in vivo confocal Raman spectroscopy. The results pointed out that the total water content of the dermis is 74.4 % ± 3.7, 71.8 % ± 2.4, and 73.7 % ± 3.7 for diabetic elderly, healthy young adults, and healthy elderly women, respectively. The difference in total water content between elderly diabetic women vs healthy young women and for healthy elderly women vs healthy young women was 2.7 and 1.6 %, respectively. A way to analyze only bounded water (independent of the use of skin – tools) in the amino acids chain of collagen was performed subtracting the Raman water spectrum of the mean Raman spectra of the free groups of participants. The bounded water in the collagen fibers was found at 3515 – 3700 cm−1 and corresponds to 31.84 % in healthy young, 34.69 % in healthy elderly, and 33.47 % in diabetic elderly women. This study showed that both the total human dermal water concentration and bounded water could be measured in vivo using confocal Raman spectroscopy.