Noninvasive in vivo application of confocal Raman spectroscopy in identifying age-related biochemical changes in human stratum corneum and epidermis

Stratum corneum, and epidermis, regions of human skin were analyzed in vivo using confocal Raman spectroscopy to evaluate age-related biochemical and spectral changes. The data consisted of two defined age groups comprising 71 volunteers (27 ± 3 and 55 ± 4 years old). Multivariate statistical analyses were used to interpret and classify the average spectral data for each skin layer. The analyses demonstrated the measurement of two different groups of skin with different ages and revealed the most representative peaks for both the stratum corneum and epidermis. The Amide III and Amide I, both in α-helix conformation, exhibited increased signals in the spectra of the epidermis and stratum corneum of the younger group, and it was observed that an increased crosslinking of keratin filaments with age is a potential contributor to the stiffness increment, which consequently leads to a decrease in the Raman signal in the older group. The opposite occurred for the lipids signal, as changes in the lateral packing of lipids indicate skin ageing and an increase in the Raman signal. The disparity in the means of total natural moisturizing factor, was statistically significant between the two age groups. The statistical results demonstrated the emergence of distinct groups pertaining to the epidermis and stratum corneum, as well as pertaining to group I or II.