Aplicação in vivo não invasiva da espectroscopia Raman confocal na identificação de alterações relacionadas à idade no estrato córneo e epiderme humana

Abstract

Human skin comprises layers known as the stratum corneum and the epidermis, each possessing biomolecules, structure and functions. The Raman spectroscopy technique enables research on the biochemical composition of biological samples in vivo, such as skin, its biomolecules and biomarkers, in a selective and non-destructive way, allowing for in vivo examination of tissue layers. This elucidates the biophysical links between vibrational characteristics and changes in specific chemical compositions. This study aims to use confocal Raman spectroscopy to evaluate age related biochemical and spectral changes in the stratum corneum and human epidermis, focusing specifically on spectral modifications in the natural moisturizing factor (NMF), keratin, lipids and proteins. Skin-related data were acquired using a confocal Raman system with a 785 nm diode laser, which consisted of two defined age groups, group I, 27±3 years, and group II, 55±4 years, comprising 71 volunteers. Multivariate statistical analyses were used to interpret and classify the average spectral data from each skin layer. Analyses measured two different skin groups and revealed the most representative peaks for the stratum corneum and epidermis. Amide III and amide I, both in the α-helical conformation, showed increased signals in the spectra of the epidermis and stratum corneum of group I. It was observed that increased keratin filament cross-linking with age is a possible contributor to the increase in stiffness, which consequently led to a decrease in the Raman signal in group II. The opposite occurred with the lipid signal, as changes in the lateral packaging of lipids indicated skin aging with an increase in the Raman signal in group II. The difference between the NMF means was statistically significant between the two age groups. Thus, the present research fills an important current research gap in differentiating skin characteristics across different age groups and their layers using confocal Raman spectroscopy.