In vivo analysis of endogenous hyaluronic acid in the dermis by confocal Raman spectroscopy after application of a dermocosmetic

Evaluating endogenous hyaluronic acid (HA) in the skin is essential to understanding the ageing process and analysing the effectiveness of dermocosmetics. In this sense, this study evaluated the skin of 10 individuals between 51 and 65 years old before and after applying a dermocosmetic to stimulate HA production. For this, Gen2 confocal Raman (Rivers Diagnostic) coupled to a 785 nm laser was used. Participants underwent a 7-day washout and then had their skin measured (T0 - control). After the control measure, they used the product for 60 days, applying it twice a day (morning and evening). Measurements were made at times T0, T30 and T60 days in the spectral range of 400 to 1800 cm^-1. Spectral data was processed by removing the baseline, smoothing and vector normalization. The T30 and T60 spectra were subtracted from the control measurement (T0) and compared with the second derivative spectrum of hyaluronic acid. It was observed that the main peaks of HA were presented in the difference between the spectra before and after using the dermocosmetic. The main peaks observed were 1076, 1084, 1096, 1126, 1132 and 1208 cm^-1. The difference between these peaks increased after 30 and 60 days of using the dermocosmetic product, indicating an increase in the concentration of HA in the skin. Therefore, the in vivo assessment of cutaneous HA by confocal Raman spectroscopy can be used to understand the role of dermocosmetics in skin ageing, allowing for more effective treatments.