MCR Approach Revealing Protein, Water, and Lipid Depth Profile in Atopic Dermatitis Patients’ Stratum Corneum via in Vivo Confocal Raman Spectroscopy

Abstract

Confocal Raman has been widely used for measuring the water concentration profile inside skin to calculate clinical end-points such as stratum corneum thickness. In this paper, multivariate curve resolution was applied to resolve the pure com-ponents contained in high frequency (2500 – 4000 cm-1) in vivo confocal Raman data. Three components were identified by comparing with reference spectra of materials in skin. These three components are water, protein and lipid. The score values associated with these three components were transformed to mass ratio by leveraging the response factors for protein and lipid in a calibration model utilizing the pure material spectra. The concentration profiles for protein and lipid as a func-tion of depth across the stratum corneum are utilized as new clinical endpoints. Results from an in vivo study with individu-als who experience atopic dermatitis symptoms successfully demonstrated a statistical difference between Raman spectra from non-lesion and lesion skin sites. Trends in the depth profiles of the skin components are consistent with previous litera-ture reports.