Quantification of Lipid Phase Order of In Vivo Human Skin Using Attenuated Total Reflection Fourier Transform...

Area of Science:

• Biophysics
• Spectroscopy
• Dermatology

Background:

• Human skin's stratum corneum contains ordered lipid structures crucial for barrier function.
• Understanding lipid organization at different depths is key to skin physiology and disease.

Purpose of the Study:

• To develop and validate a method combining multivariate curve resolution (MCR) with in vivo Fourier transform infrared (FT-IR) spectroscopy for analyzing skin lipid order.
• To investigate the depth-dependent changes in lipid phase constituents within the human stratum corneum.

Main Methods:

• In vivo ATR FT-IR spectroscopy was used on human forearm skin.
• Depth profiling was achieved through sequential tape stripping.
• Multivariate curve resolution (MCR) and traditional analysis were applied to spectral data from specific vibrational modes (-CH2 stretching, scissoring, rocking).

Main Results:

• Lipid order, quantified as the ratio of orthorhombic to total lipids, increases exponentially with stratum corneum depth.
• Lipid order depth profiles (LODP) showed consistent trends across different vibrational modes.
• Inter-individual variation in LODP was significantly higher than intra-individual variation.

Conclusions:

• The MCR-FT-IR methodology effectively resolves lipid phase constituents and quantifies lipid order in vivo.
• Lipid ordering increases with depth in the stratum corneum, following an exponential pattern.
• The scissoring vibrational mode offers the highest sensitivity for LODP determination, and specific arm sites are suitable for comparative studies.