Integral characterization of normal and alopecic hair at different degeneration stages by in-situ visible and chemical imaging.

Direct exploration to differences between normal hair (NH) and alopecic hair (AH) at different degeneration stages is still lacking. To reveal compositional and structural variation of AH with reference to NH internally and externally, infrared spectroscopic imaging combined with scanning electron microscopy was applied to investigate integral changes of hair chemical profiles and surface texture structures, and infrared macro-fingerprinting analysis revealed detailed chemical compositions of NH and AH. Results showed that AH had excessive irregular laminated structures compared to NH, leading to a lower weight bearing capacity. Spatial distributions of lipids, phosphates, lipoproteins and phospholipids in hair transverse sections showed that their infrared absorptions were intensified and gradually centralized to medulla with average variable-areas increasing upto 2.3 folds (lipoproteins area changed from 13% in NH to 30% in AH)as the alopecia progressed. Extracted pixel spectra from the chemical images showed different fingerprint characteristics in 1075-1120 cm-1. Specifically, compared to NH, AH showed red shift of phosphate peaks, indicating the occurrence of phosphates transformation. In this study, in-situ visible and infrared chemical imaging directly revealed more irregular laminated scalps with decreasing weight bearing capacity and increasing distributive areas expanding to medulla of key components (phosphates, phospholipids, etc.) that were relevant to alopecia development from NH to AH, and offered a fast, eco-friendly and effective method for hair research.