Profiling lipids across Caucasian and Afro‐American hair transverse cuts, using synchrotron infrared microspectrometry

Abstract

Synchrotron-based infrared microscopic measurements have been performed on various hair transverse sections, sampled either from the heads of Caucasian or Afro-American subjects. Lipid content of various virgin hair transverse sections was established, with an unprecedented resolution. The variations in shape and intensity of the CH(2), CH(3), amide I and amide II bands, before and after lipid removal by solvent extraction, were profiled, showing clearly that Caucasian hair often contains lipids localized inside the medulla and to a lesser extent inside the cuticle. This statement does not hold for the Afro-American hair analysed. For this, the FT-IR spectra do not change within the hair section and are insensitive to solvent extraction. The importance of the origin of hair on its physical and chemical properties has to be taken into account in future investigations.

Lipid loses and barrier function modifications of the brown‐to‐white hair transition

“…The medulla, which is not always present, is located in the inner part of the hair and is formed by loosely packed cells with a variable thickness of 5‐10 μm. Some studies have detected the presence of lipids in the medulla, but the function of that region or the importance of the lipids has not been determined as of yet …”

Highly resolved transmission infrared microscopy in polymer science

“…Examples include biological or biomedical systems [44][45][46][47][48][49][50][51][52][53], food science [54][55][56][57], geology and geochemistry [58][59][60][61], electrochemistry and surface science [62][63][64][65], high pressure studies [66,67], industrial research and forensics [68][69][70][71][72][73], and time-resolved spectroscopy [59,74]. However, to date only a few examples for the study of synthetic polymers have appeared in the literature [75][76][77][78][79].…”

Quantitative detection of chemical compounds in human hair with coherent anti-Stokes Raman scattering microscopy

“…In the medulla, a higher contribution from the symmetric CH 2 stretching mode (2840 cm −1 ) is observed, an indication of a higher density of lipid aliphatic chains. A higher relative lipid concentration in the medulla was also observed in infrared microspectroscopy studies 23. Importantly, compared to infrared microscopy techniques, the higher resolution in CARS allows for a much finer assessment of the distribution of lipids in the medulla.…”