Structure of Water, Proteins, and Lipids in Intact Human Skin, Hair, and Nail

Abstract

Raman spectroscopy is a nondestructive analytical method for determining the structure and conformation of molecular compounds. It does not require sample preparation or pretreatment. Recently, near-infrared Fourier transform Raman spectroscopy has emerged as being specially suited for investigations of biologic material. In this study, we obtained near-infrared Fourier transform Raman spectra of intact human skin, hair, nail, and stratum corneum. We disclosed major spectral differences in conformational behavior of lipids and proteins between normal skin, hair, and nail. The amide I and III band location indicated that the majority of proteins in all samples have the same secondary alpha-helix structure. Positions of (S-S) stretching bands of proteins revealed a higher stability of the disulfide bonds in the hair and the nail. Analysis of vibrations of protein -CH groups showed that in the hair and the nail the proteins are apparently highly folded, interacting with the surroundings only to a small degree. The position of lipid specific peaks in spectra of hair, nail, and stratum corneum suggested a highly ordered, lamellar crystalline lipid structure. A greater lipid fluidity was found in whole skin. Assessment of the structure of water clusters revealed that mainly bound water is present in the human skin, stratum corneum, and nail. In conclusion, structural changes of water, proteins, and lipids in intact skin and skin appendages may be analyzed by Raman spectroscopy. This technique may be used in the future in a noninvasive analysis of structural changes in molecular compounds in the skin, hair, and nail associated with different dermatologic diseases.

The influence of surface charge and photo-reactivity on skin-permeation enhancer property of nano-TiO2 in ex vivo pig skin model under indoor light

“…In fact, in lipids, the ratio of the symmetric methylene C-H stretching-mode intensities (peak height I2890/I2850) is sensitive to the packing order of the acyl chains and the observed relative increase of intensity of the 2850 cm -1 band with respect to 2890 cm -1 may account for a change of the lipids bilayer structure (Vyumvuhore et al, 2013). This phenomenon, occurring with naked AR, but not with coated TiO2 with similar titania core, is possibly due to physical interaction of nano-TiO2 with the SC lipids and/or to some TiO2-induced chemical oxidative damage (Gaber and Peticolas, 1977;Gniadecka et al, 1998 andWegener et al, 1996).…”

Molecular characterization of reconstructed skin model by Raman microspectroscopy: Comparison with excised human skin

“…These results agree with the previous studies about the evaluation of the secondary conformations of the epidermis. 25,29,[47][48][49][50][51] Lipids of the Episkin Model. The lipids of the epidermis are mainly constituted of ceramides, cholesterol, fatty acids, and membrane phospholipids of cells.…”

“…29,31,33 This fluidity and the intramolecular conformation can be studied by analyzing the peaks intensity in the 1000-1150 cm 21 region. 29,31,33,39,52 FIGURE 1 Raman spectrum of the reconstructed epidermis.…”

“…[16][17][18][19][20][21][22][23][24] Other research works studied the molecular composition of the skin, 25,26 followed the effects induced by different types of drugs, 25,27 and established in depth concentration profiles (starting from the surface and going deeper into the skin) of different molecules (water and endogenous molecules). [27][28][29][30][31][32][33][34] The follow-up, in real-time analysis, of the diffusion of the exogenous products through skin layers has also been performed. [35][36][37] To evaluate the potential of the Raman spectroscopy for future investigations on reconstructed skin samples, such as percutaneous absorption studies, toxicological risks investigations, drugs development, cosmetic products safety, and assessment of the effect of environmental aggressions like UV radiations, we have tried for the first time to establish a vibrational identity and a spectral characterization of a synthetic epidermis model, Episkin 1 , reconstructed from a culture of keratinocytes on a type-I collagen matrix.…”

“…The lipids disorganization corresponds to a transition toward a gauche conformation, which is proved by the disappearance of the 1062 and 1127 cm 21 peaks simultaneously with the appearance of the 1086 and 1102 cm 21 peaks. 25,29,31,33 In the Episkin spectrum, the four peaks are all present, but with a clear predominance of 1062 and 1127 cm 21 compared with 1086 and 1102 cm 21 , which indicates a domination of organized conformations for the lipid components of the Episkin model.…”