Exposure to ultraviolet(UV) radiation damages hair fiber. UV light induced hair photoaging is difficult to avoid during daily life. Integral hair lipid has major significance in determining the structural properties of hair. We performed this study to observe the photodegradation of integral hair lipid.
We studied the changes of hair fiber after UV irradiation with conventional scanning and transmission eletron microscope. We checked the soluble hair protein released from damaged hair with protein analysis, electrophoresis and western blot analysis. We also evaluated the changes of integral hair lipid quantitatively and qualitatively using HPTLC, weighing balance and LC-Mass. Then, we checked the changes of integral hair lipid present in the cell membrane complex(CMC)in hair cuticle with lipid transmission electron microscope.
Photodamaged hair showed cortical and cuticular alterations especially severe in the endocuticular layer of each cuticle cells. Release of soluble hair protein and partial degeneration of integral hair lipid of CMC were noted. These showed relatively more destructive cuticular changes after UVB irradiation than after UVA irradiation. In lipid analysis, decrease of free fatty acids especially 18-methyl eicosanoic acid(18-MEA) which belongs to the species of covalently bound fatty acids were noted by UV irradiation.
From these results, we can conclude that UV induced hair photoaging show morphological and biochemical changes of human hair especially severe on integral hair lipid of CMC.