Elucidating Penetration Pathways Into the Hair Fiber Using Novel Microscopic Techniques

The study explored the penetration pathways of molecules into hair fibers using advanced microscopic techniques. It addressed two main theories: one suggesting molecules enter via the cell membrane complex (CMC) and diffuse through the cortex, and another proposing entry through the endocuticle and non-keratinous parts, excluding the CMC. The findings indicated that both theories are valid and complementary. The research demonstrated that high-sulfur proteins in the cuticle, previously thought to be impenetrable, are accessible. Thus, all hair fiber structures should be considered potential penetration routes for industrial and cosmetic materials, viewing hair as a composite of compartments with varying properties rather than continuous pathways.