Elucidating penetration pathways into the hair fiber using novel microscopic techniques

Area of Science:

• Hair fiber science
• Materials science
• Cosmetic science

Background:

• Controversy exists regarding molecular penetration pathways into hair fibers.
• Two main theories propose entry via the cell membrane complex (cmc) or non-keratinous parts.
• Current imaging techniques provide static snapshots of a dynamic process, complicating interpretation.

Purpose of the Study:

• To investigate and clarify the routes of molecular penetration into hair fibers.
• To utilize novel electron microscopy and photographic chemistry techniques.
• To reconcile conflicting theories on hair fiber penetration.

Main Methods:

• Novel derivations of conventional electron microscopy.
• Application of early photographic chemistry principles.
• Analysis of molecular distribution within hair fiber structures.

Main Results:

• Confirmed that the cell membrane complex (cmc) is a viable penetration route.
• Demonstrated that high-sulfur proteins in the cuticle are accessible.
• Showed that both previously proposed pathways are complementary and valid.

Conclusions:

• All structures within a hair fiber can serve as penetration routes.
• Hair should be viewed as a series of accessible compartments, not just continuous pathways.
• These findings have implications for delivering industrial and cosmetic materials into hair.