Characterisation of alpha-keratin fibres

Human hair is comprised of a highly complex biomaterial, α-keratin. Some of the key features of keratin are its robust nature and strong mechanical stability. These qualities originate from the molecular assembly of the proteins and are described by a two-phase model. Highly ordered crystalline intermediate filaments are interspersed within a less-ordered amorphous matrix. Developing a further understanding of the internal sub-structures of hair fibres, particularly with relation to the effect of chemical agents on these structures is imperative to the personal care and cosmetic industries. This information could direct the growth and expansion of new cosmetic treatments. Nuclear magnetic resonance experiments have been utilised as a method to measure and quantify “damage” to hair fibres caused by chemical modifications. X-ray scattering experiments were employed to investigate the effect of chemical agents on the sub-structures of hair. Equilibrium and time-resolved hydration experiments were used to ascertain both the lateral and axial swelling of the intermediate filaments and how “damage” affects this. Micro-focus x-ray scattering techniques provided information on the scattering patterns produced by the three principal hair structures; the cuticle, the cortex and the medulla. Some of the key findings of this research include the use of spin-lattice relaxation times as a robust and reproducible method for quantifying hair damage. Time-resolved hydration experiments demonstrated that both the magnitude and rate of swelling a fibre undergoes can be altered through chemical agents. The distribution of intermediate filaments within the cortex was measured for the first time by x-ray scattering, showing a clear increase in the density towards the centre of the fibres. These findings and use of the various 3 techniques begin to produce a tool-kit for measuring and quantifying the effect of chemical treatments on human hair fibres.Open Acces