Abstract
ObjectiveTo investigate the effects of different molecular weight (MW), wool derived hydrolysed keratins (i.e. peptides) on the physical properties of relaxed textured hair.MethodsVery curly hair of African origin was relaxed using sodium hydroxide‐based treatment. Relaxed hair was treated with different MW peptides derived from keratin protein and an amino acid, L‐Leucine. The low‐MW keratin peptides were 221 Da, the mid‐MW keratin peptides were approximately 2577 Da, and the high‐MW keratin peptides were approximately 75 440 Da. The penetration of these different peptides into relaxed hair was evaluated using a laser scanning micrometre and by fluorescence microscopy. The effect of these compounds on single‐fibre mechanical properties and thermal properties was evaluated using tensile and DSC testing, respectively.ResultsLow‐ and mid‐MW compounds were able to penetrate deep into the hair cortex. High‐MW peptide adsorbed onto the hair surface and possibly slightly penetrated into the outer layers of the fibre surface. Both mid‐ and high‐MW keratin peptides, increased Young’s modulus and reduced hair breakage at 20% and 80% relative humidity. With the exception of mid‐MW peptide, other peptides and amino acid were not able to modify thermal properties of relaxed textured hair.ConclusionsOur data suggest that low‐MW compounds may increase hair volume, and high‐MW peptides may repair damage on freshly relaxed textured hair.
Highlights
Human hair is a unique bio-substrate, ideally adapted to fulfil its function as a protective and insulating shield for our skin
Statistical analysis showed that cross-sectional areas of hair treated with 1% low-molecular weight (MW) keratin peptide and 1% leucine-treated hair were significantly higher than that of both virgin and relaxed hair controls (11.7% and 11.0%, respectively, higher than relaxed hair control)
These results suggest that low-MW actives effectively penetrated into the damaged hair cortex
Summary
Human hair is a unique bio-substrate, ideally adapted to fulfil its function as a protective and insulating shield for our skin. The key structural proteins in the hair cortex are (a) the keratins that constitute the intermediate filaments, and (b) keratin-associated proteins that form the matrix surrounding intermediate filaments Both protein types are responsible for the hair’s tensile strength. Hair is naturally a very flexible and strong material, consumers choose to chemically modify, wash, treat and style their hair to change their appearance and look their best. These practices can induce severe alterations in the hair. Hair condition is made worse daily through exposure to chlorine from swimming pool water and environmental factors such as sunlight and pollution To address these problems, a multitude of materials are available for the cosmetic formulator to develop various cosmetic treatments.
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