HAIR CARE


33


Bioactive peptides for hair restructuring and hair plex


Guglielmo Bifulco, Francesco Rastrelli, Gianbattista Rastrelli – Kalichem


Faced with the continuous evolution of the global cosmetic market, the hair care industry continues its growth supported by a marked extension and diversification of claims and consumer needs, as well as by the growth of expanding economic realities. Recent market research identifies emerging


economies such as India, Indonesia, Brazil, South Africa, Colombia and China with extremely high CAGR (compound annual growth rate) values linked to the development of hair care products. More mature markets such as USA, Japan,


UK and France are instead set for growth in the per capita economic value of hair care products. The raising of the quality of hair care products plays a decisive role in such context, mainly in connection to the diversification of marketing claims, closely linked both to ethical issues and to the increasing consumer needs. In this new ecosystem, the need to choose


products compliant to consumer demands linked to philosophies such as clean and clinical beauty, or the search for environmentally sustainable specialities or relevant to social inclusion matters - such as gender, and heterogeneity of hair textures - have emerged. The common denominator of these new


elements remains the search of versatile specialities with proven activity and specificity. Not surprisingly, today we hear about ‘skinification’ of the hair care industry (intended as the need to target more effectively the hair products with the same depth of evaluation that applies in skin care), to demonstrate the radical change in the selection requirements of the NPD.


Kerashaft technology rationale In line with the hair care skinification trend, Kalichem has developed Kerashaft technology, a family of actives aimed to regenerate the hair and privilege applicative and post-applicative sensory pleasantness. The actives discussed here are Kerashaft V (INCI: Hydrolyzed Vegetable Protein) and Kerashaft Q (INCI: Hydroxypropyltrimonium Hydrolyzed Vegetable Protein), both developed through a meticulous selection of vegetable bio-active peptides in full compliance with the restrictive parameters of eco-sustainability required by the market. The development rationale for these


products focused on restoring hair fibre integrity based on the knowledge of its structural composition, tridimensional order and interactions established by its components with external factors.


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The structure of hair Hair structure is composed of cuticle, cortex, and medulla.1


The cuticle is the outermost


protective layer that provides sensory and shine characteristics. The cuticles overlap like roof shingles, protecting the hair from chemical and physical treatments. The cortex is the major component of hair and is responsible for its mechanical strength and pigmentation. The innermost layer is the medulla. The structural integrity of hair is due to its specific chemical composition, primarily keratin proteins, lipids, and water. These proteins are complex natural compounds that contribute to hair’s physicochemical properties. Human hair keratin is unique due to its higher cysteine residue content than skin keratin, which is 7.6% and 2.9% respectively.2


Higher levels of cysteine


residues in hair lead to higher amount of inter- and intramolecular disulfide bonds, which translates to a durable structure due to covalent bonds.3 The remarkable mechanical resilience of


hair fibre is due to its complex protein structure enforced by multiple types of bonds: covalent bonds, ionic bonds, hydrophobic forces, and hydrogen bonds.4


Tensile strength, as


manifestation of the hair overall mechanical properties, has been studied extensively and is best described by the strain/stress curve of a single hair fibre.1 The fibre elongation due to continuous


extension force exhibits distinct regions of elastic and thixotropic behaviour, which are significantly influenced by the humidity


conditions.1,5


While the precise impact of all


bond types on hair’s tensile strength is not yet fully understood, the role of disulfide bonds has been researched extensively.2 Disulfide bridges (bonds) across the amorphous proteins in the cortex create a matrix within which the crystalline microfibrils are embedded and stabilized. Due to the permanent conversion of cystine to cysteic acid during bleaching, the matrix cross-linking degree is expected to be reduced. Hair is also comprised of 1-9% lipids, which


contribute to enhanced conditioning properties such as flexibility, surface gloss, and lubricity of hair.3


Lipids in the internal part of hair provide


structural reinforcement and rigidity water is another component that can comprise up to 32% w/w of hair.6


It supports the formation of


a network of hydrogen bonds with proteins, thereby influencing the tensile strength, swelling, flexibility, and shape of hair and the formation of salt bridges. Kerashaft development rationale is based


on providing the hair shaft with bio-available sulphurated and low polar aminoacids able to re-establish the homeostatic conditions of the hair fibres, especially after exposure to aggressive daily cosmetics treatments (frequent use of aggressive formulations), stressful environmental conditions (excessive UV exposure) and salon treatments (bleaching, dyes, perms, straightening etc.), repairing structural damages leading to dry and straw- like properties that make hair frizzy, difficult to style, comb and easily broken. 7


January 2023 PERSONAL CARE


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