KERASHAFT: Bioactive peptides for hair restructuring and hair plex

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.

Hair structure is composed of cuticle, cortex, and medulla. 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. 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.

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. 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.

The fibre elongation due to continuous extension force exhibits distinct regions of elastic and thixotropic behaviour, which are significantly influenced by the humidity conditions. 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.

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. 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. 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. 

Caucasian hair strands were bleached, to damage both the cuticle and cortex. Subsequently each strand was washed with shampoo, treated with 0.5 ml of sample and dried: the tresses were analyzed with four samples (hydrolyzed keratin solution, Kerashaft V solution, Kerashaft Q solution and control) and dried after five minutes.

Additional assessment was made on Caucasian hair, comparing longitudinal and transversal sections of virgin hair subject to bleaching. Homogeneous locks were collected, standardized in number, weight, and length. The analysis was carried out in a closed room, at controlled temperature and humidity at the same time of day. All the strands were subject to washing with a 3% (v/v) solution in SLES- purified water, to remove dirt and cosmetic products.

Afterwards, the washed and dry hair, after a stationing time of 24 hours, was divided into two groups for each type, treated and untreated. Treated hair was then put in contact for five minutes with a serum, subsequently subject to drying with hairdryer for five minutes; the untreated hair is directly subject to analysis. The images of virgin hair, dyed and bleached, treated and not, were compared through scanning electron microscopy (SEM).

A lock was subject to washing with common shampoo, dried with hairdryer and subsequent plate at 220 °C in order to obtain the reference standard. The same treatment was made on locks treated with three samples: 0.5 ml Kerashaft V, hydrolyzed keratin and Kerashaft Q solutions, each of them used at 5%.

Additional studies aimed to evaluate the comparison against a market benchmark based on vegetable derived protein hydrolysate were carried out. In this case, the treatment was made using both the active object of the study and the benchmark at a 1.5% dosage; before this treatment, 12 tresses were subject to level- ten bleaching and chemical physical damage through ammonium thioglycolate and hydrogen peroxide, followed by oven heating.

The treated hair was placed on a pretreated slide and subject to polarized microscope analysis. The hair pictures before and after treatment were compared. Instrumental measurements in image quality were conducted with polarized light microscope and image recording.

These parameters were analyzed through a treatment on twelve strands of Caucasian bleached hair. Six strands were treated with a standard conditioning benchmark treatment (shampoo + conditioner based on vegetable amino-acids complex claimed as “phyto- keratin”).

Another six locks were treated with a shampoo and conditioner (containing Kerashaft @ 1.5%). The tensile test was run through the digital dynamometer ZTS 550N made by Imada. The bundle was strained and after the breakage, the maximum force, average force, and time to reach the max peak were obtained.

For the combing test, combing was analyzed through ZTS 550N that measures the friction generated between a comb/brush and hair during grooming. Therefore, lubrication is evaluated by decreasing grooming forces for product-treated hair relative to the standard control. After grooming, the following parameters were obtained (maximum force and average force).

SEM analysis prove that the bleached hair treated with control sample shows uneven weft with fiberisation and non-overlapped crusting, while the leave-on treatments with Kerashaft V and hydrolyzed keratin @5% (Figure 1), induce remarkable improvement in longitudinal section of the cuticle crusting overlapping and effective and homogeneous filling in the transversal section (data not shown, available on demand).

The longitudinal and transversal sections were also analyzed with a lower dosage treatment of Kerashaft V @ 1.5%. The treatment shows a visible strengthening of the cuticular scales, given by the active ingredient’s capability of settling on the surface of the hair and filling of the cracks and holes caused by the invasive chemical treatments (clearly visible in the untreated bleached hair). The formation of the white flakes at the joints detected on the untreated hair is totally avoided by the treatment, as proven by the sealing of the end portions after the application.

Hair restructuring and plex effect PLM tests show that compared to hydrolyzed keratin, Kerashaft V @ 5% used in leave-on application shows more effective restructuring action at cortex and peri-medular area than a benchmark hydrolyzed keratin treatment, as its crystallography follows the same pattern of virgin hair.

Similar behaviour and performances were observed with a treatment @1.5% against a benchmark phyto-keratin. Kerashaft V treated hair shows more defined and diversified polarization colours, particularly after the drying treatment. This specific activity pattern is likely ascribable to the restructuring features linked to: