EURO COSMETICS: Hair damage is a common occurrence that we experience on a regular basis. What are the key factors contributing to hair damage, the “weak points”, and the biochemical consequences?
Dr. Sabrina Behnke: Hair damage can occur via different routes: Bleaching, chemical straightening or curling (“perm”) will cleave disulfide bonds and create cysteic acid residues. Ultimately, chemical treatments will affect all types of cross-linking bonds – disulfide bonds, ionic bonds, and hydrogen bonds – as these treatments require harsh conditions (high pH) to open the cuticle and allow for structural changes of the hair.
Besides chemical damage, other types of damage that can affect hair:
- Mechanical damage from brushing, hair ties which results in cuticle damage or even breakage.
- Heat damage from the effect of blow drying and hot iron tools where excessive heat can damage bonds as well.
On a molecular level, the biochemical consequences can be described as follows: Disulfide bonds are the cross-links between pairs of cysteine residues on adjacent peptide chains. High levels of disulfide bonds are a unique feature of hair proteins. The matrix proteins contain higher levels of cysteine relative to intermediate filament proteins and are heavily cross-linked with disulfide bonds. On the other hand, ionic bonds form between ionized functional groups – the basic side groups on arginine, histidine, and lysine, and the acidic side groups on aspartic acid and glutamic acid. Ionic bonds, also called salt linkages, help to construct tertiary and quaternary protein structures that occur in hair.
The third type of bonds, so-called hydrogen bonds form between atoms that have partial electrical charges, and they also form between atoms on adjacent protein chains. Hydrogen bonds can also form between water molecules and proteins and are important in the creation of secondary protein structures such as α-helixes and β-sheets, and many other protein structures.
EURO COSMETICS: How does the industry differentiate between reversible and irreversible hair damage? And how does this compare with consumer insights?
Dr. Sabrina Behnke: There is no exact scientific definition of a bond builder for hair, although some have proposed the following definition: “A formulation component that is able to penetrate into the hair and improve or restore the internal structure of hair, giving rise to an improvement in hair mechanical properties” (How Bond Builders “Repair” Hair by Paul Cornwell Ph.D TRI Princeton, Princeton, NJ. and Jennifer Marsh, Ph.D., Procter & Gamble, Mason, OH. Cosmetics & Toiletries. 27 February 2023).
Since the term “hair bonding” is very loosely used in the industry, the customer does not have an in-depth understanding of the different bonds and which products or ingredients are able to address or repair them.
Currently, the market features bonding ingredients based on acids (citric acid, maleic acid, glycolic acids) that simply restore hydrogen and salt bonds but are unable to restore disulfide bonds. The acid-based products are suitable for the mass market because of the affordability of the so-called bond building ingredient.
While this makes the bonding market accessible for mass market brands, consumers need to understand that these acid-based products are not able to provide the damage repair that more advanced technologies can provide.
EURO COSMETICS: Hair keratin is a composite structure whereby filaments are embedded or integrated into a protein matrix. The amino acid cysteine is vital in the formation of (disulphide)-bonding. What happens in the destabilization process that causes “damage” to keratin and thus hair? Can you also explain the importance of “reduction” in restoration of ”bonding”?
Dr. Sabrina Behnke: Disulfide bonds are the cross-links between pairs of cysteine residues on adjacent peptide chains. High levels of disulfide bonds are a unique feature of hair proteins. The matrix proteins contain higher levels of cysteine relative to intermediate filament proteins and are heavily cross-linked with disulfide bonds.
The breaking of disulfide bonds is required to make permanent changes to the hair e.g. bleaching, removing color or melanin, curling (also known as perming) or straightening of hair. In a sense, temporary damage is desired as it makes the hair amenable to structural changes (changing of the shape or color). The goal is to repair bonds as much as possible after the treatment so that long-term damage is not part of the new “look”.
Several types of bonds get damaged (oxidative damage) when the hair gets chemically treated. While hydrogen and ionic bonds are weak and easily damaged during washing, this damage is generally reversible with conditioners (since ionic bonds are repaired when hair is restored to its natural pH of 4.5–5.5) and during gentle drying (hydrogen bonds are restored to a new shape when hair is dried). Disulfide bonds are not easily repaired. A key component is a “reducing” environment at lower pH value (<5.5). High pH will break open the bonds, while a reducing environment promotes repair of the damaged bonds with materials high in cysteine such as our new ingredient.
EverBond™, is high in cysteine and we have shown that it not only repairs disulfide bonds but also increases break resistance and elasticity of the hair.
EURO COSMETICS: EverBond™ is one of TRI-K’s newest additions to their portfolio of products, and will be presented at your booth 1P110 at In-Cosmetics Paris and NYSCC Suppliers’Day. What makes this bonding product different from other types of hair bonders? What performance criteria did you measure?
Dr. Sabrina Behnke: Disulfide bond damage has been deemed non-reversible by leading scientists in the field, but we are demonstrating that our new ingredient has the ability to increase the quantity of disulfide bonds post-chemical treatment of the hair which caused the damaged bonds in the first place.
In today’s hair bonding market, we see a lot of synthetic peptides but a natural solution is often more desired by consumers. EverBond™ was created to satisfy the need for more natural and sustainable formulations while not compromising on efficacy and performance.
Another fantastic benefit is the instant results on strength of the hair. We show an immediate increase of hair elasticity and breakage resistance vs. a placebo product after just a single application of either a shampoo containing 1% EverBond™ or a leave-on conditioner containing 1% EverBond™ This means that the hair will be more resilient to everyday stressors such as brushing even after just ONE application.
To showcase the multitude of hair health benefits, we measured several parameters. To demonstrate that the ingredient has penetrated deep into the cortex (instead of remaining on the surface), we used fluorescence microscopy to image cross-sectional hair fiber treated with Rhodamine B. Hair fibers treated with EverBond™ will only allow small amounts of the dye to penetrate the hair as space has been taken up by our bonding ingredient.
A key feature of the new launch is its ability to re-bond cleaved disulfide bonds which can be shown via FTIR- ATR measurements. The tool can measure the presence of specific molecular bonds such as S=O and C=O bonds. A high level of S=O bonds (compared to C=O) indicates that disulfide bonds have been cleaved and higher levels of cysteic acid (a type of sulfonic acid and a product of the oxidative cleavage reaction) can be detected. Cysteine repair as a function of decreased detection of cysteic acid is then characterized in the hair fibers via FTIR-ATR (see chart 1).
An effect that will be immediately noticeable to consumers, is the improvement of hair strength and resilience. A well-known tool to measure this so-called tensile strength is the Dia-stron fiber testing system. Individual hair fibers are tested for different strength parameters by applying strains. We have the ability to apply partial forces (25% strain) to test the hair’s resilience under everyday conditions such as brushing or extreme strain to show much force it would take to break the hair. We have tested EverBond™ treated hair versus a placebo and a control (popular bond-
building shampoo on the market) and EverBond™ is the clear winner in terms of immediate tensile strength improvement (see chart 2).
Additionally, we measured Keratin integrity of hair fibers via differential scanning calorimetry (DSC), showing that hair trea-ted with EverBond™ has a higher resistance to heat (meaning higher potential of protection of α-keratin and amorphous phase of keratin, respectively). α-keratin enhances elasticity and reduces breakage. Amorphous Keratin prevents and protect from heat damage.
EURO COSMETICS: We see a variety of so-called protein treatments to help repair damaged hair by coating the strands. Obviously, this is likely to cause considerable build-up over time, and even make the problem worse. How does using EverBond™ help people that seem to be at higher risk for protein buildup (hair that tends to be dry, and hair that’s textured or curly)? Will the consumer notice a difference? If so what?
Dr. Sabrina Behnke: Many protein treatments barely coat the surface of the hair, resulting in film-formation. Over time this film formation can cause more and more build-up. In this case, the hair might feel dry and look lifeless and dull. It can also be prone to tangling, making it hard to blow-dry, style and manage. The theory here is that too much protein on top of the hair can prevent water and other products from fully hydrating strands, causing hair to become dry and brittle.
However, it will be hard to tell the difference between hair that is dry from excess protein or from damage such as heat styling and chemical treatments. When such hair is examined under a scanning electron microscope (SEM), one will see damage to hair cuticles such as lifting of hair cuticles or even holes in the cuticle, possibly exposing the cortex.
The studies we described above show nicely that EverBond™ penetrates into the hair cortex instead of being a film former.
To verify our results, we have additionally performed a build-up study and examined the hair after 20 applications. Image 1 shows a very smooth hair texture without any dryness e.g. lifting of cuticles.
EURO COSMETICS: To counteract hair damage caused by perming, straightening, bleaching, dyeing and electrical hair stylers, how is EverBond™ limited in its ability to manage this? Do you believe that better education is required by consumers and industry alike in the way the treat their hair? How so?
Dr. Sabrina Behnke: EverBond™ is a hair bonding ingredient that is very well suited to address the damage caused by perming, chemical straightening, bleaching, and styling as it addresses the repair of the main bonds in hair fibers. With the growing trend of hair repair and hair bonding, we see many interesting innovations in the space, and we now have the ability to repair damaged hair better than ever before.
Consumers could benefit from better education around the types of hair bonds, and potential solutions to repair them. We see a lot of products on the market claiming “bond repair” that mostly use specific acids that intend to repair ionic bonds. These products while beneficial to overall hair repair, will likely not be able to repair disulfide bonds. Consumers with extremely damaged hair may require the use of other products to really achieve the repair and strengthening benefits they require.
EURO COSMETICS: On a personal note you are the Business Director – Biopolymers & Modern Preservatives at TRI-K Industries. How do you see this role in the development of TRI-K excellence in the field of hair care, especially in light of current and new developments in the cosmetic industry? Feel-free!
Dr. Sabrina Behnke: TRI-K has been a strong player in the hair care ingredients market in the past few years and we have launched new innovations annually. In our labs at the Denville, NJ headquarter we have built up impressive hair testing capabilities (fluorescence microscopy, SEM microscopy, tensile strength, shine measurements, friction analysis, and many more) and we are currently constructing an in-house salon on-site to be able to test formulations and perform expert sensory evaluations.
Besides our testing capabilities, we are also strengthening our library of so-called TRIssentials formulations that are designed to inspire our customers with interesting new product formats, showcasing our newly launched ingredients. We will be presenting 4 formulations at our booth 1P110 at In-Cosmetics Paris as well as NYSCC Supplier’s Day and we encourage anyone who is interested to try them out.
EURO COSMETICS: Thank you for the conversation
Dr. Sabrina Behnke
Dr. Sabrina Behnke holds a BSc in Water Sciences from the University of Duisburg-Essen in Germany and a PhD in Microbiology from Montana State University. During her graduate studies she investigated microbial biofilms in water distribution systems at the Center for Biofilm Engineering in Bozeman, MT, where she collaborated with multinational consumer goods companies. Dr. Behnke then joined Reckitt Benckiser as a R&D microbiologist, supporting EPA claim substation for disinfectant household products. Additionally, she held roles in Personal Care Formulation Innovation and Technology Scouting. In 2018, she switched from the manufacturer’s to the supplier’s side of the industry as a Global Product Manager for Symrise where she managed a portfolio of Multifunctionals and Preservatives. Today, Dr. Behnke is an Associate Business Director for biopolymers and preservatives with TRI-K Industries.
