Jennifer Mary Marsh

Quantitative detection of chemical compounds in human hair with coherent anti-Stokes Raman scattering microscopy

Coherent anti-Stokes Raman scattering (CARS) microscopy is used to determine the distribution and concentration of selected compounds in intact human hair. By generating images based on ratiometric CARS contrast, quantitative concentration maps of both water and externally applied d-glycine are produced in the cortex of human hair fibers. Both water and d-glycine are found to homogeneously distribute throughout the cortical regions of the hair. The ability to selectively detect molecular agents in hair fibers is of direct relevance to understanding the chemical and physical mechanisms that underlie the performance of hair-care products.

Liquid crystal colloidal structures for increased silicone deposition efficiency on colour-treated hair

An approach is described to increase the deposition efficiency of silicone conditioning actives from a shampoo on colour‐treated hair via liquid crystal (LC) colloidal structures, created with a high charge density cationic polymer, poly(diallyldimethyl ammonium chloride) and negatively charged surfactants. LCs are materials existing structurally between the solid crystalline and liquid phases, and several techniques, including polarized light microscopy, small angle X‐Ray analysis, and differential scanning calorimetry, were used to confirm the presence of the LC structures in the shampoo formula. Silicone deposition from the LC‐containing shampoo and a control shampoo was measured on a range of hair substrates, and data from inductively coupled plasma optical emission spectroscopy analysis and ToF‐SIMS imaging illustrate the enhancement in silicone deposition for the LC shampoo on all hair types tested, with the most pronounced enhancement occurring on hair that had undergone oxidative treatments, such as colouring. A model is proposed in which the LC structure deposits from the shampoo onto the hair to: (i) provide ‘slip planes’ along the hair surface for wet conditioning purposes and (ii) form a hydrophobic layer which changes the surface energy of the fibres. This increase in hydrophobicity of the hair surface thereby increases the deposition efficiency of silicone conditioning ingredients. Zeta potential measurements, dynamic absorbency testing analysis and ToF‐SIMS imaging were used to better understand the mechanisms of action. This approach to increasing silicone deposition is an improvement relative to conventional conditioning shampoos, especially for colour‐treated hair.

Role of copper in photochemical damage to hair

The objective of this work was to identify whether low levels of redox metals such as copper will accelerate damage to hair on exposure to UV irradiation and whether this damage can be prevented.

Thermal denaturation and structural changes of α-helical proteins in keratins.

To gain insight into the thermal stability of intermediate filaments and matrix in the biological composite structure of α-keratins, the thermal denaturation performance of human hair fibers was investigated by Modulated Differential Scanning Calorimetry (MDSC) in the dry and the wet state. Denaturation enthalpy ΔH(D) in water was found to be independent of heating rate (11.5J/g) and to be approximately double as high as in the dry state (5.2J/g). The lower enthalpy (dry) and its dependency on heating rate are attributed to effects of pyrolysis. The stepwise change of reversing heat capacity ΔC(p) marks the denaturation process as a classic two-stage transition. The increase of ΔC(p) with heating rate reflects a continuous shift of the nature of the denaturation of the α-helical material, first, into random coil and then towards random β-materials for lower heating rates. Denaturation temperatures follow Arrhenius relationships with heating rate, yielding activation energies of 416kJ/mol (dry) and 263kJ/mol (wet), respectively. A decrease of activation energy (wet) for high heating rates supports the hypothesis of systematic changes of the pathway of denaturation.

Advanced hair damage model from ultra-violet radiation in the presence of copper

Damage to hair from UV exposure has been well reported in the literature and is known to be a highly complex process involving initiation via absorption of UV light followed by formation and propagation of reactive oxygen species (ROS). The objective of this work was to understand these mechanisms, explain the role of copper in accelerating the formation of ROS and identify strategies to reduce the hair damage caused by these reactive species.

The role of chelants in controlling Cu(II)-induced radical chemistry in oxidative hair colouring products

The catalytic formation of hydroxyl radicals in oxidative hair colourant systems in the presence of added copper ions was measured and quantified using a colorimetric probe N,N′‐(5‐nitro‐1,3‐phenylene)bisglutaramide. Also monitored in the same experiments was the decomposition of hydrogen peroxide.

Metals in female scalp hair globally and its impact on perceived hair health

Globally, billions of individuals wash their hair in water, which acts as an exogenous metal source. Many studies which measure the metal levels found on human hair specifically aim to remove exogenous materials prior to analysis. Although this is needed when using hair analysis to probe the impact of the local environment on endogenous metal levels, it is not relevant for understanding exactly what is on hair as a result of contact with its daily environment. Understanding these levels are important, as the presence of redox active metals, such as copper and iron, can impact fibre health, either as a result of UV irradiation, or during the hair colouring process. A global hair sampling study of over 300 individuals from nine countries has been performed, and the combined endogenous and exogenous metals analysed. The levels measured vary widely, even within the narrow geography of each hair sampling location. The levels of calcium, magnesium, copper and iron were not correlated, and within each location, there are expected to be individuals with high metal levels. Levels increased from hair root to tip for calcium, magnesium and copper, attributed to hair contact with the environment showing the impact of exogenous metals in the overall levels on hair. Levels of redox metals were comparable between individuals who coloured or did not colour their hair, although water hardness ions were statistically significantly higher for hair colouring individuals. Individuals who perceived their hair health as poor had higher metal levels on their hair. Controlling metals on hair, either by preventing their binding during environmental contact, or through controlling their ability to cause hair damage, should lead to improved consumer perceived hair health.

The structural implications of water hardness metal uptake by human hair

Human hair can extract significant levels of calcium and magnesium, water hardness metals, from tap water immediately following chemical treatments and during hygiene practices. We have previously shown that this uptake is primarily a function of the condition of the hair. Depending on the extent of chemical damage, the hair can extract notable amounts of water hardness metals even from soft water. As water hardness metals concentrate primarily in the cuticle layers of the hair fibre, it is hypothesized that their presence will affect the structural properties that are chiefly driven by the cuticle. We examined hair mechanics and styling by technical measures of single‐fibre torsional and tensile properties, combability and style retention as a function of the calcium and magnesium content of virgin and bleached hair. Our work has indicated that water hardness can affect hair properties. Fibre stiffening was induced by the presence of water hardness metals inside the fibres of both virgin and bleached hair. A reduction in combing forces was also observed, and this effect is believed to be a result of the stiffening. The style retention of virgin hair was improved by water hardness metals, whereas that of bleached hair was slightly reduced.

Mechanistic insights into the bleaching of melanin by alkaline hydrogen peroxide

Abstract This work aims to determine the roles of reactive oxygen species HO· and HO2‐ in the bleaching of melanins by alkaline hydrogen peroxide. Experiments using melanosomes isolated from human hair indicated that the HO· radical generated in the outside solution does not contribute significantly to bleaching. However, studies using soluble Sepia melanin demonstrated that both HO2‐ and HO· will individually bleach melanin. Additionally, when both oxidants are present, bleaching is increased dramatically in both rate and extent. Careful experimental design enabled the separation of the roles and effects of these key reactive species, HO· and HO2‐. Rationalisation of the results presented, and review of previous literature, allowed the postulation of a simplified general scheme whereby the strong oxidant HO· is able to pre‐oxidise melanin units to o‐quinones enabling more facile ring opening by the more nucleophilic HO2‐. In this manner the efficiency of the roles of both species is maximised. Graphical abstract Figure. No Caption available. HighlightsThe roles of oxidants in the mechanism of hair melanin bleaching are proposed.Both hydroxyl radical and perhydroxyl anion contribute to melanin bleaching.Hydroxyl radicals pre‐oxidise melanin facilitating reaction with perhydroxyl anion.Ammonia plays no role in bleaching beyond melanin solubilisation and pH control.

Preserving fibre health: reducing oxidative stress throughout the life of the hair fibre.

Hair health is an important attribute to women globally – specifically attributes such as shine, healthy tips, frizz‐free and strength. However, many women will claim to have at least moderate hair damage caused by habits and practices such as washing, combing and brushing, use of heated implements and regular use of chemical treatments. The objective of this work was to investigate two mechanisms of damage – hair colouring and UV exposure – where oxidative processes are involved. The role of copper in these oxidative processes was then investigated: its presence in hair and its consequent impact on hair damage via free radical formation. Finally, the role of chelants N,N’‐ethylene diamine disuccinic acid (EDDS) and histidine in preventing free radical formation was investigated and shown to improve hair health.