Lead-revealed lipid organization in human hair

Alterations promoted by acid straightening and/or bleaching in hair microstructures

Human hair is a biopolymer constituted mainly of keratin intermediate filaments, lipids, pigments and water. Cosmetic treatments usually interact with the hair at the molecular level, inducing changes in its components and modifying the physicochemical and mechanical properties of the fibers. Here, the effect of acid straightening on the morphology and ultrastructure of Caucasian hair was investigated by a group of complementary experimental methods: wide-, small- and ultra-small-angle X-ray scattering; high-resolution 3D X-ray microscopy; quasi-elastic neutron scattering and inelastic neutron scattering; thermogravimetry-mass spectrometry; and differential scanning calorimetry (DSC). X-ray diffraction patterns showed that acid straightening associated with a flat iron (∼180°C) changed the cortex of the fiber, shown by denaturation of the intermediate filaments (measured by DSC). The increase in the spacing of the lipid layers and the observation of the dehydration behavior of the fiber provided indications that water may be confined between these layers, while neutron spectroscopy showed alterations in the vibration mode of the CH2 groups of the lipids and an increase of the proton (H+) mobility in the hair structure. The latter may be associated with the extremely low pH of the formulation (pH ≃ 1). Additionally, this investigation showed that bleached hair (one-time bleached) is more damaged by the action of acid straightening than virgin hair, which was shown by a threefold increase in the percentage of total porosity of the tresses. The obtained results demonstrate that the investigation approach proposed here can provide very important thermodynamic and structural information on induced changes of hair structure, and certainly can be applied for the evaluation of the action mode and efficiency of cosmetic treatments.

Flexabrasion Applied to the Evaluation of the Photodegradation of Hair Fibers

Solar radiation is a significant source of damage to hair fibers. However, the instrumental measurement of the consequences of its interaction with hair fibers’ constituents remains a challenge. In this work, the flexabrasion methodology was investigated as a potential tool to quantify the damage to mechanical hair properties caused by solar rays. The in vitro experiment developed for this study simulated four initial conditions of human hair samples, which subsequently underwent different periods of exposure to the radiation emitted by a Xenon arc lamp source. The statistical analysis of the results characterized the methodology’s ability to evaluate the impact of solar radiation on the hair’s mechanical resistance. More evident effects were observed on natural fibers subjected to exposures of up to 60 h and over, corresponding to about 1.5 h per day of sun exposure in Rio de Janeiro over five months. The results point to flexabrasion as an option to evaluate the photoprotection efficacy offered by hair-care products.

Local structure of human hair spatially resolved by sub-micron X-ray beam

Human hair has three main regions, the medulla, the cortex, and the cuticle. An existing model for the cortex suggests that the α-keratin- based intermediate filaments (IFs) align with the hair's axis, but are orientationally disordered in-plane. We found that there is a new region in the cortex near the cuticle's boundary in which the IFs are aligned with the hair's axis, but additionally, they are orientationally ordered in-plane due to the presence of the cuticle/hair boundary. Further into the cortex, the IF arrangement becomes disordered, eventually losing all in-plane orientation. We also find that in the cuticle, a key diffraction feature is absent, indicating the presence of the β-keratin rather than that of the α-keratin phase. This is direct structural evidence that the cuticle contains β-keratin sheets. This work highlights the importance of using a sub-micron x-ray beam to unravel the structures of poorly ordered, multi-phase systems.

Identification of breast cancer-associated lipids in scalp hair

A correlation between the presence of breast cancer and a change in the synchrotron-generated X-ray diffraction (XRD) pattern of hair has been reported in several publications by different groups, and on average XRD-based assays detect around 75% of breast cancer patients in blinded studies. To date, the molecular mechanisms leading to this alteration are largely unknown. We have determined that the alteration is likely to be due to the presence of one or more breast cancer-associated phospholipids. Further characterization of these lipids could be used to develop a novel, sensitive and specific screening test for breast cancer, based on hair initially, and potentially extendable to other biological samples.

Hair analysis as a biomonitor for toxicology, disease and health status

Hair analysis receives a large amount of academic and commercial interest for wide-ranging applications. However, in many instances, especially for elemental or 'mineral' analysis, the degree of success of analytical interpretation has been quite minimal with respect to the extent of such endeavors. In this critical review we address the questions surrounding hair analysis with specific intent of discovering what hair concentrations can actually relate to in a biogenic sense. This is done from a chemistry perspective to explain why and how elements are incorporated into hair and their meaning. This includes an overview of variables attributed to altering hair concentrations, such as age, gender, melanin content, and other less reported factors. Hair elemental concentrations are reviewed with regard to morbidity, with specific examples of disease related effects summarized. The application of hair analysis for epidemiology and etiology studies is enforced. A section is dedicated specifically to the area of population studies with regards to mercury, which highlights how endogenous and exogenous incorporation relies on species dependant metabolism and metabolic products. Many of the considerations are relevant to other areas of interest in hair analysis, such as for drug and isotopic analysis. Inclusion of a table of elemental concentrations in hair should act as a valuable reference (298 references).

Using micro-attenuated total reflection spectroscopy to determine chemically induced changes in neat human hair: feasibility study on the effect of antipsychotic drugs

This investigation examines the feasibility of detecting changes in intact human hair upon drug exposure using diamond attenuated total reflection (ATR) infrared spectroscopy. Prior work on microtomed hair has reported spectra changes in the medulla of the hair resulting from drug exposure. This study focuses on examining the hair intact, eliminating sample preparation and thereby reducing the possibility of sample contamination. Several hair samples were first examined to determine whether the lipids in the medulla could be detected from intact hair. Once this was established, hair samples exposed to drugs were investigated to see if changes in those lipids could be detected. Both internal and external drug exposures were investigated: hair samples were externally (incorporated) exposed to Clozapine and real-life samples were obtained from a patient on alprazolam (Xanax). In both cases, spectral differences in the C-H bands were observed in the hairs with drug exposure as compared to hair with no known drug exposure. These changes are consistent with changes in the lipids in the medulla.

The occurrence and incorporation of copper and zinc in hair and their potential role as bioindicators: a review

This article reviews evidence that suggests Cu and Zn concentrations are not altered significantly by exogenous processes and may be useful in applications of hair analysis. The review attempts to identify what Cu and Zn concentrations may actually indicate biogenically and investigates the mechanisms by which they are incorporated into hair. Associations with specific hair components are proposed and avenues for development as a bioindicator are identified. Areas of research that offer promise in application or confirming the use of Cu and Zn are also indicated. Correlations and relationships with other health disorders are reviewed. Endogenous blood concentrations may also explain alterations in hair structure relating to breast cancer.

Integral lipid in human hair follicle

On the hair surface, cells are covered with a thin lipid layer (LL) covalently bonded to hair proteins. This integral hair lipid is different from sebaceus lipid. We conducted this study to examine the lipid distribution in human hair follicle. Transmission electron microscopy was performed to observe the ultrastructure of the LL. Hair follicles were cut and observed longitudinally along the hair axis. For transmission electron microscopy, new fixative (Lee's fixative: composed of OsO4 and RuO4) was designed as the conventional fixatives such as OsO4 or RuO4 alone were not appropriate for staining for hair follicle lipid. In addition, we measured the chemical composition of integral hair lipid by high-performance thin-layer chromatography. From the above experimental procedure, it was discovered that the lipid in the hair follicle was mainly distributed in hair cuticle and keratinized inner root sheath. A multitude of lamellar granule is observed in the vicinity of the above LL. The chemical composition of integral hair lipid was different from those of epidermal or sebaceous lipids. It is assumed that the LL in the hair follicle is similar to the epidermal LL playing an important role as a skin barrier in the stratum corneum. We proposed here the new terminology "hair barrier" from this point of view.

Extractable substances from human hair: a discussion about the origin of the holes

The existence of holes in the endocuticle, in the inter-macrofibrilar matrix and in the cell membrane complex of hair fibers is described. In this paper, we show that these holes are absent in the hair follicle. However, cell remnants found in young hair inside the follicle are located in the same regions and are of the same dimensions as the holes observed in mature fibers. Since holes in the endocuticle have been described to appear as a result of daily care actions, it is probable that the development of holes in the inter-macrofibrilar matrix and in the cell membrane complex is related to the removal of extractable substances. We discuss hole formation in terms of the nature of the extractable substances and the presence of cell remnants in the young fibers.

Calcium distributions in human hair by ToF-SIMS

Calcium distributions on internal and external surfaces of longitudinally sectioned hairs were analysed with Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). Externally, calcium deposits were observed at the cuticle scale edges. Internal sections showed that the bulk of calcium exists within or just inside the cuticle layer. The medulla may or may not be enriched and other localised concentrations exist in one of two forms; either associated with granular structures or the hair proteins. Calcium appears to show an affinity for proteins with low sulfur content.

Alopecia areata is a T-lymphocyte mediated autoimmune disease: lesional human T-lymphocytes transfer alopecia areata to human skin grafts on SCID mice

Much evidence suggests that alopecia areata is a tissue restricted autoimmune disease. Alopecia areata responds to immunosuppressive agents, and is associated with other tissue restricted autoimmune diseases, including autoimmune thyroiditis and vitiligo. Furthermore, hair regrows when involved scalp is transplanted to nude mice. This study was undertaken to determine whether alopecia areata is mediated by T lymphocytes. Involved scalp from alopecia areata patients was grafted onto SCID mice. Additional biopsies from lesional scalp of the same patients were used to isolate T lymphocytes. These T lymphocytes were cultured with hair follicle homogenate, as well as autologous antigen presenting cells. The T lymphocytes were then injected into autologous scalp grafts on the SCID mice, which had regrown hair. Injection of scalp T lymphocytes resulted in hair loss. Hair loss was associated with the histologic and immunochemical changes of alopecia areata, including perifollicular infiltrates of T cells, along with HLA-DR and ICAM-1 expression by the follicular epithelium. Scalp T lymphocytes that had not been cultured with hair follicle homogenate did not have this effect. Preliminary data suggests hair loss requires a collaboration between CD8+ and CD4+T cells. These studies have demonstrated that alopecia areata can be induced by the transfer of T cells that recognize a hair follicle autoantigen.