Raman spectroscopy and electronic microscopy structural studies of Caucasian and Afro 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.

Role of Race/Ethnicity, Sex, and Age in Surface-Enhanced Raman Spectroscopy- and Infrared Spectroscopy-Based Analysis of Artificial Colorants on Hair

Forensic microscopy has been used in forensic hair analysis to determine the racial origin of hair samples. However, this technique is subjective and often inconclusive. Although, to a large extent, this problem can be solved with the use of DNA analysis, which is capable of identifying the genetic code, biological sex, and racial origin from a strand of hair, this PCR-based analysis of hair is time- and labor-consuming. Infrared (IR) spectroscopy and surface-enhanced Raman spectroscopy (SERS) are emerging analytical techniques that can be used to advance forensic analysis of hair by enabling confirmatory identification of hair colorants. Having said that, it remains unclear whether the race/ethnicity, sex, and age of individuals should be considered upon IR spectroscopy- and SERS-based analysis of hair. Our results showed that both techniques enabled robust and reliable analyses of hair of different races/ethnicities, sexes, and age groups colored using four different permanent and semipermanent colorants. We also found that SERS could be used to identify the race/ethnicity, sex, and age of the individuals via spectroscopic analysis of colored hair, whereas IR spectroscopy was capable of accurately revealing this important anthropological information only from uncolored hair. These results outlined some advantages and limitations of both vibrational techniques in the forensic examination of hair samples.

An in vitro analysis of the hemostatic efficacy of fibrinogen precipitation with varied keratin fraction compositions

In preclinical studies, human hair has demonstrated effective hemostatic properties, potentially attributed to keratin proteins facilitating rapid conversion of fibrinogen to fibrin during coagulation. However, the rational use of human hair keratin for hemostasis remains unclear, given its complex mixture of proteins with diverse molecular weights and structures, leading to variable hemostatic capacity. To optimize the rational utilization of human hair keratin for hemostasis, we investigated the effects of different keratin fractions on keratin-mediated fibrinogen precipitation using a fibrin generation assay. Our study focused on high molecular weight keratin intermediate filaments (KIFs) and lower molecular weight keratin-associated proteins (KAPs) combined in various ratios during the fibrin generation. Scanning electron microscope analysis of the precipitates revealed a filamentous pattern with a broad distribution of fiber diameters, likely due to the diversity of keratin mixtures involved. An equal proportion of KIFs and KAPs in the mixture yielded the most extensive precipitation of soluble fibrinogen in an in vitro study, potentially due to structure-induced exposure of active sites. However, all hair protein samples exhibited diverse catalytic behaviors compared to thrombin, highlighting the potential of utilizing specific hair fractions to develop hair protein-based hemostatic materials with optimized capacity.

Morphological and chemical profiling for forensic hair examination: A review of quantitative methods

Within the past two decades, there have been many studies for quantitative analysis on human hair samples. Microscopical and chemical analysis techniques have been used to analyze various aspects of hair regarding biological, chemical, anthropological, cosmetic, and forensic applications. Studies have attempted to develop quantification methods to increase the evidentiary value of hair in forensic casework. The literature reviewed in this paper provides some of the current techniques used for forensic examinations and quantitative methods. Although microscopical analysis has been scrutinized in the past, using chemical and microscopical techniques can provide a myriad of information. The extraction of DNA from hair provides high-value evidence; however, it may not be readily available and may yield inconclusive results. Hair analysis can be used for many forensic applications such as comparison, toxicology, and exposure analysis. In this article, we will review published research material regarding chemical and microscopical techniques for human hair analysis. Aspects considered for this review were the sample size requirement for analysis and the destructive nature of the instrumental method. This review will focus on both macro and micro quantitative methods for human hair analysis.

Characterization by Raman and infrared spectroscopy and fluorescence microscopy of human hair treated with cosmetic products

Analytical studies on hair structures have evolved significantly over the years and vibrational spectroscopic techniques, such as Raman and infrared, have been increasingly used for such purposes. Nowadays, there is a need to understand more and more about the action of cosmetics on the hair fiber, so this work aims to analyze the permeation of cosmetic treatments into the hair. For the molecular structural characterization, Raman and infrared spectroscopy techniques were used, being verified the efficiency in the analysis of hair samples, demonstrating the internal characteristics of the fiber and the permeation of different cosmetics. Four cosmetics were chosen for this study and, due to the techniques used, it was possible to observe the diffusion of these products inside the bleached hair. It was observed with the Raman vibrational spectroscopy that the concentration of the products is found mainly in the cuticular region, decreasing the permeate content when approaching the central region, and the infrared spectroscopy showed results compatible with the Raman spectroscopy. Therefore, vibrational spectroscopy proved to be a valuable tool for the study of cosmetic permeation into the hair fiber and for the analysis of its external and internal structure.

Effects of chemical straighteners on the hair shaft and scalp: a review

Background

The effects of chemical straighteners on the scalp and hair shaft are not fully known, although such substances are widely used. Hair straightening became popular in Brazil with the use of formaldehyde and its derivatives, despite the prohibition by the current legislation.

Objective

To identify changes in hair shaft and scalp caused by the use of chemical straighteners.

Methods

A search was performed using keywords in three databases from 03/16/2020 to 05/20/2020, with publications between the years 2000 to 2020. After applying the inclusion and exclusion criteria, 33 articles were selected for review.

Results

In some studies, hair relaxers were associated with eczema, desquamation, pain, burns, and inflammation in the scalp. Hair loss, damage to the shaft, alteration in the color of the hairs and in the composition of their amino acids were observed. Findings are variable across the studies.

Study limitations

The search was restricted to three databases, in two languages, different study designs were accepted.

Conclusions

Straightening techniques can have side effects, including scalp inflammation, damage to the shaft, and hair loss. Its long-term effects remain unknown and further studies are necessary.

Recent advances of vibrational spectroscopy and chemometrics for forensic biological analysis

Biological materials found at a crime scene are crucially important evidence for forensic investigation because they provide contextual information about a crime and can be linked to the donor-individuals through combination with DNA analysis. Applications of vibrational spectroscopy to forensic biological analysis have been emerging because of its advantageous characteristics such as the non-destructivity, rapid measurement, and quantitative evaluation, compared to most current methods based on histological observation or biochemical techniques. This review presents an overview of recent developments in vibrational spectroscopy for forensic biological analysis. We also emphasize chemometric techniques, which can elicit reliable and advanced analytical outputs from highly complex spectral data from forensic biological materials. The analytical subjects addressed herein include body fluids, hair, soft tissue, bones, and bioagents. Promising applications for various analytical purposes in forensic biology are presented. Simultaneously, future avenues of study requiring further investigation are discussed.

Host factors that shape the bacterial community structure on scalp hair shaft

In this study, we performed 16S rRNA amplicon sequencing analysis of scalp hair shaft from 109 volunteers, who were surveyed using a questionnaire about daily scalp hair care, and employed multiple statistical analyses to elucidate the factors that contribute to the formation of bacterial community structures on scalp hair shaft. Scalp hair microbiota were found to be specific for each individual. Their microbiota were clearly divided into two clusters. Genus level richness of Pseudomonas (Ps) and Cutibacterium (Cu) contributed to the clusters. The clusters around Pseudomonas and Cutibacterium were named Ps-type and Cu-type, respectively. The host gender influenced the bacterial cell numbers of the major genera that included Cutibacterium, Lawsonella, Moraxella, and Staphylococcus on scalp hair shaft. In addition to host intrinsic factors, extrinsic factors such as hair styling and colouring affected the bacterial cell numbers of the major genera. These factors and chemical treatments, such as bleaching and perming, also affected the Ps-type to Cu-type ratios. These results suggest that bacterial community structures on scalp hair shaft are influenced by both intrinsic and extrinsic factors.

New Diagnostic Tools to Evaluate Hair Loss

The precise and reliable diagnosis of hair loss disorders is essential for developing a successful management plan. It is, thus, the responsibility of the dermatologist to select the appropriate diagnostic tools to effectively evaluate patients presenting with hair loss concerns. Fortunately, there is a growing body of noninvasive and invasive diagnostic resources, each with advantages and disadvantages. For the practicing dermatologist, tactile assessments and direct visualization are enhanced with scoring instruments, questionnaires, handheld trichoscopy, and scalp biopsy. For research and clinical study purposes, the more precise, high-resolution tools such as videodermoscopy, optical coherence tomography, and phototrichograms, may be useful.

Effect of varied hair protein fractions on the gel properties of keratin/chitosan hydrogels for the use in tissue engineering

Keratin/chitosan composite is a readily available source for a hybrid hydrogel in tissue engineering. While human hair keratins could provide biological functions, chitosan could further enhance the mechanical strength of the hybrid hydrogels. However, hair keratin is a group of natural proteins, and the uncontrolled hair protein contents in a hydrogel may lead to the batch-to-batch inconsistent gel properties. The purpose of this study was to investigate the role of hair protein composition, including the keratin-associated proteins (KAPs, 6-30 kDa) and keratin intermediate filaments (KIFs, 45-60 kDa) on gel characteristics of the keratin/chitosan hydrogel. The various compressive and tensile modulus of the gel was observed based on the selection of different protein fractions as the significant gel components. These results thus suggest a straightforward method of preparing hair keratin/chitosan hydrogel with much more controllable gel properties by merely modulating the KAPs/KIFs ratios in a gel.