Mechanistic insights into the bleaching of melanin by alkaline hydrogen peroxide

Effects of excessive bleaching on hair: comparative analysis of external morphology and internal microstructure

This study investigates the impact of excessive bleaching on the external morphology and internal microstructure of hair, compared to untreated hair. Using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), we observed significant changes in both the surface and internal structures of bleached hair. SEM analysis of normal hair revealed a relatively clean surface with intact cuticle scales, while bleached hair showed brittle, torn scales with a rough appearance. In areas where the cuticle was broken, remnants of endocuticle debris were still attached, contributing to the rough surface. Complete separation of the cuticle layer resulted in numerous longitudinal fissures along the exposed cortical surface of bleached hair. TEM analysis further confirmed distinct differences; in normal hair, the cuticle layer and cortex were well-separated, and a small hole was observed within the endocuticle of the cuticle cells. Conversely, in bleached hair, the cuticle layer was separated from the cortex, with numerous pores formed by the dissolution of melanin granules scattered within the cortex, specifically between the macrofibrils. No melanin granules were detected in the cortex of bleached hair, although the macrofibril structure remained intact. The findings clearly indicate that excessive bleaching leads to the loss of the cuticle layer, exposing the cortex and significantly altering the hair's structural integrity.

Automated Standardization of Melanin Bleaching Procedures of Heavily Pigmented Melanocytic Lesions With Low-Concentration Hydrogen Peroxide on an Automated Platform

Melanin is a natural pigment in the human body that is primarily found in the skin and hair. It protects the skin from damage by ultraviolet radiation. Although this pigment plays a crucial role in protecting the human body, it represents a challenge for pathologists to evaluate highly pigmented tissue samples from melanoma or pigmented skin lesions. Abundant melanin may obscure tissue morphology, which makes it very difficult for pathologists to make a differential diagnosis. Melanin pigment is brown-to-black and granular, and its distribution is often uneven in tissues. The presence of these pigments can complicate the analysis of immunohistochemistry (IHC) for 2 reasons. First, they have a direct physical masking effect on antigen-antibody interactions. Second, 3,3-diaminobenzidine, the most commonly used chromogen, has a brown color that is difficult to distinguish from melanin pigment. Therefore, melanin bleaching has become a crucial step in handling pigmented melanocytic lesions. Bleaching techniques aid pathologists in histopathologic examination of melanin-rich tissue. In this study, we integrated melanin bleaching and IHC on an automated IHC platform to set up a rapid and fully automated procedure. Bleaching steps were performed before antigen retrieval. Samples were treated with 1% hydrogen peroxide solution in Tris-HCl buffer (pH 10) at 80°C for 8 minutes, achieving optimal conditions for melanin bleaching while preserving tissue morphology and antigenicity. This rapid, effective, fully automated, and standardized workflow can be applied to routine staining procedures in clinical laboratories, thereby improving the quality of pathological diagnosis.

Advances in testing for sample manipulation in clinical and forensic toxicology-part B: hair samples

As a continuation of part A, focusing on advances in testing for sample manipulation of urine samples in clinical and forensic toxicology, part B of the review article relates to hair, another commonly used matrix for abstinence control testing. Similar to urine manipulation, relevant strategies to manipulate a hair test are lowering drug concentrations in hair to undercut the limits of detection/cut-offs, for instance, by forced washout effects or adulteration. However, distinguishing between usual, common cosmetic hair treatment and deliberate manipulation to circumvent a positive drug test is often impossible. Nevertheless, the identification of cosmetic hair treatment is very relevant in the context of hair testing and interpretation of hair analysis results. Newly evaluated techniques or elucidation of specific biomarkers to unravel adulteration or cosmetic treatment often focused on specific structures of the hair matrix with promising strategies recently proposed for daily routine work. Identification of other approaches, e.g., forced hair-washing procedures, still remains a challenge in clinical and forensic toxicology.

Evaluation of applicability of micro-segmental analysis to hair treated with heat and haircare products

PURPOSE

Micro-segmental analysis (MSA), which enables the measurement of detailed drug distributions in hair by segmenting a single hair strand at 0.4 mm intervals, is indispensable for estimating the day of drug ingestion. However, haircare with dryers and various products can influence drug concentrations in hair. Therefore, the applicability of MSA to hair that was treated with heat or various haircare products was evaluated.

METHODS

Reference hair strands containing drugs consistently along the hair shafts were collected from patients who ingested four hay-fever medicines (fexofenadine, epinastine, cetirizine, and loratadine) daily for 4 months. The hair strands were divided into eight 4 mm regions from the proximal end, and each region was placed on an electric hot plate at 100-200 °C or soaked in haircare products, such as shampoo and bleaching agent. The hair regions were subjected to MSA. Moreover, after a patient was administered midazolam at a single dose and the hair was bleached, the day of midazolam administration was estimated using MSA.

RESULTS

Repetitive heating for 1 min and daily haircare products, such as shampoo, hardly affected the drugs in hair, whereas bleaching products containing H2O2 decreased the amounts of hay-fever medicines in the hair up to 58%. However, the amount of midazolam did not decrease in bleached hair and the day of midazolam administration was successfully estimated.

CONCLUSIONS

The analytes used in this study were minimally affected by ordinary haircare and could be detected even in bleached hair. Therefore, MSA can be applicable regardless of haircare history.

The Distinction between Dematiaceous Molds and Non-Dematiaceous Fungi in Clinical and Spiked Samples Treated with Hydrogen Peroxide Using Direct Fluorescence Microscopy

Dematiaceous fungi are pigmented molds with a high content of melanin in their cell walls that can cause fatal infections in immunocompromised hosts. Direct microscopy is the main method for the rapid diagnosis of dematiaceous fungi in clinical specimens. However, it is often difficult to distinguish their hyphae from non-dematiaceous hyphae and yeast pseudohyphae. Our aim was to develop a fluorescence staining method that targets melanin for the detection of dematiaceous molds in clinical specimens. Glass slide smears of clinical samples and sterile bronchoalveolar lavage spiked with dematiaceous and non-dematiaceous fungi were treated with hydrogen peroxide, and digital images were recorded using direct microscopy with different fluorescent filters. The images of fungi were compared for their fluorescence intensity using the NIS-Elements software. The fluorescent signal between dematiaceous and non-dematiaceous fungi demonstrated a markedly increased mean intensity for dematiaceous molds following hydrogen peroxide treatment (7510.3 ± 10,427.6 vs. 0.3 ± 3.1, respectively, p < 0.0001). No fluorescent signal was detected in the absence of hydrogen peroxide. "Staining" fungal clinical specimens with hydrogen peroxide, followed by fluorescence microscopy examination, can differentiate between dematiaceous and non-dematiaceous fungi. This finding can be used for the detection of dematiaceous molds in clinical specimens and enables the early and appropriate treatment of infections.

Film-Forming Properties of Topical Formulations for Skin and Hair: In Vivo and In Vitro Studies Using Biophysical and Imaging Techniques

The film-forming effect is an important property of formulations for skin improvement and hair protection. Reflectance confocal microscopy, an advanced imaging technique, is an important tool for its evaluation. Thus, the aim of this study was to evaluate the film-forming properties of cosmetic formulations based on starches and containing a Spirulina maxima extract after their application to skin and hair, using sensorial analysis and instrumental measurements, with emphasis on reflectance confocal microscopy. Two formulations based on starches and PEG-75 lanolin containing or not (Vehicle) a Spirulina maxima dry extract were developed. The rheological behavior and sensorial properties of both formulations were evaluated. The film-forming property on the skin was evaluated in terms of skin hydration by RCM imaging analysis and transepidermal water loss (TEWL). The hair tresses were evaluated in terms of mechanical properties and RCM imaging analysis. The formulations showed pseudoplastic behavior and a low hysteresis area. In addition, the presence of Spirulina in the formulation did not interfere in the rheological parameters. Both formulations reduced TEWL and maintained the stratum corneum water content. The protective effect was also observed in the hair, since the application of the formulation with Spirulina showed a better performance in the tensile test when compared to vehicle. Thus, the proposed formulation showed film formation on the skin and hair surface that brought immediate benefits such as a reduction of TEWL. Finally, the formulations were shown to have film-forming effects and their use can be suggested for skin and hair protection against daily damage.

Combining the use of two non-invasive instruments to confirm that a formula can improve skin luminance while respecting constitutive melanogenesis

INTRODUCTION

Skin radiance products achieve perceivable benefits with different sort of mechanism of action.

AIMS

To use two non-invasive instrumental devices to evaluate the effectiveness of a cosmetic formula designed to improve skin reflectance while respecting skin integrity.

PATIENTS AND METHODS

Subjects (N = 43) aged 18-50 years old had healthy skin of phototype V-VI and Individual Typology Angle between -10° and -50°. The treatment was applied twice weekly for 4 weeks on a delineated area of the back, and an adjacent area was left untreated. Instrumental and clinical scoring assessments of treated and untreated skin were performed at baseline and Day 26.

RESULTS

Between baseline and Day 26, reflectance (Delta L*) increased by 1.27 points and was considered as clinically relevant. Dermatologist clinical scoring of radiance significantly improved from 2.6 to 3.6 after 4 weeks of treatment and the Skin Color Chart Clarity level significantly decreased from a score of 15.5 to 14.3, representing a skin reflectance improvement. Conversely, the change between baseline and Day 26 in Mexameter Melanin Density was not clinically different for treated skin versus untreated skin (difference of 2.54). At Day 26, changes from baseline for Mexameter Melanin Density and Delta L* parameters appeared to be uncorrelated (r = -0.036).

CONCLUSIONS

This combination of two non-invasive devices can be useful to confirm that a product can modulate skin reflectance without modifying constitutive pigmentation. The formula tested in this study did not interfere with constitutive melanogenesis.

Nanocrystalline cellulose derived from spruce wood: Influence of process parameters

The cellulose nanocrystals (CNCs) were produced from spruce wood using less hazardous and toxic reagents with understanding of influence of process parameters on CNCs properties. This study employed acetosolv pulping followed by alkaline-peroxide bleaching, eliminating highly reactive chemicals such as Na-chlorites and Na-sulfite for cellulose pulp extraction from spruce wood. Cellulose pulp yield of 41.5 ± 0.7 wt% of dry wood was obtained from pulping followed by bleaching treatment. Cellulose pulp was hydrolyzed with 59.0-65.0 wt% sulfuric acid followed by ultrasonic treatment to produce CNCs. CNCs yield of 8.0 ± 3.2 wt% of dry wood was obtained at 65 wt% acid concentration and yield of 25.1 ± 0.7 wt% at 62 wt% acid concentration. The optimization of acid hydrolysis and ultrasonic treatment resulted in CNCs with high aspect ratios (length/width) up to 48.1. It was demonstrated that higher acid concentration requires lower intensity of ultrasonic treatment for CNCs dispersion, and that higher intensity could enhance aspect ratio without impacting the crystallinity index. However, ultrasonic treatment for longer than 5 min led to destruction of the whisker morphology of CNCs. The extracted CNCs possess high crystallinity index of 80.8 ± 1.7 %, low residual hemicellulose (<2.0 %) and lignin (<0.7 %), and high-char content of 26.7 wt% from thermal degradation.

Taphonomic experiments resolve controls on the preservation of melanosomes and keratinous tissues in feathers

Fossils are a key source of data on the evolution of feather structure and function through deep time, but their ability to resolve macroevolutionary questions is compromised by an incomplete understanding of their taphonomy. Critically, the relative preservation potential of two key feather components, melanosomes and keratinous tissue, is not fully resolved. Recent studies suggesting that melanosomes are preferentially preserved conflict with observations that melanosomes preserve in fossil feathers as external moulds in an organic matrix. To date, there is no model to explain the latter mode of melanosome preservation. We addressed these issues by degrading feathers in systematic taphonomic experiments incorporating decay, maturation and oxidation in isolation and combination. Our results reveal that the production of mouldic melanosomes requires interactions with an oxidant and is most likely to occur prior to substantial maturation. This constrains the taphonomic conditions under which melanosomes are likely to be fossilized. Critically, our experiments also confirm that keratinous feather structures have a higher preservation potential than melanosomes under a range of diagenetic conditions, supporting hitherto controversial hypotheses that fossil feathers can retain degraded keratinous structures.

A possible new oxidation marker for hair adulteration: Detection of PTeCA (1H-pyrrole-2,3,4,5-tetracarboxylic acid) in bleached hair

Hair analysis has become a valuable tool in forensic toxicology to assess drug or alcohol abstinence. Yet, hair adulteration by cosmetic products presents a major challenge for forensic hair analysis. Oxidative treatments, e.g. bleaching, may lead to analyte loss and thereby to false negative results. Currently, the eumelanin degradation product 1H-pyrrole-2,3,5-tricarboxylic acid (PTCA) serves as a marker for oxidative hair treatment, but requires the definition of cut-off values. To investigate further eumelanin degradation products as markers for oxidative hair treatment, hair samples with and without in vitro bleaching (hydrogen peroxide (H₂ O₂ ) concentrations 1.9% up to 12%; incubation times 15 min, 30 min, 60 min) were analyzed by liquid chromatography coupled to high-resolution time of flight mass spectrometry (HPLC-HRMS). The distribution of eumelanin degradation products along the hair shaft was investigated for routine applicability after segmentation of cosmetically untreated hair samples and authentically treated hair samples. The signals of the eumelanin degradation products PTCA, 1H-pyrrole-2,3,4-tricarboxylic acid (isoPTCA), and 1H-pyrrole-2,3,4,5-tetracarboxylic acid (PTeCA) were found to be significantly elevated after in vitro bleaching already with low H₂ O₂ concentrations and after short incubation times. In contrast to PTCA and isoPTCA, PTeCA was not detectable in cosmetically untreated segments up to 12 cm from hair root and was only formed through the oxidation process. The results of the study show that the detection of PTeCA within the proximal 3 to 6 cm segment can be applied to reliably detect hair adulteration attempts through hair bleaching.

Agar quality promotion prepared by desulfation with hydrogen peroxide

The modified agars were prepared using H₂O₂ in ethanol solution at appropriate pH conditions. Some interesting physical and chemical properties of modified agar were determined and characterized compared with those of raw agar, and the underlying mechanisms were preliminarily studied. Results showed that the maximum gel strength of the modified agar was 1068 g/cm², which increased by 30.9% compared with that of raw agar (816 g/cm²), and the minimum sulfate content of the modified agar was 0.21%, which decreased by 73.4% compared with that of raw agar (0.79%). Moreover, the viscosity, molecular weight, gelling temperature and melting temperature all decreased, whereas the whiteness and transparency increased after modification. Fourier transform infrared spectroscopy, scanning electron microscopy and thermogravimetric analysis indicated that the spatial structure of agar have changed after treated with H₂O₂. Taken together, the results demonstrated that the desulfation of agar with H₂O₂ is a promising approach with practical significance.

An Electrochemical Study on the Effect of Metal Chelation and Reactive Oxygen Species on a Synthetic Neuromelanin Model

Neuromelanin is present in the cathecolaminergic neuron cells of the substantia nigra and locus coeruleus of the midbrain of primates. Neuromelanin plays a role in Parkinson's disease (PD). Literature reports that neuromelanin features, among others, antioxidant properties by metal ion chelation and free radical scavenging. The pigment has been reported to have prooxidant properties too, in certain experimental conditions. We propose an explorative electrochemical study of the effect of the presence of metal ions and reactive oxygen species (ROS) on the cyclic voltammograms of a synthetic model of neuromelanin. Our work improves the current understanding on experimental conditions where neuromelanin plays an antioxidant or prooxidant behavior, thus possibly contributing to shed light on factors promoting the appearance of PD.

Comparison of bleaching protocols utilizing hematoxylin and eosin stain and immunohistochemical proliferation marker MCM3 in pigmented melanomas

Melanomas represent the malignant transformation of melanocytes, cells found primarily in the skin to protect epithelium and underlying connective tissues from harmful effects of ultraviolet light. Melanomas vary greatly in morphology and may continue to produce melanin markedly, mildly, or not at all. Performing and evaluating hematoxylin and eosin stains as well as immunohistochemical stains on pigmented melanomas has been a long-standing challenge due to the obscuring pigment. Protocols for removing melanin to reveal cellular morphology have been used successfully for years, but coupling these protocols with stains for immunohistochemistry represents an added challenge. In this study, the investigators evaluated results of various melanin bleaching protocols on tissue morphology, completeness of melanin removal, and immunohistochemistry staining quality. It was found that 1% formamide in 3% H₂O₂ under bright light without heating outperformed other tested protocols.

Spectrophotometric determination of trace hydrogen peroxide via the oxidative coloration of DPD using a Fenton system

A low-cost and environmentally-friendly spectrophotometric method for hydrogen peroxide (H₂O₂) determination based on the oxidative coloration reaction of N,N'-diethyl-p-phenylenediamine (DPD) via the Fenton reactions in aqueous water was established. The generated pink radical cation (DPD⁺) showed maximum absorption at 551 nm. Importantly, under the optimal conditions (pH 3.0, 20 mM DPD, 1.5 mM Fe(II) and reaction time of 45 s), the increase in absorbance at 551 nm for DPD⁺ generation was linear with respect to the addition of H₂O₂ (0-12 μM). The sensitivity and the detection limit of the proposed Fenton-DPD method for H₂O₂ determination at 551 nm were (2.55 ± 0.01) × 10⁴ M^-1 cm^-1 and 0.05 μM, respectively. The stoichiometric factor for the reaction of H₂O₂ with DPD was 1:1.18. The absorbance of the generated DPD⁺ was found to be stable in different types of water within 20 min. Moreover, the proposed Fenton-DPD method could be used for the analysis of the trace H₂O₂ in rainwater and determine the rate constants that involved H₂O₂ with high accuracy.

The role of chelating agents and amino acids in preventing free radical formation in bleaching systems

The control of bleaching reaction is important in hair bleaching and laundry detergents to ensure quality of the final product. A better understanding of the reaction mechanisms is needed to minimize product failures. ³¹P NMR-spectroscopy-based spin trap technique was employed to detect and quantify the free radical species that were generated in different bleaching solutions. These solutions contained the key actives in an alkaline hair colorant/bleaching product, an ammonium salt and hydrogen peroxide at pH = 10. Generally, the main radical species detected in hair oxidative coloring or bleaching processes, were hydroperoxyl/superoxide radicals HO₂·/O₂^.-, amino radicals ·NH₂ and hydroxyl radicals ·OH. Their amounts showed a variation based on the chemical composition of the bleaching systems and the metal ion content. The generation of free radicals from reactions between transition metal ions, such as copper, and hydrogen peroxide at pH = 10 was evaluated. In the absence of chelating agents, the copper ions generated a significant level of hydroxyl radicals in a Fenton-like reaction with hydrogen peroxide at pH = 10. Besides that, an increase in copper ion content led to an increase of amino radical ·NH₂, whereas the concentration of superoxide radical O₂^·- decreased which was not yet well reported in the previous literature. The effect of chelating agents like ethylenediaminetetraacetic acid (EDTA), tetrasodium-iminodisuccinate (IDS), a mixture of basic amino acids and dicarboxylic acid on free radical formation was investigated in the presence of binary Cu²⁺-Ca²⁺ bleaching systems. As expected, in the binary Cu²⁺-Ca²⁺ ion system EDTA did not suppress hydroxyl radical formation effectively, but the mixture containing sodium succinate, lysine and arginine reduced hydroxyl radical formation, whereas IDS (nearly) completely inhibited hydroxyl radical formation. The results indicated that each bleaching solution has its characteristic performance and damage profile. Whereas the reactivity can be controlled by the usage of chelating agents.

Protective Bleaching of Camel Hair in a Neutral Ethanol⁻Water System

As conventional bleaching under alkaline conditions is chemically damaging to protein fibers, a three-stage protective bleaching process in neutral ethanol⁻water mixtures was proposed for camel hair using mordanting with ferrous salts, oxidative bleaching with hydrogen peroxide, and reductive bleaching with sodium hydrosulfite. The aim of this work was to improve the whiteness degree of camel hair without substantial tenacity loss. In addition, the roles of ethanol during the bleaching treatment were also examined by characterizing the fibers using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, and X-ray diffraction. The whiteness degree and mechanical properties of camel hair bleached in the neutral ethanol⁻water system were significantly superior to those of fibers bleached by a conventional method. SEM images showed no visible cracks on the scales of fibers bleached in the ethanol⁻water system, whereas large grooves were observed on fibers bleached in aqueous solution. TEM images confirmed the positive influence of ethanol on the mordanting process, and FTIR spectra suggested that ethanol reduced the breakage of hydrogen bonds in the fibers during the oxidative bleaching process. These findings indicate the potential of this protective bleaching method for application to a broad range of other natural protein fibers.

Persulfate Reaction in a Hair-Bleaching Formula: Unveiling the Unconventional Reactivity of 1,13-Diamino-4,7,10-Trioxatridecane

The stability and unconventional reactivity of 1,13‐diamino‐4,7,10‐trioxatridecane in the presence of NH₃, H₂O₂, and (NH₄)₂S₂O₈ are described. The ether‐diamine is an ingredient marketed to hair salons and consumers for so‐called “plex” services to compensate for hair damage during bleaching. The main reaction product identified is an unexpected azanyl ester derivative. This is considered relevant for the safety evaluation when used in cosmetic products. The mechanism of reaction was explored through DFT calculations. This study represents the first attempt to assess the stability of a plex active in an oxidative environment.