The nail and hair in forensic science

Estimation of age and sex from fingernail clippings by using ATR-FTIR spectroscopy coupled with chemometric interpretation

Fingernails can act as important forensic evidence as they can be a source of DNA that may link the victim or accused to the crime scene and may also contain traces of drugs such as cocaine and heroin, in regular users. Moreover, previous studies have shown that analyzing fingernails with various techniques can reveal important information, such as age and sex. In this work, ATR-FTIR spectroscopy with chemometric tools has been used to estimate the age and sex from fingernails by analyzing 140 fingernail samples (70 males, and 70 females) collected from volunteers aged between 10 and 70 years old. The amide bands obtained from spectra confirmed the presence of keratin proteins in the samples. PCA and PLS-R were used for the classification of samples. For sex estimation, samples were divided into four categories based on age groups, followed by the differentiation of sex in each group. Similarly, for age estimation, all samples were divided into two sets based on male and female followed by differentiation of age groups in each set. The result showed that PLS-R was able to differentiate fingernail samples based on sex in groups G1, G2, G3, and G4 with R-square values of 0.972, 0.993, 0.991, and 0.996, respectively, and based on age in females, and males with R-square values of 0.93 and 0.97, respectively. External validation and blind tests were also performed which showed results with 100% accuracy. This approach has proved to be effective for the estimation of sex and age from fingernail samples.

Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) analysis of human nails: Implications for age determination in forensics

A person's age estimation from biological evidence is a crucial aspect of forensic investigations, aiding in victim identification and criminal profiling. In this study, we present a novel approach of utilizing Attenuated Total Reflection Fourier Transform Infrared (ATR FT-IR) spectroscopy to predict the age of donors based on nail samples. A diverse dataset comprising nails from donors spanning different age groups was analyzed using ATR FT-IR, with subsequent multivariate analysis techniques used for age prediction. The developed partial least squares regression (PLS-R) model demonstrated promising accuracy in age estimation, with a root mean square error of prediction (RMSEP) equal to 11.1 during external validation. Additionally, a partial least squares discriminant analysis (PLS-DA) classification model achieved high accuracy of 88% in classifying donors into younger and older age groups during external validation. This proof-of-concept study highlights the potential of ATR FT-IR spectroscopy as a non-destructive and efficient tool for age estimation in forensic investigations, offering a new approach to forensic analysis with practical implications.

The Role of Fingernails in Death Investigation

ABSTRACT

In forensic pathology, forensic onychology studies fingernails and toenails for medicolegal purposes. It mainly deals with DNA profiling from nails, toxicological analysis for detecting poisons, and the collection of trace evidence present under the nails. Injuries to fingernails and their interpretation for medicolegal purposes are the neglected areas of this study. We have discussed the most common types of fingernail injuries and their significance. We found that their notification has significant value in drowning cases, defense wounds on the palm, self-inflicted cuts, burns, electrocution, blunt trauma, physical assault, sexual offenses, and other issues like torture. We emphasize the examination of fingernails in the autopsy and medicolegal clinical examination for better administration of law and justice.

Assessment of Essential and Toxic Element Levels in the Toenails of Children with Autism Spectrum Disorder

Autism spectrum disorder (ASD) has become a global public health concern, impacting the quality of life. The question of gene-environment interaction in the emergence of ASD remains a subject of ongoing debate, and exploring its pathophysiology is thoroughly related to metals as a risk factor. Therefore, this study aims to assess the levels of toxic (Al, Cd, Hg, and Pb) and essential (Cr, Mn, Fe, Ni, Cu, Zn, and Se) elements in toenail samples collected in children with ASD and neurotypical children, by ICP-MS. Parallelly, we will discuss the use of toenails as an exposure indicator. The study involved 208 children aged 3 to 14 from Marrakech, Morocco. One hundred two were diagnosed with ASD and 106 were neurotypical children. Significant statistical differences in the concentration of Cr, Mn, and Fe were documented between the two groups. Higher levels of Pb in toenails compared to reference values have been reported. No association was established between concentrations of elements and age. Spearman correlation coefficients revealed a significantly different pattern of mutual dependence for toxic and essential elements between the two groups. The strongest positive correlations were found in the neurotypical group (Fe-Mn (ρ = 0.750), and Se-Zn (ρ = 0.800)). These results provide additional, although inconclusive, evidence on the probable role of element disturbance in the pathogenesis of ASD. Further studies should be performed to explore other nutritional, cultural, sociodemographic, environmental, and methodological factors that may impact the levels of these elements in the nails and their possible correlation with the incidence of ASD.

A comprehensive review on application of atomic force microscopy in Forensic science

The primary objective of forensic investigation of a case is to recognize, identify, locate, and examine the evidence. Microscopy is a technique that provides crucial information for resolving a case or advancing the investigation process by analyzing the evidence obtained from a crime scene. It is often used in conjunction with suitable analytical techniques. Various microscopes are employed; scanning probe microscopes are available in diverse forensic analyses and studies. Among these, the atomic force microscope (AFM) is the most commonly used scanning probe technology, offering a unique morphological and physico-chemical perspective for analyzing multiple pieces of evidence in forensic investigations. Notably, it is a non-destructive technique capable of operating in liquid or air without complex sample preparation. The article delves into a detailed exploration of the applications of AFM in the realms of nanomechanical forensics and nanoscale characterization of forensically significant samples.

Exposome Impact on Nail Health

Background

The nail unit is a complex system with various components, each serving distinct functions. The exposome, encompassing external and internal factors such as UV radiation, air pollution, dietary habits, and cosmetic product usage, substantially influences nail health and can lead to premature nail aging.

Summary

Internal and external exposomal factors can impact differently on nail health, inducing a variety of different clinical conditions. Effective therapeutic strategies exist, but a comprehensive understanding of how the exposome affects nails is lacking. This article aims to bridge this knowledge gap by exploring the relationship between the exposome and nail health, emphasizing it as a central focus of our analysis.

Key Messages

(1) The exposome, comprising various external and internal factors, may significantly influence nail health negatively, leading to premature nail aging. (2) Different nail conditions may arise due to the exposomal influence on nails. (3) Understanding the exposome's impact on nail health is crucial for developing solutions to mitigate negative effects and improve overall nail well-being.

Sex Determination of Human Nails Based on Attenuated Total Reflection Fourier Transform Infrared Spectroscopy in Forensic Context

This study reports on the successful use of a machine learning approach using attenuated total reflectance Fourier transform infrared (ATR FT-IR) spectroscopy for the classification and prediction of a donor's sex from the fingernails of 63 individuals. A significant advantage of ATR FT-IR is its ability to provide a specific spectral signature for different samples based on their biochemical composition. The infrared spectrum reveals unique vibrational features of a sample based on the different absorption frequencies of the individual functional groups. This technique is fast, simple, non-destructive, and requires only small quantities of measured material with minimal-to-no sample preparation. However, advanced multivariate techniques are needed to elucidate multiplex spectral information and the small differences caused by donor characteristics. We developed an analytical method using ATR FT-IR spectroscopy advanced with machine learning (ML) based on 63 donors' fingernails (37 males, 26 females). The PLS-DA and ANN models were established, and their generalization abilities were compared. Here, the PLS scores from the PLS-DA model were used for an artificial neural network (ANN) to create a classification model. The proposed ANN model showed a greater potential for predictions, and it was validated against an independent dataset, which resulted in 92% correctly classified spectra. The results of the study are quite impressive, with 100% accuracy achieved in correctly classifying donors as either male or female at the donor level. Here, we underscore the potential of ML algorithms to leverage the selectivity of ATR FT-IR spectroscopy and produce predictions along with information about the level of certainty in a scientifically defensible manner. This proof-of-concept study demonstrates the value of ATR FT-IR spectroscopy as a forensic tool to discriminate between male and female donors, which is significant for forensic applications.

Attenuated Total Reflection Fourier Transform Infrared Spectroscopy for Forensic Screening of Long-Term Alcohol Consumption from Human Nails

Fourier transform infrared (FT-IR) spectroscopy is used throughout forensic laboratories for many applications. FT-IR spectroscopy can be useful with ATR accessories in forensic analysis for several reasons. It provides excellent data quality combined with high reproducibility, with minimal user-induced variations and no sample preparation. Spectra from heterogeneous biological systems, including the integumentary system, can be associated with hundreds or thousands of biomolecules. The nail matrix of keratin possesses a complicated structure with captured circulating metabolites whose presence may vary in space and time depending on context and history. We developed a new approach by using machine-learning (ML) tools to leverage the potential and enhance the selectivity of the instrument, create classification models, and provide invaluable information saved in human nails with statistical confidence. Here, we report chemometric analysis of ATR FT-IR spectra for the classification and prediction of long-term alcohol consumption from nail clippings in 63 donors. A partial least squares discriminant analysis (PLS-DA) was used to create a classification model that was validated against an independent data set which resulted in 91% correctly classified spectra. However, when considering the prediction results at the donor level, 100% accuracy was achieved, and all donors were correctly classified. To the best of our knowledge, this proof-of-concept study demonstrates for the first time the ability of ATR FT-IR spectroscopy to discriminate donors who do not drink alcohol from those who drink alcohol on a regular basis.

Selenium in drinking water and cereal grains, and biomarkers of Se status in urine and fingernails of the Main Ethiopian Rift Valley population

BACKGROUND

Selenium (Se) plays an important role in human health, yet Se overexposure or deficiency can lead to deleterious health effects. This study aims to determine the concentration of Se in drinking water and staple cereal grain (maize, wheat, and teff) samples from the Main Ethiopian Rift (MER) Valley, and correspondingly, assesses Se biomarkers and their status as measured in the urine and fingernails of 230 individuals living in 25 MER communities.

METHOD

The concentration of Se in drinking water and cereal grain (maize, wheat, and teff) samples, and urine and fingernail samples were measured using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Demographic, anthropometric, and elemental concentrations were described by their quartiles and mean ± standard deviations. The 5th and 95th percentiles were used to describe the concentrations Se biomarkers ranges. The Se biomarker distributions in different study communities were further characterized according to Se levels found in drinking water, sex, and age using ANOVA, and multivariate regression. We conducted a correlation analysis (with Pearson correlation coefficient) and fitted a regression to evaluate the associations between these variables.

RESULTS

The mean concentration of Se in the drinking water samples was 0.66 (range: 0.015-2.64 µg/L; n = 25), and all samples were below the threshold value of 10 μg/L for Se in drinking water set by the World Health Organiation (WHO). In Ethiopia, most rural communities rely on locally produced cereal grains. We found mean Se concentrations (µg/kg) of 357 ± 190 (n = 14), 289 ± 123 (n = 14), and 145 ± 100 (n = 14) in wheat, teff, and maize, respectively. Furthermore, Se concentrations in drinking water showed no significant correlation with biomarker measures, indicating that the primary source of dietary Se is likely from local foods including staple grains. The mean±SD (5th-95th percentiles) of Se concentrations in fingernails and urine among study subjects were 1022 ± 320 (624-1551 µg/kg), and 38 ± 30 (1.9-100 µg/L), respectively.

CONCLUSION

A sizeable share of study participants (31%) fell below the lower limits of what is considered the currently accepted Se range of 20-90 µg/L in urine, though relatively few (only 4%) had similarly low fingernail levels. On the other hand, none of the samples reached Se toxicity levels, and the biomarker levels in this study are comparable to results from other studies that find adequate Se. Our results show that Se toxicity or deficiency is unlikely in the study population.

An Investigation for Heavy Metals’ Contamination in Farmers’ Fingernails: Case Study in Libya

This study aims to assess the concentration levels of heavy metals, which are associated with health hazards: arsenic (As), cadmium (Cd), and lead (Pb) among Libyan farmers using fingernails as a biomarker. Factors that may contribute for accumulation of these toxic heavy metals in the farmers’ fingernails were also evaluated. This cross-sectional study involved 127 farmers and 25 high school teachers living in the same geographical area as the farmers (served as the control group). Fingernail samples of the participants were collected, treated, and analyzed by inductively coupled plasma mass spectrometry (ICP-MS) for As, Cd, and Pb contents after microwave acid digestion. Results of this study indicated that the concentration levels of the investigated heavy metals in fingernail samples of both participating farmers and control group were in order of Pb > Cd > As. Also, the results showed that As, Cd, and Pb levels in the farmers’ fingernails were found to be higher than in the control group by about 9-, 5-, and 2-fold, respectively. This difference for all heavy metals analyzed was found to be statistically significant $\left(P<0.05\right)$ . As a conclusion, the results of this study clearly indicated that Libyan farmers have been exposed to high levels of toxic heavy metals as a result of their agricultural activities compared with the general population living in the same geographical area as farmers, which, in turn, pose a high risk to their health. Thus, toxicological, epidemiological, and clinical studies for the Libyan farmers are strongly recommended.

Unlocking the potential of forensic traces: Analytical approaches to generate investigative leads

Forensic investigation involves gathering the information necessary to understand the criminal events as well as linking objects or individuals to an item, location or other individual(s) for investigative purposes. For years techniques such as presumptive chemical tests, DNA profiling or fingermark analysis have been of great value to this process. However, these techniques have their limitations, whether it is a lack of confidence in the results obtained due to cross-reactivity, subjectivity and low sensitivity; or because they are dependent on holding reference samples in a pre-existing database. There is currently a need to devise new ways to gather as much information as possible from a single trace, particularly from biological traces commonly encountered in forensic casework. This review outlines the most recent advancements in the forensic analysis of biological fluids, fingermarks and hair. Special emphasis is placed on analytical methods that can expand the information obtained from the trace beyond what is achieved in the usual practices. Special attention is paid to those methods that accurately determine the nature of the sample, as well as how long it has been at the crime scene, along with individualising information regarding the donor source of the trace.

Biomarkers of disease in human nails: a comprehensive review

Diagnostic, monitoring, response, predictive, risk, and prognostic biomarkers of disease are all widely studied, for the most part in biological fluids or tissues, but there is steadily growing interest in alternative matrices such as nails. Here we comprehensively review studies dealing with molecular or elemental biomarkers of disease, as opposed to semiological, pharmacological, toxicological, or biomonitoring studies. Nails have a long history of use in medicine as indicators of pathological processes and have also been used extensively as a matrix for monitoring exposure to environmental pollution. Nail clippings are simple to collect noninvasively as well as to transport and store, and the matrix itself is relatively stable. Nails incorporate, and are influenced by, circulating molecules and elements over their several months of growth, and it is widely held that markers of biological processes will remain in the nail, even when their levels in blood have declined. Nails thus offer the possibility to not only look back into a subject's metabolic history but also to study biomarkers of processes that operate over a longer time scale such as the post-translational modification of proteins. Reports on ungual biomarkers of metabolic and endocrine diseases, cancer, and psychological and neurological disorders will be presented, and an overview of the sampling and analytical techniques provided.

A review on the analytical procedures of halogenated flame retardants by gas chromatography coupled with single quadrupole mass spectrometry and their levels in human samples

Halogenated flame retardants (HFRs) market is continuously evolving and have moved from the extensive use of polybrominated diphenyl ether (PBDE) to more recent introduced mixtures such as Firemaster 550, Firemaster 680, DP-25, DP-35, and DP-515. These substitutes are mainly composed of non-PBDEs HFRs such as 2-ethyl-hexyl tetrabromobenzoate (TBB), bis(2-ethylhexyl) tetrabromophthalate (TBPH), 1,2-bis-(2,4,6-tribromophenoxy) ethane (BTBPE) and decabromodiphenyl ethane (DBDPE). Other HFRs commonly being monitored include Dechlorane Plus (DP), Dechlorane 602 (Dec602), Dechlorane 603 (Dec603), Dechlorane 604 (Dec604), 5,6-dibromo-1,10, 11, 12,13,13-hexachloro- 11-tricyclo[8.2.1.02,9]tridecane (HCDBCO) and 4,5,6,7-tetrabromo-1,1,3-trimethyl-3-(2,3,4,5-tetrabromophenyl)-2,3-dihydro-1H-indene (OBTMPI). This review aims at highlighting the advances in the past decade (2010-2020) on both the analytical procedures of HFRs in human bio-specimens using gas chromatography coupled with single quadrupole mass spectrometry and synthesizing the information on the levels of these HFRs in human samples. Human specimen included in this review are blood, milk, stool/meconium, hair and nail. The review summarizes the analytical methods, including extraction and clean-up techniques, used for measuring HFRs in biological samples, which are largely adopted from those for analysing PBDEs. In addition, new challenges in the analysis to include both PBDEs and a wide range of other HFRs are also discussed in this review. Review of the levels of HFRs in human samples shows that PBDEs are still the most predominant HFRs in many cases, followed by DP. However, emerging HFRs are also being detected in human despite of the fact that both their detection frequencies and levels are lower than PBDEs and DP. It is clearly demonstrated in this review that people working in the industry or living close to the industrial areas have higher HFR levels in their bodies.

Determination of ultraviolet filters in human nails using an acid sample digestion followed by ultra-high performance liquid chromatography-mass spectrometry analysis

Ultraviolet filters (UV-filters) are specific chemicals that absorb and reflect UVA and UVB radiation from the sun. They are regularly used in sunscreens and in other personal care products (PCPs), and in products like plastics, adhesives, toys, or furniture finishes. This work develops and validates a new method to determine concentrations of UV-filters (BP-1, BP-2, BP-3, BP-6, BP-8, 4-OH-BP, THB, AVB) in human nail samples. Nails are easily available and are considered to be suitable indicators of cumulative and continued exposure to harmful chemicals. The treatment of nail samples includes microwave assisted digestion/extraction (MAE) in a methanolic solution of o-phosphoric acid (0.05 mol L^-1) followed by analyte determination using ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS/MS) in multiple reaction monitoring mode. The analytes were separated in less than 10 min. The digestion procedure was optimized using multivariate techniques. Matrix-matched calibration with a pig hoof matrix was used for validating the method. A study of accuracy with spiked blank samples was also conducted. The calculated detection limits varied between 0.2 and 1.5 ng g^-1, and quantification limits between 1.0 and 5.0 ng g^-1. The trueness of the method was an estimation of the recovery, which was between 90.2% and 112.2%; with an estimated precision (relative standard deviation, % RSD) lower than 12.3% for all UV-filters. Nail samples were obtained from 22 volunteers (male and female). The results showed that BP-1 and BP-3 mainly bioaccumulate in human nails.

Nail is Systemic Disorders: Main Signs and Clues

Describing and listing all nail symptoms and signs in systemic disorders has already been widely detailed in dedicated textbooks. To be tutorial, this article described most common nails signs and the systemic disorders one may encounter in routine dermatologic consultation. Capsule summaries are presented for each section.

Frequency of biological non-skeletal materials in dry bone scenarios

In forensic anthropology, many small biological non-osseous materials may be found associated to skeletonized remains and can provide crucial information to the biological profile. Indeed, their careful recovery and correct identification can add information related to age-at-death, sex, ancestry, health, diet, migration and habits, and may be used in specific analysis such as DNA typing. However, and despite their potential, little is known about these non-osteological materials. Indeed, how frequent are they in dry bone cases? To answer this question, 100 skeletal remains with postmortem intervals ranging from 23 to 76 years from the CAL Milano Cemetery Skeletal Collection were meticulously examined for the presence of non-skeletal materials and in particular ossified cartilage, vascular calcifications, hair and nails. As a result, non-skeletal materials were found in 81 skeletal remains and showed high frequencies of recovery, despite the less-than-optimal conditions of exhumation of the skeletons. The high frequencies of non-skeletal materials obtained demonstrate the need for additional training and research given their informative power in forensic cases.

[Differential diagnosis of common nail disorders in childhood]

BACKGROUND

Correct diagnosis of nail changes in childhood may be challenging. Knowing the anatomy of the nail apparatus and some pathophysiologic principles helps to categorize nail disorders correctly.

OBJECTIVES

This article gives a structured overview of nail disorders in childhood, thus, facilitating correct diagnosis of nail abnormalities in childhood.

MATERIALS AND METHODS

A review of literature and our own experience are presented.

RESULTS

In the first part we present fundamental anatomical characteristics of the nail apparatus based on embryonal development of the nails. In the main part we categorize nail disorders according to clinical presentation: transient nail changes, congenital nail abnormalities, infectious diseases of the nails, nail changes in the context of chronic inflammatory skin diseases, pigmented nail changes, tumors and nail changes due to trauma.

Analysis of Nicotine Metabolites in Hair and Nails Using QuEChERS Method Followed by Liquid Chromatography-Tandem Mass Spectrometry

Many studies have analyzed nicotine metabolites in blood and urine to determine the toxicity caused by smoking, and assess exposure to cigarettes. Recently, hair and nails have been used as alternative samples for the evaluation of smoking, as not only do they reflect long-term exposure but they are also stable and easy to collect. Liquid-liquid or solid-phase extraction has mainly been used to detect nicotine metabolites in biological samples; however, these have disadvantages, such as the use of toxic organic solvents and complex pretreatments. In this study, a modified QuEChERS method was proposed for the first time to prepare samples for the detection of nicotine metabolite cotinine (COT) and trans-3′-hydroxycotinine (3-HCOT) in hair and nails. High-performance liquid chromatography–tandem mass spectrometry (LC–MS/MS) was used to analyze traces of nicotine metabolites. The established method was validated for selectivity, linearity, lower limit of quantitation, accuracy, precision and recovery. In comparison with conventional liquid-liquid extraction (LLE), the proposed method was more robust, and resulted in higher recoveries with favorable analytical sensitivity. Using this method, clinical samples from 26 Korean infants were successfully analyzed. This method is expected to be applicable in the routine analysis of nicotine metabolites for environmental and biological exposure monitoring.

Details of a thallium poisoning case revealed by single hair analysis using laser ablation inductively coupled plasma mass spectrometry

Heavy metals pose significant morbidity and mortality threats to humans in connection with both acute and chronic exposure. The often-delayed manifestations of some toxic effects and the wide-spectrum of symptoms caused by heavy metal poisoning may perplex the clinical diagnosis and, when involved in crimes, complicate the forensic investigation. To investigate the original intoxication process of a thallium poisoning case, which occurred in China more than two decades ago, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used to analyze several hairs of the victim from before, during and after the poisoning period. Ablation line scans of the entire length of a ∼7cm hair revealed ∼4months of repeated exposure to thallium with increased doses and frequency toward the end, while scan of a ∼0.7cm hair revealed ∼2weeks of constant ingestions of large doses of thallium accompanied by elevated amount of lead. The endogenous origin of thallium was confirmed by the preservation of the same longitudinal distribution profile in the inner part of hair, but the source of lead could not be unambiguously determined due to the intrinsic limitation of hair analysis to distinguish ingested lead from exogenous contaminants. The overall thallium distribution profiles in the analyzed hairs suggested both chronic and acute thallium exposures that correlated well with the sequential presentation of a plethora of symptoms experienced by the victim. Aligning the time-resolved thallium peaks with symptoms also provided clues on possible routes of exposure at different poisoning stages. This work demonstrated the capability of using single hair LA-ICP-MS analysis to reconstitute a prolonged and complicated heavy metal poisoning case, and highlighted the necessity of assessing multiple elements in the medico-legal investigation of suspicious heavy metal poisonings.

Metabolomic profiling of maternal hair suggests rapid development of intrahepatic cholestasis of pregnancy

INTRODUCTION

Intrahepatic cholestasis of pregnancy (ICP) is a common maternal liver disease; development can result in devastating consequences, including sudden fetal death and stillbirth. Currently, recognition of ICP only occurs following onset of clinical symptoms.

OBJECTIVE

Investigate the maternal hair metabolome for predictive biomarkers of ICP.

METHODS

The maternal hair metabolome (gestational age of sampling between 17 and 41 weeks) of 38 Chinese women with ICP and 46 pregnant controls was analysed using gas chromatography-mass spectrometry.

RESULTS

Of 105 metabolites detected in hair, none were significantly associated with ICP.

CONCLUSION

Hair samples represent accumulative environmental exposure over time. Samples collected at the onset of ICP did not reveal any metabolic shifts, suggesting rapid development of the disease.

Deciphering the molecular events during arsenic induced transcription signal cascade activation in cellular milieu

Anthropogenic sources of arsenic poses and creates unintentional toxico-pathological concerns to humans in many parts of the world. The understanding of toxicity of this metalloid, which shares properties of both metal and non-metal is principally structured on speciation types and holy grail of toxicity prevention. Visible symptoms of arsenic toxicity include nausea, vomiting, diarrhea and abdominal pain. In this review, we focused on the dermal cell stress caused by trivalent arsenic trioxide and pentavalent arsanilic acid. Deciphering the molecular events involved during arsenic toxicity and signaling cascade interaction is key in arsenicosis prevention. FoxO1 and FoxO2 transcription factors, members of the Forkhead/Fox family, play important roles in this aspect. Like Foxo family proteins, ATM/CHK signaling junction also plays important role in DNA nuclear factor guided cellular development. This review will summarize and discuss current knowledge about the interplay of these pathways in arsenic induced dermal pathogenesis.

Chinese population exposure to triclosan and triclocarban as measured via human urine and nails

Triclosan (TCS) and triclocarban (TCC) exposures are highly concerned due to their suspected endocrine-disrupting effects. The present study investigated TCS and TCC exposure levels in the general Chinese population by biomonitoring human urine and nail samples. TCS (69-80 %) and TCC (99-100 %) were frequently detected, which demonstrates that the general Chinese population has extensive exposure to these chemicals. The geometric mean (GM) urinary concentrations were 0.40 μg/g creatinine (creat), 95 % confidence interval (CI) 0.30-0.56, for TCS and 0.40 μg/g creat, 95 % CI 0.29-0.56, for TCC. On the other hand, the GM levels of TCS and TCC were 13.57 (5.67 μg/kg) and 84.66 μg/kg (41.50 μg/kg) in fingernail (toenail) samples, respectively, indicating that the levels in fingernails were approximately twice as high as those in toenails. Pearson's correlation coefficients between the urine and fingernail (toenail) samples were 0.715 (0.614) for TCS and 0.829 (0.812) for TCC. These data suggest that nail samples can be applied to the biomonitoring for TCS and TCC in the general population. We observed that the levels of both chemicals were higher in females than in males for urine and fingernail samples, but no significant differences were found between different genders for either compound in toenails. Nineteen- to 29-year-olds had the highest TCS levels in their nail samples, whereas TCC levels did not differ with regard to age. Region of residence significantly influenced TCS and TCC concentrations in the three biological matrices measured.

Hair and Nails as Noninvasive Biomarkers of Human Exposure to Brominated and Organophosphate Flame Retardants

After the phase-out of polybrominated diphenyl ethers (PBDEs), the use of alternative flame retardants (AFRs), such as FireMaster 550, and of organophosphate esters (OPEs) has increased. However, little is known about human exposure to these chemicals. This lack of biomonitoring studies is partially due to the absence of reliable noninvasive biomarkers of exposure. Human hair and nails can provide integrated exposure measurements, and as such, these matrices can potentially be used as noninvasive biomarkers of exposure to these flame retardants. Paired human hair, fingernail, toenail, and serum samples obtained from 50 adult participants recruited at Indiana University Bloomington campus were analyzed by gas chromatographic mass spectrometry for 36 PBDEs, 9 AFRs, and 12 OPEs. BDE-47, BDE-99, 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (TBB), di(2-ethylhexyl) tetrabromophthalate (TBPH), tris(1,3-dichloro-2-propyl)phosphate (TDCIPP), and triphenyl phosphate (TPHP) were the most abundant compounds detected in almost all hair, fingernail, and toenail samples. The concentrations followed the order OPEs > TBB+TBPH > Σpenta-BDE. PBDE levels in the hair and nail samples were significantly correlated with their levels in serum (P < 0.05), suggesting that human hair and nails can be used as biomarkers to assess human exposure to PBDEs.

How to assess stress biomarkers for idiographic research?

Associations between stress-related biomarkers, like cortisol or catecholamines, and somatic or psychological symptoms have often been examined at the group level. Studies using this nomothetic approach reported equivocal findings, which may be due to high levels of intra-individual variance of stress biomarkers. More importantly, analyses at the group level provide information about the average patient, but do not necessarily have meaning for individual patients. An alternative approach is to examine data at the level of individual patients in so-called idiographic research. This method allows identifying individuals in whom symptoms are explained by preceding alterations in specific stress biomarkers, based on time series of symptoms and stress biomarkers. To create time series of sufficient length for statistical analysis, many subsequent stress biomarker measurements are needed for each participant. In the current paper, different matrices (i.e. saliva, urine, nail and hair) are discussed in light of their applicability for idiographic research. This innovative approach might lead to promising new insights in the association between stress biomarkers and psychological or somatic symptoms. New collection tools for stress biomarkers, like the use of sweat pads, automated microdialysis systems, dried blood spots, or smartphone applications, might contribute to the feasibility and implementation of idiographic research in the future.

Toxicological importance of human biomonitoring of metallic and metalloid elements in different biological samples

Human biomonitoring has become an important tool for the assessment of internal doses of metallic and metalloid elements. These elements are of great significance because of their toxic properties and wide distribution in environmental compartments. Although blood and urine are the most used and accepted matrices for human biomonitoring, other non-conventional samples (saliva, placenta, meconium, hair, nails, teeth, breast milk) may have practical advantages and would provide additional information on health risk. Nevertheless, the analysis of these compounds in biological matrices other than blood and urine has not yet been accepted as a useful tool for biomonitoring. The validation of analytical procedures is absolutely necessary for a proper implementation of non-conventional samples in biomonitoring programs. However, the lack of reliable and useful analytical methodologies to assess exposure to metallic elements, and the potential interference of external contamination and variation in biological features of non-conventional samples are important limitations for setting health-based reference values. The influence of potential confounding factors on metallic concentration should always be considered. More research is needed to ascertain whether or not non-conventional matrices offer definitive advantages over the traditional samples and to broaden the available database for establishing worldwide accepted reference values in non-exposed populations.

Toenail as a biomarker of heavy metal exposure via drinking water: a systematic review

Toenail is metabolic end product of the skin, which can provide information about heavy metal accumulation in human cells. Slow growth rates of toenail can represent heavy metal exposure from 2 to 12 months before the clipping. The toenail is a non-invasive biomarker that is easy to collect and store and is stable over time. In this systematic review, the suitability of toenail as a long-term biomarker was reviewed, along with the analysis and validation of toenail and confounders to heavy metal. This systematic review has included 30 articles chosen from a total of 132 articles searched from online electronic databases like Pubmed, Proquest, Science Direct, and SCOPUS. Keywords used in the search included "toenail", "biomarker", "heavy metal", and "drinking water". Heavy metal in toenail can be accurately analyzed using an ICP-MS instrument. The validation of toenail heavy metal concentration data is very crucial; however, the Certified Reference Material (CRM) for toenail is still unavailable. Usually, CRM for hair is used in toenail studies. Confounders that have major effects on heavy metal accumulation in toenail are dietary intake of food and supplement, smoking habit, and overall health condition. This review has identified the advantages and limitations of using toenail as a biomarker for long-term exposure, which can help future researchers design a study on heavy metal exposure using toenail.

[Anatomy, biology, physiology and basic pathology of the nail organ]

The nail is the largest skin appendage. It grows continuously through life in a non-cyclical manner; its growth is not hormone-dependent. The nail of the middle finger of the dominant hand grows fastest with approximately 0.1 mm/day, whereas the big toe nail grows only 0.03-0.05 mm/d. The nails' size and shape vary characteristically from finger to finger and from toe to toe, for which the size and shape of the bone of the terminal phalanx is responsible. The nail apparatus consists of both epithelial and connective tissue components. The matrix epithelium is responsible for the production of the nail plate whereas the nail bed epithelium mediates firm attachment. The hyponychium is a specialized structure sealing the subungual space and allowing the nail plate to physiologically detach from the nail bed. The proximal nail fold covers most of the matrix. Its free end forms the cuticle which seals the nail pocket or cul-de-sac. The dermis of the matrix and nail bed is specialized with a morphogenetic potency. The proximal and lateral nail folds form a frame on three sides giving the nail stability and allowing it to grow out. The nail protects the distal phalanx, is an extremely versatile tool for defense and dexterity and increases the sensitivity of the tip of the finger. Nail apparatus, finger tip, tendons and ligaments of the distal interphalangeal joint form a functional unit and cannot be seen independently. The nail organ has only a certain number of reaction patterns that differ in many respects from hairy and palmoplantar skin.

Advances in detection of antipsychotics in biological matrices

Measuring antipsychotic concentrations in human matrices is important for both therapeutic drug monitoring and forensic toxicology. This review provides a critical overview of the analytical methods for detection and quantification of antipsychotics published in the last four years. Focus lies on advances in sample preparation, analytical techniques and alternative matrices. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is used most often for quantification of antipsychotics. This sensitive technique makes it possible to determine low concentrations not only in serum, plasma or whole blood, but also in alternative matrices like oral fluid, dried blood spots, hair, nails and other body tissues. Current literature on analytical techniques for alternative matrices is still limited and often requires a more thorough validation including a comparison between conventional and alternative results to determine their actual value. Ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) makes it possible to quantify a high amount of compounds within a shorter run time. This technique is widely used for multi-analyte methods. Only recently, high-resolution mass spectrometry has gained importance when a combination of screening of (un)known metabolites, and quantification is required.

The neurological effects of prenatal and postnatal mercury/methylmercury exposure on three-year-old children in Taiwan

This study attempts to elucidate the relationship between neurological effects and mercury/methylmercury concentrations in various biomarkers, including meconium, hair, fingernail, and toenail. Eight-three mother-infant pairs were recruited between August 2008 and December 2009, and follow-up examinations on these children were completed after three years. The Bayley Scales of Infant and Toddler Development (Bayley-III) for evaluating the cognitive, language, and motor development of three-year-old children were calculated and validated. The geometric mean of the total mercury concentration in meconium was 89.6 ng g(-1). The methylmercury concentrations in hair, fingernail, and toenail samples were 1.96, 0.64, and 0.55 μg g(-1), respectively. Seventy percent of children had hair methylmercury concentrations exceeding the U.S. environmental protection agency (EPA) reference of 1 μg g(-1). A significantly positive correlation was obtained between methylmercury levels in hair, fingernail, and toenail. These methylmercury levels were also significantly positively correlated with the children's fish intake and negatively correlated with a Bayley-III scale score of expressive language. The prenatal mercury exposure, however, did not show significant influence on neurological development. High fish consumption appears to be a critical risk factor for methylmercury levels in children and may cause a lower expressive language score.

Hormones in infant rhesus monkeys' (Macaca mulatta) hair at birth provide a window into the fetal environment

BACKGROUND

It is established that maternal parity can affect infant growth and risk for several disorders, but the prenatal endocrine milieu that contributes to these outcomes is still largely unknown. Recently, it has been shown that hormones deposited in hair can provide a retrospective reflection of hormone levels while the hair was growing. Taking advantage of this finding, our study utilized hair at birth to investigate if maternal parity affected fetal hormone exposure during late gestation.

METHODS

Hair was collected from primiparous and multiparous mother and infant monkeys at birth and used to determine steroid hormones embedded in hair while the infant was in utero. A high-pressure liquid chromatography-triple quadrupole mass spectrometry technique was refined, which enabled the simultaneous measurement of eight hormones.

RESULTS

Hormone concentrations were dramatically higher in neonatal compared to maternal hair, reflecting extended fetal exposure as the first hair was growing. Further, hair cortisone was higher in primiparous mothers and infants when compared to the multiparous dyads.

CONCLUSION

This research demonstrates that infant hair can be used to track fetal hormone exposure and a panel of steroid hormones can be quantified from hair specimens. Given the utility in nonhuman primates, this approach can be translated to a clinical setting with human infants.

A quantitative analysis of the polyamine in lung cancer patient fingernails by LC-ESI-MS/MS

A quantitative analysis of polyamines in lung cancer patient fingernails by the combination of 4-(N,N-dimethylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole derivatives and liquid chromatography-electrospray ionization tandem mass spectrometry is described. The reaction of the reagent with eight kinds of polyamines, that is, N(1) -acetylputrescine (N(1) -actPUT), N(8) -acetylspermidine, N(1) -acetylspermine, 1,3-diaminopropane, putrescine (PUT), cadaverine, spermidine and spermine (SPM) effectively occurs at 60 °C for 30 min. The detection limits (signal-to-noise ratio 5) were 5-100 fmol. A good linearity was achieved from the calibration curves, which was obtained by plotting the peak area ratios of the analytes relative to the internal standard (IS), that is, 1,6-diaminohexane, vs the injected amounts of polyamines (r(2)  > 0.996), and the intra-day and inter-day assay precisions were <9.84%. Furthermore, the recoveries (%) of the polyamines spiked in the human fingernails were 89.14-110.64. The present method was applied to human fingernail samples from 17 lung cancer patients and 39 healthy volunteers. The polyamine concentration was different based on the gender, that is, the N(1) -actPUT and PUT contents were 3.10 times and 2.56 times higher in healthy men than in women, respectively. Additionally, in the lung cancer patient group, as compared with the healthy volunteers, the concentrations of SPM had a statistically significant (p < 0.05) correlation. Therefore, because the proposed method provides a good mass accuracy and the trace detection of the polyamines in human fingernails, this analytical technique could be a noninvasive technique to assist in the diagnosis and assessment of disease activity in lung cancer patients.

Exposure to nickel by hair mineral analysis

The aim of the present work was to investigate the exposure to nickel from various sources by investigation of mineral composition of human scalp hair. The research was carried out on hair sampled from subjects, including 87 males and 178 females (22 ± 2 years). The samples of hair were analyzed by ICP-OES. The effect of several factors on nickel content in hair was examined: lifestyle habits (e.g. hair coloring, hair spray, hair straighteners, hair drier, drugs); dietary factors (e.g. yoghurts, blue cheese, lettuce, lemon, mushroom, egg, butter); other (e.g. solarium, cigarette smoking, tap water pipes, tinned food, PVC foil, photocopier, amalgam filling). These outcomes were reached by linking the results of nickel level in hair with the results of questionnaire survey. Basing on the results it can be concluded that exposure to nickel ions can occur from different sources: lifestyle, eating habits and environmental exposure.

Rapid and sensitive determination of the intermediates of advanced glycation end products in the human nail by ultra-performance liquid chromatography with electrospray ionization time-of-flight mass spectrometry

The resolution of the intermediate advanced glycation end products (AGEs) in the human nail was carried out by the combination of 4,5-dimethyl-1,2-phenylenediamine (DMPD) derivatives and ultra-performance liquid chromatography with electrospray ionization time-of-flight mass spectrometry (UPLC-ESI-TOF-MS). The reaction of the reagent with 3-deoxyglucosone (3-DG), methylglyoxal (MG), and glyoxal (GO) effectively proceeds at 60°C for 2h. The resulting derivatives were efficiently separated by a gradient program (a mixture of water and acetonitrile containing 0.1% formic acid) using a reversed-phase ACQUITY UPLC BEH C(18) column (1.7 μm, 50×2.1 mm i.d.) and sensitively detected by TOF-MS. The detection limits (signal-to-noise ratio=5) of the TOF-MS were 10 to 50 fmol. A good linearity was achieved from the calibration curve, which was obtained by plotting the peak area ratios of the analytes relative to the internal standard (IS) (i.e., 2,3-hexanedione) versus the injected amounts of 3-DG, MG, and GO (r(2)>0.999), and the intra- and interday assay precisions were less than 6.89%. The derivatives of the compounds in the human nail were successfully identified by the proposed procedure. As we know, these three kinds of dicarbonyl intermediates in the formation of AGEs-3-DG, MG, and GO-were first found in human nail samples. Using these methods, the amounts of compound in the nails of healthy volunteers and diabetic patients were determined. When comparing the index from the diabetic patients with that from healthy volunteers, there is no significant difference in the content of the MG and GO in the nails. However, a statistically significant (P<0.001) correlation was observed between the 3-DG concentrations. Because the proposed method provides a good mass accuracy and the trace detection of the dicarbonyl intermediates of AGEs in the human nail, this analytical technique could be a noninvasive technique to assist in the diagnosis and assessment of disease activity in diabetic patients. Here we present a novel, sensitive, and simple method for the simultaneous determination of dicarbonyl compounds in the human nail.

What is the best biomarker to assess arsenic exposure via drinking water?

Arsenic (As) is a ubiquitous element. The current WHO guideline for As in drinking water is 10 μg/L. Furthermore, about 130 million people have only access to drinking water containing more than 10 g As/L. Although numerous studies have shown the related adverse effects of As, sensitive appropriate biomarkers are still required for studies of environmental epidemiology. A review of the literature has shown that various biomarkers are used for such research. Their limits and advantages are highlighted in this paper: (i) the detection of As or its derivatives in the blood is an indication of the dose ingested but it is not evidence of chronic intoxication. (ii) The detection of As in urine is an indispensible procedure because it is a good marker for internal dose. It has been demonstrated to correlate well for a number of chronic effects related to As levels in drinking water. However confounding factors must be taken into account to avoid misinterpretation and this may require As speciation. (iii) As in the hair and nails reflects the level of long term exposure but it is difficult to relate the level with the dose ingested. (iv) Some studies showed a correlation between urinary As and urinary and blood porphyrins. However, it is difficult to use only porphyrins as a biomarker in a population survey carried out without doing further studies. (v) Genotoxic effects are based on the characterization of these potential effects. Most studies have detected increases in DNA damage, sister chromatid exchange, micronuclei or chromosomal aberrations in populations exposed to As in drinking water. Micronuclei assay is the technique of choice to follow these populations, because it is sensitive and easy to use. To conclude, whatever epidemiological studies are, the urinary and toenail biomarkers are useful to provide indications of internal dose. Moreover, micronuclei assay can be complementary use as biomarker of early effects.