Human Fingernails Research Articles

Dataset of human skin and fingernails images for non-invasive haemoglobin level assessment

Anaemia, a decrease in total concentration of haemoglobin (Hb) in blood, affects substantial percentage of the population worldwide. Currently, the gold standard for determining the Hb level is the invasive analysis of venous blood. Yet, more and more research groups demonstrate the possibility of non-invasive Hb assessment using white light imaging of tissue sites where Hb is the main chromophore, in particular, fingernails. Despite the promising declarations, non-invasive Hb assessment via RGB-imaging is still poorly used in practice. The main reason is the difficulty in establishing the true accuracy of the methods presented in different works since they are tested on private datasets collected under different experimental conditions. Here we present an open dataset containing RGB images of skin and fingernails for patients with a known level of Hb, thus providing a single benchmark for researchers and engineers in the field, aimed at fostering translation of non-invasive imaging methods to the bedside.

The Normal Growth Rate of Human Fingernails in Indian Population.

Background: India, with a large population working in industries, has a considerable amount of nail bed injuries day to day as well as infections and other issues with nails. However, there are no normative data for nail growth in our population. This study aims to measure and analyze the rate of nail growth in the Indian population, which will be a valuable tool for clinical assessment and treatment. Objective: The aim of the study was to estimate the average rate of nail growth of all fingers in the Indian population between the age group of 18 to 40 years. Materials and Methods: Fifty young adults whose 500 fingernails were painted with three coats of nail polish following a standardized protocol, and the rate of the growth of the nails was recorded with a digital Vernier caliper from the nail fold every 10 days for 1 month. Results: The average fingernail growth is 0.103 mm/d. There is no correlation of nail growth with sex or hand dominance. Nail growth is more in the left index finger (0.13 mm/d) and the left thumb, while it is the least in little fingers (0.101 mm/d). Initial fingernail growth was higher in older individuals, however. At the end of the study period, nail growth was equal. The nail growth rate reduces as the days progress. Conclusion: We have reported the normative data of nail growth as 0.103 mm per day. In the majority of the healthy population, this rate would hold true.

Precise tactile localization on the human fingernail.

Fingernails are specialized features of the primate hand, which are believed to contribute to manual dexterity. The sensorimotor functions of fingernails, however, remain poorly understood. This study investigates the ability of humans to precisely localize touches applied to the fingernail plate. Nine different locations on the fingernail were touched and participants judged the location by clicking a mouse cursor on a photograph of their finger. Performance in this condition was compared with stimuli applied to the skin of the fingertip. The results showed that participants are able to localize touch on the fingernails at substantially higher than chance levels. Moreover, the precision of this ability is not appreciably lower than that of the fingertips. These results show that the fingernail is a highly sensitive sensory organ, which is capable of providing rich spatial information about tactile stimuli.

Structural and retrospective bio-dosimetric study of gamma-irradiated human fingernails

Emergency involving ionising radiation is a rare occurrence, yet it can leave severe damage if a population is not equipped with necessary preparation. In such a situation, there is no viable way to know how much radiation dose is received by human beings. However, in present time only personnel of rescue teams have accessed to active dosimetry such as a personal dosimeter. Preliminary study has been made of human fingernails, a model in examining the potential of nails of the human fingers in retrospective and emergency bio-dosimetry applications, also offering effective atomic number near to that of soft human tissues at 7.4. Human fingernails were sampled from different age groups and exposed to 60Co gamma rays, delivering doses from 2 to 10 Gy. Structural alterations were observed, use being made of Raman spectroscopy and the crystalline structure of alpha keratin is studied using X-ray diffraction (XRD), while the elemental composition of the sample is determined by energy dispersive x-ray (EDX) analysis. Raman shows the ‘fingerprint’ of nail sample is identical in which the peak assignment concerns on the disulfide (S–S) bond and the alpha helix content at the amide 1 region. These are the few regions which displayed major Raman shift and intensity difference from a normal nail sample and an effected nail which have the same analogy as a non-irradiated nail and an irradiated nail sample. XRD shows the molecular structure of hard α-keratin from different age groups of fingernails, examining crystallite diameters (D) and crystallinity index (C.I.). The α-keratin characteristic bands can be seen in all groups of fingernails, albeit they become much weaker and shift to smaller angles with higher gamma doses. The results obtained by Raman spectroscopy and X-ray diffraction are complementary and suggest that the α-helix structure of keratin is partially destroyed by the presence of radiation.

Effects of two types of surface treatments on the structural elasticity of human fingernails.

The human nail has a three-layered structure. Although it would be useful to quantitatively evaluate the changes in deformability of the nail due to various surface treatments, few studies have been conducted. The effects of two types of surface treatment-a chemically acting nail softener and a physically acting nail strengthener-on the deformability of human fingernails were investigated. The Young's modulus of each plate of the nail samples before and after softening treatment was determined by nanoindentation. The Young's modulus of the strengthener was determined by conducting a three-point bending test on a polyethylene sheet coated with the strengthener. Young's modulus decreased in order from the top plate against the softening treatment time, and the structural elasticity for bending deformation (SEB) of the nail sample, which expresses the deformability against bending deformation independent of its external dimensions, decreased to 60% after 6h of treatment. The Young's modulus of the nail strengthener was 244.5MPa, which is less than 10% of the SEB of the nail. When the nail strengthener was applied to the nail surface, the SEB decreased to 73%, whereas the flexural rigidity increased to 117%. Changes in nail deformability caused by various surface treatments for softening and hardening were quantitatively evaluated successfully.

Simultaneous identification and differentiation of human fingernails and hair from different regions by Terahertz time-domain spectroscopy and chemometrics for forensic purpose

Hair and fingernails, emerging as crucial biological physical evidence, play a prominent role in geographical traceability studies within the forensic anthropology. This study explored the potential of terahertz spectroscopy and chemometrics techniques in identifying hair and fingernail samples from various geographical regions. A total of 196 hair and fingernail samples underwent scanning with terahertz time-domain spectroscopy. Different chemometric tools, including multilayer perceptron, support vector machine, and Fisher discriminant analysis, were employed for model building on fingernail dataset, hair dataset, and fusion data, respectively. The performance of models constructed based on different datasets was compared and evaluated using metrics such as accuracy, precision, recall, and F-score. Results revealed that the fusion data, employing the Fisher discriminant analysis (FDA) algorithm, exhibited the best recognition ability, achieving a 100 % accuracy rate and F-value. Terahertz spectroscopy combined with FDA algorithm emerged as an effective and convenient tool for differentiating hair and fingernail samples from diverse geographical regions. This innovative technique boasts environmental friendliness, rapid analyses, and minimal sample preparation requirements compared to traditional methods.

Comparative study on the impact of storage conditions on ESR signals in fingernail dosimetry

Human fingernails in combination with electron spin/paramagnetic resonance (ESR/EPR; hereafter “ESR”) spectroscopy have high potential as an individual dosimetry tool in radiological accidents. For the practical realization of this technique, it is necessary to reduce the uncertainty due to the instability of ESR signals affected by both individual and environmental factors. In the present study, we examined the effects of different storage conditions (in a laboratory room, refrigerator, freezer, and vacuum) and prior sample treatment on the intensity and stability of ESR signals from the fingernails of a child, which has not been investigated in previous studies, in comparison with those of an adult. Fingernail samples collected from a 10 y/o female child and a 37 y/o male adult were irradiated with 160 kV X-rays at 10 Gy, and the time changes of radiation-induced ESR signal (RIS) and background signal (BKG) under different conditions were measured for up to 30 days. As results, the ESR signal intensities (peak-to-peak amplitudes) of both child and adult fingernails were the most stable under freezing conditions, while the intensities of both RIS and BKG of fingernails were notably higher and more stable in the child samples than in the adult samples. In addition, the child samples showed a better response to the prior treatment using ethanol and water; BKG faded significantly after treatment despite the original higher background. Further investigations with more samples from donors of different ages are needed to clarify and reduce inter- and intra-individual variability in the dosimetric properties of human fingernails.

Healthcare Wearable Sensors Adhesion to Human Fingernails and Toenails.

A novel adhesion method of a sensor to a fingernail is described. Wearable sensors can provide health insights to humans for a wide variety of benefits, such as continuous wellness monitoring and disease monitoring throughout a patient's daily life. While there are many locations to place these wearable sensors on the body, we will focus on the fingertip, one significant way that people interact with the world. Like artificial fingernails used for aesthetics, wearable healthcare sensors can be attached to the fingernail for short or long time periods with minimal irritation and disruption to daily life. In this study the structure and methods of healthcare sensors' attachment and removal have been explored to support (1) the sensor functional requirements, (2) biological and environmentally compatible solutions and (3) ease of attachment and removal for short- and long-term user applications. Initial fingernail sensors were attached using a thin adhesive layer of commonly available cosmetic nail glue. While this approach allowed for easy application and strong adhesion to the nail, the removal could expose the fingernail and finger to a commercially available cosmetic nail removal (acetone-based chemical) for extended times measured in minutes. Therefore, a novel structure and method were developed for rapid healthcare sensor attachment and removal in seconds, which supported both the sensor functional objectives and the biologically and environmentally safe use objectives.

Discerning animal-sourced food in diet using isotope analysis of human scalp hair and fingernails.

Diet-related diseases are advancing as the leading cause of death globally. As self-reporting of diet by patients can be associated with errors, stable isotopes of human tissues can be used to diagnose diseases, understand physiology, and detect change in diet. This study investigates the effect of type and amount of food on the nitrogen and carbon concentration (Nconc and Cconc) and isotopic composition (δ15N and δ13C) in human scalp hair and fingernails. A total of 100 residents participated in the study whereas only 74 individuals provided complete diet history. Sixty-six food items majorly available to them were also collected. The Nconc, Cconc, δ15N and δ13C values of human hair, nails and food items were determined. The Nconc, Cconc, δ15N and δ13C values between plant-sourced and animal-sourced food items, as well as human hair and nail tissue were significantly different (p < 0.05). The δ15N value of human tissues was distinct between lacto-vegetarians and omnivores by 0.9‰. The δ15N and δ13C values of human tissues increased by 0.4-0.5‰ with every 5% increase in the consumption of animal protein. The study helps to demarcate lacto-vegetarians from omnivores, and estimate the percentage of animal protein in diet based on the dual isotope values of human tissues. It also acts as a reference to determine isotopic composition of hair tissue provided the isotope value of nail tissue is known and vice versa.

Raman spectroscopy as a tool for monitoring osteoporosis therapy in postmenopausal osteoporosis

AbstractBisphosphonate‐based pharmacological therapy of osteoporosis reduces risk of fracture, but modulation of bone mineral density does not solely explain this. Additional bone quality aspects affecting fragility need to be better understood, alongside methods to monitor them. Systemic factors that influence bone collagen remodelling also remodel keratin in parallel processes. In this study, human fingernail clippings from subjects with and without bone active pharmaceutical intervention are compared. A discriminant model was able to distinguish between the nails from patients that were treatment‐naive and treated with an area under the curve of 71% in the test set. A time series of changes relative to baseline revealed that after 1 year, the scores of the treated group (95 confidence interval 37% to 377% change) differed from both the 12 week measurements (−198% to 34%) and scores from untreated subjects (−92% to −674%). Analysis of the spectral differences and model coefficients revealed features that were inverse to those observed in three previous osteoporosis models, indicating that treatment was reverting damaged protein structure. This study provides preliminary evidence that bone active medication systemically influences keratin structure in humans and provides some discussion on the underlying mechanism. The study demonstrates that bisphosphonates have a direct influence on protein structure, warranting further investigation of these effects.

Nanoindentation study of human fingernail for determining its structural elasticity.

Human nails play an important role in transmitting force to the fingertips, and their mechanical properties are important indices. The nail has a three-layered structure consisting of top dorsal, middle intermediate, and under ventral plates, and its internal structure is believed to affect its mechanical properties. However, this has not been investigated in previous studies. The Young's moduli of the top, middle, and under plates were measured using nanoindentation, and a theoretical model was developed to estimate the structural elasticity for the bending deformation of human nails, which is an index describing the deformability of the nail without depending on its external dimensions. The structural elasticity of human nails was compared with that of human hair collected from the same person. The effect of the softening treatment on the nails was also evaluated. The Young's moduli of the top, middle, and under plates measured using nanoindentation were 2.9, 3.1, and 2.8GPa, respectively. The structural elasticity of the nail was estimated to be 2.9GPa, approximately 75% that of hair. Moreover, softening treatment with a urea cream reduced the structural elasticity of the nail to 70%. This paper proposed a method for estimating the structural elasticity of a human nail with a three-layered structure. This index is a mechanical property with "Pa" as a unit, and is useful for comparing deformability with the Young's modulus of other homogeneous materials or for investigating the effect of various treatments quantitatively.

Development of a novel method for analysing N-acetyl-DL-leucine enantiomers in human fingernail by UPLC-ESI-MS/MS and the evaluation in diabetes mellitus

BackgroundRecent research has been reported that N-acetyl-leucine content is significantly reduced in the saliva of diabetic patients, but no reports of detection in human nails have been found. This study aims to develop a novel method for the chiral separation of N-acetyl-DL-leucine (Ac-DL-Leu) in human fingernails to investigate the differences between healthy volunteers (HVs), prediabetes (PDs) and diabetic patients (DPs), and to verify its effectiveness in early warning of diabetes. MethodChiral resolution was performed using DBD-Apy pre-column derivatization on a C18 column (2.1 × 150 mm, 1.9 μm) at 40 °C, and detected by UPLC-ESI-MS/MS. ResultsThe resolution and the limit of detection (LOD) of Ac-DL-Leu were 1.75 and 1.50 fmol, respectively. The linear range of Ac-DL-Leu was 10–2000 fmol and the determination coefficient (R2) was above 0.9997. The recovery of Ac-DL-Leu in human nails was 96.92–105.69 %. The contents of Ac-D-Leu and Ac-L-Leu were analyzed in 18 HVs, 13 PDs and 16 DPs fingernails. The results showed that their contents were significantly lower in DPs than in PDs and HVs (p < 0.0001). ConclusionsA method for evaluating the effectiveness of Ac-DL-Leu enantiomers in human fingernails as a biomarker for diabetes was firstly developed.

Change of the polarization properties of the human dermis with directions of incident and observation

In this work, a simplified cylinder-birefringence optical model of the human skin dermis model is reported. The actual polarization parameters of human fingernail skin were measured. And the accuracy and stability of the Mueller matrix polarization decomposition (MMPD) and the direct Mueller matrix (DMM) methods were compared under different incident and scattering angles. One main novelty of the present work is that the value of birefringence of the skin dermis was obtained from images of living human index finger nails by using a polarization-sensitive optical coherence tomography device. The results obtained in this work provide a basis for the selection of incident and scattering angles when measuring biological samples containing fibrous structures in the future.

In situ characterization of human fingernails by optical front-face fluorescence for the identification of primary hypothyroidism

Primary hypothyroidism is classified as a public health issue by the World Health Organization. The technique for diagnosing hypothyroidism is the measurement of thyroid stimulating hormone (TSH) and thyroxine (FT4). It is necessary to develop new methods that are more accessible, especially for developing countries. The aim of this work is the in-situ use of nail fluorescence for a simple and rapid preliminary diagnosis of primary hypothyroidism. The choice of the nail as biological tissue is justified because nails have a long-term memory, act as a mirror of health, and serve as an early warning system as well as a window of systemic disease. The in situ analysis of the nails of the patients shows good results. Specially, a clear separation was obtained between healthy controls and patients and also between low- and high-level hypothyroidism. Moreover, a strong correlation between fluorescence spectra and TSH values for the population with hypothyroidism was clearly established. Moreover, linear discriminant analysis shows that it is possible to predict the state of test patients after the training of a fraction of the population.

Loop-mediated isothermal amplification-microfluidic chip for the detection of Trichophyton infection

Trichophyton is the most pathogenic type of fungal skin infection. It often invades and grows in a keratin-rich matrix, and lesions include human skin, hair, and fingernails (toenails). We designed LAMP primers for Trichophyton and developed a LAMP-Microfluidic chip detection system for Trichophyton. This system detects six common species of Trichophyton in the genus Trichophyton, including Trichophyton rubrum, Trichophyton mentagrophyte, Trichophyton violaceum, Trichophyton tonsurans, Trichophyton verrucosum, and Trichophyton schoenleinii. The specificity reached 100%, and the sensitivity could reach about 1 × 102 copies/μl. The entire detection process can be completed within 60 min and does not cross-react with other dermatophytes. The established LAMP-Microfluidic chip detection system has the advantages of simple operation, high specificity, and high sensitivity, and has the potential for clinical application.

Experimental Study on the Effects of L(+)-Ascorbic Acid Treatment to the ESR Signals of Human Fingernails

The effects of L(+)-ascorbic acid (AA) (an antioxidant commonly known as vitamin C) on the electron spin resonance (ESR) signals from fingernails were examined in relation to X-ray and UV irradiation. The ESR signal intensity, stability, and sensitivity to radiation were measured under different storage conditions. The experimental results indicated that the behavior of the increase in the ESR intensity of the AA samples varied depending on the storage and location conditions, showing sensitivity to light and signal instability at room temperature. It was found that the AA treatment caused a large increase in the peak-to-peak intensities with continuous signal growth with storage time, which may provide an enhancement to the radiation-dependent signal in fingernails. It was also suggested that the use of AA for pre-treatment could sufficiently remove the disturbing signals induced by heat or UV light exposure, which is expected to improve the reliability of radiation dosimetry using fingernails. Further studies with different antioxidant conditions are needed to better characterize the complex changes of the ESR signals from fingernails.

Environmental effects on trace elements in the fingernails of centenarians and their offspring

Bio-monitoring is commonly used to investigate trace elements, and the human nail provides an ideal medium for such testing. Toxic and essential trace metals (Cd, Pb, Fe, and Se) in the fingernails of participants from the Hainan Province were investigated. Samples included 136 centenarians and 197 offspring (101 older adult children and 96 middle-aged grandchildren) who were also sampled for comparison. As a hotspot for longevity, participants in the Hainan Province were found to have high essential nutrients of Fe and Se, and lacked the toxic element Pb. A similar trend was found for trace elements in soil and rice in the Hainan Province. The trace elements preserved in nails revealed dietary and environmental influences that varied among different generations. For the grandchildren's generation, the environment played an important role in elements in their nails, and a significant correlation and linear relationships were found, especially for Fe and Se. As the participants increased in age (from the grandchildren to the centenarians), the correlation between various elements decreased. For centenarians, the influence of beneficial or harmful properties of the elements became more important than their environment. The results also pointed to the important role of trace elements in human health, especially Fe and Se as essential elements. This study can provide information on the factors that influence the existence of trace elements in the human body and demonstrate the advantage of using the human fingernail in bio-monitoring.

Formulation and Evaluation of Herbal Based Nail Polish

Cosmetics have been in utilization for more than thousands years. Cosmetics are applied mostly to the skin, hair and nails. Nail polish is a lacquer that can be applied to the human fingernail to decorate and protect the nail plates. The formulation has been revised repeatedly to increases its decorative effects. Adverse events may occur with various nail cosmetics specifically prepared with synthetic colours. Synthetic cosmetic being harsh and prone to more side- effects, herbal cosmetic is quickly replacing it and gaining a lot of popularity. The objective of the study was to deliver an herbal nail paint to reduce the damage to the nails due to chemicals. The nail paint formulation is prepare by simple mixing by using natural colour pigments and analysed for drying time, appearance, smoothness, hardness, colour, stability, Spreadibillity. Formulations, prepared with 8% cellulose 2.5% formaldehyde, 1.5% castor oil, 1.5% colour. Evaluation tests were found to in normal range according to I.P. This was expected to improve appearance, safety while applying and improve the user compliance. We can conclude that the herbal nail paint may be one of the novel products that can revolutionize the cosmeceutical and health care sector. Article contain anatomical structure of nail.

Effect of heating on the ESR signal of human fingernails

The potential confounding influence of heat on the electron spin resonance (ESR) spectra of fingernails has been studied in irradiated and unirradiated samples. The samples were heated at different temperatures between 20 and 160 °C for 1 h. The experimental temperature range was selected considering that the fingernails may be accidentally exposed to heat during normal daily activities or in a certain working environment. Changes in the overall visual shape of the ESR spectra were observed in the γ-ray irradiated and unirradiated samples heated above 100 °C, thereby showing that a heat-induced signal was present in the fingernail spectrum. The effect of heating showed an evident bulge in the spectra (between g = 2.014 and 2.024), which was more pronounced in both the irradiated and unirradiated samples heated at higher temperatures, with reduced peak-to-peak intensities and broadened spectra. The heat-induced signal was unstable, decayed for about a few days, and was easily removed upon treatment with water. While the radiation-induced signal (RIS) was stable up to 160 °C, our results also suggest that heating up to 160 °C did not affect the sensitivity of the RIS, but the heat-induced signal was still observed after irradiation. Similar thermal stability was also found in both the irradiated and unirradiated samples, suggesting that the heat-induced signal and RIS were overlapped, but probably independent. Overall, these findings will be useful to obtain a more reliable radiation dose assessment using fingernails that could be accidentally exposed to heat in various situations.

Modeling the 3D shape of a fingernail and pre-distorting an image to be printed on the fingernail to yield the correct appearance

In this paper, we explore a technique for printing on the curved surface of a human fingernail. We start by reproducing the shape of the fingernail via a 3D model. In our future work, we will apply a distortion to the halftone image to correct the deformation of the printed image.