Quantitative analysis and classification of AFM images of human hair

Exploring the Effects of Wetting and Free Fatty Acid Deposition on an Atomistic Hair Fiber Surface Model Incorporating Keratin-Associated Protein 5-1

The complex development of cosmetic and medical formulations relies on an ever-growing accuracy of predictive models of hair surfaces. Hitherto, modeling efforts have focused on the description of 18-methyl eicosanoic acid (18-MEA), the primary fatty acid covalently attached to the hair surface, without explicit modeling of the protein layer. Herein, the molecular details of the outermost surface of the human hair fiber surface, also called the F-layer, were studied using molecular dynamics (MD) simulations. The F-layer is composed primarily of keratin-associated proteins KAP5 and KAP10, which are decorated with 18-MEA on the outer surface of a hair fiber. In our molecular model, we incorporated KAP5-1 and evaluated the surface properties of 18-MEA through MD simulations, resulting in 18-MEA surface density, layer thickness, and tilt angles in agreement with previous experimental and computational studies. Subsequent models with reduced 18-MEA surface density were also generated to mimic damaged hair surfaces. Response to wetting of virgin and damaged hair showed rearrangement of 18-MEA on the surface, allowing for water penetration into the protein layer. To demonstrate a potential use case for these atomistic models, we deposited naturally occurring fatty acids and measured 18-MEA's response in both dry and wet conditions. As fatty acids are often incorporated in shampoo formulations, this work demonstrates the ability to model the adsorption of ingredients on hair surfaces. This study illustrates, for the first time, the complex behavior of a realistic F-layer at the molecular level and opens up the possibility of studying the adsorption behavior of larger, more complex molecules and formulations.

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

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

Coarse-grained molecular models of the surface of hair

We present a coarse-grained molecular model of the surface of human hair, which consists of a supported lipid monolayer, in the MARTINI framework. Using coarse-grained molecular dynamics (MD) simulations, we identify a lipid grafting distance that yields a monolayer thickness consistent with both atomistic MD simulations and experimental measurements of the hair surface. Coarse-grained models for fully-functionalised, partially damaged, and fully damaged hair surfaces are created by randomly replacing neutral thioesters with anionic sulfonate groups. This mimics the progressive removal of fatty acids from the hair surface by bleaching and leads to chemically heterogeneous surfaces. Using molecular dynamics (MD) simulations, we study the island structures formed by the lipid monolayers at different degrees of damage in vacuum and in the presence of polar (water) and non-polar (n-hexadecane) solvents. We also use MD simulations to compare the wetting behaviour of water and n-hexadecane droplets on the model surfaces through contact angle measurements, which are compared to experiments using virgin and bleached hair. The model surfaces capture the experimentally-observed transition of the hair surface from hydrophobic (and oleophilic) to hydrophilic (and oleophobic) as the level of bleaching damage increases. By selecting surfaces with specific damage ratios, we obtain contact angles from the MD simulations that are in good agreement with experiments for both solvents on virgin and bleached human hairs. To negate the possible effects of microscale curvature and roughness of real hairs on wetting, we also conduct additional experiments using biomimetic surfaces that are co-functionalised with fatty acids and sulfonate groups. In both the MD simulations and experiments, the cosine of the water contact angle increases linearly with the sulfonate group surface coverage with a similar slope. We expect that the proposed systems will be useful for future molecular dynamics simulations of the adsorption and tribological behaviour of hair, as well as other chemically heterogeneous surfaces.

Atomic force microscopy as a biophysical tool for nanoscale forensic investigations

The atomic force microscope (AFM) has found its way to the arsenal of tools available to the forensic practitioner for the analysis of samples at the nano and microscales. As a non-destructive probing tool that requires minimal sample preparation, the AFM is very attractive, particularly in the case of minimal or precious sample. To date, the use of the AFM has primarily been in the arena of imaging where it has been complementary to other microscopic examination tools. Forensic applications in the visual examination of evidence such as blood stains, questioned documents, and hair samples have been reported. While a number of reviews have focused on the use of AFM as an imaging tool for forensic analyses, here we not only discuss these works, but also point to a versatile enhancement in the capabilities of this nanoscale tool - namely its use for force spectroscopy. In this mode, the AFM can determine elastic moduli, adhesion forces, energy dissipation, and the interaction forces between cognate ligands, that can be spatially mapped to provide a unique spatial visualization of properties. Our goals in this review are to provide a context for this capability of the AFM, explain its workings, cover some exemplary works pertaining to forensic sciences, and present a critical analysis on the advantages and disadvantages of this modality. Equipped with this high-resolution tool, imaging and biophysical analysis by the AFM can provide a unique complement to other tools available to the researcher for the analysis and characterization of forensic evidence.

Automated analysis of scanning electron microscopic images for assessment of hair surface damage

Mechanical damage of hair can serve as an indicator of health status and its assessment relies on the measurement of morphological features via microscopic analysis, yet few studies have categorized the extent of damage sustained, and instead have depended on qualitative profiling based on the presence or absence of specific features. We describe the development and application of a novel quantitative measure for scoring hair surface damage in scanning electron microscopic (SEM) images without predefined features, and automation of image analysis for characterization of morphological hair damage after exposure to an explosive blast. Application of an automated normalization procedure for SEM images revealed features indicative of contact with materials in an explosive device and characteristic of heat damage, though many were similar to features from physical and chemical weathering. Assessment of hair damage with tailing factor, a measure of asymmetry in pixel brightness histograms and proxy for surface roughness, yielded 81% classification accuracy to an existing damage classification system, indicating good agreement between the two metrics. Further ability of the tailing factor to score features of hair damage reflecting explosion conditions demonstrates the broad applicability of the metric to assess damage to hairs containing a diverse set of morphological features.

Friction Determination by Atomic Force Microscopy in Field of Biochemical Science

Atomic force microscopy (AFM) is an analytical nanotechnology in friction determination between microscale and nanoscale surfaces. AFM has advantages in mechanical measurement, including high sensitivity, resolution, accuracy, and simplicity of operation. This paper will introduce the principles of mechanical measurement by using AFM and reviewing the progress of AFM methods in determining frictions in the field of biochemical science over the past decade. While three friction measurement assays-friction morphology, friction curve and friction process in experimental cases-are mainly introduced, important advances of technology, facilitating future development of AFM are also discussed. In addition to the principles and advances, the authors also give an overview of the shortcomings and restrictions of current AFM methods, and propose potential directions of AFM techniques by combining it with other well-established characterization techniques. AFM methods are expected to see an increase in development and attract wide attention in scientific research.

Quantitative Scanning Probe Microscopy for Nanomechanical Forensics

Atomic force microscopy (AFM) was used to assess the indentation modulus M_s and pull-off force F_po in four case studies of distinct evidence types, namely hair, questioned documents, fingerprints, and explosive particle-surface interactions. In the hair study, M_s decreased and F_po increased after adding conditioner and bleach to the hair. For the questioned documents, M_s and F_po of two inks were markedly different; ballpoint pen ink exhibited smaller variations relative to the mean value than printer ink. The fingerprint case study revealed that both maximum height and F_po decreased over a three-day period. Finally, the study on explosive particle-surface interactions illustrated that two fabrics exhibited similar M_s, but different F_po. Overall, it was found that AFM addresses needs in forensic science as defined by several federal agencies, in particular an improved ability to expand the information extracted from evidence and to quantify its evidentiary value.

Investigation of the hair of patients with scalp psoriasis using atomic force microscopy

BACKGROUND

Psoriasis affects not only the soft keratin of the skin, but also hard keratin, such as nails and hair. However, few studies have described the changes induced in the hair of patients with psoriasis.

AIM

Using atomic force microscopy (AFM), we investigated the morphological property of hair samples taken from the scalp of patients with psoriasis.

METHODS

Lesional and nonlesional hairs taken from 15 patients with scalp psoriasis were investigated. Hairs from 15 healthy adults were also examined as controls. Using AFM, surface images were taken of an area of 20 × 20 μm(2), with 512 × 512 pixels and a scan speed of 0.8 lines/s. results: Pits were frequently seen in the hair shafts of patients with psoriasis, similar to those seen in their nail plates. Macropit number, scale thickness and surface roughness were all significantly increased in lesional hairs compared with both nonlesional and control hairs, and macropits and scale thickness were also increased in nonlesional hairs compared with control hairs.

CONCLUSIONS

The hair shafts of patients with scalp psoriasis exhibited the same macropits seen in their nails. Both lesional and nonlesional hairs had similar changes in morphological structure compared with controls. This supports the generalized nature of psoriasis, with changes in hair structure being analogous to the changes seen in skin and nails.

Effects of atopic dermatitis on the morphology and water content of scalp hair

The effects of atopic dermatitis (AD) on scalp hair properties, such as morphology and water content, were investigated using atomic force microscopy (AFM) and thermogravimetric analyzer. Hairs from lesional and nonlesional scalp regions of eight patients with AD were investigated. The severity of the disease, which was evaluated using the SCORing Atopic Dermatitis index, was 48.75 (range, 40-80). Hairs from 15 normal adults were also examined as controls. The surface images were taken in an area of 20 × 20 μm(2) with 512 × 512 pixels and a scan speed of 0.8 line/s. AD affected the cuticle structures and scales of scalp hair. The edges of cuticles were torn and collapsed, and the scales were very thick. The water contents of both types of AD hair were less than the control: 12% ± 0.7%, 11.7% ± 0.4%, and 13% ± 0.8% for lesional AD hair, nonlesional AD hair, and control hair, respectively. The scalp hair of patients with AD can be characterized by thick and globular scale patterns. The hair of patients with AD has less water content than normal hair showing a good agreement with the property of skin having AD.

Characterization of human ovarian teratoma hair by using AFM, FT-IR, and Raman spectroscopy

The structural, physical, and chemical properties of hair taken from an ovarian teratoma (teratoma hair) was first examined by atomic force microscopy (AFM), Fourier transform infrared (FT-IR), and Raman spectroscopy. The similarities and differences between the teratoma hair and scalp hair were also investigated. Teratoma hair showed a similar morphology and chemical composition to scalp hair. Teratoma hair was covered with a cuticle in the same manner as scalp hair and showed the same amide bonding modes as scalp hair according to FT-IR and Raman spectroscopy. On the other hand, teratoma hair showed different physical properties and cysteic acid bands from scalp hair: the surface was rougher and the adhesive force was lower than the scalp hair. The cystine oxides modes did not change with the position unlike scalp hair. These differences can be understood by environmental effects not by the intrinsic properties of the teratoma hair.

Investigation of aging effects in human hair using atomic force microscopy

BACKGROUND

A thorough characterization of the morphological structure and physical properties is essential for an understanding of human hair. A number of techniques such as scanning electron microscopy, transmission electron microscopy and confocal microscopy have been used to study hair surfaces. Recently, atomic force microscopy (AFM) has emerged as an ideal method for the non-invasive examination of hair surfaces.

PURPOSE

To investigate the effects of aging on normal Korean hair diameter and surface features using AFM.

METHODS

We enrolled 60 Korean volunteers of various ages who had no hair diseases. We analyzed hair diameter, AFM images of the hair surface, cuticular descriptors and micro-scale mechanical properties for their associations with aging.

RESULTS

Hair diameter was found to increase for the first 20-30 years of life, after which it began to decrease. AFM images of most of the younger subjects showed typical step-like topographic properties with clear scale edges. The AFM images of most of the older subjects revealed dilapidated structures, poorly demarcated scale edges and undulated surfaces. Among the cuticular descriptors, surface roughness increased significantly with age. Force to distance analysis demonstrated a dependence on age.

CONCLUSION

These results suggest that aging causes changes in hair diameter and surface structure.

Effect of SDS on human hair: Study on the molecular structure and morphology

This paper presents a model study to understand the effect of surfactants on the physicochemical properties of human hair. FT-IR ATR spectroscopy has been employed to understand the chemical changes induced by sodium dodecyl sulfate (SDS) on human scalp hair. In particular, the SDS induced changes in the secondary structure of protein present in the outer protective layer of hair, i.e. cuticle, have been investigated. Conformational changes in the secondary structure of protein were studied by curve fitting of the amide I band after every phase of SDS treatment. It has been found that SDS brings rearrangements in the protein backbone conformations by transforming β -sheet structure to random coil and β -turn. Additionally, AFM and SEM studies were carried out to understand the morphological changes induced on the hair surface. SEM and AFM images demonstrated the rupture and partial erosion of cuticle sublayers.

Investigation of hair shaft in seborrheic dermatitis using atomic force microscopy

BACKGROUND/PURPOSE

We have investigated the changes of seborrheic dermatitis (SD) on the hair shaft in the morphological and physical properties using atomic force microscopy (AFM).

METHODS

Hair samples were obtained from the lesional and perilesional regions in 15 patients with SD. Fifteen healthy adults were included as the control group. From the topography of hair obtained by AFM, the height of the scale, step height, roughness, diameter, and pit were determined.

RESULTS

The scale thickness of the SD-affected hair was sevenfold more than in the control hair showing statistically significance. The lesional hair showed greater roughness parameters of Sa, Sq, and Sz than the perilesional and the control hair, but this difference was not significant. The cuticle of the lesional hair was significantly damaged while perilesional hair showed a very distinct cuticle structure with smooth edges and a regular interval between the cuticles. The diameter of the lesional hair was significantly lesser by 10-35% than that of the perilesional hair. The pit was rarely observed in the SD-affected hair collected from both the lesional and perilesional regions.

CONCLUSION

The changes in the hair shaft affected SD was measured using AFM non-invasively. AFM could be a useful tool in monitoring the treatment response and the severity of SD.

Diagnosis of hair disorders

Hair disorders include hair loss, increased hair growth, and hair structure defects with increased breakage, as well as unacceptable cosmetic appearance, such as reduced shine, strength, curliness, and elasticity. It is the task of the dermatologist to choose the right diagnostic tool depending on the suspected clinical diagnosis. Moreover, certain tools are best suited for diagnosis in private practice, whereas others can only be used to monitor hair growth under treatment in clinical studies. The techniques can be classified as either invasive (eg, biopsies in scarring alopecia), semi-invasive (trichogram, unit area trichogram), or noninvasive (eg, global hair counts, phototrichogram, electron microscopy, laser scanning microscopy) methods. Further, one must differentiate between subjective and objective techniques. For the practicing dermatologist, body and scalp hair distribution by use of different grading systems, the hair pull test, and dermoscopy belong in the category of basic diagnostic tools. Basic techniques may be extended by computer-assisted phototrichogram and, in selected cases, by use of the trichogram and/or scalp biopsies. For research purposes optical coherent tomography, electron microscopy, biochemical methods, atomic force microscopy, and confocal laser scanning microscopy are optional tools. For clinical studies global photographs (global expert panel), hair weighing, phototrichogram, and different clinical scoring systems have proven to be objective tools for documentation and evaluation of hair growth and hair quality.

Hair fiber characteristics and methods to evaluate hair physical and mechanical properties

The hair thread is a natural fiber formed by keratin, a protein containing high concentration of sulfur coming from the amino acid cystine. The main physical proprieties of the hair depend mostly on its geometry; the physical and mechanical properties of hair involve characteristics to improve: elasticity, smoothness, volume, shine, and softness due to both the significant adherence of the cuticle scales and the movement control (malleability), as well as the easiness of combing, since they reduce the fibers static electricity. The evaluation of these effects on hair may be carried out by several methods, as: optical and electron microscopy, mechanical resistance measuring, shine evaluation and optical coherence tomography (OCT).

Membrane deformation of unfixed erythrocytes in air with time lapse investigated by tapping mode atomic force microscopy

Estimation of the time of death is one of the most important problems for forensic medicine and law. Physical and chemical postmortem changes are evaluated together while estimating the time of death. The pattern analysis of antemortem and postmortem bloodstains is one of the important parameters for forensic science, and cellular changes of blood cells can be useful for the quantitative assessment of the time of death. In this study, by successively investigating erythrocytes exposed in air on mica for 5 days using tapping mode atomic force microscopy (TM-AFM), we observed deformation of whole cell and membrane surface of unfixed erythrocytes with time lapse. We found that the time-dependent cellular changes occurred after exposure of erythrocytes in air for several days. At 0.5 days of exposure, fissures and cell shrinkage were observed. At 2.5 days of exposure, the emergence of nanometer-scale protuberances were observed and these protuberances increased in number with increasing time. The changes of cell shape and cell membrane surface ultrastructure can be used to estimate the time of death. Futhermore, smear-induced abnormal erythrocytes and immunostained erythrocytes were observed here. The need for more precise research is indicated, such as the correlation of membrane changes to intervals of less than 0.5 day of air exposure, and use of various substrates in addition to mica, including glass, metals, fabrics, among others, on which the bloodstains appear in crime scenes. The results of this research demonstrate the efficacy of AFM as a potentially powerful analytical tool in forensic science.