Fourier transform infrared imaging of human hair with a high spatial resolution without the use of a synchrotron

Interactions between Damaged Hair Keratin and Juglone as a Possible Restoring Agent: A Vibrational and Scanning Electron Microscopy Study

Juglone, a quinonic compound present in walnut extracts, was proposed as a restoring agent for hair keratin treated with permanent or discoloration processes. The proposed mechanism of restoration by juglone involves the formation of a Michael adduct between the quinone and the thiol moieties of cysteine residues. To this purpose, the first part of the present paper involved the spectroscopic study of the product of the reaction between juglone and N-acetyl-L-cysteine as a model compound. IR spectroscopy and Scanning Electron Microscopy (SEM) monitored the chemical and morphological variations induced by applying juglone to hair keratin. In order to simulate the most common hair treatments (i.e., permanent and discoloration), juglone was applied to hair that had been previously treated with a reducing agent, i.e., methyl thioglycolate (MT) or with bleaching agents (based on hydrogen peroxide and persulfates) followed by sodium hydrogen sulfite. IR spectroscopy allowed us to monitor the formation of Michael adducts between juglone and cysteine residues: the Michael adducts' content was related to the cysteine content of the samples. In fact, MT and sodium hydrogen sulfite favored the reduction of the disulfide bonds and increased the content of free cysteine residues, which can react with juglone. SEM analyses confirmed the trend observed by IR spectroscopy since hair samples treated with juglone adopted a more regular hair surface and more imbricated scales, thus supporting the possible use of juglone as a restoring agent for damaged hair keratins.

Transmission infrared micro-spectroscopic study of individual human hair

Significance

Understanding the optical transmission property of human hair, especially in the infrared regime, is vital in physical, clinical, and biomedical research. However, the majority of infrared spectroscopy on human hair is performed in the reflection mode, which only probes the absorptance of the surface layer.

Aim

The direct transmission spectrum of individual hair without horizontal cut offers a rapid and non-destructive test of the hair cortex but is less investigated experimentally due to the small size and strong absorption of the hair.

Approach

In this work, we conduct a transmission infrared micro-spectroscopic study on individual human hair with the help of Fourier-transform infrared microscope experimentally. Its high spatial resolution of infrared micro-spectroscopy further allows the comparison among different regions of hair. The geometry effect of the internal hair structure is also quantified using the finite-element simulation, which supports the experimental results.

Results

By utilizing direct measurements of the transmission spectrum using a Fourier-transform infrared microscope, the human hair is found to display prominent band filtering behavior. In a case study of adult-onset Still's disease, the corresponding infrared transmission exhibits systematic variations of spectral weight as the disease evolves.

Conclusions

Our work implies that the variation of spectral weight may relate to the disordered microscopic structure variation of the hair cortex during an inflammatory attack. Our work reveals the potential of hair infrared transmission spectrum in tracing the variation of hair cortex retrospectively.

Selective IR super-resolution imaging of β-keratins at the bulk or interface in feather detected by using a nonlinear optical process

We developed the new IR super-resolution microscope by using a 4-wave mixing (4-wave), which is a third-order nonlinear optical process, and carried out the IR super-resolution imaging of the cross section of the rachis of an avian feather. We clearly observed strong signals in the entire region of the rachis at the amide I vibration of β-keratin in both of the XXYY and YYXX polarization combination. These results are different from images detected by using the vibrational sum-frequency generation (VSFG) method. While the VSFG imaging detects molecules only from the interface, the 4-wave method enables us to observe the signal from the bulk area. We concluded that the four repeating units of β-keratins in the bulk area which are suggested by X-ray diffraction studies are visualized in the 4-wave detected method. We also applied two IR super-resolution microscopies for the barb and discuss the site dependence of the orientation, distribution and concentration of β-keratin.

α-Fe2O3 Nanoparticles Aided-Dual Conversion for Self-Powered Bio-Based Photodetector

Eco-friendly energy harvesting from the surrounding environment has been triggered extensive researching enthusiasm due to the threat of global energy crisis and environmental pollutions. By the conversion of mechanical energy that is omnipresent in our environment into electrical energy, triboelectric nanogenerator (TENG) can potentially power up small electronic devices, serves as a self-powered detectors and predominantly, it can minimize the energy crisis by credibly saving the traditional non-renewable energy. In this study, we present a novel bio-based TENG comprising PDMS/α-Fe2O3 nanocomposite film and a processed human hair-based film, that harvests the vibrating energy and solar energy simultaneously by the integration of triboelectric technology and photoelectric conversion techniques. Upon illumination, the output voltage and current signals rapidly increased by 1.4 times approximately, compared to the dark state. Experimental results reveal that the photo-induced enhancement appears due to the effective charge separation depending on the photosensitivity of the hematite nanoparticles (α-Fe2O3 nanoparticles) over the near ultraviolet (UV), visible and near infrared (IR) regions. Our work provides a new approach towards the self-powered photo-detection, while developing a propitious green energy resource for the circular bio-economy.

A new typology of human hair medullas based on lipid composition analysis by synchrotron FTIR microspectroscopy

Human hair is an organ that connects fundamental and applied research with everyday life through the cosmetic industry. Yet, the accurate compositional description of the human hair medulla is lacking due to their small size and difficulty with microextraction. Medullas are thus generally classified based on morphology. We investigated the chemical composition of the human hair medulla using synchrotron based infrared microspectroscopy. We confirmed that lipid signatures dominate the medulla infrared spectrum having 3-20 times higher lipid concentration compared to their surrounding cortex. Human hair medullas contain a mixture of non-esterified and esterified lipids, and carboxylate soaps in various proportions. We reveal the first direct spectroscopic evidence that medulla carboxylates are coordinated to calcium since they exhibit the specific calcium carboxylate signature. Using a representative sample, we observed a strong compositional variability between medullas that was unreported before. We detected calcium carboxylates in 76% of the medullas with one order of magnitude concentration variability between samples. All medullas contained esters with esterification varying by a factor of 30. Moreover, we detected the presence of crystalline calcium stearate in 9% of the medullas. We described a series of spectral markers to characterize medullas based on their lipid composition and propose to classify medullas in four to five groups. Our analysis provides a more detailed understanding of the chemical composition of human hair medullas that may impact cosmetics and biology. The origin and biological meaning of these variations must still be investigated.

Mapping sub-cellular protein aggregates and lipid inclusions using synchrotron ATR-FTIR microspectroscopy

Visualising direct biochemical markers of cell physiology and disease pathology at the sub-cellular level is an ongoing challenge in the biological sciences. A suite of microscopies exists to either visualise sub-cellular architecture or to indirectly view biochemical markers (e.g. histochemistry), but further technique developments and innovations are required to increase the range of biochemical parameters that can be imaged directly, in situ, within cells and tissue. Here, we report our continued advancements in the application of synchrotron radiation attenuated total reflectance Fourier transform infrared (SR-ATR-FTIR) microspectroscopy to study sub-cellular biochemistry. Our recent applications demonstrate the much needed capability to map or image directly sub-cellular protein aggregates within degenerating neurons as well as lipid inclusions within bacterial cells. We also characterise the effect of spectral acquisition parameters on speed of data collection and the associated trade-offs between a realistic experimental time frame and spectral/image quality. Specifically, the study highlights that the choice of 8 cm^-1 spectral resolutions provide a suitable trade-off between spectral quality and collection time, enabling identification of important spectroscopic markers, while increasing image acquisition by ∼30% (relative to 4 cm^-1 spectral resolution). Further, this study explores coupling a focal plane array detector with SR-ATR-FTIR, revealing a modest time improvement in image acquisition time (factor of 2.8). Such information continues to lay the foundation for these spectroscopic methods to be readily available for, and adopted by, the biological science community to facilitate new interdisciplinary endeavours to unravel complex biochemical questions and expand emerging areas of study.

Perspectives on infrared spectroscopic imaging from cancer diagnostics to process analysis

This perspective paper discusses the recent and potential developments in the application of infrared spectroscopic imaging, with a focus on Fourier transform infrared (FTIR) spectroscopic imaging. The current state-of-the-art has been briefly reported, that includes recent trends and advances in applications of FTIR spectroscopic imaging to biomedical systems. Here, some new opportunities for research in the biomedical field, particularly for cancer diagnostics, and also in the engineering field of process analysis; as well as challenges in FTIR spectroscopic imaging are discussed. Current and future prospects that will bring spectroscopic imaging technologies to the frontier of advanced medical diagnostics and to process analytics in engineering applications will be outlined in this opinion paper.

Evaluation of Melanoma (SK-MEL-2) Cell Growth between Three-Dimensional (3D) and Two-Dimensional (2D) Cell Cultures with Fourier Transform Infrared (FTIR) Microspectroscopy

Fourier transform infrared (FTIR) microspectroscopy was used to evaluate the growth of human melanoma cells (SK-MEL-2) in two-dimensional (2D) versus three-dimensional (3D) spheroid culture systems. FTIR microspectroscopy, coupled with multivariate analysis, could be used to monitor the variability of spheroid morphologies prepared from different cell densities. The characteristic shift in absorbance bands of the 2D cells were different from the spectra of cells from 3D spheroids. FTIR microspectroscopy can also be used to monitor cell death similar to fluorescence cell staining in 3D spheroids. A change in the secondary structure of protein was observed in cells from the 3D spheroid versus the 2D culture system. FTIR microspectroscopy can detect specific alterations in the biological components inside the spheroid, which cannot be detected using fluorescence cell death staining. In the cells from 3D spheroids, the respective lipid, DNA, and RNA region content represent specific markers directly proportional to the spheroid size and central area of necrotic cell death, which can be confirmed using unsupervised PCA and hierarchical cluster analysis. FTIR microspectroscopy could be used as an alternative tool for spheroid cell culture discrimination, and validation of the usual biochemical technique.

Transmission Fourier Transform Infrared Spectroscopic Imaging, Mapping, and Synchrotron Scanning Microscopy with Zinc Sulfide Hemispheres on Living Mammalian Cells at Sub-Cellular Resolution

Fourier transform infrared (FT-IR) spectroscopic imaging and microscopy of single living cells are established label-free technique for the study of cell biology. The constant driver to improve the spatial resolution of the technique is due to the diffraction limit given by infrared (IR) wavelength making subcellular study challenging. Recently, we have reported, with the use of a prototype zinc sulfide (ZnS) transmission cell made of two hemispheres, that the spatial resolution is improved by the factor of the refractive index of ZnS, achieving a λ/2.7 spatial resolution using the synchrotron-IR microscopy with a 36× objective with numerical aperture of 0.5. To refine and to demonstrate that the ZnS hemisphere transmission device can be translated to standard bench-top FT-IR imaging systems, we have, in this work, modified the device to achieve a more precise path length, which has improved the spectral quality of the living cells, and showed for the first time that the device can be applied to study live cells with three different bench-top FT-IR imaging systems. We applied focal plane array (FPA) imaging, linear array, and a synchrotron radiation single-point scanning method and demonstrated that in all cases, subcellular details of individual living cells can be obtained. Results have shown that imaging with the FPA detector can measure the largest area in a given time, while measurements from the scanning methods produced a smoother image. Synchrotron radiation single-point mapping produced the best quality image and has the flexibility to introduce over sampling to produce images of cells with great details, but it is time consuming in scanning mode. In summary, this work has demonstrated that the ZnS hemispheres can be applied in all three spectroscopic approaches to improve the spatial resolution without any modification to the existing microscopes.

Ethnic hair: Thermoanalytical and spectroscopic differences

BACKGROUND

The aim of this study is to characterize and detect the possible differences among the hair of three different ethnicities: African, Asiatic and Caucasian.

MATERIALS AND METHODS

The differences in water adsorption/desorption behaviour of hairs were studied using a thermogravimetric balance and compared with the analysis of the lipid distribution and order using synchrotron-based Fourier transform infrared microspectroscopy. Besides, the thermal thermogravimetry (TG) and differential scanning calorimetry (DSC) analyses on human hair were executed.

RESULTS

Differences in the diffusion coefficients were evidenced. African hair exhibited increased permeability. Caucasian hair displayed a higher water absorption capability with increasing humidity but with a slow diffusion rate. The Asian fibre appeared to be more resistant to hydration changes. The spectroscopic analysis showed notable differences in the cuticle lipids. The African cuticle exhibited more lipids with a lower order bilayer. The outmost layer of Caucasian fibres contained more ordered lipids, and the Asian fibres show a very low level of lipids on the cuticle region. The DSC results indicate no difference in the thermal stability and TG showed higher water content in the Caucasian fibre and a possible lower cysteine disulphide bond content in the African hair matrix.

CONCLUSION

The triple approach demonstrated the permeability differences among the ethnic fibres and their correlation with the properties of their cuticle lipids. These differences could have particular relevance to the hair care cosmetic market.

Lipid loses and barrier function modifications of the brown-to-white hair transition

BACKGROUND

The main objective of this study was to determine the lipid profile of brown and white Caucasian hair fibres and the effects of lipids on the properties of fibres.

MATERIALS AND METHODS

To determine the structures of white and brown hair lipid bilayers, cross sections of fibres of both hair types were examined using synchrotron-based μ-FTIR mapping. Dynamic vapour sorption (DVS) analyses were also performed to determine the differences in the barrier function of both fibres.

RESULTS

Spatial identification of lipids showed that a great amount of lipids was present in the medulla of fibres of both hair types, but important differences were also observed between cuticles of the different fibres. The cuticle of a white hair fibre showed a significant decrease in its lipid content, but did not show differences in the lateral packing order with respect to the cuticle of a brown hair fibre. The cortex and medulla of the white hair fibre also exhibited a significant decrease in its lipid content but with a higher lateral packing order than brown hair. Using DVS analysis, it was found that the water dynamics of white hair fibres differed from those of brown hair fibres, showing a decrease in their total capacity to absorb water and an increase in the velocity of the exchange of water with the environment.

CONCLUSION

The results of both techniques demonstrated a high correlation between the characteristics of the lipids located in the cuticle and the water dynamics of the fibres.

Fourier transform infrared spectroscopic imaging of wear and corrosion products within joint capsule tissue from total hip replacements patients

Implant debris generated by wear and corrosion is a prominent cause of joint replacement failure. This study utilized Fourier transform infrared spectroscopic imaging (FTIR-I) to gain a better understanding of the chemical structure of implant debris and its impact on the surrounding biological environment. Therefore, retrieved joint capsule tissue from five total hip replacement patients was analyzed. All five cases presented different implant designs and histopathological patterns. All tissue samples were formalin-fixed and paraffin-embedded. Unstained, 5 μm thick sections were prepared. The unstained sections were placed on BaF₂ windows and deparaffinized with xylene prior to analysis. FTIR-I data were collected at a spectral resolution of 4 cm^-1 using an Agilent Cary 670 spectrometer coupled with Cary 620 FTIR microscope. The results of study demonstrated that FTIR-I is a powerful tool that can be used complimentary to the existing histopathological evaluation of tissue. FTIR-I was able to distinguish areas with different cell types (macrophages, lymphocytes). Small, but distinct differences could be detected depending on the state of cells (viable, necrotic) and depending on what type of debris was present (polyethylene [PE], suture material, and metal oxides). Although, metal oxides were mainly below the measurable range of FTIR-I, the infrared spectra of tissues exhibited noticeable difference in their presence. Tens of micrometer sized polyethylene particles could be easily imaged, but also accumulations of submicron particles could be detected within macrophages. FTIR-I was also able to distinguish between PE debris, and other birefringent materials such as suture. Chromium-phosphate particles originating from corrosion processes within modular taper junctions of hip implants could be identified and easily distinguished from other phosphorous materials such as bone. In conclusion, this study successfully demonstrated that FTIR-I is a useful tool that can image and determine the biochemical information of retrieved tissue samples over tens of square millimeters in a completely label free, nondestructive, and objective manner. The resulting chemical images provide a deeper understanding of the chemical nature of implant debris and their impact on chemical changes of the tissue within which they are embedded.

Integrated recognition and quantitative detection of starch in surimi by infrared spectroscopy and spectroscopic imaging

Surimi products have become increasingly-consumed food with prominent characteristics of high nutrition and convenience and its supply falls short of demand. However, due to exhausted fishery resource in recent years, surimi adulteration, such as addition of plant proteins, starch and other animal origin meat, is becoming serious, so recognition of these exogenous substances has become an urgent issue. In this study, Fourier transform infrared spectroscopy (FT-IR) combined with infrared spectroscopic imaging could distinguish heterogeneity in surimi qualitatively and quantitatively and obtain integral chemical images so that spatial distribution of each component in surimi could be visually displayed, thus a rapid recognition method and a prediction model were developed. The different starch contents in surimi had been primarily identified through intensity change of infrared absorption peaks at 1045cm^-1 and 988cm^-1, specifically with peak shifts to 1041cm^-1 and to 992cm^-1, respectively. In infrared imaging analysis, principal components (PCs) were separated and one key PC was confirmed as starch by characteristic peaks comparison at 1147cm^-1, 1075cm^-1, 997cm^-1 and 930cm^-1. Meanwhile, an established statistic model could predict starch content in surimi correctly with a reliable correlation coefficient (R=0.9856) and root mean square error of prediction (RMSEP=5.64). Therefore, FT-IR combined with infrared spectroscopic imaging could be applicable to integrally recognize and quantitatively detect starch in surimi.

Infrared Evaluation of Enantiometric Amount and Application to Racemization at the Interface Between L- and D-Alanine

Amino acids, except for glycine, have two types of molecular structures, L- and D-forms, which are enantiomers. As the L- and D-form molecules have identical chemical and physical properties, they cannot be easily identified by conventional methods. In this study, we found that the amount and the spatial distribution of D-enantiomers in an L-alanine (CH₃CH(COOH)NH₂) matrix in evaporated thin films, which is one of amino acid molecules, can be evaluated quantitatively using an infrared micro spectroscopy with synchrotron radiation. This method was applied to the evaluation of the volume fraction of a racemic component appearing at the interface between L- and D-alanine thin films.

Spectroscopic imaging of biomaterials and biological systems with FTIR microscopy or with quantum cascade lasers

Spectroscopic imaging of biomaterials and biological systems has received increased interest within the last decade because of its potential to aid in the detection of disease using biomaterials/biopsy samples and to probe the states of live cells in a label-free manner. The factors behind this increased attention include the availability of improved infrared microscopes and systems that do not require the use of a synchrotron as a light source, as well as the decreasing costs of these systems. This article highlights the current technical challenges and future directions of mid-infrared spectroscopic imaging within this field. Specifically, these are improvements in spatial resolution and spectral quality through the use of novel added lenses and computational algorithms, as well as quantum cascade laser imaging systems, which offer advantages over traditional Fourier transform infrared systems with respect to the speed of acquisition and field of view. Overcoming these challenges will push forward spectroscopic imaging as a viable tool for disease diagnostics and medical research.

Graphical abstract

Molecular modeling and structural characterization of a high glycine–tyrosine hair keratin associated protein

For the first time, the molecular structure of a hair cortical matrix protein KAP8.1 has been characterised using modelling and spectroscopy.

Attenuated total reflection Fourier-transform infrared (ATR-FTIR) imaging of tissues and live cells

FTIR spectroscopic imaging is a label-free, non-destructive and chemically specific technique that can be utilised to study a wide range of biomedical applications such as imaging of biopsy tissues, fixed cells and live cells, including cancer cells. In particular, the use of FTIR imaging in attenuated total reflection (ATR) mode has attracted much attention because of the small, but well controlled, depth of penetration and corresponding path length of infrared light into the sample. This has enabled the study of samples containing large amounts of water, as well as achieving an increased spatial resolution provided by the high refractive index of the micro-ATR element. This review is focused on discussing the recent developments in FTIR spectroscopic imaging, particularly in ATR sampling mode, and its applications in the biomedical science field as well as discussing the future opportunities possible as the imaging technology continues to advance.

Fundamental developments in infrared spectroscopic imaging for biomedical applications

Infrared chemical imaging is a rapidly emerging field with new advances in instrumentation, data acquisition and data analysis. These developments have had significant impact in biomedical applications and numerous studies have now shown that this technology offers great promise for the improved diagnosis of the diseased state. Relying on purely biochemical signatures rather than contrast from exogenous dyes and stains, infrared chemical imaging has the potential to revolutionise histopathology for improved disease diagnosis. In this review we discuss the recent advances in infrared spectroscopic imaging specifically related to spectral histopathology (SHP) and consider the current state of the field. Finally we consider the practical application of SHP for disease diagnosis and consider potential barriers to clinical translation highlighting current directions and the future outlook.

Towards microfluidic reactors for in situ synchrotron infrared studies

Anodically bonded etched silicon microfluidic devices that allow infrared spectroscopic measurement of solutions are reported. These extend spatially well-resolved in situ infrared measurement to higher temperatures and pressures than previously reported, making them useful for effectively time-resolved measurement of realistic catalytic processes. A data processing technique necessary for the mitigation of interference fringes caused by multiple reflections of the probe beam is also described.

Localization of human hair structural lipids using nanoscale infrared spectroscopy and imaging

Atomic force microscopy (AFM) and infrared (IR) spectroscopy have been combined in a single instrument (AFM-IR) capable of producing IR spectra and absorption images at a sub-micrometer spatial resolution. This new device enables human hair to be spectroscopically characterized at levels not previously possible. In particular, it was possible to determine the location of structural lipids in the cuticle and cortex of hair. Samples of human hair were embedded, cross-sectioned, and mounted on ZnSe prisms. A tunable IR laser generating pulses of the order of 10 ns was used to excite sample films. Short duration thermomechanical waves, due to infrared absorption and resulting thermal expansion, were studied by monitoring the resulting excitation of the contact resonance modes of the AFM cantilever. Differences are observed in the IR absorbance intensity of long-chain methylene-containing functional groups between the outer cuticle, middle cortex, and inner medulla of the hair. An accumulation of structural lipids is clearly observed at the individual cuticle layer boundaries. This method should prove useful in the future for understanding the penetration mechanism of substances into hair as well as elucidating the chemical nature of alteration or possible damage according to depth and hair morphology.

Confocal Raman spectroscopy of whole hairs

This paper describes the application of Raman spectroscopy to whole hair fibers. Previously this has proved difficult because the hairs are relatively opaque, and spatial resolution diminishes with depth because of the change in refractive index. A solution is to couple confocal Raman with multivariate curve resolution (MCR) data analysis, which separates spectral differences with depth despite this reduction in resolution. Initially, it is shown that the cuticle can be separated from the cortex, showing the differences in the proteins, which can then be plotted as a function of depth, with the cuticle factor being seen only at the surface as expected. Hairs that had been treated in different ways, e.g., by bleaching, treatment with the active molecule resorcinol followed by rinsing and treatment with a full hair care product, were also examined. In all cases, changes to the hair are identified and are associated with specific parts of the fiber. Since the hair fiber is kept intact, it can be repeatedly treated and measured, hence multistep treatment processes can be followed. This method expands the potential use of Raman spectroscopy in hair research.

Recent applications of ATR FTIR spectroscopy and imaging to proteins

Attenuated Total Reflection (ATR) Fourier Transform Infrared (FTIR) spectroscopy is a label-free, non-destructive analytical technique that can be used extensively to study a wide variety of different molecules in a range of different conditions. The aim of this review is to discuss and highlight the recent advances in the applications of ATR FTIR spectroscopic imaging to proteins. It briefly covers the basic principles of ATR FTIR spectroscopy and ATR FTIR spectroscopic imaging as well as their advantages to the study of proteins compared to other techniques and other forms of FTIR spectroscopy. It will then go on to examine the advances that have been made within the field over the last several years, particularly the use of ATR FTIR spectroscopy for the understanding and development of protein interaction with surfaces. Additionally, the growing potential of Surface Enhanced Infrared Spectroscopy (SEIRAS) within this area of applications will be discussed. The review includes the applications of ATR FTIR imaging to protein crystallisation and for high-throughput studies, highlighting the future potential of the technology within the field of protein structural studies and beyond.

Effects of scalp dermatitis on chemical property of hair keratin

The effects of scalp dermatitis (seborrheic dermatitis (SD), psoriasis, and atopic dermatitis (AD)) on chemical properties of hair keratin were investigated by Fourier transform infrared (FT-IR) spectroscopy. Hairs were collected from lesional regions affected by SD, psoriasis, and AD and non-lesional regions separately. The hairs with SD were taken from patients with ages of 16-80 years. The ages of patients with psoriasis ranged from 8 to 67 years, and all patients exhibited moderate disease. Hairs with AD were taken from the patients with ages of 24-45 years and the average SCORing atopic dermatitis (SCORAD) was 48.75. Hairs from 20 normal adults were collected as a control. The FT-IR absorbance bands were analyzed by the Gaussian model to obtain the center frequency, half width, height, and area of each band. The height and area of all bands in the spectra were normalized to the amide I centered at 1652 cm(-1) to quantitatively analyze the chemical composition of keratin. The spectra of hair with scalp dermatitis were different with that of control, the amide A components centered at 3278 cm(-1) were smaller than those of the control. The psoriasis hair showed a large difference in the IR absorbance band between lesional and non-lesional hairs indicating good agreement with the morphological changes. The hairs with diseases did not show differences in the content of cystine, which was centered at 1054 cm(-1), from the control. The chemical properties of keratin were not significantly different between the hairs affected by SD, psoriasis, and AD. However, the changes induced by scalp dermatitis were different with weathering. Therefore, FT-IR analysis could be used to screen differences between the physiological and pathological conditions of scalp hair.

Aberration-free FTIR spectroscopic imaging of live cells in microfluidic devices

The label-free, non-destructive chemical analysis offered by FTIR spectroscopic imaging is a very attractive and potentially powerful tool for studies of live biological cells. FTIR imaging of live cells is a challenging task, due to the fact that cells are cultured in an aqueous environment. While the synchrotron facility has proven to be a valuable tool for FTIR microspectroscopic studies of single live cells, we have demonstrated that high quality infrared spectra of single live cells using an ordinary Globar source can also be obtained by adding a pair of lenses to a common transmission liquid cell. The lenses, when placed on the transmission cell window, form pseudo hemispheres which removes the refraction of light and hence improve the imaging and spectral quality of the obtained data. This study demonstrates that infrared spectra of single live cells can be obtained without the focus shifting effect at different wavenumbers, caused by the chromatic aberration. Spectra of the single cells have confirmed that the measured spectral region remains in focus across the whole range, while spectra of the single cells measured without the lenses have shown some erroneous features as a result of the shift of focus. It has also been demonstrated that the addition of lenses can be applied to the imaging of cells in microfabricated devices. We have shown that it was not possible to obtain a focused image of an isolated cell in a droplet of DPBS in oil unless the lenses are applied. The use of the approach described herein allows for well focused images of single cells in DPBS droplets to be obtained.

The study of a single BGC823 cell using Fourier transform infrared microspectroscopic imaging

In order to investigate gastric cancer at cellular and sub-cellular level, a single human gastric adenocarcinoma BGC823 cell was studied by an infrared microscope equipped with a focal plane array (FPA) detector. The spectra showed difference between the nucleus and the endoplasmic reticulum (ER) of the BGC823 cell. The peak of vasPO2- was shifted to a higher wavenumber at the nucleus compared with that at the ER. The height ratios of 2954 cm(-1)/2922 cm(-1) (CH3/CH2) and 1088 cm(-1)/1539 cm(-1) (DNA/amide II) of the nucleus were significantly higher than those of the ER. Furthermore, chemical images reveal the intensity distributions of lipids, proteins and DNA of the single BGC823 cell, and the intense absorptions of proteins and DNA were observed in the nuclear region of the cell while the intense absorption of lipids was found in the ER region of the cell. The Fourier transform infrared (FTIR) microspectroscopic imaging result indicates the study of the single gastric cancer cell at sub-cellular level can be beneficial for knowing gastric cancer more which will be of great importance for the study and diagnosis of gastric cancer. The result also suggests that FPA is a useful tool in the study of a single cell and may be a powerful tool for study and diagnosis of gastric cancer.

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.

Measuring changes in chemistry, composition, and molecular structure within hair fibers by infrared and Raman spectroscopic imaging

Spatially resolved infrared (IR) and Raman images are acquired from human hair cross sections or intact hair fibers. The full informational content of these spectra are spatially correlated to hair chemistry, anatomy, and structural organization through univariate and multivariate data analysis. Specific IR and Raman images from untreated human hair describing the spatial dependence of lipid and protein distribution, protein secondary structure, lipid chain conformational order, and distribution of disulfide cross-links in hair protein are presented in this study. Factor analysis of the image plane acquired with IR microscopy in hair sections, permits delineation of specific micro-regions within the hair. These data indicate that both IR and Raman imaging of molecular structural changes in a specific region of hair will prove to be valuable tools in the understanding of hair structure, physiology, and the effect of various stresses upon its integrity.

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.

Micro- and macro-attenuated total reflection Fourier transform infrared spectroscopic imaging. Plenary Lecture at the 5th International Conference on Advanced Vibrational Spectroscopy, 2009, Melbourne, Australia

Fourier transform infrared (FT-IR) spectroscopic imaging has become a very powerful method in chemical analysis. In this review paper we describe a variety of opportunities for obtaining FT-IR images using the attenuated total reflection (ATR) approach and provide an overview of fundamental aspects, accessories, and applications in both micro- and macro-ATR imaging modes. The advantages and versatility of both ATR imaging modes are discussed and the spatial resolution of micro-ATR imaging is demonstrated. Micro-ATR imaging has opened up many new areas of study that were previously precluded by inadequate spatial resolution (polymer blends, pharmaceutical tablets, cross-sections of blood vessels or hair, surface of skin, single live cells, cancerous tissues). Recent applications of ATR imaging in polymer research, biomedical and forensic sciences, objects of cultural heritage, and other complex materials are outlined. The latest advances include obtaining spatially resolved chemical images from different depths within a sample, and surface-enhanced images for macro-ATR imaging have also been presented. Macro-ATR imaging is a valuable approach for high-throughput analysis of materials under controlled environments. Opportunities exist for chemical imaging of dynamic aqueous systems, such as dissolution, diffusion, microfluidics, or imaging of dynamic processes in live cells.

Facing the challenge of biosample imaging by FTIR with a synchrotron radiation source

Fourier-transform infrared (FTIR) synchrotron radiation (SR) microspectroscopy is a powerful molecular probe of biological samples at cellular resolution (<10 microm). As the brilliance of SR is 100-1000 times higher than that of a conventional Globar source, FTIR microscopes are now available in almost all advanced SR facilities around the world. However, in spite of this superior performance, the expected advances in IR SR microscopy have not yet been realised, particularly with regard to bio-analytical studies of single cells and soft tissues. In recent decades solid-state array detectors have revolutionized the fields of molecular spectroscopy and chemical imaging, and now new IR focal plane array detectors implemented at ultra-bright SR facilities will extend the performance and overcome the existing limitations, possibly allowing IR SR instrumentation to achieve the highest sensitivity and resolution of molecular imaging. The impact of IR imaging on large tissue area and the complexity of the analysis are discussed. In view of the high brilliance of SR sources, a comparison of published microscope images is given. Finally, it is briefly outlined how an optimized combination of IR instrumentation and SR optical systems could reach the expected advantages of a SR-based FTIR imaging system.

Vibrational spectroscopy: a clinical tool for cancer diagnostics

Vibrational spectroscopy techniques have demonstrated potential to provide non-destructive, rapid, clinically relevant diagnostic information. Early detection is the most important factor in the prevention of cancer. Raman and infrared spectroscopy enable the biochemical signatures from biological tissues to be extracted and analysed. In conjunction with advanced chemometrics such measurements can contribute to the diagnostic assessment of biological material. This paper also illustrates the complementary advantage of using Raman and FTIR spectroscopy technologies together. Clinical requirements are increasingly met by technological developments which show promise to become a clinical reality. This review summarises recent advances in vibrational spectroscopy and their impact on the diagnosis of cancer.

Preliminary investigations into macroscopic attenuated total reflection-fourier transform infrared imaging of intact spherical domains: spatial resolution and image distortion

This paper describes preliminary investigations into the spatial resolution of macro attenuated total reflection (ATR) Fourier transform infrared (FT-IR) imaging and the distortions that arise when imaging intact, convex domains, using spheres as an extreme example. The competing effects of shallow evanescent wave penetration and blurring due to finite spatial resolution meant that spheres within the range 20-140 microm all appeared to be approximately the same size ( approximately 30-35 microm) when imaged with a numerical aperture (NA) of approximately 0.2. A very simple model was developed that predicted this extreme insensitivity to particle size. On the basis of these studies, it is anticipated that ATR imaging at this NA will be insensitive to the size of intact highly convex objects. A higher numerical aperture device should give a better estimate of the size of small spheres, owing to superior spatial resolution, but large spheres should still appear undersized due to the shallow sampling depth. An estimate of the point spread function (PSF) was required in order to develop and apply the model. The PSF was measured by imaging a sharp interface; assuming an Airy profile, the PSF width (distance from central maximum to first minimum) was estimated to be approximately 20 and 30 microm for IR bands at 1600 and 1000 cm(-1), respectively. This work has two significant limitations. First, underestimation of domain size only arises when imaging intact convex objects; if surfaces are prepared that randomly and representatively section through domains, the images can be analyzed to calculate parameters such as domain size, area, and volume. Second, the model ignores reflection and refraction and assumes weak absorption; hence, the predicted intensity profiles are not expected to be accurate; they merely give a rough estimate of the apparent sphere size. Much further work is required to place the field of quantitative ATR-FT-IR imaging on a sound basis.

Application of Fourier transform infrared spectroscopic imaging to the study of effects of age and dietary L-arginine on aortic lesion composition in cholesterol-fed rabbits

Diet-induced atherosclerotic lesions in the descending thoracic segment of rabbit aorta were analysed ex vivo by micro-attenuated total reflection (ATR)-Fourier transform infrared (FTIR) spectroscopic imaging. The distribution and chemical character of lipid deposits within the arterial wall near intercostal branch ostia were assessed in histological sections from immature and mature rabbits fed cholesterol with or without l-arginine supplements. Previous studies have shown that both these properties change with age in cholesterol-fed rabbits, putatively owing to changes in the synthesis of nitric oxide (NO) from l-arginine. Immature animals developed lesions at the downstream margin of the branch ostium, whereas lipid deposition was observed at the lateral margins in mature animals. Dietary l-arginine supplements had beneficial effects in mature rabbit aorta, with overall disappearance of the plaques; on the other hand, they caused only a slight decrease of the lipid load in lesions at the downstream margin of the ostium in immature rabbits. ATR-FTIR imaging enabled differences in the lipid to protein density ratio of atherosclerotic lesions caused by age and diet to be visualized. Lipid deposits in immature rabbits showed higher relative absorbance values of their characteristic spectral bands compared with those in immature l-arginine-fed rabbits and mature rabbits. The multivariate methods of principal component analysis (PCA) and factor analysis (FA) were employed, and relevant chemical and structural information were obtained. Two distinct protein constituents of the intima-media layer at different locations of the wall were identified using the method of FA. This approach provides a valuable means of investigating the structure and chemistry of complex heterogeneous systems. It has potential for in vivo diagnosis of pathology.

Attenuated total reflection-Fourier transform infrared imaging of large areas using inverted prism crystals and combining imaging and mapping

Attenuated total reflection-Fourier transform infrared (ATR-FT-IR) imaging is a very useful tool for capturing chemical images of various materials due to the simple sample preparation and the ability to measure wet samples or samples in an aqueous environment. However, the size of the array detector used for image acquisition is often limited and there is usually a trade off between spatial resolution and the field of view (FOV). The combination of mapping and imaging can be used to acquire images with a larger FOV without sacrificing spatial resolution. Previous attempts have demonstrated this using an infrared microscope and a Germanium hemispherical ATR crystal to achieve images of up to 2.5 mm x 2.5 mm but with varying spatial resolution and depth of penetration across the imaged area. In this paper, we demonstrate a combination of mapping and imaging with a different approach using an external optics housing for large ATR accessories and inverted ATR prisms to achieve ATR-FT-IR images with a large FOV and reasonable spatial resolution. The results have shown that a FOV of 10 mm x 14 mm can be obtained with a spatial resolution of approximately 40-60 microm when using an accessory that gives no magnification. A FOV of 1.3 mm x 1.3 mm can be obtained with spatial resolution of approximately 15-20 microm when using a diamond ATR imaging accessory with 4x magnification. No significant change in image quality such as spatial resolution or depth of penetration has been observed across the whole FOV with this method and the measurement time was approximately 15 minutes for an image consisting of 16 image tiles.

Using micro-attenuated total reflection spectroscopy to determine chemically induced changes in neat human hair: feasibility study on the effect of antipsychotic drugs

This investigation examines the feasibility of detecting changes in intact human hair upon drug exposure using diamond attenuated total reflection (ATR) infrared spectroscopy. Prior work on microtomed hair has reported spectra changes in the medulla of the hair resulting from drug exposure. This study focuses on examining the hair intact, eliminating sample preparation and thereby reducing the possibility of sample contamination. Several hair samples were first examined to determine whether the lipids in the medulla could be detected from intact hair. Once this was established, hair samples exposed to drugs were investigated to see if changes in those lipids could be detected. Both internal and external drug exposures were investigated: hair samples were externally (incorporated) exposed to Clozapine and real-life samples were obtained from a patient on alprazolam (Xanax). In both cases, spectral differences in the C-H bands were observed in the hairs with drug exposure as compared to hair with no known drug exposure. These changes are consistent with changes in the lipids in the medulla.

Micro-attenuated total reflection spectral imaging in archaeology: application to Maya paint and plaster wall decorations

Fourier transform infrared (FT-IR) attenuated total reflection (ATR) imaging has been successfully used to identify individual mineral components of ancient Maya paint. The high spatial resolution of a micro FT-IR-ATR system in combination with a focal plane array detector has allowed individual particles in the paint to be resolved and identified from their spectra. This system has been used in combination with micro-Raman spectroscopy to characterize the paint, which was found to be a mixture of hematite and silicate particles with minor amounts of calcite, carbon, and magnetite particles in a sub-micrometer hematite and calcite matrix. The underlying stucco was also investigated and found to be a combination of calcite with fine carbon particles, making a dark sub-ground for the paint.

Infrared microspectroscopic imaging using a large radius germanium internal reflection element and a focal plane array detector

Previously, we established the ability to collect infrared microspectroscopic images of large areas using a large radius hemisphere internal reflection element (IRE) with both a single point and a linear array detector. In this paper, preliminary work in applying this same method to a focal plane array (FPA) infrared imaging system is demonstrated. Mosaic tile imaging using a large radius germanium hemispherical IRE on a FPA Fourier transform infrared microscope imaging system can be used to image samples nearly 1.5 mm x 2 mm in size. A polymer film with a metal mask is imaged using this method for comparison to previous work. Images of hair and skin samples are presented, highlighting the complexity of this method. Comparisons are made between the linear array and FPA methods.