Fourier Transform Infrared Microspectroscopic Imaging Research Articles

Fourier-transform infrared spectroscopy imaging is a useful adjunct to routine histopathology to identify failure of polyethylene inlays in revision total hiparthroplasty.

The use of highly crosslinked ultra-high molecular weight polyethylene (XLPE) has significantly reduced the volumetric wear of acetabular liners, thereby reducing the incidence of osteolysis. However, contemporary components tend to generate smaller wear particles, which can no longer be identified using conventional histology. This technical limitation can result in imprecise diagnosis. Here, we report on two uncemented total hip arthroplasty cases (~7 years in situ) revised for periprosthetic fracture of the femur and femoral loosening, respectively. Both liners exhibited prominent wear. The retrieved pseudocapsular tissue exhibited a strong macrophage infiltration without microscopically identifiable polyethylene particles. Yet, using Fourier-transform infrared micro-spectroscopic imaging (FTIR-I), we demonstrated the prominent intracellular accumulation of polyethylene debris in both cases. This study shows that particle induced osteolysis can still occur with XLPE liners, even under 10 years in situ. Furthermore, we demonstrate the difficulty of determining the presence of polyethylene debris within periprosthetic tissue. Considering the potentially increased bioactivity of finer particles from XLPE compared to conventional liners, an accurate detection method is required, and new histopathological hallmarks of particle induced osteolysis are needed. FTIR-I is a great tool to that end and can help the accurate determination of foreign body tissue responses.

Visualization and Semiquantitative Study of the Distribution of Major Components in Wheat Straw in Mesoscopic Scale using Fourier Transform Infrared Microspectroscopic Imaging.

Understanding the biochemical heterogeneity of plant tissue linked to crop straw anatomy is attractive to plant researchers and researchers in the field of biomass refinery. This study provides an in situ analysis and semiquantitative visualization of major components distribution in internodal transverse sections of wheat straw based on Fourier transform infrared (FTIR) microspectroscopic imaging, with a fast non-negativity-constrained least squares (fast NNLS) fitting. This paper investigates changes in biochemical components of tissue during stages of elongation, booting, heading, flowering, grain-filling, milk-ripening, dough, and full-ripening. Visualization analysis was carried out with reference spectra for five components (microcrystalline cellulose, xylan, lignin, pectin, and starch) of wheat straw. Our result showed that (a) the cellulose and lignin distribution is consistent with that from tissue-dyeing with safranin O-fast green and (b) the distribution of cellulose, lignin, and starch is consistent with chemical images for characteristic wavelength at 1432, 1507, and 987 cm-1, respectively, showing no interference from the other components analyzed. With the validation from biochemical images using characteristic wavelength and tissue-dyeing techniques, further semiquantitative analysis in local tissues based on fast NNLS was carried out, and the result showed that (a) the contents of cellulose in various tissues are very different, with most in parenchyma tissue and least in the epidermis and (b) during plant development, the fluctuation of each component in tissues follows nearly the same trend, especially within vascular bundles and parenchyma tissue. Thus, FTIR microspectroscopic imaging combined with suitable chemometric methods can be successfully applied to study chemical distributions within the internodes transverse sections of wheat straw, providing semiquantitative chemical information.

Direct chemical characterization of natural wood resins by temperature-resolved and space-resolved Fourier transform infrared spectroscopy

Wood resins are valuable natural products with wide utilizations. Either in the form of resin exudates or in the form of resin-containing woods, natural wood resins are usually complex mixtures consisting of various compounds. Therefore, effective chemical characterization methods are necessary for the research and quality control of natural wood resins. No need for separation or labeling, wood resin samples can be measured directly by Fourier transform infrared (FT-IR) spectroscopy, which reduces the testing costs and avoids the possible distortions caused by the pretreatments. However, the absorption bands of various compositions in the resin sample are assembled in a single spectrum by the separation-free measurement, which makes it difficult to identify the compounds of interest and decreases the limits of detection. In this research, the temperature-resolved and space-resolved FT-IR techniques are proposed to resolve the overlapped signals for the direct, selective, and sensitive characterization of natural wood resins. For resin exudates, the temperature-resolved FT-IR spectroscopy and two-dimensional correlation analysis can resolve the absorption bands of different compounds according to their responses to the thermal perturbations. For resin-containing woods, the FT-IR microspectroscopic imaging and principal component analysis can resolve the absorption bands of different compounds according to their positions. The study of six kinds of wood resins proves the feasibility of temperature-resolved and space-resolved FT-IR techniques for the direct, selective, and sensitive chemical characterization of natural wood resins.

Importance of tissue preparation methods in FTIR micro-spectroscopical analysis of biological tissues: 'traps for new users'.

Fourier Transform Infrared (FTIR) micro-spectroscopy is an emerging technique for the biochemical analysis of tissues and cellular materials. It provides objective information on the holistic biochemistry of a cell or tissue sample and has been applied in many areas of medical research. However, it has become apparent that how the tissue is handled prior to FTIR micro-spectroscopic imaging requires special consideration, particularly with regards to methods for preservation of the samples. We have performed FTIR micro-spectroscopy on rodent heart and liver tissue sections (two spectroscopically very different biological tissues) that were prepared by desiccation drying, ethanol substitution and formalin fixation and have compared the resulting spectra with that of fully hydrated freshly excised tissues. We have systematically examined the spectra for any biochemical changes to the native state of the tissue caused by the three methods of preparation and have detected changes in infrared (IR) absorption band intensities and peak positions. In particular, the position and profile of the amide I, key in assigning protein secondary structure, changes depending on preparation method and the lipid absorptions lose intensity drastically when these tissues are hydrated with ethanol. Indeed, we demonstrate that preserving samples through desiccation drying, ethanol substitution or formalin fixation significantly alters the biochemical information detected using spectroscopic methods when compared to spectra of fresh hydrated tissue. It is therefore imperative to consider tissue preparative effects when preparing, measuring, and analyzing samples using FTIR spectroscopy.

Study on in situ analysis of cellulose, hemicelluloses and lignin distribution linked to tissue structure of crop stalk internodal transverse section based on FTIR microspectroscopic imaging

Crop stalks are an important source of lignocellulosic biomass, and have been broadly developed as one kind of renewable resources. Tissue compositional heterogeneity linked to crop stalks anatomy is attractive to plant researchers and researchers in the field of the biomass-refinery. This study is to develop a high-efficiency and rich-information characterization technique based on Fourier transform infrared (FTIR) microspectroscopic imaging for achieving an insight into the crop stalks, in which corn and cotton are taken for example, by creatively “seeing” crop stalks tissue structure in a chemical sense. Chemical images of cellulose, hemicelluloses and lignin that can be intuitively linked to tissue structure were produced based on FTIR microspectroscopic imaging with diagnostic spectral peaks. The principal components analysis was then applied to reveal the major spectral variances among different tissues. For cotton stalk transverse section, lignin is highly distributed in the xylem, while cellulose is uniformly distributed, and hemicellulose is highly distributed in the pith, in contrast to lignin. For corn stalk internodal transverse section, lignin is concentrated in the mechanical tissues, and again, cellulose is relatively uniformly distributed, while hemicellulose is concentrated in the parenchymal cells, in contrast to lignin. The results show that FTIR microspectroscopic imaging is an ideal technique for analyzing the chemical characterization linked to tissue structure in crop stalk transverse section.

Tissue acquisition and storage associated oxidation considerations for FTIR microspectroscopic imaging of polyunsaturated fatty acids

The dietary intake of polyunsaturated fatty acids (PUFAs), e.g., docosahexaenoic acid, eicosapentaenoic acid and arachidonic acid, is reflected in the biochemical makeup of tissues. In the course of analyzing mouse retina and brain tissue with Fourier Transform infrared (FTIR) microspectroscopy, we discovered that special considerations are required to minimize loss of PUFA. Traditionally, imaging of the 3012cm−1 band (olefinic C–H stretch) has been carried out on cryosectioned tissues that have been mounted on appropriate substrates and stored in dark, dry, room temperature conditions prior to data collection. This storage condition is inadequate, due to surprisingly rapid oxidation of the CC–H functional group in PUFA and to a lesser extent, of lipid carbonyl, CO. Olefinic degradation is illustrated by the decrease in intensity of the 3012cm−1 peak over time in the rod cell outer segment (ROS) in retina, a region that contains highly concentrated PUFA. Time-lapse experiments on samples stored under traditional conditions illustrate that the storage lifetime is limited to a few days. We have tested new protocols for sample preparation and storage that permit more accurate assessment of PUFA in biological tissues by FTIR analysis. This information will enable larger ongoing research efforts into the analysis of PUFA in biological tissue samples with FTIR microspectroscopy in healthy and diseased animal models.

FT-IR microscopic imaging of calcified deposit of rotator cuff tendonitis: A pilot study and a randomised identification of the compositional components after extrusion from tendon to muscle

Fourier transform infrared (FT-IR) microspectroscopy with mapping system was applied to identify and evaluate what difference in the distribution and compositional components of the calcified deposit of rotator cuff tendonitis after dislocation from tendon to muscle. A 49 year-old female patient suffered from severe shoulder pain was enrolled in this study. Diagnostic high-resolution ultrasonography (HRUS) was initially carried out to verify the calcific tendonitis. The calcified deposits were then examined by histopathologic assessment and FT-IR microspectroscopy. Diagnostic HRUS reveals that the calcified deposits were observed in the subscapularis tendon and infraspinatus muscle of the shoulder for this patient. FT-IR microspectroscopic imaging results clearly indicate that both IR spectra of the calcified deposits in tendon and muscle were almost the same as that of the IR spectrum of hydroxyapatite except the peak at 873 cm −1. It is also found that the peak intensity at 1030 cm −1 for tendon sample was somewhat more intense than that of the peak at 1031 cm −1 for muscle sample, implying that the calcified sample in the tendon seems to be mature than that in the muscle. The second-derivative IR spectra of two calcified samples exhibit two specific sharp peaks at 880 and 872 cm −1, indicating that the type A and type B carbonated apatites were markedly co-existed in both calcified deposits of tendon and muscle even the calcified deposit was dislocated from tendon to muscle. These carbonated apatites presented in the calcified deposits of either tendon or muscle of the shoulder were also consistent with the nodular or nodular nodular–cystic morphology of calcified plaque of the shoulder after HRUS examination.

Zone-Specific Changes in Micromechanical, Biochemical, and Structural Properties in Articular Cartilage from a Rabbit Joint Flexion Model

AbstractMetacarpophalangeal (MCP) joint proximal bone-cartilage specimens from the fourth digit were collected from repetitively flexed and non-flexed (control) paws of four New Zealand White rabbits. The specimens were cryo-fractured to reveal a sagittal cut containing the cartilage zones of different collagen microstructure. Nanoindentation, Fourier Transform infrared microspectroscopic imaging (FTIRMI), and histology were performed on a region of interest (ROI) ∼400 microns wide and through the thickness of the cartilage with two goals in mind: (1) to examine the effect of collagen network structure (random in the mid zone versus organized in the deep zone) on the biomechanical and biochemical properties of cartilage; and (2) to understand the changes in these properties due to physical forces. We found that zone microstructure significantly affected the measurement of the local relaxed modulus measured by nanoindentation. The deep zone had a higher modulus than the mid zone (Wilcoxon paired test, p<0.05). We also found that flexion significantly decreased the proteoglycan content in both the mid and deep zones (Wilcoxon paired test, p<0.05), suggesting indirect repetitive loading in the rabbit paw can be damaging to the joint via down regulating proteoglycan synthesis in the mid and deep zone cartilage. This is the first study to simultaneously report the local zone-specific mechanical and biochemical properties in the rabbit joint flexion model.

Hepatobiliary and pancreatic: Liver histopathology: Fourier transform infrared microspectroscopic imaging for objective and quantifiable assessment of liver biopsies

Histopathological changes in the liver are conventionally assessed using histochemical stains and examination by an experienced histopathologist. Sampling error and interobserver variation were addressed by Bedossa et al. who called for objective measurements by imaging technologies. We are investigating the applicability of FourierTransform Infrared Microspectroscopic Imaging (FTIRMI) to the analysis of liver biopsies. One previous study has been reported. Moreover, microimaging could find additional applications, including investigating lesions not amenable to histochemical study such as drug accumulations in liver cells. The applications of infrared spectroscopy range from analysis of interstellar dust particles to detection of cancer cells in cervical biopsies. The infrared spectrum of any compound is in effect a unique molecular fingerprint. The positions of observed peaks depend on the masses of the atoms, the strengths of the bonds between them, and the interaction with the surrounding molecular environment. Furthermore, the absorbance is directly proportional to analyte concentration. Lewis et al. revolutionized infrared imaging analysis by combining a focal plane array detector with a FTIR microscope, allowing insight into the molecular structure of tissues. The diagnostic and monitoring capacity of FTIRMI has the premise that a chemical change must accompany morphological expression. Thus, morphological changes are readily detected by FTIRMI as changes in the concentration and conformational orientation of functional groups associated with proteins, lipids, nucleic acids and carbohydrates. Techniques such as Unsupervised Hierarchical Cluster Analysis (UHCA) can be used to analyze the ‘spectral data hypercubes’ that constitute the individual pixels in the focal plane array. Our images exemplify the technique applied to a cirrhotic liver. Figure 1 is a Masson stain (original magnification ¥ 100) while Figure 2 is an image derived by performing UHCA on spectral data obtained with the DigiLab ‘Stingray’ FPA system. The images show regions both with measurably high levels of collagen (fibrosis) and glycogen (liver parenchyma).

Minimization of optical non-linearities in Fourier transform-infrared microspectroscopic imaging

This paper describes the FT-IR microspectroscopic imaging measurements of 5-μm diameter particles and demonstrates the associated optical non-linearities, due to chromatic aberration and diffraction. FT-IR microscopes with single-element detector use image masking in order to minimize the optical effect due to diffraction. Image masking cannot be used in the focal-plane array detector microscopes. The work presented here demonstrates that, through the application of multivariate curve resolution (MCR), the chemically significant information can be separated from the optical non-linearities. An improvement of the spatial resolution is achieved through the use of multivariate images of individual components, compared to univariate images at long wavelength.