Correction: Empirical study on the effects of acquisition parameters for FTIR hyperspectral imaging of brain tissue.

Correction for 'Empirical study on the effects of acquisition parameters for FTIR hyperspectral imaging of brain tissue' by J. Sacharz et al., Anal. Methods, 2020, 12, 4334-4342, DOI: 10.1039/C9AY01200A.

Empirical study on the effects of acquisition parameters for FTIR hyperspectral imaging of brain tissue.

Fourier transform infrared (FTIR) spectroscopic imaging is a powerful technique for molecular imaging of pathologies associated with the nervous systems including multiple sclerosis research. However, there is no standard methodology or standardized protocol for FTIR imaging of tissue sections that maximize the ability to discriminate between the molecular, white and granular layers, which is essential in the investigation of the mechanism of demyelination process. Tissue sections are heterogeneous, complex and delicate, hence the parameters to generate high quality images in minimal time becomes essential in the modern clinical laboratory. This article presents an FTIR spectroscopic imaging study of post-mortem human brain tissue testing the effects of various measurement parameters and data analysis methods on image quality and acquisition time. Hyperspectral images acquired from the same region of a tissue using a range of the most common optical and collection parameters in different combinations were compared. These included magnification (4× and 15×), number of co-added scans (1, 4, 8, 16, 32, 64 and 128 scans) and spectral resolution (4, 8 and 16 cm-1). Images were compared in terms of acquisition time, signal-to-noise (S/N) ratio, and accuracy of the discrimination between three major tissue types in a section from the cerebellum (white matter, granular and molecular layers). In the latter case, unsupervised k-means cluster (KMC) analysis was employed to generate images from the hyperspectral images, which were compared to a reference image. The classification accuracy for tissue class discrimination was highest for the 4× magnifying objective, with 4 cm-1 spectral resolution and 128 co-added scans. The 15× magnifying objective gave the best accuracy for a spectral resolution of 4 cm-1 and 64 scans (96.3%), which was just above what was achieved using the 4× magnifying objective, with 4 cm-1 spectral resolution and 32 and 64 co-added scans (95.4 and 95.6%, respectively). These findings were correlated with a decrease in S/N ratio with increasing number of scans and was generally lower for the 15× objective. However, longer scan times were required using the 15× magnifying objective, which did not justify the very small improvement in the classification of tissue types.

An attenuated total reflection (ATR) and Raman spectroscopic investigation into the effects of chloroquine on Plasmodium falciparum-infected red blood cells.

Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) and Raman spectroscopy were used to compare chloroquine (CQ)-treated and untreated cultured Plasmodium falciparum-infected human red blood cells (iRBCs). The studies were carried out in parallel from the same starting cultures using both spectroscopic techniques, in duplicate. ATR FTIR spectra showed modifications in the heme vibrational bands as well as increases in the CH2/CH3 stretching bands in the 3100-2800 cm(-1) region of CQ-treated iRBCs consistent with an increase in lipid content. Other changes consisted of secondary structural variations including shifts in the amide I and II modes, along with changes in RNA and carbohydrate bands. Raman microspectroscopy of single red blood cells using 532 nm revealed subtle changes in the positions and intensity of ν37 of the core size region marker band and ν4 in the pyrrole ring-stretching region between untreated and CQ-treated iRBCs. Similar patterns in the corresponding relations were also observed in the non-fundamental (overtone region) between the control and treated cells. These differences were consistent with higher levels of oxygenated hemoglobin (oxyHb) in the treated cells as shown in a Principle Component Analysis (PCA) loadings plot. The results obtained demonstrate that vibrational spectroscopic techniques can provide insight into the effect of quinolines on iRBCs and thus may assist understanding the sensitivity and resistance of new and existing anti-malarial drugs.

Raman spectroscopy and the material study of nanocomposite membranes from poly(ε-caprolactone) with biocompatibility testing in osteoblast-like cells.

Modern medical treatment can be improved by nanotechnology methods for preparing nanocomposites with novel physical, chemical and biological properties. The materials studied and analysed as membranes were produced from poly(ε-caprolactone) (PCL), which contained identical amounts of nano-additives, either montmorillonite (MMT) or functionalized multi-walled carbon nanotubes (MWCNT-f), while the reference membranes were obtained from unmodified PCL. In addition to the conventional methods used in the study of materials for medical purposes such as DSC, contact angle measurements, surface topography, Raman spectroscopy was also applied. Raman microspectroscopy can decode the phenomenon that occurs in the polymer in contact with the nanoparticles. Besides identifying the vibrations of certain functional groups, the calculation of crystallinity parameters is also possible, by which the most intense interactions within the nanocomposites can be analysed. The Raman studies indicate that each of the nano-additives reacts differently with the polymer matrix, which results in material properties that influence its biological properties. MWCNT-f interacts preferentially with the oxygen-containing groups, and particularly with the backbone regions in the vicinity of the single CO bond. The human osteoblast-like MG-63 cells, cultured on the PCL/MWCNT-f membrane for three days, show almost 100% viability.

Clostridium difficile the hospital plague.

Clostridium difficile infection (CDI) has become one of the major public health threats in the last two decades. An increase has been observed not only in the rate of CDI, but also in its severity and mortality. Symptoms caused by this pathogen are accompanied by intense local and systemic inflammation. We confirmed that Raman microspectroscopy can help us in understanding CDI pathogenesis. A single erythrocyte of patients with CDI shows a difference, approximately 10 times, in the intensity of the Raman spectra at the beginning of hospitalization and after one week of treatment. The intensity level is an indicator of the spread of the inflammation within the cell, confirmed by standard laboratory tests. Many of the observed bands with enormously enhanced intensity, e.g. 1587, 1344, 1253, 1118 and 664 cm(-1), come from the symmetric vibration of the pyrrole ring. Heme variation of recovered cells in the acute CDI state between the first and the seventh day of treatment seems to show increased levels of oxygenated hemoglobin. Intense inflammation alters the conformation of the protein which is reflected in the significant changes in the amide I, II and III bands. There is an observed shift and a significant intensity increase of 1253 and 970 cm(-1) amide III and skeletal protein backbone CC stretching vibration bands, respectively. Principal Component Analysis (PCA) was used to find the variance in the data collected on the first and seventh day. PC2 loading in the 1645-1500 cm(-1) range shows an increase of heme, Tyr, Trp, or Phe vibrations because of changes in the protein microenvironment due to their exposure. Positive maxima at 1621, 1563 and 1550 in the PC2 loading originated from the ring vibrations. These observations indicate that Clostridium difficile toxins induce cytopathogenicity by altering cellular proteins.

Raman micro-spectroscopy tracing human lymphocyte activation.

The activation of lymphocytes occurs when they are exposed to viruses or other foreign antigens. The aim of this work was to verify if Raman spectroscopy can be used to screen the activation of lymphocytes during viral infection. There are distinct peaks that reveal differences between activated and intact cells. The most important marker of the lymphocyte activation process is the prominent 521 cm(-1) disulfide band which marks the immunoglobulin formation. The up shift of the S-S mode from the broad band centered at 510 cm(-1) of human normal immunoglobulin to a single band at 521 cm(-1) of human B cells indicates a selection of the optimal geometry of the disulphide bridges to bind to a foreign antigen. Polarization data is used to detect the structural alteration between domain fragments. Differences in other band intensities may be due to different protein compositions in both the investigated forms. B cell activation causes the change of the intracellular cytoplasm composition due to the secretion of immunoglobulins during the fighting of the infection.

Raman microspectroscopy of organic inclusions in spodumenes from Nilaw (Nuristan, Afghanistan).

The color varieties of spodumene (green spodumene, kunzite) from Nilaw mine (Nuristan, Afghanistan) have been investigated by microthermometry and Raman spectroscopy analyses. These minerals are rich in primary and secondary fluid inclusions. Measured values of temperature homogenization (T(h)) and pressure (P) for selected fluid-inclusion assemblages (I-IV) FIA in green spodumene and (I-II) FIA in kunzite ranges from 370 to 430°C, 1.16 to 1.44 kbar and 300 to 334°C, 0.81 to 1.12 kbar, respectively. The brine content and concentration varies from 4.3 to 6.6 wt.% eq. NaCl. Numerous and diverse mineral phases (quartz, feldspars, mica, beryl, zirconium, apatite, calcite, gypsum) present in this mineral as solid inclusions were studied by Raman microspectroscopy. Raman spectra of selected fluid, organic and solid inclusions were collected as line or rectangular maps and also depth profiles to study their size and contents. There appeared very interesting calcite (156, 283, 711 and 1085 cm(-1)), beryl (324, 397, 686, 1068 and 3610 cm(-1)), topaz (231, 285, 707, 780 and 910 cm(-1)) and spodumene (355, 707 and 1073 cm(-1)) inclusions accompanied by fluid and/or organic inclusions (liquid and gas hydrocarbons) with bands at 2350 cm(-1) (CO(2), N(2)), 2550 cm(-1) (H(2)S) and 2900 cm(-1) (C(2)H(6)-CH(3)). Some solid inclusions contain carbonaceous matter (D-band at ca. 1320 cm(-1) and/or G-band at ca. 1600 cm(-1)).

Direct characterization of hydrogen peroxide bleached thermomechanical pulp using spectroscopic methods.

The effects of thermomechanical pulp (TMP) bleaching with hydrogen peroxide under acidic and alkaline conditions were studied using different spectroscopic analytical methods. The results of hydroxyl radical determination in bleaching solutions, analyses of carbonyl and carboxyl groups contents in the pulp, and the cellulose fiber surface analysis by X-ray photoelectron spectroscopy (XPS) elucidate the chemistry of the hydrogen peroxide treatment. Diffuse reflectance laser flash photolysis (DRLFP) method showed the differences in the photochemical behavior that reflect the changes of the chromophoric system after the preliminary peroxide bleaching stage under acidic conditions. Fourier transform infrared (FTIR) spectroscopy confirmed the non-delignifying character of the bleaching process. Suppression of carbonyl and formation of carboxyl groups in the case of the two-stage peroxide bleaching performed in the presence of catalysts and stabilizers was also confirmed. FT-Raman studies showed the removal of coniferaldehyde groups after treatment under acidic and alkaline conditions.

Flexibility of CuCl4-tetrahedra in bis[cinchoninium tetrachlorocuprate(II)]trihydrate single crystals. X-ray diffraction and EPR studies.

Crystal structure of bis[cinchoninium tetrachlorocuprate(II)] trihydrate, [(C19H24N2O)CuCl4]2-3H2O, has been determined by X-ray diffraction at 100 K and reexamined at 293 K. The compound crystallizes in orthorhombic system with a P2(1)2(1)2(1) space group and unit cell parameters a = 15.3031(14), b = 36.415(3), and c = 7.8341(5) A at 100 K, and Z = 4. The asymmetric unit consists of two (CuCl4)(2-) tetrahedral anions linked by hydrogen bonds to two doubly protonated cinchonine molecules and three water molecules. The tetrahedra are strongly flattened, to approximately D(2d) symmetry, with different deformation for two inequivalent (CuCl4)(2-) -ions in the asymmetric unit. The deformation of (CuCl4)(2-) and cinchoninium cations varies with temperature due to a rearrangement of the bifurcated hydrogen bond network. This is a continuous process observed as a monotonic variation of the EPR spectral parameters and the unit cell dimensions. EPR spectra show that very weak exchange coupling J(12) = 0.0030 cm(-1) operates between Cu(2+) ions within asymmetric units, corresponding to the general formula of the compound, as well as between equivalent Cu(2+) sites of different molecules, whereas the coupling is negligible between inequivalent sites. The intermolecular J(12) coupling is temperature-independent indicating that the whole asymmetric unit behaves as a magnetic unit (pseudodimer) in the whole temperature range.