Near infrared Raman spectroscopic characterization of blood plasma of normal,oral premalignant and malignant conditions—a pilot study

The metabolic end products from cells/tissues that are released into the circulating blood stream and any changes in their level because of pathological conditions may be used as markers in disease diagnosis. Raman spectroscopy has been exploited to characterize the biomolecules present in the blood plasma of clinically confirmed normal group, premalignant (Oral Sub Mucous Fibrosis) and malignant (Oral Squamous Cell Carcinoma) at 784.15 nm. Raman spectral signatures show relatively less intense Raman bands of phenylalanine, lipid and antioxidant beta carotene but higher intense bands for proteins, DNA base components and amino acids (tyrosine and tryptophan) for malignant group than that of normal group. However premalignant group possess high intense Raman bands for amino acids (tyrosine and tryptophan) at 830, 1020 and 1620 cm⁻¹ and protein peaks at 913, 978 and 1646 cm⁻¹ when compared to that of malignant and normal group. Principal component analysis coupled with linear discriminant analysis (PCA‐LDA) yielded a diagnostic sensitivity of 96.3% and 91.2%, and a specificity of 80.0% and 96.7% in the classification of normal from premalignant and normal from malignant, respectively. This indicates that Raman spectroscopy of blood plasma has the potential in classifying normal and oral malignancy conditions. Copyright © 2015 John Wiley & Sons, Ltd.     

Raman spectroscopic characterization of urine of normal and oral cancer subjects

Urine is considered as one of the diagnostically important bio fluids, as it has many metabolites. The distribution and the physiochemical properties of the metabolites may vary during any altered metabolic and pathological conditions. Raman spectroscopy was employed in the characterization of the metabolites of human urine of normal subjects and oral cancer patients in the finger print region (500–1800 cm⁻¹). Principal component analysis‐based linear discriminant analysis was performed to discriminate cancer patients from normal subjects. The discriminant analysis classifies the cancer patients from normal subjects with a sensitivity and specificity of 98.6% and 87.1%, respectively, with an overall accuracy of 93.7%. Copyright © 2014 John Wiley & Sons, Ltd.     

Method development: Raman spectroscopy‐based histopathology of oral mucosa

An earlier and more accurate detection of (small) cancerous and precancerous lesions in the oral cavity is essential to improve the prognosis of oral squamous cell carcinomas. Raman spectroscopy is being pursued as a potential method to realize this improvement, since the technique provides objective information on a biochemical level and can be used for real‐time guidance of the diagnostic procedure. Since oral mucosal tissue is inhomogeneous and comprises different layers and histological structures, a good understanding of the signal contributions of the individual layers and structures is required for an accurate interpretation of in vivo tissue spectra measurement volumes. The aim of this study was to create a standardized method to collect and analyse the spectral contributions of individual histopathological structures in oral mucosa. The method is based on Raman microspectroscopic mapping of unstained frozen tissue sections and subsequent histopathological annotation of the features in the resulting Raman images. The obtained annotated reference spectra were used as input in an unsupervised hierarchical cluster analysis in order to determine the spectral characteristics and variance within one histo(patho)logical structure. The described method resulted in an annotated database of Raman spectral characteristics of individual histopathological structures encountered in oral tissue. This database can be used as input for the development of classification and quantification algorithms, in order to achieve a high specificity and sensitivity for clinical diagnostic instruments. Additionally, this database can be used to optimize the exact location and measurement volume of in vivo measurements. Copyright © 2013 John Wiley & Sons, Ltd.     

Characterizing variability in in vivo Raman spectroscopic properties of different anatomical sites of normal tissue in the oral cavity

Raman spectroscopy is an inelastic light scattering technique that is capable of probing biochemical and biomolecular structures and conformations of tissue. This study aims to characterize the in vivo Raman spectroscopic properties of different normal oral tissues in the fingerprint region (800–1800 cm⁻¹) and to assess distinctive biochemical variations of different anatomical regions in the oral cavity. A specially designed fiber‐optic Raman probe with a ball lens was utilized for real‐time, in vivo Raman measurements of various oral tissue sites (i.e. inner lip, attached gingiva, floor, dorsal tongue, ventral tongue, hard palate, soft palate, and buccal). The semiquantitative non‐negativity‐constrained least squares minimization fitting of reference biochemicals representing oral tissue constituents (i.e. hydroxyapatite, keratin, collagen, DNA, and oleic acid) and partial least squares‐discriminant analysis (PLS‐DA) were employed to assess the significance of inter‐anatomical variability. A total of 402 high‐quality in vivo oral Raman spectra were acquired from 20 subjects. The histological characteristics of different oral tissues were found to have influence on the in vivo Raman spectra and could be grossly divided into three major clusterings: (1) buccal, inner lip, and soft palate; (2) dorsal, ventral tongue, and floor; (3) gingiva and hard palate. The PLS‐DA multiclass algorithms were able to identify different tissue sites with varying accuracies (inner lip 83.1%, attached gingiva 91.3%, floor 86.1%, dorsal tongue 88.8%, ventral tongue 83.1%, hard palate 87.6%, soft palate 83.3%, and buccal mucosa 85.3%), bringing out the similarities among different oral tissues at the biomolecular level. This study discloses that inter‐anatomical variability is significant and should be considered as an important parameter in the interpretation and rendering of Raman diagnostic algorithms for oral tissue diagnosis and characterization. Copyright © 2011 John Wiley & Sons, Ltd.     

Size‐dependent Raman and infrared studies of PbSe nanoparticles

Micro‐probe Raman and far‐infrared absorption spectroscopies were used to prove the existence of optical phonon modes of PbSe nanoparticles prepared by colloidal chemistry and preliminarily characterized by transmission electron microscopy. To the best of our knowledge, this is the first time that evidence of the surface phonon (SP) mode by Raman spectroscopy has been experimentally observed. The wavenumber of the SP mode is consistent with its prediction by a dielectric continuum model. While for different PbSe nanoparticle sizes the observed SP mode does not show any obvious change in its position, there is a clear shift by approximately 4 cm⁻¹ toward higher wavenumber in the appearance of the LO(Γ) in the Raman spectra from the 3 nm to the 7 nm PbSe nanoparticles. Far‐infrared measurements demonstrate the presence of the transverse optical TO(Γ) and of the coupled phonon modes. Copyright © 2008 John Wiley & Sons, Ltd.     

FT‐Raman and FTIR spectroscopic characterization of biogenic carbonates from Philippine venus seashell and Porites sp. coral

Some seashells of the Philippine venus species and sea coral of Porites sp. were studied by means of FT‐Raman, Fourier transform infrared spectroscopy (FTIR) and Far‐FTIR spectroscopic methods. The Raman spectra show that both Porites sp. and P. venus are of aragonite‐structured CaCO₃. Detailed spectral analysis, however, reveals some small differences, due to differences in the crystallite size or habit and to different minor element contents. IR spectra show that Porites sp. contains also some small quantities of calcite‐structured carbonates. The ν₂ band (shoulder) of calcite at 875.7 cm⁻¹ is present in the IR spectrum. The separation of the two ν₂ bands (856.4 cm⁻¹ for aragonite and 875.7 cm⁻¹ for calcite) suggests the absence of solid solution of the two polymorphic phases of CaCO₃. Spectroscopic results were confirmed also by X‐ray powder diffraction measurements. Copyright © 2008 John Wiley & Sons, Ltd.     

Raman spectroscopic characterization of novel carbon‐bonded filter compositions for steel melt filtration

In this work, Raman scattering results on novel carbon‐bonded filter compositions are presented. Such filters are already used for steel melt filtration; however, the potential of this carbon‐bonded Al₂O₃–C system regarding material characteristics and filtration efficiency has not been fully understood yet. In order to investigate thermally induced structural changes of the filter compositions, micro‐Raman spectroscopy was applied. Analyzing the position, intensity, and full width at half maximum of G and D peaks in the Raman spectra, it could be determined that the carbon appears in graphitic form and the graphitic cluster size was estimated. We found an increase of the lateral cluster size L_a with increasing coking temperature. Copyright © 2013 John Wiley & Sons, Ltd.     

Research on the Raman spectral character and diagnostic value of squamous cell carcinoma of oral mucosa

Early diagnosis of oral carcinomas is essential for successful treatment. The purpose of the present study is to apply near‐infrared Raman spectroscopy to detect oral squamous cell carcinoma (SCC) and leukoplakia (OLK), in order to establish the diagnostic model of the Raman spectra of oral diseases. We collected Raman spectra of normal, OLK and SCC by near‐infrared Fourier transform Raman spectroscopy. The biochemical variations between different lesions were analyzed by the characteristic bands in the subtracted mean spectra. Gaussian radial basis function support vector machines (SVM) were used to classify spectra and establish the diagnostic models. Major differences were observed in the range between 800 and 1800 cm⁻¹. Compared with normal mucosa, high contents of protein, DNA and lipid in SCC and OLK were observed, but the difference between OLK and normal tissue was not as much as that between normal and SCC. SVM displayed a powerful ability in the classifying of normal and SCC, and the specificity, sensitivity and accuracy were 100, 97.56 and 98.75%, respectively. In discriminating between the OLK and normal groups, the three parameters were 85, 68 and 72.5%. The algorithm showed good ability in grouping and modeling of OLK and SCC, and the three parameters were 95, 97.43 and 96.25%. Combined with SVM, near‐infrared Raman spectroscopy can detect biochemical variations in oral normal mucosa, OLK and SCC, and establish diagnostic models accurately. Copyright © 2009 John Wiley & Sons, Ltd.     

Raman spectroscopy monitoring of the cellular activities of a tissue‐engineered ex vivo produced oral mucosal equivalent

To ensure quality control and assurance in tissue engineering, noninvasive, real‐time and aseptic evaluation of cell‐based devices is required before product release. In this study, Raman spectroscopy was applied to monitor the cellular activities of an oral mucosa equivalent (EVPOME) produced ex vivo from cultured autogenous oral keratinocytes and acellular dermis—AlloDerm. Raman spectra showed a positive correlation of the peak area ratio of amide I (1655 cm⁻¹)/phenylalanine (1004 cm⁻¹) with a negative linear regression (R² > 0.95) according to the number of cultured days, especially on the 14thand 21st day. This work demonstrates the successful application of Raman spectroscopy for quantitatively monitoring and evaluating the maturity of EVPOME. Copyright © 2010 John Wiley & Sons, Ltd.     

Food additives characterization by infrared,Raman, and surface‐enhanced Raman spectroscopies

Fourier‐transform infrared (FT‐IR), Raman (RS), and surface‐enhanced Raman scattering (SERS) spectra of β‐hydroxy‐β‐methylobutanoic acid (HMB), L ‐carnitine, and N‐methylglycocyamine (creatine) have been measured. The SERS spectra have been taken from species adsorbed on a colloidal silver surface. The respective FT‐IR and RS band assignments (solid‐state samples) based on the literature data have been proposed. The strongest absorptions in the FT‐IR spectrum of creatine are observed at 1398, 1615, and 1699 cm⁻¹, which are due to ν_s(COOH) + ν(CN) + δ(CN), ρ_s(NH₂), and ν(C O) modes, respectively, whereas those of L ‐carnitine (at 1396/1586 cm⁻¹ and 1480 cm⁻¹) and HMB (at 1405/1555/1585 cm⁻¹ and 1437–1473 cm⁻¹) are associated with carboxyl and methyl/methylene group vibrations, respectively. On the other hand, the strongest bands in the RS spectrum of HMB observed at 748/1442/1462 cm⁻¹ and 1408 cm⁻¹ are due to methyl/methylene deformations and carboxyl group vibrations, respectively. The strongest Raman band of creatine at 831 cm⁻¹ (ρ_w(R NH₂)) is accompanied by two weaker bands at 1054 and 1397 cm⁻¹ due to ν(CN) + ν(R NH₂) and ν_s(COOH) + ν(CN) + δ(CN) modes, respectively. In the case of L ‐carnitine, its RS spectrum is dominated by bands at 772 and 1461 cm⁻¹ assigned to ρ_r(CH₂) and δ(CH₃), respectively. The analysis of the SERS spectra shows that HMB interacts with the silver surface mainly through the  COO⁻, hydroxyl, and  CH₂ groups, whereas L ‐carnitine binds to the surface via  COO⁻ and  N⁺(CH₃)₃ which is rarely enhanced at pH = 8.3. On the other hand, it seems that creatine binds weakly to the silver surface mainly by  NH₂, and C O from the  COO⁻ group. Copyright © 2006 John Wiley & Sons, Ltd.     

Micro‐Raman spectroscopic characterization of a tunable electrochromic device for application in smart windows

An asymmetric electrochromic (EC) device based on an active EC tungsten oxide–titanium oxide (WO₃–TiO₂) layer was constructed. The EC active layer consisted predominantly of monoclinic WO₃ nanocrystallites with a minor additional component of hexagonal WO₃ and amorphous TiO₂. Detailed micro‐Raman spectroscopic studies of the intercalation and deintercalation of lithium in the EC active layer of the EC device as a function of the applied voltage were performed. Three significant structural stages occur upon intercalating Li into the WO₃–TiO₂ layer when coloration potentials of 1.0, 1.5, 2.0, and 3.0 V are applied to the EC device. In the first stage (applied potential of 1.0 V), the m‐Li_x WO₃ phase is retained. In the second stage, (applied potential of 1.5 and 2.0 V) the m‐Li_x WO₃ transforms to a tetragonal phase. In the third stage, (applied potential of 3.0 V) the Raman spectrum exhibits no spectral bands, showing that Li_x WO₃ has attained the highest‐symmetry cubic phase. This phase sequence is confirmed by the X‐ray diffraction (XRD) measurement. These phase transitions can be reversed and, upon complete deintercalation, m‐WO₃ with traces of h‐WO₃ is recovered. Optical transmission studies were performed in conjunction with Raman and XRD studies. A shift of the optical transmittance peak position from 639 to 466 nm and reduction in the width of the transmittance curve with increasing applied potential opens up the possibility of smart window applications for the nanocrystalline WO₃‐based EC device. Copyright © 2008 John Wiley & Sons, Ltd.     

Raman spectroscopic study of the multi‐anion uranyl mineral schroeckingerite

Raman spectroscopy complemented with infrared (IR) spectroscopy has been used to study the mineral schroeckingerite. The mineral is a multi‐anion mineral and has (UO₂)²⁺, (SO₄)²⁻ and (CO₃)²⁻ units in its structure, and bands attributed to these vibrating units are readily identified in the Raman spectra. Symmetric stretching modes at 815, 983 and 1092 cm⁻¹ are assigned to (UO₂)²⁺, (SO₄)²⁻ and (CO₃)²⁻ units, respectively. The antisymmetric stretching modes of (UO₂)²⁺, (SO₄)²⁻ are not observed in the Raman spectra but may be readily observed in the IR spectrum at 898 and 1180 cm⁻¹. The antisymmetric stretching mode of (CO₃)²⁻ is observed in the Raman spectrum at 1374 cm⁻¹, as is also the ν₄ (CO₃)²⁻ bending modes at 742 and 707 cm⁻¹. No ν₂ (CO₃)²⁻ bending modes are observed in the Raman spectrum of schroeckingerite. All the spectroscopic evidence points to a highly ordered structure of this mineral. Copyright © 2007 John Wiley & Sons, Ltd.     

Evaluation of Raman spectroscopy for prediction of antitumor response to silibinin and its nanoparticulates in DMBA‐induced oral carcinogenesis

Raman spectroscopy is a vibrational spectroscopic technique that can be used to monitor the therapeutic efficacy of anticancer drugs during carcinogenesis in a non‐invasive and label‐free manner. The present study aims to investigate the biochemical changes exerted upon free silibinin (SIL) and its nanoparticulate (SILNPs) treatment against 7,12‐dimethylbenz[a]anthracene (DMBA)‐induced oral carcinogenesis in the fingerprint region of 1800–500 cm⁻¹ using HE‐785 Raman spectrometer. Raman spectra differed significantly between the control and tumor tissues, with tumor tissues characterized by increased intensities of vibrational bands such as nucleic acids, phenylalanine and tryptophan and a lower percentage of lipids when compared to the control tissues. Further, oral administration of free SIL and SILNPs significantly increased lipids and decreased the levels of tryptophan, phenylalanine and nucleic acid contents. Overall, the treatment of nanoparticulate SIL was found to be a more potent antitumor effect than free SIL in preventing the formation of tumor and also brought back the several Raman bands to a normal range in the buccal mucosa of hamsters during DMBA‐induced oral carcinogenesis. In addition, the detailed secondary structure of proteins in the control and experimental groups is also presented. Furthermore, the diagnostic algorithms based on principal component linear discriminant analysis (PC‐LDA) achieved an overall sensitivity of 94–100% and specificity of 76–100%. These results further demonstrate that Raman spectroscopy associated with PC‐LDA diagnostic algorithms could be a valuable tool for rapid and sensitive detection of specific biomolecular changes at the molecular level in response to anticancer drug. Copyright © 2015 John Wiley & Sons, Ltd.     

Visible,near‐infrared,and ultraviolet laser‐excited Raman spectroscopy of the monocytes/macrophages (U937) cells

Raman spectra of the monocytes were recorded with laser excitation at 532, 785, 830, and 244 nm. The measurements of the Raman spectra of monocytes excited with visible, near‐infrared (NIR), and ultraviolet (UV) lasers lad to the following conclusions. (1) The Raman peak pattern of the monocytes can be easily distinguished from those of HeLa and yeast cells; (2) Positions of the Raman peaks of the dried cell are in coincidence with those of the monocytes in a culture cell media. However, the relative intensities of the peaks are changed: the peak centered around 1045 cm⁻¹ is strongly intensified. (3) Raman spectra of the dead monocytes are similar to those of living cells with only one exception: the Raman peak centered around 1004 cm⁻¹ associated with breathing mode of phenylalanine is strongly intensified. The Raman spectra of monocytes excited with 244‐nm UV laser were measured on cells in a cell culture medium. A peak centered at 1485 cm⁻¹ dominates the UV Raman spectra of monocytes. The ratio I₁₅₇₄/I₁₆₁₃ for monocytes is found to be around 0.71. This number reflects the ratio between proteins and DNA content inside a cell and it is found to be twice as high as that of E. coli and 5 times as high as that of gram‐positive bacteria. Copyright © 2009 John Wiley & Sons, Ltd.     

Micro‐Raman spectroscopic study of artificially aged natural and dyed wool

The objective of this study was to evaluate the use of micro‐Raman spectroscopy as a non‐invasive vibrational spectroscopic technique applied to the examination of wool samples, which may be applied to textile materials of cultural heritage interest. In this work, a selection of wool materials were primarily investigated in their unaged states through the utility of a natural wool reference together with selected samples dyed with different natural colorants, namely woad, weld and madder. The identification of the main modes of vibration of the wool fibre keratin was assessed in all the samples, which aided the determination of the changes within the protein structure, in particular, through the cysteine and peptide cross‐linkages brought about by the addition of the dyes that can produce effects similar to degradation. The dye too was assessed importantly to enable its identification through its characteristic scattering or fluorescence emissions on a woollen matrix, as well as to ascertain whether a uniform covering across the surface of the wool was achieved or not. Regarding the artificial degradation of the samples it was possible to observe numerous modifications within the molecular structure of the wool, in particular, within the amide I, C H bending, amide III and S‐S stretchings along with the physical photo‐yellowing of fibres given by the presence of lipids dispersed across the surface of the wool. The effects of ageing on the dyed samples were also investigated, indicating that many of the bands relative to the colorants were still present, yet so too were numerous vibrations from the wool that also indicated a certain level of stress and degradation to the underlying wool. Copyright © 2008 John Wiley & Sons, Ltd.     

Micro‐Raman and infrared analysis of medieval pottery findings from Braničevo,Serbia

A selection of Byzantine table pottery (17 samples) dating from the period between the beginning of the 12th century and the first half of the 13th century, discovered at Braničevo in Serbia, were analysed by Fourier transform infrared, micro‐Raman and scanning electron microscopy with energy dispersive spectroscopy and petrography analysis. The aim of the investigation was to determine the chemical and mineralogical composition of the body and of the glaze and thus to determine the production technology. Fourier transform infrared spectroscopy provided data for estimating the firing temperature and the basic mineralogical composition, and micro‐Raman spectroscopy was applied to study and characterise both the glaze and the body of the analysed sherds. It was found that noncalcareous clays, characterised by a rich mineral assemblage, were fired at temperatures between 700 and 900 °C. Oxidizing atmosphere was applied in the production of the red colour pottery. The dark and grey coloured paste of one group of sherds was produced by firing organic matter‐rich clays in a reducing environment. The main type of transparent glaze was identified as lead‐rich, and two samples were alkali–lime glazed. Copyright © 2011 John Wiley & Sons, Ltd.     

Correlation of monomer structures of tripalmitin with the spectroscopic fingerprint of polymorphs: infrared,Raman, and DFT study

In the light of application of vibrational spectroscopy in medical diagnosis, it is necessary to have a tool to distinguish between different lipids that may be present in biochemical samples such as cells and tissues. One of the most common lipids in the human body are triglycerides. Therefore, the aim of this work was to investigate the model triglyceride, namely tripalmitin in order to find the differences between the vibrational signatures of its polymorphs and interpret them with the help of quantum‐chemical computations. Although monomeric models are not sufficient to reproduce polymorphs structure, analysis of these models is very helpful in understanding of relations between the structure and changes in vibrational spectra. Copyright © 2012 John Wiley & Sons, Ltd.     

Automated detection and characterization of graphene and few‐layer graphite via Raman spectroscopy

Several processes have to be automated in order to use graphene in future industrial applications. One of these is the detection and characterization of graphene and few‐layer graphite (FLG) flakes on a substrate. Raman spectroscopy is an ideal tool for this purpose, as it allows not only the identification of these graphitic materials on arbitrary substrates but also monitoring the quality of flakes within the sample. In this paper, we report how graphene and FLG crystallites can be automatically detected and characterized by monitoring the evolution of Raman bands. We present an algorithm that achieves this purpose and thus has special potential in industrial applications of graphene. Copyright © 2010 John Wiley & Sons, Ltd.     

Electrochemical in situ surface enhanced Raman spectroscopic characterization of a trinuclear ruthenium complex,Ru‐red

To study the fate of a molecular di‐μ‐oxo‐bridged trinuclear ruthenium complex, [(NH₃)₅Ru–O–Ru(NH₃)₄–O–Ru(NH₃)₅]⁶⁺, also known as Ru‐red, during the electro‐driven water oxidation reaction, electrochemical in situ surface enhanced Raman spectroscopy (SERS) investigations have been conducted on an electrochemically roughened gold surface in acidic condition. It was previously described that on a basal plane pyrolitic graphite electrode in 0.1 M H₂SO₄ aqueous solution, Ru‐red undergoes one electron oxidative conversion into a stable higher oxidation state ruthenium complex, Ru‐brown, at <1.0 V (vs normal hydrogen electrode (NHE)), and this leads to water oxidation and dioxygen release, but the fate of Ru‐red during electrochemistry was not studied in much detail. In this investigation, Ru‐red dispersed in acid electrolyte and immobilized on a roughened gold electrode without Ru‐red in solution has been subjected to anodic controlled potential experiments, and in situ SERS was carried out at various potentials in succession. The electrochemical SERS data obtained for Ru‐red are also compared with in situ SERS results of an electrodeposited ruthenium oxide thin film on the Au disk. Our study suggests that on a gold electrode in sulfuric acid solution containing Ru‐red, one electron oxidative conversion of Ru‐red to a higher oxidation state ruthenium compound, Ru‐brown, occurs at ca. 0.74 V (vs NHE), as supported by the electrochemical in situ SERS experiments. Moreover, at higher potentials and on Au disk, the Ru‐red / Ru‐brown are not stable and slowly decompose or electro‐oxidize leading to deactivation of the tri‐ruthenium catalytic system in acidic medium. Copyright © 2013 John Wiley & Sons, Ltd.     

Raman spectroscopic characterization of CH4 density over a wide range of temperature and pressure

The positions of the CH₄ Raman ν₁ symmetric stretching bands were measured in a wide range of temperature (from −180 °C to 350 °C) and density (up to 0.45 g/cm³) using high‐pressure optical cell and fused silica capillary capsule. The results show that the Raman band shift is a function of both methane density and temperature; the band shifts to lower wavenumbers as the density increases and the temperature decreases. An equation representing the observed relationship among the CH₄ ν₁ band position, temperature, and density can be used to calculate the density in natural or synthetic CH₄‐bearing inclusions. Copyright © 2014 John Wiley & Sons, Ltd.