Raman Spectroscopic Fingerprints Research Articles

Raman Spectroscopic Analysis of the Reaction between Al-Si Coatings and Steel.

Hot-stamped ultrahigh strength steel components are pivotal to automotive light-weighting. Steel blanks, often coated with an aluminum-silicon (Al-Si) layer to protect them from oxidation and decarburization, are austenitized within a furnace and then simultaneously quenched and formed into shape. The Al-Si coating melts within the furnace and reacts with iron from the steel to yield an intermetallic phase that provides some long-term corrosion protection. During the intermediate liquid phase, some of the coating may transfer to the furnace components, leading to maintenance costs and operational downtime. A detailed understanding of the coating transformation mechanism is needed to avoid such production issues while ensuring that final intermetallic coatings conform to specifications. We introduce cross-sectional Raman microscopic mapping as a method to rapidly elucidate the coating transformation mechanism. Raman spectroscopic fingerprints for relevant intermetallic compounds were determined using synthesized Al-Fe-Si ternary and Al-Fe binary compounds. These fingerprints were used to map the spatial distribution of intermetallic compounds through cross sections of Al-Si-coated 22MnB5 specimens that were heated at temperatures between 570 and 900 °C. These chemical maps show that the intermetallic fraction of the coating does not grow significantly until formation of η (Al5Fe2) at the steel interface, suggesting that η facilitates extraction of iron from the steel and subsequent diffusion through the coating. Under the heating conditions used here, a series of reactions ultimately lead to a silicon-rich τ2 (Al3FeSi) phase on top of the binary η phase. The technique presented here simplifies structural analysis of intermetallic compounds, which will facilitate prototyping of strategies to optimize hot stamping.

Shifted Excitation Raman Difference Spectroscopy Combined with Wide Area Illumination and Sample Rotation for Wood Species Classification.

Raman spectroscopy has found its way into a wide range of applications and is successfully applied for qualitative and quantitative studies. Despite significant technical progress over the last few decades, there are still some challenges that limit its more widespread usage. This paper presents a holistic approach to addressing simultaneously the problems of fluorescence interference, sample heterogeneity, and laser-induced sample heating. Long wavelength shifted excitation Raman difference spectroscopy (SERDS) at 830 nm excitation combined with wide-area illumination and sample rotation is presented as a suitable approach for the investigation of selected wood species. Wood as a natural specimen represents a well-suited model system for our study as it is fluorescent, heterogeneous, and susceptible to laser-induced modifications. Two different subacquisition times (50 and 100 ms) and two sample rotation speeds (12 and 60 r/min) were exemplarily assessed. Results demonstrate that SERDS can effectively separate the Raman spectroscopic fingerprints of the wood species balsa, beech, birch, hickory, and pine from intense fluorescence interference. Sample rotation in conjunction with 1 mm-diameter wide-area illumination was suitable to obtain representative SERDS spectra of the wood species within 4.6 s. Using partial least squares discriminant analysis, a classification accuracy of 99.4% for the five investigated wood species was realized. This study highlights the large potential of SERDS combined with wide-area illumination and sample rotation for the effective analysis of fluorescent, heterogeneous, and thermally sensitive specimens in a wide range of application areas.

Effect of Internal Donors on Raman and IR Spectroscopic Fingerprints of MgCl2/TiCl4 Nanoclusters Determined by Machine Learning and DFT.

To go deep into the origin of MgCl supported Ziegler-Natta catalysis we need to fully understand the structure and properties of precatalytic nanoclusters MgCl/TiCl in presence of Lewis bases as internal donors (ID). In this work MgCl/TiCl nanoplatelets derived by machine learning and DFT calculations have been used to model the interaction with ethyl-benzoate EB as ID, with available exposed sites of binary TiCl/MgCl systems. The influence of vicinal TiCl and coadsorbed TiCl on energetic, structural and spectroscopic behaviour of EB has been considered. The adsorption of homogeneous-like TiClEB and TiCl(EB) at the various surface sites have been also simulated. B3LYP-D2 and M06 functionals combined with TZVP quality basis set have been adopted for calculations. The adducts have been characterized by computing IR and Raman spectra that have been found to provide specific fingerprints useful to identify surface species; IR spectra have been successfully compared to available experimental data.

Leukocyte Activation Profile Assessed by Raman Spectroscopy Helps Diagnosing Infection and Sepsis.

Leukocytes are first responders to infection. Their activation state can reveal information about specific host immune response and identify dysregulation in sepsis. This study aims to use the Raman spectroscopic fingerprints of blood-derived leukocytes to differentiate inflammation, infection, and sepsis in hospitalized patients. Diagnostic sensitivity and specificity shall demonstrate the added value of the direct characterization of leukocyte's phenotype. Prospective nonrandomized, single-center, observational phase-II study (DRKS00006265). Jena University Hospital, Germany. Sixty-one hospitalized patients (19 with sterile inflammation, 23 with infection without organ dysfunction, 18 with sepsis according to Sepsis-3 definition). None (blood withdrawal). Individual peripheral blood leukocytes were characterized by Raman spectroscopy. Reference diagnostics included established clinical scores, blood count, and biomarkers (C-reactive protein, procalcitonin and interleukin-6). Binary classification models using Raman data were able to distinguish patients with infection from patients without infection, as well as sepsis patients from patients without sepsis, with accuracies achieved with established biomarkers. Compared with biomarker information alone, an increase of 10% (to 93%) accuracy for the detection of infection and an increase of 18% (to 92%) for detection of sepsis were reached by adding the Raman information. Leukocytes from sepsis patients showed different Raman spectral features in comparison to the patients with infection that point to the special immune phenotype of sepsis patients. Raman spectroscopy can extract information on leukocyte's activation state in a nondestructive, label-free manner to differentiate sterile inflammation, infection, and sepsis.

Correlation of surface-enhanced Raman spectroscopic fingerprints of kidney transplant recipient urine with kidney function parameters

Routine monitoring of kidney transplant function is required for the standard care in post-transplantation management, including frequent measurements of serum creatinine with or without kidney biopsy. However, the invasiveness of these methods with potential for clinically significant complications makes them less than ideal. The objective of this study was to develop a non-invasive tool to monitor the kidney transplant function by using Surface-Enhanced Raman Spectroscopy (SERS). Urine and blood samples were collected from kidney transplant recipients after surgery. Silver nanoparticle-based SERS spectra of the urine were measured and evaluated using partial least squires (PLS) analysis. The SERS spectra were compared with conventional chemical markers of kidney transplant function to assess its predictive ability. A total of 110 kidney transplant recipients were included in this study. PLS results showed significant correlation with urine protein (R2 = 0.4660, p < 0.01), creatinine (R2 = 0.8106, p < 0.01), and urea (R2 = 0.7808, p < 0.01). Furthermore, the prediction of the blood markers of kidney transplant function using the urine SERS spectra was indicated by R2 = 0.7628 (p < 0.01) for serum creatinine and R2 = 0.6539 (p < 0.01) for blood urea nitrogen. This preliminary study suggested that the urine SERS spectral analysis could be used as a convenient method for rapid assessment of kidney transplant function.

Construction of Raman spectroscopic fingerprints for the detection of Fusarium wilt of banana in Taiwan.

Banana (Musa sp.) is cultivated worldwide and is one of the most popular fruits. The soil-borne fungal disease Fusarium wilt of banana (FWB), commonly known as Panama disease, is caused by Fusarium oxysporum f. sp. cubense (Foc) and is a highly lethal vascular fungal disease in banana plants. Raman spectroscopy, an emerging laser-based technology based on Raman scattering, has been used for the qualitative characterization of biological tissues such as foodborne pathogens, cancer cells, and melamine. In this study, we describe a Raman spectroscopic technique that could potentially be used as a method for diagnosing FWB. To that end, the Raman fingerprints of Foc (including mycelia and conidia) and Foc-infected banana pseudostems with varying levels of symptoms were determined. Our results showed that eight, eleven, and eleven characteristic surface-enhanced Raman spectroscopy peaks were observed in the mycelia, microconidia, and macroconidia of Foc, respectively. In addition, we constructed the Raman spectroscopic fingerprints of banana pseudostem samples with varying levels of symptoms in order to be able to differentiate Foc-infected bananas from healthy bananas. The rate at which FWB was detected in asymptomatic Foc-infected samples by using the spectral method was 76.2%, which was comparable to the rates previously reported for other FWB detection methods based on real-time PCR assays, suggesting that the spectral method described herein could potentially serve as an alternative tool for detecting FWB in fields. As such, we hope that the developed spectral method will open up new possibilities for the on-site diagnosis of FWB.

Raman-Enhanced Spectroscopy (RESpect) Probe for Childhood Non-Hodgkin Lymphoma.

Raman-enhanced spectroscopy (RESpect) probe, which enhances Raman spectroscopy technology through a portable fiber-optic device, characterizes tissues and cells by identifying molecular chemical composition showing distinct differences/similarities for potential tumor markers or diagnosis. In a feasibility study with the ultimate objective to translate the technology to the clinic, a panel of pediatric non-Hodgkin lymphoma tissues and non-malignant specimens had RS analyses compared between standard Raman spectroscopy microscope instrument and RESpect probe. Cryopreserved tissues were mounted on front-coated aluminum mirror slides and analyzed by standard Raman spectroscopy and RESpect probe. Principal Component Analysis revealed similarities between non-Hodgkin lymphoma subtypes but not follicular hyperplasia. Standard Raman spectroscopy and RESpect probe fingerprint comparisons demonstrated comparable primary peaks. Raman spectroscopic fingerprints and peaks of pediatric non-Hodgkin lymphoma subtypes and follicular hyperplasia provided novel avenues to pursue diagnostic approaches and identify potential new therapeutic targets. The information could inform new insights into molecular cellular pathogenesis. Translating Raman spectroscopy technology by using the RESpect probe as a potential point-of-care screening instrument has the potential to change the paradigm of screening for cancer as an initial step to determine when a definitive tissue biopsy would be necessary.

Raman spectroscopy reveals LPS-induced changes of biomolecular composition in monocytic THP-1 cells in a label-free manner.

The human innate immune system is able to recognize pathogen-associated molecular patterns like lipopolysaccharides (LPS) leading to the activation of signal cascades and the release of different cytokines. Activation of the immune cells can be assessed in different ways which are either indirect (ELISA of cytokine release), require staining protocols (flow cytometry) or lysis of the cells (mRNA analysis). Here, Raman spectroscopy as a non-destructive spectroscopic method is presented to enable direct and label-free monitoring of changes in cellular metabolism, biomolecular composition as well as morphology. Exemplarily, the potential of Raman spectroscopy is presented for the characterization of LPS-stimulation of monocytic THP-1 cells over a time course of 16 h. The cell culture stimulation model is characterized using gene transcription and expression of the two cytokines TNFα and IL-1β. After 1 h, 3 h, 8 h and 16 h specific Raman spectroscopic fingerprints are generated which encode cell activation pattern after TLR4 stimulation. Most prevalent changes in the spectra occur after 8 h, but slight differences are already detectable after 1 h. Spatially highly resolved Raman scans are used to generate false-color Raman images which provide spatial information of the biochemical state of the cells and changes over time. One of the most significant observed differences is an increase in Raman signal from DNA/RNA content in LPS-stimulated cells when compared to unstimulated cells. The systematic assignment of Raman spectroscopic profiles of LPS-activated cells to cellular activation assessed by cytokine gene transcription and expression opens new ways for label-free and direct immunological studies of specific pathogen recognizing receptors and their downstream signaling pathways.

Abstract A04: Unique Raman spectroscopic fingerprints of Burkitt non-Hodgkin lymphoma

Abstract Purpose: Raman spectroscopy (RS) is a noninvasive laser-based technique that provides a very high level of confidence in detecting various molecules through their vibrational modes. A monochromatic laser is used to excite a sample, and inelastic scattered light generated by the sample is used to measure Raman spectra of the sample. Because vibration modes of a molecule are very unique to the molecule, RS is sensitive and highly selective to the molecular composition of various chemicals including biologic tissues and cells. By using micro-Raman systems capable of measuring Raman spectra of single biologic cell, the objective of the study focused on identifying molecular differences between normal B-cells and Burkitt non-Hodgkin lymphoma (BNHL) cells, hypothesizing that unique RS fingerprints of BL could be identified with the overall goal to apply the information for novel diagnostic or treatment strategies. Methods: Normal B-cells were isolated from peripheral blood using a negative selection Robosep kit (EasySep Human B-Cell Isolation Kit, Stemcell Technologies, Cambridge, MA). BNHL cell lines (Ramos and CA46, ATCC, Manassas, VA), were cultured, washed, and resuspended in a 0.9% saline solution at a concentration of 1 x 106 cells/mL. The cells were mounted on a clean aluminum reflective slide and single cells were analyzed with a micro-Raman system utilizing a 785-nm laser excitation and an automated xyz microscope stage. Asymmetric Least Squares (AsLS) was applied to the spectral data (n=20 spectra per cell type) to obtain baseline spectra. Principal Component Analysis (PCA) followed by k-nearest neighboring (KNN) method was applied to analyze the variance in the spectral data and assess the diagnostic accuracy of the loadings from PCA. Results: The Raman fingerprints of normal B-cells and BNHL cells identified characteristic peak differences between the cell types, ranging from DNA/protein concentrations to saccharide bonds. These were further analyzed using AsLS and PCA. AsLS informed the PCA, which identified variances in the peaks that formed distinct clusters to differentiate normal B-cells from BL NHL cells. PCA effectively compiles the peaks, demonstrating that the first three components accounted for 97.45% of variance in the data. Several peaks were identified as the major contributors to the loadings, and some (e.g., 831, 1083, 1210, 1257, 1360, 1578, 1658 cm-1) were also reported as biomarkers of BNHL. The KNN on the PCs revealed that diagnostic accuracy was 100% and specificity was 100%. Conclusions: Raman fingerprints of normal B-cells versus BNHL cells demonstrated unique clustering of molecular changes that could potentially distinguish neoplastic cells from normal cells. As a novel and innovative tool, RS could contribute towards diagnostic resources and new paradigms for intervention for BNHL and other diseases. This study was supported by the St. Baldrick’s and McCabe Foundations and in part by NIH U54MD007584. Citation Format: Natalie Kamada, Robert Oda, Tiffany Shieh, Melissa Agsalda-Garcia, Tayro Acosta-Maeda, Anupam Misra, So Yung Choi, Eunjung Lim, Bruce Shiramizu. Unique Raman spectroscopic fingerprints of Burkitt non-Hodgkin lymphoma [abstract]. In: Proceedings of the AACR Special Conference: Pediatric Cancer Research: From Basic Science to the Clinic; 2017 Dec 3-6; Atlanta, Georgia. Philadelphia (PA): AACR; Cancer Res 2018;78(19 Suppl):Abstract nr A04.

Synthesis and characterization of carbon nanostructures by evaporating pure graphite and carbon black in detonation-gas arc discharge

Arc discharge experiments combined with explosive detonation have been carried out to probe the transformation of pure graphite and carbon black evaporated in detonation gas. Under respective conditions, different kinds of carbon nanostructures have been synthesized including few-layer graphene (FLG) nanosheets, polyhedral graphite particles (PGPs), carbonaceous monocrystals and graphene oxide (GO). The evaporation of graphite facilitates the formation of FLG and PGPs, which exhibits competitive growth according to the pressure of detonation gas. By evaporating carbon black, a considerable amount of high-crystalline GO with low oxygen concentration are acquired. The morphology, crystal structures, Raman spectroscopic fingerprints and chemical compositions of these products are investigated by the characterizations of transmission electron microscopy (TEM), high-resolution TEM, Raman spectra and X-ray photoelectron spectroscopy. The formation mechanisms of such carbon nanostructures in arc evaporation are discussed according to the chemical nature and pressure of detonation gas.

Raman spectroscopic fingerprints of scytonemin-imine: density functional theory calculations of a novel potential biomarker.

Scytonemin-imine, a novel derivative of scytonemin, has been isolated and identified very recently and proposed to serve as a photoprotective biomarker for certain bacteria growing under intense photon flux density. This study predicts theoretically the Raman spectrum of scytonemin-imine by density functional theory calculations and provides comparison of major bands to those of scytonemin, the parent compound for which both the experimentally characterized and theoretically predicted spectra exist in the literature. It is proposed to be an addendum to the collection of our previous work on scytonamin and its derivatives to facilitate recognition of the diagnostic Raman spectral signatures for scytonemin-imine.

Antibody–drug gold nanoantennas with Raman spectroscopic fingerprints for in vivo tumour theranostics

Inspired by the ability of SERS nanoantennas to provide an integrated platform to enhance disease targeting in vivo, we developed a highly sensitive probe for in vivo tumour recognition with the capacity to target specific cancer biomarkers such as epidermal growth factor receptors (EGFR) on human cancer cells and xenograft tumour models. Here, we used ~90nm gold nanoparticles capped by a Raman reporter, encapsulated and entrapped by larger polymers and a FDA antibody–drug conjugate – Cetuximab (Erbitux®) – that specifically targets EGFR and turns off a main signalling cascade for cancer cells to proliferate and survive. These drug/SERS gold nanoantennas present a high Raman signal both in cancer cells and in mice bearing xenograft tumours. Moreover, the Raman detection signal is accomplished simultaneously by extensive tumour growth inhibition in mice, making these gold nanoantennas ideal for cancer nanotheranostics, i.e. tumour detection and tumour cell inhibition at the same time.

Towards label-free and site-specific probing of the local pH in proteins: pH-dependent deep UV Raman spectra of histidine and tyrosine

The site-specific pH is an experimental probe for assessing models of structural folding and function of a protein as well as protein–protein and protein–ligand interactions. It can be determined by various techniques such as NMR, FT-IR, fluorescence and EPR spectroscopy. The latter require the use of external labels, i.e., employ pH-dependent dyes and spin labels, respectively. In this contribution, we outline an approach to a label-free and site-specific method for determining the local pH using deep ultraviolet resonance Raman (UVRR) spectroscopic fingerprints of the aromatic amino acids histidine and tyrosine in combination with a robust algorithm that determines the pH value using three UVRR reference spectra and without prior knowledge of the pKa.