Raman spectroscopy of single human tumour cells exposed to ionizing radiationin vitro

Comparison of biochemical changes induced in radioresistant prostate cancer cells by X-rays, radiosensitizing drugs, and a combined therapy using Raman microspectroscopy

Cancer radioresistance is a major problem in radiotherapy. Many strategies have been proposed to overcome this process including the use of radiosensitizing drugs such as C75 or silibinin. The overall result of all treatments (radiotherapy, chemotherapy, and combined treatment) is cancer cell death. On the other hand, each treatment affects cancer cells differently at the molecular level. However, little is known about biochemical changes induced in cancer cells by these treatments (especially in combined therapy) at the submicroscale. In this study, Raman microspectroscopy was applied to follow such changes induced in radioresistant prostate cancer cells by X-rays, radiosensitizing drugs (C75, silibinin), and a combined treatment. The analysis was supported by the Partial Least Squares Regression method to reveal spectral changes induced by an increasing dose of X-rays and concentrations of the drugs. The obtained regression coefficient (β) plots were compared to each other using a correlation coefficient (R). Our results show that PC-3 cells exhibit dose- and concentration-dependent responses to the treatment with different biochemical changes induced by X-rays in the presence of C75 and silibinin. Moreover, both drugs affect the cells differently at the submicroscale and independently from the X-ray's presence. Finally, C75 shows significant efficiency in the reduction of cell radioresistance.

Nucleic Acid-Rich Stress Granules Are Not Merely Crowded Condensates: A Quantitative Raman Imaging Study

Liquid droplets, formed by intracellular liquid-liquid phase separation (LLPS), are called membraneless organelles. They provide transient enzymatic reaction fields for maintaining cellular homeostasis, although they might transform into aggregates, leading to neurodegenerative diseases. To understand the nature of intracellular droplets, it is crucial to quantify the liquid droplets inside a living cell as well as to elucidate the underlying biological mechanism. In this study, we performed near-infrared fluorescence and Raman imaging to quantify chemical components inside stress granules (SGs) formed by LLPS in living cells. The Raman images reveal that the nucleic acid concentration inside the SGs was more than 20% higher than the surrounding cytoplasm, whereas the lipid concentration was lower. Quantitative Raman intensity analysis using a water Raman band as an internal standard enables in situ concentration determination of nucleic acids in the SGs and other organelles. The intensity of the biomolecular C-H bands relative to the water band indicates that the crowding environment inside the SGs depends on the stress type; under oxidative stress, the inside of the SGs was nearly identical to the outside, whereas it was sparser in hyperosmotic stressed cells, suggesting that the high concentrations of nucleic acids play a pivotal role in maintaining the environments inside the SGs. These results demonstrate that intracellular droplets are not always highly condensed.

FABP4 Enhances Lipidic and Fibrotic Cardiac Structural and Ca2+ Dynamic Changes

BACKGROUND

Adipocyte FABP4 (fatty acid-binding protein 4) is augmented in the epicardial stroma of patients with long-standing persistent atrial fibrillation. Because this molecule is released mainly by adipocytes, our objective was to study its role in atrial cardiomyopathy, focusing our attention on fibrosis, metabolism, and electrophysiological changes. These results might clarify the role of adiposity as a mediator of atrial cardiomyopathy.

METHODS

We used several preclinical cellular models, epicardial and subcutaneous stroma primary cell cultures from patients undergoing open heart surgery, human atrial fibroblasts, atrial cardiomyocytes derived from human induced pluripotent stem cells and isolated from adult mice, and Nav1.5 transfected Chinese hamster ovary cells. Fibrosis, glucose, mitochondrial and adipogenesis activity, gene expression, and proteomics were determined by wound healing, enzymatic, colorimetric, fluorescence assays, real-time quantitative polymerase chain reaction, and TripleTOF proteomics. Molecular changes were analyzed by Raman confocal microspectroscopy, calcium dynamics by confocal microscopy, and ion currents by patch clamp. Epicardial, subcutaneous, and atrial fibroblasts and cardiomyocytes were incubated with FABP4 at 100 ng/mL.

RESULTS

Our results showed that FABP4 induced fibrosis, glucose metabolism, and lipid accumulation on epicardial and subcutaneous stroma cells and atrial fibroblasts. Besides, it modified lipid content and calcium dynamics in atrial cardiomyocytes without effects on INa.

CONCLUSIONS

FABP4 exerts fibrotic and metabolic changes on epicardial stroma and modifies lipid content and calcium dynamic on atrial cardiomyocytes. These results suggest its possible role as an atrial cardiomyopathy mediator.

Vibrational spectroscopies for biochemical investigation of X-ray exposure effects on SH-SY5Y human neuroblastoma cells

Neuroblastoma is the most recurring cancer in childhood and adolescence. The SH-SY5Y neuroblastoma cell line is generally adopted for elaborating new therapeutical approaches and/or elaborating strategies for the prevention of central nervous system disturbances. In fact, it represents a valid model system for investigating in vitro the effects on the brain of X-ray exposure using vibrational spectroscopies that can detect early radiation-induced molecular alterations of potential clinical usefulness. In recent years, we dedicated significant efforts in the use of Fourier-transform and Raman microspectroscopy techniques for characterizing such radiation-induced effects on SH-SY5Y cells by examining the contributions from different cell components (DNA, proteins, lipids, and carbohydrates) to the vibrational spectra. In this review, we aim at revising and comparing the main results of our studies to provide a wide outlook of the latest outcomes and a framework for future radiobiology research using vibrational spectroscopies. A short description of our experimental approaches and data analysis procedures is also reported.

Toward Gene-Correlated Spatially Resolved Metabolomics with Fingerprint Coherent Raman Imaging

Raman spectroscopy has long been known to provide sufficient information to discriminate distinct cell phenotypes. Underlying this discriminating capability is that Raman spectra provide an overall readout of the metabolic profiles that change with transcriptomic activity. Robustly associating Raman spectral changes with the regulation of specific signaling pathways may be possible, but the spectral signals of interest may be weak and vary somewhat among individuals. Establishing a Raman-to-transcriptome mapping will thus require tightly controlled and easily manipulated biological systems and high-throughput spectral acquisition. We attempt to meet these requirements using broadband coherent anti-Stokes Raman scattering (BCARS) microscopy to spatio-spectrally map the C. elegans hermaphrodite gonad in vivo at subcellular resolution. The C. elegans hermaphrodite gonad is an ideal model system with a sequential, continuous process of highly regulated spatiotemporal cellular events. We demonstrate that the BCARS spatio-spectral signatures correlate with gene expression profiles in the gonad, evincing that BCARS has potential as a spatially resolved omics surrogate.

Understanding radiation response and cell cycle variation in brain tumour cells using Raman spectroscopy

Radiation therapy is currently utilised in the treatment of approximately 50% of cancer patients. A move towards patient tailored radiation therapy would help to improve the treatment outcome for patients as the inter-patient and intra-patient heterogeneity of cancer leads to large differences in treatment responses. In radiation therapy, a typical treatment outcome is cell cycle arrest which leads to cell cycle synchronisation. As treatment is typically given over multiple fractions it is important to understand how variation in the cell cycle can affect treatment response. Raman spectroscopy has previously been assessed as a method for monitoring radiation response in cancer cells and has shown promise in detecting the subtle biochemical changes following radiation exposure. This study evaluated Raman spectroscopy as a potential tool for monitoring cellular response to radiation in synchronised versus unsynchronised UVW human glioma cells in vitro. Specifically, it was hypothesised that the UVW cells would demonstrate a greater radiation resistance if the cell cycle phase of the cells was synchronised to the G1/S boundary prior to radiation exposure. Here we evaluated whether Raman spectroscopy, combined with cell cycle analysis and DNA damage and repair analysis (γ-H2AX assay), could discriminate the subtle cellular changes associated with radiation response. Raman spectroscopy combined with principal component analysis (PCA) was able to show the changes in radiation response over 24 hours following radiation exposure. Spectral changes were assigned to variations in protein, specifically changes in protein signals from amides as well as changes in lipid expression. A different response was observed between cells synchronised in the cell cycle and unsynchronised cells. After 24 hours following irradiation, the unsynchronised cells showed greater spectral changes compared to the synchronised cells demonstrating that the cell cycle plays an important role in the radiation resistance or sensitivity of the UVW cells, and that radiation resistance could be induced by controlling the cell cycle. One of the main aims of cancer treatment is to stop the proliferation of cells by controlling or halting progression through the cell cycle, thereby highlighting the importance of controlling the cell cycle when studying the effects of cancer treatments such as radiation therapy. Raman spectroscopy has been shown to be a useful tool for evaluating the changes in radiation response when the cell cycle phase is controlled and therefore highlighting its potential for assessing radiation response and resistance.

Raman Spectroscopy Revealed Cell Passage-Dependent Distinct Biochemical Alterations in Radiation-Resistant Breast Cancer Cells

Recapitulating radioresistant cell features in pertinent cell line models is essential for deciphering fundamental cellular mechanisms. The limited understanding of passage and cell cycle phases on radioresistant cells revived post-cryopreservation led us to investigate the effect of sub-culturing in parental and radioresistant MCF-7 cells. In this study, the radioresistant cells showed high-intensity nucleic acid and cytochrome bands, which are potentially a radiation-induced spectral marker. Raman spectroscopy data showed dynamic biochemical alterations in revived radioresistant G₂/M synchronized cells at early cell passages 1 and 3 with stabilization at a latter cell passage, 5. The study highlights the importance of cell passaging and cell cycle phases in potentially changing the biochemical parameters during in vitro experiments after the revival of radioresistant cells post-cryopreservation.

Evaluation of Proton-Induced Biomolecular Changes in MCF-10A Breast Cells by Means of FT-IR Microspectroscopy

Radiotherapy (RT) with accelerated beams of charged particles (protons and carbon ions), also known as hadrontherapy, is a treatment modality that is increasingly being adopted thanks to the several benefits that it grants compared to conventional radiotherapy (CRT) treatments performed by means of high-energy photons/electrons. Hence, information about the biomolecular effects in exposed cells caused by such particles is needed to better realize the underlying radiobiological mechanisms and to improve this therapeutic strategy. To this end, Fourier transform infrared microspectroscopy (μ-FT-IR) can be usefully employed, in addition to long-established radiobiological techniques, since it is currently considered a helpful tool for examining radiation-induced cellular changes. In the present study, MCF-10A breast cells were chosen to evaluate the effects of proton exposure using μ-FT-IR. They were exposed to different proton doses and fixed at various times after exposure to evaluate direct effects due to proton exposure and the kinetics of DNA damage repair. Irradiated and control cells were examined in transflection mode using low-e substrates that have been recently demonstrated to offer a fast and direct way to examine proton-exposed cells. The acquired spectra were analyzed using a deconvolution procedure and a ratiometric approach, both of which showed the different contributions of DNA, protein, lipid, and carbohydrate cell components. These changes were particularly significant for cells fixed 48 and 72 h after exposure. Lipid changes were related to variations in membrane fluidity, and evidence of DNA damage was highlighted. The analysis of the Amide III band also indicated changes that could be related to different enzyme contributions in DNA repair.

High spatial resolution dosimetry with uncertainty analysis using Raman micro-spectroscopy readout of radiochromic films

PURPOSE

The purpose of this work is to develop a new approach for high spatial resolution dosimetry based on Raman micro-spectroscopy scanning of radiochromic film (RCF). The goal is to generate dose calibration curves over an extended dose range from 0 to 50 Gy and with improved sensitivity to low (<2 Gy) doses, in addition to evaluating the uncertainties in dose estimation associated with the calibration curves.

METHODS

Samples of RCF (EBT3) were irradiated at a broad dose range of 0.03-50 Gy using an Elekta Synergy clinical linear accelerator. Raman spectra were acquired with a custom-built Raman micro-spectroscopy setup involving a 500 mW, multimode 785 nm laser focused to a lateral spot diameter of 30 µm on the RCF. The depth of focus of 34 µm enabled the concurrent collection of Raman spectra from the RCF active layer and the polyester laminate. The preprocessed Raman spectra were normalized to the intensity of the 1614 cm^-1 Raman peak from the polyester laminate that was unaltered by radiation. The mean intensities and the corresponding standard deviation of the active layer Raman peaks at 696, 1445, and 2060 cm^-1 were determined for the 150 × 100 µm² scan area per dose value. This was used to generate three calibration curves that enabled the conversion of the measured Raman intensity to dose values. The experimental, fitting, and total dose uncertainty was determined across the entire dose range for the dosimetry system of Raman micro-spectroscopy and RCF.

RESULTS

In contrast to previous work that investigated the Raman response of RCFs using different methods, high resolution in the dose response of the RCF, even down to 0.03 Gy, was obtained in this study. The dynamic range of the calibration curves based on all three Raman peaks in the RCF extended up to 50 Gy with no saturation. At a spatial resolution of 30 × 30 µm² , the total uncertainty in estimating dose in the 0.5-50 Gy dose range was [6-9]% for all three Raman calibration curves. This consisted of the experimental uncertainty of [5-8]%, and the fitting uncertainty of [2.5-4.5]%. The main contribution to the experimental uncertainty was determined to be from the scan area inhomogeneity which can be readily reduced in future experiments. The fitting uncertainty could be reduced by performing Raman measurements on RCF samples at further intermediate dose values in the high and low dose range.

CONCLUSIONS

The high spatial resolution experimental dosimetry technique based on Raman micro-spectroscopy and RCF presented here, could become potentially useful for applications in microdosimetry to produce meaningful dose estimates in cellular targets, as well as for applications based on small field dosimetry that involve high dose gradients.

Visualizing intra-medulla lipids in human hair using ultra-multiplex CARS, SHG, and THG microscopy

We performed label-free imaging of human-hair medulla using multi-modal nonlinear optical microscopy. Intra-medulla lipids (IMLs) were clearly visualized by ultra-multiplex coherent anti-Stokes Raman scattering (CARS) spectroscopic imaging. Two groups of IMLs were found: second harmonic generation (SHG) active and inactive. By combining SHG analysis with CARS, the two groups were identified as free fatty acids and wax esters, respectively.

Physicochemical damage and early-stage biological response to X-ray radiation studied in prostate cancer cells by Raman spectroscopy

Exposure to ionizing radiation significantly affects biochemistry of cancer cells. The effect of irradiation can be divided into two stages, that is, the physicochemical stage and the biological response. Both effects induce different biochemical changes in the cells and should be analyzed as two separate phenomena. Thus, in the current study, Raman spectroscopy of prostate cancer cells fixed before (the physicochemical damage model) and just after (the biological response model) irradiation was undertaken to compare biochemical composition of irradiated cancer cells at both stages. Spectroscopic analysis of the cells was performed separately for cytoplasmic and nuclear regions. Biochemical changes of irradiated cells were analyzed using partial least squares regression (PLSR) method on the basis of the collected Raman spectra. Regression coefficients were therefore used to describe differences and similarities between biochemical composition of cancer cells undergoing the physicochemical stage and biological response. Additionally, PLSR models of both phenomena were compared for linear dose-dependence and a cross prediction.

Raman profile alterations of irradiated human nasopharyngeal cancer cells detected with laser tweezer Raman spectroscopy

Radiotherapy has been widely used for nasopharyngeal carcinoma (NPC) treatment, which causes DNA damage and alterations of macromolecules of cancer cells. However, the Raman profile alterations of irradiated NPC cells remain unclear. In the present study, we used laser tweezers Raman spectroscopy (LTRS) to monitor internal structural changes and chemical modifications in NPC cells after exposure at a clinical dose (2.3 Gy) to X-ray irradiation (IR) at a single-cell level. Two types of NPC cell lines, CNE2 (EBV-negative cell line) and C666-1 (EBV-positive cell line), were used. The Raman spectra of cells before and after radiation treatment were recorded by LTRS. The analysis of spectral differences indicated that the IR caused Raman profile alterations of intracellular proteins, DNA base and lipids. Moreover, by using the multivariate statistical analysis including principal component analysis (PCA) and linear discriminant analysis (LDA) algorithm, an accuracy of 90.0% for classification between CNE2 cells before and after IR could be achieved, which was 10% better than that of C666-1 cells. The results demonstrated that CNE2 cells were more sensitive to IR in comparison to C666-1 cells, providing useful information for creating a treatment strategy in clinical practice. This exploratory study suggested that LTRS combined with multivariate statistical analysis would be a novel and effective tool for evaluating the radiotherapeutic effect on tumor cells, and for detection of the corresponding alterations at the molecular level.

Laser tweezer Raman spectroscopy combined with multivariate statistical analysis was used for evaluating the radiotherapeutic effect on a single tumor cell.

Discrimination of radiosensitive and radioresistant murine lymphoma cells by Raman spectroscopy and SERS

Intrinsic radiosensitivity is a biological parameter known to influence the response to radiation therapy in cancer treatment. In this study, Raman spectroscopy and surface enhanced Raman spectroscopy (SERS) were successfully used in conjunction with principal component analysis (PCA) to discriminate between radioresistant (LY-R) and radiosensitive (LY-S) murine lymphoma sublines (L5178Y). PCA results for normal Raman analysis showed a differentiation between the radioresistant and radiosensitive cell lines based on their specific spectral fingerprint. In the case of SERS with gold nanoparticles (AuNPs), greater spectral enhancements were observed in the radioresistant subline in comparison to its radiosensitive counterpart, suggesting that each subline displays different interaction with AuNPs. Our results indicate that spectroscopic and chemometric techniques could be used as complementary tools for the prediction of intrinsic radiosensitivity of lymphoma samples.

Optical Imaging Approaches to Investigating Radiation Resistance

Radiation therapy is frequently the first line of treatment for over 50% of cancer patients. While great advances have been made in improving treatment response rates and reducing damage to normal tissue, radiation resistance remains a persistent clinical problem. While hypoxia or a lack of tumor oxygenation has long been considered a key factor in causing treatment failure, recent evidence points to metabolic reprogramming under well-oxygenated conditions as a potential route to promoting radiation resistance. In this review, we present recent studies from our lab and others that use high-resolution optical imaging as well as clinical translational optical spectroscopy to shine light on the biological basis of radiation resistance. Two-photon microscopy of endogenous cellular metabolism has identified key changes in both mitochondrial structure and function that are specific to radiation-resistant cells and help promote cell survival in response to radiation. Optical spectroscopic approaches, such as diffuse reflectance and Raman spectroscopy have demonstrated functional and molecular differences between radiation-resistant and sensitive tumors in response to radiation. These studies have uncovered key changes in metabolic pathways and present a viable route to clinical translation of optical technologies to determine radiation resistance at a very early stage in the clinic.

Multivariate Analysis of Difference Raman Spectra of the Irradiated Nucleus and Cytoplasm Region of SH-SY5Y Human Neuroblastoma Cells

Previous works showed that spatially resolved Raman spectra of cytoplasm and nucleus region of single cells exposed to X-rays evidence different features. The present work aims to introduce a new approach to profit from these differences to deeper investigate X-ray irradiation effects on single SH-SY5Y human neuroblastoma cells. For this aim, Raman micro-spectroscopy was performed in vitro on single cells after irradiation by graded X-ray doses (2, 4, 6, 8 Gy). Spectra from nucleus and cytoplasm regions were selectively acquired. The examination by interval Principal Component Analysis (i-PCA) of the difference spectra obtained by subtracting each cytoplasm-related spectrum from the corresponding one detected at the nucleus enabled us to reveal the subtle modifications of Raman features specific of different spatial cell regions. They were discussed in terms of effects induced by X-ray irradiation on DNA/RNA, lipids, and proteins. The proposed approach enabled us to evidence some features not outlined in previous investigations.

DNA-Related Modifications in a Mixture of Human Lympho-Monocyte Exposed to Radiofrequency Fields and Detected by Raman Microspectroscopy Analysis

Human exposure to electromagnetic fields (EMFs) has risen considerably during the last decades, because of the industrial and technical development and the consequent increase of artificial EMFs sources. In particular, blood is largely involved in the environmental EMF exposure, because it is located everywhere in the human body. Lympho-monocyte cells are blood components that protect the human organism against infections. In this study, we investigate biochemical changes in lympho-monocyte cells extracted from human peripheral blood after exposure to EMFs at 1.8 GHz frequency and 200 V/m electric field strength for times ranging from 5 to 20 h inside a reverberation chamber. Some mixtures of cells, coming from many human subjects, were exposed and successively investigated by means of Raman micro-spectroscopy technique and principal components analysis. The spectral analysis was able to detect variations of the biochemical composition of the nucleus of exposed cells. Such modifications are mainly detectable as an intensity decrease of some DNA and nucleic acid Raman peaks with respect to the intensity of some protein peaks and they were most evident in the case of 20 h exposed samples. These results were in agreement with the increase of reactive oxygen species (ROS) production, observed in the exposed cells. Overall, the obtained results point out that EMFs exposure may induce modifications of the DNA in some blood cells of long-term exposed people.

Exploring subcellular responses of prostate cancer cells to X-ray exposure by Raman mapping

Understanding the response of cancer cells to ionising radiation is a crucial step in modern radiotherapy. Raman microspectroscopy, together with Partial Least Squares Regression (PLSR) analysis has been shown to be a powerful tool for monitoring biochemical changes of irradiated cells on the subcellular level. However, to date, the majority of Raman studies have been performed using a single spectrum per cell, giving a limited view of the total biochemical response of the cell. In the current study, Raman mapping of the whole cell area was undertaken to ensure a more comprehensive understanding of the changes induced by X-ray radiation. On the basis of the collected Raman spectral maps, PLSR models were constructed to elucidate the time-dependent evolution of chemical changes induced in cells by irradiation, and the performance of PLSR models based on whole cell averages as compared to those based on average Raman spectra of cytoplasm and nuclear region. On the other hand, prediction of X-ray doses for individual cellular components showed that cytoplasmic and nuclear regions should be analysed separately. Finally, the advantage of the mapping technique over single point measurements was verified by a comparison of the corresponding PLSR models.

Raman spectroscopy for the evaluation of the radiobiological sensitivity of normal human breast cells at different time points after irradiation by a clinical proton beam

Radiobiological effects occurring in normal human breast cells exposed to a low dose of a clinical proton beam are detectable by means of Raman spectra and the ratiometric analysis of Raman peak intensities.

Histological coherent Raman imaging: a prognostic review

Histopathology plays a central role in diagnosis of many diseases including solid cancers. Efforts are underway to transform this subjective art to an objective and quantitative science. Coherent Raman imaging (CRI), a label-free imaging modality with sub-cellular spatial resolution and molecule-specific contrast possesses characteristics which could support the qualitative-to-quantitative transition of histopathology. In this work we briefly survey major themes related to modernization of histopathology, review applications of CRI to histopathology and, finally, discuss potential roles for CRI in the transformation of histopathology that is already underway.

Development of a Nanostructured Platform for Identifying HER2-Heterogeneity of Breast Cancer Cells by Surface-Enhanced Raman Scattering

Biosensor technology has great potential for the detection of cancer through tumor-associated molecular biomarkers. In this work, we describe the immobilization of the recombinant humanized anti-HER2 monoclonal antibody (trastuzumab) on a silver nanostructured plate made by pulsed laser deposition (PLD), over a thin film of Au(111). Immobilization was performed via 4-mercapto benzoic acid self-assembled monolayers (4-MBA SAMs) that were activated with coupling reagents. A combination of immunofluorescence images and z-stack analysis by confocal laser scanning microscopy (CLSM) allowed us to detect HER2 presence and distribution in the cell membranes. Four different HER2-expressing breast cancer cell lines (SKBR3 +++, MCF-7 +/-, T47D +/-, MDA-MB-231 -) were incubated during 24 h on functionalized silver nanostructured plates (FSNP) and also on Au(111) thin films. The cells were fixed by means of an ethanol dehydration train, then characterized by atomic force microscopy (AFM) and surface-enhanced Raman scattering (SERS). SERS results showed the same tendency as CLSM findings (SKBR3 > MCF-7 > T47D > MDA-MB-231), especially when the Raman peak associated with phenylalanine amino acid (1002 cm-1) was monitored. Given the high selectivity and high sensitivity of SERS with a functionalized silver nanostructured plate (FSNP), we propose this method for identifying the presence of HER2 and consequently, of breast cancer cells.

Application of spectral methods for studying DNA damage induced by gamma-radiation

Spectral methods can provide a variety of possibilities to determine several types of radiation-induced DNA damage, such as nucleobase destruction and local denaturation. DNA UV absorption and CD spectra measured at room temperature undergo noticeable alteration under the action of γ-radiation. We have applied the Spirin method of total nucleobases determination, and have measured the molar extinction coefficient of DNA and DNA CD spectra for solutions with different NaCl concentrations (3mM-3.2M) and containing MgCl₂, exposed to γ-radiation with the doses of 0-10³Gy. The melting temperatures of DNA in irradiated solutions at the doses of 0-50Gy were obtained with the help of spectrophotometric melting. It was found that the amount of destructed nucleobases and radiation-induced loss of DNA helicity significantly decreases with the rise of the ionic strength of the irradiated solution. Substitution of a portion of Na⁺ ions on Mg²⁺ while keeping the total ionic strength constant (μ=5mM) does not affect the considered radiation effects. The role of the structure and composition of the DNA secondary hydration layer in the radiation-induced damages is discussed.

Smart-Dust-Nanorice for Enhancement of Endogenous Raman Signal, Contrast in Photoacoustic Imaging, and T2-Shortening in Magnetic Resonance Imaging

Raman microspectroscopy provides chemo-selective image contrast, sub-micrometer resolution, and multiplexing capabilities. However, it suffers from weak signals resulting in image-acquisition times of up to several hours. Surface-enhanced Raman scattering (SERS) can dramatically enhance signals of molecules in close vicinity of metallic surfaces and overcome this limitation. Multimodal, SERS-active nanoparticles are usually labeled with Raman marker molecules, limiting SERS to the coating material. In order to realize multimodal imaging while acquiring the rich endogenous vibronic information of the specimen, a core-shell particle based on "Nanorice", where a spindle-shaped iron oxide core is encapsulated by a closed gold shell, is developed. An ultrathin layer of silica prevents agglomeration and unwanted chemical interaction with the specimen. This approach provides Raman signal enhancement due to plasmon resonance effects of the shell while the optical absorption in the near-infrared spectral region provides contrast in photoacoustic tomography. Finally, T2-relaxation of a magnetic resonance imaging (MRI) experiment is altered by taking advantage of the iron oxide core. The feasibility for Raman imaging is evaluated by nearfield simulations and experimental studies on the primate cell line COS1. MRI and photoacoustics are demonstrated in agarose phantoms illustrating the promising translational nature of this strategy for clinical applications in radiology.

Multi-centre Raman spectral mapping of oesophageal cancer tissues: a study to assess system transferability

The potential for Raman spectroscopy to provide early and improved diagnosis on a wide range of tissue and biopsy samples in situ is well documented. The standard histopathology diagnostic methods of reviewing H&E and/or immunohistochemical (IHC) stained tissue sections provides valuable clinical information, but requires both logistics (review, analysis and interpretation by an expert) and costly processing and reagents. Vibrational spectroscopy offers a complimentary diagnostic tool providing specific and multiplexed information relating to molecular structure and composition, but is not yet used to a significant extent in a clinical setting. One of the challenges for clinical implementation is that each Raman spectrometer system will have different characteristics and therefore spectra are not readily compatible between systems. This is essential for clinical implementation where classification models are used to compare measured biochemical or tissue spectra against a library training dataset. In this study, we demonstrate the development and validation of a classification model to discriminate between adenocarcinoma (AC) and non-cancerous intraepithelial metaplasia (IM) oesophageal tissue samples, measured on three different Raman instruments across three different locations. Spectra were corrected using system transfer spectral correction algorithms including wavenumber shift (offset) correction, instrument response correction and baseline removal. The results from this study indicate that the combined correction methods do minimize the instrument and sample quality variations within and between the instrument sites. However, more tissue samples of varying pathology states and greater tissue area coverage (per sample) are needed to properly assess the ability of Raman spectroscopy and system transferability algorithms over multiple instrument sites.

The molecular cues for the biological effects of ionizing radiation dose and post-irradiation time on human breast cancer SKBR3 cell line: A Raman spectroscopy study

Radiotherapy is one of the main modalities of cancer treatment. The utility of Raman spectroscopy (RS) for detecting the distinct radiobiological responses in human cancer cells is currently under investigation. RS holds great promises to provide good opportunities for personalizing radiotherapy treatments. Here, we report the effects of the radiation dose and post-irradiation time on the molecular changes in the human breast cancer SKBR3 cells, using RS. The SKBR3 cells were irradiated by gamma radiation with different doses of 0, 1, 2, 4, and 6 Gy. The Raman signals were acquired 24 and 48 h after the gamma radiation. The collected Raman spectra were analyzed by different statistical methods such as principal component analysis, linear discriminant analysis, and genetic algorithm. A thorough analysis of the obtained Raman signals revealed that 2 Gy of gamma radiation induces remarkable molecular and structural changes in the SKBR3 cells. We found that the wavenumbers in the range of 1000-1400 cm^-1 in Raman spectra are selective for discriminating between the effects of the different doses of irradiation. The results also revealed that longer post-irradiation time leads to the relaxation of the cells to their initial state. The molecular changes that occurred in the 2Gy samples were mostly reversible. On the other hand, the exposure to doses higher than 4Gy induced serious irreversible changes, mainly seen in 2700-2800 cm^-1 in Raman spectra. The classification models developed in this study would help to predict the radiation-based molecular changes induced in the cancer cells by only using RS. Also, this designed framework may facilitate the process of biodosimetry.

Breast cancer subtype specific biochemical responses to radiation

External beam radiotherapy is a common form of treatment for breast cancer.

Raman spectroscopy identifies radiation response in human non-small cell lung cancer xenografts

External beam radiation therapy is a standard form of treatment for numerous cancers. Despite this, there are no approved methods to account for patient specific radiation sensitivity. In this report, Raman spectroscopy (RS) was used to identify radiation-induced biochemical changes in human non-small cell lung cancer xenografts. Chemometric analysis revealed unique radiation-related Raman signatures that were specific to nucleic acid, lipid, protein and carbohydrate spectral features. Among these changes was a dramatic shift in the accumulation of glycogen spectral bands for doses of 5 or 15 Gy when compared to unirradiated tumours. When spatial mapping was applied in this analysis there was considerable variability as we found substantial intra- and inter-tumour heterogeneity in the distribution of glycogen and other RS spectral features. Collectively, these data provide unique insight into the biochemical response of tumours, irradiated in vivo, and demonstrate the utility of RS for detecting distinct radiobiological responses in human tumour xenografts.

Vibrational spectroscopy in sensing radiobiological effects: analyses of targeted and non-targeted effects in human keratinocytes

Modern models of radiobiological effects include mechanisms of damage initiation, sensing and repair, for those cells that directly absorb ionizing radiation as well as those that experience molecular signals from directly irradiated cells. In the former case, the effects are termed targeted effects while, in the latter, non-targeted effects. It has emerged that phenomena occur at low doses below 1 Gy in directly irradiated cells that are associated with cell-cycle-dependent mechanisms of DNA damage sensing and repair. Likewise in non-targeted bystander-irradiated cells the effect saturates at 0.5 Gy. Both effects at these doses challenge the limits of detection of vibrational spectroscopy. In this paper, a study of the sensing of both targeted and non-targeted effects in HaCaT human keratinocytes irradiated with gamma ray photons is conducted with vibrational spectroscopy. In the case of directly irradiated cells, it is shown that the HaCaT cell line does exhibit both hyperradiosensitivity and increased radioresistance at low doses, a transition between the two effects occurring at a dose of 200 mGy, and that cell survival and other physiological effects as a function of dose follow the induced repair model. Both Raman and FTIR signatures are shown to follow a similar model, suggesting that the spectra include signatures of DNA damage sensing and repair. In bystander-irradiated cells, pro- and anti-apoptotic signalling and mechanisms of ROS damage were inhibited in the mitogen-activated protein kinase (MAPK) transduction pathway. It is shown that Raman spectral profiles of bystander-irradiated cells are correlated with markers of bystander signalling and molecular transduction. This work demonstrates for the first time that both targeted and non-targeted effects of ionizing radiation damage are detected by vibrational spectroscopy in vitro.

Radiation-Induced Glycogen Accumulation Detected by Single Cell Raman Spectroscopy Is Associated with Radioresistance that Can Be Reversed by Metformin

Altered cellular metabolism is a hallmark of tumor cells and contributes to a host of properties associated with resistance to radiotherapy. Detection of radiation-induced biochemical changes can reveal unique metabolic pathways affecting radiosensitivity that may serve as attractive therapeutic targets. Using clinically relevant doses of radiation, we performed label-free single cell Raman spectroscopy on a series of human cancer cell lines and detected radiation-induced accumulation of intracellular glycogen. The increase in glycogen post-irradiation was highest in lung (H460) and breast (MCF7) tumor cells compared to prostate (LNCaP) tumor cells. In response to radiation, the appearance of this glycogen signature correlated with radiation resistance. Moreover, the buildup of glycogen was linked to the phosphorylation of GSK-3β, a canonical modulator of cell survival following radiation exposure and a key regulator of glycogen metabolism. When MCF7 cells were irradiated in the presence of the anti-diabetic drug metformin, there was a significant decrease in the amount of radiation-induced glycogen. The suppression of glycogen by metformin following radiation was associated with increased radiosensitivity. In contrast to MCF7 cells, metformin had minimal effects on both the level of glycogen in H460 cells following radiation and radiosensitivity. Our data demonstrate a novel approach of spectral monitoring by Raman spectroscopy to assess changes in the levels of intracellular glycogen as a potential marker and resistance mechanism to radiation therapy.

Visible micro-Raman spectroscopy of single human mammary epithelial cells exposed to x-ray radiation

A micro-Raman spectroscopy investigation has been performed in vitro on single human mammary epithelial cells after irradiation by graded x-ray doses. The analysis by principal component analysis (PCA) and interval-PCA (i-PCA) methods has allowed us to point out the small differences in the Raman spectra induced by irradiation. This experimental approach has enabled us to delineate radiation-induced changes in protein, nucleic acid, lipid, and carbohydrate content. In particular, the dose dependence of PCA and i-PCA components has been analyzed. Our results have confirmed that micro-Raman spectroscopy coupled to properly chosen data analysis methods is a very sensitive technique to detect early molecular changes at the single-cell level following exposure to ionizing radiation. This would help in developing innovative approaches to monitor radiation cancer radiotherapy outcome so as to reduce the overall radiation dose and minimize damage to the surrounding healthy cells, both aspects being of great importance in the field of radiation therapy.

A Raman spectroscopic study of cell response to clinical doses of ionizing radiation

The drive toward personalized radiation therapy (RT) has created significant interest in determining patient-specific tumor and normal tissue responses to radiation. Raman spectroscopy (RS) is a non-invasive and label-free technique that can detect radiation response through assessment of radiation-induced biochemical changes in tumor cells. In the current study, single-cell RS identified specific radiation-induced responses in four human epithelial tumor cell lines: lung (H460), breast (MCF-7, MDA-MB-231), and prostate (LNCaP), following exposure to clinical doses of radiation (2-10 Gy). At low radiation doses (2 Gy), H460 and MCF-7 cell lines showed an increase in glycogen-related spectral features, and the LNCaP cell line showed a membrane phospholipid-related radiation response. In these cell lines, only spectral information from populations receiving 10 Gy or less was required to identify radiation-related features using principal component analysis (PCA). In contrast, the MDA-MB-231 cell line showed a significant increase in protein relative to nucleic acid and lipid spectral features at doses of 6 Gy or higher, and high-dose information (30, 50 Gy) was required for PCA to identify this biological response. The biochemical nature of the radiation-related changes occurring in cells exposed to clinical doses was found to segregate by status of p53 and radiation sensitivity. Furthermore, the utility of RS to identify a biological response in human tumor cells exposed to therapeutic doses of radiation was found to be governed by the extent of the biochemical changes induced by a radiation response and is therefore cell line specific. The results of this study demonstrate the utility and effectiveness of single-cell RS to identify and measure biological responses in tumor cells exposed to standard radiotherapy doses.

Raman spectroscopic study of radioresistant oral cancer sublines established by fractionated ionizing radiation

Radiotherapy is an important treatment modality for oral cancer. However, development of radioresistance is a major hurdle in the efficacy of radiotherapy in oral cancer patients. Identifying predictors of radioresistance is a challenging task and has met with little success. The aim of the present study was to explore the differential spectral profiles of the established radioresistant sublines and parental oral cancer cell lines by Raman spectroscopy. We have established radioresistant sublines namely, 50Gy-UPCI:SCC029B and 70Gy-UPCI:SCC029B from its parental UPCI:SCC029B cell line, by using clinically admissible 2Gy fractionated ionizing radiation (FIR). The developed radioresistant character was validated by clonogenic cell survival assay and known radioresistance-related protein markers like Mcl-1, Bcl-2, Cox-2 and Survivin. Altered cellular morphology with significant increase (p<0.001) in the number of filopodia in radioresistant cells with respect to parental cells was observed. The Raman spectra of parental UPCI:SCC029B, 50Gy-UPCI:SCC029B and 70Gy-UPCI:SCC029B cells were acquired and spectral features indicate possible differences in biomolecules like proteins, lipids and nucleic acids. Principal component analysis (PCA) provided three clusters corresponding to radioresistant 50Gy, 70Gy-UPCI:SCC029B sublines and parental UPCI:SCC029B cell line with minor overlap, which suggest altered molecular profile acquired by the radioresistant cells due to multiple doses of irradiation. The findings of this study support the potential of Raman spectroscopy in prediction of radioresistance and possibly contribute to better prognosis of oral cancer.

Raman spectroscopy of human neuronal and epidermal cells exposed to an insecticide mixture of chlorpyrifos and deltamethrin

Many pesticides are increasingly used in combinations for crop protection. Their chemical stability ensures the presence of such mixtures, both in the workspaces of the operators involved in agricultural activities and in foodstuffs, thus making probable human exposure to such chemicals in the environment. This investigation, performed by means of Raman microspectroscopy and principal component analysis, concerns the effects of in vitro cellular exposure to a commercial insecticide based on a chlorpyrifos and deltamethrin mixture. The investigated cells belong to the SHSY-5Y and human keratinocyte (HUKE) cell lines, which can be considered representative of neuronal and epidermal cells, respectively. After 24 h exposure at a concentration one-tenth of that usually used by operators, about 50% of the investigated cells were dead and the relative content of the biochemical components of both types of cells that were still alive had been affected by the exposure. A statistically significant decrease in the protein and nucleic acid content occurred in the SHSY-5Y cells, and a lowering of the lipid and carbohydrate content was observed in the HUKE cells. This study shows the utility of Raman microspectroscopy and principal component analysis for the investigation of the effects on human cells of environmental exposure to any chemicals.

Structural differences between native Hen egg white lysozyme and its fibrils under different environmental conditions

The difference in molecular structure of native HEWL and its fibrils, grown at a pH value near physiological pH 7.4 and at a pH value just above the pI, 10.7 in presence and absence of Cu(II) ions, is discussed. We focus on differences between the molecular structure of the native protein and fibrils using principal component analysis of their Raman spectra. The overlap areas of the scores of each species are used to quantify the difference in the structure of the native HEWL and fibrils in different environments. The overall molecular structures are significantly different for fibrils grown at two pH values. However, in presence of Cu(II) ions, the fibrils have similarities in their molecular structures at these pH environments. Spectral variation within each species, as obtained from the standard deviations of the scores in PCA plots, reveals the variability in the structure within a particular species.

Raman microspectroscopy as a diagnostic tool to study single living nasopharyngeal carcinoma cell lines

Raman spectroscopy can provide molecular-level fingerprint information about the biochemical composition and structure of cells and tissues with excellent spatial resolution. In this study, Raman spectroscopy of 3 different nasopharyngeal carcinoma cell lines C666-1, CNE1, and CNE2 and 1 nasopharyngeal normal cell line NP69 acquired on a piece of silica glass slide are presented to investigate the differences among them. The results show the ratio of I1657/I1449 (= 0.7) could provide good distinction between tumor and normal cell lines very easily, which coincides with existing reports about the study of different cell lines and bronchial tissue. In addition, several statistical analytical methods were used to classify these 4 different cell lines and then achieved an exciting result with great sensitivity and specificity of >90%, respectively. The findings of this work further support former work where cells' Raman spectra were acquired on a different substrate. All of these results indicate Raman spectroscopy has the potential to discriminate between normal and tumor cells and have potential use in early diagnosis of nasopharyngeal carcinoma.

Biochemical signatures of in vitro radiation response in human lung, breast and prostate tumour cells observed with Raman spectroscopy

This work applies noninvasive single-cell Raman spectroscopy (RS) and principal component analysis (PCA) to analyze and correlate radiation-induced biochemical changes in a panel of human tumour cell lines that vary by tissue of origin, p53 status and intrinsic radiosensitivity. Six human tumour cell lines, derived from prostate (DU145, PC3 and LNCaP), breast (MDA-MB-231 and MCF7) and lung (H460), were irradiated in vitro with single fractions (15, 30 or 50 Gy) of 6 MV photons. Remaining live cells were harvested for RS analysis at 0, 24, 48 and 72 h post-irradiation, along with unirradiated controls. Single-cell Raman spectra were acquired from 20 cells per sample utilizing a 785 nm excitation laser. All spectra (200 per cell line) were individually post-processed using established methods and the total data set for each cell line was analyzed with PCA using standard algorithms. One radiation-induced PCA component was detected for each cell line by identification of statistically significant changes in the PCA score distributions for irradiated samples, as compared to unirradiated samples, in the first 24-72 h post-irradiation. These RS response signatures arise from radiation-induced changes in cellular concentrations of aromatic amino acids, conformational protein structures and certain nucleic acid and lipid functional groups. Correlation analysis between the radiation-induced PCA components separates the cell lines into three distinct RS response categories: R1 (H460 and MCF7), R2 (MDA-MB-231 and PC3) and R3 (DU145 and LNCaP). These RS categories partially segregate according to radiosensitivity, as the R1 and R2 cell lines are radioresistant (SF(2) > 0.6) and the R3 cell lines are radiosensitive (SF(2) < 0.5). The R1 and R2 cell lines further segregate according to p53 gene status, corroborated by cell cycle analysis post-irradiation. Potential radiation-induced biochemical response mechanisms underlying our RS observations are proposed, such as (1) the regulated synthesis and degradation of structured proteins and (2) the expression of anti-apoptosis factors or other survival signals. This study demonstrates the utility of RS for noninvasive radiobiological analysis of tumour cell radiation response, and indicates the potential for future RS studies designed to investigate, monitor or predict radiation response.