69,010 research outputs found
Advanced methods for enhanced sensing in biomedical Raman spectroscopy
No full textRaman spectroscopy is a powerful tool in the field of biomedicine for disease
diagnosis owing to its potential to provide the molecular fingerprint of biological
samples. However due to the inherent weak nature of the Raman process, there is a
constant quest for enhancing the sensitivity of this technique for enhanced diagnostic
efficiency. This thesis focuses on achieving this goal by integrating advanced methods
with Raman spectroscopy.
Firstly this thesis explores the applicability of a laser based fluorescence
suppression technique – Wavelength Modulated Raman Spectroscopy (WMRS) - for
suppressing the broad luminescence background which often obscure the Raman peaks.
The WMRS technique was optimized for its applications in single cell studies and tissue
studies for enhanced sensing without compromising the throughput. It has been
demonstrated that the optimized parameter would help to chemically profile single cell
within 6 s. A two fold enhancement in SNR of Raman bands was demonstrated when
WMRS was implemented in fiber Raman based systems for tissue analysis. The
suitability of WMRS on highly sensitive single molecule detection techniques such as
Surface Enhanced Raman Spectroscopy (SERS) and Surface Enhanced Resonance
Raman Spectroscopy (SERRS) was also explored. Further this optimized technique was
successfully used to address an important biological problem in the field of immunology.
This involved label-free identification of major immune cell subsets from human blood.
Later part of this thesis explores a multimodal approach where Raman
spectroscopy was combined with Optical Coherence Tomography (OCT) for enhanced
diagnostic sensitivity (>10%). This approach was used to successfully discriminate
between ex-vivo adenocarcinoma tissues and normal colon tissues.
Finally this thesis explores the design and implementation of a specialized fiber
Raman probe that is compatible with surgical environments. This probe was originally
developed to be compatible with Magnetic Resonance Imaging (MRI) environment. It
has the potential to be used for performing minimally invasive optical biopsy during
interventional MRI procedures
A Raman fibre amplifier generating simultaneous gain across multiple Stokes orders by using step shaped optical pulses
No full textOptical amplification based on stimulated Raman scattering (SRS) in optical fibres offers the potential to generate gain at any arbitrary wavelength with an appropriate pump source. This has proved a very effective and successful way of providing gain at those wavelengths not directly available with rare-earth doped fibres. However most of this success has been achieved using CW pump sources, but in recent years there has been renewed interest in the pulsed pumping of Raman amplifiers
Confocal Raman data analysis enables identifying apoptosis of MCF-7 cells caused by anticancer drug paclitaxel
No full textConfocal Raman microscopy is a noninvasive, label-free imaging technique used to study apoptosis of live MCF-7 cells. The images are based on Raman spectra of cells components, and their apoptosis is monitored through diffusion of cytochrome c in cytoplasm. K-mean clustering is used to identify mitochondria in cells, and correlation analysis provides the cytochrome c distribution inside the cells. Our results demonstrate that incubation of cells for 3 h with 10 mu M of paclitaxel does not induce apoptosis in MCF-7 cells. On the contrary, incubation for 30 min at a higher concentration (100 mu M) of paclitaxel induces gradual release of the cytochrome c into the cytoplasm, indicating cell apoptosis via a caspase independent pathway. (C) 2013 Society of Photo-Optical Instrumentation Engineers (SPIE) [DOI: 10.1117/1.JBO.18.5.056010
The further assessment of a handheld Raman spectroscopy probe for the intraoperative diagnosis of axillary lymph nodes in breast cancer
No full textAxillary sentinel lymph node biopsy plays an important role in breast cancer management
in determining further surgical and medical treatment options. Intraoperative assessment of
the sentinel lymph node might allow immediate axillary surgery, which would incur
benefits to both the patient and healthcare trusts. A handheld Raman spectroscopy probe
has already been shown to be a comparable option for intraoperative assessment through
previous published and unpublished studies, delivering a sensitivity of up to 92% and
specificity of up to 99%.
This research aims to define further the role of the hand-held Raman spectroscopy probe as
an accurate, rapid and non-destructive technique for intra-operative axillary node
assessment, making it a strong competitor in the clinical market. It also looks to improve
the sensitivity of the probe by altering the methodology used in previous studies.
122 lymph node halves were collected intraoperatively from 37 patients diagnosed with
breast cancer and spectra measured using a commercially available handheld Raman
spectroscopy probe. Spectra were then fed into a specialist software programme and
analysed using principal component fed linear discriminant analysis trained by
histopathology results.
A “2 group” training model defining the probe‟s ability to distinguish between benign and
malignant tissue produced an overall performance of 86.4%, with a sensitivity of 71% and
specificity of 91%.
The results were not as impressive as previous studies. This was possibly due to a broken
probe, leading to four different phases of measurements (original probe/failing
probe/temporary replacement/mended probe). Secondly a smaller, less balanced data set, in
terms of spectra per pathology group, was collected and there appeared to be more
fluorescence in some of the data which may have originated from varying blue dye
injection protocols. However, that said further research using a robust, high specification
system may help establish its role as a reliable assessment tool intraoperatively as well as
a non-invasive means of assessing lymph nodes in the initial assessment clinic
Modulated Raman spectroscopy for enhanced identification of bladder tumor cells in urine samples
No full textStandard Raman spectroscopy (SRS) is a noninvasive technique that is used in the biomedical field to discriminate between normal and cancer cells. However, the presence of a strong fluorescence background detracts from the use of SRS in real-time clinical applications. Recently, we have reported a novel modulated Raman spectroscopy (MRS) technique to extract the Raman spectra from the background. In this paper, we present the first application of MRS to the identification of human urothelial cells (SV-HUC-1) and bladder cancer cells (MGH) in urine samples. These results are compared to those obtained by SRS. Classification using the principal component analysis clearly shows thatMRS allows discrimination between Raman spectra of SV-HUC-1 andMGH cells with high sensitivity (98%) and specificity (95%). MRS is also used to distinguish between SV-HUC-1 and MGH cells after exposure to urine for up to 6 h.We observe a marked change in the MRS of SV-HUC-1 and MGH cells with time in urine, indicating that the conditions of sample collection will be important for the application of this methodology to clinical urine samples.Peer reviewe
Advanced techniques in Raman tweezers microspectroscopy for applications in biomedicine
No full textThis thesis investigates the use of Raman tweezers microspectroscopy to interrogate the biochemistry of single biological cells. Raman tweezers microspectroscopy is a powerful technique, which combines traditional Raman microspectroscopy and optical trapping, allowing the manipulation and environmental isolation of a biological cell of interest whilst simultaneously probing its biochemistry gleaning a wealth of pertinent information.
The studies carried out in this thesis can be split into two broad categories: firstly, the exploitation of Raman tweezers microspectroscopy to study biological cells and secondly developments to the Raman tweezers microspectroscopy technique that extend its capabilities and the range of samples that can be studied. In the application of Raman tweezers, the stacking and interrogation of multiple cells is reported allowing a rapid representative Raman signal to be recorded from a small cell population with improved signal to noise. Also demonstrated is the ability of Raman spectroscopy to identify and grade the development of Human Papillomavirus induced cervical neoplasia with sensitivities of up to 96 %. These studies demonstrate the potential of Raman spectroscopy to study biological cells but it was noted that the traditional Raman tweezers system struggled to manipulate large cells thus a decoupled Raman tweezers microspectroscopy system is presented where a dual beam fibre optical trap is used to perform the trapping function and a separate Raman probe is introduced to probe the biochemical nature of the trapped cell. This development allowed the trapping and examination of very large cells whilst opening up the possibility of creating Raman maps of trapped objects. Raman tweezers microspectroscopy could potentially become an important clinical diagnostic and biological monitoring tool but is held back by the long signal integration times required due to the weak nature of Raman scattering. The final study presented in this thesis examines the potential of wavelength modulated Raman spectroscopy to improve signal to noise ratios and reduce integration times.
All these studies aim to demonstrate the potential and extend the performance of Raman tweezers microspectroscopy
Studying carbonisation with raman spectroscopy
No full textRaman spectroscopy can provide fast and non-destructive analysis of carbonaceous materials. As it is able to detect nanometre-sized structural features, Raman spectroscopy is widely used in the study of carbon nanotubes, fullerenes, graphenes, and many other carbon-rich materials. Raman analysis has previously shown potential for estimating the heat treatment temperatures (HTT) employed in the preparation of Japanese cedar charcoals which suggested future usefulness in quality control . In the current work, Raman spectroscopy was used to investigate the nanostructural development which had occurred within various chars prepared and carbonised at a range of heat treatment temperatures between ≈ 340°C and 1000°C. Chars were produced from sucrose sugar as standard precursor of high purity and two sources of biomass common in New Zealand (Radiata pine wood and Harakeke leaf fibres). In chars produced at lower HTTs, signals could be detected which were interpreted as representing hydrogen-rich amorphous carbon structures. In contrast, the Raman spectra of well-carbonised chars produced at higher HTTs featured signals consistent with graphene-like structures with coherent domains limited in size to below a few nanometres across. Measurement of such signals provides the ability to evaluate the extent of nanostructural development, identify char samples which are ‘undercooked’ when compared to other char samples, and estimate effective HTTs used in the production of a given char sample. More detailed Raman analysis of Radiata-derived chars was carried out, including analysis of chars produced from carbonising pyrolysis tars. Results of Raman analysis were correlated to H/C atom ratios obtained through elemental analysis for these chars produced from Radiata pine
Applications of Raman spectroscopy to urology
No full textRaman spectroscopy is an optical technique that can interrogate biological tissues. In
doing so it gives us an understanding of the changes in the molecular structure that are
associated with disease development. The Kerr gating technique uses a picosecond
pulsed laser and fast temporal gating of inelastically (Raman) scattered light.
The tissue samples used were taken following fully informed consent and ethics
approval. Bladder samples were obtained by taking a biopsy during a TURBT or
TURP, prostate samples were taken during TURP and the liver and kidney (pigs)
were bought at a supermarket. The bladder and prostate samples were snap frozen in
liquid nitrogen and stored in an -80°C freezer until required for experimentation. The
liver and kidney tissue were used fresh. The constituent samples were bought from
Sigma – Aldrich.
Multivariate and least squares analysis were used to ascertain the biochemical basis of
the differing pathologies within the bladder and the prostate gland, as well as to test
diagnostic algorithms produced by a colleague in our group. Depth profiling through
the bladder and prostate gland was shown to be feasible by utilizing the Kerr gating
technique as was the suppression of fluorescence from dark tissue (liver and kidney).
We have shown for the first time, that we can utilise Raman spectroscopy to
determine the biochemical basis of pathologies of the bladder and the prostate gland.
With the help of the Kerr gating technique we also obtained spectra from different
depths through them. We also suppressed fluorescence and resonantly enhanced
Raman spectra from dark tissue. These have major implications in terms of
understanding pathogenesis and disease progression and also the potential to
accurately assess depth of tumour invasion
Técnicas alternativas para amplificação de Raman em telecomunicações
No full textDoutoramento em FísicaO presente trabalho centra-se no estudo dos amplificadores de
Raman em fibra ótica e suas aplicações em sistemas modernos
de comunicações óticas. Abordaram-se tópicos específicos como
a simulação espacial do amplificador de Raman, a equalização
e alargamento do ganho, o uso de abordagens híbridas de
amplificação através da associação de amplificadores de Raman
em fibra ótica com amplificadores de fibra dopada com Érbio
(EDFA) e os efeitos transitórios no ganho dos amplificadores. As
actividades realizadas basearam-se em modelos teóricos, sendo os
resultados validados experimentalmente.
De entre as contribuições mais importantes desta tese, destaca-se
(i) o desenvolvimento de um simulador eficiente para amplificadores
de Raman que suporta arquitecturas de bombeamento
contraprogantes e bidirecionais num contexto com multiplexagem
no comprimento de onda (WDM); (ii) a implementação de um
algoritmo de alocação de sinais de bombeamento usando a
combinação do algoritmo genético com o método de Nelder-
Mead; (iii) a apreciação de soluções de amplificação híbridas por
associação dos amplificadores de Raman com EDFA em cenários
de redes óticas passivas, nomeadamente WDM/TDM-PON com
extensão a região espectral C+L; e (iv) a avaliação e caracterização
de fenómenos transitórios em amplificadores para tráfego em
rajadas/pacotes óticos e consequente desenvolvimento de soluções
de mitigação baseadas em técnicas de clamping ótico.The present work is based on Raman Fiber Amplifiers and their
applications in modern fiber communication systems. Specific topics
were approached, namely the spatial simulation of Raman fiber
amplifiers, the gain enlargement and equalization the use of hybrid
amplification approaches by association of Raman amplifiers with
Erbium doped fiber amplifiers (EDFA) and the transient effect on
optical amplifiers gain. The work is based on theoretical models,
being the obtained results validated experimentally.
Among the main contributions, we remark: (i) the development of an
efficient simulator for Raman fiber amplifiers that supports backward
and bidirectional pumping architectures in a wavelength division
multiplexing (WDM) context; (ii) the implementation of an algorithm
to obtain enlargement and equalization of gain by allocation of
pumps based on the association of the genetic algorithm with the
Nelder-Mead method; (iii) the assessment of hybrid amplification
solutions using Raman amplifiers and EDFA in the context of passive
optical networks, namely WDM/TDM-PON with extension the C+L
spectral bands; (iv) the assessment and characterization of transient
effects on optical amplifiers with bursty/packeted traffic and the
development of mitigation solutions based on optical clamping
Infrared and Raman studies of thin polymer films
No full text[Keywords:- Waveguide; Raman; Attenuated Total Reflection; Infrared; Polymer Films; Barrier Films; Epoxy; Diffusion; Isocyanate; Crosslinking Agents; Cure Time; Kinetics; Urethane; Film Quality]This thesis describes the experimental work carried out between October l(^st), 1990 and 30th September, 1993, in the Chemistry Department of the University of Durham, in association with Courtaulds Coatings plc, m partial fulfilment of the requirements for the degree of Doctor of Philosophy. The thesis is divided into three sections, namely Theoretical Considerations (three Chapters), Experimental Results (three Chapters) and Discussion of Results (one Chapter). There are also three appendices. The theoretical section presents a working description of Paint Chemistry, Vibrational spectroscopy, Waveguide Raman Spectroscopy, Attenuated Total Reflection Fourier Transform Infrared Spectroscopy and Diffusion Processes. The experimental section is divided into three chapters. The first describes methods of film preparation and characterisation and includes methods of film thickness determination and the development of an off-line waveguiding rig at the University of Durham. Raman spectroscopic results are detailed in the second chapter, and include waveguide experiments on both single polymer films and laminate systems, some of which are reported for the first time, along with some FT-Raman results, also reported for the first time. The FT-IR ATR spectroscopic results are presented in the third chapter and include some barrier film studies on polymeric laminate systems, plus the study of certain diffusion processes, along with an estimation of the associated diffusion coefficients and some kinetic parameters, occurring in epoxy resins, which are reported for the first time. The discussion section concentrates on a full elucidation of the results, and conclusions that may be drawn from them, and ends with suggestions for future work. Refractive indices quoted, unless otherwise stated, refer to indices measured usmg 632.8 nm radiation, and have been estimated either using previous literature, or with the off-line rig. It is accepted that electric field calculations performed with these values will be slightly different to the actual fields observed in the Raman experiments, due to slightly different refractive indices at 514.5 nm. T in tables, unless otherwise stated, refers to band intensities in absorbance units. Finally, the attention of the reader is drawn to the fact that some of the materials used in the course of this project have no precise structure given. This is due to the fact that some of the substances used are of either a highly complicated and/or confidential nature
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