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| 2. |
- Eliasson, Charlotte, 1973
(författare)
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Applications in Surface Enhanced Raman Spectroscopy
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this thesis is to address specific applications of Raman spectroscopy and specifically surface enhanced Raman spectroscopy, SERS. It includes an introduction to the techniques and several applications. The focus has been on how to achieve high precision SERS measurements, both qualitatively and quantitatively. The overall goal has been to measure biomolecules in complex matrices, such as chemotherapeutic drugs in human blood plasma and in single living cells. The capability to perform these SERS measurements offers exciting possibilities for development of new analytical methodology to be used to improve medical treatment protocols. Surface enhancement was achieved utilising metal colloids, and multivariate statistics have been used throughout this work to aid spectral interpretation. This combination has enabled quantitative studies, and allowed extraction of as much information as possible in spite of the, at times, low signal to noise ratios. Specifically, we have shown that in the complex matrix, blood plasma, with many overlapping spectra, it was possible to identify the spectra of doxorubicin (Paper I). The PCA analysis of spectra led to a feasibility study to quantify doxorubicin in plasma with SERS and PLS modelling (Paper II). The detection limit of doxorubicin in 1 % plasma was 70 nM, which corresponds to 7 µM in whole blood samples. A step towards quantification of chemotherapeutic drugs in lymphocytes was taken when rhodamine 6G was detected simultaneously with the intrinsic components of the cell (Paper III). Rhodamine 6G has the same pathway into and within the cell as doxorubicin, and is also a substrate for glycoprotein The aim of this thesis is to address specific applications of Raman spectroscopy and specifically surface enhanced Raman spectroscopy, SERS. It includes an introduction to the techniques and several applications. The focus has been on how to achieve high precision SERS measurements, both qualitatively and quantitatively. The overall goal has been to measure biomolecules in complex matrices, such as chemotherapeutic drugs in human blood plasma and in single living cells. The capability to perform these SERS measurements offers exciting possibilities for development of new analytical methodology to be used to improve medical treatment protocols. Surface enhancement was achieved utilising metal colloids, and multivariate statistics have been used throughout this work to aid spectral interpretation. This combination has enabled quantitative studies, and allowed extraction of as much information as possible in spite of the, at times, low signal to noise ratios. Specifically, we have shown that in the complex matrix, blood plasma, with many overlapping spectra, it was possible to identify the spectra of doxorubicin (Paper I). The PCA analysis of spectra led to a feasibility study to quantify doxorubicin in plasma with SERS and PLS modelling (Paper II). The detection limit of doxorubicin in 1 % plasma was 70 nM, which corresponds to 7 μM in whole blood samples. A step towards quantification of chemotherapeutic drugs in lymphocytes was taken when rhodamine 6G was detected simultaneously with the intrinsic components of the cell (Paper III). Rhodamine 6G has the same pathway into and within the cell as doxorubicin, and is also a substrate for glycoprotein P-gp. In order to facilitate the spectral interpretation of the mapped cells, multivariate chemical imaging methods in high noise surface enhanced Raman images were developed further to streamline the analysis work (Paper IV).
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| 3. |
- Eliasson, Charlotte, 1973, et al.
(författare)
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Multivariate evaluation of doxorubicin surface-enhanced Raman spectra.
- 2001
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Ingår i: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy. - 1386-1425. ; 57:9, s. 1907-15
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Tidskriftsartikel (refereegranskat)abstract
- Multivariate evaluation of surface-enhanced Raman spectra of doxorubicin in plasma was performed. In a principal component analysis (PCA) all spectral features were modelled into three principal components. The major variation of the data was shown to be the variation of doxorubicin Raman signal together with the doxorubicin fluorescence, whereas the variation due to plasma was of minor importance. It was also shown that the surface-enhanced Raman scattering (SERS) measurements were independent on such factors as measurement occasion and silver colloids. The presented results show that with some improvements, quantification of doxorubicin directly in plasma could be possible.
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| 4. |
- Eliasson, Charlotte, 1973, et al.
(författare)
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Multivariate methodology for surface enhanced Raman chemical imaging of lymphocytes
- 2006
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Ingår i: Chemometrics and Intelligent Laboratory Systems. - : Elsevier BV. - 0169-7439 .- 1873-3239. ; 81:1, s. 13-20
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Tidskriftsartikel (refereegranskat)abstract
- Surface enhanced Raman spectroscopy (SERS) was used to study the uptake of rhodamine 6G in human lymphocytes. In total four Raman images of lymphocytes were used. The aim was to find a multivariate methodology capable of separating spectra with chemical information from those that mainly contained the surface enhanced background, in order to create chemical images. The standard PCA procedure was compared with PCA of standard normal variate (SNV) corrected spectra, spectra baseline corrected in the wavelet domain, and variable trimming before PCA, to isolate unique spectra. It was not straightforward to perform a standard PCA for overview, since the small background variation in many variables dominated over the Raman band variation that only occur in few variables. It was shown that wavelet filtering could remove background variations and that variable trimming followed by PCA modelling left the unique Raman spectra as outliers, which facilitated interpretation of the Raman score images.
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| 5. |
- Eliasson, Charlotte, 1973, et al.
(författare)
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Surface-enhanced Raman scattering imaging of single living lymphocytes with multivariate evaluation
- 2005
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Ingår i: Spectrochimica Acta Part A-Molecular and Biomolecular Spectroscopy. - : Elsevier BV. - 1386-1425. ; 61:4, s. 755-760
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Tidskriftsartikel (refereegranskat)abstract
- This paper is aimed to show the possibility to determine individual organic compounds introduced into single living cells with surface-enhanced Raman spectroscopy (SERS). Surface enhancement was achieved with gold colloids that were allowed to diffuse into lymphocytes. An introduced analyte, rhodamine 6G, could be imaged together with for example nucleotides and amino acids of the cell. Multivariate evaluation of surface-enhanced Raman images proved to be a powerful tool for the separation of spectral information of various intracellular components. The principal component analysis (PCA) enabled identification of spectra containing different chemical information and separation of the spectral contribution of rhodamine 6G from the complex cellular matrix.
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| 6. |
- Lorén, Anders, 1974, et al.
(författare)
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Internal standard in surface-enhanced Raman spectroscopy
- 2004
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 76:24, s. 7391-7395
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Tidskriftsartikel (refereegranskat)abstract
- A method is presented for the use of SAM layers as internal standards for calibration in surface-enhanced Raman spectroscopy. Three cyano-containing compounds were attached to gold colloids via a metal-sulfur bond and evaluated for spectral stability and normalization capacity. The results show that the analyte, rhodamine 6G, and the internal standard signal enhancement covaried, and it was possible to quantify the analyte with PLS. The fact that the enhancing substrate was chaotic assemblies with large variation in signal enhancement shows the versatility of this method.
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- Lorén, Anders, 1974, et al.
(författare)
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Self-assembled monolayer coating for normalization of surface enhanced Raman spectra
- 2004
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Ingår i: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 4:2, s. 309-312
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate that the use of a self-assembled monolayer, consisting of a thiol derivative of Dabcyl, can be used to normalize surface enhanced Raman signals (SERS) with respect to varying enhancement. Chaotic assemblies of gold nanoparticles exhibit large spatial variation in enhancement. Our work shows that in such a system the signals from the reporting molecules in the SAM co-vary with the signal from the analyte solution. With this knowledge, a normalization procedure was used to increase the precision of the analyte signal by 1 order of magnitude, to 8-13%, fully acceptable for quantitative work.
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