| 1. |
- Ahlinder, Linnea, et al.
(författare)
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Noise Removal with Maintained Spatial Resolution in Raman Images of Cells Exposed to Submicron Polystyrene Particles
- 2016
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Ingår i: Nanomaterials. - : MDPI AG. - 2079-4991. ; 6:5
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Tidskriftsartikel (refereegranskat)abstract
- The biodistribution of 300 nm polystyrene particles in A549 lung epithelial cells has been studied with confocal Raman spectroscopy. This is a label-free method in which particles and cells can be imaged without using dyes or fluorescent labels. The main drawback with Raman imaging is the comparatively low spatial resolution, which is aggravated in heterogeneous systems such as biological samples, which in addition often require long measurement times because of their weak Raman signal. Long measurement times may however induce laser-induced damage. In this study we use a super-resolution algorithm with Tikhonov regularization, intended to improve the image quality without demanding an increased number of collected pixels. Images of cells exposed to polystyrene particles have been acquired with two different step lengths, i.e., the distance between pixels, and compared to each other and to corresponding images treated with the super-resolution algorithm. It is shown that the resolution after application of super-resolution algorithms is not significantly improved compared to the theoretical limit for optical microscopy. However, to reduce noise and artefacts in the hyperspectral Raman images while maintaining the spatial resolution, we show that it is advantageous to use short mapping step lengths and super-resolution algorithms with appropriate regularization. The proposed methodology should be generally applicable for Raman imaging of biological samples and other photo-sensitive samples.
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| 2. |
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| 3. |
- Andersson, Per Ola, et al.
(författare)
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Polymorph and size dependent uptake and toxicity of TiO2 nanoparticles in living lung epithelial cells
- 2011
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Ingår i: Small. - : Wiley. - 1613-6810 .- 1613-6829. ; 7:4, s. 514-523
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Tidskriftsartikel (refereegranskat)abstract
- The cellular uptake and distribution of five types of well-characterized anatase and rutile TiO(2) nanoparticles (NPs) in A549 lung epithelial cells is reported. Static light scattering (SLS), in-vitro Raman microspectroscopy (mu-Raman) and transmission electron spectroscopy (TEM) reveal an intimate correlation between the intrinsic physicochemical properties of the NPs, particle agglomeration, and cellular NP uptake. It is shown that mu-Raman facilitates chemical-, polymorph-, and size-specific discrimination of endosomal-particle cell uptake and the retention of particles in the vicinity of organelles, including the cell nucleus, which quantitatively correlates with TEM and SLS data. Depth-profiling mu-Raman coupled with hyperspectral data analysis confirms the location of the NPs in the cells and shows that the NPs induce modifications of the biological matrix. NP uptake is found to be kinetically activated and strongly dependent on the hard agglomeration size-not the primary particle size-which quantitatively agrees with the measured intracellular oxidative stress. Pro-inflammatory responses are also found to be sensitive to primary particle size.
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| 4. |
- Andersson, Per Ola, et al.
(författare)
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Towards Fingermark Dating : A Raman Spectroscopy Proof-of-Concept Study
- 2017
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Ingår i: ChemistryOpen. - : Wiley. - 2191-1363. ; 6:6, s. 706-709
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Tidskriftsartikel (refereegranskat)abstract
- Fingermarks have, for a long time, been vital in the forensic community for the identification of individuals, and a possibility to non-destructively date the fingermarks would of course be beneficial. Raman spectroscopy is, herein, evaluated for the purpose of estimating the age of fingermarks deposits. Well-resolved spectra were non-destructively acquired to reveal spectral uniqueness, resembling those of epidermis, and several molecular markers were identified that showed different decay kinetics: carotenoids > squalene > unsaturated fatty acids > proteins. The degradation rates were accelerated, less pronounced for proteins, when samples were stored under ambient light conditions, likely owing to photo-oxidation. It is hypothesized that fibrous proteins are present and that oxidation of amino acid side chains can be observed both through Raman and fluorescence spectroscopy. Clearly, Raman spectroscopy is a useful technique to non-destructively study the aging processes of fingermarks.
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| 5. |
- Ekstrand-Hammarström, Barbro, et al.
(författare)
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Human Primary Bronchial Epithelial Cells are more Responsive to Titanium Dioxide Nanoparticles than the Lung Epithelial Cell Lines A549 and BEAS-2B
- 2012
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Ingår i: Nanotoxicology. - : Informa Healthcare. - 1743-5390 .- 1743-5404. ; 6:6, s. 623-634
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Tidskriftsartikel (refereegranskat)abstract
- We have compared the cellular uptake and responses of fivepreparations of nanocrystalline titanium dioxide (TiO2) betweennormal human bronchial epithelial (NHBE) cells and epithelialcell lines (A549 and BEAS-2B). The P25 nanoparticles, containingboth anatase and rutile modifications, induced reactive oxygenspecies (ROS) and secretion of the neutrophil chemoattractantIL-8 in all three cell types used. Pure anatase and rutile particlesprovoked differential IL-8 response in A549 and no response inBEAS-2B cells despite similar formation of ROS. The pure TiO2modifications also provoked release of the inflammatorymediators: IL-6, G-CSF and VEGF, in NHBE cells but not in the twocell lines. We conclude that the responsiveness of lung epithelialcells is strongly dependent on both the physicochemicalproperties of TiO2 nanoparticles and the type of responder cells.The differential pro-inflammatory responsiveness of primarylung epithelial cells compared with immortalized cell linesshould be considered in the assessment of adverse reactions toinhaled nanoparticles.
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| 6. |
- Ekstrand-Hammarström, Barbro, et al.
(författare)
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Human primary bronchial epithelial cells respond differently to titanium dioxide nanoparticles than the lung epithelial cell lines A549 and BEAS-2B
- 2012
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Ingår i: Nanotoxicology. - : Informa UK Limited. - 1743-5390 .- 1743-5404. ; 6:6, s. 623-634
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Tidskriftsartikel (refereegranskat)abstract
- We have compared the cellular uptake and responses of five preparations of nanocrystalline titanium dioxide (TiO(2)) between normal human bronchial epithelial (NHBE) cells and epithelial cell lines (A549 and BEAS-2B). The P25 nanoparticles, containing both anatase and rutile modifications, induced reactive oxygen species (ROS) and secretion of the neutrophil chemoattractant IL-8 in all three cell types used. Pure anatase and rutile particles provoked differential IL-8 response in A549 and no response in BEAS-2B cells despite similar formation of ROS. The pure TiO(2) modifications also provoked release of the inflammatory mediators: IL-6, G-CSF and VEGF, in NHBE cells but not in the two cell lines. We conclude that the responsiveness of lung epithelial cells is strongly dependent on both the physicochemical properties of TiO(2) nanoparticles and the type of responder cells. The differential pro-inflammatory responsiveness of primary lung epithelial cells compared with immortalized cell lines should be considered in the assessment of adverse reactions to inhaled nanoparticles.
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| 7. |
- Fager, Christian, 1974, et al.
(författare)
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Voltage/Current mode class D amplifiers and their applications
- 2008
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Ingår i: Proc. IEEE Radio Wireless Symposium (Workshop: Transmitter Design for High Power Efficiency: The path from device to advanced system architectures).
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 8. |
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| 9. |
- Lejon, Christian, et al.
(författare)
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Influence of quantum confinement, hydrostatic pressure and critical Zr dopant concentration on the Raman vibrational properties of Zr doped anatase TiO2 nanoparticles
- 2011
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Ingår i: Journal of Raman Spectroscopy. - : John Wiley & Sons. - 0377-0486 .- 1097-4555. ; 42:11, s. 2026-2035
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Tidskriftsartikel (refereegranskat)abstract
- We present a comprehensive analysis of the Ramanspectra of pure and zirconium-doped anatase TiO2 nanoparticles. To accountfor the wavenumber shifts of the Eg(ν6)mode as a function of particle size (L) and dopant concentration (x), a modification of the standard phonon confinement model (PCM) is introduced, which takes into account the contribution of surface stress by means of the Laplace–Young equation. Together with X-ray diffraction (XRD) and transmission electronmicroscopy data, our analysis shows that the surface stress contribution to the observed blue shift of the Ramanwavenumber is of the same magnitude as the spatial phonon confinement effect. Annealing experiments show that Zr-doped nanoparticles exhibit retarded grain growth and delayed anatase-to-rutile phase transition by up to 200 K compared to pure anatase TiO2. XRD shows that Zr doping leads to a unit cell expansion of the anatase structure. Applying themodified PCM to the x-dependent variations of the Eg(ν6) Raman mode, the mode-Gr ¨ uneisen parameter is found to increase abruptly at x > 0.07 with a concomitant mode softening. This coincides with the x range over which the Zr cations are reported to be displaced from their position in the tetrahedral lattice, and where Zr precipitation occurs upon annealing. The results have implications for the interpretation of Raman spectra of ionic metal oxide nanoparticles and how these are modified upon cation doping
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| 10. |
- Mattsson, Andreas, et al.
(författare)
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Characterisation, phase-stability and surface chemical properties of photocatalytic active Zr and Y co-doped anatase TiO2 nanoparticles
- 2013
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Ingår i: Journal of Solid State Chemistry. - : Elsevier. - 0022-4596 .- 1095-726X. ; 199, s. 212-223
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Tidskriftsartikel (refereegranskat)abstract
- We report on the characterization, phase stability, surface chemical andphotocatalytic properties of Zr and Y co-doped anatase TiO2 nanoparticles prepared by homogenous hydrolysis methods using urea as precipitating agent. The materials were analyzed by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, BET isotherm and BJH pore size distribution measurements. It is shown that Y and Zr ions replace Ti ions in the anatase TiO2 structures up to a critical total dopant concentration of approximately 13 wt%. The co-doped particles show increased phase stability compared to pure anatase TiO2nanoparticles. The anatase to rutile phase transformation is shown to be preceded by cation segregation and dissolution with concomitant precipitation of Y2Ti2-xZrxO7 and ZrTiO4. Co-doping modifies the optical absorption edge with a resulting attenuation of the Urbach tail. The band gap is slightly blue-shifted at high doping concentrations, and red shifted at lower doping concentrations. Formic acid adsorption was used as a probe molecule to investigate surfacechemical properties and adsorbate structures. It was found that the relative abundance ofmonodentate formate compared to bidentate coordinated formate decreases with increasing doping concentration. This is attributed to an increased surface acidity with increasing dopant concentration. Photodegradation of formic acid occurred on all samples. With mode-resolved in situ FTIR spectroscopy it is shown that the rate of photodegradation of monodentate formate species are higher than for bidentate formate species. Thus our results show that the trend ofdecreasing photo-degradation rate with increasing dopant concentration can be explained by the adsorbate structure, which is controlled by the acidity of the surface.
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