Christian Lejon

Polymorph‐ and Size‐Dependent Uptake and Toxicity of TiO2 Nanoparticles in Living Lung Epithelial Cells

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 (μ-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 μ-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 μ-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.

Human primary bronchial epithelial cells respond differently to titanium dioxide nanoparticles than the lung epithelial cell lines A549 and BEAS-2B

Abstract We have compared the cellular uptake and responses of five preparations of nanocrystalline titanium dioxide (TiO2) 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 TiO2 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 TiO2 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.

Noise Removal with Maintained Spatial Resolution in Raman Images of Cells Exposed to Submicron Polystyrene Particles

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.

Initial evaluation of an axial passive sampler for PAHs and OPAHs using substrates with and without gas sampling capacity and varying diffusion distances

Abstract Semi–volatile polycyclic aromatic hydrocarbons (PAHs) and their oxygenated analogues (OPAHs) are associated with adverse health effects. They are normally sampled by active sampling but recently a number of passive samplers that rely on calibrated sampling rates ( R s ), have successfully captured the full suite of PAHs associated with both the gas–and particulate phases. However, there have been few studies on the mechanisms controlling particle deposition during passive sampling. To address this issue, a diesel exhaust aerosol with a number mode of ~120 nm containing PAHs and OPAHs that are partitioned approximately equally between the gas and particle phases was used to study the performance of a passive sampler design of axial badge type. The sampler was tested with two different collection substrates and the diffusion distance was varied to determine its effects on sample collection. The results obtained were compared to data gathered by active sampling of the gas and particle phases. In addition, R s values were calculated for selected PAHs and OPAHs. The material collected by the passive samplers was analyzed using a highly sensitive protocol involving thermal desorption followed by GC–MS. The passive sampler yielded highly reproducible R s values and its PAH uptake was shown to be enhanced by using a collection substrate modified with a gas–adsorbing coating (Tenax ® ) which was exclusively addressed being uptake from the gaseous phase. However, the uptake of the less volatile OPAHs was not affected by the use of a coated substrate. Experimental data and theoretical calculations showed that particle diffusion may have substantially less impact on particulate matter collection than other deposition mechanisms. The high sensitivity and small size of the sampler suggest that after testing in other environments it may have diverse applications in sampling campaigns and as a promising candidate for a personal sampler.

Towards Fingermark Dating : A Raman Spectroscopy Proof-of-Concept Study

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.