Investigation of polycapillary half lenses for quantitative confocal micro-X-ray fluorescence analysis.

The use of polycapillary optics in confocal micro-X-ray fluorescence analysis (CMXRF) enables the destruction-free 3D investigation of the elemental composition of samples. The energy-dependent transmission properties, concerning intensity and spatial beam propagation of three polycapillary half lenses, which are vital for the quantitative interpretation of such CMXRF measurements, are investigated in a monochromatic confocal laboratory setup at the Atominstitut of TU Wien, and a synchrotron setup on the BAMline beamline at the BESSY II Synchrotron, Helmholtz-Zentrum-Berlin. The empirically established results, concerning the intensity of the transmitted beam, are compared with theoretical values calculated with the polycap software package and a newly presented analytical model for the transmission function. The resulting form of the newly modelled energy-dependent transmission function is shown to be in good agreement with Monte Carlo simulated results for the complete energy regime, as well as the empirically established results for the energy regime between 6 keV and 20 keV. An analysis of possible fabrication errors was conducted via pinhole scans showing only minor fabrication errors in two of the investigated polycapillary optics. The energy-dependent focal spot size of the primary polycapillary was investigated in the laboratory via the channel-wise evaluation of knife-edge scans. Experimental results are compared with data given by the manufacturer as well as geometric estimations for the minimal focal spot size. Again, the resulting measurement points show a trend in agreement with geometrically estimated results and manufacturer data.

Metal transport capabilities of anticancer copper chelators.

In the present study, several Cu chelators [2,2'-biquinoline, 8-hydroxiquinoline (oxine), ammonium pyrrolidinedithiocarbamate (APDTC), Dp44mT, dithizone, neocuproine] were used to study Cu uptake, depletion and localization in different cancer cell lines. To better understand the concentration dependent fluctuations in the Cu intracellular metal content and Cu-dependent in vitro antiproliferative data, the conditional stability constants of the Cu complex species of the investigated ligands were calculated. Each investigated chelator increased the intracellular Cu content on HT-29 cells causing Cu accumulation depending on the amount of the free Cu(II). Copper accumulation was 159 times higher for Dp44mT compared to the control. Investigating a number of other transition metals, intracellular accumulation of Cd was observed only for two chelators. Intracellular Zn content slightly decreased (cca. 10%) for MCF-7 cells, while a dramatic decrease was observed on MDA-MB-231 ones (cca. 50%). A similar decrease was observed for HCT-116, while Zn depletion for HT-29 corresponded to cca. 20%. The IC50 values were registered for the investigated four cell lines at increasing external Cu(II) concentration, namely, MDA-MB-231 cells had the lowest IC50 values for Dp44mT ranging between 7 and 35 nM. Thus, Zn depletion could be associated with lower IC50 values. Copper depletion was observed for all ligands being less pronounced for Dp44mT and neocuproine. Copper localization and its colocalization with Zn were determined by µ-XRF imaging. Loose correlation (0.57) was observed for the MCF-7 cells independently of the applied chelator. Similarly, a weak correlation (0.47) was observed for HT-29 cells treated with Cu(II) and oxine. Colocalization of Cu and Zn in the nucleus of HT-29 cells was observed for Dp44mT (correlation coefficient of 0.85).

Iron overload of human colon adenocarcinoma cells studied by synchrotron-based X-ray techniques.

Fast- and slow-proliferating human adenocarcinoma colorectal cells, HT-29 and HCA-7, respectively, overloaded with transferrin (Tf), Fe(III) citrate, Fe(III) chloride and Fe(II) sulfate were studied by synchrotron radiation total-reflection X-ray spectrometry (TXRF), TXRF-X-ray absorption near edge structure (TXRF-XANES), and micro-X-ray fluorescence imaging to obtain information on the intracellular storage of overloaded iron (Fe). The determined TfR1 mRNA expression for the investigated cells correlated with their proliferation rate. In all cases, the Fe XANES of cells overloaded with inorganic Fe was found to be similar to that of deliquescent Fe(III) sulfate characterized by a distorted octahedral geometry. A fitting model using a linear combination of the XANES of Tf and deliquescent Fe(III) sulfate allowed to explain the near edge structure recorded for HT-29 cells indicating that cellular overload with inorganic Fe results in a non-ferritin-like fast Fe storage. Hierarchical cluster analysis of XANES spectra recorded for Fe overloaded HT-29 and HCA-7 cells was able to distinguish between Fe treatments performed with different Fe species with a 95% hit rate, indicating clear differences in the Fe storage system. Micro-X-ray fluorescence imaging of Fe overloaded HT-29 cells revealed that Fe is primarily located in the cytosol of the cells. By characterizing the cellular Fe uptake, Fe/S content ratios were calculated based on the X-ray fluorescence signals of the analytes. These Fe/S ratios were dramatically lower for HCA-7 treated with organic Fe(III) treatments suggesting dissimilarities from the Tf-like Fe uptake.