ArtTAX--a new mobile spectrometer for energy-dispersive micro X-ray fluorescence spectrometry on art and archaeological objects.

A newly developed spectrometer for energy-dispersive micro X-ray fluorescence spectrometry has been designed for the demands of archaeometry. ArtTAX combines the advantages of non-destructive and sensitive multi-elemental analysis at sub-mm resolution with the possibility of working outside the laboratory. The spectrometer consists of an air-cooled, low-power molybdenum tube, new generation polycapillary X-ray optics, a silicon drift detector without the need for liquid-nitrogen cooling, a CCD camera, and three light diodes for sample positioning. The motor-driven measurement head is fixed on a x,y,z-flexible tripod support which can be assembled and dismantled within minutes. The spot size of the primary X-ray beam was determined to be 94 microm for the Cu(Kalpha) energy, the detection limits are in a range of a few tens of microg g(-1) for the medium energy-range in glass. Additional open helium purging in the excitation and detection paths enables the determination of elements down to sodium, thus avoiding vacuum conditions or a size-limiting sample chamber. A selection of qualitative and quantitative results on pigment, metal, glass, and enamel analyses are presented to show the potential of ArtTAX in the field of art and archaeology.

New methods for the investigation of blood-biomaterial interaction.

Quantitative microscopy with integrated image processing is a useful tool for investigation of the interaction of blood components with biomaterials. We have developed new automated measuring devices suitable for simultaneously characterizing biological cells (size, shape, localization, migration, electrophoresis), synthetic particles (electrophoretic fingerprinting), and dialysis membranes (morphology, electric charge). These techniques are useful for the investigation of cell adherence on biomaterials, localization of cells in membrane filters (Chemotaxis), characterization of the protein adsorption on model systems, detection of cytokines (produced after lymphocyte-biomaterial contact), and estimation of morphological properties and charge distribution in dialysis membranes.

Bromodeoxyuridine distribution patterns in L 929 fibroblasts and influence of tumor necrosis factor.

Incorporation of bromodeoxyuridine during the S phase of the cell cycle provides an appropriate method to study the replication of DNA in proliferating cells. We analyzed the distribution patterns of incorporated bromodeoxyuridine in L 929 cells and studied the influence of tumor necrosis factor-alpha in vitro by indirect immunofluorescence. Using conventional epifluorescent and confocal laser scanning microscopy, we defined three types of bromodeoxyuridine distribution patterns in synchronized L 929 cells which showed typical differences in their percentages during the time course of the S phase. Type I with small spots and unstained areas was typical for the early S phase. Type II was characterized by a texture of homogeneously distributed fluorescence and increased during middle and late S phase. Type III with a small number of larger clusters revealed its highest proportion in the late S phase. Incubation with tumor necrosis factor reduced the number of bromodeoxyuridine-positive cells. We found that the cytokine, when present in late S phase, provoked an increase in the percentage of type III distribution pattern. The results show that bromodeoxyuridine distribution pattern analysis can be used to detect influences on cell cycle kinetics induced by therapeutics.

Detection of charges and their distribution on dialysis membranes with cationic/anionic dyes using confocal laser scanning microscopy.

Methods for the detection of positive or negative charges on the surface of biomaterials/membranes and inside a membrane are important for the characterisation of such materials. We tested different dyes and optimized staining procedures. Under standardized conditions negatively charged membranes were stained with cationic triarylmethane compounds such as crystal violet and positively charged membranes with the anionic anthraquinone dye anthralan blue B. There was no staining of uncharged cellulose membranes. The applicability of these methods was demonstrated on membranes coated to varying degrees with charged compounds such as heparin, these changes in charge being detectible quantitatively by photometry. The distribution of charges inside a membrane was detected by optical sectioning across the stained (FITC labelled poly-L-lysine) membrane using confocal laser scanning microscopy (LSM). LSM offers a completely new application possibility in biomaterial and biocompatibility research.