Three differently sized, highly dispersed platinum nanoparticle (Pt-NP) preparations were generated by supercritical fluid reactive deposition (SFRD) and deposited on a β-cyclodextrin matrix. The average particle size and size distribution were steered by the precursor reduction conditions, resulting in particle preparations of <20, <100 and >100 nm as characterised by TEM and SEM. As reported previously, these Pt-NPs were found to cause DNA strand breaks in human colon carcinoma cells (HT29) in a concentration- and time-dependent manner and a distinct size dependency. Here, we addressed the question whether Pt-NPs might affect directly DNA integrity in these cells and thus behave analogous to platinum-based chemotherapeutics such as cisplatin. Therefore, DNA-associated Pt as well as the translocation of Pt-NPs through a Caco-2 monolayer was quantified by ICP-MS. STEM imaging demonstrated that Pt-NPs were taken up into HT29 cells in their particulate and aggregated form, but appear not to translocate into the nucleus or interact with mitochondria. The platinum content of the DNA of HT29 cells was found to increase in a time- and concentration-dependent manner with a maximal effect at 1,000 ng/cm(2). ICP-MS analysis of the cell culture medium indicated the formation of soluble Pt species, although to a limited extent. The observations suggest that DNA strand breaks mediated by metallic Pt-NPs are caused by Pt ions forming during the incubation of cells with these nanoparticles.

Supercritical fluid reactive deposition was used for the deposition of highly dispersed platinum nanoparticles with controllable metal content and particle size distribution on beta-cyclodextrin. The average particle size and size distribution were steered by the precursor reduction conditions, resulting in particle preparations <20, <100, and >100 nm as characterized by transmission electron microscopy and scanning electron microscopy (SEM). These particle preparations of different size distributions were used to address the question as to whether metallic platinum particles are able to invade cells of the gastrointestinal tract as exemplified for the human colon carcinoma cell line HT29 and thus affect the cellular redox status and DNA integrity. Combined focused ion beam and SEM demonstrated that platinum nanoparticles were taken up into HT29 cells in their particulate form. The chemical composition of the particles within the cells was confirmed by energy-dispersive X-ray spectroscopy. The potential influence of platinum nanoparticles on cellular redoxsystems was determined in the DCF assay, on the translocation of Nrf-2 and by monitoring the intracellular glutathione (GSH) levels. The impact on DNA integrity was investigated by single cell gel electrophoresis (comet assay) including the formation of sites sensitive to formamidopyrimidine-DNA-glycosylase. Platinum nanoparticles were found to decrease the cellular GSH level and to impair DNA integrity with a maximal effect at 1 ng/cm(2). These effects were correlated with the particle size in an inverse manner and were enhanced with increasing incubation time but appeared not to be based on the formation of reactive oxygen species.

A more precise interpretation of the defect structure of wurtzite crystals as observed in the electron microscope is presented. It was found previously that the crystals contain faults in the basal planes (b‐faults) and in prism planes (p‐faults). Direct evidence is presented indicating that the transition wurtzite sphalerite is a martensitic transformation due to the movement of partial dislocations. The transformation leads to a faulted structure. Evidence is further presented for the occurrence of a domain structure. Possible models for this domain structure are proposed. According to the first, the domain boundaries result from the contact between two crystal regions for which the polar c‐axes have opposite sense. The origin of the contrast at such boundaries is discussed, and it is concluded that this type of boundary has presumably not yet been observed in wurtzite. According to the second model the boundaries result from the contact between two crystal regions which are displaced with respect to each other over a displacement vector which is identical to the Burgers vectors of a partial in the basal plane, or to the sum of such a vector with a vector (000 c/2) Evidence is presented to show that the domain structure results from the introduction during growth of single stacking faults. A generation mechanism for basal and prismatic faults is discussed. The contrast effects at single and double faults in the hexagonal closed packed structure are discussed in detail and a method is proposed to distinguish these two types of faults.

The use of nanostructured silica (SiO2) particles is no longer restricted to biomedical and (bio-) technological fields but rather finding applications in products of the food industry. Thus, our studies on the toxicological relevance of SiO2 nanoparticles focused on cytotoxic effects, the modulation of the cellular redox status and the impact on DNA integrity in human colon carcinoma cells (HT29). The results indicate that these SiO2 nanoparticles stimulate the proliferation of HT29 cells, depending on the incubation time and the particle size. The cytotoxicity of the investigated SiO2 nanoparticles was found to depend on the concentration, size and on the FCS content of the culture medium. Furthermore, SiO2 seem to interfere with glutathione biosynthesis. The results indicate further that effects of SiO2 NPs are not mediated by oxidative stress but by interference with the MAPK/ERK1/2 as well as the Nrf2/ARE signalling pathways. Additionally, investigations regarding DNA integrity revealed no substantial (oxidative) DNA damage.

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The Howie‐Whelan system of equations [2] is extended to non‐centro symmetrical crystals. This system of equations, which is valid for the Laue case, describes the scattering of electrons by a perfect crystal in the two‐beam approximation and takes anomalous absorption into account. The theory predicts that Friedel's law no longer holds for the dark field image but is still valid in the bright field. Observations on 180° walls in barium titanate support the theory. In addition the theory shows that 180° walls in inclined planes should produce α‐type fringes. This phenomenon is also observed experimentally.

In part I of this paper the dynamic two‐beam theory of domain fringes was developed. In the present paper the properties of the fringe patterns, derived in part I, are observed and illustrated by means of examples. In particular, fringes resulting from ferroelectric domain‐walls in barium titanate, and anti‐ferromagnetic domain‐walls in nickel oxide, are discussed in detail. It is shown how from the nature of the first and last fringes, and a knowledge of the diffraction vector, the geometry of the domains on both sides of the domain wall can be deduced. In the case of barium titanate this procedure gives the direction of the tetragonal axes in both domains. In nickel oxide the directions of the contractions due to ferromagnetic ordering can be deduced. In niobium, domains can be produced by the insertion of gaseous interstitial impurities, which leads to a small deformation of the niobium matrix. The walls between such domains show the same type of fringes. Also the fringe patterns observed by Fourie et al. at twins in tin are discussed. Finally some numerical calculations based on the exact analytical expressions are compared with the observations and also with the approximate analytical treatment given in part I.

The overall permeation rate through asymmetric oxygen transport membranes is significantly governed by the porous support. Therefore, the microstructuring of the support's pore structure is essential to achieving the highest performances. Freeze casting is already proven to obtain hierarchical porous structures with low tortuosity, which potentially enhances the oxygen flux of oxygen transport membranes. Although a performance improvement has been reported, such improvement is not self-evident. There has yet to be a detailed comparison of the achieved microstructures in order to identify the relevant microstructural parameters. Asymmetric membranes from Ba0.5Sr0.5(Co0.8Fe0.2)0.97Zr0.03O3- consisting of a surface-activated 20 µm membrane layer with tape-or freeze-cast supports that have identical pore volume and layer thickness were manufactured, characterized, and compared by means of oxygen flux measurements. They were also microstructurally investigated via computed X-Ray tomography and flow simulation experiments. In the air/Ar gradient, the freeze-cast support membrane performs below the tape-cast-supported membrane. In particular, the transition zone close to the membrane, which is caused by the freezing process, significantly constrains the diffusivity and permeability of the support, and therefore leads to concentration polarizations. At temperatures below 800 °C, surface exchange kinetics at the membrane-support interface become rate-limiting.