Zeitschriftenaufsätze

This paper describes the preparation and obtained magnetic properties of large single domain iron oxide nanoparticles. Such ferrimagnetic particles are particularly interesting for diagnostic and therapeutic applications in medicine or (bio)technology. The particles were prepared by a modified oxidation method of non-magnetic precursors following the green rust synthesis and characterized regarding their structural and magnetic properties. For increasing preparation temperatures (5 to 85 ˚C), an increasing particle size in the range of 30 to 60 nm is observed. Magnetic measurements confirm a single domain ferrimagnetic behavior with a mean saturation magnetization of ca. 90 Am2/kg and a size-dependent coercivity in the range of 6 to 15 kA/m. The samples show a specific absorption rate (SAR) of up to 600 W/g, which is promising for magnetic hyperthermia application. For particle preparation temperatures above 45 ˚C, a non-magnetic impurity phase occurs besides the magnetic iron oxides that results in a reduced net saturation magnetization.

Real biological tissues show a great variety of different geometric morphologies with special features on different geometric scales. An interesting example is the liver lobule that is the basic subunit of a liver. The lobule is a quasihexagonal macroscopic structure with periodic like so-called sinusoidal elements with structural features on the micro- and macroscale made of proteins, cells, and fluids. Various tools from micromachining and nanotechnology have demonstrated their capabilities to construct micromorphologies precisely, but even the reconstruction of such a system in technical polymers is challenging. In this work, the rapidly evolving technique of multiphoton polymerization has been explored for the construction of a scaffold that mimics the micromorphology of the liver with high resolution and detail up to the millimeter scale. At the end, a highly complex fluidically perfusable structure was achieved and simulations showed that the occurring shear stress, fluid velocity, and stream lines are comparable to the native liver lobule. Hereby, the photoresists SU-8 and SUEX TDFS were compared in terms of their processability, achievable resolution, and suitability for the intended application. Our results have shown that SUEX needs lower writing velocities but is easier to process and achieves a considerable higher resolution than SU-8. The scaffold could provide a base frame with a geometrically defined morphology for hepatic cells to adhere to, which could act as a starting point for cells to build new liver tissue for further integration in more complex systems.

Since the 1950ies Design Theory and Methodology has described product and system development as a process that goes through the stages of requirements definition, considerations of functions, allocation of solution principles and, finally, detailing. Computer support of this process has more or less evolved backwards: Starting with manufacturing information (i.e. supporting processes after product development), going through geometric modelling to simulation - which is basically our present state. Functional modelling and requirements management has been very difficult to realise with conventional methods. Today, Model-Based Systems Engineering (MBSE) offers new ways to come to a holistic coverage of the product development process providing and - very importantly - linking model elements for all of its stages. Starting from the needs, as seen from Design Theory and Methodology, this article describes the current state of MBSE as a new, integrative approach for product and system development and identifies needs for further progress in this field.

Si sources involved in the growth of Au-SiOx nanostructures are investigated through the rapid thermal annealing of gold thin films on SiO2/Si substrates with various SiO2 layer thicknesses (3, 25, 100, 500 nm) in a reducing atmosphere. This method reveals three Si sources whose involvement depends on the thickness of the SiO2 layers, i.e., Si diffusion from the substrate, and SiO from SiO2 decomposition and from Si active oxidation. Increasing thicknesses of the SiO2 layer hampers the Si diffusion and the decomposition of regions of the SiO2 layer, which decreases the concentrations of discovered regions weakening the Si active oxidation. These discovered regions appear in systems with a SiO2 layer of 25 or 100 nm, while they are absent for a 500 nm layer. Furthermore, Au-SiOx nanostructures of different shapes form in each system. Both behaviors indicate that the influence and transport mechanisms of the different Si sources are largely dependent on the thicknesses of the SiO2 layers and that they control the evolution of the Au-SiOx nanostructures. A clear understanding of the relationship between these thicknesses and the possible Si sources and their roles in the evolution of the nanostructures makes the tailored fabrication of nanostructures possible.

Noncovalent water-soluble nanocomplexes of C60 fullerene (C60) with chemotherapeutic drugs (Doxorubicin (Dox), Cisplatin (Cis), and herbal alkaloid Berberine (Ber)) were created. Their anticancer action toward various tumor cells was studied in vitro, addressing specifically their biological synergy, compared with the action of these drugs in the non-immobilized form. Different theoretical and experimental (SEM and AFM microscopy, UV-Vis, DLS, NMR and SANS spectroscopy, ITC calorimetry) methods were applied for getting insight into the nature of the nanocomplexes with drug molecules, as well as into the physical forces enabling stabilization of these complexes. Physicochemical mechanisms were proposed for drug interaction with C60. An enhancement of the toxic action of the created water-soluble C60-drug nanocomplexes toward cancer cells, compared to the action of free drug, was found. Specifically, the C60-Dox nanocomplexes demonstrated ˜3.5 higher cytotoxic potential in the leukemic cell lines (CCRF-CEM, Jurkat, THP1, and Molt-16) in comparison with free Dox in the nanometer range of concentrations. Besides, C60 doubled the intracellular level of the up-taken Dox, which also evidenced its function as a nanocarrier. The toxic effect of C60-Cis nanocomplex toward Lewis lung carcinoma (LLC) cells was shown to be higher with IC50 values 3.3 and 4.5 times at 48 h and 72 h, respectively, as compared to the IC50 of free drug. 12.5 [my] Cis had no effect on LLC cells' viability. The C60-Cis nanocomplex in Cis-equivalent concentration substantially decreased the viability of tumor cells, impaired their shape and adhesion, inhibited migration, and induced their accumulation in the pro-apoptotic sub-G1 phase of cell cycle. An induction of apoptosis by the C60-Cis nanocomplex was confirmed by the activation of caspase 3/7 and externalization of phosphatidylserine on the outer membrane of LLC cells after their double staining with the Annexin V-FITC/PI. The complexation with C60 promoted intracellular uptake of the Ber. An increase in C60 concentration in the C60-Ber nanocomplexes was accompanied by the elevation of their antiproliferative potential toward CCRF-CEM cells in the order: free Ber < 1:2 < 1:1 < 2:1.These findings suggest a universal potential of water-soluble pristine C60 as a unique nano-platform for the delivery of the chemotherapeutic drugs in cytotoxic effect of these drugs.