Publikationen

SnO2 nanostructures were directly synthesised by chemical vapour transport on different substrates in a horizontal furnace. The influence of substrate on the morphology of these nanostructures was investigated by changing the substrate type, coating, and temperature. The SnO2 nanowires and nanorods were one dimensional (1D) structures with widths and lengths of 50-200 nm and several micrometers respectively. Scanning electron microscope (SEM) images show formation of short nanorods with lengths of less than 1 µm on indium-tin oxide (ITO) substrates. The effect of substrate temperature on growth was studied. SnO2 nanowires were obtained using silicon substrate, and the effect of Au coating on the size and morphology of these structures was proposed. By coating the Si wafer with a thin layer of Au, the size of the nanostructure was reduced and the length increased. The differences in size and morphology are shown by transmission electron microscopy (TEM). X-ray diffraction (XRD) spectra show tetragonal structures for both substrates.

In the mononuclear title compound, [Tb(C13H9OS3)3-(C4H8O)3]·C4H8O, the lanthanide cation is located on a threefold rotation axis and is surrounded by electron-rich ligands in an approximately octahedral geometry. One of the thienyl groups and the bound THF are disordered with 0.5:0.5 occupancy. The free THF is disordered around the threefold axis.

Dense and uniform particle films are deposited using a robust version of the convective particle assembly process. We analyze how the shape of the gas-liquid interface and the three-phase contact line govern the stability of convective deposition and, thus, the achievable quality of films. Interference microscopy indicates that a highly curved meniscus cannot compensate for the ubiquitous perturbation during deposition. A moderately curved meniscus provides flexibility to compensate and localize perturbation and enables reliable homogeneous deposition. We analyze which setup geometry and meniscus velocity yield appropriate meniscus shapes. The quality of the resulting films is analyzed and compared to the deposition conditions. Uniform films over areas beyond the centimeter range are accessible using the optimized process, which is suitable for functional particle coatings and templates for microstructured materials.

The ability of nanoparticles to penetrate the stratum corneum was the focus of several studies. Yet, there are controversial issues available for particle penetration due to different experimental setups. Meanwhile, there is little known about the mechanism and determinants of their penetration. In this paper the penetration of four model gold nanoparticles of diameter 6 and 15 nm, differing in surface polarity and the nature of the vehicle, through human skin was studied using multiphoton microscopy. This is in an attempt to profoundly investigate the parameters governing particle penetration through human skin. Our results imply that nanoparticles at this size range permeate the stratum corneum in a similar manner to drug molecules, mainly through the intercellular pathways. However, due to their particulate nature, permeation is also dependent on the complex microstructure of the stratum corneum with its tortuous aqueous and lipidic channels, as shown from our experiments performed using skin of different grades of barrier integrity. The vehicle (toluene-versus-water) had a minimal effect on skin penetration of gold nanoparticles. Other considerations in setting up a penetration experiment for nanoparticles were also studied. The results obtained are important for designing a new transdermal carrier and for a basic understanding of skin-nanoparticle interaction.

Interaction of nanoparticles with the skin barrier is a recent area of research that draws a lot of attention from the researchers. However, monitoring nanoparticles in or through the skin is mainly based on qualitative microscopical techniques. Yet, a quantitative approach is required for a better basic understanding. In response, a combined "multiphoton-pixel analysis" method was developed in this study for semiquantitation of gold nanoparticles penetration into different skin layers. The developed approach provides a useful tool for future studies focusing on skin penetration of nanoparticles for the aim of health risk assessment or for the design of topical and transdermal drug delivery systems.

Purpose: To measure penetration and metabolic effects of ion-stabilized, polar, 15 nm gold nanoparticles in aqueous solution (AuNP-Aq) and sterically stabilized, non-polar, 6 nm gold nanoparticles in toluene (AuNP-TOL) on excised human skin. Methods: Gold nanoparticles were characterized with dynamic light scattering and transmission electron microscopy (TEM). Skin penetration studies were done on frozen or fresh excised skin using static Franz diffusion cells. Viable treated skin was assessed by dermoscopy, reflectance confocal microscopy (RCM), multiphoton tomography (MPT) with fluorescence lifetime imaging microscopy (FLIM), and TEM. Results: Dermoscopy and RCM showed large aggregates in the furrows of AuNP-Aq-treated skin. Treatment of thawed and viable skin only showed enhanced permeability to nanoparticles in the AuNP-TOL group with MPT and FLIM imaging to stratum spinosum of epidermis. TEM analysis revealed gold nanoparticles within AuNP-treated stratum corneum. FLIM analysis of NAD(P)H showed a significant decrease in total NAD(P)H in all toluene-treated groups. Conclusions: Gold nanoparticles, 15 nm, in aqueous solution aggregated on the skin surface. Toluene treatment eliminated skin metabolism; skin treated with toluene/gold nanoparticles (6 nm) for 24 h, but not at 4 h, showed increased nanoparticle permeability. These results are of value to nanotoxicology.

Interactive materials that specifically respond to environmental stimuli hold high promise as energy-autonomous sensors and actuators in biomedicine, analytics or microsystems engineering. However, the implementation of materials specifically responsive to a given small molecule has so far been hampered by a lack of generically applicable stimulus sensors. In this study, a novel and likely general strategy for the synthesis of biohybrid materials with desired stimulus specificity is established. The strategy is based on allosterically regulated DNA-binding proteins, a conserved protein family that has evolved in prokaryotes to sense and respond to most diverse molecules in order to enable bacterial survival in a changing environment. The novel hydrogel design concept is demonstrated with the example of single-chain TetR, a protein that binds the tetO DNA motif and dissociates thereof in the presence of the antibiotic tetracycline. Therefore, linear polyacrylamide is crosslinked via the TetR/tetO interaction to a biohybrid material that can subsequently be dissolved by tetracycline in a dose-dependent manner. This drug-induced dissolution is applied for the adjustable release of the cytokine interleukin 4 in a tetracycline-dependent manner. The design concept developed in this study might serve as a blueprint for the synthesis of biohybrid materials responsive to drugs, metabolites or toxins by replacing TetR/tetO with another protein/DNA pair showing the desired stimulus specificity. A biohybrid hydrogel is synthesized for the drug-inducible release of biopharmaceuticals. The hydrogel consists of linear polyacrylamide crosslinked by the interaction of the tetracycline repressor scTetR with its target DNA sequence tetO. Addition of tetracycline dissociates the protein-DNA interaction and triggers the release of a previously embedded payload protein. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Inducible expression systems represent the founding technology for the emergence of synthetic biology in mammalian cells. The core molecules in these systems are bacterial regulator proteins that bind to or dissociate from a cognate DNA operator sequence in response to an exogenous stimulus like a small-molecule inducer. In this chapter, we describe a generic protocol of how bacterial regulator proteins can be applied to the design, construction, and optimization of an inducible expression system in mammalian cells. By choosing regulator proteins with an appropriate small-molecule inducer, this protocol provides a straightforward approach for establishing biosensors, cell-to-cell communication systems, or tools to control gene expression in vivo. © 2011 Elsevier Inc. All rights reserved.

The rapid development of synthetic biology is a paradigm of how the molecular diversity of naturally occurring gene control components can be used to design synthetic control devices and gene networks that provide precisely programmed transgene expression dynamics in space and time. Here we offer an overview on recent advances in the modular design of trigger-inducible mammalian expression devices that are either responsive by exogenous stimuli such as chemicals and physical cues or controlled by endogenous metabolites driving prosthetic circuits to treat metabolic disorders in a self-sufficient manner. Compatible genetic switches can also be assembled to synthetic gene networks that show highly complex expression dynamics such as temporally resolved band-detect functions or oscillating transgene expression profiles. The ongoing metagenomic discovery and characterization of the unexplored sequence space is constantly increasing the molecular diversity in fundamental control components that fuels the further development of synthetic biology. © 2011 Elsevier Ltd.