Publikationen

Abstract Pure and Nb-doped TiO2 photocatalysts with highly ordered alternating gyroid architecture and well-controllable mesopore size of 15 nm via co-assembly of a poly(isoprene)-block-poly(styrene)-block-poly(ethylene oxide) block copolymer are synthesized. A combined effort by electron microscopy, X-ray scattering, photoluminescence, X-ray photoelectron spectroscopy, Raman spectroscopy, and density functional theory simulations reveals that the addition of small amounts of Nb results in the substitution of Ti4+ with isolated Nb5+ species that introduces inter-bandgap states, while at high concentrations, Nb prefers to cluster forming shallow trap states within the conduction band minimum of TiO2. The gyroidal photocatalysts are remarkably active toward hydrogen evolution under UV and visible light due to the open 3D network, where large mesopores ensure efficient pore diffusion and high photon harvesting. The gyroids yield unprecedented high evolution rates beyond 1000 µmol h−1 (per 10 mg catalyst), outperforming even the benchmark P25-TiO2 more than fivefold. Under UV light, the Nb-doping reduces the activity due to the introduction of charge recombination centers, while the activity in the visible triple upon incorporation is owed to a more efficient absorption due to inter-bandgap states. This unique pore architecture may further offer hitherto undiscovered optical benefits to photocatalysis, related to chiral and metamaterial-like behavior, which will stimulate further studies focusing on novel light–matter interactions.

Abstract In searching for polymer‐based electrolytes with improved performance for lithium ion and lithium metal batteries, we studied block copolymer electrolytes with high amounts of bis(trifluoromethane)sulfonimide lithium obtained by macromolecular co‐assembly of a poly(isoprene)‐block‐poly(styrene)‐block‐poly(ethylene oxide) and the salt from tetrahydrofuran. Particularly, an ultra‐short poly(ethylene oxide) block of 2100 g mol−1 was applied, giving rise to 2D continuous lamellar microstructures. The macroscopic stability was ensured with major blocks from poly(isoprene) and poly(styrene), which separated the ionic conductive PEO/salt lamellae. Thermal annealing led to high ionic conductivities of 1.4 mS cm−1 at 20 °C with low activation energy and a superior lithium ion transference number of 0.7, accompanied by an improved mechanical stability (storage modulus of up to 107 Pa). With high Li:O ratios >1, we show a viable concept to achieve fast Li+ transport in block copolymers (BCP), decoupled from slow polymer relaxation.

Iron (Fe) is an essential element for plant growth and development. The cultivation of leguminous plants has generated strong interest because of their growth even on poor soils. Calcareous and saline soils with poor mineral availability are wide-spread in Tunisia. In an attempt to select better forage crops adapted to Tunisian soils, we characterized Fe deficiency responses of three different isolates of Hedysarum carnosum, an endemic Tunisian extremophile species growing in native stands in salt and calcareous soil conditions. H. carnosum is a non-model crop. The three isolates, named according to their habitats Karkar, Thelja and Douiret, differed in the expression of Fe deficiency symptoms like morphology, leaf chlorosis with compromised leaf chlorophyll content and photosynthetic capacity and leaf metal contents. Across these parameters Thelja was found to be tolerant, while Karkar and Douiret were susceptible to Fe deficiency stress. The three physiological and molecular indicators of the iron deficiency response in roots, Fe reductase activity, growth medium acidification and induction of the IRON-REGULATED TRANSPORTER1 homolog, indicated that all lines responded to -Fe, however, varied in the strength of the different responses. We conclude that the individual lines have distinct adaptation capacities to react to iron deficiency, presumably involving mechanisms of whole-plant iron homeostasis and internal metal distribution. The Fe deficiency tolerance of Thelja might be linked with adaptation to its natural habitat on calcareous soil.

Over the last two decades, the rapid development and widespread application of nanomaterials has significantly influenced research in various fields, including analytical chemistry and biosensing technologies. In particular, the simple functionalization and tuning of noble metal nanoparticle (NP) surface chemistry resulted in the development of a series of novel biosensing platforms with quick read-out and enhanced capabilities towards specific analyte detection. Moreover, noble metal NPs possess a number of unique properties, viz. high surface-to-volume ratio and excellent spectral, optical, thermal, electrical and catalytic characteristics. This manuscript provides an elaborate review on galvanic noble metal NPs deposited onto semiconductor surfaces, from the preparation stage towards their application in biosensors and gas sensing. Two types of deposition approaches, viz. galvanic displacement/electroless and conventional electroplating, are introduced and compared. Furthermore, the analytical merit of hybrid nanomaterials towards the improvement of sensing abilities is highlighted. Finally, some limitations and challenges related to progress in the development and application of analytical devices based on electroless and electroplated noble metal NPs-semiconductor hybrids (NMNPsHs) in biochemical and environmental sensing are discussed.

In the past decade the significant progress in the cellular stress response was witnessed. Nevertheless, the development of the minimally-invasive and accurate sensing tools for the identification of the increasing number of potentially relevant species in clinical diagnostics, using smaller sample volumes is a major challenge. Herein, the potential of the electroplated nanomaterials towards biomedical sensing and diagnostics is summarized. The key factors affecting the surface functionality, dimensionality, S/N ratio and analytical response of the prepared chips are highlighted. Furthermore, the application of electroplated chips as a fast “read out” platform for profiling of clinical samples was demonstrated.

The development of an in vitro model resembling the alveolar-capillary barrier might be a highly beneficial tool to study lung physiology as well as the immune response of the lung to infection or after exposure to nanoparticles. This study is based on an in vitro alveolar barrier developed on a basement membrane mimic, composed of ultrathin nanofiber meshes generated via electrospinning using bioresorbable poly(ɛ-caprolactone). As cellular components, NCI H441, resembling the alveolar epithelial cells, and ISO-HAS-1, an endothelial cell line, were used to perform bipolar coculture experiments for a total cultivation period of 14 days. In addition to immunohistochemical and immunofluorescent studies, transepithelial electrical resistance (TER) and transport capabilities of the in vitro model system were investigated. Alveolar barrier function could be clearly determined for the postulated bipolar coculture system on the basement membrane mimic, since TER increased during the course of bipolar cultivation. Furthermore, to gain first insights into possible lung inflammatory reactions in vitro, this coculture model was further expanded by a human leukemia monocyte cell line (THP-1). This triple-culture system was able to maintain adequately the barrier properties of the bipolar coculture, thus making this in vitro model consisting of epithelial, endothelial, and immune cells on a basement membrane mimic a promising basis for further studies in tissue engineering.

Abstract Neuro-regeneration after trauma requires growth and reconnection of neurons to reestablish information flow in particular directions across the damaged tissue. To support this process, biomaterials for nerve tissue regeneration need to provide spatial information to adhesion receptors on the cell membrane and to provide directionality to growing neurites. Here, photoactivatable adhesive peptides based on the CASIKVAVSADR laminin peptidomimetic are presented and applied to spatiotemporal control of neuronal growth to biomaterials in vitro. The introduction of a photoremovable group [6-nitroveratryl (NVOC), 3-(4,5-dimethoxy-2-nitrophenyl)butan-2-yl (DMNPB), or 2,2′-((3′-(1-hydroxypropan-2-yl)-4′-nitro-[1,1′-biphenyl]-4-yl)azanediyl)bis(ethan-1-ol) (HANBP)] at the amino terminal group of the K residue temporally inhibited the activity of the peptide. The bioactivity was regained through controlled light exposure. When used in neuronal culture substrates, the peptides allowed light-based control of the attachment and differentiation of neuronal cells. Site-selective irradiation activated adhesion and differentiation cues and guided seeded neurons to grow in predefined patterns. This is the first demonstration of ligand-based light-controlled interaction between neuronal cells and biomaterials.

Strategies for neural tissue repair heavily depend on our ability to temporally reconstruct the natural cellular microenvironment of neural cells. Biomaterials play a fundamental role in this context, as they provide the mechanical support for cells to attach and migrate to the injury site, as well as fundamental signals for differentiation. This review describes how different cellular processes (attachment, proliferation, and (directional) migration and differentiation) have been supported by different material parameters, in vitro and in vivo. Although incipient guidelines for biomaterial design become visible, literature in the field remains rather phenomenological. As in other fields of tissue regeneration, progress will depend on more systematic studies on cell-materials response, better understanding on how cells behave and understand signals in their natural milieu from neurobiology studies, and the translation of this knowledge into engineered microenvironments for clinical use.

The ability to guide the growth of neurites is relevant for reconstructing neural networks and for nerve tissue regeneration. Here, a biofunctional hydrogel that allows light-based directional control of axon growth in situ is presented. The gel is covalently modified with a photoactivatable derivative of the short laminin peptidomimetic IKVAV. This adhesive peptide contains the photoremovable group 2-(4′-amino-4-nitro-[1,1′-biphenyl]-3-yl)propan-1-ol (HANBP) on the Lys rest that inhibits its activity. The modified peptide is highly soluble in water and can be simply conjugated to −COOH containing hydrogels via its terminal −NH2 group. Light exposure allows presentation of the IKVAV adhesive motif on a soft hydrogel at desired concentration and at defined position and time point. The photoactivated gel supports neurite outgrowth in embryonic neural progenitor cells culture and allows site-selective guidance of neurites extension. In situ exposure of cell cultures using a scanning laser allows outgrowth of neurites in desired pathways.

Abstract The integrin α5β1 is overexpressed in colon, breast, ovarian, lung and brain tumours, and has been identified as key component in mechanosensing. In order to study how dynamic changes in α5β1 engagement affect cellular behaviour, photoactivatable derivatives of α5β1-specific ligands are presented in this article. A photoremovable protecting group (PRPG) was introduced into the ligand structure at a relevant position for integrin recognition. The presence of the chromophore temporarily inhibited ligand bioactivity. Light exposure at a cell-compatible dose efficiently cleaved the protecting group and restored functionality. The photoactive ligand had an azide end-functional group for covalent immobilisation onto biomaterials by click chemistry. Selective cell responses (attachment, spreading, migration) to the activated ligand on the surface are achieved by controlled exposure to light, at similar levels to the native ligand. Spatial and temporal control of the cellular response is demonstrated, including the possibility of in situ activation. Photoactivatable integrin-selective ligands in model microenvironments will allow the study of cellular behaviour in response to changes in the activation of individual integrins as consequence of dynamic variations in matrix composition.