Publikationen

We have prepared the first crystalline and 3D periodically ordered mesoporous quaternary semiconductor photocatalyst in an evaporation-induced self-assembly assisted soft-templating process. Using lab synthesized triblock-terpolymer poly(isoprene-b-styrene-b-ethylene oxide) (ISO) a highly ordered 3D interconnected alternating gyroid morphology was achieved exhibiting near and long-range order, as evidenced by small angle X-ray scattering (SAXS) and electron microscopy (TEM/SEM). Moreover, we reveal the formation process on the phase-pure construction of the material's pore-walls with its high crystallinity, which proceeds along a highly stable W5+ compound, by both in situ and ex situ analyses, including X-ray powder diffraction (XRPD), Fourier transform infrared spectroscopy (FTIR) and electron paramagnetic resonance (EPR). The resulting photocatalyst CsTaWO6 with its optimum balance between surface area and ordered mesoporosity ultimately shows superior hydrogen evolution rates over its non-ordered reference in photocatalytic hydrogen production. This work will help to advance new self-assembly preparation pathways towards multi-element multifunctional compounds for different applications, including improved battery and sensor electrode materials.

Manufactured nanomaterials (MNMs) are regarded as key components of innovations in various fields with high potential impact (e.g., energy generation and storage, electronics, photonics, diagnostics, theranostics, or drug delivery agents). Widespread use of MNMs raises concerns about their safety for humans and the environment, possibly limiting the impact of the nanotechnology-based innovation. The development of safe MNMs and nanoproducts has to result in a safe as well as functional material or product. Its safe use, and disposal at the end of its life cycle must be taken into account too. However, not all MNMs are similarly useful for all applications, some might bear a higher hazard potential than others, and use scenarios could lead to different exposure probabilities. To improve both safety and efficacy of nanotechnology, we think that a new proactive approach is necessary, based on pre-regulatory safety assessment and dialogue between stakeholders. On the basis of the work carried out in different European Union (EU) initiatives, developing and integrating MNMs Safe-by-Design and Trusted Environments (NANoREG, ProSafe, and NanoReg2), we present our point of view here. This concept, when fully developed, will allow for cost effective industrial innovation, and an exchange of key information between regulators and innovators. Regulators are thus informed about incoming innovations in good time, supporting a proactive regulatory action. The final goal is to contribute to the nanotechnology governance, having faster, cheaper, effective, and safer nano-products on the market.

The epidermal growth factor receptor (EGFR) is an abundant membrane protein, which is essential for regulating many cellular processes including cell proliferation. In our earlier studies, we observed an activation of the EGFR and subsequent signaling events after the exposure of epithelial cells to carbon nanoparticles. In the current study, we describe molecular mechanisms that allow for discriminating carbon nanoparticle-specific from ligand-dependent receptor activation. Caveolin-1 is a key player that co-localizes with the EGFR upon receptor activation by carbon nanoparticles. This specific process mediated by nanoparticle-induced reactive oxygen species and the accumulation of ceramides in the plasma membrane is not triggered when cells are exposed to non-nano carbon particles or the physiological ligand EGF. The role of caveolae formation was demonstrated by the induction of higher order structures of caveolin-1 and by the inhibition of caveolae formation. Using an in vivo model with genetically modified mice lacking caveolin-1, it was possible to demonstrate that carbon nanoparticles in vivo trigger EGFR downstream signaling cascades via caveolin-1. The identified molecular mechanisms are, therefore, of toxicological relevance for inhaled nanoparticles. However, nanoparticles that are intentionally applied to humans might cause side effects depending on this phenomenon

Anti-reflection and photocatalytic properties are desirable for improving the optical properties of electronic devices. We describe a method of fabrication a single-layer, anti-reflective (AR) thin film with an additional photocatalytic property. The layer is deposited on glass substrates by means of a low-cost dip-coating method using a SiO2-TiO2 solution. A comparative study was undertaken to investigate the effects of TiO2 concentrations on the photocatalytic properties of the film and to determine the optimal balance between transmittance and photocatalysis. The average transmittance increases from T = 90.51% to T = 95.46 ± 0.07% for the wavelengths between 380 and 1200 nm. The structural characterization indicated the formation of thin, porous SiO2-TiO2 films with a roughness of less than 7.5 nm. The quality of the samples was evaluated by a complete test program of the mechanical, chemical and accelerated weathering stability. This results open up new possibilities for cost-effective AR coatings for the glass and solar cell industries.

A vital issue for the manufacture of multifunctional thin films is to synthesize polymer/ceramic hybrid particles. Silicon dioxide (SiO2)/polymer composite particles were synthesized through dispersion copolymerization of methyl methacrylate (MMA) in the presence of SiO2 bullet-like particles, using a “grafting-through” approach. The SiO2 particles were previously modified with the silane-coupling agent 3-(trimethoxysilyl)propyl methacrylate (MPTS). Scanning electron microscopy and transmission electron microscopy analyses confirmed the formation of particles with a rough surface and flower-like morphology. Fourier transform infrared spectroscopy, thermogravimetric analysis, and energy-dispersive X-ray investigations indicated that a nucleation and aggregation process of the growing copolymer MPTS/poly(methyl methacrylate) (PMMA) occurred on the surface of the modified SiO2 particles. As a result, the SiO2 core became embedded in a PMMA shell. The influence of MPTS and the concentration of polyvinylpyrrolidone as a steric stabilizer on the flower-like morphology was demonstrated. Dispersion polymerizations have been proven to be simple and effective ways to synthesize composite particles with a high surface area. By using homogeneous systems (i.e., the monomer was soluble in the reaction solvent), no emulsification process was required, and copious amounts of well-dispersed particles were produced. These characteristics open many application possibilities for the use of the synthesized particles in functional coatings and optical devices, for mechanical reinforcement in polymeric materials, and as biomaterials.

Up to 25,000 people die each year from resistant infections in Europe alone, with increasing incidence. It is estimated that a continued rise in bacterial resistance by 2050 would lead up to 10 million annual deaths worldwide, exceeding the incidence of cancer deaths. Although the design of new antibiotics is still one way to tackle the problem, pharmaceutical companies investigate far less into new drugs than 30 years ago. Incorporation of antibiotics into nanoparticle drug carriers (“nanoantibiotics”) is currently investigated as a promising strategy to make existing antibiotics regain antimicrobial strength and overcome certain types of microbial drug resistance. Many of these synthetic systems enhance the antimicrobial effect of drugs by protecting antibiotics from degradation and reducing their side effects. Nevertheless, they often cannot selectively target pathogenic bacteria and – due to their synthetic origin – may induce side-effects themselves. In this work, we present the characterisation of naturally derived outer membrane vesicles (OMVs) as biocompatible and inherently antibiotic drug carriers. We isolated OMVs from two representative strains of myxobacteria, Cystobacter velatus Cbv34 and Sorangiineae species strain SBSr073, a bacterial order with the ability of lysing other bacterial strains and currently investigated as sources of new secondary metabolites. We investigated the myxobacterias' inherent antibacterial properties after isolation by differential centrifugation and purification by size-exclusion chromatography. OMVs have an average size range of 145–194 nm. We characterised their morphology by electron cryomicroscopy and found that OMVs are biocompatible with epithelial cells and differentiated macrophages. They showed a low endotoxin activity comparable to those of control samples, indicating a low acute inflammatory potential. In addition, OMVs showed inherent stability under different storage conditions, including 4 °C, −20 °C, −80 °C and freeze-drying. OMV uptake in Gram-negative model bacterium Escherichia coli (E. coli) showed similar to better incorporation than liposome controls, indicating the OMVs may interact with model bacteria via membrane fusion. Bacterial uptake correlated with antimicrobial activity of OMVs as measured by growth inhibition of E. coli. OMVs from Cbv34 inhibited growth of E. coli to a comparable extent as the clinically established antibiotic gentamicin. Liquid-chromatography coupled mass spectrometry analyses revealed the presence of cystobactamids in OMVs, inhibitors of bacterial topoisomerase currently studied to treat different Gram-negative and Gram-positive pathogens. This work, may serve as an important basis for further evaluation of OMVs derived from myxobacteria as novel therapeutic delivery systems against bacterial infections.

Granular metal thin films have a strain sensitivity much larger than continuous metal films. Experiments at high strain can help reveal their piezoresistive mechanisms. We deposit films of platinum nanoparticles in boron nitride (Pt:BN) as well as platinum particles in aluminum oxide (Pt:Al2O3) on polyimide foil as strain gauges. Under low strain of 0.1%, the films exhibit enhanced gauge factors, k=23 for Pt:BN and k=6 for Pt:Al2O3. Toward higher strain of 1.5%, Pt:BN shows reproducible and linear resistance-strain curves. In contrast, Pt:Al2O3 exhibits anomalies: The resistance-strain curves are highly nonlinear with an increasing slope before reaching saturation. The differential gauge factor versus strain increases from 9 to 9500, and the return curve shows large hysteresis. With scanning electron microscopy unstrained and in situ strained films are compared, Pt:BN shows no changes, whereas in Pt:Al2O3, large cracks develop. The relatively soft BN is less prone to cracks than the hard and brittle Al2O3. Hence, the gauge factor in Pt:BN can still be attributed to an electron tunneling mechanism, whereas Pt:Al2O3 becomes dominated by the influence of cracks. A model is presented, and we argue that the reproducible opening and closing of these cracks leads to the gigantic resistance increases at high strain.

Messenger RNA (mRNA) has gained remarkable attention as an alternative to DNA-based therapies in biomedical research. A variety of biodegradable nanoparticles (NPs) has been developed including lipid-based and polymer-based systems for mRNA delivery. However, both systems still lack in achieving an efficient transfection rate and a detailed understanding of the mRNA transgene expression kinetics. Therefore, quantitative analysis of the time-dependent translation behavior would provide a better understanding of mRNA’s transient nature and further aid the enhancement of appropriate carriers with the perspective to generate future precision nanomedicines with quick response to treat various diseases.

Low coefficient of thermal expansion (CTE) lattices occupy a unique area of property space. With such a system, it is possible to achieve relatively high stiffness, with opportunities to combine low thermal expansion and with a range of advantageous properties. Possibilities include combinations that are not rivaled by any bulk material, e.g., low CTE and high melting temperature, and low CTE with low conductivity. One design in particular, the UCSB Lattice, has biaxial stiffness very near theoretical upper bounds when the joints are pinned. Bonded lattices are found to inherit the near optimal performance of the parent pin-jointed design. Despite near optimal performance, however, stiffnesses and strengths are limited to a few percent of the relative property of the constituents. The local deformations necessary to accommodate low net CTE are similar to those of auxetic lattices, with similar behavior, having a low, zero, or negative tunable Poisson’s ratio. An investigative framework, including experiments, finite element, and analytical formulas, is used to construct these assessments.