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Fibrinogen nanofibers are very attractive biomaterials to mimic the native blood clot architecture. Previously, we reported the self-assembly of fibrinogen nanofibers in the presence of monovalent salts and have now studied how divalent salts influence fibrinogen precipitation. Although the secondary fibrinogen structure was significantly altered with divalent metal ions, morphological analysis revealed exclusively smooth fibrinogen precipitates. In situ monitoring of the surface roughness facilitated predicting the tendency of various salts to form fibrinogen fibers or smooth films. Analysis of the chemical composition revealed that divalent salts were removed from smooth fibrinogen films upon rinsing while monovalent Na+ species were still present in fibrinogen fibers. Therefore, we assume that the decisive factor controlling the morphology of fibrinogen precipitates is direct ion-protein contact, which requires disruption of the ion-surrounding hydration shells. We conclude that in fibrinogen aggregates, this mechanism is effective only for monovalent ions, whereas divalent ions are limited to indirect fibrinogen adsorption.

Die Elektrifizierung von Fahrzeugen stellt die OEMs und deren Zulieferer vor komplexe Herausforderungen. Dabei müssen auch Materialien, die in anderen Industrien bereits als Stand der Technik bekannt sind, für den neuen Anwendungsfall adaptiert werden. Ein Beispiel hierfür sind Wärmeleitpasten als Gapfiller, die nun für wärmeleitende Verbindungen zur Batteriekühlung in Serien-Elektrofahrzeugen verwendet werden sollen. Hierbei spielen Eigenschaften, wie die Dichte, die Viskosität sowie die damit einhergehende Verarbeitbarkeit, neben den Kosten eine entscheidende Rolle.

In this study, electron beam (EB) curable acrylates are investigated for their use as planarization layers. Planarization layers can be used in multilayer thin film encapsulations for all kinds of flexible electronics, such as organic light emitting diodes (OLED), organic photovoltaics (OPV) and printed switching circuits, antennas, and sensors. Planarization layers cover particles and defects of the substrate and thus a plain smooth surface is created for optimized growing conditions of thin films, optimizing encapsulation properties. The thin film encapsulation prevents organic electronics from degradation due to invasive oxygen and water vapor. Several commercially available monomers and oligomers with different molar mass and number of reactive double bonds are investigated. The acrylates are deposited on polyethylene terephthalate (PET) web and glass substrates and cured by EB. The surfaces are analyzed using white light interferometry (WLI) and scanning electron microscopy (SEM). Density measurements and nanoindentation are also carried out to get information about the volume shrinkage and the elastic modulus. The correlation between chemical properties, degree of crosslinking, volume shrinkage and surface roughness are investigated. This work demonstrates that electron beam curing of acrylates is a promising method to generate smooth surfaces. It presents an increasing degree of crosslinking and volume shrinkage with decreasing molecular weight between crosslinks. Also, for comparable molecular weight between crosslinks, the volume shrinkage is higher for acrylates forming thermoplastics than for elastomers or duromers.

As a key player in blood coagulation and tissue repair, fibrinogen has gained increasing attention to develop nanofibrous biomaterial scaffolds for wound healing. Current techniques to prepare protein nanofibers, like electrospinning or extrusion, are known to induce lasting changes in the protein conformation. Often, such secondary changes are associated with amyloid transitions, which can evoke unwanted disease mechanisms. Starting from our recently introduced technique to self-assemble fibrinogen scaffolds in physiological salt buffers, we here investigated the morphology and secondary structure of our novel fibrinogen nanofibers. Aiming at optimum self-assembly conditions for wound healing scaffolds, we studied the influence of fibrinogen concentration and pH on the protein conformation. Using circular dichroism and Fourier-transform infrared spectroscopy, we observed partial transitions from α-helical structures to β-strands upon fiber formation. Interestingly, a staining with thioflavin T revealed that this conformational transition was not associated with any amyloid formation. Toward novel scaffolds for wound healing, which are stable in aqueous environment, we also introduced cross-linking of fibrinogen scaffolds in formaldehyde vapor. This treatment allowed us to maintain the nanofibrous morphology while the conformation of fibrinogen nanofibers was redeveloped toward a more native state after rehydration. Altogether, self-assembled fibrinogen scaffolds are excellent candidates for novel wound healing systems since their multiscale structures can be well controlled without inducing any pathogenic amyloid transitions.

Peptides and proteins have been largely neglected in the analysis of insect tarsal adhesives. After extraction of the protein fraction of the tarsal secretion of the desert locust, Schistocerca gregaria, and Madagascar hissing cockroach, Gromphadorhina portentosa, we combined Fourier transform infrared spectroscopy (FTIR), sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS) analyses for protein mass detection. In both these insects, SDS-PAGE analysis revealed several protein bands ranging from 8-190 kDa in both the tarsal secretion and the tibia control sample. Two (S. gregaria) and one (G. portentosa) protein bands exclusively occurred in the tarsal secretion and can be considered to belong to peptides and proteins specific to this secretion. MALDI-TOF analyses revealed 83 different proteins/peptides of 1-7 kDa in S. gregaria, and 48 of 1-11 kDa in G. portentosa. 59 (S. gregaria) and 27 (G. portentosa) proteins exclusively occurred in the tarsal secretion. In G. portentosa, a characteristic series of signal peaks occurred in the range of c. 10-12 kDa, each peak being approximately 160 Da apart. Such a pattern is indicative of proteins modified by glycosylation. Our approach demonstrates that extensive sampling involving considerable time and manpower to sample the adhesive fluid directly from the tarsi opens up a perspective for extracting peptides and proteins in sufficient quantities. This makes them accessible to the field of proteomics and thus to elucidate their possible function in the adhesive process.

Structural parts made of fiber reinforced plastics do not play a predominant role in automobile mass production due to the costs associated with storage condition, low level of automation, long processing times and safety and health regulations. The idea was to develop a holistic approach which can solve the problems with understanding the whole process chain from molecule to the finished product and integration in common technical infrastructure. A promising strategy was to create a matrix resin which combines easy processing of thermoplastics with superior mechanical properties of thermosets. The new matrix can pre-applied on all type of fibers. The resulting tack-free prepreg has a long shelf life at room temperature in consequence of phase separation of matrix raw materials which can be eliminated by raising the temperature. The resulting material has high reactivity and can be cured to a thermoset within a few minutes. Individual specification of the material like glass temperature, cure rate and toughness can be adjusted.

Die Werkstoffexoten Holzschaum und Metallschwamm besitzen interessante Eigenschaften, die von denen gebräuchlicher Werkstoffe abweichen. Die Fraunhofer-Institute WKI, IFAM und IWU erzeugen durch das Verschmelzen beider Werkstoffe einen neuartigen Leichtbauverbund, der in Herstellung und Nutzung nachhaltig ist.

Wood foam and metal sponges are exotic materials with interesting properties that deviate from those of conventional materials. By merging both materials, the Fraunhofer Institutes WKI, IFAM and IWU generate a novel, lightweight composite that is sustainable both in its production and in its use.

The goose barnacle Dosima fascicularis produces an excessive amount of adhesive (cement), which has a double function, being used for attachment to various substrata and also as a float (buoy). This paper focuses on the chemical composition of the cement, which has a water content of 92%. Scanning electron microscopy with EDX was used to measure the organic elements C, O and N in the foam-like cement. Vibrational spectroscopy (FTIR, Raman) provided further information about the overall secondary structure, which tended towards a β-sheet. Disulphide bonds could not be detected by Raman spectroscopy. The cystine, methionine, histidine and tryptophan contents were each below 1% in the cement. Analyses of the cement revealed a protein content of 84% and a total carbohydrate content of 1.5% in the dry cement. The amino acid composition, 1D/2D-PAGE and MS/MS sequence analysis revealed a de novo set of peptides/proteins with low homologies with other proteins such as the barnacle cement proteins, largely with an acidic pI between 3.5 and 6.0. The biochemical composition of the cement of D. fascicularis is similar to that of other barnacles, but it shows interesting variations.

The onycophoran Epiperipatus hilkae secrets a sticky slime that solidifies almost immediately upon contact with air and under high humidy environmental condition forming a glassy like material. The general adhesive biochemical composition, the releasing and hardening mechanism have been partially described. In this study, the structural characterization of the extracellular microstructures and nanostructures forming the solid adhesive of the secretion from Epiperipatus hilkae velvet worm is presented. The adhesive secretion is formed by macro-threads, which, in their solid state, are composed of globular particles approximately 700 nm in diameter that are distributed homogeneously throughout the matrix surface, and nanoparticles approximately 70 nm in diameter that self-assemble forming fiber-like structures. Nanoparticles with non roundish forms are also observed. These 70 nm particles could be associated to proteins that form high density coverage films with low roughness; suggesting the formation of two dimensional ordered films. A crystalline and an amorphous phase composes the solidified secretion. The glassy or viscoelastic properties depend on the time in contact with air before being adhered to a solid surface and/or the mechanical stimulus; suggesting a key role of the drying on the hardening process.

For the use as RFID antennas conductive adhesives were developed and investigated which are UV curable and could be applied with printing methods like offset printing or flexography. Further investigated aspects of the materials have been the range of the distance between emitter and receiver. The resulting formulations which are based on acrylates filled with silver pigments for the conductivity allow to cure layers with a thickness of up to 50 μm with a maximal volume resistance of 1.6 x 10 -5 Ω/cm.

Cement of the barnacle species, Balanus crenatus, was isolated and separated by SDS-PAGE. Reductive and nonreductive conditions yielded the same result of six major proteins (in the range up to 100 kDa) occurring as two triplets. A third triplet of lower molecular mass was faintly visible. The presence of a reductive agent had only little impact on the solubility of B. crenatus cement. The strong effect of the denaturing conditions (the presence of SDS and the incubation at elevated temperature) on the solubility of the barnacle cement and the absence of disulfide signals in Raman spectra suggest a complex structure of the barnacle cement noncovalently bound. It can be speculated that this protein complex in its quaternary structure is formed by small subunits and is equivalent to the globular cement structures previously detected.

Cellulose as natural and non-toxic material is very interesting for biological applications. Its poor solubility in organic solvents can be improved by introduction of long alkyl chains. Phosphate-substituted cellulose derivatives form ultra-thin layers on several metal surfaces [1, 2]. The layers were applied on the surfaces via dip coating from dilute solutions and characterised by contact angle measurements. Initial corrosion tests were performed. These polymers were applied as adhesion promoters for steel-, titanium- and hydroxy apatite surfaces. Medical implants were pre-treated by UV irradiation, coated with the cellulose derivatives and activated by hot water treatment. The adhesion of the implants surpassed that of conventionally used PMMA systems.

Different mono- and bifunctional amine ligands have been used to stabilize Pt NPs for catalytic H2 gas sensing. Depending on the chemical structure and properties of the ligand, the catalysts show different overall sensor performances, activation periods, and long-term stabilities. These sensor characteristics are put into relation with chemical processes like cleaning of the surface, degradation processes of the ligands and nanoparticle (NP) sintering. It has been found that during activation free adsorption sites are formed primarily due to desorption of synthetic residues. Furthermore, partial desorption of the ligands followed by their degradation may occur. For monoamines the latter process results in destabilization of the NPs followed by catalyst deactivation through particle sintering. The use of bifunctional ligands that link individual NPs shows significantly enhanced stabilities which can be related to the reduction of the ligand desorption rates and degradation. Besides the functionality of the ligands it was observed that the chemical nature of their hydrocarbon skeleton affects the catalyst stability: aromatic substructures remain intact upon H2 oxidation, while alkyl fragments undergo oxidation and decomposition. The advantages of bifunctionality and an aromatic hydrocarbon skeleton can be combined by the use of para-phenylenediamine (PDA) as a linking ligand. Networks formed by this ligand were indeed found to be stable under the applied catalytic conditions for more than 24 h.

In recent works the self-assembly process has been investigated to replace the present chromating procedure on reactive metals like aluminium and the improve the lacquer adhesion and corrosion inhibition. These self-assembling layers were formed of small bifunctional organic molecules with phosphate or phosphonic acid groups attached to the metal substrate. The idea of this work was to apply these results and techniques to cellulose derivatives on implant metals. The formation of ultra-thin layers of phosphorylated cellulose derivatives has been reported previously. These ultrathin layers were built on metal substrates like aluminium, titanium or steel for adhesion promotion and corrosion inhibition. Hydroxypropyl-2-phosphatepropyl cellulose was synthesised for adhesion on hydrophilic metallic surface. Hydroxypropyl-2-cinnamoylpropylester cellulose was prepared in order to crosslink the adsorbed layers. The layers were formed on metal surfaces via dip coating from dilute solutions and characterised by means of contact angle measurements, SEM investigations and FT-IR spectroscopy. Initial corrosion tests were performed.

New hairy-rod like cellulose polymer layers were developed as a model system for corrosion protection and adhesion promotion in medical technology. Using the Langmuir-Blodgett technique a mixture of a cinnemate containing and a phosphate containing cellulose were transferred on titanium and steel surfaces. The cinnemate can be crosslinked by ultraviolet light (UV). Differences in the formation of multilayers were found and analyzed by atomic force microscopy, scanning auger microscopy and ellipsometric measurements. Phosphate cellulose forms homogenous layers at all substrate surfaces. With increasing layer thickness a mixture with low phosphate content becomes homogenous, too. Only mixtures with high content of phosphate keep imperfections with increasing layer thickness. For the pure component cinnemate cellulose the imperfections arise only in the case of titanium surfaces.

A new coupling strategy for biomacromolecules with (3-mercaptopropyl)trimethoxysilane (3MPTMS) and 11-(triethoxysilyl)undecanal (TESU) on gold surfaces is. This immobilization protocol was utilized for the enzyme horseradish peroxidase (HRP). To study the reactions and resulting structures, PM-IRRAS measurements were performed. PM-IRRAS shows there is structure preservation of the HRP when the new coupling strategy is used in contrast to non-specific adsorption on gold. The biological activity of adsorbed and immobilized HRP was measured by the enzyme catalyzed oxidation of 3,5,3',5'-tetramethylbenzidine. Covalent immobilization of HRP on TESU film compared to physisorption of HRP shows higher enzyme activity on gold surfaces, confirming the structural preservation detected by PM-IRRAS.

Vibrational circular dichroism (VCD) spectra of anisotropic thin solid samples are often superimposed with large contributions of linear birefringence and linear dichroism. In this study a theoretical approach is given on how to extract the true VCD spectrum out of such superimposed spectra. To verify this approach, the VCD spectra of achiral polymer films were examined. The polymers are supposed to give a zero line as VCD spectrum after eliminating the linear contributions. Applying our approach, in which four VCD spectra in different but selected sample orientations are recorded, and calculating their average, leads to the expected result, i.e., a zero line for achiral polymers. The advantage of this method for the elimination of artifacts from solid-state VCD spectra is that no further measurements are required (e.g., linear dichroism measurements or the determination of the orientation with the maximum anisotropy).

Common available conductive adhesives are filled with about 70-90 weight percent of silver particles. There is the technical need to lower the filler content for decreasing the viscosity and the pressure to finally decrease the costs for the highly expensive silver. Our approach to decrease the silver content with at the same time similar conductivity was to use nano-sized silver particles with different modified surfaces to obtain self-organized distribution of the silver particles in the liquid adhesive film followed by conventional curing techniques like temperature or UV curing. Through the self-organization, a bridging of the particles should be achieved which gives a similar conductivity as in highly filled commercial adhesives which follows percolation theory. The influence of the surface modification on the strength of the interaction between differently modified silver particles and the distribution in the liquid adhesive was simulated with Dissipative Particle Dynamics (DPD). Surface modification was verified with surface enhanced Raman spectroscopy (SERS) and X-ray photoelectron spectroscopy (XPS). The distribution of the silver particles in the cured adhesive film was investigated with scanning electron microscopy (SEM).