Peterbrough, United Kingdom
Peterbrough, United Kingdom

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Staehlke S.,University of Rostock | Koertge A.,Electronic Appliances | Nebe B.,University of Rostock
Biomaterials | Year: 2015

Detailed insights into the complex cellular behavior at the biomaterial interface are crucial for the improvement of implant surfaces with respect to their acceptance and integration. The cells perceive microtopographical features and, in consequence, rearrange their adhesion structures like the actin cytoskeleton and adaptor proteins. But little is known about whether these altered cellular phenotypes have consequences for intracellular calcium signaling and its dynamics. To elucidate if an artificial, geometrical microtopography influences calcium ion (Ca2+) mobilization in osteoblasts, human MG-63 cells were stained with the calcium dye Fluo 3-acetoxymethyl ester and set on defined silicon-titanium (Ti) arrays with regular pillar structures (P5, 5×5×5μm) and compared with planar Ti. To induce an immediate calcium signal, cells were stimulated with adenosine 5'-triphosphate (ATP). Interestingly, osteoblasts on micropillars expressing a shortened actin cytoskeleton were hampered in their calcium mobilization potential in signal height as well duration. Even the basal level of the intracellular Ca2+ concentration was reduced, which was accompanied by a disturbed fibronectin synthesis. The expression of the voltage-sensitive calcium channels Cav1.2, Cav1.3 (L-type) and Cav3.1, Cav3.2, Cav3.3 (T-type) as well as the signaling proteins phospho-AKT and phospho-GSK3α/β remained unaffected on pillars. The topography-dependent calcium dynamics observed here provide new insights into how topographical cues alter cell functions - via the intracellular Ca2+ signaling. © 2014 Elsevier Ltd.

Koester P.J.,University of Rostock | Tautorat C.,University of Rostock | Beikirch H.,Electronic Appliances | Gimsa J.,University of Rostock | Baumann W.,University of Rostock
Biosensors and Bioelectronics | Year: 2010

This short communication reports on the innovative method of the local micro-invasive needle electroporation (LOMINE) of single adherent cells. The investigation of cellular reactions in living cell cultures represents a fundamental method, e.g. for drug development and environmental monitoring. Existing classical methods for intracellular measurements using, e.g. patch clamp techniques are time-consuming and complex. Present patch-on-chip systems are limited to the investigation of single cells in suspension. Nevertheless, the most part of the cells of the human body is adherently growing. Therefore, we develop a new chip system for the growth of adherent cells with 64 micro-structured needle electrodes as well as 128 dielectrophoretic electrodes, located within a measuring area of 1mm2. With this analytical chip, the intracellular investigation of electro-chemical changes and processes in adherently growing cells will become possible in the near future. Here, we present first intracellular measurements with this chip system. © 2010 Elsevier B.V.

Elter P.,Electronic Appliances | Weihe T.,University of Rostock | Buhler S.,University of Rostock | Gimsa J.,University of Rostock | Beck U.,Electronic Appliances
Colloids and Surfaces B: Biointerfaces | Year: 2012

Using single-cell force spectroscopy, we compared the initial adhesion of L929 fibroblasts to planar and nanostructured silicon substrates as a function of fibronectin concentration. The nanostructures were periodically grooved with a symmetric groove-summit period of 180. nm and a groove depth of 120. nm. Cell adhesion strength to the bare nanostructure was lower (79. ± 13%) than to the planar substrate, which we attribute to reduced contact area. After pre-incubation with a low fibronectin concentration (5μg/ml) the adhesion strengths to both surfaces increased, with adhesion strength on the nanostructure outweighing that of the planar substrate by 133% ± 14%. At a high fibronectin concentration (25μg/ml) the adhesion strengths on both surfaces further increased and showed wide variations. In parallel, the nanostructure lost its clear advantage over the planar substrate. Our results demonstrate that cell adhesion is influenced by substrate topography and fibronectin, which mediate the interplay between specific interactions, non-specific interactions, and cell mechanics. Two parallel processes govern the initial adhesion strength: the detachment of the cell body from the substrate and the extraction of tethers from the cell membrane. The duration of the latter process is determined by tether lifetimes, and is a major contributor to the overall work required for cell-substrate detachment. Cell body detachment and tether lifetimes are affected by surface topography and may be strongly modulated by the presence of adsorbed proteins, whereas the tether extraction forces remained unchanged by these factors. © 2012 Elsevier B.V..

Zietz C.,University of Rostock | Bergschmidt P.,University of Rostock | Lange R.,Electronic Appliances | Mittelmeier W.,University of Rostock | Bader R.,University of Rostock
International Journal of Artificial Organs | Year: 2013

Aim: Total knee arthroplasties have reached a high grade of quality and safety, but most often fail because of aseptic implant loosening caused by polyethylene wear debris. Wear is generated at the articulating surfaces, e.g. caused by third-body particles. The objective of this experimental study was to determine the wear of tibial polyethylene inserts combined with metallic and ceramic femoral com-ponents under third-body wear conditions initiated by bone cement particles. Methods and Materials: Wear testing using a cemented unconstrained bicondylar knee endoprosthe-sis (Multigen Plus CR knee system) was performed in a knee wear simulator. Tibial polyethylene inserts were combined with the identical femoral component design, but made of two different materials (cobalt-chromium and ceramic). Bone cement debris including zirconium oxide particles was added every 500,000 cycles between the articulating surfaces. After 5 million load cycles, the amount of wear was determined gravimetrically and compared with results from standard wear test conditions. The surfaces of tibial inserts were also analyzed. Results: The average gravimetrical wear of the tibial polyethylene inserts in combination with cobalt-chromium and ceramic femoral components under third-body wear conditions amounted to 31.88 ± 4.53 mg and 13.06 ± 1.88 mg after 5 million cycles, respectively, and was higher than under standard wear test conditions in both cases. Conclusions: The wear simulator test demonstrates that wear of polyethylene inserts under third-body wear conditions, in combination with ceramic femoral components, was significantly lower than with metallic femoral components. © 2013 Wichtig Editore.

Elter P.,Electronic Appliances | Lange R.,Electronic Appliances | Beck U.,Electronic Appliances
Langmuir | Year: 2011

Recently, biomaterials research has focused on developing functional implant surfaces with well-defined topographic nanostructures in order to influence protein adsorption and cellular behavior. To enhance our understanding of how proteins interact with such surfaces, we analyze the adsorption of lysozyme on an oppositely charged nanostructure using a computer simulation. We present an algorithm that combines simulated Brownian dynamics with numerical field calculation methods to predict the preferred adsorption sites for arbitrarily shaped substrates. Either proteins can be immobilized at their initial adsorption sites or surface diffusion can be considered. Interactions are analyzed on the basis of Derjaguin-Landau-Verway-Overbeek (DLVO) theory, including electrostatic and London dispersion forces, and numerical solutions are derived using the Poisson-Boltzmann and Hamaker equations. Our calculations show that for a grooved nanostructure (i.e., groove and plateau width 8 nm, height 4 nm), proteins first contact the substrate primarily near convex edges because of better geometric accessibility and increased electric field strengths. Subsequently, molecules migrate by surface diffusion into grooves and concave corners, where short-range dispersion interactions are maximized. In equilibrium, this mechanism leads to an increased surface protein concentration in the grooves, demonstrating that the total amount of protein per surface area can be increased if substrates have concave nanostructures. © 2011 American Chemical Society.

Elter P.,Electronic Appliances | Lange R.,Electronic Appliances | Beck U.,Electronic Appliances
Colloids and Surfaces B: Biointerfaces | Year: 2012

Atomic force microscopy (AFM)-based force spectroscopy was used to analyze the adsorption of bovine plasma fibronectin on periodically grooved nanostructures (groove/summit width: 90. nm; depth: 120. nm). We present a simple procedure that allowed us to directly compare the local protein density and conformation for the convex summits, the concave grooves and planar reference regions of the substrate. At a bulk fibronectin concentration of 5 μg/ml, the amount of adsorbed protein per surface area was significantly higher in all regions of the nanostructure than on the planar reference, and fibronectin tended to adsorb preferentially in the concave grooves. The increased surface concentration resulted in an additional stabilization of the molecules by protein-protein interactions and a lower degree of denaturized fibronectin in the nanostructured regions. The stabilization was less pronounced in concave regions, indicating that the increased contact area in the grooves counteracted the stabilization by increased protein-substrate interactions and must be compensated for by additional protein-protein interactions. Less favorable sites were occupied at higher bulk fibronectin concentrations (25 μg/ml, 100 μg/ml), and a high degree of native folded fibronectin was observed in both the nanostructured and planar regions. Our results demonstrate that the amount of adsorbed fibronectin per surface area can be increased if a substrate is provided with a topographic nanostructure. Our results also show that the local conformational state of fibronectin is determined by the locally different interplay of protein-protein and protein-substrate interactions. © 2011 Elsevier B.V.

Gassmann S.,Electronic Appliances | Pagel L.,Electronic Appliances
IECON Proceedings (Industrial Electronics Conference) | Year: 2011

A pressure relief valve with excellent properties and feasible in a simple structure is presented here. The structure is flat and is optimized for the usage in the fluidic printed circuit board technology. The here presented pressure relief valve is alike conventional solutions with an orifice closed with a sealing element. As a force generating element permanent magnets are proposed here. This leads to excellent opening and closing behavior, self alignment and to a very simple structure. The here described pressure relief valve works in a range of 300mBar, but a wide range of set pressures can be achieved by the variation of design properties. © 2011 IEEE.

Bechtold T.,Electronic Appliances | Hohlfeld D.,Electronic Appliances
2016 17th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems, EuroSimE 2016 | Year: 2016

This work presents a general simulation approach for all relevant physical effects in electro-optical circuit boards. Such printed circuit boards integrate electrical components and connections together with optical wave-guides as signal lines for applications in data transmission and sensing. The proposed modelling approach includes a calculation of heat distribution based on convective cooling and the thermally induced mechanical stress. We also present results on mode shapes within straight and uniformly curved waveguides as well as a consideration of ray tracing. © 2016 IEEE.

Novikov A.,Electronic Appliances | Nowottnick M.,Electronic Appliances
Physica Status Solidi (A) Applications and Materials Science | Year: 2012

The properties of nanoscaled layers of pure tin have been studied. The layers were produced by sputtering in different thicknesses between 10 and 100 nm. The surface topography and the influence of process parameters on the sputtering rate were characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM) methods. To avoid oxidation carbon and silicon nitride protective layers were sputtered in the same process chamber. The function of this coating was investigated by X-ray diffraction (XRD). The crystallographic structure of tin layer under silicon nitride was measured directly after sputtering, melting and cooling processes. The crystalline tin film after cooling down and the absence of tin oxide peaks were used as indicators for impermeability of oxygen. For investigation of phase change the method of chip differential calorimetry (DSC) was used. The samples were prepared as standalone samples for reuse of DSC-chips and also sputtered directly on the DSC chip for single use. The prepared samples with one tin layer and multilayer of tin scaled down to 10 nm were investigated with this method. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electronic Appliances | Date: 2015-05-27

Grills cooking appliances; cooling installations for liquids; water sterilizers; friction lighters for igniting gas.

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