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Markhoff J.,University of Rostock | Wieding J.,University of Rostock | Weissmann V.,Institute for Polymer Technology | Pasold J.,University of Rostock | And 2 more authors.
Materials | Year: 2015

In the treatment of osseous defects micro-structured three-dimensional materials for bone replacement serve as leading structure for cell migration, proliferation and bone formation. The scaffold design and culture conditions are crucial for the limited diffusion distance of nutrients and oxygen. In static culture, decreased cell activity and irregular distribution occur within the scaffold. Dynamic conditions entail physical stimulation and constant medium perfusion imitating physiological nutrient supply and metabolite disposal. Therefore, we investigated the influence of different scaffold configurations and cultivation methods on human osteoblasts. Cells were seeded on three-dimensional porous Ti-6Al-4V scaffolds manufactured with selective laser melting (SLM) or electron beam melting (EBM) varying in porosity, pore size and basic structure (cubic, diagonal, pyramidal) and cultured under static and dynamic conditions. Cell viability, migration and matrix production were examined via mitochondrial activity assay, fluorescence staining and ELISA. All scaffolds showed an increasing cell activity and matrix production under static conditions over time. Expectations about the dynamic culture were only partially fulfilled, since it enabled proliferation alike the static one and enhanced cell migration. Overall, the SLM manufactured scaffold with the highest porosity, small pore size and pyramidal basic structure proved to be the most suitable structure for cell proliferation and migration. © 2015 by the authors.

Bergemann C.,University of Rostock | Elter P.,Mittelhessen University of Applied Sciences | Lange R.,Electronic Appliances | Weissmann V.,Institute for Polymer Technology | And 3 more authors.
International Journal of Biomaterials | Year: 2015

Studies on bone cell ingrowth into synthetic, porous three-dimensional (3D) implants showed difficulties arising from impaired cellular proliferation and differentiation in the core region of these scaffolds with increasing scaffold volume in vitro. Therefore, we developed an in vitro perfusion cell culture module, which allows the analysis of cells in the interior of scaffolds under different medium flow rates. For each flow rate the cell viability was measured and compared with results from computer simulations that predict the local oxygen supply and shear stress inside the scaffold based on the finite element method. We found that the local cell viability correlates with the local oxygen concentration and the local shear stress. On the one hand the oxygen supply of the cells in the core becomes optimal with a higher perfusion flow. On the other hand shear stress caused by high flow rates impedes cell vitality, especially at the surface of the scaffold. Our results demonstrate that both parameters must be considered to derive an optimal nutrient flow rate. © 2015 Claudia Bergemann et al.

Solodov I.,Institute for Polymer Technology | Doring D.,Institute for Polymer Technology | Busse G.,Institute for Polymer Technology
Strojniski Vestnik/Journal of Mechanical Engineering | Year: 2010

Conventional air-coupled ultrasound (ACU) is a well-established tool for acoustic NDT and material characterization. Its major shortcoming is concerned with a week penetration into solid materials due to a severe impedance mismatch at the air-solid interface. A dramatic rise in acoustic coupling is obtained by using acoustic mode conversion into plate and surface waves in slanted configurations. In our experiments, an increase of the ultrasound amplitude by up to one order of magnitude was observed in various materials (metals, wood, concrete, composite) under phase matching conditions. On this basis, fully air-coupled configurations are developed and applied for non-contact NDT. The methods based on this principle enable precise measurements of fibre directions and quantification of in-plane anisotropy in composites and natural materials, elastic depth profiling, drying of coatings, advanced imaging of cracked defects and delaminations. © 2010 Journal of Mechanical Engineering. All rights reserved.

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