Biomineralisation von Knochengewebe unter dem Einfluss von Metallionen

Bei der Implantation eines metallischen Hüftprothesenschafts in den Oberschenkelknochen kommt es zum Austritt von Metallionen in das umliegende Gewebe. Der Vorgang der mit der Osteointegration einhergehenden Knochenneubildung erfolgt also in einem metallionenhaltigen Milieu. In der vorliegenden Arbeit wurde der Einfluss der Metalle Titan, Vanadium, Kobalt, Chrom und Aluminium auf die Mineralisation des wichtigen Knochenminerals Hydroxylapatit untersucht, die in einem vereinfachten chemischen Modellsystem simuliert wurde. Zusätzliche Versuche mit einem komplexeren, den physiologischen Bedingungen angenäherten Modellsystem dienten der Verifizierung der erhaltenen Resultate. Die mit verschiedenen Metallzusätzen hergestellten Apatite wurden mit Hilfe der Röntgendiffraktometrie hinsichtlich ihrer kristallographischen Eigenschaften und ihrer Phasenzusammensetzung untersucht. Dabei konnte die durch Metallionen induzierte Bildung zusätzlicher Kalziumphosphate und die Inkorporation von Metallionen in die apatitische Phase belegt werden

Nanotopographical Coatings Induce an Early Phenotype-Specific Response of Primary Material-Resident M1 and M2 Macrophages

Implants elicit an immunological response after implantation that results in the worst case in a complete implant rejection. This biomaterial-induced inflammation is modulated by macrophages and can be influenced by nanotopographical surface structures such as titania nanotubes or fractal titanium nitride (TiN) surfaces. However, their specific impact on a distinct macrophage phenotype has not been identified. By using two different levels of nanostructures and smooth samples as controls, the influence of tubular TiO2 and fractal TiN nanostructures on primary human macrophages with M1 or M2-phenotype was investigated. Therefore, nanotopographical coatings were either, directly generated by physical vapor deposition (PVD) or by electrochemical anodization of titanium PVD coatings. The cellular response of macrophages was quantitatively assessed to demonstrate a difference in biocompatibility of nanotubes in respect to human M1 and M2-macrophages. Depending on the tube diameter of the nanotubular surfaces, low cell numbers and impaired cellular activity, was detected for M2-macrophages, whereas the impact of nanotubes on M1-polarized macrophages was negligible. Importantly, we could confirm this phenotypic response on the fractal TiN surfaces. The results indicate that the investigated topographies specifically impact the macrophage M2-subtype that modulates the formation of the fibrotic capsule and the long-term response to an implant

Additive manufacturing of scaffolds with sub-micron filaments via melt electrospinning writing

The aim of this study was to explore the lower resolution limits of an electrohydrodynamic process combined with direct writing technology of polymer melts. Termed melt electrospinning writing, filaments are deposited layer-by-layer to produce discrete three-dimensional scaffolds for in vitro research. Through optimization of the parameters (flow rate, spinneret diameter, voltage, collector distance) for poly-ε-caprolactone, we could direct-write coherent scaffolds with ultrafine filaments, the smallest being 817 ± 165 nm. These low diameter filaments were deposited to form box-structures with a periodicity of 100.6 ± 5.1 μmand a height of 80 μm(50 stacked filaments; 100 overlap at intersections).Wealso observed oriented crystalline regions within such ultrafine filaments after annealing at 55 °C. The scaffolds were printed upon NCO-sP(EO-stat-PO)-coated glass slide surfaces and withstood frequent liquid exchanges with negligible scaffold detachment for at least 10 days in vitro

Degradation of 3D-printed magnesium phosphate ceramics in vitro and a prognosis on their bone regeneration potential

Regenerative bone implants promote new bone formation and ideally degrade simultaneously to osteogenesis. Although clinically established calcium phosphate bone grafts provide excellent osseointegration and osteoconductive efficacy, they are limited in terms of bioresorption. Magnesium phosphate (MP) based ceramics are a promising alternative, because they are biocompatible, mechanically extremely stable, and degrade much faster than calcium phosphates under physiological conditions. Bioresorption of an implant material can include both chemical dissolution as well as cellular resorption. We investigated the bioresorption of 3D powder printed struvite and newberyite based MP ceramics in vitro by a direct human osteoclast culture approach. The osteoclast response and cellular resorption was evaluated by means of fluorescence and TRAP staining, determination of osteoclast activities (CA II and TRAP), SEM imaging as well as by quantification of the ion release during cell culture. Furthermore, the bioactivity of the materials was investigated via SBF immersion, whereas hydroxyapatite precipitates were analyzed by SEM and EDX measurements. This bioactive coating was resorbed by osteoclasts. In contrast, only chemical dissolution contributed to bioresorption of MP, while no cellular resorption of the materials was observed. Based on our results, we expect an increased bone regeneration effect of MP compared to calcium phosphate based bone grafts and complete chemical degradation within a maximum of 1.5–3.1 years