Abstract:The oxidation behavior of International Thermonuclear Experimental Reactor (ITER) reference tungsten grade has been evaluated in dry air in the temperature range 600 800 °C. At 600 °C, the scale remained protective while the integrity of W 18 O 49 layer was kept. Rapid increase in mass gain resulted from mas sive cracking at local areas in the W 18 O 49 layer. Then, a coarse non protective columnar WO 2.92 scale was developed which favoured rapid inward oxygen transport into the alloy. At 700 and 800 °C, growth stres ses in the scale were released through local cracking. At this stage, WO 2.92 became progressively trans formed into WO 3 when the oxygen partial pressure increased across the scale thickness.

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BackgroundWith additive manufacturing (AM) individual and biocompatible implants can be generated by using suitable materials. The aim of this study was to investigate the biological effects of polylactic acid (PLA) manufactured by Fused Deposition Modeling (FDM) on osteoblasts in vitro according to European Norm / International Organization for Standardization 10,993–5.MethodHuman osteoblasts (hFOB 1.19) were seeded onto PLA samples produced by FDM and investigated for cell viability by fluorescence staining after 24 h. Cell proliferation was measured after 1, 3, 7 and 10 days by cell-counting and cell morphology was evaluated by scanning electron microscopy. For control, we used titanium samples and polystyrene (PS).ResultsCell viability showed higher viability on PLA (95,3% ± 2.1%) than in control (91,7% ±2,7%). Cell proliferation was highest in the control group (polystyrene) and higher on PLA samples compared to the titanium samples.Scanning electron microscopy revealed homogenous covering of sample surface with regularly spread cells on PLA as well as on titanium.ConclusionThe manufacturing of PLA discs from polylactic acid using FDM was successful. The in vitro investigation with human fetal osteoblasts showed no cytotoxic effects. Furthermore, FDM does not seem to alter biocompatibility of PLA. Nonetheless osteoblasts showed reduced growth on PLA compared to the polystyrene control within the cell experiments. This could be attributed to surface roughness and possible release of residual monomers. Those influences could be investigated in further studies and thus lead to improvement in the additive manufacturing process. In addition, further research focused on the effect of PLA on bone growth should follow.In summary, PLA processed in Fused Deposition Modelling seems to be an attractive material and method for reconstructive surgery because of their biocompatibility and the possibility to produce individually shaped scaffolds.

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In this work, we investigated a new approach to incorporate Mg particles within a PDLLA matrix using a solvent‐free commercially available process. PDLLA/Mg composites were manufactured by injection moulding and the effects of Mg incorporated into PDLLA on MSC and macrophage responses were evaluated. Small amounts of Mg particles (≤1 wt %) do not cause thermal degradation of PDLLA, which retains its mechanical properties. PDLLA/Mg composites release hydrogen, alkaline products and Mg2+ ions without changing pH of culture media. Mg‐containing materials provide a noncytotoxic environment that enhances MSC viability. Concentration of Mg2+ ions in extracts of MSCs increases with the increment of Mg content in the composites. Incorporation of Mg particles into PDLLA stimulates FN production, ALP activity, and VEGF secretion in MSCs, an effect mediated by degradation products dissolved from the composites. Degradation products of PDLLA induce an increase in MCP‐1, RANTES, and MIP‐1α secretion in macrophages while products of composites have minimal effect on these chemokines. Regulation of MSC behavior at the biomaterial's interface and macrophage‐mediated inflammatory response to the degradation products is related to the incorporation of Mg in the composites. These findings suggest that including small amounts of Mg particles into polymeric devices can be a valuable strategy to promote osseointegration and reduce host inflammatory response. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 866–878, 2016.