Innovative surface modification of Ti6Al4V alloy by electron beam technique for biomedical application.

The low elastic modulus, high corrosion resistance and excellent biological response allow titanium alloys to be used for permanent orthopaedic devices. Furthermore, the design of specific multi scale surface topographies on titanium alloys can provide a fast osseointegration. This work highlights the use of electron beam as a promising technique to produce a designed surface topography and improve the tribological behaviour of Ti6Al4V alloy. The produced surface topography due to the transport of molten material is influenced by the deflection figure, the physical properties of the material and the energy input. The analysis of the surface roughness shows an increment of the area up to 26% and a canal shape in a range from 1.3µm up to 9µm depth and from 68.6µm up to 119.7µm width. The high solidification rate reached during the process affects the microstructure, provoking the formation of martensite and thus the improvement of hardness. In vitro studies with pre-osteoblastic MC3T3-E1 cells performed for several cultivation times show the cells with a polygonal shape and built connections through elongated filopodia. A notable increase of cell spreading area on surface structure with a finer canal shape is found after 48h cultivation time.

Effects of Corroded and Non-Corroded Biodegradable Mg and Mg Alloys on Viability, Morphology and Differentiation of MC3T3-E1 Cells Elicited by Direct Cell/Material Interaction.

This study investigated the effect of biodegradable Mg and Mg alloys on selected properties of MC3T3-E1 cells elicited by direct cell/material interaction. The chemical composition and morphology of the surface of Mg and Mg based alloys (Mg2Ag and Mg10Gd) were analysed by scanning electron microscopy (SEM) and EDX, following corrosion in cell culture medium for 1, 2, 3 and 8 days. The most pronounced difference in surface morphology, namely crystal formation, was observed when Pure Mg and Mg2Ag were immersed in cell medium for 8 days, and was associated with an increase in atomic % of oxygen and a decrease of surface calcium and phosphorous. Crystal formation on the surface of Mg10Gd was, in contrast, negligible at all time points. Time-dependent changes in oxygen, calcium and phosphorous surface content were furthermore not observed for Mg10Gd. MC3T3-E1 cell viability was reduced by culture on the surfaces of corroded Mg, Mg2Ag and Mg10Gd in a corrosion time-independent manner. Cells did not survive when cultured on 3 day pre-corroded Pure Mg and Mg2Ag, indicating crystal formation to be particular detrimental in this regard. Cell viability was not affected when cells were cultured on non-corroded Mg and Mg alloys for up to 12 days. These results suggest that corrosion associated changes in surface morphology and chemical composition significantly hamper cell viability and, thus, that non-corroded surfaces are more conducive to cell survival. An analysis of the differentiation potential of MC3T3-E1 cells cultured on non-corroded samples based on measurement of Collagen I and Runx2 expression, revealed a down-regulation of these markers within the first 6 days following cell seeding on all samples, despite persistent survival and proliferation. Cells cultured on Mg10Gd, however, exhibited a pronounced upregulation of collagen I and Runx2 between days 8 and 12, indicating an enhancement of osteointegration by this alloy that could be valuable for in vivo orthopedic applications.