Cytocompatibility of a free machining titanium alloy containing lanthanum

Abstract

Titanium alloys like Ti6Al4V are widely used in medical engineering. However, the mechanical and chemical properties of titanium alloys lead to poor machinability, resulting in high production costs of medical products. To improve the machinability of Ti6Al4V, 0.9% of the rare earth element lanthanum (La) was added. The microstructure, the machinability as well as the mechanical and corrosion properties were determined. In vitro experiments with mouse macrophages (RAW 264.7) and human bone-derived cells (MG-63, HBDC) were performed. Lanthanum containing alloys exhibited discrete particles of cubic lanthanum. The machinability was improved due to the formation of short breaking chips and a reduction in tool wear. The mechanical properties and corrosion resistance were slightly decreased but are still sufficient for many applications in the field of medical engineering. Cell experiments revealed that macrophages showed a dose response below and above a LaCl3 concentration of 200 μM, while MG-63 and HBDC tolerated three times higher concentrations without reduction of viability. The viability of cells cultured on disks of the materials showed no differences between the reference and the lanthanum containing alloy. We therefore propose that lanthanum containing alloy appears to be a good alternative for biomedical applications, where machining of parts is necessary.