Mechanical properties and cell proliferation response of borided biomedical titanium alloys with different crystalline structures

Abstract

A comparative study was conducted in order to investigate hardness, fracture toughness, adhesion and cell proliferation properties of boride layers produced on medical grade titanium materials with different crystalline structures. For this purpose, α type Cp-Ti, α + β type Ti-6Al-4V and β type Ti-45Nb were borided by using powder-pack boriding technique. Boride layers on titanium alloys exhibited hardness values up to 40.2 ± 2.7 GPa with low fracture toughness depending on the types of borides formed in boride layers. The adhesion tests showed that thickness, brittleness and morphology of boride layers have strong effect on adhesion of boride layers. However, no intensive failure developed on boride layers which proofs that adhesions of surface layers are sufficient. The influence of surface topography and chemical composition of boride layers on biocompatibility was examined. The proliferation of Saos-2 cells on each sample was quantified after 72 h by MTT assay. It was demonstrated that cell growth on borided Cp-Ti and Ti-6Al-4V alloy are less than their unborided ones (control). In comparison to Cp-Ti and Ti-6Al-4V alloy, Ti-45Nb alloy has increased number of cells proliferated on its both borided and unborided surfaces.