Processing and Bioactivity Evaluation of Ultrafine-Grained Titanium

Titanium has been the material of choice for hard tissue replacements due to its excellent biocompatibility and high strength to weight ratio. Since, cells live in a nano-featured environment of extracellular matrix; there is great interest in the formation of submicron to nano size grain materials over conventional biomaterials. Equal channel angular pressing, groove pressing and mechanical milling of commercially pure titanium (cpTi) was carried out to obtain submicron/nano grain size materials. The processed samples were characterized using optical microscope, scanning electron microscope (SEM), X-ray diffraction (XRD), transmission electron microscope (TEM), hardness, tensile properties, atomic force microscope (AFM), and contact angle measurements. Microstructural and mechanical characterization of the processed samples exhibited grain refinement and improved mechanical properties when compared to as received condition. The bioactivity study of the fine grained samples in SBF exhibited dense and homogenous apatite layer on the surface. All samples were found to be non-toxic by MTT [3-(4, 5-Dimethylthiazole-2-yl)-2, 5-diphenyl tetrazolium bromide] assay to fibroblast cells and culture study using osteoblast cells show more cell adhesion and spreading on ultra fine grained samples compared to as received cpTi. The enhanced bioactivity in the fine grained samples is due to submicron/nano surface features with high wettability and surface energy.