In vitro comparative investigation of bioactivity and biocompatibility behavior of titanium nano-composites fabricated by friction stir processing

The aim of the present work is to fabricate the surface nano-composite through the friction stir process (FSP) followed by emphasizing on the comparative study from the surface characteristics (wettability and roughness), bioactivity and biocompatibility aspects. Toward this end, three different categories of conventional biocompatible powders include Hydroxyapatite, bioactive glass 45S5 and natural bone powder have been selected as second phase particles. Bone apatite formation, Mesenchymal stem cells (MSCs) adhesion and morphology have been characterized by scanning electron microscopy coupled with electron dispersive spectroscopy. The results of the contact angle demonstrate enhancing the hydrophilicity of titanium surfaces after surface modification due to the surface chemistry alteration. According to the immersion results in simulated body fluid, the surface modification by FSP enhances the bioactivity of titanium. Additionally, the biocompatibility of all the specimens except for titanium/hydroxyapatite (Ti/HA) composite is approved by MSCs culture. The unpleasant behavior of Ti/HA could be due to the changing the pH so it leads to cell death. Eventually, the MSCs are well-attached on the surface of titanium composites and possess polygonal morphology, while as a result of deviation from standard pH, cells get rounded on Ti/HA surface and cell death occurred.