The Effect of the Nanostructured Surface Modification on the Morphology and Biocompatibility of Ultrafine-Grained Titanium Alloy for Medical Application

Abstract

Primary implant stability after implantation is in relation with its good mechanical contact with the touching tissue. Adequate integration of the implant with the bone tissue is necessary to provide safety and efficiency of the implant over its life. Generally, two surface properties are the most important facts for tissue response to the implant: the surface topography and chemical composition. Compared to a smooth implant surface, a controlled rough surface provides more surface area for integration with the surrounding tissues and allows successful implant ingrowth into the tissues. It was found that the nanostructured modification of the titanium surface on the level of nano-sized pores influences the adhesion, spreading and growing of osteoblastic cells. There are many methods for nanostructure modification of biomedical alloy surfaces, but one of the common techniques is electrochemical anodization (anodic oxidation). Electrochemical anodization is a method that leads to the creation of a nanotubular oxide film on the material surface. The advantage of anodic oxidation is the possibility of controlling the nanostructured morphology of the surface and dimensions of nanotubes, such as diameter, length, wall thickness and shape of nanotubes through variation of the solution, pH value, potential or duration of anodic oxidation. Surface modification of Ti-13Nb-13Zr alloy in a coarse-grained (as received) and ultrafine-grained state induced by high pressure torsion was conducted using an electrochemical anodization process in a 1 M H3PO4 + NaF electrolyte, for 30, 60, 90 and 120 minutes. Scanning electron microscopy (SEM) was used to analyze the morphology, while atomic force microscopy (AFM) was used to characterize the topography of the modified surface. The results showed that a homogenous nanotubular oxide film consisting of nanotubes could be obtained using the electrochemical anodization treatment, while the roughness of the nanostructured surface increased compared to the bare surface. The aim of the studies given in this chapter is to examine the morphology of the nanostructured surface and estimate in vitro biocompatibility of the above-mentioned titanium alloy after the creation of the nanotubular oxide film. In vitro examinations were performed on mouse fibroblast (L929) and human fibroblast (MRC-5) cell lines. The results showed that the nanotubular oxide film obtained on the coarse-grained Ti-13Nb-13Zr alloy (CG TNZ) and the ultrafine-grained Ti-13Nb-13Zr alloy (UFG TNZ) increased the fractions of surviving cells compared to their counterpart alloy, while the cells had better spreading and adhesion on the nanostructured and bare surfaces of the UFG titanium alloy.