Abstract
Besides the wide applications of titanium and its alloys for orthopedic and biomedical implants, the biocompatible nature of titanium has emerged various surface modification techniques to enhance its bioactivity and osteointegration with living tissues. In this work, we present a new procedure for nanoscale surface modification of titanium implants by integration of magnesium-rich islands combined with controlled formation of pores and refinement of the surface grain structure. Through severe plastic deformation of the titanium surface with fine magnesium hydride powder, Mg-rich islands with varying sizes ranging from 100 nm to 1000 nm can be integrated inside a thin surface layer (100–500 µm) of the implant. Selective etching of the surface forms a fine structure of surface pores which their average size varies in the range of 200–500 nm depending on the processing condition. In vitro biocompatibility and hemocompatibility assays show that the Mg-rich islands and the induced surface pores significantly enhance cell attachment and biocompatibility without an adverse effect on the cell viability. Therefore, severe plastic integration of Mg-rich islands on titanium surface accompanying with porosification is a new and promising procedure with high potential for nanoscale modification of biomedical implants.
Highlights
Titanium and its alloys have various applications in biomedical devices mainly in orthopedic and dentistry due to their superior mechanical strength, toughness, biocompatibility, and corrosion resistance[1,2,3,4,5]
Small pores were observed in stir zone (SZ) (Fig. 1c)
Due to the low solubility of Mg in Ti matrix, a solid-state surface deformation technique was employed to locally incorporate magnesium islands in few hundred micrometers (100–500 μm) of the surface layer through mechanical stirring and plunging of MgH2 particles
Summary
Titanium and its alloys have various applications in biomedical devices mainly in orthopedic and dentistry due to their superior mechanical strength, toughness, biocompatibility, and corrosion resistance[1,2,3,4,5]. The lower amount of magnesium in the form of islands, which are integrated in the surface layer, do not adversely affect osteointegration of the implant while providing enhanced bioactivity. The magnesium islands can be leached out either before implantation or degraded in the body, leaving surface pores which further promote cell attachment and osteointegration. The inherent nature of FSP refines the surface grain structure of titanium and induces surface roughening which can affect its cellular behavior[48] This method has recently been utilized for processing of various ultrafine grained materials and composites as well as microstructural modification of castings both in micro- and nano- scales[49]. Limited studies have been carried out on utilizing FSP for biomedical applications, for example, deposition of hydroxyapatite nanoparticles on commercially pure Ti50, Mg51 and a Mg-Al-Zn alloy (AZ31)[52]. The proposed procedure is a new and promising method for nanoscale surface modification of titanium-based implants for biomedical applications
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