Comparing Biocompatibility of Nanocrystalline Titanium and Titanium-Oxide with Microcrystalline Titanium

Abstract

Titanium (Ti) is the material of choice for orthopaedic applications because it is biocompatible and encourages osteoblast ingrowth. It was shown that the biocompatibility of Ti metal is due to the presence of a thin native sub-stoichiometric titanium oxide layer which enhances the adsorption of mediating proteins on the surface [1]. The present studies were devised to evaluate the adhesion, survival, and growth of cells on the surface of new engineered nano-crystal films of titanium and titanium oxides and compare them with orthopaedic-grade titanium with microcrystals. The engineered nano-crystal films with hydrophilic properties are produced by employing an ion beam assisted deposition (IBAD) technique. IBAD combines physical vapor deposition with concurrent ion beam bombardment in a high vacuum environment to produce films (with 3 to 70 nm grain size) with superior properties. These films are “stitched” to the artificial orthopaedic implant materials with characteristics that affect the wettability and mechanical properties of the coatings.To characterize the biocompatibility of these nano-engineered surfaces, we have studied osteoblast function including cell adhesion, growth, and differentiation on different nanostructured samples. Cell responses to surfaces were examined using SAOS-2 osteoblast-like cells. We also studied a correlation between the surface nanostructures and the cell growth by characterizing the SAOS-2 cells with immunofluorescence and measuring the amount alizarin red concentration produced after 7 and 14 days. The number of adherent cells was determined by means of nuclei quantification on the nanocrystalline Ti, TiO2, and microcrystalline Ti and analysis was performed with Image J. Our experimental results indicated that nanocrystalline TiO2 is superior to both nano and microcrystalline Ti in supporting growth, adhesion, and proliferation. Improving the quality of surface oxide, i.e. fabricating stoichiometric oxides as well as nanoengineering the surface topology, is crucial for increasing the biocompatibility of Ti implant materials.

Effects of nano-engineered surfaces on osteoblast adhesion, growth, differentiation, and apoptosis

“…[23][24][25][26][27][28][29][30] Using the IBAD technique to modify surface properties was previously shown to result in stressfree films with more durable adhesion to a titanium substrate. 31 Although this study tested nano-coatings on glass substrates, our previous study using titanium substrates showed similar results. 31 The main reason for choosing glass substrates for this study was to avoid the effect of any surface roughness other than the nanoroughness produced by the IBAD technique.…”

“…31 Although this study tested nano-coatings on glass substrates, our previous study using titanium substrates showed similar results. 31 The main reason for choosing glass substrates for this study was to avoid the effect of any surface roughness other than the nanoroughness produced by the IBAD technique. Using smooth glass substrates instead of any other material with inherent microscale roughness and porosity made it possible for us to isolate the specific effects of the nano-roughness produced by the IBAD technique from other factors that might influence cell interactions with surfaces.…”

Surface properties and biocompatibility of nanostructured TiO2 film deposited by RF magnetron sputtering

“…The number of adherent cells was determined by means of nuclei quantification on the TiO 2 -nano, Ti-nano, and Ti-micro substrates [ 34 ]. The interaction between the outermost surface of a biomaterial and its environment was a highly dynamic process, in which direct and indirect cell adhesions induced by protein previously adsorbed onto the surface were two competing processes.…”