Titanium Nanosurface Modification by Anodization for Orthopedic Applications
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Titanium Nanosurface Modification by Anodization for Orthopedic Applications Chang Yao1, Elliott B. Slamovich1 and Thomas J. Webster1,2 1 School of Materials Engineering and 2Weldon School of Biomedical Engineering Purdue University, West Lafayette, IN 47907 ABSTRACT Titanium is broadly used in orthopedic and dental applications mainly because of its optimal mechanical properties in load-bearing applications. However, insufficient new bone formation is frequently observed on titanium which sometimes leads to implant loosening and failure. For this reason, the objective of the present in vitro study was to modify the surface of conventional titanium to include nanostructured surface features that promote the functions of osteoblasts (bone-forming cells). This study focused on creating nanostructured titanium surfaces since bone itself has a large degree of nanostructured roughness that bone cells are accustomed to interacting with. In this study, the surface of titanium was modified by anodic oxidation techniques. The electrolyte used for anodization was hydrofluoric acid. Depending on acid concentration and anodization time, two kinds of different nano-architectures, either particulate or tube-like structures, were formed on the titanium surface. X-ray diffraction results confirmed that the titanium oxide formed on the surface of titanium was amorphous. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to characterize the surface morphology. Cell adhesion studies showed that the anodized nanostructured titanium surface promoted osteoblast adhesion compared to non-anodized titanium. This result indicated that anodization may be a simple method to modify the surface of titanium implants to enhance bone-forming cell function thereby increasing orthopedic implant efficacy. INTRODUCTION Titanium and its alloys are among the most utilized biomaterials and are still the materials of choice for many structural implantable device applications [1]. However, current titanium implants face long-term failure problems due to poor bonding to juxtaposed bone, severe stress shielding and generation of debris that may lead to bone cell death and perhaps eventual necrotic bone [2-5]. Improving the bioactivity of titanium implants, especially with respect to bone cells, is a major concern in the near and intermediate future. Surface properties such as wettability, chemical composition and topography govern the biocompatibility of titanium. Conventionally processed (e.g., cast, forged, etc.) titanium currently used in the orthopedic and dental applications exhibits a micro-rough surface and is smooth at the nanoscale. Surface smoothness on the nanoscale has been showed to favor fibrous tissue encapsulation [4-6]. An approach to design the next-generation of implants has recently focused on creating unique nanotopography (or roughness) on the implant surface, considering that natural bone consists of nanostructured materials like collagen and hydroxyapatite. Some
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