Design a Biologically Inspired Nanostructured Coating for Better Osseointegration
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Design a Biologically Inspired Nanostructured Coating for Better Osseointegration Mian Wang, Jian Li, Michael Keidar and Lijie Grace Zhang Department of Mechanical and Aerospace Engineering, GW Institute for Biomedical Engineering and GW Institute for Nanotechnology, The George Washington University, 801 22nd Street NW, Washington DC 20052 ABSTRACT To date, there are a strikingly growing number of patients who need various orthopedic implants. However, traditional orthopedic implants face many complications such as infection and implant loosening which may lead to implant failures. Conventional metal implants such as titanium were chosen for orthopedic applications mainly based on their excellent mechanical properties and biological inertness. Since natural bone matrix is nanometer in dimension, it is desirable to design a biologically inspired nanostructured coating that can turn conventional inert titanium surfaces into biomimetic active interfaces, thus enhance bone cell adhesion and osseointegration. For this purpose, we designed a biomimetic nanostructured coating based on nanocrystalline hydroxyapatites (nHA) and single wall carbon nanotubes (SWCNTs). Specifically, nHA with good crystallinity and biomimetic dimensions were prepared via a wet chemistry method and hydrothermal treatment; and the SWCNTs were synthesized via an arc plasma method with or without magnetic fields. TEM images showed that the hydrothermally treated nHA possessed regular rod-like nanocrystals and biomimetic nanostructure. In addition, the length of SWCNTs can be significantly increased under external magnetic fields when compared to nanotubes produced without magnetic fields. More importantly, our results showed that the above nHA and SWCNTs nanomaterials can greatly promote osteoblast (bone-forming cell) adhesion on titanium in vitro, thus holding great promise to improve osseointegration and lengthen the lifetime of current orthopedic implants. INTRODUCTION With the increasing aging population in the U.S., there exists a strikingly increasing number of patients suffering from a variety of orthopedic problems. For example, the American Academy of Orthopedic Surgeons reported that in just a 4 year period, there was 83.72% increase in the number of hip replacements performed from nearly 258,000 procedures in 2000 to 474,000 procedures in 2004 [1]. The total hospitalization costs for knee replacements doubled to $11.38 billion in 2003 compared with $5.67 billion in 1999 [1]. Traditional orthopedic implant devices are mainly composed of various metals such as titanium (Ti) and its alloys. These materials are commonly used in orthopedic and dental prostheses because of their desirable properties such as relatively low modulus, good fatigue strength, formability, machinability, corrosion resistance, and suitable biocompatibility. However, it is important to note that current Ti based implant materials are not perfect. They still cannot meet many critical clinical requirements such as direct and sufficient bone bonding in lesser time periods b
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