In Situ Characterization of Surface Evolution on Titanium in Hydrogen Peroxide Containing Solutions
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In Situ Characterization of Surface Evolution on Titanium in Hydrogen Peroxide Containing Solutions Julie J. Muyco1; Jeremy J. Gray1; Timothy V. Ratto1; Christine A. Orme1; Joanna McKittrick2; John Frangos3 1 Lawrence Livermore National Laboratory, Livermore, CA 2 University of California, San Diego La Jolla, CA 3 La Jolla Bioengineering Institute, La Jolla, CA Abstract Titanium implants have been used for decades with success in various applications. The characteristics of titanium that allows acceptance in the body are not well defined. It is known that hydrogen peroxide is a chemical species produced during the inflammatory response following implantation. When titanium is exposed to hydrogen peroxide, a Ti-peroxy gel (TiOOH) is formed.1,2 Three possible functions of Ti-peroxy gel are: reduction of the inflammatory response through the reduction of hydrogen peroxide and other reactive oxygen species;2 creation of a favorable surface for calcium phosphate nucleation;3-6 and as a transitional layer between the soft tissue and the stiff titanium. These studies utilized atomic force microscopy (AFM) force spectroscopy, electrochemical techniques, Raman spectroscopy, and optical transparency in situ to define kinetic and mechanical properties of Ti-peroxy gel as it forms on titanium during exposure to hydrogen peroxide. Peaks attributed to Ti-peroxy gel were seen to emerge over the course of several hours using in situ Raman spectroscopy. Forcedistance curves suggest a layer that thickens with time on the titanium sample surface. Background Titanium implants have been used for many decades in load bearing applications such as orthopedic and dental prostheses. It is desirable for implants in load bearing applications to have a close physio-chemical bond to the surrounding bone tissue. Such a close bond is called osseointegration.7 Titanium implants have been seen to osseointegrate, but to varying degrees.810 The goal of this study is to add to the understanding of the chemistry at the interface of titanium implants and bodily fluid that promotes osseointegration. After insertion of an implant into the body, a cascade of events occurs. Adsorption and desorption of proteins on the surface of the implant alter the surface and the body’s immune system responds to this surface.7 The immune response includes inflammation. During inflammation white blood cells such as macrophages are recruited to the inflammation site. These cells attempt to remove the offending materials that are recognized as ‘not self.’ In this attempt at removal, chemicals meant to harm bacteria and other foreign organisms are secreted. These chemicals include reactive oxygen species such as super oxide (O2-) and hydrogen peroxide.11 If produced in excess these chemicals, alone and in combination with other chemicals that are secreted during inflammation, will cause damage to surrounding tissue and eventually lead to chronic inflammation.11 It is known that titanium will form a Ti-peroxy gel (TiOOH) in the presence of hydrogen peroxide.1,2 It is
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