Hydroxyapatite Coatings Produced by Right Angle Magnetron Sputtering for Biomedical Applications
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1008-T10-04
Hydroxyapatite Coatings Produced by Right Angle Magnetron Sputtering for Biomedical Applications Zhendong Hong1, Alexandre Mello2, Tomohiko Yoshida3, Lan Luan1, Paula H. Stern3, Alexandre Rossi2, Donald E Ellis1,4, and John B. Ketterson1,5 1 Department of Physics and Astronomy, Northwestern University, Evanston, IL, 60208 2 Centro Brasileiro de Pesquisas Fisicas, Rio de Janeiro, 22290, Brazil 3 Department of Molecular Pharmacology and Biological Chemistry, Northwestern University, Chicago, IL, 60611 4 Department of Chemistry, Northwestern University, Evanston, IL, 60208 5 Department of Electrical and Computer Engineering, Northwestern University, Evanston, IL, 60208 ABSTRACT Hydroxyapatite coatings have been widely recognized for their biocompatibility and utility in promoting biointegration of implants in both osseous and soft tissue. Conventional sputtering techniques have shown some advantages over the commercially available plasma spraying method; however, the as-sputtered coatings are usually non-stoichiometric and amorphous which can cause some serious problems such as poor adhesion and excessive coating dissolution rate. A versatile right-angle radio frequency magnetron sputtering (RAMS) approach has been developed to deposit HA coatings on various substrates at low power levels. Using this alternative magnetron geometry, as-sputtered HA coatings are nearly stoichiometric, highly crystalline, and strongly bound to the substrate, as evidenced by analyses using x-ray diffraction (XRD), atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). In particular, coatings deposited on oriented substrates show a polycrystalline XRD pattern but with some strongly preferred orientations, indicating that HA crystallization is sensitive to the nature of the substrate. Post deposition heat treatment under high temperature does not result in a marked improvement in the degree of crystallinity of the coatings. To study the biocompatibility of these coatings, murine osteoblast cells were seeded onto various substrates. Cell density counts using fluorescence microscopy show that the best osteoblast proliferation is achieved on an HA RAMS-coated titanium substrate. These experiments demonstrate that RAMS is a promising coating technique for biomedical applications. INTRODUCTION Hydroxyapatite (HA), with the chemical formula Ca10(PO4)6(OH)2, is chemically similar to the main inorganic constituent of natural bone (bone mineral is a carbonate-containing calcium deficient hydroxyapatite). Thanks to its inherent biocompatibility synthetic HA forms a strong bond with human bone and is thus a widely used implant material. Since ceramic HA is brittle, and thus not suitable for load-bearing applications, HA coatings are applied to dental and medical implant materials to combine the superior mechanical properties of the implant metals with the biocompatibility of HA [1,2]. Currently the most commercially utilized technique to deposit HA is plasma spraying. Alth
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