Novel silicon‐doped hydroxyapatite (Si‐HA) for biomedical coatings: An in vitro study using acellular simulated body fluid

Abstract

Magnetron co‐sputtering was used to produce silicon‐doped hydroxyapatite (Si‐HA) as coatings intended for potential applications such as orthopedic and dental implants. It was found that the crystallinity of the as‐sputtered coatings increased after annealing, resulting in a nanocrystalline apatite structure. Subsequently, the bioactivity of the coatings was evaluated in an acellular simulated body fluid (SBF). Physicochemical evaluation demonstrated that a carbonate‐containing apatite layer, which is essential for bonding at the bone/implant interface, was formed on the coating surfaces after immersion in SBF between 4 and 7 days. The annealed coatings exhibited enhanced bioactivity and chemical stability under physiological conditions, as compared with the as‐sputtered coatings. It is proposed that the rate at which the carbonate‐containing apatite layer forms is dependent on the scale factor of the structure. A nanocrystalline structure can provide a higher number of nucleation sites for the formation of apatite crystallites, leading to a more rapid precipitation of carbonate‐containing apatite layer. This work shows that Si‐HA coatings offer considerable potential for applications in hard tissue replacement, owing to their ability to form a carbonate‐containing apatite layer rapidly. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006