Nanophase Ceramics as Bone Implant Coatings

DESCRIPTION (provided by applicant): The overall objective of the proposed study is to create a new family of "smart" orthopedic and dental implant coating materials that enhance new bone formation over existing implants. "Smart" coating materials are necessary to selectively increase bone cell function while, at the same time, inhibit functions of competitive cells that lead to soft, instead of bony, tissue formation. Such osseointegration provides mechanical stability to an implant in situ, minimizes motion-induced damage to surrounding tissues, and is imperative for the clinical success of bone implants. In this manner, the health relatedness of the proposed project is to increase bonding between an implant and juxtaposed bone so that a patient who has received joint or dental replacement surgery may quickly return to a normal active lifestyle. Furthermore, the present proposal aims to increase the service-life of an orthopedic material by creating materials that form a strong, long lasting, bond with juxtaposed bone. The material proposed in the present study as a more effective orthopedic implant coating is: nanophase hydroxyapatite doped with yttrium. Nanophase ceramics are intriguing new material formulations since they possess grain sizes less than 100 nm in diameter. For this reason, nanophase ceramics simulate the grain size and topography of bone. Hydroxyapatite doped with yttrium coatings may increase initial absorption of calcium from serum leading to select protein adsorption to enhance bone cell function. This is speculated since yttrium has a high affinity for calcium. When not used as an implant coating, previous studies have determined that nanophase hydroxyapatite doped with yttrium increases bone cell function over existing hydroxyapatite formulations. The present study will build upon these results by using a novel technique to coat a currently utilized bone prosthetic material (titanium) with nanophase hydroxyapatite doped with yttrium. For Phase I studies, the ability of the titanium coated nanophase hydroxyapatite doped with yttrium to promote new bone synthesis and limit competitive cell function will be determined using in vitro cellular models. Specifically, osteoblast (bone-forming cells) and fibroblast (cells that have been associated with competitive soft tissue formation) function will be determined on the proposed coated materials. The specific aims of this proposal are therefore to combine previously designed materials that enhance new bone formation with a novel technique that will transform these bioactive materials into a practical bone prosthetic coating. Undoubtedly, design criteria used in the proposed study to investigate new coating techniques coupled with a new coating material could have great impact in the development of the "next-generation" of orthopedic implants with an improved ability to bind to juxtaposed bone.