I-Corps: Electrically Polarized Hydroxyapatite Coatings

University Of Rochester, Rochester NY

Investigators

Abstract

The project will use a coating method that results in uniform hydroxyapatite coatings with near perfect alignment of crystal domains. The unique structure of the coating promotes high temperature proton conduction, and allows the coating to have a strong, permanent electrical polarization near room temperature. Experimental conditions will be tuned to make uniform coatings of controlled thickness and porosity on titanium alloy parts of complex shape, such as small pins and screws, used in actual surgical implant applications. Electrically polarized hydroxyapatite coatings have been shown by others to promote bone growth and healing. The aligned crystal domains in the novel coatings allow much higher stored electrical charge after polarization than any previously measured for hydroxyapatite. The total stored charge of the polarized coatings on implants will be measured through thermally stimulated depolarization experiments. The prototype implants with highly polarized coatings will be investigated for their ability to adsorb and release drugs and other species through ion exchange with the surface. Synthetic hydroxyapatite has found widespread use as a coating to improve bio-compatibility of load bearing metallic implants. The unique electrical and surface properties of the hydroxyapatite coatings in the present study can improve performance in orthopedic and dental applications, as well as present a number of potential applications previously not possible with this material. Strong electrical polarization of the coatings can potentially speed healing by promoting osteoblast adhesion and enhancing calcium phosphate deposition. Infections can slow recovery, necessitate additional surgery to replace the implant, or in worst cases lead to amputation or even lethal sepsis. Strong electrostatic charge on the surface can be utilized for controlled delivery of antibiotics or other drugs at the site of surgery through ion exchange with the surface in order to reduce complications. The strong polarization and high proton conductivity also opens up potential applications in membrane filters, sensors, and fuel cells.