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.
Hydroxyapatite is a type of calcium phosphate that is the main mineral component of teeth and bone. Synthetic hydroxyapatite is often coated onto titanium-based orthopedic and dental implants to improve the bioactivity of the implant surface. While working on a previously funded NSF project involving the development of hydroxyapatite membranes for use in fuel cells, it was discovered that electrochemically synthesized hydroxyapatite coatings retain an unexpectedly large stored electrical charge. The magnitude of the stored charge was far larger than any previously measured. It is known that negative electrostatic surface charge enhances bone growth around implants. Therefore, the novel electrically polarized hydroxyapatite coatings hold promise to benefit society by reducing the post-surgical recovery time for implant patients with poor bone quality and function due to conditions such as osteoporosis, diabetes, and impaired immune system. The goal of the I-Corps project was to determine if a company should be formed to supply the electrically polarized coating technology for dental and orthopedic implant applications. To that end, the research team developed, tested, and revised a business model canvas throughout the funding period. Feedback on the business model was obtained from nearly one hundred face to face interviews that included physicians, surgeons, researchers, representatives from implant manufacturers, and regulatory advisors. It became clear that the technology would not garner significant commercial interest without demonstrated performance in living animals and a clear regulatory approval path. The in vitro experiments demonstrated a number of promising features of the technology, including rapid, low cost synthesis of coatings, the ability to coat complex shapes (such as implant screws) uniformly, enhanced adhesion and proliferation of osteoblast cells on the polarized coatings, and the fact that the coatings are comprised of hydroxyapatite, a material approved by the FDA for use in implants. However, implant manufacturers and surgeons clearly require in vivo demonstration of significant enhancement of performance without harmful side effects before seriously considering the adoption of new technology. The research team made the decision that a company should not be formed because additional research is required. The team has continued to aggressively pursue research funding after the I-Corps project ended, and were successful in obtaining a grant for a pilot animal study. The animal study will be completed this year by a researcher/clinician who became excited about the technology during the I-Corps interview process. The team is optimistic that significant commercial interest can be developed pending successful in vivo demonstration of performance.
