NSF Award
2323499
Non-technical Abstract:<br/>When implants, like hip implants made of cobalt and chrome degrade, they can release atoms of those heavy metals into the surrounding bone. Some of those atoms can make their way into the bone itself; more specifically they can get inside the hard part of your bones which is made up of a mineral called apatite. The movement of these atoms into the apatite can change the way your bones work, making them more likely to break. However, because the apatite minerals in your bones are extremely small, it has been very difficult to study where these heavy metal ions go and how they affect bone strength. The goal of this project is therefore to use a combination of computer modelling and experiments using very powerful X-rays to figure out where the metal atoms go in the apatite mineral and determine whether or not they make the bone more breakable. By combining computer models and experiments, techniques will be developed that allow researchers to understand how metal atoms interact with bone apatite and predict how those atoms affect bone strength in the millions of people with cobalt and chromium containing bone implants. Integrated with this research, the principal investigators will strive to create environments that make students more confident about their scientific abilities. This will be done by providing opportunities for students to work in the lab, by teaching inclusive classes that reach broad audiences, and by acting as role models for students who do not often see people like them (women and racial minorities) in scientific roles. <br/><br/>Technical Abstract:<br/>Degradation of cobalt (Co) and chromium (Cr) containing implants are associated with release of heavy metal ions and an increase in bone fracture risk. Since bone is primarily composed of apatite mineral which exhibits a high propensity for cationic substitutions, it is likely that the bone matrix is absorbing these ions resulting in significant changes in crystal structure and mechanics. The principal investigators hypothesize that the incorporation of cobalt (Co) and chromium (Cr) in the near-implant bone plays a significant role in promoting fracture. However, due to the difficulty in studying nano-sized apatites, there remain several unanswered questions relative to this process including how Co and Cr substitute into apatite, how the ions affect the apatite mechanical properties, and what Co and Cr concentrations are needed to affect bone fracture. To answer these questions, an ab initio-based model of apatite crystals with Co and Cr substitutions will be developed to predict the change in crystallographic and mechanical properties of apatite crystals at the nanoscale. These predictions will be validated by experimental approaches using biomimetic apatite systems and high-energy synchrotron X-ray diffraction techniques. These data will be combined to create multiscale models of apatite crystals to study fracture initiation processes due to Co and Cr substitutions. The results from this study can benefit millions of North Americans with cobalt-chrome implants by creating a new avenue for treatment developments to minimize fracture in this already at-risk population. In addition, they will facilitate the tunability of apatite biomaterials for future bone graft and scaffolding applications. Integrated with the research, is an educational plan which seeks to increase self-efficacy in the realm of science for a variety of students. This will be accomplished by providing lab access to undergraduate and graduate students, developing culturally relevant inclusive scientific courses, and acting as role models for under-represented students.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
