UC Riverside

The potential of Magnesium (Mg)-based temporary biodegradable metallic implants relies most heavily on the mechanical and electrochemical properties of Mg, as well as on the fact that the human body contains a large amount of Mg ions and can effectively metabolize the degradation products of Mg. To realize the benefits of Mg for orthopedic fixation device applications, however, it is critical to engineer the rate of Mg degradation in the body based on end-goal design specifications. Firstly, we developed and studied Mg-xZn-0.5Ca alloys, Mg-4Zn-xSr alloys, and anodically oxidized surface treatments, all of which present innovative strategies to engineer the corrosion rates, mechanical properties, and/or improve cell-biomaterial interactions to meet clinical requirements. Secondly, we developed and implemented physiologically relevant in vitro models to evaluate cellular responses at the cell-biomaterial interface between various mammalian cell types and Mg-based biomaterials. Optimization of the methods allowed us to identify key aspects that influence Mg degradation in vitro and cellular responses to concomitant degradation products, thereby providing more comprehensive in vitro method for examining and screening bioresorbable materials compared with current standards. Lastly, we evaluated for the first time the in vivo degradation and host-response to Mg-4Zn-1Sr alloys, not only to evaluate and optimize performance of our novel materials, but also to identify factors that affect degradation and bridge the existing gap between in vitro and in vivo measurements of Mg-based biomaterials. Collectively, the results and conclusions of this dissertation supported the promising potential of bioresorbable Mg-based biomaterials for musculoskeletal implant applications. It is likely that the solution that enables clinical translation of Mg-based biomaterials will be a combination of biomedical-designed alloys and surface treatments/coatings. Furthermore, this dissertation provided design guidelines and in vitro tools to screen and optimize: alloy composition, degradation rates, cytocompatibility, and cellular responses at the cell-biomaterial interface to fine tune Mg-based biomaterials for specific implant applications.