Millions of medical implants and devices (e.g., screws, plates, pins, wires, suture anchors) are used each year worldwide in surgery, and traditionally the components have been limited to permanent metals (e.g., stainless steel, titanium alloys) and polyester-based absorbable polymers. Because of clinical problems associated with these traditional materials, a novel class of biodegradable metallic materials, i.e., magnesium based alloys, has been actively pursued. Magnesium (Mg) is particularly attractive for orthopedic applications because it has comparable modulus and strength to cortical bone. Controlling the interface of magnesium with the biological environment is the key challenge that currently limits this biodegradable metal for broad applications in medical devices and implants. Therefore, the long-term research objective is to determine the fundamentals of Mg degradation in a variety of bodily fluid environments and engineer its interface with tissues. This knowledge will enable researchers to design biodegradable metallic implants/devices with tunable degradation properties compatible with new tissue growth. This two-year BRIGE project will particularly focus on how to create a biomimetic interface between the biodegradable metallic implant and surrounding tissue for the dual purposes of (1) enhancing tissue integration and regeneration and (2) simultaneously mediating the degradation of the metallic implant in a deterministic programmable fashion. INTELLECTUAL MERIT: The idea of biodegradable Mg implants was discarded a century ago because of their rapid degradation. Recent advances in the design and processing of metal alloys has revived interest in Mg-based materials and devices. Most recent research has focused on decreasing Mg degradation through the addition of alloying elements (e.g., rare earth elements), but their long-term toxicity is a concern. The novelty of this project is to make Mg degradation tunable and biocompatible without adding alloying elements. Specifically, this project will develop a library of biomimetic nanocomposite coatings on Mg to control the material-structure degradation-healing relationships that manage tissue regeneration, and to use this nanocomposite library to build a predictive model that will guide the design of medical implant/devices with tunable degradation. It is hypothesized that the biodegradation rate of Mg could be moderated when coated with nanostructured bone-like composites, and this would also promote osseointegration to accelerate healing at the interface of Mg and bone tissue. This project will produce fundamental knowledge that will advance the design of biodegradable implants/devices and transform the concept of biodegradation from traditional polymer domain to a new era of smart metals. The success of this project will lead to a revolution in biomaterials - specifically unlock the full potential of biodegradable metals through developing novel engineering strategies to control the degradation. BROADER IMPACTS: This research will build the foundation for practical design guidelines for biodegradable metallic implants/devices. These, in turn, will increase the competitiveness of U.S. companies in the medical implant industry. The PI will use the knowledge developed in this project to develop graduate and undergraduate courses and modules in UCR's interdisciplinary Materials Science and Engineering program; her first priority is to establish an interdisciplinary Biomaterials Design course. She also will team up with UCR?s ALPHA Center (Academy of Learning through Partnerships for Higher Achievement) to integrate her research into a new outreach initiative, NanoDays. NanoDays is a national program designed to increase public awareness of nanotechnology, and the ALPHA Center will use it as a tool to inspire more young people from inland Southern California - a highly diverse region that lags behind much of California in economic opportunity and educational achievement - to pursue studies in science and engineering fields. The PI and her students will work actively in the community to inspire more young people to pursue engineering careers through outreach, mentoring, and serving as role models to young women
