CAREER: Bioactive Weight-Bearing Bone/Polymer Composites

Vanderbilt University, Nashville TN

Investigators

Abstract

ID: MPS/DMR/BMAT(7623) 0847711 PI: Guelcher, Scott ORG: Vanderbilt Title: CAREER: Bioactive Weight-Bearing Bone/Polymer Composites INTELLECTUAL MERIT: A common location of disabling fractures occurs in the vertebral bodies of the spine, accompanied by painful spinal instability and pronounced bowing of the spine. Injectable poly(methyl methacrylate) (PMMA) bone cements stabilize compression fractures in vertebral bodies and restore support to the spine. However, PMMA cements can induce tissue necrosis arising from high polymerization temperatures, and can promote bone resorption near the implant/bone interface due to stress-shielding. Consequently, a physiological alternative to existing materials is needed that: (1) has biomechanical properties comparable to those of trabecular bone to stabilize the fracture and minimize stress-shielding, (2) is administered by minimally invasive surgical techniques, and (3) actively participates in the healing process by integrating with recipient bone and remodeling. Composites comprising mineralized allograft bone particles (MBPs) and resorbable thermoplastic polymers have mechanical properties comparable to trabecular bone and actively participate in the healing process. However, these biomaterials are fabricated by compression-molding at elevated temperatures and therefore cannot be injected. To overcome these limitations, a family of composites comprising MBPs and resorbable polyurethane (PUR) networks will be designed and developed. They are processed as reactive liquids at ambient temperature and cure in situ at 37 C, which renders them suitable for injection. Reactive liquid molding also enables control over binding between the polymer and both the reinforcing MBPs and host trabecular bone, thus strengthening the implant after cure. Dynamic mechanical, compression, bending, and rheological properties will be measured. Remodeling of the composites will be investigated in vitro in a co-culture model of osteoblasts and osteoclast-like cells. A key component of the project will focus on establishing relationships governing the effects of the bone-polymer interfacial structure on mechanical properties and in vitro remodeling of the composites. BROADER IMPACTS: The project will integrate research and education through activities aligned with the goals of the Vanderbilt School for Science and Math (VSSM) and the Department of Chemical and Biomolecular Engineering (CBE). The VSSM, a part-time high school located on Vanderbilt campus and dedicated to public school students grades 9-12, is a joint venture with Metropolitan Nashville Public Schools (MNPS). In conjunction with core instructors at the VSSM, the PI will develop grade-appropriate (e.g., 9-12) curriculum components incorporating biomaterials, regenerative medicine, and bioprocess engineering. Scientific knowledge discovered during the execution of the project will also be disseminated through the development of two required undergraduate courses: Introduction to Engineering and Bioprocess Engineering. Both courses will be developed to support recent changes to the undergraduate curriculum in the PI?s home department (CBE). Additionally, through research assistantships, graduate, undergraduate, and high school (through the School for Science and Math) students will gain experience in the design, synthesis, and characterization of biomaterials for bone regeneration.