Collaborative Research: Bone Adaptation-Driven Design of Scaffolds with Spatially-Varying Architecture for Enhanced Growth

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Synthetic bone scaffolds are porous inserts used to repair bone defects that would not otherwise heal on their own, providing mechanical support while allowing bone regeneration inside the pores. Among the biocompatible materials used for their fabrication, calcium phosphate ceramics (CaPs) have received significant attention because their stiffness is similar to that of bone. The material system considered in this project consists of CaP scaffolds made by Direct Ink Writing, an additive manufacturing technique whereby rods of a colloidal ink are deposited in alternating layers and subsequently sintered. An outstanding challenge in the clinical use of these scaffolds is the lack of complete integration of the bone into the scaffold pores. Complete osteointegration is hindered by two limitations in existing scaffold design methods: they only consider scaffolds made of straight rods, and they are not directly driven by a measure of bone integration. This award supports fundamental research to formulate the first computational framework for the design of patient-specific CaP scaffolds made of curvilinear rods and driven by bone adaptation. Results of this research have the potential to substantially increase the clinical viability of synthetic scaffolds for large defect repair, with tangible and significant treatment and financial benefits for patients. In addition to bone scaffolds, this research will advance design methodology that may be applied to related material systems, such as architected porous surfaces in orthopedic implants, scaffolds for cell tissue culture, particulate filters and self-healing materials. A summer exchange of undergraduate and graduate students between the two collaborating institutions will provide training opportunities for the next generation of material designers. This award will also support outreach to high school students via summer residential camps. To achieve the goal of formulating the first computational design methodology for patient-specific bone scaffolds with spatially-varying architecture for complete bone regeneration, this project will couple topology optimization techniques with bone adaptation simulation. In particular, this project will 1) formulate a framework to simultaneously model bone adaptation within the bone-scaffold system while readily accommodating changes in the scaffold design; 2) incorporate adequate measures of osteointegration and scaffold strength to incorporate as design criteria; and 3) formulate a design representation of the scaffold architecture that allows for local property control while ensuring manufacturability. The computational design framework will be validated via material and mechanical characterization of scaffolds designed, and via an in vivo study in pigs.