Poster M13 - Design and Fabrication of Bone Scaffolds with Complex Porous Microstructures, Composed of Polypropylene and Glass Fibers for Bone Regeneration

Introduction: Osseous fractures account for 16% of all musculoskeletal injuries in the U.S. annually. Various tissue engineering methods, such as grafting, scaffold-based, and scaffold-free techniques have emerged, contributing to creating bone-like tissues for the repair or regeneration of damaged or diseased bone. This damage is caused by factors such as infections, inflammation, trauma, tumors, metabolic disorders, congenital anomalies, and aging. Furthermore, additive biomanufacturing methods, such as extrusion-based bioprinting, droplet-based bioprinting, and laser-based bioprinting, have been successfully utilized for fabrication of bone-like tissue constructs. The overarching goal of this work is to fabricate mechanically robust, dimensionally accurate, and biocompatible bone tissue scaffolds for the treatment of bone pathology. The overall objective of the work is to investigate the influence of (i) single-screw filament extrusion temperature and (ii) internal scaffold microstructures, on the physical as well as mechanical properties of bone tissue scaffolds, fabricated using fused deposition modeling (FDM) additive manufacturing process.

Materials and

Methods: In this study, uniform monofilaments, composed of polypropylene (PP) and glass fibers (GF) pellets, were extruded (prior to FDM-based scaffold fabrication) using a single-screw material extrusion system, operating at three extrusion temperatures of 185 °C, 210 °C, and 235 °C. Subsequently, the extruded monofilaments (having a standard diameter of 1.75 mm) were fed into an FDM manufacturing system for fabrication of bone tissue scaffolds. In addition, four scaffolds with complex microstructures and novel mathematical formulations were parametrically designed and fabricated (each replicated eight times, n=8), based on the fundamental concepts of triply periodic minimal surfaces (TPMS). The physical and mechanical properties of the fabricated scaffolds, such as deposition mass, compression modulus, density, and shrinkage (which is indicative of deviation from design dimensions), were characterized in order to identify an optimal composite filament extrusion temperature as well as TPMS scaffold design.

Results, Conclusions, and Discussions: It was observed that TPMS Design #2 (out of the four novel designs) had the highest level of compression modulus followed by TPMS Designs #3 and #4, while TPMS Design #1 appeared to have the lowest level of stiffness. This can be attributed to the relatively compact and regular microstructure of Design #2. In addition, it was observed that the extrusion temperatures of 210 °C and 235 °C had comparable influence on the deposition mass, density, as well as the compression modulus of the fabricated scaffolds (in contrast to the extrusion temperatures of 185 °C). Overall, the outcomes of this study will aid in converting research-developed bone scaffolds to clinical applications (where practicality and reproducibility are vital) and will also pave the way for future development of more effective, consistent, and practical scaffold designs and compositions to potentially enhance tissue engineering and regenerative medicine practices.

Acknowledgements (Optional): This research work was made possible by the NASA Established Program to Stimulate Competitive Research (EPSCoR) - Rapid Response Research (R3), Grant # 80NSSC22M0249.