Designing for Growth: Structural Insights into 3D-Printed Composite Scaffolds for Bone Repair

Critical-sized bone defects remain a significant clinical challenge, as their size prevents spontaneous healing and necessitates surgical intervention. Although autografts are considered the clinical gold standard, their use is limited by donor site morbidity and tissue availability, while allografts carry risks of disease transmission and long-term failure. In this study, we developed a composite polymer ink for high-resolution digital light processing (DLP) 3D printing of bone tissue engineering scaffolds intended for load-bearing applications. A combination of poly(propylene fumarate) (PPF), poly(caprolactone fumarate) (PCLF), and hydroxyapatite (HA) was formulated to achieve tunable mechanical properties and controlled scaffold architecture. Scaffolds with varying porosities and material compositions were fabricated and evaluated using compressive mechanical testing and finite element modeling to assess structural integrity and stress distributions. In vitro studies using preosteoblast cells demonstrated consistently high cell viability (>75%) across all scaffold designs, with sustained proliferation over 7 days. Notably, scaffold porosity and material composition influenced proliferative responses, with significant increases observed in select formulations. Collectively, these results demonstrate that DLP-printed PPF/PCLF/HA composite scaffolds provide a mechanically viable and cytocompatible platform with tunable properties, supporting their potential utility in bone tissue engineering applications.Impact StatementCritical-sized bone defects lack effective, widely accessible treatment options due to the limitations of current grafting strategies. This work introduces a digitally light processed (DLP) 3D-printable composite scaffold with tunable mechanical properties and architecture suitable for load-bearing applications. By integrating poly(propylene fumarate), poly(caprolactone fumarate), and hydroxyapatite, the platform enables control over structural and biological performance while maintaining high cytocompatibility. These findings highlight a scalable and customizable approach to bone tissue engineering that may reduce reliance on traditional grafts and improve outcomes in complex bone repair.