3D printed Gel/PTH@PAHA scaffolds with both enhanced osteogenesis and mechanical properties for repair of large bone defects

The repair of large bone defects continues to pose a significant challenge in clinical orthopedics. Successful repairs require not only adequate mechanical strength but also exceptional osteogenic activity for successful clinical translation. Composite materials based on polyamide 66 (PA66) and hydroxyapatite have been widely used in various clinical settings. However, existing PA66/hydroxyapatite composites often lack sufficient osteogenic stimulation despite their favorable mechanical properties, which limit their overall clinical efficacy. In this study, we fabricated a polyamide 66/nano-hydroxyapatite (PAHA) scaffold using an extruder and fused deposition modeling-based 3D printing technology. Subsequently, gelatin methacrylamide (GelMA) containing teriparatide (PTH) was incorporated into the PAHA scaffold to construct the Gel/PTH@PAHA scaffold. Material characterization results indicated that the compressive modulus of elasticity and compressive strength of the Gel/PTH@PAHA scaffold were 172.47 ± 5.48 MPa and 25.55 ± 2.19 MPa, respectively. <i>In vitro</i> evaluations demonstrated that the Gel/PTH@PAHA scaffold significantly enhanced osteoblast adhesion and proliferation while promoting osteogenic differentiation of BMSCs. <i>In vivo</i> studies further revealed that this scaffold notably promoted new bone regeneration in rabbit femoral defects. These findings suggest that the 3D-printed Gel/PTH@PAHA scaffold exhibits excellent mechanical properties alongside remarkable osteogenic activity, thereby meeting the dual requirements for load-bearing applications and bone regeneration. This innovative approach may be a promising candidate for customized orthopedic implants with substantial potential for clinical application.