Salt template fabrication of MgO-laden bone-mimetic gyroid scaffolds

The incorporation of bioactive nanoparticles into polymer scaffolds is essential for enhanced bone regeneration, yet conventional 3D printing is often limited by the rheological constraints of composite resins. High particle loading typically compromises printability, forcing a trade-off between bioactivity and structural fidelity. To overcome this barrier, we employed a salt-templating strategy that decouples the fabrication of complex geometries from the material formulation. This approach enabled the successful shaping of a poly(ϵ-caprolactone) (PCL) matrix heavily reinforced with magnesium oxide (MgO) nanoparticles—a formulation challenging to process via direct additive manufacturing. By infiltrating this high-viscosity composite into sacrificial salt molds, we fabricated gyroid scaffolds that retained precise bone-mimetic architectures while maximizing the functional benefits of the inorganic filler. The incorporated MgO nanoparticles acted as dual-functional agents, serving as nucleating sites to increase polymer crystallinity and mechanical stiffness, while simultaneously altering surface nanotopography to boost protein adsorption. Consequently, the scaffolds provided a potent osteoinductive microenvironment, promoting deep cellular infiltration and significantly accelerating the osteogenic differentiation of human mesenchymal stem cells. Significantly, this work establishes salt-templating as a powerful platform that resolves the long-standing “printability–bioactivity” trade-off. By unlocking the use of “unprintable” high-loading bioactive composites, it enables the fabrication of precise, mathematically defined gyroid architectures that conventional 3D printing cannot achieve, offering a new avenue for next-generation bone tissue engineering.