Material extrusion 3D printing of bioactive smart scaffolds for bone tissue engineering

3D printing of smart scaffolds, based on material extrusion-based additive manufacturing techniques, offers a novel solution for the treatment of irregular bone defects using minimally invasive techniques. However, the progress of this approach has been hindered by the lack of printable shape-memory materials and functional biomedical scaffolds that exhibit high shape recovery and closely match the core properties of human bone. Herein, we present the 3D printing of novel bioactive smart scaffolds with tunable architecture, mechanical properties, and shape memory performance. To achieve this, we developed a thermo-responsive biocompatible shape memory filament comprising poly (ε-caprolactone) and thermoplastic polyurethane, specifically tailored for material extrusion 3D printing. Careful printability assessment of the smart filament enabled successful 3D printing of scaffolds with diverse densities, pore geometries, and architectures. The scaffolds were also functionalized with a bioactive polydopamine (PDA) coating to enhance their hydrophilicity and cytocompatibility without compromising their mechanical and shape memory performance. Thermomechanical cyclic tests demonstrated that the shape fixity, shape recovery, and transition temperature of programmed scaffolds can be tailored by controlling scaffold architecture and density. The scaffolds with gyroid, rectilinear, and triangular architecture and 50% infill density exhibited excellent shape recovery performance at the transition temperature of 52°C, achieving shape recovery percentages of 98%, 91.1%, and 89.5%, respectively. Additionally, all scaffolds exhibited rapid recovery, with a maximum response time of 180 seconds. MG-63 cell evaluation confirmed the bioactivity and cytocompatibility of both untreated and PDA-treated scaffolds, with the PDA-coated scaffolds showing improved proliferation and biomineralization.