Simulation of cortico-cancellous bone structure by 3D printing of bilayer calcium phosphate-based scaffolds

Traditional methods of fabrication for porous bone scaffolds are unable to accurately mimic the desirable cortico-cancellous morphology and the structure of the bone. In this study, 3D printing of a β-Tricalcium phosphate (TCP)-based paste was used to develop scaffolds simulating the two distinct cortical and cancellous layers of the natural bone. Laser microscope imaging showed that the pore sizes were 242.2±24.3. μm and 410.5±27.9. μm for the cortical and cancellous layers, respectively. Micro CT analysis revealed overall porosity and interconnectivity of 61.8±1.4% and 208707.5±52405, respectively. Mechanical properties were within the range of human cancellous bone with 10.0±2.4. MPa strength and 55.5±5.7. MPa young's modulus. The X-ray diffraction (XRD) analysis showed that the phase composition of the printed scaffolds was almost identical to pure TCP. Scanning electron microscopy (SEM) and cell vitality assessment indicated significant osteoblastic proliferation on the surface of the scaffolds. The gene expression analysis showed an increase in the level of Collagen I (Col I), Osteonectin (ON), Ostocalcin (OC), and Osteopontin (OPN) with a significant increase in OC and OPN at day 10. In conclusion, 3D printing can be used to develop a TCP-based scaffold with controllable and reproducible microstructures and favourable in vitro biological properties with potential to be further developed to be used for clinical bone regeneration.