3D-printed carbonate apatite scaffolds inspired by cuttlebone biomechanics and blood flow dynamics for layer-by-layer...

In bone tissue engineering, scaffolds are required to resist mechanical impact and promote bone regeneration, both are highly dependent on the structure of the scaffolds. In this study, we aimed to develop scaffolds inspired by the uniquely layered and curved structure of cuttlebone, which underlies its distinctive biomechanical behavior, and it is hypothesized to promote favorable blood flow dynamics. The scaffolds were composed of carbonate apatite, bone mineral analog, and designed with three structures: one with straight interlayer walls (SW) and two with curved walls (CW). In the CW designs, the bottom curvature amplitude was fixed at 0.3 mm, while the top was 0.6 mm (CW-2) or 0.9 mm (CW-3). Upon compression, CW-3 scaffolds exhibited a distinct layer-by-layer collapse pattern, whereas SW and CW-2 scaffolds collapsed as a whole. Computational fluid dynamics revealed that SW scaffolds had uniformly fast blood flow throughout their channels. Compared to SW, CW scaffolds showed reduced flow velocities across their channels, with markedly slower flow near the concave regions of their curved walls. These flow dynamics affected the distribution of wall shear stress (WSS); CW scaffolds showed a higher proportion of WSS values favorable for cell adhesion and proliferation than SW. At both 4 and 12 weeks post-surgery, the in vivo bone formation in the CW scaffold groups was significantly greater than that observed in the SW scaffold and sham groups. This study elucidates CW-3 structure offers both mechanical resilience and enhanced bone formation, representing a significant advancement in the field of bone tissue engineering.