Control of pore structure and mechanical property in hydroxyapatite/collagen composite using unidirectional ice growth

The porous hydroxyapatite/collagen (HAp/Col = 80/20 in weight ratio) composite with unique three-dimensional pore structures was fabricated by the control of ice crystal growth using the liquid N2 as a cooling medium and subsequent freeze-dry process, and the pore structure and mechanical properties were evaluated by SEM and compression tests. The porous composite had the unidirectionally interconnected micropores along the ice growth direction with a spindle-shaped cross-section (distributed from 40.1 × 11.0 to 110 × 21.8 μm in size). When the container was set on a cooling stage at − 30 °C, the length of the long-axes (distributed from 75.2 to 134.3 μm) reached the range that is necessary to bone tissue penetration. The defined pore structure improved its mechanical resistance against the compression and gave anisotropic compression properties against the pore directions. The porous HAp/Col composite with flexibility and shape recover properties will be a promised biomaterial for bone regeneration and other scaffold for tissue engineering.