3D printing of biphasic osteochondral scaffold with sintered hydroxyapatite and polycaprolactone

Biphasic scaffolds with biomimetic structure are essential to osteochondral tissue engineering. However, insufficient mechanical properties limit their applications. Here, a novel biphasic scaffold was designed and fabricated using a multi-nozzle three-dimensional (3D) printer with hydroxyapatite (HAp) and polycaprolactone (PCL). HAp was first printed as the subchondral layer and strengthened by sintering, followed by printing PCL as the cartilage layer on top of the HAp layer. High interface bonding strength between the two layers was obtained by controlling the temperature of the printing platform. Compression tests showed that the biphasic scaffold had properties between those of pure HAp and PCL scaffolds, and its compressive modulus was about 18 MPa at the strain of 0–5% and 143 MPa at the strain of 5–10%, which was separately at the range of native cartilage and subchondral bone. Finite element simulation was adopted to investigate the variation of inner structure of the biphasic scaffold under compression, demonstrating a biomimetic strengthened structure with a deformable cartilage layer. Therefore, the biphasic HAp/PCL scaffold takes advantage of both the rigidity of HAp and the elasticity of PCL, thus has biomimetic mechanical properties for its further applications.