Microwave-sintered 3D printed tricalcium phosphate scaffolds for bone tissue engineering.

This study reports the manufacturing process of 3D interconnected macroporous tricalcium phosphate (TCP) scaffolds with controlled internal architecture by direct 3D printing (3DP), and high mechanical strength obtained by microwave sintering. TCP scaffolds with 27%, 35% and 41% designed macroporosity with pore sizes of 500 μm, 750 μm and 1000 μm, respectively, were manufactured by direct 3DP. These scaffolds were then sintered at 1150 °C and 1250 °C in conventional electric muffle and microwave furnaces, respectively. Total open porosity between 42% and 63% was obtained in the sintered scaffolds due to the presence of intrinsic micropores along with designed pores. A significant increase in compressive strength between 46% and 69% was achieved by microwave compared to conventional sintering as a result of efficient densification. Maximum compressive strengths of 10.95 ± 1.28 MPa and 6.62 ± 0.67 MPa were achieved for scaffolds with 500 μm designed pores (~ 400 μm after sintering) sintered in microwave and conventional furnaces, respectively. An increase in cell density with a decrease in macropore size was observed during in vitro cell-material interactions using human osteoblast cells. Histomorphological analysis revealed that the presence of both micro- and macropores facilitated osteoid-like new bone formation when tested in femoral defects of Sprague-Dawley rats. Our results show that bioresorbable 3D-printed TCP scaffolds have great potential in tissue engineering applications for bone tissue repair and regeneration.