Evaluation of 3D printed polycaprolactone/tetracalcium phosphate nanocomposite as potential scaffold for bone tissue engineering

Three-dimensional (3D) printing is a novel technique for fabrication of bone tissue engineering scaffolds. Several inks and fillers have been used as the main components of scaffolds. This study develops scaffolds based on polycaprolactone (PCL), as printing ink, and different contents of tetracalcium phosphate nanoparticles (N-TTCP) (10-40 wt%), as a calcium-releasing source and antibacterial agent. Scanning electron microscopy and mercury porosimetry were used to investigate morphology and porosity of the scaffolds. The results showed the PCL/NTTCP scaffolds possessed controllable porosity, in the range of 35-62 %, in which adding N-TTCP decreased the pore volume and size, in a concentration-dependent manner. Moreover, incorporating N-TTCP increased biodegradation of the PCL scaffold and improved its hydrophilicity. The compressive strength of pure PCL scaffold with the strand thickness of 355 mu m was about 19 MPa. It reached to about 40 MPa by adding 40 wt% NTTCP, with the strand thickness of 470 mu m. The antibacterial activity of the pure PCL scaffold against staphylococcus aureus was 6.6 %, which increased to 58.6 % for the nanocomposite scaffold containing 40 wt % tetracalcium phosphate nanoparticles. The results of cell studies demonstrated that tetracalcium phosphate nanoparticles acted as a calcium releasing source and promoted adhesion, proliferation and ALP activity of MC3T3-E1 cells on the scaffold surfaces. Additionally, the PCL/N-TTCP scaffolds induced a higher level of bone metastasis-related proteins than the pure PCL scaffolds. Overall, the findings suggest that 3D-printed PCL/NTTCP nanocomposite scaffold is an appropriate candidate for bone tissue engineering; however, complementary in-vivo and human clinical studies are expected.