[Establishment of a 3D printing system for bone tissue engineering scaffold fabrication and the evaluation of its controllability over macro and micro structure precision].

OBJECTIVE: To establish a 3D printing system for bone tissue engineering scaffold fabrication based on the principle of fused deposition modeling, and to evaluate the controllability over macro and micro structure precision of polylactide (PLA) and polycaprolactone (PCL) scaffolds.

METHODS: The system was composed of the elements mixture-I bioprinter and its supporting slicing software which generated printing control code in the G code file format. With a diameter of 0.3 mm, the nozzle of the bioprinter was controlled by a triaxial stepper motor and extruded melting material. In this study, a 10 mm×10 mm×2 mm cuboid CAD model was designed in the image ware software and saved as STL file. The file was imported into the slicing software and the internal structure was designed in a pattern of cuboid pore uniform distribution, with a layer thickness of 0.2 mm. Then the data were exported as Gcode file and ready for printing. Both polylactic acid (PLA) and polycaprolactone (PCL) filaments were used to print the cuboid parts and each material was printed 10 times repeatedly. After natural cooling, the PLA and PCL scaffolds were removed from the platform and the macro dimensions of each one were measured using a vernier caliper. Three scaffolds of each material were randomly selected and scanned by a 3D measurement laser microscope. Measurements of thediameter of struts and the size of pores both in the interlayer overlapping area and non-interlayer overlapping area were taken.

RESULTS: The pores in the printed PLA and PCL scaffolds were regular and interconnected. The printed PLA scaffolds were 9.950 (0.020) mm long, 9.950 (0.003) mm wide and 1.970 (0.023) mm high, while the PCL scaffolds were 9.845 (0.025) mm long, 9.845 (0.045) mm wide and 1.950 (0.043) mm high. The struts of both the PLA and PCL parts became wider inthe interlayer overlapping area, and the former was more obvious. The difference between the designed size and the printed size was greatest in the pore size of the PLA scaffolds in interlayer overlapping area [(274.09 ± 8.35) μm)], which was 26.91 μm. However, it satisfied the requirements for research application.

CONCLUSION: The self-established 3D printing system for bone tissue engineering scaffold can be used to print PLA and PCL porous scaffolds. The controllability of this system over macro and micro structure can meet the precision requirements for research application.