Journal of Peking University(Health Sciences) ›› 2019, Vol. 51 ›› Issue (1): 115-119. doi: 10.19723/j.issn.1671-167X.2019.01.021

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

Rong LI1,Ke-long CHEN2,Yong WANG1,Yun-song LIU1,Yong-sheng ZHOU1,(),Yu-chun SUN1,()   

  1. 1. Center for Digital Dentistry, Department of Prosthodontics, Peking University School and Hospital of Stomatology & National Clinical Research Center for Oral Diseases & National Engineering Laboratory for Digital and Material Technology of Stomatology & Beijing Key Laboratory of Digital Stomatology, Beijing 100081, China
    2. Shinotech Co., Ltd, Beijing 100080, China
  • Received:2017-05-06 Online:2019-02-18 Published:2019-02-26
  • Contact: Yong-sheng ZHOU,Yu-chun SUN E-mail:kqzhouysh@hsc.pku.edu.cn;polarshining@163.com
  • Supported by:
    Supported by the National Natural Science Foundation of China(51475004);the National Key Research and Development Program of China(2016YFC1102900);the Project for Culturing Leading Talents in Scientific and Technological Innovation of Beijing(Z171100001117169);and Joint Grant from PKUHSC-KCL Joint Institute for Medical Research

Abstract:

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 fromthe 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.

Key words: Bone tissue engineering, Scaffold, Polylactide, Polycaprolactone, Fused deposition modeling

CLC Number: 

  • R78

Figure 1

Cuboid CAD model (dimensions: 10 mm×10 mm×2 mm)"

Figure 2

Print path generated by the slicing software"

Figure 3

Cuboid scaffolds printed by the elements mixture-Ⅰ bioprinter A, upper surface of the PLA scaffold; B, upper surface of the PCL scaffold; C, vertical section of PLA scaffold; D, vertical section of PCL scaffold (cut by a scalpel)."

Table 1

Macro dimensions of printed PLA and PCL scaffolds [median (IQR)]"

Items PLA/mm PCL/mm Kolmogorov-Smirnov Z value P value
Length 9.950 (0.020) 9.845 (0.025) 2.236 0.000
Width 9.950 (0.003) 9.845 (0.045) 2.236 0.000
Height 1.970 (0.023) 1.950 (0.043) 0.894 0.400

Figure 4

3D measurement laser microscope observations of the printed cuboid scaffolds (×200) A, laser graphical representation of PLA scaffold; B, laser graphical representation of PCL scaffold; C, 3D graphical representation of PLA scaffold(select two points in the laser graphical representation under the “Outline-Set 2 Measure” command and further adjust the points in the 3D graphical representation to take measurements; arrows refer to the artifacts)."

Table 2

Micro structure parameters of printed PLA and PCL scaffolds (x?±s)"

Items PLA/μm PCL/μm t value P value Difference value of mean (PLA-PCL) 95% confidence interval
Pore 1 297.99±6.89 297.87±3.02 0.064 0.949 0.11 -3.49-3.72
Strut 1 295.90±4.59 291.97±3.75 2.813 0.008 3.93 1.09-6.77
Pore 2 274.09±8.35 281.96±5.34 -3.367 0.002 -7.87 -12.61--3.12
Strut 2 321.12±5.74 303.63±5.12 9.641 0.000 17.49 13.80-21.17

Figure 5

Laser graphical representation of the vertical section of PCL scaffold (×200,cut by a scalpel)"

Figure 6

3D graphical representation of a two-layer PLA scaffold structure(×200)"

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