Influence of 3D Printing Parameters on the Mechanical Stability of PCL Scaffolds and the Proliferation Behavior of Bone Cells

Abstract

Introduction The use of scaffolds in tissue engineering is becoming increasingly important as solutions need to be found for the problem of preserving human tissue, such as bone or cartilage. In this work, scaffolds were printed from the biomaterial known as polycaprolactone (PCL) on a 3D Bioplotter. Both the external and internal geometry were varied to investigate their influence on mechanical stability and biocompatibility. Materials and Methods: An Envisiontec 3D Bioplotter was used to fabricate the scaffolds. First, square scaffolds were printed with variations in the strand width and strand spacing. Then, the filling structure was varied: either lines, waves, and honeycombs were used. This was followed by variation in the outer shape, produced as either a square, hexagon, octagon, or circle. Finally, the internal and external geometry was varied. To improve interaction with the cells, the printed PCL scaffolds were coated with type-I collagen. MG-63 cells were then cultured on the scaffolds and various tests were performed to investigate the biocompatibility of the scaffolds. Results: With increasing strand thickness and strand spacing, the compressive strengths decreased from 86.18 + 2.34 MPa (200 µm) to 46.38 + 0.52 MPa (600 µm). The circle was the outer shape with the highest compressive strength of 76.07 + 1.49 MPa, compared to the octagon, which had the lowest value of 52.96 ± 0.98 MPa. Varying the external shape (toward roundness) geometry, as well as the filling configuration, resulted in the highest values of compressive strength for the round specimens with honeycomb filling, which had a value of 91.4 + 1.4 MPa. In the biocompatibility tests, the round specimens with honeycomb filling also showed the highest cell count per mm², with 1591 ± 239 live cells/mm2 after 10 days and the highest value in cell proliferation, but with minimal cytotoxic effects (9.19 ± 2.47% after 3 days).

Alternative Geometries for 3D Bioprinting of Calcium Phosphate Cement as Bone Substitute

“…Compared to this, the compressive strengths of our scaffolds were in a similar range to Mullah et al [ 17 ] between 5 and 25 MPa. In our other works [ 27 ], we also investigated the compressive strength of PCL scaffolds with different inner and outer geometries. They reached 91.4 ± 1.4 MPa and were even smaller dimensioned than the CPC scaffolds.…”

The Mineralization of Various 3D-Printed PCL Composites

“…Collagen coating in the present project was performed analogously to work we have already published [ 11 , 14 ].…”

“…This captures both images of the surface and laser scans. Surface-specific values such as surface roughness (center roughness Sa) can then be measured, analogous to our previous work [ 11 , 14 ]. To investigate the surface roughness before and after plasma treatment of the scaffolds, images were acquired using the 3D laser microscope and the surface roughness was measured at four random locations.…”

“…The PCL scaffolds were manufactured by using a 3D-BioPlotter (EnvisionTEC, Gladbeck, Germany) according to our previous work [ 11 , 14 ]. For this purpose, a 3D model of the scaffold was created in Autodesk Inventor (Autodesk Inventor 2019; Autodesk, San Raphael, CA, USA).…”

About 3D Printability of Thermoplastic Collagen for Biomedical Applications

“…The results of 3D laser scanning microscopy to determine the surface roughness of the TC scaffolds showed slightly lower values of 2.15 ± 0.43 µm compared to our other studies of scaffolds printed with the 3D bioplotter. The studies of Weingartner et al [ 26 ] and Huber et al [ 27 ] on the effect of collagen I coatings of 3D printed PCL scaffolds for bone replacement determined a surface roughness of 4.11 ± 0.27 µm and 5.42 ± 0.82 µm for uncoated specimens and 3.35 ± 0.3 µm and 2.75 ± 0.48 µm for specimens coated with type I collagen. However, these were only coatings with collagen in the micrometre range and not scaffolds of collagen.…”