Inversely 3D-Printed β-TCP Scaffolds for Bone Replacement

Abstract

The aim of this study was to predefine the pore structure of β-tricalcium phosphate (β-TCP) scaffolds with different macro pore sizes (500, 750, and 1000 µm), to characterize β-TCP scaffolds, and to investigate the growth behavior of cells within these scaffolds. The lead structures for directional bone growth (sacrificial structures) were produced from polylactide (PLA) using the fused deposition modeling techniques. The molds were then filled with β-TCP slurry and sintered at 1250 °C, whereby the lead structures (voids) were burnt out. The scaffolds were mechanically characterized (native and after incubation in simulated body fluid (SBF) for 28 d). In addition, biocompatibility was investigated by live/dead, cell proliferation and lactate dehydrogenase assays. The scaffolds with a strand spacing of 500 µm showed the highest compressive strength, both untreated (3.4 ± 0.2 MPa) and treated with simulated body fluid (2.8 ± 0.2 MPa). The simulated body fluid reduced the stability of the samples to 82% (500), 62% (750) and 56% (1000). The strand spacing and the powder properties of the samples were decisive factors for stability. The fact that β-TCP is a biocompatible material is confirmed by the experiments. No lactate dehydrogenase activity of the cells was measured, which means that no cytotoxicity of the material could be detected. In addition, the proliferation rate of all three sizes increased steadily over the test days until saturation. The cells were largely adhered to or within the scaffolds and did not migrate through the scaffolds to the bottom of the cell culture plate. The cells showed increased growth, not only on the outer surface (e.g., 500: 36 ± 33 vital cells/mm² after three days, 180 ± 33 cells/mm² after seven days, and 308 ± 69 cells/mm² after 10 days), but also on the inner surface of the samples (e.g., 750: 49 ± 17 vital cells/mm² after three days, 200 ± 84 cells/mm² after seven days, and 218 ± 99 living cells/mm² after 10 days). This means that the inverse 3D printing method is very suitable for the presetting of the pore structure and for the ingrowth of the cells. The experiments on which this work is based have shown that the fused deposition modeling process with subsequent slip casting and sintering is well suited for the production of scaffolds for bone replacement.

Mechanical Properties of the Composite Material consisting of β-TCP and Alginate-Di-Aldehyde-Gelatin Hydrogel and Its Degradation Behavior

“…The samples were weighed before and after loading and every 2 days during the experiment by means of a precision balance, Kern PCB 250-3 (KERN & SOHN GmbH, Balingen, Germany). The incubation in SBF was 30 days, according to our previous studies [ 21 , 22 ]. All experiments (TRIS + SBF) were performed at 37 °C by using a Memmert drying oven UF500 (Memmert, Schwabach, Germany).…”

Bone Regeneration, Reconstruction and Use of Osteogenic Cells; from Basic Knowledge, Animal Models to Clinical Trials

“…The synthetic scaffold may be deemed sufficient in treatment but, in more severe cases, molecules like growth factors or hormones may be used in addition, possibly supplemented by cell therapy [115]. Such approaches were reported to achieve the desired effects, improving healing rates during the use of scaffolds [122].…”

“…However, time is needed for the 3D scaffold to be made and it is not always possible to be manufactured in the same location as the surgery [115]. Types of 3D printing include powder-based, selective laser sintering (SLS), 3D plotting using ceramic cement, and fused deposition modelling (FDM) [122]. Strategies are also being developed to improve the critical process of post-surgery vascularization, including methods using stem cells [123,124].…”

Inverse 3D Printing with Variations of the Strand Width of the Resulting Scaffolds for Bone Replacement

“…CaP are a non-toxic biomaterial and they do not cause foreign body reactions [ 29 , 34 , 38 ]. Since all previous studies have only printed 3D scaffolds into which bone is then arbitrarily grown, this study, like the previous one [ 39 ], focuses on inverse printing. The aim of this work was to vary the wall thickness and pore structure within a 3D construct and to investigate the influence on the strength as well as the degradation behavior.…”