Morphologies, mechanical and in vitro behaviors of DLP-based 3D printed HA scaffolds with different structural configurations

Abstract

In the field of bone engineering, porous ceramic scaffolds are in great demand for repairing bone defects. In this study, hydroxyapatite (HA) ceramic scaffolds with three different structural configurations, including the body-centered cubic (BCC), the face-centered cubic (FCC), and the triply periodic minimal surface (TPMS), were fabricated through digital light processing (DLP) based 3D printing technologies. The effects of the structural configurations on the morphologies and mechanical properties of the DLP-based 3D printed HA scaffolds were characterized. Furthermore, in vitro evaluations, including in vitro cytocompatibility, bone alkaline phosphatase (ALP) activity assay, and protein expression, were conducted to assess HA scaffold behavior. Finally, we evaluated the effects of structural configurations from these aspects and selected the most suitable structure of HA scaffold for bone repair.

Fig. 1. Schematic diagram of the study on morphologies, mechanical and in vitro behaviors of DLP 3D printed HA scaffolds.

Fig. 2. Single cell, scaffold, and top view of (a) BCC, (b) FCC, and (c) TPMS.

Fig. 3. Macro and microstructures of three HA scaffolds: (a) BCC, (b) FCC, and (c) TPMS. Footnote 1 means photograph; footnotes 2 and 3 represent enlarged SEM images.

Fig. 4. (a) Compressive strain–compressive stress, and (b) compressive strength of HA scaffolds.

Fig. 5. (a) Detection of cell growth of BMSCs cells at 1, 4, and 7 days using the CCK8 method; (b) live/dead assay of stent-cultured rat bone marrow mesenchymal stem cells (red indicates dead, green indicates alive): (i) experiments were performed using rat bone marrow mesenchymal stem cells. Live/dead BMSCs on (ii) BCC, (iii) FCC, and (iv) TPMS (* indicates the statistical difference between this group and the blank group; where N, difference is not statistically significant. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001).

Fig. 6. Expression activity of ALP on DLP 3D printed HA scaffolds after BMSCs cells were cultured on scaffolds for 1, 4, and 7 days (* indicates the statistical difference between this group and the blank group; where N, difference is not statistically significant. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001).

Fig. 7. Expression of osteogenic proteins on DLP 3D printed HA scaffolds of BCC, FCC, and TPMS structures: (a) OPN; (b) Runx2; (c) Col-1 (d); (d) VEGFR2; (e) vWF; and (f) CD31 (* indicates the statistical difference between this group and the blank group; where N, difference is not statistically significant. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001).