Effects of sintering temperature on surface morphology/microstructure, in vitro degradability, mineralization and osteoblast response to magnesium phosphate as biomedical material

Abstract

Magnesium phosphate (MP) was fabricated using a chemical precipitation method, and the biological performances of MP sintered at different temperatures as a biomedical material was investigated. The results indicated that the densification and crystallinity of MP increased as the sintering temperature increased. As the sintering temperature increased, the degradability of MP in PBS decreased, and the mineralization ability in SBF significantly increased. In addition, the MP sintered at 800 °C (MP8) possessed the lowest degradability and highest mineralization ability. Moreover, the positive response of MG63 cells to MP significantly increased as the sintering temperature increased, and MP8 significantly promoted the cell spreading, proliferation, differentiation and expressions of osteogenic differentiation-related genes. Faster degradation of MP0 resulted in higher pH environments and ion concentrations, which led to negative responses to osteoblasts. However, the appropriate degradation of MP8 resulted in suitable pH environments and ion concentrations, which led to positive responses to osteoblasts. This study demonstrated that the sintering temperature substantially affected the surface morphology/microstructure, degradability and mineralization, and osteoblasts response to magnesium phosphate.

Figure 1

TEM image (a) and EDS (b), XRD (c) and FTIR (d) results for the as-prepared MP0.

Figure 2

SEM images of the surface morphology/microstructure of MP0 (a), MP4 (b), MP6 (c) and MP8 (d) as well as the XRD (A) and IR (B) results for MP4, MP6 and MP8 after sintering MP0 at 400 °C, 600 °C and 800 °C.

Figure 3

Weight loss (A) and pH change in the solutions (B) after MP0, MP4, MP6 and MP8 were immersed in a PBS solution for different time periods. In addition, the SEM images show the surface morphology after MP0 (a), MP4 (b), MP6 (c) and MP8 (d) were soaked in a PBS solution for 3 weeks.

Figure 4

SEM images of MP0 (a), MP4 (b), MP6 (c) and MP8 (d) after soaking in SBF for 7 days.

Figure 5

EDS and XRD results for MP0 (a), MP4 (b), MP6 (c) and MP8 (d) after soaking in SBF for 7 days.

Figure 6

Changes in the Ca, Mg and P ion concentration in the solutions after MP0 (a), MP4 (b), MP6 (c) and MP8 (d) were soaked in SBF for different time periods.

Figure 7

MTT essay (A) and ALP activity (B) of MG63 cells cultured on MP0 (a), MP4 (b), MP6 (c) and MP8 (d) for different time periods. The SEM images show the cell morphology of MG63 cells cultured on MP0 (a), MP4 (b), MP6 (c) and MP8 (d) for 5 days. “*” denotes significant differences compared to MP0 and MP4,“#” denotes significant differences compared to MP6.

Figure 8

Relative mRNA expression of osteogenic differentiation-related genes: ALP (a), COL-1 (b), OPN (c) and OC (d) for MG63 cells grown on MP0, MP4, MP6 and MP8.