Development of magnesium calcium phosphate biocement for bone regeneration

Abstract

Magnesium calcium phosphate biocement (MCPB) with rapid-setting characteristics was fabricated by using the mixed powders of magnesium oxide (MgO) and calcium dihydrogen phosphate (Ca(H(2)PO(4))(2).H(2)O). The results revealed that the MCPB hardened after mixing the powders with water for about 7 min, and the compressive strength reached 43 MPa after setting for 1 h, indicating that the MCPB had a short setting time and high initial mechanical strength. After the acid-base reaction of MCPB containing MgO and Ca(H(2)PO(4))(2).H(2)O in a molar ratio of 2 : 1, the final hydrated products were Mg(3)(PO(4))(2) and Ca(3)(PO(4))(2). The MCPB was degradable in Tris-HCl solution and the degradation ratio was obviously higher than calcium phosphate biocement (CPB) because of its fast dissolution. The attachment and proliferation of the MG(63) cells on the MCPB were significantly enhanced in comparison with CPB, and the alkaline phosphatase activity of MG(63) cells on the MCPB was significantly higher than on the CPB at 7 and 14 days. The MG(63) cells with normal phenotype spread well on the MCPB surfaces, and were attached in close proximity to the substrate, as seen by scanning electron microscopy (SEM). The results demonstrated that the MCPB had a good ability to support cell attachment, proliferation and differentiation, and exhibited good cytocompatibility.

Figure 1.

Effect of P/L mass ratio on (a) setting time and (b) compressive strength of MCPB after setting for 48 h. Diamonds, MCPB; squares, CPB.

Figure 2.

Effect of hardening time on compressive strength of MCPB with a P/L ratio of 2.8 g g⁻¹. Black bar, MCPB; grey bar, CPB.

Figure 3.

XRD patterns of MCPB after setting for 7 days with a P/L mass ratio of 2.8 g g⁻¹. Open circles, Ca₃(PO₄)₂; asterisks, Mg₃(PO₄)₂.

Figure 4.

FT-IR spectra of MCPB after setting for 7 days with a P/L mass ratio of 2.8 g g⁻¹.

Figure 5.

SEM images of the morphology and microstructure of MCPB after setting for 7 days with a P/L mass ratio of 2.8 g g⁻¹ under different magnifications (a, 5000× and b, 10 000×); long arrow represents Mg₃(PO₄)₂; short arrow represents Ca₃(PO₄)₂. Mg₃(PO₄)₂ (c, 10 000×) and Ca₃(PO₄)₂ (d, 5000×) as controls.

Figure 6.

Weight loss ratios of MCPB (CPB as a control) immersed in Tris–HCl solution with time (a: diamonds, MCPB; circles, CPB), and SEM images of the morphology/microstructure of MCPB after immersion in Tris–HCl solution for 30 days under different magnifications, (b) 30× and (c) 5000×.

Figure 7.

Tendency of Ca, Mg, P ion concentrations to change in Tris–HCl solution after immersion of MCPB and CPB for 3 days. Diamonds, MCPB[Ca]; open squares, MCPB[Mg]; triangles, MCPB[P]; circles, CPB[Ca]; filled squares, CPB[P].

Figure 8.

Change in pH of Tris–HCl solution after MCPB and CPB immersion for 7 days. Diamonds, MCPB; squares, CPB.

Figure 9.

Cell proliferation on MCPB, CPB and control (TCP) at 1, 3 and 5 days. Black bar, MCPB; grey bar, CPB; unfilled bars, control. *p < 0.05.

Figure 10.

SEM images of MG₆₃ cells cultured on MCPB for (a) 3 and (b) 5 days.

Figure 11.

ALP activity of MG₆₃ cells cultured on the MCPB, CPB and control (TCP) at 4 (black bars), 7 (grey bars) and 14 (unfilled bars) days. *p < 0.05.