Effect of sintering temperature and cooling rate on the morphology, mechanical behavior and apatite-forming ability of a novel nanostructured magnesium calcium silicate scaffold prepared by a freeze casting method

In this research, sol–gel-derived nanostructured calcium magnesium silicate (merwinite)-based scaffolds were fabricated by water-based freeze casting method. The effect of cooling rate and sintering temperature on pore sizes and mechanical characteristics of the scaffolds was studied. Microstructure and surface morphology of scaffolds were also observed by scanning electron microscopy before and after various time intervals of soaking in simulated body fluid. The results showed that increasing temperature at the constant rate led to increasing the parameters of volume and linear shrinkage, strength (σ), and Young’s modulus (E) but decreasing porosity. This increase was significant for strength and Young’s modulus. In addition, with the increase of rate at the constant temperature, the parameters of volume and linear shrinkage and also porosity decreased whereas strength and Young’s modulus increased significantly. According to the obtained mechanical results, the best mechanical properties were achieved when the scaffold was prepared at cooling rate and sintering temperature of 277.15°K/min and 1623.15°K, respectively (E = 0.048 GPa and σ = 2 MPa). These values were closer to the lower limit of the values for cancellous bone. The acellular in vitro bioactivity revealed that different apatite morphologies were formed on the surfaces for various periods of soaking time when the scaffolds prepared at the freezing temperature of 277.15°K/min and at the two different sintering temperatures. The favorable mechanical behavior of the porous constructs, coupled with the ability of forming apatite particles on the surface of scaffold, indicates the potential of the present freeze casting route for the production of porous scaffolds for bone tissue engineering.