Evaluation of microstructure effect of the porous spherical β-tricalcium phosphate granules on cellular responses

We have developed spherical β-tricalcium phosphate (β-TCP) granules with outer pores and internal micro-channels for the use of filling bone voids. In this study, we describe the cellular behaviors associated with the variations in granule structure. By utilizing the biodegradability properties of β-TCP, we documented four different modifications of the internal structures and the outer pores, which were based on β-TCP concentration (between 0.25 and 0.67 g/mL). Pore size, specific surface area and compressive strength of the granules were also evaluated. These results were then compared with the biodegradability of β-TCP using phosphate buffered saline (PBS). The significant reduction in the mass of the granules was demonstrated from the lowest β-TCP concentration group at 7 days. To ascertain the interactions between biodegradability and cellular behaviors, proliferation and osteogenic differentiation of preosteoblasts were evaluated by 3D culture configuration. A significant difference in cell proliferation was demonstrated between the highest and the lowest β-TCP concentration group at day 1 (P<0.036), and steady increment was observed in all groups thereafter. The alkaline phosphatase (ALP) activity, which is known as the early stage of osteogenic differentiation marker, showed the typical increase during cultivation. However, the specific β-TCP concentration (0.33–0.50 g/mL) showed remarkable activity compared to the lowest and highest β-TCP concentration groups at day 21. Based on these findings, we posit that the porous spherical β-TCP granules using the β-TCP concentration at 0.33–0.50 g/mL are of clinical interest, especially for bone regeneration.