Feasibility study on surface morphology regulation of β-tricalcium phosphate bone graft for enhancing cellular response

Beta-tricalcium phosphate (βTCP) granules are commonly used as an artificial bone graft material. Meanwhile, the surface morphology of the bone graft is an important factor for cellular response. In this study, feasibility study on surface morphology regulation of βTCP bone graft for enhancing cellular response were investigated. The regulation was achieved on the basis of a multistep heating process. Briefly, initial heat treatment of βTCP granules at 1300 °C for 12 h resulted in fabrication of alpha-tricalcium phosphate (αTCP) granules with interconnected micropores. In the second heat treatment, exposure of αTCP granules to 100% relative humidity at 100 °C resulted in partial hydrolysis of αTCP, leading to the fabrication of needle-like calcium-deficient hydroxyapatite (cdHAp) crystals on the αTCP surface. After the third heat treatment at 1100 °C, both cdHAp and αTCP converted back to βTCP, and interconnected micropores with a roughened surface structure were formed. In vitro cell evaluation demonstrated that βTCP granules obtained by the series of heat treatments exhibited 24 times higher cell proliferation at day 9, and four times higher alkaline phosphatase activity compared with untreated βTCP granules. Therefore, we concluded that regulation of surface morphology by a series of heat treatments is useful for improving cellular response to βTCP bone grafting materials.