Three Dimensionally Printed Octacalcium Phosphate via Binder Jetting for Use in Bone Grafting Applications

This study investigates the fabrication and bioactivity of monophasic octacalcium phosphate (OCP) constructs using 3D-printed calcium sulfate precursors. A single-step and a two-step process were employed, transforming calcium sulfate into OCP through a controlled phase transformation in a disodium hydrogen phosphate solution. The results revealed that a single-step process for OCP conversion in 3D printed samples was unsuccessful due to incomplete transformation and the formation of intermediate phases such as brushite and monetite. In contrast, the two-step process enabled the efficient production of monophasic OCP in a shorter timeframe. The converted OCP samples exhibited a compressive strength of 7.65 ± 0.46 MPa and a contact angle of zero, indicating adequate handling strength and high wettability. The resorbability of 3D-printed OCP in simulated body fluid (SBF) was evaluated, showing weight loss through gradual dissolution accompanied by the release of calcium and phosphorus ions, followed by the consumption of these ions for reprecipitation back into OCP without direct transformation into hydroxyapatite (HA). Biocompatibility and bioactivity testing demonstrated high cell viability (96.67 ± 0.18%) using the MTT assay, indicating that the 3D-printed OCP was not cytotoxic. Alamar blue and alkaline phosphatase (ALP) activity assay showed that 3D-printed OCP supported preosteoblast proliferation and osteogenic differentiation.