COPPER WHITLOCKITE SYNTHESIZED VIA HYDROTHERMAL TRANSFORMATION OF CALCIUM HYDROGEN PHOSPHATE DIHYDRATE

Abstract

Metal ion substitution in calcium phosphate provides a vehicle for therapeutic delivery of metal ions at low cost and with a long shelf life. The whitlockite structure can incorporate metal ions, which enables the introduction of antibacterial and antiviral agents such as copper ions. The present study describes the synthesis of copper whitlockite (CuWH) via a single-step hydrothermal transformation of calcium hydrogen phosphate dihydrate in the presence of copper ions. Hexahedral morphology of single-phase CuWH was synthesized at 220 °C for 12 h at pH 2.0 in the presence of 5 to 7 mol% Cu 2+ ions, suggesting that CuWH precipitation was both dose-and pH-dependent. The CuWH structure contained protonated phosphate, which also suggests that Cu 2+ ions were incorporated not only into the Ca(5) site but also the Ca(4) site. The dissolution test mimicking a bioresorption environment created by osteoclasts showed similar dissolution characteristics of Ca 2+ and Cu 2+ ions in acetic acid-sodium acetate buffer solution containing potassium nitrate at pH 5.5.