Hard-templating synthesis of a novel rod-like nanoporous calcium phosphate bioceramics and their capacity as antibiotic carriers

Calcium phosphate ceramics analogous to the mineral component of bones, their biocompatibility and osteoconductive properties make them desirable as implant materials and delivery agents of drug and DNA molecules. Here we report a hard-templating synthesis of nanoporous calcium phosphate ceramics, which is based on filling the calcium and phosphorus sources into the nanospaces of rod-like ordered mesoporous carbon (CMK-3). The removal of the carbon template by combustion leads to rod-like nanoporous calcium phosphate bioceramics. They have disordered three-dimensional (3D) interconnected nanopores with diameter of 20-30 nm. The wall thickness is approximately 20-30 nm. Based on nitrogen sorption isotherms, the pore size, surface area and pore volume of this material is ∼30 nm, 27 m² g^-1 and 0.27 cm³ g^-1, respectively. Wide-angle XRD and IR measurements reveal that the inorganic walls of products consist of highly crystalline calcium phosphates with main hydroxyapatite phases. In antibiotic charging experiments, these nanoporous bioceramics show a much higher charging capacity (1621 μg g^-1) than that of commercially available calcium phosphate (100 μg g^-1), which does not have any nanoporosity.