Fabrication, biological effects, and medical applications of calcium phosphate nanoceramics

Due to large grain sizes, the biological properties of the conventional calcium phosphate (Ca–P) bioceramics are limited to a great extent. Progresses in nanotechnological approaches now allow the fabrication of nanocrystalline Ca–P bioceramics. In this article we first review current methodologies of the Ca–P nanocrystal syntheses and nanoceramic processes. In particular, we emphasize in this article the fabrication of porous Ca–P nanoceramics using a modified co-precipitation synthesis and its microwave sintering. Subsequently, the biological properties of the three-dimensional porous Ca–P nanoceramics, involving protein adsorption, cell adhesion, bone repair, osteoconductivity and osteoinductivity, are introduced in detail on the basis of the in vitro protein adsorption and cell adhesion, and in vivo intramuscular and bone implant experiments. Because of high specific surface area, nano-level surface topography, high surface defects and interconnecting macropores with abundant micropores, the Ca–P nanoceramics can well initiate and regulate a cascade of gene activities of cells, thereby resulting in higher in vivo osteoconductivity and osteoinductivity than the conventional ones. Finally, the degradability, potential risk, and anticancer activity of the nanoceramics are discussed. In summary, because of the chemical and macro-/nanoscale structural similarities with bone, the Ca–P nanoceramics are hopeful of becoming a new generation of biomaterials for hard tissue repair.