Trace fluorine substituted calcium deficient hydroxyapatite with excellent osteoblastic activity and antibacterial ability

Abstract

In natural metabolic apatite, defects play an important role in osteoblastic activity and have attracted considerable interest in biomaterials chemistry. In the present study, we have synthesized a trace fluorine substituted calcium deficient hydroxyapatite, which exhibited excellent osteoblastic activity as well as high antibacterial ability. The Ca(II) vacancy and related defects in the crystal lattice are characterized by high-resolution TEM and crystal models. It was found that calcium deficient hydroxyapatite with fluorine at a molar ratio of 0.02 exhibited a unique microstructure and corresponding properties, including high antibacterial activity, maximum adsorption of proteins, superior biocompatibility, excellent osteoblastic cell attachment, proliferation, and differentiation, and upregulated osteogenesis-related gene expressions. It is suggested that the trace fluorine induced Ca(II) vacancy and lattice defects result in the formation of a net dipole moment, changes of potential energy levels, and stronger acid sites for the necessary bioactive centers, which may induce the antibacterial ability and excellent osteoblastic activity. These results might reveal the influential role of trace fluorine in the unique crystal structure and bioactivity of biological hydroxyapatite, and furthermore suggest the promising application of trace fluorine hydroxyapatite in biomedical materials.