Bone resembling apatite by amorphous-to-crystalline transition driven self-organisation

Abstract

Calcium apatite is the main inorganic constituent of mammalian hard tissues such as bones and teeth. Its formation in vivo is likely to be preceded by a transient amorphous phase. If so, the amorphous-to-crystalline transition would have some crucial role in the biomineralisation process. To investigate this possibility, a two-step biomimetic experiment was designed. First, a stable amorphous calcium apatite precursor was synthesized in simulated body fluid (SBF) and was then transformed into a low crystalline apatite. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, vacuum FTIR, inductively coupled plasma-atomic emission spectrometry (ICP-AES), scanning electron microscopy (SEM) and N(2) adsorption measurements were used to characterise both the precursor and the apatite. The latter exhibits numerous bone-like features including lack of OH, nanometer size, low crystallinity, etc. An amorphous-to-crystalline transition driven self-organisation is observed. The amorphous precursor seems to be the essential step for the creation of bone resembling apatite.