Phase Transformation Dynamic Of Amorphous Calcium Phosphate

Amorphous calcium phosphate (ACP) is a kind of biomineralized materials which has a high rate of biological degradation and excellent bone conductibility. Recent research results reveal that nano-amorphous calcium phosphate plays important roles in calcium phosphate biomineralization. The assembly and phase transformation of ACP have great effects on the construction and orientation of crystals during the mineralization process. ACP widely present in vivo, and many organism use magnesium to stabilize it since it’s very unstable. This dissertation uses the method of rapidly mixing low concentration of calcium and phosphate solutions to synthesize nano-amorphous calcium phosphate powders. The ACP transformation process with and without magnesium were tracked in-situ by a high precision pH-meter. Using infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction to characterize each stage samples.In chapter one, we reviews the recent research achievements in biomineralization, especially the development from the original organic-inorganic interface molecular recognition model to recent mesoscopic assembly and precursor phase-based transformation models. Different from the classical atom/molecule mediated crystallization mechanisms, scientists have found that the colloidal amorphous phase deposits firstly in solution during biomineralization, and then organic matrix induces and controls the organized assembly of the mineral nanoparticles via the pathways of phase transformation and assembly kinetics. This new understanding provides a new strategy for biomimetic synthesis and biomedical applications. Based on the above understanding, we undertake our research.In chapter two, we synthesized nano-amorphous calcium phosphate powder using the method of rapidly mixing low concentration of calcium and phosphate solutions. The products have no difference compare with synthesized products under organic additives regulation.In chapter three, the ACP transformation process with and without magnesium was tracked in-situ by a high precision pH-meter. Since amorphous calcium phosphate’s v4stretching single peak can splitting into two peaks when it is crystallized, we use splitting function to reflect the crystalline degree of calcium phosphate. The results show that magnesium ion can prolong the induction time of amorphous calcium phosphate, but do not change the structure of final crystallized hydroxyapatite. The increasing concentration of magnesium, the longer extended time.