The Influence Of Amino Acids On The Phase Transformation And Morphology Of Calcium Phosphate

Recent studies demonstrate that a strategy widespread in biomineralization is that the initial formation of precursors followed by subsequent transformation into biologically functional mineralized tissues. The interaction between biomolecules and precursors and the influence of biomolecules on the phase transformation as well as the modulation of biomolecules on the morphology of biomaterials are the main problems in the research of biomineralization. In the present dissertation, the calcium phosphate is chosen as the research system, we have studied the effect of amino acids on the phase transformation of brushite (DCPD) to hydroxyapatite (HAP) as well as the modulation of different amino acids on the growth morphology of DCPD. The thesis consists of four chapters:In the first chapter, basic framework of biomineralization and its recent progress are introduced, especially the studies on phase transformation. The research proposals are introduced briefly in the end.In chapter 2, we focus on the effect of amino acids on the phase transformation from DCPD to HAP. At first, DCPD is synthesized, and then the phase transformation in the present of different amino acids is studied. Experimental results demonstrate that only the acidic amino acids (Asp and Glu) could trigger and promote the phase transformation, while in the control experiment as well as in the present of other amino acids, phase transformation phenomena are not detected. By the test of contact angles and constant composition, we found the mechanism that acidic amino acids promote the phase transformation both in thermodynamics and kinetics.In chapter 3, we study the modulation of different amino acids on the morphology during the growth of DCPD. The experimental results demonstrate that Cys, Asp and Glu have the most significant influence on the morphology, the influence of Ser is not so significant while the modulation of Gly and Ala on the morphology of DCPD is very weak. By testing the absorption amount of different amino acids with HPLC, we propose the amino acids with specific structure could modulate the morphology of DCPD by effective absorption in the calcium phosphate system. Chapter 4 Summary and outlook.