碳酸物种和氯离子对生物磷灰石磷酸钙成核的影响

Effects of carbonate species and chloride ions on calcium phosphate nucleation of biological apatite

磷灰石是骨骼和牙齿等生物硬组织的主要无机成分,对脊椎动物至关重要.生物系统的体液中普遍存在碳酸物种和Cl^(-)离子,了解这些阴离子对生物磷灰石成核过程的影响有助于解释生物矿化的控制作用.理论研究表明,Ca-O配位数在CaP成核和CaP与添加剂的界面相互作用中是一个重要描述符.CaP团簇最外层的Ca^(2+)离子能够通过静电作用吸引碳酸物种和Cl^(-)离子,从而促进CaP相的形成.在碳酸物种和Cl^(-)离子存在的情况下,钙磷石(DCPD)可以转化为羟基磷灰石(HA).平衡氧同位素分馏和振动光谱分析结果表明,Cl^(-)离子掺杂的B型HA是最有可能的生物磷灰石.上述结果可以指导阴离子掺杂的具有生物功能的磷灰石材料的合成.

Apatite is the principal inorganic component of biological hard tissues such as bone and teeth,and thus is essential to the existence of vertebrate life.Because carbonate species and chloride ions are ubiquitous in the fluids of vertebrate life forms,and these species are known to compete with phosphate species,it is critical to understand the influence of these anions on the nucleation of biological apatite.In this study,the important roles of carbonate and chloride ions in mediating inorganic calcium phosphate(CaP)phase nucleation are revealed both theoretically and experimentally.Theoretical investigations suggest that the Ca-O coordination number is an important descriptor for the nucleation of CaP and the interface interaction of the CaP-additive.Positive surface charges on the outermost Ca^(2+)ions of CaP clusters could attract carbonate species and Cl^(-)ions,promoting the formation of CaP phase.In the presence of carbonate species and Cl^(-)ions,the crystallization of hydroxyapatite(HA)from its precursor brushite(DCPD)has been observed in our experimental studies.The Cl^(-)ion-doped B-type HA is proposed to be the most likely biological apatite based on equilibrium oxygen isotope fractionation and vibrational spectroscopic analysis.The insight gained here may help rationalize the control of biomineralization,and will guide the synthesis of anion-doped biological functional apatite materials.