Pietak Alexis M, Reid Joel W, Sayer Michael
Physics Department, Queen's University, Stirling Hall, Kingston, Ont, K7L 3N6, Canada.
Biomaterials. 2005 Jun;26(18):3819-30. doi: 10.1016/j.biomaterials.2004.10.013.
Impurity centers associated with silicon have been observed in the phase mixture of silicon substituted apatite (Si-Ap) and silicon stabilized tricalcium phosphate (Si-TCP) using electron spin resonance (ESR). Two unique centers occur upon addition of SiO2 to the calcium phosphate system: an orthorhombic center with g-values 2.0072+/-0.0001, 2.0024+/-0.0001 and 2.0003+/-0.0001 (Si-h1) and a center with tetrahedral symmetry having g-values components 2.0054+/-0.0001 and 1.9992+/-0.0003 (Si-h2). Both centers are hypothesized to be characteristic of defects associated with silicon in the Si-Ap phase. Through comparison of the intensity of F-OH centers in undoped calcium hydroxyapatite (HA) prepared with various levels of OH occupancy, a relationship is demonstrated between the ESR intensity of an F-center signal with g = 2.0019+0.0004 (F-OH) and the OH occupation of HA. Relative changes in the intensity of ESR signals Si-h1 and F-OH are consistent with a chemical model describing the substitution of SiO4(4-) for PO4(3-) in HA with the creation of OH- vacancies as charge compensation, resulting in a mixed phase composition of Si-Ap and Si-TCP that results when a hydroxyapatite precipitate (HA) is heated in the presence of added SiO2.
利用电子自旋共振（ESR）在硅取代磷灰石（Si-Ap）和硅稳定磷酸三钙（Si-TCP）的相混合物中观察到了与硅相关的杂质中心。向磷酸钙体系中添加SiO₂时会出现两个独特的中心：一个正交中心，其g值为2.0072±0.0001、2.0024±0.0001和2.0003±0.0001（Si-h1），以及一个具有四面体对称性的中心，其g值分量为2.0054±0.0001和1.9992±0.0003（Si-h2）。这两个中心都被假定为Si-Ap相中与硅相关的缺陷的特征。通过比较用不同OH占据水平制备的未掺杂羟基磷灰石（HA）中F-OH中心的强度，证明了g = 2.0019+0.0004的F中心信号（F-OH）的ESR强度与HA的OH占据之间的关系。ESR信号Si-h1和F-OH强度的相对变化与一个化学模型一致，该模型描述了在HA中用SiO₄⁴⁻取代PO₄³⁻并产生OH空位作为电荷补偿，从而导致当羟基磷灰石沉淀（HA）在添加了SiO₂的情况下加热时形成Si-Ap和Si-TCP的混合相组成。
