Müller Lenka, Conforto Egle, Caillard Daniel, Müller Frank A
University of Erlangen-Nuernberg, Department of Materials Science - Biomaterials, Henkestr. 91, D-91052 Erlangen, Germany.
Biomol Eng. 2007 Nov;24(5):462-6. doi: 10.1016/j.bioeng.2007.07.011. Epub 2007 Aug 7.
Biomimetic apatite coatings were obtained by soaking chemically treated titanium in SBF with different HCO(3)(-) concentration. XRD, FTIR and Raman analyses were used to characterize phase composition and degree of carbonate substitution. The microstructure, elemental composition and preferred alignment of biomimetically precipitated crystallites were characterized by cross-sectional TEM analyses. According to XRD, the phase composition of precipitated coatings on chemically pre-treated titanium after exposure to SBF was identified as hydroxy carbonated apatite (HCA). A preferred c-axis orientation of the deposited crystals can be supposed due to the high relative peak intensities of the (002) diffraction line at 2theta=26 degrees compared to the 100% intensity peak of the (211) plane at 2theta=32 degrees . The crystallite size in direction of the c-axis of HCA decreased from 26 nm in SBF5 with a HCO(3)(-) concentration of 5 mmol/l to 19 nm in SBF27 with a HCO(3)(-) concentration of 27 mmol/l. Cross-sectional TEM analyses revealed that all distances correspond exactly to the hexagonal structure of hydroxyapatite. The HCO(3)(-) content in SBF also influences the composition of precipitated calcium phosphates. Biomimetic apatites were shown to have a general formula of Ca(10-x-y)Mg(y)(HPO(4))(x-z)(CO(3))(z)(PO(4))(6-x)(OH)(2-x-w)(CO(3))(w/2). According to FTIR and Raman analyses, it can be supposed that as long as the HCO(3)(-) concentration in the testing solutions is below 20 mmol/l, only B-type HCA (0<z<1; w=0) precipitates. At higher HCO(3)(-) concentration, it can be assumed that AB-type HCA (z=1;0<w<1) is formed.
通过将化学处理后的钛浸泡在具有不同HCO₃⁻浓度的模拟体液（SBF）中获得仿生磷灰石涂层。利用X射线衍射（XRD）、傅里叶变换红外光谱（FTIR）和拉曼分析来表征相组成和碳酸盐取代程度。通过横截面透射电子显微镜（TEM）分析来表征仿生沉淀微晶的微观结构、元素组成和择优取向。根据XRD分析，暴露于SBF后化学预处理钛上沉淀涂层的相组成被鉴定为羟基碳酸磷灰石（HCA）。由于在2θ = 26°处（002）衍射线的相对峰强度较高，与在2θ = 32°处（211）平面的100%强度峰相比，可以推测沉积晶体具有择优c轴取向。HCA的c轴方向微晶尺寸从HCO₃⁻浓度为5 mmol/l的SBF5中的26 nm减小到HCO₃⁻浓度为27 mmol/l的SBF27中的19 nm。横截面TEM分析表明，所有间距与羟基磷灰石的六方结构完全对应。SBF中的HCO₃⁻含量也会影响沉淀磷酸钙的组成。仿生磷灰石的通式显示为Ca(10 - x - y)Mg(y)(HPO₄)(x - z)(CO₃)(z)(PO₄)(6 - x)(OH)(2 - x - w)(CO₃)(w/2)。根据FTIR和拉曼分析，可以推测只要测试溶液中的HCO₃⁻浓度低于20 mmol/l，只会沉淀出B型HCA（0 < z < 1；w = 0）。在较高的HCO₃⁻浓度下，可以假定形成AB型HCA（z = 1；0 < w < 1）。
