Laboratoire de Biomécanique & Bioingénierie, Université de Technologie de Compiègne, CNRS, BP 20529, CEDEX, F-60205 Compiègne, France.
Laboratoire de Réactivité de Surface, Sorbonne Université, CNRS, F-75005 Paris, France.
Int J Mol Sci. 2022 Dec 20;24(1):43. doi: 10.3390/ijms24010043.
While it has long been mimicked by simple precipitation reactions under biologically relevant conditions, calcium phosphate biomineralization is a complex process, which is highly regulated by physicochemical factors and involves a variety of proteins and other biomolecules. Alkaline phosphatase (ALP), in particular, is a conductor of sorts, directly regulating the amount of orthophosphate ions available for mineralization. Herein, we explore enzyme-assisted mineralization in the homogeneous phase as a method for biomimetic mineralization and focus on how relevant ionic substitution types affect the obtained minerals. For this purpose, mineralization is performed over a range of enzyme substrate concentrations and fluoride concentrations at physiologically relevant conditions (pH 7.4, T = 37 °C). Refinement of X-ray diffraction data is used to study the crystallographic unit cell parameters for evidence of ionic substitution in the lattice, and infrared (IR) spectroscopy and X-ray photoelectron spectroscopy (XPS) are used for complementary information regarding the chemical composition of the minerals. The results show the formation of substituted hydroxyapatite (HAP) after 48 h mineralization in all conditions. Interestingly, an expansion of the crystalline unit cell with an increasing concentration of the enzyme substrate is observed, with only slight changes in the particle morphology. On the contrary, by increasing the amount of fluoride, while keeping the enzyme substrate concentration unchanged, a contraction of the crystalline unit cell and the formation of elongated, well-crystallized rods are observed. Complementary IR and XPS data indicate that these trends are explained by the incorporation of substituted ions, namely CO and F, in the HAP lattice at different positions.
虽然在生物相关条件下通过简单的沉淀反应长期以来一直被模仿，但磷酸钙生物矿化是一个复杂的过程，它受到物理化学因素的高度调节，涉及多种蛋白质和其他生物分子。特别是碱性磷酸酶 (ALP)，是一种导体，直接调节可用于矿化的正磷酸盐离子的数量。在此，我们探索了均相中的酶辅助矿化作为仿生矿化的一种方法，并重点研究了相关离子取代类型如何影响所获得的矿物质。为此，在生理相关条件 (pH 7.4，T = 37°C) 下，在一系列酶底物浓度和氟化物浓度下进行矿化。X 射线衍射数据的细化用于研究晶格中离子取代的晶胞参数，红外 (IR) 光谱和 X 射线光电子能谱 (XPS) 用于补充有关矿物质化学成分的信息。结果表明，在所有条件下，经过 48 小时矿化后都会形成取代的羟基磷灰石 (HAP)。有趣的是，观察到随着酶底物浓度的增加，晶胞参数的膨胀，而颗粒形态只有微小变化。相反，通过增加氟化物的量，同时保持酶底物浓度不变，观察到晶胞参数的收缩和长而结晶良好的棒的形成。补充的 IR 和 XPS 数据表明，这些趋势可以通过在 HAP 晶格中不同位置掺入取代离子（即 CO 和 F）来解释。
