Department of Materials and Engineering, Imperial College London, London, UK.
The Francis Crick Institute, London, UK.
Sci Rep. 2018 Feb 14;8(1):3024. doi: 10.1038/s41598-018-20072-2.
The macro- and micro-structures of mineralised tissues hierarchy are well described and understood. However, investigation of their nanostructure is limited due to the intrinsic complexity of biological systems. Preceding transmission electron microscopy studies investigating mineralising tissues have not resolved fully the initial stages of mineral nucleation and growth within the collagen fibrils. In this study, analytical scanning transmission electron microscopy and electron energy-loss spectroscopy were employed to characterise the morphology, crystallinity and chemistry of the mineral at different stages of mineralization using a turkey tendon model. In the poorly mineralised regions, calcium ions associated with the collagen fibrils and ellipsoidal granules and larger clusters composed of amorphous calcium phosphate were detected. In the fully mineralised regions, the mineral had transformed into crystalline apatite with a plate-like morphology. A change in the nitrogen K-edge was observed and related to modifications of the functional groups associated with the mineralisation process. This transformation seen in the nitrogen K-edge might be an important step in maturation and mineralisation of collagen and lend fundamental insight into how tendon mineralises.
矿化组织的宏观和微观结构已得到很好的描述和理解。然而，由于生物系统的固有复杂性，对其纳米结构的研究受到限制。在研究矿化组织的先前透射电子显微镜研究中，未能完全解决胶原纤维内矿化初始阶段的矿核形成和生长。在这项研究中，采用火鸡肌腱模型，使用分析扫描透射电子显微镜和电子能量损失光谱，在矿化的不同阶段，对矿物质的形态、结晶度和化学性质进行了表征。在矿化程度较低的区域，检测到与胶原纤维结合的钙离子以及椭圆形颗粒和由无定形磷酸钙组成的较大簇。在完全矿化的区域，矿物质已转化为具有板状形态的结晶磷灰石。观察到氮 K 边的变化，并与矿化过程中相关的官能团的修饰有关。氮 K 边的这种转变可能是胶原成熟和矿化的重要步骤，为肌腱矿化的方式提供了基本的见解。
