Minerals such as hydroxyapatite form bones and other hard tissues, like tooth enamel. The precise pathways of formation of these tissues, particularly at the early stages, are not understood in detail. Insight into these processes could help to treat problems in hard tissues or prevent unwanted calcification in soft tissues.
Yu-peng Lu, Shandong University, Ji’nan, China, Petr Král, Tolou Shokuhfar, Reza Shahbazian-Yassar, University of Illinois at Chicago, USA, and colleagues have captured high-resolution, real-time images of hydroxyapatite mineralization process in an artificial saliva model. The team used artificial saliva, a solution containing all necessary inorganic ions, to induce the mineralization of hydroxyapatite and a microfluidic liquid cell transmission electron microscopy (TEM) setup to observe the formation of crystals.
The researchers observed that at first, ion-rich and ion-poor solutions form in the saliva solution and separate. Then, two coexisting nucleation paths lead to the formation of hydroxyapatite. In a “nonclassical” path, amorphous calcium phosphate (ACP) forms first and acts as the substrate for hydroxyapatite nucleation. The growth of hydroxyapatite then occurs concurrently with the dissolution of ACP. The “classical” path features direct hydroxyapatite nucleation from the solution. The work could have implications for medical research on the mineralization of bones and teeth.
- Revealing nanoscale mineralization pathways of hydroxyapatite using in situ liquid cell transmission electron microscopy,
Kun He, Michal Sawczyk, Cong Liu, Yifei Yuan, Boao Song, Ram Deivanayagam, Anmin Nie, Xiaobing Hu, Vinayak P. Dravid, Jun Lu, Cortino Sukotjo, Yu-peng Lu, Petr Král, Tolou Shokuhfar, Reza Shahbazian-Yassar,
Sci. Adv. 2020, 6, eaaz7524.