Zhou Zihuai, Zhang Leiqing, Li Jiachen, Shi Ying, Wu Zhifang, Zheng Haiyan, Wang Zhe, Zhao Weijia, Pan Haihua, Wang Qi, Jin Xiaogang, Zhang Xing, Tang Ruikang, Fu Baiping
The Affiliated Hospital of Stomatology, School of Stomatology, Zhejiang University School of Medicine, and Key Laboratory of Oral Biomedical Research of Zhejiang Province, Hangzhou, Zhejiang 310006, China.
Nanoscale. 2021 Jan 14;13(2):953-967. doi: 10.1039/d0nr05640e. Epub 2020 Dec 24.
Polyelectrolytes such as polyaspartic acid (PAsp) are critical in biomimetic mineralization as stabilizers of amorphous calcium phosphate (ACP) precursors and as nucleation inhibitors similar to non-collagenous proteins (NCPs). Nevertheless, the application of polyelectrolyte-calcium complexes as a pre-precursor, such as PAsp-Ca complexes, in the mineralization of collagen is unexplored. Herein, we propose a polyelectrolyte-Ca complex pre-precursor (PCCP) process for collagen mineralization. By combining three-dimensional (3D) STORM, potential measurements, and cryogenic transmission electron microscopy with molecular dynamics simulations, we show that liquid-like electropositive PAsp-Ca complexes along with free calcium ions infiltrate electronegative collagen fibrils. The PAsp-Ca complexes are immobilized within the fibrils via chelation and hydrogen bonds, and outward movement of free calcium ions is prevented while phosphate and hydroxide are recruited through electrostatic attractions. Afterwards, ACP instantly forms and gradually crystallizes. The PCCP process not only unites two distinct crystallization pathways (classical (free Ca/P ions) and non-classical (polyelectrolyte-Ca complexes)), but also provides a novel strategy for rapid biomimetic mineralization of collagen.
聚电解质如聚天冬氨酸（PAsp）在仿生矿化中起着关键作用，它可作为无定形磷酸钙（ACP）前体的稳定剂，以及类似于非胶原蛋白（NCPs）的成核抑制剂。然而，聚电解质 - 钙复合物作为预前体，如PAsp - Ca复合物，在胶原蛋白矿化中的应用尚未得到探索。在此，我们提出了一种用于胶原蛋白矿化的聚电解质 - 钙复合物预前体（PCCP）方法。通过将三维（3D）STORM、电位测量、低温透射电子显微镜与分子动力学模拟相结合，我们发现类似液体的带正电的PAsp - Ca复合物以及游离钙离子会渗入带负电的胶原纤维。PAsp - Ca复合物通过螯合作用和氢键固定在纤维内，阻止了游离钙离子的向外移动，同时通过静电吸引作用招募磷酸根和氢氧根。之后，ACP立即形成并逐渐结晶。PCCP方法不仅结合了两种不同的结晶途径（经典途径（游离Ca/P离子）和非经典途径（聚电解质 - 钙复合物）），还为胶原蛋白的快速仿生矿化提供了一种新策略。
