Laboratory of Physical Chemistry and Center for Multiscale Electron Microscopy, Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, P.O. Box 513, Eindhoven 5600 MB, The Netherlands.
ACS Biomater Sci Eng. 2021 Jul 12;7(7):3123-3131. doi: 10.1021/acsbiomaterials.1c00416. Epub 2021 Jun 23.
The mineralization of collagen via synthetic procedures has been extensively investigated for hydroxyapatite as well as for silica and calcium carbonate. From a fundamental point of view, it is interesting to investigate whether collagen could serve as a generic mineralization template for other minerals, like iron oxides. Here, bio-inspired coprecipitation reaction, generally leading to the formation of magnetite, is used to mineralize collagen with iron hydroxides. Platelet-shaped green rust crystals form outside the collagen matrix, while inside the collagen, nanoparticles with a size of 2.6 nm are formed, which are hypothesized to be iron (III) hydroxide. Mineralization with nanoparticles inside the collagen solely occurs in the presence of poly(aspartic acid) (pAsp). In the absence of pAsp, magnetite particles are formed around the collagen. Time-resolved cryo-TEM shows that during the coprecipitation reaction, initially a beam-sensitive phase is formed, possibly an Fe-pAsp complex. This beam-sensitive phase transforms into nanoparticles. In a later stage, sheet-like crystals are also found. After 48 h of mineralization, ordering of the nanoparticles around one of the collagen sub-bands (the a-band) is observed. This is very similar to the collagen-hydroxyapatite system, indicating that mineralization with iron hydroxides inside collagen is possible and proceeds via a similar mechanism as hydroxyapatite mineralization.
通过合成方法对胶原蛋白进行矿化已广泛研究了羟磷灰石以及硅和碳酸钙。从根本的角度来看，研究胶原蛋白是否可以作为其他矿物质（如氧化铁）的通用矿化模板是很有趣的。在这里，生物启发共沉淀反应，通常导致磁铁矿的形成，被用来用铁氢氧化物矿化胶原蛋白。血小板形绿锈晶体在胶原蛋白基质外形成，而在胶原蛋白内形成 2.6nm 大小的纳米颗粒，推测为氢氧化铁（III）。只有在存在聚天冬氨酸（pAsp）的情况下，胶原蛋白内才会发生纳米颗粒矿化。在没有 pAsp 的情况下，磁铁矿颗粒在胶原蛋白周围形成。时间分辨冷冻透射电镜显示，在共沉淀反应过程中，最初形成了一个对束流敏感的相，可能是 Fe-pAsp 配合物。这个对束流敏感的相转化为纳米颗粒。在后期阶段，也发现了片状晶体。矿化 48 小时后，观察到纳米颗粒在其中一条胶原蛋白亚带（a 带）周围有序排列。这与胶原蛋白-羟磷灰石系统非常相似，表明胶原蛋白内的氢氧化铁矿化是可能的，并且其过程与羟磷灰石矿化类似。
