Molding mineral within microporous hydrogels by a polymer-induced liquid-precursor (PILP) process
Molding mineral within microporous hydrogels by a polymer-induced liquid-precursor (PILP) process
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DOI：
10.1021/bp050166
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发表时间：
2006-01-01
影响因子：
2.9
通讯作者：
Gower, LB
中科院分区：
文献类型：
--
作者：
Cheng, XG;Gower, LB
天然生物矿物质通常具有精致的形态，其中细胞通过分泌生物大分子和调节离子运输来行使高度的晶体学控制。一个重要的例子是海胆脊椎。最近的研究表明，它是通过沉积瞬态无定形碳酸钙（ACC）前驱相形成的，该前驱相随后转变为单晶线方解石，最终形成一个精细的三维微孔碳酸钙结构，具有相互连接的孔隙。与矿物相相关的大分子被认为在调节这种转变中起着关键作用。这里描述的工作通过在多孔聚（2-羟乙基甲基丙烯酸酯）（PHEMA）水凝胶中“成型”无定形碳酸钙前体来模拟这种形态控制，这种水凝胶是从海胆脊柱的空隙空间制备的负复制品。使用酸性仿生聚合物作为过程导向剂，我们发现聚天冬氨酸诱导无定形碳酸钙（ACC）纳米颗粒，这些纳米颗粒具有流体特性，因此能够渗透到PHEMA水凝胶复制物中并合并成弯曲的形态，复制海胆脊柱的原始微孔结构。通过使用由仿生酸性大分子诱导的前体过程，在室温下将碳酸钙“成型”成复杂的形态，PILP过程是一个有用的体外模型，用于研究各种生物矿化生物明显使用的非晶到结晶转变过程的不同方面。例如，虽然我们能够复制脊柱的整体形态，但它具有多晶纹理；该体系的进一步研究将集中于控制成核事件，这可能有助于阐明如何通过非晶前驱体制备具有单晶织构的这种卷曲结构。通过更好地理解生物体调节晶体性质的机制，这种仿生过程可以合成具有优越电子、机械和光学性质的材料。
Natural biominerals often have exquisite morphologies, where the cells exercise a high degree of crystallographic control through secretion of biological macromolecules and regulation of ion transport. One important example is the sea urchin spine. It has recently been shown to be formed through deposition of a transient amorphous calcium carbonate (ACC) precursor phase that later transforms to single-crystal line calcite, ultimately forming an elaborate three-dimensional microporous calcium carbonate structure with interconnected pores. Macromolecules associated with the mineral phase are thought to play a key role in regulating this transformation. The work described here mimics this type of morphological control by "molding" an amorphous calcium carbonate precursor within a porous poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogel that has been prepared as a negative replica from the void space of an urchin spine. Using an acidic biomimetic polymer as a process-directing agent, we show that polyaspartic acid induces amorphous calcium carbonate (ACC) nanoparticles, which have fluidic character and therefore are able to infiltrate the PHEMA hydrogel replica and coalesce into the convoluted morphology that replicates the original microporous structure of the sea urchin spine. By "molding" calcium carbonate into a complex morphology at room temperature, using a precursor process that is induced by a biomimetic acidic macromolecule, the PILP process is a useful in vitro model for examining different aspects of the amorphous-to-crystalline transformation process that is apparently used by a variety of biomineralizing organisms. For example, although we were able to replicate the overall morphology of the spine, it had polycrystalline texture; further studies with this system will focus on controlling the nucleation event, which may help to elucidate how such a convoluted structure can be prepared with single-crystalline texture via an amorphous precursor. Through a better understanding of the mechanisms used by organisms to regulate crystal properties, such biomimetic processes can lead to the synthesis of materials with superior electronic, mechanical, and optical properties.