Hu Changmin, Zhang Lichun, Wei Mei
Department of Materials Science and Engineering and ‡Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269, United States.
Department of Materials Science and Engineering and Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269, United States.
ACS Biomater Sci Eng. 2015 Aug 10;1(8):669-676. doi: 10.1021/acsbiomaterials.5b00088. Epub 2015 Jul 6.
Bone is an organic-inorganic hierarchical biocomposite. Its basic building block is mineralized collagen fibers with both intrafibrillar and extrafibrillar mineralization, which is believed to be regulated by noncollagenous proteins (NCPs) with polyanionic domains. In this study, collagen fibrils with both intrafibrillar and extrafibrillar mineralization were successfully prepared and the mechanism of biomineralization was proposed. Building on this success, a unique biomimetic lamellar scaffold composed of collagen fibrils with both intrafibrillar and extrafibrillar mineralization was fabricated using a combination of self-compression and unidirectional freeze-drying approach. To achieve intrafibrillar mineralization, we used poly(acrylic acid) (PAA) to sequester calcium and phosphate ions to form fluidic PAA-amorphous calcium phosphate (PAA-ACP) nanoprecursors. At the presence of sodium tripolyphosphate (TPP), PAA-ACP nanoprecursors were modulated to orderly deposit within the gap zone of collagen fibrils. The effect of PAA concentration on the intrafibrillar and extrafibrillar mineralization of reconstituted collagen fibrils was investigated. It was found that with the decrease in PAA concentration, the inhibitory effect of PAA on mineralization and the stability of ACP nanoprecursors decreased. As a result, more minerals were deposited both within and on the surface of the collagen fibrils. Moreover, with the ability to reproduce biomineralization of collagen fibrils, it allowed us to fabricate biomimetic hierarchical collagen/hydroxyapatite scaffolds composed of both intrafibrillar and extrafibrillar minerals using a bottom-up approach. This technique renders a promising biomimetic scaffold, which will be suitable for bone repair and regeneration.
骨骼是一种有机-无机分层生物复合材料。其基本构建单元是具有原纤维内矿化和原纤维外矿化的矿化胶原纤维，据信这受具有聚阴离子结构域的非胶原蛋白（NCPs）调控。在本研究中，成功制备了具有原纤维内矿化和原纤维外矿化的胶原纤维，并提出了生物矿化机制。基于这一成功，采用自压缩和单向冷冻干燥相结合的方法，制备了一种由具有原纤维内矿化和原纤维外矿化的胶原纤维组成的独特仿生层状支架。为实现原纤维内矿化，我们使用聚丙烯酸（PAA）螯合钙和磷酸根离子，形成流体状的PAA-无定形磷酸钙（PAA-ACP）纳米前驱体。在三聚磷酸钠（TPP）存在的情况下，PAA-ACP纳米前驱体被调控以有序沉积在胶原纤维的间隙区域内。研究了PAA浓度对重组胶原纤维原纤维内矿化和原纤维外矿化的影响。发现随着PAA浓度的降低，PAA对矿化的抑制作用以及ACP纳米前驱体的稳定性降低。结果，更多的矿物质沉积在胶原纤维内部和表面。此外，由于能够重现胶原纤维的生物矿化，这使我们能够采用自下而上的方法制备由原纤维内和原纤维外矿物质组成的仿生分层胶原/羟基磷灰石支架。这项技术提供了一种有前景的仿生支架，适用于骨修复和再生。
