Department of Materials Sciences and Engineering, Stony Brook University, Stony Brook, NY 11794-2275, USA.
J Struct Biol. 2010 Apr;170(1):83-92. doi: 10.1016/j.jsb.2009.12.018. Epub 2009 Dec 24.
The extracellular matrix (ECM) is composed of mixed protein fibers whose precise composition affects biomineralization. New methods are needed to probe the interactions of these proteins with calcium phosphate mineral and with each other. Here we follow calcium phosphate mineralization on protein fibers self-assembled in vitro from solutions of fibronectin, elastin and their mixture. We probe the surface morphology and mechanical properties of the protein fibers during the early stages. The development of mineral crystals on the protein matrices is also investigated. In physiological mineralization solution, the elastic modulus of the fibers in the fibronectin-elastin mixture increases to a greater extent than that of the fibers from either pure protein. In the presence of fibronectin, longer exposure in the mineral solution leads to the formation of amorphous calcium phosphate particles templated along the self-assembled fibers, while elastin fibers only collect calcium without any mineral observed during early stage. TEM images confirm that small needle-shape crystals are confined inside elastin fibers which suppress the release of mineral outside the fibers during late stage, while hydroxyapatite crystals form when fibronectin is present. These results demonstrate complementary actions of the two ECM proteins fibronectin and elastin to collect cations and template mineral, respectively.
细胞外基质（ECM）由混合的蛋白质纤维组成，其精确组成会影响生物矿化。需要新的方法来探测这些蛋白质与磷酸钙矿物质以及彼此之间的相互作用。在这里，我们研究了从纤维连接蛋白、弹性蛋白及其混合物的溶液中体外自组装的蛋白质纤维上的磷酸钙矿化过程。我们在早期阶段探测了蛋白质纤维的表面形貌和力学性能。还研究了在蛋白质基质上晶体矿化的发展。在生理矿化溶液中，纤维连接蛋白-弹性蛋白混合物中纤维的弹性模量增加幅度大于纯蛋白纤维。在纤维连接蛋白存在的情况下，更长时间地暴露在矿化溶液中会导致无定形磷酸钙颗粒沿着自组装纤维形成模板，而弹性蛋白纤维在早期阶段则没有观察到任何矿物质。TEM 图像证实，在弹性蛋白纤维内存在小的针状晶体，这些晶体抑制了矿物质在纤维外的释放，而在纤维连接蛋白存在的情况下则形成了羟基磷灰石晶体。这些结果表明，两种 ECM 蛋白纤维连接蛋白和弹性蛋白分别通过收集阳离子和模板化矿物质来发挥互补作用。
