Li Li, Wei Ke-Min, Lin Feng, Kong Xiang-Dong, Yao Ju-Ming
The Key Laboratory of Advanced Textile Materials and Manufacturing Technology of Ministry of Education, College of Materials and Textile, Zhejiang Sci-Tech University, Hangzhou, China.
J Mater Sci Mater Med. 2008 Feb;19(2):577-82. doi: 10.1007/s10856-007-3004-y. Epub 2007 Jul 10.
The silk fibroin/calcium phosphate composites were prepared by adding the different amount of Na(2)SiO(3) to assess the effect of silicon on the HA (hydroxyapatite) formation in the composites. FTIR and XRD results suggested that the inorganic phase was constituted mainly by the amorphous DCPD (dicalcium phosphate dehydrate), a precursor of HA in the bone mineral, when the composites were prepared at the final Na(2)SiO(3) concentration lower than 0.008%. Otherwise, HA was formed as the predominant one in the as-prepared composite, accompanied with a conformational transition in the organic phase of silk fibroin protein from silk I (alpha-helix and/or polyglycine II (3(1)-helix) conformations) to silk II (antiparallel beta-sheet conformation). SEM images showed the different morphologies with the samples, i.e., sheet-like crystals in the composites prepared at a low Na(2)SiO(3) concentration and rod-like bundles in other composites. The rod-like bundles were connected together to form the porous network, due to the fact that the HA crystals grew with the aggregation of silk fibroin, and further accreted onto the silk fibroin fibrils. TG curves indicated that the composites prepared with a certain amount of additional SiO (3) (2-) had the higher thermal stability because of its high molecular orientation and crystallinity, and high water-holding capacity due to the porous microstructure.
通过添加不同量的硅酸钠制备丝素蛋白/磷酸钙复合材料，以评估硅对复合材料中羟基磷灰石（HA）形成的影响。傅里叶变换红外光谱（FTIR）和X射线衍射（XRD）结果表明，当最终硅酸钠浓度低于0.008%时制备复合材料，无机相主要由无定形磷酸二钙（DCPD）构成，它是骨矿物质中HA的前体。否则，在制备的复合材料中HA形成为主要成分，同时丝素蛋白的有机相从丝I（α-螺旋和/或聚甘氨酸II（3(1)-螺旋）构象）转变为丝II（反平行β-折叠构象）。扫描电子显微镜（SEM）图像显示样品具有不同形态，即在低硅酸钠浓度下制备的复合材料中为片状晶体，而在其他复合材料中为棒状束。棒状束相互连接形成多孔网络，这是因为HA晶体随着丝素蛋白的聚集而生长，并进一步附着在丝素蛋白原纤维上。热重（TG）曲线表明，由于其高分子取向度和结晶度以及多孔微观结构导致的高持水能力，添加一定量额外SiO₃²⁻制备的复合材料具有更高的热稳定性。
