Kokubo T, Kim H M, Kawashita M, Nakamura T
Department of Material Chemistry, Graduate School of Engineering, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan.
Z Kardiol. 2001;90 Suppl 3:86-91. doi: 10.1007/s003920170048.
CaO, SiO2-based glasses form the bonelike apatite on their surfaces in an acellular simulated body fluid (SBF) with ion concentrations nearly equal to those of the human blood plasma. The apatite formation of the former glasses is attributed to the catalytic effect of the Si-OH groups, which are formed on their surfaces in SBF, for the apatite nucleation. The gels of SiO2, TiO2, ZrO2, Ta2O5, and Nb2O5 formed the apatite on their surfaces in SBF, but Al2O3 gel did not. This indicates that the Ti-OH, Zr-OH, Ta-OH, and Nb-OH groups besides the Si-OH groups are also effective for the apatite nucleation, but Al-OH groups are not effective. Apatite formation on self-assembled monolayer terminated with various functional groups in SBF showed that COOH and H2PO4 groups are also effective for the apatite nucleation. All these groups are negatively charged around pH 7.40. Their apatite nucleating ability is varied with their arrangements. Among the Ti-OH groups, those in anatase structure are most effective for the apatite nucleation. Transmission electron microscope attached with energy dispersive X-ray spectrometer showed that these functional groups induce the apatite nucleation not directly, but through formation of their calcium compounds and subsequent formation of amorphous calcium phosphate with low Ca/P atomic ratios.
CaO-SiO₂基玻璃在离子浓度几乎与人体血浆相同的无细胞模拟体液(SBF)中,其表面会形成类骨磷灰石。前者玻璃的磷灰石形成归因于在SBF中其表面形成的Si-OH基团对磷灰石成核的催化作用。SiO₂、TiO₂、ZrO₂、Ta₂O₅和Nb₂O₅的凝胶在SBF中其表面形成了磷灰石,但Al₂O₃凝胶没有。这表明除了Si-OH基团外,Ti-OH、Zr-OH、Ta-OH和Nb-OH基团对磷灰石成核也有效,但Al-OH基团无效。在SBF中用各种官能团封端的自组装单分子层上的磷灰石形成表明,COOH和H₂PO₄基团对磷灰石成核也有效。所有这些基团在pH 7.40左右都带负电荷。它们的磷灰石成核能力随其排列而变化。在Ti-OH基团中,锐钛矿结构中的那些对磷灰石成核最有效。配备能量色散X射线光谱仪的透射电子显微镜表明,这些官能团不是直接诱导磷灰石成核,而是通过形成它们的钙化合物以及随后形成低Ca/P原子比的无定形磷酸钙来实现的。