Department of Materials Science and Technology, Nagaoka University of Technology, Kamitomioka 1603-1, Nagaoka, Niigata 940-2188, Japan.
J Mater Chem B. 2021 Feb 25;9(7):1896-1907. doi: 10.1039/d0tb02456b.
Transparent phosphorus-containing MPS (PMPS) films were synthesized by the introduction and reaction of phosphoric acid into the silica framework during the sol-gel reaction. We then investigated the hydration layer structures formed on the PMPS films and achieved the selective adsorption of fibronectin (Fn). In particular, the surface analyses indicated that the P atom was distributed at the outermost surfaces of the PMPS films. The PMPS films exhibited a high transparency (e.g., averaged transmittance value in the visible light region: 79%), and the haze value (0.14%) decreased with the increasing P/Si molar concentration. Solid-state 29Si-NMR and Fourier transform infrared spectroscopy (FT-IR) spectra indicated the formation of Si-O-P bonds, suggesting that the condensation reaction between the Si-O- and P-O- groups effectively occurs in the silica framework. The larger amount of P-O- and P[double bond, length as m-dash]O groups at the Si-O-P bonding site on the films affects the water molecular adsorption states (i.e., formation of the hydration layer), which was supported by the Brunauer-Emmett-Teller (BET) surface areas of N2 and water vapor, leading to enhancement of the hydrogen bondability of the PMPS films with the increased formation of Si-O-P bonds. The deconvolution results of the FT-IR spectra demonstrated that the ratio of free water to bonding water increased significantly with an increase in the formation of Si-O-P bonding, and the resulting O-H stretching vibration in the hydration layer became more asymmetric. It is suggested that the water molecules are irregularly hydrogen-bonded with the different functional groups of Si-O-, P-O- and P[double bond, length as m-dash]O. In the immersion experiment of the PMPS films in phosphate buffer, the resultant P/Si molar concentration of the PMPS film decreased upon increasing the immersion time and the mesostructures were preserved. The amount of Fn adsorption significantly increased as the O-H stretching vibration of the water molecules became more asymmetric, whereas the adsorption of fibrinogen was completely suppressed by the films. Therefore, we found that the addition of phosphoric acid in the MPS film synthesis significantly affects the hydration layer structures on the film surfaces to provide the possibility of selective protein adsorption.
透明含磷 MPS（PMPS）薄膜是通过在溶胶-凝胶反应过程中将磷酸引入到二氧化硅骨架中并进行反应而合成的。我们研究了在 PMPS 薄膜上形成的水合层结构，并实现了对纤维连接蛋白（Fn）的选择性吸附。特别是，表面分析表明 P 原子分布在 PMPS 薄膜的最外层表面上。PMPS 薄膜具有高透明度（例如，可见光区域的平均透光率值：79％），并且随着 P/Si 摩尔浓度的增加，浊度值（0.14％）降低。固态 29Si-NMR 和傅立叶变换红外光谱（FT-IR）谱表明 Si-O-P 键的形成，表明 Si-O-和 P-O-基团之间的缩合反应在二氧化硅骨架中有效发生。在薄膜上 Si-O-P 键合位点处的 P-O-和 P[双键，长度为 m-dash]O 基团的大量存在影响水分子吸附状态（即水合层的形成），这得到了氮气和水蒸气 BET 表面积的支持，导致 PMPS 薄膜的氢键能力增强，Si-O-P 键的形成增加。FT-IR 光谱的分峰结果表明，随着 Si-O-P 键合形成的增加，自由水与键合水的比例显著增加，水合层中的 O-H 伸缩振动变得更加不对称。表明水分子与 Si-O-、P-O-和 P[双键，长度为 m-dash]O 的不同官能团不规则地形成氢键。在 PMPS 薄膜在磷酸盐缓冲液中的浸泡实验中，随着浸泡时间的增加，PMPS 薄膜的 P/Si 摩尔浓度降低，介孔结构得以保留。随着水分子的 O-H 伸缩振动变得更加不对称，Fn 的吸附量显著增加，而纤维蛋白原的吸附被薄膜完全抑制。因此，我们发现 MPS 薄膜合成中添加磷酸会显著影响薄膜表面上水合层结构，从而为选择性蛋白质吸附提供可能性。
