Stevensson Baltzar, Mathew Renny, Edén Mattias
Physical Chemistry Division, Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University , SE-106 91 Stockholm, Sweden.
J Phys Chem B. 2014 Jul 24;118(29):8863-76. doi: 10.1021/jp504601c. Epub 2014 Jul 9.
Melt-derived bioactive phosphosilicate glasses are widely utilized as bone-grafting materials for various surgical applications. However, the insight into their structural features over a medium-range scale up to ∼ 1 nm remains limited. We present a comprehensive assessment of the spatial distribution of phosphate groups across the structures of 11 Na2O-CaO-SiO2-P2O5 glasses that encompass both bioactive and nonbioactive compositions, with the P contents and silicate network connectivities varied independently. Both parameters are known to strongly influence the bioactivity of the glass in vitro. The phosphate distribution was investigated by double-quantum (31)P nuclear magnetic resonance (NMR) experiments under magic-angle spinning (MAS) conditions and by molecular dynamics (MD) simulations. The details of the phosphate-ion dispersion were probed by evaluating the MD-derived glass models against various scenarios of randomly distributed, as well as clustered, phosphate groups. From comparisons of the P-P interatomic-distance spreads and the statistics of small phosphate clusters assessed for variable cutoff radii, we conclude that the spatial arrangement of the P atoms in phosphosilicate glasses is well-approximated by a statistical distribution, particularly across a short-range scale of ≤ 450 pm. The primary distinction is reflected in slightly closer P-P interatomic contacts in the MD-derived structures over the distance span of 450-600 pm relative to that of randomly distributed phosphate groups. The nature of the phosphate-ion dispersion remains independent of the silicate network polymerization and nearly independent of the P content of the glass throughout our explored parameter space of 1-6 mol % P2O5 and silicate network connectivities up to 2.9.
熔融衍生的生物活性磷硅酸盐玻璃被广泛用作各种外科手术应用的骨移植材料。然而，在高达约1纳米的中程尺度上对其结构特征的了解仍然有限。我们对11种Na2O-CaO-SiO2-P2O5玻璃的结构中磷酸基团的空间分布进行了全面评估，这些玻璃涵盖了生物活性和非生物活性成分，其中磷含量和硅酸盐网络连接性是独立变化的。已知这两个参数都会强烈影响玻璃在体外的生物活性。通过在魔角旋转（MAS）条件下的双量子（31）P核磁共振（NMR）实验和分子动力学（MD）模拟研究了磷酸盐分布。通过针对随机分布以及聚集的磷酸盐基团的各种情况评估MD衍生的玻璃模型，探究了磷酸根离子分散的细节。通过比较P-P原子间距离分布以及针对可变截止半径评估的小磷酸盐簇的统计数据，我们得出结论，磷硅酸盐玻璃中P原子的空间排列可以通过统计分布很好地近似，特别是在≤450 pm的短程尺度上。主要区别体现在相对于随机分布的磷酸盐基团，MD衍生结构在450 - 600 pm的距离范围内P-P原子间接触稍近。在我们探索的1 - 6 mol% P2O5和高达2.9的硅酸盐网络连接性的参数空间中，磷酸根离子分散的性质与硅酸盐网络聚合无关，并且几乎与玻璃的P含量无关。
