Tilocca Antonio, Cormack Alastair N
Department of Chemistry, University College London, United Kingdom.
J Phys Chem B. 2007 Dec 27;111(51):14256-64. doi: 10.1021/jp075677o. Epub 2007 Nov 30.
Molecular dynamics simulations of four bioactive silicate glasses containing between 0 (P0) and 12 (P12) mol % P2O5 have been carried out in order to elucidate the structural role of phosphorus in these materials. In particular, we have focused on structural features which can have a direct role in the bioactive mechanism of dissolution and bone bonding. The higher affinity of modifier Na and Ca cations for coordinating phosphate rather than silicate, together with the formation of P-O-Si linkages, lead to increasing repolymerization of the silicate network with increasing P2O5 content, which in principle would represent a negative effect of P inclusion on the glass bioactivity. However, this effect is counterbalanced by the concomitant increase in the amount of free orthophosphate groups, whose fast release is deemed to enhance the bioactivity. The strong affinity of the orthophosphates for calcium ions leads to a clear tendency toward separation of silicate-rich and phosphate-rich phases for the P12 composition. Although this could reduce the bioactivity in the case of P12, in general, the favorable balance between the effects mentioned above should result in a positive effect of partial Si --> P substitution on the glass bioactivity.
为了阐明磷在这些材料中的结构作用，我们对四种含有0（P0）至12（P12）摩尔％五氧化二磷的生物活性硅酸盐玻璃进行了分子动力学模拟。特别是，我们专注于那些可能在溶解和骨结合的生物活性机制中起直接作用的结构特征。改性剂钠和钙阳离子对配位磷酸盐而非硅酸盐具有更高的亲和力，以及P-O-Si键的形成，导致随着五氧化二磷含量的增加，硅酸盐网络的再聚合增加，原则上这将代表磷的加入对玻璃生物活性的负面影响。然而，这种影响被游离正磷酸基团数量的相应增加所抵消，其快速释放被认为可增强生物活性。正磷酸盐对钙离子的强亲和力导致P12组成明显倾向于分离出富硅相和富磷相。尽管这在P12的情况下可能会降低生物活性，但总体而言，上述影响之间的有利平衡应会导致部分Si→P取代对玻璃生物活性产生积极影响。
