Incorporation of Phosphorus into Mesostructured Silicas: A Novel Approach to Reduce the SiO₂ Leaching in Water

Abstract

Nanostructured mesoporous silica networks with phosphorus substitutions have been obtained through evaporation induced self-assembly (EISA) method using a nonionic surfactant as structure directing agent and triethylorthosilicate and phosphoric acid as SiO2 and P2O5 sources, respectively. Diverse mesopore arrangement symmetries and textural properties have been obtained by modifying the Si/P molar ratio. Therefore mesoporous matrices exhibited an evolution from 3D cubic to 2D hexagonal and wormlike structure with the increase in the substitution degree of the silica network by P2O5 centers. Studies carried out by soaking these materials into water at 37 °C revealed that P-containing nanostructured materials, with P2O5 contents above 1.25% mol, release smaller amounts of silica to the aqueous medium than pure silica matrix. The increase in the cross-linking degree of the silica network together with the increase of the acid character due to the presence of phosphorus centers could explain the decrease of silica leaching in water. Preliminary in vitro biocompatibility assays in osteoblastic cell culture evidence the lowest cellular damage induced by the sample with the highest P-content. These materials are promising candidates to be applied in diverse technological fields including biomaterials science.