Essential Role of Calcium Phosphate Heterogeneities in 2D-Hexagonal and 3D-Cubic SiO₂−CaO−P₂O₅ Mesoporous Bioactive Glasses

Abstract

Mesoporous bioactive glasses (MBGs) with a compoisition of 85SiO 2 -10CaO-5P 2 O 5 (mol %) have been prepared through the evaporation-induced self-assembly (EISA) method, using P123 as a structure directing agent. For the first time, SiO 2 -CaO-P 2 O 5 MBGs with identical composition and textural properties, but exhibiting different bicontinuous 3D-cubic and 2D-hexagonal structures, have been prepared. These materials allow us to discriminate the role of the structure on the bioactivity, from other parameters. To understand the role of each component on the mesostructure, local environment, and bioactive behavior, mesoporous 100SiO 2 , 95SiO 2 -5P 2 O 5 , and 90SiO 2 -10CaO (mol %) materials were also prepared under the same conditions. The results demonstrate that the joint presence of CaO and P 2 O 5 results in amorphous calcium phosphate (ACP) clusters sited at the pore wall surface. This heterogeneity highly improves the bioactive behavior of these materials. In addition, the presence of ACP clusters within the silica network leads to different mesoporous structures. The mesoporous order can be tuned through a rigorous control of the solvent evaporation temperature during the mesophase formation, resulting in p6mm, p6mm/Ia3d coexistence, and Ia3d phases for 20, 30, and 40°C, respectively. Preliminary results indicate that, in the case of identical composition and textural properties, the mesoporous structure does not have influence on the apatite formation, although initial ionic exchange is slightly enhanced for 3D cubic bicontinuous structures.

Nanotechnology in the targeted drug delivery for bone diseases and bone regeneration

“…Compared to conventional nonmesoporous bioactive glasses, the MBG possesses a more optimal surface area, pore volume, ability to induce in vitro apatite mineralization in simulated body fluids, and excellent cytocompatibility. [92][93][94][95] For better bone regeneration application, MBG can also be prepared as 3D porous scaffolds for bone tissue engineering and drug delivery applications. 96 Currently, there are three methods to prepare MBG scaffolds.…”

Structure and functionalization of mesoporous bioceramics for bone tissue regeneration and local drug delivery

“…in presence and absence of phosphorus, respectively, were prepared under the same experimental conditions. Moreover, the molar ratio between the network formers (SiO 2 + P 2 O 5 ) and surfactant was always kept constant [56]. Transmission electron microscopy (TEM) studies evidenced that in the presence of phosphorus, the mesoporous arrangement consisted of a threedimensional bicontinuous cubic structure while in the absence of phosphorus, the structure evolved to two-dimensional hexagonal (figure 3b).…”

“…The evaporation temperature used during the EISA process also affects the final mesostructure of TGs [56]. It has been observed that the structure of a TG evolves from three-dimensional bicontinuous cubic structure to two-dimensional hexagonal structure when decreasing the solvent evaporation temperature.…”

A study of the effect of precursors on physical and biological properties of mesoporous bioactive glass

“…These are absent in FTIR spectrum of calcined MBG-TEP. A weak peak observed at 560 cm -1 shows the presence of calcium phosphate (Ca-P) clusters [24]. The small bands between 610 and 592 cm -1 are attributed to the m 2 and m 4 bending vibrations of O-P-O linkage in phosphate groups.…”