Effect of glycerol and H3PO4 on the bioactivity and degradability of rod-like SBA-15 particles with active surface for bone tissue engineering applications

Abstract

In the quest to increase the quality of life and life expectancy, there is a great demand to develop advanced medical devices capable of facing current health challenges. Santa Barbara Amorphous (SBA-15) mesoporous silica has been demonstrated to be a remarkable option for a variety of biomedical applications, from tissue engineering to drug delivery, due to its unique hierarchical porous structure. This work reports on the effect of using different ratios and concentrations of an acid mixture mediated by HCl/H 3 PO 4 that in combination with a glycerol-modified silane precursor favoured obtaining bioactive SBA-15 mesoporous silica rods. The surfactant was removed by solvent extraction which allowed to keep a substantial amount of silanol groups (SiOH) at the surface. All the evaluated samples showed homogeneous rod shape and particle size, as well as high bioactivity after being immersed for 14 days in simulated body fluid (SBF). Different structural arrangements of needle-type carbonate hydroxyapatite (HCA) crystals were produced from SBA-15 upon immersion in SBF. By scanning electron microscopy (SEM) characterization, it was observed that rod-shaped SBA-15 materials displayed higher degradability when the concentration of H 3 PO 4 was increased. An indirect cell viability assay with MC3T3-E1 osteoblast precursor cells was performed by incubating cells in cell culture medium exposed to SBA-15 particles for 1 and 4 days. The results obtained from the WST-8 assay and fluorescent staining showed no negative effect on cell viability, indicating a lack of cytotoxicity of the rod-like SBA-15 particles. • Solvent extraction allowed keeping a large amount of silanol groups at the surface. • Higher the concentration of H 3 PO 4 smaller the size of the SBA-15 rods. • PO 4 3− species and SiOH promoted the formation of carbonate hydroxyapatite crystals. • The use of H 3 PO 4 and glycerol facilitated the degradation process at body pH. • The species released from SBA-15 particles after 4 days boosted cell proliferation.