A novel route to highly porous bioactive silica gels

Silica gels with a distribution of pore sizes from the sub-micrometre to hundreds of micrometers were produced by a novel method in which precursor solutions, such as a colloidal silica sol or pre-hydrolyzed tetraethoxysilane (TEOS), were solidified in the presence of a space-filling agent (CaCO3) and CO2 generator (sodium bicarbonate–hydrogen pyrophosphate). A range of macroporous organically modified silica gels with covalently linked phenyl, amino or thiol moieties were also prepared by a similar method using mixtures of TEOS and organotrialkoxysilanes. The highly porous monoliths were characterized by SEM, FTIR and solid state 29Si and 13C MAS NMR spectroscopies. In vitro bioactivity of the gels was demonstrated by their ability to nucleate calcium phosphate from simulated body fluid, bind and slowly release the drug ibuprofen, and support in vitro adhesion and proliferation of human osteoprogenitor cells and C2C12 pro-myoblast cells.