Preparation and in vitro evaluation of porous silica gels

Porous silica gels with high surface areas were prepared from tetraethylothosilicate and polyacrylic acid (PAA) of high molecular weight in acidic media by a sol–gel method. PAA content and ageing temperatures were varied in order to obtain different microstructures. Samples were sintered at temperatures up to 400°C, and subjected to in vitro evaluation by soaking them in acellular inorganic solutions at 37°C and pH 7.3. Surface precipitation of carbonate–apatite on some of the gels was observed by FTIR spectroscopy, scanning electron microscopy and EPMA. Silica dissolution and re-precipitation phenomena were also observed. The relationship between both phenomena during the in vitro test is discussed mainly in terms of structural and microstructural features of the gel.