The influence of sol-gel processing method on physical properties and acellular in vitro reactivity of bioactive glasses based on CaO-SiO2-P2O5: acidic catalysed single step process versus acid- base two step quick-gelling method

The physical characteristics of the materials such as specific surface area and particles size have great effect on their cellular properties and rate of bone bonding. In this study، bioactive glass based on CaO-SiO2-P2O5 system was produced through sol-gel technique at two different processing single step sol-gel route in which precursors are hydrolysis to oxides in an acidic medium and gelation occur at a long period of time and quick alkali-mediated method in which hydrolyzed precursors forms a gel network quickly، due to the use of ammonia solution. Specific surface area and morphology of the glasses were determined by BET and TEM techniques، respectively. For surface reactivity measurements، the powders immersed in simulated body fluid (SBF) for different intervals and then characterized by XRD، FTIR and SEM. The results of TEM and BET measurements showed that both methods provided nano-particles of bioactive glass. The glasses produced through both traditional and quick alkali-mediated methods had approximately the same particle size، but higher specific surface area was obtained for the former (168m2/g) because of its highly porous structure. Precipitation of apatite phase was confirmed on surfaces of glasses though the rate of precipitation was higher for the glass specimen produced by single step process. It seems that the surface reactivity (and hence bone bonding ability) of bioactive glass materials can be controlled using appropriate processing techniques.