Porous hydroxyapatite-titanium dioxide composites prepared by a sol-gel / supercritical CO2-drying combined process

In this work, porous nanostructured materials based on hydroxyapatite (HA) and titanium dioxide (TiO2) were prepared by integrating the sol-gel process and supercritical CO2 drying. These combined processes constitute a synergistic methodology that allows modulating the porosity generated in the gel and preserving it after drying. HA nanoparticles and a pore-generating agent (Polyvinylpyrrolidone) were included without significant modifications to gel consolidation times or integrity by using this methodology. The presence of HA nanoparticles within the TiO2 matrix helped preserving the anatase phase after the calcination stage. No reactivity between the present phases was detected, indicating their successful integration in the final composite material structure, which was one of the most challenging aspects of the research. This allowed HA-TiO2 composites to improve the adhesion of MG63 osteoblast-like cells and their proliferation, being the sample with high HA content (∼37 % wt/wt) the one that presented the best response. The present work puts forward a new way for the synthesis of scaffolds composed of HA and TiO2 with retention of the anatase phase for applications in bone tissue engineering.