Effect of mass concentration on bioactivity and cell viability of calcined silica aerogel synthesized from rice husk ash as silica source

The biocompatibility of calcined silica aerogel (900 °C) synthesized from rice husk ash via sol–gel ambient-pressure drying technique was studied. The silica aerogel was characterized by Fourier transform infrared spectroscopy, X-ray diffraction and field emission-scanning electron microscopy. The structure of silica aerogel remains intact but is deficient in silanol groups after calcination. The bioactivity of the silica aerogel was tested by immersion in simulated body fluid for 7 days with various mass concentrations (0.08–0.8 wt%). The results from Fourier transform infrared, X-ray diffraction, field emission-scanning electron microscopy and phosphorous analyses confirm that the silica aerogel could facilitate the nucleation of apatite. The silica aerogel was simultaneously resorbed and the broken Si–O–Si bonds were replaced with new apatite bonds. The optimal mass concentration was 0.16 wt%. At a higher mass concentration (0.8 wt%), silica aerogel tends to form polymeric interactions with tris-hydroxymethyl-aminomethane, a chemical compound in simulated body fluid. In the in vitro cell viability assay of the calcined silica aerogel against human dermal fibroblast cells, the cell viability increased with the increase of silica aerogel mass concentration. This early evidence shows that the calcined silica aerogel synthesized from rice husk ash via the sol–gel ambient-pressure drying technique can be considered as a potential alternative material for tissue engineering applications.