In this study, biocompatibility of nano composites of silica doped in HA/collagen was compared against those doped in HA/gelatin. For this purpose, hydrothermal samples were synthesized before being investigated by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). Size and morphology of the samples were further characterized by scanning and transmission electron microscopy (SEM). Moreover, energy-dispersive X-ray spectroscopy (EDS) was used to undertake an elemental analysis on the prepared composites. FTIR spectras confirmed chemical structure of the nano composites and EDS patterns showed that, even though the nano composites of silica doped in HA/collagen had equivalent Ca/P ratios to the theoretical value as repeated for HA chemical structure of Ca 10 (PO 4 ) 6 (OH) 2 , corresponding Ca/P ratios to the nano composites of silica doped in HA/gelatin were just close to the theoretical value. A comparison on the obtained XRD patterns showed that, the nano composites of silica doped in HA/collagen had their crystallite size smaller than that of the nano composites of silica doped in HA/gelatin. FESEM images indicated smaller particle sizes for the nano composites of silica doped in HA/collagen, as compared to those doped in HA/gelatin. Reduced crystallite size and decreased particle size are known to be associated with larger contact surface in chemical reactions, leading to better pharmacological efficacy in terms of bone repair.