In vitro characterisation of a sol-gel derived in situ silica-coated silicate and carbonate co-doped hydroxyapatite nanopowder for bone grafting

- Substitution of CO3− 2 and SiO44 − into HA for improvement of its dissolution rate
- Surface modification of HA with a silica layer and its formation mechanism
- Increase the bioactivity of HA due to the positive effect of silica surface layer
- Improvement of cell attachment due to the positive effect of silica surface layer

Design and synthesis of materials with better properties and performance are essential requirements in the field of biomaterials science that would directly improve patient quality of life. For this purpose, in situ silica-coated silicate and carbonate co-doped hydroxyapatite (Sc/S.C.HA) nanopowder was synthesized via the sol-gel method. Characterisation of the prepared nanopowder was carried out by XRD, FTIR, TEM, SEM, EDX, ICP, zeta potential, acid dissolution test, and cell culture test. The substitution of the silicate and carbonate ions into hydroxyapatite structure was confirmed by FTIR analysis. XRD analysis showed that silica is an amorphous phase, which played a role in covering the surface of the S.C.HA nanoparticles as confirmed by acid dissolution test. Low thickness and low integrity of the amorphous silica surface layer facilitated ions release from S.C.HA nanoparticles into physiological saline solution. Zeta potential of the prepared nanopowder suspended in physiological saline solution was − 27.3 ± 0.2 mV at pH 7.4. This negatively charged surface, due to the presence of amorphous silica layer upon the S.C.HA nanoparticles, not only had an accelerating effect on in vitro biomineralization of apatite, but also had a positive effect on cell attachment.