Synthesis of nano HA/βTCP mesoporous particles using a simple modification in granulation method

Granulation method in the mixture of oil, water, and polymer was used to synthesize HA/βTCP porous nano-powders. The effects of different types of polymeric-substrate, drying process, and thermal heat-treatment on the crystallization process of calcium phosphate nano-particles were studied. As-synthesized particles were treated with different chemical surface agents to improve their surface charge, cell growth, and cell adhesion properties. X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) analyses were employed to explore the phase composition and specific surface area of synthesized powders, respectively. Results showed that the presence of oil in PVA/oil system results in crystallization of mesoporous HA/βTCP particles with the surface area of 93 cm²/g, while using gelatin/oil mixture leads to crystallization of pure HA nano-particles with the surface area of 115 cm²/g. Using Rietveld method, the amounts of HA/βTCP and amorphous phases in the oven-dried PVA substrated powders after heat-treatment were calculated as about 65, 13, and 22 wt%, respectively. Interfacial tension energy (IFT) results indicated that PVA could reduce interfacial tension energy of oil/water mixture from 21.6 mN/m to 7.0 mN/m. The ZETA potential measurements showed that using 25 wt% of tetraethyl orthosilicate (TEOS) as surface modifier could increase zeta values from -21 ± 1 to -42 ± 1 mV. According to cell viability results, synthesized powder in the presence of oil/PVA, which was then modified by 25 wt% of TEOS, did not cause toxicity. Using Alizarin Red S staining quantification assay, it was found that after modification by TEOS, bone-nodule formation was enhanced by 25%. Furthermore, cell adhesion of the TEOS-modified surface was found to be significantly higher than that of non-modified one. Altogether, granulation method successfully led to improvement of synthesized porous HA/βTCP nanoparticles' physio-chemical properties.