Effect of the modification of spray drying parameters on the fabrication of bovine-derived hydroxyapatite microspheres for biomedical applications

In this work, the effect of the spray dryer parameters on bovine-derived hydroxyapatite (BHAp) was studied to fabricate microspheres with controlled particle size distribution and morphology. A factorial design was implemented to establish the impact of spray drying process parameters on the final BHAp powder properties. The critical process factors were solid content in the slurry, atomization pressure, and hot air flow rate, whereas the studied experimental outputs were particle size distribution and morphology, characterized by laser diffraction and scanning electron microscopy, respectively. Additionally, the Ca/P molar ratio was evaluated from X-ray diffraction data. The obtained results showed a strong influence of the atomization pressure and the solid slurry content on the particle size distribution (increasing from 2.56 ± 0.02 µm to 32.46 ± 0.78 µm) and particle morphology (with an increased circularity from 0.3502 ± 0.0172 to 0.8688 ± 0.0039), being both properties suitable for thermal spray (TS) applications. Moreover, the BHAp crystalline structure and Ca/P molar ratio did not present any changes with the spray drying process parameters employed. Finally, it was found that magnesium was preserved in the spray dried particles, the former being also present in the starting powder feedstock.