Hydroxyapatite/SiO₂ Composites via Freeze Casting for Bone Tissue Engineering

Abstract Freeze casting is a fabrication method that allows producing near‐net‐shaped ceramics with variable porosity. Hydroxyapatite (HA) was modified by the addition of different amounts of SiO₂ nanoparticles during freeze cast preparation. The addition of SiO₂ introduced a partial phase transformation of HA to β‐tricalcium phosphate and improved the form stability due to less shrinkage after sintering. The impact of surface roughness of pure HA ceramics and the influence of SiO₂ introduction during freeze casting on adhesion, proliferation, and differentiation of human osteoblast‐like cells (MG‐63) was investigated. While both cell attachment and proliferation of smooth pressed HA was significantly enhanced compared to rough freeze cast HA, the addition of SiO₂ improved the cell numbers of the latter. The expression of cell differentiation markers osteocalcin and collagen I was found to be supported by rough surfaces (R_a = 5–6 µm) in particular on ceramics containing SiO₂