Piezoelectric effect induced osteoblast oriented growth behavior of HA/BaTiO₃bio-piezoelectric composites with a regular lamellar distribution

Bioelectroactive bone implant materials that closely resemble the characteristics of natural bone can be developed by combining hydroxyapatite (HA) with barium titanate (BaTiO₃). The significant disparity in sintering temperatures between BaTiO₃and HA precludes their co-sintering to achieve optimal mechanical properties. Furthermore, the dispersed distribution of BaTiO₃within HA inhibits the formation of a continuous piezoelectric pathway, leading to suboptimal piezoelectric performance. In this work, porous BaTiO₃scaffolds featuring orderly through-pore structures were fabricated utilizing a combination of multi-cold source freeze-casting and sintering. Subsequently, calcium phosphate bone cement (CPC) was infiltrated into the scaffold pores under pressure. HA/BaTiO₃bioactive piezoelectric composites were obtained through hydration reaction, eliminating the need for sintering. The axial compressive strength and radial fracture load of the fabricated composite reached 16.25 MPa and 701.53 N, respectively. When the BaTiO₃content was 46 vol%, the piezoelectric constant d₃₃of the composite was 14 pC N⁻¹, improving the composite's mechanical load responsiveness and surface charge generation. The negatively charged surface of the polarized composite promotes Ca²⁺deposition and stimulates osteoblast proliferation, thus accelerating bone-like apatite formation and enhancing osteoblast growth. The negative surface charge of BaTiO₃facilitates osteoblast adhesion and induces pseudopodium extension along or attachment to the BaTiO₃layers, thus promoting their preferred orientation and alignment. This mechanism provides key insights for designing bone repair materials that mimic the microstructure of oriented bone tissue in Haversian systems.