Preparation, Biocompatibility, and In Vitro Bioactivity of High-Entropy Bio-Piezoelectric Ceramics

A high-entropy strategy has emerged as a promising approach to enhance the functional properties of piezoelectric ceramics for biomedical applications. For this reason, we have designed two novel high-entropy ceramics, (Bi_1/2Na_1/2)(Zr_1/3Sn_1/3Ti_1/3)O₃(BNZST) and (Bi_1/2Na_1/2)(Zr_1/4Sn_1/4Hf_1/4Ti_1/4)O₃(BNZSHT), which were synthesized via a two-step solid-state reaction. The phase structure, surface morphology, biocompatibility, and in vitro bioactivity were assessed. The results showed both ceramics adopted perovskite structures. BNZST and BNZSHT ceramics had relatively even crystallite sizes and element distribution, as well as achieving piezoelectric (d₃₃ ≥ 78 pC/N) properties. In vitro tests confirmed a high relative cell growth rate (RSG, >80%) after co-culturing BNZST or BNZSHT ceramic with murine fibroblasts L929 for more than 3 days. In particular, the surface with electric charge enhanced L929 with more extensive, widespread, and dense proliferation for the BNZST ceramic compared to ceramics without BNZST or unpolarized BNZST. The above indicated that multi-element doping and entropy stabilization established a novel pathway for developing a high-entropy bio-piezoelectric ceramics with high biocompatibility and bioactivity, providing the possibility for their use in bone repair materials.