Co-incorporation of Phosphorus and zinc into wollastonite ceramic granules synergically facilitating thin-walled structures regeneration

Bone regeneration of oral and maxillofacial defects in situ remains a significant clinical challenge. This study investigates the synergistic effects of phosphorus (P) and zinc (Zn) co-doping in wollastonite bioceramics to enhance osteogenic activity and antibacterial potential for bone repair. Cylindrical bioceramic granules with varying P/Zn ratios (CSi-P8: CSi-Zn6 = 3:0, 2:1, 1:2 and 0:3) were fabricated via co-precipitation and evaluated for in-vitro bioactivity, cell proliferation, osteogenic differentiation, and antibacterial performance. The experimental results demonstrated that the co-doped groups (8P/6Zn-2:1 and 8P/6Zn-1:2) exhibited superior hydroxyapatite formation in simulated body fluid (SBF), sustained Ca²⁺/Si⁴⁺ ion release, and synergistic osteogenic effects, as evidenced by elevated RUNX2/β-catenin expression and BMSC proliferation. Zn doping conferred dose-dependent antibacterial activity against Staphylococcus aureus (93% inhibition for 8P/6Zn-0:3). In vivo cranial defect experiments in rabbits revealed that the 8P/6Zn-2:1 granules significantly promoted new bone trabeculae formation and defect closure within 16 weeks, outperforming single-doped and control groups. Histological and micro-CT analyses confirmed enhanced bone volume fraction (BV/TV%) and trabecular density (Tb.N) in the co-doped groups. These findings highlight the dual functionality of P/Zn co-doped wollastonite (e.g. 8P/6Zn-2:1), where P enhances osteogenesis via increasing the expression of RUNX2/β-catenin and apatite deposition, while Zn provides antibacterial protection, offering more promising implants for infected oral bone defects.