Time-sequentially released bilayer sandwich cerium oxide nanoparticles on femtosecond laser-treated zirconia implant surface for enhanced antibacterial and osseointegration capacity.

Zirconia implants offer excellent aesthetics and biocompatibility but are limited by intrinsic biocatalytic inertness, which impairs osseointegration and antimicrobial activity. Unlike existing zirconia surface modifications (e.g., passive micro/nano structuring or single-layer coatings) that lack time-controlled, multi-stage functionality. Here, we developed a bilayer "sandwich" structure (Trbs-CeO2) of cerium dioxide nanoparticles (CeO2 NPs) on the surface of zirconia by combining high-repetition-rate femtosecond laser physical modification with chemical modification using (CeO2 NPs). The outer layer functions as a rapid-release layer, delivering high CeO2 concentrations within hours to days post-implantation to emphasize anti-inflammatory and antibacterial effects; the inner layer is a slow-release layer characterized by a femtosecond laser-engineered micro-nano surface infused with CeO2, which continues to release low CeO2 concentrations for several weeks after the outer layer is exhausted, thereby synergizing with the micro-nano structure of the zirconia substrate to enhance long-term osteogenesis. The anti-inflammatory, antibacterial, and osteogenic differentiation effects of Trbs-CeO2 were evaluated in vitro, whereas its osteointegration capacity was evaluated in animal models. Compared with the control group, the Trbs-CeO2 group exhibited significantly improved surface roughness, wettability, and biocompatibility of the zirconia surface. Trbs-CeO2 exerts potent antibacterial activity by compromising bacterial cell membranes, induces M2 macrophage polarization, exhibits anti-inflammatory properties by inhibiting the TLR4/MyD88/NF-κB signaling pathway in RAW264.7 cells, and facilitates osteogenic MC3T3-E1 cell differentiation. Trbs-CeO2 significantly enhances in vivo osseointegration efficiency. Trbs-CeO2 provides a distinct, time-programmed bilayer strategy that integrates antibacterial, anti-inflammatory, and osteogenesis-promoting functions, offering valuable insights for advanced zirconia-based implants.