Zirconium Dioxide Nanoparticles in Bone Tissue Engineering: Recent Advances, Biological Interactions, and Future Perspectives

Bone defects from trauma, tumor resection, infection, and degenerative disease remain a large clinical problem, and the grafting strategies used to treat them still carry familiar limitations: donor-site morbidity for autografts, variable integration and supply constraints for allografts. Synthetic substitutes have narrowed the gap but rarely combine mechanical competence with biological activity in a single material. Zirconium dioxide (ZrO2) has been used in orthopedics and dentistry for decades on the strength of its fracture toughness, which derives from the stress-induced tetragonal-to-monoclinic transformation, together with chemical stability and an established safety record. At the nanoscale, ZrO2 can provide functionalities beyond mechanical reinforcement in appropriately engineered systems. Its high surface area, tunable surface chemistry, and potential mesoporosity have been exploited in selected formulations for matrix reinforcement, surface-mediated cellular interactions, therapeutic cargo loading and release, and antibacterial applications. This review covers the physicochemical basis of ZrO2 behavior, including crystal phases, transformation toughening, surface chemistry and hydrothermal stability, and the influence of synthesis route on particle size and dispersion, and links these to protein adsorption, osteoblast response, osteogenic signaling, and immunomodulatory and antibacterial effects. Recent applications are surveyed across scaffold reinforcement, bone cements and fillers, implant surface modification, local drug delivery, and infection control. Recurring issues are examined throughout, including the reported loading ranges associated with mechanical performance and the effects of particle agglomeration, the confounding effect of porosity on reported strength, and the need to pair ZrO2’s bioinertness with bioactive phases. The review closes with cytotoxicity, long-term particle fate, scale-up and regulatory barriers, and prospects in additive manufacturing, personalized grafts, and theragnostic design.