Antimicrobial Bioceramics: Advanced Scaffolds and Coatings for Enhanced Orthopaedic Implant Integration

Abstract

Orthopaedic implants are crucial in treating bone-related conditions. However, implant-associated infections (IAIs) remain a significant challenge, often leading to implant failure and exacerbating antibiotic resistance. Baghdadite bioceramics (BAG, Ca3ZrSi2O9) have shown great promise due to their bioactivity and bone compatibility, but they inherently lack antibacterial properties. This research addresses this limitation by enhancing the antibacterial of BAG through chemical and physical modification achieved by doping BAG with biocompatible metal ions, magnesium-doped baghdadite (Mg-BAG) and bismuth-doped baghdadite (Bi-BAG) for scaffold and coating applications. This study demonstrates the synergistic chemistry and antibacterial activity of Mg-BAG and Bi-BAG against representative Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus. Multifaceted antibacterial mechanisms are elucidated, including biomolecule alterations, generation of intracellular reactive oxygen species (ROS), and membrane depolarisation. Furthermore, this study presents pioneers using flame spray pyrolysis (FSP) technology to develop Bi-BAG coating nanostructured spike-like coatings on titanium substrates. This is the first study to utilise FSP for creating multifunctional nanocoating with Bi-BAG spikes on orthopedic implants. This unique surface modification significantly enhances the synergy of antibacterial chemicals and topography properties while maintaining the biocompatibility of the titanium substrate. Furthermore, the bioactivity of the Bi-BAG coating promotes human osteoblast cells (HOBs) proliferation and mineralisation over seven days. The FSP technique ensures uniform coating, enhancing the overall biological activity of the implant. This research provides a promising non-antibiotic strategy to combat IAIs, offering multifunctional bioceramics that contribute to advancing next-generation biomaterials for orthopaedic applications.