Multifunctional rGO/Y₂O₃@hydroxyapatite bioceramics: structural, optical, and biomedical properties

Hydroxyapatite (HAp)/reduced graphene oxide (rGO)/yttrium oxide (Y₂O₃) composites were prepared by ethanol-assisted wet blending (colloidal dispersion), followed by drying and heat treatment, and systematically characterized. This study investigates the structural, optical, and functional enhancement in hydroxyapatite (HAp) after the incorporation of reduced graphene oxide (rGO) and yttrium oxide (Y₂O₃), aiming to develop multifunctional bioceramics for dual applications in bone regeneration. HAp/rGO/Y₂O₃ composites were prepared by ethanol-assisted wet blending (colloidal dispersion), followed by drying and heat treatment, and systematically characterized. XRD analysis confirmed the phase purity of the composites and revealed reduced crystallite sizes upon doping, while FT-IR spectroscopy validated the presence of functional groups linked with phosphate, hydroxyl, and rGO/Y₂O₃ interactions. SEM investigation displayed dense, homogeneous morphologies with reduced particle sizes (∼380 nm), which are favorable for biomedical integration. UV/visible spectroscopy showed a significant narrowing of the optical bandgap from 5.42 eV in pure HAp to 4.73 eV in HAp/rGO/Y₂O₃ composites. This bandgap reduction was attributed to the π-conjugation of rGO and defect states introduced by Y₂O₃, thereby enhancing light absorption and rendering the composites promising candidates for photothermal and oxidative cancer therapies. The combined effect of rGO's electron transport and Y₂O₃'s reactive oxygen species (ROS) generation potential is expected to induce synergistic anticancer activity while preserving osteoconductivity. The tested AA3 formula demonstrated a promising level of biofilm reduction rates against Gram-positive bacteria, e.g. Streptococcus pneumoniae (97.27% ± 5.36%), Staphylococcus epidermidis (95.89% ± 2.85%), Staphylococcus aureus (94.77% ± 1.24%), and Bacillus cereus (92.90% ± 0.95%). Additionally, its minimum inhibitory dosage (MIC) against Gram-positive bacteria ranged from 80 to 100 µg mL^-1, with a bactericidal effect (MBC) at 120 µg mL^-1. In vitro cytotoxicity studies on Vero cells demonstrated the safety of our tested materials and composites. The MTT assay showed that HAP, Y₂O₃, rGO and their different composites (AA1 and AA3-AA5) exhibited CC₅₀ values above 100 µg mL^-1. By contrast, the CC₅₀ value of the AA2 composite was detected at 8.5 µg L^-1. Consequently, our composites have the potential to be used in biomedical applications. Overall, our results suggest that HAp/rGO/Y₂O₃ nanocomposites exhibit improved physicochemical and optical properties and hold substantial promise as dual-functional materials for integrated bone healing and localized cancer treatment platforms.