Innovative diopside–MnFe₂O₄ nanocomposites: a multifunctional platform for bone regeneration and hyperthermia therapy featuring MnFe₂O₄ nanoparticles with near-bulk magnetic performance

This study explores the novel integration of MnFe₂O₄ nanoparticles into diopside bioceramics, paving the way for advanced multifunctional nanocomposites tailored for orthopedic and oncological applications. Diopside is synthesized using biowaste-derived eggshells and rice husks <i>via</i> solid-state reaction at an optimal sintering temperature of 1200 °C. MnFe₂O₄ nanoparticles, with an average particle size of 46 nm, are produced through a facile hydrothermal method coupled with magnetic separation, achieving an impressive saturation magnetization (<i>M</i>_s) of 81.6 emu g^-1 (99.5% of bulk MnFe₂O₄) - the highest reported to date. This exceptional performance is attributed to the nanoparticles' excellent crystallinity, single-domain behavior, and minimized surface effects. Incorporating MnFe₂O₄ nanoparticles into diopside significantly enhances the sinterability, density, and hardness by 2-2.5 times while reducing porosity to ∼1%. Even at a low addition of 10 wt% MnFe₂O₄, the nanocomposites demonstrate effective hyperthermia within a safe therapeutic range (41-46 °C) under an alternating magnetic field, with negligible coercivity and remanence. Biocompatibility evaluations confirm no cytotoxicity and reveal enhanced osteoblast differentiation and mineralization. This study successfully synthesizes MnFe₂O₄ nanoparticles with near-bulk saturation magnetization and highlights diopside-MnFe₂O₄ nanocomposites as promising candidates for sustainable and multifunctional biomaterials, offering load-bearing support, efficient hyperthermia for osteosarcoma therapy, and accelerated bone regeneration.