Multifunctional hybrid chitosan/κ-carrageenan sponges integrating engineered SBA-15@Fe3O4 composites and nano-hydroxyapatite for bone tissue engineering

Conventional therapies often struggle to overcome key challenges associated with bone tissue disorders that demand advanced and sustained therapy solutions. This underscores the urgent need for multifunctional platforms that combine diagnostic and therapeutic functions with bioactive, degradable, and mechanically robust components. Herein, BDDE-crosslinked chitosan/κ-carrageenan sponges incorporating engineered SBA-15/Fe₃O₄ composites and nano-sized hydroxyapatite (nHAp) crystals were fabricated and investigated. The resulting hybrid sponges exhibited full shape recovery after mechanical compression under wet conditions and a remarkable absorption capacity without compromising their porous structure, attributed to strong structural integrity. The encapsulated SBA-15/Fe₃O₄ particles imparted hierarchical porosity and significant surface roughness, enabling high loading (≥150 mg/g) of simvastatin, a drug with potential to enhance bone regeneration, as well as its controlled release over extended periods ≥30 days. Additionally, these engineered composites conferred magnetic hyperthermia functionality, achieving specific absorption rates (SAR) ranging from 1.82 W·g^-1 to 22.44 W·g^-1 when applied a magnetic field of 28 mT at different kHz, providing them with the ability to modulate the heat response. The incorporation of nHAp into the sponge formulation enhanced both their bioactivity when tested in simulated physiological media, and cell adhesion and proliferation, as confirmed by in vitro direct and indirect contact assays. Cytocompatibility assessments using mouse macrophage (RAW 264.7), human osteosarcoma (MG-63), and preosteoblast (MC3T3-E1) cell lines demonstrated ≥80% viability across all models, revealing the highest proliferation in direct contact. These synergistic and versatile sponges hold promise for applications in bone tissue engineering.