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