Effect of silane-NH3 surface functionalization of cobalt ferrite on the structural and physical properties of chitosan/hydroxyapatite composite scaffolds

Interfacial incompatibility between inorganic nanoparticles and biopolymeric matrices is a central limitation in developing composite magnetic scaffolds for bone tissue engineering. In this work, cobalt ferrite nanoparticles (CoFe₂O₄, CFO) were functionalized with a silica-amine shell (CFO@SiO₂-NH₂, CFOcs) via the Stöber sol-gel method followed by APTES aminosilane grafting, and incorporated into freeze-dried chitosan (CH) and hydroxyapatite (HAp) scaffolds at 0, 7.5, and 10 wt% (designated SH, SHC75, and SHC10, respectively). The scaffolds were characterized by Fourier-transform infrared spectroscopy in attenuated total reflectance mode (FTIR-ATR), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDS), vibrating sample magnetometry (VSM), apparent porosity, swelling, uniaxial compression, and in vitro biodegradation. FTIR analysis revealed shifts of the chitosan Amide I and Amide II bands toward higher wavenumbers, alongside retention of the Si-O-Si band, in the composite scaffolds, providing direct spectroscopic evidence of non-covalent interfacial integration between CFOcs and the CH/HAp matrix. SEM/EDS confirmed porous architectures in all formulations, with EDS elemental mapping demonstrating the presence and distribution of Si, Fe, and Co within the scaffold cross-sections. VSM confirmed ferrimagnetic behavior, with saturation magnetization of 0.92 and 1.26 emu·g −1 for SHC7 and SHC10, respectively; consistent with preservation of the dominant magnetocrystalline anisotropy contribution of the CFO core. SHC7 presented the most balanced profile of porosity (81.26 ± 4.5%), swelling capacity, compressive strength, and biodegradation rate (49.1 ± 0.5% over 21 days). The results indicate that aminosilane functionalization promotes measurable interfacial chemical integration in the ternary scaffold system, simultaneously influencing its morphological, mechanical, magnetic, and degradation response.