Electrostatic self-assembly of pFe₃O₄ nanoparticles on graphene oxide: A co-dispersed nanosystem reinforces PLLA scaffolds

Cell responses and mechanical properties are vital for scaffold in bone regeneration. Fe₃O₄ nanoparticles with excellent magnetism can provide magnetic stimulation for cell growth, while graphene oxide (GO) nanosheets are commonly used as reinforcement phases due to their high strength. However, Fe₃O₄ or GO is tended to agglomerate in matrix. In present study, a novel co-dispersed Fe₃O₄-GO nanosystem was constructed through electrostatic self-assembly of positively charged Fe₃O₄ (pFe₃O₄) on negatively charged GO nanosheets. In the nanosystem, pFe₃O₄ nanoparticles and GO nanosheets support each other, which effectively alleviates the π-π stacking between GO nanosheets and magnetic attraction between pFe₃O₄ nanoparticles. Subsequently, the nanosystem was incorporated into poly _L-lactic acid (PLLA) scaffolds fabricated using selective laser sintering. The results confirmed that the pFe₃O₄-GO nanosystem exhibited a synergistic enhancement effect on stimulating cell responses by integrating the capturing effect of GO and the magnetic simulation effect of pFe₃O₄. The activity, proliferation and differentiation of cells grown on scaffolds were significantly enhanced. Moreover, the nanosystem also exhibited a synergistic enhancement effect on mechanical properties of scaffolds, since the pFe₃O₄ loaded on GO improved the efficiency of stress transfer in matrix. The tensile stress and compressive strength of scaffolds were increased by 67.1% and 132%, respectively. In addition, the nanosystem improved the degradation capability and hydrophilicity of scaffolds.