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

Cell responses and mechanical properties are vital for scaffold in bone regeneration. FeO 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, FeO or GO is tended to agglomerate in matrix. In present study, a novel co-dispersed FeO-GO nanosystem was constructed through electrostatic self-assembly of positively charged FeO (FeO) on negatively charged GO nanosheets. In the nanosystem, FeO nanoparticles and GO nanosheets support each other, which effectively alleviates the π-π stacking between GO nanosheets and magnetic attraction between FeO nanoparticles. Subsequently, the nanosystem was incorporated into poly -lactic acid (PLLA) scaffolds fabricated using selective laser sintering. The results confirmed that the FeO-GO nanosystem exhibited a synergistic enhancement effect on stimulating cell responses by integrating the capturing effect of GO and the magnetic simulation effect of FeO. 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 FeO 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.