Background Fe 3 O 4 nanoparticles are highly desired for constructing endogenous magnetic microenvironment in scaffold to accelerate bone regeneration due to their superior magnetism. However, their random arrangement easily leads to mutual consumption of magnetic poles, thereby weakening the magnetic stimulation effect. Methods In this study, magnetic nanochains are synthesized by magnetic-field-guided interface co-assembly of Fe 3 O 4 nanoparticles. In detail, multiple Fe 3 O 4 nanoparticles are aligned along the direction of magnetic force lines and are connected in series to form nanochain structures under an external magnetic field. Subsequently, the nanochain structures are covered and fixed by depositing a thin layer of silica (SiO 2 ), and consequently forming linear magnetic nanochains (Fe 3 O 4 @SiO 2 ). The Fe 3 O 4 @SiO 2 nanochains are then incorporated into poly l-lactic acid (PLLA) scaffold prepared by selective laser sintering technology. Results The results show that the Fe 3 O 4 @SiO 2 nanochains with unique core–shell structure are successfully constructed. Meanwhile, the orderly assembly of nanoparticles in the Fe 3 O 4 @SiO 2 nanochains enable to form magnetic energy coupling and obtain a highly magnetic micro-field. The in vitro tests indicate that the PLLA/Fe 3 O 4 @SiO 2 scaffolds exhibit superior capacity in enhancing cell activity, improving osteogenesis-related gene expressions, and inducing cell mineralization compared with PLLA and PLLA/Fe 3 O 4 scaffolds. Conclusion In short, the Fe 3 O 4 @SiO 2 nanochains endow scaffolds with good magnetism and cytocompatibility, which have great potential in accelerating bone repair.
Cell responses and mechanical properties are vital for scaffold in bone regeneration. Fe 3 O 4 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, Fe 3 O 4 or GO is tended to agglomerate in matrix. In present study, a novel co-dispersed Fe 3 O 4 -GO nanosystem was constructed through electrostatic self-assembly of positively charged Fe 3 O 4 ( p Fe 3 O 4 ) on negatively charged GO nanosheets. In the nanosystem, p Fe 3 O 4 nanoparticles and GO nanosheets support each other, which effectively alleviates the π-π stacking between GO nanosheets and magnetic attraction between p Fe 3 O 4 nanoparticles. Subsequently, the nanosystem was incorporated into poly L -lactic acid (PLLA) scaffolds fabricated using selective laser sintering. The results confirmed that the p Fe 3 O 4 -GO nanosystem exhibited a synergistic enhancement effect on stimulating cell responses by integrating the capturing effect of GO and the magnetic simulation effect of p Fe 3 O 4 . 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 p Fe 3 O 4 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.
Artesunate, as a semi-synthetic artemisinin derivative, exhibits a broad-spectrum bactericidal effect via the release of singlet oxygen. However, its release is slow due to the difficulty breaking the endoperoxide bridge bond. Ammoniated graphene oxide could be electrostatic adsorbed with artesunate and efficiently transfer thermal energy to artesunate by interfacial heat transfer, thereby facilitating the breaking of the endoperoxide bridge bond. In detail, artesunate was anchored on graphene oxide by a one-pot hydrothermal synthesis method and introduced to the PLLA scaffold fabricated by selective laser sintering. Under near-infrared light irradiation, graphene oxide could convert light to heat through photothermal conversion. Then the heat energy was transferred to artesunate by interfacial heat transfer, accelerating the release of singlet oxygen. Meanwhile, graphene oxide could achieve the purpose of thermal ablation for bacterial infection by increasing the local temperature. Based on the combination of singlet oxygen and thermal ablation therapy, the scaffold possesses a high bactericidal ability triggered by near-infrared light. Under the near-infrared light irradiation, the singlet oxygen production from artesunate increased by 39 %, and the antibacterial ratio against S. aureus and E. coli reached 91.6 % and 93.3 %, respectively. Additionally, the scaffold was favorable cytocompatibility with mBMSCs. All the results highlight the great potential of artesunate-mediated graphene oxide scaffold in eliminating bacterial infections.
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