Superparamagnetic nano-composite scaffolds for promoting bone cell proliferation and defect reparation without a magnetic field

Apart from chemical molecules, physical regulations also greatly determine the efficiency of healing in regenerating functional tissues. In this study, we fabricated superparamagnetic nano-composite scaffolds for tissue engineering and investigated their effects on different bone cells without an external magnetic field. Poly(lactic-co-glycolic acid) (PLGA) and hydrophobic superparamagnetic magnetite nanoparticles (MNPs) were combined together with different mass ratios in order to construct composite scaffolds using an electrospinning method for the first time. The diameters of the fibers were 400-600 nm with the MNPs uniformly dispersed in them, as shown by transmission (TEM) and scanning (SEM) electron microscopy observations. All composite scaffolds retained superparamagnetism at room temperature, but the saturation magnetization did not increase linearly as the magnetite content increased. The composite scaffolds with different MNP content showed excellent biocompatibility and significantly promoted cell proliferation compared with PLGA nanofibrous scaffold without an external magnetic field. Cell cycle analysis proved that the composite scaffolds decreased cell numbers in G0/G1 phase while increasing those in S phase, which resulted in positive effects on cell proliferation. However, the composite scaffolds had no effect on the differentiation of MC3T3-E1 cells because of the different impact mechanism between proliferation and differentiation. Therefore, the composite scaffolds composed of superparamagnetic MNPs could be considered as an ideal substrate for accelerating osteoblast cell proliferation and tissue repair.