Fig. 4. PEI-SPION can efficiently deliver genes to ADSCs with the help of the external magnetic field. (A) 24 hours after transfection, the eGFP expression of ADSCs in each group was observed by fluorescence microscope, ×20. (B) Live/dead assay showed that most ADSCs survived after treatment with gene complexes containing SPION, ×20. (C) The eGFP expression level assessed by flow cytometry showed that PEI-SPION efficiently transferred genes to ADSCs in the presence of external magnetic field (^*p<0.05). (D) Cell viability evaluation showed that the SPION gene complex had hardly any harmful effect on the proliferation of ADSCs with or without the external magnetic field. eGFP, enhanced green fluorescent protein; PEI-SPION, superparamagnetic iron oxide nanoparticles modified with polyethyleneimine; ADSC, adipose-derived stem cell; NRG1, Neuregulin-1; ns, not significant.