In vitro CCK-8 assay was used to detect cytotoxicity of Fe3O4–PLGA and Fe3O4/GOx–PLGA. PC-12 cells were placed into 96-well plate with 5 × 103 cells per well and cultured for 24 h. Cell culture medium was extracted and fresh culture medium containing various concentrations of Fe3O4–PLGA and Fe3O4/GOx–PLGA was added respectively. After incubation for 24 h, the medium was treated with fresh medium (100 μL) and CCK-8 solution (10 μL), and then incubated at 37 °C for another 4 h. The absorbance of each well OD 490 was determined on the microplate reader.