Structural effect of Fe3O4 nanoparticles on peroxidase-like activity for cancer therapy.

Ferromagnetic nanoparticles (Fe3O4 NPs) have been proven to have the intrinsic peroxidase-like activity. This property has been used for analyte detection, tumor tissue visualization, and cancer therapy, etc. However, the effect of particle structure and morphology on its peroxidase-like activity has been rarely reported. In this work, we fabricated Fe3O4 nanoparticles with different structures (nanoclusters, nanoflowers, and nanodiamonds) by facilely tuning the pH values in the hydrothermal reaction. Their in vitro peroxidase-like activity was evaluated via chromogenic reaction of 3,3',5,5'-tetramethylbenzidine (TMB) by the reduction of H2O2 to H2O. It was found the nanostructures had a great influence on their peroxidase-like activity, following the order of nanoclusters>nanoflowers>nanodiamonds. With this activity, the peroxidase-like activity of Fe3O4 NPs was used for cancer therapy with the addition of low-concentration H2O2. The cancer cell-killing activity was due to the intracellular generated reactive oxygen species (ROS) after endocytosis of Fe3O4 NPs into the Hela cells. It was interesting that the cell killing ability of these three kinds of Fe3O4 NPs was not consistent with the in vitro enzyme-like activity. It was deduced that the cell endocytosis of the nanoparticles along with their enzyme-like activity co-determined their cancer cell-killing performance.