Ultra-small Fe3O4 nanoparticles for nuclei targeting drug delivery and photothermal therapy

The aim of this study is to investigate the size-dependent behaviors of the Fe3O4 nanoparticles. We synthesize Fe3O4 nanoparticles with average diameters of 2.1, 4.3 and 9.5 nm then systematically study their photothermal effects and biological behaviors as drug carriers in MCF-7 cells. The results indicate that the Fe3O4 nanoparticles with size below 5 nm can enter the nuclei, while larger ones (9.5 nm) are only located in the cytoplasm. All nanoparticles exhibit favorable photothermal effect and can trigger the release of doxorubicin (DOX) that loaded on the nanoparticles to kill the cancer cells. 2.1 nm and 4.3 nm Fe3O4 nanoparticles demonstrate superior toxicity to 9.5 nm nanoparticles due to the outstanding nuclei targeting ability. This work presents a strategy for the drug carrier design to enhance the therapeutic effect.