Fe3O4 Mesocrystals with Distinctive Magnetothermal and Nano-Enzyme Activity Enabling Self-Reinforcing Synergistic Cancer Therapy.

Magnetite (Fe3O4) nanoparticles (NPs) have been extensively explored in non-invasive cancer treatment, e.g., magnetic hyperthermia (MH) and chemodynamic therapy (CDT). However, how to achieve highly efficient MH-CDT synergistic therapy based on only single component of Fe3O4 still remains a challenge. Herein, hollow Fe3O4 mesocrystals (MCs) are constructed via a modified solvothermal method. Owing to the distinctive magnetic property of mesocrystalline structure, Fe3O4 MCs show excellent magnetothermal conversion efficiency with a specific absorption rate (SAR) of high up to 722 w g-1 at the Fe concentration of 0.6 mg mL-1, much higher than that of Fe3O4 polycrystals (PCs). Moreover, Fe3O4 MCs also exhibit higher peroxidase (POD)-like activity than that of Fe3O4 PCs, which may ascribe to higher ratio of Fe2+/Fe3+ and more oxygen defects in the Fe3O4 MCs. Detailed in vivo results confirm that Fe3O4 MCs can instantly initiate CDT by producing the detrimental ˙OH, and such boosted reactive oxygen level not only induces cell apoptosis but also reduces the expression of heat shock protein (HSP), thus enabling low-temperature mediated MH. More importantly, the in-situ rising temperature resulted from MH in turn facilitates the CDT, thus achieving self-augmented synergistic effect between MH and CDT.