Fe3O4 Mesocrystals with Distinctive Magnetothermal and Nanoenzyme Activity Enabling Self-Reinforcing Synergistic Cancer Therapy

Magnetite (Fe 3 O 4 ) nanoparticles have been extensively used in noninvasive cancer treatment, for example, magnetic hyperthermia (MH) and chemodynamic therapy (CDT). However, how to achieve a highly efficient MH–CDT synergistic therapy based only on a single component of Fe 3 O 4 still remains a challenge. Herein, hollow Fe 3 O 4 mesocrystals (MCs) are constructed via a modified solvothermal method. Owing to the distinctive magnetic property of the mesocrystalline structure, Fe 3 O 4 MCs show excellent magnetothermal conversion efficiency with a specific absorption rate of 722 w g –1 at a Fe concentration of 0.6 mg mL –1, much higher than that of Fe 3 O 4 polycrystals (PCs). Moreover, Fe 3 O 4 MCs also exhibit higher peroxidase-like activity than Fe 3 O 4 PCs, which may be ascribed to the higher ratio of Fe 2+ /Fe 3+ and more oxygen defects in the Fe 3 O 4 MCs. Detailed in vivo results confirm that Fe 3 O 4 MCs can instantly initiate CDT by producing the detrimental • OH, and such boosted reactive oxygen levels not only induces cell apoptosis but also reduces the expression of heat shock proteins, thus enabling low-temperature-mediated MH. More importantly, the in situ rising temperature resulted from MH in turn facilitates CDT, thus achieving a self-augmented synergistic effect between MH and CDT.