A biodegradable "Nano-donut" for magnetic resonance imaging and enhanced chemo/photothermal/chemodynamic therapy through responsive catalysis in tumor microenvironment.

Prussian blue (PB) is a safe photothermal agent for tumor therapy, yet poor photothermal effect and single therapeutic function severely restrict its further clinical applications. Herein, a biodegradable "Nano-donut" (CMPB-MoS2-PEG) is fabricated for magnetic resonance (MR) imaging and enhanced photothermal therapy (PTT)/ chemodynamic therapy (CDT)/chemotherapy through responsive catalysis in tumor microenvironment (TME). The "Nano-donut" is organically composed of Cu/Mn ions doped-PB and MoS2. The porous donut structure of CMPB-MoS2-PEG endows them as a carrier for delivery of doxorubicin hydrochloride (DOX) to tumor site. The framework of Nano-donut specifically decomposes in TME due to the reaction between Fe2+/Fe3+ and H2O2. The multivalent elements (Cu/Fe/Mn ions) decrease the bandgap and then enhance CDT by synergistically catalyzing H2O2 into toxic ·OH. Meanwhile, the Mn4+ also reacts with H2O2 to generate O2, improving the hypoxia of TME and enhancing the chemotherapy effect of released DOX. The MoS2 mingles in the PB, which significantly enhances photothermal conversion efficiency (η) effect of PB from 16.02% to 38.0%. In addition, Fe3+ as T2-weighted MR imaging agent can achieve MR imaging-guided therapy. The data clearly shows Nano-donut/DOX nanocomposites (NCs) have a remarkable inhibition for cancer cells and excellent biological safety in tumor treatment.