Multistage pH/H2O2/redox-responsive 3D nanoflowers that fully exploit the tumor microenvironment achieve highly specific guided multimode diagnosis with excellent synergistic chemotherapy and photodynamic therapy effects both in vitro and in vivo.

Metal–organic frameworks (MOFs) are significant useful molecular materials as a result of their high surface area and flexible catalytic activities by tuning the metal centers and ligands. MOFs have attracted great attention as efficient nanozymes recently; however, it is still difficult to understand polymetallic MOFs for enzymatic catalysis because of their complicated structure and interactions. Herein, bimetallic NiFe2 MOF octahedra were well prepared and exhibited enhanced peroxidase-like activities. The synergistic effect of Fe and Ni atoms was systematically investigated by electrochemistry, X-ray photoelectron spectrometry, (XPS) and in situ Raman techniques. The electrons tend to transfer from Ni2+ to Fe3+ in NiFe2 MOFs, and the resulting Fe2+ is ready to decompose H2O2 and generate ·OH by a Fenton-like reaction. After integration with glucose oxidase (GOx), which can downgrade the pH value and generate H2O2 by oxidation of glucose, a self-activated cascade reagent is therefore established for efficiently inducing cell death. The changes of cell morphology, DNA, and protein are also successfully recorded during the cell death process by Raman spectroscopy and fluorescence imaging.

Multifunctional nanodrugs with the integration of precise diagnostic and effective therapeutic functions have shown great promise in improving the efficacy of cancer therapy.