A multifunctional oxygen-producing MnO2-based nanoplatform for tumor microenvironment-activated imaging and combination therapy in vitro.

The current trend of cancer therapy has changed from monotherapy to synergistic or combination therapies. Among the treatment strategies, photodynamic therapy (PDT) and starvation therapy are widely employed together. However, the therapeutic effect of these treatments could lead to strong resistance and poor prognosis due to tumor hypoxia. Therefore, a smart nanoplatform (MONs-GOx@MnO2-Ce6) has been constructed herein by the assembly of glucose oxidase (GOx)-coated mesoporous organosilica nanoparticles (MONs) and MnO2 nanosheets-chlorin e6 (Ce6), which form a nanosystem. Once MONs-GOx@MnO2-Ce6 enter tumor cells, it catalyzes the oxidation of glucose using oxygen (O2) and generates hydrogen peroxide (H2O2) and gluconic acid, the former of which may accelerate the decomposition of MnO2 nanosheets. The released MnO2 nanosheets would regenerate O2 in the presence of H2O2. In this case, MnO2 nanosheets serve as (i) a nanocarrier and fluorescence quencher for the photosensitizer Ce6, (ii) a degradable material that is activated by the tumor microenvironment (TME) for fluorescence recovery, and (iii) an O2-producing carrier that reacts with H2O2 for relieving hypoxia in the tumor, which contributes to the combined starvation/photodynamic cancer therapy since these treatment strategies need O2. MONs-GOx@MnO2-Ce6 could not only realize cancer cell imaging, but also reduce intracellular glucose uptake and Glut1 expression, inhibiting the metabolism of cancer cells. This strategy shows great potential for clinical applications.