Manganese Dioxide Coated WS 2 @Fe 3 O 4 /sSiO 2 Nanocomposites for pH-Responsive MR Imaging and Oxygen-Elevated Synergetic Therapy.

Recently, the development of multifunctional theranostic nanoplatforms to realize tumor-specific imaging and enhanced cancer therapy via responding or modulating the tumor microenvironment (TME) has attracted tremendous interests in the field of nanomedicine. Herein, tungsten disulfide (WS2 ) nanoflakes with their surface adsorbed with iron oxide nanoparticles (IONPs) via self-assembly are coated with silica and then subsequently with manganese dioxide (MnO2 ), on to which polyethylene glycol (PEG) is attached. The obtained WS2 -IO/S@MO-PEG appears to be highly sensitive to pH, enabling tumor pH-responsive magnetic resonance imaging with IONPs as the pH-inert T2 contrast probe and MnO2 as the pH-sensitive T1 contrast probe. Meanwhile, synergistic combination tumor therapy is realized with such WS2 -IO/S@MO-PEG, by utilizing the strong near-infrared light and X-ray absorbance of WS2 for photothermal therapy (PTT) and enhanced cancer radiotherapy (RT), respectively, as well as the ability of MnO2 to decompose tumor endogenous H2 O2 and relieve tumor hypoxia to further overcome hypoxia-associated radiotherapy resistance. The combination of PTT and RT with WS2 -IO/S@MO-PEG results in a remarkable synergistic effect to destruct tumors. This work highlights the promise of developing multifunction nanocomposites for TME-specific imaging and TME modulation, aiming at precision cancer synergistic treatment.