NIR-II-driven intracellular photocatalytic oxygen-generation on Z-Scheme iron sulfide/cobalt sulfide nanosheets for hypoxic tumor therapy

Tumor hypoxia not only promotes the proliferation, invasion and metastasis of cancer cells but also seriously hinders photodynamic therapy (PDT). Here, second near-infrared (NIR-II) photocatalytic O2 generation is introduced to relieve hypoxia. FeS2/CoS2@PEG (FCs@PEG) nanosheets (∼80 nm) are prepared with Fe-Co layered double hydroxides (LDHs) as precursor. As-synthesized samples have great NIR-II harvest and photothermal conversion efficiency (50.5 %, 1064 nm). In addition, photothermal effect can elevate the thermal energy of nanocomposite to supply extra energy and to excite FeS2 (1.16 eV) and CoS2 (1.37 eV) simultaneously by low-energy NIR-II (1064 nm, 1.16 eV) irradiation. Band structure is further investigated to discover the Z-Scheme mechanism of FCs@PEG, whose photogenerated charges remains high redox potential to oxidize water forming O2 and to capture O2 producing reactive oxygen species (ROS), respectively. In addition, FC2@PEG enhances peroxidase and catalase activities attributing to the lower resistance for charge transfer in heterostructure. Besides, the nanocomposite also can be used as glutathione oxidase (GSHOD) to deplete GSH and break intracellular redox balance, facilitating oxidative stress. Most importantly, FC2@PEG reveals excellent biodegradation and elimination via feces and urine within 14 D. FCs@PEG integrate magnetic resonance and photothermal imaging (MRI and PTI), O2 in situ supply, and synergistic photothermal therapy (PTT)/PDT/chemotherapy (CDT) to arouse immune response for anticancer.