Two-dimensional highly oxidized ilmenite nanosheets equipped with Z-scheme heterojunction for regulating tumor microenvironment and enhancing reactive oxygen species generation

Excessive reactive oxygen species (ROS), as effective cancer therapeutic agents, can promote tumor apoptosis. However, the clinical applications of ROS-mediated cancer therapies still have many limitations, such as self-defects of traditional photosensitizer, adverse tumor microenvironment (TME), and insufficient ROS production. Here, two-dimensional and highly oxidized ilmenite nanosheets (HOIL NSs, formula: FeTiO3@Fe2O3), one of perovskite analogues, were developed through combining ball-milling, probe sonication assisted liquid exfoliation, and probe sonication assisted surface oxidation. The HOIL NSs with surface oxidized Fe2O3 shell and FeTiO3 core cleverly developed a direct Z-scheme heterojunction, in which much stronger oxidation and reduction potentials in the valence band (VB) of Fe2O3 and the conduction band (CB) of FeTiO3 respectively were obtained via recombining the electrons in the CB of Fe2O3 with the holes in the VB of FeTiO3. Under irradiation of 650 nm laser, the generation of O-center dot(2)- from O-2 and center dot OH from OH- on the CB of FeTiO3 and VB of Fe2O3, respectively, were enhanced largely. Besides, the Fe2O3 shell and Fe3+/Fe2+ inside HOIL NSs can not only damage the TME through glutathione consumption and O-2 production, but also produce center dot OH by Fenton reaction. Moreover, the NSs can be triggered by an 808 nm laser to generate local hyperthermia for photothermal therapy. The fluorescent and photothermal imaging capabilities of the HOIL-PEG NSs also allow dual-modal imaging-guided cancer therapy.