Schottky heterojunction CeO₂@MXene nanosheets with synergistic type I and type II PDT for anti-osteosarcoma

Photodynamic therapy (PDT) has shown great potential for tumor treatment as the method is noninvasive, highly selective, and causes minimal side effects. However, conventional type II PDT, which relies on ¹O₂, presents poor therapeutic efficacy for hypoxic tumors due to its reliance on oxygen. Here, CeO₂/Ti₃C₂-MXene (CeO₂@MXene) hybrids were successfully designed by growing CeO₂in situ using Ti₃C₂-MXene (MXene) nanosheets. CeO₂@MXene serves as a reduction-oxidation (REDOX) center due to the presence of Ce in the lattice of CeO₂ nanoparticles. This REDOX center reacts with H₂O₂ to generate oxygen and weakens the hypoxic tumor cell environment, achieving type II PDT. At the same time, many other ROS (such as ⋅O₂^- and ⋅OH) can be produced via a type I photodynamic mechanism (electron transfer process). The CeO₂@MXene heterojunction performs nanoenzymatic functions for synergistic type I and type II PDT, which improves cancer treatment.