Schottky heterojunction CeO 2 @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 1 O 2 , presents poor therapeutic efficacy for hypoxic tumors due to its reliance on oxygen. Here, CeO 2 /Ti 3 C 2 -MXene (CeO 2 @MXene) hybrids were successfully designed by growing CeO 2 in situ using Ti 3 C 2 -MXene (MXene) nanosheets. CeO 2 @MXene serves as a reduction-oxidation (REDOX) center due to the presence of Ce in the lattice of CeO 2 nanoparticles. This REDOX center reacts with H 2 O 2 to generate oxygen and weakens the hypoxic tumor cell environment, achieving type II PDT. At the same time, many other ROS (such as ⋅O 2 - and ⋅OH) can be produced via a type I photodynamic mechanism (electron transfer process). The CeO 2 @MXene heterojunction performs nanoenzymatic functions for synergistic type I and type II PDT, which improves cancer treatment.