Engineered silicon-titania heterojunction elicits catalytic cancer cell death

Photocatalyst is generally capable of generating electron-hole pairs under the suitable external light stimulation, and the water and oxygen in the tumor microenvironment would be oxidized and reduced into hydroxyl radicals and superoxide anions, respectively by the redox reactions with photo-generated holes and electrons, triggering irreversible and permanent damage to the tumor cells. Herein, we have successfully designed and synthesized a silicon/titania (Si/TiO₂, referred to as STO) heterojunction structure photocatalyst, which combines the advantages of both TiO₂ and Si particles. The heterojunction features effective light absorption in the range of 300–800 nm, enabling the efficient oxidation of water and the reduction of oxygen, as demonstrated by in vitro methylene blue (MB) degradation and ESR characterization, proving the abundant generations of hydroxyl radicals and superoxide anions, respectively. Further cell and animal experiments confirm that STO heterojunctions can catalyze the generation of superoxide anions and hydroxyl radicals under visible light stimulation in vivo, thus serving the purpose of efficient photocatalytic tumor therapy.