A small pore black TiO2/-large pore Fe3O4 cascade nanoreactor for chemodynamic/photothermal synergetic tumour therapy

Various unique spatial structures are often found in the enzymes of biological systems. From the consideration of bionics, it is challenging but meaningful to design nanozymes with distinctive structures to enhance their bioactivities. To explore the relationship between the structure and activity of nanozymes, in this work, a special structural nanoreactor, namely small pore black TiO₂ coated/doped large pore Fe₃O₄ (TiO₂/-Fe₃O₄) loaded with lactate oxidase (LOD), was constructed for chemodynamic and photothermal synergistic therapy. Specifically, LOD loaded on the surface of the TiO₂/-Fe₃O₄ nanozyme alleviates the low level of H₂O₂ in the tumour microenvironment (TME); the black TiO₂ shell with multiple pinhole channels and a large specific surface area not only facilitates LOD loading, but also enhances the affinity of the nanozyme for H₂O₂; H₂O₂ is continuously enriched on the surface of the TiO₂/-Fe₃O₄ nanozyme and transmitted to mesoporous Fe₃O₄, in turn efficiently producing abundant toxic hydroxyl radicals (˙OH) for chemodynamic therapy. Meanwhile, the TiO₂/-Fe₃O₄ nanozyme under 1120 nm laser irradiation has excellent photothermal conversion efficiency (η = 41.9%), and further accelerates the production of ˙OH for amplifying the chemodynamic therapy efficiency. This self-cascading, special structure nanozyme provides a novel strategy for application in highly efficient tumour synergetic therapy.