Spatiotemporally Synchronous Oxygen Self-Supply and Reactive Oxygen Species Production on Z-Scheme Heterostructures for Hypoxic Tumor Therapy

Abstract

Photodynamic therapy (PDT) efficacy has been severely limited by oxygen (O₂ ) deficiency in tumors and the electron-hole separation inefficiency in photosensitizers, especially the long-range diffusion of O₂ toward photosensitizers during the PDT process. Herein, novel bismuth sulfide (Bi₂ S₃ )@bismuth (Bi) Z-scheme heterostructured nanorods (NRs) are designed to realize the spatiotemporally synchronous O₂ self-supply and production of reactive oxygen species for hypoxic tumor therapy. Both narrow-bandgap Bi₂ S₃ and Bi components can be excited by a near-infrared laser to generate abundant electrons and holes. The Z-scheme heterostructure endows Bi₂ S₃ @Bi NRs with an efficient electron-hole separation ability and potent redox potentials, where the hole on the valence band of Bi₂ S₃ can react with water to supply O₂ for the electron on the conduction band of Bi to produce reactive oxygen species. The Bi₂ S₃ @Bi NRs overcome the major obstacles of conventional photosensitizers during the PDT process and exhibit a promising phototherapeutic effect, supplying a new strategy for hypoxic tumor elimination.

Keywords: Z-scheme heterostructures; hypoxic tumors; oxygen self-supply; photodynamic therapy; reactive oxygen species.