Reductive surfactant-assisted one-step fabrication of a BiOI/BiOIO3 heterojunction biophotocatalyst for enhanced photodynamic theranostics overcoming tumor hypoxia

Abstract

Inorganic biophotocatalysts with suitable size are greatly attractive in photodynamic therapy (PDT) with enhanced permeability and retention effect and the capability to produce reactive oxygen species via type-I reaction for overcoming tumor hypoxia. Herein, we develop a facile one-step hydrothermal method to prepare biocompatible BiOI/BiOIO₃ heterostructure nanocomposites (BB NCs) by introducing reductive trithiol-terminated poly-(methacrylic acid) (PTMP-PMAA) as the surfactant, which can reduce partial KIO₃ (raw material) into KI, resulting in the generation of BiOI and BiOIO₃ in one nanocomposite. Under irradiation with a 650 nm laser, the photogenerated holes/electrons of the agent can effectively generate hydroxyl radicals (˙OH) and singlet oxygen (¹O₂) through a type I and O₂ self-supplying type II PDT process, respectively, under both normoxic and hypoxic environments, which could lead to a reduced mitochondrial membrane potential (MMP) and in turn inhibit the production of ATP to initiate the death of HeLa cells, eventually causing the complete destruction of the tumor at a low dose (0.64 mg kg⁻¹). In addition, the agent also shows extraordinary computed tomography imaging capability due to the high X-ray absorption coefficient (∼41.39 HU L g⁻¹). Our study provides a robust biowindow-responsive hypoxic tumor theranostic agent to break through the limitations of PDT.